1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

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

9. 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

10. 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

11. 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

12. 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

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

14. 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

15. 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

16. 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

17. Third Demo – Online TX
RF roundtable 2012

18. 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

19. 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

20. 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

21. Thank you.