Multiplex communications – Communication over free space
Reexamination Certificate
1999-08-09
2003-04-22
Ton, Dang (Department: 2666)
Multiplex communications
Communication over free space
C370S337000
Reexamination Certificate
active
06553006
ABSTRACT:
The present invention relates to a method according to the preamble of the appended claim
1
, a communication device according to the preamble of the appended claim
7
, and a communication system according to the preamble of the appended claim
10
.
The term “wireless communication system” refers generally to any communication system which enables wireless communication between a wireless communication device (MS) and the fixed parts of the system, when the user of the wireless communication device is moving within the service area of the system. A typical wireless communication system is a public land mobile network PLMN. The majority of wireless communication systems in use at the time of filing this application belong to so-called second generation mobile communication systems, of which the widely known GSM mobile communication system (Global System for Mobile telecommunications) can be mentioned as an example. The present invention is especially well applicable to third generation mobile communication systems currently under development. In this specification, a GPRS system (General Packet Radio Service) which is being standardized at present, will be used as an example of such a mobile communication system. It is obvious that the invention is also applicable in other mobile communication systems, in which it is possible to define different quality of service levels, or the like, for a data transmission connection.
The GPRS system defines the concept of bearer services. Generally it corresponds to the communication channel of prior systems, which is used to define e.g. a user data rate and quality of service (QoS), both provided by the system in the data transmission between a wireless communication device and some other part of the mobile communication network.
One of the most difficult functions of the bearer services is to provide a sufficient quality of service level reliably for each user. The general packet radio service GPRS is a new service under development for the GSM mobile communication system. The functional environment of the GPRS system comprises one or more subnetwork service areas, which are connected to form a GPRS backbone network. The subnetwork comprises numerous support nodes (SN), of which serving GPRS support nodes (SGSN) will be used as an example in this specification. The serving GPRS support nodes are connected to the mobile communication network (typically to a base station via an interface unit) in such a way that they can provide packet switching services for wireless communication devices via base stations (cells). The mobile communication network provides packet-switched data transmission between the support node and the wireless communication device. Different subnetworks are, in turn, connected to an external data network, for example to a public switched data network (PSDN), via GPRS gateway support nodes (GGSN). Thus, the GPRS service enables packet-format data transmission between a wireless communication device and an external data network, wherein certain parts of the mobile communication network form an access network.
In order to use the GPRS services, the wireless communication device first performs a GPRS attach, with which the wireless communication device indicates to the network that it is ready for packet data transmission. The GPRS attach establishes a logical link between the wireless communication device and the support node SGSN, and thereby allows short message services (SMS) via the GPRS network, paging services via the support node, and notifying the wireless communication device of incoming packet data. Furthermore, in connection with the GPRS attach of the wireless communication device, the support node provides a mobility management function (MM) and performs user authentication. To transmit and receive information, a packet data protocol (PDP) is activated, with which a packet data address to be used in packet data connection is defined for the wireless communication device, wherein the address of the wireless communication device is known in the gateway support node. Thus, in the GPRS attach, a data transmission connection is established to the wireless communication device, to the support node and to the gateway support node, and a protocol (e.g. X.25 or IP), a connection address (e.g. X.121 address), a quality of service level, and a network service access point identifier (NSAPI) are defined for this connection. The wireless communication device activates the packet data connection with an activate PDP context request, in which the wireless communication device reports the temporary logical link identity (TLLI), the packet data connection type, the address, the required quality of service level, the network service access point identifier, and possibly also the access point name (APN).
The quality of service level defines, for instance, how packet data units (PDU) are processed in the GPRS network during transmission. For example the quality of service levels defined for the connection addresses are used to control the transmission order, buffering (packet queues) and discarding packets in the support node and in the gateway support node, especially when there are simultaneously two or more connections which have packets to be transmitted. Different quality of service levels define different delays for packet transmissions between different ends of the connection, different bit rates and the number of discarded packet data units can vary in connections of different quality of service level.
For each connection (connection address), it is possible to request a different quality of service level. For example in e-mail connections, a relatively long delay can be allowed in the message transmission. However, interactive applications, for example, require high-speed packet transmission. In some applications, as in file transfer, it is important that the packet transmission is virtually flawless, wherein packet data units are re-transmitted in error situations, if necessary.
In the current GPRS system, the quality of service level profile contains five different parameters: service precedence, delay class, reliability, mean bit rate and maximum bit rate. Service precedence defines a kind of priority for the packets belonging to a certain connection. Delay class defines average and maximum delays for all the packets belonging to the same connection. Reliability defines whether in the data transmission an acknowledgement (ARQ) is used or not (no ARQ) in the logical link control layer LLC and in the radio link control layer RLC. Furthermore, reliability is used to define whether a protected mode is used in unacknowledged data transmission, and whether the GPRS backbone network uses the TCP or the UDP protocol when transmitting packets belonging to the connection. On the basis of these said parameters, four quality of service classes are established in the GPRS system, which define the quality of service provided by the LLC layer to the connection. These quality classes are distinguished by a special service access point identifier (SAPI).
The appended
FIG. 1
presents the function of a known LLC protocol layer
101
in a wireless communication device and in a GPRS support node. Block
102
illustrates the functions of a known RLC/MAC (Radio Link Control/Media Access Control) layer, which are necessary between the LLC layer
101
and the wireless communication device (not shown). Correspondingly, block
103
illustrates the functions of a known BSSGP (Base Station Subsystem GPRS Part) layer, which are necessary between the LLC layer
101
and the nearest serving GPRS support node (not shown). The interface between the LLC layer
101
and the RLC/MAC layers is called the RR interface, and the interface between the LLC layer
101
and the BSSGP layers is called the BSSGP interface.
Above the LLC layer
101
, there are known GPRS mobility management functions
104
, SNDCP functions
105
, and short message service functions
106
, which all belong to a layer
3
in the presented layer structure. Each one of these blocks
Kalliokulju Juha
Turunen Matti
Duong Frank
Nokia Mobile Phones Limited
Perman & Green LLP
Ton Dang
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