为了解决毫米波无线通信中模数转换器(analog to digital converter,ADC)无法在接收信号上实现高倍的过采样以及多径影响所导致的定时跟踪问题,该文基于2倍过采样数据,根据相关波形,利用Farrow插值给出2种适用于多径信道的定时跟踪方案,分别在频域均衡之前和之后进行误差精补偿。仿真结果表明:在Rummler信道下,定时频偏为时钟频率的20×10^(-6)、误比特率为10^(-5)时,这2种方案的信噪比(signal-to-noise ratio,SNR)与无定时频偏时的只相差2.5dB左右,说明这2种方案在多径信道下具有良好的定时跟踪性能。
It is not difficult to predict that wireless data traffic will continue to grow and new cellular systems are to be built to provide higher data rates.Thus,for 5G(fifth generation)cellular systems,various approaches are studied including millimeter-wave(mm-wave)communications and HetNets(Heterogeneous Networks)with small cells.In mm-wave bands,since a much wider bandwidth is available,higher data rates can be achieved.However,mm-wave transmissions suffer from blockage.In order to take advantage of a wide bandwidth in mm-wave bands with mitigating the blockage problem,A HetNet consisting of micro-wave Base Stations(BSs)for macro cells and mm-wave BSs for small cells were consider and its energy efficiency in terms of the communication range of mm-wave BSs were studied.It is shown that the optimal communication range of mm-wave BSs can improve the energy efficiency.
Although large-scale MIMO can offer a high spectral efficie ncy,there are a number of difficulties in its implementation.Among those,the computational complexity of MIMO detection is crucial and may limit its use at devices of limited computing power such as users’mobile devices.Random sampling for large-scale MIMO detection of low complexity were studied.In particular,a MMSE approach for random sampling,was formulated from which an iterative detector can be derived for better performances.
