Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1999-03-11
2004-04-27
Urban, Edward F. (Department: 2685)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C455S453000, C455S435100, C370S339000
Reexamination Certificate
active
06728237
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an arrangement in a cellular communication system supporting packet data communication, a cellular communication system supporting packet data communication and a method of controlling the load distribution in an arrangement or in a node in a communication system supporting packet data communication.
BACKGROUND
Cellular communication systems which, in addition to supporting communication of speech and circuit switched data, also support communication of packet data, are becoming more and more attractive. For example, for GSM (Global System for Mobile Communications) support for communication of packet data is developing through the general packet radio service (GPRS). Similarly the PDC system (Pacific Digital Communications) is provided with packet data communication support through the PPDC (Packet PDC). CDPD is another such packet data communication supporting service for the AMPS system.
The general packet radio service (GPRS) of GSM uses a packet mode technique for the transfer of data as well as signalling and GPRS radio channels are defined the allocation of which is flexible and time slots in a TDMA frame (Time Division Multiple Access) are shared by the users that are active and uplink and downlink are allocated separately. In GPRS, as well as in other packet data communication supporting cellular systems, nodes are introduced for management of the packet data communication. Such nodes are here called packet data nodes. In GPRS the packet data node is called the serving GPRS support node (SGSN) which is at the same hierarchical level as an ordinary MSC (Mobile Switching Center) and it keeps track of the locations of individual mobile subscriber stations, performs security functions and access control. The SGSN is connected to the base station system with Frame Relay. GPRS also comprises another node, the gateway GSN (GGSN) providing interworking with external packet switched networks and it is connected with SGSN via an IP-based GPRS backbone network. Generally the amount of data packets sent from a mobile station through the data network via the packet data node is much lower than the traffic from the data network, via the packet data node, towards a mobile subscriber station. One reason therefore is that the mobile subscriber station, which for example may be connected to a small personal computer (PC) it reads E-mails from a mail server etc. Thus the subscriber station here for example only sends a short packet whereas it receives a large amount of packets or long messages. If for example connecting to Internet, the mobile subscriber station may for example just send a short message requesting a file whereupon it receives a large file. The problem is that the demands as to bandwidth are very asymmetrical in the packet data node handling mobile subscriber stations for all of which the situation may be similar, i.e. the load on the uplink is low whereas the load on the downlink is high. A packet data node may thus need several processors and it is a problem to handle the distribution of the load on the processors.
Information about the load status in different processors therefore has to be maintained in the node in some way. However, when a message is sent from one processor to another, a certain amount of system resources are required (communication media bandwidth, CPU-power, and so on). A message containing such information is small, but the ratio of the resources needed for such messages and the resources used for the sum of the bytes in the message are high. This means that it is very expensive, from an information density point of view, to send messages and the overhead caused by such a kind of information distribution would be high.
SUMMARY
What is needed is therefore a processing arrangement to be used in a packet data node particularly having asymmetrical requirements as to bandwidth for packets sent in one direction in relation to the amount of packets sent in the other direction which assures a safe and reliable transmission of packets in both directions without overload situations occurring or causing any delays or even worse, giving rise to loss of packets. Furthermore a cellular communication system supporting packet data communication is needed through which the above mentioned objects can be achieved. Still further, a method of controlling the load distribution in a packet data node in a cellular communication system supporting packet data communication is needed.
Therefore an arrangement is provided which comprises a processing arrangement at least comprising a number of first processing means and a number of second processing means. The first processing means communicate with a number of base stations and terminate a first communication protocol. The second processing means are given another functionality, namely that of managing the mobile subscriber stations which communicate with any of the base stations and terminating a second communication protocol for communication between the mobile subscriber stations and the packet data node in which the processing arrangement is provided. Each second processing means contains mobile subscriber station information for a number of mobile subscriber stations which are registered with the packet data node, each mobile subscriber station registered with the packet data node being assigned a particular second processing means. The first processing means are provided with information on the load on each second processing means and said first processing means use said information to assign mobile subscriber stations not actually registered with the arrangement to one of the second processing means. Information about the load status in the second processing means is provided to first processing means using the payload traffic sent from or via the data network to the mobile subscriber stations via the first processing means, at least if the load status in a second processing means exceeds a given value. In a particular embodiment separate load status information messages are created and sent from a second processing means to a first processing means if the packet communication load is low. In a exemplary embodiment information about the load status in a second processing means is included in each packet data message sent from a second processing means to a first processing means. In addition thereto, or as an alternative, load status information is provided with at least a given frequency to the first processing means and if no data packets are sent, a separate load status information message is sent so as to meet the requirements on the load status information transmission frequency. Alternatively, if the traffic is high, not every packet or message sent from a second processing means to a first processing means is provided with information about the load status of the particular second processing means but only with the given frequency.
At least of number of the second processing means may be provided with a timer, upon expiry of which a separate load status information message about the current load in the concerned second processing means is created and sent to the concerned first processing means. Alternatively, or additionally, the timer may be used to control the provision of load status information to the first processing means when load status information is added to the conventional traffic data packets sent.
In an advantageous embodiment each second processing means comprises a second message transportation system, second packet data handling means and load status information indicating means which are provided for keeping updated load status information about the local load status in the second processing means. First and second processing means communicate with each other using an interprocessor communication protocol. Examples thereon are ATM (Asynchronous Transfer Mode), Ethernet, FDDI (which is a token ring architecture). Other alternatives are however also possible.
In an exemplary embodiment load status information is added to a packet received in
Chow C.
Telefonaktiebolaget LM Ericsson (publ)
Urban Edward F.
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