80 research outputs found

    Towards 5G Cellular: Understanding 3D In-Building Single Band and Multi-band Small Cells with Control/User-plane Coupled and Separation Architectures with a Novel Resource Reuse Approach

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    In this paper, we present numerous small cell base station, i.e. femtocell base station (FCBS), with control-/user-plane coupled and separation architectures based on the number of transceivers and operating frequency bands to serve control-/user-plane traffic. A single transceiver enabled FCBS can operate at either a co-channel microwave of the overlaid macrocell or a millimeter wave band. For multiple transceivers, dual transceivers are considered operating at both bands. FCBSs are deployed in a number of buildings with each floor modeled as 5×5 square-grid apartments. The co-channel interference with FCBSs is avoided using enhanced intercell interference coordination techniques. We propose a static frequency reuse approach and develop an algorithm by avoiding adjacent channel interferences from reusing frequencies in FCBSs. We also develop a resource scheduling algorithm for FCBSs with CUCA and CUSA to evaluate system level performances with a multi-tier network. It is found that a single transceiver co-channel microwave enabled FCBS with CUCA provides the worse, whereas a single or dual transceivers millimeter wave enabled FCBS with CUSA provides the best overall system capacity and FCBSs’ energy efficiency performances. Besides, we show the outperformances of the proposed resource reuse approach over an existing approach in literature in terms of system capacity and fairness among FCBSs with CUCA. Finally, we point out the applicability of a multi-band enabled FCBS and several features and issues of FCBSs with CUCA and CUSA.In this paper, we present numerous small cell base station, i.e. femtocell base station (FCBS), with control-/user-plane coupled and separation architectures based on the number of transceivers and operating frequency bands to serve control-/user-plane traffic. A single transceiver enabled FCBS can operate at either a co-channel microwave of the overlaid macrocell or a millimeter wave band. For multiple transceivers, dual transceivers are considered operating at both bands. FCBSs are deployed in a number of buildings with each floor modeled as 5 by 5 square-grid apartments. The co-channel interference with FCBSs is avoided using enhanced intercell interference coordination techniques. We propose a static frequency reuse approach and develop an algorithm by avoiding adjacent channel interferences from reusing frequencies in FCBSs. We also develop a resource scheduling algorithm for FCBSs with CUCA and CUSA to evaluate system level performances with a multi-tier network. It is found that a single transceiver co-channel microwave enabled FCBS with CUCA provides the worse, whereas a single or dual transceivers millimeter wave enabled FCBS with CUSA provides the best overall system capacity and FCBSs' energy efficiency performances. Besides, we show the outperformances of the proposed resource reuse approach over an existing approach in literature in terms of system capacity and fairness among FCBSs with CUCA. Finally, we point out the applicability of a multi-band enabled FCBS and several features and issues of FCBSs with CUCA and CUSA

    Radio resource scheduling in homogeneous coordinated multi-point joint transmission of future mobile networks

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    A thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD)The demand of mobile users with high data-rate services continues to increase. To satisfy the needs of such mobile users, operators must continue to enhance their existing networks. The radio interface is a well-known bottleneck because the radio spectrum is limited and therefore expensive. Efficient use of the radio spectrum is, therefore, very important. To utilise the spectrum efficiently, any of the channels can be used simultaneously in any of the cells as long as interference generated by the base stations using the same channels is below an acceptable level. In cellular networks based on Orthogonal Frequency Division Multiple Access (OFDMA), inter-cell interference reduces the performance of the link throughput to users close to the cell edge. To improve the performance of cell-edge users, a technique called Coordinated Multi-Point (CoMP) transmission is being researched for use in the next generation of cellular networks. For a network to benefit from CoMP, its utilisation of resources should be scheduled efficiently. The thesis focuses on the resource scheduling algorithm development for CoMP joint transmission scheme in OFDMA-based cellular networks. In addition to the algorithm, the thesis provides an analytical framework for the performance evaluation of the CoMP technique. From the system level simulation results, it has been shown that the proposed resource scheduling based on a joint maximum throughput provides higher spectral efficiency compared with a joint proportional fairness scheduling algorithm under different traffic loads in the network and under different criteria of making cell-edge decision. A hybrid model combining the analytical and simulation approaches has been developed to evaluate the average system throughput. It has been found that the results of the hybrid model are in line with the simulation based results. The benefit of the model is that the throughput of any possible call state in the system can be evaluated. Two empirical path loss models in an indoor-to-outdoor environment of a residential area have been developed based on the measurement data at carrier frequencies 900 MHz and 2 GHz. The models can be used as analytical expressions to estimate the level of interference by a femtocell to a macrocell user in link-level simulations

    Downlink system characterisation in LiFi Attocell networks

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    There is a trend to move the frequency band for wireless transmission to ever higher frequencies in the radio frequency (RF) spectrum to fulfil the exponentially increasing demand in wireless communication capacity. Research work has gone into improving the spectral efficiency of wireless communication system to use the scarce and expensive resources in the most efficient way. However, to make wireless communication future-proof, it is essential to explore ways to transmit wirelessly outside the traditional RF spectrum. The visible light (VL) spectrum bandwidth is 1000 times wider than the entire 300 GHz RF spectrum and is, therefore, a viable alternative. Visible light communication (VLC) enables existing lighting infrastructures to provide not only illumination but also wireless communication. In conjunction with the concept of cell densification, a networked VLC system, light fidelity attocell (LAC) network, has been proposed to offer wide coverage and high speed wireless data transmission. In this study, many issues related to the downlink system in LAC networks have been investigated. When analysing the downlink performance of LAC networks, a large number of random channel samples are required for the empirical calculation of some system metrics, such as the signal-to-interference-plus-noise ratio (SINR). However, using state-of-the-art approaches to calculate the non-line-of-sight (NLoS) channel component leads to significant computational complexity and prolonged computation time. An analytical method has been presented in this thesis to efficiently calculate the NLoS channel impulse response (CIR) in VLC systems. The results show that the proposed method offers significant reduction in computation time compared to the state-of-the-art approaches. A comprehensive performance evaluation of the downlink system of LAC networks is carried out in this thesis. Based on the research results in the literature in the field of optical wireless communication (OWC), a system level framework for the downlink system in LAC networks is developed. By using this framework, the downlink performance subject to a large number of parameters is evaluated. Additionally, the effect of varying network size, cell deployment and key system parameters are investigated. The calculation of downlink SINR statistics, cell data rate and outage probability are considered and analysed. The results show that the downlink performance of LAC networks is promising in terms of achievable data rate per unit area compared to other state-of-the-art RF small-cell networks. It is found that co-channel interference (CCI) is a major source of signal impairment in the downlink of LAC network. In order to mitigate the influence of CCI on signal distortion in LAC networks, widely used interference mitigation techniques for RF cellular systems are borrowed and extensively investigated. In this study, fractional frequency reuse (FFR) is adapted to the downlink of LAC networks. The SINR statistics and the spectral efficiency in LAC downlink system with FFR schemes are evaluated. Results show that the FFR technique can greatly improve the performance of cell edge users and as well the overall spectral efficiency. Further performance improvements can be achieved by incorporating angular diversity transmitters (ADTs) with FFR and coordinated multi-point joint transmission (JT) techniques
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