Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1997-10-22
2001-05-01
Kizou, Hassan (Department: 2662)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S328000, C370S346000, C370S347000
Reexamination Certificate
active
06226279
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to U.S. patent application Ser. No. 08/955,664, filed on even date herewith in the name of the same inventors and entitled “Access Scheme for Packet Data in a Digital Cellular Communications System” which is hereby incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to radio telecommunications and, more particularly, to a packet data telecommunication system for a cellular radio network.
2. Description of the Related Art
In radio telecommunications, such as cellular radio systems, digital modulation schemes, such as time division multiple access (TDMA), are used to transmit both control information and voice traffic over the radio network. In addition, in recent years the transmission of data between computers and other data processing devices over the radio network is increasingly common. One technique which is used for the handling of data traffic over the radio network is circuit switched data services in which a dedicated circuit between transmitting and a receiving station conveys the data from one to the other. An attractive alternative to such circuit switched data services for operators of mobile telephony networks are packet data services. The use of packet data switching enables several mobile users to share the available channel capacity within the system. This technique is well suited to modern data communication applications since data transmissions are usually of a bursty nature and thus do not continuously require a dedicated communications circuit.
A number of different channel access schemes are commonly used in radio communication systems. Each such access scheme has distinct advantages and disadvantages for various applications. For example, fixed assignment access schemes within a radio telecommunications system are used for circuit switched services such as conventional voice telephony and fax. Although not yet widely used in cellular systems, polling schemes may also be employed to enhance the frequency efficiency of a radio system. The most common scheme used for multiple access in a radio system are random access schemes, conventionally employed in many cellular radio telecommunications systems.
In conventional mobile packet radio communication systems, a base station (BS) communicates with a plurality of mobile stations (MSs) over one or more shared packet radio channels. Downlink packet traffic is scheduled by the base station, so that downlink contention between mobile stations is avoided. However, in order for the mobile stations to gain access to the base station on the uplink, they must compete using a random multiple access protocol which inevitably leads to contention and multiple collisions between the different mobile stations which are competing with one another for access on the uplink. Referring to
FIG. 1
, there is shown a simplified block diagram of a radio communications system which includes facilities for transferring packet data to and from a mobile station. The system
10
includes a communication network
12
which includes a base station/transceiver section
14
. The network
12
can be a public land mobile network (PLMN) such as the Personal (formerly, Pacific) Digital Cellular (PDC) system, a digital TDMA cellular radio network.
Network
12
communicates with a mobile station
16
which has the capacity of sending and receiving packet data, via a base station
14
using existing air interface and switching communication protocols. The network
12
also communicates with other mobile stations
20
via a second base station
18
in the network
12
, fixed telephones
22
in a public switch telephone network (PSTN), and terminal work stations
24
and
26
. As shown, the communication between computer terminal
24
and network
12
are made over a wired line connection. The communication between computer terminal
26
and the network
12
are via a wireless radio connection through base station
14
. Consequently, communications to and from phone
22
and computer terminals
24
and
26
can be routed to and from the mobile stations
20
and
16
by means of a network
12
.
Referring next to
FIG. 2
, there is shown the channel structure of an illustrative air interface in a cellular radio system of the type illustrated in
FIG. 1
which accommodates random access packet data channel. The channel structure includes a broadcast channel (BCCH) which is used by the network to broadcast various information to mobile stations such as channel allocation and system information. A set of common control channels (CCCH), including a paging channel (PCH) and a single cell signaling channel (SCCH) are used for transmitting signal information. The PCH is used to page a mobile station while the SCCH is used for transmitting information between the network and the mobile units, for example, requests by a mobile seeking access to the network. The uplink channel of the SCCH is of the random access type. A user packet channel (UPCH) is a channel which is available to multiple users for the transmission of user packet data. The uplink channel of the UPCH is also a random access type.
The appended control channels (ACCH) comprise an auxiliary channel appended to the traffic channel (TCH) for transmitting signal information between the network and the mobile station. The ACCH is further divided into the slow appended control channel (SACCH) which comprises a data channel carrying continuous system administration information such as measurement reports from each mobile of received signal strength measurements obtained for both its presently serving cell and adjacent cells. The fast appended control channel (FACCH) is also appended to a TCH and is a channel which temporarily steals the TCH to perform high speed transmissions. A housekeeping channel (RCH) sometimes replaces the SACCH and is used for transmitting maintenance information on the radio channel. Finally, the traffic channel (TCH) is used for transferring encoded speech and circuit switched user data. It is often further divided into full rate TCH and a half rate TCH for encoded speech.
It is conventional today to use the random access method for uplinking data transfer from a mobile station on the user packet channel (UPCH). The channel structure of the cell is communicated to the mobile users within that cell through the information transmitted on the broadcast channel (BCCH). For example, in the PDC system there is broadcast on the BCCH (and on other channels from time to time) a broadcast information message which contains numerous mandatory and optional parameters, including packet channel structure information and channel restriction information. The latter comprises one octet of data of which a small number of the possible 256 bit combinations are used to indicate to the mobile whether or not particular channels are restricted from access by those mobiles.
In accordance with conventional random access procedures, as soon as the user packet data channel (UPCH) is idle, all mobile users which want to send user data packets to the network will simultaneously compete for the use of that channel. If there is only one access during this competition phase, that user will get hold of the channel and remain its user until the complete data packet has been sent. During the time when the user utilizes the channel, no other mobile seeking to transmit a data packet will try to access it. However, if during the competition phase there is more than one user which simultaneously accesses the channel, a collision occurs and a maximum of one, or often none of those competing users, will get data through the channel. In such cases, each failing user must wait a random time period before it can make a new attempt to seize the channel.
The use of shared random access data channels in conventional packet services within radio networks has numerous disadvantages. For example, during high traffic loads and long packet messages, the probability of a mobile station being able to s
Frid Lars
Hansson Rolf
Herlitz Anders
Ho Duc
Jenkens & Gilchrist
Kizou Hassan
Telefonaktiebolaget L M Ericsson (publ)
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