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ABSTRACT: The de facto quality-of-service provisioning mechanism for wireless LANs is the Enhanced Distributed Channel Access (EDCA),
which provides enhanced service differentiation based on four different prioritized Access Categories (ACs). In this paper,
we show that the multiple category mechanism of EDCA causes a new type of unfairness problem among the ACs of same priority
class when the numbers of active ACs in competing nodes are different. We present a simple analytical model to capture the
impact of virtual collision, external collision, and Arbitration Interframe Space on the degree of this intra-class unfairness. Based on its analytical insight, we present a simple remedy scheme for resolving the unfairness and evaluate its efficiency
using ns-2 simulations.
KeywordsWLAN QoS–802.11 EDCA–Intra-class unfairness–Virtual collision
Wireless Personal Communications 04/2012; 63(2):431-445. · 0.46 Impact Factor
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Proceedings of the IFIP Wireless Days Conference 2011, Niagara Falls, ON, Canada, October 10-12, 2011; 01/2011
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Ad Hoc Networks. 01/2011; 9:1343-1358.
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Computer Networks. 01/2011; 55:3774-3783.
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2011 IEEE Wireless Communications and Networking Conference, WCNC 2011, Proceedings, Cancun, Mexico, 28-31 March, 2011; 01/2011
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ABSTRACT: In this paper, we propose a distributed load balancing using association control, especially for Tactical Information Communication Networks (TICNs). We develop a scheme for effectively balancing the load at the Base Stations (BSs), where a BS's load represents the amount of resources utilized by a BS, thus minimizing the blocking probability as well as the transmission failure probability. In order to make it more suitable to the military environment, we develop the proposed scheme in a completely distributed manner. Extensive simulations are performed and the proposed scheme is found to outperform the association schemes existing in the literature.
Vehicular Technology Conference (VTC 2010-Spring), 2010 IEEE 71st; 06/2010
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Proceedings of the 72nd IEEE Vehicular Technology Conference, VTC Fall 2010, 6-9 September 2010, Ottawa, Canada; 01/2010
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Proceedings of the 71st IEEE Vehicular Technology Conference, VTC Spring 2010, 16-19 May 2010, Taipei, Taiwan; 01/2010
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Proceedings of IEEE International Conference on Communications, ICC 2010, Cape Town, South Africa, 23-27 May 2010; 01/2010
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ABSTRACT: We propose a novel scanning scheme for IEEE 802.11 by equipping Access Points (APs) with multiple Wireless Network Interface Cards (Multi-WNICs), one of which is set to operate in an exclusively reserved channel for the scanning purpose. In this environment, a STAtion (STA) can easily search neighboring APs by scanning the reserved channel. Our simulation results demonstrate that the proposed scheme ultimately reduces the overall scanning time to improve the handoff latency.
IEEE Communications Letters 11/2009; · 0.98 Impact Factor
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ABSTRACT: One-way delay is an important metric to evaluate the performance of communication networks. In this paper, we analyze the one-way delay performance of the commercial WiBro networks based on the traffic measurement. In measurements, much large delay is observed in the uplink than downlink, and we find that such asymmetry due mainly to the impact of the uplink bandwidth request mechanism. Due to this large uplink delay, the performance of commercial IEEE 802.16e service can be severely degraded. We also discuss some possible solutions to ameliorate this problem.
Vehicular Technology Conference Fall (VTC 2009-Fall), 2009 IEEE 70th; 10/2009
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ABSTRACT: We provide a comparative analysis of various routing strategies that affect the end-to-end performance in wireless mesh networks. We first improve well-known link quality metrics and routing algorithms to better operate in wireless mesh environments. We then investigate the route optimality and its impact on the network performance by comparing the achieved end-to-end performance with the optimal offline routing. Various network topologies, number of concurrent flows, and interference types are considered in our evaluation and we reveal that a nonoptimal route is easily established because of routing protocol's misbehavior, interflow interference, and their interplay, thus affecting the end-to-end performance.
Personal, Indoor and Mobile Radio Communications, 2009 IEEE 20th International Symposium on; 10/2009
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ABSTRACT: We develop a new wireless link quality metric, ECOT (Estimated Channel Occupancy Time) that enables a high throughput route setup in wireless mesh networks. The key feature of ECOT is being applicable to diverse mesh network environments where IEEE 802.11 MAC (Medium Access Control) variants are used. We take into account the detailed operational features of various 802.11 MAC protocols, such as 802.11 DCF (Distributed Coordination Function), 802.11e EDCA (Enhanced Distributed Channel Access) with BACK (Block Acknowledgment), and 802.11n A-MPDU (Aggregate MAC Protocol Data Unit), and derive an integrated link metric that enables finding maximum throughput end-to-end routes. Through simulations in randomized topological environments, we evaluate the performance of the proposed link metric and routing strategy to demonstrate that our proposed schemes can achieve up to 354.4% throughput gain over existing ones.
Personal, Indoor and Mobile Radio Communications, 2009 IEEE 20th International Symposium on; 10/2009
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ABSTRACT: Femto BS (base station) is emerging as a key technology to secure the coverage and capacity in indoor environments. However, since the existing macrocell network is overlaid on femtocell networks utilizing the same set of frequency channels, femtocell networks can originate severe co-channel interference to the macrocell network unless the femtocell network is carefully configured. Therefore, according to a desired network-wide objective, we optimize the femtocell network with constraints such that the service connectivity with a femto BS is secured in the target indoor area while the signal emitted out of the building, playing as interference to the outdoor users, should be controlled with an appropriate strength in order not to interrupt the communication between macro BS and outdoor users. Each optimization problem is formulated as a mixed integer programming, and as the results, we obtain not only the transmit power and operational frequency channel of each femto BS, but also the optimal femto BS-to-user association pair at each geographical position.
Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks, 2009. WiOPT 2009. 7th International Symposium on; 07/2009
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ABSTRACT: Cognitive radios are typically known to exploit vacant spectrum resources yet not interfering with primary communication systems. However, cognitive radios may not be able to secure a clear spectrum band, i.e., white hole, in certain environments. Underlay spectrum sharing provides a way to cope with such a spectrum sharing problem in a bustling spectrum band; cognitive radios share the spectrum band with the spectrum licensees, i.e., primary users, by adjusting signal transmit power so as not to severely deteriorate the performance of the primary users. In this paper, we propose an underlay spectrum sharing policy for cognitive radios. Primary users are assumed to form a cellular network, and a point-to-point link of cognitive radio leverages uplink spectrum resource of the primary network. We formulate the transmit power constraints of the cognitive radio transmitter and propose a practical uplink band sharing framework. We also demonstrate that such an uplink band sharing can enhance the throughput performance of point- to-point link, while the interference to the primary users can be regulated under the allowed level decided by the primary users.
Cognitive Radio Oriented Wireless Networks and Communications, 2009. CROWNCOM '09. 4th International Conference on; 07/2009
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MONET. 01/2009; 14:470-485.
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Quality of Service in Heterogeneous Networks, 6th International ICST Conference on Heterogeneous Networking for Quality, Reliability, Security and Robustness, QShine 2009 and 3rd International Workshop on Advanced Architectures and Algorithms for Internet Delivery and Applications, AAA-IDEA 2009, Las Palmas, Gran Canaria, Spain, November 23-25, 2009, Proceedings; 01/2009
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Proceedings of the IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2009, 13-16 September 2009, Tokyo, Japan; 01/2009
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Future Generation Information Technology, First International Conference, FGIT 2009, Jeju Island, Korea, December 10-12, 2009. Proceedings; 01/2009
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IEEE Trans. Mob. Comput. 01/2009; 8:1596-1609.
