Open networking infrastructure: boosting wireless networks in the era of cloud

In recent years, the Mobile Internet has undergone revolutionary changes, and has fundamentally changed the way users access the Internet, which results in an unprecedented demand for ubiquitous network access. However, due to the fundamental radio frequency communication constraints, the service quality and scalability of cellular systems is limited. In contrast, Wi-Fi, now being a well-developed standard technology, has been densely deployed, especially in urban areas. My research work is primarily motivated by these exciting trends in mobile networks. We believe WiFi has the unique potential to form a community based infrastructure that provides a truly scalable, efficient and ubiquitous access to wireless and data, especially in urban areas. In this work, we propose a research framework called Open Infrastructure. Based upon this framework, we explore a group of mechanisms to boost the mobile computing experience by leveraging urban WiFi. To evaluate the applicability of such framework, we have built and deployed an Open Infrastructure testbed, consisting of 30 customized home WiFi Access Points 1 in the urban areas of Boston and Houston. This testbed provides researchers with first-hand information on urban WiFi and a realistic setup to try out a variety of research ideas. We have conducted an extensive measurement on the testbed, complemented with a large scale Wardriving in Greater Boston. With a 1.3TB network traffic trace, over 70 million home WiFi network statistics and over 26K urban WiFi APs identified during Wardriving, our data analysis has characterized the urban WiFi settings and revealed a set of interesting insights to the potential of urban WiFi forming an infrastructure to provide a scalable and ubiquitous access to wireless and data. Motivated by our observations, our research has been focusing on two domains, urban WiFi assisted energy saving on mobile devices and idle bandwidth harnessing from home WiFi APs. We have initiated two projects, WiZi-Cloud and BaPu, and developed a set of enabling mechanism and prototypes to demonstrate the feasibility of our ideas. In WiZi-Cloud, we extend current WiFi AP and mobile device with an alternative ultra-low power ZigBee radio interface, to offload network traffic from energy consuming interfaces like WiFi and GSM. WiZi-Cloud reduces the battery consumption on mobile devices. The WiZi-Cloud architecture and its support for multiple heterogeneous radios is transparent to the applications and allows seamless interface switching. Also, WiZi-Cloud supports multiple ZigBee transceivers and channel coding schemes to maximize the coverage performance. We design and prototype a complete suite of hardware/software solution. Our experimental results show that the WiZi-Cloud well supports a large set of mainstream mobile applications and improves the energy efficiency by 3 fold with comparable, if not better, coverage than WiFi. Besides, with a large set of ZigBee packet trace collected from our testbed, we are able to examine the frame error patterns of ZigBee transmission in bit level. With a combined empirical and analytical model, we show that a simple dual-antenna solution can greatly improves the ZigBee coverage close to its limit, and the gain of any Forward Error Correction mechanism is negligible. BaPu is motivated by the fact that today's residential broadband have limited bandwidth, especially in uplinks, which highly constrains many fast growing applications, such as HD content sharing, efficient cloud storage backup. In BaPu, we design the mechanisms of aggregating the idle broadband uplinks, by having the mobile device communicate with multiple proximate WiFi APs in the same neighbour- hood. BaPu is a complete software solution running on home WiFi APs, and requires no modification to client devices. This makes an easy progressive adoption of BaPu technology. Our architecture and protocols design provide aclean solution to several challenges in efficiently sup- porting both TCP and UDP. Our prototype system shows that BaPu can efficiently aggregate the backhaul bandwidth of multiple access points and achieve up to 90% of the theoretical maximum throughput. 1In this work, Access Point, AP and router are used interchangeably.