Broadband PLC channel estimation and equalization techniques

HADAD, M.; DONATO, PATRICIO G.; MOYA, S.; FUNES, M.

Advances in Engineering Research

Nova Science

Lugar: Nueva York; Año: 2020; p. 101 - 133

Over the last years,high-speed broadband power line communications (BB-PLC) over lowvoltage networks have become an option worth of consideration forresidential data transmission. This technology have specificstandards that take into account the modulation technique, amongother things. Multi-carrier systems, like orthogonalfrequency-division multiplexing (OFDM), or alternatively the use ofsingle-carrier are mainly considered. Both modulation techniquesrequire the use of channel equalization techniques in order tomitigate the effect of the physical medium on the transmitted signal,which behaves like a time-variant multipath channel that severelydistorting the transmitted signal. The equalization can be performedin the time or frequency domain, with time domain equalizationtechniques often requiring more processing load than frequency domaintechniques. To perform frequency domain equalization (FDE), a cyclicprefix is added to the transmitted signal to transform the effect ofthe channel into a periodic signal, allowing to process the datapacket with a Discrete Fourier Transform (DFT), minimizing thecalculation errors as long as the prefix is longer than the channelimpulse response. A crucial part of the equalization process is thecorrect identification of the channel response, as it is necessary inorder to obtain a correct equalization term. There are severaltechniques in the literature that allow to obtain the channelresponse dynamically, which is required because the channel istime-variant. One of these techniques is the use of ComplementarySets of Sequences (CSS) as pilot symbols. These sequences have theproperty that the sum of autocorrelation functions of the sequencesproduces a Kronecker delta, which allows to obtain the discreteimpulse response of the channel by transmitting them over the medium.This chapter will show frequency domain equalization techniques basedon CSS for single-carrier and OFDM . These techniques will becompared to well known techniques like least squares (LS) and LinearMinimum Mean-Square Error (LMMSE) for OFDM, and Zero-Forcing (ZF) andMinimum Mean-Square Error (MMSE) for single carrier. The comparisonswill be done considering the Bit Error Rate (BER) with respect toSignal-to-Noise ratio (SNR) of transmissions over a realisticsimulation of PLC channels. The channel simulation is composed by atime-varying channel response model and Middleton Class-A noise,which is considered as the model closer to the real PLC noise. Theshown methods are also compared over a real data transmission, withthe number of received errors as comparison metric. Finally acomparison between the OFDM and single-carrier techniques is shown.