Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
2000-03-27
2004-08-03
Chin, Wellington (Department: 2664)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
Reexamination Certificate
active
06771635
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the allocation of IP addresses to mobile terminals and in particular to the allocation of a host part of an IP address to a mobile terminal.
BACKGROUND TO THE INVENTION
Subscribers to existing mobile telecommunications networks may under certain circumstances access the Internet using either an Internet enabled mobile telephone (a device often referred to as a “communicator”) or by coupling a palmptop or laptop computer to a conventional mobile telephone, for example using a software or hardware modem.
In digital mobile telephone networks, such as the European GSM (Global System for Mobile communications) system, a mobile telecommunications network can be divided into two parts. The first part is referred to as the “radio network” and consists of base stations (BSs) and base station controllers (BSCs) where a single BSC controls a number of BSs. The second part of the network is referred to as the “core network” and comprises mobile switching centres (MSCs), each MSC being responsible for a number of BSCs. An MSC is analogous to an exchange of a conventional telephone network. Internet traffic is carried over a circuit switched connection established between the mobile terminal and an Internet Service Provider (ISP) via the core network.
The development of future mobile communication standards is currently ongoing. In particular, an enhancement to GSM known as General Packet Radio Service (GPRS) is being developed to introduce a packet switched service into GSM. The introduction of GPRS will effectively add an additional core network to GSM systems, with switching functions being performed in the GPRS core network by Serving GPRS Switching Nodes (SGSNs) and Gateway GPRS Switching Nodes (GGSNs). A third generation digital system is also under development and is known as Universal Mobile Telecommunications System (UMTS). UMTS is likely to incorporate GPRS or a similar packet switched system.
Under current proposals, in both GSM GPRS and UMTS systems, Internet access will be obtained via the packet switched core network. When a mobile terminal requests Internet access, the request is directed via a BS and a Radio Network Controller (RNC, equivalent to the traditional BSC) to a GGSN. The GGSN may act as an Internet Access Server (IAS) or direct the request to a separate IAS. Such a separate IAS is typically operated by an Internet Service Provider (ISP) which is independent from the operator of the mobile network. However, the IAS may alternatively be operated by the mobile network operator. In any case, the integrated or separate IAS allocates to the calling mobile terminal an Internet Protocol (IP) address. According to the existing Internet Protocol version 4 (IPv4), the IP address has 32 bits. According to the proposed Internet Protocol version 6 (IPv6), the IP address is enlarged to 128 bits and comprises a 64 bit routing prefix which uniquely identifies the LAS to the Internet, and also a 64 bit host prefix which uniquely identifies the mobile terminal to the IAS.
The allocated IP address is returned to the mobile terminal via the packet switched core network and the radio network whereupon the mobile terminal is able to commence an Internet session. Assuming that the mobile terminal is registered with its home network when the Internet access is requested, the Internet session is routed via the GGSN of the home network. However, when a mobile terminal is “roaming” and is registered with a foreign network, the Internet session may be conducted via both a GGSN of the home network and a SGSN of the foreign network.
As subscribers of existing digital networks may be aware, Internet access via a mobile terminal is generally extremely slow and unreliable. This is due in part to the need for a slow set-up phase, required each time a new transfer session is commenced, during which session parameters including an IP address are negotiated. Another reason for slow speed (as well as unreliability) is the possibly large distance between the node (e.g. IAS) which allocates an IP address and the mobile terminal, possibly involving one or more intermediate nodes. IP datagrams must be tunnelled between the two end points, often involving additional protocols (e.g. Point-to Point Protocol, Layer
2
Tunnelling Protocol, etc), consuming extra processing and transmission capacity.
Whilst the current proposals for GPRS and UMTS will result in a faster and more reliable radio connection between a mobile terminal and the radio and core networks, they will not eliminate the need to negotiate the IP address prior to commencing an Internet session nor the need to route IP datagrams via one or more switching nodes of the packet switched core network(s).
It is anticipated that in Pv6, two Internet Control Message Protocol (ICMP) messages will be utilised for the purpose of negotiating a host part of an IP address for a mobile terminal connected to a fixed line communications network. A mobile terminal proposes a host part which may be a host part permanently allocated to the mobile terminal or may be the host part last used by the mobile terminal. The proposed host part is included in a Neighbour Solicitation message which is sent by the mobile terminal to other mobile terminals currently connected to the same fixed line network. If it transpires that another of the connected terminals is currently using the same host part, then that other mobile terminal responds by returning a Neighbour Advertisement message to the newly connected mobile terminal. In the event that the newly connected mobile terminal receives such a Neighbour Advertisement message, it must reject the originally proposed host part and propose a new host part. The mobile terminal then includes this newly proposed host part in a Neighbour Solicitation message and the process is repeated until a unique host part has been arrived at.
As already noted, the host part generation process of Pv6 is concerned with mobile terminals connected to fixed line networks. However, the process is not necessarily easily applied in the case of mobile wireless terminals connected to a mobile telecommunications network. For example, a mobile network will not necessarily provide for a mobile wireless terminal to broadcast Neighbour Solicitation messages to other mobile terminals connected to the same network (GPRS and UMTS do not provide for mobile terminal to mobile terminal signalling). Whilst it may be possible to transmit a Neighbour Solicitation message to the mobile network and thereafter to broadcast the Neighbour Solicitation message to other mobile terminals, such a solution would be wasteful of radio interface resources.
A further disadvantage of the proposed IPv6 in so far as it relates to IP address allocation, is that, if a mobile terminal is permanently allocated a host part, it may be possible for third parties to track the movement of a mobile terminal and hence of the user of a mobile terminal. Assuming that such a third party is aware of the host part allocated to a given mobile terminal, and has knowledge of the unique routing prefixes allocated to the various networks, then he could determine the current location of a mobile terminal.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome or at least mitigate the above noted disadvantages of existing systems and methods of allocating IP addresses to mobile terminals. This and other objects are achieved at least in part by negotiating a temporary host part during the establishment of a radio link between a mobile terminal and a mobile telecommunications network. The temporary host part may be used for subsequent IP sessions whilst the mobile terminal is within the mobile network.
According to a first aspect of the present invention there is provided a method of allocating an IP address to a mobile wireless terminal within a mobile telecommunications network, the method comprising conducting a negotiation between the mobile terminal and the network during the establishment of a radio link, to determine a host
Nordman Tom Mikael
Vilander Harri Tapani
Mais Mark A
Telefonaktiebolaget LM Ericsson (publ)
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