Title :
Multiuser receivers for randomly spread signals: fundamental limits with and without decision-feedback
Author_Institution :
Telecommun. Lab., Erlangen-Nurnberg Univ., Germany
fDate :
1/1/2001 12:00:00 AM
Abstract :
Synchronous code-division multiple-access (CDMA) communication systems with randomly chosen spreading sequences and capacity-achieving forward error correction coding are analyzed in terms of spectral efficiency. Emphasis is on the penalties paid by applying single-user coding in conjunction with suboptimal multiuser receivers as opposed to optimal joint decoding which involves complexity that is exponential in the number of users times the code word length. The conventional, the decorrelating, and the (re-encoded) decorrelating decision-feedback detectors are analyzed in the nonasymptotic case for spherical random sequences. The re-encoded minimum mean-squared error (MMSE) decision-feedback receiver achieving the same performance as joint multiuser decoding for equal power users is shown to be suboptimal in the case of equal rates
Keywords :
channel coding; code division multiple access; decorrelation; forward error correction; least mean squares methods; receivers; spread spectrum communication; CDMA communication systems; MMSE; capacity-achieving forward error correction coding; code word length; complexity; decorrelating decision-feedback detectors; equal power users; multiuser receivers; nonasymptotic case; optimal joint decoding; randomly spread signals; re-encoded minimum mean-squared error decision-feedback receiver; single-user coding; spectral efficiency; spherical random sequences; spreading sequences; suboptimal multiuser receivers; synchronous code-division multiple-access communication systems; AWGN; Associate members; Decoding; Decorrelation; Detectors; Multiaccess communication; Random sequences; Signal analysis; Signal to noise ratio; Vectors;
Journal_Title :
Information Theory, IEEE Transactions on