Computationally efficient smart antennas for CDMA wireless communications

The analysis in this paper concerns the performance of smart antenna algori thms when used in code-division multiple access (CDMA) wireless communicati on systems. Complex pseudonoise (PN) spreading, despreading, and pilot-aide d channel estimates in the cdma2000 reverse link are some of major characte ristics that are different from those in the IS-95 CDMA systems. These diff erent features are included in our analysis. Four computationally efficient smart antenna algorithms are introduced: 1) smart antenna based on maximum output power criteria without lagrange multiplier; 2) smart antenna based on maximum signal-to-interference-plus-noise output power ratio (SINR) crit eria with eigenvector solution; 3) smart antenna based on maximum SINR outp ut criteria without eigenvector solution; 4) more simplified smart antenna based on maximum SINR output criteria without eigenvector solution. Algorit hms (1) and (4) require only 4M computational instruction cycles per snapsh ot where M is the number of antenna array elements. Algorithms (2) and (3) require M-2 and (4M + 2M(2)) operations per snapshot, respectively. These c omputational loads are significantly smaller than those of typical eigenval ue decomposition blind detection approaches. Bit error rates (BERs) resulti ng from these algorithms are evaluated through simulation. Double spike pow er delay profile with equal or unequal power is used. Also, a cluster of in terfering users and scattered interference users are considered. For BER co mparisons, antenna diversity using equal gain combining is also analyzed. T he four smart antenna algorithms show significant capacity improvement comp ared to the antenna array diversity using equal gain combining under the do uble spike power delay profile with equal power and scattered interference environments.