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Improving fast and smooth handoff in ieee 802.11 wireless networks

TL;DR: The Fast Scan scheme is proposed which reduces the scanning delay by using a client-based database and the net handoff delay is reduced for IEEE 802.11b networks.
Abstract: IEEE 802.11 Wireless LANs are increasingly being used in real environments for broad-band access. Such large scale IEEE 802.11 WLAN implies the need for client station support from one Access Point to another. The client stations (STA) can move freely, but because of the short range of their Access Points (APs), they usually need to reassociate with different APs and communicate through them. When changing APs, a client station starts a process known as a handoff that can take up to few seconds, which is too long for real-time applications such as Voice over IP (VoIP).Various solutions have been proposed to change or improve the client behavior when doing a handoff. The delay incurred in scanning for APs across channels contributes to 90% of the total handoff delay. In this paper, the Fast Scan scheme is proposed which reduces the scanning delay by using a client-based database. The net handoff delay is reduced for IEEE 802.11b networks. The proposed schemes do not need any changes in the infrastructure (access points) and require only a single radio and a small cache memory at the client side.
Citations
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Patent
16 Dec 2014
TL;DR: In this article, a dual network access point capable of establishing a home wireless network and a further secondary wireless network for a number of wireless devices is proposed, where the access point monitors the devices connected to the first network and adjusts the advertised minimum supportable rate on the second network.
Abstract: A dual network access point capable of establishing a home wireless network and a further secondary wireless network for a number of wireless devices. The first wireless network is a private home WLAN while the second wireless network is a guest network or a hotspot network. To prevent secondary network users impacting the performance of the first network, the access point monitors the devices connected to the first network and adjusts the advertised minimum supportable rate on the second network.

5 citations

References
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Proceedings ArticleDOI
20 Jun 2004
TL;DR: Analysis of the link-layer handoff process in wireless LANs based on the IEEE 802.11b standard and suggests how to reduce its duration indicates that the detection and search phases are the main contributors to the handoff time.
Abstract: We analyze the link-layer handoff process in wireless LANs based on the IEEE 802.11b standard and suggests how to reduce its duration. Firstly, we divide the process into three phases: detection, search and execution. Our performance measurements indicate that the detection and search phases are the main contributors to the handoff time. We show that the link-layer detection time can be reduced to three consecutive lost frames. We also show that the search time can be reduced at least by 20% using active scanning with the two timers that control its duration set to 1 ms and 10.24 ms. Several simulations illustrate the achieved reduction in handoff time.

273 citations


"Improving fast and smooth handoff i..." refers background in this paper

  • ...In infrastructure mode - the most common form of deployments - if a mobile station (STA) wishes to send or receive data [7], it needs to associate with an Access Point (AP)....

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  • ...Related Work Apart from solutions several layer-2 handoff mechanisms for WLAN have been proposed in recent papers [1], [2], [3], [4], [7]....

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  • ...In Sync Scan [7], clients passively scan the channel by switching its current working channels....

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Proceedings ArticleDOI
19 Apr 2009
TL;DR: This paper studies the handoff process in large AP-dense 802.11 networks, which is one of the most common forms of WiFi under usage, and develops a solution to significantly improve the essential process of AP scan, a bottleneck towards fast and smooth handoffs.
Abstract: wireless networks have gained ever greater popularity nowadays. Apart from static wireless connections, people begin to expect more user-friendly features from this kind of networks, such as support for seamless roaming. In this paper, we study the handoff process in large AP-dense 802.11 networks, which is one of the most common forms of WiFi under usage. A series of field experiments are carried out and some critical handoff parameters are evaluated. With some newly discovered features, i.e. differentiated probe response time and rich AP information hidden in wireless traffic, we have managed to sig- nificantly improve the essential process of AP scan, a bottleneck towards fast and smooth handoffs. The solution is collectively called D-Scan (Scan in AP-Dense 802.11 networks). Real experi- ments are conducted to show the superiority of our solution.

58 citations

Proceedings ArticleDOI
15 May 2011
TL;DR: This work has developed a solution called Multichannel Virtual Access Points (mVAP), which is a new efficient technique for seamless handoffs without performance degradation to take advantage of APs operating on multiple channels.
Abstract: Within IEEE 802.11 Wireless Local Area Networks (WLANs), client stations can move freely, but because of the short range of their Access Points (APs), they usually need to reassociate with different APs to continue to communicate. When changing APs, a client station starts a process known as a handoff that can take up to 2 seconds, which is too long for real-time applications such as Voice over IP (VoIP). Various solutions have been proposed to change or improve the client behaviour when doing a handoff. Previously, we proposed the idea of Virtual Access Points (VAP) implemented on APs in which a client station changes APs without disrupting its current communication. Based on this new concept, we have developed a solution called Multichannel Virtual Access Points (mVAP) to take advantage of APs operating on multiple channels. We have implemented mVAP using PACMAP, a tool for packet manipulation, and evaluated its performance. Our results show that mVAP is a new efficient technique for seamless handoffs without performance degradation.

42 citations


"Improving fast and smooth handoff i..." refers background or methods in this paper

  • ...Related Work Apart from solutions several layer-2 handoff mechanisms for WLAN have been proposed in recent papers [1], [2], [3], [4], [7]....

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  • ...Messages are sent over reliable TCP connections between APs[1]....

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  • ...In [1], the authors propose an algorithm in which an AP informs the client about its neighbour list and the client scans only those channels which are in that list....

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  • ...11 WLAN that is to reduce the time required by handoff procedure using tool PACMAP [1]: PACket MAniPulation framework....

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  • ...Protocol details In this section [1], we describe the Multichannel Virtual Access Point protocol in detail....

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Proceedings ArticleDOI
14 Mar 2010
TL;DR: A unique fast handoff scheme called HaND (Handoff with Null Dwell time), which adopts a novel zero-channel-dwell-time architecture which leverages on the communication backbone between APs to relay the information about wireless channels, and allows the AP to make appropriate handoff decisions aiming at providing fair service satisfaction to all stations.
Abstract: How to reduce the handoff delay and how to make appropriate handoff decisions are two fundamental challenges in designing an effective handoff scheme for 802.11 networks to provide seamless and satisfactory data roaming services to mobile users. In this paper, we propose a unique fast handoff scheme called HaND (Handoff with Null Dwell time). HaND adopts a novel zero-channel-dwell-time architecture which leverages on the communication backbone between APs to relay the information about wireless channels, and allows the AP (rather than the station) to make appropriate handoff decisions aiming at providing fair service satisfaction to all stations. HaND is a software-only solution and compatible with the 802.11 standard without modifying the 802.11 protocol or introducing new wireless frames. We have implemented it in the Madwifi device driver and demonstrated its effectiveness via experiments.

38 citations

Proceedings ArticleDOI
18 Apr 2010
TL;DR: In this scheme, stations are not aware that they move, and all the complexity is pushed back inside the network, making it possible to control mobility from a global point of vue, to optimize network resources for mobile stations, hence providing a better quality of service.
Abstract: Mobility management in WiFi networks is still an open issue today: there is no standard method defined, and client station mobility is handled either via proprietary protocols, or simply by re- association. However, managing mobility in an infrastructure network is utterly important for several reasons: controlling delay and jitter in communications, managing clients from the network, optimizing performance. We propose the concept of virtual access points to manage mobile station in infrastructure networks. In this scheme, stations are not aware that they move, and all the complexity is pushed back inside the network. It is then possible to control mobility from a global point of vue, to optimize network resources for mobile stations, hence providing a better quality of service. Finally, this scheme is compatible with existing clients without any hardware nor software modification.

34 citations


"Improving fast and smooth handoff i..." refers background in this paper

  • ...In [2], a client measures the signal strength of received beacon of all the APs operating on the current, and the overlapping channels....

    [...]

  • ...Related Work Apart from solutions several layer-2 handoff mechanisms for WLAN have been proposed in recent papers [1], [2], [3], [4], [7]....

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  • ...In this context, we propose to get rid of mobility management in mobile stations and put it entirely inside the network of interconnected access points [2]....

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