SWIM (Seamless WIreless Mesh network)

 


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Overview

SWIM (Seamless WIreless Mesh network) is an experimental wireless mesh network test bed at Nanjing University. Wireless mesh networks (WMNs) have been proposed as an effective solution for ubiquitous last-mile wideband access, and it is expected to achieve a spread application in the 4G networks.

SWIM currently consists of 10 nodes and is capable of running in 802.11b/g mode. SWIM is targeted at providing seamlessly handover between applications and supporting QoS assurance for video streaming service in mobile terminal like PDAs and smartphones without interrupting when users roaming inside our SWIM network.

We are focusing on the following research issues.


People


Funding


Selected Publications (Full list)

 


Hardware

Aiming at easy deploying, programming and updating, we implement PCs to construct the backbone of our Mesh network. The Hardware includes the D-Link DWL-G122 USB wireless interface, and tp-link TL-WN550G Card and linksys WRV200 router which connect two separate networks.

D-Link DWL_G122 USB wireless interface tp-link TL-WN550G Card linksys WRV200 router

Routing

We implement the LQSR (Link Quality Source Routing) multi-hop routing protocol to route packets between wireless nodes in the test bed. LQSR uses periodical packet exchange to get the information of link state which is evaluated by bandwidth, delay and loss rate. It is obvious that the routing metric like ETT, ETX and WCETT can be easily computed by the link state information. This routing protocol is especially appropriate for the application of seamless video streaming which is sensitive and largely rely on the link quality of the network.


Applications

We are developing and testing several applications on SWIM. Besides the ordinary internet access, our work is focusing on the seamless video streaming application. In detail, there are multi-source of video in the SWIM network. A user is roaming in SWIM and watching a video from the source server. As is knowing to all that the video streaming is critical for the network throughput which is just the drawback of wireless network. The throughput of the wireless network is restrict and limited. It is especially true when it comes to the multi-hop communication. Thus some sophisticated schemes and methods are applied to ease this limitation. First, considering the multi-sources condition, we could utilize the link state information which collected by the LQSR routing protocol to help us to switch between the best sources. Further, the prediction of user mobility which is implemented by the seamless handover scheme could also help the cooperatively cache the video data in advance in the nearest node. This scenario is illustrated below.

 

The seamless video streaming for the moving user requires seamless handoff and constant identify. Considering these requirements, we develop new version of handover scheme and mobile ip which fulfill these requirements. Moreover, to ease the dynamic joining for the mobile users, we develop a scheme of multi-hop DHCP for SWIM. Furthermore some up level services like the surveillance are still in progressing.

 


Deployment

SWIM is now deployed in the 3rd floor of the MMW buildings in Nanjing University. The network is continuously growing. Two pictures showed below are the logic and physic map of SWIM. The current network consists of 10 nodes and more are being deployed/upgraded continuously.

The logic map of SWIM
The physic map of SWIM

Reading List for SWIMers

Last updated:  Nov. 17th, 2008.