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Tightly synchronizing transmissions of the same packet from different sources theoretically results in constructive interference. Exploiting this property potentially speeds up network-wide packet propagation with minimal latencies. Our empirical results suggest the timing constraints can be relaxed in the real world, especially for radios using lower frequencies such as the IEEE 802.15.4 radios at 900 MHz. Based on these observations we propose PEASST, a topology-free protocol that leverages synchronized transmissions to lower the cost of end-toend data transfers, and enables multiple traffic flows. In addition, PEASST integrates a receiver-initiated duty-cycling mechanism to further reduce node energy consumption. Results from both our Matlab-based simulations and indoor testbed reveal that PEASST can achieve a packet delivery latency matching the current state-of-the-art schemes that also leverages synchronized transmissions. In addition, PEASST reduces the radio dutycycling by three-fold. Furthermore, comparisons with a multihop routing protocol shows that PEASST effectively reduces the per-packet control overhead. This translates to a ⇠10% higher packet delivery performance with a duty cycle of less than half.978-1-4799-4657-0/14/$31.00

Many low-power wireless network system deployments are planned on a two-dimensional plane, while in reality, we live in a three-dimensional space. Therefore, although it is essential to well consider the impact of height on the overall wireless system performance, this aspect has often been overlooked if not neglected with simplifying assumptions. Our work takes an empirical effort in quantifying the impact of height on a low-power wireless system's performance. Specifically, we use CC2420 radio-based wireless sensor network motes to quantify the impact of device deployment height on the connectivity and energy efficiency of low-power wireless networks. In addition, to validate the newly proposed sub-GHz low-power radios, we also experiment on the performance of CC1200 narrowband low-power radios to show that increasing a small amount of height in the node deployment phase can lead to drastic improvements in radio coverage and packet delivery performance. Such an observation can naturally lead to the reduction of network depth in a multihop wireless network for a given target deployment field; thus, it can potentially improve the energy efficiency of the overall system by suppressing the number of packet relay transmissions. We support our findings and observations through experiments on real embedded devices.

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There were the attempts to prevent the spread of harmful materials of the agri-food through the record tracking of the products with the bar code, the partial information tracking of the agri-food storage and the delivery vehicle, or the control of the temperature by intuition. However, there were many problems in the attempts because of the insufficient information, the information distortion and the independent information network of each distribution company. As a result, it is difficult to prevent the spread over the life-cycle of the agri-food using the attempts. To solve the problems, we propose the mechanism mainly to do context awareness, predict, and track the harmful materials of agri-food using big data processing.