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APT/AWG/REP-75

APT REPORT ON

in-band full duplex TECHNOLOGY for fixed wireless SYSTEM

No. APT/AWG/REP-75Edition: September 2017

Adopted by

22nd Meeting of APT Wireless Group25 29 September 2017 Busan, Republic of Korea

(Source: AWG-22/OUT-08)

APT REPORT ON in-band full duplex TECHNOLOGY for fixed wireless SYSTEM

Table of Contents

1.Introduction4

2.Scope4

3.Vocabulary of terms4

4.References5

5.System and technology characteristics6

5.1 Antenna isolation7

5.2 RF interference cancellation9

5.3 IF interference cancellation9

5.4 Baseband interference cancellation10

6.Application scenario10

7.Spectrum usage and network plan analysis11

8.Example of demonstration experiment12

8.1 15GHz demonstration experiment13

8.2 40GHz demonstration experiment16

9.Conclusion23

ANNEX25

Introduction

In recent years, along with the significant increasing of mobile applications, bandwidth requirement is growing rapidly in all kinds of networks, including fixed wireless network. In fixed wireless network, bandwidth is highly related to spectrum.

However, spectrum is the key precious resource in radio communication industry. The main way of increasing bandwidth is to improve spectrum efficiency. Now the traditional methods of improving spectrum efficiency include following options, but all are facing bottlenecks:

1) High order modulation. Now 2048QAM is widely used in nowadays microwave communication industry. As the physical limitation of radio device and super high requirement of algorithm performance, it is so hard to increase modulation order. And even the modulation order would be increased from 2048QAM to 4096QAM, the spectrum efficiency would only be increased by 8.3%.

2) Polarization multiplexing. Now XPIC is maturely used and could double spectrum efficiency. However, multi-polarization technology is still unclear, and then the possibility to continue increasing spectrum efficiency by polarization multiplexing is rarely low.

3) Space multiplexing (MIMO). This technology can increase spectrum efficiency through space multiplexing technology. But according to the characteristics of spectrum and channel used for fixed wireless system, there will be a certain distance between each antenna. Usually, this distance is not short. So the MIMO array cant be too large and maximum only 2*2 could be supported by now.

As discussed above, spectrum efficiency cant be further increased efficiently by the traditional methods. Industry is searching for new ways to move forward. In band Duplex (short for IBD) system could double the spectrum efficiency by using the same frequency slot to transmit and receive signals simultaneously in the same channel. Then it has become the hottest topic in recent research area.

FWS sharing the frequency band, polarization, and time slot for bidirectional links is called In Band Full Duplex generally. However, in the field of wireless systems in a broad sense including multiple access, by using the duplexing method classification for more accuracy, sometimes also referred to as Directional Division Duplex.

See ANNEX for more information. In this document "In band Full Duplex" is abbreviated as IBD.

Scope

This report covers system and technology characteristics, application scenario, spectrum usage, and network plan analysis of IBD technology. Field trial results and analysis are also provided at last to show the discussed techniques.

Vocabulary of terms

IBDIn band full Duplex

DDDDirectional Division Duplex

FWAFixed Wireless Access

FWSFixed Wireless System(s)

FDDFrequency Division Duplex

TDDTime Division Duplex

IFIntermediate Frequency

RFRadio Frequency

SNRSignal to Noise Ratio

MIMOMultiple-Input Multiple-Output

XPICCross-Polarization Interference Cancellation

References

D.Bharadia, E. McMilin, and S.Katti, Full Duplex Radios, Proceedings of the ACM SIGCOMM 2013 conference on SIGCOMM, 375-386(2013).

Melissa Duarte, Full-duplex Wireless: Design, Implementation and Characterization, Rice university, dissertation and thesis, NO. 3521362 (2012).

Duarte, M.; Sabharwal, A., "Full-duplex wireless communications using off-the-shelf radios: Feasibility and first results," Signals, Systems and Computers (ASILOMAR), 2010 Conference Record of the Forty Fourth Asilomar Conference on , vol., no., pp.1558,1562, 7-10 Nov( 2010).

D. Bharadia, E. McMilin, and S. Katti, "Full duplex radios," in SIGCOMM' 13, Hong Kong, China, Aug(2013)

Y. Hua, P. Liang, Y. Ma, et. al, A Method for Broad band Full-Duplex MIMO Radio, IEEE Signal Processing Letters, vol.19, no.12, pp.793~796, Dec(2012).

Lee, W.C.Y., "The most spectrum-efficient duplexing system: CDD," Communications Magazine, IEEE , vol.40, no.3, pp.163,166, Mar (2002).

K. Akahori, T. Taniguchi, M. Nagayasu, Y. Toriyama, K. Kojima and M. Zhang, Implementation of Millimeter Wave Band DDD Radio System, 2016 IEEE Radio and Wireless Symposium (RWS), Austin, Texas, January 2016.

K. Kojima, T. Taniguchi, M. Nagayasu, Y. Toriyama and M. Zhang, A Study of Interference Canceller for DDD System on Millimeter-Wave Band Fixed Wireless Access System, in 9th European Conference on Antennas and Propagation (EuCAP), Lisbon, Portugal, April 2015.

H. Yoshida, T. Taniguchi, Y. Toriyama, K. Kojima, T.Shirosaki, S. Nagamine, J. Kobayashi, Ef fective throughput 1 Gbps wireless system by single-carrier 64QAM for millimeter-wave applications, IEEE Radio and Wireless Symposium (RWS) 2011, Phoenix, pp. 323-326, 16th to 19th Jan., 2011.

T. Taniguchi, K. Kojima, A. Matsuzawa, K. Matsunaga, Y. Hirachi, Developments of the SoC for High-Multi-Level QAM 1 Gbps Class Wireless System and its Evaluation with RF Hardware of 38 GHz Band FWA, IEEE NORCHIP Conference 2010, Tampere, pp. 1-4, 15th to 16th Nov., 2010.

Y. Toriyama, K. Kojima, T. Taniguchi, M. Zhang, and J.Hirokawa, Multi-level QAM single-carrier high-efficiency broadband wireless s system for millimeter wave applications, IEEE Radio and Wireless Symposium (RWS) 2010, New Orleans, pp. 677-680, 10th to 14th Jan., 2010.

S. Nagamine, F. Ozawa, T. Shirosaki, T. Taniguchi, K.Okada, Multifunctional frequency converter MMIC for 38GHz band 600Mbps multi-level QAM wireless system, IEEE International Symposium on Radio-Frequency Integration Technology (RFIT) 2009, Singapore, pp. 229-232, 9th to 11th Dec., 2009.

K. Kojima, Y. Toriyama, T. Taniguchi, M. Miyahara, and A. Matsuzawa, Development of Baseband Processing SoC with Ultrahigh-Speed QAM Modem and Broadband Radio System for Demonstration Experiment Thereof, IEEE International Conference on Electronics, Circuits, and Systems (ICECS) 2009, Tunisia, pp. 687-690, 13th to 16th Dec., 2009.

K. Kojima, Y. Toriyama, M. Nagayasu, T. Taniguchi, IMPROVED DESIGN OF THE BB-SOC WHICH INCORPORATED THE ULTRA HIGH SPEED MULTI LEVEL QAM MODEM FOR MM-WAVE RADI O SYSTEMS , AND ITS PERFORMANCE, IEEE International Conference on Electronics, Circuits, and Systems (ICECS) 2010, Athens, pp. 515-518, 12th to 15th Dec., 2010.

System and technology characteristics

IBD technology uses radio in the same band and with the same polarization to provide simultaneous bi-directional communication. As transmitting frequency and receiving frequency are within the same spectrum slot simultaneously, self-interference from transmitted signal to its own reception circuit is the main problem of IBD system. Thus the most important issue in system design is to cancel or reduce such self-interference. The self-interference which consists of short-delayed interference signals and long-delayed interference signals as shown in Fig. 1. The block diagram of typical IBD system is shown below in Fig. 2.

Fig. 1 Interference sources in IBD system

Fig. 2 Block diagram of IBD system

Interference cancellation is implemented in four stages: antenna isolation, IF interference cancellation, RF interference cancellation and baseband interference cancellation.

Antenna isolation

Short-delayed interference is the interference from transmitting signal to receiving antenna. Antenna isolation is the appropriate way to reduce this kind of interference. There are three types of antennas which could be used in IBD system.

1. Transmitting and receiving with the same antenna

It is implemented by using circulator to isolate transmitting signal and receiving signal at antenna port, shown in Fig. 3. It is widely used in microwave radar area. As the nonreciprocity of ferrite material, transmitting signal cant enter receiver. Then transmitting and receiving can share the same antenna. This kind of antenna holds the merits of concise equipment form and easy installation. However, as the transmitting-receiving isolation of ferrite circulator in fixed point to point wireless communication band usually would only be 20dB to 30dB, it is so hard to achieve in band transmitting and receiving with enough high isolation. At meanwhile, the standing-wave ratio from antenna to transmitting/receiving sharing interface has also limited the transmitting/receiving isolation. Even though the isolation of circulator would increase more, the isolation of antenna sharing the same transmitting /receiving port couldnt increase along with it as a result of standing-wave ratio. So, this type of antenna is a good choice to the IBD system with lower requirement of antenna isolation.

Fig. 3 Antenna using circulator to share transmitting/receiving port

2. Transmitting and receiving with different antennas

In this way, circ