This paper addresses the issues related with conventional near-far user pairing in non-orthogonal multiple access. Performance effects of near-far pairing on regions with negligible channel gain differences between users are investigated. These regions occur when pairing is performed between cell center and cell edge users, thus leaving the cell mid users to be either paired with each other or kept unpaired. Pairing these mid users with each other causes successive interference cancelation (SIC) performance degradation resulting in capacity reduction for these users. On the other hand, leaving these mid users unpaired perfectly avoids the SIC issue but makes these users unable to benefit from the capacity gains provided by non-orthogonal multiple access. Therefore, two user pairing strategies have been proposed that can provide capacity gains to almost all the users by accommodating them in pairs, while avoiding or minimizing the mid users pairing problem. A generalized M-users pairing scheme is also proposed. Simulations have been performed to investigate the performance of proposed schemes for both perfect and imperfect SIC receiver scenarios in comparison with conventional pairing where the mid users are kept paired with each other. Simulation results show that proposed schemes achieve high capacity gains, especially when imperfect SIC is considered.

Non-orthogonal multiple access (NOMA) is a promising candidate for 5G networks. NOMA achieves superior spectral efficiency than conventional orthogonal multiple access (OMA), as in NOMA multiple users can use the same time and frequency resources. Multiple-Input-multiple-output is a promising technique that can enhance system performance. In this paper we present a multiple antenna based NOMA, known as spatially modulated NOMA. In proposed scheme different users are multiplexed in power domain while cell edge users are multiplexed in spatial domain. The information to cell edge users are conveyed using antenna indices thereby reduces number of decoding steps at NOMA users, cell edge interference reduces as no power is allocated to cell edge users and hence is more energy efficient as compare to conventional NOMA. Simulation results shows that proposed scheme achieves superior spectral efficiency as compare to conventional NOMA.

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Abstract:In this paper, real-time monitoring of multiple lead-acid batteries based on Internet of things is proposed and evaluated. Our proposed system monitors and stores parameters that provide an indication of the lead acid battery's acid level, state of charge, voltage, current, and the remaining charge capacity in a real-time scenario. To monitor these lead-acid battery parameters, we have developed a data acquisition system by building an embedded system, i.e., dedicated hardware and software. The wireless local area network is used as the backbone network. The information collected from all the connected battery clients in the system is analyzed in an asynchronous transmission control protocol/user datagram protocol-based C server program running on a personal computer (server) to determine important parameters like the state of charge of the individual battery, and if required, appropriate action can be taken in advance to prevent excessive impairment to the battery. Further, data are also displayed on an Android mobile device and are stored in an SQL server database. We have developed a real prototype to devise an end product for our proposed system.