The next wave of wireless technologies is proliferating in connecting things among themselves as well as to humans. In the era of the Internet of things (IoT), billions of sensors, machines, vehicles, drones, and robots will be connected, making the world around us smarter. The IoT will encompass devices that must wirelessly communicate a diverse set of data gathered from the environment for myriad new applications. The ultimate goal is to extract insights from this data and develop solutions that improve quality of life and generate new revenue. Providing large-scale, long-lasting, reliable, and near real-time connectivity is the major challenge in enabling a smart connected world. This paper provides a comprehensive survey on existing and emerging communication solutions for serving IoT applications in the context of cellular, wide-area, as well as non-terrestrial networks. Specifically, wireless technology enhancements for providing IoT access in fifth-generation (5G) and beyond cellular networks, and communication networks over the unlicensed spectrum are presented. Aligned with the main key performance indicators of 5G and beyond 5G networks, we investigate solutions and standards that enable energy efficiency, reliability, low latency, and scalability (connection density) of current and future IoT networks. The solutions include grant-free access and channel coding for short-packet communications, non-orthogonal multiple access, and on-device intelligence. Further, a vision of new paradigm shifts in communication networks in the 2030s is provided, and the integration of the associated new technologies like artificial intelligence, non-terrestrial networks, and new spectra is elaborated. Finally, future research directions toward beyond 5G IoT networks are pointed out.

Cellular, Wide-Area, and Non-Terrestrial IoT: A Survey on 5G Advances and the Road Towards 6G.

This paper presents an 802.11g/n compliant wake-up radio solution that consists of an innovative on–off keying (OOK) emulating orthogonal frequency division multiplexing (OFDM) modulation scheme, and a fully integrated, highly scaled, ultra-low power wake-up receiver design in 14-nm FinFET CMOS technology requiring only a 32-kHz real-time clock reference. The receiver achieves −72-dBm sensitivity and +20 dBr adjacent channel interference (ACI) rejection at 10−3 bit error rate (BER) while consuming $95~\mu \text{W}$ . This receiver can be utilized along with any legacy Wi-Fi transmitter without changing any hardware.

802.11g/n Compliant Fully Integrated Wake-Up Receiver With −72-dBm Sensitivity in 14-nm FinFET CMOS

This article presents an 802.11ba-based wake-up radio (WUR) receiver that is fully integrated within an 802.11a/b/g/n/ac Wi-Fi transceiver. Low-cost integration is achieved with the WUR only occupying 0.13 mm2 while not adding any additional overhead to the Wi-Fi platform. The WUR consumes 667 $\mu \text{W}$ from 1.1-V Wi-Fi system supply. When measured from internal 0.6- and 0.9-V supplies, the receiver consumes 495 $\mu \text{W}$ . The receiver has a measured sensitivity of −92.6 dBm and can tolerate −40.5-dBm Wi-Fi adjacent channel blocker with 3-dB receiver de-sensitization. The WUR and Wi-Fi system co-operation is also demonstrated. The WUR receiver can operate when the Wi-Fi system is in sleep mode and can turn on Wi-Fi radio upon receiving 802.11ba-based wake-up packet.

An 802.11ba-Based Wake-Up Radio Receiver With Wi-Fi Transceiver Integration

Efficient wireless connectivity is an important requirement for IoT applications and has attracted a lot of research interest recently. The receivers designed for such applications need to be low power while still supporting sufficient communication range and co-existing with other receivers that share the same frequency band. In addition, supporting adopted communication standards is key for ubiquitous integration with the existing infrastructure. This paper presents a review of the recent design trends and techniques in ultra-low power receivers for IoT applications.

Ultra-Low Power Receivers for IoT Applications: A Review

A standalone, fully integrated 0.2V 578µW ultra-low voltage (ULV) 2.4GHz 802.11ba WiFi wake-up receiver (WRX) is presented. It includes a current-efficient ULV noise cancelling LNA with a high turn step-up transformer, and Q-enhanced RF gain stages for low noise figure. A 1/3 f RF mixer and ULV FLL are implemented to reduce current. The chip includes micro-power managers for regulating all internal voltages from a single 0.2V supply. Fabricated in 40nm CMOS, the ULV WRX achieves -91.5dBm sensitivity at 10-3 BER and data-rate of 62.5kbps, while rejecting a 45dB adjacent blocker with only 0.2V supply. The WRX includes an energy-efficient 5ms startup sequence which interfaces to an external node controller over serial peripheral interface (SPI).

A Fully Integrated 0.2V 802.11ba Wake-Up Receiver with -91.5dBm Sensitivity

An ULP back-channel receiver is presented that demodulates binary a FSK back-channel signal embedded in 5.8GHz IEEE 802.11a Wi-Fi OFDM packets. The architecture of the back-channel receiver employs a two-step down-conversion where the first mixing stage downconverts using the 3rd harmonic of the LO for power efficiency. The LP-65nm CMOS receiver consumes 335µW with a sensitivity of −72dBm at a BER of 10−3 and data-rate of 31.25kb/s. The radio uses a balun and a 250kHz reference crystal as external components. The receiver uses a 1V supply voltage for analog blocks, and 0.85V for digital blocks including the LO and FLL.

A 335µW −72dBm receiver for FSK back-channel embedded in 5.8GHz Wi-Fi OFDM packets

A 40-nm CMOS IEEE 802.11ba low-power wake-up receiver (LP-WUR) is presented. It receives 802.11ba messages generated by an 802.11 orthogonal frequency-division multiplexing (OFDM) transmitter operating at 5.8 GHz. The power consumption of the RF front-end is minimized by removing active RF gain stages and using a third harmonic passive mixer with a ring-based local oscillator (LO) operating at one-third of the RF frequency. The noise figure is 14 dB, taking advantage of a 1:3 transformer that provides passive voltage gain in front of the high switch loss mixer-first RF front-end, and matching across 5.5–5.8 GHz with $S_{11}$ . The receiver achieves a sensitivity of −83-dBm and −20-dB adjacent channel signal-to-interference ratio (SIR) while consuming $220~\mu \text{W}$ at a bit error rate (BER) of $10^{-3}$ and data rate of 62.5 kb/s, which shows the best sensitivity-power tradeoff among >3-GHz receivers.

A 220- $\mu$ W −83-dBm 5.8-GHz Third-Harmonic Passive Mixer-First LP-WUR for IEEE 802.11ba

An IEEE 802.11 WiFi LP-WUR receiver in 40nm CMOS technology is presented. The direct down-conversion receiver improves sensitivity by allocating single sidebands above the flicker noise corner for received signals. The receiver demodulates wideband FSK/OOK modulated wake-up messages generated by an 802.11 OFDM WiFi transmitter operating at 5.8GHz. The receiver achieves a sensitivity of −92.5dBm while consuming 470µW in OOK demodulation, and sensitivity of −90dBm while consuming 490µW in FSK demodulation at a BER of 10−3 and data-rate of 62.5kb/s. The radio uses an external clock as external component for baseband demodulation, and frequency calibration.

Jaeho Im

Papers

Ultra-Low Power Receivers for IoT Applications: A Review

A Fully Integrated 0.2V 802.11ba Wake-Up Receiver with -91.5dBm Sensitivity

A 335µW −72dBm receiver for FSK back-channel embedded in 5.8GHz Wi-Fi OFDM packets

A 220- $\mu$ W −83-dBm 5.8-GHz Third-Harmonic Passive Mixer-First LP-WUR for IEEE 802.11ba

A 470µW −92.5dBm OOK/FSK Receiver for IEEE 802.11 WiFi LP-WUR