KR100667399B1 - Base station handover in a hybrid gsm/cdma network - Google Patents

Abstract

A mobile wireless communications system, comprising: a first type base station operating according to a first air interface and a second type base station operating according to a second air interface. Methods and apparatuses for handing over a mobile station from a first base station of a first type to a second base station of a second type in a system are provided. The communication link is established through a first air interface between the mobile station and the first base station. Data is received from the mobile station in response to a signal received by the mobile station from a second base station via a second air interface substantially without breaking the communication link with the first base station. The mobile station is handed over to a second base station in response to the data received at the first base station from the first base station.

Description

BASE STATION HANDOVER IN A HYBRID GSM / CDMA NETWORK

FIELD OF THE INVENTION The present invention relates generally to wireless communications, and more particularly to improved cellular telephone networks.

Global System for Mobile telecommunications (GSM) is used in wireless telephone networks in many countries around the world. GSM provides a useful range for network services and standards. Current GSM networks are based on time-division multiple access (TDMA) digital communication technology. In a TDMA-based wireless network, each mobile subscriber unit communicates with only one base station at a given time. When a subscriber moves from one cell to another, a "hard handover or handoff" occurs, the base station to which the subscriber was communicating suddenly loses its link with the subscriber, and the new base station assumes the task.

Code Division Multiple Access (CDMA) is an advanced digital communication technology that not only uses radio bandwidth more efficiently than TDMA, but also provides a more reliable and fade-free link between wireless subscribers and base stations. A major CDMA standard is IS-95, published by the Telecommunication Industry Assocation (TIA). This standard provides a "soft handover" function, whereby when moving from one cell to another, the subscriber unit is tentatively linked with two or more base stations simultaneously. Soft handovers that can be made by the code division approach reduce the likelihood of link loss that can occur frequently in hard handovers.

PCT Patent Application No. PCT / US96 / 20764, referred to herein, describes a wireless communication system that implements GSM network services and protocols using a CDMA air interface (ie, an underlying RF communication protocol). Using this system, at least some TDMA base stations (BSSs) and subscriber units of the current GSM network will be replaced or supplemented by corresponding CDMA equipment. The system's CDMA BSSs are made to communicate with GSM mobile switching centers (MSCs) via standard GSM A-interfaces. Thus, while maintaining the core of the GSM network, a transition from TDMA to CDMA can be achieved.

Hybrid wireless communication networks including both GSM and CDMA are also described in PCT Patent Publication Nos. WO95 / 24771 and WO96 / 21999 and by Tscha et al., Entitled "Subscriber Signal Pathway between CDMA Mobile Stations and GSM Mobile Switching Centers." 2nd International Conference on Communications, Ottawa (1993), pp. 181-185, which are incorporated herein by reference. None of these publications address the specific problem of how to perform efficient handover of a subscription unit between different base stations of a hybrid network.

In addition, PCT Patent Application No. PCT / US97 / 00926, referred to herein, describes an intersystem handover method between CDMA and TDMA BSSs in a hybrid GSM / CDMA communication system. CDMA / TDMA BSSs generate pilot beacon signals in accordance with CDMA technology. During the call, the subscriber unit detects a pilot signal and informs the base station controller that the signal has been detected. The subscriber unit is handed over from CDMA to TDMA without interrupting the call.

It is an object of the present invention to provide a method and apparatus for use in a mixed TDMA / CDMA wireless communication network.

It is a further object from another aspect of the present invention to provide an improved method and apparatus for enabling subscriber unit handover between TDMA / CDMA base stations without interrupting communication.

In a more preferred embodiment of the present invention, a mixed GSM / CDMA wireless communication system includes both TDMA and CDMA base stations co-controlled by a mobile switching center (MSC). Systems of this type are outlined in the PCT patent application mentioned above. Preferably using the GSM network protocol for both interfaces, a subscriber unit, also referred to herein as a mobile station (MS), can communicate with both types of base stations by appropriately switching between TDMA and CDMA air interfaces. A feature of the present invention is that the communication system is based on the existing GSM / TDMA infrastructure and adds CDMA BSSs to it, and does not make any other modifications to the existing infrastructure.

To determine when a handover occurs, an MS in communication with a current base station of one type (TDMA or CDMA) monitors RF signals originating at other base stations that may be of different types. The message sequence between the current base station and the MS allows the MS to obtain appropriate synchronization information for the new base station and report this information back to the current base station. The information is used by the system to allow the MS to establish an interface with the new base station, and handover occurs without actually interrupting communication between the MS and the network.

In the context of this patent application, handovers between base stations are also referred to as " mobile-assisted handovers. &Quot; Mobile station assisted handover is used in GSM and CDMA systems known in the art, where a mobile station measures and reports the strength of a signal received from a base station transceiver in that cell before being handed over to a neighboring cell. However, in a hybrid GSM / CSMA system, mobile stations may receive signals at any given time from either a CDMA or TDMA base station (or a CDMA beacon associated with a TDMA base station as in PCT patent application PCT / US97 / 00926 mentioned above). Assume that you can. However, it is not possible to receive signals at both CDMA and TDMA base stations and thus cannot provide this type of support. Mobile station support in accordance with the principles of the present invention allows handover to be performed more smoothly and reliably.

In a preferred embodiment of the present invention, the MS switches between TDMA and CDMA operations during a phone call, in accordance with commands received from the base station with which it is communicating. Before a handover occurs, the MS receives signals from both the TDMA and CDMA base stations and reports back to the base station for the received signals. The reported information is thus passed back to the BSC and used by the BSC to initiate handover. Preferably, the MS comprises a single wireless transceiver, so that at any given time the MS can communicate with a TDMA or CDMA base station, but not both at the same time. According to the IS-95 standard, the unit can communicate with more than one base station at a time.) Each GSM / TDMA base station has its own synchronization clock, while the communicating MSs are synchronized to that clock, It is noted that the CDMA base stations are synchronized with each other in real time. Therefore, when switching between TDMA and CDMA base stations, the MS in each case acquires synchronization without actually interrupting the phone call and synchronizes its operation to the appropriate clock signal.

In this preferred embodiment, the MS is determined whether it will be handed over to the GSM / TDMA base station while communicating with the CDMA base station. CDMA transmissions by the MS transceiver are temporarily interrupted, during which time the unit performs a GSM neighbor scan, generally according to the GSM standard, to capture and synchronize to the TDMA base station. Advantageously, said CDMA transmission is interrupted for one frame, typically 20 ms, resulting in idle time slots in accordance with the IS-95 standard. After the TDMA base station has been identified and the appropriate messages exchanged, the traffic channel between the base stations is opened and the MS is switched to the TDMA base station, and the interruption of the telephone call being performed is significantly reduced.

In addition to these more preferred embodiments, the MS communicates with the TDMA base station and it is determined when to hand over to the CDMA base station.

Although more preferred embodiments are described with reference to an MS having a single transceiver for the use of TDMA and CDMA, the principles of the present invention likewise use other types of subscriber unit and system hardware, in particular separately or only partially. It will be appreciated that it can be applied even when using subscriber units with integrated TDMA and CDMA transceivers.

Thus, there is provided a mobile station handover method presented in accordance with claim 1.

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Preferably, receiving data comprises receiving a measurement of signal strength, and handing over the mobile station comparing the measurements of signal strength from the first and second base stations and in accordance with the comparison result. Handing over the mobile station. Preferably, receiving the data comprises applying a weighting factor to the measurement of signal strength, wherein applying the weighting factor comprises changing the factor in accordance with the network condition of the system. . More preferably, applying the weighted party includes sending the weighted party for the communication link to the mobile station, the mobile station applying the weighted party to the measurement.

Advantageously, receiving the data comprises receiving a second base station identification signal based on decoding by the mobile station received via the second air interface.

In a more preferred embodiment, the mobile station attempts to receive a signal having a frequency in the list by transmitting a frequency list of the second type base station of the system from the first base station to the mobile station.

Preferably, handing over the mobile station includes sending a handover command from the first base station.

Advantageously, establishing a communication link and receiving data in response to the signal comprises establishing the link and receiving a signal at the mobile station using a single RF transceiver of the mobile station.

In a more preferred embodiment, the first or second air interface comprises a TDMA interface and the other interface comprises a CDMA interface. Wherein the TDMA interface preferably comprises a GSM interface, and the CDMA interface is configured to carry GSM network messages. Preferably, the CDMA interface is based on the IS-95 standard.

Advantageously, establishing the communication link comprises using a single radio resource management protocol layer for managing the first air interface, wherein handing over the mobile station comprises: Using a single radio resource control protocol layer to manage.

More preferably, receiving data from the mobile station comprises defining an overlap area between the first area serviced by the first air interface and the second area serviced by the second air interface and when the mobile station is in the overlap area. Triggering the mobile station to receive data.

In a more preferred embodiment, the first air interface comprises a CDMA interface, the second air interface comprises a GSM / TDMA interface, and receiving data from the mobile station comprises receiving a mobile station to receive and decode a GSM / TDMA signal. Gating to cause the mobile station to interrupt the CDMA communication link. Preferably, gating the mobile station includes stopping CDMA communication for one IS-95 frame duration, and receiving data is based on GSM frequency modification of the signal by the mobile station and decoding of the synchronization channel. Receiving the identification signal of the second base station.

In another preferred embodiment, the first air interface comprises a GSM / TDMA interface, the second air interface comprises a CDMA interface, and receiving data from the mobile station controls the mobile station to receive and decode the CDMA signal. Interrupting the communication link.

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Alternatively or additionally, receiving data includes delivering a GSM cell broadcast service message to the mobile station to begin searching for a signal from a base station of a second type by the mobile station. Preferably, delivering the GSM cell broadcast service message to the mobile station includes delivering a message to be received by the mobile station while the mobile station is operating in dedicated mode.

Preferably, receiving data from the mobile station comprises receiving an identification signal of the CDMA pilot beam decoded by the mobile station. More preferably, the method includes mapping a second base station to a GSM base station to control the handover.

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According to a preferred embodiment of the present invention the mobile communication system is a GSM mobile wireless communication system.

Mapping a base station operating according to a CDMA air interface to a GSM / TDMA subsystem;

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Comparing the strengths of the first and second signals, assuming substantially both the first and second base station subsystems are GSM / TDMA base stations; And

A handover method is further provided comprising the step of handing over the mobile station to a second base station according to a result of the comparison of the signal strengths in the first base station.

Preferably, mapping the CDMA base station comprises assigning a GSM frequency and a location to the base station.

More preferably, establishing the communication link and handing over the mobile station includes communicating messages between the first and second subsystems of the system and the mobile switching center via the GSM A-interface. Advantageously, both the first and second base station subsystems operate according to a CDMA air interface, and handing over the mobile station does not substantially violate an A-interface protocol, but rather a new IS- over the A-interface. Passing a 95 long code.

Preferably, receiving data from the mobile station comprises applying a weighting factor to the second signal, and comparing the strengths of the signals comprises comparing the weighted signals, The applying step includes delivering the weighted party to the mobile station, the mobile station applying the weighted party to a second signal. Advantageously, applying the weighter includes changing the factor in accordance with the network condition of the system.

According to a preferred embodiment of the present invention,

In the wireless communication device for use in a mobile communication system,

A base station of a first type transmitting and receiving a first signal in accordance with a first air interface;

A second type of base station for transmitting and receiving a second signal in accordance with a second air interface; And

Receive a second signal over the second air interface from the second type base station while maintaining a communication link over the first air interface with the base station of the first type, and also in response to the second signal to the base station of the first type. And transmitting data to cause the mobile station to hand over from the first base station to the second base station in response to the transmitted data.

Preferably, the data transmitted by the mobile station includes a measurement of signal strength and the mobile station is handed over in response to a comparison result of the first and second signals. Preferably, the weights are applied to the measurement of signal strength, which weights change according to the network condition of the system. Preferably, the weighted party is delivered to the mobile station via a communication link, and the mobile station applies the weighted party to measurements.

More preferably, the mobile station decodes the second signal to identify the base station of the second type.

Preferably, the base station of the first type transmits a frequency list of the mobile station of the second type of the system to the mobile station so that the mobile station attempts to receive a signal at the frequency of the list.

Preferably, the base station of the first type sends a handover command to the mobile station, whereby the mobile station is handed over from the first base station to the second base station.

More preferably, the mobile station comprises a single RF transceiver capable of communicating with both base stations of the first and second types.

In a preferred embodiment, one of the first and second air interfaces comprises a TDMA interface, the other interface comprises a CDMA interface, the TDMA interface preferably comprises a GSM interface, and the CDMA interface is a GSM network message. It is configured to send. Preferably, the CDMA interface is based on the IS-95 standard.

Preferably, the base station triggers the mobile station via the second air interface when the mobile station is in an overlap area between the first area serviced by the first air interface and the second area serviced by the second air interface. Receive a second signal.

In a preferred embodiment, the first air interface comprises a CDMA interface, the second air interface comprises a GSM / TDMA interface, and the first type of base station gates the mobile station to receive and decode the GSM signal to establish a communication link. Stop it.

Preferably, the mobile station breaks the link for one IS-95 frame duration.

More preferably, the mobile station processes the second signal to decode the GSM frequency correction and synchronization channel of the signal.

In another preferred embodiment, the first air interface comprises a GSM / TDMA interface, the second air interface comprises a CDMA interface, and the first type of base station communicates to control and receive and decode the CDMA signal with the mobile station. Stop the link.

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Preferably, a GSM cell broadcast center forwards a cell broadcast service message to the mobile station to initiate a second signal search by the mobile station. Wherein the mobile station receives the cell broadcast service message while operating in a dedicated mode.

Alternatively or additionally, the mobile station processes the CDMA signal to identify a CDMA pilot beam.

Advantageously, said mobile station receives said CDMA signal during a first TDMA time slot and communicates said signal during a subsequent TDMA time slot, communicating with said base station via a TDMA interface to generate data for transmission to a base station. do.

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According to a preferred embodiment of the present invention, the mobile wireless communication system is a GSM communication system,

Means for mapping a CDMA base station in the GSM system to a GSM base station,

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The mobile station substantially assumes that the first and second base station systems operate according to the GSM / TDMA air interface, and the second station in the first subsystem according to the comparison result of the first and second signal strengths received by the mobile station. Handover to the subsystem.

Preferably, the base station transmitting the CDMA signal is assigned a GSM frequency and a location in the system. More preferably, the messages are transferred between the first and second base stations and the mobile switching center in the system via the GSM A-interface, both of which are CDMA signals. Preferably, a new IS-95 long code is communicated over the A-interface from the second base station to the first base station without substantially violating the A-interface protocol to handover the mobile station.

Advantageously, said mobile station applies a weighting factor to said second signal before said signal strength is compared.

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The invention will be explained through the preferred embodiments in conjunction with the accompanying drawings.

1 is a schematic block diagram of a hybrid GSM / CDMA mobile communication system according to a preferred embodiment of the present invention.

2A is a schematic block diagram illustrating a communication protocol between a mobile station and a base station subsystem in the system of FIG. 1 in accordance with a preferred embodiment of the present invention.

2B is a schematic block diagram of a hybrid GSM / CDMA mobile station in accordance with a preferred embodiment of the present invention.

3A and 3B are schematic block diagrams illustrating communication protocol stacks between elements of the system in FIG. 1 in accordance with a preferred embodiment of the present invention.

4A is a schematic block diagram illustrating mobile station handover from a CDMA base station to a GSM base station in the system of FIG. 1 in accordance with a preferred embodiment of the present invention.

4B is a schematic block diagram illustrating the signal flow associated with the handover of FIG. 4A in accordance with a preferred embodiment of the present invention.

5 is a schematic block diagram illustrating the signal flow associated with the supply of time information in the system of FIG.

6 is a schematic diagram illustrating cells in a hybrid GSM / CDMA mobile communication system that may help in understanding a method for handing over a mobile station from a GSM base station to a CDMA base station in accordance with a preferred embodiment of the present invention.

7 is a schematic block diagram illustrating signal flow associated with handover from a GSM base station to a CDMA base station in accordance with a preferred embodiment of the present invention.

8 is a schematic block diagram illustrating handover of a mobile station between CDMA base stations in a hybrid GSM / CDMA mobile communication system according to a preferred embodiment of the present invention.

9 is a schematic diagram illustrating a signal flow associated with the handover of FIG. 8 in accordance with a preferred embodiment of the present invention.

1 is a schematic block diagram of a hybrid GSM / CDMA mobile communication system 20. System 20 is built around a public land mobile network (PLMN) 22, which is based on the GSM communication standard described above. The infrastructure for these networks already exists and is widely used in many countries. The present invention has the advantage that it is possible to introduce CDMA services associated with these networks in stages without making major changes to existing infrastructure. PLMN 22 includes at least one mobile-services switching center (MSC) 24, or a number of such centers (only one MSC is shown for simplicity of description), which centers Control network operation within the geographic domain. Among other functions, the MSC 24 connects the PNMN 22 to a public switched telephone network (PSTN) and / or packet data network (PSTN), as well as regional registration of the subscriber unit and handover of the subscriber unit between base stations. PDN; 48) also plays a role. The PLMN also includes a network management center (NMC) 26 and a cell broadcast center (CBC) 28. These functions are described further below.

System 20 includes a number of mobile stations (MS) 40 and communicates with PLMN 22 through a number of base station subsystems (BSS) 30 and 32. The MS 40, also known as the subscriber unit, can communicate with both the GSM BSS 30 using substantially the GSM TDMA standard signal protocol and the CDMA BSS 32 using the CDMA based communication method described below. In addition, in a GSM standard system, a mobile station can typically receive broadcasts from the CBC 28 only in idle mode, but the MS 40 calls through the BSS 30 as described further below. Such broadcasts may be received. Although only one MS 40, GSM BSS 30 and CDMA BSS 32 are shown in FIG. 1 for simplicity, in practice, the system 20 will typically include a number of such system elements.

The GSM BSS 30 and the CDMA BSS 32 communicate with the MSC 24 and are simultaneously controlled by the MSC 24. The communication between the GSM BSS 30 and the MSC 24 is substantially in accordance with the GSM standard. The CDMA BSS 32 is IS- to communicate with the PLMN according to the GSM standard, in particular to communicate with the MSC 24 via the GSM standard A-interface, as will be described further below with reference to FIGS. 3A and 3B. The 95 CDMA standard is amended. The BSS 32 also communicates with the CBC 28 to receive messages to be broadcast in the air and includes a radio operation and maintenance center (OMC-R) 38. The OMC-R preferably communicates with the NMC 26 via a GSM-standard Q3 interface using an information model based on the GSM 12.XX series of specifications referenced herein. Optionally, the BSS 32 is linked to a general packet data service (GPRS) 50 as proposed by the European Telecommunications Standards Institute (ETSI). Alternatively or additionally, the BSS 32 may be connected directly to the PSTN / PDN 48 for the transmission of packet data, preferably using an internet link (this connection is shown in FIG. 1 for simplicity of explanation). Not shown).

CDMA BSS 32 and MS 40 are preferably built on a CDMA “air interface” in accordance with the IS-95 standard for CDMA communication in general. The BSS 32 is built around a base station controller (BSC) 34, and the BSC 34 communicates with a number of base station transceivers (BTSs) 36. Each BTS transmits an RF signal to the MS 40 and also receives an RF signal from the MS 40. As is known in the CDMA technology, when a MS moves from a cell in one CDMA BTS 36 to another during a phone call, a "soft handover" (or handoff) occurs between the BTSs.

However, there may be a system 20 service area that does not have CDMA coverage (ie, CDMA BTS 36 is not in that area), or that coverage is weak or congested. If the MS 40 is moved to such an area during a phone call, the MS is handed over from the CDMA BTS to the BTS associated with the GSM BSS 30 without interrupting the call. Likewise, if the MS 40 is moved to a cell of the CDMA BTS 36 in an area serviced only by the GSM BSS 30 during a call, the MS is preferably handed over from GSM to the CDMA BSS. Methods for performing this handover between CDMA and GSM / TDMA services, and vice versa and between CDMA BSS 32 and another CDMA BSS 32 will be described further below. By the same method and structure as the system 20 shown in FIG. 1, the MS 40 can execute the CDMA in the areas served by the system 20 without the service being lost in the TDMA areas. Receive the benefits of the service. The transition between the CDMA and TDMA regions is substantially evident to the users of the MS 40. This is because high-level GSM network protocols are observed throughout the system, and only low-level RF air interfaces are changed during the transition.

2A is a block diagram schematically illustrating communication protocol stacks between MS 40 and BSSs 30 and 32 in accordance with a preferred embodiment of the present invention. The MS 40 communicates with the GSM BSS 30 via a GSM Um interface based on a standard TDMA air interface and is substantially free of BSS 30 GSM layer 1 and GSM layer 2 to accommodate the MS 40. No modification is necessary. The MS 40 communicates with the CDMA BSS 32 via the CDMA Um interface based on any modified CDMA IS-95 air interface. Subscriber units known in the art can operate via either the GSM Um or CDMA Um interface, but cannot communicate via both.

To support both of these interfaces, MS 40 includes mobile equipment (ME) 42, which includes two wireless transceivers, including both configured for TDMA operation and configured for CDMA. It must include a single transceiver that can dynamically switch between TDMA and CDMA. The ME includes a mobile termination (MT), and the MT supports terminal equipment (TE) 46 for voice and / or data input and output. In addition, the MS 40 includes a subscriber identity module (SIM) 44 in accordance with the GSM standard.

2B is a schematic block diagram illustrating an MS 40 that includes a single wireless transceiver in an ME 42 in accordance with a preferred embodiment of the present invention. MS 40 is built around modem unit 59, and unit 59 includes a DSP core 60 capable of generating and processing both TDMA and CDMA signals. Preferably, core 60 includes an ASIC device, which includes standalone CDMA transmit and receive processing supported by GSM timing logic 64 and GSM hardware accelerator (or DSP) 62, and SIM 44. Has a port for Core 60 receives the input and passes the output to TE 46. In this case, TE 46 is represented as a microphone and speaker, and core 60 performs D / A and A / D conversion and vocoding for the audio signal, as known in the art. do. Either GSM or CDMA vocoding is applied depending on whether the MS 40 is connected to the GSM BSS 30 or the CDMA BSS 32. The core 60 may additionally or alternatively be configured to operate with a TE 46 that inputs / outputs digital data, such as a fax machine.

The core 60 outputs digital data, which is one of TDMA or CDMA, to the mixed-signal output device 66. Device 66 processes and converts the data into an analog baseband form for input to RF transmitter 68. The duplexer 70 passes the resulting RF signal via the antenna to the GSM or CDMA base station as appropriate. The signals received from the base station are delivered by the duplexer 70 to the core 60 through the RF receiver 72 and the mixed-signal input device 74 performing baseband conversion and AGC functions. Preferably, transmitter 68, receiver 72 and mixed-signal devices 66 and 74 are controlled by core 60.

RF transmission and reception by the MS 40 is preferably in the GSM 900 or 1800 MHz band for compatibility with current GSM equipment, in particular the BSS 30. Assuming that the MS 40 includes only a single transceiver shown in FIG. 2B operating only in the GSM band, the CDMA equipment of the system 20 must also be properly configured to operate in this frequency range.

Returning to FIG. 2A, whether the MS 40 physically includes one or two transceivers, the MS 40 interfaces with the protocol stack 1 and the protocol stack for operation with the GSM BSS 30 and the CDMA BSS 32, respectively. Layer 2 should be supported. The CDMA air interface between the MS 40 and the CDMA BSS 32 includes GSM-CDMA Layer 2, where CDMA Layer 1 and IS-95 operations that operate on standard IS-95 protocols are modified to accommodate the needs of GSM network services. do. Layer 2 supports frame transmission between the MS 40 and the BSS 30 or 32. GSM-CDMA Layer 2 includes functionality supported by standard GSM Layer 2, not supported by normal CDMA-95 such as message sorting, priority and fragmentation, and suspension and resumption of communication. When operating with the GSM BSS 30, the air interface layers 1 and 2 conform to the GSM standard without modification.

The standard GSM protocol includes third Radio Interface Layers (RIL3), including three sublayers, on GSM Layer 1 and Layer 2. At the bottom of these three sublayers is a Radio Resource (RR) management layer, which supports a mobile management (MM) layer. The RIL3 sublayers of the GSM BSS 30 remain substantially unchanged with respect to the GSM standard, and the GSM MM and CM sublayers likewise remain without substantial change in the MS 40. The CM layer supports GSM supplementary service and short message service (SMS) as well as signal generation for call processing. The MM sublayer supports signaling, authentication, and encryption key management to locate the MS 40.

To support the MM and CM layers, a GSM-CDMA RR layer is introduced into the MS 40 and BSS 32 protocol stacks. The GSM-CDMA RR layer, which manages radio resources and maintains a radio link between the MS 40 and the BSSs 30 and 32, monitors the presence of dual GSM and CDMA underlayers (layers 1 and 2) of the MS 40 protocol stack. Recognize. The GSM-CDMA RR layer causes the lower layers (layers 1 and 2) of the MS stack to send the standard RIL3-RR layer over the GSM Um interface or BSS over the CDMA Um interface according to the instructions received from the BSS currently in communication. 32) to communicate with the GSM-CDMA RR layer. The MM and CM layers are not processed by the BSS 32 but are relayed between the MS 40 and the MSC 24 for processing in a substantially transparent manner to the underlying CDMA air interface layer. The RR layer of the MS stack also controls handover between corresponding air interfaces, defined in layers 1 and 2, under instructions from the MSC 24 and BSS, and assists in cell selection for handover. .

Regardless of which air interface is being used, the GSM-CDMA RR layer supports the standard GSM RIL3-MM and CM layers thereon. The RR layer preferably provides complete radio resource management functionality as defined by GSM specifications 04.07 and 04.08, which are referenced herein. Although the "RR" layer is not defined by the CDMA IS-95 standard, the GSM-CDMA RR layer described herein maintains full IS-95 radio resource functionality.

According to the GSM standard, the functionality of the RR layer includes both standby mode operation and dedicated mode services (ie, services performed during a phone call). Standby mode operation of the RR layer includes automatic cell selection and standby handover between GSM cells and CDMA cells, between CDMA cells, and between GSM cells, with cell change indications defined by the GSM standard. The RR layer in standby mode also performs broadcast channel processing and establishment of RR connections as specified by the GSM and CDMA standards.

In dedicated mode, the RR layer performs the following services.

라우팅 서비스, 서비스 요청, 메시지의 전달 및 실질적으로 GSM 표준에 의해 지정된 다른 모든 기능들.

Routing services, service requests, delivery of messages and virtually all other functions specified by the GSM standard.

아래에 설명될 하드 핸드오버 및 CDMA에서 CDMA로의 소프트 및 "소프터(softer)" 핸드오버를 포함하는 전용 채널의 변경(핸드오버).

Dedicated channel changes (handovers), including hard handovers and soft and "softer" handovers from CDMA to CDMA, described below.

전송 모드, 채널의 타입 및 코딩/디코딩/트랜스코딩 모드를 포함하는 RR 채널을 위한 모드 세팅.

Mode settings for the RR channel, including the transmission mode, type of channel and coding / decoding / transcoding mode.

IS-95 표준에 기초한 MS 파라미터 관리.

MS parameter management based on the IS-95 standard.

GSM 표준에 기초한 MS 클래스마크 관리.

MS classmark management based on GSM standard.

Those skilled in the art will appreciate that the above features of the RR layer are only listed roughly, and that other features may be added based on the published GSM and CDMA standards.

3A is a block diagram schematically illustrating a protocol stack used to signal interfaces between an MS 40, a CDMA BSS 32, and a GSM MSC 24 according to a preferred embodiment of the present invention. These interfaces allow the MS 40 to communicate with the GSM MSC 24 via the CDMA air interface. The operation of these interfaces and in particular the message flow through these interfaces is described in more detail in the PCT patent application PCT / US96 / 20764 mentioned above. When the MS 40 is communicating over the GSM BSS 30, the protocol stack conforms to the GSM standard without substantially modifying it.

As noted above, the MS 40 exchanges signals with the CDMA BSS 32 via the CDMA Um interface, with the MS and BSS protocol stacks modified to include the GSM-CDMA RR layer and Layer 2. In FIG. 3A, the RELAY layer explicitly expresses the BSS 32 protocol stack to transfer RIL3-CM and MM signaling between the MS 40 and the MSC 24, without processing by the BSS 32. Is shown. Other layers included in the Um interface have been described above with reference to FIG. 2A.

CDMA BSS 32 communicates with GSM MSC 24 via a substantially unmodified standard GSM A-interface. This interface is based on GSM SS7 and BSS Application Part (BSSAP) protocols, preferably in accordance with the GSM 08.08 standard, as known in the art. The BSSAP establishes a procedure between the MSC 24 and the BSS 32 that requires the interpretation and processing of information related to single call and resource management and the transfer of call control and mobility control between the MSC 24 and the MS 40. Support. BSS 32 translates the RR protocol and CDMA Layer 1 and GSM-CDMA Layer 2 exchanged between BBS and MS into the appropriate SS7 and BSSAP protocols for transmission to MSC 24.

Since the CDMA BSC 34 communicates with the GSM MSC 24 using a standard A-interface, substantially no modification is required to the core GSM MSC to add the CDMA BSS 32 to the GSM system 20. . In addition, the MSC 24 need not be aware that any difference exists in the identification between the GSM / TDMA BSS 30 and the CDMA BSS 32. Because both communicate in substantially the same way via the A-interface. Preferably, the cells associated with the BTS 36 of the BSS 32 are mapped by the MSC 24 in substantially the same manner as the GSM / TDMA cells, and according to the GSM standard, the GSM absolute radio frequency channel number (ARFCN) frequency channel number (BSC) and base station identity code (BSIC) values are assigned. From the point of view of the MSC 24, in a typical GSM / TDMA based system, two different CDMA may be used, even handover between the GSM BSS 30 and the CDMA BSS 32 or even between two different CDMA BSSs. It is not different from handover between BSSs. The BSIC of the CDMA cell is assigned to distinguish it from a typical GSM cell in system 20.

3B is a block diagram schematically illustrating a protocol stack involved in transferring voice data between a MS 40 and an MSC 24 via a CDMA BSS 32 in accordance with a preferred embodiment of the present invention. Speech data between the MS 40 and the BSS 32 is coded and decoded by a CDMA vocoder, which is one of the standard IS-95 vocoder protocols known in the art. The BSS 32 translates CDMA Layer 1 into a GSM E1 TDMA signal and converts the CDMA vocoded data into PCM A-rule companded voice data in accordance with the requirements of the A-Interface Standard. The MSC 24 is substantially BSS from or to the MS 40 as if the MS 40 was operating in GSM / TDMA mode, regardless of the fact that the data between the BSS and the MS was CDMA encoded. Voice data is transmitted and received via (32).

4A is a schematic block diagram showing system 20 in detail and is useful for understanding a method for mobile station assisted handover from CDMA BSS 32 to GSM BSS 30 in accordance with a preferred embodiment of the present invention. Unlike FIG. 1, BSS 30 is shown here in detail including BSC 77 and BTS 78 and 80. 4A illustrates a handover of the MS 40 from one of the BTSs 76 associated with the BSS 32 to the BTS 78 of the BSS 30. The BSS 32 also includes a GSM-CDMA BSC 34 and a BTS 36 as described with reference to FIG. 1.

Handover from the CDMA BTS 76 to the TDMA BTS 78 is preferably initiated by the BSS 32 when the MS 40 is in the desired position for such handover to occur. This situation occurs when the signal received from the BTS 76 is weak, when the MS 40 is known to reach the edge of the CDMA coverage area, or when there is heavy traffic on the CDMA channel. Similarly, BSS 32 sometimes directs MS 40 to search for a signal from BTS 78 (or other GSM BTSs).

4B is a schematic signal flow diagram illustrating signals carried between MS 40, BSS 30 and 32 and MSC 24 in the handover process of FIG. 4A, in accordance with a preferred embodiment of the present invention. The BSC 34 instructs the MS 40 to start a gated search for a neighboring GSM BTS, and for a short period of time, the MS 40 stops communicating with the BTS 76 to search and receive TDMA signals. Instruct them to. Preferably, the MS 40 is operating in the IS-95 standard, which allows CDMA transmissions to stay idle for a period of 20 msec frames, where the 20 msec GSM TDMA neighbor scan substantially This can happen without interruption. Likewise, such latency can also be introduced under other CDMA standards. As also described above, the MS 40 may include separate TDMA and CDMA transceivers that may be used simultaneously for this purpose.

Preferably, BSC 34 provides MS 40 with a frequency list of neighboring GSM TDMA cells associated with BTSs 78 and 80. Such a list is effective in reducing the time required to search and find the BTS 78. This is because the MS 40 will search only the frequencies of the cells on the list. This list is updated as the MS 40 moves from one cell to another, and is maintained during handover between TDMA and CDMA base stations.

When the MS 40 receives a signal at the BTS 78 frequency, the MS 40 attempts to decode the GSM Frequency Correction (FCCH) and Synchronization (SCH) channels from the signal. This decoding takes several gated CDMA wait times to complete. Once decoding is successfully performed, the MS 40 determines the power level of the TDMA signal and reports it to the BSS 32 along with the GSM cell identification. Based on this information, the BSS decides when and when to perform a handover. At the appropriate time, the BSS 32 initiates a handover request to the MSC 24. The MSC 24 forwards the handover request to the GSM BSS 30 and notifies that the request has been received. The GSM BSS 30 then sends a handover command to the MS 40 via the MSC 24 and the CDMA BSS 32, and the GSM BSS 30 opens a new traffic channel (TCH) with the MS. . At this point, the handover is complete and the MS 40 switches over to the BTS 78.

The handover initiation decision occurs whenever the signal from the GSM BTS 78 is stronger than the signal from the CDMA BTS 76. However, other criteria preferably apply. For example, since a CDMA channel typically supports better transmission than a GSM channel, the handover preferably begins only when the GSM signal is stronger by some predetermined weight than the CDMA signal. The factor may be preprogrammed in the system 20 or set by the user of the MS 40. The factor is dynamically adjusted according to parameters such as the geographic location of the MS and the relative amount of traffic on the CDMA and TDMA channels in the system.

FIG. 5 is a schematic block diagram showing signal flow in the system 20 of FIG. 1 related to providing time of the day information to the system's appropriate GSM BSC and BTS, according to a preferred embodiment of the present invention. It is a diagram. Normally, the GSM BSS of the system 20 will not be informed of the time information. This is because this information is not required by the GSM standard. On the other hand, the IS-95 standard requires CDMA base stations to be synchronized because synchronization is required for identification and decoding of signals and soft handover between cells. Therefore, for mobile station assisted handover of the MS 40 from the TDMA BTS 78 to the CDMA 76 (as shown in FIG. 4A, the direction of the arrow is reversed), time information is provided by the system 20. Need to be.

The method of FIG. 5 allows time information to be provided to the system 20 without any hardware or software changes in the MSC 24, the GSM BSS 30 or the BTSs 78 and 80. Normally, the CBC 28 provides a cell broadcast service (CBS) in accordance with the GSM interface standards 03.41 and 03.49 to allow a general short message to be broadcast in the system 20. The messages are received by the MS 40 while in the ready or standby mode (ie, while the MS is not in a phone call). However, to provide time information, the MS 40 may preferably receive a CBS message not only when in the standby mode defined by the GSM standard, but also when the MS is in a dedicated mode, i. The use of a CBS to provide time information to the MS 40 is particularly desirable when the MS includes only one wireless transceiver, as shown in FIG. 2B. That is, when one dual transceiver is used for CDMA and the other dual receiver for TDMA, the CDMA wireless transceiver can receive time information even when the TDMA wireless transceiver is used for a telephone call.

In a preferred embodiment of the present invention, CBS messages are used to initiate a search of neighbor cells by the MS 40, as described with reference to FIG. 4B above.

A special MS 90 with a GPS receiver 91 is located in one or more GSM / TDMA cells in the system 20 where time information is needed. In FIG. 5, MS 90 receives time information from receiver 91 and associates this time with concurrent TDMA frame number identification based on a synchronization signal sent by BTS 78 according to the GSM standard. . Alternatively, the MS 90 may be configured to receive time information from the CDMA BSS, in which case the GPS receiver 91 is not required. The MS 90 opens the data call to the CBC 28 via the BTS 78, BSC 77, MSC 24 and PSTN / PDN 48, and sends the cell identification and current time and frame number to the CBC. To pass. The MS 90 may communicate the information in other suitable ways, such as using GSM SMS. The CBC 28 sends this information to the cell via the CBC, and the MS 40 receives time information even when operating in the GSM / TDMA mode. Therefore, when the MS 40 is handed over to the CDMA BTS 76, there is no need to obtain synchronization / time information from the CDMA BTS, and the handover can proceed faster and smoother.

Introducing time information into the system 20 also has advantages for the GSM system itself without regard to CDMA handover. For example, the MS 40 can pass time information to different GSM BTSs 78 and 80, and the time delay from the MS to each BTS can be measured and used to determine the location of the MS.

6 is a schematic map of overlapping of GSM / TDMA cell 92 and CDMA cell 94 in network 20, from GSM BTS 78 to CDMA BTS 76 according to a preferred embodiment of the present invention. Aspects of mobile station assisted handover are described. The operator of the system 20 will recognize that if the MS 40 is located in any of the cells 1-5 shown in FIG. 6, TDMA / CDMA handover occurs. Therefore, the CBC 28 will broadcast a CBC message to all dual-mode (GSM / CDMA) MSs in these cells, and the CBC message contains the following information and instructions.

MS에 의한 CDMA 신호 서치 개시(서치 트리거).

CDMA signal search initiation (search trigger) by the MS.

오버래핑 및 이웃하는 셀에서의 CDMA BTS의 주파수.

Frequency of CDMA BTS in overlapping and neighboring cells.

GSM MSC(24)에 따라 CDMA 셀(94)의 GSM 매핑.

GSM mapping of CDMA cell 94 according to GSM MSC 24.

다른 방법들도 시간 정보를 제공하는데 사용될 수 있지만, 바람직하게 MS(90)에서 유도되는 것과 같이 현재의 TDMA 프레임 번호와 함께 시간 정보를 식별.

Other methods may also be used to provide the time information, but preferably identify the time information along with the current TDMA frame number as derived at the MS 90.

선택적으로, 위에 설명된 바와 같이, TDMA 신호와 비교하여 CDMA 신호 강도에 곱하여질 인자.

Optionally, a factor to be multiplied by the CDMA signal strength as compared to the TDMA signal as described above.

Such a message need not be broadcast to cells 6-10. In addition, it will be appreciated that only dual mode MSs are programmed to receive and interpret this message, while a normal GSM / TDMA MS will ignore it. Unlike the hybrid GSM / CDMA system proposed in the prior art, the CBS message collects information for assisting the handover to one of the CDMA BSSs by the dual-mode MS, and the GSM BSS 30 and the MSC 24 To be available).

7 is a block diagram illustrating signal flow in a system 20 associated with mobile station assisted handover from BTS 78 to BTS 76, in accordance with a more preferred embodiment of the present invention. As discussed above with reference to FIG. 6, the handover begins with the delivery of search triggers and other information. The search trigger is sent by the BTS 78 periodically whenever the MS 40 is in one of GSM cells 1-5, or in accordance with some other pre-programmed condition.

Upon receiving the trigger, MS 40 shuts down the TDMA traffic of BTS 78 and tunes its receiver to the appropriate CDMA frequency for a short period of time, preferably about 5 msec. The MS attempts to decode any CDMA signal received by the MS after reestablishing communication with the BTS 78, for example to identify the pilot beam of the BTS from the BTS 76. As seen above, the BTS 76 is mapped to the system 20, assuming a typical GSM / TDMA BTS. Therefore, the MS 40, together with the GSM map identification signal of the BTS 76, reports a signal indicating the power of the signal received from the BTS 76 (optionally multiplied by the relative CDMA / TDMA weighting factor mentioned above). Is sent back to the GSM BTS 78. From the perspective of the GSM BSS 30 and the MSC 24, there is no substantial difference between the message sent by the MS 40 and the message sent as a result of a normal GSM neighbor scan in this case.

This measurement and reporting process continues until the BSS 30 determines that the MS 40 should be handed over to the BTS 76. At this point, BSS 30 sends a message to MSC 24 indicating that handover is required. The MSC 24 forwards the handover request to the BSS 32, which sends a receipt notification back to the BSS 30 via the MSC 24. The GSM BSS 30 passes a handover command to the MS 40, and a traffic channel is opened between the MS 40 and the CDMA BTS 76, and the handover is completed.

The above mentioned process allows mobile station assisted handover to be delivered from GSM / TDMA BSS 30 to CDMA BSS 32 with minimal interruption of call service during high speed, high reliability and handover. For this handover, the GSM cells of the system 20 receive time information and CDMA cells are mapped to the GSM system with minimal hardware cost and substantially no need to reprogram the current GSM system element.

Similar TDMA-CDMA handover process may be performed without time information in GSM BSS 30. In this case, after the MS 40 acquires the pilot channel signal associated with the BTS 76, the MS 40 must be tuned to the CDMA synchronization channel of the BTS to derive time information and set up the CDMA synchronization channel of the BTS. Must be decoded. This operation takes about 300 msec and results in a non-negligible but interruption of the voice service during the call. Alternatively, as described above, a similar handover process may be performed using an MS having a total of two transceivers, one for TDMA and the other for CDMA.

8 is a schematic block diagram illustrating handover between two different CDMA BSSs 101 and 103 in a system 20, according to a preferred embodiment of the present invention. BSS 101 includes BSC 102 and multiple BTSs 106 and 108, and BSS 103 includes BSC 104 and multiple BTSs 110 and 112. The BSSs 101 and 103 are substantially similar to the BSS 32 shown in FIG. 1 and described above, are interchangeable with the BSS 32 and communicate with the GSM MSC 24 via an A-interface. Can be. MS 40 is presented as being in handover from BTS 108 to BTS 110 under the control of MSC 24. From the system's point of view, although the handover occurs between two CDMA BSSs, this is a handover between two GSM BSSs, and the BTSs 108 and 110 are mapped to GSM cells by the MSC 24, respectively. do.

FIG. 9 is a schematic diagram illustrating signal flow between elements of the system 20 during handover shown in FIG. 8, in accordance with a preferred embodiment of the present invention. The handover is triggered when the MS 40 reports to the BSS 101 that it is receiving a signal from the BTS 110 having a power level higher than that of the BTS 108. The BSS 101 sends a standard GSM handover-needed message to the MSC 24, which defines the GSM cell identification of the BTS 110 as a new cell assignment desirable for handover. The MSC 24 sends a handover request to the BSS 103, and the BSS 103 responds by sending an acknowledgment signal insulating the RIL3-RR handover command message to the MSC 24, and RIL3-RR. The handover command message is sent to the BSS 101. Thus, all messages sent between BSSs 101 and 103 are subject to the A-Interface requirement, and the CDMA parameters associated with IS-95 are the GSM full, in the 13K QCELP vocoder type of CDMA, for example The mapping is done with a rate vocoder. The handover request, receipt notification and command are delivered by MSC 24 without substantial change.

After receiving the handover command, the old BSS 101 sends an RR handover command message to the MS 40 to achieve a handover to the new BSS 103. The message to the MS 40 is

CDMA 표준에 따른 새로운 긴 코드 마스크

New long code masks according to the CDMA standard

공칭 전력 레벨 파라미터

Nominal power level parameter

프레임 오프셋

Frame offset

코드 채널

Code channel

층2 수신 확인 넘버링(numbering)

Layer 2 acknowledgment numbering

순방향 트래픽 채널 전력 제어 파라미터

Forward Traffic Channel Power Control Parameters

프리앰블 번호

Preamble number

새로운 밴드의 클래스 및 주파수.

New band class and frequency.

Although preferred embodiments have been described above with reference to a specific hybrid GSM / CDMA system, the principles of the present invention can similarly be applied to achieving mobile station assisted handover in other hybrid communication systems. In addition, while the preferred embodiments refer to specific TDMA- and CDMA-based communication standards, those skilled in the art will recognize that the methods and principles described above may be used in connection with other data encoding and signal modulation methods. The scope of the present invention includes not only the complete system and communication process described above, but also various innovative elements of such systems and processes and their combinations and subcombinations.

It will be appreciated that the preferred embodiments described above are merely exemplary and that the scope of the present invention is limited only by the claims.

Claims (92)

Receiving at the mobile station 40 a signal transmitted from a second base station over a second air interface while maintaining communication with the first base station; Transmitting data to the first base station 32 over the first air interface in response to the signal received from the mobile station 40; Handing over the mobile station from the first base station 32 to the second base station 30 in response to the data received from the mobile station, the handover using a handover command received by the mobile station 40. A method of performing a handover of a mobile station 40 communicating with a first base station 32 over a first air interface of the mobile communication system 20 to a second base station 30 operating according to a second air interface, as performed. , The first base station 32 is one of a CDMA or TDMA base station, the first air interface is a CDMA or TDMA air interface, respectively, Wherein the second base station (30) is the other of the CDMA or TDMA base stations, and the second air interface is the CDMA or TDMA air interface, respectively. 2. The method of claim 1, wherein the data includes measurements of signal strength, and wherein handing over the mobile station comprises comparing signal strength measurements from the first and second base stations and handing over the mobile station according to the comparison result. And wherein the comparing step is performed by at least one of the first base station (32), the second base station (30), the mobile station (40), and the MSC (24). 3. The handover method of claim 2, further comprising applying a weighting factor to the measurement of the signal strength. 4. The method of claim 3 wherein applying the weighter comprises changing the weighting factor in accordance with a network condition of a system. 4. The handover method of claim 3, wherein applying the weighted party comprises transmitting the weighted party to the mobile station via a communication link, the mobile station applying the weighted party to the measurement. . 2. The method of claim 1 wherein the data comprises identification of a second base station based on decoding by a mobile station of a signal received via a second air interface. 2. The method of claim 1, further comprising the mobile station transmitting a frequency list of a second type base station in the system from the first base station to the mobile station to attempt to receive a signal at a frequency in a second type base station frequency list. A handover method characterized by the above. 2. The method of claim 1 wherein handing over the mobile station comprises sending a handover command from the first base station. 2. The method of claim 1 wherein the step of receiving a signal at the mobile station uses a single RF transceiver at the mobile station. delete 10. The method according to any one of the preceding claims, wherein the TDMA interface comprises a GSM interface, and the GSM interface is configured to carry a GSM network message. 10. The method according to any one of the preceding claims, wherein the CDMA interface is based on the IS-95 standard. 10. A method according to any of the preceding claims, wherein a single radio resource management protocol layer is used to manage the first air interface, and handing over the mobile station comprises the single air resource to manage the second air interface. Using a radio resource management protocol layer. 2. The method of claim 1, wherein an overlap area is defined between a first area serviced by the first air interface and a second area serviced by the second air interface, and triggering the mobile station when the mobile station is in the overlap area. Handover method further comprising the step of. 10. The method of any of claims 1 to 9, wherein the first air interface comprises a CDMA interface, the second air interface comprises a GSM / TDMA interface, and receiving data from the mobile station comprises: GSM / Gating said mobile station to receive and decode a TDMA signal, thereby interrupting a CDMA communication link. 16. The method of claim 15, wherein gating the mobile station comprises suspending CDMA communication for one IS-95 frame duration. 16. The handover method of claim 15, wherein transmitting the data comprises transmitting a second base station identification based on a GSM frequency correction and decoding of a synchronization channel for the signal by the mobile station. . 2. The method of claim 1, wherein the first air interface comprises a GSM / TDMA interface, the second air interface comprises a CDMA interface, and receiving a signal at the mobile station comprises receiving the mobile station to receive and decode a CDMA signal. Stopping the communication link by controlling the handover method. delete delete delete delete 19. The method of claim 18, further comprising forwarding a GSM cell broadcast service message to the mobile station to cause the mobile station to begin searching for a signal from a second type base station. 24. The method of claim 23, wherein forwarding the GSM cell broadcast service message to the mobile station comprises forwarding the message to be received by the mobile station while the mobile station is operating in dedicated mode. Handover method. 19. The method of claim 18, wherein transmitting data from the mobile station comprises transmitting an identification of a CDMA pilot beam decoded by the mobile station. A handover method characterized by the above. 19. The handover method of claim 18, further comprising mapping the second base station to a GSM base station to control the handover. 19. The method of claim 18, wherein controlling the mobile station comprises receiving the CDMA signal during a first TDMA time slot, communicating with a base station via a TDMA interface to generate data to be transmitted by the base station. Controlling the mobile station to decode the signal during a TDMA time slot. delete delete delete delete delete delete delete delete delete The method of claim 1 wherein the mobile wireless communications system 20 is a GSM mobile wireless communications system, the method comprising Mapping a CDMA base station operating according to a CDMA air interface to a GSM / TDMA base station; Substantially assuming both the first and second base stations are GSM / TDMA base stations, the signal strength received from the first base station over the first air interface is compared with the signal strength transmitted from the second base station over the second air interface. Making; And And handing over the mobile station from the first base station to the second base station according to the comparison result of the signal strengths. 38. The method of claim 37, wherein mapping the CDMA base station comprises assigning a GSM frequency and location to the base station. 38. The method of claim 37, further comprising communicating a message between the first and second base stations and a mobile switching center of the system via a GSM A-interface. 40. The method of claim 39 wherein both the first and second base stations operate according to the CDMA air interface. 41. The handover of claim 40, wherein handing over the mobile station comprises passing a new IS-95 long code over the A-interface without substantially violating the A-Interface protocol. Way. 38. The handover of claim 37, further comprising applying a weighter to a second signal, wherein comparing the strength of the signal comprises comparing the signal given the weighter Way. 43. The method of claim 42 wherein applying the weighted party comprises delivering the weighted party to the mobile station and the mobile station applying the weighted party to a second signal. 43. The method of claim 42 wherein applying the weighted party comprises changing the factor according to the network state of the system. A base station 32 of a first type for transmitting and receiving a first signal in accordance with a first air interface; A base station 30 of a second type for transmitting and receiving a second signal in accordance with a second air interface; And Receive a second signal over a second air interface from a second type base station while maintaining a communication link over the first air interface with a base station of the first type, and also in response to the second signal to the base station of the first type. A wireless communication device for use in a wireless mobile communication system 20 comprising a mobile station 40 which transmits data and causes the mobile station to hand over from the first base station to the second base station in response to the transmitted data, The first base station 32 is one of a CDMA or TDMA base station, the first air interface is a CDMA or TDMA air interface, respectively, The second base station (30) is the other of the CDMA or TDMA base station, and the second air interface is a CDMA or TDMA air interface, respectively. 46. The wireless communications apparatus of claim 45, wherein the data transmitted by the mobile station includes a measure of signal strength, the mobile station being handed over in response to a signal strength comparison of the first and second signals. 47. The wireless communications apparatus of claim 46, wherein the weighting factor is applied to signal strength measurements. 48. The wireless communication device of claim 47, wherein the weighting factor is changed in accordance with a network state of the system. 47. The wireless communications apparatus of claim 46, wherein the weighted party is sent to the mobile station via a communication link and the mobile station applies the weighted party to the measurements. 46. The wireless communications apparatus of claim 45, wherein the mobile station decodes a second signal to determine identification of a second type base station. 46. The wireless system of claim 45, wherein the first type base station transmits to the mobile station a frequency list of the second type mobile station of the system, the mobile station attempting to receive a second signal at a frequency in the list. Communication device. 46. The wireless communications apparatus of claim 45, wherein the first type base station sends a handover command to the mobile station, whereby the mobile station is handed over from the first base station to the second base station. 46. The wireless communications apparatus of claim 45, wherein the mobile station comprises a single RF transceiver (42) in communication with both the first and second types of base stations. delete 54. The wireless communication device of any one of claims 45-53, wherein the TDMA interface comprises a GSM interface and the CDMA interface is configured to carry a GSM network message. 54. The wireless communications device of any one of claims 45-53, wherein the CDMA interface is based on an IS-95 standard. 54. The wireless communications apparatus of any of claims 45-53, wherein the mobile station adjusts the first and second air interfaces using a single radio resource management protocol layer. 46. The mobile station of claim 45, wherein the base station triggers the mobile station when the mobile station is in an overlap area between a first area serviced by the first air interface and a second area serviced by the second air interface. 2 receive a second signal via an air interface. 46. The mobile station of claim 45 wherein the first air interface comprises a CDMA interface, the second air interface comprises a GSM / TDMA interface, and wherein the first type base station is configured to receive and decode a GSM signal. Gating to interrupt the communication link. 60. The wireless communications apparatus of claim 59, wherein the mobile station suspends the link for one IS-95 frame duration. 60. The wireless communications apparatus of claim 59, wherein the mobile station processes a second signal to decode a GSM frequency correction and synchronization channel of the signal. 46. The method of claim 45, wherein the first air interface comprises a GSM / TDMA interface, the second air interface comprises a CDMA interface, and the first type base station controls the mobile station to receive and decode CDMA signals. Wireless communication device for interrupting the communication link. 63. The wireless communications apparatus of claim 62, further comprising means for mapping a second base station to a GSM base station to control handover. delete delete delete 63. The wireless communications apparatus of claim 62, comprising a GSM cell broadcast center (28) for delivering a cell broadcast service message to the mobile station to initiate a second signal search by the mobile station. 68. The wireless communications apparatus of claim 67, wherein while the mobile station is operating in a dedicated mode, the mobile station receives the cell broadcast service message. 63. The wireless communications apparatus of claim 62, wherein the mobile station processes the CDMA signal to identify a CDMA pilot beam. 63. The mobile station of claim 62, wherein the mobile station receives the CDMA signal during a first TDMA time slot and processes the signal during a subsequent TDMA time slot while communicating with the base station via a TDMA interface to generate data for transmission to the base station. A wireless communication device, characterized in that. delete delete delete delete delete delete delete delete delete delete delete 46. The system of claim 45 wherein the mobile wireless communications system 20 is a GSM communications system. Means for mapping the CDMA base station in a GSM system to a GSM base station, wherein the first base station and the second base station are both operated by the mobile station as if both were operating substantially in accordance with a GSM / TDMA air interface. And the mobile station is handed over from the first base station to the second base station according to a signal strength comparison between the first base station and the second base station signals. 83. The wireless communications apparatus of claim 82, wherein the CDMA base station is assigned a GSM frequency and a location in the system. 83. The wireless communications apparatus of claim 82, wherein messages are communicated over a GSM A-interface between first and second base stations and a mobile switching center of the system. 86. The wireless communications apparatus of claim 84, wherein both the first and second signals comprise CDMA signals. 86. The method of claim 85, wherein a new IS-95 long code is communicated from a second base station to a first base station via the A-interface without substantially violating an A-interface protocol to handover the mobile station. Wireless communication device. 83. The wireless communications apparatus of claim 82, wherein the mobile station applies a weighting factor to the second signal before the signal strengths are compared. delete delete delete delete delete

Images