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Asymptotic spectral efficiency of multiuser multisignature CDMA in frequency-selective channels

机译：选频信道中多用户多签名CDMA的渐近频谱效率

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This paper presents an asymptotic analysis of multisignature code-division multiple access (CDMA) in the presence of frequency-selective channels. We characterize the sum spectral efficiency and spectral efficiency regions for both the optimal and linear minimum mean-squared error (MMSE) multiuser receivers. Both independent and identically distributed (i.i.d). signatures and isometric signatures, which are orthogonal at each transmitter, are considered. Our results are asymptotic as the number of signatures per user and processing gain both tend to infinity with fixed ratio. The spectral efficiency of the MMSE receiver is determined from the asymptotic output signal-to-interference-plus noise ratio (SINR). For isometric signatures, our results rely on approximating certain covariance matrices with unitarily invariant matrices that are asymptotically free. This approximation is shown to be very accurate through comparison with both simulation and an "incremental-signature" analysis, which can be used to compute asymptotic moments. Also, a novel proof of the convergence of the empirical spectral distribution of the signal correlation matrix is presented. From these results, we derive the optimal coding-spreading tradeoff, which maximizes the MMSE spectral efficiency, for the case of a single user with multiple i.i.d. signatures. Simulation studies demonstrate that the asymptotic results accurately predict the performance of finite-size systems of interest. The resulting expressions are used to highlight and infer properties of the multisignature CDMA system, including the benefit of orthogonal relative to i.i.d. signatures, and the tradeoff between spectral efficiency and the versatility of providing a variable data rate service through multiple signatures.
机译：本文提出了在存在频率选择信道的情况下对多签名码分多址（CDMA）的渐近分析。我们表征了最佳和线性最小均方误差（MMSE）多用户接收机的总频谱效率和频谱效率区域。既独立又均匀分布（i.i.d）。考虑在每个发射机处正交的签名和等距签名。我们的结果是渐近的，因为每个用户的签名数和处理增益都趋于以固定比率成无穷大。 MMSE接收机的频谱效率由渐近输出信号与干扰加噪声比（SINR）确定。对于等距签名，我们的结果依赖于某些协方差矩阵与渐近自由的unit不变矩阵的近似值。通过与仿真和“增量签名”分析（可用于计算渐近矩）进行比较，表明该近似值非常准确。此外，提出了信号相关矩阵经验频谱分布收敛的新颖证明。从这些结果中，我们得出最佳编码-扩展折衷，对于单个用户具有多个i.d.的情况，可以最大化MMSE频谱效率。签名。仿真研究表明，渐近结果可准确预测目标有限尺寸系统的性能。所得的表达式用于强调和推断多签名CDMA系统的特性，包括相对于i.d.d正交的好处。签名，以及频谱效率与通过多个签名提供可变数据速率服务的多功能性之间的权衡。

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