Beamforming Using Tapped Delay Line Filters for Broadband Cdma Systems
نویسندگان
چکیده
We investigate the performance of uncoded uplink transmissions in a broadband code division multiple access (CDMA) system using a tapped delay line (TDL) antenna array. First, the weights of a TDL antenna array are derived for broadband CDMA. Using these weights, we perform simulations to demonstration how TDL antenna arrays can help reduce multi-access interference (MAI), allow the use of spreading codes with higher cross correlations, and increase the number of supportable users. Using the two-ray channel model, Kasami spreading codes, and placing users at the angles uniformly distributed around the antenna array, we identify the numbers of antennas and tap delays required to increase the number of supportable users from 15 in the baseline case to 30 and 60 with the uncoded BER fixed at 10. At the signal-to-noise ratio (SNR) of 20 dB, one antenna with one tap is sufficient to support 15 users. For the same SNR, two antennas with four taps each can support 30 users. Finally, three antennas with six taps each can support 60 users. Keywords— Antenna array, beamforming, code division multiple access.
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