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On Frequency-Hopping and Non-Coherent Reception in PLC Applications

Abstract

A problem in power line communications (PLC) is the time-varying characteristics of the channel and the noise. Robust communication methods are therefore considered as possible candidates for PLC. At the receiver, robust detection techniques are of interest, and one important issue is the amount of knowledge about the channel that is needed in the receiver. Non-coherent reception is an example of a robust technique, where the channel's influence on the phase of the carrier-wave is ignored. This simplifies the receiver since the phase of the carrier does not need to be estimated. In this paper we investigate non-coherent detection of FSK signals (orthogonal frequency shift keying) with unequal energies. Such signals are often the result of a channel having different attenuation at different frequencies. Here we focus on a minimum Euclidean distance based non-coherent receiver, which is assumed to know (through measurements) the envelope, but not the phase, of the received signal alternatives. An alternative approach is to always use a non-coherent receiver designed for the equal-energy case. However, if such a receiver is used in a situation when the received signal alternatives have different energies, then the bit error probability can be significantly increased (compared with a non-coherent receiver which uses the fact that the signal energies are different). In this paper we also discuss coding combined with frequency-hopping, and non-coherent detection of OFDM-type signals (orthogonal frequency division multiplex), which is a more bandwidth efficient signaling scheme.

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