Case Study: Implementation Aspects of a GFDM-based Prototype for 5G Cellular Communications Ivan Simões Gaspar With the Vodafone Chair (Prof. Fettweis) since February 2012 Studies: Electrical Engineering (M.Sc.) at the National Institute of Telecommunications in Brazil – INATEL Research area: robust non-orthogonal multi-carrier modulation schemes for future cellular systems NI RF Roundtable 2012 December 10-11, 2012, Bristol, UK

Motivations for 5G M2M dominating subscribers 06.04.2017 M2M dominating subscribers diverse requirements (high and lows) : data rate, latency, mobility, quality, security asynchronous and non-orthogonal modulation Opportunistic use of spectrum time and frequency agility accurate sensing no interferer (filtering) 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Challenges RRM CoMP Wireless Access: flexible scalable content aware 06.04.2017 RRM flexible fine-grained sharing of fragmented spectrum CoMP High rate, low latency, interactive video, apps, increased signaling Wireless Access: flexible scalable content aware robust reliable t f vast # M2M devices low rate / complexity asynchronous access 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Our approach 06.04.2017 Question the strict synchronism, orthogonality and high out of band radiation of OFDM based systems with the introduction of new non-orthogonal filtered waveforms that carry the data on the physical layer. Deal with crosstalk and interference with a transceiver structure termed GFDM (Generalized Frequency Division Multiplexing). Explore the tradeoff of an increased computational complexity at the Base Stations with a more flexible construction of millions of machine type communications (MTC) devices Proof of concept prototype with a highly scalable implementation on NI’s PXI platform 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

GFDM Transmitter Model 06.04.2017 generalization of OFDM 1 up to M symbols per subcarrier Pulse shaping with circular convolution (block structure - burst) Up sampling Filtering Up conversion Mapping we can achieve this in GFDM by combining several multicarrier symbols to one block, where the pulse shaping filter spans over the whole duration what we basically get is a mix between single carrier (pulse shaping) and OFDM (subcarriers) M = number of symbols per subcarrier K = number of active subcarriers 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Matrix Model, x=Ad 06.04.2017 The A matrix contains all the possible impulse responses of the system Circular impulse response whenever we filter a data sequence, the resulting signal is longer than the input these 'tails' can either be cut  impacts the spectrum addressed with a GI  reduces efficiency in GFDM we introduce tail biting: use circular convolution for the pulse shaping the result of this operation is then the same length as the input there was no Rx tail biting in the first version of GFDM 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

First Demo – ‘Player Approach’ Demo Setup Transmit Signals System Parameters parameter value Channel bandwidth 20 MHz Max. number of subcarriers 2048 PRB 30 active subcarriers 360 occupied bandwidth 9.8 MHz carrier frequency 2,4 GHz modulation QPSK filter, roll-off RRC, a = 0.5 block size 14 10.12.2012 RF roundtable 2012

First Demo – ‘Player Approach’ Few weeks after receiving the HW we get a real time signal coming out of the box 10.12.2012 RF roundtable 2012

A Low Complexity Model Time approach: 06.04.2017 Time approach: up sampling, circular convolution and up conversion Frequency approach: DFT, spectrum repetition, windowing and position shift, IDFT 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

A Low Complexity Model zero stuff repetition circ. convolution 06.04.2017 zero stuff repetition circ. convolution windowing Subcarrier processing time vs. frequency domain Subcarrier superposition in frequency domain 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Low Complexity Model (Matrix) 06.04.2017 GFDM is a digital multicarrier system with pulse shaping each branch can be considered as a single carrier system note that we do not have the CP block here, because we are intentionally looking at the AWGN channel one of the contributions of this paper is that the whole system can be now expressed with a matrix model as a linear system, while before each subcarrier has been considered individually OFDM is a special case where rectangular pulses are used and the modulation matrix becomes an IFFT matrix 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Low Complexity Model GFDM Matrix Model GFDM non sparse spectrum 06.04.2017 GFDM Matrix Model GFDM non sparse spectrum GFDM Low Complex OFDM reference 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

LabView Style TX Model 06.04.2017 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Second Demo – Offline TX LabVIEW interactive transmitter (offline) LabView based implementation in less than 2 months after basic training Very friendly graphical interface 10.12.2012 RF roundtable 2012

Out of band Radiation GFDM (red curve) vs. OFDM (blue curve) 06.04.2017 GFDM (red curve) vs. OFDM (blue curve) 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Third Demo – Online TX PXI based implementation in less than 6 months LabVIEW interactive transmitter (online) PXI based implementation in less than 6 months Very friendly RT and FPGA enviroments integration 10.12.2012 RF roundtable 2012

Third Demo – Online TX 10.12.2012 RF roundtable 2012

Current studies (RX) Math model Block Diagram ICI Channel distortions 06.04.2017 Math model Block Diagram GFDM is a digital multicarrier system with pulse shaping each branch can be considered as a single carrier system note that we do not have the CP block here, because we are intentionally looking at the AWGN channel one of the contributions of this paper is that the whole system can be now expressed with a matrix model as a linear system, while before each subcarrier has been considered individually OFDM is a special case where rectangular pulses are used and the modulation matrix becomes an IFFT matrix ICI Channel distortions 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Future directions UHF white spaces 06.04.2017 UHF white spaces GFDM is a digital multicarrier system with pulse shaping each branch can be considered as a single carrier system note that we do not have the CP block here, because we are intentionally looking at the AWGN channel one of the contributions of this paper is that the whole system can be now expressed with a matrix model as a linear system, while before each subcarrier has been considered individually OFDM is a special case where rectangular pulses are used and the modulation matrix becomes an IFFT matrix 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Conclusions 06.04.2017 Pulse shaped subcarriers can be achieved in GFDM at reasonable computational cost Out of band radiation in GFDM can outperform OFDM by several orders of magnitude Outlook A hardware implementation of the GFDM transceiver and its multi-user case application 10.12.2012 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

Thank you.