Rather than a single carrier solution, OFDM is chosen as a result that its equalizer dealing with the problem of high channel delay spread has lower complexity. 采用正交分频多工而不采用单载波技术的原因为其用于处理高通道延迟扩散问题的等化器具有较低的复杂度。
Then we focus on the channel estimation, including the channel delay estimation by the auto-correlation of the training sequence, the adaptive channel order estimation by noise floor method and the channel impulse estimation by LS method. 然后给出信道参数估计的原理和方法,具体介绍了用训练序列的自相关特性进行信道延时估计、用噪声门限的方法进行信道阶数自适应估计和用最小二乘法进行信道冲击响应的估计。
Then simulation analyzes the relation be-tween theR ( S / N ) ratio of the DRM system and channel delay (τ) as well as the gain of multi-path ()ρ, proving that appropriate guard interval has great immunity to the ISI. 同时仿真分析了DRM系统的信噪比R(S/N)与信道时延τ和路径增益ρ之间的关系,证明了采用合适的保护间隔可以有效的克服符号间干扰ISI。
Based on minimum mean square error, we found optimal time domain training sequences must have impulse-like autocorrelation and zero cross-correlation at least in maximum channel delay range. According to this criterion we proposed four optimal time domain training sequence design methods. 根据最小均方误差准则,发现最优时域训练序列需要在信道最大延迟时间内满足理想的自相关性和互相关性,据此提出了四种不同的设计方法。
When feedback bits are increased ( quantization error is decreased ), channel delay is decreased, and rate loss will be decreased. The simulations showns that. 仿真结果表明,当反馈比特数逐渐增加(量化误差减小)和信道时延逐渐减小时,系统容量损失会随之减小。