|dc.description.abstract||The communications phenomena at the end of the 20th century were the Internet and mobile
telephony. Now, entering the new millennium, an effective combination of the two should
become a similarly everyday experience. Current limitations include scarce, exorbitantly priced
bandwidth and considerable power consumption at higher data rates.
Relaying systems use several shorter communications links instead of the conventional
point-to-point transmission. This can allow for a lower power requirement and, due to the
shorter broadcast range, bandwidth re-use may be more efficiently exploited. Code division
multiple access (CDMA) is emerging as one of the most common methods for multi user
access. Combining CDMA with time division duplexing (TDD) provides a system that
supports asymmetric communications and relaying cost-effectively. The capacity of CDMA
may be reduced by interference from other users, hence it is important that the routing of
relays is performed to minimise interference at receivers.
This thesis analyses relaying within the context of TDD-CDMA systems. Such a system was
included in the initial draft of the European 3G specifications as opportunity driven multiple
access (ODMA). Results are presented which demonstrate that ODMA allows for a more
flexible capacity coverage trade-off than non-relaying systems. An investigation into the
interference characteristics of ODMA shows that most interference occurs close to the base
station (BS). Hence it is possible that in-cell routing to avoid the BS may increase capacity.
As a result, a novel hybrid network topology is presented. ODMA uses path loss as a metric
for routing. This technique does not avoid interference, and hence ODMA shows no capacity
increase with the hybrid network. Consequently, a novel interference based routing algorithm
and admission control are developed. When at least half the network is engaged in in-cell
transmission, the interference based system allows for a higher capacity than a conventional
cellular system. In an attempt to reduce transmitted power, a novel congestion based routing algorithm is introduced. This system is shown to have lower power requirement than any other analysed system and, when more than 2 hops are allowed, the highest capacity.
The allocation of time slots affects system performance through co-channel interference. To
attempt to minimise this, a novel dynamic channel allocation (DCA) algorithm is developed
based on the congestion routing algorithm. By combining the global minimisation of system
congestion in both time slots and routing, the DCA further increases throughput. Implementing
congestion routed relaying, especially with DCA, in any TDD-CDMA system with in-cell calls
can show significant performance improvements over conventional cellular systems.||en