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Device-to-device (D2D) communications are widely seen as an efficient network capacity scaling technology. The co-existence of D2D with conventional cellular (CC) transmissions causes unwanted interference. Existing techniques have focused on improving the throughput of D2D communications by optimising the radio-resource management and power allocation. However, very little is understood about the impact of the route selection of the users and how optimal routing can reduce interference and improve the overall network capacity. In fact, traditional wisdom indicates that minimising the number of hops or the total path distance is preferable. Yet, when interference is considered, the authors show that this is not the case. In this study, they show that by understanding the location of the user an interference-aware-routing (IAR) algorithm can be devised. They propose an adaptive IAR algorithm that on average achieves a 30% increase in hop distance, but can improve the overall network capacity by 50% whilst only incurring a minor 2% degradation to the CC capacity. The analysis framework and the results open up new avenues of research in location-dependent optimisation in wireless systems, which is particularly important for increasingly dense and semantic-aware deployments. [ABSTRACT FROM AUTHOR]

Energy-efficient wireless communication is important for wireless devices with a limited battery life and cannot be recharged. In this study, a bit allocation algorithm to minimise the total energy consumption for transmitting a bit successfully is proposed for a two-way orthogonal frequency-division multiplexing relay system, whilst considering the constraints of quality-of-service and total transmit power. Unlike existing bit allocation schemes, which maximise the energy efficiency (EE) by measuring 'bits-per-Joule' with fixed bidirectional total bit rates constraint and no power limitation, their scheme adapts the bidirectional total bit rates and their allocation on each subcarrier with a total transmit power constraint. To do so, they propose an idea to decompose the optimisation problem. The problem is solved in two general steps. The first step allocates the bit rates on each subcarrier when the total bit rate of each user is fixed. In the second step, the Lagrangian multipliers are used as the optimisation variants, and the dimension of the variant optimisation is reduced from 2N to 2, where N is the number of subcarriers. They also prove that the optimal point is on the bounds of the feasible region, thus the optimal solution could be searched through the bounds. [ABSTRACT FROM AUTHOR]

Mobile phone usage has changed significantly over the past few years and smartphone data usage is still not well understood on a statistically significant scale. This Letter analyses 2.1 million smartphone usage data values and explore the current wireless downlink-uplink demand asymmetry for different time periods and across different radio access networks. The current data demand over 2G networks remains largely symmetric with strong temporal variations, whereas the demand over 3G networks is asymmetric with surprisingly weak temporal variations is shown here. [ABSTRACT FROM AUTHOR]

A molecular communication system operating in a pipe propagation channel with no induced flow is considered. Experimentally, it is shown that discrepancies in channel impulse response can be accurately modelled by an additive noise model. The noise amplitude is Nakagami distributed, and the shape and spread parameters of the distribution increase monotonically with propagation distance. Furthermore, demonstrated how the proposed noise model can be used to calculate the bit-error-rate and the capacity of a binary symmetric channel. [ABSTRACT FROM AUTHOR]