Design Of Distributed Antenna System Aided Cellular Networks And Coalition Network Elements Aided Base Station Cooperative Transmission

Distributed Antenna System (DAS) and Femtocell are important transmitting elementsin future wireless communication systems. Typically, both DAS and Femtocells have smallertransmit power, smaller coverage and lower cost. First, they are capable of supporting highercoverage because of more-density deployment. Then, more resource can be allocated into eachuser supported, since less users are supported within each Femtocell or each distributed antenna,compared with macrocell. As a result, DAS-aided cellular network or DAS-aided macro-femtotwin-layer networks are one of future wireless networks.A more sophisticated technique of exploiting the available frequency band is constitutedby the Fractional Frequency Reuse (FFR), which improves the area spectral efficiency of clas-sic Frequency Reuse (FR), while maintaining a high Signal-to-Interference-and-Noise Ratio(SINR) in the cell-edge area. To elaborate a little further, the philosophy of FFR is that eachcell is divided into a Cell-Centre Region (CCR) having access to the cell-centre’s frequencyband and the Cell-Edge Region (CER) having access to the cell-edge’s frequency band.In which case, the users within the CER no longer suffer from strong Co-Channel Interfer-ence (CCI) from adjacent cells. In order to meet the traffic demands of indoor mobile users,Femtocells have been invoked as a cost-effective way of balancing the traffic of the entire cel-lular system. Femtocells may be overlaid onto macrocells, forming a hierarchical twin-layernetwork structure. This paper investigates the DAS-aided cellular network relying on FFR aswell as DAS-aided macro-femto twin-layer network. Our main works and achievements aresummarized as follows:1. DAS-aided Unity Frequency Reuse (UFR) as well as FFR transmission scenarios areinvestigated in this paper employing the classic multi-objective of Non-dominated Sorting Ge-netic Algorithm II (NSGA-II) for maximising the cell-throughput and the coverage. Morespecifically, Coordinated-Multi-Point (CoMP) cooperation is invoked amongst the distributedantennas and the Base Station (BS) in support of the Mobile Stations (MSs) roaming at the cell-edge, while considering a range of practical impairments. Although CoMP-aided transmissionsare capable of achieving a higher throughput and coverage with the aid of idealised perfect CSIat the transmitters’ side, the practical CSI impairments dramatically degrade the performance,which hence became worse than that of Non-CoMP transmissions. 2. CoMP transmission aided DAS are proposed for increasing the received SINR in thecell-edge area of a cellular system employing FFR in the presence of realistic imperfect Chan-nel State Information (CSI) as well as synchronisation errors between the transmitters and re-ceivers. Our simulation results demonstrate that the CoMP-aided DAS scenario is capable ofincreasing the attainable SINR by up to3dB in the presence of a wide range of realistic imper-fections. Our numerical results demonstrated that the CoMP transmission scenario achieved a5dB SINR improvement than that of Non-CoMP transmission, even when only6quantisationbits involved in quantisation feedback process. Synchronisation studies showed that the Non-CoMP and UFR transmission scenarios are more invulnerable to the synchronisation errors.3. DAS and femtocells are capable of improving the attainable performance in the cell-edge area and in indoor residential areas, respectively. In order to achieve a high spectralefficiency, both the distributed antenna and Femtocells may have to reuse the spectrum of themacrocellular network. As a result, the performance of both outdoor macrocell users and in-door femtocell users suffers from CCI. Hence in this paper, heterogenous cellular networks areinvestigated, where the DAS-aided macrocells and femtocells co-exist within the same area.Both the outage probability and the spatially averaged throughput are derived and the networkis optimised either for minimising the outage probability or for maximising the macrocell’sthroughput. Our analysis demonstrates that surprisingly, the Unity Frequency Reuse (UFR)based macrocellular system can be optimised in isolation, without considering the impact offemtocells. We found that the macrocells relying on FFR tend to migrate to several small cells,illuminated by the distributed antennas, when the density of femtocells becomes high.4. Remote Coalition Network Elements (CNE) are proposed for BS cooperation, wherethe CNEs carry traffic in the second hop for the primary BS in support of its cell-edge MSs byexploiting the unused frequency bands of the main BS network, while considering a range ofpractical impairments. We derive the coalition probability of the CNEs by taking into accountboth the specific system load as well as the CNE’s greediness factor. Our simulation resultsdemonstrate that the proposed solution is capable of substantially increasing the attainableSINR in a wide range of scenarios and it is also robust to diverse practical imperfections. Ina nutshell, the advocated scheme may be found especially beneficial as a fall-back solution,when the conventional BS-Cooperation malfunctions, or when it is prone to CSI signallingimperfections. Our simulation results show that the maximal sum-profit is achieved, when thegreedy factor is around=0.45and a coalition is established with MSs roaming in the range of <0.25...