| Wireless networks have become an increasingly important part of our daily lives. The rise in number of mobile clients and the subsequent services being offered on them has led to not just an increase in demand for wireless data but also change in network traffic characteristics. The proliferation of mobile devices also causes change in wireless topologies over time. However, the available bandwidth remains scarce. Thus, the need for wireless networks to be more spectral efficient is critical. This dissertation investigates a suite of solutions to address this trend in changing wireless networks. We first investigate physical layer solutions at the node level to enhance wireless networks and then look at collaborative techniques across distributed nodes to improve wireless networks.;First, collaborative communication techniques such as interference alignment, distributed MIMO have been theoretically explored to enhance the spectral efficiency of wireless networks. However, implementing such solutions in practice require tight synchronization requirements either in time, frequency or both. We present Vidyut, which uses the power lines to provide time and frequency synchronization across distributed nodes to implement such techniques in practice. The advantage of using an orthogonal medium (the power lines) for synchronization purposes alleviates the MAC overhead required to simply synchonize nodes distributed in space. We demonstrate the realized synchronization is sufficient to implement distributed MIMO/ OFDM schemes in practice.;Then, we exploit synchronization to enhance performance of wireless networks of single antenna/ single radio wireless nodes using interference alignment techniques by introducing the notion of shadow channel.;Secondly, rising wireless demand data has led to increased development and deployment of multi-antenna, multi-radio wireless nodes. This has led to advancement of physical layer solutions such as MIMO, full-duplex, Multi-User MIMO (MU-MIMO) and so on. We first present FlexRadio, a multi-antenna wireless node, that provides to the higher layers in a wireless network with the flexibility to decide the number of radio resources at each node to service a desired client. This flexibility provides a wireless network controller to potentially adapt to changing network topologies, channel conditions and traffic flow directions. Finally, most of the radio resource advancements can be expected to be deployed on Access Points (AP) in wireless network for incremental costs and perhaps not at every client. We motivate the need for light collaboration across different APs (potentially multi-antenna/multi-radio full-duplex capable) in a wireless network that would eventually support MU-MIMO in both the downlink and uplink directions simultaneously, both within and across cells. We exploit time synchronization across distributed APs, and propose a light-weight distributed algorithm to enable each AP to choose its client set locally.;The dissertation investigates the problems, the solutions and the potential practical challenges in detail. |
