Abstract—Current IEEE 802.11 WLANs suffer from the well-known rate anomaly problem, which can drastically reduce network performance. Opportunistic relaying can address this problem, but three major considerations, typically considered separately by prior work, need to be taken into account for an efficient deployment in real-world systems: 1) relaying could imply increased power consumption, and nodes might be hetero-geneous, both in power source (e.g., battery-powered vs. socket-powered) and power consumption profile; 2) similarly, nodes in the network are expected to have heterogeneous throughput needs and preferences in terms of the throughput vs. energy consumption trade-off; and 3) any proposed solution should be backwards-compatible, given the large number of legacy 802.11 devices already present in existing networks. In this paper, we propose a novel framework, Self-Optimizing, Legacy-Compatible Opportunistic Relaying (SOLOR), which jointly takes into account the above considerations and greatly improves network performance even in systems comprised mostly of vanilla nodes and legacy access points. SOLOR jointly op-timizes the topology of the network, i.e., which are the nodes associated to each relay-capable node; and the relay schedules, i.e., how the relays split time between the downstream nodes they relay for and the upstream flow to access points. Our results, obtained for a large variety of scenarios and different node preferences, illustrate the significant gains achieved by our approach. Specifically, SOLOR greatly improves network throughput performance (more than doubling it) and power consumption (up to 75 % reduction) even in systems comprised mostly of vanilla nodes and legacy access points. Its feasibility is demonstrated through test-bed experimentation in a realistic deployment. Index Terms—Wireless LAN, 802.11, rate anomaly, relays I.

The huge adoption of 802.11 technologies has triggered a vast amount of experimentally-driven research works. These works range from performance analysis to protocol enhancements, including the proposal of novel applications and services. Due to the affordability of the technology, this experimental research is typically based on commercial off-the-shelf (COTS) devices, and given the rate at which 802.11 releases new standards (which are adopted into new, affordable devices), the field is likely to continue to produce results. In this paper, we review and categorise the most prevalent works carried out with 802.11 COTS devices over the past fifteen years, to present a timely snapshot of the areas that have attracted to most attention so far, though a taxonomy that distinguishes between performance studies, enhancements, services and methodology. In this way, we provide a quick overview of the results achieved by the research community that enables prospective authors to identify potential areas of new research, some of which are discussed after the presentation of the survey.

Studies of ad hoc wireless networks are rapidly gaining popularity due to its varied and innovative applications. Medium Access Control (MAC) protocols in such networks are responsible to coordinate access among active nodes. Wireless nodes are largely powered by batteries which restricts the quantity of energy available to the nodes. Routing for wireless nodes is incorporated with power saving mechanisms to conserve energy. The most common techniques for power saving is by allowing a node to be in sleep state when possible or by varying transmitting power to reduce energy consumption. The energy saving power control can possibly be used to increase spatial reuse of the wireless channel and at the same time reduce power consumption. In this paper, a MAC protocol is proposed which achieves better spatial reuse of spectrum due to power adjustments established on the number of neighbors in the two-hop neighborhood. Simulation results show improved performance compared to MAC-DCF.

ploits multiuser diversity in wireless networks without the re-quirement of a central scheduler. With DOS, users take their own scheduling decisions based on a local observation of the channel to maximize performance. While DOS has been used in the past to optimize throughput-related figures, in this paper we use DOS to optimize the energy performance of the network. We first derive the optimal configuration for the homogeneous scenario, where all devices share the same power consumption behavior, and then propose a heuristic to address the heterogeneous scenario, where devices have different power consumption figures. Simulation results confirm the effectiveness of our approaches. I.