1. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. Kari Rikkinen, University of Oulu Pre-FIA Workshop 17 March 2014, Athens A new full-duplex radio transmission paradigm

2. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. Contents Introduction FD transceiver FD system Summary References 2

3. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. Why Full-Duplex ? Full-duplex (FD) radio transmission paradigm = the same carrier frequency is simultaneously used both for transmission and reception at the wireless transceiver. FD transmission can provide significant improvements to wireless communications systems operation increased link capacity flexibility in spectrum usage improved security in transmission efficient solutions for channel access (e.g., for cognitive radio) Lot of activity and progress in full-duplex research during past two-three years to develop transceiver solutions and applications for FD FD is a potential technology component for 5G networks, but could even be applied earlier into the evolution path of 4G and WLAN systems FD has already been proposed to IEEE 802.11 standardization 3

4. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. DUPLO project DUPLO: Full-Duplex Radios for Local Access EU FP7 ICT project (STREP) Duration: November 2012 – April 2015 Partners: University of Oulu (coordinator), IMEC, TTI, Thales, University of Surrey, University of Twente Main objectives Full-duplex technology development for wireless communications transceivers RF, antenna and digital baseband solutions enabling efficient self- interference cancellation in wireless transceiver System solutions for full-duplex transmission focus in small area radio communication solutions potential use cases, performance analysis, network level solutions Proof-of-concept verification 4

5. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. FD transceiver implementation challenge – self-interference Self-interference in the FD transceiver The self-interference is caused by multiple mechanisms direct crosstalk between TX and RX paths in the transceiver limited antenna isolation transmit signal reflections from the objects close to the FD transceiver How much self-interference suppression is needed ? In general, self-interference level in the receiver should be reduced to noise floor to get full benefit out from full-duplex transmission. The amount of self-interference cancellation (SIC) in total (isolation + cancellation) depends on system operation assumptions, example budget: 5 o PTX: +10 dBm o 10 MHz bandwidth and 15 dB NF  RX noise floor at -89 dBm/10 MHz  99 dB of self-interference cancellation in total (isolation + cancellation) needed

6. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. Measurement set-up wideband channel measurement (measurement bw 7 GHz) test transceiver with separate TX and Rx antennas (antenna separation 30 cm) different measurement locations anechoic chamber, lab environment (with/without strong reflectors close to the transceiver), office environment 6 Self-interference channel characteristics a) Antenna orientations b) c) d) Measurement results  SI channel is a multipath channel [1] [1] A.Sethi, V.Tapio, M.Juntti,”Self-interference Channel for Full Duplex Transceivers”, To appear in IEEE WCNC2014, Istanbul, Turkey.

7. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. FD transceiver structure Three main means to reduce self-interference at the FD transceiver Antenna(s) isolation of the transmit signal from the receiver chain at the antenna level e.g., use of separate TX and RX antennas, use of different polarizations for TX and RX, use of MIMO techniques Analog RF (or baseband) cancellation subtraction of self-interference at RX analog path Digital baseband cancellation removal of remaining self-interference at digital baseband transceiver chain impairments (e.g., PA nonlinearity and phase noise in oscillators) should be included in the SI channel model for the optimum performance Combination of these techniques is needed to achieve good self-interference cancellation capability. 7 Block diagram of full-duplex transceiver

8. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. FD transceiver solutions ReferenceSolutionSIC performance Stanford [3] (2011) Separate TX and RX antennas (20cm distance) RF cancellation with balun circuit Digital BB interference cancellation RF (balun) cancellation 43 dB Digital BB cancellation 30 dB (digital + balun) 73 dB + additional 40 dB from antenna separation (estimate) (measurement bandwidth: 10 MHz, in 2.4 GHz band) Rice [5] (2012) Separate TX and RX antennas (20cm distance) RF cancellation with additional RF chain Digital BB interference cancellation Antenna separation (AS) 41 dB AS + RF + Digital BB 78 dB (measurement bandwidth: 625 kHz, in 2.4 GHz band) Rice [6] (2012) Separate TX and RX antennas (50 cm distance, with 90 o beamwidth and different tilting), optional use of cross- polarized antennas Active RF and BB cancellation Antenna only w/o cross-pol. 60 dB Antenna only with cross-pol. 70 dB Antenna (w/o cross-pol.)+ RF + BB 86 dB Antenna (with cross-pol.)+ RF + BB 95 dB (measurement bandwidth: 20 MHz, in 2.4 GHz band) NYU [7] (2012) Circularly polarized patch antenna + balanced feed network (single antenna solution) Active RF interference cancellation No digital BB (in the analysis) Antenna & balanced feed network 40-45 dB Antenna/feed network + RF canceller 59 dB (measurement bandwidth: 8 MHz, in 914 MHz band) Stanford [4] (2013) Single antenna + circulator Adaptive analog RF canceller Digital BB interference cancellation Circulator + analog cancellation 62 dB Digital BB cancellation 48 dB Total 110 dB (measurement bandwidth: 80 MHz, in 2.4 GHz band) 8  90-110 dB total SIC cancellation capability is achievable Different FD transceiver solutions and their reported performance

9. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. To enable wide application areas for the full-duplex technology in the evolved 4G/WLAN and 5G systems, the FD transceiver solutions need to be implementable for small form factor radio devices, e.g., femto-cell nodes, tablets, smart phones, or sensor nodes (’extremely’ small form factor) Two different analog/RF solution approaches selected for the DUPLO compact FD transceiver design,i.e., 9 Potential analog/RF solutions for compact FD transceivers 1.Dual-polarized antenna with active RF canceller use of different polarizations for TX and RX signals pacth antenna structure (prototype dimensions 60 x 60 x 8 mm) isolation > 50 dB (simulated, in 10 MHz bw) low antenna loss additional 10 dB cancellation with active RF canceller potential solution for femto-cell nodes, laptops etc 2.Electrical balance duplexer use of electrical balance circuit to isolate TX and RX enables very small size implementation into CMOS (≈ 1 mm 2 ) can be combined with miniature antenna isolation ≈ 50 dB (simulated, in 6 MHz bw) duplexer insertion loss (3 dB) potential solution for smartphones, sensor nodes etc [9] B.Debaillie, D.J. van den Broek, C.Lavin, B. van Liempd, E.A.M. Klumperink, C. Palacios, J. Craninckx, B. Nauta, A. Pärssinen ”Analog/RF Solutions Enabling Compact Full-Duplex Radios”, accepted to IEEE JSAC Special Issue on Full-duplex Wireless Communications and Networks, 2014.

10. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. Use of FD transmission paradigm in wireless systems Potential applications of full-duplex transmission technology in wireless systems include M2M communications, D2D connections, relays, backhaul connections, terminal to access point connections, mesh network solutions, etc. Most straightforward application for FD transmission is a single (isolated) point- to-point link Applying FD transmission to legacy systems may require modifications to scheduling and radio resource management solutions due to additional interference paths FD introduces to system operation inter-user interference inter-cell interference (in multicell scenario) 10 Example of a small cell with a full-duplex BS and half-duplex UEs (Blue and red arrows denote different radio resources) Example of two neighboring small cells with full-duplex BS and UEs A point-to-point full-duplex link

11. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. Summary The main challenges with full-duplex transmission are related to transceiver design and system solutions. State-of-the-art results indicate that it is possible to achieve 90-110 dB total self- interference cancellation capability (at least with experimental demonstrator, by now). To enable wide application areas for the full-duplex technology in the evolved 4G/WLAN and 5G systems, the FD transceiver solutions need to be implementable for small form factor radio devices. System level studies are needed to clarify what is the total impact of full-duplex transmission to wireless system performance and how to manage with additional interferences (inter-node, inter-cell interference). DUPLO project is working with FD transceiver design and system level simulations and analysis aiming for solutions applicable to evolved 4G/WLAN and 5G systems. 11

12. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. 12 DUPLO Workshop on Full-Duplex Radios and Systems June 4, 2014 Oulu, Finland http://duploworkshop.crowncom.org/2014/show/home (Attached to CrownCom 2014 conference, June 2–4, 2014 Oulu, Finland)

13. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. 13 THANK YOU

14. © 2012 DUPLO - full-DUPlex radios for LOcal access. All rights reserved. References [1] A.Sethi, V.Tapio, M.Juntti,”Self-interference Channel for Full Duplex Transceivers”, To appear in IEEE WCNC2014, Istanbul, Turkey. [2] W.Li, J.Lilleberg,”On Full-Duplex Link Performance Under Consideration of Error Vector Magnitude”, To appear in IEEE WCNC2014, Istanbul, Turkey. [3] J. Choi, T. Kim, D. Bharadia, S. Seth, K. Srinivasan, P. Levis, S. Katti, P. Sinha, "Practical, Real-time, Full Duplex Wireless," International Conference on Mobile Computing and Networking, Sept. 2011. [4] D.Bharadia, E.McMilin, S.Katti, ”Full Duplex Radios”, SIGCOMM’13, Aug 12-16, 2013, Hong Kong, China. [5] M.Duarte, C.Dick, A.Sabharwal,”Experiment-Driven Characterization of Full-Duplex Wireless Systems’, IEEE Tr. On Wireless Communications, Vol.11, NO.12, Dec 2012,pp.4296-4307. [6] E.Everett, A. Sahai, A. Sabharwal,”Passive Self-Interference Suppression for Full-Duplex Infrastructure Nodes”, IEEE Transactions on Wireless Communication, October 2013. [7] M. E. Knox, “Single antenna full duplex communications using a common carrier,” in Proc. 13th Annual Wireless and Microwave Technology Conference (WAMICON), 2012, pp. 1 –6. [8] R.Taori, W-C. Kuo, J. Kaushik, H-R Shao, H. Kang, S. Chang, ”Considerations for In-Band Simultaneous Transmit and Receive (STR) feature in HEW”, IEEE 11-13/1122r1. [9] B.Debaillie, D.J. van den Broek, C.Lavin, B. van Liempd, E.A.M. Klumperink, C. Palacios, J. Craninckx, B. Nauta, A. Pärssinen ”Analog/RF Solutions Enabling Compact Full-Duplex Radios”, accepted to IEEE JSAC Special Issue on Full-duplex Wireless Communications and Networks, 2014. 14