[论文解读] A Novel Cooperative Strategy for Wireless Multihop Backhaul Networks

Song-Nam Hong, Ivana Marić+1 more|arXiv (Cornell University)|Aug 1, 2015

Cooperative Communication and Network Coding参考文献 29被引用 3

一句话总结

本文提出了一种新型协作传输方案，用于5G无线多跳回传网络，采用分组连续中继和优化的量化-映射-转发（QMF）编码方案。通过利用干扰作为有用信号，结合干扰利用型路由和低复杂度连续MIMO解码器，该方案在密集网络中显著提升了频谱效率，相较于传统解码转发多跳路由，实现了更低的中继发射功率和更低的解码复杂度。

ABSTRACT

The 5G wireless network architecture will bring dense deployments of base stations called {\em small cells} for both outdoors and indoors traffic. The feasibility of their dense deployments depends on the existence of a high data-rate transport network that can provide high-data backhaul from an aggregation node where data traffic originates and terminates, to every such small cell. Due to the limited range of radio signals in the high frequency bands, multihop wireless connection may need to be established between each access node and an aggregation node. In this paper, we present a novel transmission scheme for wireless multihop backhaul for 5G networks. The scheme consists of 1) {\em group successive relaying} that established a relay schedule to efficiently exploit half-duplex relays and 2) an optimized quantize-map-and-forward (QMF) coding scheme that improves the performance of QMF and reduces the decoding complexity and the delay. We derive an achievable rate region of the proposed scheme and attain a closed-form expression in the asymptotic case for several network models of interests. It is shown that the proposed scheme provides a significant gain over multihop routing (based on decode-and-forward), which is a solution currently proposed for wireless multihop backhaul network. Furthermore, the performance gap increases as a network becomes denser. For the proposed scheme, we then develop energy-efficient routing that determines {\em groups} of participating relays for every hop. To reflect the metric used in the routing algorithm, we refer to it as {\em interference-harnessing} routing. By turning interference into a useful signal, each relay requires a lower transmission power to achieve a desired performance compared to other routing schemes. Finally, we present a low-complexity successive decoder, which makes it feasible to use the proposed scheme in practice.

研究动机与目标

• 通过无线多跳中继技术解决密集5G小细胞部署中的回传容量瓶颈问题。
• 克服高密度网络中干扰感知型路由和解码转发多跳方案的局限性。
• 设计一种协作传输方案，将干扰建设性地利用，而非将其视为噪声。
• 设计一种节能的中继选择算法，通过利用干扰降低发射功率。
• 通过引入低复杂度连续MIMO解码器实现近似最优性能，提升实际部署可行性。

提出的方法

• 提出分组连续中继，即所有L个源节点同时发送，每跳的L个中继转发所有接收到信号的函数。
• 提出一种优化的QMF方案，中继对收到的信号进行最优量化，以提升性能并减少解码延迟。
• 设计干扰利用型路由，基于最大接收功率选择中继，将干扰转化为有益信号。
• 推导出在渐近网络模型下所提方案的闭式可实现速率区域。
• 设计一种低复杂度连续MIMO解码器，采用线性接收机（如无干扰（IF）接收机），在极低复杂度下实现接近最大似然（ML）的性能。
• 应用点对点信道编码（如LDPC、极化码），实现中等复杂度下的实际部署。

实验结果

研究问题

• RQ1 如何在多跳回传网络中利用干扰而非规避干扰，以提升频谱效率？
• RQ2 所提出的基于QMF的方案相较于传统解码转发多跳路由，在密集网络中的可实现速率增益是多少？
• RQ3 随着网络密度增加（即源节点数L增加），所提方案的性能如何变化？
• RQ4 低复杂度连续解码器是否能在保持实际可行性的同时实现接近最优性能？
• RQ5 与干扰感知型或传统路由相比，干扰利用型路由在多大程度上降低了中继发射功率？

主要发现

• 所提方案相较于多跳路由（解码转发）实现了显著的频谱效率增益，且随着网络密度（L）增加，性能差距进一步扩大。
• 在高信噪比（SNR）区域，由于能够利用强干扰，所提方案优于多跳路由，而多跳路由受限于单条链路上的干扰。
• 所提方案的能量效率随网络密度增加而提升，可在相同性能下降低中继发射功率。
• 干扰利用型路由通过选择受益于相长干扰的中继，降低中继发射功率，而干扰感知型路由则避免干扰。
• 采用无干扰（IF）接收机的连续MIMO解码器性能接近最大似然（ML）性能，误差不超过1 bit，且在少于四跳的网络中显著优于多跳路由。
• 优化的QMF方案显著优于传统QMF，同时降低了解码复杂度，使该方案适用于5G回传网络的实时部署。