Abstract:
A method of allocating an address to a mobile station operating in a wireless communication system is described in order to facilitate a communication link to a fixed communication system. The method is characterised by the steps of receiving ( 100 ) an address mapping inquiry from the fixed communication system; locating ( 102 ) a respective terminal identifier ( 58 ) of the mobile station in response to the supplied address mapping inquiry; and determining whether an address has been allocated for the mobile station. If an address has not been allocated to the mobile station, an address allocation request ( 112 ) is activated and an address corresponding to the respective terminal identifier ( 58 ) of the mobile station is allocated.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to the allocation of addresses to communication units in order for data to be subsequently routed to such units. The invention is particularly applicable to, but not limited to, addressing of communication units in the internet protocol (IP) domain.  
         BACKGROUND OF THE INVENTION  
         [0002]    Present day communications systems, both wireless and wire-line, have a requirement to transfer data between communications units. Data, in this context, includes speech communication. Such data transfer needs to be effectively and efficiently provided for, in order to optimise use of limited communication resources.  
           [0003]    For data to be transferred across communications networks, a communication unit addressing protocol is required. The communication units are generally allocated addresses that are read by a communication bridge, gateway and/or router, in order to determine how to transfer the data to the addressed unit. The interconnection between networks is generally known as internetworking (or internet).  
           [0004]    Networks are often divided into sub-networks, with protocols being set up to define a set of rules that allow the orderly exchange of information. Currently, the two most popular protocols used to transfer data in communications systems are: Transfer Control Protocol (TCP) and Internet Protocol (IP). In all but the simplest of communications systems, these two protocols often work as a complementary pair. The IP portion corresponds to data transfer in the network layer of the well-known OSI model and the TCP portion to data transfer in the transport layer of the OSI model. Their operation is transparent to the physical and data link layers and can thus be used on any of the standard cabling networks such as Ethernet, FDDI or token ring.  
           [0005]    The Internet Protocol adds a data header on to the information passed from the transport layer. The resultant data packet is known as an Internet datagram. The header of the datagram contains information such as destination and source IP addresses, the version number of the IP protocol etc. An IP address is assigned to each node on the internet. It is used to identify the location of the network and any sub-networks.  
           [0006]    The IP program running on each node knows the location of a gateway on the network, where the gateway links the interconnected networks. Data then passes from node to gateway through the Internet. If the data to be transmitted is particularly large, the Internet Protocol also facilitates fragmentation of the data into smaller units. When a datagram is being routed, or is being reassembled, errors can occur. When such errors occur, the node that detects the error, reports back to the source node.  
           [0007]    When transmitted from the source node, each datagram is routed separately through the Internet and the received fragments are finally reassembled at the destination node, prior to forwarding the data to the respective communication unit. The TCP-IP version number helps gateways and nodes interpret the data packet correctly.  
           [0008]    Each node using TCP-IP communications requires an IP address that is then matched to its token ring or Ethernet MAC address. The MAC address allows nodes on the same segment to communicate with each other. In order for nodes on a different network to communicate with one another, each node must be configured with an IP address.  
           [0009]    Nodes on a TCP-IP network are either hosts or gateways. Any nodes that run application software, or are terminals, are defined as hosts. Any node which is able to route TCP-IP packets between networks is called a TCP/IP gateway node. This node must have the necessary network controller boards to physically interface to other networks.  
           [0010]    A typical IP address consists of two fields: the prefix field—a network number identifies the network associated with that particular address, and the suffix field—a host number identifies the particular host within that network. The IP address is 32 bits long and can therefore theoretically address 2 32  (over four billion) physical networks. One problem, however, associated with using an IP address containing prefixes and suffixes lies in the decision on how large to make each field. If the prefix is too small, only a few networks will be able to be connected to the internet. However, if the prefix is made larger, then the suffix has to be reduced, which results in a network being able to support only a few hosts.  
           [0011]    The present version of the internet protocol addressing scheme (IPv4) can accommodate a few very large networks or many small networks. In reality, a reasonable number of networks of various sizes are required to be supported. However, most organisations tend to have an IP addressing scheme arranged to accommodate a larger network than they generally need, to allow for future network expansion.  
           [0012]    As a consequence, the current version of Internet Protocol (IPv4) has scarce addressing space and future versions are currently being developed. It is envisaged that each Public Land Mobile Network (PLMN) will be unable to allocate a unique permanent IP address to each MS using IPv4. Moreover, even in the event that IPv6 were to be deployed in the future, many networks will still consist of legacy networks implementing IPv4.  
           [0013]    An IP address can be defined in the form: 
           ‘aaa’.‘bbb’.‘ccc’.‘ddd’; 
           [0014]    where: ‘aaa’, ‘bbb’, ‘ccc’ and ‘ddd’ are integer values in the range 0 to 255.  
           [0015]    On the Internet the ‘aaa’.‘bbb’.‘ccc’ part normally define the sub-network and the ‘ddd’ the host. Such numbering schemes are difficult to remember. Hence, symbolic names (often termed domain names) are frequently used instead of IP addresses to identify individual communication units.  
           [0016]    Each individual network on the Internet has a host that runs a process called a domain name server (DNS). The DNS maintains a database called the directory information base (DIB) that contains directory information for that network. When a new host is added, the system manager adds its name and its associated IP address to the DIB. The host is than able to access the Internet.  
           [0017]    Normally, the DNS server is reachable by all the hosts on the network via the IP transport protocol. Therefore the DNS protocol for performing address lookup can be carried over IP.  
           [0018]    The directory network services on the Internet determine the IP address of the named destination user or application program. This has the advantage that users and application programs can move around the Internet and are not fixed to a particular node and/or IP address.  
           [0019]    Due to the recent growth in communications, particularly in internet and wireless communications, there exists a need to provide TCP-IP data transfer techniques in a wireless communications domain.  
           [0020]    An established harmonised cellular radio communication system is GSM (Global System for Mobile Communications) An enhancement to this cellular technology can be found in the Global Packet Radio System (GPRS), which provides packet switched technology on a basic cellular platform, such as GSM. A further harmonised wireless communications system currently being defined is the universal mobile telecommunication system (UMTS), which is intended to provide a harmonised standard under which cellular radio communications networks and systems will provide enhanced levels of interfacing and compatibility with other types of communications systems and networks, including fixed communications systems such as the Internet.  
           [0021]    Information to be transmitted across the Internet is packetised, with packet switching routes established between a source node and a destination node. Hence, GPRS and UMTS networks have been designed to accommodate packet switched data to facilitate Internet services, such as message service, information service, conversational service and casting service.  
           [0022]    Most services are initiated and activated from UMTS terminals. However, some services may be initiated from an Internet node, for example an audio or video conferencing service, home automation notification, job dispatching and information broadcast. These latter types of services are generally referred to as Internet-initiated services.  
           [0023]    In order to support these services, GPRS and UMTS terminals are seen and treated as stand-alone Internet hosts uniquely identified by a name or an address. In systems employing a limited number of addresses by which to identify individual communication units, a technique called dynamic addressing is used.  
           [0024]    Dynamic addressing requires a pool of addresses to be maintained by an address allocation server, for example a Dynamic Host Configuration Protocol (DHCP) server. Whenever a host is connected to a network, a signalling process is performed between the host and DHCP server to assign an available IP address to the host. In order to do so, the host needs to send the DHCP server its unique ID. When the signalling process is de-activated, the IP address will be returned to the addressing pool and will wait to be assigned to other terminals.  
           [0025]    If a mobile station (MS) initiates an Internet connection, the DHCP server recognises the need to identify the MS and typically informs a domain name server (DNS) that a new Internet Protocol address assignment has occurred. Subsequently, the local DNS can then map the mobile station&#39;s domain name to an Internet Protocol address allocated by the DHCP, and pass the address information to an Internet Host.  
           [0026]    Due to the static nature of typical devices using IP, such as networked PCs and servers, DHCP has been widely used in the Intranet environment to allocate IP addresses dynamically to any hosts that are connected to a network.  
           [0027]    However, it is clear that such an arrangement is unacceptable in a wireless domain when the communicating unit requiring an IP address, is not physically connected to the Internet. With such wireless technology, the mobile station needs to have previously established a logical connection with the Internet, in order to have been allocated an IP address and access Internet services, information and applications. This logical connection is generally referred to as a packet data protocol (PDP) context.  
           [0028]    Furthermore, as the wireless communications units will not be permanently connected to the Internet, there will be many occasions when the MS will be in a mode where no PDP context with the Internet has been established. In such cases, the Internet Host cannot transfer data to a particular domain name of the mobile station until a corresponding IP address is allocated. Such a problematic scenario always occurs for Internet-initiated services when the MS has not previously accessed the network and been allocated (and maintained) an IP address from the DHCP.  
           [0029]    In the 3 rd  Generation cellular Packet data Protocol (3GPP) “Technical Specification 23.060 v3.3.0 for UMTS; GPRS Service description; stage 2, April 2000”, currently being developed by the European Telecommunications Standards Institute (ETSI), it is specified that a gateway can request the activation of a PDP context for a mobile station, upon the gateway receiving a packet from a mobile station that does not have a PDP Context established.  
           [0030]    However, in the Technical Specification, there is no recognition of a desire to obtain, or for that matter an indication on how to obtain, an IP address for a MS in order to deliver the first packet of data in a case when the Internet Host initiates the service, particularly when the MS is identified by a domain name.  
           [0031]    In summary, a problematic situation occurs when a wireless communications unit has not been allocated an IP address, and the Internet Host initiates a communication. Without having an IP address allocated to the MS, a local DNS server has no means of relating the MS&#39;s address (Domain Name or other), as identified by the Internet Host, to a MS&#39;s IP address.  
           [0032]    In particular, the Internet Host needs to obtain the MS&#39;s IP address from the hierarchical DNS before any IP packet is sent to the MS, if it is identified by its corresponding domain name. As a result, a need exists to provide a communications system, and method of addressing communication units, wherein the abovementioned disadvantage(s) may be alleviated.  
         SUMMARY OF THE INVENTION  
         [0033]    In accordance with a first aspect of the preferred embodiment of the present invention, a method of allocating an address to a mobile station operating in a wireless communication system is provided in accordance with claim 1.  
           [0034]    In a second aspect of the preferred embodiment of the present invention, a communications system in accordance with claim 9 is provided.  
           [0035]    In a third aspect of the preferred embodiment of the present invention, a method of mapping an Internet Protocol address in response to a Domain Name inquiry of a mobile station in accordance with claim 14 is provided.  
           [0036]    In a fourth aspect of the preferred embodiment of the present invention, a communications unit substantially complying with the operational functions of the aforementioned methods of claim 1 or 14, or the communications system of claim 9, is provided. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0037]    Exemplary embodiments of the present invention will now be described, with reference to the accompanying drawings, in which:  
         [0038]    [0038]FIG. 1 shows a prior art Internet-initiated service IP addressing arrangement;  
         [0039]    [0039]FIG. 2 shows a block diagram of a respective GPRS or UMTS network operator&#39;s domain network adapted to support the inventive concepts of the preferred embodiments of the present invention; and  
         [0040]    [0040]FIG. 3 shows a message sequence chart for performing Domain Name to IP address mapping in accordance with the inventive concepts of the preferred embodiments of the present invention. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0041]    As previously discussed, domain names are often used to identify communicating units, e.g. MSs in UMTS or GPRS networks. FIG. 1 shows a prior art Internet-initiated service arrangement  10  for enabling a Gateway GPRS Serving Node (GGSN)  26  to request a mobile station IP address based on a known domain name.  
         [0042]    The Internet-initiated service arrangement  10  includes an Internet Host  12  connected via connection  20  to a Network Operator&#39;s Network Domain  18 . The Network Operator&#39;s Network Domain  18  includes:  
         [0043]    (i) a core network, namely a GGSN  26 ; and  
         [0044]    (ii) an access network  36 , namely a GPRS (or UMTS) Base Site Controller (BSC) and/or Base Transceiver Station (BTS).  
         [0045]    The GGSN  26  is responsible for GPRS (or UMTS) interfacing with a Public Switched Data Network (PSDN) such as the Internet  22 . The GGSN also performs a routing and tunnelling function for traffic within the GPRS core network.  
         [0046]    The Network Operator&#39;s Network Domain  18  also contains a local DNS  24  having a mapping table that maps domain name addresses to IP addresses for communications units operating on the Network Operator&#39;s Network Domain  18 . For the scenario of a wireless communications system connected to a wire-line communication system, the local DNS  24  would map the MS&#39;s domain name addresses to their respective IP addresses. In addition, the Network Operator&#39;s Network Domain  18  contains a DHCP  30  coupled to GGSN  26  via connection  32  to facilitate dynamic allocation of IP addresses.  
         [0047]    Furthermore, the Internet Host  12  is connected to a global DNS server  14  via connection  16 . The global DNS server  14  is connected to local DNS server  24  in the Network Operator&#39;s Network Domain  18  via connection  38 . The connections  16 ,  20  and  38  are connections made over the Internet  22 .  
         [0048]    When Domain Name (DN) addressing is used to identify a MS  40  in an Internet-initiated service situation, the Internet Host  12  (service initiator) needs to perform a DNS lookup to obtain the IP address of the MS  40 . The DNS query is performed by DNS servers. Therefore the Internet Host  12  requests an IP address that corresponds to the MS&#39;s domain name from global DNS  14 , which consequently polls local DNS  24 . Local DNS  24  then provides the corresponding IP address from its mapping table  28  to the Internet Host  12  via global DNS  14 .  
         [0049]    Such an approach, namely obtaining an IP address that corresponds to a domain name in a wireless communication system, is not possible when IP addresses are allocated dynamically. This is a function of the MS  40  being connected to the network but not having been allocated an IP address due to there being no earlier data transfer. Hence, the DIB will only have details of a Domain Name, without a corresponding IP address.  
         [0050]    In the preferred embodiment of the present invention described below, the subscriber&#39;s Subscriber Identity number (ISDN-number or IMSI—generally referred to in the following text as “Terminal Number”), is used instead of the IP address portion in the DIB, to uniquely identify the terminal.  
         [0051]    Referring now to FIG. 2, a block diagram of a respective Network Operator&#39;s Network Domain  18  is shown, adapted to support the inventive concepts of the preferred embodiments of the present invention. The preferred embodiment of the invention is described with regard to a wireless domain such as GPRS or UMTS technology.  
         [0052]    The Network Operator&#39;s Network Domain now includes a local DNS  50  coupled to a GGSN  62  via a signalling interface Gdns  62  adapted in accordance with the preferred embodiments of the present invention. The GGSN  62  portion of the core network includes a PDP Context table  64  for storing details of whether respective MSs in the particular wireless system have been allocated an IP address, and therefore established a current IP connection.  
         [0053]    The local DNS  50  includes a number of processes for triggering the PDP Context inquiry upon receiving a DNS lookup and a modified mapping table  54 . The modified mapping table  54  includes a list of domain names  56  corresponding to individual MS Terminal Numbers  58 , for each MS in the particular wireless system.  
         [0054]    The signalling interface Gdns  60  carries signalling information between the Network Operator&#39;s Network Domain DNS  50  and GGSN  62 . Across this interface  60 , the Network Operator&#39;s Network Domain&#39;s DNS  50  sends PDP context queries to GGSN  62  and receives IP address related information from GGSN  62 .  
         [0055]    Advantageously, in the case where a DNS query has been initiated by the Internet Host  12 , and an IP address has not been allocated for the MS corresponding to the requested domain name, the DNS  50  triggers the PDP Context Request of the DHCP  30  via GGSN  62  and the Gdns interface. After the GGSN  62  deals with the request, an allocated IP address to the MS will be returned to local DNS  50  via interface Gdns.  
         [0056]    Referring now to FIG. 3, a message sequence chart is shown for performing Domain Name to IP address mapping, in accordance with the inventive concepts of the preferred embodiments of the present invention.  
         [0057]    The message sequence chart, in step  100 , starts by the Network Operator&#39;s Network Domain, and particularly the DNS  50 , receiving an address-mapping inquiry corresponding to a supplied Domain Name from the Internet Host  12 . The domain name corresponds to a mobile station operating on a GPRS or UMTS wireless communications system.  
         [0058]    Based on the supplied Domain Name, the DNS  50  locates the respective “Terminal Number”  58  of the MS having that domain name  56  from the address mapping table  54 , as shown in step  102 . This request triggers the IP Address Searching process, as in step  104 . As part of the IP Address Searching process, the DNS  50  sends a PDP Context Query Request to the GGSN  62  with the respective “Terminal Number”  58 , as shown in step  106 .  
         [0059]    If an IP address has previously been allocated to the MS associated with that domain name, namely a PDP Context has been established for that particular “Terminal Number”, then the DNS  50  receives the PDP Context information from the GGSN  62 , as shown in step  108 . In such a case, the IP address is extracted from the PDP Context, as in step  110 , and the DNS  50  responds to the Internet Host  12  with the associated IP address, as shown in step  111  and  116 , thereby terminating the process.  
         [0060]    If, on making a PDP Context request in step  106 , the PDP Context has not been established for the respective “Terminal Number”, the DNS  50  activates a PDP Context Request to GGSN, as shown in step  112 . The use of the DNS to activate a PDP context request facilitates the Domain Name to dynamic address mapping whereas the use of a GGSN requesting an activation of a PDP Context request only allows an IP address to be allocated upon receipt of an IP packet.  
         [0061]    However, it is noteworthy that the PDP Context Request includes the new feature of the “Terminal Number” of the associated MS, to advantageously facilitate easy handling of subsequent DNS query requests.  
         [0062]    The GGSN, together with the DHCP  30  allocate an IP address corresponding to the domain name of the MS. The GGSN transmits the IP address to the DNS  50  over the signalling interface Gdns  60 , as shown in step  114 . The IP address is then extracted from the PDP Context by the DNS  50 . The DNS  50  responds to the Internet Host  12  with the associated IP address, as shown in step  116 , thereby terminating the process.  
         [0063]    Whilst the present invention finds particular application in a wireless communication system, such as the UMTS or GPRS systems being developed by ETSI, for interacting with a fixed data communication, such as the Internet on a PSDN, a skilled person would readily recognise that the present invention could be employed in other wireless/fixed arrangements.  
         [0064]    In summary, the present invention is generally related to a method and apparatus for assigning addresses, particularly Internet Protocol addresses, in a communication system that links a wireless system to a fixed system. Preferably, a domain name server of a network operator&#39;s network domain receives an address mapping inquiry from the fixed communication system and locates a respective terminal identifier (terminal number) of the mobile station in response to the supplied address mapping inquiry. Preferably the address-mapping inquiry includes a domain name associated with the mobile station.  
         [0065]    The domain name server then determines whether an address, preferably an Internet Protocol address, has been allocated for the mobile station. In response to a negative determination the domain name server activates an address allocation request, preferably sent to a gateway. The gateway (in isolation or preferably in conjunction with a DHCP) then allocates an (IP) address corresponding to the respective terminal identifier of the mobile station.  
         [0066]    The inventive concepts described herein also detail, inter-alia, a modified address mapping table, preferably for use in a domain name server associated with a GPRS/UMTS domain. Furthermore, a signalling interface is provided between preferably a domain name server and a gateway, for example a GGSN, for (IP) address query transmissions. The address query transmission is preferably a Packet Data Protocol context inquiry. In the case where an (IP) address has not previously been allocated to a mobile station, a means of triggering an (IP) address allocation in the case of Internet-initiated services, is provided.  
         [0067]    The present invention finds particular application in wireless communication systems such as the UMTS or GPRS systems. However, the inventive concepts contained herein are equally applicable to alternative fixed and wireless communications systems. Whilst the specific, and preferred, implementations of the present invention are described above, it is clear that variations and modifications of such inventive concepts could be readily applied by one skilled in the art.  
         [0068]    One such modification could be made in the allocation of an Internet Protocol address being made by the gateway, a DHCP, another device operably connected to the gateway or any combination thereof.  
         [0069]    Thus, a communications system, and method of addressing communication units, has been provided that alleviates some of the abovementioned disadvantages.