FI113138B - Signaling Load Reduction in a Packet Radio Network - Google Patents

Description

113138

Signaling Load Reduction in a Packet Radio Network

Background of the Invention

The invention relates to packet radio networks, and in particular to reducing the signaling load when a mobile station changes its routing area.

5 Mobile communication systems have been developed because of the need to free people from moving away from fixed telephone terminals without hampering their accessibility. While the use of different data transmission services in offices has increased, different data services have also entered mobile communication systems. Laptops allow efficient 10 processing of data wherever the user is on the move. Mobile networks, in turn, provide the user with an efficient access network for mobile data transmission, which gives access to the actual data networks. To this end, various new data service formats are being planned for existing and future mobile networks. Particularly well-mobile data transmission is supported by digital mobile communication systems, such as the Global System for Mobile Communication (GSM).

General Packet Radio Service (GPRS) is a new service for the GSM system and is one of the topics of GSM Phase 2+ standardization work in ETSI (European Telecommunication Standard Institute). 20 A GPRS operating environment consists of one or more sub-network service areas that are interconnected by a GPRS backbone network.

The subnet comprises a plurality of packet data service nodes, referred to herein as GPRS support nodes (or agents), each connected to a GSM mobile network capable of providing a packet data service; . '] * 25 for mobile data terminals through multiple base stations, i.e., cells. The intermediate mobile network provides circuit-switched or packet-switched data transmission between the support node and mobile data terminals. The different subnets, in turn, are connected to an external data network, e.g., a public switched packet data network (PSPDN). Thus, by means of GPRS pairing 30, packet data transmission between mobile data terminals and external data networks is provided, with the GSM network serving as an access network. One of the features of the GPRS »· ..... service network is that it operates almost independently of the GSM network.

. One of the requirements for GPRS is that it must work with different types of external PSPDN networks, such as the Internet or · ”ί 35 X.25 networks. In other words, the GPRS service and the GSM network should be able to serve all users, regardless of the type of data networks they want to connect to via the GSM network. This means that the GSM network and the GPRS service must support and handle various network addressing and da-packet formats. This processing of data packets also includes their routing over a packet radio network. In addition, users should be able to roam from 5 GPRS home networks to a foreign GPRS network whose operator backbone network may support a different protocol (e.g. CLNP) than the home network (e.g. X.25).

Referring now to Figure 1, a typical GPRS network arrangement will be described. It will be appreciated that the architecture of GPRS systems is not as mature as that of GSM systems. Therefore, all GPRS terms should be understood as descriptive rather than restrictive. A typical mobile terminal constituting a mobile data terminal consists of a mobile station MS of a mobile network and a portable computer PC connected to its data interface. The mobile station may be, for example, the Nokia 2110 manufactured by Nokia Mobile Phones Oy, Finland. With the Nokia Cellular Datacard PCMCIA type manufactured by Nokia Mobile Phones Oy, you can connect your mobile device to any PC with a PCMCIA slot. In this case, the PCMCIA card provides the PC with an access point that supports the communication application protocol used in the PC, such as CCITT X.25 or Internet Protocol IP. Alternatively, the mobile station may directly provide an access point that supports the protocol used by the PC application. Further, it is possible that the mobile: message 3 and the PC 4 are integrated into a single entity within which the application program is provided with an access point that supports its protocol. Pre-; the symbol of such a mobile phone with integrated PC is Nokia, · ·. 25 Communicator 9000, also manufactured by Nokia Mobile Phones Oy, Finland.

The network elements BSC and MSC are known for a typical GSM • I · \. the network. The arrangement of Figure 1 includes a separate GPRS service support node SGSN (Serving GPRS Support Node). This support node controls certain packet radio service functions on the network side. These functions include: · logging in and out of the mobile station MS, updating the mobile network MS area, and routing the data packets to their correct destinations.

A: In the context of this application, the term "data" should be understood broadly to mean any information transmitted in a digital communication system. Such information may comprise digitally encoded * 35 speech, computer-to-computer data traffic, telefax data, short pieces of program code, etc. The SGSN may be located at a base station BTS, a base station BSC or a mobile switching center MSC, or of all these elements. The interface between the SGSN and the base station controller BSC is called the GB interface. The area managed by one base station controller BSC is called a Base Station Subsystem 5 BSS.

The intermediate mobile network provides packet-switched communication between the support node and the mobile data terminal equipment. The different subnetworks, in turn, are connected to an external data network, e.g., a public switched data network, PSPDN, through dedicated GPRS gateway nodes GGSN. Thus, 10 GPRS services provide packet data transmission between mobile data terminals and external data networks while the GSM network is an access network. As an alternative to the gateway node GGSN, a router may be used. In the following application, the term "gateway node GGSN" also means a structure in which the gateway node is replaced by a router.

In Figure 1, a GPRS network connected to a GSM network comprises a plurality of serving GPRS support nodes (SGS ^ - SGSN4) and one GPRS gateway support node (GGSN). These different support nodes SGSN and GGSN are interconnected by an Intra-operator Backbone Network. It is to be understood that a GPRS network can have any number of support and gateway nodes. In addition, it may have so-called. home support nodes HGSN, although usually the HGSN functions are connected to the GGSN.

Each support node SGSN manages a packet data service in the area of one or more cells in a cellular packet radio network. To this end, each support node SGSN is connected to a specific local part of the GSM-25 mobile communication system. This connection is typically made by a mobile station. but in some situations it may be advantageous to connect directly to the base station system BSS, i.e., the base station controller BSC or one of the base stations BTS. The mobile station MS in the cell communicates over the radio boundary with the base station BTS and further through the mobile network with the 30 support nodes SGSN to which the cell belongs. In principle, the mobile network between the support node SGSN and the mobile station MS only ·: ·: transmits packets between the two. For this purpose, the mobile communication network may: · · · provide either a circuit switched connection or packet switched data packet transmission between its mobile station MS and the serving support node SGSN. An example of a circuit 35 interconnected connection between a mobile station MS and a support node (Agent) is disclosed in patent application F1 934115. that the mobile communication network provides only a physical connection between the mobile station MS and the support node SGSN, and its precise operation and structure are not essential to the invention.

The intra-operator backbone network 11 which interconnects the operator's SGSN and GGSN may be implemented, for example, in a local area network. It will be appreciated that it is also possible to implement an operator's GPRS network without an operator's backbone network, for example, by implementing all the features on a single computer, but this change does not result in any change to the call setup principles of the invention.

The GPRS gateway support node GGSN connects the operator's GPRS network to the GPRS systems of other operators as well as to data networks such as the Inter-Operator Backbone 15 Network, the IP network or the X.25 network. There may be a Network Adapter IWF between the gateway support node GGSN and other networks. The inter-operator backbone network 12 is a network through which gateway support nodes GGSN of different operators can communicate with each other. This communication is needed to support GPRS roaming between different GPRS networks.

The gateway support node GGSN is also used to store GPRS mobile location information. The GGSN also routes mobile terminating (MT) data packets. The GGSN also includes a database that interconnects a mobile station's network address, e.g., in an IP network, an X.25 network, a CLNP network, or simultaneously in several of these, and a 25 mobile station identifier in a GPRS network. When the mobile station moves from one cell to another within the area of one support node SGSN, the location update need only be done on the support node SGSN and there is no need to inform the gateway node GGSN of the change of location. As the mobile station moves from one support node ... t SGSN cell to another SGSN cell within the same or different operator area, an update is also performed to the (home) gateway support node GGSN to store the new visitor node identifier and the mobile station identifier.

: The GPRS register GR is used to authenticate subscribers at the beginning of the GPRS: · · session. It contains the definition between the subscriber's packet data protocol (PDP) address (s) and the subscriber's IMSI (International Mobile Subscriber Identity). In the GSM network, the subscriber is identified by IMSI. The GR may be a separate register, or it may preferably be integrated with the HLR of the home system of the mobile communication system. In the figure, the HLR / GR is connected via the SS7 (Signaling System 7) signaling system e.g. to the MSC and to the operator's backbone network. There may be a direct connection or an SS7-5 gateway between the SS7 signaling system and the operator's backbone network. In this way, the HLR / GR can, in principle, exchange packet-switched messages with any GPRS node. However, the manner in which the HLR / GR communicates and interfaces with the GPRS network is not essential to the invention. Alternatively, for example, there may be a direct connection to a node or GR is a single node in the GPRS network.

Figure 2 shows signaling associated with maintaining a routing area. For the sake of clarity, Figure 2 is greatly simplified and only the most relevant messages are displayed. For example, resource allocations and releases controlled by one of ordinary skill in the art are not shown in Figure 2.

In step 2-1, the mobile station MS logs on to the network and sends a routing area update message to the network 15, which is transmitted to the SGSNi. In step 2-2, the SGSNi node forwards the message to the home location register HLR / GR. In steps 2-3 and 2-4, respective acknowledgments are sent to the SGSNi and to the mobile station MS. At the horizontal dashed line in Figure 2, the mobile station MS moves from the area of cell SGSN1 to cell area SGSN2. Steps 2 to 5 to 2 to 8 correspond to steps 2 to 1 to 2 to 4 except that this time the routing area update message passes through the node SGSN2. In addition, in step 2-9, the home location register HLR / GR sends a routing area cancellation to the SGSNi, which deletes the mobile station MS from its register. : information. In Fig. 2, it is assumed that the mobile station MS roams within its own home network area. If the mobile station MS roamed in a foreign network, the update of the routing area • · Y 'should be routed further through the gateway nodes GGSN to the home network.

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One problem with the prior art arrangement described above is the high signaling load generated therein, on the one hand, by the support node SGSN and ''; Between the 30 gateway nodes GGSN and the support node SGSN and the home

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between HLR / GR. Significantly, the signaling load is generated when the service area of the * * * I support node SGSN is small. In this case, roaming the mobile station on the network causes a lot of signaling (Routing Area Update Y's). Whenever the mobile station MS moves from the area of the old support node (e.g. SGSN1) 35 to the area of the new support node (e.g. SGSN2), it sends a routing area update message to the network. This results in signaling between the gateway node 113138 6 mun GGSN and both support nodes SGSN. The problem is worst when a mobile station roams in an area other than its home network, because information about the change in the routing area has to be conveyed all the way to the mobile home network.

In addition, prior art GPRS recommendations suggest that information on the routing area of the mobile station MS (to the accuracy of the SGSN) is always maintained in the home location register HLR / GR. It can be assumed that continuously updating the location of all mobile stations in the network to a single network element (home location register HLR / GR) will cause an unreasonable load on these 10 network elements.

Brief Description of the Invention

It is therefore an object of the invention to provide a method and apparatus implementing the method so that the above problems of high signaling load and HLR / GR loading of the home location register can be resolved. The objects of the invention are achieved by a method and system which are characterized by what is stated in the independent claims. Preferred embodiments of the invention are claimed in the dependent claims.

The invention is based on adding a new functionality and / or network element to the packet radio network architecture. The network element according to the invention adds a packet radio network according to the GPRS recommendation.

the size of the new hierarchical level support nodes SGSN and the home location register HLR / GR

, j. According to a preferred embodiment of the invention, the network element at the new hierarchical level operates in the direction of the support node SGSN as the gateway node GGSN and in the direction of the gateway node GGSN as the support node SGSN. needed at all.

... An advantage of the method and arrangement according to the invention is the significant reduction in signaling and load on the HLR / GR home register.

I · '·; · 30 When a mobile station enters the network, information about the routing area (to the accuracy of the new network: test element) is entered into the home location register HLR / GR but the mobile station; When moving from one SGSN to another, the information is passed only to the new network element at the hierarchical intermediate level. These new network elements can

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[be multiple, for example one for every ten SGSN nodes. Thus, the address of the actual: 35 SGSNs need not be forwarded to the HLR / GR home location register, so that when the mobile station moves from one SGSN node to another within the same new network element of the invention, the home location register HLR / GR does not need to be informed.

The reduction of the signaling need caused by the arrangement according to the invention is greatest when the mobile station roams in the area of a foreign network. The reduction in Sig-5's need for neutralization is due to the fact that when a mobile station changes its routing area, signaling occurs only locally between the old and new support node SGSN on the one hand and the new network element according to the invention on the other. Thus, the signaling need not be carried to the mobile home network. In the home network, the situation looks similar to the prior art packet-10 diode network, i.e., in the home network, it appears as if the location of the mobile station is known to the accuracy of the support node SGSN. In reality, in a home network, the location of the mobile station is known to the accuracy of the new network element according to the invention, and the location of the mobile station within this network element is known based on its own registers. Since the signaling does not need to be carried to the mobile home network, updating the routing area is faster than in a network where the arrangement according to the invention is not implemented.

The arrangement according to the invention is transparent to other network elements, users and other networks of the cellular network. Thus, the invention does not require modifications to the support nodes SGSN, the gateway nodes GGSN (or their routers in their vicinity), or other networks.

. . ·, Brief Description of the Drawings I l »» tsp

The invention will now be described in more detail in the '·,'; with reference to the accompanying drawings, of which:

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;,. 'Figure 1 shows a prior art packet network architecture; "Figure 2 illustrates signaling associated with maintaining a routing area in accordance with the prior art;

Figure 3 shows a packet network architecture supplemented according to the invention; and FIG. 4 illustrates signaling associated with routing area maintenance, implemented in accordance with the invention.

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DETAILED DESCRIPTION OF THE INVENTION: Referring to FIG. 3, the additional hierarchical> .. of the invention between the support nodes SGSN and the home location register HLR / GR can be implemented by a new network element referred to as an Intermediate Register Support Node IR133 in this application. ), the operation of which can be described as follows: - Seen from the direction of the support nodes SGSN, the IRSN node acts as a common gateway to a plurality of 5 support nodes SGSN in the direction of the signaling system (such as SS7).

Seen from the direction of the signaling system (such as SS7), the IRSN node functions like a single large support node SGSN.

When the mobile station is connected to a packet network, the IRSN node maintains information about the support node SGSN in whose area the mobile station MS is.

When the mobile station is switched off from the packet network, the IRSN node remembers information about the support node SGSN in whose area the mobile station MS was last located.

The IRSN node stores mobile related information when the mobile station 15 changes the area of the support node SGSN in the network of the same operator.

According to a preferred embodiment of the invention, the traffic towards other operators is also supplemented with a similar functionality called Intermediate Backbone Support Node (IBSN) within the scope of this application. Figure 3 shows a situation in which this functionality is implemented in the network of the first operator 1 in the direction of the network 2 of the second operator. In Figure 3, the IBSN proxy node is integrated with the gateway node GGSN ^, but the IBSN proxy node can also be implemented as: a separate network element. The operation of the IBSN proxy node can be described * »as follows: * 25 - Viewed from the direction of the GGSN of the gateway node, the IBSN, · ·, IBSN functions as one large support node SGSN.

»· - Seen from the direction of the support node SGSN, the IBSN functions like a conventional gateway node GGSN.

When the gateway node GGSN transmits to the mobile station an I (* ·; · '30) packet to the intermediate support node IBSN, it searches its register for the mobile station.

: · I created the serving support node SGSN and passed the packet to it. Support node SGSN

from the point of view the situation is the same as if the packet had arrived directly from the gateway node GGSN. For the gateway node GGSN, the situation looks the same as if it had sent a packet received directly to the support node 35 SGSN.

113138 g - Similarly, when the support node SGSN sends the outgoing packet from the mobile station to the proxy support node IBSN, it forwards the packet to the right gateway node GGSN. Here too, for the support node SGSN and the gateway node GGSN, the situation looks as if they had communicated directly with one another.

When the mobile station MS moves from an area of an old support node (e.g. SGSNJ) to a new support node (e.g. SGSN2) in a foreign network (e.g. network 1 of the first operator), routing area update messages proceed to IBSN but to the gateway node Up to GGSN2 they do not need to be transmitted because from this point of view the SGSN node does not change.

Figure 4 illustrates signaling associated with maintaining a routing area implemented in accordance with the invention. Steps 4-1 through 4-4 correspond to steps 2-1 through 2-4 except that in step 4-2 the information about the change of the routing area is also passed to the intermediate register 15 IRSN which acknowledges this information in step 4-3. At this interval, in step 4-2 ', the IRSN transmits the same information to the home location register HLR / GR, which acknowledges it in step 4-3'. Similarly, steps 4-5 ... 4-9 correspond to steps 2-5 ... 2-9 except that in this case (when the support node SGSN changes in the IRSN region of the same intermediate register node), the routing area update message 20 is transmitted only to the intermediate register node IRSN but not to the home location register HLR / GR.

Alternative embodiments of the invention may be noted. For example: the intermediate support node IBSN can always be used, whereby all support nodes: SGSNs, including IBSN, act outwardly as one large SGSN, · ·. node. Alternatively, the IBSN can be used for all traffic that · 25 is routed outside the carrier's network. The advantage of this embodiment is, *. , that information on changing the support node SGSN does not need to be updated to the GGSN '*' node when the mobile station roams only within the PLMN network. In yet another alternative embodiment, the IRSN can communicate with the signaling system SS7 or the mobile services switching center MSC, without having to make changes to the support node SGSN.

It will be obvious to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in many different ways. Thus, the invention and its embodiments are not limited to the examples described above, but may vary within the scope of the claims.

Claims (7)

A method for maintaining the position of a mobile station (MS) hierarchically in a packet radio network (1, 2), belonging to at least one home register (HLR / GR) and at least two support nodes (SGSN), so that the home register is at the top of the hierarchy level and the support nodes at a lower level; - in which method when the mobile station (MS) registers in the packet radio network (1, 2), information about the support node (SGSN) serving the mobile station (MS) is transmitted to the home directory (HLR / GR); characterized in that 10. at least one intermediate register (IRSN) is arranged in the packet radio network (1, 2), which has the task of maintaining information about the support node (SGSN) serving the mobile station (MS); - the intermediate register is placed in the position update hierarchy at a level lower than the home register but higher than the support nodes; 15. where the mobile station (MS) moves from the area of the first support node (SGSNi) to the area of the second support node (SGSN2), Information on the change of support node (SGSNi, SGSN2) is stored in said intermediate register (IRSN); and - if the first and second support nodes (SGSNi, SGSN2) belong to the same intermediate register (IRSN), information on the change of support node: to the home directory (CPR / GR) is not conveyed. • t The method of claim 1 for maintaining a mobile * station's (MS) position in a packet radio network (1) which is not the mobile station's (MS) home network (2) and which network (1) is connected via a gateway node / router (GGSN1) to the mobile station's home network (2), characterized in that: - in the gateway node / router (GGSN1) is included or added another intermediate register (IBSN) for storing information on the support nodes (SGSN) serving such mobile stations (MS) that are not within the scope of their home network; 30. where the mobile station (MS) moves in a foreign network (1): from the area of the first support node (SGSNi) to the second support node (SGSN2), information about the change of support node (SGSNi, SGSN2) is stored in said *. other intermediate registers (IBSN), whereby this information need not be conveyed to the home network (2). 113138 14 Method according to claim 1, characterized in that the first intermediate register (IRSN) uses the home node (SGSN) protocol in the direction of the home register (SGSN) and in the direction of the support node (SGSN) in the home register protocol. 5 Method according to Claim 2 or 3, characterized in that the second intermediate register (IBSN) uses in the direction of the gateway node / router (GGSN) the protocol of the support node (SGSN) and in the direction of the gateway node (SGSN) of the gateway node / router (GGSN). Method according to claim 2 or 4, characterized in that a packet terminating at a mobile station (MS) roaming in a foreign network (1) is routed from an external network (2) using the second intermediate register (IBSN), which retrieves from its memory information about the support node (SGSN) serving the mobile station (MS). 6. Arrangement for maintaining a position of a mobile station (MS) in a packet radio network (1, 2), which includes at least two support nodes (SGSNi, SGSN2 ...) and at least one home directory (HLR / GR), in which arrangement: - the home directory (CPR / GR) is at the top level of the hierarchy and the support nodes (SGSNi, SGSN2 ...) at a lower level; and - the home directory (CPR / GR) contains information on that support node: 20 (SGSN !, SGSN2 ...), within whose area the mobile station (MS) registered I in itself in the network (1, 2); : feel unsigned, ···. * - to the packet radio network (1,2) also includes at least one intermediate register. utilities (IRSN) for storing information on the support node (SGSNi, SGSN2 ...) serving, at each occasion, the mobile station (MS); - the intermediate register (IRSN) is in the position update hierarchy at a level lower than the home directory (HLR / GR) but higher than the »support nodes (SGSNi, SGSN2 ...); The packet radio network (1,2) is arranged to store information about the transition of the mobile station (MS) from the area of the first support node (SGSNi); to the area of the second support node (SGSN2) in said intermediate register (IRSN), but not to the home directory (HLR / GR), if the first and second support nodes: (SGSNi, SGSN2) belong to the same intermediate register (IRSN). 113138 15 7. Arrangement according to claim 6 for maintaining the position of a mobile station (MS) in a packet radio network (1) which is not the mobile station (MS) home network and which network (1) is connected via a gateway node / router (GGSNi) to The home station of the mobile station (2), characterized by: 5. The gateway node / router (GGSNh) is included or added to another intermediate register (IBSN) for storing information about the support nodes (SGSNi, SGSN2 ...). serving such mobile stations (MS) that are not within the scope of their home network (2); - the packet radio network (1) is arranged to store information about the transition of the mobile station (MS) in a foreign network (1) from the area of the first support node (SGSN-i) to the area of the second support node (SGSN2) in the said other intermediate registers (IBSN), whereby this information need not be conveyed to the home network (2). I 1 »• · · * · • (I 1» 1 »·» »» · • »·> ·