Wireless penetration has witnessed explosive growth over the last two decades. Accordingly, wireless devices have become much denser per unit area, resulting in an over-crowded usage of wireless resources. To avoid radio interferences and maximize the channel capacity, wireless stations have to exchange control messages to coordinate well. The existing wisdoms of conveying control messages consume valuable communication resources, and introduce massive coordination overheads. Therefore, how to provide cost-effective coordination mechanisms becomes a critical problem in wireless design.

In this thesis, we first present a survey on the recent advances in wireless communications, including a variety of PHY and MAC layer coordination mechanisms, and reviews of classic problems i...[ Read more ]

Wireless penetration has witnessed explosive growth over the last two decades. Accordingly, wireless devices have become much denser per unit area, resulting in an over-crowded usage of wireless resources. To avoid radio interferences and maximize the channel capacity, wireless stations have to exchange control messages to coordinate well. The existing wisdoms of conveying control messages consume valuable communication resources, and introduce massive coordination overheads. Therefore, how to provide cost-effective coordination mechanisms becomes a critical problem in wireless design.

In this thesis, we first present a survey on the recent advances in wireless communications, including a variety of PHY and MAC layer coordination mechanisms, and reviews of classic problems in wireless networks.

The state-of-the-art expensive coordination mechanisms motivate us to propose lightweight control for future wireless networks. Recent prevailing OFDM techniques enable us to get access to the subcarrier level control of the network. Based on the OFDM subcarriers, two classes of lightweight control systems are presented. First, we propose a novel PHY layer technique termed Attachment Transmission. It provides an extra control panel with minimum overhead. In a traditional transmission paradigm, control messages compete for communication resources with data packets. On the contrary, attachment transmission enable control messages to be transmitted along with data packets, without degrading the effective throughput of the original data packets.

To demonstrate the effectiveness of the attachment transmission, we apply it to a number of classic problems in wireless networks, including the multi-channel allocation problem in OFDMA-based networks, the hidden and exposed terminal problem in ad-hoc networks, and the multiple access problem in wireless local area networks (WLAN). Extensive experiments demonstrate that attachment transmission is capable of exploiting channel redundancy to deliver control information, thus provides significant support to numerous higher layer applications.

In addition to attachment transmission, we further present subcarrier coordination for cogitative radio networks (CRNs) and subcarrier coding for wireless rate adaptation (WRA). Subcarrier coordination moves cooperative sensing and multi-channel contention from time domain into frequency domain, which significantly reduce the control overhead. Subcarrier coding aims to conduct fine-grained rate adaptation at subcarrier level, and thus approaches the channel capacity. We validate subcarrier control through extensive experiments, and discuss potential research directions of fine-grained and lightweight control over wireless communications.

keywords: Wireless Network, PHY Layer, MAC layer, Control