Association stability and handoff latency tradeoff in dense IEEE 802.11 networks: A case study
TL;DR: It is argued that the findings presented in this study can help develop more stable handoff algorithms for dense wireless networks, by analyzing the implementation used by the most common devices and conducting comparative tests in a real network.
About: This article is published in Computer Communications.The article was published on 2020-06-01. It has received 6 citations till now. The article focuses on the topics: Wireless network & IEEE 802.11.
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Journal Article•
TL;DR: The advances in photonic device technologies are bringing ultra-high-bit-rate networking-at speeds towards 100 Gb/s and beyond-much closer to practical reality, making it possible now to envisage the use of OTDM techniques not just in the highest layers of national and international networks, but also much closer to the user.
Abstract: The advances in photonic device technologies are bringing ultra-high-bit-rate networking-at speeds towards 100 Gb/s and beyond-much closer to practical reality. It is increasingly likely that in the longer term ultrafast optical time-division techniques-together with wavelength multiplexing-will be used in networks at all levels, from the transcontinental backbone to the desktop. Examples of devices include a subpicosecond clock source packaged inside a laptop personal computer and an OTDM switch on a single semiconductor chip, both produced at HHI. Advances similar to these make it possible now to envisage the use of OTDM techniques, not just in the highest layers of national and international networks, but also much closer to the user-such as the world-first demonstrations at BT Laboratories of a 40 Gb/s TDMA LAN and a 100 Gb/s packet self-routing switch for multiprocessor interconnection. Ultrafast networks might even provide the interconnection backplane inside future desktop routers and servers with massive throughput.
168 citations
13 Oct 2020
TL;DR: This work proposes CSIscan, a deep learning framework that exploits the broadcast nature of WiFi channels by embedding discovery related information within an AP’s ongoing regular transmissions and shows that CSIscan delivers up to 40 discovery information bits in the outgoing WiFi packet in an indoor environment.
Abstract: Network densification through the deployment of WiFi access points (APs) is a promising solution towards achieving high connectivity rates required for emerging applications. A critical first step is to discover an AP before an active association between the client and the AP can be established. Legacy AP discovery procedures initiated by the client result in high latency in the order of a few 100 ms and waste spectrum, especially when clients need to frequently switch between multiple APs. We propose CSIscan that exploits the broadcast nature of WiFi channels by embedding discovery related information within an AP’s ongoing regular transmissions. The AP does this by intelligently distorting the transmitted OFDM frame by inducing perturbations in the preamble, and these injected ‘bits’ of information are detected via changes in the perceived channel state information (CSI). A deep learning framework allocates the optimal level of distortion on a per-subcarrier basis that keeps the resulting packet error rate to less than 1%. Existing clients perceive no changes in their ongoing communication, while potential new clients quickly obtain discovery information at the same time. We experimentally demonstrate that CSIscan reduces the overall WiFi latency from 150 ms to 10 ms and improves spectrum utilization with ~72% reduction in the probe traffic. We show that CSIscan delivers up to 40 discovery information bits in the outgoing WiFi packet in an indoor environment.
4 citations
Cites background from "Association stability and handoff l..."
...As reported in [4]–[6], excessive attempts to discover APs not only lead to severe energy wastage in client devices but also reduce the overall WiFi throughput....
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TL;DR: In this paper, the authors proposed a new and simple filtering mechanism called Maximum which targets to eliminate these valleys in the RSSI time series, which can avoid the occurrence of ping-pong effect.
1 citations
TL;DR: A novel joint optimization of handoff, BS association, and total transmit power is presented that maximizes the system‐wide and handoff utilities and minimizes power consumption simultaneously.
Abstract: This article investigates the handoff optimization in an uplink non‐orthogonal multiple access‐based small cell network (SCN) with successive interference cancellation that takes both the base station (BS) association and power control into consideration. Due to user mobility and varying communication environment, it is important to associate a user with the proper BS and control its transmit power by considering the user mobility for the SCNs. To overcome overly frequent re‐association and handoffs between BSs, a novel joint optimization of handoff, BS association, and total transmit power is presented that maximizes the system‐wide and handoff utilities and minimizes power consumption simultaneously. We define the handoff utility function by considering the BS association in each time frame with the previous time frame. Then, we formulate two inter‐related optimization problems under the minimum average‐rate and maximum allowable transmit power of mobile users (MUs) constraints. The designed optimization problems are combined through the weighted sum method into a single‐stage optimization problem. The transformed problem is solved by adopting the coalition formation game and primal decomposition theories. We design the coalition value function by collectively considering the handoff number of each BS in every time frame, transmit power of all MUs, and the number of associated MUs to every BS. The simulation results show the efficiency of the proposed handoff algorithm in comparison to another BS association algorithm in terms of the number of handoffs.
1 citations
TL;DR: In this article , the authors proposed a new and simple filtering mechanism called Maximum which targets to eliminate these valleys in the RSSI time series, which can avoid the occurrence of ping-pong effect.
1 citations
References
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01 Apr 2003
TL;DR: This paper presents an empirical study of this handoff process at the link layer, with a detailed breakup of the latency into various components, showing that a MAC layer function - probe is the primary contributor to the overall handoff latency.
Abstract: IEEE 802.11 based wireless networks have seen rapid growth and deployment in the recent years. Critical to the 802.11 MAC operation, is the handoff function which occurs when a mobile node moves its association from one access point to another. In this paper, we present an empirical study of this handoff process at the link layer, with a detailed breakup of the latency into various components. In particular, we show that a MAC layer function - probe is the primary contributor to the overall handoff latency. In our study, we observe that the latency is significant enough to affect the quality of service for many applications (or network connections). Further we find variations in the latency from one hand-off to another as well as with APs and STAs used from different vendors. Finally, we discuss optimizations on the probe phase which can potentially reduce the probe latency by as much as 98% (and a minimum of 12% in our experiments). Based on the study, we draw some guidelines for future handoff schemes.
954 citations
TL;DR: In this article, the authors address Rayleigh fading, primarily in the UHF band, that affects mobile systems such as cellular and personal communication systems (PCS) and itemizes the fundamental fading mani.
Abstract: The paper addresses Rayleigh fading, primarily in the UHF band, that affects mobile systems such as cellular and personal communication systems (PCS) The paper itemizes the fundamental fading mani
953 citations
13 Mar 2005
TL;DR: SyncScan is described, a low-cost technique for continuously tracking nearby base stations by synchronizing short listening periods at the client with periodic transmissions from each base station and it is demonstrated that it allows better handoff decisions and over an order of magnitude improvement in handoff delay.
Abstract: Wireless access networks scale by replicating base stations geographically and then allowing mobile clients to seamlessly "hand off" from one station to the next as they traverse the network. However, providing the illusion of continuous connectivity requires selecting the right moment to handoff and the right base station to transfer to. Unfortunately, 802.11-based networks only attempt a handoff when a client's service degrades to a point where connectivity is threatened. Worse, the overhead of scanning for nearby base stations is routinely over 250 ms - during which incoming packets are dropped - far longer than what can be tolerated by highly interactive applications such as voice telephony. In this paper we describe SyncScan, a low-cost technique for continuously tracking nearby base stations by synchronizing short listening periods at the client with periodic transmissions from each base station. We have implemented this SyncScan algorithm using commodity 802.11 hardware and we demonstrate that it allows better handoff decisions and over an order of magnitude improvement in handoff delay. Finally, our approach only requires trivial implementation changes, is incrementally deployable and is completely backward compatible with existing 802.11 standards.
556 citations
19 Oct 2005
TL;DR: A methodology for the estimation of potential upstream and downstream bandwidth between a client and an AP based on measurements of delay incurred by 802.11 Beacon frames from the AP is proposed.
Abstract: The performance experienced by wireless clients in IEEE 802.11 wireless networks heavily depends on the clients' ability to identify the Access Point (AP) that will offer the best service. The current AP affiliation mechanism implemented in most wireless clients is based on signal strength measurements received by the client from all the APs in its neighborhood. The client then affiliates with the AP from which it receives the strongest signal. It is well-known that such an algorithm can lead to sub-optimal performance, due to its ignorance of the load at different APs.In this work, we consider the problem of AP selection. We identify potential bandwidth as the metric based on which hosts should make affiliation decisions, and define it as the (MAC-layer) bandwidth that the client is likely to receive after affiliating with a particular AP. We further limit ourselves to the use of passive measurements that do not require an end-host to affiliate with the AP, thus allowing the end-host to simultaneously evaluate the potential bandwidth to multiple APs in range. This can also facilitate more informed roaming decisions. We propose a methodology for the estimation of potential upstream and downstream bandwidth between a client and an AP based on measurements of delay incurred by 802.11 Beacon frames from the AP. Preliminary experiments conducted in a controlled environment demonstrate that the proposed methodology looks promising, yielding fairly accurate results under varying conditions.
205 citations
19 Oct 2005
TL;DR: The implementation of MultiScan is described, detailed evaluations of its effect on handoff latency are presented, and performance gains for MultiScan-enhanced wireless clients running Skype, a popular commercial VoIP application are evaluated.
Abstract: Deployment of Voice-over IP (VoIP) and other real-time streaming applications has been somewhat limited in wireless LANs today, partially because of the high handoff latencies experienced by mobile users. Our goal in this work is to eliminate handoff latency by exploiting the potential of multiple radios in WLAN devices. Our proposed approach, called MultiScan, is implemented entirely on the client-side, and, unlike prior work, MultiScan requires neither changing the Access Points (APs), nor having knowledge of wireless network topology. MultiScan nodes rely on using their (potentially idle) second wireless interface to opportunistically scan and pre-associate with alternate APs and eventually seamlessly handoff ongoing connections. In this paper we describe our implementation of MultiScan, present detailed evaluations of its effect on handoff latency and evaluate performance gains for MultiScan-enhanced wireless clients running Skype, a popular commercial VoIP application.
192 citations