MXPA01000672A - Base station handover in a hybrid gsm/cdma network. - Google Patents
Base station handover in a hybrid gsm/cdma network.Info
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- MXPA01000672A MXPA01000672A MXPA01000672A MXPA01000672A MXPA01000672A MX PA01000672 A MXPA01000672 A MX PA01000672A MX PA01000672 A MXPA01000672 A MX PA01000672A MX PA01000672 A MXPA01000672 A MX PA01000672A MX PA01000672 A MXPA01000672 A MX PA01000672A
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- mobile station
- gsm
- cdma
- base station
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/14—Reselecting a network or an air interface
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/0005—Control or signalling for completing the hand-off
- H04W36/0055—Transmission or use of information for re-establishing the radio link
- H04W36/0066—Transmission or use of information for re-establishing the radio link of control information between different types of networks in order to establish a new radio link in the target network
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/14—Reselecting a network or an air interface
- H04W36/142—Reselecting a network or an air interface over the same radio air interface technology
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/10—Reselecting an access point controller
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W36/00—Hand-off or reselection arrangements
- H04W36/16—Performing reselection for specific purposes
- H04W36/18—Performing reselection for specific purposes for allowing seamless reselection, e.g. soft reselection
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- Mobile Radio Communication Systems (AREA)
Abstract
A mobile wireless telecommunication system includes base stations of a first type operating according to a first air interface, and base stations of a second type operating according to a second air interface. Methods and apparatus are provided for handing over a mobile station in the system from a first base station, which is of the first type, to a second base station, which is of the second type. A communications link is established over the first air interface between the mobile station and the first base station. Data are received from the mobile station responsive to a signal received by the mobile station over the second air interface from the second base station, substantially without breaking the communications link with the first base station. The mobile station is handed over from the first to the second base station responsive to the data received therefrom.
Description
TRANSFER OF STATIONS BASED ON A HYBRID NETWORK OF GLOBAL SYSTEM FOR TELECOMMUNICATIONS
MOBILE / MULTIPLE ACCESS BY CODE DIVISION
FIELD OF THE INVENTION The present invention relates generally to wireless telecommunications, and specifically to advanced cellular telephone networks.
BACKGROUND OF THE INVENTION The global system for mobile communications (GSM) is used in cellular telephone networks in many countries around the world. GSM offers a useful range of services and network standards. Existing GSM networks are based on time-division multiple access digital communication (TDMA) technology. In a cellular network based on TDMA, each mobile subscriber unit communicates only with an individual base station at any given time. When a subscriber moves from one cell to another, a "difficult transfer" takes place in which the base station with which the subscriber is communicating is disconnected from its link with the subscriber and a new base station is taken. Multiple access with code division (CDMA) is an enhanced digital communications technology, which offers more efficient use of radio bandwidth than TDMA, as well as a more reliable fading-free link between cell phone subscribers and the base stations. The CDMA guideline is IS-95, promulgated by the Telecommunications Industry Association (TIA), which provides the capability of "soft transfer" or "transfer", where the movement of a cell to another, the subscriber unit is temporarily in contact with two or more base stations at the same time.This smooth transfer, made possible by the code division approach, decreases the probability of a connection loss, which can occur frequently in Difficult transfers The PCT application, PCT / US96 / 2076, which is incorporated herein by reference, describes a wireless telecommunications system that uses a CDMA air interface (i.e., basic RF communications protocols) to implement GSM network services and protocols using this system, at least some of the TDMA base stations (BSS) and subscriber units of a network Existing GSM's will be replaced or supplemented by the corresponding CDMA equipment. The CDMA BSS in this system is adapted to communicate with GSM mobile switching centers (MSCs) via a normal GSM A interface. The core of GSM network services is maintained in this way, and it is transparent to users to change from TDMA to CDMA. Hybrid cellular communications networks, which incorporate both GSM and CDMA elements, are also described in PCT patent publications, WO 95/24771 and WO 96/21999, in the article by Tscha et al, entitled "A Subscriber Signaling Gateway between CDMA Mobile Station and GSM Mobile Switching Center ", in Proceedings og the 2nd International Conference on Universal Personal Communication, Ottawa (1993), pp. 181-185. which are incorporated herein by reference. None of these publications deals with the specific issues of how to make sufficient transfers of subscriber units between different base stations in these hybrid networks. PCT patent application, PCT / US97 / 00926, which is also incorporated herein by reference discloses transfer methods between systems between the CDMA and TDMA BSS in a hybrid GSM / CDMA telecommunications system, The GSM / BSS BSS TDMA generates beacon pilot signals according to CDMA technology. During a telephone call, a subscriber unit detects the pilot signals and notifies a base station controller that the signals have been detected. The subscriber unit is then transferred from the CDMA to the BS? of TDMA without interrupting the call.
SUMMARY OF THE INVENTION It is an object of the present invention to provide methods and apparatus for use in a mixed network of TDMA / CDMA cellular communications. It is a further object of some aspects of the present invention to provide improved methods and apparatus that allows the transfer of a subscriber unit between TDMA and CDMA base stations without interrupting communications. In preferred embodiments of the present invention a mixed GSM / DMA cellular communications system includes both TDMA and CDMA base stations, jointly controlled by a mobile switching center (MSC). Systems of this type are generally described in the PCT patent applications mentioned above, which are incorporated herein by reference. A subscriber unit in the network, also referred to herein as a mobile station (MS), is capable of communicating with both types of base stations, by appropriately switching between the TDMA and CDMA overhead interfaces, while preferentially using protocols of GSM network over both types of interface. It is a feature of the preferred embodiments of the present invention that the communication system may be based on a GSM / TDMA infrastructure with the addition of CDMA BSS, and substantially without any other modification to the existing infrastructure. In order to determine when a transfer should occur, an MS in communication with a base station of one type (CDMA or TDMA) monitors RF signals that are oriented from another base station, which may be a base station of the other type (TDMA or CDMA), respectively. A message sequence between the current base station and the MS allows the MS to acquire the appropriate synchronization information with respect to the new base station, and report this information back to the current base station. The information is used by the system to allow the MS to establish an air interface with the new base station, after which the transfer occurs without substantially disrupting communications between the MS and the network. In the context of the present patent application, these transfers between base stations are referred to as "assisted mobile transfers". Assisted mobile transfer is used in GSM and CDMA systems known in the art, wherein a mobile station measures and reports the strength of the signals received from a base station transceiver in a neighboring cell before it is transferred to that cell . In hybrid GSM / CDMA systems that have been proposed to date, however, mobile stations are presumed to be capable of receiving signals from either a CDMA or TDMA base station at any given time (or a CDMA beacon). associated with a TDMA base station, as in the aforementioned patent application, PCT / US97 / 00927), but not both, and therefore are not able to provide this type of assistance. The provision of mobile assistance in accordance with the principles of the present invention allows transfers to be made more smoothly and reliably than would otherwise be possible. In some preferred embodiments of the present invention, the MS switches between the operation of TDMA and CDMA in the course of a telephone call, according to the instructions received from the base station with which the unit is in communication. Before the transfer occurs, the MS receives signals from the base signals of both TDMA and CDMA, and reports back to the base station with respect to the signals it is receiving. The information reported in this way is reported back and used by the BSC to initiate the transfer. Preferably, the MS comprises an individual radio transceiver, and therefore, at any given time the MS can communicate with either the TDMA or CDMA base station, but not both. (In accordance with the principles of IS-95, however, as described above, the unit can communicate with more than one CDMA base station at a time). It is further noted that each GSM / TDMA base station has its own synchronization clock, to which the MSs in communication with it are synchronized, while the CDMA base stations synchronize to each other at a real time of the day. Therefore, in the switching between the TDMA and CDMA stations, the MS in each case acquires and synchronizes its operation to the appropriate clock signal without substantially interrupting the telephone call. In some of these preferred modalities, the MS is in communication with a CDMA base station when it is determined that the unit can be transferred to a GSM / TDMA base station. The transmission of CDMA by the MS transceiver is temporarily interrupted, during which time the unit performs a neighboring GSM scan in general in accordance with GSM standards for acquiring and synchronizing the TDMA base station. Preferably, the CDMA transmission is interrupted by an individual frame typically 20 msec. Long, creating an idle time interval according to the IS-95 standard. After the TDMA base station is identified and the appropriate messages exchanged, a traffic channel is opened between the base station, and the MS is switched to the TDMA base station while the interruption is minimized substantially of a telephone call that is carried out by the MS. In other of these preferred modalities, the
MS is in communication with a TDMA base station when it is determined that the unit can be transferred to a CDMA base station. In order to synchronize with the CDMA station, the MS acquires the time of the day, preferably by receiving an exact time of the day from the TDMA base station, where the GSM network is provided with the necessary equipment to generate and spread the time of the day. Preferably, the network includes a cellular broadcast system (CBS), in accordance with the GSM standard, which is used to receive day time, provided for example by the global positioning system (GPS) or received from a or more of the CDMA base stations, and disseminate it through the network to the MS. Alternatively, the MS temporarily interrupts the reception of TDMA in order to acquire and synchronize the day time of the CDMA station. In this way, although some degradation of the signal may result from TDMA time slots, thus lost, the mobile assisted transfer from TDMA to CDMA in general is more reliable and less disruptive to a user of the MS than that would be otherwise possible.
Although preferred embodiments are described herein with reference to MSs having an individual transceiver for the use of TDMA and CDMA, it will be appreciated that the principles of the present invention can be applied in a similar manner using subscriber units and physical equipment of the system. other types, particularly using a subscriber unit having TDMA and CDMA transceivers, separated or only partially integrated. Therefore, a mobile wireless telecommunication system, including base stations of a first type operating according to a first air interface, and base stations of a second type, is provided, according to a preferred embodiment of the present invention. which operates according to a second air interface, vn method for transferring a mobile station in the system from a first base station, which is of the first type, to a second base station, which is of the second type, which includes: establishing a link communication on the first air interface between the mobile station and the first base station; receiving the data from the mobile station responsive to a signal received by the mobile station on the second air interface from the second base station, substantially without breaking the communication link with the first base station; and transferring the mobile station from the first to the second base station responsive to the data received therefrom. Preferably, the reception of the data includes the reception of a signal strength measurement, and the transfer of the mobile station includes comparing the measurements of the signal strengths of the first and second base stations and transferring the sensitive mobile station to the comparison. Preferably, the application of the data includes the application of a weighting factor to the measurement of the signal strength, wherein the application of the weighting factor includes varying the factor according to a condition of the network in the system. Additionally, the application of the weighting factor includes transmitting a weighting factor over the communication link to the mobile station, which applies the weighting factor to the measurement. Preferably, the reception of the data includes the reception of an identification of the second base station based on a decoding by the mobile station of the received signal on the second air interface. In a preferred embodiment, the transmission from the first base station to the mobile station of a list of base station frequencies of the second type in the system, such that the mobile station seeks to receive the signal at a frequency in the list.
Preferably, the transfer of the mobile station includes transmitting a transfer command from the first base station. Preferably, the establishment of the communication link and the reception of the signal sensitive data includes' the establishment of the link and the reception of the signal in the mobile station using an individual RF transceiver in the mobile station. In a preferred embodiment, one of the first and second air interfaces includes a TDMA interface and the other of the interfaces includes a CDMA interface, wherein the TDMA interface preferably includes a GSM interface, and wherein the interface of C'DMA is configured to carry GSM network messages. Preferably, the CDMA interface is based on an IS-95 standard. Preferably, the establishment of the communication link includes using a single layer of radio resource management protocol to administer the first air interface, and wherein the transfer of the mobile station includes using the individual layer of resource management protocol. radio to manage or manage the second air interface. Additionally, the reception of the data from the mobile station includes defining an area of overlap between a first region that is served by the first air interface and a second region that is served by the second air interface, and activate the mobile station to receive the data when the mobile station is in the overlap area. In a preferred embodiment, the first air interface includes a CDMA interface, and wherein the second air interface includes a GSM / TDMA interface, and the reception of data from the mobile station includes activation of the mobile station to interrupt a CDMA communication link to receive and decode a GSM / TDMA signal. Preferably, the activation of the mobile station includes the interruption of the CDMA communications for the duration of an IS-95 frame, wherein the reception of the data includes receiving an identification of the second base station based on the decoding of the GSM frequency and frequency correction channels of the signal by the mobile station. In another preferred embodiment, the first air interface includes a GSM / TDMA interface, and the second air interface includes a CDMA interface, and the reception of the data from the mobile station includes control of the mobile station to interrupt the communication link. communications to receive and decode a CDMA signal.
Preferably, the reception of the data includes the transport of day time information through the GSM / TDMA interface. Additionally, the transport of the day time information includes the diffusion of the time information information of the time of day through the system using a GSM cell broadcast service, where the diffusion of the day time information includes receiving a day time and an associated GSM frame number from a transceiver in communication with a first type base station in the system. Preferably, the mobile station decodes a synchronization channel of the CDMA signal to derive the time of day. Alternatively or additionally, the reception of the data includes transporting a message from the GSM cell broadcast service to the mobile station to initiate a search by the mobile station for a signal from the base station of the second type. Preferably, the transport of the GSM cell broadcast service message to the mobile station includes the transport of the message to be received by the mobile station while the mobile station is operating in a delicate mode. Preferably, the reception of the data from the mobile station includes the reception of an identification of a CDMA pilot beam decoded by the mobile station. Additionally, the method includes correlating the second base station as a GSM base station to control the transfer. Preferably, control of the mobile station includes control of the mobile station to receive the CDMA signal during a first time segment of TDMA and to decode the signal during a subsequent TDMA time segment while communicating with the base station on the TDMA interface to generate the data that will be received by the base station. Further provided, according to a preferred embodiment of the present invention, a method for transporting the day time information to a mobile station in a wireless GSM telecommunications system, includes: entering the day time information into the system; and disseminate the information to the mobile station about the system. Preferably, the GSM wireless telecommunications system includes a cell broadcast system, and the broadcast of the day time information includes the dissemination of information about the cell broadcast system. Preferably, the broadcasting of the day time information includes the broadcasting of a message to be received by the mobile station while the station is operating in a dedicated mode. Additionally, the broadcast of day time information includes receiving a day time and an associated GSM frame number from a transceiver in communication with the system, and the method includes synchronizing the mobile station to a signal of CDMA transmission using day time information. In a preferred embodiment, the method includes determining a location of the mobile station responsive to a transmission whereby day time information to a plurality of base stations in the system. Preferably, the introduction of the day time includes opening a data call from a transceiver having the information of the day time to the cell broadcast center, where the opening of the data call preferably includes receiving the information of day time from a GPS device. Alternatively, the opening of the data call includes receiving the day time information from a CDMA cell associated with the GSM system. Further provided, in accordance with a preferred embodiment of the present invention, is a GSM mobile wireless telecommunications system, which includes a first base station subsystem and a second base station subsystem, at least one of the subsystems it operates on. according to a CDMA air interface, a method for transferring a mobile station in the system from the first to the second base station subsystem, which includes: correlating at least the first and second subsystems operating in accordance with the CDMA air interface as a GSM / TDMA subsystem; establishing a communication link between the mobile station and the first base station subsystem, so that the mobile station receives a first signal from the first base station subsystem; receiving data from the mobile station responsive to a second signal received by the mobile station from the second base station subsystem, without substantially disrupting the communication link with the first base station subsystem; comparing the strengths of the first and second signals, substantially as if both of the first and second base station subsystems were GSM / TDMA subsystems; and transferring the mobile station from the first the second sensitive base station subsystem to the comparison of signal strengths. Preferably, the correlation of at least one of the subsystems operating according to the CDMA air interface includes assigning a GSM frequency and location to the subsystem. Further preferably, the establishment of the communication link and the transfer of the mobile station include transporting messages between the first and second subsystems that a mobile switching center in the system via a GSM interface A. Preferably, both the first and the second base station subsystems operate according to the CDMA air interface, where the transfer of the mobile station includes the transport of a new long code of IS-95 through the interface A, substantially without violating the protocols of the interface A. Preferably, the reception of the data from the mobile station includes applying a weighting factor to the second signal, and wherein the comparison of the signal strengths includes comparing the weighted signal , wherein the application of the weighting factor includes transporting the weighting factor to the mobile station, which applies the weighting factor to the second signal. Preferably, the application of the weighting factor includes varying the factor according to a condition of the network in the system. Also provided, according to a preferred embodiment of the present invention, is a wireless communication apparatus, for use in a mobile telecommunications system, which includes: A base station of a first type that transmits and receives a first signal of agreement to a first air interface; a base station of a second type that transmits and receives a second signal according to a second air interface; and a mobile station, which receives the second signal on the second air interface from the base station of the second type in so far as it maintains a communication link on the first air interface with the base station of the first type, and transmits data to the base station of the first type sensitive to the second signal so that the mobile station is transferred from the first to the second base station in response to the transmitted data. Preferably, the data transmitted by the mobile station includes a measurement of the signal strength, such that the mobile station is transferred in response to a comparison of the signal strengths of the first and second signals. Preferably, a weighting factor is applied to the signal strength measurement, wherein the weighting factor is varied according to a network condition in the system. Preferably, the weighting factor is transmitted over the communication link to the mobile station, which applies the weighting factor to the measurement. Additionally, the mobile station decodes the second signal to determine an identification of the base station of the second type. Preferably, the base station of the first type transmits to the mobile station a list of frequencies of mobile stations of the second type in the system, such that the mobile station seeks to receive the second signal at a frequency in the list. Preferably, the base station of the first type transmits a transfer order to the mobile station, whereby the mobile station is transferred from the first to the second base station. Additionally, the mobile station includes an individual RF transceiver that communicates with both base stations of the first and second types. In a preferred embodiment, one of the first and second air interface includes a TDMA interface, and the other of the interfaces includes a CDMA interface, wherein the TDMA interface preferably includes a GSM interface, and wherein the CDMA interface is configured to transport GSM network messages. Preferably, the CDMA interface is based on an IS-95 standard. Further preferably, the mobile station uses a single layer of the radio resource management protocol to administer both the first and the second air interfaces. Preferably, the base station activates the mobile station to receive the second signal on the second air interface when the mobile station is in an area of overlap between a first region that is served by the first air interface and a second region that is it serves for the second air interface. In a preferred embodiment, the first air interface includes a CDMA interface, and the second air interface includes a GSM / TDMA interface, and the base station of the first type activates the mobile station to interrupt the communication link for receiving and decoding a GSM signal. Preferably, the mobile station interrupts the link for the duration of an IS-95 frame. Additionally, the mobile station processes the second signal to decode the GSM frequency synchronization and corron channels of the signal.
In another preferred embodiment, the air interface unit includes a GSM / TDMA interface, and the second air interface includes a CDMA interface, and the base station of the first type controls the mobile station to interrupt the communication link to receive and decode a CDMA signal. Preferably, the base station of the first type transports the daytime information to the mobile station through the GSM / TDMA interface. Preferably, the apparatus includes a GSM cell broadcast center, which transports the day time information through the mobile station system using a GSM cell broadcast service, wherein the cell broadcast center it receives the day time information and a GSM frame number associated with it is from a transceiver in communication with a base station of the first type of the system. Alternatively or additionally, the mobile station decodes a synchronization channel of the CDMA signal to derive the day time. Preferably, the GSM cell broadcast center transports a cell broadcast service message to the mobile station to initiate a search by the mobile station for the second signal, wherein the mobile station receives the broadcast service message of cell while the mobile station is operating in a dedicated mode. Alternatively or additionally, the mobile station processes the CDMA signal to identify a pilot CDMA beam. Preferably, the mobile station receives the CDMA signal during a first TDMA time segment and processes the signal during a subsequent TDMA time segment while communicating with the base station over the TDMA interface to generate the data. for transmission to the base station. There is further provided, according to a preferred embodiment of the present invention, an apparatus for transporting the day time information to a mobile station in a GSM wireless telecommunications system, which includes a cell broadcast center, which broadcasts the information to the mobile station using a GSM cell broadcast system. Preferably, the apparatus includes a transceiver in communication with the system, which transmits a day time and a GSM frame number associated with the cell broadcast center, where the transceiver operates a data call through the system to the cell broadcast center to transport the day time and the box number associated with it.
Preferably, the mobile station is synchronized to a CDMA transmission signal using the day time information. Further preferably, the mobile station receives the information from the cell broadcast system while operating in a dedicated mode. There is further provided, according to a preferred embodiment of the present invention, an apparatus for introducing day time information to a communications controller in a wireless telecommunications system, which includes: a clock receiver, which receives day time information from a clock source; and a radio transceiver, which receives the daytime information from the radio signal receiver, and which opens a data call through a system to the communications controller to transport the information thereto. Preferably, the communication controller includes a GSM cell broadcast center, wherein the radio transceiver receives a GSM frame number from a base station in the system, and transports the frame number to the broadcast center of the GSM network. cell along with the day time information. Preferably, the clock receiver includes a radio receiver that receives the day time information from a CDMA communications cell, wherein the radio transceiver includes the radio receiver. Alternatively, the clock signal receiver includes a GPS device. Further, in accordance with a preferred embodiment of the present invention, an apparatus for wireless mobile telecommunications in a telecommunications system is provided.
GSM, which includes: a mobile station; and a first- and a second base station subsystem, which transmits the first and second signals to the mobile station, at least one of which is a CDMA signal, and both of the subsystems that correlate with the GSM system as GSM base station subsystems, wherein the mobile station is transferred from the first to the second subsystem in response to a comparison of the strengths of the first and second signals received by the mobile station, substantially as if both the first and the second subsystems of base station were operated in accordance with a GSM / TDMA air interface. Preferably, the subsystem that transmits the CDMA signal is assigned to a GSM frequency and location in the system. Additionally, messages are transported in the first and second subsystems of a mobile switching center in a system via the GSM interface A, wherein the first and second signals include CDMA signals. Preferably, a new long code of IS-95 is transported through the interface A from the second to the first subsystem in order to transfer the mobile station substantially without violating the protocols of the interface A. Preferably, the mobile station applies a weighting factor to the second signal before the signal strengths are compared. Further provided, in accordance with a preferred embodiment of the present invention, is a mobile station for use in a wireless telecommunications system that includes CDMA and TDMA base stations, which includes: an individual mobile radio transceiver, which communicates with the CDMA and TDM base stations; a modem unit, which encodes signals for transmission by the mobile transceiver and decodes signals received by it, such that the signals are encoded in CDMA for communication with the CDMA base station and are encoded in TDMA for communication with the station TDMA base; and a terminal equipment, through which a user of the mobile station communicates with the modem unit. Preferably, the modem unit encodes the signals according to the protocols of the GSM radio interface layer. Further preferably, the mobile station receives and processes a signal from one of the CDMA base stations substantially without interrupting a communication link between the mobile station and the other one of the CDMA and TDMA base stations. Also provided, according to a preferred embodiment of the present invention, is a method for transporting messages to a plurality of mobile stations operating in a dedicated mode in a GSM wireless telecommunications system including cell broadcast service, which includes : broadcast the messages in the mobile stations about the cell broadcasting service; and receiving the messages in the mobile stations substantially without interrupting the operation of the dedicated mode of the mobile stations. Additionally, in accordance with a preferred embodiment of the present invention, an apparatus for wireless mobile telecommunications in a telecommunications system is provided.
GSM, which includes: a cell broadcast center, which broadcasts messages on a cell broadcast system; and a mobile station, which receives the messages as long as it communicates in a dedicated mode, substantially without interrupting the communications in the dedicated mode. The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic block diagram of a hybrid GSM / CDMA cellular communications system, in accordance with a preferred embodiment of the present invention; Figure 2A is a schematic block diagram illustrating the communication protocols between a mobile station and the base station subsystems in the system of Figure 1, in accordance with a preferred embodiment of the present invention; Figure 2B is a schematic block diagram of a GSM / CDMA hybrid mobile station, in accordance with a preferred embodiment of the present invention; Figures 3A and 3B are schematic block diagrams illustrating stacks of communication protocol between the elements of the system of Figure 1, according to a preferred embodiment of the present invention; Figure 4A is a schematic block diagram illustrating the transfer of a mobile station from a CDMA base station to a GSM base station in the system of Figure 1, in accordance with a preferred embodiment of the present invention; Figure 4B is a schematic block diagram illustrating the signal flow associated with the transfer of Figure 4A, in accordance with a preferred embodiment of the present invention; Figure 5 is a schematic block diagram illustrating the signal flow associated with the provision of day time information, in the system of Figure 1, according to a preferred embodiment of the present invention; Figure 6 is a schematic illustration showing cells in a GSM / CDMA hybrid cellular communications system, useful in understanding a method for transferring a mobile station from a GSM base station to a CDMA base station, in accordance with a preferred embodiment of the present invention; Figure 7 is a schematic block diagram illustrating the signal flow associated with the transfer from a GSM base station to a CDMA base station, in accordance with a preferred embodiment of the present invention; Figure 8 is a schematic block diagram illustrating the transfer of a mobile station between the CDMA base stations in a hybrid GSM / CDMA cellular communications system, in accordance with a preferred embodiment of the present invention; and Figure 9 is a schematic illustration showing the associated signal flow in the transfer of Figure 8, according to a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Reference is now made to Figure 1, which is a schematic block diagram of a hybrid GSM / CDMA cellular communications system, in accordance with a preferred embodiment of the present invention. The system 20 is constituted around a public land mobile network (PLMN) 22, which is based on the GSM communications standard, as described hereinabove. The infrastructure for these networks already exists and is widely used in many countries, and the present invention has the advantage of allowing the gradual introduction of the CDMA service in conjunction with this network without requiring major changes in the existing infrastructure. The PLMN 22 comprises at least one mobile services switching center (MSC) 24, or possibly several of these centers (although only one MSC is shown for clarity of illustration), which controls network operations within a geographical area. Among other functions, the MSC is responsible for the registration of the location of the subscriber units and the transfer of the subscriber units in the base transfer, as well as the link of the PLMN 22 to a public switched telephone network (PSTN) and / or a network packet data (PDN) 48. The PLN also comprises a network management center (NMC) 26 and a cell broadcast center (CBC) 28. These functions are further described later. The system 20 includes a plurality of stations 20 (MS) 40, which communicate with the PLMN 22 via a plurality of subsystems 30 and 32 of base stations (BSS) on a wireless RF link at one or more of the accepted frequencies of cellular communication The MS 40, which is also known as a subscriber unit, is capable of communicating with both the GSM BSS 30, using a substantially normal GSM TDMA signaling protocol, and the CDMA BSS 32, using the communication methods based in CDMA described later in the present. Additionally, although in normal GSM systems, the mobile stations may typically receive CBC broadcasts 28 only in the idle state, the MS 40 is capable of receiving these broadcasts during a call through the BSS 30, as will be further described in FIG. later way. Although for security of clarity, only one of each of MS 40, GSM BSS 30 and CDMA BSS is shown in Figure 1, it will be understood that in reality, the system 20 typically comprises a plurality of each of these elements of system. BSS 30 of GSM as the BSS 32 of CDMA are communicated and controlled by MSC 24. Communication between GSM BSC 30 and MSC 24 is substantially in accordance with GSM standards. The CDMA BSS 32 is modified in relation to the CDMA standard of IS-95 to communicate with the PLMN 22 according to the GSM standards, and particularly to communicate with MSC 24 via the GSM standard interface A, as it is further described further with reference to Figures 3A and 3B. The BSS 32 also communicates with CBC 28, to receive messages to be broadcast on air, and comprises a radio maintenance and operation center (OMC-R) 38. The OMC-R communicates with the NMC 26 only on a Q3 interface of GSM standard, preferably using an information model based on the series of specifications 12. XX of GSM which are incorporated herein by reference. Optionally, the BSS 32 can be linked to a general packet data service (GPRS) 50, as proposed by the European Telecommunications Standards Institute (ETST). Alternatively or additionally, the BSS 32 can be coupled for the transmission of packet data directly to the PSTN / PDN 48 (although this connection is not shown for reasons of simplicity, in Figure 1), preferably with a link to the Internet through this. The communications between the CDMA BSS 32 and the MS 40 are constituted in an "air interface" of CDMA, which in general is in a preferential agreement with the IS-95 standard for CDMA communications. The BSS 32 is constituted around a base station controller (BSC) 34, which controls and communicates with several base station transceivers 36 (BTS). Each BTS transmits RF signals and receives RF signals from MS 40 when the MS is within a geographical area, or cell, that is served by the particular BTS. When during a telephone call, the MS moves from the cell of one CDMA BTS 36 to another, a "soft transfer" (or transfer and between the BTSs, as is known in the CDMA technique) is presented. system service regions 20, however, that do not have CDMA coverage (ie, CDMA BTS 36 does not exist in this region), or in which coverage is weak or congested. to this region during a telephone call, the MS is transferred from the CDMA BTS to a BTS associated with the GSM BCB 30 without interrupting the call Similarly, if the MS 40 moves from a region served only by the BSS 30 of GSM to the CDMA BTS 36 cell during a call, the MS is preferably transferred from the GSM to the CDMA BSS, the methods for performing these transfers between the CDMA and GSM / TDMA services and vice versa, as well as as between a CDMA BSS 32 and another, they are described adi secondarily later. By virtue of these methods and the architecture of the system 20, as shown in Figure 1, the MS 40 receives the benefits of the CDMA service in those regions served by the system 20 in which the service has been implemented, without lose service in the TDMA regions. The transitions between the CDMA and TDMA regions are substantially transparent to users of the MS 40, because high-level GSM network protocols are observed throughout the system and only the low-frequency RF air interface is changed. level during the transition. Figure 2A is a block diagram schematically illustrating communication protocol stacks between el-MS 40 and BSS 30 and 32, according to a preferred embodiment of the present invention. The MS 40 communicates with the GSM BSS 30 over a GSM Um interface, which is based on a normal TDMA air interface, so that substantially no modification to the BSS 30 or normal Layer interface protocols is required. 1 and GSM Layer 2 in order to adjust the MS 40. The MS 40 communicates with the CDMA BSS 32 over a CDMA Um interface, based on the CDMA IS-95 air interface with certain modifications. The descriptor units known in the art are capable of operating on either a GSM Um or a CDMA Um interface, but not both. In order to support both of these interfaces, the MS 34 comprises a mobile (ME) equipment (Figure 1), which must include any of the two radio transceivers, one configured for operation in TDMA and the other for CDMA, or a individual transceiver that can dynamically switch between TDMA and CDMA. The ME includes a mobile termination (MT), which supports the terminal equipment (TE) 46 for the input and output of data and / or voice. In addition, MS 40 comprises a subscriber identity module (SIM) 44, in accordance with GSM standards. Figure 2B is a schematic block diagram illustrating the MS 40 comprising an individual radio transceiver in the ME 42, in accordance with a preferred embodiment of the present invention. The MS 40 is constituted around a modem unit 59, which includes a DSP core 60 capable of generating and processing both TDMA and CDMA signals. Preferably, the core 60 comprises an ASIC device, which includes a self-contained CDMA transmission / reception processing, which is supported by the GSM synchronization logic circuit 64 and a GSM hardware accelerator 62 (or DSP) ), as well as having a port for SIM 44. The core 60 receives inputs and distributes the output to TE 46. in this case, TE 46 is represented as a microphone and high audio voice, and the core 60 reviews D / A and A / D conversions, as well as speech coding functions in the audio signals, as is known in the art. The voice coding of either GSM or CDMA is applied, depending on whether MS 40 is in contact with the GSM BSS 30 or the CDMA BSS 32. The core 60 can be configured, additionally or alternatively to work with TE 46 provided with the input / output of digital data, such as a facsimile device. The core 60 transfers the digital data, which may be in either TDMA or CDMA format, to a mixed signal output device 66. The device 66 processes and converts the data to a form of analog baseband, for introduction to the RF transmitter 68. A duplexer 70 transports the resulting RF signals via the antenna to the GSM or CDMA base station, as appropriate. The signals received from the base station are passed through the duplexer 70 through the RF receiver 72 and a mixed signal input device 74, which performs baseband conversion and AGC functions, to the core 60. Preferably , the transmitter 68, the receiver 12 and the mixed signal devices 66 and 74 are controlled by the core 60. The transmission and reception of RF by MS 40 are preferably at frequencies in the 900 to 1800 MHz band of GSM, for compatibility with the existing GSM equipment, particularly the BSS 30. Assuming that the MS 40 includes only the individual transceiver shown in Figure 2B, operating in the GSM band, the CDMA equipment in the system 20 must be configured in an appropriate manner for operate in this frequency range, too. Returning to Figure 2A, if the MS 40 physically includes a transceiver or two, it must support Layers 1 and 2 dual air interface in each protocol row, for the operation in relation to the GSM BSS 30 and the BSS 32 of CDMA, respectively. The CDMA air interface between MS 40 and CDMA BSS 32 comprises CDMA Layer 1, which operates in a normal IS-95 protocol, and GSM-CDMA Layer 2, in which the operation of IS-95 it is modified to adjust the needs of the GSM network services. Layer 2 supports the transmission of frames between MS 40 and BSS 30 or 32. Layer 2 of GSM-CDMA includes functionality, such as message ordering, priority and fragmentation, and suspension and resumption of communications, which is they normally support by normal GSM Layer 2, but not by CDMA IS-95. With respect to GSM BSS 30, Layers 1 and 2 of air interface are in accordance with GSM standards, substantially without modification. The normal GSM protocols include a third Radio Interface Layer (RIL3), which includes 3 sublayers, above the Layer 1 and Layer 2 of GSM, the smaller of these three sublayers of the RIL3 is a Resource Management layer. Radio (RR), which supports the sublayers of Mobile Administration (MM) and Connection Management (CM) above it. The sublayers of RIL3 in the GSM BSS 30 are substantially unchanged with respect to the GSM standard, and the GSM sub-layers MM and CM remain equally substantially unchanged in the MS 40. The sub-layer of the CM supports the signaling for call processing, as well as the complementary services of GSM and short message service (SMS). The MM sub-layer supports the signaling required to locate MS 40, administration of authentication and encryption keys. In order to support the MM and CM layers, a GSM-CDMA RR layer is introduced in the MS 40 and the BSS 32 protocol stacks. The GSM-CDMA RR layer, which manages the radio resources and maintains the radio links between MS 40 and BSS 30 and 32, is "aware" of the existence of the dual lower layers of GSM and CDMA (Layers 1 and 2) in the protocol stack of MS 40. Calls the lower layers appropriate in the MS stack to communicate with either the normal RIL3 RR layer over the GSM Um interface or the GSM-CDMA RR layer of BSS 32 over the CDMA Um interface, depending on the instructions received from the BSS with which it is in communication. The MM and CM layers are not processed by BSS 32, but rather they are delayed between MS 40 and MSC 24 for processing in a substantially transparent manner to the subsequent CDMA air interface layers. The RR layer in the MS stack also controls the transfer between the corresponding air interfaces defined in Layers 1 and 2 and assists in cell selection for transfer, under instructions of MSC 24 and the BSS. Regardless of which of the air interfaces is in use, the GSM-CDMA RR layer supports the GSM RIL3-MM and CM normal layers above it. The RR layer preferentially offers a complete radio resource management functionality as defined by GSM specifications 04.08 and 04.08, which are incorporated herein by reference. Although a "RR" layer per se is not defined by the CDMA IS-95 standard, the GSM-CDMA RR layer described herein maintains the full functionality of the IS-95 radio resources, as well. In accordance with GSM standards, the functionality of the RR layer includes services in both the dedicated mode and the idle mode operation (that is, services performed during a telephone conversation). Operation in the unoccupied mode of the RR layer includes automatic cell selection and unoccupied transfer between GSM and CDMA cells, as well as between pairs of CDMA cells and GSM cell pairs, with indication of cell change as specified by the GSM standard. The RR layer in idle mode also performs broadcast channel processing, as specified by the GSM and CDMA standards, and the establishment of RR connections. In dedicated mode, the RR layer performs the following services: • Routing services, service request, message transfer and substantially all other functions specified by GSM standards. • Change of dedicated channels (transfer), including difficult transfers as described below and soft transfers from CDMA to CDMA and "softer". • Mode settings for the RR channel, including transmission mode, channel type and encoding / decoding / transcoding mode. • Management of MS parameters based on the specifications of IS-95. • MS class brand management based on GSM specifications. It will be understood by those skilled in the art that the above characteristics of the RR layer are listed only by way of a brief description and that additional details and characteristics can be added based on. the published specifications of GSM and CDMA. Figure 3A is a block diagram schematically illustrating the protocol stacks used in the signaling interfaces between MS 40, CDMA BSS 32 and GSM MSC 24, in accordance with a preferred embodiment of the present invention. These interfaces enable MS 40 to communicate with GSM MSC 24 over a CDMA air interface. The operation of those interfaces, and particularly the flow of messages through these interfaces, is described in greater detail in the above-mentioned patent application PCT / US96 / 20764 and incorporated herein by reference. When the MS 40 is in communication with MSC 24 via the GSM BSS 30, the protocol stacks are in accordance with GSM standards, substantially unmodified. As noted hereinabove, the MS 40 exchanges signals with the CDMA BSS 32 over the CDMA Um interface, where the BSS and MS protocol stacks are modified to include the GSM-CDMA RR layer and the Layer 2, In Figure 3A, a relay layer is explicitly displayed in the BSS 32 protocol stack, to carry the signaling of RIL3-CM and MM between MS 40 and MSC 24, without greatly processing by BSS 32. Other layers comprised in interface Um are described hereinabove with reference to Figure 2A. The CDMA BSS 32 communicates with GSM MSC 24 over a GSM interface A substantially unchangednormal This interface is based on the protocols of the application part of GSM SS7 and BSS (BSSAP), as is known in the art, preferably in accordance with GSM standard 08.08. The BSSAP supports procedures between MSC 24 and BSS 32 that require interpretation and processing of information related to individual calls and resource management, as well as transfer of call control and mobility management messages and between MSC 2.4 and MS 40. BSS 32 translates the CDMA Layer 1 and the GSM-CDMA Layer 2 and the RR protocols exchanged between the BSS and MS 40 into appropriate protocols of SS7 and BSSAP for transmission to MSC 24 and vice versa. Because the CDMA BSC 34 communicates with GSM MSC 24 using the normal A interface, substantially no modifications are required in the GSM core MSC in order to allow the addition of the CDMA BSS 32 to the GSM system 20. In addition, MSC 24 need not be aware that there is any difference in identity between the GSM / TDMA BSS 30 and the CDMA BSS 32, since both communicate with the MSC in a substantially identical manner on the A interface. Preferred, cells associated with BTS 36 of BSS 32 are mapped by MSC 24 in substantially the same manner as GSM / TDMA cells, and are thus assigned an absolute radiofrequency channel number (ARFCN) of GSM and values of the base station entity code (BSIC) in accordance with the GSM standard. From the point of view of MSC 24, a transfer between the BSS 30 of GSM and the BSS 32 of CDMA, or even between two different BSS of CDMA, is not different from a transfer between two BSS of GSM in a conventional system based on GSM / TDMA. The BSIC of the CDMA cells is assigned to be distinguishable within the system 20 of conventional GSM cells. Figure 3B is a block diagram schematically illustrating the protocol stacks comprised in the transport of voice data between MS 40 and MSC 24 via CDMA BSS 32, in accordance with a preferred embodiment of the present invention. The voice data between MS 40 and BSS 32 is encoded by a CDMA speech encoder, which may comprise any of the standard IS-95 vocoder protocols known in the art. BSS 32 translates CDMA layer 1 into TDMA El signals from GSM, and converts CDMA voice encoded data into compressed-expanded voice data, of PCM grade A, in accordance with the requirements of the standard of the interface A. The MSC 24 transmits and thus receives the voice data to the MS 40 via BSS 32 substantially without considering the fact that the data between the BSS and the MS are encoded in CDMA, as if the MS 40 were operating in GSM / TDMA mode. Figure 4A is a schematic block diagram showing the details of the system 20, useful in understanding a method for the mobile, assisted transfer of MS 40 from CDMA BSS 32 to GSM BSS 30, in accordance with a preferred embodiment of the present invention. Different from Figure 1, the BSS 30 is shown here in detail that includes a BSC 77 and a plurality of BTS 78 and 80. Figure 4A illustrates the transfer of MS 40 from one of the BTS associated with BSS 32, marked here BTS 76, to BTS 78 of the BSS 30. The BSS 32 also includes the BSC 34 of GSM-CDMA and the BTS 36, as described with reference to Figure 1. The transfer from the BTS 76 of CDMA to the BTS 78 of TDMA it is preferentially initiated by the BSS 32 when the MS is determined. 40 is in a location at which this transfer may be desirable. This situation can arise when the signal received from BTS 76 is weak, or when the MS 40 is known to reach the limit of a CDMA coverage, or when the traffic on the CDMA channels is very heavy, alternatively, the BSS 32 may instruct the MS 40 to search for a BTS 78 signal (or other GSM BTS), from time to time independent of any specific pressure to do so. Figure 4B is a signal flow diagram, schematic, illustrating the signals carried between MS 40, BSS 30 and 32 and the MSC 24 in the transfer process of Figure 4A, according to a preferred embodiment of the present invention. The BSC 34 instructs the MS 40 to begin an activated search for neighboring GSM BTSs, where for brief periods, the MS 40 interrupts its communications with the BTS 76 to search for and receive TDMA signals. Preferably, the MS 40 is operating in the IS-95 standard, which allows the transmission of CDMA to be idle for the duration of a 20 msec frame, during which the neighboring GSM-TDMA scan could occur without substantially interrupting CDMA voice communications. Alternatively, this unoccupied period can also be introduced under other CDMA standards, as well. Additionally, as noted above, the MS 40 may comprise separate transceivers of TDMA and CDMA that may be used simultaneously for this purpose. Preferably, the BSC 34 provides the MS 40 with a list of the frequencies of the neighboring GSM-TDMA cells, such as those associated with the BTS 78 and 80. This list is useful in reducing the time needed to search and find the BTS 78, since the MS 40 will be reached only at the frequencies of the cells in the list. The list is updated as MS 40 moves from one cell to another and is maintained during transfers between the TDMA and CDMA base stations. When the MS 40 receives a signal at the BTS frequency 78, it attempts to decode the frequency correction (FCCH) and synchronization (SCH) channels of GSM frequency in the signal. This decoding can take to end several idle periods of CDMA enabled. Once the decoding is successfully achieved, the MS 40 .determines the TDMA signal power level and reports it to the BSS 32 together with the identity of the GSM cell. Based on this information, the BSS determines if and when it will take a transfer. At an appropriate time, the BSS 32 initiates a transfer request to MSC 24. The MSC 24 transports the transfer request to the GSM BSS 30, which recognizes the request. The GSM BSS 30 then carries a transfer order via the MSC 24 and the BSS 32 of CDMA to the MS 40, and the GSM BSS 30 opens a new traffic channel (TCH) with the MS. At this point, the transfer is terminated and the MS 40 switches over the BTS 78. The decision to initiate the transfer may take place if the signal from the GSM BTS 78 becomes stronger than that of the CDMA BTS 76, but from Other criteria are applied preferentially. For example, since the CDMA channels typically offer better transmission quality than the GSM channels, the transfer is preferably initiated only when the GSM signal is stronger than the CDMA signal by a predetermined weighting factor. The factor can be pre-programmed in the system 20, or it can be sent by an MS 40 user. It can also be adjusted dynamically in response to parameters such as the geographical location of the MS and the relative amounts of traffic in the channels of CDMA and TDMA in the system. Figure 5 is a schematic block diagram showing the signal flow in the system 20 (Figure 1) associated with the provision of the time to the relevant BSC and BTS of GSM in the system, according to a preferred embodiment of the present invention. "Ordinarily, the GSM BSS in the system 20 will not report the time of day, since this information is not required by the GSM standard, on the other hand, the IS-95 standard requires that the CDMA base stations is synchronized, since this synchronization is necessary for the identification and decoding of the signals and for the smooth transfer between the cells.Therefore, for the mobile assisted transfer of the MS 40 from BTS 78 from TDMA to CDMA 76
(as shown in Figure 4A, but with the address of the date of inverted transfer), it is necessary that the time of day be provided by the system 20. The method of Figure 5 allows the time of day to be provided to a system 20 without the need for changes in the physical equipment or computer programs in the MSC 24 or in the BSS 30 of GSM or BTS 78 and 80, when using the CBC 28, which is a normal part of the PLMN 22, for spread, 'the time of day on the system. Ordinarily, the CBC 28 provides a cell broadcast service (CBS) in accordance with the GSM interface standards 03.41 and 03.49, allowing general short messages not recognized to the defined geographical areas within the system 20 to be broadcast. Messages are received by MS 40 while it is in a standby or idle mode (ie, when the MS is comprised in a telephone call). For the purpose of providing day time information, however, the MS 40 is preferably able to receive CBS messages not only when it is in idle mode, when prescribed by GSM standards, but also when the MS is in a dedicated mode, that is, during a phone call. The use of the CBS provides the day time information to the MS 40 is particularly desirable when the MS includes only a single radio transmitter and receiver, as shown in Figure 2B; when dual radios are used, one for CDMA and the other for TDMA, the CDMA radio can receive day time while the TDMA radio is in use in a telephone call. In a preferred embodiment of the present invention, CBS messages are also used to initiate an MS 40 search for neighboring cells, as described above with reference to Figure 4B. A special MS 90, which is equipped with a GPS receiver 91 (global processing system), is located in one or more of the GSM / TDMA cells of the system 20 in which the day time is needed. In Figure 5, the MS 90 receives the day time -from the receiver 91 and associates the time with an identification of the current TDMA frame number, based on the synchronization signals transmitted by BTS 78, in accordance with the GSM standard. . Alternatively, the MS 90 can be configured to receive the day time of a CDMA BSS, in which case the GPS receiver 91 will not be required. The MS 90 opens a data call via BTS 78, BSC 77, MSC 24 and PSTN / PDN 58 to the CBC 28, and sends the CBC the cell identification and the correspondence of the current day time and the frame number. Alternatively, the MS 90 may carry the information by any other frame method, such as when using GSM SMS. The CBC 28 then transmits this information about the CBS to the cell, so that the MS 40 receives the day time even when it is operating in the GSM / TDMA mode. Therefore, when the MS 40 is to be transferred to BTS 76 of CDMA, there is no need to acquire the day / time information of the CDMA BTS and the transfer can proceed more quickly and smoothly. The introduction of day time in the system 20 also has benefits for the GSM portion of the system itself, with no connection to the CDMA transfer. For example, the MS 40 can transmit its daytime to different BTS 78 and 80 of GSM, and the synchronization delay of the MS and each of the BTS can be measured and used to determine the location of the MS.
Figure 6 is a schematic mapping map of the overlaying GSM / TDMA cells 92 and the CDMA cells 94 in the network 20, which illustrate aspects of the mobile, assisted transfer of BTS 78 from GSM to BTS 76 of CDMA , according to a preferred embodiment of the present invention. A system operator 20 will recognize that when MS 40 is located in any of the cells 1-5 shown in Figure 6, it can take place in a TDMA / CDMA transfer. Thus, the CBC 28 will broadcast a CBS message to all the dual mode MS (GSM / CDMA) in these cells, including the following information and instructions. • MS starts looking for CDMA (search trigger) signals. • Frequencies of CDMA BTS in overlapping and neighboring cells. • GSM correlation of CDMA cells 94, in accordance with GSM MSC 24. • Identification of the time of day with the current TDMA frame number, preferably as derived from MS 90, although other methods can also be used to supply day time. • Optionally, the factor by which the CDMA signal strength will be multiplied for comparison with the TDMA signal, as described hereinabove.
There is no need for this message to be broadcast in cells 6-10. In addition, it will be understood that only dual-mode MSs are programmed to receive and interpret this message, while ordinary GSM / TDMA MSs will be ignored. The CBS message activates and allows the dual mode MSs to activate and provide information to the GSM BSS 30 and MSC 24 for assistance in carrying out the transfer to one of the CDMA BSS, different from the GSM / hybrid systems. CDMA that have been suggested in the prior art. Figure 7 is a block diagram illustrating the signal flow in the system 20 associated with a mobile assisted transfer from BTS 78 to BTS 76 according to a preferred embodiment of the present invention. As noted above with reference to Figure 6, the transfer begins with the transmission of the search trigger and other information. The search trigger is periodically transmitted by the BTS 78 if the MS 40 is in one of the cells 1-5 (Figure 6) of GSM, with response to some other preprogrammed condition. At the reception of the trigger, the MS 40 shuts down its TDMA traffic with BTS 78 and tunes its receiver to an appropriate CDMA frequency for a short period, preferably for approximately 5 msec. Then after the MS has resumed communication with the BTS 78, it attempts to decode any received CDMA signal in order to identify a pilot beam of the BTS whose transmission it has received, so to speak from BTS 76. As noted above, the BTS 76 correlates in the system 20 as if it were a conventional GSM / TDMA BTS. The MS 40 therefore transmits a report message back to the GSM BTS 78 indicating that the received signal power of MTS 76 (optionally multiplied by the CDMA / TDMA relative weighting actor mentioned above), together with the correlation identification of the GSM system of the BTS 76. From the point of view of the BSS 30 of GSM and MSC 24, there is no substantial difference between the message transmitted by the MS 40 in this case and the message that will be issued as a result of an ordinary neighbor scan of GSM. This measurement and reporting process proceeds until the BSS 30 determines that the MS 40 must be transferred to the BTS 76. At this point, the BSS 30 carries a message to MSC 24 indicating that the transfer is required. The MSC 24 passes a transfer request to the BSS 32, which sends a return acknowledgment via MSC 24 to BSS 30. The GSM BSS 30 which gives a transfer order to MS 40, and a traffic channel is opened between MS 40 and CDMA BTS 76, the transfer finished. The process described above thus allows the assisted, mobile transfer from the BSS 30 of GSM / TDMA to the BSS 32 of CDMA with high speed and reliability, and with a minimum interruption to give service in the intermediate point of a call during which happens the transfer. For the purposes of this transfer, the GSM cells in the system 20 receive the information of the daytime, and the CDMA cells are correlated in the GSM system, at a minimum cost of physical equipment and substantially without the need for reprogram the existing elements of the GSM system. A similar TDMA-CDMA transfer process can be carried out even in the absence of the day time information in the GSM BSS 30. In this case, after the MS 40 has acquired a pilot channel signal associated with the BTS 76, the synchronization channel of the BTS CDMA must be tuned to and decoded in order to derive the day time. This operation takes approximately 300 msec, creating a perceptible, but still tolerable interruption in voice service during a call. Additionally, a similar transfer process may be performed using an MS having two transceivers, one for TDMA and the other for CDMA, as described hereinabove. Figure 8 is a schematic block diagram illustrating the transfer between two different CDMA BSS 101 and 103 within the system 20, in accordance with a preferred embodiment of the present invention. The BSS 101 comprises a BSC 102 and a plurality of BTS 106 and 108; BSS 103 comprises a BSC 104 and a plurality of BTS 110 and 112. BSS 101 and 103 are substantially similar and interchangeable with BSS 32, as shown in Figure 1 described hereinabove, and communicated with MSC 24 of GSM via the GSM interface A. The MS 40 is shown in the figure at the center of a transfer from BTS 108 to BTS 110 under the control of MSC 24. Although the transfer takes place between two CDMA BSS, from the system point of view, it is a transfer between two GSM BSS, wherein the BTS 108 and 110 is correlated respectively by MSC 24 as GSM cells. Figure 9 is a schematic diagram illustrating the signal flow between system elements 20 shown in Figure 8 in the course of the transfer, according to a preferred embodiment of the present invention. The transfer is activated when the MS 40 reports to BSS 101 that it is receiving a BTS 110 signal with a higher power level than that of BTS 108. The BSS 101 then sends a normal message requested by GSM transfer to MSC 24, specifying the identity of the GSM cell of BTS 110 as the new cell assignment desired for the transfer. The MSC 24 sends a transfer request to the BSS 103, which responds by sending an acknowledgment to the MSC encapsulating a transfer order message RIL3-RR, which passes back to BSS 101. In this way, all messages sent between BSS 101 and 103 meet the requirements of interface A, and the CDMA parameters associated with IS-95 are correlated to corresponding GSM parameters, for example, identification of 13K QCELP vocoder type in CDMA to full-proportion vocoder of GSM. The request, acknowledgment and transfer order are passed through MSC 24 substantially without change. After receiving the transfer order, the previous BSS 101 sends the order message and RR transfer to the MS 40 to effect the transfer to the new BSS 103. The message to MS 40 includes: • A new long code mask, of in accordance with CDMA standards • Power level nominal parameters • Frame shift • Code channel • Layer 2 recognition number • Transmission traffic channel power control parameters • Preamble number • New band class and Frequency Although preferred embodiments are described above with reference to a particular hybrid GSM / CDMA system, it will be appreciated that the principles of the invention can be similarly applied to effect assisted, mobile transfers in other hybrid communication systems as well. . In addition, although preferred embodiments refer to specific communication standards based on TDMA and CDMA, those skilled in the art will appreciate that the methods and principles described hereinbefore can also be used in conjunction with other methods of data coding and modulation. of signal. The scope of the present invention encompasses not only the complete systems and communication processes described hereinabove, but also various innovative elements of these systems and processes, as well as combinations and subcombinations thereof. In this way, it will be appreciated that the preferred embodiments described above are cited by way of example, and the scope of the invention is limited only by the claims.
Claims (92)
- NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1. In a wireless mobile telecommunications system, which includes base stations of a first type that operate according to a first air interface, and base stations of a second type operating according to a second air interface, a method for transferring a mobile station in the system from the first base station, which is of the first type, to a second base station, which is of the second type, comprising: establishing a communication link on the first air interface between the mobile station and the first base station; receiving data from the mobile station in response to a signal received by the mobile station on the second air interface from the second base station, without substantially disrupting the communication link with the first base station; and transferring the mobile station from the first to the second base station in response to the data received therefrom. A method according to claim 1, wherein the reception of the data comprises receiving a measurement of the signal strength, and wherein the transfer of the mobile station comprises comparing the measurements of the signal strengths from the first and second stations base and transfer the mobile station in response to the comparison. 3. A method according to claim 2, wherein the reception of the data comprises applying a weighting factor to the measurement of the signal strength. 4. A method according to claim 3, wherein the application of the weighting factor comprises varying the factor of, according to a network condition in the system. A method according to claim 3, wherein the application of the weighting factor comprises transmitting a weighting factor over communication link to the mobile station, which applies the weighting factor to the measurement. 6. A method according to claim 1, wherein the reception of the data comprises receiving an identification of the second base station based on the decoding by the mobile station of the received signal on the second air interface. A method according to claim 1, and comprising transmitting from the first base station to the mobile station a list of frequencies of base stations and the second type in the system, such that the mobile station seeks to receive the signal at a frequency in the list. A method according to claim 1, wherein the transfer of the mobile station comprises transmitting a transfer command from the first base station. A method according to claim 1, wherein establishing the communication link and receiving the data in response to the signal comprises establishing the link and receiving the signal at the mobile station using an individual RF transceiver at the mobile station . A method according to claim 1, wherein one of the first and second air interfaces comprises a TDMA interface, and the other of the interfaces comprises a CDMA interface. A method according to claim 10, wherein the TDMA interface comprises a GSM interface, and wherein the CDMA interface is configured to carry GSM network messages. 12. A method according to claim 10, wherein the CDMA interface is based on an IS-95 standard. 13. A method according to claim 10, wherein the establishment of the communication link comprises the use of a single layer of radio resource management protocol to administer the first air interface, and wherein the transfer of the mobile station comprises the use of the individual layer of radio resource management protocol to administer the second air interface. A method according to claim 1, wherein the reception of the data from the first mobile station comprises defining an area of overlap between a first region served by the first air interface and a second region served by the second air interface ~~ and activate the mobile station to receive the data when the mobile station is in the -tracking area. 15. A method according to claim 1, wherein the first air interface comprises a CDMA interface, and wherein the second air interface comprises a GSM / TDMA interface, and wherein the reception of data from the mobile station comprises activating the mobile station to interrupt a radio link. CDMA communications to receive and decode a GSM / TDMA signal. 16. A method according to claim 15, wherein the activation of the mobile station comprises the interruption of the CDMA communications for the duration of a frame of IS-95. 17. A method according to claim 15, wherein the reception of the data comprises receiving an identification of the second base station based on the decoding of the GSM frequency synchronization correction channels of the signal by the mobile station. . 18. A method according to claim 1, wherein the first air interface comprises a GSM / TDMA interface, and the second air interface comprises a CDMA interface, and wherein the reception of the data is from the mobile station and comprises controlling the mobile station to interrupt the communication link to receive and decode a CDMA signal. 19. A method according to claim 18, wherein the reception of the data comprises transporting the day time information through the GSM / TDMA interface. 20. A method according to claim 19, wherein the transport of the day time information comprises the diffusion of the time of day information through the system using a GSM cell broadcast service. A method according to claim 20, wherein the diffusion of the day time information comprises the reception of a day time and a GSM frame number associated from a transceiver in communication with a base station of the first type in the system. 22. A method according to claim 19, wherein the mobile station decodes a synchronization channel of the CDMA signal to derive the time or day 23. A method according to claim 18, wherein the reception of the data comprises the transporting a GSM cell broadcast service message to the mobile station to initiate a search by the mobile station for a signal from a base station of the second type 24. A method according to claim 23, wherein the transport of the GSM cell broadcast service message to the mobile station comprises transporting the message to be received by the mobile station while the mobile station is operating in a dedicated mode 25. A method according to claim 18, wherein The reception of the data from the mobile station comprises receiving an identification of a CDMA pilot beam decoded by the mobile station 26. A method according to the claim ation 18, which comprises correlating the second base station as a GSM base station to control the transfer. 27. A method according to claim 18, wherein the control of the mobile station comprises controlling the mobile station to receive the CDMA signal during a first time segment of TDMA and to decode the signal during a subsequent time segment of TDMA in so much that it communicates with the base station on the TDMA interface to generate the data to be received by the base station. 28. A method for transporting time-of-day information to a mobile station in a GSM wireless telecommunications system, comprising: entering the day time information into the system; and disseminate the information to the mobile station about the system. 29. A method according to claim 28, wherein the GSM wireless telecommunications system includes a cell broadcast system, and wherein the broadcast of the day time information comprises the broadcast and information about the broadcast system of cell. 30. A method according to claim 29, wherein the broadcasting of the day time information comprises the broadcasting of a message to be received by the mobile station while the station is operating in a dedicated mode. 31. A method according to claim 28, wherein the broadcasting of the day time information comprises receiving a day time and an associated GSM frame number and a transceiver in communication with the system. 32. A method according to claim 31, comprising synchronizing the mobile station to a CDMA transmission signal using the time-of-day information. 33. A method according to claim 28, and comprising determining a location of the mobile station in response to a transmission by it of the day time information to a plurality of base stations in the system. 34. A method according to claim 28, wherein the introduction of day time comprises opening a data call from a receiver having the time-of-day information to the ceida broadcast center. 35. A method according to claim 34, wherein the opening of the data call comprises receiving the time information of a GPS device. 36. A method according to claim 34, wherein the opening of the data call comprises receiving the day time information from a CDMA cell associated with the GSM system. 37. In a GSM mobile wireless telecommunications system, which includes a first base station subsystem and a second base station subsystem, at least one of the base station subsystems operating according to a CDMA air interface, a method for transferring a mobile station in the system from the first to the second base station subsystem, comprising: correlating at least one of the first and second subsystems operating according to the CDMA air interface as a GSM / TDMA subsystem; establishing a communication link between the mobile station and the first base station subsystem, so that the mobile station receives a first signal from the first base station subsystem; receiving the data from the mobile station in response to a second signal received by the mobile station from the second subsystem of the base station, without substantially interrupting the communication link with the first base station subsystem; comparing the strengths of the first and second signals, substantially as if both the first and the second base station subsystems were GSM / TDMA subsystems; and transferring the mobile station from the first to the second base station subsystem in response to the comparison of signal strengths. 38. A method according to claim 37, wherein the correlation of at least one of the subsystems cooperates according to the CDMA air interface comprises assigning a GSM frequency and location to the subsystem. 39. A method according to claim 37, wherein the establishment of the communication link and the transfer of the mobile station comprises transporting messages between the first and second subsystems and a mobile switching center in the system via a GSM interface A. 40. A method according to claim 39, wherein the first as the second base station subsystem operates according to the CDMA air interface. 41. A method according to claim 40, wherein the transfer of the base station comprises transporting a new long code of IS-95 through the interface A, without substantially violating the protocols of the interface A. 42. A method according to claim 37, wherein the reception of the data from the mobile station comprises applying a weighting factor to the second signal, and wherein comparing the strengths of the signals comprises comparing the weighted signal. 43. A method according to claim 42, wherein the application of the weighting factor comprises transporting the weighting factor to the mobile station, which applies the weighting factor to the second signal. 44. A method according to claim 42, wherein the application of the operation factor comprises varying the factor according to a network condition in the system. 45. The wireless communication apparatus, for use in a mobile communications system, comprising: a base station of a first type that transmits and receives a first signal according to a first air interface; a base station of a second type that transmits or receives a second signal according to a second air interface; and a mobile station, which receives a second signal on the second air interface from the base station of the second type while maintaining a communication link on the first air interface with the base station of the first type, and transmitting data to the station base of the first type in response to the second signal so that the mobile station is transferred from the first to the second base station in response to the transmitted data. 46. The apparatus according to claim 45, wherein the data transmitted by the base station comprises a measurement of the signal strength, such that the mobile station is transferred in response to a comparison of the signal strengths of the first and second signals. . 47. The apparatus according to claim 46, wherein a weighting factor is applied to the measurement of the signal strength. 48. The apparatus according to claim 47, wherein the weighting factor is varied according to a network condition in the system. 49. The apparatus according to claim 46, wherein the weighting factor is transmitted over the communication link to the mobile station, which applies the weighting factor to the measurement. 50. The apparatus according to claim 45, wherein the mobile station decodes the second signal to determine an identification of the base station of the second type. 51. The apparatus according to claim 45, wherein the base station of the first type transmits to the mobile station a frequency list of mobile stations of the second type in the system, such that the mobile station seeks to receive the second signal at a frequency in the list. 52. The apparatus according to claim 45, wherein the base station of the first type transmits a transfer command to the mobile station, whereby the mobile station is transferred from the first to the second base station. 53. The apparatus according to claim 45, wherein the mobile station comprises an individual RF transceiver that communicates with both first and second rail base stations. 54. The apparatus according to claim 45, wherein the first and second air interfaces comprise a TDMA interface, and the other of the interfaces comprises a CDMA interface. 55. The apparatus according to claim 54, wherein the TDMA interface comprises a GSM interface and wherein the CDMA interface is configured to carry GSM network messages. 56. The apparatus according to claim 54, wherein the CDMA interface is based on an IS-95 standard. 57. The apparatus according to claim 54, wherein the base station uses a single layer of radio resource management protocol to administer both the first and the second air interfaces. 58. The apparatus according to claim 45, wherein the base station activates the mobile station to receive the second signal on the second air interface where the second mobile station is in an overlap area between a first region served by the first air interface and a second region served by the second air interface. 59. The apparatus according to claim 45, wherein the first air interface comprises a CDMA interface, and wherein the second air interface comprises a GSM / TDMA interface, and wherein the base station of the first type activates the mobile station for interrupting the communication link to receive and decode a GSM signal. 60. The apparatus according to claim 59, where the mobile station interrupts the link for the duration of an IS-95 frame. 61. The apparatus according to claim 59, wherein the mobile station processes the second signal to decode the GSM frequency synchronization correction channels of the signal. 62. The apparatus according to claim 45, wherein the first air interface comprises a GSM / TDMA interface, and the second area interface comprises a CDMA interface, and wherein the base station of the first type controls the mobile station to interrupt the communications link to receive and decode a CDMA signal. 63. The apparatus according to claim 62, wherein the base station of the first type transports the day time information to the mobile station through the GSM / TDMA interface. 64. The apparatus according to claim 63, comprising a GSM cell broadcast center, which transports the day time information through the system to the mobile station using the GSM cell broadcast service. 65. The apparatus according to claim 64, wherein the cell broadcast center receives the information of the time of day and an associated GSM frame number from a transceiver in communication with a base station of the first type of the system. 66. The apparatus according to claim 63, wherein the mobile station decodes a synchronization channel of the CDMA signal to derive the day time. 67. The apparatus according to claim 62, and comprising a GSM cell broadcast center that transports a cell broadcast service message to the mobile station to initiate a search by the mobile station for the second signal. 68. The apparatus according to claim 67, wherein the mobile station receives the cell broadcast service message while the mobile station is operating in a dedicated mode. 69. The apparatus according to claim 62, wherein the mobile station processes the CDMA signal to identify a pilot CDMA beam. 70. The apparatus according to claim 62, wherein the mobile station receives the CDMA signal during a first time segment of TDMA and processes the signal during a subsequent TDMA time segment while communicating with the base station over the TDMA interface to generate the data for transmission at the base station. 71. The apparatus for transporting day information to a mobile station in a GSM wireless telecommunications system, comprising a cell broadcast center, which broadcasts the information to the mobile station using a GSM cell broadcast system. 72. The apparatus according to claim 71, and comprising a transceiver in communication with the system, which transmits a day time and a GSM frame number associated with the cell broadcast center. 73. The apparatus according to claim 72, wherein the transceiver opens a data call through the system to the cell broadcast center for transporting the day time and the associated frame number thereof. 74. The apparatus according to claim 71, wherein the mobile station is synchronized to a CDMA transmission signal using the day time information. 75. The apparatus according to claim 71, wherein the mobile station receives the cell broadcast system information while operating in a dedicated mode. 76. The apparatus for introducing time-of-day information to a controller in communications in a wireless telecommunications system, comprising: f a clock signal receiver, which receives the day time information from a clock source; and a radio transceiver, which receives the day-time information from the receiver of the clock signal, and which opens a data call through the system to the communications controller to transport the information thereof. 77. The apparatus according to claim 76, wherein the communication control comprises a GSM cell broadcast center. 78. The apparatus according to claim 77, wherein the radio transceiver receives a GSM frame number from a base station in the system, and transports the frame number to the cell broadcast center along with the weather information. at daytime. 79. The apparatus according to claim 77, wherein the clock signal receiver comprises a radio receiver that receives the day time information from a CDMA communications cell. 80. The apparatus according to claim 79, wherein the radio transceiver comprises a radio receiver. 81. The apparatus according to claim 76, wherein the receiver of the clock signal comprises a GPS device. 82. The apparatus for mobile wireless telecommunications in a GSM telecommunications system, comprising: a mobile station; and a first and a second base station subsystem, which transmits the first and second signals to the mobile station, at least one of which is a CDMA signal, and both of the subsystems that are correlated in the GSM system as subsystems from GSM base station; wherein the mobile station is transferred from the first to the second subsystem in response to a comparison of the strengths of the first and second signals received by the mobile station, substantially as if both of the first and second base station subsystems operated according to a GSM / TDMA air interface. 83. The apparatus according to claim 82, wherein the subsystem transmitting the CDMA signal is assigned to a CDMA frequency and the location in the system. 84. The apparatus according to claim 82, wherein messages are transported between the first and second subsystems and a mobile communication center in the system via a GSM interface A. - 85. The apparatus according to claim 84, wherein the first and second signals comprise CDMA signals. 86. The apparatus according to claim 85, wherein a new long code of IS-95 is transported through the interface A from the second to the first subsystem in order to transfer the mobile station, substantially without violating the protocols of the interface A 87. The apparatus according to claim 82, wherein the mobile station applies a weighting factor to the second signal before the signal strengths are compared. 88. A mobile station for use in a wireless telecommunications system that includes CDMA and TDMA base stations, comprising: an individual mobile radio transceiver, which communicates with the CDMA and TDMA base stations; a modem unit, which encodes the signals for transmission by the mobile transceiver and decodes the signals received by it, such that the signals are encoded in CDMA for communication with the CDMA base station and are coded in TDMA for communication with the TDMA base station; and terminal equipment, through which a user of the mobile station communicates with the modem unit. 89. A mobile station according to claim 88, wherein the mobile unit codes for the signals according to the GSM radio interface layer protocols. 90. A mobile station according to claim 88, wherein the mobile station receives and processes a signal from one of the CDMA and TDMA base stations substantially without interrupting a communication link between the mobile station and the other of the base stations of the mobile station. CDMA and TDMA. 91. A method for transporting messages to a plurality of mobile stations operating in a dedicated mode in a GSM wireless telecommunications system that includes a cell broadcast service, comprising: broadcasting messages from mobile stations about the service of cell broadcast; and receiving the messages in the mobile stations substantially without interrupting the dedicated mode operation of the mobile stations. 92. The apparatus for mobile wireless telecommunications in a GSM telecommunications system, comprising: a cell broadcast center, which broadcasts messages on a cell broadcast system; and a mobile station, which receives the messages while communicating in a dedicated mode, substantially without interrupting the communications in the dedicated mode.
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| KR100403746B1 (en) * | 2002-01-07 | 2003-10-30 | 삼성전자주식회사 | System for hand off using multi party service in mobile communication system and method thereof |
| KR100876746B1 (en) * | 2002-05-13 | 2009-01-07 | 삼성전자주식회사 | Mthod of measurement for handover from nb-tdd comunication system to gsm comunication system |
| US7251490B2 (en) * | 2003-06-18 | 2007-07-31 | Qualcomm Incorporated | System and method for GSM hard handoff |
| JP2005130473A (en) | 2003-10-03 | 2005-05-19 | Matsushita Electric Ind Co Ltd | Radio communication system, base station, and mobile station |
| WO2005089249A2 (en) | 2004-03-12 | 2005-09-29 | Interdigital Technology Corporation | Method and system for switching a radio access technology between wireless communicaiton systems with a multi-mode wireless transmit/receive unit |
| CN101175325B (en) * | 2007-10-19 | 2010-06-16 | 中兴通讯股份有限公司 | Terminal switching method and device under multi-network mode |
| US10523304B2 (en) * | 2015-07-31 | 2019-12-31 | Intel IP Corporation | Network discovery and beam acquisition in 5G rat beam cell operation |
| CN109644341B (en) * | 2016-07-01 | 2022-11-04 | 诺基亚技术有限公司 | Method, apparatus, communication device, radio access system and computer readable medium for communication |
| AU2018335277B2 (en) * | 2017-09-21 | 2023-08-10 | Smartsky Networks LLC | Architecture for integration of multiple networks in an air-to-ground context |
| CN115484195A (en) * | 2022-08-31 | 2022-12-16 | 朗新科技集团股份有限公司 | A receiving and dispatching integrative system, power consumption management system for electric power information acquisition |
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| GB2282730B (en) * | 1993-10-08 | 1998-01-28 | Nokia Telecommunications Oy | Dual mode subscriber terminal and a handover procedure of the dual mode subscriber terminal in a mobile telecommunication network |
| JP3215018B2 (en) * | 1994-09-09 | 2001-10-02 | 三菱電機株式会社 | Mobile communication system |
| GB2296626B (en) * | 1994-12-23 | 1999-07-28 | Nokia Mobile Phones Ltd | Multi-mode radio telephone |
| US5978679A (en) * | 1996-02-23 | 1999-11-02 | Qualcomm Inc. | Coexisting GSM and CDMA wireless telecommunications networks |
| US5870673A (en) * | 1996-08-30 | 1999-02-09 | Telefonaktiebolaget Lm Ericsson | Methods and systems for concurrent receipt of incoming calls from a wide area cellular network and a private radio communications network |
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| MXPA01000672A (en) | Base station handover in a hybrid gsm/cdma network. |
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