Vertical handoffs in wireless overlay networks
30 Dec 1998-Mobile Networks and Applications (Springer-Verlag New York, Inc.)-Vol. 3, Iss: 4, pp 335-350
TL;DR: This work has implemented a vertical handoff system that allows users to roam between cells in wireless overlay networks and presents enhancements to the basic scheme that significantly reduce the discovery time without assuming any knowledge about specific channel characteristics.
Abstract: No single wireless network technology simultaneously provides a low latency, high bandwidth, wide area data service to a large number of mobile users. Wireless Overlay Networks – a hierarchical structure of room-size, building-size, and wide area data networks – solve the problem of providing network connectivity to a large number of mobile users in an efficient and scalable way. The specific topology of cells and the wide variety of network technologies that comprise wireless overlay networks present new problems that have not been encountered in previous cellular handoff systems. We have implemented a vertical handoff system that allows users to roam between cells in wireless overlay networks. Our goal is to provide a user with the best possible connectivity for as long as possible with a minimum of disruption during handoff. Results of our initial implementation show that the handoff latency is bounded by the discovery time, the amount of time before the mobile host discovers that it has moved into or out of a new wireless overlay. This discovery time is measured in seconds: large enough to disrupt reliable transport protocols such as TCP and introduce significant disruptions in continuous multimedia transmission. To efficiently support applications that cannot tolerate these disruptions, we present enhancements to the basic scheme that significantly reduce the discovery time without assuming any knowledge about specific channel characteristics. For handoffs between room-size and building-size overlays, these enhancements lead to a best-case handoff latency of approximately 170 ms with a 1.5% overhead in terms of network resources. For handoffs between building-size and wide-area data networks, the best-case handoff latency is approximately 800 ms with a similarly low overhead.
Citations
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26 Sep 2004
TL;DR: A new metric for routing in multi-radio, multi-hop wireless networks with stationary nodes called Weighted Cumulative ETT (WCETT) significantly outperforms previously-proposed routing metrics by making judicious use of the second radio.
Abstract: We present a new metric for routing in multi-radio, multi-hop wireless networks. We focus on wireless networks with stationary nodes, such as community wireless networks.The goal of the metric is to choose a high-throughput path between a source and a destination. Our metric assigns weights to individual links based on the Expected Transmission Time (ETT) of a packet over the link. The ETT is a function of the loss rate and the bandwidth of the link. The individual link weights are combined into a path metric called Weighted Cumulative ETT (WCETT) that explicitly accounts for the interference among links that use the same channel. The WCETT metric is incorporated into a routing protocol that we call Multi-Radio Link-Quality Source Routing.We studied the performance of our metric by implementing it in a wireless testbed consisting of 23 nodes, each equipped with two 802.11 wireless cards. We find that in a multi-radio environment, our metric significantly outperforms previously-proposed routing metrics by making judicious use of the second radio.
2,633 citations
Cites background from "Vertical handoffs in wireless overl..."
...The BARWAN project [39] enabled seamless handoffs between heterogeneous networks for a mobile user....
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09 Jul 2003
TL;DR: In this paper, a simple, cheat-proof, credit-based system for stimulating cooperation among selfish nodes in mobile ad hoc networks is proposed, which does not require any tamper-proof hardware at any node.
Abstract: Mobile ad hoc networking has been an active research area for several years. How to stimulate cooperation among selfish mobile nodes, however, is not well addressed yet. In this paper, we propose Sprite, a simple, cheat-proof, credit-based system for stimulating cooperation among selfish nodes in mobile ad hoc networks. Our system provides incentive for mobile nodes to cooperate and report actions honestly. Compared with previous approaches, our system does not require any tamper-proof hardware at any node. Furthermore, we present a formal model of our system and prove its properties. Evaluations of a prototype implementation show that the overhead of our system is small. Simulations and analysis show that mobile nodes can cooperate and forward each other's messages, unless the resource of each node is extremely low.
1,330 citations
Cites background from "Vertical handoffs in wireless overl..."
...The nodes are equipped with network interfaces that allow them to send and receive messages through a wireless overlay network [25], e....
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Patent•
27 May 2005
TL;DR: In this article, a Mobility Management Server coupled to the mobile network maintains the state of any number of mobile end systems and handles the complex session management required to maintain persistent connections to the network and to other peer processes.
Abstract: A seamless solution transparently addresses the characteristics of nomadic systems, and enables existing network applications to run reliably in mobile environments. The solution extends the enterprise network, letting network managers provide mobile users with easy access to the same applications as stationary users without sacrificing reliability or centralized management. The solution combines advantages of existing wire-line network standards with emerging mobile standards to create a solution that works with existing network applications. A Mobility Management Server coupled to the mobile network maintains the state of each of any number of Mobile End Systems and handles the complex session management required to maintain persistent connections to the network and to other peer processes. If a Mobile End System becomes unreachable, suspends, or changes network address (e.g., due to roaming from one network interconnect to another), the Mobility Management Server maintains the connection to the associated peer task—allowing the Mobile End System to maintain a continuous connection even though it may temporarily lose contact with its network medium. In one example, Mobility Management Server communicates with Mobile End Systems using Remote Procedure Call and Internet Mobility Protocols.
1,040 citations
TL;DR: In this article, the current state of the art for mobility management in next-generation all-IP-based wireless systems is presented, and the previously proposed solutions based on different layers are reviewed, and their qualitative comparisons are given.
Abstract: Next-generation wireless systems are envisioned to have an IP-based infrastructure with the support of heterogeneous access technologies. One of the research challenges for next generation all-IP-based wireless systems is the design of intelligent mobility management techniques that take advantage of IP-based technologies to achieve global roaming among various access technologies. Next-generation wireless systems call for the integration and interoperation of mobility management techniques in heterogeneous networks. In this article the current state of the art for mobility management in next-generation all-IP-based wireless systems is presented. The previously proposed solutions based on different layers are reviewed, and their qualitative comparisons are given. A new wireless network architecture for mobility management is introduced, and related open research issues are discussed in detail.
672 citations
Dissertation•
09 Apr 2004
TL;DR: The current state of the art for mobility management in next-generation all-IP-based wireless systems is presented, and the previously proposed solutions based on different layers are reviewed, and their qualitative comparisons are given.
647 citations
Cites background from "Vertical handoffs in wireless overl..."
...Moreover, in wireless overlay networks the choice of the “best” network for location and handoff management places a new challenge because different overlay levels may have widely varying characteristics [ 24 ]....
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...Vertical handoff in wireless overlay networks is designed in [ 24 ] where heterogeneous networks in a hierarchical structure has fully overlapping service areas....
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...Other proposals developed new architectures to support intersystem roaming between different networks [23, 24 ]....
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References
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01 Oct 1996
TL;DR: This document specifies protocol enhancements that allow transparent routing of IP datagrams to mobile nodes in the Internet.
Abstract: This document specifies protocol enhancements that allow transparent routing of IP datagrams to mobile nodes in the Internet. Each mobile node is always identified by its home address, regardless of its current point of attachment to the Internet. While situated away from its home, a mobile node is also associated with a care-of address, which provides information about its current point of attachment to the Internet. The protocol provides for registering the care-of address with a home agent. The home agent sends datagrams destined for the mobile node through a tunnel to the care- of address. After arriving at the end of the tunnel, each datagram is then delivered to the mobile node.
2,094 citations
"Vertical handoffs in wireless overl..." refers background or methods in this paper
...There have been numerous papers dealing with handoff across homogeneous cellular [23], ATM [1], and picocellular [13] networks and mobility in IP networks [15,16,22]....
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...The infrastructure we use is similar to the one described in [24] and the Mobile IP specification [22]....
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28 Aug 1996
TL;DR: The RLM protocol is described, its performance is evaluated with a preliminary simulation study that characterizes user-perceived quality by assessing loss rates over multiple time scales, and the implementation of a software-based Internet video codec is discussed.
Abstract: State of the art, real-time, rate-adaptive, multimedia applications adjust their transmission rate to match the available network capacity. Unfortunately, this source-based rate-adaptation performs poorly in a heterogeneous multicast environment because there is no single target rate --- the conflicting bandwidth requirements of all receivers cannot be simultaneously satisfied with one transmission rate. If the burden of rate-adaption is moved from the source to the receivers, heterogeneity is accommodated. One approach to receiver-driven adaptation is to combine a layered source coding algorithm with a layered transmission system. By selectively forwarding subsets of layers at constrained network links, each user receives the best quality signal that the network can deliver. We and others have proposed that selective-forwarding be carried out using multiple IP-Multicast groups where each receiver specifies its level of subscription by joining a subset of the groups. In this paper, we extend the multiple group framework with a rate-adaptation protocol called Receiver-driven Layered Multicast, or RLM. Under RLM, multicast receivers adapt to both the static heterogeneity of link bandwidths as well as dynamic variations in network capacity (i.e., congestion). We describe the RLM protocol and evaluate its performance with a preliminary simulation study that characterizes user-perceived quality by assessing loss rates over multiple time scales. For the configurations we simulated, RLM results in good throughput with transient short-term loss rates on the order of a few percent and long-term loss rates on the order of one percent. Finally, we discuss our implementation of a software-based Internet video codec and its integration with RLM.
1,284 citations
"Vertical handoffs in wireless overl..." refers background in this paper
...[ MJV96 ], we are experimenting with the idea of delivery classes of trafficspecified at the source...
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25 Jan 1993
TL;DR: The BSD Packet Filter (BPF) uses a new, register-based filter evaluator that is up to 20 times faster than the original design, and uses a straighforward buffering strategy that makes its overall performance up to 100 times better than Sun's NIT running on the same hardware.
Abstract: Many versions of Unix provide facilities for user-level packet capture, making possible the use of general purpose workstations for network monitoring. Because network monitors run as user-level processes, packets must be copied across the kernel/user-space protection boundary. This copying can be minimized by deploying a kernel agent called a packet filter, which discards unwanted packets as early as possible. The original Unix packet filter was designed around a stack-based filter evaluator that performs sub-optimally on current RISC CPUs. The BSD Packet Filter (BPF) uses a new, register-based filter evaluator that is up to 20 times faster than the original design. BPF alson uses a straighforward buffering strategy that makes its overall performance up to 100 times faster than Sun's NIT running on the same hardware.
1,036 citations
"Vertical handoffs in wireless overl..." refers methods in this paper
...An observer machine was running tcpdump [19] and the resulting packet trace was post-processed to determine when the external messages triggered the turn-on and turn-off of the interface, when the MH sent the control messages to the BSs, and when the first packets arrived over the new interface to the MH....
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TL;DR: The authors focus on the goal of large-scale, hand-held mobile computing as a way to reveal a wide assortment of issues and look at some promising approaches under investigation and also consider their limitations.
Abstract: The technical challenges that mobile computing must surmount to achieve its potential are hardly trivial. Some of the challenges in designing software for mobile computing systems are quite different from those involved in the design of software for today's stationary networked systems. The authors focus on the issues pertinent to software designers without delving into the lower level details of the hardware realization of mobile computers. They look at some promising approaches under investigation and also consider their limitations. The many issues to be dealt with stem from three essential properties of mobile computing: communication, mobility, and portability. Of course, special-purpose systems may avoid some design pressures by doing without certain desirable properties. For instance portability would be less of a concern for mobile computers installed in the dashboards of cars than with hand-held mobile computers. However, the authors concentrate on the goal of large-scale, hand-held mobile computing as a way to reveal a wide assortment of issues. >
988 citations
"Vertical handoffs in wireless overl..." refers background in this paper
...This is approximately 20% of the total power drain of a typical laptop computer [11]....
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TL;DR: This paper describes the additions and modifications to the standard Internet protocol stack (TCP/IP) to improve end-to-end reliable transport performance in mobile environments and implements a routing protocol that enables low-latency handoff to occur with negligible data loss.
Abstract: TCP is a reliable transport protocol tuned to perform well in traditional networks where congestion is the primary cause of packet loss. However, networks with wireless links and mobile hosts incur significant losses due to bit-errors and hand-offs. This environment violates many of the assumptions made by TCP, causing degraded end-to-end performance. In this paper, we describe the additions and modifications to the standard Internet protocol stack (TCP/IP) to improve end-to-end reliable transport performance in mobile environments. The protocol changes are made to network-layer software at the base station and mobile host, and preserve the end-to-end semantics of TCP. One part of the modifications, called the snoop module, caches packets at the base station and performs local retransmissions across the wireless link to alleviate the problems caused by high bit-error rates. The second part is a routing protocol that enables low-latency handoff to occur with negligible data loss. We have implemented this new protocol stack on a wireless testbed. Our experiments show that this system is significantly more robust at dealing with unreliable wireless links than normal TCP; we have achieved throughput speedups of up to 20 times over regular TCP and handoff latencies over 10 times shorter than other mobile routing protocols.
729 citations
"Vertical handoffs in wireless overl..." refers background in this paper
...IEEE Journal on Selected Areas in Communications , 13(5), June 1995....
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