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Title: Physical layer enhancements for LTE-advanced for 4G and beyond wireless networks
Author: Ameen, Araz Sabir
ISNI:       0000 0004 5923 6771
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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This thesis presents a comprehensive analysis of the LTE-Advanced Physical Downlink Shared Channel (PDSCH) in outdoor environments. Bit accurate and a Received Bit mutual Information Rate (RBIR) simulators are developed and used for system and link level performance evaluation studies. The RBIR is shown to reduce simulation run time by a factor of more than 300. The radio channel is modelled using a site-specific 3D ray-tracing tool combined with measured BS and UE 3D antenna patterns. A 3D extension of the standardized 2D ITU-R channel model is implemented by exploiting ray tracing statistics. A comparison study between the 2D ITU-R, extended 3D ITUR, and 3D ray tracing channel models is performed to highlight the advantages of 3D modelling over 2D modelling and the deficiencies of the ITU-R models compared to 3D ray tracing. Performance results on the impact of handset rotation show higher throughputs for UEs at 45° rotation in elevation (single antenna system) as a result of higher K factors and total received power levels. For a 2x2 MIMO, the study recommends an antenna switching scheme for tablet UEs that activate two from three antennas based on device orientation to achieve the highest channel capacity. The study also suggests the planar array deployment of antennas in both smartphones and tablets for 4x4 MIMO systems in order to reduce handset rotation sensitivity and to achieve higher capacity. This thesis also considers carrier aggregation (CA) between the 800 MHz and 2.6 GHz bands. Results show similar average throughput vs SNR performance in both bands. Furthermore, for mobile users in specific routes with inter cell interference (lCI) the 800 MHz band is shown to have no significant improvement on downlink throughput. Hence there are no additional advantages of intra-band CA at 800 MHz compared to inter-band CA between the two bands. Finally the thesis provides a detailed analysis of the effect ofICI on LTE-Advanced for different macro cell diameters, base station (BS) antenna heights and carrier frequencies. A 3D ray-tracing tool is used to model the communication channel between the base stations (main and interfering links) and user equipment (UE) terminals. The Inter Site Interference (ISI) is first modelled in terms of its Dominant Interference PropOttion (DIP) and then validated using previously repOtted field measurements in London. ISI and Inter Sector Interference are modelled as a function ofUE relative position from the main BS. System performance is evaluated in terms of average spectrum efficiency, cell edge throughput and outage probability. Two 3D analogue beamforming algorithms are proposed to mitigate the harmful effects ofIC!. These are applied at the BS and/or the UE and the obtained results are compared with a more traditional fractional frequency reuse deployment. Simulations demonstrate that the proposed beamforming algorithms provide significant system level improvements, especially for low BS antenna heights. With 1 Oxl 0 and 2x2 antenna alTays at the BS and UE respectively, the MaxMin-BF algorithm provides an average spectrum efficiency of3.6 bps/Hz and a cell edge throughput of 0.56 bps/Hz up to a cell diameter of 1250 m. ImpOttantly, these results satisfy the IMT-Advanced requirements for candidate 4G and beyond Radio Interface Technologies (RITs). Furthermore, the proposed techniques outperform fractional frequency reuse method.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available