The Research Of RAKE Receiver In60GHz Wireless Communication System

60GHz system has potential applications in various fields, due to its highbandwidth, high rate of data transmission and strong anti-interference ability, and it’sespecially suitable for short-range indoor transmission. Currently, most of60GHzsystem uses orthogonal frequency division multiplexing (OFDM) or the single-carrier(SC) modulation to obtain high data rate, but it is difficult to implement, because ithas a complex circuit configuration and large power consumption. In order toovercome these drawbacks, a60GHz pulse communication system based on theimpulse radio is proposed. The60GHz signal through IEEE802.15.3c channel willproduce clustering of phenomenon, and cause severe fading and time dispersion. Thesystem adopts RAKE receiver at the receiving end for capturing multipath energy asmuch as possible. However, the receiving signal has big delay, inter symbolinterference is strong，and the performance of system is significantly reduced in thepropagation, since the reflection, diffraction and scatter was produced through theobstacle. Combining RAKE receiver with diversity and equalization technologies, anew RAKE receiver is presented to weaken frequency selective fading andinter-symbol interference of3c channel, and then system performance is discussed.This paper has several main works and contributions. First, to study3c channeland impulse response, the detailed analysis on both large-scale and small-scale fadingcharacteristics of two channel models residence CM1and CM2was presented. Thiswill provide a basis for the later chapters study. Second, three60GHz pluses areproposed from with carrier and without carrier; the time hopping(TH) anddirect-sequence(DS) spread-spectrum modulation are employed to improve the datarate. Third, with the conventional RAKE receiver for coherent combining anddetection, the system performance is analysed using different modulation anddifferent60GHz pulses, and then the appropriate pulse is selected to establish60GHzwireless communication system. Fourth, in practical applications, frequency selective fading, inter-symbol interference and the multiuser interference are not negligible.The diversity and equalization techniques are proposed to overcome adverse factorseffect. The paper researches the performance of multi-antenna RAKE receiver with aminimum mean square error (MMSE) equalizer on single user.This paper studies the performance of60GHz system based on DS-2PAM andTH-2PPM modulation in CM1and CM2channel，and draws a conclusion that theperformance of system based on DS-2PAM is better than based on TH-2PPM. The60GHz pulse based on inverse Fourier transform without carrier and Gaussian pulsewith carrier can meet the FCC spectral mask, and the performance of pulse withoutcarrier system is better than the carrier pulse system, because it has higher spectrumefficiency. However, the performance improvement is not obvious, and carrier pulsesystem is easier to implementation, so to achieve equalization betweenimplementation and performance, carrier Gaussian pulse is selected to system.3cchannel is researched in the paper. In CM1channel signal energy is highlyconcentrated on the direct path arriving firstly, the other multi-path energy is verysmall and negligible. Therefore, it is feasible to consider CM1as AWGN channel.CM2channel is frequency-selective fading channel, and has severe multipath fadingwhich will cause inter-symbol interference. In order to weaken the inter-symbolinterference, the multi-antenna RAKE-MMSE receiver is adopted. When signal tonoise ratio (SNR) is11dB, the bit error rate of4antennas RAKR-MMSE receiverachieves-40dB, and the system performance is excellent. In general, the error rate ofthe system will decrease, when the number of the reception antenna increases.Compared to the traditional RAKE receiver, multi-antenna RAKE-MMSE receiverhas better performance. This paper analyzes the60GHz pulse waveform design,channel model, receiver scheme and bit error rate, improves the60GHz receiver andsystem, and provides some theoretical basis for60GHz wireless communicationsystem.