THESIS
2015
xvi, 137 pages : illustrations ; 30 cm
Abstract
The intense demands for higher data rates and ubiquitous network coverage have raised the stakes
on developing new network topology and architecture to meet these ever-increasing demands
in a cost-effective manner. The telecommunication industry and international standardization bodies
have placed considerable attention to the deployment of extremely dense networks, referred to as
DenseNets, which creates a bundle of opportunities for high spatial reuse and energy efficiency by
reducing the distance between Access Points (APs) and clients. Industrial practices of DenseNets
include small-scale femtocells in LTE/LTE-A based cellular systems and WiFi hotspots in public
places in IEEE 802.11 based High Efficiency WLAN (HEW). Both empirical experiences and theoretical
analyses sugges...[
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The intense demands for higher data rates and ubiquitous network coverage have raised the stakes
on developing new network topology and architecture to meet these ever-increasing demands
in a cost-effective manner. The telecommunication industry and international standardization bodies
have placed considerable attention to the deployment of extremely dense networks, referred to as
DenseNets, which creates a bundle of opportunities for high spatial reuse and energy efficiency by
reducing the distance between Access Points (APs) and clients. Industrial practices of DenseNets
include small-scale femtocells in LTE/LTE-A based cellular systems and WiFi hotspots in public
places in IEEE 802.11 based High Efficiency WLAN (HEW). Both empirical experiences and theoretical
analyses suggest that DenseNets will encompass significant technical challenges related to
reliable and efficient access and management. On the one hand, DenseNets contain a significant
number of densely-deployed APs with highly overlapped regions, making network maintenance
a complicated and challenging task. On the other hand, there are normally a crowd of clients
in DenseNets, and thus efficient access control is expected to meet the high per-user-throughput
demands with a limited amount of bandwidth.
We have two proposals for DenseNets, where each aims to address one challenge as mentioned
above. First, we propose an automatic fault management framework for dense femtocell networks.
Under this framework, we propose three system designs for outage detection, fault diagnosis, and
self-healing functions. As the first step of our automatic management framework, the proposed
outage detection design exploits signal correlations among multiple femtocells to improve detection accuracy for small-size densely-deployed femtocell networks. The outage detection system
triggers fault diagnostic system. In our diagnostic system design, we develop a transfer learning
based approach to overcome the data scarcity issue in small-size femtocells. After identifying the
specific fault, outage is compensated by a self-healing scheme. We study the interference outage
case, and propose a local cooperative grouping architecture to iteratively recover the network outage.
Second, we propose an efficient access framework for WiFi networks with large audience
environments. We analyze the poor performance of WiFi for large audience environments, and
propose a PHY/MAC design to improve efficiency in public WLANs. The proposed design aggregates
multi-user’s transmissions into one transmission so as to reduce contention overhead. The
above studies demonstrate that with appropriate system designs, reliable and efficient DenseNets
can be achieved to meet high data rate and ubiquitous connection demands.
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