Linear CE and 1-bit Quantized Precoding With Optimized Dithering
Linear CE and 1-bit Quantized Precoding With Optimized Dithering
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DOI：
10.1109/ojsp.2020.3040590
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发表时间：
2020
影响因子：
2.8
通讯作者：
A. K. Saxena;A. Mezghani;R. Heath
中科院分区：
文献类型：
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作者：
A. K. Saxena;A. Mezghani;R. Heath
用于传输的高功率放大器（HPA）增加了输出信号的非线性损伤。通过恒包络（CE）传输，可以避免信号失真，而不会浪费功率在放大器线性化上。一种更受限制的CE传输形式，1位量化传输，进一步简化了RF链并降低了DAC功耗。本文针对BS天线的CE传输和1位量化传输，分析了低复杂度线性预编码的下行传输。我们观察到，当下行链路的用户数量较少时，跨BS天线的量化误差分量之间的相关性较高，随着用户数量的减少，性能会迅速恶化。为了提高较小数量下行用户的性能，我们提出在量化和后续传输之前在预编码信号中添加相关高斯抖动。我们观察到在有限非平凡抖动功率下接收到的SQINR峰值。对于给定的发射功率、BS天线数和用户数，发射机解析最大化SQINR，利用Bussgang分解找到最优抖动功率。我们观察到，随着优化抖动的实现，在高发射功率下，对于CE和1位量化传输，编码误码率的错误层显着降低。我们还观察到，最佳抖动功率随发射功率的增加而单调增加，随发射功率的增加而减小。此外，最佳抖动功率随着BS天线数量的增加而严格增加。
High power amplifiers (HPA), used at transmission, add nonlinear impairments to the output signals. Through Constant envelope (CE) transmission, distortion in the signal can be avoided without wasting power on PA linearization. A more restricted form of CE transmission, 1-bit quantized transmission, further simplifies the RF chain and reduces the DAC power consumption. In this paper, for CE transmission and 1-bit quantized transmission at the BS antennas, we analyze downlink transmission for low complexity linear precoding. We observe that for small numbers of users in the downlink, correlation among the quantization error components across BS antennas is high, deteriorating the performance rapidly as number of users become smaller. To improve performance for smaller numbers of downlink users, we propose the addition of correlated Gaussian dither to the precoded signal before quantization and subsequent transmission. We observe that the receive SQINR peaks for finite non-trivial dither power. For given value of transmit power, number of BS antennas and number of users, SQINR is maximized analytically by the transmitter, to find the optimum dither power, using the Bussgang decomposition. We observe that with the implementation of optimized dithering, the error floor in the coded BER at high transmit power, for CE and 1-bit quantized transmissions, is pushed down significantly. We also observe that optimum dither power increases monotonically with transmit power, with rate of increase decreasing with increasing transmit power. Further, the optimum dither power strictly increases with number of BS antennas.