WO2013155680A1

WO2013155680A1 - Mechanism for controlling discovery of small cells

Info

Publication number: WO2013155680A1
Application number: PCT/CN2012/074254
Authority: WO
Inventors: Pengfei Sun; Na WEI; Gilles Charbit; Erlin Zeng; Wei Bai; Wei Hong; Haiming Wang
Original assignee: Renesas Mobile Corporation
Priority date: 2012-04-18
Filing date: 2012-04-18
Publication date: 2013-10-24

Abstract

There is proposed a mechanism for controlling a discovery of small cells or secondary cells located in a macro cell or primary cell. An eNB signals to a UE located in a primary cell area configuration data related to a physical discovery channel used for transmission of discovery signals in one or more secondary cells. The configuration data comprises a unique Scell ID for each secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique ID of each secondary cell for atfocating each unique ID to a specific communication resource. The UE detects for discovery signals on the basis of the information included in the configuration data.

Description

MECHANISM FOR CONTROLLING DISCOVERY OF SMALL CELLS

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to a mechanism for controlling a discovery of small cells or secondary cells located in a macro cell or primary cell. In particular, the present invention is directed to apparatuses, methods and computer program products by means of which the discovery of small cells in a macro cell by a user equipment can be improved.

Related background Art

Prior art which is related to this technical field can e.g. be found in technical specifications according to 3GPP TS 36.211 (e.g. version 10.4.0).

The following meanings for the abbreviations used in this specification apply:

BS : base station

BW: bandwidth

CA: carrier aggregation

CDM : code division multiplex

CPU : central processing unit

CRS : common reference signal

DL: downlink

eNB: evolved node B

GPS : global positioning system

HO : handover

ID : identification

LI : layer 1 (physical layer) LTE: Long Term Evolution

LTE-A : LTE Advanced

MAC: medium access control

OFDM : orthogonal frequency division multiplex

PCell : primary cell

PDCH : physical discovery channel

P ACH : physical random access channel

PRS : position reference signal

PSS : primary synchronization signal

PTP: precision time protocol

RRC : radio resource control

RRH : radio remote head

RRM : radio resource management

RS : reference signal

SCell : secondary cell

SSS : secondary synchronization signal

TA; timing advance

UE: user equipment

UL: uplink

ZC: Zadoff-Chu (sequence)

In the last years, an increasing extension of communication networks, e.g . of wire based communication networks, such as the Integrated Services Digital Network (ISDN), DSL, or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) communication networks like the Universal Mobile Telecommunications System (UMTS), enhanced communication networks based e.g . on LTE, cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolutions (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN), Bluetooth or Worldwide Interoperability for Microwave Access (WiMAX), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project (3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), the International Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers), the WiMAX Forum and the like are working on standards for telecommunication network and access environments.

For Improving the performance of new communication networks, such as that of LTE or LTE-A based networks, carrier aggregation (CA) is employed so as to support wider transmission bandwidths. CA in LTE-A extends the maximum bandwidth in the UL or DL directions by aggregating multiple carriers within a frequency band (intra-band CA) or across frequency bands (inter-band CA).

In order to support all CA deployment scenarios, it is contemplated to design an additional carrier type. Such a new carrier type does not need to be backward compatible and allows thus a certain flexibility in its configuration. In other words, as such a new type of carrier does not necessarily be usable by legacy UE, some enhancement may be supported on it, for example a reduction of the density or even a re-design of reference signals which may allow to save overhead, and to consider some optimization to suit to specific application scenarios.

A further item of new communication network system is the implementation of heterogeneous networks consisting of e.g. a "normal" communication cell (referred to as macro cell) and plural small cells which allows a better coverage and possibly outsourcing options from a communication to the macro cell to a small cell (which may be connected to the network e.g. by a backhaul network offering higher capacity), or the like. In the following, it is assumed that a macro cell is used as a primary cell (PCell) for a UE communication, and the small cells are used as secondary cells (SCells) for the UE communication.

In order to enhance the usage of heterogeneous networks, i.e. to achieve heterogeneous network mobility enhancements for e.g. LTE based networks, it is necessary to provide suitable mechanisms for small cell discovery/identification. In this context, it is considered to use also the new carrier type for a quick cell identification of small cells, for example in a scenario where the small ceils are constituted by using RRHs.

An example for a new physical channel is the so-called Physical Discovery Channel (PDCH). The PDCH is configured such that is has a relative long periodicity, i.e. a few seconds assuming relaxed measurement requirements for energy saving and low mobility and sufficient time/frequency radio resource density for one-shot PDCH reception by the UE for efficient UE battery consumption (e.g. full use of a few subframes).

However, due to the long periodicity of DPCH, it may introduce larger cell access/detection delay. An attempt to solve this by, for example, a simple reduction of the periodicity is not feasible as the other advantages of PDCH, such as low power consumption, would be affected thereby. SUMMARY OF THE INVENTION

Examples of embodiments of the invention provide an apparatus, method and computer program product by means of which a discovery/identification of small cells or secondary cells located in a macro cell or primary cell is improved. In particular, examples of embodiments of the invention provide apparatuses, methods and computer program products providing an improved discovery mechanism for small cells in a macro cell by a user equipment, for example when using a PDCH for signaling a discovery signal for the small cells.

This is achieved by the measures defined in the attached claims.

According to an example of an embodiment of the proposed solution, there is provided, for example, a method comprising signaling to a communication element located in a primary cell area configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell, wherein the configuration data comprises an indication of a unique identification for each of the at least one secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique identification of each of the at least one secondary cell for allocating each unique identification element to a specific communication resource. Furthermore, according to an example of an embodiment of the proposed solution, there is provided, for example, an apparatus comprising at least one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to perform a configuration data signaling function configured to signal, to a communication element located in a primary cell area, configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell, wherein the configuration data comprises an indication of a unique identification for each of the at least one secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique identification of each of the at least one secondary cell for allocating each unique identification element to a specific communication resource.

In addition, according to a further example of an embodiment of the proposed solution, there is provided, for example a method comprising grouping secondary cells located in a primary cell area into at least one secondary cell group, wherein each secondary cell group comprises one or more secondary cells, allocating to each of the secondary cells a unique identification, and assigning to each secondary cell grouped in the same secondary cell group a dedicated communication resource for transmitting the unique identification in a physical discovery channel signaling. Furthermore, according to the further example of an embodiment of the proposed solution, there is provided, for example an apparatus comprising at least one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at feast to perform a grouping function configured to group secondary cells located in a primary ce!! area into at least one secondary cell group, wherein each secondary cell group comprises one or more secondary cells, an identification allocating function configured to allocate to each of the secondary cells a unique identification, and a communication resources assigning function configured to assign to each secondary cell grouped in the same secondary cell group a dedicated communication resource for transmitting the unique identification in a physical discovery channel signaling.

In addition, according to a further example of an embodiment of the proposed solution, there is provided, for example a method comprising receiving, from a communication network control element of a primary cell area, and processing configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell, wherein the configuration data comprises an indication of a unique identification for each of the at least one secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique identification of each of the at least one secondary cell for allocating each unique identification element to a specific communication resource, and detecting for discovery signals of secondary cells on the communication resources indicated in the configuration data.

Furthermore, according to the further example of an embodiment of the proposed solution, there is provided, for example an apparatus comprising at least one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to perform a configuration data receiving and processing function configured to receive, from a communication network control element of a primary cell area, configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell and to process the configuration data, wherein the configuration data comprises an indication of a unique identification for each of the at least one secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique identification of each of the at least one secondary cell for allocating each unique identification element to a specific communication resource, and a discovery signal detection function configured to detect for discovery signals of secondary cells on the communication resources indicated in the configuration data.

In addition, according to a further example of an embodiment of the proposed solution, there is provided, for example a method comprising preparing a discovery signal transmission by applying a unique identification allocated to one secondary cell, and transmitting the discovery signal by using a dedicated communication resource for sending the unique identification on a physical discovery channel with a preset periodicity.

Furthermore, according to the further example of an embodiment of the proposed solution, there is provided, for example an apparatus comprising at least one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to perform a discovery signal preparation function configured to prepare a discovery signal transmission by applying a unique identification allocated to one secondary cell, and a discovery signal transmission function configured to cause transmission of the discovery signal by using a dedicated communication resource for sending the unique identification on a physical discovery channel with a preset periodicity.

In addition, according to examples of the proposed solution, there is provided, for example, a computer program product for a computer, comprising software code portions for performing the steps of the above defined methods, when said product is run on the computer. The computer program product may comprise a computer-readable medium on which said software code portions are stored. Furthermore, the computer program product may be directly loadable into the internal memory of the computer and/or transmittable via a network by means of at least one of upload, download and push procedures.

By virtue of the proposed solutions, it is possible to provide a mechanism for controlling the discovery/identification of small cells or secondary cells located in a macro cell or primary cell by a UE wherein the complexity of the cell detection on the terminal or UE side is low. For example, by using a preselection of possible small cells to be detected the workload on the terminal side can be reduced. Furthermore, the interference level can be kept low, for example by a suitable assignment of communication resources.

The above and still further objects, features and advantages of the invention will become more apparent upon referring to the description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a diagram illustrating a communication network structure in which examples of embodiments of the invention are applicable.

Fig. 2 shows a diagram illustrating a radio frame structure for a transmission of a PDCH according to examples of embodiments of the invention.

Fig. 3 shows a flowchart illustrating an example of a configuration procedure for arranging a communication network as shown in Fig. 1 according to examples of embodiment of the invention.

Fig. 4 shows a flowchart illustrating a procedure conducted by a communication network control element according to an example of an embodiment of the invention.

Fig. 5 shows a flowchart illustrating a procedure conducted by a communication element according to an example of an embodiment of the invention. Fig. 6 shows a flowchart illustrating a procedure conducted by a transceiver network element such as an RH according to an example of an embodiment of the invention.

Fig. 7 shows a block circuit diagram of a communication network control element including processing portions conducting functions according to examples of embodiments of the invention.

Fig. 8 shows a block circuit diagram of a communication element including processing portions conducting functions according to examples of embodiments of the invention.

Fig. 9 shows a block circuit diagram of a transceiver network element such as an RRH including processing portions conducting functions according to examples of embodiments of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, examples and embodiments of the present invention are described with reference to the drawings. For illustrating the present invention, the examples and embodiments will be described in connection with a cellular communication network based on a 3GPP LTE-A system wherein a heterogeneous network configuration comprising a macro cell controlled by a communication network control element, such as a eNB, and plural small cells located in the macro cell and constituted by a subcell transceiver element such as an RRH is employed (the macro cell is referred to also as primary cell or PCell while the small cells are referred to as secondary cells or SCells). However, it is to be noted that the present invention is not limited to an application using such types of communication systems, but is also applicable in other types of communication systems and the like as long as a heterogeneous network configuration with a PCell and one or more SCells is present. A basic system architecture of a communication network where examples of embodiments of the invention are applicable may comprise a commonly known architecture of one or more communication systems comprising a wired or wireless access network subsystem and a core network. Such an architecture may comprise one or more access network control elements, radio access network elements, access service network gateways or base transceiver stations, such as a base station (BS) or eNB, which control a coverage area also referred to as a macro cell and with which a communication element or terminal device such as a UE or another device having a simitar function, such as a modem chipset, a chip, a module etc., which can also be part of a UE or attached as a separate element to a UE, or the like, is capable to communicate via one or more channels for transmitting several types of data. Furthermore, core network elements such as gateway network elements, policy and charging control network elements, mobility management entities and the like may be comprised. In addition to the macro cell access network element, plural small cells forming a secondary coverage area (e.g. in addition to the macro cell coverage or in sites where the macro cell coverage is weak or non-existent) are present, which are constituted by using R H, relay nodes or the like.

The general functions and interconnections of the described elements, which also depend on the actual network type, are known to those skilled in the art and described in corresponding specifications, so that a detailed description thereof is omitted herein. However, it is to be noted that several additional network elements and signaling links may be employed for a communication to or from a communication element like a UE or a communication network control element like an eNB etc., besides those described in detail herein below. Furthermore, the described network elements, such as communication elements like UEs, communication network control elements like BSs, elMBs, RRHs and the like, as well as corresponding functions as described herein may be implemented by software, e.g. by a computer program product for a computer, and/or by hardware. In any case, for executing their respective functions and/or algorithms, correspondingly used devices, nodes or network elements may comprise several means and components (not shown) which are required for control, processing and communication/signaling functionality. Such means may comprise, for example, one or more processor units including one or more processing portions for executing instructions, programs and for processing data, memory means for storing instructions, programs and data, for serving as a work area of the processor or processing portion and the like (e.g. ROM, RAM, EEPROM, and the like), input means for inputting data and instructions by software (e.g. floppy disc, CD-ROM, EEPROM, and the like), user interface means for providing monitor and manipulation possibilities to a user (e.g. a screen, a keyboard and the like), interface means for establishing links and/or connections under the control of the processor unit or portion (e.g. wired and wireless interface means, an antenna, etc.) and the like. It is to be noted that in the present specification processing portions should not be only considered to represent physical portions of one or more processors, but may also be considered as a logical division of the referred processing tasks performed by one or more processors.

As described above, in new communication networks, such as those being based on the release 11 of 3GPP LTE-A, the Physical Discovery Channel (PDCH) is employed.

For detecting cells and for conducting synchronization with the cell thus detected by using PDCH signaling, several approaches are conceivable.

For example, according to a comparative example, PSS/SSS channels which are used for initial synchronization and new cell identification in current networks according to LTE standards could be employed.

PSS/SSS are generated in the frequency domain by using so-called ZC sequences (for PSS) and M sequences (for SSS) respectively which span e.g. one OFDM symbol. ZC sequences are codes which have a property of having zero cyclic autocorrelation at all non-zero lags. When used as a synchronization code, the correlation between the ideal sequence and a received sequence is greatest when the lag is zero. When there is any lag between the two sequences the correlation is nil. On the other hand, M sequences are pseudo-random binary sequences which can be created for example by cycling through every possible state of a shift register of a length n resulting in a sequence of length 2" - 1 The periodicity of PSS/SSS is 5ms and it is possible to provide up to 504 cell

IDs. However, when considering the aforementioned requirement for PDCH, a usage of PSS/SSS design according to this comparative example is not optimal. For example, as the PDCH has a significantly longer periodicity, the detection is desired to be succeed within "one-shot". However, as one shot of PSS/SSS is usually not reliable and since is to necessary to provide a frequent PSS/SSS transmission so as to achieve a sufficient robustness, the detection performance of PDCH will be unsatisfactory if PSS/SSS is directly reused . Furthermore, in case of a scenario of a Pcell/Scell arrangement, the Sceli (provided e.g . by an RH) is usually associated to the Pcell . Therefore, the required amount of Scell IDs is smaller than the 504 cell Ids which can be provided by PSS/SSS. Moreover, after synchronization and cell identification, PDCH has to provide fast measurement results for the UE so as to be able to report to the eN B, so that a decision can be made which of the detected Scells is to be used . However, such a fast measurement is not optimally supported by PSS/SSS and CRS, for example.

According to another comparative example, the PSS/SSS approach could be modified by reusing a positioning reference signal (PRS) for the PDCH . Furthermore, in order to overcome drawbacks caused by a fixed mapping pattern with six sub-carrier separations, a modified PRS with a more randomized mapping pattern or an application of a CDM-based sequence such as a PRACH may be considered. According to examples of embodiments of the invention, in order to improve the usage of PDCH in identification/discovery processing of e.g. small cells in a macro cell, it is considered to utilize the fact that the Pcell (i.e. the communication network control element controlling the Pcell, such as the eN B) is available. That is, the Pcell is used to deliver relevant configuration information usable for the Scell discovery/identification. Furthermore, according to examples of embodiments of the invention, since the Scell (or the RRH constituting the Scell) are usually geographically separated, additional advantages can be achieved. In addition, for example, some (even rather coarse) location/sector information concerning the position of the UE or neighbor information presented by the UE (if available) can be used to improve the PDCH design .

Hence, according to examples of embodiments of the present invention, a new PDCH design is proposed having a physical layer design optimized for e.g . a detection of small cells in particular in a CA scenario. For this purpose, according to examples of embodiments of the invention, a flexible deployment of IDs (based e.g. on a ZC sequence) for cell detection is provided. Furthermore, according to examples of embodiments of the invention, the small cells (e.g . the R Hs constituting the same) are suitably grouped wherein dedicated communication resources for transmitting the respective cell ID are allocated and mapped to the respective ID. Furthermore, according to examples of embodiments of the invention, the detection of the Scells by the UE is assisted by the macro cell communication network control element (the eNB) .

With regard to Fig. 1, a diagram illustrating a general configuration of a communication network is shown where examples of embodiments of the invention are applicable. It is to be noted that the structure indicated in Fig. 1 shows only those devices, network elements and parts which are useful for understanding principles underlying the examples of embodiments of the invention. As also known by those skilled in the art there may be several other network elements or devices involved in a connection between the communication element (UE) and the network which are omitted here for the sake of simplicity.

In Fig. 1, reference sign 10 denotes a communication element or terminal device such as a UE or the like which is capable of communicating with the communication network. Γη Fig. 1, two UEs 10, i.e. UE1 and UE2 are shown, which shall represent different positions of a UE in communication network.

Reference sign 20 denotes a communication network control element such as a BS or eNB controlling a communication area or macro cell 200 (indicated by a dashed line). It is to be noted that there may be several cells or sectors in the communication network which are controlled, for example, by the communication network control element 20. The UE 10 may communicate with the eNB 20 via one or more communication paths.

In addition, due to the heterogeneous network configuration, there are provided several small cells 300 in the macro cell 200. These small cells 300 are constituted, for example, by a respective transceiver network element 30 like an RRH. In the example shown in Fig. 1, six RRHs (RRH1 to RRH6) are provided forming correspondingly six small cells. The RRHs are connected to the macro cell communication network control element by means of corresponding links (backhaul links) as shown in Fig. 1.

According to examples of embodiments of the invention, in order to support synchronization and cell identification, the small cells 300 located in the macro cell 200 are suitably grouped. For example, in the deployment scenario shown in Fig. 1, the cells constituted by the RRHs 30 (RRH1 to RRH6) and thus the small cells (or Scells) are divided into several RRH groups, e.g. in RRH group 1 comprising RRHs RRH1 to RRH3, and RRH group 2 comprising RRHs RRH4 to RRH6.

The division of the RRHs in a respective group is based, for example, on the position/location of the RRH/Scell or on coverage properties like overlapping coverage areas etc.. That is, according to examples of the invention, the grouping of the RRHs is based on their geographical location which is assumed to be known by the network. By means of this, RRHs being close to each other are assigned to the same group.

It is to be noted that according to examples of embodiments of the invention, the geographical location of the RRHs in the network can be determined by GPS signals when the RRHs are equipped with a GPS modem technology, by Precision Time Protocol (PTP) signaling (as specified in IEEE 1588, for example) wherein it is assumed that the RRHs have a fixed backhaul connection to the eNB 20, for example, or in another manner.

Furthermore, according to examples of embodiments of the invention, the grouping of the RRHs in the respective groups can be executed e.g. in a network setup phase on basis of a network management procedure or by operator specification, or by the communication network control element of the macro cell. In the latter case, the configuration (i.e. allocation of cell IDs and resources) can be done statically, semi-statically or dynamically, wherein for example in case of an introduction of a new small cell or RRH or in case of an break down of a RRH or the like in particular the resources are newly assigned. According to examples of embodiments of the invention, the assignment of cell IDs and resources to the respective RRHs (mapping) is stored in the eNB 20, for example, or a database connected thereto for a further processing described below.

In addition, according to examples of embodiments of the invention, each small cell or each RRH is provided with a unique ID, which is In accordance with embodiments of the invention a dedicated and configurable ZC sequence. The ZC sequence can be unique for each RRH within one group (i.e. the same ZC sequence can be reused in another group) or for each

RRH within the network (i.e. each RRH has its own ZC sequence). Moreover, according to examples of embodiments of the invention, communication resources (such as time and frequency for corresponding resource blocks or the like) for transmitting the unique ID on the PDCH are assigned to each small cell or RRH. Again, according to examples of embodiments of the invention, the assigned communication resource can be unique for each RRH within one group (i.e. the same resource can be allocated to another RRH in another group) or for each RRH within the network (i.e. each RRH has assigned its own communication resource). Thus, it is possible to map a cell ID to a dedicated communication resource.

In the example shown in Fig. 1, the following mapping is assumed. Each RRH has allocated its own unique ZC sequence, while the communication resources are assigned group specific, i.e. the resources assigned to the RRHs in one group are different, but the resources assigned to the groups are the same. The resulting mapping between cell IDs and resources is indicated in the following table 1.

Table 1 : Cell ID and resource mapping in network according to Fig. 1

That is, each RRH takes a unique ZC sequence (ZC#1 to ZC#6) and a dedicated communication resource, wherein the RRHs in the same resource are placed apart geographically (i.e. located in different groups). For example, resource #2 (time/frequency) is assigned to RRHs having IDs of ZC#2 and ZC#5. Within one group, however, different resources are assigned to different RRHs, for example resources #1 and #2 to RRHs having IDs of ZC#1 and ZC#2, respectively. By means of this grouping, for example, it is possible to create a low interference condition in one RRH group which supports a fast and reliable Scell detection.

As described above, according to examples of embodiments of the invention, as a cell ID for the small cells, unique ZC sequences can be used. In case the PDCH contains ZC sequences, proper correlation properties are achieved. Furthermore, according to examples of embodiments of the invention, the respective ZC sequence is mapped to configurable (under eNB control) time and frequency resources. Moreover, according to examples of embodiments of the invention, since the length of a ZC sequence is sufficiently long, a subset of the ZC sequence, which is for example differentiated by at least one of a different root index and a cyclic shift, is selected and used to accommodate information indicating a number for indicating a cell IDs. Thus, it is possible, for example, to support 64 different IDs. According to examples of embodiments of the invention, the ZC sequence length is configurable. A corresponding indication of the length can be also stored in the eNB or the database so as to enable it to update configuration data to include the configured length or a link relation to a

RRH ID.

Fig. 2 shows an example according to embodiments of the invention of a radio frame structure of the PDCH transmitted by Scells according to a configuration as described above.

Two resources are indicated by a (horizontal) time axis and a (vertical) frequency axis. In the upper half, radio frames transmitted in the Pcell are shown each comprising PSS and SSS. In the lower half, radio frames (PDCH) transmitted in the Scell are shown. For example, three PDCH resources #1 to #3 are configured by the eNB 20 for each PDCH burst (PDCH#1, PDCH#2). The PDCH bursts are transmitted with a preset (configured) periodicity in a configured bandwidth BW. It is to be noted that there may be a certain delay between the radio frames of the Scell and that of the Pcell; as described below, this delay may be used as a basis for a (coarse) synchronization to the Scell signaling by a UE when communicating with the Pcell .

When assuming an allocation as indicated in above table 1, then RRHs RRH1 to RRH3 send in resource #1 to #3 a corresponding ZC sequence. According to examples of embodiments of the invention, as indicated in connection with resource #3 (i.e. RRH3), each resource consists of a predetermined number IM (N equal to or greater 1) of repetitions of the same ZC sequence. In Fig. 2, three repetitions of ZC#3 are shown . By repeating the ZC sequence in the time domain reliability can be increased, for example.

According to examples of embodiments of the invention, a UE (such as UE 10) learns the configuration of the Scel!s before detecting a discovery signal from the Scells. This is achieved by transmitting configuration data related to the Scells in the Pcell (or a subset of the Scells) and indicating the cell

IDs, the allocated resources for the PDCH bursts and the mapping between cell IDs and resources. According to examples of embodiments of the invention, the configuration data comprises also indications related to the configured PDCH periodicity, resource (time and frequency) allocation of each group as well as the mapping of e.g. the ZC sequence to the RRHs.

The signaling of the configuration data is shown in Fig . 1 by means of an arrow.

For signaling the configuration data from the eNB 20 to the UE 10, different mechanisms are possible. For example, according to examples of embodiments of the invention, the eNB 20 broadcasts the PDCH configuration data in the macro cell so as to assist UEs located therein to perform a Scell detection. According to further examples of embodiments of the invention, the configuration data are sent in a dedicated manner to a UE having an established connection to the eN B.

By means of transmitting the mapping of the ZC sequences to the communication resources, the number of blind detection performed by a UE can be reduced . According to a further example of embodiments of the invention, in addition to the link of the ZC sequence to a cell ID, the eNB may signal or broadcast geographical location information of each RRH, if available. By means of this, in case the UE is able to determine own geographical location information and match this with the location information of the RRHs, the selection of proper candidates of Scells (i.e. for a detection of known resources for known (mapped) ID information or ZC sequence) can be executed or at least assisted by the UE. Hence, the UE can increase the detection reliability.

As means for signaling the configuration data to the UE, the eNB 20 can use, according to examples of embodiments of the invention, signaling paths in the PCell which comprise, for example, at least one of RRC/ AC/L1 signaling paths. Via the selected path, configuration data comprising e.g. time and frequency resource allocation information, PDCH periodicity information, information about Scell bandwidth for PDCH, and a configured RS channel for RRM measurement can be signaled. Also geographic location information of the RRHs can be included. According to examples of embodiments of the invention, for detecting Scells by a UE, the UE 10 (e.g. UE1) accesses first to the Pcell (i.e. eNB 20) and receives the configuration data being required for the Scell detection from the eNB 20 (resource allocation and RRH ID mapping, etc.). The synchronization to the Pcell is used as coarse synchronization reference for Scell detection. With the transmission of the configuration data, according to examples of embodiments of the invention, the eNB 20 controls the UE 10 to detect a set of ZC sequences in corresponding resources, which are linked to the corresponding RRHs. According to examples of embodiments of the invention, in order to facilitate the PDCH detection, the eNB 20 indicate in the configuration data only information related to specific RRHs or groups of RRHs. The determination which of the Scells (or RRHs) belong to these RRHs being of interest for the UE is based, according to examples of embodiments of the invention, on a determination of the position of the UE in the macro cell

(and thus in relation to the known locations of Scells), e.g. on an approximate determination of the UE geographical location within the Pceil. For example, according to examples of embodiments of the invention, the position determination of the UE is based on at least one of a determination of the Pcell or the sector in the macro cell, on a determination of a timing advance (TA) as obtained by the UL timing alignment procedure on the Pcell

(which provides an indication on how far the UE is to eNB in a Line Of Sight), and on RRM measurements including a neighbor list for a handover (HO) of the Pcell (this provides an indication in which part of the Pcell the UE could be located, in relation to known positions of neighboring cells or the like).

For example, when referring to Fig. 1, RRH group #1 is indicated for UE1 being located in the upper part of the PCell 200 (for example based on a neighbor list used for HO of the PCell) towards the cell edge (for example based on TA information) of the macro cell. On the other hand, RRH group#2 is indicated for UE2 being positioned in the center of the PCell 200 (e.g. based on neighbor list used for HO of PCell) towards the mid-point of the cell (e.g. based on TA information) of the macro cell. That is, according to examples of embodiments of the invention, the e B 20 provides, by preparing the configuration data sent to the UE 10 in a suitable manner, specific information so as to avoid that the UE tries all the RRH groups within a PCell (which could be many in case PCell is implemented by a large macro cell containing many RRHs), but rather a subset of RRH groups which are determined (e.g. on basis of a location comparison) to be the most likely ones to include the UE within their coverage areas. It is to be noted that since the coverage area of a RRH group or a subset of RRH groups can be rather large in practice, it is sufficient that only an approximation of the UE location is determined (i.e. within a few hundred meter squares or even kilometer squares).

After successfully detecting an Scell on the basis of the information provided in the configuration data, measurements can be executed based e.g. on reference signal, such as CRS, or another RS signal so as to activate a connection of the UE to a suitable RRH . Furthermore, according to examples of embodiments of the invention, a discovery signal detection report is sent from the UE to the communication network control element (such as the eNB) informing about the results of the detection for discovery signals. This report is sent, for example, in predetermined intervals or event-specific, i.e. when one or more of the Scells indicated in the configuration data (i.e. the respective unique Seed ID) is received. In other words, when the UE detects a discovery signal coming from one of the Scells on the corresponding communication resource as indicated in the configuration data, this is reported to the elMB. According to examples of embodiments of the invention, the report is related only to those Scells which are indicated in the configuration data, i.e. other Scells are ignored or at least indicated to be not part of the configuration data. Furthermore, according to examples of embodiments of the invention, measurement results regarding a receiving quality of the discovery signals of the respective Scells being detected by the UE on the basis of the information in the configuration data are determined and indicated in the detection report, wherein according to further examples of embodiments of the invention only the measurement results regarding the best Scell (i.e. having the best receiving quality) are included so as to decrease overhead.

Fig. 3 shows a flowchart illustrating a processing for configuring a communication network as shown in Fig. 1 according to examples of embodiments of the invention. Specifically, Fig. 3 shows a processing used for grouping the RHs and for allocating the IDs and resources. The method in Fig. 3 is executed, according to examples of embodiments of the invention, in a communication network control element like the eNB 20.

In step S100, small cells (SCells) located in a macro cell (PCell) area are grouped into Scell group (RRH groups 1 and 2), wherein each group comprises at least one Scell. For the grouping, corresponding criteria are applied which comprises, for example, geographical location and/or coverage of the respective Scell (RRH). In step SI 10, each Scell of a group (or each Scell in the macro cell) is allocated to a unique ID. The unique ID allocated to each of the Scells (or RRHs) is formed by a configurable ZC sequence, for example. In step S120, a dedicated communication resource (time/frequency) is allocated to each SCell (RRH) of a same group for transmitting on PDCH. The resources can be reused in another group, but in one group each SCell or RRH is assigned to an own resource. Fig. 4 shows a flowchart illustrating a procedure conducted by a communication network control element such as eNB 20 according to an example of an embodiment of the invention. Specifically, Fig. 4 shows a processing used for providing the configuration data to a UE 10 in a macro cell.

In step S200, configuration data related to Scells in the macro cell are prepared. The configuration data comprises an indication of a unique ID (ZC sequence) for each of Scell (or subgroup of Scells), an indication of communication resources (time/frequency) used for the PDCH transmission in the Scells, and information indicating a mapping between the indicated communication resources and the unique ID of each Scell for allocating each unique identification element to a specific communication resource. The configuration data may further comprises at least one of an indication of a periodicity of a transmission of the PDCH, an indication of time and frequency resources as the communication resources, an indication of a bandwidth used in the SCells for the transmission of the PDCH, an indication of a configured RS channel to be used for a RRM measurement, and an indication of a geographical location of SCell. In step S210 (which is optional as described above), a position of the UE in the macro cell is determined, for example based on a determination of a sector in the Pcell area, a processing of TA information being based on signals received from the UE, and information related to RRM measurements including neighbor lists. Based on the determined location, suitable Scells or groups of Scells are selected which is/are suitably located to the determined position of the UE, wherein the configuration data signaled to the UE are related to the selected SCells (i.e. only to a subset of all Seeds in the Pcell).

In step S220, the configuration data (of step S200 or S210) are signaled to the UE 10. The signaling of the configuration data can be conducted, for example, via an RRC signaling path, a MAC signaling path, a LI (physical layer) signaling path, or by broadcasting.

Fig. 5 shows a flowchart illustrating a procedure conducted by a communication element such as UE 10 according to an example of an embodiment of the invention. Specifically, Fig. 5 shows a processing used for receiving and processing the configuration data sent from the eIMB 20.

In step S300, from a communication network control element of a macro cell (e.g. eIMB 20), the UE receives, e.g. via an RRC signaling path, a MAC signaling path, a LI (physical layer) signaling path, or by broadcasting, the configuration data (as described in connection with steps S200 and S210) related to the PDCH in SCells (being located in the vicinity of a position of the UE 10).

In step S310, the UE 10 starts a detection for discovery signals of the SCells by using the information in the configuration data (resource allocation information, Scell IDs, mapping therebetween, etc.).

In step S320, based on the results of step S310, it is determined from which of the Scells indicated in the configuration data a discovery signal is detected, wherein on the basis thereof a discovery signal detection report is prepared and sent to the eNB, wherein the report comprises information indicating those Scells which match to a unique ID (ZC sequence) indicated in the configuration data and of which a discovery signal is received on the respective communication resources. Furthermore, information indicating a reception quality of the detected discovery signal of these Scells is included in the report. It is to be noted that the method of Fig. 5 may comprise, according to further examples of embodiments of the invention, also steps (not shown) related to a determination of a position of the UE and a comparison of this position with geographical location information of RRHs received in the configuration data, and steps for selecting, on the basis of a comparison between the geographical location of the UE and the received indication of the geographical location of Scells, candidates of Scells for a discovery signal detection.

Fig. 6 shows a flowchart illustrating a procedure conducted by a transceiver network element such as an RRH according to an example of an embodiment of the invention. Specifically, Fig. 6 shows a processing used for preparing and transmitting a discovery signal via the PDCH from the RRH 30.

In step 400, a discovery signal transmission on PDCH resources is prepared.

For this purpose, a unique ID (ZC sequence) allocated to the Scell preparing the discovery signal transmission is applied in step S410 (as indicated in Fig. 2).

Then, in step S420, the discovery signal is transmitting on the dedicated communication resources assigned to the Scell for sending on the PDCH with a preset periodicity.

In Fig. 7, a block circuit diagram illustrating a circuitry indicating a configuration of a communication network control element, such as the eNB 20, is shown which is configured to implement the processing for controlling the discovery procedure of small cells as described in connection with the examples of embodiments of the invention. That is, a circuitry is shown which comprises at least one processor and at least one memory including computer program code the at least one memory and the computer program code being configured to, with the at least one processor, cause the eNB 20 to perform functions described below, for example by executing a corresponding algorithm. It is to be noted that the communication network control element or eNB 20 shown in Fig. 7 may comprise several further elements or functions besides those described herein below, which are omitted for the sake of simplicity as they are not essential for understanding the invention. Furthermore, even though reference is made to an eNB, the communication network control element may be also another device having a similar function, such as a modem chipset, a chip, a module etc., which can also be part of a BS or eNB or attached as a separate element to a BS or eNB, or the like. The communication network control element or eNB 20 may comprise a processing function or processor 21, such as a CPU or the like, which executes instructions given by programs or the like related to the control signal transmission control. The processor 21 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference signs 22 and 23 denote transceiver or input/output (I/O) units connected to the processor 21. The I/O units 22 may be used for communicating with a communication element like UE 10 and the I/O units 23 may be used for communicating with a transceiver network element like one or more of the RHs 30. The I/O units 22 and 23 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. . Reference sign 24 denotes a memory usable, for example, for storing data and programs to be executed by the processor 21 and/or as a working storage of the processor 21. The processor 21 is configured to execute processing related to the above described mechanism for controlling a discovery of small cells. In particular, the processor 21 comprises a sub-portion 211 as a processing portion which is usable for grouping and configuring the small cells (ID allocation and resource assignment). The portion 211 may be configured to perform a processing according to Fig. 3, for example. Furthermore, the processor 21 comprises a sub-portion 212 usable as a portion for determining a position of a UE in the macro cell. The portion 212 may be configured to perform processing according to step S210 according to Fig. 4, for example. In addition, the processor 21 comprises a sub-portion 213 as a processing portion which is usabte for conducting the preparation and transmission of the configuration data to the UE 10. The portion 213 may be configured to perform processing according to steps S200 and S220 according to Fig. 4, for example. In Fig. 8, a block circuit diagram illustrating a circuitry indicating a configuration of a communication element, such as the UE 10, is shown which is configured to implement the processing for controlling the discovery procedure of small cells as described in connection with the examples of embodiments of the invention. That is, a circuitry is shown which comprises at least one processor and at least one memory including computer program code the at least one memory and the computer program code being configured to, with the at least one processor, cause the UE 10 to perform functions described below, for example by executing a corresponding algorithm. It is to be noted that the communication element or UE 10 shown in Fig. 8 may comprise several further elements or functions besides those described herein below, which are omitted for the sake of simplicity as they are not essentia! for understanding the invention. Furthermore, even though reference is made to an UE, the communication element may be also another terminal device having a similar function, such as a modem chipset, a chip, a module etc., which can also be part of an UE or attached as a separate element to a UE, or the like.

The communication element or UE 10 may comprise a processing function or processor 11, such as a CPU or the like, which executes instructions given by programs or the like related to the control signal transmission control. The processor 11 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference sign 12 denotes transceiver or input/output (I/O) units connected to the processor 11. The I/O unit 12 may be used for communicating with a communication network control element like eNB 20 and for communicating with a transceiver network element like one or more of the RRHs 30. The I/O unit 12 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. Reference sign 13 denotes a memory usable, for example, for storing data and programs to be executed by the processor 11 and/or as a working storage of the processor 11.

The processor 11 is configured to execute processing related to the above described mechanism for controlling a discovery of small cells. In particular, the processor 11 comprises a sub-portion 111 as a processing portion which is usable for receiving and processing configuration data related to the SCells. The portion 111 may be configured to perform a processing of step S300 according to Fig. 5, for example. Furthermore, the processor 11 comprises a sub-portion 112 usable as a portion for detecting a position of the UE 10 in the macro cell and for select a suitable SCell by comparing location information. In addition, the processor 11 comprises a sub-portion 113 as a processing portion which is usable for conducting a discovery signal detection on PDCH from RRHs 30. The portion 113 may be configured to perform processing according to step S310 according to Fig. 5_f for example. Moreover, the processor 11 comprises a sub-portion 114 as a processing portion which is usable for conducting a discovery signal detection reporting processing. The portion 114 may be configured to perform processing according to step S320 according to Fig. 5, for example.

In Fig. 9, a block circuit diagram illustrating a circuitry indicating a configuration of a transceiver network element, such as the RRH 30, is shown which is configured to implement the processing for controlling the discovery procedure of small cells as described in connection with the examples of embodiments of the invention. That is, a circuitry is shown which comprises at least one processor and at least one memory including computer program code the at least one memory and the computer program code being configured to, with the at least one processor, cause the RH 30 to perform functions described be!ow, for example by executing a corresponding algorithm. It is to be noted that the transceiver network element or RRH 30 shown in Fig. 9 may comprise several further elements or functions besides those described herein below, which are omitted for the sake of simplicity as they are not essential for understanding the invention. Furthermore, even though reference is made to an RRH, the transceiver network element may be also another device having a similar function, such as a modem chipset, a chip, a module etc., which can also be part of an RRH or attached as a separate element to an RRH, or the like.

The transceiver network element or RRH 30 may comprise a processing function or processor 31, such as a CPU or the like, which executes instructions given by programs or the like related to the control signal transmission control. The processor 31 may comprise one or more processing portions dedicated to specific processing as described below, or the processing may be run in a single processor. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors or processing portions, such as in one physical processor like a CPU or in several physical entities, for example. Reference signs 32 and 33 denote transceiver or input/output (I/O) units connected to the processor 31. The I/O unit 32 may be used for communicating with a communication element like UE 10, and the I/O unit 33 may be used for communicating with a communication network control element like eNB 20. The I/O units 32 and 33 may be a combined unit comprising communication equipment towards several network elements, or may comprise a distributed structure with a plurality of different interfaces for different network elements. Reference sign 34 denotes a memory usable, for example, for storing data and programs to be executed by the processor 31 and/or as a working storage of the processor 31.

The processor 31 is configured to execute processing related to the above described mechanism for controlling a discovery of small cells. In particular, the processor 31 comprises a sub-portion 311 as a processing portion which is usable for preparing a discovery signal based on a configuration of the network (e.g. eNB 20). The portion 311 may be configured to perform a processing of steps S400 and S410 according to Fig. 6, for example. Furthermore, the processor 31 comprises a sub-portion 312 usable as a portion for transmitting the discovery signal by using resources configured by the eNB 20, for example. The portion 312 may be configured to perform processing according to step S420 according to Fig. 6, for example.

According to further examples of embodiments of the invention, there is provided, for example, an apparatus comprising configuration data signaling means for signaling, to a communication element located in a primary cell area, configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell, wherein the configuration data comprises an indication of a unique identification for each of the at least one secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique identification of each of the at least one secondary cell for allocating each unique identification element to a specific communication resource.

Moreover, according to further examples of embodiments of the invention, there is provided, for example, an apparatus comprising grouping means for grouping secondary cells located in a primary cell area into at least one secondary cell group, wherein each secondary cell group comprises one or more secondary cells, identification allocating means for allocating to each of the secondary cells a unique identification, and communication resources assigning means for assigning to each secondary cell grouped in the same secondary cell group a dedicated communication resource for transmitting the unique identification in a physical discovery channel signaling.

In addition, according to further examples of embodiments of the invention, there is provided, for example, an apparatus comprising configuration data receiving and processing means for receiving, from a communication network control element of a primary cell area, configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell and for processing the configuration data, wherein the configuration data comprises an indication of a unique identification for each of the at least one secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique identification of each of the at least one secondary cell for allocating each unique identification element to a specific communication resource, and discovery signal detection means for detecting for discovery signals of secondary cells on the communication resources indicated in the configuration data.

Furthermore, according to further examples of embodiments of the invention, there is provided, for example, an apparatus comprising discovery signal preparation means for preparing a discovery signal transmission by applying a unique identification allocated to one secondary cell, and discovery signal transmission means for causing transmission of the discovery signal by using a dedicated communication resource for sending the unique identification on a physical discovery channel with a preset periodicity.

For the purpose of the present invention as described herein above, it should be noted that

- an access technology via which signaling is transferred to and from a network element may be any technology by means of which a network element or sensor node can access another network element or node (e.g. via a base station or generally an access node). Any present or future technology, such as WLAN (Wireless Local Access Network), WiMAX (Worldwide Interoperability for Microwave Access), LTE, LTE-A, Bluetooth, Infrared, and the like may be used; although the above technologies are mostly wireless access technologies, e.g. in different radio spectra, access technology in the sense of the present invention implies also wired technologies, e.g. IP based access technologies like cable networks or fixed lines but also circuit switched access technologies; access technologies may be distinguishable in at least two categories or access domains such as packet switched and circuit switched, but the existence of more than two access domains does not impede the invention being applied thereto, - usable communication networks and transmission nodes may be or comprise any device, apparatus, unit or means by which a station, entity or other user equipment may connect to and/or utilize services offered by the access network; such services include, among others, data and/or (audio-) visual communication, data download etc.;

- a user equipment or communication network element may be any device, apparatus, unit or means which is usable as a user communication device and by which a system user or subscriber may experience services from an access network, such as a mobile phone, a wireless mobile terminal, a personal digital assistant PDA, a smart phone, a personal computer (PC), a laptop computer, a desktop computer or a device having a corresponding functionality, such as a modem chipset, a chip, a module etc., which can also be part of a UE or attached as a separate element to a UE, or the like, wherein corresponding devices or terminals may be, for example, an LTE, an LTE-A, a TETRA (Terrestrial Trunked Radio), an UMTS, a GSM/EDGE etc. smart mobile terminal or the like;

- method steps likely to be implemented as software code portions and being run using a processor at a network element or terminal (as examples of devices, apparatuses and/or modules thereof, or as examples of entities including apparatuses and/or modules for it), are software code independent and can be specified using any known or future developed programming language as long as the functionality defined by the method steps is preserved;

- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the invention in terms of the functionality implemented;

- method steps and/or devices, apparatuses, units or means likely to be implemented as hardware components at a terminal or network element, or any module(s) thereof, are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as a microprocessor or CPU (Central Processing Unit), MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transistor-Transistor Logic), etc., using for example ASIC (Application Specific IC (Integrated Circuit)) components, FPGA (Field-programmable

Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components; in addition, any method steps and/or devices, units or means likely to be implemented as software components may for example be based on any security architecture capable e.g. of authentication, authorization, keying and/or traffic protection;

- devices, apparatuses, units or means can be implemented as individual devices, apparatuses, units or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device, apparatus, unit or means is preserved; for example, for executing operations and functions according to examples of embodiments of the invention, one or more processors may be used or shared in the processing, or one or more processing sections or processing portions may be used and shared in the processing, wherein one physical processor or more than one physical processor may be used for implementing one or more processing portions dedicated to specific processing as described,

- an apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a

(software) module such as a computer program or a computer program product comprising executable software code portions for execution/being run on a processor;

- a device may be regarded as an apparatus or as an assembly of more than one apparatus, whether functionally in cooperation with each other or functionally independently of each other but in a same device housing, for example.

Furthermore, as used in this application, the terms , device' or ,circuitry' refer to all of the following : (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of circuits and software (and/or firmware), such as (as applicable) : (i) a combination of processor(s) or (ii) portions of processor(s)/software (including digital signal processor(s)), software, and memory(or memories) working together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) circuits, such as a microprocessor (or plural microprocessors) or a portion of a microprocessor (or plural microprocessors), that requires/require software or firmware for operation, even if the software or firmware is not physically present. This definition of 'circuitry' applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device

As described above, there is provided a mechanism for controlling a discovery of sma!! cells or secondary cells located in a macro ceil or primary cell. An eNB signals to a UE located in a primary cell area configuration data related to a physical discovery channel used for transmission of discovery signals in one or more secondary cells. The configuration data comprises a unique Scell ID for each secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique ID of each secondary cell for allocating each unique ID to a specific communication resource. The UE detects for discovery signals on the basis of the information included in the configuration data.

Although the present invention has been described herein before with reference to particular embodiments thereof, the present invention is not limited thereto and various modifications can be made thereto.

Claims

WHAT IS CLAIMED IS:

1. A method comprising

signaling to a communication element located in a primary cell area configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell, wherein the configuration data comprises

an indication of a unique identification for each of the at least one secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique identification of each of the at least one secondary cell for allocating each unique identification element to a specific communication resource.

2. The method according to claim 1, wherein the configuration data further comprises at least one of

an indication of a periodicity of a transmission of the physical discovery channel, an indication of time and frequency resources as the communication resources, an indication of a bandwidth used in the secondary cell for the transmission of the physical discovery channel, an indication of a configured reference signal channel to be used for a radio resource management measurement, and an indication of a geographical location of the secondary cell.

3. The method according to claim 1 or 2, further comprising

determining a position of the communication element in the primary ce!! area, and

selecting a secondary cell or a group of secondary cells being suitably located to the determined position of the communication element, wherein the configuration data signaled to the communication element are related to the selected secondary cell or group of secondary cells.

4. The method according to claim 3, wherein the determining of the position of the communication element is based on at least one of

a determination of a sector in the primary cell area where the communication element is communicating, a processing of timing advance information being based on signals received from the communication element, and information related to radio resource management measurements including neighbor lists for the communication element.

5. The method according to any of claims 1 to 4, wherein the signaling of the configuration data is conducted via at least one of a radio resource control signaling path, a medium access control signaling path, a physical layer signaling path, and a broadcasting signaling path.

6. The method according to any of claims 1 to 5, wherein the unique identification is formed by a Zadoff-Chu sequence.

7. The method according to any of claims 1 to 6, wherein the method is implemented by a communication network control element, such as an evolved node B of a Long Term Evolution or Long Term Evolution Advanced communication network, which controls the primary cell, wherein the communication element is a terminal device or user equipment located and communicating in the primary cell, and the secondary cell is a constituted by a remote radio head connected to the communication network control element.

8. An apparatus comprising

at least one processor; and

at least one memory including computer program code;

wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to perform

a configuration data signaling function configured to signal, to a communication element located in a primary cell area, configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell, wherein the configuration data comprises

9. The apparatus according to claim 8, wherein the configuration data further comprises at least one of

10. The apparatus according to claim 8 or 9, wherein the at least one memory and the computer program code are further configured, with the at least one processor, to cause the apparatus at least to perform

a position determination function configured to determine a position of the communication element in the primary cell area, and

a selection function configured to select a secondary cell or a group of secondary cells being suitably located to the determined position of the communication element, wherein the configuration data signaling function is further configured to signal those configuration data to the communication element which are related to the selected secondary cell or group of secondary cells.

11. The apparatus according to claim 10, wherein the position determination function is configured to determine the position of the communication element on the basis of at least one of

12. The apparatus according to any of claims 8 to 11, wherein the configuration data signaling function is further configured to cause the signaling of the configuration data via at least one of a radio resource control signaling path, a medium access control signaling path, a physical layer signaling path, and a broadcasting signaling path.

13. The apparatus according to any of claims 8 to 12, wherein the unique identification is formed by a Zadoff-Chu sequence.

14. The apparatus according to any of claims 8 to 13, wherein the apparatus is comprised in a communication network control element, such as an evolved node B of a Long Term Evolution or Long Term Evolution Advanced communication network, which controls the primary cell, wherein the communication element is a terminal device or user equipment located and communicating in the primary cell, and the secondary cell is a constituted by a remote radio head connected to the communication network control element.

15. A method comprising

grouping secondary cells located in a primary cell area into at least one secondary cell group, wherein each secondary cell group comprises one or more secondary cells,

allocating to each of the secondary cells a unique identification, and assigning to each secondary cell grouped in the same secondary cell group a dedicated communication resource for transmitting the unique identification in a physical discovery channel signaling.

16. The method according to claim 15, wherein the grouping is based on at least one of geographical location information and coverage information of the secondary cells in the primary cell area.

17. The method according to claim 15 or 16, wherein the unique identification allocated to each of the secondary cells is formed by a configurable Zadoff-Chu sequence.

18. The method according to any of claims 15 to 17, wherein communication resources assigned to the secondary cells of one of the secondary cell groups are also assigned to the secondary cells of another of the secondary cell groups.

19. The method according to any of claims 15 to 18, wherein the secondary cell is constituted by a remote radio head connected to a communication network control element, such as an evolved node B of a Long Term Evolution or Long Term Evolution Advanced communication network, which controls the primary cell.

20, The method according to claim 19, wherein the method is executed by the communication network control element, wherein the communication network control element is further configured to execute the method according to any of claims 1 to 7.

21. An apparatus comprising

at least one processor; and

at least one memory including computer program code;

a grouping function configured to group secondary cells located in a primary cell area into at least one secondary cell group, wherein each secondary cell group comprises one or more secondary cells,

an identification allocating function configured to allocate to each of the secondary cells a unique identification, and

a communication resources assigning function configured to assign to each secondary cell grouped in the same secondary cell group a dedicated communication resource for transmitting the unique identification in a physical discovery channel signaling.

22. The apparatus according to claim 21, wherein the grouping function is further configured to conduct the grouping on the basis of at least one of geographical location information and coverage information of the secondary cells in the primary cell area.

23. The apparatus according to claim 21 or 22, wherein the identification allocating function is further configured to allocate as the unique identification a configurable Zadoff-Chu sequence.

24. The apparatus according to any of claims 21 to 23, wherein the communication resources assigning function is further configured to assign communication resources being assigned to the secondary cells of one of the secondary cell groups also to the secondary cells of another of the secondary cell groups.

25. The apparatus according to any of claims 21 to 24, wherein the secondary cell is constituted by a remote radio head connected to a communication network control element, such as an evolved node B of a Long Term Evolution or Long Term Evolution Advanced communication network, which controls the primary cell.

26. The apparatus according to claim 25, wherein the apparatus is comprised in the communication network control element, wherein the communication network control element further comprises an apparatus according to any of claims 8 to 14.

27. A method comprising

receiving, from a communication network control element of a primary cell area, and processing configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell, wherein the configuration data comprises

an indication of a unique identification for each of the at least one secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique identification of each of the at least one secondary cell for allocating each unique identification element to a specific communication resource, and

detecting for discovery signals of secondary cells on the communication resources indicated in the configuration data.

28. The method according to claim 27, wherein the configuration data further comprises at least one of

29. The method according to claim 28, wherein in case the configuration data comprises an indication of a geographical location of the secondary cell, the method further comprises

determining a geographical location of a communication element conducting the method, and

selecting, on the basis of a comparison between the geographical location of the communication element and the received indication of the geographical location of each secondary cell, candidates of secondary cells for a discovery signal receipt,

wherein the detecting for discovery signals of secondary cells is conducted for the selected candidates of the secondary cells.

30. The method according to any of claims 27 to 29, wherein

the configuration data are related to a specific secondary cell or a specific group of secondary cells being located in the vicinity of a position of a communication element executing the method.

31. The method according to any of claims 27 to 30, wherein the configuration data are received via at least one of a radio resource control signaling path, a medium access control signaling path, a physical layer signaling path, and a broadcasting signaling path.

32. The method according to any of claims 27 to 31, wherein the unique identification is formed by a configurable Zadoff-Chu sequence.

33. The method according to any of claims 27 to 32, further comprising determining, on the basis of a result of detecting for discovery signals of secondary cells on the communication resources indicated in the configuration data, from which of the secondary cells of which a unique identification is indicated in the configuration data a discovery signal is detected, and

sending to the communication network control element a discovery signal detection report comprising information indicating those secondary cells of which a unique identification is indicated in the configuration data and of which a discovery signal is received, and information indicating a reception quality of the respective detected discovery signal being related to those secondary cells of which a unique identification is indicated in the configuration data.

34. The method according to any of claims 27 to 33, wherein the method is implemented by a communication element, such as terminal device or user equipment located and communicating in the primary cell, wherein the communication network control element is an evolved node B of a Long Term Evolution or Long Term Evolution Advanced communication network, which controls the primary cell, and the secondary cell is a constituted by a remote radio head connected to the communication network control element.

35. An apparatus comprising

at least one processor; and

at least one memory including computer program code;

a configuration data receiving and processing function configured to receive, from a communication network control element of a primary cell area, configuration data related to a physical discovery channel used for transmission of discovery signals in at least one secondary cell and to process the configuration data, wherein the configuration data comprises an indication of a unique identification for each of the at least one secondary cell, an indication of communication resources used for the physical discovery channel, and information indicating a mapping between the indicated communication resources and the unique identification of each of the at least one secondary cell for allocating each unique identification element to a specific communication resource, and

a discovery signal detection function configured to detect for discovery signals of secondary cells on the communication resources indicated in the configuration data.

36. The apparatus according to claim 35, wherein the configuration data further comprises at least one of

37. The apparatus according to claim 36, wherein the at least one memory and the computer program code are further configured, with the at least one processor, to cause the apparatus at least to perform

a location determination function configured to determine a geographical location of a communication element comprising the apparatus, and

a candidate selection function configured to select candidates of secondary cells for a discovery signal receipt,

wherein in case the configuration data comprises an indication of a geographical location of the secondary cell, the candidate selection function is further configured to select the candidates of secondary cells on the basis of a comparison between the geographical location of the communication element determined by the location determination function and the received indication of the geographical location of each secondary cell,

wherein the discovery signal detection function is configured to detect for discovery signals of secondary ceils for the selected candidates of the secondary cells.

38. The apparatus according to any of claims 35 to 37, wherein the configuration data are related to a specific secondary cell or a specific group of secondary cells being located in the vicinity of a position of a communication element comprising the apparatus.

39. The apparatus according to any of claims 35 to 38, wherein the configuration data receiving and processing function is configured to receive the configuration data via at least one of a radio resource control signaling path, a medium access control signaling path, a physical layer signaling path, and a broadcasting signaling path.

40. The apparatus according to any of claims 35 to 39, wherein the unique identification is formed by a configurable Zadoff-Chu sequence.

41. The apparatus according to any of claims 35 to 40, wherein the at least one memory and the computer program code are further configured, with the at least one processor, to cause the apparatus at least to perform

a secondary cell determining function configured to determine, on the basis of a detection result of the discovery signal detection function, from which of the secondary cells of which a unique identification is indicated in the configuration data a discovery signal is detected, and

a reporting function configured to cause sending, to the communication network control element, of a discovery signal detection report comprising information indicating those secondary cells of which a unique identification is indicated in the configuration data and of which a discovery signal is received, and information indicating a reception quality of the respective detected discovery signal being related to those secondary ceils of which a unique identification is indicated in the configuration data.

42. The apparatus according to any of claims 35 to 41, wherein the apparatus is comprised in a communication element, such as terminal device or user equipment located and communicating in the primary cell, wherein the communication network control element is an evolved node B of a Long Term Evolution or Long Term Evolution Advanced communication network, which controls the primary cell, and the secondary cell is a constituted by a remote radio head connected to the communication network control element.

43. A method comprising

preparing a discovery signal transmission by applying a unique identification allocated to one secondary cell, and

transmitting the discovery signal by using a dedicated communication resource for sending the unique identification on a physical discovery channel with a preset periodicity.

44. The method according to claim 43, wherein

the unique identification is transmitted repeatedly for a predetermined number of times in one resource cycle of the preset periodicity.

45. The method according to claim 43 or 44, wherein the unique identification is formed by a configurable Zadoff-Chu sequence.

46. The method according to claim 45, wherein a subset of the configurable Zadoff-Chu sequence being differentiated by at least one of a root index and a cyclic shift comprises an information element for indicating the identification of the secondary cell.

47. The method according to claim 45 or 46, wherein a length of the Zadoff- Chu sequence is configurable.

48. The method according to any of claims 43 to 47, wherein the dedicated communication resource is allocated by a communication network control element controlling a primary ceil are in which the secondary cell is located.

49. The method according to any of claims 43 to 48, wherein the method is implemented by a transceiver element of a secondary cell, such as a remote radio head which is controlled by a communication network control element such as an evolved node B of a Long Term Evolution or Long Term Evolution Advanced communication network.

50. An apparatus comprising

at least one processor; and at least one memory including computer program code;

a discovery signal preparation function configured to prepare a discovery signal transmission by applying a unique identification allocated to one secondary cell, and

a discovery signal transmission function configured to cause transmission of the discovery signal by using a dedicated communication resource for sending the unique identification on a physical discovery channel with a preset periodicity.

51. The apparatus according to claim 50, wherein

the discovery signal transmission function is further configured to cause to transmit the unique identification repeatedly for a predetermined number of times in one resource cycle of the preset periodicity.

52. The apparatus according to claim 50 or 51, wherein the unique identification is formed by a configurable Zadoff-Chu sequence.

53. The apparatus according to claim 52, wherein a subset of the configurable Zadoff-Chu sequence being differentiated by at least one of a root index and a cyclic shift comprises an information element for indicating the identification of the secondary cell.

54. The apparatus according to claim 52 or 53, wherein a length of the Zadoff-Chu sequence is configurable.

55. The apparatus according to any of claims 50 to 54, wherein the dedicated communication resource is allocated by a communication network control element controlling a primary cell are in which the secondary cell is located.

56. The apparatus according to any of claims 50 to 55, wherein the apparatus is comprised in a transceiver element of a secondary cell, such as a remote radio head which is controlled by a communication network control element such as an evolved node B of a Long Term Evolution or Long Term Evolution Advanced communication network.

57. A computer program product for a computer, comprising software code portions for performing the steps of any of claims 1 to 7, or of claims 15 to 20, or of claims 27 to 34, or of claims 43 to 49, when said product is run on the computer.

58. The computer program product according to claim 57, further comprising a computer-readable medium on which said software code portions are stored.

59. The computer program product according to claim 57, wherein the computer program product is directly loadable into the internal memory of the computer and/or transmittable via a network by means of at least one of upload, download and push procedures.