Bringing cross-layer MIMO to today's wireless LANs

Abstract

Recent years have seen major innovations in cross-layer wireless designs. Despite demonstrating significant throughput gains, hardly any of these technologies have made it into real networks. Deploying cross-layer innovations requires adoption from Wi-Fi chip manufacturers. Yet, manufacturers hesitate to undertake major investments without a better understanding of how these designs interact with real networks and applications.This paper presents the first step towards breaking this stalemate, by enabling the adoption of cross-layer designs in today's networks with commodity Wi-Fi cards and actual applications. We present OpenRF, a cross-layer architecture for managing MIMO signal processing. OpenRF enables access points on the same channel to cancel their interference at each other's clients, while beamforming their signal to their own clients. OpenRF is self-configuring, so that network administrators need not understand MIMO or physical layer techniques.We patch the iwlwifi driver to support OpenRF on off-the-shelf Intel cards. We deploy OpenRF on a 20-node network, showing how it manages the complex interaction of cross-layer design with a real network stack, TCP, bursty traffic, and real applications. Our results demonstrate an average gain of 1.6× for TCP traffic and a significant reduction in response time for real-time applications, like remote desktop.

SDN-Based Centralized Downlink Scheduling with Multiple APs Cooperation in WLANs

“…us, it also can be adopted easily as a novel paradigm for WLANs, which enables the controller to mitigate signal interference and improve further the channel efficiency by a centralized framework. For instance, in [22], a SDWN-based framework called OpenRF is proposed to manage MIMO (multiple-input multiple-out) interference among APs, which adjusts the relative power used to transmit the traffic on each of the AP's antennas to degrade the cochannel interference. In [23], the authors adopt a centralized SDWN architecture to schedule downlink for multiple APs in WLANs, where all activated downlinks are cooperated to reduce the occurrence of collision by combining the DCF and a centralized queue scheduling algorithm for APs.…”

Alocação dinâmica de largura de banda para redes sem fio infraestruturadas

“…OpenRF [Kumar et al 2013] apresenta uma arquitetura cross layer para gerenciar processamento de sinal MIMO que permite os pontos de acesso no mesmo canal cancelarem a interferência nos clientes uns dos outros. O foco desta propostaé em técnicas de camada física, e ela não manipula a largura de banda variável.…”

High-rate WiFi broadcasting in crowded scenarios via lightweight coordination of multiple access points

“…[31] explores how such a system scales as the number of relay hops increases. In [24] the authors study the alignment of OFDM symbols within the duration of a CP for cooperative transmissions purposes, [25,11] use similar ideas for concurrent transmissions in the context of a distributed MU-MIMO system, and [20] enables basic coordination when using specific off-the-shelf WiFi chipsets. Last, [28] theoretically analyzes the effect of CTO and CCFO on top of OFDM and suggests scalable ways to achieve synchronization and calibration in large-scale networks in the context of OFDM based distributed MU-MIMO systems.…”

“…Clearly, the PAP contends for the channel with uplink traffic and, perhaps, other APs that do not belong to the PAP's cluster. To guarantee contention fairness for the broadcast traffic, the PAP can adjust its contention window in order to increase the chance of grabbing the channel, see, for example,[20] where the authors have implemented this feature in the context of a real world WiFi chipset.…”