WO2013141771A1 - Enhancing uplink positioning - Google Patents

Description

ENHANCING UPLINK POSITIONING

RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application Serial No.

61/614234, filed 22 March 2012 and titled "Methods for Enhancing UL Positioning," the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to wireless communication networks and in particular to networks and devices performing positioning of devices based on

measurements of uplink transmissions. BACKGROUND

The development of technologies to determine the position of a mobile device has enabled application developers and wireless network operators to provide location-based and location-aware services. Examples of these are guiding systems, shopping assistance, friend finder, presence services, community and communication services and other information services that give the mobile user information about his or her surroundings or that use this information to enhance their services.

In addition to the commercial services facilitated by these technologies, location-based emergency services are also being deployed. The governments in several countries have put specific requirements on the network operators to be able to determine the position of an emergency call. For instance, governmental requirements in the United States specify that mobile networks must be able to determine the position of a certain percentage of all emergency calls and further include accuracy requirements. The requirements make no distinctions between indoor and outdoor environments.

In many environments, the position can be accurately estimated by using positioning methods based on Global Navigation Satellite Systems (GNSS), such as the well-known Global Positioning System (GPS). However, GPS-based positioning may often have unsatisfactory performance, especially in urban and/or indoor environments.

Complementary positioning methods may also be provided by a wireless network to augment GPS technology. In addition to mobile terminal-based GNSS (including GPS), the following methods are currently available or will be soon be included in the Long-Term Evolution (LTE) standards developed by the 3^rd-Generation Partnership Project (3GPP):

• Cell ID (CID),

• E-CID, including network-based angle-of-arrival (AoA),

• Assisted-GNSS (A-GNSS), including Assisted-GPS (A-GPS), based on satellite signals, • Observed Time Difference of Arrival (OTDOA),

• Uplink Time Difference of Arrival (UTDOA) -currently being standardized.

Several positioning techniques are based on time-difference-of-arrival (TDOA) or time- of-arrival (TOA) measurements. Examples include OTDOA, UTDOA, GNSS, and Assisted- GNSS (A-GNSS). A typical, though not the only, format for the positioning result with these techniques is an ellipsoid point with an uncertainty circle/ellipse/ellipsoid, which is the result of intersection of multiple hyperbolas/hyperbolic arcs (e.g., OTDOA or UTDOA) or circles/arcs (e.g., UTDOA, GNSS, or A-GNSS).

Several techniques, such as Adaptive Enhanced Cell Identity (AECID), may involve a mix of any of the methods above, and are thus regarded as "hybrid" positioning methods. With these methods, the position result can be almost any shape, but in many cases it is likely to be a polygon.

Cellular-based positioning methods (as opposed to satellite-based methods, for example) rely on knowledge of anchor nodes' locations, i.e., the fixed locations from which measured signals are transmitted (e.g., for OTDOA) or the fixed locations at which signals transmitted by mobile devices are measured (e.g., for UTDOA). These fixed locations may correspond, for example, to base station or beacon device locations for OTDOA, Location Measurement Unit (LMU) antenna locations for UTDOA, and base station locations for E- CID. The anchor nodes' locations may also be used to enhance AECID, hybrid positioning, etc.

Positioning Architecture

In 3GPP, location-based services are known as Location Services (LCS). Three key network elements in an LTE positioning architecture are the LCS Client, the LCS target and the LCS Server. The LCS Server is a physical or logical entity that manages positioning for a LCS target device by collecting measurements and other location information, assists the target device in measurements when necessary, and estimating the LCS target location. A LCS Client is a software-based and/or hardware entity that interacts with a LCS Server for the purpose of obtaining location information for one or more LCS targets, i.e., the entities being positioned. LCS Clients may reside in a network node, an external node (i.e., a network external to a cellular network), a Public Safety Access Point (PSAP), a user equipment (or "UE," 3GPP terminology for an end-user wireless station), a radio base station, etc. In some cases, the LCS Client may reside in the LCS target itself. An LCS Client (e.g., an external LCS Client) sends a request to LCS Server (e.g., a positioning node) to obtain location information. The LCS Server processes and services the received requests and sends the positioning result (sometimes including a velocity estimate) to the LCS Client.

In some cases, the position calculation is conducted by a positioning server, such as an Enhanced Serving Mobile Location Center (E-SMLC) or a Secure User-Plane Location (SUPL) Location Platform (SLP) in LTE. In other cases, the position calculation is carried out by the UE. The latter approach is known as the UE-based positioning mode, while the former approach includes both network-based positioning, i.e., position calculation in a network node based on measurements collected from network nodes such as LMUs or eNodeBs, and UE-assisted positioning, where the position calculation in the positioning network node is based on measurements received from UE.

LTE Positioning Protocol (LPP) is a positioning protocol for control plane signaling between a UE and an E-SMLC, which is used by the E-SMLC to provide assistance data to the UE and by the UE for reporting measurements to the E-SMLC. LPP has been designed in such a way that it can also be utilized outside the control plane domain such as in the user plane in the context of SUPL. LPP is used for downlink positioning.

LTE Positioning Protocol Annex (LPPa), sometimes referred to as LTE Positioning Protocol A, is a protocol between the eNodeB and the E-SMLC, and is specified only for control-plane positioning procedures, although it still can assist user-plane positioning by querying eNodeBs for information. For example, LPPa can be used to retrieve information such as positioning reference symbol (PRS) configuration in a cell for OTDOA positioning, or UE sounding reference signal (SRS) configuration for UTDOA positioning, and/or eNodeB measurements. LPPa may be used for downlink positioning and uplink positioning.

Figure 1 illustrates the UTDOA architecture currently under discussion in 3GPP, including nodes found in the Radio Access Network (RAN) and the core network, as well as an external LCS Client. Although uplink (UL) measurements may in principle be performed by any radio network node, such as the illustrated LTE eNodeB 1 10, the UL positioning architecture also includes specific UL measurement units, known as Location Measurement Units (LMUs), which are logical and/or physical nodes that measure signals transmitted by a target UE, such as the UE 130 illustrated in Figure 1. Several LMU deployment options are possible. For example, referring to Figure 1 , LMU 120a is integrated into eNodeB 1 10, while LMU 120b shares some equipment, e.g., at least antennas, with eNodeB 1 10. LMU 120c, on the other hand, is a standalone physical node comprising its own radio components and antenna(s).

While the UTDOA architecture is not finalized, there will likely be communication protocols established for communications between a LMU and positioning node, and there may be some enhancements to support UL positioning added to the existing LPPa or to similar protocols. In particular, a new interface between the E-SMLC and LMU is being standardized for uplink positioning. This interface, known as SLm, is terminated between a positioning server, e.g., the E-SMLC 140 pictured in Figure 1 , and an LMU. It is used to transport messages according to the SLmAP protocol, a new protocol being specified for UL positioning, between the E-SMLC and the LMU. SLmAP can be used to provide assistance data to an LMU, as discussed in further detail below. This protocol may also be used by the LMU to report to the E-SMLC results of measurements on radio signals performed by the LMU. The SLmAP protocol was previously referred to as the LMUp protocol; thus it should be understood that references herein to SLmAP are referring to a developing protocol referred to as LMUp elsewhere, and vice versa.

Table 1

Currently, in LTE, UTDOA measurements, known as UL relative time-of-arrival (RTOA) measurements, are performed on Sounding Reference Signals (SRS). To detect an SRS signal, an LMU 120 needs a number of SRS parameters to generate an SRS sequence that is correlated against the received signal. These parameters are not necessarily known to LMU 120. Thus, to allow the LMU to generate the SRS sequence and detect the SRS signals transmitted by a UE, SRS parameters must be provided in the assistance data transmitted by the positioning node to LMU; these assistance data would be provided via SLmAP. The specific contents of the assistance data to be provided to LMUs by a positioning node are currently being discussed. One example of possible contents of such assistance data is illustrated in Table 1. It has been proposed that the same parameters should be signaled from the eNodeB to a positioning node.

Measurements for UL positioning and UTDOA are performed on UL transmissions, which may include, for example, reference signal transmissions or data channel

transmissions. UL RTOA is the currently standardized UTDOA timing measurement, and may be performed on Sounding Reference Signals (SRS). The results of the measurements are signaled by the measuring node (e.g., LMU) to the positioning node (e.g., E-SMLC), e.g., over SLmAP.

A positioning result is a result of processing of obtained measurements, including Cell IDs, power levels, received radio signal strengths or quality, etc. The positioning result is often based on radio measurements (e.g., timing measurements such as timing advance and RTT or power-based measurements such as received signal strength) received from measuring radio nodes (e.g., UE or eNodeB or LMU).

The positioning result may be exchanged among nodes in one of several pre-defined formats. The signaled positioning result is represented in a pre-defined format, e.g., corresponding to one of the seven Universal Geographical Area Description (GAD) shapes. Currently, a positioning result may be signaled between:

• an LCS target, e.g., a UE, and an LCS server, e.g., over LPP protocol;

• two positioning nodes, e.g., an E-SMLC or SLP, e.g., over a proprietary interface; · a positioning server (such as an E-SMLC,) and other network nodes, e.g., a Mobility

Management Entity (MME), a Mobile Switching Center (MSC), a Gateway Mobile Location Center (GMLC), an Operations and Maintenance (O&M) node, a Self- Organizing Network (SON) node, and/or a Minimization of Drive Tests (MDT) node;

• a positioning node and an LCS Client, e.g., between an E-SMLC and a Public Safety Access Point (PSAP), or between an SLP and an External LCS Client, or between an

E-SMLC and a UE.

Note that in emergency positioning, the LCS Client may reside in a PSAP.

A general problem with current uplink positioning techniques is a lack of information in the assistance data provided to LMUs and the lack of information from LMUs. This lack of information can increase measurement times and/or lead to incomplete and/or missing measurements, all of which contribute to measurement quality degradation. Further, the lack of certain information from LMU may make position calculation in E-SMLC inaccurate or even impossible, in certain deployment scenarios.

SUMMARY

Several types of information are currently unavailable to LMUs. For instance, no search window information is included in the assistance data provided to LMUs to facilitate uplink positioning measurements. Further, information of signals used for positioning and associated with virtual cells is not currently provided to LMUs. Similarly, while a UE may have multiple serving cells for which SRS are configured for non-positioning purposes, where SRS may or may not be configured on the primary cell (PCell), multi-cell information is currently not available to the LMUs and is not possible to configure for positioning. Still further, only limited information from LMUs, insufficient for performing accurate positioning, has been only discussed for LTE.

The technical solutions described herein were developed to address these problems and include several aspects, such as: methods for configuring and using search window for uplink positioning; methods for configuring and using search window for downlink or uplink Coordinated Multi-Point (CoMP), distributed antenna systems (DAS), carrier aggregation, elCIC, etc.; methods for configuring and using multi-cell SRS for positioning; methods for signaling and using pseudo IDs for uplink positioning; and methods of providing LMU location information to positioning node.

An example method according to several embodiments of the present invention, implemented in a first node in a wireless communications network, begins with obtaining search window information corresponding to signals to be used for uplink positioning measurements for a wireless device. This search window information is then used to configure one or more uplink measurements for the wireless device.

In some embodiments, the first node is a positioning node, in which case using the search window information to configure one or more uplink measurements for the wireless device comprises providing the search window information to a radio network node, such as an eNodeB or an LMU, for use in configuring the one or more uplink measurements. In other embodiments, the first node is a radio network node, which obtains the search window information by receiving the search window information from a positioning node or a second radio network node. The search window information may be received according to a protocol for signaling between an enhanced Serving Mobile Location Center (E-SMLC) and an LMU, for example. In still other embodiments, the first node obtains the search window information by retrieving pre-defined or pre-configured search window information stored in the radio network node. In some cases this may involve selecting a stored search window configuration from a plurality of stored search window configurations, based on a condition relating to the wireless device or to the radio network node, or both.

In several embodiments of the invention, obtaining the search window information includes determining the search window information based on one or more of: radio measurements; timing information or distance information for the wireless device;

information about the distance between the wireless device's serving node location and the first node; and historical positioning data. In some of these embodiments, the timing information or distance information is received from a second node.

In any of the embodiments summarized above, the search window information may include a time or distance value and a search window width or uncertainty. In some of these embodiments, the search window information further includes a confidence value associated with the window width. In several embodiments, obtaining the search window information comprises calculating a search window based on a time or distance value corresponding to a distance between the first node and a serving cell for the wireless device, and an uncertainty value. In several of these embodiments, the time or distance value and the uncertainty value may be received from a second node.

In some embodiments of the invention, the first node may obtain pseudo identifiers associated with the wireless device transmissions to be used for UL positioning

measurements. In some of these embodiments, search window information provided to the radio network node may be accompanied by one or more pseudo identifiers or codes, or both, wherein the pseudo identifiers or codes are used to differentiate sounding reference signals transmitted in a cell having a single physical cell identity. The pseudo identifiers or codes may be received from a serving node for the wireless device, prior to providing the search window information to the radio network node. In some cases, a subset of the pseudo identifiers or codes received by the positioning node from the serving node is provided to the radio network node. In still other embodiments of the invention, search window information provided to the radio network node comprises search window

information for two or more serving nodes for the wireless device to be positioned.

Another example method according to some embodiments of the invention, suitable for implementation in a positioning node, begins with receiving multi-cell sounding reference signal (SRS) configuration information for a wireless device. The multi-cell SRS configuration may comprise configuration information about SRS transmitted in multiple serving cells associated with the wireless device. All or part of the received multi-cell SRS configuration information is then signaled to one or more radio network nodes, for use in configuring uplink measurements on SRS from the wireless device. A related method may be implemented in a positioning node (e.g., E-SMLC), starting from receiving the multi-cell SRS configuration from an eNodeB serving the wireless device and then signaling all or part of the information to LMU for assisting the LMU in performing UL positioning measurements based on SRS transmissions from the wireless device. Another related method may be implemented in a radio network node, e.g., an LMU or eNodeB performing uplink measurements based on SRS transmissions by the wireless device, and begins with receiving multi-cell SRS configuration information for a wireless device from a positioning node. The radio network node then uses all or part of the multi-cell SRS configuration information to configure uplink measurements on SRS from the wireless device.

Network node apparatus adapted to carry out several of the techniques summarized above, and variants thereof, are also disclosed in the detailed discussion that follows. For example, an example radio network node configured to assist positioning of a target wireless device includes radio circuitry adapted to receive signals from the target wireless device, a network interface adapted for communication with one or more other network nodes, and processing circuitry, wherein the processing circuitry is adapted to: obtain search window information corresponding to signals to be used for uplink positioning measurements for a wireless device; and use the search window information to perform one or more uplink measurements for the wireless device, using the radio circuitry. Details of positioning node apparatus are also described in detail below.

Of course, the present invention is not limited to the above-summarized features and advantages. Indeed, those skilled in the art will recognize additional features and

advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates several nodes in an example network configured according to the LTE positioning architecture.

Figures 2-8 illustrate example processes for assisting positioning measurements in a wireless communication network.

Figure 9 illustrates an example network node according to several embodiments of the invention.

Figure 10 illustrates an example radio network node according to several embodiments of the invention.

Figure 1 1 illustrates an example calculation of a search window, as might be used in several embodiments of the invention.

Figure 12 is a process flow diagram illustrating an example method for handling pseudo identifiers, according to some embodiments of the invention.

Figure 13 is another process flow diagram, illustrating another example method for handling pseudo identifiers.

Figure 14 is a process flow diagram illustrating an example method for handling location information for a Location Measurement Unit. DETAILED DESCRIPTION

While terminology from 3GPP LTE is used in this disclosure to exemplify the invention, this should not be seen as limiting the scope of the invention to LTE systems or systems using the LTE Radio Access Technology (RAT). Other wireless systems, including those based on WCDMA, WiMAX, UMB and GSM, may also benefit from exploiting the ideas covered within this disclosure. Furthermore, the inventive techniques disclosed herein are not limited to single-RAT systems, but may also be applied in the multi-RAT context. Some other RAT examples are LTE-Advanced, UMTS, HSPA, GSM, cdma2000, WiMAX, and WiFi.

Still further, the techniques and apparatus described herein may be considered as standalone embodiments or may be used in any combination with each other, unless their descriptions herein clearly indicate otherwise.

The terms "wireless device" and "UE" are used interchangeably in the description that follows. A UE may comprise any device equipped with a radio interface and capable of at least generating and transmitting a radio signal to a radio network node. Note that some radio network nodes, e.g., a femto base station, or "home base station," and LMUs, may be equipped with a UE-like interface, and in some cases may need to be positioned in the same manner as UEs are positioned. Examples of UEs that are to be understood in a general sense are wireless PDAs, wireless-equipped laptop computers, mobile telephones, wireless sensors, fixed relay nodes, mobile relay nodes, and any radio network node equipped with a UE-like interface (e.g., small RBS, eNodeB, femto BS).

A "radio node" is characterized by its ability to transmit and/or receive radio signals, and comprises at least a transmitting or receiving antenna. A radio node may be a UE or a radio network node. Some examples of radio nodes are a radio base station (e.g., eNodeB in LTE or NodeB in UTRAN), a relay, a mobile relay, a remote radio unit (RRU), a remote radio head (RRH), a wireless sensor, a beacon device, a measurement unit capable of transmitting downlink signals (e.g., LMUs), a user terminal, a wireless PDA, a mobile telephone, a smartphone, a wireless-equipped laptop, etc.

A "radio network node" is a radio node in a radio communications network and is typically characterized by having its own network address. For example, a mobile device in a cellular network may have no network address, but a wireless device involved in an ad hoc network is likely to have a network address. A radio node may be capable of operating or receiving radio signals or transmitting radio signals in one or more frequencies, and may operate in single-RAT, multi-RAT or multi-standard mode (for example, a dual-mode user equipment may operate with any one or combination of WFi and LTE or HSPA and

LTE/LTE-A). A radio network node, including eNodeB, RRH, RRU, LMU, or transmitting- only/receiving-only nodes, may or may not create own cell. It may also share a cell with another radio node which creates own cell. More than one cell may be associated with one radio node. Further, one or more serving cells (in DL and/or UL) may be configured for a UE, e.g., in a carrier aggregation system where a UE may have one Primary Cell (PCell) and one or more Secondary Cells (SCells). A cell may also be a virtual cell, e.g., characterized by a cell ID but not providing a full cell-like service, associated with a transmit node.

A "network node" may be a radio network node or a core network node. Some non- limiting examples of a network node are an eNodeB, a Radio Network Controller (RNC), a positioning node, an MME, a PSAP, a SON node, an MDT node, and an O&M node. A "coordinating node," as described below may be but is not necessarily a network node.

A "positioning node" as described in several embodiments herein is a node that has positioning functionality. For example, for LTE it may be understood as a positioning platform in the user plane (e.g., SLP in LTE) or a positioning node in the control plane (e.g., E-SMLC in LTE). An SLP may also consist of a SUPL Location Center (SLC) and a SUPL Positioning Center (SPC), where the SPC may also have a proprietary interface with E- SMLC. Positioning functionality may also be split among two or more nodes. For example, there may be a gateway node between LMUs and E-SMLC, where the gateway node may be a radio base station or another network node; in this case, the term "positioning node" may relate to E-SMLC and the gateway node. In a testing environment, a positioning node may be simulated or emulated by test equipment.

The term "coordinating node" as used herein is a network and/or node that coordinates radio resources among one or more radio nodes. Examples of a coordinating node are a network monitoring and configuration node, an OSS node, an O&M node, an MDT node, a SON node, a positioning node, an MME, a gateway node such as Packet Data Network Gateway (P-GW) or Serving Gateway (S-GW) network node or femto gateway node, a macro node coordinating smaller radio nodes associated with it, an eNodeB coordinating resources with other eNodeBs, etc.

The signaling described below in connection with various embodiments of the invention is either via direct links or logical links (e.g., via higher layer protocols and/or via one or more network and/or radio nodes). For example, signaling from a coordinating node may pass through another network node, e.g., a radio network node.

The term "subframe" as used in the description herein (typically related to LTE) is an example resource in the time domain, and in general it may be any pre-defined time instance or time period.

The technical embodiments described herein are described primarily in the context of uplink (UL) positioning, i.e., positioning techniques based on measurements of uplink transmissions. The most typical example of such a positioning method is UTDOA, but the techniques described herein may be applied to other UL positioning approaches as well. UL measurements may be timing measurements (e.g., time of arrival, UE Rx-Tx, eNodeB Rx- Tx, RTT, propagation delay, time-difference of arrival) or power-based measurements (e.g., received signal strength or received signal quality).

A general problem with current uplink positioning techniques is a lack of information in the assistance data provided to LMUs. This lack of information can increase measurement times and/or lead to incomplete and/or missing measurements, all of which contribute to measurement quality degradation.

Table 2

Parameters that may be signaled from E-SMLC to LMU, e.g., over SLmAP

As noted above, the specific contents of the assistance data provided to LMUs by a positioning node, over SLmAP, are currently being discussed in 3GPP. One intention of the assistance data is to indicate the SRS configuration for the uplink signals that the LMUs will measure. A more specific example of the specific assistance data that might be provided to an LMU by a positioning node, using SLmAP, is shown in Table 2. This assistance data, which can be based on information provided to the E-SMLC by an eNodeB, can be used by the LMU to configure UL RTOA measurements, for example.

However, the SRS parameters are also generally unknown to the positioning node. Since the eNodeB is configuring UE transmissions in general, including the SRS

transmissions, it has to communicate to the positioning node the configuration information for the UL transmissions to be measured for UL positioning; this information can be provided to the positioning node via LPPa or a similar protocol. Table 3 thus illustrates examples of parameters that might be signaled from an eNodeB to E-SMLC, using LPPa, for example.

Table 3

Parameters that may be signaled from eNodeB to E-SMLC, e.g., over LPPa

Another example of information that could be signaled to and from positioning node and to an LMU is information specifying the duplex mode used by the wireless device. The LTE specification enables distinct Frequency Division Duplex (FDD) and Time Division Duplex (TDD) operation modes. Additionally, half duplex operation is also specified, which is essentially FDD operation mode but with transmission and receptions not occurring simultaneously as in TDD. Half duplex mode has advantages with some frequency arrangements where the duplex filter may be unreasonable, resulting in high cost and high power consumption. Since carrier frequency number (EARFCN) is unique, by knowing it, it is possible to determine the frequency band, which is either FDD or TDD. However, it may be more difficult to find difference between full duplex FDD and half-duplex FDD (HD-FDD) without explicit information since same FDD band can be used as full FDD or HD-FDD.

In addition to duplex mode information, several other types of information are currently unavailable to LMUs. For instance, no search window information is included in the assistance data provided to LMUs to facilitate uplink positioning measurements. While reference IDs or codes for UE-specific SRS signals have been discussed, this information is not currently provided to LMUs. Similarly, while a UE may have multiple serving cells for which SRS are configured, where SRS may or may not be configured on the primary cell (PCell), multi-cell information is currently not available to the LMUs.

Another general problem is a lack of information from LMUs. This information could be beneficial to the positioning node for position calculation purposes. For example, LMUs do not currently provide measurement quality information along with measurements. Also, LMUs do not provide a reference time for timing measurements or identify a reference cell for the measurements. Still further, it is not currently possible for LMU nodes to provide their location information to the positioning node. Likewise, LMU location information uncertainty and confidence for the LMU node's location is unknown.

Developed in response to some of the above problems, the technical solutions described herein include several aspects, such as: methods for configuring and using search window for uplink positioning; methods for configuring and using search window for downlink or uplink Coordinated Multi-Point (CoMP), distributed antenna systems (DAS), carrier aggregation, elCIC, etc.; methods for configuring and using multi-cell SRS for positioning; methods for signaling and using pseudo IDs for uplink positioning; and methods of providing LMU location information to positioning node. It should be noted that any of these techniques may be combined with any others, unless it is clear from the following description or the technical context that a particular combination is not possible.

Some of these techniques may be viewed generally as techniques for enhancing assistance data to facilitate receiving weak signals and performing measurements on such signals. One example category of techniques that fits this description is techniques related to the determination and use of a "search window," which may be used for uplink positioning measurements and other purposes. For instance, the process flow diagram of Figure 2 illustrates generally a method, implemented in a node of a wireless communication system, for assisting positioning measurements. As shown at block 210, the illustrated method begins with obtaining search window information corresponding to signals to be used for uplink positioning measurements for a wireless device. Next, the search window information is used to perform one or more uplink measurements for the wireless device. Described below are several more detailed embodiments of this general approach. Some of these are suitable for implementation in a positioning node, such as an E-SMLC, while others are suitable for implementation in a radio network node, such as an LMU or eNodeB.

The search window information may be signaled between network nodes in several ways. For example, search window information may be signaled:

• from a coordinating node (e.g., positioning node) to a radio node (e.g., a radio node assisting in UL positioning for a UE; a radio node may be a UE or a radio network node, e.g. eNodeB or LMU);

· between two network nodes (e.g., over X2 interface);

• from a radio node to positioning node (e.g., a timing measurement that can be used for deriving search window for UL measurements - may be provided, e.g., via LPPa, with or without request; this information may be provided by the serving node together with the UL signal configuration for the UL positioning of its UE).

For instance, according to several embodiments of the invention, a positioning node selects assisting radio nodes (e.g., standalone or integrated LMUs, eNodeBs, or other wireless devices) that will perform measurements to be used for uplink positioning of an LCS target (e.g., a UE), and provides a search window information to at least one of the selected LMUs to facilitate performing uplink positioning measurements. An assisting radio node (e.g., LMU, eNodeB or another wireless device) receives the search window information in the assistance data from a positioning node (e.g., E-SMLC in LTE) and uses this information for performing at least one uplink measurement for the UE. The positioning node, prior to including the search window information in the assistance data sent to an LMU, obtains the search window information for the given UE and the LMU. The assistance data may be provided, e.g., in LMUp protocol. Uplink measurements may be timing measurements (e.g., time of arrival, RTT, propagation delay, time difference of arrival) or power-based measurements (e.g., received signal strength or received signal quality).

In other example embodiments, the search window used by an assisting node may be one or more of the following, for example:

· pre-defined (e.g., by the uplink measurement requirements);

• pre-configured (e.g., by software in LMU); • autonomously determined (e.g., by LMU based on downlink and/or other uplink measurements performed by LMU, information about the distance between the UE's serving node location and the LMU, based on historical positioning data, etc.);

• obtained from a database for given condition(s), e.g., the database may store

more than one search window configurations (a combination of one or more search window characteristics) where each configuration may be associated with at least one condition (e.g., a certain search window configuration applies for a specific serving cell ID and LMU ID);

• explicitly received from another node (e.g., from a positioning node);

· calculated based on a timing information (e.g., a timing measurement such as a timing advance, RTT, etc.) or distance for the UE with respect to the UE's serving node (the timing information may be provided to the assisting radio node in the assistance data received from a network node, e.g., a positioning node or serving eNodeB);

· calculated based on a set of pre-defined rules based, e.g., on other information received in the assistance data; or

• any combination of the above (e.g., expected time of arrival is received in the

assistance data, whilst the maximum search window is pre-defined by a

measurement requirement or autonomously determined by the assisting radio node), etc.

Figure 3 is a process flow diagram illustrating an example method suitable for implementation in a positioning node. It should be appreciated that the process illustrated in Figure 3 is a more specific example of the process illustrated in Figure 2. More specifically, the operations illustrated in boxes 310 and 320 of Figure 3 correspond directly to the more general operations shown in boxes 210 and 220 of Figure 2.

Thus, as shown at box 310 of Figure 3, the positioning node obtains the search window information by determining the search window information based on one or more of:

measurements performed by one or more radio nodes; timing information or distance information for the wireless device; information about the distance between the wireless device's serving node location and the radio node; and historical positioning data. More detailed examples of several of these approaches will be provided below. Note that this may be preceded, in some embodiments, by receiving from another node, all or some of the information used to determine the search window. This is illustrated as an optional operation at block 305 of Figure 3. For example, a positioning node may receive timing information for the wireless device from a radio node (e.g., an eNodeB), in some embodiments. Next, as seen at box 320 of Figure 3, using the search window information in this example comprises providing the search window information to a radio network node (e.g., an LMU) for use in performing one or more uplink measurements. Note that the radio network performing the UL measurements node may or may not be the same radio node that performs/provides radio measurements used to determine the search window. Note also that providing search window information can be done according to the LMUp protocol, in some embodiments. In some cases, the search window information provided to the radio network node includes one or more pseudo identifiers or codes, as shown at block 330. As will be explained in further detail below, the pseudo identifiers or codes are used to differentiate sounding reference signals transmitted in a cell having a single physical cell identity. However, not all embodiments provide this information. Accordingly, this operation is shown as "optional" in Figure 3.

Figure 4 illustrates a corresponding method performed in a radio network node, such as an LMU. Again, it should be appreciated that the process illustrated in Figure 4 is a more specific example of the process illustrated in Figure 2. More specifically, the operations illustrated in boxes 410 and 420 of Figure 4 correspond directly to the more general operations shown in boxes 210 and 220 of Figure 2. Thus, as seen at block 410, the radio network node obtains the search window information by receiving the search window information from a positioning node or a second radio network node. The search window information may be received according to the LMUp protocol, in some cases. As shown at block 420, the received search window information is then used to perform uplink positioning measurements for a wireless device to be positioned.

Figure 5 illustrates another approach for obtaining and using search window

information. Again, it should be appreciated that this is a more specific example of the process illustrated in Figure 2. In this case, however, the illustrated approach might be implemented in either a positioning node or in a radio network node.

As shown at block 510, at least part of the search window information in this case is retrieved from pre-defined or pre-configured search window information stored in the node. As shown at block 520, the retrieved search window information is then used to perform uplink positioning measurements for a wireless device to be positioned. In the case of a positioning node, this may include sending the search window information to one or more radio network nodes. In the case of a radio network node (e.g., an LMU), this may instead include making measurements on uplink signals from the wireless device, such as SRS.

In either case, retrieving the pre-defined or pre-configured search window information may involve selecting a stored search window configuration from a plurality of stored search window configurations, based on a condition relating to the wireless device or to the first node, or both. For example, a certain search window configuration out of several possible configures might apply to a specific serving cell ID and LMU ID.

Still another approach is illustrated in Figure 6. While this approach is similar to that illustrated in Figure 3, the process flow diagram of Figure 6 illustrates an example method that is suitable for implementation in a radio network node. One more, it should be appreciated that the process illustrated in Figure 6 is a more specific example of the process illustrated in Figure 2. Thus, as shown at box 610 of Figure 6, the radio network node obtains the search window information by determining the search window information based on one or more of: measurements performed by the radio network node; timing information or distance information for the wireless device; information about the distance between the wireless device's serving node location and the radio network node; and historical positioning data. Next, as seen at box 620 of Figure 6, the search window information is then used to perform uplink positioning measurements for a wireless device to be positioned, e.g., to make measurements on uplink signals from the wireless device, such as SRS.

In all of the embodiments discussed above, the search window information is intended to help the radio network node, e.g., an LMU or eNodeB, to speed up uplink measurements, increase detection probability, perform more accurate measurements, reduce the node's receiver complexity, etc. The quality of the search window information impacts both response time and measurement accuracy and is therefore very important for positioning. Poor-quality search window information may result in worse positioning measurement quality than would be achieved without the search window information;

however, an accurately estimated search window is of great help for receivers performing uplink measurements for positioning.

Examples of search window characteristics and/or parameters that are applicable to any of the embodiments described above include an expected time or distance

corresponding to a given signal occurrence or occurrences, as well as a window width, e.g., an uncertainty. It will be appreciated that a distance parameter for a signal may be easily converted to a time parameter and vice-versa, e.g., assuming propagation at the speed of light, and thus these parameters are equivalent for practical purposes. The search window width may also be associated with a certain confidence level, which may be explicitly provided with the search window width or may be pre-defined (e.g., 95% confidence). Thus, an example interpretation of a given search window/window width combination might be as follows: with X% confidence, the search window width (or uncertainty) is Δ ns, centered at an expected time T. However, in various embodiments the search window may be specified in a symmetric way (e.g., [Τ-Δ, Τ+Δ] ns) or in an asymmetric way (e.g., [Τ-Δ1 , Τ+Δ2]. The offset from a symmetrical search window may be a parameter of the search window and may depend, for example, on direction or angular information of the UE's location with respect to its serving node.

In any of the embodiments discussed above, the search window information may include information indicative of at least one of the search window characteristics, such as its width (uncertainty), or the expected time when the uplink signal should be expected to be received, accounting for the propagation delay, and/or information that can be used for deriving at least one search window characteristic, such as a timing measurement or distance of the UE with respect to the serving node.

Some further non-limiting examples of specifying a search window are:

· an expected time-of-arrival of the UE signal received at an assisting radio node

(e.g., an LMU);

• an expected time-difference-of-arrival of the signal received at an assisting radio node (e.g., LMU) with respect to a reference time (for uplink positioning, the reference time may be pre-defined or configurable being, for example, any one of GPS time, GNSS time, UTC time, system time, etc.);

• expected time-difference-of-arrival of the signal received at an assisting radio node (e.g., LMU) with respect to the time of arrival of a downlink signal received by the assisting radio node from another radio node (e.g., an eNodeB associated with the assisting LMU);

· an estimated distance between the UE and the assisting radio node (the distance may also be converted to time, e.g., assuming the speed of light), etc.

Figure 1 1 illustrates an example of calculating search window characteristics for an assisting radio node (e.g., LMU or another eNodeB) performing measurements on uplink signals transmitted by a UE served by an eNodeB. In this example, the distance between the LMU and the serving eNodeB is d. The distance between any given UE and the LMU is generally unknown. In the figure, location A represents the closest possible UE location to LMU, at distance d1, while location B, at distance d3, represents the most remote possible UE location with respect to the LMU. Assume that an estimated distance between a given UE and serving eNodeB (e.g., based on a timing advance measurement) is d2. The search window in this example may be calculated, e.g., as [Τ-Δ, Τ+Δ] where T is the time

corresponding to distance d and Δ is the time corresponding to d2. The LMU may be provided search window information that includes at least one of the parameters T and Δ. Alternatively, if the LMU knows the distance d, then there may be no need to signal T.

Parameter Δ may be provided in the search window data or may be predefined by a measurement requirement (e.g., the receiver is not required to search within a time window larger than Amax, thus A=Amax in one example).

Note that a serving node would typically be aware of d2 or Δ (unless a worst case, e.g., based on a minimum performance requirement, is assumed by the receiver) but not the LMU. On the other hand, the positioning node is the node providing the assistance data. Hence, a positioning node may obtain d2 or Δ from the serving eNodeB (e.g., receive with other information or request it from eNodeB, e.g., via LPPa) and then use this information for specifying the search window information to be provided by the positioning node to LMU.

Uses of the search window information described above are not limited to uplink positioning applications. Search window information may be provided to enhance DL signal measurements as well. Further, search window information as described above may also be configured and effectively used to improve techniques such as uplink Coordinated Multipoint (CoMP) transmission, distributed antenna systems (DAS), or uplink carrier aggregation where multiple serving cells are configured for a UE in carrier aggregation, e.g., one PCell and one or more SCells. (Note that these serving cells do not have to be co-located at the same radio node). For these scenarios, several of the techniques described above may be used, where instead of a positioning node there is a coordinating node, e.g., a coordinating eNodeB or PCell. The search window information may be exchanged between any two of the involved network nodes, e.g., via X2 interface between two eNodeBs. For any of these techniques, the search window calculation may also be performed according to the example illustrated in Figure 1 1 and detailed above.

In general, the search information may also be configured and used to facilitate measurements for uplink CoMP, downlink CoMP, DAS, carrier aggregation, enhanced inter- cell interference coordination (elCIC), e.g., where a UE in cell range expansion zone has to deal with weak signals due to a significant downlink transmit power difference in neighbor cells (e.g., 6 dB or greater). Not necessarily limited to positioning purposes, the search window information may thus be provided, for example, in the assistance data to facilitate downlink measurements, such as cell detection, cell identification, system information reading and receiving broadcast channel, performing RRM measurements or for mobility purpose, etc. Likewise, search window information may be used to facilitate uplink measurements, such as to detect a UE transmission.

As noted earlier, uplink measurements are performed on Sounding Reference Signals (SRS). In the current standard, SRS sequences are generated based on the serving cell's Physical Cell Identity (PCI). This approach makes it difficult to "direct" an SRS transmission of one UE to one receiving node and an SRS transmission of another UE in the same cell (and thus having the same PCI) to another receiving node. In other words, it is difficult to differentiate among different signals generated by UEs in a cell with the same PCI, since all the SRS transmissions are generated based on the PCI.

To enable UE-specific configuration of SRS base sequences, it has been proposed to create "virtual cells" and use pseudo IDs (also known as reference IDs) or codes (e.g., an additional scrambling code is used to differentiate among SRS transmissions). The use of these pseudo IDs for data communication within a serving cell has been discussed.

However, there is currently no use of virtual cells for SRS or for positioning, and LMUs are currently not aware of virtual cells.

According to some embodiments of the present invention, then, the pseudo IDs are received together with SRS configuration information by the positioning node from the serving node of the UE to be positioned, e.g., via LPPa. This may be upon a request from the positioning node, or in an unsolicited way, in various embodiments.

In other embodiments, the positioning node is aware of a pre-defined rule by which the pseudo ID may be derived, in which case the positioning node may autonomously derive the pseudo ID or IDs. In various systems, the LMU may or may not be aware of this predefined rule. As an example of such a rule, the pseudo ID may be calculated based on an associated cell information, where the associated cell may be a serving cell of the UE and the cell information may comprise, e.g., at least PCI of this cell. In another example rule, UEs with different TA (timing advance) or TA belonging to different TA ranges may use different pseudo IDs.

In some cases, pseudo ID information may be provided by the positioning node to the selected LMUs that will assist in uplink positioning, together with the SRS configuration, e.g., via SLmAP protocol. In still other embodiments, the LMU is aware of (i.e., configured with or programmed with) a pre-defined rule by which the pseudo ID may be derived, which may then be done by the LMU autonomously.

The LMUs will use the received pseudo ID information to generate SRS sequence for performing uplink measurements on the SRS signals transmitted by the UE, where the UE is using the same pseudo ID when generating the transmitted SRS sequence. The uplink positioning measurements performed for SRS using pseudo IDs may then be signaled to positioning node.

In some embodiments, a pseudo ID may be associated with a radio network node receiving UE's data. In other embodiments, a pseudo ID may be associated with a radio network node receiving only UE's physical signals (e.g., reference signals). In other embodiments, a pseudo ID may be associated with an area (e.g., a local area, a tracking area, a cell sector, etc.). In still other embodiments, a pseudo ID may be associated with positioning, e.g., an LMU ID, a node ID or an area ID selected or generated by the positioning node, a pseudo ID in general selected or generated by the positioning node. In this case, when a UE is being configured for positioning purposes, its serving eNodeB may obtain the positioning-associated pseudo ID and provide it to the UE. The positioning- associated pseudo ID may be provided to an eNodeB by the positioning node or other network node, e.g., when the positioning node indicates to the eNodeB the need for configuring a UE (e.g., to transmit SRS) to enable uplink positioning measurements for the UE.

An example method for handling pseudo identifiers, as might be carried out by a positioning node, is illustrated in Figure 12. The method begins, as shown at block 1210, with receiving pseudo identifiers or codes from a serving node of a user equipment to be positioned by the positioning node. As noted above, a positioning node might be configured to derive pseudo identifier information according to a pre-determined rule, so the receiving operation illustrated in block 1210 may be considered optional, as indicated by the dashed outline of block 1210. The method continues, as shown at block 1220, with providing one or more pseudo identifiers or codes to a radio network node, such as an LMU. These pseudo identifiers or codes are used by the radio network node to differentiate sounding reference signals, e.g., to differentiate SRS transmitted in a cell and based on the same physical cell identity. As shown at block 1230, the positioning node subsequently receives, from the radio network node, positioning measurements for sounding reference signals corresponding to the one or more pseudo identifiers or codes.

A UE capable of carrier aggregation may be configured with SRS transmissions in more than one cell for positioning purposes, or configured for SRS transmission in at least one cell that is not the PCell. The UE may or may not be configured with SRS transmissions in the PCell. These cells may be on the same frequency, may be on different frequencies or may even belong to different RATs. Multi-cell SRS configuration may be optimized for positioning, e.g., to ensure SRS hearability at distinct assisting radio node locations. In particular, configuring multi-cell SRS may be used to enable interference coordination, e.g., select best cell to measure for each LMU, and/or increase the processing gain of SRS signals and thus improve positioning measurements accuracy and/or decrease

measurement period.

Multi-cell SRS configuration may then be communicated by the eNodeB to the positioning node, and the positioning node may signal the multi-cell SRS configuration to the selected radio nodes assisting in UL positioning of a UE. An assisting radio node, e.g., LMU, uses the received multi-cell SRS configuration information for performing UL measurements on the configured SRS signals. The performed multi-cell SRS-based measurements may then be reported to positioning node. In some embodiments, a positioning node receiving multi-cell SRS configuration for a UE selects SRS configuration information for a subset of cells or SRS configurations comprised in the multi-cell SRS configuration. This selected subset of multi-cell SRS configuration is sent to the LMU, which then uses this information for performing uplink measurements for the UE. The selection in the positioning node may be based on, for example, a frequency-related LMU capability or capabilities, interference-coordination at LMUs, a maximum number cells that can be measured by LMU at the same time, a maximum number of cells that can be measured per UE by LMU, etc.

In other embodiments, a positioning node receiving multi-cell SRS configuration for a UE, selects one-cell SRS configuration from the multi-cell SRS configuration for each assisting node. The selected one-cell SRS configuration may or may not be the same for all LMUs.

In still other embodiments, there may be defined a capability parameter indicating support of multi-cell SRS for the purpose of positioning. Such capability parameter may be defined for any one or more of: positioning node, assisting radio nodes, for UE, or for eNodeB to configure multi-cell SRS for the purpose of positioning. These capabilities may be exchanged between the corresponding node (for which the capability is defined) and another node, e.g., between positioning node and a radio network node (e.g., eNodeB or LMU).

One example of a set of multi-cell SRS configuration information was illustrated above, in Table 3. It should be appreciated that other SRS-related parameters might be included in multi-cell SRS configuration information signaled between nodes.

Figures 7 and 8 illustrate example techniques for using multi-cell SRS configuration information in a positioning node and a radio network node, respectively. Referring first to Figure 7, the illustrated process begins with receiving multi-cell (SRS) configuration information for a wireless device from one or more serving nodes for the wireless device, as shown at block 710. The multi-cell SRS configuration information is then signaled to one or more radio network nodes, as shown at block 730, for use in performing uplink

measurements on SRS from the wireless device. In some cases, the positioning node selects a part of the multi-cell SRS configuration information received from the one or more serving nodes, and sends only the selected part to the one or more radio network nodes. This is shown as an "optional" step at block 720.

Figure 8 shows a related process as implemented in a radio network node. This process begins, as shown at block 810, with receiving multi-cell SRS configuration information for a wireless device from a positioning node. The radio network node then uses all or part of the received multi-cell SRS configuration information to perform uplink measurements on SRS from the wireless device, as shown at block 830. Again, in some cases the radio network node selects a part of the multi-cell SRS configuration information received from the positioning node, and uses only the selected part. This is shown as an "optional" step at block 820. Other enhancements to uplink positioning techniques are possible, many of which can be combined with the techniques described above. One such enhancement is to provide measurement quality information together with measurement results. In one example, the measurement quality may be calculated as a variance measure, standard deviation, or may be obtained by mapping environment or propagation characteristics (e.g., multi-path rich environment or large-delay-spread environment) to a typical measurement quality, etc.

Also, since reference time may be configurable for UTDOA for uplink RTOA measurements (e.g., may be UTC, GPS, GNSS, system time, etc.), it is beneficial for the positioning node that the assisting node (e.g., eNodeB or LMU) indicates which type of reference time is used for the uplink measurements being reported. If no reference time type is indicated a default (e.g., GPS for standalone LMUs or system time for integrated LMUs) may be assumed. If the type is not indicated, then the assisting node using a different type of reference time for the UL timing measurement should convert the obtained UL timing measurements to the timing measurements using a pre-defined time reference. In some embodiments, the timing reference for UL measurements may be a downlink timing measurement.

Another possible enhancement to uplink positioning involves the LMU receive antenna location. To calculate UE position, the positioning node must know the LMU receive antenna location (or, more generally, the receive antenna location for any measuring node whose measurements are used in the position calculation.) Given that there is no requirement on that the LMU receive antenna is co-located with that of an eNodeB and fully standalone LMUs, with own antennas, are also supported by the UTDOA positioning architecture, it is essential that LMUs have a possibility to provide their location information to the positioning node. This location information may be obtained in many different ways, e.g., GPS, A-GPS, GNSS, manual configuration, reusing eNodeB location information (e.g., for integrated LMUs and LMU may acquire this information or received via internal or proprietary interface from eNodeB), etc. The UL positioning assisting radio node (e.g., LMU or eNodeB) may also obtain own information by calculating its position based on own (DL and/or UL) measurements, proximity detection, sensing, etc.

Currently, only measurements can be provided by LMUs and there is no possibility for LMUs to provide their locations to the positioning node when available. In several embodiments of the present invention, then, an LMU is configured to send its location to a positioning node. Note that uncertainty and confidence levels of location estimates may be available as a part of location information, as a result of a position calculation. Such information may also benefit the LMU location information. The LMU's uncertainty and confidence information together (note that they depend on each other) are of a high value to the positioning node when calculating the UE location. The uncertainty and confidence levels for LMU location are essential for accurate UE location calculation, and for estimation UE location uncertainty and confidence levels, which are normally calculated by the positioning node and provided together with the UE positioning result.

Therefore, an LMU according to some aspects of the present invention provides its location information to the positioning node, e.g., via LMUp protocol. This may be particularly beneficial for standalone LMUs. The reported location information may comprise one or more of: LMU location estimate, LMU location uncertainty, and the corresponding LMU location confidence level. The location information may be provided by the LMU upon a request from a positioning node or in an unsolicited way; once, periodically or upon a changed. In some embodiments, the location information may be provided in a message together with at least one uplink positioning measurement result. In other embodiments the location information is provided in a message comprising only LMU location information or in a message comprising LMU information.

Figure 14 illustrates an example method according to this approach, as might be carried out by a location measurement unit (LMU), for example. The method begins, as shown at block 1410, with obtaining location information for the LMU, e.g., an LMU performing uplink positioning measurements on transmissions from a wireless device of interest. This location information comprises at least an LMU location estimate and an LMU location uncertainty. As shown at block 1420, the LMU location information is sent to another node, such as a positioning node (e.g., E-SLMC). The information sent includes at , least the LMU location estimate and LMU location uncertainty. In some cases, confidence information for the LMU location estimate is also sent, together with the LMU location estimate. This is shown at block 1430.

The LMU location information format may be any one of 3GPP location formation, e.g., describing one of GAD shapes (e.g., an ellipsoid point with uncertainty circle). In some embodiments, location information may comprise an indication on whether the LMU's location is the same as a radio network node location (e.g., LMU is integrated into eNodeB). In other embodiments, the LMU provides a cell identity of a cell or a radio network node in which it is integrated to or sharing the radio equipment, indicating hereby that LMU location is the same as the radio network node's location. In other embodiments, a positioning node may selectively request LMU location information for standalone LMUs, while not requesting location information for integrated LMUs or LMUs sharing the location with other nodes for which the location may be known.

As noted above, several of the various techniques might be combined, in some embodiments of the invention. For example, an LMU configured to send its location information to a positioning node may also be configured to carry out one or more of the other techniques described above, such as those techniques related to the handling of pseudo identifiers or codes. Figure 13 illustrates a process flow diagram based on this combination of techniques, as might be implemented in a radio network node, such as an LMU. As shown at block 1310, the illustrated process begins with receiving one or more pseudo identifiers or codes from a positioning node, where the pseudo identifiers or codes are used to differentiate sounding reference signals transmitted in a cell having a single physical cell identity. The radio network node generates one or more sounding reference signal sequences, based on the received pseudo identifiers or codes, and performs positioning measurements on the corresponding sounding reference signals, as shown at block 1320. As seen at block 1330, positioning measurements for sounding reference signals corresponding to the one or more pseudo identifiers or codes are then sent to the positioning node. The radio network node might also send location information to the positioning node, as shown at block 1340. This location information includes a location estimate and a location uncertainty for the radio network node, and may also include a confidence level for the location estimate and location uncertainty. While illustrated as the last operation in Figure 13, this operation might take place at any time, including before positioning measurements are sent to the positioning node. Although the techniques described above may be implemented in any appropriate type of telecommunication system, supporting any suitable communication standards and using any suitable components, particular embodiments of the described solutions may be implemented in an LTE network, such as in any of several of the nodes illustrated in Figure 1. The example network may further include any additional elements suitable to support communication between wireless devices or between a wireless device and another communication device (such as a landline telephone). Although each of the illustrated network nodes in Figure 1 may represent a network communication device that includes any suitable combination of hardware and/or software, these network nodes may, in particular embodiments, represent a device such as the example network node 900 illustrated in Figure 9. As shown in Figure 9, the example network node 900 includes processing circuitry 920, a memory 930, and network interface circuitry 910. In particular embodiments, some or all of the functionality described above as being provided by a network node may be provided by processing circuitry 920, executing instructions stored on a computer-readable medium, such as the memory 930 shown in Figure 9. Alternative embodiments of the network node 900 may include additional components beyond those shown in Figure 9 that may be responsible for providing certain aspects of the node's functionality, including any of the functionality described above and/or any functionality necessary to support the solution described above.

More particularly, embodiments of the present invention include positioning nodes having a configuration like that illustrated in Figure 9, e.g., including a network interface 910 adapted for communication with one or more other network nodes as well as processing circuitry 920, where the processing circuitry 920 is adapted to, for example, obtain search window information corresponding to signals to be used for uplink positioning measurements for a wireless device, and provide the search window information to a radio network node for use in performing the one or more uplink measurements.

Processing circuit 920 may include one or more microprocessors or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), special- purpose digital logic, and the like. Either or both of the microprocessor(s) and the digital hardware may be configured to execute program code stored in memory, along with radio parameters. The program code stored in this memory, which may comprise one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc., includes program instructions for executing one or more telecommunications and/or data communications protocols, as well as instructions for carrying out one or more of the several techniques described above. Because the various details and engineering tradeoffs associated with the design of baseband processing circuitry for wireless base stations and other wireless devices are well known and are unnecessary to a full understanding of the invention, additional details are not shown here.

Accordingly, in various embodiments of the invention, processing circuits, such as the processing circuits 920 of Figure 9, are configured to carry out one or more of the techniques described above for assisting in uplink positioning of a target wireless device. In some cases, these processing circuits are configured with appropriate program code, stored in one or more suitable memory devices, to implement one or more of the techniques described herein. Of course, it will be appreciated that not all of the steps of these techniques are necessarily performed in a single microprocessor or even in a single module. A variant of the network node 900 illustrated in Figure 9 is shown in Figure 10. Here, the illustrated network node is a radio network node 940. The example radio network node 940 shown in Figure 10 includes processing circuitry 960, a memory 970, radio circuitry 950, and a network interface 990. The processing circuitry 960 may comprise additional radio- frequency circuitry and baseband processing circuitry (not shown). In particular

embodiments, some or all of the functionality described above as being provided by a mobile base station, a base station controller, a relay node, a NodeB, an enhanced NodeB, an LMU, and/or any other type of mobile communications node may be provided by the processing circuitry 960 executing instructions stored on a computer-readable medium, such as the memory 970 shown in Figure 10. Alternative embodiments of the network node 940 may include additional components responsible for providing additional functionality, including any of the functionality identified above and/or any functionality necessary to support the solution described above.

The radio network node 940 of Figure 10 may be configured to operate as a base station according to Release 1 1 specifications for LTE, in some cases. In general, a base station communicates with access terminals and is referred to in various contexts as an access point, Node B, Evolved Node B (eNodeB or eNB) or some other terminology.

Although the various base stations discussed herein are generally described and illustrated as though each base station is a single physical entity, those skilled in the art will recognize that various physical configurations are possible, including those in which the functional aspects discussed here are split between two physically separated units. Thus, the term "base station" is used herein to refer to a collection of functional elements (one of which is a radio transceiver that communicates wirelessly with one or more mobile stations), which may or may not be implemented as a single physical unit.

In some cases, radio network node 940 includes an additional interface 980, adapted for communications with an internal or external LMU function, or both. This additional interface 980 may include circuitry and/or programmed logic that is additional to network interface 990, in some cases, or may comprise functionality added to the circuitry and/or programmed logic used to implement network interface 990. When configured as a base station, radio network node 940 may include an integrated LMU, or may share one or more components with an LMU, and/or may communicate with a standalone LMU via additional interface 980. In any of these cases, the processing circuitry 960 may be further configured to carry out the necessary communications between the base station functionality of radio network node 940 and the LMU functionality.

In other embodiments, radio network node 940 of Figure 10 is configured to operate as an LMU or other radio signal measurement unit. In this case, radio network node 940 may include radio circuitry 950 that is adapted only for receiving and measuring uplink transmissions from UEs, in some cases. As noted earlier, an LMU may be integrated with an eNodeB, or share one or more components with an eNodeB, or may be standalone; in any of these cases, an LMU configured as shown in Figure 10 is adapted to communicate with an eNodeB and/or a positioning node, e.g., using network interface 990.

Referring again to Figure 10, it should be appreciated that radio circuitry 950 includes receiver circuits and/or transmitter circuits that use known radio processing and signal processing components and techniques, typically according to a particular

telecommunications standard such as the 3GPP standard for LTE and/or LTE-Advanced. In some cases, radio network node may be a measurement node that includes only radio receiver circuitry, and not radio transmitter circuits. In either case, because the various details and engineering trade-offs associated with the design and implementation of such circuitry are well known and are unnecessary to a full understanding of the invention, additional details are not shown here.

Processing circuitry 960 may include one or more microprocessors or microcontrollers, as well as other digital hardware, which may include digital signal processors (DSPs), special-purpose digital logic, and the like. Either or both of the microprocessor(s) and the digital hardware may be configured to execute program code stored in memory, along with radio parameters. The program code stored in this memory, which may comprise one or several types of memory such as read-only memory (ROM), random-access memory, cache memory, flash memory devices, optical storage devices, etc., includes program instructions for executing one or more telecommunications and/or data communications protocols, as well as instructions for carrying out one or more of the several techniques described above. Again, because the various details and engineering tradeoffs associated with the design of processing circuitry for wireless base stations and other wireless devices are well known and are unnecessary to a full understanding of the invention, additional details are not shown here.

Accordingly, in various embodiments of the invention, processing circuits, such as the processing circuits 960 of Figure 10, are configured to carry out one or more of the techniques described above for assisting in the positioning of a target wireless device. In some cases, these processing circuits are configured with appropriate program code, stored in one or more suitable memory devices, to implement one or more of the techniques described herein. Of course, it will be appreciated that not all of the steps of these techniques are necessarily performed in a single microprocessor or even in a single module. Several advantages may be achieved using the various techniques and apparatus described above. Some of the advantages provided by some embodiments of the invention are:

• more accurate uplink timing measurements for positioning, lower receiver

complexity;

• LMU location estimate, location information uncertainty, and confidence

information are made available to the positioning node over LMUp protocol;

• pseudo IDs are used for uplink positioning;

• multi-cell SRS configuration information is made available for uplink positioning measurements.

Examples of several embodiments of the present invention have been described in detail above, with reference to the attached illustrations of specific embodiments. Because it is not possible, of course, to describe every conceivable combination of components or techniques, those skilled in the art will appreciate that the present invention can be implemented in other ways than those specifically set forth herein, without departing from essential characteristics of the invention. Modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention(s) is/are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. The present embodiments are thus to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS What is claimed is:

1. A method, in a first node in a wireless communications network, for configuring positioning measurements, characterized in that the method comprises:

obtaining (210, 310, 410, 510, 610) search window information corresponding to radio signals to be used for uplink positioning measurements for a wireless device; and

using (220, 320, 420, 520, 620) the search window information to configure one or more uplink measurements for the wireless device.

2. The method of claim 1 , wherein the first node is a positioning node and wherein using the search window information to configure one or more uplink measurements for the wireless device comprises providing (320) the search window information to a radio network node for use in configuring the one or more uplink measurements.

3. The method of claim 2, wherein the radio network node is a Location Measurement Unit, LMU.

4. The method of claim 1 , wherein the first node is a radio network node and wherein obtaining the search window information comprises receiving (410) the search window information from a positioning node or a second radio network node.

5. The method of claim 4, wherein receiving (410) the search window information from the positioning node or the second radio network node comprises receiving the search window information according a protocol for signaling between an enhanced Serving Mobile Location Center, E-SMLC, and a Location Measurement Unit, LMU.

6. The method of any of claims 2-4, further comprising:

determining the quality of at least one uplink measurement; and

reporting the at least one measurement and the quality to another node.

7. The method of claim 6, wherein the determined quality comprises at least one of:

a variance measure;

a standard deviation; and

a quality measure obtained by mapping environment or propagation characteristics to a typical corresponding measurement quality.

8. The method of claim 1 , wherein obtaining the search window information comprises retrieving (510) pre-defined or pre-configured search window information stored in the first node.

9. The method of claim 8, wherein retrieving (510) the pre-defined or pre-configured search window information comprises selecting a stored search window configuration from a plurality of stored search window configurations, based on a condition relating to the wireless device or to the first node, or both.

10. The method of any of claims 1 to 9, wherein obtaining the search window information comprises determining (310, 610) the search window information based on second search window information that comprises one or more of:

radio measurements;

timing advance measurement;

timing information or distance information for the wireless device;

information about the distance between the wireless device's serving node location and the first node; and

historical positioning data.

1 1. The method of claim 10, wherein said second search window information is received from another node.

12. The method of any of claims 1 to 1 1 , wherein the search window information comprises a time or distance value and an uncertainty parameter indicative of the search window width.

13. The method of claim 12, wherein the search window information further comprises a confidence value associated with the search window width.

14. The method of any of claims 1-13, wherein obtaining the search window information comprises calculating a search window based on a time or distance value corresponding to a distance between the first node and a serving cell for the wireless device, and an uncertainty value associated with the wireless device location.

15. The method of claim 14, wherein the time or distance value and the uncertainty value is received from a second node.

16. The method of claim 14, wherein the uncertainty value is a predetermined maximum uncertainty value.

17. The method of claim 2, further comprising providing one or more pseudo identifiers or codes to the radio network node, wherein the pseudo identifiers or codes are used to differentiate sounding reference signals.

18. The method of claim 17, further comprising receiving the pseudo identifiers or codes, or both, from a serving node for the wireless device, prior to providing the search window information to the radio network node.

19. The method of claim 18, wherein providing one or more pseudo identifiers or codes to the radio network node comprises providing the radio network node with a subset of pseudo identifiers or codes received by the positioning node from the serving node.

20. The method of claim 16, further comprising deriving the pseudo identifiers or codes, or both, based on a pre-defined rule, prior to providing the search window information to the radio network node.

21. A method, in a positioning node in a wireless communications network, for assisting positioning measurements, characterized in that the method comprises:

receiving (710), from a serving node for a wireless device, multi-cell sounding

reference signal, SRS, configuration information for the wireless device; and signaling (730) all or part of the received multi-cell SRS configuration information to one or more radio network nodes, for use in configuring uplink measurements on SRS transmitted by the wireless device.

22. The method of claim 21 , further comprising selecting (720) a part of the multi-cell SRS configuration information received from the serving node, and sending the selected part to the one or more radio network nodes.

23. The method of claim 22, wherein said selecting is based on one or more of:

frequency-related capabilities of the one or more radio network nodes;

interference coordination at the one or more radio network nodes; and

a maximum number of cells that can be measured by the one or more radio network nodes.

24. The method of any of claims 21-23, wherein said multi-cell SRS configuration information comprises search window information corresponding to one or more SRS.

25. The method of any of claims 21-24, wherein said multi-cell SRS configuration information comprises one or more pseudo identifiers or codes associated with one or more SRS.

26. A method, in a radio network node in a wireless communications network, for assisting positioning measurements, characterized in that the method comprises:

receiving (810) multi-cell sounding reference signal, SRS, configuration information for a wireless device from a positioning node; and

using (830) all or part of the multi-cell SRS configuration information to configure uplink measurements on SRS from the wireless device.

27. The method of claim 26, further comprising selecting (820) a part of the multi-cell SRS configuration information received from the positioning node, and using only the selected part for configuring uplink measurements on SRS from the wireless device.

28. The method of claim 27, wherein said selecting is based on one or more of:

frequency-related capabilities of the radio network node;

interference coordination at the radio network node; and

a maximum number of cells that can be measured by the radio network node.

29. The method of any of claims 26-28, wherein said multi-cell SRS configuration information comprises search window information corresponding to one or more SRS.

30. The method of any of claims 26-29, wherein said multi-cell SRS configuration information comprises one or more pseudo identifiers or codes associated with one or more SRS.

31. A radio network node (940), comprising radio circuitry (950) adapted to receive radio signals from the target wireless device, a network interface (990) adapted for communication with one or more other network nodes, and processing circuitry (960), characterized in that the processing circuitry (960) is adapted to:

obtain search window information corresponding to signals to be used for uplink positioning measurements for a wireless device; and use the search window information to configure one or more uplink measurements for the wireless device, using the radio circuitry (950).

32. The radio network node (940) of claim 31 , wherein the processing circuitry (960) is configured to obtain the search window information by receiving the search window information from a positioning node or a second radio network node, via the network interface.

33. The radio network node (940) of claim 32, wherein the radio network node (940) is a Location Measurement Unit, LMU.

34. The radio network node (940) of claim 31 , wherein the processing circuitry (960) is configured to obtain at least part of the search window information by retrieving pre-defined or pre-configured search window information stored in the radio network node (940).

35. The radio network node (940) of claim 34, wherein the processing circuitry (960) is configured to retrieve the pre-defined or pre-configured search window information by selecting a stored search window configuration from a plurality of stored search window configurations, based on a condition relating to the wireless device or to the radio network node (940), or both.

36. The radio network node (940) of any of claims 31 to 35, wherein the processing circuitry (960) is configured to obtain the search window information by determining the search window information based on second search window information that comprises one or more of:

measurements performed by the radio network node or another radio node;

timing advance measurements;

timing information or distance information for the wireless device;

information about the distance between the wireless device's serving node location and the radio network node; and

historical positioning data.

37. The radio network node (940) of claim 36, wherein said second search window information is received from another node.

38. The radio network node (940) of any of claims 31 to 37, wherein the processing circuitry (960) is configured to obtain the search window information by calculating a search window based on a time or distance value corresponding to a distance between the first node and a serving cell for the wireless device, and an uncertainty value associated with the wireless device location.

39. The radio network node (940) of claim 38, wherein the time or distance value and the uncertainty value is received from another node.

40. The radio network node (940) of claim 32, wherein the processing circuitry (960) is further adapted to receive one or more pseudo identifiers or codes, or both, wherein the pseudo identifiers or codes are used to differentiate sounding reference signals.

41. The radio network node (940) of any of claims 31-40, wherein the processing circuitry (960) is further adapted to:

determine the quality of at least one uplink measurement; and

report the at least one measurement and the quality to another node.

42. The radio network node (940) of claim 41 , wherein the determined quality comprises at least one of:

a variance measure;

a standard deviation; and

a quality measure obtained by mapping environment or propagation characteristics to a typical corresponding measurement quality.

43. A positioning node (800) in a wireless communication system, the node (800) comprising a network interface circuit (810) adapted for communication with one or more other nodes in the wireless communication system and a processing circuit (820), characterized in that the processing circuit (820) is adapted to:

obtain search window information corresponding to signals to be used for uplink positioning measurements for a wireless device; and

provide the search window information to a radio network node for use in configuring the one or more uplink measurements.

44. The positioning node (800) of claim 43, wherein the processing circuit (820) is adapted to obtain at least part of the search window information by retrieving pre-defined or pre- configured search window information stored in the positioning node (800).

45. The positioning node (800) of claim 44, wherein the processing circuit (820) is adapted to retrieve the pre-defined or pre-configured search window information by selecting a stored search window configuration from a plurality of stored search window configurations, based on a condition relating to the wireless device or to the first node, or both.

46. The positioning node (800) of claim 43, wherein the processing circuit (820) is adapted to obtain the search window information by determining the search window information based on one or more of:

measurements performed by one or more radio network nodes;

timing advance measurements;

timing information or distance information for the wireless device;

information about the distance between the wireless device's serving node location and one or more radio network nodes; and

historical positioning data.

47. The positioning node (800) of claim 46, wherein the processing circuit (820) is adapted to determine the search window based on timing information or distance information received from a second node.

48. The positioning node (800) of any of claims 43 to 47, wherein the processing circuit (820) is adapted to determine the search window information by calculating a search window based on a time or distance value corresponding to a distance between the first node and a serving cell for the wireless device, and an uncertainty value.

49. The positioning node (800) of claim 48, wherein the processing circuit (820) is adapted to determine the search window based on a time or distance value and uncertainty value received from a second node.

50. The positioning node (800) of any of claims 43 to 49, wherein the search window information provided to the radio network node comprises one or more pseudo identifiers or codes, or both, wherein the pseudo identifiers or codes are used to differentiate sounding reference signals transmitted in a cell having a single physical cell identity.

51. The positioning node (800) of claim 50, wherein the processing circuit (820) is adapted to receive the pseudo identifiers or codes, or both, from a serving node for the wireless device, prior to providing the search window information to the radio network node.

52. The positioning node (800) of claim 51 , wherein the processing circuit (820) is adapted to provide the radio network node with a subset of pseudo identifiers or codes received by the positioning node from the serving node.

53. The positioning node (800) of claim 50, wherein the processing circuit (820) is adapted to derive the pseudo identifiers or codes, or both, based on a pre-defined rule, prior to providing the search window information to the radio network node.

54. A method, in a positioning node in a wireless communications network, for configuring positioning measurements, characterized in that the method comprises:

providing (1220) one or more pseudo identifiers or codes to a radio network node, wherein the pseudo identifiers or codes are used to differentiate sounding reference signals; and

receiving (1230), from the radio network node, at least one positioning measurement performed based on sounding reference signals corresponding to the one or more pseudo identifiers or codes.

55. The method of claim 54, further comprising first receiving (1210) the pseudo identifiers or codes from a serving node of a user equipment to be positioned by the positioning node.

56. The method of claim 54 or 55, further comprising providing sounding reference symbol configuration information to the radio network node, together with the pseudo identifiers or codes.

57. A method, in a radio network node in a wireless communications, for configuring positioning measurements, characterized in that the method comprises:

receiving (1310) one or more pseudo identifiers or codes from a positioning node, wherein the pseudo identifiers or codes are used to differentiate sounding reference signals;

generating (1320) one or more sounding reference signal sequences based on the received pseudo identifiers or codes, and performing positioning measurements on the corresponding sounding reference signals; and sending (1330), to the positioning node, at least one positioning measurement

performed based on sounding reference signals corresponding to the one or more pseudo identifiers or codes.

58. The method of claim 57, further comprising sending (1340), to the positioning node, a location estimate for the radio network node and a location uncertainty for the location estimate.

59. The method of claim 58, further comprising sending, to the positioning node, a confidence level corresponding to the location estimate and the location uncertainty.