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11
Divert: Fine-grained Path Selection for Wireless LANs
, 2004
"... The performance of Wireless Local Area Networks (WLANs) often suffers from link-layer frame losses caused by noise, interference, multipath, attenuation, and user mobility. We observe that frame losses often occur in bursts and that three of the five main causes of frame losses--- multipath, attenua ..."
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Cited by 47 (4 self)
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The performance of Wireless Local Area Networks (WLANs) often suffers from link-layer frame losses caused by noise, interference, multipath, attenuation, and user mobility. We observe that frame losses often occur in bursts and that three of the five main causes of frame losses--- multipath, attenuation, mobility---depends on the transmission path traversed between an access point (AP) and a client station. In a typical WLAN
Fast-responsive link adaptation for IEEE 802.11 WLANs
- in Proc. IEEE ICC’05, Seoul, Korea
, 2005
"... Abstract-The mechanism to select one out of multiple available transmission rates at a given time is referred to as link adaptation. The effectiveness of a link adaptation scheme depends on how fast it can respond to the wireless channel variation. In this paper, we propose a truly-adaptive fast-re ..."
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Cited by 14 (1 self)
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Abstract-The mechanism to select one out of multiple available transmission rates at a given time is referred to as link adaptation. The effectiveness of a link adaptation scheme depends on how fast it can respond to the wireless channel variation. In this paper, we propose a truly-adaptive fast-responsive link adaptation scheme for IEEE 802.11 WLANs (Wireless LANs). The key idea is to direct the transmitter station's rate-increasing attempts in a controlled manner such that the responsiveness of the link adaptation scheme can be guaranteed with minimum number of rate-increasing attempts. Since our scheme allows the transmitter station to make the link adaptation decision solely based on its local acknowledgment information, it does not require any change to the current 802.11 standard, thus facilitating its deployment with existing 802.11 devices. Our indepth simulation shows that our scheme yields significantlyhigher throughput than other existing schemes including singlerate schemes, the ARF (Auto Rate Fallback) scheme and its variants, in various fading channels.
Picasso: Full Duplex Signal Shaping to Exploit Fragmented Spectrum
"... Wireless spectrum is increasingly fragmented due to the growing proliferation of unlicensed wireless devices and piecemeal licensed spectrum allocations. Current radios are ill-equipped to exploit such fragmented spectrum since they expect large contiguous chunks of spectrum to operate on. In this p ..."
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Cited by 4 (1 self)
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Wireless spectrum is increasingly fragmented due to the growing proliferation of unlicensed wireless devices and piecemeal licensed spectrum allocations. Current radios are ill-equipped to exploit such fragmented spectrum since they expect large contiguous chunks of spectrum to operate on. In this paper we argue that future radios should provide full duplex signal shaping to the higher layers to systematically exploit fragmented spectrum. Such an architectural design would allow the radio to decouple the use of different spcetrum fragments. We present the design and implementation of Picasso, a system that provides such a general signal shaping abstraction. Picasso has two novel components: a self-interference cancellation technique and a programmable filter engine that enables it to simultaneously send and receive over different spectrum fragments. We provide an initial design and empirically evaluate the feasibility of both components. 1.
Dwell Adaptive Fragmentation : how to cope with short dwells required by multimedia wireless LANs
"... wireless, radio, ..."
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LINK ADAPTATION IN WIRELESS NETWORKS: A CROSS-LAYER APPROACH
, 2010
"... Conventional Link Adaptation Techniques in wireless networks aim to overcome harsh link conditions caused by physical environmental properties, by adaptively regulating modulation, coding and other signal and protocol specific parameters. These techniques are essential for the overall performance of ..."
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Cited by 1 (0 self)
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Conventional Link Adaptation Techniques in wireless networks aim to overcome harsh link conditions caused by physical environmental properties, by adaptively regulating modulation, coding and other signal and protocol specific parameters. These techniques are essential for the overall performance of the networks, especially for environments where the ambient noise level is high or the noise level changes rapidly. Link adaptation techniques answer the questions of What to change? and When to change? in order to improve the present layer performance. Once these decisions are made, other layers are expected to function perfectly with the new communication channel conditions. In our work, we have shown that this assumption does not always hold; and provide two mechanisms that lessen the negative outcomes caused by these decisions. Our first solution, MORAL, is a MAC layer link adaptation technique which utilizes the physical transmission information in order to create differentiation between wireless users with different communication capabilities. MORAL passively collects information from its neighbors and re-aligns the MAC layer parameters
Improving Packet Delivery Efficiency Using Multi-Radio Diversity in Wireless LANs
, 2006
"... Data transmissions in Wireless Local Area Networks (WLANs) often suffer from bit errors that arise from the notoriously complex and time-varying signal propagation characteristics of the wireless medium. A number of physical factors such as attenuation and multi-path are prevalent indoors and can le ..."
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Cited by 1 (0 self)
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Data transmissions in Wireless Local Area Networks (WLANs) often suffer from bit errors that arise from the notoriously complex and time-varying signal propagation characteristics of the wireless medium. A number of physical factors such as attenuation and multi-path are prevalent indoors and can lead to high bit-error rates at the link layer. These in turn lead to packet losses, low throughput, and higher and more variable packet latencies observed at higher layers, degrading the performance of many delay-sensitive and traffic-intensive wireless applications such as games, file-sharing, voice-over-IP, and streaming video. We use the notion of path diversity to develop an approach that improves data delivery efficiency and throughput in presence of transmission errors. Path diversity relies on multiple
> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < Early Multicast Collision Detection
"... Abstract—Reliable multicast is especially difficult to achieve in CSMA/CA networks when multiple multicast and unicast senders compete for the medium. Motivated by capacity problems in a sports infotainment product the authors developed Early Multicast Collision Detection (EMCD). The algorithm is sp ..."
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Abstract—Reliable multicast is especially difficult to achieve in CSMA/CA networks when multiple multicast and unicast senders compete for the medium. Motivated by capacity problems in a sports infotainment product the authors developed Early Multicast Collision Detection (EMCD). The algorithm is specifically tailored to accommodate a very large number of legacy terminals in multiple overlapping cells. The algorithm is based on the fact that in the absence of hidden terminals two stations must start their transmissions simultaneously to cause a collision. A station using EMCD will introduce an early pause in the multicast transmission, perform a clear channel assessment (CCA), and if another sender is detected, schedule a retransmission. Simulations shows that EMCD lead to better multicast reliability even at relatively moderate network loads. EMCD gains priority over unicast traffic leading to higher media access delays and lower throughput for unicast traffic at relatively high network loads.
Series
, 2006
"... The growing adoption of 802.11 networks in the enterprise segment has led to the emergence of High Density (HD) WLAN scenarios where large (100-1000) numbers of clients are serviced by 10-100s of APs in a multi-cell environment. This leads to an interference limited environment due to limited spectr ..."
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The growing adoption of 802.11 networks in the enterprise segment has led to the emergence of High Density (HD) WLAN scenarios where large (100-1000) numbers of clients are serviced by 10-100s of APs in a multi-cell environment. This leads to an interference limited environment due to limited spectrum availability; hence network design for throughput scalability becomes the primary design challenge. Broadly speaking, we espouse adaptive tuning of 802.11 PHY/MAC parameters such as receiver sensitivity, clear channel assessment (CCA) threshold and link rates to improve network throughput for any network topology, traffic and interference conditions. This work seeks to corroborate, via measurements on an experimental multi-radio tested, an algorithm for CCA threshold adaptation based on our earlier work [2, 4].
The performance of Wireless Local Area Networks
"... (WLANs) often suffers from link-layer frame losses caused by noise, interference, multipath, attenuation, and user mobility. We observe that frame losses often occur in bursts and that three of the five main causes of frame losses— multipath, attenuation, mobility—depends on the transmission path tr ..."
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(WLANs) often suffers from link-layer frame losses caused by noise, interference, multipath, attenuation, and user mobility. We observe that frame losses often occur in bursts and that three of the five main causes of frame losses— multipath, attenuation, mobility—depends on the transmission path traversed between an access point (AP) and a client station. In a typical WLAN deployment, different transmission paths to a client exist in places where overlapping coverage is provided by a set of neighboring APs. Using experimental measurements and analysis on a 802.11b testbed, we show that fine-grained path selection among a set of neighboring APs can significantly reduce path-dependent losses in WLANs. We design and implement a WLAN distribution system called Divert, which supports fine-grained path selection for downlink communications, on an 802.11b testbed. Divert reduces frame losses without consuming any extra bandwidth in the wireless medium. Our experimental results show that Divert can reduce frame loss rates in realistic scenarios by as much as 26 % compared to a fixed-path scheme that uses the best available transmitter.
Dwell Adaptive Fragmentation:
, 2000
"... This paper studies the impact on CSMA / CA traffic of a reduction of the dwell size, a fundamental parameter of some wireless LANs. First, we explain why we want to reduce the dwell size and what are the consequences. Then, we present some ways to overcome the overhead of short dwell, mostly ba ..."
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This paper studies the impact on CSMA / CA traffic of a reduction of the dwell size, a fundamental parameter of some wireless LANs. First, we explain why we want to reduce the dwell size and what are the consequences. Then, we present some ways to overcome the overhead of short dwell, mostly based on fragmentation. We finish by some exhaustive simulations of the short dwell size impact and variations, and the way those fragmentation schemes improve the network performance
