Wideband Self-Interference Cancellation based on RF Frequency-Domain Equalization
Full-duplex (FD) wireless -- simultaneous transmission and reception at the same frequency -- has the potential to significantly improve wireless network performance. However, the biggest challenge associated with FD wireless is the tremendous amount of self-interference (SI) right on top of the desired signal. Self-interference cancellation (SIC) in the RF domain is critical for full-duplex radios as it protects the RF front-end. One of the fundamental challenges associated with RF SIC is to achieve cancellation across a wide bandwidth (BW). The achievable SIC BW is typically limited by the frequency selectivity of the antenna interface.
Our work presented at ISSCC 2015 and in JSSC introduces the concept of frequency-domain equalization (FDE) at RF, a technique and functionality that is traditionally implemented in the digital domain. Specifically, multiple widely-tunable N-path-filter-based bandpass filters (BPFs) are introduced in the RF canceller. A second-order BPF combined with amplitude and phase scaling features four degrees of freedom. This can be leveraged for the replication of not just the amplitude and phase responses of the antenna isolation at a frequency point, but also the slope of the amplitude and the slope of the phase (i.e. group delay), enhancing cancellation bandwidth. A bank of such filters with independently controllable parameters enables such replication at multiple points in different sub-bands (essentially FDE in the RF domain), further enhancing cancellation bandwidth. The FDE-based RF SIC improves the cancellation BW by nearly ten times, enabling FD operation in advanced wireless systems with tens of megahertz of signal BW.
Our work presented at ISSCC 2015 and in JSSC introduces the concept of frequency-domain equalization (FDE) at RF, a technique and functionality that is traditionally implemented in the digital domain. Specifically, multiple widely-tunable N-path-filter-based bandpass filters (BPFs) are introduced in the RF canceller. A second-order BPF combined with amplitude and phase scaling features four degrees of freedom. This can be leveraged for the replication of not just the amplitude and phase responses of the antenna isolation at a frequency point, but also the slope of the amplitude and the slope of the phase (i.e. group delay), enhancing cancellation bandwidth. A bank of such filters with independently controllable parameters enables such replication at multiple points in different sub-bands (essentially FDE in the RF domain), further enhancing cancellation bandwidth. The FDE-based RF SIC improves the cancellation BW by nearly ten times, enabling FD operation in advanced wireless systems with tens of megahertz of signal BW.
- Selected Publications:
- Jin Zhou, Tsung-Hao Chuang, Tolga Dinc and Harish Krishnaswamy, "Reconfigurable receiver with >20MHz bandwidth self-interference cancellation suitable for FDD, co-existence and full-duplex applications," in the 2015 IEEE International Solid-State Circuits Conference (ISSCC) Digest of Technical Papers, pp. 283-286, February 2015.
- Jin Zhou, Tsung-Hao Chuang, Tolga Dinc and Harish Krishnaswamy, "Integrated Reconfigurable Wideband Cancellation of Transmitter Self-Interference in the RF Domain for FDD and Full- Duplex Wireless," (invited) IEEE Journal of Solid State Circuits (JSSC), vol. 50, no. 12, pp. 3015 - 3031, December 2015.
Cross-Layer Analysis and Design of Full-Duplex Networks: From Circuits to MAC Layer
To fully utilize the benefits of full-duplex (FD) communication, wireless systems will require a careful redesign of both the physical layer and the medium access control (MAC) layer. This collaborative project is aimed at addressing this highly interdisciplinary challenge. As a first step, we generalized the SI cancellation results from our SI-cancelling RFIC receivers, obtaining a realistic physical model for a small form-factor (e.g. smartphone) FD radio. Based on this model, the work in ACM 2015 SIGMETRICS characterized the rate gains in different scenarios and solved power allocation and channel allocation problems, making one of the first steps towards a practical FD wireless network. This collaboration has evolved into a multi-PI collaborative project at Columbia University called the Columbia FlexICoN project.
- Selected Publications:
- Jin Zhou, Negar Reiskarimian, Jelena Marasevic, Tolga Dinc, Tingjun Chen, Gil Zussman, and Harish Krishnaswamy, "Integrated Full Duplex Radios," (invited) to appear in IEEE Communication Magazine.
- Jelena Marasevic, Jin Zhou, Harish Krishnaswamy, Yuan Zhong and Gil Zussman, "Resource Allocation and Rate Gains in Practical Full-Duplex Systems," in Proceedings of the 2015 ACM (Association for Computing Machinery) SIGMETRICS, June 2015 (one of 32 papers accepted out of 239 submissions to be part of the full program, or an acceptance rate of 13%).
- Selected Press: Columbia Engineering
Reconfigurable Wireless Receivers with Low-Noise Active Transmitter Self-Interference Cancellation for Multi-Band Frequency-Division Duplexing (FDD) Applications
Multiband FDD operation requires numerous fixed-frequency duplexers, which limit form factor. Widely-tunable RF active self-interference cancellation (SIC) allows duplexers to have relaxed TX-RX isolation requirement, making tunable low-loss duplexers a viable solution. However, the fundamental challenge associated with reconfigurable active SIC is the degradation of receiver performance due to the noise and distortion of the active canceller, particularly when designed to handle powerful self-interference (SI) and performed at the receiver input.
Our work reported at ISSCC 2014 and in JSSC breaks the trade-off between the amount of SI that can be cancelled and the noise and distortion introduced by the SI canceller. This is achieved through the insight that a canceller that is integrated with the receiver on the RFIC can be co-designed with the receiver . Specifically, this co-design is accomplished by embedding active RF SIC in a noise-cancelling low-noise transconductance amplifier so that the noise and the distortion of the cancellation circuitry are cancelled along with SI, resulting in a noise-cancelling, self-interference-cancelling receiver.
Our work reported at ISSCC 2014 and in JSSC breaks the trade-off between the amount of SI that can be cancelled and the noise and distortion introduced by the SI canceller. This is achieved through the insight that a canceller that is integrated with the receiver on the RFIC can be co-designed with the receiver . Specifically, this co-design is accomplished by embedding active RF SIC in a noise-cancelling low-noise transconductance amplifier so that the noise and the distortion of the cancellation circuitry are cancelled along with SI, resulting in a noise-cancelling, self-interference-cancelling receiver.
- Selected Publications:
- Jin Zhou, Peter R. Kinget and Harish Krishnaswamy, "A Blocker-Resilient Wideband Receiver with Low-Noise Active Two-Point Cancellation of >0dBm TX Leakage and TX Noise in RX Band for FDD/Co-Existence," in 2014 IEEE International Solid-State Circuits Conference (ISSCC) Digest of Technical Papers, pp. 352 – 353, Feb. 2014.
- Jin Zhou, Anandaroop Chakrabarti, Peter R. Kinget, Harish Krishnaswamy, "Low-Noise Active Cancellation of Transmitter Leakage and Transmitter Noise in Broadband Wireless Receivers for FDD/Co-Existence," (invited) IEEE Journal of Solid State Circuits (JSSC), vol. 49, no. 12, pp. 3046-3062, Dec. 2014.
- Mohammad Abu Khater, Jin Zhou, Yu-Chen Wu, Harish Krishnaswamy and Dimitrios Peroulis, “A Tunable 0.86–1.03 GHz FDD Wireless Communication System With an Evanescent-Mode Diplexer and a Self-Interference-Cancelling Receiver,” accepted and to appear in the 2017 IEEE International Microwave Symposium (IMS).
Frequency Synthesizers Using Coupled Oscillators for Software-Defined Radios
- Selected Publications:
- Jin Zhou, Wei Li, Deping Huang, Ning Li, Junyan Ren and Jinghong Chen, "A 0.4-to-6-GHz Frequency Synthesizer Using Dual-Mode VCO for Software-Defined Radio," IEEE Transactions on Microwave Theory and Techniques (TMTT), vol. 61, no. 2, pp. 848-859, Feb. 2013.
- Deping Huang, Wei Li, Jin Zhou, Ning Li, Junyan Ren and Jinghong Chen, "A Frequency Synthesizer with Optimally Coupled QVCO and Harmonic-rejection Mixer for Multi-standard Wireless Receiver," IEEE Journal of Solid State Circuits (JSSC), vol. 46, no. 6, pp. 1307-1320, Jun. 2011.