Multiplex communications – Communication over free space – Combining or distributing information via time channels
Patent
1996-10-22
1999-08-17
Ton, Dang
Multiplex communications
Communication over free space
Combining or distributing information via time channels
370389, 370402, 370474, 370476, H04J 324
Patent
active
059403853
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a multicellular transmission method which assembles data sent from a plurality of communication terminals into fixed length packets, and transfers them to other nodes in a network, and more particularly to a multicellular transmission method and apparatus capable of reducing the delay and degradation of signals involved in assembling the fixed length packets.
BACKGROUND ART
FIG. 1 is a block diagram showing a conventional mobile communication network. A signal output from a mobile terminal 10 is received by a radio base station 100 through a radio channel ch. The corresponding signal output from the radio base station 100 is sent to a destination fixed terminal (telephone set) 610 in a public network through a mobile local switching center 200, a mobile transit switching center 300, a mobile gateway switching center 400 and a point of interference (POI) 500 which connects the public network and the mobile communication network. The nodes from the radio base station to the mobile gateway switching center 400 are termed mobile intra-network nodes, or simply intra-network nodes in this specification. Similar intra-network nodes are provided in the public network.
Communications between these intra-network nodes are carried out by exchanging fixed length packets. As a communication method using the fixed length packets, ATM (Asynchronous Transfer Mode) is established as an international standard.
FIG. 2A is a schematic diagram showing the structure of the fixed length packet used by an ATM system. The ATM system generates a 53-byte fixed length packet 20, called an ATM cell, by dividing data to be transferred and by adding a header H0 including routing information. The fixed length packet is used between the intra-network nodes (see, for example, Hideyoshi Tominaga, et al. "Simple B-ISDN technology", edited by The New ITU Association of Japan, or ITU-RECOMMENDATION I.150).
When applying the ATM architecture to a mobile communication system, information to be transmitted is compressed as much as possible to effectively use radio channels. For example, a voice signal is compressed with a CODEC to 4-8 kbps, which is much lower than 64 kbps, the fundamental transmission rate of a fixed network. Accordingly, low speed data will cause a rather long delay time (cellularizing delay time) in comparison with that of the public network when the data is simply converted into the ATM cell. This poses a problem in that it results in an increase of the delay of information transmission, and a degradation of communication quality.
FIG. 2B is a schematic diagram illustrating a partial cell 30, the ATM cell which includes a smaller amount of data to limit the cellularizing delay time. Using this partial cell (a fixed length packet) 30 makes it possible to eliminate the problem involved in the cellularizing time. This, however, presents a new problem in that it results in a blank in the cell, and the data transmission is not carried out during the blank, which reduces the transmission efficiency.
To solve this problem, the assignee of the present application proposed Japanese Patent Application No. 6-1368, "A mobile radio communication system" (U.S. patent application Ser. No. 08/371,547). It discloses a method and apparatus for multiplexing a plurality of short packets into a single ATM cell. Here, a short packet refers to a packet whose length is shorter than the data part of the ATM cell.
This prior art system, however, has the following drawback. For example, when the mobile gateway switching center 400 transfers a plurality of short packets to the radio base station after multiplexing them into a single fixed length packet, the fixed length packet must be disassembled and assembled again in both the mobile transit switching center 300 and the mobile local switching center 200, through which the packet passes. This is because each center carries out multiplexing by only considering the next center, regardless of whether the fixed length packets are bound for the same or di
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IEICE Technical Research Report, SSE95-115 IEICE, Takashi Joho, Yasushi Hibino "Proposal of the Packet Train Exchange System and Performance Evaluation by Simulation" pp. 37-42, Nov. 17, 1995.
IEICE, SSE91-80 IEICE, Masashi Ohno, Tatsuo Mochinaga "A Study of Band Management in Facility ATM" pp. 49-54, Sep. 18, 1991.
NTT R & D, vol. 40, No. 10, 1991 NTT, Takemi Arita and others, Oct. 10, 1991.
Mita Yasuhiro
Umeda Narumi
Yabusaki Masami
Hom Shick
NTT Mobile Communications Network Inc.
Ton Dang
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