A Differential Weighted Accumulation Algorithm Using Variable Sliding Window

Focusing on inbound uplink signal acquisition of the short message communication service in BeiDou system, a differential weighted accumulation algorithm using variable sliding window (DWAVSW) is proposed for the fast acquisition of short burst signal in low carrier-power to noise-density ratio (C/N₀), large Doppler dynamic, and multiuser environment. In the new algorithm, the correlation results are processed by differential multiplication, and then, the output is multiplied by a weight coefficient and added to the accumulated value. The value of weight coefficient becomes larger as the accumulation time increases, and the detection and decision can be carried out after each accumulation operation. The acquisition performance of the DWAVSW algorithm is derived theoretically and verified by Monte Carlo simulations and is better than that of non-coherent differential detector. More specifically, the DWAVSW algorithm can achieve a detection rate of 0.9 and a false alarm rate of 10^-4 at C/N₀ = 28 dBHz. In terms of the multiple access interference (MAI) in multiuser acquisition, the DWAVSW algorithm is combined with subspace projection to solve the problem, since the sliding window width can be adjusted adaptively according to C/N₀. The simulation results demonstrate that the improved algorithm can efficiently eliminate the MAI and achieve acquisition in a multiuser system by taking no extra time consumption.