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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