Noncoherent Multiple-Symbol Detector of Binary CPFSK in Physical-Layer Network Coding

It is well known that the binary continuous phase frequency shift keying (CPFSK) signal is power efficient with constant envelope, because it allows transmission with inexpensive and energy efficient nonlinear amplifiers. Recently, physical-layer network coding (PNC) using the binary CPFSK is considered as a potentially attractive solution to the dual needs of high throughput and high power efficiency in two-way relay wireless network. However, most recent studies on PNC have assumed that the carrier phases of the two transmitted signals arriving at the relay are ideally aligned. In fact, the carrier phase offset between the two node-signals always exists in practice. In this letter, a noncoherent multiple-symbol detector of binary CPFSK signals with unknown carrier phase offset in physical-layer network coding is proposed, which is based on the log-likelihood ratio test. It is shown by simulation that the algorithm with five symbol observation interval achieves 6.7 dB performance gain, compared with only one symbol observation interval.