Abstract-Low Power Wide Area (LPWA) networks are attracting a lot of attention primarily because of their ability to offer affordable connectivity to the low-power devices distributed over very large geographical areas. In realizing the vision of the Internet of Things (IoT), LPWA technologies complement and sometimes supersede the conventional cellular and short range wireless technologies in performance for various emerging smart city and machine-to-machine (M2M) applications. This review paper presents the design goals and the techniques, which different LPWA technologies exploit to offer wide-area coverage to lowpower devices at the expense of low data rates. We survey several emerging LPWA technologies and the standardization activities carried out by different standards development organizations (e.g., IEEE, IETF, 3GPP, ETSI) as well as the industrial consortia built around individual LPWA technologies (e.g., LORa™ Alliance, WEIGHTLESS-SIG, and DASH7 Alliance). We further note that LPWA technologies adopt similar approaches, thus sharing similar limitations and challenges. This paper expands on these research challenges and identifies potential directions to address them. While the proprietary LPWA technologies are already hitting the market with large nationwide roll-outs, this paper encourages an active engagement of the research community in solving problems that will shape the connectivity of tens of billions of devices in the next decade.

Abstract-Optimization of energy consumption in future intelligent energy networks (or Smart Grids) will be based on grid-integrated near-real-time communications between various grid elements in generation, transmission, distribution and loads. This paper discusses some of the challenges and opportunities of communications research in the areas of smart grid and smart metering. In particular, we focus on some of the key communications challenges for realizing interoperable and futureproof smart grid/metering networks, smart grid security and privacy, and how some of the existing networking technologies can be applied to energy management. Finally, we also discuss the coordinated standardization efforts in Europe to harmonize communications standards and protocols.

We propose a novel multiplier architecture with tunable error characteristics, that leverages a modified inaccurate 2x2 building block. Our inaccurate multipliers achieve an average power saving of 31.78% − 45.4% over corresponding accurate multiplier designs, for an average error of 1.39% − 3.32%. Using image filtering and JPEG compression as sample applications we show that our architecture can achieve 2X -8X better Signal-Noise-Ratio (SNR) for the same power savings when compared to recent voltage over-scaling based power-error tradeoff methods. We project the multiplier power savings to bigger designs highlighting the fact that the benefits are strongly designdependent. We compare this circuit-centric approach to powerquality tradeoffs with a pure software adaptation approach for a JPEG example. We also enhance the design to allow for correct operation of the multiplier using a residual adder, for non errorresilient applications.

The need for low power, long range and low cost connectivity to meet the requirements of IoT applications has led to the emergence of Low Power Wide Area (LPWA) networking technologies. The promise of these technologies to wirelessly connect massive numbers of geographically dispersed devices at a low cost continues to attract a great deal of attention in the academic and commercial communities. Several rollouts are already underway even though the performance of these technologies is yet to be fully understood. In light of these developments, tools to carry out 'what-if analyses' and predeployment studies are needed to understand the implications of choices that are made at design time. While there are several promising technologies in the LPWA space, this paper specifically focuses on the LoRa/LoRaWAN technology. In particular, we present LoRaWANSim, a simulator which extends the LoRaSim tool to add support for the LoRaWAN MAC protocol, which employs bidirectional communication. This is a salient feature not available in any other LoRa simulator. Subsequently, we provide vital insights into the performance of LoRaWAN based networks through extensive simulations. In particular, we show that the achievable network capacity reported in earlier studies is quite optimistic. The introduction of downlink traffic can have a significant impact on the uplink throughput. The number of transmit attempts recommended in the LoRaWAN specification may not always be the best choice. We also highlight the energy consumption versus reliability trade-offs associated with the choice of number of retransmission attempts.

Certain classes of applications are inherently capable of absorbing some error in computation, which allows for quality to be traded off for power. Such a tradeoff is often achieved through voltage over-scaling. We propose a novel multiplier architecture with tunable error characteristics, that leverages a modified inaccurate 2x2 multiplier as its building block. Our inaccurate multipliers achieve an average power saving of 31.78% − 45.4% over corresponding accurate multiplier designs, for an average error of 1.39% − 3.32%. We compare our architecture with other approaches, such as voltage scaling, for introducing error in a multiplier. Using image filtering and JPEG compression as sample applications we show that our architecture can achieve 2X-8X better Signal-Noise-Ratio (SNR) for the same power savings when compared to recent voltage over-scaling based power-error tradeoff methods. We project the multiplier power savings to bigger designs highlighting the fact that the benefits are strongly design-dependent. We compare this circuit-centric approach to power-quality tradeoffs with a pure software adaptation approach for a JPEG example. Unlike recent design-for-error approaches for arithmetic logic, we also enhance the design to allow for correct operation of the multiplier using a correction unit, for non error-resilient applications which share the hardware resource.