平坦衰落環(huán)境中多輸入多輸出系統(tǒng)衰落相關(guān)與信道容量研究
On Fading Correlation and Channel Capacity of MIMO Systems under Flat Fading
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摘要: 為分析模型物理參數(shù)和天線排列方式對多輸入多輸出系統(tǒng)信道容量的影響，提出了一種平坦衰落環(huán)境中信道容量的研究方法。該方法基于接收均勻圓陣和均勻線陣分別構(gòu)建了蘊含模型物理參數(shù)的相關(guān)矩陣，并利用Wishart分布的性質(zhì)推導了信道容量上下限。該方法回避了求取衰落相關(guān)矩陣特征值的概率密度函數(shù)，降低了運算量；可被推廣到多天線-頻分復用系統(tǒng)。仿真結(jié)果表明，天線間距較小時，采用均勻圓陣比均勻線陣的系統(tǒng)信道容量要高；天線間距增大到一定程度后，系統(tǒng)信道容量達到飽和。散射角越大，信道容量的增長速率越快且采用均勻線陣比均勻圓陣系統(tǒng)的信道容量高。接收信噪比較大時，平均信道容量上下限基本接近其實際值。
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關(guān)鍵詞:
- 移動通信;多輸入多輸出;信道容量;衰落相關(guān)
Abstract: In order to study the impacts of array configuration and channel model parameters including antenna spacing and scattering angle on the channel capacity of a MIMO (Multiple Input Multiple Output) system, a novel method is proposed to explore the channel capacity under flat fading. Fading correlation matrix is constructed based on uniform circular antenna and uniform linear antenna at the receiver side, respectively. And then using the properties of Wishart distribution, closed-form expressions for the upper and lower bounds on the ergodic capacity of N by M MIMO system are presented in detail. The problem of calculating the probability density function of eigenvalues of the fading channel matrix is avoided and the computational complexity is lower in contrast to the previous methods. The novel method also could be generalized to MIMO-OFDM systems with any number of transmit and receive antennas. Computer simulation results show that for small spacing the UCA yields higher channel capacity than ULA. The channel capacity is maximized when the antenna spacing increases to a certain point, and further more, the larger the scattering angle, the quicker the channel capacity converges to its maximum. And at high SNR, the upper and lower bounds on the ergodic capacity are close to its true value. -
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