Optimum energy partition between data and midamble for channel estimation in TD-CDMA

Channel estimation in the uplink of a TD-CDTMA system can be accomplished by inserting 11 known sequence of symbols at the chip rate, usually in the middle of the burst, and therefore called midamble. In this paper we found the analytical solution to the problem of optimum energy partition, given the total energy per burst, between the midamble and data fields, in joint detected TD-CDMA systems. We show that, given the lengths of the data and midamble, in general the optimal solution requires different amplitude levels. We also show the burst structure in order to reach the optimum energy partition with equal amplitude symbols, and the performance degradation with traditional choices. The analysis is validated, for different channels, by comparison with simulation results of the TD-CDMA radio interlace specified for third generation cellular systems, where gains in terms of signal-to-noise ratio of 0.5-0.9 dB are achieveable