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In IEEE 802.11 DCF, performance unfairness inevitably occurs between downlink (AP-to-station) and uplink (station-to-AP) directions. The asymmetry of the DCF operation degrades downlink traffic severely. Therefore, it is important to enhance downlink QoS by alleviating link congestion. In this paper, we propose a novel medium access control scheme, BDCF (Burst DCF), to enhance the legacy DCF. It is...
Cognitive radio and femtocells are recent technology breakthroughs that aim at achieving throughput improvement by means of spectrum management and interference mitigation, respectively. However, these technologies are limited by the former's susceptibility to interference and the latter's dependence on bandwidth availability. In this paper, we overcome these limitations by integrating cognitive radio...
We propose a novel congestion-aware routing protocol, which leverages local and remote congestion information for routing decisions. Path congestion is difficult to measure, therefore congestion aware protocols consider only local status. This protocol uses an innovative representation of congestion for router-router links. These congestion statistics are then distributed via an aggregation protocol...
Congestion in Wireless Sensor Networks (WSN) can be a severe problem, as it causes a plethora of malfunctions such as packet loss, lower throughput, energy inefficiency, and short lifetime. As a result, the performance of the whole network is subject to undesirable change; an issue that renders congestion control an issue of uttermost importance for such networks. As far as data-collection applications...
As ZigBee networks operate on the license-free 2.4 GHz Industrial, Scientific, and Medical (ISM) frequency band, coexistence issues arise because many other wireless technologies such as IEEE 802.11b/g Wireless Local Area Networks (WLANs), Bluetooth, cordless telephones, etc., also use the same frequency band. To mitigate interference, ZigBee specification proposes a feature called frequency agility,...
In this paper a new DT-based adaptive BLUE is proposed to overcome the shortcoming of BLUE. The buffer is managed by dynamic threshold algorithm. The packet-dropping probability is determined by packet loss event, link idle event and the buffer usage ratio. The simulation results prove that the proposed approach can effectively stabilize the queue occupation at a level and improve link utilization...
This paper proposes a new TCP congestion control supporting loss-fairness, which also contributes to improving RTT fairness. It has been well known that smaller RTT flows grab more bandwidth than larger ones when they compete on the shared link. This is called RTT unfairness and is caused by congestion control mechanism of the current TCP. To solve this problem, many protocols have been proposed....
In this paper we study a WDM network architecture of passive star topology that uses a Multi-channel Control Architecture (MCA) to reduce the electronic processing bottleneck. The control information is effectively exploited in conjunction with the propagation delay latency to introduce a synchronous transmission WDMA protocol that avoids both the data channels collisions and the destination conflicts...
TCP-Illinois aims to address TCP's low throughput when operating in high-speed, high-delay networks. Previous research has shown that, due to its linear increase behaviour and to its relatively long congestion epochs, TCP-Illinois exhibits suboptimal scaling behaviour with an increasing path Bandwidth- Delay Product (BDP). This paper discloses our contributions towards improving the aggressiveness...
In order to improve transmission throughput of a multi-hop wireless network, many efforts have been made in recent years to reduce traffic and hence transmission collisions by constructing backbone networks with minimum size. However, many other important issues need to be considered. Instead of simply minimizing the number of backbone nodes or supporting some isolated network features, in this work,...
Data center switches need to satisfy stringent low-delay and high-capacity requirements. To do so, they rely on small switch buffers. However, in case of congestion, data center switches can incur throughput collapse for short TCP flows as well as temporary starvation for long TCP flows. In this paper, we introduce a lightweight hash-based algorithm called HCF (Hashed Credits Fair) to solve these...
This paper defines a theoretical framework based on Markov Decision Processes (MDP) to deal with call control algorithms in links with variable capacity supporting multiple classes of service. The variable capacity problem, which arises in wireless network scenarios, is addressed by incorporating the link model into the MDP formulation and by introducing, beside the standard call admission policy,...
RFID promises to revolutionize the inventory management in large warehouses, retail stores, hospitals, transportation systems, etc. Periodically reading the IDs of the tags is an important function to guard against administration error, vendor fraud and employee theft. Given the low-speed communication channel in which a RFID system operates, the reading throughput is one of the most important performance...
Protocol sequences are used in channel access for the multiple-access collision channel without feedback. A new construction of protocol sequences with a guarantee of worst-case system throughput is proposed. The construction is based on Chinese remainder theorem. The Hamming cross-correlation is proved to be concentrated around the mean. The sequence period is much shorter than existing protocol...
Current Internet protocols like TCP have been designed to work well on channels with low channel error rates. Wireless channels on the other hand exhibit high loss rates when compared to wired channels. Current TCP implementations usually attribute packet losses caused by channel errors as being actually caused by congestion. The result is an unnecessary reduction of the sending rate which leads to...
The fact that the on-chip network will suddenly get saturated indicates that it is necessary to devise an effective flow control strategy. Through tracing the status of the network buffer space we found that the payload of the on-chip network can not get beyond an upper bound to avoid vicious congestion. Specifically, quarter of the total network buffer space is such a threshold, which is termed Quarter...
The purpose of this study is to guarantee Quality of Service (QoS) in wireless multi-hop networks by introducing an admission control scheme. In wireless single-hop networks, IEEE 802.11e Enhanced Distributed Channel Access (EDCA) is the standard for QoS control. However, to control QoS, it is necessary to modify the currently used IEEE 802.11 Distributed Coordination Function (DCF)-compliant terminals...
The purpose of this paper is to analyze the maximum throughput when using RTS/CTS (Request To Send/Clear To Send) in IEEE 802.11 Distributed Coordination Function (DCF) multi-hop networks with a novel approach. Wireless multi-hop networks, in which nodes communicate with each other and convey packets via intermediate nodes without centralized control, have gained increasing attention because of the...
In wireless multihop networks, techniques such as multipath, local retransmissions and network coding have been successfully used to increase throughput and reduce losses. However, while these techniques improve forwarding performance for UDP, they often introduce side effects such as packet reordering and delay that heavily affect TCP traffic. In this paper we introduce CoMP, a network coding multipath...
In recent years the research on Vehicular Ad Hoc Network (VANET) has been paid much attention due to the development of wireless network becoming mature, people think highly of traffic safety issue, the popularity of Global Positioning System (GPS), promising applications of VANET being exploited. However, VANET has the essential property of rapid change of large scale network topology. Besides, the...
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