Vodafone Chair Mobile Communications Systems, Prof. Dr.-Ing. G. Fettweis 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 multicarrier modulation schemes for future cellular systems NI RF Roundtable 2012 December 10-11, 2012, Bristol, UK Motivations for 5G 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 2 Challenges RRM flexible fine-grained sharing of fragmented spectrum CoMP High rate, low latency, interactive video, apps, increased signaling f vast # M2M devices low rate / complexity 10.12.2012 t asynchronous access RF roundtable 2012 Wireless Access: • flexible • scalable • content aware • robust • reliable 3 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 10.12.2012 RF roundtable 2012 4 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 M = number of symbols per subcarrier K = number of active subcarriers 10.12.2012 RF roundtable 2012 5 Matrix Model, x=Ad The A matrix contains all the possible impulse responses of the system Circular impulse response 10.12.2012 RF roundtable 2012 6 First Demo – ‘Player Approach’ Demo Setup control computer spectrum analyzer FlexRIO Ethernet RT-OS FPGA board Transmit Signals Transceiver board coax System Parameters 10 power spectral density in dB DAC OFDM GFDM parameter value Channel bandwidth 20 MHz Max. number of subcarriers 2048 PRB 30 -30 active subcarriers 360 -40 occupied bandwidth 9.8 MHz -50 carrier frequency 2,4 GHz -60 modulation QPSK filter, roll-off RRC, a = 0.5 block size 14 0 -10 -20 -70 -4 10.12.2012 -2 0 2 frequency in MHz 4 RF roundtable 2012 7 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 8 A Low Complexity Model Time approach: up sampling, circular convolution and up conversion j 2 n N d k [ m ] [ n m N ] # gg T x [ n ] ·e m k x[n ] k Frequency approach: DFT, spectrum repetition, windowing and position shift, IDFT 1 x [ n ] F F d k [ m ] [ n m N m k N tim es repetition of F k j 2 n N ] ·F g T x [ n ] # F e d k [m ] [n m ] m copy from m em ory low com plex k f N shift in m em ory im plem entation! 10.12.2012 RF roundtable 2012 9 A Low Complexity Model zero stuff repetition circ. convolution windowing Subcarrier processing time vs. frequency domain 10.12.2012 Subcarrier superposition in frequency domain RF roundtable 2012 10 Low Complexity Model (Matrix) 10.12.2012 RF roundtable 2012 11 Low Complexity Model GFDM Matrix Model GFDM non sparse spectrum GFDM Low Complex OFDM reference 10.12.2012 RF roundtable 2012 12 LabView Style TX Model 10.12.2012 RF roundtable 2012 13 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 14 Out of band Radiation GFDM (red curve) vs. OFDM (blue curve) 10.12.2012 RF roundtable 2012 15 Third Demo – Online TX 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 16 Third Demo – Online TX 10.12.2012 RF roundtable 2012 17 Current studies (RX) Math model Block Diagram ICI 10.12.2012 Channel distortions RF roundtable 2012 18 Future directions UHF white spaces 10.12.2012 RF roundtable 2012 19 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 10.12.2012 RF roundtable 2012 20 Vodafone Chair Mobile Communications Systems, Prof. Dr.-Ing. G. Fettweis Thank you.