Coelho Ferreira Ricardo, Facina Michelle S P, de Figueiredo Felipe A P, Fraidenraich Gustavo, de Lima Eduardo Rodrigues
DECOM/FEEC, State University of Campinas, Av. Albert Einstein 400, Campinas 13083-970, Brazil.
Instituto Nacional de Telecomunicações, Santa Rita do Sapucaí 37540-000, Brazil.
Sensors (Basel). 2020 Nov 22;20(22):6679. doi: 10.3390/s20226679.
Large intelligent surfaces (LIS) promises not only to improve the signal to noise ratio, and spectral efficiency but also to reduce the energy consumption during the transmission. We consider a base station equipped with an antenna array using the maximum ratio transmission (MRT), and a large reflector array sending signals to a single user. Each subchannel is affected by the Rayleigh flat fading, and the reflecting elements perform non-perfect phase correction which introduces a Von Mises distributed phase error. Based on the central limit theorem (CLT), we conclude that the overall channel has an equivalent Gamma fading whose parameters are derived from the moments of the channel fading between the antenna array and LIS, and also from the LIS to the single user. Assuming that the equivalent channel can be modeled as a Gamma distribution, we propose very accurate closed-form expressions for the bit error probability and a very tight upper bound. For the case where the LIS is not able to perform perfect phase cancellation, that is, under phase errors, it is possible to analyze the system performance considering the analytical approximations and the simulated results obtained using the well known Monte Carlo method. The analytical expressions for the parameters of the Gamma distribution are very difficult to be obtained due to the complexity of the nonlinear transformations of random variables with non-zero mean and correlated terms. Even with perfect phase cancellation, all the fading coefficients are complex due to the link between the user and the base station that is not neglected in this paper.
大型智能表面（LIS）不仅有望提高信噪比和频谱效率，还能降低传输过程中的能耗。我们考虑一个配备天线阵列并采用最大比传输（MRT）的基站，以及一个向单个用户发送信号的大型反射器阵列。每个子信道都受到瑞利平坦衰落的影响，并且反射元件进行的相位校正并不完美，这会引入一个服从冯·米塞斯分布的相位误差。基于中心极限定理（CLT），我们得出总体信道具有等效伽马衰落，其参数源自天线阵列与LIS之间以及LIS与单个用户之间信道衰落的矩。假设等效信道可以建模为伽马分布，我们提出了非常精确的闭式表达式用于误码率以及一个非常紧密的上界。对于LIS无法进行完美相位抵消的情况，即在存在相位误差的情况下，可以考虑解析近似和使用著名的蒙特卡罗方法获得的模拟结果来分析系统性能。由于具有非零均值和相关项的随机变量的非线性变换的复杂性，很难获得伽马分布参数的解析表达式。即使进行了完美的相位抵消，由于本文中未忽略的用户与基站之间的链路，所有衰落系数都是复数。
