Presenter: Gerhard Wunder, gerhard.wunder@hhi.fraunhofer.de EuCNC Workshop “Enablers on the road to 5G” June 23rd, 2014

5G Waveform Approaches In Highly Asynchronous Settings

What is 5GNOW? 5GNOW (5th Generation Non-Orthogonal Waveforms for Asynchronous Signalling) is an European collaborative research project supported by the European Commission within FP7 ICT Call 8.

Who is in the consortium? Fraunhofer HHI (coordinator), Germany, Dr. Gerhard Wunder Alcatel Lucent (technical coord.), Germany, Thorsten Wild Technische Universität Dresden, Germany, Prof. Gerhard Fettweis CEA-LETI, France, Dr. Dimitri Ktenas IS-Wireless, Poland, Dr. Slawomir Pietrzyk National Instruments, Hungary, Dr. Bertalan Eged

www.5gnow.eu, LinkedIn group

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Vision:

• 5GNOW is the physical layer evolution of mobile communication network technology such as LTE-Advanced towards emerging application challenges.

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Outline

(1) 5GNOW Application Challenges

(2) 5GNOW Frame Structure

(3) 5GNOW Waveform Approaches

(4) Conclusions

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Gigabit Wireless Connectivity

2013

2005

Examples: 3D video streaming, large crowd gatherings

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Internet of Things (IoT)

Battery (10 years)

Cost below 10$ Coverage (deep indoor)

„Plug&secure“, human in the loop

■ Connecting the things of every day life, scalable connectivity for billions of devices

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Tactile Internet (TI)

Real-time cyber-physical control applications

100ms

10ms

1ms 100 µs latency on physical layer!

Spectrum paradox: spectrum scarce and expensive but underutilized!

EC Digital Agenda forces the systems to deal with fragmented spectrum and white spaces communication (PAPR, 100x better localization)

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Fragmented Spectrum

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Application Challenges

Wireless Access: • flexible • scalable • fast • robust

• efficient (energy, spectrum)

• reliable

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Frame Structure Concept

Target for 5G integrated air interface: Efficiently combine various types of service and performance classes within a radio frame (from small packet service to high rate ‘bit-pipe’)

Unified Frame Structure

Traffic Type Synch? Access Type Properties

I closed-loop scheduled classical high volume data services

II open-loop

scheduled HetNet and/or cell edge multi-layered high data traffic

III

open-loop sporadic, contention-based few bits, supporting low latency, e.g. smartphone apps

IV open-loop/none* contention-based energy-efficient, high latency, few bits

Type I Type II

Layer

Time

Type III and Type IV

Frequency

*: none for maximal energy savings at Tx, open-loop for reduced complexity at Rx

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Requirements

Some arguments against OFDM: • Flexibility: Cyclic prefixes reduce spectral efficiency

and prohibit flexible handling of frame formats

• Scalable: Spectral localization is too bad, e.g. in narrowband setting up to 4-6 subcarrier gain by different waveforms

• Robust and Reliable: OFDM is very sensitive both in time and frequency domain due to FFT

• Fast: Very difficult to support short symbols with given channel delay spread

• Efficient (energy, spectrum): OFDM is not robust under incomplete channel state information

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-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5-30

-28

-26

-24

-22

-20

-18

relative delay

MSE

[dB

]

UFMC, no CFOUFMC, 5% CFOUFMC, 10% CFOCPOFDM, no CFOCPOFDM, 5% CFOCPOFDM, 10% CFO

Main observation: OFDM fails in highly asynchronous access scenarios, e.g. for massive MTC communication.

Outside CP: New waveforms really make a difference!

G. Wunder, P. Jung, M. Kasparick, T. Wild, F. Schaich, S. ten Brink, Y. Chen, I. Gaspar, N. Michailow, A. Festtag, G. Fettweis, N. Cassiau, D. Ktenas, M. Dryjanski, S. Pietrzyk, B. Eged, P. Vago, and F. Wiedmann, “5GNOW: Non-Orthogonal, Asynchronous Waveforms for Future Mobile Applications“, IEEE Communications Magazine, 5G Special Issue, Feb. 2014

Asynchronous Reference Scenario

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Waveform Concepts

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Filter Bank Multicarrier (FBMC) Features: Non-orthogonal multicarrier modulation (in complex domain) OQAM Prototype filter optimized for time and frequency localization trade-off

(PHYDYAS, K=4 optimized for ACLR) Non-adjacent subcarriers are almost perfectly separated Spectral efficiency improved as no cyclic prefix is required Efficient implementation with IFFT/FFT

FBMC transmitter with filtering in the frequency domain

Overlapping of time symbols: ISI solved by OQAM modulation

Nicolas Cassiau, Dimitri Kténas, Jean Baptiste Doré, “Time and frequency synchronization for CoMP with FBMC”, Tenth International Symposium on Wireless Communication Systems (ISWCS’13), Ilmenau, Germany, August, 2013

High performance receiver for frequency-spreading FBMC A receiver suited for asynchronous uplink multiuser access and fragmented spectrum operation

One unique (larger) FFT for all users Relaxed synchro requirements

All treatments are realized in the frequency domain BEFORE filtering by prototype filter

one-tap equalizer

Low complexity CFO correction (see on next slide)

Three interpolation filters (left, middle and right) prototype filter

Performance of FBMC Multiple Access with Relaxed Synchronization

• Due to fair frequency localization e.g. with fragmented spectrum, only the carriers located at the edges of the active spectrum are affected by interference (OFDM: interference is spread over all the active carriers)

• FBMC waveforms permit a simple way of sharing resources between cell-edge users without strict synchronization between users due to the low level of uplink interference generated by the built-in waveform filter.

• In case of QPSK, without guard carrier, the capacity is close to synchronous transmission and the level of interference is much lower than the required SNR to allow the decoding of QPSK.

• For 16-QAM modulation, FBMC gives a significantly better capacity, particularly in the range of [10-20]dB of SNR. Due to the better frequency localization, only the carriers located at the border of the user spectrum are affected by interference.

• For 64-QAM, the FBMC waveform clearly outperforms the OFDM waveform. Interference dominates the SINR for OFDM waveform and consequently for a given capacity of 5 bits/s/carrier, the SNR loss is of around 5dB.

Performance of FBMC Multiple Access with Relaxed Synchronization

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Universal Filtered Multicarrier (UFMC) • Generalization of Filtered OFDM and FBMC (FMT)

• UFMC complexity similar to OFDM

• Huge knowledge base of OFDM processing can be re-applied to UFMC

IDFT spreader V1k

+ P/S

Filter F1k with

length L s1k

x1k

+

IDFT spreader V2k

+ P/S

Filter F2k with

length L s2k

x2k

IDFT spreader VBk

+ P/S

Filter FBk with

length L sBk

xBk

Baseband to RF

channel

+ noise n

RF to Baseband

other users

xk

Time domain pre-processing

(e.g. windowing)

+ S/P 2N point-

FFT

Frequency domain symbol

processing (e.g. per

subcarrier equalization)

zeropadding

0 0

0 V. Vakilian, T. Wild, F. Schaich, S.t. Brink, J.-F. Frigon, "Universal-Filtered Multi-Carrier Technique for Wireless Systems Beyond LTE", IEEE Globecom'13, Atlanta, December 2013

Uplink CoMP: UFMC vs OFDM

• CFO is estimated and compensated.

• CFO estimation error Δε

Parameters

• CFO 10% of subcarrier spacing

• QPSK

• FFT size 128

• 12 subc. per PRB

• 6 PRBs allocated

• Filter length / CP length 16

• UFMC: Dolph-Chebychev filters with 120 dB att.

• Frequency-selective fading channel (16 taps)

• UFMC adds increased robustness in CoMP against time-frequency misalignments

UFMC OFDM

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Generalized Frequency Division Multiplexing (GFDM)

Multidimensional block structure with cyclic prefix:

Circular sub-carrier pulse shape: Overlapping (non-orthogonal) sub-carriers:

Waveform Properties

I. Gaspar, N. Michailow, A. Navarro Caldevilla, E. Ohlmer, S. Krone and G. Fettweis, „Low Complexity GFDM Receiver Based On Sparse Frequency Domain Processing“, 77th IEEE Vehicular Technology Conference (VTC Spring'13), Dresden, Germany, June 2013

256QAM, RRC, a=0.4 64QAM, RRC, a=0.4

28.06.2014 21 19. September 2013 Nicola Michailow Slide 21

64QAM, RRC, a=0.2

AWGN

Rayleigh multipath

GDFM Successive Interference Cancellation (SIC)

Theoretical BER of orthogonal system can be reached with SIC

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Conclusions

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Conclusions

5G visions like the IoT have very specific application demands and require highly asynchronous access in time and frequency

New waveforms such as FBMC, UFMC, GFDM have very desirable properties and are significantly more robust to temporal and spectral fragmentation of traffic

Two major upcoming things: System simulation to show benefit for fragmented traffic Unifying theory to explore in terms of Gabor signaling

Demonstration of multiuser uplink

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Contact

Dr. Gerhard Wunder – gerhard.wunder@hhi.fraunhofer,de www.hhi.fraunhofer.de/wn Fraunhofer Heinrich Hertz Institute Berlin, Germany

Thank you for your attention!

www.5gnow.eu