For time delay estimation of OFDM signal, three approaches, namely peak detection, modified maximum peak-to-leaking rate detection and channel frequency
response (CFR) reconstruction are proposed in , and in WINNER A1 LOS channel, the CFR reconstruction method can achieve the best performance, but this method is mainly based on the received preamble sequence.
PLC channel frequency
and noise characteristics, in the frequency range devoted to the NB PLC communication systems.
Figure 5 shows the channel frequency
responses of the subcarriers in OFDM signal.
The measured channel impulse response (CIR) [h.sup.m]([tau], [[phi].sub.l]) for each rotation angle [[phi].sub.l] (with l = [1, ..., L]) can be calculated via inverse Fourier transform of the channel frequency
response directly recorded in the measurements.
Caption: Figure 1: Channel frequency
Moreover, the number of channel taps required for estimation in the time domain is significantly fewer than the number of FFT points where the channel frequency
response needs to be estimated .
ZF equalization may lead to great noise enhancements at the frequencies where the channel frequency
response has spectral nulls.
response for different lengths between modems
During this time, TV broadcasters that typically command the top-mounted position on the towers willneed to establish a temporary antenna to accommodate their new channel frequency
. This oftenrequires the installation ofa side-mount antenna that best replicates the coverage they had in the top-mounted position.
[H.sub.r,t] is an N x N diagonal matrix with the main diagonal entries given by the channel frequency
responses, which can be expressed as
The estimation of the channel frequency
response on the kth subcarrier in the frequency domain, [??][k], is given as follows: