WO2012148325A1

WO2012148325A1 - Handover for cs-based mobile telephony in fixed wireless access

Info

Publication number: WO2012148325A1
Application number: PCT/SE2011/050505
Authority: WO
Inventors: Jari Vikberg; Håkan OLOFSSON; Tomas Nylander
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2011-04-27
Filing date: 2011-04-27
Publication date: 2012-11-01

Abstract

ABSTRACT OF THE DISCLOSURE A fixed wireless terminal (FWT) (12) receives cellular communications service, and there is a circuit-switched (CS) call involving a mobile radio user equipment (UE) (36). Messages are sent to facilitate handover of the circuit-switched call from (1) being connected through the fixed wireless terminal to a radio access network to being connected directly to a radio access network without connection to the fixed wireless terminal or (2) being connected directly to a radio access network without connection to the fixed wireless terminal to being connected to a radio access network through the fixed wireless terminal.

Description

HANDOVER FOR CS-BASED MOBILE TELEPHONY IN FIXED WIRELESS

ACCESS

TECHNICAL FIELD

[0001] The technology relates to communications, and in particular, to Fixed

Wireless Terminals (FWTs).

BACKGROUND

[0002] The technology described in this application relates to Fixed Wireless

Access (FWA) and Fixed Wireless Terminals (FWT). Another name for FWT is Mobile Broadband Router (MBR). FWA provides an end user with fixed line services by utilizing a wireless technology, e.g., GSM, UMTS/HSPA/W CDMA, SAE/LTE, CDMA or WiMAX technologies. Fixed Wireless Terminals offer, for example, a cost efficient way to provide high speed data, voice, and fax services to small office / home office and residential users. Although there is reference to the SAE/LTE technology as an example of wireless technology providing the backhaul connection to core and other networks and how FWT devices could be connected to the mobile networks, the technology described is more related to mobile networks that comprise a Circuit Switched (CS) domain and may apply to any such access technologies and mobile networks like GSM/GPRS/EDGE, UMTS/HSPA/W CDMA and CDMA.

[0003] A FWT device is for example located in an end user' s home or office, normally in the same location all the time. There is no real mobility related to the FWT itself except "nomadicity" where the FWT could be powered off in one place, moved to another location and then powered on again. The FWT provides local connectivity and services for end user equipment located in the home using for example WLAN/WiFi or Ethernet as the media. In addition, the FWT may provide support for multiple legacy services. For example, a black phone (a good old fixed phone) or a fax can be connected to the FWT. The FWT is directly connected to the mobile operator's radio access and core networks and can for example provide access towards the Internet. However, a fixed wireless terminal may also be located in a moving object, for example, a train, a bus, or a car and fixed in this case in terms of being fixedly installed in the moving object.

[0004] The technology also relates to a Generic Access Network (GAN) based on Unlicensed Mobile Access (UMA) specifications. A GAN provides a new Radio Access Network (RAN) and includes a Generic Access Network Controller (GANC). GAN is specified in the 3 GPP TS 43.318 and TS 44.318. In GAN, a mobile station (MS) is a dual-mode, dual radio handset including for example both WiFi and 3GPP- macro radio support (GSM, WCDMA or both). The MS connects to a WiFi Access point (AP) using the WiFi radio and can also function in a GAN mode to access cellular radio services, e.g., provided by the Circuit Switched (CS) and/or Packet Switched (PS) CN (Core Network).

[0005] Wireless access technologies, as opposed to wired technologies like Ethernet, will likely be used in the future in the home LAN, e.g., between the FWT and the home devices). WLAN/WiFi (e.g., the different variants of IEEE 802.11) will likely become a commodity in mobile terminals. As a result, the FWT device can be used to access Packet- Switched (PS) services for mobile terminals. But known FWT solutions or products do not provide mobile terminals with the ability to use the FWT device and the Home LAN for mobile telephony. In other words, there is no way for the mobile terminal to access the mobile telephony services provided by the Circuit- Switched (CS) Core Network (CN), (e.g., a mobile switching center (MSC) node). This is a significant limitation of the FWT-based configurations because the existing CS CN services will likely be used for a very long time in the mobile networks as Voice-Over- Packet- Switched (PS) domain services (like IP Multimedia Services (IMS)) are still in their infancy. Accordingly, providing CS -domain based mobile telephony services using an FWT is important for end users, mobile operators, and vendors.

[0006] A challenge with FWT configurations is handover of CS calls from or to the FWT. Taking the first situation, there currently is no mechanism for handing over a mobile UE call being supported via a FWT radio link with a radio access network (RAN) to another radio link to be established from the mobile UE directly to the RAN without support from the FWT. This handover situation is referred to as "handover- out" meaning handover the CS call away from the FWT. Another issue is how to handle the UE and the FWT having different RAN coverage, e.g., a cell used by the FWT for the mobile telephony service may not be the optimal cell for the mobile UE. The main reason to support handover-out is continued service to the end users. If handover-out is not supported, then the mobile telephony service for the mobile UE's CS call would be abruptly terminated when the mobile UE leaves the WLAN coverage provided by the FWT.

[0007] The other situation not provided for is handover of an existing CS mobile

UE call directly connected to the RAN to a situation where the call is routed through an FWT. This handover situation is referred to as "handover-in" meaning handing over the CS call directly linked to the RAN to the FWT. A challenge in this situation is how to establish separate radio links between the mobile UE and the FWT and between the FWT and the RAN. Support for handover-in permits better utilization of the radio interface usage and more optimized battery consumption in the mobile UE. Otherwise, the mobile UE would enter the FWT's coverage area and remain connected to the macro network. In that case, the mobile UE is either delayed from using the FWT (in the case when the mobile UE enters the FWT's coverage area first after going idle in the macro network), or the mobile UE is simultaneously connected to both the macro network and the FWT (in the case when the mobile UE immediately starts also using the FWT device).

SUMMARY

[0008] The technology allows handover of circuit- switched calls from or to a fixed wireless terminal (FWT). One aspect of the technology relates to a fixed wireless terminal which receives cellular communications service. A circuit- switched (CS) call involving a mobile radio user equipment (UE) is established. Messages are sent to facilitate handover of the circuit- switched call from (1) being connected through the fixed wireless terminal to a radio access network to being connected directly to a radio access network without connection to the fixed wireless terminal or (2) being connected directly to a radio access network without connection to the fixed wireless terminal to being connected to a radio access network through the fixed wireless terminal.

[0009] In a "handover- out" example embodiment, the fixed wireless terminal, which supports the circuit- switched call using a first radio link between the fixed wireless terminal and a radio access network (RAN), receives handover-related information associated with the mobile UE. The FWT determines whether the mobile UE should continue the circuit- switched call using a second radio link directly between the UE and the radio access network or a different radio access network and sends information to the mobile UE for the mobile UE to continue the circuit- switched call using the second radio link.

[0010] In a non-limiting example implementation where the fixed wireless terminal and the mobile UE are located in a source cell, the FWT receives one or more cell lists or one or more signal quality reports from the mobile UE, and scans through the received one or more cell lists or the one or more signal quality reports to determine whether the mobile UE can not continue the call in the source cell. The FWT selects a target cell different from the source cell included in a current neighbor cell list received from the source cell for which a reported received signal level meets a predetermined value if the fixed wireless terminal can receive a system information signal from that target cell. The FWT may send a message to the radio access network that includes the reported received signal level for the target cell.

[0011] The FWT may receive a handover command from the radio access network to hand the call over to the target cell, and in response thereto, sends a handover command using a generic access network protocol to the mobile UE for the mobile UE to conduct the call using the target cell.

[0012] The source cell and the target cell may different cells in the same radio access network, different cells in different types of radio access networks, or the same cell in the same radio access network.

[0013] In a "handover- out" example embodiment, the fixed wireless terminal interacts with the radio access network and/or the mobile UE to set up a handover of the circuit- switched call to a target cell supported by a second radio link between the mobile UE and the fixed wireless terminal and a third radio link between the fixed wireless terminal and a base station associated with the target cell. In a non-limiting example implementation, the FWT receives a generic access registration message from the mobile UE prior to the handover and can generate current circuit- switched call state information for the call. The FWT may be part of a local area network, and the radio access network may be based on a 2G or 3G cellular wireless standard. The fixed wireless terminal may include a generic access controller which uses a generic access network protocol to support the call between the fixed wireless terminal and the mobile UE and which uses a mobile circuit- switched protocol for access to a radio access network protocol to support the call between the fixed wireless terminal and the radio access network. The FWT performs an interworking function to translate between generic access network protocol messages and mobile circuit- switched protocol for access to a radio access network protocol messages.

[0014] In an example implementation, the first and second radio links are to the same radio access network.

[0015] In another example implementation, the mobile UE is in a cell different from the source cell prior to handover.

[0016] In yet another example implementation, the fixed wireless terminal and the mobile UE are in the same cell prior to handover.

[0017] Another aspect of the technology relates to a mobile user equipment (UE) receiving cellular communications service supporting a circuit- switched (CS) call involving the mobile UE. After detecting a need for a handover of the circuit- switched call, the mobile UE sends and receives messages to facilitate handover of the circuit- switched call from (1) being connected through a fixed wireless terminal to a radio access network to being connected directly to a radio access network without connection to the fixed wireless terminal or (2) being connected directly to a radio access network without connection to the fixed wireless terminal to being connected through the fixed wireless terminal to a radio access network.

[0018] In a "handover- out" example embodiment, after establishing the circuit- switched call using a first radio link between the fixed wireless terminal and a radio access network (RAN), the mobile UE sends a handover-related message to the fixed wireless terminal and receives a handover execution message from the fixed wireless terminal. The UE continues the circuit- switched call using a second radio link directly between the UE and the radio access network or a different radio access network. The first and second radio links may be to the same radio access network. Prior to handover, the mobile UE may be in a cell different from a cell in which the fixed wireless terminal is located or they can be in the same cell. The mobile may transmit one or more cell lists or one or more signal quality reports.

[0019] In a "handover-in" example embodiment, after establishing the circuit- switched call using a first radio link between the fixed wireless terminal and a radio access network (RAN), the mobile UE interacts with the radio access network and/or the fixed wireless terminal to set up a handover of the circuit- switched call to a target cell in which the fixed wireless terminal is registered so that the circuit- switched call uses a second radio link between the mobile UE and the fixed wireless terminal and a third radio link between the fixed wireless terminal and a base station associated with the target cell. The source cell and the target cell may be different cells in the same radio access network, different cells in different types of radio access networks, or the same cell in the same radio access network.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a function block diagram showing an example

communications system using a fixed wireless terminal;

[0021] Figure 2 is a function block diagram showing an LTE-based

communications system where a fixed wireless terminal functions as a fixed UE and home gateway;

[0022] Figure 3 is a function block diagram showing a UMTS -based

[0023] Figure 4 is a diagram showing a non-limiting example of CS-Domain protocol stacks that using a Generic Access Network (GAN)-concept; [0024] Figure 5 is a diagram illustrating how a mobile UE can access mobile telephony services provided by an existing Circuit Switched (CS) Core Network (CN) via an FWT;

[0025] Figure 6 is a non-limiting flowchart illustrating example procedures for handover of a circuit- switched mobile UE call either to or from a fixed wireless terminal;

[0026] Figure 7A is a non-limiting flowchart illustrating example procedures of a handover- out situation from the FWT's perspective;

[0027] Figure 7B is a non-limiting flowchart illustrating example procedures of a handover- out situation from the UE's perspective;

[0028] Figure 8 is a diagram showing an example, non-limiting handover-out embodiment where the FWT and the mobile UE are in the same cell;

[0029] Figure 9 is an example, non-limiting signaling diagram for the same cell handover-out embodiment;

[0030] Figure 10 is a diagram showing an example, non-limiting handover-out embodiment where the FWT and the mobile UE are in different cells;

[0031] Figure 11 is an example, non-limiting signaling diagram for the different cell handover- out embodiment;

[0032] Figure 12 A is a non-limiting flowchart illustrating example procedures of a handover- in situation from the FWT's perspective;

[0033] Figure 12B is a non-limiting flowchart illustrating example procedures of a handover- in situation from the UE's perspective;

[0034] Figure 13 is a diagram showing an example, non-limiting handover- in embodiment where the FWT and the mobile UE are in different cells;

[0035] Figure 14 is an example, non-limiting signaling diagram for the different cell handover-in embodiment;

[0036] Figure 15 is a diagram showing an example, non-limiting handover-in embodiment where the FWT and the mobile UE are in the same cell;

[0037] Figure 16 is an example, non-limiting signaling diagram for the same cell handover-in embodiment; [0038] Figure 17 is a non-limiting function block diagram of an FWT; and

[0039] Figure 18 is a non-limiting function block diagram of a mobile UE.

DETAILED DESCRIPTION

[0040] The following description sets forth specific details, such as particular embodiments for purposes of explanation and not limitation. But it will be appreciated by one skilled in the art that other embodiments may be employed apart from these specific details. In some instances, detailed descriptions of well known methods, interfaces, circuits, and devices are omitted so as not to obscure the description with unnecessary detail. Individual blocks may be shown in the figures corresponding to various nodes. Those skilled in the art will appreciate that the functions of those blocks may be implemented using individual hardware circuits, using software programs and data in conjunction with a suitably programmed digital microprocessor or general purpose computer, and/or using applications specific integrated circuitry (ASIC), and/or using one or more digital signal processors (DSPs). Nodes that communicate using the air interface also have suitable radio communications circuitry. The software program instructions and data may be stored on computer-readable storage medium, and when the instructions are executed by a computer or other suitable processor control, the computer or processor performs the functions.

[0041] Thus, for example, it will be appreciated by those skilled in the art that diagrams herein can represent conceptual views of illustrative circuitry or other functional units. Similarly, it will be appreciated that any flow charts, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

[0042] The functions of the various illustrated elements may be provided through the use of hardware such as circuit hardware and/or hardware capable of executing software in the form of coded instructions stored on computer-readable medium. Thus, such functions and illustrated functional blocks are to be understood as being either hardware-implemented and/or computer-implemented, and thus machine-implemented. [0043] In terms of hardware implementation, the functional blocks may include or encompass, without limitation, digital signal processor (DSP) hardware, reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

[0044] In terms of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers, and the terms computer, processor, and controller may be employed interchangeably. When provided by a computer, processor, or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Moreover, the term "processor" or "controller" also refers to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

[0045] The technology may be applied to any cellular communications system and/or network. Herein, a user equipment (UE) is understood to be any type of mobile radio node, e.g., mobile station (MS), mobile terminal, laptop, cell phone, PDA, small base station, sensor, relay, etc.

[0046] Figure 1 is a function block diagram showing an example

communications system using a fixed wireless terminal (FWT) 12 in a home

environment 10 with the FWT 12 coupled for communication with a facsimile 14, a conventional "black phone" 16, an Ethernet connection 18, and a personal computing device 22, printer 24, cable box 26, and network attached storage (NAS) device 28 via a a wireless LAN (WLAN) 20. The FWT 12 is connected to a mobile operator's radio access network 30 (via one or more base stations) and mobile core network(s) 32 that can for example provide access towards the Internet 34. The FWT 12 also contains an (U)SIM card in the same way as mobile handsets and terminals to allow the FWT 12 to connect to the mobile operator's network. [0047] Figure 2 is a function block diagram showing a non-limiting example embodiment of a LTE-based communications system where a FWT device is connected to the E-UTRAN (i.e. LTE radio access network). Figure 3 is a function block diagram showing a non-limiting example embodiment of a UMTS/HSPA/WCDMA- based communications system where a UE accesses circuit switched-based services from a core network node, e.g., a circuit- switched call, using a fixed wireless terminal. GSM and CDMA are other examples of access technologies and mobile networks that may be used to support UE access to circuit switched-based services from a core network node, e.g., a circuit- switched call, via a fixed wireless terminal. In both Figures, the FWT is logically built up of a Home Gateway and an UE towards the LTE or UMTS network. The right side of the FWT is shown as a fixed UE that uses the LTE-Uu or Uu interface towards the mobile operator's network. The FWT also contains an (U)SIM card like mobile UEs connected to the mobile operator's network. The left side of the FWT is shown as a Home gateway (GW) that provides a "Home or Residential LAN" for the devices in the Home (or in the office).

[0048] 3GPP has standardized the Generic Access Network (GAN)-concept starting from 3GPP Release-6. A GAN provides a radio access network (RAN) and is specified in the 3 GPP TS 43.318 and TS 44.318. The mobile UE may be a dual-mode, dual radio handset including, for example, both WiFi and 3GPP-macro radio support (GSM, WCDMA, or both). The mobile UE connects to the FWT using the WiFi radio. The GAN standard defines for example how the mobile UE can function in a GAN mode and access core network services using a Up interface between the mobile UE and a GAN controller (GANC). An example of such a system with non-limiting representative protocol stacks is illustrated in Figure 4. More specifically, Figure 4 shows a CS Domain Control Plane Architecture related to GAN and the Up-interface. In this example, the GANC uses the normal A-in terf ace signaling towards the MSC and interworks a related protocol, like BSSAP, towards the relevant GAN-protocols, like Generic Access, Circuit Switched Resources (GA-CSR) in both directions. A stage-2 description of GERAN to GAN and GAN to GERAN CS handover procedures may be found in figures 26 and 27 in 3 GPP TS 43.318 VIO.0.0. [0049] Known GAN solutions use fixed access networks such as DSL between the cellular network edge (GANC) and, e.g., the WiFi access point. In contrast, in the technology described here, the cellular network is used as backhaul link all the way to the WiFi access point (the fixed wireless terminal), and the GANC is placed in the fixed wireless terminal. This provides support for handover in both directions (in and out) in the case when interworking and adaptation protocol functions carry the GAN CS signalling and traffic over the local WiFi hop and further to interwork these towards the CS and NAS signalling used in the mobile network. Unfortunately, the current GAN standard does not support any mechanism in which a CS call may be handed over either to or from a FWT device when CS signaling is used between the FWT device and the mobile network.

[0050] Figure 5 is a diagram illustrating how a mobile UE 36 can access mobile telephony services provided by an existing Circuit Switched (CS) Core Network (CN) which includes a radio access network (RAN) 30 via an FWT 12. GAN protocols may be used over the Home LAN 20 (e.g., WLAN/WiFi) between the mobile UE 36 and the FWT 12. The FWT 12 contains a GANC 37, an interworking function 38 that provides interworking between GAN protocol signaling (unfilled dashes) and mobile CS protocol signaling (dashes) in both directions, and a security gateway (SEGW) 39 that assists in security functions like authentication, ciphering, etc. Multiple simultaneous CS connections may be supported.

[0051] As explained in the background, there is a need to enable handover of a mobile UE CS call so that it uses an FWT (handover- in) or does not use an FWT (handover- out) at appropriate times and situations. The focus of the description below is on procedures implemented in the FWT and in the mobile UE and includes interworking between the mobile UE/FWT interface and the FWT/RAN interface and providing new triggers and procedures for enabling handover. Although the description below focuses on a single UE example having a CS connection, this example is not limiting, and the technology may also be applied to multiple UEs having CS

connections, where handover may be accomplished for one or more of those CS connections. [0052] Figure 6 is a non-limiting flowchart illustrating example procedures for handover of a circuit- switched mobile UE call either to or from a fixed wireless terminal (FWT). The fixed wireless terminal (FWT) receives cellular communications service in a cell labeled for convenience as an FWT cell (a FWT cell is the cell used by the FWT device to connect to the mobile network), and the mobile UE engages in CS call (step SI). The UE and/or the FWT may detect a need for handover of the CS call (step S2). In that case, messages are sent to facilitate handover of the circuit- switched call from (1) being connected through the fixed wireless terminal to a radio access network to being connected directly to a radio access network without connection to the fixed wireless terminal or (2) being connected directly to a radio access network without connection to the fixed wireless terminal to being connected to a radio access network through the fixed wireless terminal (step S3). There are two main handover situations covered by this method: handover-out of a CS call from an FWT and handover-in of a CS call to an FWT.

[0053] Figure 7A is a non-limiting flowchart illustrating example procedures of a handover-out situation from the FWT's perspective. A circuit- switched (CS) call for a mobile UE uses a first radio link between the fixed wireless terminal and a radio access network (RAN) (step S5). Handover-related information associated with the mobile UE is communicated (step S6), and a determination is made whether the mobile UE should continue the circuit- switched call using a second radio link directly between the UE and the radio access network or a different radio access network (step S7). Circuit- switched call state information is sent to the mobile UE based on the determination to permit the mobile UE to continue the circuit- switched call using the second radio link (step S8).

[0054] Figure 7B is a non-limiting flowchart illustrating example procedures of a handover-out situation from the UE's perspective. Initially, the circuit- switched call involving the mobile UE is established using a first radio link between the fixed wireless terminal (FWT) and a radio access network (RAN) (step S10). Sometime during the CS call, the mobile UE sends a handover-related message to the FWT (step SI 1). In response, the mobile UE receives a handover execution message from the FWT (step S12). The circuit- switched call is continued using a second radio link directly between the UE and the radio access network or a different radio access network (step S13).

[0055] Figure 8 is a diagram showing an example, non-limiting handover-out embodiment where the FWT and the mobile UE are in the same cell. The mobile UE (labeled as MS/UE in the figures) is shown as moving out of the home LAN coverage but still within the same macro cell-1 that covers the FWT. As a result, the mobile UE CS call is handed out so that the call is no longer supported by a first radio link between the mobile UE and the FWT and a second radio link between the FWT and the RAN shown as a base station BTS coupled to a BSC. After the handover, the mobile UE CS call is supported by a direct radio link between the mobile UE and the RAN, i.e., the base station BTS in this figure. This technology applies to all other types of RANs, e.g., UTRAN, LTE, etc.

[0056] Figure 9 is an example, non-limiting signaling diagram for the same cell handover-out embodiment. The different signaling steps are described in detail in the figure. Note that the BTS and BSC are shown as combined BSS because the signaling between the BTS and BSC is not important to understanding this non-limiting, example implementation. The MS/UE has an active CS call via the FWT. GAN signaling is used between the MS/UE and FWT, and GERAN signaling is used between the FWT and BSS.

[0057] At step 1 , there is an active CS call connection involving the mobile UE which is supported by the FWT. At step 2, the MS/UE detects that the WLAN coverage provided by the FWT is deteriorating, or the MS/UE may receive an indication about deteriorating radio conditions from the FWT as a GA-CSR UPLINK QUALITY INDICATION message (not shown in Figure 9). At step 3, the mobile UE sends a GA-CSR HANDOVER INFORMATION message to the FWT indicating a list of target GERAN cells identified by a cell global identity (CGI). The target cells may be listed in order of preference, e.g., ranked by a CI path loss parameter, for handover. The list may include a received signal strength for each identified GERAN cell. In addition, the GA-CSR HANDOVER INFORMATION message may include a list of target UTRAN cells, preferably ranked in order of preference for handover, and the received signal strength for each identified UTRAN cell.

[0058] At step 4, the FWT scans through the received cell lists and detects that the current GERAN cell (i.e., the FWT cell) is included in the list of target GERAN cells and that the received signal strength for that current cell is sufficient to support the CS call. The FWT then creates locally information about the current "CS Call State" at step 5. This information includes GERAN radio resource (RR) connection used to support the CS call between the FWT and the BSS. At step 6, the FWT sends a GA- CSR MOVE CS CALL message to the MS/UE that includes locally-created "CS Call State" information. The MS/UE uses the received "CS Call State" information at step 7 to take over the GERAN RR connection from the FWT. At this point, the call has been moved to a new radio link between the mobile UE and the BSS (RAN), and the FWT is no longer included in the CS call path.

[0059] Figure 10 is a diagram showing an example, non-limiting handover-out embodiment where the FWT and the mobile UE are in different cells. The MS/UE and the FWT-device are "connected" in different cells post-handover, i.e., the MS/UE is connected to the "Macro cell-2" after the handover, and the FWT device is connected to "Macro cell-1" before and after the handover. Figure 10 shows a non-limiting example where these two cells are controlled by two different BSCs. Other cases are also possible. For example, both cells may be controlled by the same BSC, the cells may employ different radio access technologies (RATs), etc.

[0060] Figure 11 is an example, non-limiting signaling diagram for the different cell handover-out embodiment. The MS/UE has an active CS call via the FWT. GAN signaling is used between the MS/UE and FWT, and GERAN signaling is used between the FWT and BSS.

[0061] At step 1, there is an active CS call connection involving the mobile UE which is supported by the FWT. At step 2, the MS/UE detects that the WLAN coverage provided by the FWT is deteriorating, or the MS/UE may receive an indication about deteriorating radio conditions from the FWT as a GA-CSR UPLINK QUALITY INDICATION message (not shown in Figure 9). At step 3, the mobile UE sends a GA-CSR HANDOVER INFORMATION message to the FWT indicating a list of target GERAN cells identified by a cell global identity (CGI). The target cells may be listed in order of preference, e.g., ranked by a CI path loss parameter, for handover. The list may include a received signal strength for each identified GERAN cell. In addition, the GA-CSR HANDOVER INFORMATION message may include a list of target UTRAN cells, preferably ranked in order of preference for handover, and the received signal strength for each identified UTRAN cell.

[0062] At step 4, the FWT scans through the received cell lists and detects that the current GERAN cell (i.e., the FWT cell) is not included in the list of target GERAN cells or that the received signal strength for that cell is not satisfactory. In step 5, the FWT selects one of the received cells that fulfills the following: a) the cell is included in the current neighbor cell list received from the source BSS-1, b) the received signal level for this cell from the MS/UE is satisfactory, and c) the FWT can also receive the signal from that cell to read its system information (SI). Because the cells lists received from the MS/UE include global cell identifiers, and the FWT neighbor cells are typically known using a short identity, the FWT may need to perform additional operations to make the above selection. The FWT reads the global cell identifiers from all cells included in the current neighbor cell lists to correlate them to the cell lists received from the MS/UE. In this example, the selected cell is "Macro cell-2".

[0063] In step 6, the FWT includes the "Macro cell-2" in the Measurement Report message to the GERAN. The reported signal level may be the value received from the MS/UE or it may be the highest possible signal level. The FWT may also report lower signal level for the current cell, i.e., Macro cell-1. The Source BSS-1 decides to trigger handover from "Macro Cell-1" to "Macro Cell-2" and the handover preparation phase is performed between the Source BSS-1 and Target BSS-2 via the core network (CN) as is typically done, as shown in step 7. The source BSS-1 sends a Um Handover Command message to the FWT in step 8 to initiate handover to "Macro Cell-2". The FWT interworks the received Um Handover Command message to the GA-CSR HANDOVER COMMAND message sent to the mobile UE in step 9. [0064] In step 10, the MS/UE transmits the Um: Handover Access containing the handover reference element to allow the Target BSS-2 to correlate this handover access with the previous handover preparation phase. The Target BSS-2 confirms the detection of the handover to the CN in step 11, using the Handover Detect message. The CN may at this point switch the user plane to the Target BSS-2 as shown at step 12. In step 13, the Target BSS-2 provides Um Physical Information to the mobile UE, e.g., a Timing Advance, to allow the mobile UE to synchronize with the GERAN. The MS/UE signals to the Target BSS-2 that the handover is completed, using Handover Complete in step 14. The Target BSS-2 confirms to the CN the completion of the handover, via Handover Complete message in step 15, and the MS/UE is now active in the CS call in the "Macro cell-2" as shown at step 16.

[0065] The signaling in Figure 11 may also continue with for example radio access capability updates to the current cell if the FWT-UE and the MS/UE have different radio capabilities. Although the example shows both the source and target cell as GERAN cells, the technology may be applied for all different RATs/cases where the source and target cells are different cells in this example embodiment.

[0066] Another aspect of the technology relates to handover-in procedures that allow mobile terminals to perform handover of a CS call into a CS -based mobile telephony situation that uses an FWT. Figure 12A is a non-limiting flowchart illustrating example procedures of a handover-in situation from the FWT's perspective. A fixed wireless terminal (FWT) receives cellular communications service from a target cell (step S20). A handover is determined for a circuit- switched (CS) call involving a mobile UE using a first radio link with a base station associated with a source cell in a radio access network (RAN) (step S21). A handover is set up of the circuit- switched call to the target cell supported by a second radio link between the mobile UE and the fixed wireless terminal and a third radio link between the fixed wireless terminal and a base station associated with the target cell (step S22), and handover is completed (step S23).

[0067] Figure 12B is a non-limiting flowchart illustrating example procedures of a handover-in situation from the UE's perspective. Initially, a circuit- switched call for the mobile UE is established using a first radio link between the mobile UE and a radio access network (RAN) (step S25). The mobile UE interacts with the RAN and/or the fixed wireless terminal (FWT) to set up a handover of the circuit- switched call to a target cell in which the FWT is registered so that the circuit- switched call uses a second radio link between the mobile UE and the FWT and a third radio link between the FWT and a base station associated with the target cell (step S26).

[0068] Figure 13 is a diagram showing an example, non-limiting handover- in embodiment where the FWT and the mobile UE are in different cells. The MS/UE is connected to the "Macro cell-2" and the FWT device is connected to "Macro cell-1". Figure 13 shows the case when these two cells are controlled by two different BSCs. But this is a non-limiting example, and the technology applies to other cases and RATs. For example, both the cells may be controlled by the same BSC, the cells may employ different RATs, etc.

[0069] Figure 14 is an example, non-limiting signaling diagram for the different cell handover-in embodiment. In step 1, the FWT (labeled in the figure as FWT-UE) is either camping on or active on Macro cell-1. Step 2 shows that the mobile UE (labeled in the figure as MS/UE) is active on Macro cell-2. In step 3, the MS/UE detects the FWT and performs a GAN registration to the GANC part of the FWT, e.g., as defined in 3GPP TS 43.318 and 44.318 incorporated herein by reference. In step 3, cell information, such as for example ARFCN and BSIC in this case, is returned to the MS/UE in the GAN-registration for the cell where the FWT-UE is camping on (Macro cell-1 in this example).

[0070] In step 4, the MS/UE sends a measurement report to the "controller" of the Macro cell-2. In this example, that cell is a GERAN cell, so the measurement report is sent to the BSS-2 labeled "Source" BSS-2 in the figure. The Source BSS-2 decides to trigger handover to the Macro cell-1, and a HANDOVER REQUIRED message is sent to the core network (CN) node, e.g., an MSC, in step 5. The MSC performs handover routing and sends a HANDOVER REQUEST message in step 6 to the BSS-1 (labeled as "Target" BSS-1 in the figure) controlling the handover target cell, i.e., Macro cell-1. In step 7, the Target BSS-1 performs handover preparation and returns a HANDOVER REQUEST ACKNOWLEDGE to the MSC. Then in step 8, the MSC returns a HANDOVER COMMAND message to the Source BSS-2.

[0071] In step 9, the Source BSS-2 sends a Um Handover Command message to the MS/UE, which sends a GA-CSR HANDOVER ACCESS message to the GANC part of the FWT in step 10. The FWT interworks between Up and Um interfaces, and based on the GA-CSR HANDOVER ACCESS message, sends the Um Handover Access message to the target BSS-1 in step 11. In step 12, the Target BSS-1 sends a HANDOVER DETECT message to the MSC indicating that the UE has been detected in the target cell. A voice connection is enabled between the MSC and the target BSS-1 as shown at 13.

[0072] In step 14, the Target BSS-1 returns the Um Physical Information message to the FWT, and in parallel to steps 11 to 14, an RTP stream is setup between the FWT-GANC and the MS/UE in step 15. For example, the FWT may trigger step 15 towards the MS/UE in parallel with the initiation of step 11. The MS/UE sends a GA- CSR HANDOVER COMPLETE to the FWT-GANC at step 16, and thereafter, the FWT-UE sends the Um Handover Complete message to the Target BSS-1 at step 17. In step 18, the Target BSS-1 sends the HANDOVER COMPLETE message to the MSC, and the resources at the source side, i.e., at Source BSS-2, are released, e.g., according to existing mechanisms as shown at step 19. Step 20 indicates that the call has been moved to the new path so that the FWT terminates the interface towards the Macro cell 1 and the GAN interface is used between the MS/UE and the FWT.

[0073] Even though the source and target cells are GERAN cells controlled by different BSSs the above example, the same principle applies for all different cases where the source and target cells are different cells. Non-limiting examples include (1) both source and target are GERAN cells in the same BSS and (2) one of the cells is GERAN cell and the other one is UTRAN cell.

[0074] Figure 15 is a diagram showing an example, non-limiting handover- in embodiment where the FWT and the mobile UE are in the same cell. Both the MS/UE and the FWT are "connected" in the same cell (shown as "Macro cell-1"). The MS/UE is in active mode with a CS call, and the FWT may either be camping or active in the same cell. In this non-limiting example, the cell is a GERAN cell.

[0075] Figure 16 is an example, non-limiting signaling diagram for the same cell handover- in embodiment. The FWT-UE is camping on Macro cell- 1 , or it may also be active on this cell as indicated in steps 1 and 2. The MS/UE's "CS active state" means that information about the air interface resources used in the Macro cell-1 is known by the MS/UE. In step 3, the MS/UE detects the FWT and performs GAN registration to the GANC part of the FWT, e.g., as defined in 3 GPP TS 43.318 and 44.318. The MS/UE sends information about the current serving cell to the FWT-GANC in as part of the GAN registration. The FWT identifies that the same cell is also used by the FWT-UE part for camping or active mode communication in step 4. Another approach for or extension of step 4 is that the FWT is not initially camping on the same cell as the MS/UE reports. But if the FWT can "hear" the signal in the cell reported by the MS/UE, the FWT can change its camping cell to this cell.

[0076] In step 5, the FWT indicates to the MS/UE the possibility that the CS call could be moved to the FWT because the FWT is also connected to the same cell. In the figure, this indication is called "GAN CS Call Move possible" message and may also include the cell identity of the cell. In step 6, the MS/UE replies to the FWT by returning a message called "GAN CS Call Move Information" which also preferably contains information about the "CS active state" described above in step 2. Now the FWT holds the "CS active state" for the call as indicated at step 7. The RTP Stream is setup in step 8 between the FWT-GANC and the MS/UE. Now both the MS/UE and the FWT move the call to the new path so that the FWT terminates the interface towards the Macro cell 1 and the GAN interface is used between the MS/UE and the FWT as indicated at step 9.

[0077] The above signaling may also continue with, for example, a radio access capability update to the current cell if the FWT and the MS/UE have different radio capabilities. Although both the source and target cell are GERAN cells in the above example, the same principles apply for all different RATs/cases where the source and target cells are the same cell. [0078] Figure 17 is a non-limiting function block diagram of the FWT 12.

Processing circuitry 40 performs the various control tasks of the FWT and may include a handover controller 41 for performing the handover related operations for the FWT such those described above. The processing circuitry 40 is coupled to a U(SIM) card 42, radio circuitry 43, memory 44, and interface circuitry 45. The U(SIM) card 42 is used to authenticate the FWT 12 with the network. The radio circuitry 43 provides radio communications with the UE 36 and one or more radio access networks. Memory 44 stores data and program instructions needed for the FWT operation.

[0079] Figure 18 is a non-limiting function block diagram of the mobile UE 36.

Processing circuitry 50 performs the various control tasks of the mobile UE 36 and may include a measurements report controller 52, coupled to signal quality monitor unit 57, and a handover controller 53 for performing the handover related operations for the mobile UE 36 such those described above. The processing circuitry 50 is coupled to a U(SIM) card 54, radio circuitry 56, memory 58, and a user interface 55. The U(SIM) card 54 is used to authenticate the mobile UE 36 with the network. The radio circuitry 56 provides radio communications with the FWT and one or more radio access networks. Memory 58 stores data and program instructions needed for the mobile UE 36 operation as well as various neighbor cell lists 59.

[0080] The technology described in this application offers multiple advantages. First, the technology extends FWT solutions to mobile telephony with its attendant advantages. A mobile UE can move freely within a home or business and outside the home or business and still continue a call. Second, providing handover-out and handover-in allows the mobile UE to use only a single radio when moving to or from FWT coverage in a CS active state.

[0081] Although various embodiments have been shown and described in detail, the claims are not limited to any particular embodiment or example. None of the above description should be read as implying that any particular element, step, range, or function is essential such that it must be included in the claims scope. The scope of patented subject matter is defined only by the claims. The extent of legal protection is defined by the words recited in the allowed claims and their equivalents. All structural and functional equivalents to the elements of the above-described preferred

embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the technology described, for it to be encompassed by the present claims. No claim is intended to invoke paragraph 6 of 35 USC §112 unless the words "means for" or "step for" are used. Furthermore, no embodiment, feature, component, or step in this specification is intended to be dedicated to the public regardless of whether the embodiment, feature, component, or step is recited in the claims.

Claims

1. A method in a fixed wireless terminal (FWT) ( 12) receiving cellular

communications service, characterized by the fixed wireless terminal:

detecting a need for handover of a circuit-switched (CS) call for a mobile radio user equipment (UE) (36); and

sending messages to facilitate handover of the circuit-switched call from (1 ) being connected through the fixed wireless terminal to a radio access network to being connected directly to a radio access network without connection to the fixed wireless terminal or (2) being connected directly to a radio access network without connection to the fixed wireless terminal to being connected to a radio access network through the fixed wireless terminal.

2. The method in claim 1 , wherein the fixed wireless terminal performs the further steps of:

supporting the circuit-switched call using a first radio link between the fixed wireless terminal and a radio access network (RAN) (30);

receiving handover-related information associated with the mobile UE;

determining whether the mobile UE should continue the circuit-switched call using a second radio link directly between the UE and the radio access network or a different radio access network; and

sending information to the mobile UE for the mobile UE to continue the circuit- switched call using the second radio link.

3. The method in claim 2, wherein the fixed wireless terminal and the mobile UE are located in a source cell, the method further comprising:

receiving one or more cell lists or one or more signal quality reports from the mobile UE, and scanning through the received one or more cell lists or the one or more signal quality reports to determine whether the mobile UE can not continue the call in the source cell.

4. The method in claim 3, further comprising:

selecting a target cell different from the source cell included in a current neighbor cell list received from the source cell for which a reported received signal level meets a predetermined value if the fixed wireless terminal can receive a system information signal from that target cell.

5. The method in claim 4, further comprising:

sending a message to the radio access network that includes the reported received signal level for the target cell.

6. The method in claim 4, further comprising:

receiving a handover command from the radio access network to hand the call over to the target cell, and

in response thereto, sending a handover command using a generic access network protocol to the mobile UE for the mobile UE to conduct the call using the target cell.

7. The method in claim 4, wherein the source cell and the target cell are different cells in the same radio access network or different cells in different types of radio access networks.

8. The method in claim 4, wherein the source cell and the target cell are the same cell in the same radio access network.

9. The method in claim 1 , wherein the circuit-switched call is supported using a first radio link with a base station associated with a source cell in a radio access network (RAN)(30), the fixed wireless terminal performing the further steps of:

interacting with the radio access network and/or the mobile UE to set up a handover of the circuit- switched call to a target cell supported by a second radio link between the mobile UE and the fixed wireless terminal and a third radio link between the fixed wireless terminal and a base station associated with the target cell; and

supporting the handed over circuit- switched call.

10. The method in claim 9, further comprising receiving a generic access registration message from the mobile UE prior to the receiving step.

1 1. The method in any of the above claims, wherein the FWT is part of a local area network.

12. The method in any of the above claims, wherein the radio access network is one that is based on a 2G or 3G cellular wireless standard.

13. The method in any of the above claims, further comprising creating at the fixed wireless terminal current circuit-switched call state information for the call.

14. The method in any of the above claims, wherein the fixed wireless terminal includes a generic access controller (37) which uses a generic access network protocol to support the call between the fixed wireless terminal and the mobile UE and which uses a mobile circuit-switched protocol for access to a radio access network protocol to support the call between the fixed wireless terminal and the radio access network, and wherein the fixed wireless terminal performs an interworking function (38) to translate between generic access network protocol messages and mobile circuit-switched protocol for access to a radio access network protocol messages.

15. The method in claim 2 or 10, wherein the first and second radio links are to the same radio access network.

16. The method in claim 2 or 10, wherein prior to handover, the mobile UE is in a cell different from the source cell.

17. The method in claim 2 or 10, wherein prior to handover, the fixed wireless terminal and the mobile UE are in the same cell.

18. A method in a mobile user equipment (UE) (36) receiving cellular communications service supporting a circuit-switched (CS) call involving the mobile UE characterized by the mobile UE:

detecting a need for a handover of the circuit-switched call; and

sending and receiving messages to facilitate handover of the circuit-switched call from (1 ) being connected through a fixed wireless terminal (FWT) (12) to a radio access network to being connected directly to a radio access network without connection to the fixed wireless terminal or (2) being connected directly to a radio access network without connection to the fixed wireless terminal to being connected through the fixed wireless terminal to a radio access network.

19. The method in claim 18, wherein the mobile UE performs the further steps of: establishing the circuit-switched call using a first radio link between the fixed wireless terminal and a radio access network (RAN)(30);

sending a handover-related message to the fixed wireless terminal;

receiving a handover execution message from the fixed wireless terminal; and continuing the circuit-switched call using a second radio link directly between the UE and the radio access network or a different radio access network.

20. The method in claim 19, wherein the first and second radio links are to the same radio access network.

21. The method in claim 19, wherein prior to handover, the mobile UE is in a cell different from a cell in which the fixed wireless terminal is located.

22. The method in claim 19, wherein prior to handover, the fixed wireless terminal and the mobile UE are in the same cell.

23. The method in claim 19, the method further comprising transmitting one or more cell lists or one or more signal quality reports.

24. The method in claim 18, wherein the mobile UE performs the further steps of: establishing the circuit-switched call using a first radio link between the mobile UE and a radio access network (RAN)(30), and

interacting with the radio access network and/or the fixed wireless terminal (FWT) to set up a handover of the circuit-switched call to a target cell in which the fixed wireless terminal is registered so that the circuit-switched call uses a second radio link between the mobile UE and the fixed wireless terminal and a third radio link between the fixed wireless terminal and a base station associated with the target cell.

25. The method in claim 24, wherein the source cell and the target cell are different cells in the same radio access network or different cells in different types of radio access networks.

26. The method in claim 24, wherein the source cell and the target cell are the same cell in the same radio access network.

27. A fixed wireless terminal (FWT) ( 12) apparatus receiving cellular communications service, comprising:

radio circuitry (43), and

processing circuitry (40),

the processing circuitry characterized by being configured to detect a need for handover of a circuit-switched (CS) call for a mobile radio user equipment (UE) (36) and to send messages to facilitate handover of the circuit-switched call from ( 1 ) being connected through the fixed wireless terminal to a radio access network to being connected directly to a radio access network without connection to the fixed wireless terminal or (2) being connected directly to a radio access network without connection to the fixed wireless terminal to being connected to a radio access network through the fixed wireless terminal.

28. The FWT apparatus in claim 27, wherein the FWT apparatus is configured to support the circuit-switched call using a first radio link between the fixed wireless terminal and a radio access network (RAN) (30), and wherein the processing circuitry is further configured to:

receive handover-related information associated with the mobile UE;

determine whether the mobile UE should continue the circuit-switched call using a second radio link directly between the UE and the radio access network or a different radio access network; and

send information to the mobile UE for the mobile UE to continue the circuit- switched call using the second radio link.

29. The FWT apparatus in claim 28, wherein the first and second radio links are to the same radio access network.

30. The FWT apparatus in claim 28, wherein prior to handover, the mobile UE is in cell different from a cell in which the fixed wireless terminal is located.

31. The F WT apparatus in claim 28, wherein prior to handover, the fixed wireless terminal and the mobile UE are in the same cell.

32. The FWT apparatus in claim 28, wherein the fixed wireless terminal and the mobile UE are located in a source cell, the radio circuitry is configured to receive one or more cell lists or one or more signal quality reports from the mobile UE, and the processing circuitry is configured to process the received one or more cell lists or the one or more signal quality reports to determine whether the mobile UE can not continue the call in the source cell.

33. The FWT apparatus in claim 32, wherein the processing circuitry is configured to select a target cell different from the source cell included in a current neighbor cell list received from the source cell for which a reported received signal level meets a

predetermined value if the fixed wireless terminal can receive a system information signal from that target cell.

34. The FWT apparatus in claim 32, wherein the processing circuitry is configured to receive a handover command from the radio access network to hand the call over to the target cell, and in response thereto, send a handover command using a generic access network protocol to the mobile UE for the mobile UE to conduct the call using the target cell.

35. The FWT apparatus in claim 27, the FWT apparatus is configured to support the circuit-switched call using a first radio link between the fixed wireless terminal and a radio access network (RAN) (30), and wherein the processing circuitry is further configured to:

interact with the radio access network and/or the mobile UE to set up a handover of the circuit-switched call to a target cell supported by a second radio link between the mobile UE and the fixed wireless terminal and a third radio link between the fixed wireless terminal and a base station associated with the target cell; and

support the handed-over, circuit-switched call.

36. The FWT apparatus in claim 35, wherein a source cell and the target cell are different cells in the same radio access network or different cells in different types of radio access networks.

37. The FWT apparatus in claim 35, wherein a source cell and the target cell are the same cell in the same radio access network.

38. The FWT apparatus in any of claims 27-35, wherein the FWT is part of a local area network.

39. The FWT apparatus in any of claims 27-35, wherein the radio access network is one that is based on a 2G or 3G cellular wireless standard.

40. The FWT apparatus in any of claims 27-35, wherein the fixed wireless terminal includes a generic access controller (37) which is configured to use a generic access network protocol to support the call between the fixed wireless terminal and the mobile UE and to use a mobile circuit-switched protocol for access to a radio access network protocol to support the call between the fixed wireless terminal and the radio access network, and wherein the fixed wireless terminal apparatus is configured to perform an interworking function (38) to translate between generic access network protocol messages and mobile circuit-switched protocol for access to a radio access network protocol messages.

41. A fixed wireless terminal incorporating the FWT apparatus in any of claims 28-40.

42. Mobile user equipment (UE) (36) apparatus for receiving cellular communications service from a first cell supporting a circuit-switched (CS) call involving the mobile UE, comprising:

processing circuitry (50) configured to detect a need for a handover of the circuit- switched call; and

radio circuitry (56) coupled to the processing circuitry,

wherein the processing circuitry and the radio circuitry are characterized by being configured to send and receive messages to facilitate handover of the circuit-switched call from ( 1) being connected through a fixed wireless terminal (FWT) ( 12) to a radio access network to being connected directly to a radio access network without connection to the fixed wireless terminal or (2) being connected directly to a radio access network without connection to the fixed wireless terminal to being connected through the fixed wireless terminal to a radio access network.

43. The mobile UE apparatus in claim 42, wherein the radio circuitry is configured to: use a first radio link between the fixed wireless terminal and a radio access network (RAN)(30) to support the circuit-switched call;

send a handover-related message to the fixed wireless terminal;

receive a handover execution message from the fixed wireless terminal; and continue the circuit-switched call using a second radio link directly between the

UE and the radio access network or a different radio access network.

44. The mobile UE apparatus in claim 43, wherein the first and second radio links are arranged to be to the same radio access network.

45. The mobile UE apparatus in claim 43, wherein prior to handover, the mobile UE is arranged to be in cell different from a cell in which the fixed wireless terminal is located.

46. The mobile UE apparatus in claim 43, wherein prior to handover, the fixed wireless terminal and the mobile UE are arranged to be in the same cell.

47. The mobile UE apparatus in claim 42, wherein the radio circuitry is configured to: use a first radio link, between the fixed wireless terminal and a radio access network (RAN)(30) to support the circuit-switched call, and

interact with the radio access network and/or a fixed wireless terminal (FWT) to set up a handover of the circuit-switched call to a target cell in which the fixed wireless terminal is registered so that the circuit-switched call uses a second radio link between the mobile UE and the fixed wireless terminal and a third radio link between the fixed wireless terminal and a base station associated with the target cell.

48. The mobile UE apparatus in claim 47, wherein a source cell and the target cell are different cells in the same radio access network or different cells in different types of radio access networks.

49. The mobile UE apparatus in claim 47, wherein a source cell and the target cell are the same cell in the same radio access network.