System for connecting a packet data network to a digital radio n

Details System for connecting a packet data network to a digital radio n System for connecting a packet data network to a digital radio n

1998-07-28

2000-06-13

Ton, Dang

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

370401, 370413, H04L 1228, H04L 1256

Patent

active

060757892

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to transferring data from a packet network to a digital radio network whose transmission channel enables transmission of audio and data services and selective reception of these services.
A known packet relay mechanism is represented by Frame Relay FR. In FR transfer technique, error correction and flow control are carried out at termination points of the network and not in every link as in packet data transfer according to the X.25 standard. FR speeds up routing of packets via several connection points to their destination, because it is not necessary to check, as far as errors are concerned, every packet received before transferring them to the next connection point. Originally, FR was intended for interconnecting private data networks, such as LAN networks, and it therefore defines the interface for the high-rate data between the FR network and the computers of the user. The routing is based on a local address conveyed in the frame. The frame structure per se is specified in the recommendation CCITT I.441, and parameters related to the protocol are specified in the recommendations I.233 and Q.922. The significant matter as far as the method of transfer is concerned is that the frame length is not constant, but the transfer participants negotiate the frame length to be used prior to the transfer.
No fixed bandwidth will be allocated for the service, but specific service parameters relevant to the nature of the service will be determined. These include committed information rate CIR, committed burst size Bc and excess burst size Be.
FIG. 1A shows the structure of an FR frame. The frame comprises five fields. A frame begins and ends with a flag one octet long which is a specified bit sequence containing six successive 1 bits. For logical channel numbering, an address field is used, the contents of which will be disclosed below. An information field succeeding the address field does not have a fixed length, but contains an even number of octets of user data. The user and the FR network on the one hand, and the FR networks on the other hand, negotiate with one another the data field length to be used, whereby the frame length may be up to 4096 octets. The information field is followed by a frame check sequence FCS, two octets in length.
FIG. 1B shows the contents of an FR frame address field. The field contains address field extension bits EA, a C/R (Command/Response) identifier bit allocated for use by the end-user's equipment, forward and backward explicit congestion indicator bits FECN and BECN on the basis of which the system is able to reduce traffic rate, a discard eligibility indicator DE which means that frames containing this indicator can under specific conditions be discarded, and, essential to the present invention, a permanent virtual circuit or a data link connection identifier DLCI. The DLCI thus indicates at each nodal point of the network where a packet is to be routed. The minimum length of the address field is two octets as in FIG. 1B, but it can be prolonged to be three or four octets in length, as illustrated in FIGS. 1C and 1D. By employing two or three octets in the address field, it is possible to support a wider DLCI address space between the user and the network, or within the network.
Relating to a wideband ISDN network, an asynchronous transfer mode ATM has been developed. The ATM outlines data transfer in a packet or circuit-switched fixed network. The data are transferred in fixed-length 53-byte ATM cells, each cell having five bytes as header of the cell and the remaining 48 bytes as actual information. The ATM cells are specified in the recommendations CCITT Recommendation I.361 and CCITT Draft Recommendation I.150. In simplified terms, it can be noted that the user information to be transferred is split into segments of fixed length, and each segment is inserted in the information field of the ATM cell. The number of segments in a unit time represents the transfer capacity required by the user. In addition, a header,

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Assmus et al: "Ubermittlung von codierten audiosignalen niedriger bitrate in einem zukunftigen ATM-netz", Rundfunktechnische Mitteilungen, vol. 38 No. 3, 1994, p. 85-p. 91.

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