Results 1 -
9 of
9
Building Efficient Spectrum-Agile Devices for Dummies
"... Spectrum management and device coordination for Dynamic Spectrum Access (DSA) networks have received significant research attention. However, current wireless devices have yet to fully embrace DSA networks due to the difficulties in realizing spectrumagile communications. We address the practical hu ..."
Abstract
-
Cited by 4 (1 self)
- Add to MetaCart
(Show Context)
Spectrum management and device coordination for Dynamic Spectrum Access (DSA) networks have received significant research attention. However, current wireless devices have yet to fully embrace DSA networks due to the difficulties in realizing spectrumagile communications. We address the practical hurdles and present solutions towards implementing DSA devices, answering an important question “what is a simple practical extension to current wireless devices that makes them spectrum-agile? ” To this end, we propose RODIN, a general per-frame spectrum-shaping protocol that has the following features to support DSA in commercial off-the-shelf (COTS) wireless devices: (a) direct manipulation of passband signals from COTS devices, (b) fast FPGA-based spectrum shaping, and (c) a novel preamble design for spectrum agreement. RODIN uses an FPGA-based spectrum shaper together with a preamble I-FOP to achieve per-frame spectrum shaping with a delay of under 10µs.
An Overview of WLAN Performance, Some Important Case-Scenarios and their Associated Models
"... Abstract—The study of the 802.11 standard has been very intense for more than a decade now. Several works have striven at understanding its performance, even in the simplest topology of a wireless local area network (WLAN) with a single access point (AP). The present survey is an effort to classify ..."
Abstract
-
Cited by 1 (1 self)
- Add to MetaCart
(Show Context)
Abstract—The study of the 802.11 standard has been very intense for more than a decade now. Several works have striven at understanding its performance, even in the simplest topology of a wireless local area network (WLAN) with a single access point (AP). The present survey is an effort to classify and present the enormous literature on the subject into several important case-scenarios, and summarizes the current understanding of WLAN performance. The resulting performance and associated models are discussed (and sometimes extended) and simulation results are used to illustrate them. We also highlight interesting open research problems that we believe the community should address. I.
Comparison of Routing Metrics in 802.11n Wireless Mesh Networks
"... Abstract—We conduct the first experimental study of the performance of link quality-based routing metrics in an 802.11n wireless mesh network (WMN). Link quality-based metrics have been shown to significantly outperform the traditional hopcount metric but they have only been evaluated over legacy 80 ..."
Abstract
-
Cited by 1 (0 self)
- Add to MetaCart
(Show Context)
Abstract—We conduct the first experimental study of the performance of link quality-based routing metrics in an 802.11n wireless mesh network (WMN). Link quality-based metrics have been shown to significantly outperform the traditional hopcount metric but they have only been evaluated over legacy 802.11a/b/g radios. The new 802.11n standard introduces a number of enhancements at the MAC and PHY layers (MIMO technology, channel bonding, frame aggregation, short guard interval, and more aggressive modulation and coding schemes) marking the beginning of a new generation of 802.11 radios. Our study in a 21-node indoor 802.11n WMN testbed reveals that the gains of link quality-based metrics over the hopcount metric in legacy 802.11 WMNs do not carry over in 802.11n MIMO WMNs. We analyze the causes of this behavior and make recommendations for the design of new routing metrics in 802.11n WMNs. I.
ShiftFFT: An Efficient Approach to Mitigate Adjacent Channel Interference in OFDM Systems
"... ABSTRACT Adjacent channel interference (ACI) in wireless systems is commonly mitigated through the use of guard bands and filters. Guard bands are not used for any transmissions and are therefore wasted spectrum. The use of sharp filters can reduce the size of required guard bands but they are cost ..."
Abstract
- Add to MetaCart
(Show Context)
ABSTRACT Adjacent channel interference (ACI) in wireless systems is commonly mitigated through the use of guard bands and filters. Guard bands are not used for any transmissions and are therefore wasted spectrum. The use of sharp filters can reduce the size of required guard bands but they are costly and often not present in devices that are already deployed. We focus on OFDM wireless systems, which form the basis for almost all modern wireless networks, and propose a novel technique called ShiftFFT that can be deployed at an OFDM receiver to mitigate ACI from legacy OFDM transmitters. ShiftFFT exploits the presence of over-provisioned cyclic prefixes in most OFDM wireless standards to optimize the starting time of the FFT operation at the receiver, which we show to have significant potential to reduce the amount of guard band required to avoid ACI and thereby enable efficient spectrum use. We evaluate ShiftFFT with a SDR testbed and using simulations across diverse settings, and show that using it can significantly reduce the guard band required by at least 10MHz in most cases while maintaining the same packet error rate performance.
Joint Rate and Channel Width Adaptation for 802.11 MIMO Wireless Networks
"... Abstract—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 selec ..."
Abstract
- Add to MetaCart
(Show Context)
Abstract—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 channelconditionsandselect theappropriatetransmission 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. I.
Power-Throughput Tradeoffs of 802.11n/ac in
"... Abstract—This paper presents the first, to the best of our knowledge, detailed experimental study of 802.11n/ac throughput and power consumption in modern smartphones. We experiment with a variety of smartphones, supporting different subsets of 802.11n/ac features. We investigate the power consumpti ..."
Abstract
- Add to MetaCart
(Show Context)
Abstract—This paper presents the first, to the best of our knowledge, detailed experimental study of 802.11n/ac throughput and power consumption in modern smartphones. We experiment with a variety of smartphones, supporting different subsets of 802.11n/ac features. We investigate the power consumption in various states of the wireless interface (sleep, idle, active), the impact of various features of 802.11n/ac (PHY bitrate, frame aggregation, channel bonding, MIMO) on both throughput and power consumption, and the tradeoffs between these two met-rics. Some of our findings are significantly different from the findings of previous studies using 802.11n/ac wireless cards for laptop/desktop computers. We believe that these findings will help in understanding various performance and power consumption issues in today’s smartphones and will guide the design of power optimization algorithms for the next generation of mobile devices. I.
1Intelligent Channel Bonding
"... Abstract—The IEEE 802.11n standard defines channel bonding that allows wireless devices to operate on 40MHz channels by doubling their bandwidth from standard 20MHz channels. Increasing channel width increases capacity, but it comes at the cost of decreased transmission range and greater susceptibil ..."
Abstract
- Add to MetaCart
(Show Context)
Abstract—The IEEE 802.11n standard defines channel bonding that allows wireless devices to operate on 40MHz channels by doubling their bandwidth from standard 20MHz 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 link’s 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.
Potential Pitfalls of the Message in Message Mechanism in Modern 802.11 Networks
"... We study the performance impact of the Message in Mes-sage (MIM) mechanism in modern 802.11 networks. The MIM mechanism refers to the capability of receiver to aban-don an ongoing reception of an 802.11 MAC frame and shift to decode another frame with a higher signal strength. MIM is a common featur ..."
Abstract
- Add to MetaCart
(Show Context)
We study the performance impact of the Message in Mes-sage (MIM) mechanism in modern 802.11 networks. The MIM mechanism refers to the capability of receiver to aban-don an ongoing reception of an 802.11 MAC frame and shift to decode another frame with a higher signal strength. MIM is a common feature in modern 802.11 adapters and it has been shown to improve spatial concurrency. However, our measurement study in a campus WLAN shows that under certain conditions, MIM could cause a throughput degra-dation of more than 30 % when enabled, instead of improv-ing it as expected. With comprehensive experiments using commercial 802.11n adapters, we characterize the impact of MIM for a range of parameters and for different scenarios. We show that a simple adaptive MIM scheme can poten-tially achieve throughput that is close to the optimal. Our method is practical because it can be easily implemented in existing commodity 802.11 adapters.
Rethinking Wireless: Building Next-Generation Networks
, 2013
"... Contents List of Figures vi Abstract x ..."
(Show Context)
