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Mir Ghoraishi July 8, 2015

multiple access for in-band full-duplex wireless

5G INNOVATION CENTRE

outline What is full-duplex? what is the main challenge? A brief look at the tate-of-the-art Short introduction of FP7 DUPLO project Full-duplexing gain beyond the physical layer MAC design challenges for full-duplex systems A brief look at existing full-duplex MACs Asymmetrical traffic accommodation by optimum power allocation Resource (power, subcarrier) allocation in full-duplex enabled scenarios

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self-interference cancellation in a full-duplex transceiver Antenna(s)

isolation of the receiver chain from the transmit signal at 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 e.g. balun circuits, duplexers, extra transmit chain

Digital baseband cancellation removal of the remaining (residual) self-interference at digital baseband residual nonlinear component shall be taken into account



full-duplex transceiver solutions Reported self-interference cancellations by different solutions


Reference Solution SIC capability

Stanford [1] (2011) Separate TX and RX antennas RF cancellation with balun circuit Digital BB interference cancellation

RF (Balun) cancellation 43 dB Digital baseband cancellation 30 dB Digital + Balun 73 dB + additional 40 dB from antenna separation (estimate) (measurement at 10 MHz in 2.4 GHz band )

Rice [2] (2012) Separate TX and RX antennas (20 cm separation) RF cancellation with additional RF chain Digital BB interference cancellation

Antenna separation 41 dB Antenna + RF + digital baseband 78 dB (measurement bandwidth 625 kHz, in 2.4 GHz band)

Rice [3] (2012) Separate TX and RX antennas (50 cm distance, with 90 degrees beamwidth and different tilting), optional use of cross polarized antennas Active RF and BB cancellation

Antenna separation 60 dB Antenna separation with cross pol. 70 dB Antenna + RF +BB 86 dB Antenna with cross pol. + RF + BB 95 dB (measurement bandwidth 20 MHz, in 2.4 GHz band)

NYU [4] (2012) Circularly polarized patch antenna + balanced feed network (single antenna solution) Active RF interference cancellation No digital BB (in the analysis)

Antenna + balance feed network 40-45 dB Antenna/feed network + RF canceller 59 dB (measurement bandwidth 8 MHz, in 914 MHz band)

Stanford [5] (2013) Single antenna + circulator Adaptive analog RF canceller Digital BB interference cancellation

Circulator + analog cancellation 62 dB Digital baseband cancellation 48 dB Total 110 dB (measurement bandwidth 80 MHz, in 2.4 GHz band)

90 – 110 dB self-interference cancellation is achievable


FP7 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 Integrated solutions for small-form factor devices can achieve up to more than 80 dB self-interference

cancellation


http://www.fp7-duplo.eu/


DUPLO solutions

To enable mass usage of FD technology in various 5G scenarios/applications, the full-duplex 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 [6]

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 mm2) • 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


Upper Patch

Lower Patch & Feeding Network

PORT 1

PORT 2

Electrical Balance SIC

TX RX


in-band full-duplexing in wireless networks Recent advancements in self-interference cancellation indicates that efficiently full-duplex

enabled transceivers/UEs/BSs can be manufactured Most straight forward application is single (isolated) point-to-point link In-band full-duple technology is often introduced as a potential technology to double the

spectrum efficiency, but this needs symmetrical traffic to happen (assuming perfect self-interference cancellation) Cellular applications need further investigations, mainly on interference (interuser/intercell)

management and asymmetrical traffic arrangement In-band full-duplex technology probably can better serve other purposes, such as low latency,

physical layer secrecy, wireless power transfer, etc. Potential applications in M2M communications, D2D connections, relays, backhaul

connections, mesh/cognitive network solutions, etc.,



multiple access for full-duplex Full-duplexing gain is beyond physical layer ! Practical full-duplexing can provide intuitive solutions to the problems of

current wireless systems: Improvement spectrum utilization Reduce delays/latency No DL/UL switching Mitigate hidden/expose terminal problem Make collision detection better Improve quality of service



full-duplex MAC design challenges Selecting a set of nodes and an FD transmission mode to maximize the overall

throughput -> RTS/CTS, header snooping, random back-off Fairness, due to double communication capability of FD nodes -> tuning

access channel probability Residual hidden node, e.g. when offset or different packet lengths -> busy

tone Interuser/intercellular interference management -> scheduling Asymmetrical traffic accommodation

asymmetric traffic accommodation and interference management by

resource (power, subcarrier, rate) allocation



missing in full-duplex MACs Proposed full-duplex MAC protocols do not provide any solution for the key

features, i.e. asymmetric traffic accommodation, interference management, power efficiency and fair participation of half-duplex nodes It is necessary to try MAC designs for large networks, e.g. including multiple

cells, with full-duplex nodes and to account for different interference topologies and traffic types can further improve the understanding of MAC protocol performance under full-duplex conditions In large-scale wireless networks, spatial reuse and asynchronous contention

effects significantly undermine the actual benefits of full-duplex, even if full-duplex can double the capacity for a single link In order to translate the PHY layer full-duplex gain into network layer

throughput improvement, the MAC protocols need to be redesigned for efficient full-duplex potential utilization by taking into account the aforementioned factors



full-duplex link with asymmetric traffic Cross layer approach in analysis of the full-duplex link with asymmetric traffic

accommodation The proposed model considers power and rate allocation for the downlink

and uplink users based on the observation of the (SINR) from the physical layer and uplink traffic buffer The problem is to maximize the down

link throughput subject to the uplink throughput, BS and UE transmit powers, and BS and UE self- interference cancellation


DL path loss

BS SIC

UL path loss

UE SIC

BS Pt

SI level

UE Pt

SI level

BS SINR UE SINR

BS UE


throughput gain With proposed scheme the downlink rate can be increased with the

degradation in uplink while satisfying the SINR and QoS constraints At the optimal SINR the physical layer and the MAC layer are balanced to

achieve the maximum throughput



throughput - traffic asymmetry The proposed scheme improve the downlink greatly while the uplink

throughput is decreased Reaching the saturation point at downlink, there is degradation to overall

system throughput. The proposed model with power and rate control is effective for asymmetric

traffic accommodation in full-duplex networks



multiuser scenario To reflect the results achieved with proposed scheme in multiuser scenario,

the medium access is based on time-slot with each user having downlink and uplink at the same time The power and rate allocation is optimized for each slot independently Same improvement in throughput with the proposed scheme is observed

when employ on a network with multiple nodes The average throughput of the

downlink improve resulting in increase overall system performance



power & subcarrier allocation Single cell scenario


self-interference at BS interuser interference at UEs

self-interference at BS Self-interference at Ues No interuser interference

Full-duplex BS /half-duplex UEs Full-duplex BS /full-duplex UEs


power & subcarrier allocation Single cell scenario


100 120 140 160 180 200 220 240 260 2800

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Sum-Rate (Mbps)

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FD-EqPwrFD: !70dBFD: !80dBFD: !85dBFD: !90dBFD: !100dBHalf-Duplex

80 100 120 140 160 180 200 220 240 260 2800

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Sum-Rate (Mbps)

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FD-EqPwr

FD: !85dBFD: !90dBFD: !95dB

FD: !100dBHalf-Duplex

self-interference at BS interuser interference at UEs

self-interference at BS Self-interference at UEs No interuser interference

Full-duplex BS /half-duplex UEs Full-duplex BS /full-duplex UEs


References [1] 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.

[2] 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.

[3] E.Everett, A. Sahai, A. Sabharwal,”Passive Self-Interference Suppression for Full-Duplex Infrastructure Nodes”, IEEE Transactions on Wireless Communication, October 2013.

[4] 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.

[5] D.Bharadia, E.McMilin, S.Katti, ”Full Duplex Radios”, SIGCOMM’13, Aug 12-16, 2013, Hong Kong, China.

DUPLO deliverables available at http://www.fp7-duplo.eu/index.php/deliverables

Mir Ghoraishi, Wei Jiang, Pei Xiao, Rahim Tafazolli, “Subband Approach for Wideband Self-Interference Cancellation in Full-Duplex Transceiver,” submitted to IWCMC 2015, August 2015.

Mohammed Al-Imari, Mir Ghoraishi, Pei Xiao, Rahim Tafazolli, “Game Theory Based Radio Resource Allocation for Full-Duplex Systems,” VTC-Spring 2015, May 2015.

Hassan Malik,Mir Ghoraishi, Rahim Tafazolli, “Cross-Layer Approach for Asymmetric Traffic Accommodation in Full-Duplex Wireless Network,” EUCNC 2015, July 2015.

Mohammed Al-Imari, Mir Ghoraishi, Pei Xiao, Rahim Tafazolli, “Radio Resource Allocation and System-Level Evaluation for Full-Duplex Systems ,” IEEE CAMAD 2015, Sep. 2015.

DUPLO proof-of-concept demo videos available at http://www.fp7-duplo.eu/index.php/dissemination/116-videos


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Thank you ! Mir Ghoraishi, PhD Project Leader, 5G Testbed and Proof-of-Concept Senior Research Fellow [email protected] [email protected] Office: (+44) 01483 683641

mailto:[email protected]

mailto:[email protected]

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