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Congestion-Aware Rate Adaptation in Wireless Networks: A Measurement-Driven Approach
"... Abstract—Traditional rate adaptation solutions for IEEE 802.11 wireless networks perform poorly in congested networks. Measurement studies show that congestion in a wireless network leads to the use of lower transmission data rates and thus reduces overall network throughput and capacity. The lack o ..."
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Abstract—Traditional rate adaptation solutions for IEEE 802.11 wireless networks perform poorly in congested networks. Measurement studies show that congestion in a wireless network leads to the use of lower transmission data rates and thus reduces overall network throughput and capacity. The lack of techniques to reliably identify and characterize congestion in wireless networks has prevented development of rate adaptation solutions that incorporate congestion information in their decision framework. To this end, our main contributions in this paper are two-fold. First, we present a technique that identifies and measures congestion in an 802.11 network in real time. Second, we design Wireless cOngestion Optimized Fallback (WOOF), a measurement-driven rate adaptation scheme for 802.11 devices that uses the congestion measurement to identify congestion related packet losses. Through experimental evaluation, we show that WOOF achieves up to 300% higher throughput in congested networks, compared to other well-known adaptation algorithms. I.
No time to countdown: migrating backoff to the frequency domain
- In ACM MobiCom
, 2011
"... Conventional WiFi networks perform channel contention in time domain. This is known to be wasteful because the chan-nel is forced to remain idle while all contending nodes are backing off for multiple time slots. This paper proposes to break away from convention and recreate the backing off op-erati ..."
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Cited by 16 (0 self)
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Conventional WiFi networks perform channel contention in time domain. This is known to be wasteful because the chan-nel is forced to remain idle while all contending nodes are backing off for multiple time slots. This paper proposes to break away from convention and recreate the backing off op-eration in the frequency domain. Our basic idea leverages the observation that OFDM subcarriers can be treated as integer numbers. Thus, instead of picking a random backoff duration in time, a contending node can signal on a randomly cho-sen subcarrier. By employing a second antenna to listen to all the subcarriers, each node can determine whether its cho-sen integer (or subcarrier) is the smallest among all others. In fact, each node can even determine the rank of its chosen subcarrier, enabling the feasibility of scheduled transmissions after every round of contention. We develop these ideas into a Back2F protocol that migrates WiFi backoff to the frequency domain. Experiments on a prototype of 10 USRPs confirm fea-sibility, along with consistent throughput gains over 802.11. Trace based simulations affirm scalability to larger, real-world network topologies.
An experimental study of inter-cell interference effects on system performance in . . .
, 2008
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Association control in mobile wireless networks
- In IEEE INFOCOM
, 2008
"... Abstract—As mobile nodes roam in a wireless network, they continuously associate with different access points and perform handoff operations. However, frequent handoffs can potentially incur unacceptable delays and even interruptions for interactive applications. To alleviate these negative impacts, ..."
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Cited by 5 (1 self)
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Abstract—As mobile nodes roam in a wireless network, they continuously associate with different access points and perform handoff operations. However, frequent handoffs can potentially incur unacceptable delays and even interruptions for interactive applications. To alleviate these negative impacts, we present novel association control algorithms that can minimize the frequency of handoffs occurred to mobile devices. Specifically, we show that a greedy LookAhead algorithm is optimal in the offline setting, where the user’s future mobility is known. Inspired by such optimality, we further propose two online algorithms, namely LookBack and Track, that operate without any future mobility information. Instead, they seek to predict the lifetime of an association using randomization and statistical approaches, respectively. We evaluate the performance of these algorithms using both analysis and trace-driven simulations. The results show that the simple LookBack algorithm has surprisingly a competitive ratio of (log k+2), where k is the maximum number of APs that a user can hear at any time, and the Track algorithm can achieve near-optimal performance in practical scenarios. I.
Rate Adaptation in Congested Wireless Networks through Real-Time Measurements
"... Rate adaptation is a critical component that impacts the performance of IEEE 802.11 wireless networks. In congested networks, traditional rate adaptation algorithms have been shown to choose lower data-rates for packet transmissions, leading to reduced total network throughput and capacity. A primar ..."
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Cited by 5 (0 self)
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Rate adaptation is a critical component that impacts the performance of IEEE 802.11 wireless networks. In congested networks, traditional rate adaptation algorithms have been shown to choose lower data-rates for packet transmissions, leading to reduced total network throughput and capacity. A primary reason for this behavior is the lack of real-time congestion measurement techniques that can assist in the identification of congestion related packet losses in a wireless network. In this work, we first propose two real-time congestion measurement techniques, namely an active probe-based method called Channel Access Delay, and a passive method called Channel Busy Time. We evaluate the two techniques in a testbed network and a large WLAN connected to the Internet. We then present the design and evaluation of Wireless cOngestion Optimized Fallback (WOOF), a rate adaptation scheme that uses congestion measurement to identify congestion related packet losses. Through simulation and testbed implementation we show that, compared to other well-known rate adaptation algorithms, WOOF achieves up to 300 % throughput improvement in congested networks.
Unwanted link layer traffic in large IEEE 802.11 wireless networks
- In Proc. of IMC
, 2007
"... Abstract—Wireless networks have evolved into an important technology for connecting users to the Internet. As the utility of wireless technology grows, wireless networks are being deployed in more widely varying conditions. The monitoring of wireless networks continues to reveal key implementation d ..."
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Abstract—Wireless networks have evolved into an important technology for connecting users to the Internet. As the utility of wireless technology grows, wireless networks are being deployed in more widely varying conditions. The monitoring of wireless networks continues to reveal key implementation deficiencies that need to be corrected in order to improve protocol operation and end-to-end network performance. In wireless networks, where the medium is shared, unwanted traffic can pose significant overhead and lead to suboptimal network performance. Much of the previous analyses of unwanted traffic in wireless networks focus on malicious traffic. However, another major contributor of unwanted traffic is incorrect link layer behavior. Using data we collected from the 67 th Internet Engineering Task Force (IETF) meeting held in November 2006, we show that a significant portion of link layer traffic stems from mechanisms that initiate, maintain, and change client-AP associations. We further show that under conditions of high medium utilization and packet loss rate, handoffs are initiated incorrectly. We analyze the traffic to understand when handoffs occur and whether the handoffs were beneficial or should have been avoided. 1
Understanding Handoffs in Large IEEE 802.11 Wireless Networks
, 2007
"... As the utility of wireless technology grows, wireless networks are being deployed in more widely varying conditions. The monitoring of these networks continues to reveal key implementation deficiencies that need to be corrected in order to improve protocol operation and end-to-end performance. Using ..."
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Cited by 3 (1 self)
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As the utility of wireless technology grows, wireless networks are being deployed in more widely varying conditions. The monitoring of these networks continues to reveal key implementation deficiencies that need to be corrected in order to improve protocol operation and end-to-end performance. Using data we collected from the 67 th Internet Engineering Task Force (IETF) meeting held in November 2006, we show that under conditions of high medium utilization and packet loss, handoffs can be incorrectly initiated. Using the notion of persistence and prevalence for the association of a client to an Access Point (AP), we show that although the clients were predominantly static, the handoff rate is surprisingly high. Through the analysis of the data set, we show that unnecessary handoff events not only increase the amount of management traffic in the network, but also severely impact client performance.
Available Bandwidth-Based Association in IEEE 802.11 Wireless LANs ∗
"... The performance of an IEEE 802.11 station heavily depends on the selection of an AP (Access Point) that the station is associated with to access the Internet. The conventional approach to the AP selection is based on the received sig-nal strength called RSSI (Received Signal Strength Indica-tion) fr ..."
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Cited by 3 (0 self)
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The performance of an IEEE 802.11 station heavily depends on the selection of an AP (Access Point) that the station is associated with to access the Internet. The conventional approach to the AP selection is based on the received sig-nal strength called RSSI (Received Signal Strength Indica-tion) from APs within the transmission range. This ap-proach however, might yield unbalanced traffic load among APs as the station chooses an AP only based on the signal strength, instead of considering the AP load and the level of contention on medium access. Accordingly, the station that is associated with the highest-RSSI AP might suffer from poor network performance. In this paper, we propose a new association metric, EVA (Estimated aVailable bAnd-width) with which a station can find the AP that provides the maximum achievable throughput among scanned APs. EVA is designed to estimate the available bandwidth on a channel with respect to a station that is to join a WLAN (Wireless Local Area Network). A station equipped with EVA observes a channel state in a per-slot basis, and yet does not request any external information from nearby APs or neighbor stations. Our estimation mechanism is non-intrusive, fully distributed, and independent of the infras-tructure. Through simulation study, we evaluate the accu-racy of the estimation and show that EVA-based association yields enhanced throughput performance compared with the legacy scheme.
Resource Estimation on Wireless Backhaul Networks
- WICON 2007
, 2007
"... The increased usage of IEEE 802.11 wireless backhaul networks and the growing popularity of real time applications, such as VoIP, presents a challenging resource management problem due to the limited capacity of wireless networks. At high traffic volumes, measurements have shown that packet collisio ..."
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Cited by 1 (1 self)
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The increased usage of IEEE 802.11 wireless backhaul networks and the growing popularity of real time applications, such as VoIP, presents a challenging resource management problem due to the limited capacity of wireless networks. At high traffic volumes, measurements have shown that packet collisions and interference in 802.11 networks can lead to degraded performance to the extent that users experience unacceptably low throughput, which can ultimately lead to complete network breakdown [1]. A resource management framework that limits network flows can prevent network breakdown and improve the performance of throughput and delay-sensitive multimedia applications. To address this problem, we present a measurementdriven framework that leverages wireless characteristics for intelligent admission control in a static wireless network. Experiments on a 25 node wireless testbed show that the proposed scheme can enhance network performance such that the QoS requirements of real time applications, such as VoIP, can be met.
Experimenting with Commodity 802.11 Hardware: Overview and Future Directions
, 2015
"... 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 experimenta ..."
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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.
