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Offset QPSK Simultaneous Carrier and Bit-Timing Recovery SchemeAgile Acquisition over Satellite Communication Channels
IEICE TRANSACTIONS on Communications
Publication Date: 1997/01/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Advances in Satellite Communications toward Multimedia Era)
Category: Modem and Coding
carrier recovery, bit-timing recovery, offset QPSK, demodulation,
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This paper proposes a new simultaneous carrier and bit-timing recovery (CBR) scheme for offset quadrature phase shift keying (O-QPSK) for agile acquisition over satellite communication channels. The proposed simultaneous CBR scheme employs a preamble shared for the carrier and bit-timing recover, which has a specific bit-pattern designed so that its baseband signal alternates between two adjacent decision points at the symbol rate. Using the preamble, the proposed simultaneous CBR scheme estimates the carrier phase and the bit-timing, simultaneously and independently, by open-loop approach. For comparison, this paper also describes the performance and configuration of a joint carrier and bit-timing recovery scheme, which is expanded for O-QPSK from the one conventionally proposed for QPSK. This paper demonstrates with simulation results that the proposed simultaneous CBR scheme significantly improves the agility of acquisition: a mere 30-symbol preamble is sufficient for low-Eb/No channels typical of satellite communication systems. The proposed CBR scheme is also advantageous from the viewpoint of digital implementation: it processes at 2 samples/symbol and eliminates an analog voltage control clock (VCC). The proposed simultaneous CBR scheme is a strong candidate for TDMA systems that require the high data-transmission and frequency utilization efficiency.