Zig bee, also known as IEEE 802.15.4 is a pop ular wireless communication standard developed for simple low-power and low-cost wireless applications. One of these applications is local positioning, which consists in inferring the position of a device in real time. In this paper, a new method to precisely measure distance using standard ZigBee devices is presented. The measurement uses only a 2 MHz bandwidth channel and compensate the lack of bandwidth by using an original technique for measuring Time Of Arrival. Simulations show that our method achieves a standard deviation of 33 cm, which is better than other approaches in the same testing conditions. The technique is tested under a real indoor environment, and the results are finally compared with the simulations.

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International audienceIn this paper, we propose a low-power technique, called RF power gating, which consists in varying the active time ratio (ATR) of the RF front end at a symbol time scale. This technique is especially well suited to adapt the power consumption of the receiver to the performance needs without changing its architecture. The effect of this technique on the bit error rate (BER) performances is studied for a basic estimator in the specific case of minimum-shift keying signaling. A system-level energy model is also derived and discussed to estimate precisely the power reduction based on the characteristics and the power consumption of each block. This model allows highlighting the different contributors of the power reduction. The BER results and the energy model are finally merged to determine the best ATR meeting the design constraints. Applying this technique to the IEEE 802.15.4 standard, this paper shows that an ATR of 20% is a good tradeoff to meet the packet error rate constraint while maximizing the energy reduction ratio. Using typical block power consumptions, an energy reduction ratio around 20% can be reached. Even better energy reduction ratios (~60%) are also achievable when most of the blocks are power-gated

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A fast I/Q imbalance compensation algorithm is presented. It is demonstrated through MATLAB simulations that with a few samples an image-to-signal ratio (ISR) lower than −25 dB was achieved. On the basis of digital processing of the received signal, this algorithm is compliant with low-cost and low-complexity wireless receivers because it does not require extra time and resources for calibration. Moreover, its fast convergence allows reaching a high enough image rejection ratio by adapting the compensation weight during the reception of a known preamble such as defined by the IEEE 802.15.4 or the Bluetooth low energy standards.