In this paper, we seek to address the data gathering in the continually growing Wireless Sensor Networks (WSNs) with the intention to save the nodes' energy. In order to address usual WSN problems, such as data losses, collisions and re-transmissions, a twofold data compression pattern is proposed. We consider that a restricted number of sensor nodes are selected to be active and represent the whole network, while the rest of nodes remain idle and do not participate at all in the data sensing and transmission. Furthermore, the set of active nodes' readings is efficiently reduced, in each time slot, according to the cluster scheduling. Relying on the existing Matrix Completion (MC) techniques, the sink node is unable to recover the entire data matrix due to the existence of completely empty rows that correspond to the inactive nodes, which can be considered as absent nodes for a very long period, or nodes that do not exist at all. Thereby, we propose a complementary interpolation technique, based on a minimization problem that benefits from sensor nodes inter-correlation, to guarantee the reconstruction of all the empty rows, despite their large number. The simulations confirm the efficiency of the proposed approach and show that it outperforms the existing one by up to 70.101% of Normalized Mean Absolute Error on all missed elements, when the number of active nodes is of about 10% of the total number of sensor nodes.

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Precise radio based positioning for low power wide area networks remains a challenging research area due to narrowband signals and multipath propagation. Multi-channel ranging provides improved temporal resolution by coherent processing. While this technique has been applied to short range radio standards, no experimental demonstration for long range radio devices exists. The present paper introduces a hardware testbed for phase coherent multi-channel processing of narrowband signals. Simulations and preliminary experimental multi-channel results show a higher ranging precision (factor 20) over time based ranging. In a frequency flat channel with a 10 kHz signal, precisions down to 10 m (phase based) and 200 m (time based) have been achieved. Precision degrades in multipath propagation scenarios.

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