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4G LTE down link and up link have different configuration and it is also depends on lots of factors like scattering environment and modulation type...
We Can Use following Modulation Techniques BPSK,QPSK,QAM,QAM, for Channel models AWGN, Rayleigh, Rician. Some Researchers found that (Using ZERO FORCING & MMSE Equalizers)Bit Error Rate is clearly low for BPSK, and this is the best modulation technique for data transmission on all the channels used and also for both the equalizers. Comparing with BPSK modulation,-QAM, then- QAM and then the QPSK modulation is more sensitive to fading for MMSE equalizer. But for ZF equalizer, when comparing with BPSK modulation,-QAM, then- QAM and then the QPSK modulation is more sensitive to fading. And also MMSE equalizer outperforms ZF equalizer.
Linear equalizer: processes the incoming signal with a linear filter.
MMSE Equalizer: designs the filter to minimize E[|e|2], where e is the error signal, which is the filter output minus the transmitted signal.
ZF (Zero Forcing Equalizer): approximates the inverse of the channel with a linear filter.
MIMO systems use array of multiple antennas and take benefit of multipath effects of the propagation instead of combating it . OFDM can transform frequency selective MIMO channels into a set of parallel frequency flat MIMO channels, thus decreases receiver complexity. Parallel increase in performance and spectral efficiency of MIMO systems is not achievable with all the available signal detection schemes as their associated computational complexity increases exponentially with the number of antennas. HIGH data rate wireless communications, nearing1Gb/s speed inMHz of bandwidth is trending in WLANs and home audio/visual networks. Designing the systems that are capable of handling high data rates while maintaining sufficient BER performance without increasing the bandwidth. MIMO combined with OFDM system is the best solution for this.
