WO2011152999A1 - Method and apparatus for implementing assisted cell selection or cooperative information cell selection - Google Patents

Abstract

A method and apparatus are described for selecting a cell to camp on in a cellular network. A search for cell selection information stored in a multi-radio access technology (RAT) wireless transmit/receive unit (WTRU) may be performed using a first RAT. On a condition that the cell selection information is not found, or a cell suitable for the WTRU to camp on was not found by implementing a stored information cell selection procedure using the first RAT, an assisted cell selection procedure or a cooperative information cell selection procedure may be implemented using a second RAT. On a condition that a cell suitable for the WTRU to camp on was not found by implementing the assisted cell selection procedure or the cooperative information cell selection procedure, an initial cell selection procedure may be implemented using the first RAT.

Description

METHOD AND APPARATUS FOR IMPLEMENTING ASSISTED CELL SELECTION OR COOPERATIVE INFORMATION CELL SELECTION

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional application

No. 61/350,240 filed June 1, 2010, the contents of which are hereby incorporated by reference herein.

BACKGROUND

[0002] A cellular radio system may be comprised of a plurality of cells.

Figure 1 is a flow diagram of a conventional cell selection procedure 100 performed when a wireless transmit/receive unit (WTRU), (i.e., a mobile station), is in idle mode. A universal subscriber identity module (USIM) is inserted into the WTRU (105). The power of the WTRU is turned on when the WTRU is within the cellular radio system (110), and the WTRU searches the USIM for suitable cell information (115), which may include cell frequencies and primary scrambling codes. For example, several WTRU users that are within range of a cell near an airport where their plane has just landed may turn on their cellphones after being granted permission by a flight attendant. On a condition that suitable cell information is found in the USIM (120), a stored information cell selection procedure is implemented (125) and a suitable cell is camped on by the WTRU (130). On a condition that suitable cell information is not found in the USIM (135), (e.g., the USIM is empty), an initial cell selection procedure is implemented (140) and a suitable cell is camped on by the WTRU (130).

[0003] When the WTRU searches for a cell, it first measures received energy for a specific frequency of a cell. If the power level is sufficiently high, then the WTRU will attempt to synchronize on that cell by detecting the primary and secondary synchronization channels and decoding the information on these channels to obtain the WTRU with frame, slot, chip and symbol synchronization information, as well as the scrambling code group used by the cell. The mobile station may decode the information on a common pilot channel from which it may ascertain the primary scrambling code of the cell, and detect and decode a broadcast channel (BCH) which carries information contained within system information blocks (SIBs). While all of the previously mentioned channels are required to synchronize with the cell, the BCHs only convey cell information broadcast by each cell.

[0004] As new network topologies and new device functionalities emerge,

WTRUs may need to establish communication with a network at an enhanced speed. However, if initial cell selection is required, meeting such an enhanced speed may not be possible, especially since the WTRU must not only acquire synchronization with the cell, but must also read and decode BCH information. Thus, modifications to the conventional cell selection procedure 100 are needed.

SUMMARY

[0005] A method and apparatus are described for selecting a cell to camp on in a cellular network. A search for cell selection information stored in a multi- radio access technology (RAT) wireless transmit/receive unit (WTRU) may be performed using a first RAT. On a condition that the cell selection information is not found, or a cell suitable for the WTRU was not found by implementing a stored information cell selection procedure using the first RAT, an assisted cell selection procedure or a cooperative information cell selection procedure may be implemented using a second RAT. On a condition that a cell suitable for the WTRU to camp on was not found by implementing the assisted cell selection procedure or the cooperative information cell selection procedure, an initial cell selection procedure may be implemented using the first RAT.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein:

[0007] Figure 1 is a flow diagram of a conventional cell selection procedure performed by a WTRU in idle mode;

[0008] Figure 2A shows an example communications system in which one or more disclosed embodiments may be implemented;

[0009] Figure 2B shows an example wireless transmit/receive unit (WTRU) that may be used within the communications system shown in Figure 2A;

[0010] Figure 2C shows an example radio access network and an example core network that may be used within the communications system shown in Figure 2A;

[0011] Figure 3 is a flow diagram of a cell selection procedure performed by a multi-RAT WTRU in conjunction with a network- deployed communication unit.

[0012] Figures 4A and 4B shows example block diagrams of a wireless communication system including a multi-RAT WTRU and a network-deployed communication unit configured to perform the cell selection procedure of Figure 3;

[0013] Figure 5 is a flow diagram of a cell selection procedure performed by a multi-RAT WTRU in conjunction with at least one camped WTRU; and

[0014] Figure 6 shows an example block diagram of a wireless communication system including a multi-RAT WTRU and at least one camped WTRU configured to implement the cell selection procedure of Figure 5.

DETAILED DESCRIPTION

[0015] Figure 2 A shows an example communications system 200 in which one or more disclosed embodiments may be implemented. The communications system 200 may be a multiple access system that provides content, such as voice, data, video, messaging, broadcast, and the like, to multiple wireless users. The communications system 200 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communications systems 200 may employ one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), and the like.

[0016] As shown in Figure 2A, the communications system 200 may include

WTRUs 202a, 202b, 202c, 202d, a radio access network (RAN) 204, a core network 206, a public switched telephone network (PSTN) 208, the Internet 210, and other networks 212, though it will be appreciated that the disclosed embodiments contemplate any number of WTRUs, base stations, networks, and/or network elements. Each of the WTRUs 202a, 202b, 202c, 202d maybe any type of device configured to operate and/or communicate in a wireless environment. By way of example, the WTRUs 202a, 202b, 202c, 202d may be configured to transmit and/or receive wireless signals and may include user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a smartphone, a laptop, a netbook, a personal computer, a wireless sensor, consumer electronics, and the like.

[0017] The communications systems 200 may also include a base station

214a and a base station 214b. Each of the base stations 214a, 214b may be any type of device configured to wirelessly interface with at least one of the WTRUs 202a, 202b, 202c, 202d to facilitate access to one or more communication networks, such as the core network 206, the Internet 210, and/or the other networks 212. By way of example, the base stations 214a, 214b may be a base transceiver station (BTS), a Node-B, an evolved Node-B (eNB), a Home Node-B (HNB), a Home eNB (HeNB), a site controller, an access point (AP), a wireless router, and the like. While the base stations 214a, 214b are each depicted as a single element, it will be appreciated that the base stations 214a, 214b may include any number of interconnected base stations and/or network elements.

[0018] The base station 214a may be part of the RAN 204, which may also include other base stations and/or network elements (not shown), such as a base station controller (BSC), a radio network controller (RNC), relay nodes, and the like. The base station 214a and/or the base station 214b may be configured to transmit and/or receive wireless signals within a particular geographic region, which may be referred to as a cell (not shown). The cell may further be divided into cell sectors. For example, the cell associated with the base station 214a may be divided into three sectors. Thus, in one embodiment, the base station 214a may include three transceivers, i.e., one for each sector of the cell. In another embodiment, the base station 214a may employ multiple-input multiple -output (MIMO) technology and, therefore, may utilize multiple transceivers for each sector of the cell.

[0019] The base stations 214a, 214b may communicate with one or more of the WTRUs 202a, 202b, 202c, 202d over an air interface 216, which may be any suitable wireless communication link, (e.g., radio frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible light, and the like). The air interface 216 may be established using any suitable radio access technology (RAT).

[0020] More specifically, as noted above, the communications system 200 may be a multiple access system and may employ one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. For example, the base station 214a in the RAN 204 and the WTRUs 202a, 202b, 202c may implement a radio technology such as universal mobile telecommunications system (UMTS) terrestrial radio access (UTRA), which may establish the air interface 216 using wideband CDMA (WCDMA). WCDMA may include communication protocols such as high-speed packet access (HSPA) and/or evolved HSPA (HSPA+). HSPA may include high-speed downlink packet access (HSDPA) and/or high-speed uplink packet access (HSUPA). [0021] In another embodiment, the base station 214a and the WTRUs 202a,

202b, 202c may implement a radio technology such as evolved UTRA (E-UTRA), which may establish the air interface 216 using long term evolution (LTE) and/or LTE- Advanced (LTE- A).

[0022] In other embodiments, the base station 214a and the WTRUs 202a,

202b, 202c may implement radio technologies such as IEEE 802.16 (i.e., worldwide interoperability for microwave access (WiMAX)), CDMA2000, CDMA2000 IX, CDMA2000 evolution- data optimized (EV-DO), Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim Standard 856 (IS-856), global system for mobile communications (GSM), enhanced data rates for GSM evolution (EDGE), GSM/EDGE RAN (GERAN), and the like.

[0023] The base station 214b in Figure 2A may be a wireless router, HNB,

HeNB, or AP, for example, and may utilize any suitable RAT for facilitating wireless connectivity in a localized area, such as a place of business, a home, a vehicle, a campus, and the like. In one embodiment, the base station 214b and the WTRUs 202c, 202d may implement a radio technology such as IEEE 802.11 to establish a wireless local area network (WLAN). In another embodiment, the base station 214b and the WTRUs 202c, 202d may implement a radio technology such as IEEE 802.15 to establish a wireless personal area network (WPAN). In yet another embodiment, the base station 214b and the WTRUs 202c, 202d may utilize a cellular-based RAT, (e.g., WCDMA, CDMA2000, GSM, LTE, LTE- A, and the like), to establish a picocell or femtocell. As shown in Figure 2A, the base station 214b may have a direct connection to the Internet 210. Thus, the base station 214b may not be required to access the Internet 210 via the core network 206.

[0024] The RAN 204 may be in communication with the core network 206, which may be any type of network configured to provide voice, data, applications, and/or voice over Internet protocol (VoIP) services to one or more of the WTRUs 202a, 202b, 202c, 202d. For example, the core network 206 may provide call control, billing services, mobile location-based services, pre-paid calling, Internet connectivity, video distribution, and the like, and/or perform high-level security functions, such as user authentication. Although not shown in Figure 2A, it will be appreciated that the RAN 204 and/or the core network 206 may be in direct or indirect communication with other RANs that employ the same RAT as the RAN 204 or a different RAT. For example, in addition to being connected to the RAN 204, which may be utilizing an E-UTRA radio technology, the core network 206 may also be in communication with another RAN (not shown) employing a GSM radio technology.

[0025] The core network 206 may also serve as a gateway for the WTRUs

202a, 202b, 202c, 202d to access the PSTN 208, the Internet 210, and/or other networks 212. The PSTN 208 may include circuit-switched telephone networks that provide plain old telephone service (POTS). The Internet 210 may include a global system of interconnected computer networks and devices that use common communication protocols, such as the transmission control protocol (TCP), user datagram protocol (UDP) and the Internet protocol (IP) in the TCP/IP suite. The networks 212 may include wired or wireless communications networks owned and/or operated by other service providers. For example, the networks 212 may include another core network connected to one or more RANs, which may employ the same RAT as the RAN 204 or a different RAT.

[0026] Some or all of the WTRUs 202a, 202b, 202c, 202d in the communications system 200 may include multi-mode capabilities, i.e., the WTRUs 202a, 202b, 202c, 202d may include multiple transceivers for communicating with different wireless networks over different wireless links. For example, the WTRU 202c shown in Figure 2A may be configured to communicate with the base station 214a, which may employ a cellular-based radio technology, and with the base station 214b, which may employ an IEEE 802 radio technology.

[0027] Figure 2B shows an example WTRU 202 that may be used within the communications system 200 shown in Figure 2A. As shown in Figure 2B, the WTRU 202 may include a processor 218, a transceiver 220, a transmit/receive element, (e.g., an antenna), 222, a speaker/microphone 224, a keypad 226, a display/touchpad 228, a non-removable memory 230, a removable memory 232, a power source 234, a global positioning system (GPS) chipset 236, and peripherals 238. It will be appreciated that the WTRU 202 may include any sub- combination of the foregoing elements while remaining consistent with an embodiment.

[0028] The processor 218 may be a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a microprocessor, one or more microprocessors in association with a DSP core, a controller, a microcontroller, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) circuit, an integrated circuit (IC), a state machine, and the like. The processor 218 may perform signal coding, data processing, power control, input/output processing, and/or any other functionality that enables the WTRU 202 to operate in a wireless environment. The processor 218 may be coupled to the transceiver 220, which may be coupled to the transmit/receive element 222. While Figure 2B depicts the processor 218 and the transceiver 220 as separate components, the processor 218 and the transceiver 220 may be integrated together in an electronic package or chip.

[0029] The transmit/receive element 222 may be configured to transmit signals to, or receive signals from, a base station (e.g., the base station 214a) over the air interface 216. For example, in one embodiment, the transmit/receive element 222 may be an antenna configured to transmit and/or receive RF signals. In another embodiment, the transmit/receive element 222 may be an emitter/detector configured to transmit and/or receive IR, UV, or visible light signals, for example. In yet another embodiment, the transmit/receive element 222 may be configured to transmit and receive both RF and light signals. The transmit/receive element 222 may be configured to transmit and/or receive any combination of wireless signals.

[0030] In addition, although the transmit/receive element 222 is depicted in

Figure 2B as a single element, the WTRU 202 may include any number of transmit/receive elements 222. More specifically, the WTRU 202 may employ MIMO technology. Thus, in one embodiment, the WTRU 202 may include two or more transmit/receive elements 222, (e.g., multiple antennas), for transmitting and receiving wireless signals over the air interface 216.

[0031] The transceiver 220 may be configured to modulate the signals that are to be transmitted by the transmit/receive element 222 and to demodulate the signals that are received by the transmit/receive element 222. As noted above, the WTRU 202 may have multi-mode capabilities. Thus, the transceiver 220 may include multiple transceivers for enabling the WTRU 202 to communicate via multiple RATs, such as UTRA and IEEE 802.11, for example.

[0032] The processor 218 of the WTRU 202 may be coupled to, and may receive user input data from, the speaker/microphone 224, the keypad 226, and/or the display/touchpad 228 (e.g., a liquid crystal display (LCD) display unit or organic light-emitting diode (OLED) display unit). The processor 218 may also output user data to the speaker/microphone 224, the keypad 226, and/or the display/touchpad 228. In addition, the processor 218 may access information from, and store data in, any type of suitable memory, such as the non-removable memory 230 and/or the removable memory 232. The non-removable memory 230 may include random-access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. The removable memory 232 may include a subscriber identity module (SIM) card, a memory stick, a secure digital (SD) memory card, and the like. In other embodiments, the processor 218 may access information from, and store data in, memory that is not physically located on the WTRU 202, such as on a server or a home computer (not shown).

[0033] The processor 218 may receive power from the power source 234, and may be configured to distribute and/or control the power to the other components in the WTRU 202. The power source 234 may be any suitable device for powering the WTRU 202. For example, the power source 234 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion), and the like), solar cells, fuel cells, and the like. [0034] The processor 218 may also be coupled to the GPS chipset 236, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 202. In addition to, or in lieu of, the information from the GPS chipset 236, the WTRU 202 may receive location information over the air interface 216 from a base station, (e.g., base stations 214a, 214b), and/or determine its location based on the timing of the signals being received from two or more nearby base stations. The WTRU 202 may acquire location information by way of any suitable location- determination method while remaining consistent with an embodiment.

[0035] The processor 218 may further be coupled to other peripherals 238, which may include one or more software and/or hardware modules that provide additional features, functionality and/or wired or wireless connectivity. For example, the peripherals 238 may include an accelerometer, an e-compass, a satellite transceiver, a digital camera (for photographs or video), a universal serial bus (USB) port, a vibration device, a television transceiver, a hands free headset, a Bluetooth® module, a frequency modulated (FM) radio unit, a digital music player, a media player, a video game player module, an Internet browser, and the like.

[0036] Figure 2C shows an example RAN 204 and an example core network

206 that may be used within the communications system 200 shown in Figure 2A. As noted above, the RAN 204 may employ an E-UTRA radio technology to communicate with the WTRUs 202a, 202b, 202c over the air interface 216. The RAN 204 may also be in communication with the core network 206.

[0037] The RAN 204 may include eNBs 240a, 240b, 240c, though it will be appreciated that the RAN 204 may include any number of eNBs while remaining consistent with an embodiment. The eNBs 240a, 240b, 240c may each include one or more transceivers for communicating with the WTRUs 202a, 202b, 202c over the air interface 216. In one embodiment, the eNBs 240a, 240b, 240c may implement MIMO technology. Thus, the eNB 240a, for example, may use multiple antennas to transmit wireless signals to, and receive wireless signals from, the WTRU 202a.

[0038] Each of the eNBs 240a, 240b, 240c may be associated with a particular cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, scheduling of users in the uplink and/or downlink, and the like. As shown in Figure 2C, the eNBs 240a, 240b, 240c may communicate with one another over an X2 interface.

[0039] The core network 206 shown in Figure 2C may include a mobility management entity (MME) 242, a serving gateway 244, and a packet data network (PDN) gateway 246. While each of the foregoing elements are depicted as part of the core network 206, it will be appreciated that any one of these elements may be owned and/or operated by an entity other than the core network operator.

[0040] The MME 242 may be connected to each of the eNBs 240a, 240b,

240c in the RAN 204 via an Si interface and may serve as a control node. For example, the MME 242 may be responsible for authenticating users of the WTRUs 202a, 202b, 202c, bearer activation/deactivation, selecting a particular serving gateway during an initial attach of the WTRUs 202a, 202b, 202c, and the like. The MME 242 may also provide a control plane function for switching between the RAN 204 and other RANs (not shown) that employ other radio technologies, such as GSM or WCDMA.

[0041] The serving gateway 244 may be connected to each of the eNBs

240a, 240b, 240c in the RAN 204 via the Si interface. The serving gateway 244 may generally route and forward user data packets to/from the WTRUs 202a, 202b, 202c. The serving gateway 244 may also perform other functions, such as anchoring user planes during inter-eNB handovers, triggering paging when downlink data is available for the WTRUs 202a, 202b, 202c, managing and storing contexts of the WTRUs 202a, 202b, 202c, and the like.

[0042] The serving gateway 244 may also be connected to the PDN gateway

246, which may provide the WTRUs 202a, 202b, 202c with access to packet- switched networks, such as the Internet 210, to facilitate communications between the WTRUs 202a, 202b, 202c and IP-enabled devices.

[0043] The core network 206 may facilitate communications with other networks. For example, the core network 206 may provide the WTRUs 202a, 202b, 202c with access to circuit-switched networks, such as the PSTN 208, to facilitate communications between the WTRUs 202a, 202b, 202c and traditional land-line communications devices. For example, the core network 206 may include, or may communicate with, an IP gateway, (e.g., an IP multimedia subsystem (IMS) server), that serves as an interface between the core network 206 and the PSTN 208. In addition, the core network 206 may provide the WTRUs 202a, 202b, 202c with access to the networks 212, which may include other wired or wireless networks that are owned and/or operated by other service providers.

[0044] When referred to hereafter, the terminology "wireless transmit/receive unit (WTRU)" includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the terminology "base station" includes but is not limited to a Node-B, a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment.

[0045] A wireless transmit/receive unit (WTRU) discovering the networks and services available in a hybrid network environment, based on assistance provided by external nodes, is described below. A hybrid network is a heterogeneous network of wireless networks, structured in a planned hierarchical architecture, or an unplanned mesh architecture. The discovery may be initial discovery, before the WTRU is camped on any network for the purpose of camping onto some network, or after the WTRU is camped onto a network, for the purpose of finding alternate networks and/or services. The assistance may be provided by either the network on which the WTRU is presently camped on, or by another helper node, such as a relay node or by one or more nearby WTRUs. Furthermore, the assistance data may be sent using cellular or other radio access technologies, such as WiFi, Bluetooth, and the like. For example, the assistance data itself may consist of parameters of the current cells in the vicinity, or the cell broadcast information. By providing such assistance, the traditional concept of cell reselection based on low signal quality is extended to cell and/or network reselection based on general reasons such as quality of service, cost, context, reliability, security, and the like.

[0046] These situations may be referred to as initial cell selection and cell reselection respectively. However, the concepts described below are not restricted to cellular wireless communication systems and may also apply to other wireless communication systems, such as WiFi and Bluetooth networks.

[0047] Many WTRUs are not in the same location when they are powered on as when they were powered off. This will happen more often with the proliferation of femtocells, picocells, converged gateways and home Node-Bs (HNBs). It also happens with travel. For example, when traveling by airplane, WTRUs are powered off or put into airplane mode. In both these cases, once the plane lands and the WTRUs are powered on or brought out of airplane mode, they may have to search for a cell. In all of these C£lSeS_; £L stored information cell selection process will most likely fail, depending on what information may be stored within the WTRU. Once a stored information cell selection has failed, an initial cell selection may be required. Even if a WTRU and network combination stores information on multiple cells that have previously been "camped on," there is no guarantee that the list of cells will contain a cell within close proximity to the current WTRU location. In this case, the stored information cell selection would be unsuccessful, and an initial cell selection may occur.

[0048] Based on previous field test experience with devices from many different manufacturers devices on many different operator networks, a WTRU that must resort to initial cell search may provide an unsatisfactory user experience. This may be because the process of camping on a suitable cell may take significant time, depending on which bands need to be scanned. If the user arrives at a new location and powers on the WTRU, it may take several minutes before an initial cell selection successfully camps on a suitable cell. After finding a cell to synchronize on and which is suitable for use, the broadcast channel must be captured and decoded. As the broadcast channel is being received, the system information may be decoded.

[0049] Additionally, a WTRU may actually register on the network before knowing the services that are available. This registration process may waste both resources and time to gain access to a network that may or may not satisfy the actions that a user wishes to perform. The WTRU may be registering on a network or cell which may be completely incompatible with the goals of the user.

[0050] Currently, network or cell reselection may be based on coverage and billing relationships. Typically, if the radio signal strength falls below certain thresholds, a network or cell reselection may be performed. Similarly, network reselection may be triggered if, for example, the network to which WTRU has a subscription, (i.e., billing relationship), may no longer be available. However, in future networks, there may be several other conditions that trigger a cell or a network reselection by a WTRU. For example, future networks are expected to be heterogeneous networks, made up of cells of varying coverage, (i.e., macro, micro, pico, femto, relay cells), cells of different RATs, (i.e., cellular, WiFi, and the like), as well as cells belonging to different operators. In such a situation, a cell/network reselection may be needed (or triggered by a need) for better service, cheaper service, better content, (e.g., a network that has more of one's friends), and the like. In such cases, solutions are needed for triggering a cell/network reselection, even when the current signal strength may not be poor, or even when the current network may still be available. In one example, a cell reselection to a femtocell is desired, even when the macrocell signal is still strong. The femtocell and the macrocell may be on different frequencies, so that the WTRU may not normally search for other frequencies, if the macrocell signal is sufficiently strong. A general way to achieve such triggering of cell/network reselection procedures is via "assistance."

[0051] Assistance may be provided by the current network, (on which the

WTRU is camped on). It may seem that there would be little incentive for a network to provide assistance to a WTRU, which may result in the WTRU moving away from the current network. While this may be true in certain situations, there are also situations where a network may provide assistance information for a WTRU to move to another cell or network. This may occur, for example, when the current network is heavily loaded. In this case, it may be advantageous for the WTRU to be moved to another network, (perhaps also owned by the current operator), thus off-loading the network to an alternative network. For example, the current network may be a cellular network and the alternate network may be a WiFi network. This situation may also be compared to the current strategy adopted by some airlines, which offers incentives to passengers to take an alternate plane, when the current plane is overbooked. In the case of heterogeneous networks, a WTRU, whether in idle mode or active mode (transferring data), may be offered "reward points" if the WTRU switches to another network, (e.g., switching to a second generation (2G) network from a third generation (3G) network), or suspends the current active transaction to a later time, when the current network may be more lightly loaded. Another example may be for the current cellular network to allow the WTRU to be moved to a WiFi network, where the quality of service is not guaranteed. Conversely, the current network may offer the WTRU access to a superior network with an associated extra cost.

[0052] Assistance may also be provided by helper nodes. For example, when a mobile station is powered on in a new location (e.g., after landing at an airport), it may be in close proximity to a network-provided non-universal mobile telecommunications system (UMTS) RAT (i.e., Bluetooth) device, which is broadcasting cell information. This non-UMTS RAT device may be under the control of the mobile operator, and provide the information needed to obviate the need for initial cell selection.

[0053] The newly powered-up WTRU may communicate with this non-

UMTS RAT device to discover the cell information of at least one local cell. The non-UMTS device may also be another WTRU, which has a multi-RAT capability. This non-UMTS RAT may require a faster time to establish a connection than the traditional cellular connection. Once the WTRU received the cell information, it may perform this "assisted cell selection."

[0054] An example of the processes to be performed include power on the device and acquire the currently used cell parameters from the network operator provided by a non-UMTS device in close proximity via, but not limited to, Bluetooth. A cell search with cell information may be performed to measure received power for an acceptable frequency, detect and synchronize to primary and secondary synchronization channels, and detect and synchronize to a common pilot channel. System information may be acquired from a broadcast channel (BCH), which may be read directly from the cell or from the network operator provided non-UMTS device (i.e., assisted BCH information sharing).

[0055] The example of assisted methods for cell search may also be extended to other network functions typically performed by a WTRU. For example, a WTRU may retrieve from the network a list of services currently available from the network, including a number of attributes about the available services. These services may include "transport" services, such as video streaming service with the list of video codes supported, instant messaging, push- to-talk services, and the like. In addition, a WTRU may also download a list of "content," presently available in the local network cache node. In such cases, a cooperative solution may consist of a new WTRU obtaining this information locally, instead of obtaining the information (all over again) from the network. This reduces the amount of macro-network traffic and improves the overall network performance. [0056] Another assistance approach is via a third party network finder service provider. The WTRU may have a client application, (e.g., a network finder application), which communicates with a network finder server using the existing network. Based on the current location of the WTRU, the network finder server may supply information about available networks, including their security, reliability, and other network performance metrics. Such a server may also contact other servers, (Internet based or otherwise), such as a television white space (TVWS) database or other centralized dynamic spectrum databases.

[0057] Alternatively, assistance may be provided by other users based on trust. Clearly, if network availability information is being provided by other WTRUs, there must be some assurance that the information is reliable. One possible way to solve this problem is to accept and/or use the information only when it comes from friends, who, for example, may be predefined in social networks, such as Facebook, and the like.

[0058] Another example approach is a combination of the above approaches, where "virtual post-it" concepts are used. In this example, a user, who has used a certain network, posts a certain rating or review, which is stored in the network. This rating may be made anonymously, marked public or made with the user's identity known only to that particular user's friends.

[0059] Another combination of the first three approaches of assistance is that network nodes, including WTRUs, may advertise their availability and other metrics, in a manner similar to those used by Internet routers for neighbor discovery, and for maintaining routing tables. In the present case of heterogeneous networks, WTRUs and/or radio access points, (e.g., WiFi APs or cellular base stations), may regularly advertise their status, as well as information about their network nodes. Such information may also be used to alter the behavior of various nodes. For example, a WTRU may transform its role to that of an AP, depending upon the radio communication needs in that physical locality. The WTRUs may also advertise their communication needs in order to solicit connectivity offers from various networks. Thus, the combination of WTRUs advertising their needs, network nodes advertising their own connectivity, and service offerings, may result in the creation of a highly dynamic heterogeneous network environment, in which various network providers, large and small, may coexist and serve the varied communications needs of people and devices in the future.

[0060] Typically, an assisted cell/network reselection procedure may be followed by a handover procedure, such as MobilelP, media independent handover, and the like. In such cases, the assisted cell/network reselection procedure may provide assistance or information to the actual handover procedure.

[0061] The highly popular WiFi networks represent yet another alternative. In one example, a WTRU may be camped on a network and may be using Channel 6 in the 2.4GHz band. Other nodes may provide network discovery services, in which information about other channels in the 2.4GHz band, (as well as the 5 GHz band), is provided by way of assistance. The assistance may be provided as Internet protocol (IP) level messages.

[0062] Figure 3 is a flow diagram of a cell selection procedure 300 performed by a multi-RAT WTRU in conjunction with a network-deployed communication unit. A USIM is inserted into the WTRU (305). The power of the WTRU is turned on when the WTRU is within the cellular radio system (310), and the WTRU searches the USIM for cell information (315), which may include cell frequencies and primary scrambling codes. On a condition that cell information is found in the USIM (320), a stored information cell selection procedure is implemented (325). The stored information cell selection procedure (325) requires stored information of carrier frequencies and, optionally, also information on cell parameters, from previously received measurement control information elements or from previously detected cells. On a condition that a suitable cell is found by implementing the stored information cell selection procedure (330), the suitable cell is camped on by the WTRU (335). [0063] Still referring to Figure 3, on a condition that a suitable cell is not found by implementing the stored information cell selection procedure (340), or cell information is not found in the USIM (345), (e.g., the USIM is empty), an assisted cell selection procedure is implemented (350), during which discovery of a nearby network operator-provided non-UMTS device is performed to obtain local cell information. Once the WTRU explores, discovers and establishes communication with the non-UMTS device, the WTRU may query the non-UMTS device for the carrier frequencies and cell parameters. In response to the query, the non-UMTS device may reply with the local cell information. On a condition that a suitable cell is found by implementing the assisted cell selection procedure (355), the suitable cell is camped on by the WTRU (335). On a condition that a suitable cell is not found by implementing the assisted cell selection procedure (360), an initial cell selection procedure is implemented (365). On a condition that a suitable cell is found by implementing the initial cell selection procedure (370), the suitable cell is camped on by the WTRU (335).

[0064] The initial cell selection procedure (365) requires no prior knowledge of which radio frequency (RF) channels are evolved universal terrestrial radio access (E-UTRA) carriers. The WTRU may scan all RF channels in the E-UTRA bands according to its capabilities, to find a suitable cell. On each carrier frequency, the WTRU may only search for the strongest cell. On a condition that a suitable cell is not found by implementing the initial cell selection procedure and it is concluded that there is no suitable cell available (375), the procedure 300 is terminated.

[0065] Instead of immediately performing the initial cell selection procedure (365), which may take several minutes when no suitable cell is found during a stored information cell search, the process 300 implements an assisted cell selection procedure (350) in order to allow the WTRU to determine the local cell information from a network operator-provided non-UMTS device, (i.e., a device that uses a RAT other than UMTS). Since the network is providing the local cell information, there is a high probability that the cell indicated by the local cell information is suitable for the WTRU, thereby allowing the user to "camp on" a suitable cell much faster by avoiding having to implement an initial cell selection procedure (355). If, for some reason, the indicated cell is not suitable, or there is no network operator-provided non-UMTS device available to broadcast the local cell information, the WTRU may still perform the initial cell selection procedure (365), but this is not expected to occur often during typical operation.

[0066] Figure 4A shows an example block diagram of a wireless communication system 400 including a multi-RAT WTRU 405 and a network- deployed communication unit 410 configured to perform the cell selection procedure 300 of Figure 3. The multi-RAT WTRU 405 includes an antenna 415, a transmitter 420, a receiver 425, a first RAT processor 430 and a second RAT processor 435. The network-deployed communication unit 410 includes an antenna 445, a transmitter 450, a receiver 455, a RAT processor 460 and a database 465. The second RAT processor 435 in the WTRU 405 uses the same RAT as the RAT processor 460 in the network-deployed communication unit 410.

[0067] For example, the first RAT processor 430 in the WTRU 405 may be used for UMTS applications, such as performing the stored information selection procedure, as well as performing a cell search with discovered local cell information provided by the network- deployed communication unit 410. The second RAT processor 435 in the WTRU 405 may be used to perform non-UMTS (i.e., other RAT) procedures, such as the assisted cell selection procedure, in conjunction with the processor 460 of the network -deployed communication unit 410.

[0068] In one scenario, the WTRU 405 may discover the network- deployed communication unit 410 and request current local cell information via at least one signal 470. In response, the network- deployed communication unit 410 may send back at least one signal 475 including the requested current local cell information retrieved from the database 465. [0069] In another scenario, the WTRU 405 may discover the network- deployed communication unit 410 and request current system information (SI) via at least one signal 470. In response, the network-deployed communication unit 410 may send back at least one signal 475 including a plurality of SI blocks (SIBs).

[0070] Although Figure 4A only illustrates the use of two signals 470 and

475, several other signals, (i.e., handshaking signals), maybe exchanged between the multi-RAT WTRU 405 and the network-deployed communication unit 410.

[0071] The signal 475 may include BCH SI that the multi-RAT WTRU 405 may decode in a similar manner as a UMTS WTRU. However, given the proliferation of multi-RAT devices, if the multi-RAT WTRU 405 is located near a network-deployed communication unit 410 that is broadcasting the same BCH SI as a nearby cell, the WTRU may access this data from this network- deployed communication unit 410 instead of the cell. The BCH SI provided by the network- deployed communication unit 410 may be identical to that broadcast by the cell. Typically, after a WTRU 405 has synchronized to a BCH of the cell, the WTRU 405 acquires and decodes the BCH SI, which may be broadcast in an SIB format according to a schedule. It may take several seconds to completely acquire the complete BCH SI. In order to improve the performance of the system 400 by reducing the BCH SI acquisition time, the WTRU 405 may be able to acquire the SIBs from the network-deployed communication unit 410 via signal 470. Subsequently, the WTRU 405 may be configured to read the BCH SI from either the cell or the network- deployed communication unit 410, since the WTRU 405 is required to periodically update the BCH SI by reading the BCH.

[0072] The BCH SI sent via the signal 475 may be divided into a master information block (MIB) and a number of SIBs. The MIB may include a limited number of most essential and most frequently transmitted parameters that may be needed to acquire other information from the cell, and may be transmitted on the BCH. SIBs other than SIB type 1 may be carried in SI messages. Mapping of SIBs to SI messages may be flexibly configurable by a scheduling information list included in the SIB type 1. Each SIB may only be contained in a single SI message. Only SIBs having the same scheduling requirement (periodicity) may be mapped to the same SI message. SIB type 1 may be mapped to the SI message that corresponds to the first entry in the list of SI messages in the scheduling information list. There may be multiple SI messages transmitted with the same periodicity. SIB type 1 and all SI messages may be transmitted on a downlink scheduling channel (DL-SCH).

[0073] The WTRU 405, in idle mode or connected mode, may apply the SI acquisition procedure to acquire access stratum (AS) and non-access stratum (NAS) SI that is broadcasted by an evolved universal terrestrial radio access network (E-UTRAN). The AS and NAS SI may received from the network- deployed communication unit 410 via the signal 475.

[0074] Figure 4B shows an example block diagram of an alternate wireless communication system 400' including a multi-RAT WTRU 405, a base station (BS)/access point (AP) 480, an IP network 485 and a network- deployed communication unit 490 configured to perform the cell selection procedure 300 of Figure 3. The BS/AP 480 may be a WiFi AP. The network-deployed communication unit 490 may be a generic access network controller (GANC), a converged gateway (CGW)/cellular assistance module (CAM), a mobility management entity (MME), a home Node-B (HNB), a wireless local area network (WLAN), an interworking WLAN (IWLAN), a home agent (HA), and the like). The BS/AP 480 serves as a relay node for forwarding the signal 470 to the network-deployed communication unit 490 and forwarding the signal 475 to the multi-RAT WTRU 405.

[0075] Figure 5 is a flow diagram of a cell selection procedure 500 performed by a multi-RAT WTRU in conjunction with at least one camped WTRU. A USIM is inserted into the WTRU (505). The power of the WTRU is turned on when the WTRU is within the cellular radio system (510), and the WTRU searches the USIM for cell information (515), which may include cell frequencies and primary scrambling codes. On a condition that cell information is found in the USIM (520), a stored information cell selection procedure is implemented (525). On a condition that a suitable cell is found by implementing the stored information cell selection procedure (530), the suitable cell is camped on by the WTRU (335).

[0076] Still referring to Figure 5, on a condition that a suitable cell is not found by implementing the stored information cell selection procedure (540), or cell information is not found in the USIM (545), (e.g., the USIM is empty), a cooperative information cell selection procedure is implemented (550), during which the WTRU explores the cells being used by other WTRUs within close proximity, and then performs a cell search with the discovered local cell information. Since other WTRUs close to the WTRU are camped on a suitable cell, the WTRU can "camp on" the suitable cell much faster than by performing an initial cell selection procedure. On a condition that a suitable cell is found by implementing the cooperative information cell selection procedure (555), the suitable cell is camped on by the WTRU (535). On a condition that a suitable cell is not found by implementing the cooperative information cell selection procedure (560), an initial cell selection procedure is implemented (565). On a condition that a suitable cell is found by implementing the initial cell selection procedure (570), the suitable cell is camped on by the WTRU (535). On a condition that a suitable cell is not found by implementing the initial cell selection procedure and it is concluded that there is no suitable cell available (575), the procedure 500 is terminated.

[0077] Figure 6 shows an example block diagram of a wireless communication system 600 including a multi-RAT WTRU 605 and at least one camped WTRU 610 configured to implement the cell selection procedure 500 of Figure 5. The multi-RAT WTRU 605 includes an antenna 615, a transmitter 620, a receiver 625, a first RAT processor 630 and a second RAT processor 635. The camped WTRU 610 includes an antenna 645, a transmitter 650, a receiver 655 and a RAT processor 660. The second RAT processor 635 in the WTRU 605 uses the same RAT as the RAT processor 660 in the camped WTRU 610. For example, the first RAT processor 630 in the multi-RAT WTRU 605 may be used for UMTS applications, such as performing the stored information selection procedure, as well as performing a cell search with discovered local cell information provided by the camped WTRU 610. The second RAT processor 635 in the multi-RAT WTRU 605 may be used to perform non-UMTS (i.e., other RAT) procedures, such as the cooperative information cell selection procedure, in conjunction with the processor 660 of the camped WTRU 610.

[0078] In one scenario, the multi-RAT WTRU 605 may discover at least one camped WTRU 610 and request current local cell information via at least one signal 665. In response, the camped WTRU 610 may send back at least one signal 670 including the requested current local cell information.

[0079] In another scenario, the WTRU 605 may discover at least one camped WTRU 610 and request current SI via at least one signal 665. In response, at least one camped WTRU 610 may send back at least one signal 670 including a plurality of SIBs.

[0080] Although Figure 6 only illustrates the use of two signals 470 and

475, several other signals, (i.e., handshaking signals), maybe exchanged between the multi-RAT WTRU 605 and the camped WTRU 610.

[0081] The cooperative information cell selection procedure requires discovery of other WTRUs that share a common RAT, (e.g., Bluetooth), and are already camped on the cellular network. Once the multi-RAT WTRU 605 explores and establishes communication with the camped WTRU 610, the multi- RAT WTRU 605 may query for local cell information including the carrier frequencies and cell parameters. The camped WTRU may reply with the requested local cell information. Since WTRUs may communicate to share carrier frequencies and cell parameters, if the multi-RAT WTRU 605 is in a camped normally state or camped on any cell state, it will have to reply to requests from other WTRUs.

[0082] While in the camped normally state, the multi-RAT WTRU 605 may select and monitor the indicated paging channels of the cell, monitor relevant SI, perform necessary measurements for performing a cell reselection evaluation procedure, and execute the cell reselection evaluation process on WTRU internal triggers. The cell reselection evaluation process may be performed when information on a broadcast control channel (BCCH) used for the cell reselection evaluation procedure has been modified. Furthermore, while the multi-RAT WTRU 605 is in a camped normally state, the multi-RAT WTRU 605 may respond to requests for current carrier frequency and cell parameters from other WTRUs via a non-UMTS RAT, (e.g., Bluetooth).

[0083] While camped on any cell state, the multi-RAT WTRU 605 may select and monitor the indicated paging channels of the cell, monitor relevant SI, perform necessary measurements for performing a cell reselection evaluation procedure, and execute the cell reselection evaluation process on WTRU internal triggers. The cell reselection evaluation process may be performed when information on a BCCH used for the cell reselection evaluation procedure has been modified. Furthermore, while the multi-RAT WTRU 605 is in a camped on any cell state, the multi-RAT WTRU 605 may regularly attempt to find a suitable cell by trying all frequencies of all RATs that are supported by the multi-RAT WTRU 605. If a suitable cell is found, the multi-RAT WTRU 605 may move to a camped normally state.

[0084] If the multi-RAT WTRU 605 supports circuit switched (CS) voice services, the multi-RAT WTRU 605 may perform cell selection/reselection to an acceptable cell of any supported RAT, (e.g., UTRAN, GERAN, CDMA2000), regardless of any predetermined priorities provided in SI from the current cell, if no suitable cell is found.

[0085] While camped on any cell state, the multi-RAT WTRU 605 may respond to requests for current carrier frequency and cell parameters from other WTRUs via a non-UMTS RAT, (e.g., Bluetooth).

[0086] Signal 670 may include BCH SI that the multi-RAT WTRU 605 may decode in a similar manner as a UMTS WTRU. However, given the proliferation of multi-RAT devices, if the multi-RAT WTRU 605 is located near another WTRU that has already received and decoded the BCH SI, the multi-RAT WTRU 605 may access the decoded BCH SI from the other WTRU. When a WTRU has acquired the BCH SI, it may broadcast that information without being prompted, or it may wait until another WTRU requests the information in order to avoid unnecessary interference problems.

[0087] Typically, after a WTRU 605 has synchronized to a BCH of the cell, the WTRU 605 acquires and decodes the BCH SI, which may be broadcast in an SIB format according to a schedule. It may take several seconds to completely acquire the complete BCH SI. In order to improve the performance of the system 600 by reducing the BCH SI acquisition time, the WTRU 405 may be able to acquire the SIBs from the WTRU 610 via signal 670. Subsequently, the WTRU 605 may be configured to read the BCH SI from either the cell or the WTRU 610, since the system 600 is required to periodically update the BCH SI by reading the BCH.

[0088] The BCH SI sent via the signal 670 may be divided into an MIB and a number of SIBs. The MIB may include a limited number of most essential and most frequently transmitted parameters that may be needed to acquire other information from the cell, and may be transmitted on the BCH. SIBs other than SIB type 1 may be carried in SI messages. Mapping of SIBs to SI messages may be flexibly configurable by a scheduling information list included in the SIB type 1. Each SIB may only be contained in a single SI message. Only SIBs having the same scheduling requirement (periodicity) may be mapped to the same SI message. SIB type 1 may be mapped to the SI message that corresponds to the first entry in the list of SI messages in the scheduling information list. There may be multiple SI messages transmitted with the same periodicity. SIB type 1 and all SI messages may be transmitted on a DL-SCH.

[0089] The WTRU 605, in idle mode or connected mode, may apply the SI acquisition procedure to acquire AS and NAS SI that is broadcasted by an E- UTRAN. The AS and NAS SI may received from a WTRU 610 via signal 670. [0090] Once the WTRU 605 has received all of the SI from either the cell or a cooperating WTRU, the WTRU 605 will make available this SI to other WTRUs that are in need of the SI.

[0091] In one embodiment, the WTRU may allow other WTRUs to query it in pursuit of the BCH system information. The procedure will accept the query from another WTRU via a non-UMTS RAT and, if the WTRU has the BCH SI available, it will provide that over the non-UMTS RAT.

[0092] The order of the stored information cell selection and cooperative information cell selection may be changed, where the cooperative information cell selection may be performed before the stored information cell selection. Alternatively, the stored information cell selection procedure may be entirely eliminated, whereby the WTRU may perform a collaborative information cell selection procedure and, if that was unsuccessful, then perform an initial cell selection procedure. The cooperative information cell selection may be augmented such that the cooperating WTRUs may provide additional information other than just the carrier frequency and cell parameters, such as cell location, network capabilities, and network availability, (e.g., information indicating how congested the network is).

[0093] If any of these embodiments are implemented among all WTRUs, only the first WTRU powered on may have to go through the initial cell selection process, because all other WTRUs would be able to discover the current cell information from the WTRU already "camped on" the cell.

[0094] The sharing of network functionality information may be accomplished in several ways. This information may be embedded within the BCH as new SIBs or as additions/extensions to existing SIBs. When a WTRU requests SI from a camped WTRU, the camped WTRU may provide this SI over a different RAT to the requesting WTRU.

[0095] Embodiments

1. A method, performed by a multi-radio access technology (RAT) wireless transmit/receive unit (WTRU), of selecting a cell to camp on, the method comprising:

searching for cell selection information stored in the multi-RAT WTRU using a first RAT;

on a condition that the cell selection information is found, implementing a stored information cell selection procedure using the first RAT; and

on a condition that the cell selection information is not found, or a cell suitable for the WTRU to camp on was not found by implementing the stored information cell selection procedure, implementing an assisted cell selection procedure using a second RAT.

2. The method of embodiment 1 further comprising:

on a condition that a cell suitable for the WTRU to camp on was not found by implementing the assisted cell selection procedure, implementing an initial cell selection procedure using the first RAT.

3. The method as in any one of embodiments 1-2 wherein the assisted cell selection procedure comprises:

discovering a network-deployed communication unit;

transmitting at least one signal to the network- deployed communication unit requesting cell selection information; and

receiving at least one signal from the network- deployed communication unit including cell selection information.

4. The method as in any one of embodiments 1-2 wherein the assisted cell selection procedure comprises:

discovering a network-deployed communication unit;

transmitting at least one signal to the network- deployed communication unit requesting system information (SI); and

receiving at least one signal from the network- deployed communication unit including SI.

5. The method as in any one of embodiments 3-4 wherein the network- deployed communication unit is not a universal mobile telecommunications system (UMTS) device. 6. The method as in any one of embodiments 1-5 wherein a universal subscriber identity module (USIM) in the multi-RAT WTRU is searched for the cell selection information.

7. The method as in any one of embodiments 3-5 wherein the network- deployed communication unit broadcasts cell selection information over a broadcast channel (BCH).

8. The method as in any one of embodiments 1-7 wherein the first RAT is universal mobile telecommunications system (UMTS) and the second RAT is Bluetooth or WiFi.

9. A method, performed by a multi-radio access technology (RAT) wireless transmit/receive unit (WTRU), of selecting a cell to camp on, the method comprising:

searching for cell selection information stored in the multi-RAT WTRU using a first RAT;

on a condition that the cell selection information is found, implementing a stored information cell selection procedure using the first RAT; and

on a condition that the cell selection information is not found, or a cell suitable for the WTRU to camp on was not found by implementing the stored information cell selection procedure, implementing a cooperative information cell selection procedure using a second RAT.

10. The method of embodiment 9 further comprising:

on a condition that a cell suitable for the WTRU to camp on was not found by implementing the cooperative information cell selection procedure, implementing an initial cell selection procedure using the first RAT.

11. The method as in any one of embodiments 9-10 wherein the cooperative information cell selection procedure comprises:

discovering at least one camped WTRU;

transmitting at least one signal to the camped WTRU requesting cell selection information; and

receiving at least one signal from the camped WTRU including cell selection information.

12. The method as in any one of embodiments 9-10 wherein the cooperative information cell selection procedure comprises:

discovering at least one camped WTRU;

transmitting at least one signal to the camped WTRU requesting system information (SI); and

receiving at least one signal from the camped WTRU including SI.

13. The method as in any one of embodiments 11-12 wherein the camped WTRU is not a universal mobile telecommunications system (UMTS) device.

14. The method as in any one of embodiments 9-13 wherein a universal subscriber identity module (USIM) in the multi-RAT WTRU is searched for the cell selection information.

15. The method as in any one of embodiments 11-13 wherein the camped WTRU broadcasts cell selection information over a broadcast channel (BCH).

16. The method as in any one of embodiments 9-15 wherein the first RAT is universal mobile telecommunications system (UMTS) and the second RAT is Bluetooth or WiFi.

17. A multi-radio access technology (RAT) wireless transmit/receive unit (WTRU) for selecting a cell to camp on, the multi-RAT WTRU comprising: a first processor configured to search for cell selection information stored in the multi-RAT WTRU using a first RAT, and implement a stored information cell selection procedure using the first RAT on a condition that the cell selection information is found; and

a second processor configured to implement an assisted cell selection procedure using a second RAT on a condition that the cell selection information is not found, or a cell suitable for the WTRU to camp on was not found by implementing the stored information cell selection procedure.

18. The WTRU of embodiment 17 wherein the first processor is further configured to implement an initial cell selection procedure using the first RAT on a condition that a cell suitable for the WTRU to camp on was not found by implementing the assisted cell selection procedure.

19. The WTRU as in any one of embodiments 17-18 further comprising: the second processor configured to discover a network- deployed communication unit;

a transmitter configured to transmit at least one signal to the network- deployed communication unit requesting cell selection information; and

a receiver configured to receive at least one signal from the network- deployed communication unit including cell selection information.

20. The WTRU as in any one of embodiments 17-18 further comprising: the second processor configured to discover a network- deployed communication unit;

a transmitter configured to transmit at least one signal to the network- deployed communication unit requesting system information (SI); and

a receiver configured to receive at least one signal from the network- deployed communication unit including SI.

21. A multi-radio access technology (RAT) wireless transmit/receive unit (WTRU) for selecting a cell to camp on, the multi-RAT WTRU comprising: a first processor configured to search for cell selection information stored in the multi-RAT WTRU using a first RAT, and implement a stored information cell selection procedure using the first RAT on a condition that the cell selection information is found; and

a second processor configured to implement a cooperative information cell selection procedure using a second RAT on a condition that the cell selection information is not found, or a cell suitable for the WTRU to camp on was not found by implementing the stored information cell selection procedure.

22. The WTRU of embodiment 21 wherein the first processor is further configured to implement an initial cell selection procedure using the first RAT on a condition that a cell suitable for the WTRU to camp on was not found by implementing the cooperative information cell selection procedure.

23. The WTRU as in any one of embodiments 21-22 further comprising: the second processor configured to discover at least one camped WTRU; a transmitter configured to transmit at least one signal to the camped

WTRU requesting cell selection information; and

a receiver configured to receive at least one signal from the camped WTRU including cell selection information.

24. The WTRU as in any one of embodiments 21-22 further comprising: the second processor configured to discover at least one camped WTRU; a transmitter configured to transmit at least one signal to the camped

WTRU requesting system information (SI); and

a receiver configured to receive at least one signal from the camped WTRU including SI.

[0096] Although features and elements are described above in particular combinations, one of ordinary skill in the art will appreciate that each feature or element may be used alone or in combination with any of the other features and elements. In addition, the embodiments described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer- readable media include electronic signals, (transmitted over wired or wireless connections), and computer-readable storage media. Examples of computer- readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), a register, a cache memory, a semiconductor memory device, a magnetic media, (e.g., an internal hard disc or a removable disc), a magneto-optical media, and an optical media such as a compact disc (CD) or a digital versatile disc (DVD). A processor in association with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, Node-B, eNB, HNB, HeNB, AP, RNC, wireless router or any host computer.

Claims

CLAIMS What is claimed is:

1. A method, performed by a multi-radio access technology (RAT) wireless transmit/receive unit (WTRU), of selecting a cell to camp on, the method comprising:

searching for cell selection information stored in the multi-RAT WTRU using a first RAT;

on a condition that the cell selection information is found, implementing a stored information cell selection procedure using the first RAT;

on a condition that the cell selection information is not found, or a cell suitable for the WTRU to camp on was not found by implementing the stored information cell selection procedure, implementing an assisted cell selection procedure using a second RAT; and

on a condition that a cell suitable for the WTRU to camp on was not found by implementing the assisted cell selection procedure, implementing an initial cell selection procedure using the first RAT.

2. The method of claim 1 wherein the assisted cell selection procedure comprises:

discovering a network-deployed communication unit;

transmitting at least one signal to the network- deployed communication unit requesting cell selection information; and

receiving at least one signal from the network- deployed communication unit including cell selection information.

3. The method of claim 1 wherein the assisted cell selection procedure comprises:

discovering a network-deployed communication unit;

transmitting at least one signal to the network- deployed communication unit requesting system information (SI); and

receiving at least one signal from the network- deployed communication unit including SI.

4. The method of claim 2 wherein the network- deployed communication unit is not a universal mobile telecommunications system (UMTS) device.

5. The method of claim 1 wherein a universal subscriber identity module (USIM) in the multi-RAT WTRU is searched for the cell selection information.

6. The method of claim 2 wherein the network- deployed communication unit broadcasts cell selection information over a broadcast channel (BCH).

7. The method of claim 1 wherein the first RAT is universal mobile telecommunications system (UMTS) and the second RAT is Bluetooth or WiFi.

8. A method, performed by a multi-radio access technology (RAT) wireless transmit/receive unit (WTRU), of selecting a cell to camp on, the method comprising:

searching for cell selection information stored in the multi-RAT WTRU using a first RAT;

on a condition that the cell selection information is found, implementing a stored information cell selection procedure using the first RAT;

on a condition that the cell selection information is not found, or a cell suitable for the WTRU to camp on was not found by implementing the stored information cell selection procedure, implementing a cooperative information cell selection procedure using a second RAT; on a condition that a cell suitable for the WTRU to camp on was not found by implementing the cooperative information cell selection procedure, implementing an initial cell selection procedure using the first RAT.

9. The method of claim 8 wherein the cooperative information cell selection procedure comprises:

discovering at least one camped WTRU;

transmitting at least one signal to the camped WTRU requesting cell selection information; and

receiving at least one signal from the camped WTRU including cell selection information.

10. The method of claim 8 wherein the cooperative information cell selection procedure comprises:

discovering at least one camped WTRU;

transmitting at least one signal to the camped WTRU requesting system information (SI); and

receiving at least one signal from the camped WTRU including SI.

11. The method of claim 8 wherein the camped WTRU is not a universal mobile telecommunications system (UMTS) device.

12. The method of claim 8 wherein a universal subscriber identity module (USIM) in the multi-RAT WTRU is searched for the cell selection information.

13. The method of claim 8 wherein the camped WTRU broadcasts cell selection information over a broadcast channel (BCH).

14. The method of claim 8 wherein the first RAT is universal mobile telecommunications system (UMTS) and the second RAT is Bluetooth or WiFi.

15. A multi-radio access technology (RAT) wireless transmit/receive unit (WTRU) for selecting a cell to camp on, the multi-RAT WTRU comprising: a first processor configured to search for cell selection information stored in the multi-RAT WTRU using a first RAT, and implement a stored information cell selection procedure using the first RAT on a condition that the cell selection information is found;

a second processor configured to implement an assisted cell selection procedure using a second RAT on a condition that the cell selection information is not found, or a cell suitable for the WTRU to camp on was not found by implementing the stored information cell selection procedure; and

the first processor further configured to implement an initial cell selection procedure using the first RAT on a condition that a cell suitable for the WTRU to camp on was not found by implementing the assisted cell selection procedure.

16. The WTRU of claim 15 further comprising:

the second processor configured to discover a network- deployed communication unit;

a transmitter configured to transmit at least one signal to the network- deployed communication unit requesting cell selection information; and

a receiver configured to receive at least one signal from the network- deployed communication unit including cell selection information.

17. The WTRU of claim 15 further comprising:

the second processor configured to discover a network- deployed communication unit;

a transmitter configured to transmit at least one signal to the network- deployed communication unit requesting system information (SI); and

a receiver configured to receive at least one signal from the network- deployed communication unit including SI.

18. A multi-radio access technology (RAT) wireless transmit/receive unit (WTRU) for selecting a cell to camp on, the multi-RAT WTRU comprising: a first processor configured to search for cell selection information stored in the multi-RAT WTRU using a first RAT, and implement a stored information cell selection procedure using the first RAT on a condition that the cell selection information is found;

a second processor configured to implement a cooperative information cell selection procedure using a second RAT on a condition that the cell selection information is not found, or a cell suitable for the WTRU to camp on was not found by implementing the stored information cell selection procedure; and the first processor further configured to implement an initial cell selection procedure using the first RAT on a condition that a cell suitable for the WTRU to camp on was not found by implementing the cooperative information cell selection procedure.

19. The WTRU of claim 18 further comprising:

the second processor configured to discover at least one camped WTRU; a transmitter configured to transmit at least one signal to the camped WTRU requesting cell selection information; and

a receiver configured to receive at least one signal from the camped WTRU including cell selection information.

20. The WTRU of claim 18 further comprising:

the second processor configured to discover at least one camped WTRU; a transmitter configured to transmit at least one signal to the camped WTRU requesting system information (SI); and

a receiver configured to receive at least one signal from the camped WTRU including SI.