Eduard Garcia-Villegas

The impact of channel bonding on 802.11n network management

The IEEE 802.11n standard allows wireless devices to operate on 40MHz-width channels by doubling their channel width from standard 20MHz channels, a concept called channel bonding. Increasing channel width should increase bandwidth, but it comes at the cost of decreased transmission range and greater susceptibility to interference. However, with the incorporation of MIMO (Multiple-Input Multiple-Output) technology in 802.11n, devices can now exploit the increased transmission rates from wider channels at a reduced sacrifice to signal quality and range. The goal of our work is to understand the characteristics of channel bonding in 802.11n networks and the factors that influence that behavior to ultimately be able to predict behavior so that network performance is maximized. We discuss the impact of channel bonding choices as well as the effects of both co-channel and adjacent channel interference on network performance. We discover that intelligent channel bonding decisions rely not only on a links signal quality, but also on the strength of neighboring links and their physical rates.

Intelligent Channel Bonding in 802.11n WLANs

The IEEE 802.11n standard defines channel bonding that allows wireless devices to operate on 40 MHz channels by doubling their bandwidth from standard 20 MHz channels. Increasing channel width increases capacity, but it comes at the cost of decreased transmission range and greater susceptibility to interference. However, with the incorporation of Multiple-Input Multiple-Output (MIMO) technology in 802.11n, devices can now exploit the increased transmission rates from wider channels with minimal sacrifice to signal quality and range. The goal of our work is to identify the network factors that influence the performance of channel bonding in 802.11n networks and make intelligent channel bonding decisions. We discover that channel width selection should consider not only a links signal quality, but also the strength of neighboring links, their physical rates, and interferer load. We use our findings to design and implement a network detector that successfully identifies interference conditions that affect channel bonding decisions in 100% of our test cases. Our detector can form the foundation for more robust and accurate algorithms that can adapt bandwidth to variations in channel conditions. Our findings allows us to predict the impact of network conditions on performance and make channel bonding decisions that maximize throughput.

Joint rate and channel width adaptation for 802.11 MIMO wireless networks

The emergence of MIMO antennas and channel bonding in 802.11n wireless networks has resulted in a huge leap in capacity compared with legacy 802.11 systems. This leap, however, adds complexity to selecting the right transmission rate. Not only does the appropriate data rate need to be selected, but also the MIMO transmission technique (e.g., Spatial Diversity or Spatial Multiplexing), the number of streams, and the channel width. Incorporating these features into a rate adaptation (RA) solution requires a new set of rules to accurately evaluate channel conditions and select the appropriate transmission setting with minimal overhead. To address these challenges, we propose ARAMIS (Agile Rate Adaptation for MIMO Systems), a standard-compliant, closed-loop RA solution that jointly adapts rate and bandwidth. ARAMIS adapts transmission rates on a per-packet basis; we believe it is the first 802.11n RA algorithm that simultaneously adapts rate and channel width. We have implemented ARAMIS on Atheros-based devices and deployed it on our 15-node testbed. Our experiments show that ARAMIS accurately adapts to a wide variety of channel conditions with negligible overhead. Furthermore, ARAMIS outperforms existing RA algorithms in 802.11n environments with up to a 10 fold increase in throughput.

Evaluation of dynamic sensitivity control algorithm for IEEE 802.11ax

The explosive growth in the usage of IEEE 802.11 network has resulted in dense deployments in diverse environments. Most recently, the IEEE working group has triggered the IEEE 802.11ax project, which aims to amend the current IEEE 802.11 standard to improve efficiency of dense WLANs. In this paper, we evaluate the Dynamic Sensitivity Control (DSC) Algorithm proposed for IEEE 802.11ax. This algorithm dynamically adjusts the Carrier Sense Threshold (CST) based on the average received signal strength. We show that the aggregate throughput of a dense network utilizing DSC is considerably improved (i.e. up to 20%) when compared with the IEEE 802.11 legacy network.

Enabling always on service discovery: Wifi neighbor awareness networking

There is untapped potential in the WiFi radios embedded in our smartphone and tablet devices. In this article we introduce the WiFi Neighbor Awareness Networking technology being standardized in the WiFi Alliance®, which leverages this potential by allowing handheld devices to continuously discover other interesting services and devices while operating in the background in an energy-efficient way. In addition, we present a thorough performance evaluation based on packet-level simulations that illustrates the performance of WiFi NAN to be expected in realistic scenarios.

IEEE 802.11ah: A Technology to Face the IoT Challenge

Since the conception of the Internet of things (IoT), a large number of promising applications and technologies have been developed, which will change different aspects in our daily life. This paper explores the key characteristics of the forthcoming IEEE 802.11ah specification. This future IEEE 802.11 standard aims to amend the IEEE 802.11 legacy specification to support IoT requirements. We present a thorough evaluation of the foregoing amendment in comparison to the most notable IEEE 802.11 standards. In addition, we expose the capabilities of future IEEE 802.11ah in supporting different IoT applications. Also, we provide a brief overview of the technology contenders that are competing to cover the IoT communications framework. Numerical results are presented showing how the future IEEE 802.11ah specification offers the features required by IoT communications, thus putting forward IEEE 802.11ah as a technology to cater the needs of the Internet of Things paradigm.

IEEE 802.11ax: Challenges and Requirements for Future High Efficiency WiFi

The popularity of IEEE 802.11 based wireless local area networks (WLANs) has increased significantly in recent years because of their ability to provide increased mobility, flexibility, and ease of use, with reduced cost of installation and maintenance. This has resulted in massive WLAN deployment in geographically limited environments that encompass multiple overlapping basic service sets (OBSSs). In this article, we introduce IEEE 802.11ax, a new standard being developed by the IEEE 802.11 Working Group, which will enable efficient usage of spectrum along with an enhanced user experience. We expose advanced technological enhancements proposed to improve the efficiency within high density WLAN networks and explore the key challenges to the upcoming amendment.

A practical framework for 802.11 MIMO rate adaptation

The emergence of MIMO antennas and channel bonding in 802.11n wireless networks has resulted in a huge leap in capacity compared with legacy 802.11 systems. This leap, however, adds complexity to optimizing transmission. Not only does the appropriate data rate need to be selected, but also the MIMO transmission technique (e.g., Spatial Diversity or Spatial Multiplexing), the number of streams, and the channel width. Incorporating these features into a rate adaptation (RA) solution requires a new set of rules to accurately evaluate channel conditions and select the appropriate transmission setting with minimal overhead. To address these challenges, our contributions in this work are two-fold. First, we propose a practical link metric that accurately captures channel conditions in MIMO 802.11n environments, and we call this metric diffSNR. Using diffSNR captured from real testbed environments, we build performance models that accuractely predict link quality in 95.5% of test cases. Practicality and deployability are guaranteed with diffSNR as it can be measured on all off-the-shelf MIMO WiFi chipsets. Second, we propose ARAMIS (Agile Rate Adaptation for MIMO Systems), a standard-compliant, closed-loop RA solution that jointly adapts rate and bandwidth, and we utilize the diffSNR-based 802.11n performance models within ARAMISs framework. ARAMIS adapts transmission rates on a per-packet basis; we believe it is the first closed-loop, 802.11 RA algorithm that simultaneously adapts rate and channel width. We have implemented ARAMIS with diffSNR on Atheros-based devices and deployed it on our 15-node testbed. Our experiments show that ARAMIS accurately adapts to a wide variety of channel conditions with negligible overhead. Furthermore, ARAMIS outperforms existing RA algorithms in 802.11n environments with up to a 10-fold increase in throughput.

Channel management in a campus-wide WLAN with partially overlapping channels

The 2.4 GHz ISM band is a battlefield where an increasingly large number of devices compete for the scarce frequency resources. IEEE 802.11 WLANs suffer the consequences of this overcrowded spectrum, especially in dense scenarios where the performance of those WLAN cells is way below the expected in ideal conditions. The harmful effects of interference can be minimized if an intelligent frequency management is implemented. In this paper, we first detail the implementation of a dynamic channel assignment solution which considers partially overlapping channels, and then we show, through measurements in a real campus-wide scenario with near 200 APs and under real traffic conditions, how this approach improves the performance of the traditional three orthogonal channels (i.e. 1, 6 and 11).

Dynamic sensitivity control of access points for IEEE 802.11ax

The popularity and wider acceptance of IEEE 802.11 based WLANs has resulted in their dense deployments in diverse environments. While this massive deployment can potentially increase capacity and coverage, the current physical carrier sensing of IEEE 802.11 cannot limit the overall interference induced and also cannot insure high concurrency among transmissions. Recently, the IEEE 802.11 working group has continued efforts on developing WLAN technology through the creation of the TGax, which aims to improve efficiency of densely deployed IEEE 802.11 networks. In this paper, we propose a Dynamic Sensitivity Control for Access Point (DSC-AP) algorithm for IEEE 802.11ax. This algorithm dynamically adjusts the Carrier Sensing Threshold (CST) of an AP based on received signal strength from its associated stations and interfering APs. We show that the aggregate throughput of a dense network (under asymmetric traffic conditions) utilizing DSC (both at the stations and AP) is considerably improved (i.e. up to 32%) when compared with legacy IEEE 802.11.