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This paper investigates low-complexity approaches to small-cell base-station (SBS) design, suitable for future 5G millimeter-wave (mmWave) indoor deployments. Using large-scale antenna systems and high-bandwidth spectrum, such SBS can theoretically achieve the anticipated future data bandwidth demand of 10 000 fold in the next 20 years. We look to exploit small cell distances to simplify SBS design, particularly considering dense indoor installations. We compare theoretical results, based on a link budget analysis, with the system simulation of a densely deployed indoor network using appropriate mmWave channel propagation conditions. The frequency diverse bands of 28 and 72 GHz of the mmWave spectrum are assumed in the analysis. We investigate the performance of low-complexity approaches using a minimal number of antennas at the base station and the user equipment. Using the appropriate power consumption models and the state-of-the-art sub-component power usage, we determine the total power consumption and the energy efficiency of such systems. With mmWave being typified nonline-of-sight communication, we further investigate and propose the use of direct sequence spread spectrum as a means to overcome this, and discuss the use of multipath detection and combining as a suitable mechanism to maximize link reliability.

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With the ever increasing demand for wireless broadband, design of energy efficient systems is paramount. Femtocells, small self installable wireless base stations, are currently being deployed as a solution to the coverage problems faced by mobile operators, particularly in indoor environments. This paper outlines the framework for evaluating the performance of multiple antenna transmit diversity techniques, based on the Alamouti scheme, relevant to minimizing femtocell transmission power. Simulation results for experiments run on appropriate femtocell channel models are provided. The presented material is given in the context of current third generation systems based on the W-CDMA air interface, however the techniques presented can be extended to future OFDM based systems. Appropriate green solutions need to consider issues of implementation complexity and embodiment which are also discussed

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