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Handoff optimization in 802.11 wireless networks  [cached]
Hsieh IP,Kao Shang-Juh
EURASIP Journal on Wireless Communications and Networking , 2011,
Abstract: In 802.11 wireless networks, a complete handoff procedure for a mobile node requires access point (AP) selection, AP switch, call admission control (CAC), IP address re-allocation, and network re-configuration. Most current handoff schemes deal only with either AP selection or IP address re-allocation. In this paper, an integrated handoff procedure is proposed. First, AP selection is accomplished by choosing an AP with the lowest channel utilization and smaller number of associated users. The information about load of each AP is reported through modified beacon frames. In the case of adopting load-based AP selection, the average throughput can be increased up to 56%, as opposed to pure SNR-based AP selection. Next, both CAC and IP address pre-fetch are performed simultaneously through the simplified DHCP procedure. Specifically, efficient limited fractional guard channel policy (ELFGCP) is proposed for the CAC phase. By adopting ELFGCP, the failure probability can be reduced as much as 45% from conventional LFGCP. Finally, the simulation results demonstrate the applicability of the integrated approach, and the overall disconnection time due to handoff can be reduced from 2.9 to 0.004 s using traditional handoff procedures.
Handoff Between a Wireless Local Area Network (WLAN) and a Wide Area Network (UMTS)
Sánchez-García, J;Villase?or-González, Luis A;Vaquera-Flores, Mario E;Aquino-Santos, Raúl;
Ingeniería, investigación y tecnología , 2009,
Abstract: with the appearance of wireless data networks with variable coverage, band width and handoff strategies, in addition to the growing need of mobile nodes to freely roam among these networks, the support of an interoperable handoff strategy for hybrid wireless data networks is a requirement that needs to be addressed. the current trend in wireless data networks is to offer multimedia access to mobile users by employing the wireless local area network (wlan) standard ieee802.11 while the user is located indoors; on the other hand, 3rd generation wireless networks (wan) are being deployed to provide coverage while the user is located outdoors. as a result, the mobile node will require a handoff mechanism to allow the user to roam between wlan and wan environments; up to this date several strategies have been proposed (sattari et al., 2004 and hyojin, 2007) in the literature, however, none of these have been standardized to date. to support this interoperability, the mobile node must be equipped with configurable wireless inetrfaces to support the handoff between the wlan and the wan networks. in this work a new algorithm is proposed to allow a mobile node to roam between a wireless local area network (ieee802.11) and a wan base station (umts), while employing ip mobility support. the algorithm is implemented in simulation, using the network simulator 2.
Handoff Between a Wireless Local Area Network (WLAN) and a Wide Area Network (UMTS)  [PDF]
J. Sánchez–García,Luis A. Villase?or–González,Mario E. Vaquera–Flores,Raúl Aquino–Santos
Ingeniería, investigación y tecnología , 2009,
Abstract: With the appearance of wireless data networks with variable coverage, band width and handoff strategies, in addition to the growing need of mobile nodes to freely roam among these networks, the support of an interoperable handoff strategy for hybrid wireless data networks is a requirement that needs to be addressed. The current trend in wireless data networks is to offer multimedia access to mobile users by employing the wireless local area network (WLAN) standard IEEE802.11 while the user is located indoors; on the other hand, 3rd generation wireless networks (WAN) are being deployed to provide coverage while the user is located outdoors. As a result, the mobile node will require a handoff mechanism to allow the user to roam between WLAN and WAN environments; up to this date several strategies have been proposed (Sattari et al., 2004 and HyoJin, 2007) in the literature, however, none of these have been standardized to date. To support this interoperability, the mobile node must be equipped with configurable wireless inetrfaces to support the handoff between the WLAN and the WAN networks. In this work a new algorithm is proposed to allow a mobile node to roam between a wireless local area network (IEEE802.11) and a WAN base station (UMTS), while employing IP mobility support. The algorithm is implemented in simulation, using the Network Simulator 2.
NACS: non-overlapping AP's caching scheme to reduce handoff in 802.11 wireless LAN  [PDF]
Usman Tariq,Yasir Malik,Man-Pyo Hong
Computer Science , 2011, DOI: 10.1109/ICON.2005.1635434
Abstract: With the escalation of the IEEE 802.11 based wireless networks, voice over IP and analogous applications are also used over wireless networks. Recently, the wireless LAN systems are spaciously deployed for public Internet services. In public wireless LAN systems, reliable user authentication and mobility support are indispensable issues. When a mobile device budges out the range of one access point (AP) and endeavor to connect to new AP, it performs handoff. Contemporarily, PNC and SNC were proposed to propagate the MN context to the entire neighboring AP's on the wireless network with the help of neighbor graph. In this paper, we proposed a non-overlapping AP's caching scheme (NACS), which propagates the mobile node context to those AP's which do not overlap with the current AP. To capture the topology of non-overlapping AP's in the wireless network, non-overlapping graph (NOG) is generated at each AP. Simulation results shows that NACS reduces the signaling cost of propagating the MN context to the neighbor AP's in the wireless network.
Minimization of Call Blocking Probability by Using an Adaptive Heterogeneous Channel Allocation Scheme for Next Generation Wireless Handoff Systems
Debabrata Sarddar,Arnab Raha,Shubhajeet Chatterjee,Ramesh Jana
International Journal of Computer Science Issues , 2011,
Abstract: Nowadays IEEE 802.11 based wireless local area networks (WLAN) have been widely deployed for business and personal applications. The main issue regarding wireless network technology is handoff or hand over management. The minimization of handoff failure due to call blocking is an important issue of research. For the last few years plenty of researches had been done to reduce the handoff failure. Here we also propose a method to minimize the handoff failure by using an adaptive heterogeneous channel allocation scheme.
An 802.11k Compliant Framework for Cooperative Handoff in Wireless Networks  [cached]
George Athanasiou,Thanasis Korakis,Leandros Tassiulas
EURASIP Journal on Wireless Communications and Networking , 2009, DOI: 10.1155/2009/350643
Abstract: In IEEE 802.11-based wireless networks, the stations (STAs) are associated with the available access points (APs) and communicate through them. In traditional handoff schemes, the STAs get information about the active APs in their neighborhood by scanning the available channels and listening to transmitted beacons. This paper proposes an 802.11k compliant framework for cooperative handoff where the STAs are informed about the active APs by exchanging information with neighboring STAs. Besides, the APs share useful information that can be used by the STAs in a handoff process. In this way, we minimize the delay of the scanning procedure. We evaluate the performance of our mechanisms through OPNET simulations. We demonstrate that our scheme reduces the scanning delay up to 92%. Consequently, our system is more capable in meeting the needs of QoS-sensitive applications.
An 802.11k Compliant Framework for Cooperative Handoff in Wireless Networks  [cached]
Athanasiou George,Korakis Thanasis,Tassiulas Leandros
EURASIP Journal on Wireless Communications and Networking , 2009,
Abstract: In IEEE 802.11-based wireless networks, the stations (STAs) are associated with the available access points (APs) and communicate through them. In traditional handoff schemes, the STAs get information about the active APs in their neighborhood by scanning the available channels and listening to transmitted beacons. This paper proposes an 802.11k compliant framework for cooperative handoff where the STAs are informed about the active APs by exchanging information with neighboring STAs. Besides, the APs share useful information that can be used by the STAs in a handoff process. In this way, we minimize the delay of the scanning procedure. We evaluate the performance of our mechanisms through OPNET simulations. We demonstrate that our scheme reduces the scanning delay up to 92%. Consequently, our system is more capable in meeting the needs of QoS-sensitive applications.
Fast Dual-Radio Cross-Layer Handoffs in Multi-Hop Infrastructure-mode 802.11 Wireless Networks for In-Vehicle Multimedia Infotainment  [PDF]
Jayaraj Poroor,Sriram Karunagaran,Sudharsan Sundararajan,Ranjith Pillai
Computer Science , 2009,
Abstract: Minimizing handoff latency and achieving near-zero packet loss is critical for delivering multimedia infotainment applications to fast-moving vehicles that are likely to encounter frequent handoffs. In this paper, we propose a dual-radio cross-layer handoff scheme for infrastructure-mode 802.11 Wireless Networks that achieve this goal. We present performance results of an implementation of our algorithm in a Linux-based On-Board-Unit prototype.
An Adaptive Multimedia-Oriented Handoff Scheme for IEEE 802.11 WLANs  [PDF]
Ahmed Riadh Rebai,Sa?d Hanafi
Computer Science , 2011, DOI: 10.5121/ijwmn.2011.3114
Abstract: Previous studies have shown that the actual handoff schemes employed in the IEEE 802.11 Wireless LANs (WLANs) do not meet the strict delay constraints placed by many multimedia applications like Voice over IP. Both the active and the passive supported scan modes in the standard handoff procedure have important delay that affects the Quality of Service (QoS) required by the real-time communications over 802.11 networks. In addition, the problem is further compounded by the fact that limited coverage areas of Access Points (APs) occupied in 802.11 infrastructure WLANs create frequent handoffs. We propose a new optimized and fast handoff scheme that decrease both handoff latency and occurrence by performing a seamless prevent scan process and an effective next-AP selection. Through simulations and performance evaluation, we show the effectiveness of the new adaptive handoff that reduces the process latency and adds new context-based parameters. The Results illustrate a QoS delay-respect required by applications and an optimized AP-choice that eliminates handoff events that are not beneficial.
Achievable Throughput-Based MAC Layer Handoff in IEEE 802.11 Wireless Local Area Networks  [cached]
Seo SungHoon,Song JooSeok,Wu Haitao,Zhang Yongguang
EURASIP Journal on Wireless Communications and Networking , 2009,
Abstract: We propose a MAC layer handoff mechanism for IEEE 802.11 Wireless Local Area Networks (WLAN) to give benefit to bandwidth-greedy applications at STAs. The proposed mechanism determines an optimal AP with the maximum achievable throughput rather than the best signal condition by estimating the AP's bandwidth with a new on-the-fly measurement method, Transient Frame Capture (TFC), and predicting the actual throughput could be achieved at STAs. Since the TFC is employed based on the promiscuous mode of WLAN NIC, STAs can avoid the service degradation through the current associated AP. In addition, the proposed mechanism is a client-only solution which does not require any modification of network protocol on APs. To evaluate the performance of the proposed mechanism, we develop an analytic model to estimate reliable and accurate bandwidth of the AP and demonstrate through testbed measurement with various experimental study methods. We also validate the fairness of the proposed mechanism through simulation studies.
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