Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-08-27
2001-11-20
Nguyen, Chau (Department: 2663)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S335000, C370S338000
Reexamination Certificate
active
06320873
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to wireless telecommunications, and specifically to data transmission over advanced cellular communications networks.
BACKGROUND OF THE INVENTION
The Global System for Mobile (GSM) telecommunications is used in cellular telephone networks in many countries around the world. GSM offers a useful range of network services and standards, including facilities for data, as well as voice, transmission. Existing GSM networks are based on time-division multiple access (TDMA) digital communications technology.
Code-division multiple access (CDMA) is an improved digital communications technology, which affords more efficient use of radio bandwidth than TDMA, as well as a more reliable, fade-free link between cellular telephone subscribers and base stations. The leading CDMA standard is IS-95, promulgated by the Telecommunications Industry Association (TIA).
PCT patent application PCT/US96/20764, 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 (BSSs) and subscriber units of an existing GSM network would be replaced or supplemented by corresponding CDMA equipment. CDMA BSSs in this system are adapted to communicate with GSM mobile switching centers (MSCs) via a standard GSM A-interface. The core of GSM network services is thus maintained, and the changeover from TDMA to CDMA is transparent to users.
Hybrid cellular communications networks, incorporating both GSM and CDMA elements, are also described in PCT patent publications WO 95/24771 and WO 96/21999, and in an article by Tscha, et al., entitled “A Subscriber Signaling Gateway between CDMA Mobile Station and GSM Mobile Switching Center,” in Proceedings of the 2nd International Conference on Universal Personal Communications, Ottawa (1993), pp. 181-185, which are incorporated herein by reference. None of these publications deals with specific issues of data communications. Such issues include both the need for protocol compatibility and the different demands of voice and data communications. Although TIA has promulgated standards of CDMA over-the-air data transmission, such as IS-657 and IS-707, the GSM BSS-MSC interface is not suited to support such transmission.
Generally speaking, because GSM was developed primarily for circuit-switched transmission, it is not well suited for packet-switched data, as is commonly transmitted over the Internet. For this reason, the European Telecommunications Standards Institute (ETSI) has proposed a general packet data service (GPRS) to operate in conjunction with GSM cellular networks. GPRS is described in a number of GSM standards, including 02.60, 03.60 and 03.64, which are incorporated herein by reference.
When a subscriber unit (or mobile station—MS) in a GSM network with GPRS wishes to send and/or receive packet-switched data, the MS through the BSS with which it is in communication makes contact with a “serving GPRS support node” (SGSN), over a GSM-standard Gb interface. The data are transmitted and received by the BSS through the SGSN, separately from the voice channels that go through the MSC, to a packet data network (PDN), such as the Internet. The SGSN likewise maintains its own separate mobility management and security facilities. Unlike GSM-TDMA voice communications, GPRS allows dynamic time slot allocation in the air interface between the subscriber units and the SGSN.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide methods and apparatus for conveying packet-switched data through a cellular communications network.
In some aspects of the present invention, the data are conveyed over a CDMA air interface.
In other aspects of the present invention, the data are conveyed in the network in accordance with GSM standards, and particularly with the proposed GPRS standard.
In preferred embodiments of the present invention, a mixed GSM/CDMA cellular communications system includes one or more CDMA base stations (BSSs), controlled by a GSM mobile switching center (MSC). Systems of this type are described in a U.S. patent application entitled “Base Station Handover in a Hybrid GSM/CDMA Network,” filed Jul. 20, 1998, which is assigned to the assignee of the present patent application and is incorporated herein by reference. A subscriber unit in the system, referred to herein as a mobile station (MS), which is in communication with one of the CDMA BSSs over a CDMA air interface, transmits and receives packet-switched data through the system via the CDMA BSS. The MS and the CDMA BSS are adapted to operate substantially in accordance with GSM data networking and signaling protocols. The data transmitted and received by the MS preferably include Internet protocol (IP) data, but other types of data may similarly be conveyed. The term “data” as used in the context of the present patent application and in the claims refers to substantially all types of data that are typically conveyed through packet-switched networks, which may even include voice transmission, as is known in the art.
In some preferred embodiments of the present invention, the system includes a GPRS network, with which the CDMA BSS communicates, in accordance with GPRS data networking and signaling standards. Preferably, the CDMA BSS and MS communicate with a SGSN associated with the GPRS network via a standard GSM/GPRS Gb interface. Signaling and data transmission over a CDMA Um interface between the MS and BSS are adapted to support GSM/GPRS protocols operating over the Gb interface, which is substantially unmodified.
In other preferred embodiments of the present invention, the CDMA BSS has a direct interface to a packet-switching network, such as the Internet. A network service node, preferably a service control point (SCP) functioning as a operator-specific service (OSS) node, is coupled between the GSM MSC and the CDMA BSS. The MSC controls services such as authentication, ciphering and billing, preferably through the SCP using a OSS interface, for example, the CAMEL (customized applications for mobile network enhanced logic) interface as has been proposed by ETSI.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a method for conveying packet data between a mobile station and a GSM network, including:
communicating with a GSM service node to establish a data link between the mobile station and the network via a radio communications base station;
conveying the packet data between the mobile station and the base station over a CDMA air interface; and
transferring the data over the link between the base station and the network.
Preferably, communicating with the node includes communicating with a GPRS node, and transferring the data includes transferring the data via the GPRS node, wherein communicating with the GPRS node includes communicating with a SGSN via a GSM Gb interface. Further preferably, conveying the data includes mapping GPRS frames onto the CDMA air interface, wherein mapping the GPRS data frames includes using a CDMA radio link control to support a GPRS logical link control.
In a preferred embodiment, transferring the data includes transferring data as a GSM operator-specific service, wherein communicating with the node includes communicating with a GSM service control point, which communicates with a switching center via a GSM operator-specific service interface. Preferably, the mobile station communicates with a home location register via a GSM unstructured supplementary service data interface. Alternatively, the service control point communicates with a switching center via a GSM customized applications for mobile network enhanced logic interface.
Preferably, the method includes handing over the mobile station from the base station to another base station, wherein transferring the data over the link includes routing data to the other base station using Mobile IP.
P
Kessler Ilan
Kolor Sergio
Levy Atai
Nevo Ron
Nizri Shlomo
Brown Charles D.
Greenhaus Bruce W.
Kwoh Jasper
Nguyen Chau
Qualcomm Incorporated
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