A 193-nW Wake-Up Receiver Achieving -84.5-dBm Sensitivity For Green Wireless Communications
Abstract : This paper presents a cost-effective, ultra-low-power and highly sensitive wake-up receiver (WuRX) to reduce overall power consumption of Wireless Sensor Networks (WSN). The proposed tuned radio frequency (TRF) receiver (RX) analogue front-end (AFE) incorporates a 400-MHz, low-power, low-noise amplifier (LNA) with a high voltage gain of 50 dB as well as a Gilbert Cell based envelop detector achieving a conversion gain of 224 V-1 to enhance the overall sensitivity of the WuRX. Meanwhile, a duty-cycling technique is used to reduce the power consumption of the WuRX AFE. In addition, a 31-bit correlator is implemented in the WuRX digital back-end (DBE) to further improve the sensitivity of the WuRX by 4 dB. A proof-of-concept WuRX circuit prototype has been fabricated in a low-cost 180-nm CMOS technology. Measurement results show the complete WuRX attains a sensitivity of -84.5 dBm at a wake-up error rate (WER) of 10-3 whilst only consuming 193 nW at the minimum data rate of 64 bps with a carrier frequency of 402 MHz. With the sensitivity unchanged, the data rate of the WuRX can be scaled up from 64 bps to 8.2 kbps. The used 4-time oversampling technique makes the WuRX robust against asynchronization and clock deviation between the TX and RX. The proposed WuRX is a promising solution for energy-efficient rendezvous between wireless sensor nodes, particularly in application scenarios where both low power consumption and high sensitivity are indispensable.
? A survey of existing FM-UWB transceiver implementations provides a glimpse into the practical capabilities of this modulation scheme.
? A wide range of wireless technologies exist that provide a different set of capabilities tailored for different applications.
? Both of these properties are highly important in the IoT and WSN applications, and guarantee that the FM-UWB will find its place among the existing radios.
? An existing degree of freedom in the proposed modulation technique is the sub-channels scaling.
? Potential to parallelize communication through sub-carrier FDMA, on top of existing TDMA could bring both latency and power savings at a network level.
? In general, the 5G networks are expected to provide high data rates in order to deliver diverse set of new services such as ultra-high-definition video streaming or augmented reality to growing number of data-hungry users.
? This problem is severe in unsaturated traffic scenarios, where many of the DRX cycles have eventually no data allocation for a particular mobile device.
? LNA deactivation together with other hardware issues easily lead to substantially reduced WRx sensitivity, compared to the sensitivity requirements of cellular devices.
? In order to further reduce the impact of any possible residual clock drift, the proposed receiver has two-stage mechanism to recover any potential symbol time offset (STO) and carrier frequency offset (CFO).
• A different scheme is proposed in, where the receiver is always duty cycled.
• One advantage of the proposed modification compared to the described multi-user scheme is that a larger number of channels can be used in the same bandwidth.
• The proposed wake-up receivers found in literature consume from 100 µW all the way down to 100 nW.
• The proposed design from to be truly power efficient, the LO generator must consume sufficiently low power.
• However, for the proposed receiver architecture this will never be the case and the amplitude of the second harmonic will depend on offset and demodulator delay.
? The wake-up receiver detection performance is first analysed, through empirical simulations, followed by the system energy saving and latency evaluations where also comparisons to the analytical results are made.
? Such flexibility is particularly interesting in the context of the wake-up scheme, as both the bandwidth and the gain performance can be adapted for the reception of the wake-up signaling.
? We begin by addressing the reliability of the wake-up signal detection at WRx, together with the achievable synchronization performance, with specific emphasis on challenging low-SNR conditions.
? The performances of the developed NM and a DRXenabled reference cellular subsystem are compared, for different values of the w-cycle and the short/long DRX cycle lengths.
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