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In orthogonal frequency division multiple access based mobile networks buffer aided nontransparent in-band half duplex decode-and-forward relay nodes aim to improve coverage and capacity under fairness considerations. The existing centralized radio resource management and inter-cell interference coordination schemes can achieve this goals, although at the cost of a heavy signalling overhead. This cost is a critical issue, particularly for the frequency division duplex downlink transmission. On the other hand, the fully decentralized schemes often focus on different types of frequency reuse schemes with smaller amount of necessary feedback. Here, it is often overseen that in a practical deployment, the backhaul link quality is the bottleneck of the two-hop transmission, and the backhaul link is often modelled way too optimistically. Moreover, it is necessary to allocate radio resources to single hop mobile stations as well, which further limits the possible data rates of the relay-attached users. The research presented in this Thesis aims to improve the backhaul link quality in relay-assisted cellular networks under full consideration of practical constraints. In order to minimize the required channel feedback overhead this work proposes a hybrid radio resource management scheme consisting of three adapted procedures. The hybrid radio resource management scheme includes an adapted decentralized cell selection metric which improves the possibility to gain from the relays in the system for each user. A macro cell-centralized synchronous procedure is proposed, which is responsible to allocate the radio resources in each transmission time interval. Furthermore, an asynchronous network-centralized subband power allocation scheme with very limited feedback is proposed to maximize the wireless backhaul link quality with no losses for single-hop Mobile Station (MS)s. Comprehensive system level simulation results show stable fairness and improved throughput of the proposed hybrid radio resource management scheme. In addition possible energy savings for the shared channel are presented.

Myrmica ruginodis ants and the gorse species U. europaeus have a national distribution in the U.K. and are considered important keystone species within British lowland heaths. These two species boost and maintain biodiversity by increasing habitat heterogeneity through ecosystem engineering of the soil physical and chemical environment, and are generally considered Keystone species in lowland heaths. Both species have been shown to increase limiting nutrients in the soil such as Nitrogen and Phosphorus. Here, for the first time in a single study, the extent to which these species augment soil chemistry and the resulting impacts on microbial communities is quantified. It was hypothesized that abiotic changes brought about by the action of keystone species directly and indirectly will lead to differences in both bacterial and fungal community diversity and composition, and such changes will be likely to modify ecosystem function. Analysis of soil cores taken from three U.K. lowland heath habitats representing a national distribution found that dissimilarities in microbial community structure (determined by T-RFLP) were largely attributable to differences in soil pH. However, pH was an imperfect predictor. To fully understand abiotic drivers and to identify the soil nutrients involved in augmenting microbial communities in heathlands, a data mining exercise was conducted using the large Countryside Survey 2007 bacterial data. The findings from this showed that as the soil pH gradient was shortened by focusing on low soil pH, and then by looking at a single type of vegetation cover (dwarf shrub heath), soil pH became less effective in explaining differences in the communities; other soil chemical properties then become more important, such as Carbon to Nitrogen (C:N) ratio and soil Phosphorus (P). The identification of these chemical attributes and the known impacts that the keystone species have on them led to the development of a controlled mesocosm experiment using Aberdeenshire lowland heath soil. In this experiment keystone species were isolated and found to impact upon soil chemistry and microbial diversity. Soil pH was identified as having an important defining role on communities, however soil P and C:N and Potassium (K) were also related to microbial community composition. Differences in respiration were also linked to the presence of the keystone species. A final field experiment was performed to test the mesocosm observations in the field site, but sampling specific soil regions (ant nest structures and rhizospheres). Less marked microbial community differentiation was found compared with the initial field experiment. Fungi had no responses to soil chemistry except for Dorset communities which responded to soil pH. Bacteria responded to all soil measures of chemistry for pooled region data and for Aberdeenshire. Cumbria communities responded P and Dorset to C:N. Soil chemistry and microbial communities were not affected by the same keystone species in the same way in any of the regions. Finally, community T-RFLP profiles for fungi and bacteria were directly compared for.any correlation; interaction was found to be limited, partly due to fundamental differences in the bacterial 16S rDNA and fungal ITS rDNA T-RFLP profiles and partly due to these microbes responding in different ways to their environment.