Dept. of Information and Communication Engineering, Dongguk University, Seoul 04602, Korea.
School of Electrical Engineering, Korea University, Seoul 02841, Korea.
Sensors (Basel). 2019 Feb 21;19(4):912. doi: 10.3390/s19040912.
One of the key requirements for next generation wireless or cellular communication systems is to efficiently support a large number of connections for Internet of Things (IoT) applications, and uplink non-orthogonal multiple access (NOMA) schemes can be used for this purpose. In uplink NOMA systems, pilot symbols, as well as data symbols can be superimposed onto shared resources. The error rate performance can be severely degraded due to channel estimation errors, especially when the number of superimposed packets is large. In this paper, we discuss uplink NOMA schemes with channel estimation errors, assuming that quadrature phase shift keying (QPSK) modulation is used. When pilot signals are superimposed onto the shared resources and a large number of devices perform random accesses concurrently to a single resource of the base station, the channels might not be accurately estimated even in high SNR environments. In this paper, we propose an uplink NOMA scheme, which can alleviate the performance degradation due to channel estimation errors.
下一代无线或蜂窝通信系统的关键要求之一是能够有效地为物联网 (IoT) 应用支持大量连接，而上行非正交多址 (NOMA) 方案可用于实现这一目标。在上行 NOMA 系统中，导频符号和数据符号可以叠加到共享资源上。由于信道估计误差，特别是当叠加的分组数量较大时，误码率性能会严重下降。本文讨论了具有信道估计误差的上行 NOMA 方案，假设使用正交相移键控 (QPSK) 调制。当导频信号叠加到共享资源上并且大量设备同时对基站的单个资源进行随机接入时，即使在高 SNR 环境下，信道也可能无法被准确估计。本文提出了一种上行 NOMA 方案，该方案可以减轻由于信道估计误差引起的性能下降。
