[论文解读] Gaussian Z-Interference Channel with a Relay Link: Achievability Region and Asymptotic Sum Capacity

Lei Zhou, Wei Yu|arXiv (Cornell University)|Jun 26, 2010

Wireless Communication Security Techniques参考文献 24被引用 8

一句话总结

本文研究了在接收机之间存在数字中继链路的高斯Z干扰广播信道，提出一种混合的解码转发与压缩转发策略以减轻干扰。在强干扰情形下，该文确定了容量区域；在弱干扰情形下，结果表明在高信噪比和高干扰噪声比条件下，每比特中继链路可使和容量渐近增加1比特。

ABSTRACT

This paper studies a Gaussian Z-interference channel with a rate-limited digital relay link from one receiver to another. Achievable rate regions are derived based on a combination of Han-Kobayashi common-private information splitting technique and several different relay strategies including compress-and-forward and a partial decode-and-forward strategy, in which the interference is partially decoded then binned and forwarded through the digital link for subtraction at the other end. For the Gaussian Z-interference channel with a digital link from the interference-free receiver to the interfered receiver, the capacity region is established in the strong interference regime; an achievable rate region is established in the weak interference regime. In the weak interference regime, the partial decode-and-forward strategy is shown to be asymptotically sum-capacity achieving in the high signal-to-noise ratio and high interference-to-noise ratio limit. In this case, each relay bit asymptotically improves the sum capacity by one bit. For the Gaussian Z-interference channel with a digital link from the interfered receiver to the interference-free receiver, the capacity region is established in the strong interference regime; achievable rate regions are established in the moderately strong and weak interference regimes. In addition, the asymptotically sum capacity is established in the limit of large relay link rate. In this case, the sum capacity improvement due to the digital link is bounded by half a bit when the interference link is weaker than certain threshold, but the sum capacity improvement becomes unbounded as the interference link becomes stronger.

研究动机与目标

• 分析速率受限的数字中继链路对高斯Z干扰广播信道和容量的影响。
• 研究通过回传链路实现接收机协作如何提升干扰受限无线网络中的频谱效率。
• 在强干扰和弱干扰情形下，表征容量区域与渐近和容量。
• 确定在蜂窝上行链路场景中，通过中继协作实现干扰抑制的根本极限。

提出的方法

• 提出一种结合Han-Kobayashi功率分裂与解码转发或压缩转发中继技术的混合编码策略。
• 采用分组与Wyner-Ziv编码，以在被干扰接收机处可靠地消除干扰。
• 基于功率分裂与中继转发，推导出以$\alpha$和$\beta$为参数的可实现速率区域。
• 应用割集界与反证法，证明在强干扰情形下容量区域的最优性。
• 在高信噪比与高干扰噪声比极限下分析渐近行为，以确定和容量的扩展规律。
• 在弱干扰条件下证明可实现速率区域的凸性，以确保实际优化的可行性。

Figure 3: The union of rate region pentagons when $\mathsf{INR_{2}\leq SNR_{2}}$ .

实验结果

研究问题

• RQ1 在干扰自由接收机到被干扰接收机之间存在数字中继链路的高斯Z干扰广播信道中，其容量区域为何？
• RQ2 在弱干扰情形下，随着中继链路速率增加，和容量如何变化？
• RQ3 在何种条件下，解码转发策略可实现渐近和容量最优？
• RQ4 当干扰链路为强或弱时，数字中继链路带来的和容量提升的根本极限是什么？
• RQ5 可实现速率区域是否可凸化，以支持高效计算与优化？

主要发现

• 在强干扰情形下，容量区域被完全表征，且与多址接入信道的容量区域一致。
• 在弱干扰情形下，解码转发策略在高信噪比与高干扰噪声比条件下渐近达到和容量最优。
• 在高信噪比、高干扰噪声比条件下，每比特中继链路可使和容量渐近提升1比特。
• 当干扰链路较弱时，中继带来的和容量提升受限于半比特。
• 当干扰链路较强时，随着中继速率增加，和容量提升趋于无界。
• 在弱干扰条件下，可实现速率区域为凸集，从而支持高效的数值优化。

Figure 4: The union of rate region pentagons when $\mathsf{INR_{2}\geq SNR_{2}}$ .