MAR: Mobile Access Router
Introduction
The Mobile Access Router (MAR) studies how to exploit different levels of diversity in wireless data networks for enabling ubiquitous access to high-speed mobile data applications. One of the key functionalities of MAR is that it can aggregate the available bandwidth in all wireless interfaces. This aggregated bandwidth is then offered as a larger, more stable pipe to the end users. The first example is a Mobile Access Router (MAR) aggregates multiple Wireless-WAN connections (e.g. UMTS, GPRS, CDMA2000). MAR provides a high-bandwidth Internet connection for commuters in trains and buses and seamless handoffs between different wireless access technologies. We are also considering a more distributed version of the MAR system that also allows to aggregate mobile devices (e.g. mobile phones) in an ad-hoc fashion (see Agora project).
At the core of the MAR system is the MAR session protocol that makes use of dynamic parallel-download techniques to aggregate the available bandwidth in multiple wireless interfaces without requiring a precise estimation of the bandwidth or the delay in the wireless links. This aggregation protocol automatically adapts to changing wireless conditions by instantaneously shifting the load from under-performing wireless interfaces to better performing ones. For instance, assume that one client ones to download three small files. The client knows that interfaces A, B, and C are available for Internet access. The standard approach is to pick one of them and download the all files from a particular interface. Rather than doing this, MAR sends each file request over a different interface, making use of all the available bandwidth. We call this Multiple Session Striping.
Similarly, assume that one client wants to download a large file X. Normally, the client would download the whole file from a single interface, limiting its throughput to the speed of the selected interface. Using parallel-downloads, the client can download different parts of the file from each of the servers. For example, the first third of the file can be downloaded from interface A, the second third from interface B and the last third from interface C. The client can reconstruct the original file after receiving the three parts. We call this Single Session Striping. To cope with highly variable and despair links, Paraload implements a more sophisticated striping policy. Such policy slices the file into many small data blocks and uses a greedy request policy among different interfaces to dynamically assign new block requests to interfaces that become idle. In this way fast interfaces download most blocks while slow interfaces download few blocks.
The MAR router has multi-home capabilities to support multiple wireless systems (e.g. four GPRS cards) from different wireless networks (e.g. GPRS, 3G, WLAN etc.) and operators (e.g., Vodafone, Orange etc.) simultaneously. The MAR router can be used as the access router in any mobile vehicle (e.g. car, bus, or train) and provides several local high-speed interfaces (e.g. 802.11, bluetooth, Ethernet) for end user access.
Fig1. Commuter Router based on MAR system
Fig2. First MAR prototype (2 GPRS phones + 1 PCMCIA GPRS). 23/10/03
Publications
MAR: A Commuter Router Infrastructure for the Mobile Internet". In ACM Mobisys 2004, June 2004 [pdf].
"Exploiting Network Diversity in Wireless Mobile Systems" (technical report attached to above paper). [pdf]
Related Projects
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