Channel estimation using time multiplexed pilot symbols for coherent Rake combining for DS-CDMA mobile radio

Coherent DS-CDMA forward and reverse links periodically transmitting pilot symbols every data slot to estimate the fading channels are considered; N_p-pilot symbols are placed at the beginning of each data slot. A pilot symbol-assisted channel estimation scheme that uses weighted multi-slot averaging (WMSA) is presented for coherent Rake combining. The BER performance achievable by WMSA coherent Rake combining is evaluated by computer simulations under multipath Rayleigh fading environments and compared with those of other channel estimation methods. For the DS-CDMA reverse link, fast transmit power control (TPC) based on measured signal-to-interference plus noise ratio (SINR) is employed so the simulation also considers fast closed loop TPC. It is demonstrated by computer simulations that the required signal energy per bit-to-background noise power spectrum density ratio (E_b/N₀) can be reduced by about 0.8 dB compared to Rake combining using simple linear interpolation and that the E_b/N₀ loss from the ideal channel estimation is as small as 0.5 dB both with and without antenna diversity. The BER performance achievable by the time multiplexed pilot is also compared with that of the parallel pilot channel.