Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-05-03
2002-10-22
Ngo, Ricky (Department: 2661)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S348000, C370S445000, C370S458000
Reexamination Certificate
active
06469997
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to communication systems, and particularly, to a method for transmitting collision-free messages in a digital selective call signaling protocol.
RELATED INVENTION (S)
The present invention is related to the following invention which is assigned to the same assignee as the present invention:
Ser. No. 09/301,679 mailed Mar. 31, 1999, by Xie et al., entitled “Method for Transmitting Collision-Free Messages in a Communication System and Apparatus Therefor.”
BACKGROUND OF THE INVENTION
Presently, there are many medium access protocols in existence for exchanging messages between decentralized communication devices utilizing a common channel. Ethernet is an example of a commonly used communication protocol in decentralized local area networks. Aloha is another.
Ethernet networks employ a channel acquisition technique generally known as CSMA/CD, which stands for Carrier Sense Multiple Access Collision Detection. Essentially, this technique requires a communication device (e.g., a personal computer) to sense a carrier signal of another communication device actively using the communication medium prior to acquiring the channel. If activity is detected, the communication device postpones acquisition of the channel according to a random delay. If no activity is detected, the communication device begins transmitting a message immediately. If upon transmitting the message a collision is detected, the communication device terminates transmission, and postpones acquisition of the channel according to a random delay.
In Aloha networks, on the other hand, a communication device acquires a channel and begins transmission of a message without sensing for other users. A collision is detected upon the communication device failing to receive an acknowledgment signal from the recipient communication device within a specified time. Upon detecting a collision, the communication device postpones reacquisition of the channel according to a random delay. It should be apparent that the potential for collisions in the decentralized communication systems described above makes their use inefficient under high traffic loads. This is especially a problem in systems where a short latency is desirable. Centralized communication systems also may insert unnecessary latency into a lightly loaded system. Accordingly, a method and apparatus is needed for minimizing message collisions without degrading channel utilization efficiency.
REFERENCES:
patent: 5721733 (1998-02-01), Wang et al.
patent: 5953344 (1999-09-01), Dail et al.
patent: 6292493 (2001-09-01), Campbell et al.
patent: 6370153 (2002-04-01), Eng
Dorenbosch Jheroen Pieter
Guntin Eduardo
Loppnow Matthew C.
Meles Pablo
Motorola Inc.
Ngo Ricky
Phan Tri H.
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