Research On Equalization And Frequency Offset Estimation Technology For Multi-h CPM

As telemetry communications require higher bandwidth and power efficiency, multi-h continuous phase modulation(Multi-h CPM) has been widespread concerned in the above fields because of its constant envelope, high bandwidth and power efficiency. However, due to its characteristic of memory, the modulation process introduces inter-symbol interference(ISI). Multi-h CPM signals will be confronted with two kinds of ISI: modulation and multipath-induced ISI, which presents difficulties for equalizers. There are also large Doppler frequency offsets in telemetry communications, and the high complexity of Multi-h CPM receivers leads to difficulties of extracting offset parameters. In order to solve the problems mentioned above, researches on equalization and large frequency offset estimation technology of Multi-h CPM signals will be conducted in this paper.Firstly, to solve the problem that the conventional equalization algorithms tend to get confused by the two sources of ISI, this paper proposes a joint minimum mean squared error(MMSE) criterion and decision feedback(DFE) algorithm, which deals with two sources of ISI separately. The simulated bit error performance of the joint equalizer shows a 1dB improvement over MMSE equalizer. In addition, the joint of time-reversed space-time block code and MMSE equalizer, which is a system involving two transmit antennas and one receive antenna, is suitable for actual application environment.In-depth researches on non-data-aided frequency estimation algorithms in large frequency offset environment for Multi-h CPM have been conducted. This paper has focused on two frequency offset algorithms and simulation results have been given. Simulation shows that the multiplying delay estimation algorithm has a low computational complexity, a wide range of frequency offset and low estimation accuracy, thus it is suitable for a coarse estimation for frequency. The maximum square soft output algorithm can accurately estimate the frequency offset, but it has a high computational complexity. On the basis of the two algorithm mentioned above, a joint the multiplying delay estimation and demodulation soft output assisted frequency offset estimation algorithm is proposed. The algorithm firstly estimates the frequency coarsely through the multiplying delay estimation, and then it searches around the value to achieve an accurate estimation through the maximum square soft output algorithm. The joint algorithm can estimate large frequency offsets accurately with lower complexity.