Mobile Network Operators (MNOs) are integrating carrier-grade Wireless Local Area Network (WLAN) to cellular networks to improve network performance and user experience. Access network selection (ANS) between cellular and WLAN plays a key role in the integration. Given the complexity of heterogeneous networks characterized by multiple network layer deployments and inhomogeneous traffic distribution, the ANS has to automatically adapt to dynamic network conditions. In this article, we present and evaluate a Self-Organizing Network (SON) algorithm for tuning the ANS between the Long Term Evolution (LTE) and WLAN systems. The proposed SON algorithm adopts a WLAN received signal strength (RSS) threshold to control the access selection. The RSS threshold is updated by the SON algorithm based on periodically monitored load in the LTE and WLAN systems. The SON algorithm is evaluated by simulations in realistic heterogeneous network scenarios and proved effective in improving user experience.

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In Massive MIMO, the pilot contamination effect reduces the spectral efficiency (SE) gains and Superimposed pilot (SP) transmission has been proposed to mitigate this effect. SP is based on transmitting pilot and data symbols simultaneously to allow for longer pilots and no pilot overhead. This work studies the optimal power control strategies in the uplink of a Massive MIMO system with SP and detection based on maximum ratio combining. The optimization objectives are maximum product of SINRs and max-min fairness, and these problems are reformulated as geometric programs which allow for efficient implementations. The numerical results indicate that the SE gains from the optimal power control with respect to the heuristic statistical channel inversion power control, are more significant when the interference from pilot symbols is subtracted before data detection.

Many positioning systems rely on accurate time of arrival measurements. In this paper, we address not only the accuracy but also the relevance of Time of Arrival (TOA) measurement error modeling. We discuss how better knowledge of these errors can improve relative distance estimation, and compare the impact of differently detailed measurement error information. These models are compared in simulations based on models derived from an Ultra Wideband (UWB) measurement campaign. The conclusion is that significant improvements can be made without providing detailed received signal information but with a generic and relevant measurement error model.978-1-5386-3531-5/17/$31.00

The world's largest and most widespread cellular technology today is GSM/EDGE. EDGE is capable of offering an attractive solution for 3 rd generation cellular services in existing GSM networks. However, the introduction of new and more delay sensitive services may require improved latency performance. Reducing the delay and increasing the bandwidth efficiency in EDGE systems is important for services with stringent latency requirements, such as conversational VoIP, but will be beneficial also to other services. Proposed is to reduce the transmission time interval from 20ms to 10ms, in combination with novel procedures for faster feedback. Simulation results show that LLC delays may be reduced by 20-40% depending on traffic scenario. Furthermore, channel resource requirements for VoIP could be substantially reduced.