Relay Selection in Two-Hop Wireless Communications
Abstract
Relay communication has been shown to be effective to
extend service coverage and mitigate channel impairments. This thesis focuses on
relay selection (RS) of both unidirectional and bidirectional
relay networks employing the amplify-and-forward (AF)
and decode-and-forward (DF) protocols.
This thesis presents four works on RS in two-hop relay networks.
In the first work, we study opportunistic relaying (OR) and
selection cooperation (SC) in
DF-based unidirectional multi-antennas relay networks.
We first propose two joint relay-and-antenna selection
schemes which combine OR and SC, respectively,
with transmit antenna selection.
For each joint selection scheme,
a single best transmit antenna at the source,
a single best relay,
and a single best transmit antenna at this selected relay
are jointly determined.
Then we derive the outage probabilities,
and show that the two schemes achieve the same outage performance.
In the second work, we study RS with
the physical-layer network coding (PNC)
in DF-based bidirectional relay networks.
By modifying the well-known SC and OR,
we first propose two RS schemes for the PNC network:
SC-PNC and OR-PNC.
Then we derive the outage probability
and diversity order of the SC-PNC.
Finally, we show that the OR-PNC achieves the same outage performance
as the SC-PNC.
In the third work, we study RS with
the analog network coding (ANC) and time division broadcast (TDBC),
in AF-based bidirectional relay networks.
We first consider RS schemes
for the ANC and TDBC protocols
based on a max-min criterion.
Then we derive outage probabilities for the ANC and TDBC protocols.
In the fourth work, we study joint relay-and-source selection
in an AF-based bidirectional relay network.
Since RS and opportunistic source selection (OSS) could individually improve
performance of relay networks,
we propose a joint RS-OSS protocol.
In this network, a best source is selected to transmit data
to the other source with the help of a selected best relay.
Then, we derive the outage probability and
average bit-error rate.
The considered RS schemes and obtained outage probability expressions will help the design of two-hop wireless communications in determining the system parameters such as relay location and the transmission power at each terminal.