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arXiv 1608.08445cs.ITmath.IT
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非理想CSI和有限长编码无线通信的时延性能

Delay Performance of Wireless Communications with Imperfect CSI and Finite Length Coding

Sebastian Schiessl, Hussein Al-Zubaidy, Mikael Skoglund, James Gross

摘要:

随着关键的机器对机器应用的兴起,下一代无线通信系统的设计必须对延迟和可靠性进行严格的限制。在此上下文中的关键问题涉及信道状态估计,其允许发射器使码率适应信道。在这项工作中,我们的特点之间的权衡估计序列长度和数据码字长度:较短的信道估计留下更多的时间用于实际的有效载荷传输,但降低了估计精度,并导致更多的解码错误。使用较低的编码速率可以减轻这种影响,但可能导致发射机处的数据积压较高。我们分析了这种权衡使用的物理层,这也占有限的块长度的信道码的精确模型的顶部上的嵌入式分析。基于一种新的封闭形式的近似的错误概率给定的速率,我们发现,找到最佳的速率自适应策略成为一个凸问题。最优速率自适应策略和最优训练序列长度都取决于应用的延迟和可靠性约束,与不考虑这些约束的次优策略相比,它们可以将延迟性能提高一个数量级。

英文摘要:

With the rise of critical machine-to-machine applications, next generation wireless communication systems must be designed with strict constraints on the latency and reliability. A key question in this context relates to channel state estimation, which allows the transmitter to adapt the code rate to the channel. In this work, we characterize the trade-off between the estimation sequence length and data codeword length: shorter channel estimation leaves more time for the actual payload transmission but reduces the estimation accuracy and causes more decoding errors. Using lower coding rates can mitigate this effect, but may result in a higher backlog of data at the transmitter. We analyze this trade-off using queueing analysis on top of accurate models of the physical layer, which also account for the finite blocklength of the channel code. Based on a novel closed-form approximation for the error probability given the rate, we show that finding the optimal rate adaptation strategy becomes a convex problem. The optimal rate adaptation strategy and the optimal training sequence length, which both depend on the latency and reliability constraints of the application, can improve the delay performance by an order of magnitude, compared to suboptimal strategies that do not consider those constraints.

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