[论文解读] Opportunistic Interference Mitigation Achieves Optimal Degrees-of-Freedom in Cellular Networks

Bang Chul Jung, Dohyung Park+1 more|arXiv (Cornell University)|Jun 11, 2010

Advanced MIMO Systems Optimization参考文献 22被引用 3

一句话总结

本文提出一种基于用户调度的机遇式干扰抑制（OIM）方案，用于K小区蜂窝网络，以最小化跨小区干扰。通过在每小区使用M个用户实施机遇式干扰对消（OIN），该方案实现了KM自由度（DoFs），且证明其为DoF最优，无需全局信道状态信息或时频扩展。

ABSTRACT

We introduce an opportunistic interference mitigation (OIM) for cellular networks, where a user scheduling strategy is utilized in uplink K-cell environments with time-invariant channel coefficients and base stations (BSs) having M receive antennas. In the OIM scheme, each BS opportunistically selects a set of users who generate the minimum interference to the other BSs. We consider two OIM protocols according to the number S of simultaneously transmitting users per cell: an opportunistic interference nulling (OIN) and an opportunistic interference alignment (OIA). Then, their performance is analyzed in terms of degrees-of-freedom (DoFs). It is shown that KM DoFs are achievable under the OIN protocol with M selected users per cell, while the OIA scheme with S selected users (smaller than M ) achieves KS DoFs. Assuming that N denotes the total number of users in a cell, we also analyze the scaling condition between system parameters K , M , N , S, and the received signal-to-noise ratio such that our achievability result holds. It is investigated that there exists a trade-off between the achievable number of DoFs and the parameter N based on the two proposed schemes. Furthermore, by deriving the corresponding upper bound on the DoFs, it is shown that the OIN scheme is DoF-optimal. Finally, numerical evaluation is performed; a two-step scheduling strategy, in which a logarithmic gain can further be obtained, is shown; and our achievability result is extended to multi-carrier systems. Note that the proposed OIM schemes do not require the global channel state information and time/frequency expansion, thereby resulting in easier implementation. Index Terms Base station (BS), channel state information, cellular network, degrees-of-freedom (DoFs), interference, opportunistic interference alignment (OIA), opportunistic interference mitigation (OIM), opportunistic interference nulling (OIN), user scheduling. *: Corresponding author. B. C. Jung was with KAIST Institute for Information Technology Convergence, Daejeon 305-701, Republic of Korea. He is now with the Department of Information and Communication Engineering, Gyeongsang National University, Tongyeong 650-160, Republic of Korea (E-mail: [e-mail]). D. Park is with SAIT, Samsung Electronics Co., Ltd., Yongin 446-712, Republic of Korea (E-mail: [e-mail]). W.-Y. Shin is with the School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138 USA (Email:[e-mail]). SUBMITTED TO IEEE TRANSACTIONS ON INFORMATION THEORY 2

研究动机与目标

• 解决具有时不变信道和多天线基站的K小区上行链路蜂窝网络中的干扰问题。
• 设计一种实用的干扰抑制策略，避免对全局信道状态信息或时频扩展的需求。
• 表征在不同用户调度协议和系统参数下可实现的自由度（DoFs）。
• 通过推导DoF上界并与其可实现速率进行比较，证明所提方案的最优性。

提出的方法

• 提出一种机遇式干扰抑制（OIM）框架，其中每个基站选择对其他小区造成最小干扰的用户。
• 引入两种协议：每小区M个用户的机遇式干扰对消（OIN）和每小区S < M个用户的机遇式干扰对齐（OIA）。
• 分析OIN和OIA下的DoF性能，推导出K、M、N、S和SNR之间实现可实现性的缩放条件。
• 推导DoFs的上界，证明OIN实现理论最大值，从而确立DoF最优性。
• 引入两步调度策略，以在实际实现中提升对数增益。
• 将OIM框架扩展至多载波系统，验证其可扩展性。

实验结果

研究问题

• RQ1 基于用户调度的干扰抑制方案是否能在无需全局CSI的K小区上行链路网络中实现最优自由度？
• RQ2 在OIM协议下，每小区用户数N与可实现DoFs之间的权衡关系如何？
• RQ3 OIN与OIA方案在DoF性能和系统参数缩放方面有何比较？
• RQ4 OIN方案是否为DoF最优？能否通过推导出的DoFs上界加以证明？
• RQ5 OIM框架能否扩展至多载波系统，同时保持DoF最优性？

主要发现

• 每小区M个用户的OIN协议实现了KM自由度，与理论DoF上界一致，证明了DoF最优性。
• 每小区S < M个用户的OIA协议实现了KS自由度，表明用户负载与DoF增益之间存在权衡。
• 在涉及K、M、N、S和接收SNR的特定缩放条件下，OIN下的KM DoFs可实现性成立。
• 所提出的OIM方案无需全局信道状态信息或时频扩展，有利于实际部署。
• 数值评估证实，两步调度策略可提供额外的对数增益，效果显著。
• OIM框架成功扩展至多载波系统，且保持了DoF最优性。