TY - JOUR
T1 - Optimal sequences for CDMA under colored noise
T2 - A schur-saddle function property
AU - Viswanath, Pramod
AU - Anantharam, Venkat
N1 - Funding Information:
Manuscript received March 27, 2001; revised December 10, 2001. The work of V. Anantharam was supported by the National Science Foundation under Grant IRI 97-12131. P. Viswanath is with the Department of Electrical and Computer Engineering, University of Illinois, Urbana-Champaign, Urbana, IL 61801 USA (e-mail: [email protected]). V. Anantharam is with the Department of Electrical Engineering and Computer Science, University of California, Berkeley, Berkeley, CA 94720 USA (e-mail: [email protected]). Communicated by S. Shamai, Guest Editor. Publisher Item Identifier S 0018-9448(02)04030-0.
PY - 2002/6
Y1 - 2002/6
N2 - We consider direct sequence code division multiple access (DS-CDMA), modeling interference from users communicating with neighboring base stations by additive colored noise. We consider two types of receiver structures: first we consider the information-theoretically optimal receiver and use the sum capacity of the channel as our performance measure. Second, we consider the linear minimum mean square error (LMMSE) receiver and use the signal-to-interference ratio (SIR) of the estimate of the symbol transmitted as our performance measure. Our main result is a constructive characterization of the possible performance in both these scenarios. A central contribution of this characterization is the derivation of a qualitative feature of the optimal performance measure in both the scenarios studied. We show that the sum capacity is a saddle function: it is convex in the additive noise covariances and concave in the user received powers. In the linear receiver case, we show that the minimum average power required to meet a set of target performance requirements of the users is a saddle function: it is convex in the additive noise covariances and concave in the set of performance requirements.
AB - We consider direct sequence code division multiple access (DS-CDMA), modeling interference from users communicating with neighboring base stations by additive colored noise. We consider two types of receiver structures: first we consider the information-theoretically optimal receiver and use the sum capacity of the channel as our performance measure. Second, we consider the linear minimum mean square error (LMMSE) receiver and use the signal-to-interference ratio (SIR) of the estimate of the symbol transmitted as our performance measure. Our main result is a constructive characterization of the possible performance in both these scenarios. A central contribution of this characterization is the derivation of a qualitative feature of the optimal performance measure in both the scenarios studied. We show that the sum capacity is a saddle function: it is convex in the additive noise covariances and concave in the user received powers. In the linear receiver case, we show that the minimum average power required to meet a set of target performance requirements of the users is a saddle function: it is convex in the additive noise covariances and concave in the set of performance requirements.
KW - Code division multiple access (CDMA)
KW - Colored noise
KW - Optimal sequences
KW - Saddle functions
KW - Sum capacity
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U2 - 10.1109/TIT.2002.1003823
DO - 10.1109/TIT.2002.1003823
M3 - Article
AN - SCOPUS:0036611603
SN - 0018-9448
VL - 48
SP - 1295
EP - 1318
JO - IEEE Transactions on Information Theory
JF - IEEE Transactions on Information Theory
IS - 6
ER -