- Link:
- http://hdl.handle.net/1783.1/7333
- Collection:
-
- Subjects
- Orthogonal frequency division multiplexing Packet switching (Data transmission) Wireless communication systems
- Creator:
- Cheung, Chun
- Description
- Thesis (Ph.D.)--Hong Kong University of Science and
Technology, 2011
- Description
- xv, 120 p. : ill. ; 30 cm
- Description
- HKUST Call Number: Thesis ECED 2011
Cheung
- Description
- The tremendous growth in wireless access for
internet and multimedia applications in recent years increases the
demand for more reliable and high speed wireless communication
capability. To face this challenge, we need to explore new wireless
radio technologies and utilize the present network resources more
efficiently. While new wireless communication technologies
including multi-band orthogonal frequency division multiplexing
(MB-OFDM) in ultra-wideband (UWB) system, network coding, Hybrid
ARQ (HARQ), and cooperative communications, are introduced and
developed, it is important to make use of these new technologies
efficiently. Adaptive and dynamic schemes based on communication
channel state information or statistics had been shown to improve
efficiency significantly. In this thesis, we study how dynamic
adaptation using these technologies can further benefit new advance
communication systems. In a point-to-point short range UWB system
where power spectral density level instead of the total power is
the limitation, traditional power allocation scheme cannot be used.
We proposed a new adaptive symbol interleaved coded modulation and
frequency spreading technique and showed how it can dynamically
combine and utilize the otherwise unused power in weak subcarriers
to increase the overall system performance. In an uplink cellular
communication system with cooperative relay, we proposed two
adaptive multiuser cooperative HARQ retransmission strategies, one
for network-coded retransmission and one for superposition
modulated retransmission. The network-coded HARQ retransmission
dynamically determines the group of packets from multiple users
that should be combined in the HARQ retransmission at the relay
station. We optimized the grouping in this strategy and evaluated
via simulation the performance improvement under various channel
conditions. For the superposition modulated retransmission scheme,
we used the information-theoretic approach to derive the outage
probability and derived the superposition weighting factor to
minimize this outage probability in a two-user system. We derived
analytically the system throughput and investigated the improvement
achieved by the proposed optimized scheme under channels with
various diversity orders. The adaptation concept is extended to the
interference channel modeling a two-cell scenario with two mobiles
accessing two base stations in a cellular network. Assuming the
presence of a backhaul connection between the base stations, we
proposed a scheme that uses the base station as a relay to
adaptively forward either the signal or the interference or nothing
at all over the backhaul connection. We derived the analytical
characterizations of the condition for each forwarding schemes and
the resulted system throughputs. Results were compared to
non-cooperative scheme. Detail analyses of the influences of the
backhaul channel capacity and the ratio of two transmitters
information bit rates on the system throughput gains of the
cooperative schemes over the non-cooperative scheme were also
given. Simulation results in fading channels showed that our
proposed dynamic cooperation scheme outperforms the individual
non-dynamic cooperative schemes significantly.
- Format
- 345 bytes
- Format
- text/html
- Language
- en_US
- Type
- Thesis
- Access:
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