HK1070531B

HK1070531B - Wireless telecommunications system utilizing cdma radio frequency signal modulation in conjunction with the gsm a-interface telecommunications network protocol

Info

Publication number: HK1070531B
Application number: HK05103126.6A
Authority: HK
Inventors: M．K．斯巴茨; B．R．罗宾斯; D．H．阿格瑞
Original assignee: 高通股份有限公司
Priority date: 1995-12-20
Filing date: 2005-04-13
Publication date: 2009-02-06

Description

Wireless telecommunications system using CDMA radio frequency signal modulation

This application is a divisional application of the invention patent application with application number 96192005.X filed by the same applicant at 12/18/1996.

Technical Field

The present invention relates to wireless telecommunications technology. More particularly, the present invention relates to a new and improved method and apparatus for providing wireless telecommunication services utilizing a Code Division Multiple Access (CDMA) "over-the-air" interface in conjunction with an interface of a global system for mobile communications (GSM) a interface protocol.

Background

The global system for mobile communications (GSM) wireless telecommunications standard is a widely used set of digital telecommunications protocols in digital wireless telephone systems. Under international co-effort, the GSM specifications were developed and have been adopted by the european telecommunications standards institute (ETSI, 06921 Sophia Antipolis Cedex, France). Figure 1 shows a radio telephone system with a structure according to the GSM standard. A GSM mobile services switching center (MSC)16 switches or connects telephone calls between a radio system access network, i.e., a Base Station Subsystem (BSS)15, and a wired Public Switched Telephone Network (PSTN)18, which may also be a Public Land Mobile Network (PLMN). The GSM-MSC 16 provides telephone switching, billing, subscriber unit tracking, subscriber unit authorization, and some handover control functions. The BSS 15 is formed by a Base Station Controller (BSC)14 and a Base Transceiver Station (BTS)12 coupled thereto. As defined by the GSM specification, the interface between the GSM-MSC 16 and the BSS 15 is referred to as the GSM "a interface," which separates the GSM network switching equipment from the Time Division Multiple Access (TDMA) radio equipment. BSC 14 is involved in the handover processing and allocation of signal processing resources within BTS12 so that multiple subscriber units 10 may be engaged in telephone calls simultaneously. The BTS12 interfaces the subscriber unit 10 to the GSM wireless network via Radio Frequency (RF) signals and a well-defined "over-the-air" protocol. The BTS12 includes radio transmitting and receiving equipment (including antenna equipment) and all signal processing specifications that interface with the radio waves. The BTS may be considered a composite radio modem. Subscriber unit 10 provides general radio and processing functions for accessing the GSM network through a radio interface with a subscriber of subscriber unit 10 or other terminal equipment, such as a facsimile machine or personal computer. A particular subscriber unit 10 may switch the BTS12 with which it interfaces as the location changes, but at a given time he may only be able to communicate with one BTS 12. In such applications, the ability to switch from one BTS12 to another BTS12 when only one radio interface is present at any one time is referred to as a subscriber unit hard handoff.

In order to make a wireless telephone call, a network connection must be established between the subscriber unit 10 (commonly referred to as a "mobile unit") and the PSTN 18. The PSTN18 is a common wired telephone system. To make a telephone call in a mobile manner, a portion of the network connection is formed between subscriber unit 10 and BTS12 via the switching of Radio Frequency (RF) signals. The remainder of the network connection is typically formed by a wired connection through the BSS 15 and the GSM-MSC 16. TDMA technology is used to establish a set of channels within the identifying RF signals that interface subscriber unit 10 with BTS12 as described above, in accordance with an "over the air" protocol, which is one of the GSM wireless telecommunications standard protocols. These channels are used to separate and distinguish groups of data associated with various telephone calls made at any given moment. Each set of data includes user data, typically digitized audio information, and signaling data consisting of signaling messages used to coordinate the processing of managed telephone calls.

The use of TDMA in GSM over-the-air protocols improves the efficiency of use of a given radio frequency bandwidth for making radiotelephone calls when the GSM standard is established. Since the amount of RF bandwidth is limited and bandwidth is often the limiting factor in the number of calls in a particular wireless cellular telephone system, there is a need to increase the efficiency of the use of radio frequency bandwidth. Since the establishment of the GSM wireless telecommunications protocol, however, other wireless technologies have evolved to enable a greater number of telephone calls within a given RF bandwidth. Since the efficiency of the use of wireless bandwidth is a particularly important consideration, there is a trend towards more efficient techniques.

One attractive and widely used more efficient wireless telecommunication technology IS Code Division Multiple Access (CDMA) signal processing and the relevant air IS-95 protocol adopted by the international telecommunications association (TIA, 2001 Pennsylvania Avenue, n.w., Washington, d.c. 20006). With CDMA modulation techniques, the traffic channel for each user consists of a carrier wave that is modulated with a different high-speed binary sequence, thereby spreading the waveform spectrum. The user traffic channel group shares the same broadband spectrum allocation and both user data and signaling messages are sent over the user traffic channel. In addition, each CDMA-based BTS transmits an additional control signaling channel carrying information that enables the subscriber unit to acquire and access the system. These additional control channels are also modulated with the high speed binary sequence and combined with the user traffic channels to form a wideband RF signal. Each CDMA-based BTS transmits a combined RF signal, referred to as a forward CDMA channel, and receives the combined RF output of a set of CDMA-based subscriber units within the associated coverage area, referred to as a reverse CDMA channel. The forward CDMA channel is the sum of a forward pilot channel, a forward synchronization channel, one or more forward paging channels, and a plurality of forward user traffic channels, all modulated with distinct channel codes and combined with a PN spreading sequence. A reverse CDMA channel is the sum of one or more access channels and a plurality of reverse user traffic channels, all modulated by a unique channel code and transmitted with a particular PN spreading sequence.

The CDMA based wireless communication system also provides an improved method of mobile handoff of a subscriber unit. A handoff procedure known as "soft handoff" may utilize the RF signal of one subscriber unit over more than one CDMA-based BTS. This ability of the subscriber unit 10 to make multiple RF interfaces with multiple CDMA based BTSs 12 simultaneously provides redundancy in the transmission path as the subscriber unit 10 moves from one location to another, thereby reducing the likelihood of call drops and voice sample loss. In addition, the IS-95 protocol provides higher quality telecommunications services than GSM because CDMA signals are less subject to attenuation and noise interference. Since the widely used power control algorithm IS involved in the normal operation of a CDMA system, subscriber units communicating according to the IS-95 protocol consume less power than those communicating according to the GSM over-the-air protocol. The reduction in power consumption extends the life of the battery powering the IS-95 subscriber unit as compared to the case of GSM subscriber units.

Despite the many advantages, many areas that employ GSM cellular telephone systems are still reluctant to provide CDMA cellular telephone service. This is because the improvement in performance of a CDMA system, while still usable in an existing system, is not sufficient to offset the expense of fully utilizing a new CDMA cellular telephone system. This situation is quite different from building a new cellular telephone system from scratch in a region where CDMA cellular telephones are less costly and provide higher quality of service than GSM cellular telephone systems. However, if a method and system were invented for a CDMA cellular system that could utilize a portion of the infrastructure of an existing GSM cellular telephone system, the cost of providing CDMA cellular telephone service in the area where the GSM cellular telephone system is operating could be reduced. More areas may benefit from the high performance provided by CDMA cellular telephone systems if the magnitude of the cost reduction is large enough. This would also benefit users of cellular telephone service in those regions and therefore a method and system for implementing a cellular telephone system would be highly desirable in the marketplace.

Disclosure of Invention

According to a first aspect of the present invention, there is provided a method for processing signaling messages in a base station subsystem, comprising the steps of: transparently transmitting a direct transfer application part message received from the subscriber unit to a mobile switching center of the global system for mobile communications; and internally processing code division multiple access signaling messages from the subscriber units.

According to a second aspect of the present invention, there is provided a method of processing signalling messages in a base station subsystem, comprising the steps of: a) transparently switching to the subscriber unit a direct handover application part signaling message received from a mobile switching center of the gsm; and b) internally processing base station subsystem mobile application part messages received from a mobile switching center of the global system for mobile communications.

According to a third aspect of the present invention there is provided a method of operating an interface system, comprising the steps of: a) receiving a signaling message containing content; b) if the signaling message is a direct transfer application part message, transparently transmitting the content of the signaling message; c) and if the message is a mobile application part message of the base station subsystem, processing the signaling message according to the content.

According to a fourth aspect of the present invention, there is provided a base station subsystem comprising: a signaling message processing system, for transparently transmitting the signaling message if the signaling message is a direct transmission application part message, and processing the signaling message according to the content if the message is a base station subsystem mobile application part message; and a radio frequency signal processing system for establishing a radio frequency interface using radio frequency signal processing according to a code division multiple access signal processing technique.

According to a fifth aspect of the present invention, there is provided a base station subsystem for use in a telecommunications system, comprising: means for providing transparent switching of a first set of signaling messages between the subscriber unit and the mobile switching center; selector means for transparently sending direct transfer application part messages received from a telecommunications network to said subscriber unit and for transparently transferring direct transfer application part messages received from said subscriber unit to said telecommunications network; interface means for transparently sending to said subscriber unit direct transfer application part messages received from a telecommunications network and for transparently transferring to said telecommunications network direct transfer application part messages received from said subscriber unit; and means for configuring the base station subsystem to respond to a second set of signaling messages from the subscriber unit and the mobile switching center.

A method and apparatus for operating a telecommunications system utilizing a CDMA over-the-air protocol in a network based on a GSM a interface is discussed below. Using the GSM a interface standard (which is defined in the GSM specification as the interface between a GSM-MSC and a BSS), a CDMA wireless telecommunications system can be implemented using a GSM-MSC that conforms to the GSM specification. This allows the CDMA wireless cellular telephone service to be provided using the already operating GSM network portion infrastructure. In the preferred embodiment of the present invention, the CDMA based BSC communicates with the GSM-MSC via the a interface (which is defined in the existing GSM standard). However, other embodiments of the present invention employ improvements to the defined GSM a interface to improve the operational capabilities and functionality of the system. According to one embodiment of the invention, the interface of the BBS with the subscriber unit is via radio frequency signals that are physically modulated according to CDMA techniques. In the preferred embodiment of the present invention, the CDMA modulation technique IS substantially identical to that contained in the previously mentioned IS-95 wireless telecommunications protocol.

Fig. 2 shows a schematic diagram of functional units used to interface a subscriber unit with a GSM-MSC according to one embodiment of the present invention. During system operation, CDMA RF interface 40 provides a bi-directional interface to subscriber unit 50, while GSM a interface SS7 transport 42 provides a bi-directional interface with GSM-MSC 52. The establishment of the CDMA air interface and the use of transparent signaling transport 44 allows signaling messages defined by the GSM a interface protocol to be exchanged between GSM-MSC52 and subscriber unit 50. The processing and service session 46 receives and examines certain signaling messages from the CDMA RF interface 40 and the GSM a interface SS7 transport 42, and then responds with various responses, including configuration and control of the signal processing resources 48. Configuration and control here includes allocation of vocoding and vocoding resources and invocation of CDMA encryption capabilities according to the type of request for service. Other responses include allocation of CDMA traffic channel processing resources and resource selection when the signaling exchange between the subscriber unit and the BSS or MSC begins. These resources are allocated to the processing of voice and data calls and the exchange of signaling (e.g., registration) between subscriber unit 50 and the system. CDMA traffic channel resources are used to implement IS-95 style CDMA modulation and demodulation functions.

To accomplish various tasks associated with properly handling a radiotelephone call or communication, a set of call handling procedures are provided. These procedures include call initiation, call release, subscriber unit registration, over-the-air signal encryption, subscriber unit acknowledgement, and serialization of signaling messages, and the processing steps associated with these procedures are described in greater detail below. In accordance with the described embodiment of the invention, call initiation and subscriber unit registration is accomplished by first establishing a CDMA air interface between the subscriber unit and a CDMA-based BSS and then establishing a telecommunications network connection between the subscriber unit and the GSM-NSC. The invention also adopts CDMA encryption technology. The CDMA encryption technique used to provide user information and location security is initialized and terminated via GSM encryption procedures controlled by GSM-MSC 52.

In one embodiment of the present invention, transparent signaling 44 transparently passes signaling information between GSM-MSC52 and subscriber unit 50. Transparent transport is defined as the exchange of signaling information between GSM-MSC52 and subscriber unit 50 such that there are no intermediate processing units to examine, modify, and use the information of the transparent transport. The transparent transport mechanism allows the key portion of the application layer information exchanged between the CDMA based BTS and the subscriber unit to be the same as the information exchanged between the GSM TDMA based BTS and the relevant GSM subscriber unit. In the preferred embodiment of the present invention, the messages passed by transparent signaling 44 are Direct Transfer Application Part (DTAP) messages defined in the GSM specification as being between GSM-MSC52 and subscriber unit 50. The DTAP message allows GSM-MSC52 to exchange data with subscriber unit 50 as needed to accurately process GSM-based telephone calls. The DTAP message classification includes call management and subscriber unit mobility management functions. The transparent transmission of call management and subscriber unit mobility management messages between GSM-MSCs allows the present invention to make use of existing procedures associated with GSM call setup. This allows the present invention to take advantage of the existing GSM a interface definition, thereby allowing an operator of a GSM wireless communication system to re-use existing GSM infrastructure equipment to form a wireless communication system site utilizing a CDMA over-the-air protocol with a GSM a interface based network.

In accordance with the present invention, a subscriber unit acquires a system, records system-related information received from a BTS located on a forward CDMA supplemental channel, and is then configured to receive, process and transmit signaling messages used to establish a bi-directional CDMA air interface and telecommunications network connection. The subscriber unit receives and appropriately processes CDMA radio resources, GSM call management, and GSM mobility management signaling messages. GSM call management and GSM mobility management include the DTAP portion of the GSMA interface. CDMA radio resource procedures include, but are not limited to, performing functions such as handoff, system access, and bi-directional RF signal traffic channel establishment. GSM call management procedures include, but are not limited to, performing functions such as call setup, supplementary service invocation, and subscriber unit alerting. GSM mobility management procedures include, but are not limited to, attach and detach procedures that perform subscriber unit validation, location updating, and international mobile station identification.

Brief description of the drawings

A further understanding of the nature, objects, and advantages of the invention will become apparent from the following description of the invention when taken in conjunction with the accompanying drawings. Like reference symbols in the various drawings indicate like elements.

FIG. 1 is a block diagram of a cellular telephone system configured in accordance with the GSM standard;

fig. 2 is a functional schematic block diagram of a message handling and service session structure for a subscriber unit interfacing with a GSM-MSC in accordance with one embodiment of the present invention;

FIG. 3 is a schematic block diagram of a cellular telephone system configured in accordance with one embodiment of the present invention;

FIG. 4 is a diagram showing various GSM A interface message formats transmitted using signaling system number 7 interface;

FIG. 5 is a schematic block diagram of a base station subsystem configured in accordance with one embodiment of the present invention;

fig. 6 is a message sequence diagram illustrating signaling messages sent during a subscriber unit terminated call initialization, performed in accordance with one embodiment of the present invention;

fig. 7 is a message sequence diagram illustrating signaling messages sent during initiation of a call by a subscriber unit, accomplished in accordance with one embodiment of the present invention;

fig. 8 is a message sequence diagram illustrating signaling messages sent during a subscriber unit initiated call release, accomplished in accordance with one embodiment of the present invention;

fig. 9 is a message sequence diagram illustrating signaling messages sent during an initial call release of a network, which is accomplished in accordance with one embodiment of the present invention;

FIGS. 10A and 10B are message sequence diagrams illustrating signaling messages sent during a subscriber unit registration completed in accordance with one embodiment of the present invention;

fig. 11 is a schematic block diagram of a BSC a interface configured in accordance with one embodiment of the invention; and

fig. 12 is a schematic block diagram of a subscriber unit configured in accordance with one embodiment of the present invention.

Best mode for carrying out the invention

A method and apparatus for providing wireless telecommunications services using a Code Division Multiple Access (CDMA) air interface and a global system for mobile communications (GSM) a-interface protocol network interface is described. In the following description, the invention IS implemented in the context of a radio frequency signal interface enabled by physical signal modulation techniques in accordance with the IS-95CDMA over-the-air protocol. Although the described invention is particularly well suited for use in such signal modulation techniques, other code division multiple access wireless telecommunications protocols are compatible with the present invention. And while the preferred embodiment of the present invention employs the GSM a interface, other a interfaces may be enabled when a transparent transport mechanism is required between the mobile switching center and the subscriber unit. The invention may also be implemented in a satellite based telecommunications system, or in a point-to-point wireless telecommunications system. The invention is useful in satellite wireless telecommunications systems that employ "bent pipe" transmission methods that must interface with telecommunications network gateways, particularly since many gateways will employ the GSM a interface protocol. It should also be understood that the present invention is intended to apply to various types of communications, including voice communications and communications that transmit information other than voice represented by digital data.

Throughout the application, the various information used and sent includes messages, requests, commands, instructions and signaling. It should be understood that this information is comprised of electronic representations of these messages, requests, commands, instructions and signaling, generated in currents, potentials, electromagnetic wave energy and combinations. Further, the following discussion relates to various systems that operate and generate such information. In the preferred embodiment of the invention, such a system is implemented using digital and analog integrated semiconductor circuits coupled in electrically conductive communication with each other, or using electromagnetic wave signals, or by a combination of both. In the example of an overall application, various well-known systems are represented in block form. This is done to avoid ambiguity in the disclosure of the present invention.

For the purpose of applying the present invention, the definition of the GSM a interface includes user data transmission and control signaling between the GSM-MSC and any connected BSCs. The control signaling consists of the physical signaling transport layer and the telephone call application information being transported. In the GSM standard, the signaling transport layer of the a interface is defined as the message switching part (MTP) and the Signaling Connection Control Part (SCCP) of signaling system 7(SS7) (defined by the International Telecommunications Union (ITU), a standard well known in the art). Telephone call application data bits are transmitted between the GSM-MSC and the BSC in various SCCP message data fields.

Fig. 3 is a schematic block diagram of a wireless telephone system during normal operation in accordance with one embodiment of the present invention. Base Transceiver Stations (BTS)102(a) - (C) are coupled to BSC 104(a) and BTSs 102(D) - (F) are coupled to BSC 104 (B). The BSCs 104(a) and (B) are in turn coupled to a GSM-MSC106, and the GSM-MSC106 is in turn coupled to a Public Switched Telephone Network (PSTN)108 (which may also be a PLMN). Subscriber unit 100(a) makes telephone calls or other communications using Radio Frequency (RF) signals exchanged with BTS102 (D). Subscriber unit 100(B) makes telephone calls or other communications using RF signals exchanged with BTS102 (B) and BTS102 (C). When occupying RF signals that interface with more than two BTSs 102, subscriber unit 100(B) is referred to as a "soft handoff" similar to the interface with subscriber unit 100 (B). The RF signals transmitted from BTS102 to subscriber unit 100 are referred to as forward link channels, and the RF signals transmitted from subscriber unit 100 to BTS102 are referred to as reverse link channels. The BSS 105 is comprised of a BSC 104 and a plurality of sets of BTSs 102 coupled thereto.

In the preferred embodiment of the present invention, the physical signal processing for both the forward and reverse channels IS performed in accordance with CDMA signal processing techniques of the IS-95 protocol. Such physical signal processing includes the use of forward and reverse link spreading codes and channel codes during forward and reverse link signal transmission and reception. The channel codes are used to establish a set of channels on which groups of data are transmitted by direct sequence modulation. For the forward link, the channel code consists of a set of 64 orthogonal binary codes called Walsh codes, while for the reverse link, the channel code consists of a set of long binary codes calculated for each subscriber unit as a function of the subscriber unit's unique identification code. Spreading codes are used to diversity the frequency range of the transmitted data to increase the likelihood of successful transmission. This diversity is called spreading and is achieved by direct sequence modulation of the transmitted data via a spreading code. In the preferred embodiment of the present invention, similar to the IS-95 system, channelization IS achieved by Binary Phase Shift Keying (BPSK) modulation and spreading IS achieved by Quadrature Phase Shift Keying (QPSK) modulation.

In one embodiment of the invention, the forward link channels include one or more pilot channels, synchronization channels, paging channels, and user traffic channels, each channel determined by modulation of a predetermined forward link channel code. The reverse link channels include one or more access channels and a plurality of user traffic channels, each modulated with a unique reverse link long code. In order to accurately accomplish the transmission and reception of the forward and reverse link signals, the channel conditions must be synchronized with the spreading codes used to process the forward and reverse link signals during reception and transmission. This synchronization is done at call setup and is called signal acquisition. Many synchronization processes are well known in the art. Data transmitted over the forward or reverse link is divided into frames that contain error correction bits and frame header bits. The frame header bits indicate whether the data contained within the frame is signaling data or traffic data, and combinations thereof. The service data is data transmitted by the user in the call, typically digitized voice or audio information, but may be any other type of user data. In order to transmit a complete signaling message, it is generally necessary to transmit multiple frames of signaling data, which are assembled into signaling data by the receiving system. As described above, signaling messages are used to exchange information between the various systems shown in fig. 3 that establish and process telephone calls. Once assembled, each signaling message includes a message header indicating the type of signaling message.

Referring again to fig. 3, as described above, the GSM-MSC106 provides telephone switching, billing and subscriber unit tracking and validation functions. The GSM-MSC106 and the BSC 104 communicate in accordance with the GSM a interface protocol that is part of the GSM standard. In order to establish a telephone call link using GSM-MSC106, a particular set of signaling messages must be generated in a particular order that contains a particular set of information. I.e., the BSC 104 must generate and send the appropriate signaling packets to the GSM-MSC in the appropriate order based on the required network links and signaling messages received from the GSM-MSC 106. The GSM a interface protocol defines the order, information and format associated with these signaling packets. As expected, the order, information and format are substantially different from any interface associated with a comparable MSC operating in a CDMA cellular telephone system. In the same manner, subscriber unit 100 operating in accordance with IS-95 or other CDMA-based protocols must exchange predetermined sets of messages with BTS102 in a predetermined order and in a predetermined format in order to accurately establish and process telephone calls. As also anticipated, the CDMA over-the-air protocol is substantially different from the over-the-air protocols associated with GSM wireless telecommunications systems.

Signaling messages associated with the GSM a interface protocol are divided into two categories: a Direct Transfer Application Part (DTAP) message and a BSS management application part (BSSMAP) message. The DTAP contains data related to the operation of the subscriber unit 100 and the MSC106 and therefore does not directly affect the operation of the BSS 105. The BSSMAP message is generally related to the operation of BSS 105 and may cause the allocation of resources or provide information needed for BSS 105 to operate accurately. The BSSMAP message may affect the overall operation of BSS 105 or the operation of only a single telephone call. And, according to the GSM a interface, signaling messages are sent over the signaling system number 7(SS7) signaling link and associated Message Transfer Part (MTP) and Signaling Connection Control Part (SCCP). The MTP sends binary data through the transmission serial link by adopting three message formats. These three message formats are known as Message Signal Unit (MSU), Link State Signal Unit (LSSU), and fill Signal Unit (FISU). Fig. 4 shows the fields associated with each message format, with the corresponding number of bits indicated below each field. The message is segmented using flag bytes (FL) comprising a logic 0 followed by a series of 6 logic 1's followed by a logic 0 (01111110). In the message defined by the flag byte, a logical 0 is inserted in any string having more than 5 logical 1 s.

Each message format consists of a header containing a Backward Sequence Number (BSN), a Backward Indication Bit (BIB), a Forward Sequence Number (FSN), a Forward Indication Bit (FIB), and a Length Indication (LI) followed by two buffer bits. In addition, each message format includes a set of check bits (CK) inserted immediately before the termination flag byte. For FISUs, no additional data fields are included. For LSSU, a Status Field (SF) is included that indicates one or two bytes relating to one of 6 different states of calibration status and non-service. For MSU, signal byte service information 8 bit group (SIO) and more than two byte Signal Information Fields (SIF) are included. Since each message format contains a different amount of information, the message type is determined by the length indicator field (LI). The signaling message sent according to the GSM A interface is sent together with the data related to the GSM A interface signaling message in SIF through the MSU and the same bit. Specifically, a message sent according to the GSM a interface is placed in an SCCP message that includes the indicated Routing Label (RL), SCCP message type code, SCCP header and SCCP data fields. The SCCP message type code is considered a subfield of the SCCP header. The SCCP message ends at an optional parameter indication (EOP) end. If the BSSMAP message switched within the SCCP message is of a type associated with a single telephone call, the telephone call associated with that message is indicated in the SCCP header connection identification field (not shown). The BSSMAP or DTAP message is contained within SCCP data parameters, the type of which is represented by a distinguishing bit (DIS) located at the beginning of the SCCP data field. The length is indicated in a Length (LEN) field if the BSSMAP message is in handoff. The length is followed by the type of BSSMAP message and other parts of the message. If the DTAP message is in transit, the length is indicated in the Length (LEN) field and the subclass of the DTAP message is indicated in the protocol discrimination field. Any additional data associated with a particular DTAP message containing the message type is placed in the message data field.

Fig. 5 is a schematic block diagram of a BSS 105 for providing CDMA air telecommunication services in conjunction with a GSM a interface protocol network interface in accordance with the present invention. The BTS102 is coupled to the BSC 104 via a wired link, which in the preferred embodiment of the invention is comprised of a T1 or T2 connection, although other connections, including microwave links, may be used. Within the BSC 104, a CDMA interworking subsystem 200 is coupled to the set of BTSs 102. CDMA interconnect subsystem 200 is also coupled to call control processor 202, selection subsystem 204, and BSC a-interface 206. The CDMA interconnect subsystem 200 serves as a message and traffic router between the connection coupling elements and, in the preferred embodiment of the present invention, is comprised of an asynchronous fixed length packet transmission system. A data processing and service selection system 210 is coupled to the selection subsystem 204 and exchanges traffic data with the switch 212. Switch 212 provides an interface to GSM-MSC106 of fig. 2 that is made up of traffic data and signaling, and also exchanges control data with call control processor 202. In the preferred embodiment of the present invention, the signaling data is sent using ITU signaling System number 7(SS7), which is defined as the GSM A interface protocol. Each connection shown in BSC 104 is a high speed digital connection such as fast Ethernet, which is well known in the art. In another embodiment of the present invention, switch 212 may be replaced with a simpler cross-connect device, thereby coupling BSC a-interface 206 directly with GSM-MSC 106. It IS preferred to choose switch 212 since BSC 104 may be coupled to multiple MSC systems if desired, each of which may provide a different type of network service, including IS-41 services, as IS well known in the art. If the BSC 104 is coupled to multiple MSC systems, an additional BSC interface system similar to the BSCA interface 206 is employed in the preferred embodiment of the present invention, which need not all be necessarily included in using the GSM a interface protocol.

In the preferred embodiment of the present invention, the systems making up BSS 105 communicate and exchange traffic and signaling data by employing a built-in BSS protocol in which fixed-length packets are exchanged between the various other systems via CDMA interconnect subsystem 200 or a direct route between the two systems. The CDMA interconnect subsystem 200 performs routing by using the address contained within each fixed-length packet. The first system, which typically sends a packet to the second system, places the address of the second system in the packet and then provides the packet to interconnect subsystem 200. If it is some neighboring system, such as the selection subsystem 204 and the data processing and service selection system 210, the packet is switched directly. The packet header bits contained within each packet indicate whether a certain length of packet contains traffic or signaling data. Data packets containing traffic data are called traffic packets and data packets containing signalling data are called signalling packets. Control information may also be exchanged between some systems within BSS 105 using a dedicated connection adapted between call control processor 202 and switch 212. In addition to the CDMA interconnect subsystem 200, other methods of constructing the various systems within the BSS 105 shown in fig. 5 are also compatible with the operation of the present invention.

The signaling messages constitute a complete instruction set for controlling the various system operations that make up the BSS and for exchanging information with the subscriber unit 100 or GSM-MSC 106. The complete signaling message is sent via one or more signaling packets assembled by the receiving system to generate a signaling message to be sent. According to the preferred embodiment of the present invention, the signaling message subclass is defined to be sent through the BSS 105 without affecting the operation of the BSS 105. For purposes of application, such signaling messages are referred to as "transport messages," and the availability of transport messages constitutes a transparent transport function within BSS 105. The transparent transport function is typically used to exchange a special class of signaling messages between the GSM-MSC106 and the subscriber unit 100, defined as DTAP messages by way of the BSS 105. During operation of BSS 105, call control processor 202 and BSC a interface 206 configure and control various other systems within BSS 105 using other signaling messages, and generally through application, any configuration or other control by call control processor 202 and BSC a interface 206 is accomplished using these signaling messages in accordance with the delivery described in the preferred embodiment of the present invention, although other message delivery mechanisms such as direct interconnection between systems are also compatible with the present invention. In the preferred embodiment of the present invention, call control processor 202 and BSC a-interface 206 are implemented using a computer system controlled by software instructions (not shown).

One configuration and control performed by BSC a-interface 206 includes the allocation of selected resources within selection subsystem 204. Selecting resources provides a bi-directional interface between the user interface 100 and any system within the BSC 104 using one or more BTSs 102. The functions associated with the bi-directional interface include matching multiple copies of a data frame generated by one or more BTSs and selecting the best quality data frame from the set of copies for further processing. This selection is made based on the quality indication information placed within each frame of each BTS 102. Multiple copies of a frame are generated when subscriber unit 100 is engaged in multiple RF interfaces with multiple BTSs 102 during soft handoff conditions. In addition, the selection resource receives packets directed to subscriber unit 100 and provides a copy of the packet to each BTS102 that is RF interfaced with subscriber unit 100. Each selection resource contains its own internal address so that data packets associated with the pending call can be routed to the selection resource within selection subsystem 204. Each selection resource also tracks the set of BTSs 102 that are assigned to the subscriber unit 100 as an interface. In the preferred embodiment of the present invention, the selection resource is comprised of a microprocessor or digital signal processor controlled by software instructions stored in a memory unit (not shown) located within the selection subsystem 204.

BSC a-interface 206 also configures data processing and service selection system 210 to process data from selection subsystem 204 in a number of ways depending on the services required to process the telephone call. The signal processing services provided include vocoding and vocoding of traffic data associated with telephone calls, modulation and demodulation of audio and other signals used to transmit facsimile and other digital data over standard PSTN connections, and encryption of user and signaling data. In the preferred embodiment of the present invention, signal processing is accomplished using digital signal processing integrated circuits within data processing and service selection system 210 and controlled using software instructions stored in a memory system, as is well known in the art (not shown). Another function performed by BSC a-interface 206 is to receive DTAP signaling messages sent from GSM-MSC106 according to the a-interface and transmit the signaling messages to the appropriate subscriber unit 100 by substituting the messages in the transmission message and provide the transmitted messages to the selector resources associated with the telephone call. Upon receipt of the transmission message, the selector resource will provide the transmission message to subscriber unit 100 over the CDMA forward user traffic channel.

As described above, data is exchanged between BTS102 and subscriber unit 100 over multiple frames that include frame header bits (indicating the type of data in the frame). In the preferred embodiment of the present invention, both signaling and traffic data may be sent in one frame according to the IS-95 standard. Since the destination and source of each frame is indicated by the channel code used to modulate the data, no address is included in the frame during over-the-air transmission. In the preferred embodiment of the present invention, each frame transmitted over the reverse link is received by a particular channel processing unit (not shown) within BTS 102. Each channel processing unit knows the internal address of the selector resource that is handling the call and is provided with frames by the channel processing unit after extracting the frames from the reverse link signal. The selector resource then assembles a signaling message from the frames containing the signaling data and determines the type of the signaling message from the signaling message header bits contained in the signaling message. The transmission signaling message is typically tunneled transparently to BSC a interface 206 using the selected resources of the BSS transmission message described above. The BSC A interface places a connection identifier associated with the telephone call in the SCCP header field based on the selected resource from which the transmission signaling message is sent, and transparently provides the transmission signaling message to the GSM-MSC based on the A interface protocol. If the message is opaque or a local signaling message, the resources selected and BSC a-interface 206 will process the message internally.

In order to accurately process a telephone call, various procedures must be accomplished, in turn, by exchanging signaling messages between the various systems shown in fig. 5, in accordance with one embodiment of the present invention. Various procedures include call initiation, call release, and subscriber unit registration. Fig. 6-10 are message sequence diagrams illustrating signaling messages exchanged during call initialization, call release, and subscriber unit registration in accordance with one embodiment of the present invention. The vertical lines in fig. 6-10 relate to the systems identified in the boxes at the top of each line. The systems are subscriber unit 100, BTS102, selector subsystem 204, call control processor 202, data processing and service selection system 210, BSC a interface 206, and GSM-MSC 106. The horizontal arrows between the two vertical lines indicate the exchange of signaling messages between the relevant systems. The direction of time is from top to bottom, so that the lower level on the paper appears earlier. As shown at the bottom of each page, messages exchanged between subscriber unit 100 and BTS102 are sent over the bidirectional air interface, while messages exchanged between GSM-MSC106 and BSC a-interface 206 are sent according to the GSM a-interface.

As described above, GSM signaling messages exchanged between GSM MSC106 and BSC a-interface 206 are transmitted in SCCP signaling messages contained within a Message Signaling Unit (MSU) according to the SS7 standard. Upon receiving the SCCP signaling message, BSC a-interface 206 first determines whether the message is associated with a particular communication or directed to operation of the entire BSS by examining the SCCP message type code field. If the message is associated with a particular communication or telephone call, BSC a interface 206 determines which communication is using the connection identifier contained in the SCCP header. BSC a-interface 206 then determines whether the message is a DTAP or BSSMAP message by examining the diff field of the GSM a-interface signaling message. If the GSM signaling message is a DTAP message, the BSC A interface transparently transmits the signaling message through the transmission message. If the message is a BSSMAP message, the BSC A interface determines the specific BSSMAP message through checking the BSSMAP message type field. According to the BSSMAP message type, the BSCA interface completes each step described below.

It is worth noting that for the purposes of the following description, the signaling messages exchanged between the selection subsystem 204 and the subscriber unit 100 are represented by a horizontal single line between the two systems. But in practice signaling messages are communicated by one or more BTSs 102. The single line is easy to draw when the signaling message does not require control processing or resource allocation by the BTS 102. Similarly, signaling messages exchanged between BSC a-interface 206 and GSM-MSC106 pass through switch 212, but a single line is shown since switch 212 does not handle the processing particularly relevant to the present invention. The CDMA air channel used to transmit messages to and from the subscriber unit 100 is indicated by brackets adjacent to the associated message, 'P' indicating a forward connection paging channel, 'a' indicating a reverse connection access channel, and 'T' indicating either a forward connection user traffic channel or a reverse connection user traffic channel depending on the direction of transmission. Also, in fig. 6, 7 and 10, the "traffic channel setup" procedure is associated with establishing forward and reverse connection user traffic channel interfaces between the subscriber unit 100 and the BTS102 and is shown at the far left of the figure. "network setup" is the process of establishing a telecommunications network connection with a telecommunications system involved in a call and is shown on the far left of the figure. The signaling messages that are transparently routed using the transport message are denoted by the notation "xport" and parenthesis with the associated signaling message inside and are referred to as "transport messages" in the specification.

In fig. 8 and 9, the "network release initialization" indicated on the far left of the figure is a procedure to start tearing down and releasing network resources related to a telephone call. In fig. 8 and 9, "traffic channel interface teardown" is the process of releasing resources associated with the bi-directional radio signal interface between the subscriber unit 100 and the BSS 105 (fig. 3). It should be noted that the message sequence diagrams shown in fig. 6-10 do not show every message sent, but only messages that are of particular relevance to the present invention. For ease of illustration, some of the signaling messages discussed below are also not shown. Each signaling message shown to be sent within BSS 105 is also exchanged according to internal data packets based on the above-described protocol and is thus passed through CDMA interconnect subsystem 200 of fig. 5 in the preferred embodiment of the present invention.

Fig. 6 is a message sequence diagram of a terminating call initialization procedure for a subscriber unit in accordance with one embodiment of the present invention. The subscriber unit terminated call initialization procedure is the result of a telephone call or communication initialization of a communication unit other than the subscriber unit 100 (e.g., a subscriber unit of the PSTN 108) that interfaces with the wireless telecommunication system shown in fig. 4, the wireless subscriber unit 100 that interfaces with another wireless telecommunication system, or a data terminal. The subscriber unit terminated call initialization begins when GSM-MSC106 sends page message 300 to BSC a-interface 206 according to the a-interface protocol. According to the a-interface protocol, paging message 300 indicates the subscriber being paged (as identified by the international mobile subscriber identity), the type of channel required for the air interface, a list of cell identities indicating the calling group associated with the nearest subscriber unit, and possibly a temporary mobile subscriber identity. BSC a-interface 206 first examines the received page message 300 to determine if it is a BSSMAP message.

After identifying page message 300 as a BSSMAP message, BSC a-interface 206 determines whether page message 300 is a page message by examining the BSSMAP message type field. Upon determining that paging message 300 is a paging message, BSC a-interface 206 generates a set of signaling messages for establishing a bi-directional CDMA modulated RF channel between BTS102 and subscriber unit 100 to which paging message 300 is directed. In the preferred embodiment of the present invention, the set of signaling messages begins sending BSS page request 302, which includes a list of cell identifiers, to call control processor 202. Call control processor 202 responds by sending a BTS page request 303 to a set of BTSs 102 indicated by the list of call identifiers. Each BTS102 responds by broadcasting a paging message 304 to the associated cell via the forward link paging channel. If the page is received by subscriber unit 100, it sends a channel request message 306 to BTS102 by accessing the channel via the reverse connection. Channel request message 306 may contain information regarding the type of service requested by the call if such information is contained in paging message 304.

BTS102 responds to the channel request by sending a BSS channel request 310 to BSC a interface 206 and a BTS acknowledge message 308 to subscriber unit 100 via the paging channel. The transmission of BTS acknowledgment messages 308 is optional in the preferred embodiment of the invention. BSC a-interface 206 continues to establish the bi-directional user traffic channel interface by replying to BSS channel request 310 when sending BSS call setup request 312 to call control processor 202. Call control processor 202 allocates the selectors and service resources for the call and indicates the results of the allocation to BSC a-interface 206 in BSS call setup answer 314. After receiving BSS call setup answer 314, BSC a-interface 206 sends a selector call setup request 316 to selection subsystem 204. The selection subsystem 204 initializes the allocated selector resources to process the call and indicates to the BSC a-interface 206 under a selector call setup answer 318. Upon receiving the selector call setup response 318, the BSC a-interface 206 sends a radio connection setup request 319 to the selection subsystem 204. The selection subsystem 204 responds by sending a channel resource request to the BTS 102.

After receiving channel resource request 320, BTS102 allocates channel processing resources to modulate and demodulate the forward and reverse link user traffic channels associated with the telephone call and sends a channel resource reply message 322 to selection subsystem 204. The selection subsystem 204 responds by sending a connection request 324 to the BTS102, and the BTS102 responds by sending a connection response 326 to the selection subsystem 204. Selection subsystem 204 then sends null traffic data 328, start traffic data message 330, and null traffic data 332 to BTS 102. BTS102 responds to start traffic data message 330 and null traffic data 332 by sending null traffic data 336 to subscriber unit 100 via the forward link user traffic channel. The selection subsystem 204 also sends a radio connection resource indication 334 to the BSC a-interface 206. Upon receiving radio connection resource indicator 334, BSC a interface 206 sends BTS channel assignment message 338 to BTS102, and BTS102 responds by sending channel assignment message 340 to subscriber unit 100 via the forward connection paging channel. Subscriber unit 100 uses the assigned channel information contained in the channel assignment message to begin processing the assigned forward link traffic channel and to transmit a reverse link traffic channel preamble 342 on the reverse link user traffic channel so that BTS102 can obtain the reverse link traffic channel from subscriber unit 100. Once the reverse link traffic channel is acquired, the BTS102 sends a reverse connection start message 344 to the selection subsystem 204. The selection subsystem 204 responds by sending a reverse link traffic approval 346 to the subscriber unit 100 over the forward traffic channel. The selection subsystem also sends a radio connection setup reply message 348 to BSC a-interface 206. Upon receiving a reverse connection grant 346, a bi-directional RF interface is established.

After establishing the forward and reverse link traffic channel interfaces with BTS102, subscriber unit 100 initiates the telecommunications network connection establishment procedure by sending a page response 350 to selector subsystem 204. Paging reply 350 causes selector subsystem 204 to send a BSS paging reply to BSC a interface. BSC a-interface 206 receives BSS page response 352 indicating that subscriber unit 100 is ready to establish a network connection, stores the class label for subscriber unit 100, and initializes an SCCP connection by sending an SCCP connection request containing a complete layer 3 information message 354 to GSM-MSC106 according to the a-interface protocol. . The full layer 3 information message 354 contains the contents of the BSS page response message 352 and is part of the GSM a interface protocol and is therefore well known in the art. GSM-MSC106 responds by sending an encryption mode command 358 to BSC a-interface 206. The encryption mode command 358 contains encryption information including a key, a list of possible encryption algorithms to use based on the capabilities of the subscriber unit 100, and an encrypted reply mode requesting an international mobile equipment identity.

After determining that encryption mode 358 is a BSSMAP message and further determining that it is an encryption mode command, BSCA interface 206 selects one of the encryption algorithms and sends a BSS encryption mode command 360 to selector subsystem 204. The selection subsystem 204 initiates the over-the-air encryption process by sending an encryption mode command 362 to the subscriber unit 100 over the forward link traffic channel. After processing the ciphering mode command 362, the subscriber unit 100 sends a ciphering mode complete message 364 to the selection subsystem 204 via the reverse link traffic channel. After receiving the encryption mode complete message 364, the selection subsystem 204 begins the encryption-decryption of all additional signaling and call data associated with the telephone call by changing to the personal reverse connection channel code or long code in accordance with the IS-95 standard. It is noted that other methods of encryption and decryption are also compatible with the operation of the present invention. Selection subsystem 204 then sends a BSS encryption mode complete message 366 to BSC a interface 206 indicating that the encryption mode configuration operation has been completed. The BSC a-interface responds by sending an encryption mode complete command 368 indicating selection of an encryption algorithm and an international mobile equipment identity to the GSM-MSC106 according to the a-interface protocol.

The GSM-MSC106 then sends a setup message 370 to the BSC a interface. The setup message 370 contains information for various established telephone calls including the type of service, the sending rate, the type of data sent, and the type of vocoding. The use of the setup message 370 is part of the GSM a interface and is therefore well known in the art. Upon determining that the setup message 370 is a DTAP message, the BSC a-interface 206 transparently transmits the message content to the selection subsystem 204 via a transmission message 372. In the preferred embodiment of the present invention, BSC a-interface 206 does not know that the setup message 370 is actually a setup message, only that it is a DTAP message, since it does not look beyond the differentiation bits. This simplifies the processing required by BSC a interface 206 and allows transparent transmission. After determining that the transmission message 372 is a transmission message, the selection subsystem 204 provides the message content to the subscriber unit 100 over the forward link traffic channel using the transmission message 374. After receiving the transmission message 374, the subscriber unit 100 passes the message content as a DTAP setup message to the GSM message processing portion of the subscriber unit 100. The subscriber unit 100 responds by sending an acknowledgement call to the selection subsystem 204 in the transmission message 376. The call confirmation confirms the type of service in the setup message 370 or proposes another type of service. Selection subsystem 204 transmits the contents of transmission message 376 to BSC a-interface 206 using transmission message 378 containing the call acknowledgement. As the transparent transmission process continues, BSC a-interface 206 provides the message content to GSM-MSC106 using DTAP call acknowledgement messages 380 according to the GSM a-interface protocol.

After receiving the call acknowledgement message 380, the GSM-MSC106 sends an assignment request 382 to the BSC a-interface 206. The allocation request 382 indicates the channel type, priority, circuit identification (network slot), downlink DTX flag (variable rate transmission), interference band used (frequency hopping), and classmark information 2 (subscriber unit type). The channel type is the type of data transmitted during transmission, such as facsimile, voice, or signaling. The assignment request 382, BSSMAP message, causes the BSC a interface to agree with the subscriber unit 100 on the type of CDMA service needed to process the telephone call. The agreement begins when a BSS service request 386 is sent to the selection subsystem 204 and the selection subsystem 204 responds by sending a service request 388 to the subscriber unit 100 over the forward link traffic channel. In order to provide the requested data service, including the data rate, the service request 388 indicates the parameters of the required radio link, and the user element 100 responds by sending a service response 389 to the selector subsystem 100 indicating whether the radio link type was received. If the service reply 389 indicates that the service type can be received, the selection subsystem 204 sends a service connection message 390 to the user element 100 via the forward link traffic channel, which causes the user element 100 to send a service connection complete message 391 to the selection subsystem 204 via the reverse link traffic channel.

The selector subsystem 204 then indicates a successful service agreement to the BSC a-interface 206 by sending a BSS service answer 392. After receiving BSS service answer 392, BSC a-interface 206 allocates resources for processing the call by sending a BSS resource allocation message 384 to data processing and service selection system 210 based on the service type. The data processing and service selection system 210 then allocates call processing resources for processing the received traffic data. In another embodiment of the invention, the service selection resource allocation is accomplished in response to a channel request message. In addition, BSC a interface 206 allocates connections within switch 212 to establish traffic channels between GSM-MSC106 and data processing and service selection system 210 to carry call-related traffic data (messages to switch 212 not shown). The BSC a-interface 206 then indicates that the service agreement has been completed by sending an assignment complete message 394 according to the GSM a-interface protocol.

After the service agreement is completed, the GSM message processing portion of the subscriber unit 100 sends a prompt message to the GSM-MSC106 indicating that this is a user of the subscriber unit 100 to be prompted by the transfer message 400. The prompt message is transmitted transparently by the selector subsystem 204 to the BSC a interface using a transmission message 398 and then transmitted by the BSC a interface to the GSM-MSC106 using a DTAP prompt message 396. The GSM-MSC106 may then generate a ring back tone towards the calling party. If the subscriber unit 100 answers the call, it indicates an answer event for the connection in the transmission message 402 sent to the selection subsystem 204 over the reverse link traffic channel. The connection is transparently transferred by the selector subsystem 204 to the BSC a interface via a transfer message 404, and then transferred by the BSC a interface to the GSM-MSC106 via a DTAP connection message 408. After receiving the connection message 408, the GSM-MSC stops ringing if provided, and sends a connection acceptance message 410 to the BSC a-interface 206. BSC a-interface 206 transparently provides a connection acceptance message 410 to selection subsystem 204 via transport message 412. The selection subsystem 204 then proceeds to transmit the message 414 to the subscriber unit 100 by transmitting it over the forward link channel. After the subscriber unit 100 receives the transmission 414, a stable call state is established and the subscriber unit terminated call initiation procedure is completed.

Figure 7 is a message sequence diagram illustrating signaling messages sent during an initial call initialization procedure for a subscriber unit in accordance with one embodiment of the present invention. The degree of initial call initiation by the wireless subscriber unit is derived from the initial telephone call of the subscriber unit 100 of fig. 2. The subscriber unit initial call initialization procedure begins with a channel request message 506 sent by subscriber unit 100 to BTS102 via a reverse link access channel. In the preferred embodiment, channel request message 506 contains information about the type of service requested, but in other embodiments this information may be provided in other messages. BTS102 responds by sending a BSS channel request 510 to BSC a interface 206 and a BTS acknowledge message 508 to subscriber unit 100, although sending BTS acknowledge message 508 is optional in the preferred embodiment of the invention. BSC a-interface 206 responds by generating a set of signaling messages that are used to establish a bi-directional CDMA modulated RF signal interface between subscriber unit 100 and BTS 102. The process of establishing a bi-directional interface begins when BSC a-interface 206 sends a BSS call setup request 512 to call control processor 202. Call control processor 202 allocates selectors and service resources for the call and indicates the results of the allocation to BSC a-interface 206 in BSS call setup answer 514. After receiving BSS call setup answer 514, BSC a-interface 206 sends a selector call setup request 516 to selection subsystem 204. The selection subsystem 204 initializes the allocated selector resources and indicates this to the BSC a-interface 206 with a selector call setup answer 518. Upon receiving the call setup answer 518, the BSC a-interface 206 sends a radio link setup request 519 to the selection subsystem 204. The selection subsystem 204 responds by transmitting the channel resources to the BTS 102.

After receiving channel resource request 520, BTS102 allocates channel processing resources to modulate and demodulate the forward and reverse link user traffic channels associated with the telephone call and sends channel resource response message 522 to selection subsystem 204. The selection subsystem responds by allocating selection resources for processing the call and sending a connection request to BTS102, while BTS102 responds by sending a connection response to selection subsystem 204. The selection subsystem 204 then sends null traffic data 528, traffic data messages 530, and null traffic data 532 to the BTS 102. BTS102 responds to start traffic data message 536 and null traffic data 532 by transmitting null traffic data 536 to subscriber unit 100 over the forward link traffic channel. The selection subsystem 204 also sends a radio link resource message 534 to the BSC a-interface 206. After receiving radio link resource message 530, BSC a interface 206 sends BTS channel assignment message 538 to BTS102 and BTS102 responds by sending channel assignment message 540 to subscriber unit 100 over the forward paging channel.

Subscriber unit 100 uses the assignment channel information contained in channel assignment message 540 to begin processing data received via the assigned forward link traffic channel. It also transmits a reverse link traffic channel preamble 542 to allow BTS102 to obtain the reverse link traffic channel from subscriber unit 100. Once the reverse traffic channel is acquired, BTS102 sends a start reverse link message 544 to selection subsystem 204. The selection subsystem 204 responds by sending a reverse link acknowledgement 546 to the subscriber unit 100 over the forward link traffic channel. The selection subsystem 204 also sends a radio link resource message 548 to the BSC a-interface 206. At this point, the bi-directional link has been established and network connection establishment begins.

After receiving the reverse link acceptance message 546, the subscriber unit 100 initiates network connection establishment by sending a call management service request 550 to the selection subsystem 204 over the reverse link traffic channel. The selection subsystem 204 responds by sending a BSS call management service request 551 to the BSC a-interface 206. BSC a-interface 206 stores the classification flag information contained in the message, generates a complete layer three information message 552 containing information within BSS call management service request 551, and initializes the SCCP connection by transmitting the complete layer three information message 552 inside the SCCP connection request message to GSM-MSC106 according to the a-interface protocol. The completion layer three information message 552 is part of the GSM a interface protocol and is therefore a well-known technique in the art.

The GSM-MSC106 responds by sending an acknowledgement request 553 to the BSC a-interface 206. The BSC a-interface 206 recognizes the message 553 as a DTAP message and transparently provides the message content to the selection subsystem 204 via transport message 554. The selection subsystem 204 determines that the transmission message 554 is a transmission message type and provides the message content to the user element 100 by sending a transmission message 555 over the forward link traffic channel. The subscriber unit 100 receives the transmission message 555 and transmits the content to the built-in GSM message processing portion and it responds by sending a transmission message 556 containing an acknowledgement to the selector subsystem 204 over the reverse link traffic channel. After confirming that the transmission message 556 is a transmission message, the selection subsystem 204 provides the content of the message to the BSC a-interface 206 via transmission message 557. BSC a-interface 206 continues the transparent transmission by providing a DTAP acknowledgement 558 to GSM-MSC106 according to the GSM a-interface protocol.

GSM-MSC106 responds by sending an encryption mode command 559 to BSC a-interface 206. Upon confirmation that message 559 is a BSSMAP message and then further confirmation that it is an encryption mode command, BSC a-interface 206 begins the over-the-air encryption initialization procedure by sending a BSS encryption mode command 560 to selection subsystem 204. After receiving BSS encryption mode command 560, selection subsystem 204 sends the encryption mode command to subscriber unit 100 via the forward link traffic channel. After processing the encryption mode command 562, the subscriber unit 100 sends an encryption mode complete message 564 over the reverse link traffic channel to the selection system 204 and begins encrypting all subsequent transmissions. After receiving the encryption mode complete message 564, the selector subsystem 204 begins the encryption-decryption process on all additional signaling and call data associated with the telephone call. In the preferred embodiment of the present invention, this encryption IS accomplished using a personal channel code in accordance with the IS-95 specification; other methods of encryption are compatible with the present invention. The selection subsystem 204 then sends a BSS encryption mode complete message 566 to the BSC a interface 206. BSC a-interface 206 responds by sending an encryption mode complete command 568, according to the GSM a-interface protocol, to GSM-MSC106 indicating that the encryption configuration has been completed.

After establishing the robust bi-directional channel, the subscriber unit 100 sends a setup message to the GSM-MSC106 by sending a setup message 570 to the selection subsystem 204. The setup message 570 contains various types of information related to setting up a telephone call, including dialed digits, type of service, sending rate, type of data sent, and type of vocoding. The selection subsystem 204 provides a setup message to the BSC a-interface 206 using the transfer message 572. BSC

The a-interface 206 continues to establish transparent transmission of messages by sending a transmission message 574 to the GSM-MSC106 according to the GSM a-interface protocol. After receiving the transfer message 572 and initiating the connection with the called party, the GSM-MSC106 sends a transfer message 576 containing the call processing message to the BSC a-interface 106. The call processing message indicates that a network connection is being established and that no other call setup information will be accepted. BSC a-interface 206 responds by transparently sending the call processing message in a transmission message 578 to the selection subsystem 204. The selection subsystem 204 responds by sending a transfer message 580 containing the call processing message to the subscriber unit 100 over the forward link traffic channel.

After sending the call processing message 576, the GSM-MSC106 also sends an assignment request 582 to the BSC a-interface 206. In response, BSC a interface 206 continues to configure the BSS for handling the call by sending a BSS assignment request 586 to selection subsystem 204, which in turn responds by sending a service connection 589 to subscriber unit 100 via the forward link traffic channel. In response, the subscriber unit 100 sends a service connection complete message 591 to the selection subsystem 204 over the reverse connection traffic channel indicating that the service type is acceptable (since the subscriber unit 100 makes an initial service request when initiating the telephone call, service is very likely to be accepted by the subscriber unit 100, thus omitting the service request message and service answer message shown in fig. 4). The selection subsystem 204 begins sending a BSS service acknowledgement 592 to the BSC a-interface 206 and the BSC a-interface 206 responds by sending an assignment complete message 594 to the GSM-MSC according to the GSM a-interface protocol. BSC a-interface 206 also sends a resource allocation message 584 to data processing and service selection system 210 in order to allocate resources for processing the call based on the type of service indicated in allocation request 582 and BSS service answer 592. The BSC a interface also allocates connections within the switch 212 (fig. 3) to establish traffic channels between the GSM-MSC106 and the data processing and service selection system 210 to carry call related traffic data (messages to the switch 212 are not shown).

After accepting the allocate complete message 594, the GSM-MSC106 sends a prompt message 596 to the BSC a-interface 206 according to the GSM a-interface protocol, which responds by transparently providing the message to the selection subsystem 204 using a transport message 598 that contains the prompt message. The selection subsystem 204 then sends a transmission message 600 containing the prompt message to the subscriber unit 100 via the forward link traffic channel to continue transparent transmission. The prompt message prompts subscriber unit 100 to begin generating a ring back tone. If the call is answered, GSM-MSC106 sends a connect message 602 to BSC a-interface 206 according to the a-interface protocol, and BSC a-interface 206 answers by sending a transport message 604 containing the connect message to selection subsystem 204. The selection subsystem 204 then sends a transmission message 606 over the forward link traffic channel to continue providing connection messages transparently to the subscriber unit 100. After accepting the transmission message 606, the subscriber unit 100 terminates the generation of the ringback tone and sends a transmission message 610 containing the connection approval to the selection subsystem 204. The selection subsystem 204 transparently provides a connection acceptance as an answer to the BSC a-interface 206 by transmitting a message 612, which then sends a connection acceptance message 614 to the GSM-MSC106 according to the GSM a protocol. After the GSM-MSC106 accepts the connection acceptance message 614, a steady state call has been established.

Fig. 8 is a message sequence chart illustrating signaling messages exchanged during an initial call release of a subscriber unit in accordance with one embodiment of the present invention. Subscriber unit initial call release is the disconnection of a telephone call in response to the release requested by subscriber unit 100 of figure 2. When the subscriber unit sends a transmission message 652 containing a disconnect message to the selection subsystem 204 via the reverse connection traffic channel, the subscriber unit initial call release is initiated during a telephone call or communication by tearing down the network connection. The selection subsystem 204 responds by providing a disconnect message to the BSC a-interface 206 using the transport message 657, causing the BSC a-interface 206 to send a disconnect message 672 to the GSM-MSC106 according to the a-interface protocol. GSM-MSC106 initiates a release connection to the other party's network connection and sends a release message 673 to BSCA interface 206. In response, BSC a-interface 206 sends a release-containing transfer message 665 to selection subsystem 204. The selection subsystem 204 then provides the release sent with the transmission message 658 to the subscriber unit 100 via the forward link traffic channel.

The subscriber unit 100 responds by providing a transmission message 653 containing the release complete to the selection subsystem 204 via the reverse link traffic channel. The selection subsystem 204 provides the release complete to the BSC a-interface 206 by sending a transfer message 660. The BSC a interface responds by providing a release complete message 676 to the GSM-MSC106 according to the GSM a interface protocol. GSM-MSC106 responds to BSC a-interface 206 with a clear command 674 indicating that bidirectional radio connection and a-interface network resources should be released according to the GSM a-interface protocol.

Upon receiving purge command 674, BSC a interface 206 generates a set of messages that tear down the traffic channel interface. The traffic channel interface teardown begins when BSC a-interface 206 sends a BSS service disconnect message 668 to selection subsystem 204. In addition, the BSC a-interface 206 instructs the switch 212 to remove the traffic channel connection (message not shown) between the data processing and service selection system 210 and the GSM-MSC 106. The selection subsystem 204 acknowledges receipt of the BSS service release request message 668 by sending a BSS service release reply 670 that causes the BSC a interface 206 to send a BSS radio link release request 663 to the selection subsystem 204. After being requested 663 by the BSS radio link release, the selection subsystem 204 sends a release command 651 to the subscriber unit 100 via the forward traffic channel. The selection subsystem 204 then sends an end forward traffic channel command 654 and a disconnect request 655 to the BTS 102. The BTS102 frees up resources to process the forward and reverse link traffic channels and then sends an end reverse connection traffic channel 656 and a disconnect acknowledgement 659 to the selection subsystem 204.

The selection subsystem 204 then sends a release resource request 662 to the BTS102 and the BTS102 acknowledges by sending a release resource acknowledgement 661 over the reverse link traffic channel. After receiving the release resource reply, selection subsystem 204 sends a radio release response 664 to the BSC a interface, which replies by sending a call release request 666 to selection subsystem 204. Selection subsystem 204 then sends a call release answer to BSC a interface 206 and releases the selected resources associated with the telephone call. BSC a interface 206 then sends a de-allocation request 671 to call control processor 202 indicating that the selection and service resources associated with the telephone call have been released and are available for use by other calls. The BSC a-interface 206 also indicates that the GSM-MSC106 call has been released by sending a flush complete 675 according to the GSM a-interface protocol. Clear complete 675 indication GSM-MSC

106 can now utilize the call processing resources. Call control processor 202 responds with a deallocation request 671 by sending a deallocation response 667 to BSC a interface 206. After BSC a interface 206 receives the deallocation response 667, the call has been released.

Fig. 9 is a message sequence diagram illustrating signaling messages exchanged during network initiated call release according to one embodiment of the invention. The network initiated call release is in response to a system request outside the subscriber unit 100 of fig. 2 to disconnect the telephone call. Network initiated call release begins during the occurrence of a telephone call or other communication. GSM-MSC106 initiates the network teardown by sending a disconnect message 772 to BSC a interface 206 according to the GSM a interface protocol. BSC a-interface 206 responds by providing a transmission message 757 containing a disconnect from selection subsystem 204, and it provides a transmission message 753 containing a disconnect to subscriber unit 100 via the forward link traffic channel. The subscriber unit 100 then sends a transmission message 758 containing the release message to the selection subsystem 204 and the selection subsystem 204 provides the transmission message containing the release message to the BSC a interface as a response. BSC a-interface 206 then sends a release message 773 to GSM-MSC106 according to the GSM a-interface protocol. The GSM-MSC106 responds by sending a release complete message 776 to the BSC a-interface 206 according to the GSM a-interface protocol. The BSCA interface 206 provides a release complete containing transmission message 760 to the selection subsystem 204 and the selection subsystem 204 responds by providing a release complete containing transmission message 752 to the user element 100 via the forward link traffic channel.

Selection subsystem 204 then sends a release resource request 762 to BTS102, and BTS102 responds by sending a release resource response 761 over the reverse link traffic channel. After accepting the release resource answer, selection subsystem 204 sends a BSS radio link release answer to BSC a-interface 206, and BSC a-interface 206 responds by sending a BSS call release request 766 to selection subsystem 204.

GSM-MSC106 requests release of the bidirectional radio link from BSC a-interface 206 when sending clear command 774 in accordance with the GSM a-interface protocol. Upon receiving clear order 774, BSC a-interface 206 initiates traffic channel interface teardown according to the IS-95 call model. Traffic channel interface teardown begins when BSC a-interface 206 sends a BSS service disconnect message request 768 to selection subsystem 204. In addition, the BSC a-interface 206 instructs the switch 212 to release the traffic channel connection (message not shown) between the data processing and service selection system 210 and the GSM-MSC 106. Selection subsystem 204 acknowledges receipt of BSS service disconnect request message 768 by sending a BSS service disconnect reply 770 which causes BSC a interface 206 to send a BSS radio link release request 763 to selection subsystem 204. Upon receipt of BSS radio link release request 763, selection subsystem 204 sends a release command 751 to subscriber unit 100 over the forward link traffic channel. The subscriber unit 100 responds by sending a release command 750 over the reverse link traffic channel to the selection subsystem 204. The selection subsystem 204 then sends an end forward traffic channel command 754 and a disconnect request 755 to the BTS 102. BTS102 frees up resources to process the forward and reverse link traffic channels and then sends an end reverse link traffic channel 756 and a disconnect acknowledgement 759 to selection subsystem 204.

Selection subsystem 204 then sends a release resource request 762 to BTS102, and BTS102 replies by sending a release resource reply 761 over the reverse link traffic channel. After receiving the release resource acknowledgement, selection subsystem 204 sends a wireless release response 764 to the BSC a interface, which responds by sending a call release request 766 to selection subsystem 204. Selection subsystem 204 then sends a call release answer to BSC a interface 206 and releases the selected resources associated with the telephone call. BSC a interface 206 then sends a de-allocation request 771 to call control processor 202 indicating that the selection and service resources associated with the telephone call have been released and are available for other calls. The BSC a-interface 206 also indicates that the GSM-MSC106 call has been released by sending a clear complete 775 according to the GSM a-interface protocol. Responds by sending a deallocation response 767 to BSC a interface 206 with deallocation request 771. After BSC a interface 206 receives de-allocation answer 767, the call has been released.

Fig. 10A and 10B are message sequence diagrams illustrating signaling messages exchanged during user registration according to one embodiment of the invention. During registration of the subscriber unit 100, the subscriber unit of fig. 2 informs the GSM-MSC106 of its own current location and status so that the GSM-MSC106 can provide service to the subscriber unit 100. Subscriber unit registration begins by sending a channel request from subscriber unit 100 to BTS102 via a reverse link access channel. In the preferred embodiment of the present invention, the channel request message 806 indicates that the user 100 is initiating registration, but this information may be provided in other messages in different embodiments. BTS102 responds to channel request 806 by sending BSS channel request 810 to BSC a interface 206 and a BTS acknowledge message to subscriber unit 100, although BTS acknowledge message 808 is optional in the preferred embodiment of the invention. BSC a-interface 206 responds by generating a set of messages to establish a bi-directional CDMA modulated RF signal interface between subscriber unit 100 and BTS102 by sending a BSS call setup request 812 to call control processor 202. Call control process 202 allocates selector service resources for the call and indicates the result to BSC a interface 206 in BSS call setup response 814. After receiving BSS call setup answer 814, BSC a-interface 206 sends a selector call setup request 816 to selection subsystem 204. The selector subsystem 204 indicates a reply to the BSC a-interface 206 by allocating a telephone call for processing the telephone call and using a selector call setup response 818. Upon receiving call answer 818, BSC a interface 206 sends a radio link setup request 819 to selection subsystem 204. The selection subsystem 204 responds by sending a channel resource request 820 to the BTS 102.

Upon receiving channel resource request 820, BTS102 allocates channel processing resources for modulating and demodulating forward and reverse link traffic channels associated with the telephone call and sends a channel resource response message 822 to selection subsystem 204. The selection subsystem 204 responds by sending a connection request 824 to the BTS102, and the BTS102 responds by sending a connection reply 826 to the selection subsystem 204. Selection subsystem 204 then sends null traffic data 828, start traffic data message 830, and null traffic data 832 to BTS 102. BTS102 responds to the start traffic data message 830 and the null traffic data 832 by transmitting null traffic data 836 to subscriber unit 100 via the forward link traffic channel. Selection subsystem 204 also sends a radio link resource message 834 to BSC a interface 206. After receiving radio link resource message 834, BSC a interface 206 sends BTS channel assignment message 838 to BTS102, and BTS102 sends channel assignment message 840 to subscriber unit 100 by transmitting it over the forward link paging channel. Subscriber unit 100 processes the assignment message 840 containing the received data on the assigned forward link traffic channel and transmits a reverse link traffic channel preamble 842 to make the reverse traffic channel available to BTS 102. Once the reverse link signal is acquired, the BTS102 sends a start reverse link message 844 to the selection subsystem 204. The selection subsystem 204 responds by sending a reverse link grant 846 to the subscriber unit 100 over the forward link traffic channel. As described above, messages exchanged between selection subsystem 204 and subscriber unit 100, such as reverse link accept 846, are passed through the BTS, but are drawn here as direct access for ease of drawing. Further, the selection subsystem 204 sends a radio link setup response 848 to the BSCA interface 206. At this point, a bi-directional channel is established.

Subscriber unit 100 initiates the registration procedure by sending a DTAP location update request 850 to selection subsystem 204. The selection subsystem 204 directs the location update request to the BSC a interface 206 that initializes the SCCP connection with the GSM-MSC106 according to the GSM a interface protocol. After storing the classmark information, BSC a interface 206 generates an SCCP connection request message that includes a complete layer three information message 852, which includes a BSS location request 851. The completion layer three message 852 is part of the GSM a interface protocol and is well known in the art. The GSM-MSC106 responds by sending an acknowledgement request 853 to the BSC a interface 206, which provides a transmission message 854 containing the acknowledgement request to the selection subsystem 204. The selection subsystem then provides a transmission message 855 containing the confirmation request to the subscriber unit 100 via the forward link traffic channel. The subscriber unit 100 communicates a transmission acknowledgement request to the GSM-based message processing portion which responds by sending a transmission acknowledgement 856 to the selector subsystem 204 over the reverse link traffic channel. The selection subsystem 204 transparently provides the transport message 857 to the BSC a-interface 206. BSC a-interface 206 then sends an acknowledgement 858 to GSM-MSC106 according to the GSM a-interface protocol. GSM-MSC106 responds by sending an encryption mode command 860 to BSC a-interface 206. BSC a-interface 206 then begins the encryption initialization procedure by sending a BSS encryption mode command 860 to selection subsystem 204, while selection subsystem 204 sends an encryption mode command 862 to subscriber unit 100 via the forward link traffic channel. After processing the ciphering mode command 862, the subscriber unit 100 sends a ciphering mode complete message 864 in ciphered form to the selection subsystem 204 via the reverse link traffic channel. Upon receiving BSS encryption mode command 860, selection subsystem 204 begins encrypting-decrypting all additional signaling and call data related to the telephone call. Selection subsystem 204 then sends a BSS encryption mode complete message 866 to BSC a-interface 206. BSC a-interface 206 responds by sending an encryption mode complete command 868 to GSM-MSC106 according to the GSM a-interface protocol.

GSM-MSC106 then sends ID request 874 to BSC a-interface 206 in accordance with the GSM a-interface protocol, and BSC a-interface responds by providing the ID request to selection subsystem 204 over the forward link traffic channel. The selection subsystem 204 then sends a provide transmission message 870 containing the ID request to the subscriber unit 100 via the forward link traffic channel. The GSM based message processing portion of the subscriber unit responds by generating an ID reply and the subscriber unit 100 sends the ID reply to the selection subsystem 204 in a transmission message 880 over the reverse link traffic channel. The selection subsystem 204 then provides an ID reply to the BSC a-interface 206 by sending a transfer message 878, and the BSC a-interface 206 replies by providing an ID reply to the GSM-MSC106 according to the GSM a-interface protocol. GSM-MSC106 receives ID response 876 and sends location update 882 to BSC a-interface 206 according to GSM a-interface protocols. BSC a-interface 206 then sends a transmission message 886 containing a location update accept to selection subsystem 204, and selection subsystem 204 responds by providing a location update accept to subscriber unit 100 by sending a transmission message 890 over the forward link traffic channel. The subscriber unit 100 responds by sending a transport message 891 containing a Temporary Mobile Subscriber Identity (TMSI) reallocation order to the selection subsystem 204, and the selection subsystem 204 then sends a transport message 892 containing a transport TMSI reallocation order to the BSC a interface. BSC a-interface 206 responds by sending a TMSI reallocation order 894 to GSM-MSC106 according to the GSM a interface protocol. After receiving TSMSI reassignment command 894, GSM-MSC106 sends a clear command 896 to BSC a-interface 206 to initiate the release of the radio link.

Referring now to fig. 10B, which illustrates signaling messages exchanged during subscriber unit registration according to one embodiment of the present invention, BSC a interface 206 sends a BSS radio link release request 902 to selection subsystem 204 after receiving a clear command 896. After receiving BSS radio link release request 902, selection subsystem 204 sends a release command 900 to subscriber unit 100 via the forward link traffic channel. The subscriber unit 100 responds by sending a release command 904 over the reverse link traffic channel to the selection subsystem 204. The selection subsystem 204 then sends an end forward traffic channel command 906 and a disconnect acknowledgement 910 to the BTS 102. The selection subsystem 204 sends a release resource request 914 to the BTS102 and the BTS102 responds by sending a release resource response 916. Upon receiving the release reply 916, the selection subsystem 204 sends a BSS radio release reply 918 to the BSC a-interface 206. Selection subsystem 204 then sends a BSS call release acknowledgement 922 to BSC a interface 206 and releases the selected resources associated with the telephone call. BSC a interface 206 sends a BSS reallocation request 924 to call control processor 202 indicating that the selection and service resources related to the telephone call have been released and that additional calls can be handled. In addition, BSC a-interface 206 indicates to GSM-MSC106 that the call has been released by sending a clear complete 926 according to the GSM a-interface protocol. Call control processor 202 responds to BSS reallocation request 924 by sending a BSS reallocation response 928 to the BSC a interface. When reassignment reply 928 is received by BSC a interface 206, the location update procedure is completed.

A wireless telecommunications system utilizing a CDMA air interface incorporating a GSM a interface protocol may be employed by first establishing a CDMA air interface between the subscriber unit 100 and the BSS 105 to complete call initialization and subscriber unit registration, and then by establishing a network telecommunications connection between the subscriber unit 100 and the GSM-MSC106 along a forward link traffic channel. A CDMA interface for use with a GSM a interface network may also be provided by employing a BSC a interface that receives GSM a interface messages and examines the GSM a interface messages and makes various response actions. These actions include translating GSM a-interface signaling messages into an internal BSS protocol and determining the appropriate response to each message based on the CDMA air interface configuration and capabilities. Suitable acknowledgements include allocation of signal processing resources in response to allocation requests. The CDMA interface used with the GSM A interface network can also be realized by adopting a selector unit, and the selector unit monitors and starts to process the encrypted message when the encrypted message is sent. This allows the encryption features of the GSMA interface network to be provided in conjunction with the soft handoff features of the IS-95 over-the-air protocol.

Fig. 11 is a schematic diagram of BSC a-interface 206 configured in accordance with one embodiment of the invention. The message processing and generation system 990, SS7 stack interface 992, and BSC packet interface 994 are coupled via a local bus. During operation, SS7 stack interface 992 passes signaling messages sent according to the GSM a interface. SS7 stack interface 992 also passes signaling messages associated with the signaling messages to message processing and generation system 990. In addition, the message processing and generation system 990 exchanges signaling messages with the BSC packet interface 994 via the local bus. BSC packet interface 994 responds by placing the received signaling message data in a BSS network packet and extracting the signaling message data from the BSS network packet and providing the data to message processing and generation system 990. Message processing and generation system 990 performs the various message validation and signaling message generation functions described above for the BSC a interface to respond to received signaling message data. In the preferred embodiment of the present invention, the message processing and generation system 990, the SS7 stack interface 992, and the BSC packet interface 994 are comprised of semiconductor microprocessors and memory systems, although in other embodiments one microprocessor and memory system may be sufficient to implement the functions of two or three systems.

Fig. 12 is a schematic diagram of a subscriber unit 100 configured in accordance with one embodiment of the present invention. Antenna 890 receives the forward link RF signals transmitted from BTS102 and passes them to RF processing system 892. The RF processing system 892 down-converts the signal to baseband and digitizes the baseband signal. Digitized signal processing system 984 processes the digitized baseband signals according to the CDMA protocol used to process the transmitted signals. As mentioned above, the CDMA protocol used in one embodiment of the present invention IS related to the physical signal modulation technique of the IS-95 protocol, although other CDMA protocols are compatible with the present invention. Signal processing by the digitized signal processing system 984 includes demodulation with forward link spreading and channel codes, as well as Viterbi decoding and block deinterleaving, as is well known in the art. The processing is performed on a frame-by-frame basis. The final frame of digitized data from the digital signal processing system 984 is switched to the control system 986. Control system 986 receives frames of digitized data and determines whether the digitized data is a signaling message or user data based on header information contained within each frame. The user data is switched to an input-output system 988 which typically converts the user data to audio information, but which can also provide the user data in a digital format for processing by other digital systems. The signaling data is assembled into signaling messages that are divided into transport signaling messages or local signaling messages by control system 986 using examination of the header bits of the messages. Non-transmitted or local signaling messages are passed to interface control 987, which processes the messages and responds accordingly. The corresponding response includes configuring the digital signal processing system 986 for transceiving the baseband digital signals by providing the necessary spreading and channel codes and generating the outgoing signaling messages for transmission to the BTS102 of fig. 4 in accordance with the various call processing procedures described above. The transport signaling messages are passed to network control 989, which is referred to as the GSM message processing portion of subscriber unit 100. Network control 989 processes the local signaling messages and generates corresponding responses, which include generating outgoing signaling messages according to the various processing procedures described above. Outgoing signaling messages generated by network control 989 are placed in transport messages by control system 986 and provided to digital signal processing system 984 along with outgoing signaling messages from interface control 987, and digital signal processing system 984 performs Viterbi encoding, block interleaving, modulation, and spreading of data in accordance with CDMA signal processing techniques. The CDMA processed data IS passed to an RF signal processing system 982 which generates Quadrature Phase Shift Keyed (QPSK) reverse link RF signals using the digitized data based on the IS-95 indicia transmitted to BTS102 of fig. 4.

In a preferred embodiment of the present invention, the digital signal processing system 984 is comprised of a Digital Signal Processor (DSP) controlled by software in a memory system (not shown). In addition, control system 986 is comprised of a microprocessor that is also controlled by software instructions in a memory system (not shown). The software instruction portions for controlling the microprocessor are used to implement interface control 987 and network control 989. In another embodiment of the invention, the control system 986 and the digital signal processing system 984 may be implemented using one or more custom integrated circuits, where the network control 989 and interface control are part of the integrated circuit used to implement the control system 986. Also in the configuration shown here, control system 986 is coupled between input-output system 988 and digital signal processing system 984. In another embodiment of the present invention, each of the three systems may be coupled using a shared data bus. In addition, the control system 986 and the digital signal processing system 984 may share the same memory system by sharing a data bus or by being disposed on the same integrated circuit.

A method and apparatus for providing wireless telecommunication services using a CDMA interface and a GSM communication network is thus described. The description of the preferred embodiment is sufficient to enable one of ordinary skill in the art to utilize the invention. To the extent that they do not depart from the scope of the invention, they will be readily apparent to those skilled in the art. The invention is therefore defined by the claims appended hereto.

Claims

1. A method of processing signaling messages in a base station subsystem of a wireless communication system, comprising the steps of:

a) transparently transmitting a direct transfer application part message received from the subscriber unit to a mobile switching center of the global system for mobile communications; and

b) internally processes cdma signaling messages from the subscriber units,

c) the direct transfer application part transmits a direct transfer application part signaling message received from a mobile switching center of the global system for mobile communications to the subscriber unit; and

d) base station subsystem mobile application part messages received from a mobile switching center of the global system for mobile communications are internally processed to allocate call processing resources necessary to provide the functionality required by the base station subsystem mobile application part messages.

2. The method according to claim 1, wherein said step a) comprises the steps of:

a.1) receiving a signaling message from the subscriber unit;

a.2) determining that the signaling message is in a transfer message;

a.3) putting any content of the signaling message into a direct transmission application part signaling message; and

a.4) sending the direct transmission application part message to a mobile switching center of a global system for mobile communication.

3. A method of processing signaling messages in a base station subsystem of a wireless communication system, comprising the steps of:

transparently transmitting to the subscriber unit a direct transfer application part signaling message received from a mobile switching center of the global system for mobile communications; and

base station subsystem mobile application part messages received from a mobile switching center of the global system for mobile communications are internally processed to allocate call processing resources necessary to provide the functionality required by the base station subsystem mobile application part messages.

4. A method according to claim 3, characterized in that the method further comprises the steps of:

transparently transmitting a direct transfer application part signaling message received from the subscriber unit to a mobile switching center of the global system for mobile communications; and

the local signaling messages received from the subscriber units are processed internally.

5. The method of claim 3, wherein said step a) comprises the steps of:

a.1) receiving a signaling message from a mobile switching center of a global system for mobile communications;

a.2) determining that the signaling message is a direct transfer application part message;

a.3) putting the signaling message into a transmission signaling message formatted according to an internal base station subsystem protocol; and

a.4) sending a transfer signaling message formatted according to said internal base station subsystem protocol to said subscriber unit.

6. A base station subsystem of a wireless communication system, the base station subsystem comprising:

a signaling message processing system for transparently transmitting the signaling message if the signaling message is a direct transfer application part message and processing the signaling message according to its contents if the message is a base station subsystem mobile application part message to allocate call processing resources necessary to provide the functions required by the base station subsystem mobile application part message; and

a radio frequency signal processing system for establishing a radio frequency interface using radio frequency signal processing according to a code division multiple access signal processing technique.