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Detection by Inherent Channel Estimation in rapidly fading channels

A binary incoherent spread spectrum transmission technique for use in correlated fast fading environments is to be presented here. The key aspect is an inherent channel estimation that is enabled by an appropriate choice of possible transmitted sequences. Due to its principle the new transmission concept is called Detection by Inherent Channel Estimation (DICE). We do not follow a classical maximum likelihood approach to derive a receiver metric that is used to directly estimate the transmitted sequence. In contrast, we analyze the consequences of the correlation of consecutive channel coefficients and find a heuristic receiver metric that is supposed to represent the plausibility of the channel's changes. Afterwards, a design rule and a recursive construction algorithm for transmitted sequences are derived that guarantee highly distinguishable blocks of estimated consecutive channel coefficients at the receiver. Using this strategy, a transmission technique is established that outperforms the differential M-ary Orthogonal Keying (DMOK) technique at a similar receiver and transmitter complexity. We identify the key parameter that influences the irreducible error floor, which is typical of incoherent detection in the DICE system and show that this error floor can be pushed to practically irrelevant levels by the presented design of the transmitted sequences, even in extreme time variant channels with normalized Doppler frequencies greater than 0.1.