Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-01-11
2004-04-27
Tran, Sinh (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S574000, C370S347000, C370S442000
Reexamination Certificate
active
06728537
ABSTRACT:
TECHNICAL FIELD
The invention relates to a cellular communications system comprising mobile communication units.
BACKGROUND
Communication systems are known in which the users of the system have mobile terminals. These terminals can communicate with each other through the infrastructure of a ‘mobile network’. This network includes base stations, which are central radio transmitter- and receiver units. The base stations are linked to one another by the network. A terminal can also communicate through the mobile network to a traditional fixed line telephone network. A packet radio system may work in this way.
A terminal establishes a communication link to a base station via a radio signal, and communicates over this link. A terminal normally communicates over a radio link set up to the base station which provides the strongest signal, this usually being the base station which is nearest to the mobile terminal at that point in time.
Typically a communication pathway within the system outlined above consists of a first bi-directional radio link between a first mobile terminal and a nearby first base-station. From the first base station the communication link may typically further connect through a fixed line system to another, second base station. The second base station will communicate over a second bi-directional radio link with a second mobile terminal. Thus two-way communication between the mobile terminals is possible.
Communication systems such as that outlined above operate in accordance with internationally agreed standards. A recent standard for such systems is the European Telecommunications Standards Institute's (ETSI) GSM standard number 05.02. Version 6.3.0 of this standard has recently been made available. This standard relates to communication networks and mobile terminals which may communicate using either circuit switched (CS) communication links and/or group switched packet (GPRS) communication links.
A communication in accordance with ETSI standard GSM 05.02 permits the exchange of voice communication and/or data between mobile terminals. Furthermore, this communication system allows mobile terminals of varying sophistication to operate within it, and also foresees the mobile network being able to operate in up to three different modes. These network modes are referred to as ‘Network mode
1
’, ‘Network mode
2
’ and ‘Network mode
3
’ respectively.
The three ‘network modes’ in which the network can operate have some similarities, but differ in several aspects. For the purposes of the invention, it is important to consider how a base station sets up a communication link with a mobile terminal in each of the three different modes.
In all three network modes, a communication link initiated by the mobile network is set up by the base station broadcasting a signal which the mobile terminal receives. The signal used to set up a communication link is referred to as a ‘paging’ signal. When a mobile terminal receives and recognises a paging signal destined for it, the mobile terminal knows that it is to set up a communication link with the base station. For the mobile terminal to receive a paging signal, the terminal must know in advance when to turn on its radio receiver to ‘listen’ for a paging signal destined for that terminal. The mobile terminal is said to be in ‘idle mode’ when it is waiting to be paged by the network.
The mobile terminals used in a communication system built in accordance with the standard GSM 05.02 may have one of three levels of capability. These are as follows:
(i) Class A Mobile Terminals
A Class A terminal is capable of communicating with a base station of the mobile network using both circuit switched and GPRS links simultaneously. This means that the user of the class A terminal can, for example, speak to another user over a circuit switched communication link and simultaneously transmit a data file over a GPRS link.
(ii) Class B Mobile Terminals
A Class B terminal is only capable of communicating with a base station either by a circuit switched link or by a GPRS link at any one time. This means that the user of the class B terminal cannot speak to another user over a circuit switched communication link and simultaneously transmit a data file over a GPRS link.
When a class B terminal is in idle mode, the network can page the mobile terminal for either circuit switched or GPRS communication.
(iii) Class C Mobile Terminals
A Class C terminal is only capable of communicating with a base station by a GPRS link.
A further type of mobile terminal may also be present in the communication system. These are mobile terminals which can only receive CCCH channels, and which have no capability of receiving GPRS signals.
Next, it is important to understand how the network transmits a paging signal to a mobile terminal in accordance with ETSI GSM standard 05.02.
The mobile network can page a mobile terminal on one of two types of channel. The base stations of the mobile network may broadcast a signal on a control channel referred to as the Common Control Channel or ‘CCCH’ channel. A CCCH channel is the standard control channel used in prior art GSM networks to set up a communication link between the base station and a mobile terminal. However, the base stations may broadcast a signal on a control channel referred to as the Packet Common Control Channel or ‘PCCCH’ channel. The PCCCH channel is a physical channel which has been newly created for GPRS networks. The PCCCH channel can serve many purposes, of which paging of GPRS terminals is just one. Notably, it is not mandatory for a GPRS cell to have PCCCH channels. If a cell does not have PCCCH channels, then the base station in the cell pages a GPRS terminal on the ‘CCCH’ channel
FIG. 1
illustrates four CCCH channels in accordance with the GSM 05.02 standard. These channels are labelled CCCH(
0
)-CCCH(
3
).
The definition of a physical channel in GSM is that it comprises a frequency, which may change value or ‘hop’, and a time slot. Each of the four channels shown in
FIG. 1
therefore represents a sequence of transmitted signals which may in reality be transmitted at different frequencies.
The number of circuit switched paging blocks available on each control channel (CCCH) is defined as N. In
FIG. 1
, N=512.
The CCCH signal is made up of a number of multiframes. In the arrangement of
FIG. 1
, this is 64. Each multiframe contains eight paging blocks, making the total of N=512 blocks.
Each block in
FIG. 1
is shown to comprise 4 time-slots. The signals in the four time slots in any one block together make up the circuit switched paging block. Although shown consecutively in
FIG. 1
, the four time slots of a paging block are in reality likely to be broadcast in four identically numbered time slots in four consecutive groups of eight time slots. In each such group of eight time slots, the other seven time slots in the group do not relate to this paging block. Each of these groups of eight time slots is in fact a frame.
The use of the control channels according to the prior art arrangement of GSM 05.02 standard now needs to be considered. In accordance with this prior art arrangement, the mobile terminals in a cell are assigned paging blocks consecutively. The first 512 mobile stations can each be assigned a paging block on channel CCCH(
0
), because it can contain 512 blocks. See FIG.
1
. If there are, for example, 1000 mobile terminals, then 512 terminals will be assigned paging blocks in channel CCCH(
0
), a further 488 terminals will be assigned paging blocks in channel CCCH(
1
), and the channels CCCH(
2
) and CCCH(
3
) will not transmit paging signals to any mobile terminals, so will remain unused.
In practice, both the network and a particular mobile terminal are able to calculate the individual paging block which the base station will use to make contact with that particular mobile terminal. Thus the mobile terminal will be able to monitor for a paging signal at the correct time point to receive any paging signal broadcast to it.
In the GSM system, there are four CCCH chann
Abdesselem Ouelid
Deparis Francois
Ulmer Lionel Frederic
Hackbart Rolland R.
Motorola Inc.
Smith Sheila
Tran Sinh
Vaas Randall S.
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