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22
Zigzag decoding: Combating hidden terminals in wireless networks
, 2008
"... This paper presents ZigZag, an 802.11 receiver design that combats hidden terminals. ZigZag’s core contribution is a new form of interference cancellation that exploits asynchrony across successive collisions. Specifically, 802.11 retransmissions, in the case of hidden terminals, cause successive co ..."
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Cited by 158 (10 self)
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This paper presents ZigZag, an 802.11 receiver design that combats hidden terminals. ZigZag’s core contribution is a new form of interference cancellation that exploits asynchrony across successive collisions. Specifically, 802.11 retransmissions, in the case of hidden terminals, cause successive collisions. These collisions have different interference-free stretches at their start, which ZigZag exploits to bootstrap its decoding. ZigZag makes no changes to the 802.11 MAC and introduces no overhead when there are no collisions. But, when senders collide, ZigZag attains the same throughput as if the colliding packets were a priori scheduled in separate time slots. We build a prototype of ZigZag in GNU Radio. In a testbed of 14 USRP nodes, ZigZag reduces the average packet loss rate at hidden terminals from 72.6% to about 0.7%.
Taking the sting out of carrier sense: interference cancellation for wireless LANs
- In Proceedings of the 14th ACM international conference on Mobile computing and networking
, 2008
"... A fundamental problem with unmanaged wireless networks is high packet loss rates and poor spatial reuse, especially with bursty traffic typical of normal use. To address these limitations, we explore the notion of interference cancellation for unmanaged networks — the ability for a single receiver t ..."
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Cited by 89 (0 self)
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A fundamental problem with unmanaged wireless networks is high packet loss rates and poor spatial reuse, especially with bursty traffic typical of normal use. To address these limitations, we explore the notion of interference cancellation for unmanaged networks — the ability for a single receiver to disambiguate and successfully receive simultaneous overlapping transmissions from multiple unsynchronized sources. We describe a practical algorithm for interference cancellation, and implement it for ZigBee using software radios. In this setting, we find that our techniques can reduce packet loss rate and substantially increase spatial reuse. With carrier sense set to prevent concurrent sends, our approach reduces the packet loss rate during collisions from 14 % to 8 % due to improved handling of hidden terminals. Conversely, disabling carrier sense reduces performance for only 7 % of all pairs of links and increases the delivery rate for the median pair of links in our testbed by a factor of 1.8 due to improved spatial reuse.
A building block approach to sensornet systems
- In Proceedings of the Sixth ACM Conference on Embedded Networked Sensor Systems (SenSys’08
, 2008
"... We present a building block approach to hardware platform design based on a decade of collective experience in this area, arriving at an architecture in which general-purpose modules that require expertise to design and incorporate commonlyused functionality are integrated with application-specific ..."
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Cited by 52 (22 self)
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We present a building block approach to hardware platform design based on a decade of collective experience in this area, arriving at an architecture in which general-purpose modules that require expertise to design and incorporate commonlyused functionality are integrated with application-specific carriers that satisfy the unique sensing, power supply, and mechanical constraints of an application. Of course, modules are widespread, but our focus is far less on the performance of any individual module and far more on an overall architecture that supports the prototype, pilot, and production stages of design, and preserves the artifacts and learnings accumulated along the way. We present heuristics for partitioning functionality between modules and carriers, and identify guidelines for their interconnection. Our approach advocates exporting a wide electrical interface, eliminating the system bus, and supporting many physical interconnect options for modules and carriers. We evaluate this approach by constructing a family of general-purpose modules and application-specific carriers that achieve a high degree of reuse despite very different application requirements. We show that this approach shortens platform development time-to-result for novice graduate students, making custom platforms broadly accessible.
Rethinking indoor wireless mesh design: Low power, low frequency, full-duplex
- In WiMesh
, 2010
"... Abstract—Existing indoor WiFi networks in the 2.5GHz and 5 GHz use too much transmit power, needed because the high carrier frequency limits signal penetration and connectivity. Instead, we propose a novel indoor wireless mesh design paradigm, based on Low Frequency, using the newly freed white spac ..."
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Cited by 24 (2 self)
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Abstract—Existing indoor WiFi networks in the 2.5GHz and 5 GHz use too much transmit power, needed because the high carrier frequency limits signal penetration and connectivity. Instead, we propose a novel indoor wireless mesh design paradigm, based on Low Frequency, using the newly freed white spaces previously used as analogue TV bands, and Low Power – 100 times less power than currently used. Preliminary experiments show that this maintains a similar level of connectivity and performance to existing networks. It also yields more uniform connectivity, thus simplifies MAC and routing protocol design. We also advocate full-duplex networking in a single band, which becomes possible in this setting (because we operate at low frequencies). It potentially doubles the throughput of each link and eliminates hidden terminals. I.
Clearing the RF smog: Making 802.11 robust to cross-technology interference
, 2011
"... Recent studies show that high-power cross-technology interference isbecomingamajorproblem intoday’s802.11networks. Devices like baby monitors and cordless phones can cause a wireless LAN to lose connectivity. The existing approach for dealing withsuch high-power interferers makes the 802.11 network ..."
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Cited by 16 (5 self)
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Recent studies show that high-power cross-technology interference isbecomingamajorproblem intoday’s802.11networks. Devices like baby monitors and cordless phones can cause a wireless LAN to lose connectivity. The existing approach for dealing withsuch high-power interferers makes the 802.11 network switch to a different channel; yet the ISM band is becoming increasingly crowded with diverse technologies, and hence many 802.11 access points may not findaninterference-free channel. ThispaperpresentsTIMO,aMIMOdesignthatenables802.11n to communicate in the presence of high-power cross-technology interference. Unlike existing MIMO designs, however, which require all concurrent transmissions to belong to the same technology, TIMO can exploit MIMO capabilities to decode in the presenceofasignalfromadifferenttechnology,henceenablingdiverse technologies to share the same frequency band. We implement a prototype of TIMO inGNURadio-USRP2and show that itenables 802.11n to communicate inthe presence of interference from baby monitors,cordlessphones,andmicrowaveovens,transformingscenarioswithacompletelossofconnectivitytooperationalnetworks.
AutoMAC: Rateless Wireless Concurrent Medium Access
"... Current wireless network design is built on the ethos of avoiding interference. In this paper we question this long-held design principle. We show that with appropriate design, successful concurrent transmissions can be enabled and exploited on both the uplink and downlink. We show that this counter ..."
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Cited by 11 (0 self)
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Current wireless network design is built on the ethos of avoiding interference. In this paper we question this long-held design principle. We show that with appropriate design, successful concurrent transmissions can be enabled and exploited on both the uplink and downlink. We show that this counterintuitive approach of encouraging interference can be exploited to increase network capacity significantly and simplify network design. We design and implement AutoMAC, a novel MAC and PHY protocol that exploits recently proposed rateless coding techniques to provide such concurrency. We show via a prototype implementation and experimental evaluation that AutoMAC can provide a 60 % increase in network capacity on the uplink compared to traditional Wifi that does omniscient rate adaptation and a 35 % median throughput gain on the downlink PHY layer as compared to an omniscient scheme that picks the best conventional bitrate.
Optimal frequency-reuse partitioning for ubiquitous coverage in cellular systems
- In 15th European Signal Processing Conference (EUSIPCO
, 2008
"... Frequency-reuse partitioning corresponds to allocating fre-quencies in a cellular system using multiple frequency-reuse factors simultaneously in each cell. Compared to single reuse-factor schemes, reuse partitioning allows an improved performance in terms of system capacity, outage probabil-ity or ..."
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Cited by 6 (1 self)
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Frequency-reuse partitioning corresponds to allocating fre-quencies in a cellular system using multiple frequency-reuse factors simultaneously in each cell. Compared to single reuse-factor schemes, reuse partitioning allows an improved performance in terms of system capacity, outage probabil-ity or QoS fairness. In this paper we derive the optimal frequency-reuse partitioning that maximizes the capacity on the downlink of a cellular system. The main issue is to en-sure a ubiquitous service in terms of user data rate assuming a total power constraint and a uniform user distribution. 1.
Improving Quality-of-Service in Wireless Sensor Networks by Mitigating “Hidden-Node Collisions”
, 2009
"... Wireless Sensor Networks (WSNs) emerge as underlying infrastructures for new classes of large-scale networked embedded systems. However, WSNs system designers must fulfill the Quality-of-Service (QoS) requirements imposed by the applications (and users). Very harsh and dynamic physical environments ..."
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Cited by 5 (0 self)
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Wireless Sensor Networks (WSNs) emerge as underlying infrastructures for new classes of large-scale networked embedded systems. However, WSNs system designers must fulfill the Quality-of-Service (QoS) requirements imposed by the applications (and users). Very harsh and dynamic physical environments and extremely limited energy/computing/memory/communication node resources are major obstacles for satisfying QoS metrics such as reliability, timeliness and system lifetime. The limited communication range of WSN nodes, link asymmetry and the characteristics of the physical environment lead to a major source of QoS degradation in WSNs – the “hidden node problem”. In wireless contention-based Medium Access Control (MAC) protocols, when two nodes that are not visible to each other transmit to a third node that is visible to the formers, there will be a collision – called hidden-node or blind collision. This problem greatly impacts network throughput, energy-efficiency and message transfer delays, and the problem dramatically increases with the number of nodes. This paper proposes H-NAMe, a very simple yet extremely efficient Hidden-Node Avoidance Mechanism for WSNs. H-NAMe relies on a grouping strategy that splits each cluster of a WSN into disjoint groups of non-hidden nodes that scales to multiple clusters via a cluster grouping strategy that guarantees no interference between overlapping clusters. Importantly, H-NAMe is instantiated in IEEE 802.15.4/ZigBee, which currently are the most widespread communication technologies for WSNs, with only minor
A Multi-Tier Network Architecture for Long Distance Rural WirelessNetworks in Developing Regions
, 2009
"... personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires pri ..."
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Cited by 2 (0 self)
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personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific
Exploiting Network Coding in Lossy Wireless Networks
, 2009
"... Users increasingly depend on Wireless LANs (WLANs) for business and entertainment. It is well-known that wireless links are error-prone and require retransmissions to recover from errors and packet losses. Previous work proposed to use network coding (NC) for more efficient MAC-layer retransmissions ..."
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Cited by 2 (0 self)
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Users increasingly depend on Wireless LANs (WLANs) for business and entertainment. It is well-known that wireless links are error-prone and require retransmissions to recover from errors and packet losses. Previous work proposed to use network coding (NC) for more efficient MAC-layer retransmissions in WLANs. However, their design is independent from underlying physical layer and MAC capabilities and algorithms. These independent design may result in inefficient utilization of network coding gain, or even impair system performance. This dissertation presents a practical network coding-aided MAC layer retransmission scheme, namely XOR Rescue (XORR). Unlike previous independent network coding design, XORR provides a global approach by integrating the utilization of network coding, adaptation to time-varying wireless channel, fairness, and multi-rate transmission in wireless networks. The main characteristic of XORR is opportunism: each node relies on local information to detect the best transmission/retransmission and exploits the benefits provided by both network coding and multiuser diversity whenever they arise. The
