The Performance Of Massive MIMO System With Low-Resolution ADC

With the continuous development of wireless communication technology,wireless terminals are exponentially growing.It is estimated that by 2025,the number of 5G network connections in the world will reach 100 billion.At the same time,a variety of new wireless services are emerging,such as mobile HD video,VR/AR,online gaming and car networking,which has created a continuing demand for hieh-capacity high-rate wireless communications.In the context of the scarcity of existing spectrum resources,improving spectrum efficiency has become a key means to solve the above challenges.Large-scale antenna(mass MIMO)technology,by deploying a large-dimensional antenna array on the base station side,is expected to greatly improve the system spectrum efficiency.It is becoming the physical layer core enabling technology of the current 5G standard.However,a large number of antennas and RF units pose important challenges to the practical deployment.How to reduce the power consumption and cost of the system becomes a bottleneck restricting the application of large-scale antenna technologyIn recent years,the academic community has proposed a new idea of using low-resolution digital-to-analog converters(ADCs)to reduce the power consumption and cost of large-scale an-tenna systems.Studying the impact of low-precision ADCs on the performance of large-scale antenna systems is becoming a hot topic.In view of this,this paper analyzes the influence of quan-tization accuracy on the capacity and power scale rate for a typical large-scale antenna systemFirst,we consider the uplink of a massive MIMO system with low-precision ADCs equipped at the base station.Different from the previous researches on low-resolution systems in a single-cell environment,this chapter mainly studies the impact of low-resolution ADCs on system perfor-mance with the pilot pollution in a multi-cell environment.We studied a complete communication process,including pilot estimation to the base station and user uplink data transmission.Using the closed-form expression of the derived rate,we discussed the difference of the performance between single-cell and multi-cell after the base station deploys the low-precision ADC.And we also stud-ied the power scaling law of the system.The analysis results show that although the introduction of low-resolution ADC will cause the system performance to decrease,increasing the number of base station antennas can effectively compensate the performance loss caused by low-resolution ADCs.Compared to the low-resolution ADCs,pilot pollution is a more deadly problem for large-scale MIMO systems.Next,we studied the performance of low-resolution ADCs in multicast systems.Similarly,in the case where the base station only knows the statistical channel state information,the chan-nel estimation is performed using the MMSE estimator.Here,the characteristic of the channels orthogonal to each other in the case of massive MIMO is utilized,and an approximately optimal beam structure is adopted.With this structure,two pilot schemes are designed:1)the user pilots in the group are orthogonal to each other,and the same set of pilot sequences are shared between the cells;2)the users in the group use the same pilot sequence,and the inter-cell pilots are mutu-ally Orthogonal.We studied the system performance under the two schemes and obtained closed expressions,respectively.Using the obtained analytical expressions,we give two optimal beam design schemes.According to the analysis,it can be seen that the impact of low-precision ADC on the system in the case of massive MIMO can be compensated by increasing the number of an-tennas,whose essence is to reduce hardware power consumption and cost by increasing the total transmit power of the base station.