Wireless communication is becoming an indispensable part of people’s daily life. Over the last decade, the widespread adoption of Wireless Local Area Networks (WLAN) has triggered the proliferation of mobile devices, resulting in a dramatic growth in the amount of the mobile data traffic. To complement this growth in demand, there has been a steady advancement of the data rate in recent years. However, the high theoretical data rate often sustains a low actual throughput in the real world transmissions, referred as a low efficiency problem in wireless communication. Therefore, it is essential to achieve efficient communication in the wireless design.

In traditional WLANs with point-to-point communication, the low efficiency problem is mainly induced by the coordination overhead...[ Read more ]

Wireless communication is becoming an indispensable part of people’s daily life. Over the last decade, the widespread adoption of Wireless Local Area Networks (WLAN) has triggered the proliferation of mobile devices, resulting in a dramatic growth in the amount of the mobile data traffic. To complement this growth in demand, there has been a steady advancement of the data rate in recent years. However, the high theoretical data rate often sustains a low actual throughput in the real world transmissions, referred as a low efficiency problem in wireless communication. Therefore, it is essential to achieve efficient communication in the wireless design.

In traditional WLANs with point-to-point communication, the low efficiency problem is mainly induced by the coordination overhead. To avoid radio interference and packet collisions, coordination is required to allow multiple access in the multi-station WLANs. But the existing coordination schemes themselves account for too much of the transmission air time by exchanging control messages, resulting in a significant control overhead. This motivates us to provide a cost-effective coordination scheme in the wireless transmission. To achieve this, we propose a cross layer design, named hJam, for OFDM-based WLANs. Rather than interleaving or separating the control messages and data traffic as the traditional communication paradigms, hJam serves them together at the same time. By exploiting the redundancy in the preamble, the control messages are able to be transmitted in an attached manner with the data traffic. Therefore, hJam eliminates the control overhead by enabling the concurrent transmission of coordination message and traffic data to improve the coordination efficiency. Through extensive experiments, we have demonstrated the significant improvement of channel efficiency based on the design of hJam.

In recent years, the emerging Multi-User Multiple-Input-Multiple-Output (MU-MIMO) has also attracted attention in wireless communication by allowing the concurrent transmissions among multiple transmitters to the same receiver. The traditional approaches only focus on the efficiency in the time domain by reducing the control overhead. Differently, the channel efficiency problem becomes even more challenging in MU-MIMO networks by introducing an extra dimension, i.e., spatial domain, for the concurrent transmission for multiple nodes. Through analysis, we investigate that it is crucial to utilize the antenna usage by ensuring as many as possible simultaneous streams sent to the AP in MU-MIMO networks. Therefore, channel utilization in MU-MIMO networks should consider both the time and spatial domain, i.e., the efficient channel time and antenna usage at AP. To achieve this, we propose a new MAC-PHY design, named CUTS, by using interference nulling for attaching the antenna information in frequency domain channel contention, combined with the technique ACK in the frequency domain using self-jamming. We have validated and proven the effectiveness on channel efficiency by using the CUTS design through extensive experiments. We also discuss the potential research issues of efficiency in wireless communications.

keywords: Wireless Network, Cross Layer, PHY Layer, MAC Layer, Efficient Communication, MU-MIMO