Energy consumption of wireless networks is now a very important research topic and several research teams worldwide are proposing solutions for the so-called green wireless networks, i.e. energy-efficient wireless networks. Although the increase of this research activity is rather recent, a great number of research papers and collaborative projects exist nowadays. We first summarise the metrics used in the related literature for performance evaluation. Then, we focus on describing the current approaches proposed by reviewing a good number of references from literature. The main research directions are presented: the component level research, where the efforts are mainly concentrated on the power amplifier section; the cell layout adaptation including the cell-breathing technique and coverage extension methods like femtocells and relays; in addition, we also include the radio resource management and the cognitive radio into the studied approaches. These methods are analysed, compared, classified and then a framework of classification and integration is proposed. We finally describe some major collaborative projects dedicated to this topic.

Up to recently, two main approaches were used for connecting the "things" in the growing Internet of Things (IoT)-one based on multi-hop mesh networks, using short-range technologies and unlicensed spectrum, and the other based on long-range cellular network technologies using corresponding licensed frequency bands. New type of connectivity used in Low-Power Wide Area networks (LPWAN), challenges these approaches by using low-rate long-range transmission technologies in unlicensed sub-GHz frequency bands. In this paper, we do performance testing on one such star-topology network, based on Semtech's LoRa TM technology, and deployed in the city of Rennes-LoRa FABIAN. In order to check the quality of service (QoS) that this network can provide, generally and in given conditions, we conducted a set of performance measurements. We performed our tests by generating and then observing the traffic between IoT nodes and LoRa TM IoT stations using our LoRa FABIAN protocol stack. With our experimental setup, we were able to generate traffic very similar to the one that can be used by real application such as sensor monitoring. This let us extract basic performance metrics, such as packet error rate (PER), but also metrics related specifically to the LoRa physical layer, such as the Received Signal Strength Indicator (RSSI) and Signal to Noise ratio (SNR), within various conditions. Our findings provide insight about the performance of LoRa networks, but also about evaluation methods for these type of networks. We gathered measurement data that we make freely available together with the tools we used.

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Abstract-Scheduling algorithms are of utmost importance in WiMAX for efficient use of radio resources. A scheduling algorithm should take into account the WiMAX QoS classes and service requirements. It should also provide high throughput. In this paper, we propose a review of scheduling algorithms proposed for WiMAX. We focus on the real-time Polling Service (rtPS) QoS class. NS-2 simulations show interesting results. We highlight a problem that may exist with the WiMAX rtPS QoS class and we provide solutions for it. Simulation results concerning proposed WiMAX schedulers are discussed. We propose an enhancement of the maximum Signal-to-Interference Ratio (mSIR) scheduler, called modified maximum Signal-to-Interference Ratio (mmSIR). We show through extensive simulations that this enhancement provides better mean sojourn time in addition to an improvement in throughput.