Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1998-07-21
2002-03-19
Olms, Douglas (Department: 2661)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C370S232000, C370S252000, C370S389000, C370S391000, C370S394000, C375S220000, C709S237000, C709S250000, C714S748000
Reexamination Certificate
active
06359877
ABSTRACT:
BACKGROUND
This invention relates generally to a method and apparatus for minimizing overhead in a communication system. More particularly, this invention relates to a method and apparatus for minimizing overhead in packet re-transmission in a communication system.
FIG. 1
is a block diagram of an exemplary cellular radiotelephone system, including an exemplary base station
110
and a mobile station
120
. Although denoted a “mobile station”, the station
120
may also be a fixed cellular station. The base station includes a control and processing unit
130
which is connected to the a mobile switching center (MSC)
140
which in turn is connected to a PSTN (not shown). General aspects of such cellular radiotelephone systems are known in the art. The base station
110
handles a plurality of voice channels through a voice channel transceiver
150
, which is controlled by the control and processing unit
130
. Also, each base station includes a control channel transceiver
160
, which may be capable of handling more than one control channel. The control channel transceiver
160
is controlled by the control and processing unit
130
. The control channel transceiver
160
broadcasts control information over the control channel of the base station or cell to mobiles locked to that control channel. It will be understood that the transceivers
150
and
160
can be implemented as a single device, like the voice and control transceiver
170
, for use with control and traffic channels that share the same radio carrier.
The mobile station
120
receives the information broadcast on a control channel at its voice and control channel transceiver
170
. Then, the processing unit
180
evaluates the received control channel information, which includes the characteristics of cells that are candidates for the mobile station to lock on to, and determines on which cell the mobile should lock. Advantageously, the received control channel information not only includes absolute information concerning the cell with which it is associated, but also contains relative information concerning other cells proximate to the cell with which the control channel is associated, as described for example in U.S. Pat. No. 5,353,332 to Raith et al., entitled “Method and Apparatus for Communication Control in a Radiotelephone System”.
Modern communication systems, such as cellular and satellite radio systems, employ various modes of operation (analog, digital, dual mode, etc.), and access techniques such as frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and hybrids of these techniques.
In North America, a digital cellular radiotelephone system using TDMA is called the digital advanced mobile phone service (D-AMPS), some of the characteristics of which are specified in the TIA/EIA/IS-136 standard published by the Telecommunications Industry Association and Electronic Industries Association (TIA/EIA). Another digital communication system using direct sequence CDMA is specified by the TIA/EIA/IS-95 standard, and a frequency hopping CDMA communication system is specified by the EIA SP 3389 standard (PCS 1900). The PCS 1900 standard is an implementation of the GSM system, which is common outside North America, that has been introduced for personal communication services (PCS) systems.
Several proposals for the next generation of digital cellular communication systems are currently under discussion in various standards setting organizations, which include the International Telecommunications Union (ITU), the European Telecommunications Standards Institute (ETSI), and Japan's Association of Radio Industries and Businesses (ARIB). Besides transmitting voice information, the next generation systems can be expected to carry packet data and to inter-operate with packet data networks that are also usually designed and based on industry-wide data standards such as the open system interface (OSI) model or the transmission control protocol/Internet protocol (TCP/IP) stack. These standards have been developed, whether formally or de facto, for many years, and the applications that use these protocols are readily available. The main objective of standards-based networks is to achieve interconnectivity with other networks. The Internet is today's most obvious example of such a standards-based packet data network in pursuit of this goal.
Advantages of introducing a packet data protocol in cellular systems include the ability to support high data rate transmissions and at the same time achieve a flexibility and efficient utilization of the radio frequency bandwidth over the radio interface. General Packet Radio Service (GPRS), which is the packet mode for the Global System for Mobile Communication (GSM) standard, is designed for so-called “multislot operations” where a single user is allowed to occupy more than one transmission resource simultaneously.
An overview of the GPRS network architecture is illustrated in FIG.
2
A. Information packets from external networks enter the GPRS network at a GGSN (Gateway GPRS Service Node)
10
. A packet is then routed from the GGSN via a backbone network,
12
, to a SGSN (Serving GPRS Support Node),
14
, that is serving the area in which the addressed GPRS remote station resides. From the SGSN
14
, the packets are routed to the correct BSS (Base Station System), in a dedicated GPRS transmission. The BSS includes a plurality of base transceiver stations (BTS), only one of which, BTS
18
, is shown and a base station controller (BSC)
20
. The interface between the BTSs and the BSCs are referred to as the A-bis interface. The BSC is a GSM specific denotation, and for other exemplary systems the term Radio Network Control (RNC) is used for a node having similar functionality as that of a BSC. Packets are then transmitted by the BTS
18
over the air interface to a remote station
21
using a selected information transmission rate.
A GPRS register holds all GPRS subscription data. The GPRS register may, or may not, be integrated with the HLR (Home Location Register)
22
of the GSM system. Subscriber data may be interchanged between the SGSN and the MSC/VLR
24
to ensure service interaction, such as restricted roaming. The access network interface between the BSC
20
and MSC/VLR
24
is a standard interface known as the A-interface, which is based on the Mobile Application Part of CCITT Signaling System No. 7. The MSC/VLR
24
also provides access to the land-line system via PSTN
26
.
In most digital communication systems, communication channels are implemented by frequency modulating radio carrier signals, which have frequencies near 800 megahertz (MHZ), 900 MHZ, and 1900 MHZ. In TDMA systems and even to varying extents in CDMA systems, each radio channel is divided into a series of time slots, each of which contains a burst of information from a user. The time slots are grouped into successive frames that each have a predetermined duration, and successive frames may be grouped into a succession of what are usually called superframes. This kind of access technique (e.g., TDMA or CDMA) used by a communication system affects how user information is represented in the slots and frames, but current access techniques all use a slot/frame structure.
Time slots assigned to the same user, which may not be consecutive time slots on the radio carrier, may be considered a logical channel assigned to the user. During each time slot, a predetermined number of digital bits are transmitted according to the particular access technique (e.g., CDMA) used by the system. In addition to logical channels for voice or data traffic, cellular radio communication systems also provide logical channels for control messages, such as paging/access channels for call-setup messages exchanged by base stations and mobile stations. In general, the transmission bit rates of these different channels need not coincide, and the lengths of the slots in the different channels need not be uniform. The set of possible transmission bit rates for a chann
Khan Farooq Ullah
Olofsson Håkan Gunnar
Rathonyi Béla Stefan Kazmir
Burns Doane Swecker & Mathis L.L.P.
Hom Shick
Olms Douglas
Telefonaktiebolaget LM Ericsson (publ)
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