The capacity for a discrete-state code division multiple-access channel

1994 ◽  
Vol 12 (5) ◽  
pp. 925-937 ◽  
Author(s):  
M.S. Alencar ◽  
I.F. Blake
Keyword(s):  
Code Division Multiple Access ◽  
Multiple Access ◽  
Multiple Access Channel ◽  
Discrete State ◽  
Access Channel ◽  
Code Division Multiple ◽  
State Code

scholarly journals Generalized Superposition Modulation and Iterative Demodulation: A Capacity Investigation

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
Christian Schlegel ◽  
Marat Burnashev ◽  
Dmitri Truhachev
Keyword(s):  
Data Streams ◽  
Multiple Access ◽  
Multiple Access Channel ◽  
Frequency Space ◽  
Time Frequency ◽  
Additional Signal ◽  
Access Channel ◽  
Inverse Multiplexing ◽  
Original Time ◽  
Code Division Multiple

Modulation with correlated signal waveforms is considered. Such correlation arises naturally in a number of modern communications systems and channels, for example, in code-division multiple-access (CDMA) and multiple-antenna systems. Data entering the channel in parallel streams either naturally or via inverse multiplexing is transmitted redundantly by adding additional signal waveforms populating the same original time-frequency space, thus not requiring additional bandwidth or power. The transmitted data is spread over a frame ofNsignaling intervals by random permutations. The receiver combines symbol likelihood values, calculates estimated signals and iteratively cancels mutual interference. For a random choice of the signal waveforms, it is shown that the capacity of the expanded waveform set is nondecreasing and achieves the capacity of the Gaussian multiple access channel as its upper limit when the number of waveforms becomes large. Furthermore, it is proven that the iterative demodulator proposed here can achieve a fraction of 0.995 or better of the channel capacity irrespective of the number of transmitted data streams. It is also shown that the complexity of this iterative demodulator grows only linearly with the number of data streams.

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