Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-11-30
2002-04-16
Kincaid, Lester G. (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S435100, C455S552100, C370S338000, C370S401000
Reexamination Certificate
active
06374108
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the field of mobile radio communication systems.
BACKGROUND
Prior art mobile radio communication systems may be divided up into cells. Mobile telephones or mobile radios, henceforth referred to as mobile stations, can move within a cell. Mobile stations can also move from one cell to another.
FIG. 1
illustrates a single cell of a cellular radio system. The elements shown in
FIG. 1
show the general scheme of a personal mobile radio (PMR) system
10
. Portable radios
2
,
4
and
6
of
FIG. 1
can communicate with a base station
8
. Radios
2
,
4
and
6
could equally well be mobile radios mounted in vehicles. Each of the radios shown in
FIG. 1
can communicate through base station
8
with one or more other radios. If radios
2
,
4
and
6
are capable of direct mode operation, then they may communicate directly with one another or with other radios, without the communication link passing through base station
8
. Radios
2
,
4
and
6
constitute mobile stations in this system.
Examples of prior art radio systems of the general type illustrated in
FIG. 1
are the iDEN and TETRA radio systems.
FIG. 2
shows the arrangement of several cells
110
,
120
,
130
,
140
,
150
of a cellular radio system. A ‘Software and Measurement Infrastructure’ (SwMI)
100
controls these five cells. The SwMI and the cells which the SwMI controls together constitute a radio ‘network’. The SwMI is responsible for a variety of functions. These typically include control of the assignment of IP addresses to mobile stations operating in the network, and the routing of communications to and amongst mobile agents in the network. A radio such as those shown as
2
,
4
or
6
in
FIG. 1
can move from cell to cell within the network, communicating in any of the cells.
The SwMI
100
shown in
FIG. 2
performs several functions, indicated as ‘FA’, ‘IP’ and ‘HA’ in block
100
. The ‘IP’ box indicates that the SwMI is responsible for allocating IP addresses (numbers) to radios operating within the cells
110
-
150
. The IP address allows packets of data with the correct IP address to be delivered to the radio within the network. The SwMI will keep a table showing the cell within which a mobile radio is located, in order to be able to route calls to a base station located within communication range of the mobile station.
The ‘HA’ block in element
100
indicates that the SwMI also performs ‘Home Agent’ (HA) functions for radios which normally operate in the network. Finally, the ‘FA’ block in element
100
indicates that the SwMI also performs ‘Foreign Agent’ (FA) functions for radios which enter the network, but which normally do not operate in that network. The Home Agent and Foreign Agent functions will be explained in greater detail below and in connection with FIG.
4
.
Mobile stations may be capable of operating in a number of different networks, for example those in different countries. This is referred to as ‘roaming’. Already, a radio designed according to the TETRA standard may roam from one network to another. Within the GSM and PCS
1800
digital mobile telephone standards, mobile telephones may roam between networks and/or countries.
In future, it will be desirable for mobile stations to be reachable easily through Internet Protocol (IP) addressing. It would be particularly desirable for IP addressable mobile stations to be able to roam from one network to another network.
Several schemes have been proposed to allow IP addressable mobile stations to roam within a cellular radio communications network, or between such networks.
Four examples of these schemes are explained below.
Mobile Internet Protocol
A fully mobile internet protocol system has been proposed. In this system, the mobile stations are capable of recognising when they are in a ‘foreign’ cell which is not part of the network within which they normally operate. The network within which they normally operate is the network in which they are under the control of their ‘Home Agent’. The home agent is provisioned with IP addresses for the mobile stations within the network within which the mobile station normally operates. A cell not under control of the home agent is referred to as being under the control of a ‘Foreign Agent’.
When a mobile station has moved from its home network to another, foreign network, data packets with IP addresses can still reach the mobile station. The mobile internet protocol allows the home agent to map and encapsulate the IP addresses of mobile stations into a ‘care of’ address of the foreign agent, for forwarding to the foreign agent.
According to the mobile internet protocol proposal, the mobile stations will be able to transmit information to their Home Agent about the Foreign Agent where they are currently situated. This requires the mobile station to be adapted to recognise that it is not in a cell which is under the control of the Home Agent, and also to recognise the identity of the Foreign Agent, and to provide that information to its Home Agent as part of performing registration with the Home Agent.
iDEN Mobile IP radio
The IDEN Mobile IP radio has a mode where it can perform a mobile IP role as a proxy for non-mobile Data Terminal Equipment (DTE) attached to it. An example of such a DTE might be a lap-top portable computer. In this case, the iDEN radio must be arranged to perform the proxy function, and must itself be mobile IP capable in the sense described above.
Cellular Digital Packet Data Mobility
Cellular Digital Packet Data (CDPD) is a wireless data system used in the USA. In this system, IP addressing whilst roaming is possible only if both the infrastructure and the mobile station are adapted for the mobility function.
Thus in CDPD, IP address roaming is only possible for those handsets which have been adapted appropriately, and for these handsets, only within cells which can support roaming.
TETRA Packet Data Standard
The TETRA packet data standard EPT WG3(98) 005 describes the means for the SwMI to allocate an IP address to a Mobile radio. The IP allocation procedure is part of TETRA ‘context activation’. A mobile station performs context activation. Context activation is the act of a mobile station registering with a network to start sending and receiving packet data using IP addressing over the network. The network assigns an IP address to the mobile station at the time of context activation. Thus context activation allows the mobile station to gain an internet connection to send and receive ‘IP packets’.
A TETRA radio does not need to perform context activation in order to simply conduct voice communication over a radio network. However, when the radio needs to send packet data over the TETRA network, then the radio must perform context activation. The TETRA radio may be commanded to perform context activation by the user. Alternatively, the radio may realise that it needs to perform context activation due to an outside stimulus, such as when the radio has been connected to a PC, and the PC boots up.
When context activation is complete, the network can map the IP address assigned to a radio to that radio's Individual TETRA Subscriber Identity (ITSI). When the network receives a packet of data for the radio, then the network can locate the radio using the location map which it holds of the radios' ITSI numbers. This then allows the network to forward the data packet to the radio's location within the network.
The IP address allocated to a mobile station in a network can be either ‘static’ or ‘dynamic’. A ‘static’ IP address is normally an address which the mobile radio asks to use when it performs context activation. This will be the IP address which the mobile radio has used previously.
However, a radio may not specify any particular IP address at context activation. If this is the case, then there are two possible outcomes. Firstly, the network may recognise the mobile station, and allocate to the mobile station the same IP address as the network has previously assigned to that mobile station. This is stati
Averbuch Rod
Crisler Kenneth James
Hughes John
Jakobsen Ken
Romano Guy George
Kincaid Lester G.
Santema Steven R.
Treleven Colin
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