The use of iterative channel estimation (ICE) to improve link margin in wideband CDMA systems

Wideband CDMA (WCDMA) systems employ coherent detection by periodically inserting pilot symbols in the data stream. Because of the small number of the pilot symbols available, the channel estimates are not perfect, and there is a loss in link margin. Iterative channel estimation (ICE) is a novel method that uses both pilot and data symbols for channel estimation. Link margin gains of 0.3 to 1.3 dB are obtained for data rates of 32 to 64 KSPS, with larger gains at higher Doppler frequencies. The extra complexity to implement ICE is very modest at 2.56 and 5.12 MIPS for 32 and 64 KSPS channels, respectively, which is easily accommodated in today´s DSP technology and represents a small fraction of the total power consumed by the mobile handset. Reducing the required E_b/N_o by even 0.4 dB will allow the system to support 10% more voice users. This paper gives the theoretical analysis of ICE, and Monte Carlo simulations are used to compare the performance of ICE against channel estimation methods which only use pilot symbols