Influence of system load on channel estimation in MC-CDMA mobile radio communication systems

This paper investigates the influence of a variable system load on the performance of the channel estimation in a multicarrier code division multiple access (MC-CDMA) transmission scheme. We consider channel estimation based on pilot symbols, which are periodically inserted into the MC-CDMA frame. Starting from the analytical expression of the decision variable, we show the impact of erroneous channel estimation as a function of system load. We derive a simple adaptation rule for the pilot symbol power in order to maintain the signal-to-noise ratio (SNR) loss due to channel estimation errors constant for all system loads. We show that this simple rule enables us to minimize the total transmitted power required at a given bit error rate (BER), particularly for systems with high spreading gain as used in mobile radio channels with high frequency diversity.