基于测量的6GHz频段大规模多天线信道容量的研究

Capacity on channel measurement at 6GHz for massive MIMO system

目前,大多数大规模多入多出(Multiple-Input Multiple-Output,MIMO)系统信道特性的研究都是针对理想的独立同分布瑞利信道条件,其传播环境为"适宜的",即大规模MIMO系统中各子信道是正交的.但在实际的物理信道中,其传播条件是"非适宜的",对"非适宜"条件下大规模MIMO系统信道特性的研究尤为重要.文章基于校园室外场景在6GHz频段下进行实地无线信道测量,利用奇异值分解,探讨了真实环境中各子信道的正交性,并进行了信道容量的计算和对比.分析结果表明,随着天线数的增加,正交性明显得到提升,当发射端天线数十倍于接收天线数时,容量值提升最为明显,相比于独立同分布的瑞利信道,真实的传播环境下,各子信道并非完全正交,容量值也存在一定的差距,说明在"非适宜"条件下,大规模多天线系统性能并没有获得满增益.

At present, most of the studies on massive multiple-input multiple-output （MIMO） system channel characteristics are based on the condition of Rayleigh channels that is independent and identically distributed （i.i.d.）. In this case, the propagation environment is ＂favorable＂,which means the sub-channels are orthogonal.However, the propagation conditionin real physical channelis not ＂favorable＂,therefore, it is of great significance to conduct the research of massive MIMO channel characteristics under a ＂unfavorable＂ condition. Based upon an outdoor wireless channel measurement conducted in campus at 6 GHz, the orthogonality between the sub-channels in real environment is discussed in this thesis by applying singular value decomposition. In addition, the channel capacities of different scenarios have been calculated and compared. The analysis results demonstrate that the orthogonality is obviously improved with more antennas while the channel capacity increases evidently when the number of antennas at the transmitter is ten times that of the receiver.Compared with the i.i.d. Rayleigh channels, the sub-channelsin real propagation environmentare not completely orthogonal and channel capacity is differentiated which indicates that massive MIMO could not achieve fullgains with ＂unfavorable＂propagation condition.