Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
1998-08-14
2001-10-09
Ton, Dang (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
Reexamination Certificate
active
06301265
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to communication systems, and more specifically, to adaptive rate communication systems.
BACKGROUND OF THE INVENTION
Modern wireless communications systems for speech communications are commonly implemented using a speech coder operating at a fixed bit rate, a channel coder operating at a fixed bit rate, and a modulator operating at a fixed modulation format. These systems ordinarily rely on specific, modestly changing channel conditions, however, in a typical system, channel conditions are continuously changing and may experience dramatic variation. A problem with such systems is a failure to allocate optimal bit rates and modulation strategies for controlling the system elements based on current channel conditions.
For example, when an analog channel for speech communications has very little noise, existing systems do not take advantage of channel conditions. Alternatively, when the same channel degrades because of the presence of noise, existing systems do not compensate for such degrading channel conditions.
Typical network communication systems also experience changing channel conditions. For example, Internet packets (e.g., a set of bits of a predetermined size) may be transmitted via Internet Protocol. Systems using Internet Protocol typically deliver a packet without error and fail to deliver a packet with errors. Packets may also be delivered “late”. Additionally, an intelligent router conveys packets via different communications paths based on system congestion. Speech communications systems using a network are designed to operate under modestly changing channel conditions. However, since channel conditions may change dramatically, a problem with such systems is an inability to adjust operating parameters when packets are delayed, lost, or out of sequence.
Another problem with existing systems is that speech quality degrades because of lower bit rate speech coding. Current systems fail to provide a graceful degradation to lower bit rate speech coding when packets are delayed, lost, or out of sequence.
Thus, what is needed are a system and method to control bit rates for a transmitter and a receiver based on changing network conditions. What is also needed are a system and method for allocating bits based on a packet error rate in a network. What is also needed are a system and method to provide graceful degradation for a low rate speech coder when a packet error rate increases for a network. What is also needed are a system and method to provide a synthetic speech output when voice packets are delayed, lost, or out of sequence between a transmitter and a receiver.
REFERENCES:
patent: 4701923 (1987-10-01), Fukasawa et al.
patent: 5383184 (1995-01-01), Champion
patent: 5978762 (1999-11-01), Smyth et al.
patent: 6163766 (2000-12-01), Kleides et al.
patent: 0713302 (1996-05-01), None
patent: 9803030 (1998-01-01), None
An article entitled “A Robust Variable-Rate Speech Coder” by A. Shen, B. Tang, A. Alwan and G. Pottie, Department of Electrical Engineering, UCLA, from 1995 IEEE.
An article entitled “Multiresolution Broadcast For Digital HDTV Using Joint Source/Channel Coding” by K. Ramchandran, A. Ortega, K. Metin Uz, and Martin Vetterli, Sr. Member IEEE, from 1993 IEEE.
An article entitled “Multiresolution Joint Source-Channel Coding Using Embedded Constellations For Power-Constrained Time-Varying Channels.” by Igor Kozintsev and Kannon Ramchandran from 1996 IEEE.
An article entitled “Variable Rate Speech And Channel Coding For Mobile Communication” by E. Yuen, P. Ho, and V. Cuperman, School of Engineering Science, Simon Fraser University from 1994 IEEE.
An article entitled “Combined Source And Channel Coding For Variable-Bit-Rate Speech Transmission” by D.J. Goodman and C.E. Sundberg from The Bell System Technical Journal, Sep. 1983.
Campbell William Michael
Fette Bruce Alan
Jaskie Cynthia Ann
Kleider John
Coleman Sharon K.
Gorrie Gregory J.
Jones Maurice J.
Motorola Inc.
Ton Dang
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