Random access system of a mobile communication system

Details Random access system of a mobile communication system Random access system of a mobile communication system

1995-11-16

1997-11-18

Olms, Douglas W.

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

370348, 370459, 370443, H04B 7212

Patent

active

056895038

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to, for example, a random access system of a mobile communication system suitable for accessing common access channels of a TDMA mobile communication system.


BACKGROUND ART

TDMA (Time division multiple access) system, which uses each of time slots into which a frame is partitioned as a traffic channel, is widely used for a digital mobile communication. In this system, a single slot (i.e., the slots having the same number) Generally forms a channel, and each mobile station accesses a base station using the unit of the slot having the same number.
In the case of packet communication, the data transfer rate is higher if a plurality of time slots are used successively. For example, as shown in FIG. 1, in the case that one frame consists of three slots, using two successive time slots for transferring packets will improve the rate drastically (about twice as fast).
In FIG. 1, (A) shows transmission time slots generated by the base station BS. (B) shows data transmission timing of the mobile station MS-A. The sequence shown in FIG. 1 is based on the frame specified by Personal Digital Cellular Telecommunication System RCR Standard in Japan, RCR STD-27B, and the time slot of the mobile station is shifted by a predetermined time interval with respect to the transmission time slot of the base station. The receiving time slots of the base station BS (i.e., the slot synchronizing to the transmission timing of the mobile station) are not shown in this figure for simplicity. The transmitting and receiving sequences which appear in the following explanations are also based on the same standard as in FIG. 1.
In the state shown in FIG. 1, all time slots TS in the frame F beginning at time t1 are in idle states. At the final portion of the first time slot TS within this time frame, data "IDLE", which shows that the time slot TS is idle, is transmitted. The mobile station MS-A, which received this data "IDLE", transmits packet data P1 at time t1' in the time slot TS which is shifted by a pre-determined time interval. Similarly, at the final portion of the second time slot TS which begins at time t2, data "IDLE" is transmitted from the base station BS. The mobile station MS-A, which received this data "IDLE", transmits packet data P2 at time t2' which is shifted by a pre-determined time interval.
The base station BS which received packets P1 and P2 generates, in the first time slot TS beginning at time t3, a "BUSY" signal which corresponds to the reception of packet P1, and generates, in the second time slot TS beginning at time t4, another "BUSY" signal which corresponds to the reception of packet P2. As a result, other mobile stations stop transmitting their data in response to the reception of the "BUSY" signal and avoid telecommunication collisions. The mobile station MS-A whose transmission channel has been assigned recognizes the establishment of a communication with the base station BS by receiving the "BUSY" signal showing the communication with the station MS-A itself, and then generates the next generative packets P3 and P4 successively. The "BUSY" signals which correspond to the reception of packets P3 and P4 are generated from the base station BS in the first and second time slots TS of the next frame which is shifted by a pre-determined time interval. Then the mobile station MS-A transmits packets P5 and P6 by the same procedure.
In the following a case of a communication collision from two mobile stations is explained. Referring to FIG. 2, (A) shows the time slots generated by the base station BS. (B) and (C) show the transmission timings for mobile stations MS-A and MS-B respectively.
The mobile station MS-A in this figure requests to transmit packets by using two successive time slots as in the case of FIG. 1. The first packet P1 has been received by the base station BS on the same timing as FIG. 1. In this figure, the mobile station MS-B generates a transmission request, at the same time t2' as the mobile station MS-A transmits packet P2. The base station BS, after

REFERENCES:
patent: 5515379 (1996-05-01), Crisler et al.
patent: 5603081 (1997-02-01), Raith

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