PreprintDelayDoppler Channel Estimation with Almost Linear ComplexityA. Fish, S. Gurevich, R. Hadani, A. Sayeed, O. SchwartzAbstractA fundamental task in wireless communication is Channel Estimation: Compute the channel parameters a signal undergoes while traveling from a transmitter to a receiver. In the case of delayDoppler channel, a widely used method is the Matched Filter algorithm. It uses a pseudorandom sequence of length \(N\), and, in case of nontrivial relative velocity between transmitter and receiver, its computational complexity is \(O(N^{2}\log(N))\). In this paper we introduce a novel approach of designing sequences that allow faster channel estimation. Using group representation techniques we construct sequences, which enable us to introduce a new algorithm, called the flag method, that significantly improves the matched filter algorithm. The flag method finds the channel parameters in \(O(mN\log(N))\) operations, for channel of sparsity \(m\). We discuss applications of the flag method to GPS, radar system, and mobile communication as well. This paper is available as a pdf (1640kB) file.
