THESIS
2014
xv, 112 pages : illustrations ; 30 cm
Abstract
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...[
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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
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