Noncoherent physical-layer network coding using binary CPFSK modulation

Abstract

Abstract-Physical-layer network coding is a high-throughput technique for communicating over the two-way relay channel, which consists of two terminals that communicate exclusively via an intermediate relay. An exchange of messages begins with both terminals transmitting binary data sequences simultaneously to the relay. The relay determines the modulo-2 sum of the sequences, which it modulates and broadcasts to the terminals. Since each terminal knows the information it transmitted, it can determine the information transmitted by the other terminal by subtracting its own information from the broadcast signal. Prior work on the topic of physical-layer network coding has assumed that the signals transmitted by the two terminals arrive at the relay with perfectly aligned phases, permitting coherent reception. In this paper, we relax the assumption of aligned phases and consider noncoherent reception of binary continuous-phase frequency-shift keying signals. A derivation of the relay receiver is given for varying amounts of channel state information, and results are provided showing the error performance of the proposed system without an outer errorcorrecting code and with an outer turbo code.

Physical-layer network coding: Tutorial, survey, and beyond

“…Refs. [77], [78], [79], [80] and [55] considered the use of non-coherent detection at the relay, in which the channel-state information is not available at the transmitter or receiver. To reduce the penalty due to noncoherent detection, Ref.…”

Receiver design for noncoherent digital network coding

“…The key distinction between DNC and LNC is that with the DNC system, the estimate of b is obtained directly from Y, while with LNC it is found by independently demodulating the two source signals and then combining them. See [8] for more detail regarding this distinction.…”

“…The fading amplitude estimates and channel observations are used to obtain soft-estimates of the network-and-channel-coded sequence b. A full description and derivation of the relay receiver can be found in [8], so we will only provide an overview of the receiver in this Section.…”

“…A turbo-coded DNC system which uses orthogonal CPFSK modulation and a noncoherent relay receiver is presented in [8]. While the relay receiver does not require knowledge of the absolute received phases of the two signals, it is able to exploit other types of channel state information (CSI), such as the received amplitudes.…”

“…By properly using CSI, a performance gain of approximately 10 dB may be achieved relative to a receiver that does not use CSI. This large performance improvement is motivation for carefully considering the issue of fading amplitude estimation, which was not considered in [8]. A training-based approach to channel estimation for coherent ANC systems is considered in [9], but such an approach decreases throughput, and hence is not desirable.…”