Development and analysis of a carrier recovery algorithm for high-speed satellite communications

Abstract

High-speed data transmission over satellite requires high technologies in which the algorithms related to demodulation should be simple and have high performance. The carrier recovery scheme by phase-locked loop (PLL), however, has a shortcoming, which is able to track in small range of the frequency offset. Moreover, it requires analog devices such as voltage controlled oscillator (VCO) that are obstacles in high-speed operation. Also, the conventional PLL requires too many symbols to obtain the desired acquisition performance in burst mode communications accessed by many users in satellite communications. Much research has been concentrated on the removal of VCO, and it results in replacing it with numerical controlled oscillator (NCO). However, PLL with NCO can not improve the acquisition performance, since it has the same architecture as the PLL with VCO. Recently, some effort for removal of NCO wins a success that replaces it with the operation of normalization. Though it has fast acquisition performance, some problems still remain in implementation in high-speed operation since it requires the complicate operations such as division and square root. The relation between frequency offsets and the bandwidth of wideband signal for high-speed communications has been investigated with oscillators used practically. In the satellite communications, the frequency offsets between transmitter and receiver can be controlled in the range of 5000PPM to 10000PPM per symbol in the case of applying oscillator used practically. For wideband signals with data rates of 45Mbps and 155Mbps, since the movement of signal spectrum compared to the signal bandwidth is very small, the energy loss by filtering by the matched filter in the receiver can be neglected. A decision-directed carrier frequency and phase recovery algorithm is devised in complex domain from the foundation mentioned above for high-speed satellite communications. The algorithm consists of two loops: One is for...