Paper Info
Title
Variable rate speech and channel coding for mobile communication
Abstract
Although the mobile communication channels are time-varying, most systems allocate the combined rate between the speech coder and error correction coder according to a nominal channel condition. This generally leads to a pessimistic design and consequently an inefficient utilization of the available resources, such as bandwidth and power. This paper describes an adaptive coding system that adjusts the rate allocation according to actual channel conditions. Two types of variable rate speech coders are considered : the embedded coders and the multimode coders and both are based on code excited linear prediction (CELP). On the other hand, the variable rate channel coders are based on the rate compatible punctured convolutional codes (RCPC). A channel estimator is used at the receiver to track both the short term and the long term fading condition in the channel. The estimated channel state information is then used to vary the rate allocation between the speech and the channel coder, on a frame by frame basis. This is achieved by sending an appropriate rate adjustment command through a feedback channel. Experimental results show that the objective and the subjective speech quality of the adaptive coders are superior than their non-adaptive counterparts. Improvements of up to 1.35 dB in SEGSNR of the speech signal and up to 0.9 in informal MOS for a combined rate of 12.8 kbit/s have been found. In addition, we found that the multimode coders perform better than their embedded counterparts
Year
DOI
Venue
1994
10.1109/VETEC.1994.345388
Stockholm
Keywords
Field
DocType
channel coding,convolutional codes,error correction codes,fading,linear predictive coding,mobile radio,speech coding,telecommunication channels,variable rate codes,vocoders,CELP,adaptive coding system,channel coding,channel conditions,channel estimator,code excited linear prediction,embedded coders,error correction coder,estimated channel state information,fading channel,feedback channel,mobile communication channels,multimode coders,objective speech quality,rate allocation,rate compatible punctured convolutional codes,receiver,speech coder,subjective speech quality,time-varying channels,variable rate speech coders,variable rate speech coding
Speech coding,Code-excited linear prediction,Computer science,Fading,Communication channel,Error detection and correction,Speech recognition,Electronic engineering,Bandwidth (signal processing),Linear predictive coding,Channel state information
Conference
ISSN
Citations 
PageRank 
1090-3038
6
1.36
References 
Authors
7
3
Name
Order
Citations
PageRank
Eric Yuen161.36
P. Ho2235192.54
Vladimir Cuperman35611.32