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**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

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**Motivations for 5G M2M dominating subscribers**

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) RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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**Challenges RRM CoMP Wireless Access: flexible scalable content aware**

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 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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Our approach 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 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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**GFDM Transmitter Model**

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 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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Matrix Model, x=Ad 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 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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**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 RF roundtable 2012

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**First Demo – ‘Player Approach’**

Few weeks after receiving the HW we get a real time signal coming out of the box RF roundtable 2012

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**A Low Complexity Model Time approach:**

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

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**A Low Complexity Model zero stuff repetition circ. convolution**

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

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**Low Complexity Model (Matrix)**

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 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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**Low Complexity Model GFDM Matrix Model GFDM non sparse spectrum**

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

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**LabView Style TX Model 06.04.2017 10.12.2012 RF roundtable 2012**

Vodafone Chair Mobile Communications Systems TU Dresden

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**Second Demo – Offline TX**

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

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**Out of band Radiation GFDM (red curve) vs. OFDM (blue curve)**

GFDM (red curve) vs. OFDM (blue curve) RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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**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 RF roundtable 2012

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Third Demo – Online TX RF roundtable 2012

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**Current studies (RX) Math model Block Diagram ICI Channel distortions**

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 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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**Future directions UHF white spaces**

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 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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Conclusions 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 RF roundtable 2012 Vodafone Chair Mobile Communications Systems TU Dresden

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Thank you.

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