A spatial filtering technique for narrow angle spread multipath signals in DS/CDMA adaptive array systems

Enhancement of Data Throughput in the AMC-Employed DS-CDMA Systems through Suppression of Channel Frequency Selectivity by a MTMR Antenna System

“…Using this delay profile, a virtual received signal is generated by taking convolution of the delay profile and preliminarily prepared QPSK baseband symbol sequence, and recursive least squares (RLS) algorithm is applied to obtain the optimum BS antenna weight vector, where reference symbol timing is synchronized to the target path timing for the used virtual delay profile [8]. When the BS antenna weights for the m-th virtual delay profile with its target path of a-th path are obtained as…”

“…Multi-transmit and multi-receive (MTMR) adaptive array antenna (AAA) scheme [5], [6] is one of the most effective techniques to suppress multipath interference along with interference canceller [7], thereby keeping orthogonality between the code multiplexed signals, and making it more probable for 16QAM or 64QAM to be employed. When an AAA scheme is employed in DS-CDMA systems [8], [9], an ideal beam directivity control is to direct a main beam toward a path having the highest received signal power, and create nulls to the directions for the rest of the paths. In practice, however, it is impossible because the number of antenna elements in the BS and MS is limited to a small number, say up to 4-8 in the BS and 2-4 in the MS, which limits degrees of freedom for the number of nulls to be created.…”