Battle of the Waveforms for 5G GUNES KARABULUT KURT, SELAHATTIN GOKCELI gkurt@ituedutr, gokcelis@ituedutr Wireless Communications and Research Laboratory (WCRL) ISTANBUL TECHNICAL UNIVERSITY
OUTLINE Introduc;on: OFDM/OFDMA 5G Challenges Waveform Design Targets Implementa;on Prespec;ve: Universally Filtered Mul;-carrier (UFMC) Systems Error Performance & Sidelobe levels Further Improvements Summary h"p://sinenicom/cs/app/doc/p/id/cs-17378# IEEE 5G GREECE SUMMIT 2
OFDM/OFDMA Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access: Enables transmission of parallel data streams þ High data rates þ Robustness to frequency selectivity ý Sensitivity to time/frequency offsets ý High peak to average power ratio (PAPR) ý High sidelobe levels IEEE 5G GREECE SUMMIT 3
5G Challenges Solutions to OFDM/OFDMA problems: ê Spectral efficiency ê Energy efficiency IEEE 5G GREECE SUMMIT 4
5G Challenges Solutions to OFDM/OFDMA problems: ê Spectral efficiency ê Energy efficiency OFDM/OFDMA may not address 5G constraints! IEEE 5G GREECE SUMMIT 5
5G Challenges Solutions to OFDM/OFDMA problems: ê Spectral efficiency ê Energy efficiency OFDM/OFDMA may not address 5G constraints! New waveforms may be a solu;on IEEE 5G GREECE SUMMIT 6
Design Targets é Spectral efficiency é Energy efficiency ê PAPR ê Sidelobe levels + Simpler synchronization IEEE 5G GREECE SUMMIT 7
Candidate Techniques ü ü Filter Bank Multicarrier Modulation [SIOHAN, 2002] Generalized Frequency Division Multiplexing [FETTWEIS, 2009] ü ü ü ü Filtered-OFDM [ABDOLI, 2015] Zero-tail DFT-spread-OFDM [BERARDINELLI, 2013] Universal Filtered Multi-Carrier [VAKILIAN, 2013] IEEE 5G GREECE SUMMIT 8
Implementation Perspective X 1 N 1 -IDFT Filtering F 1 Synchronization RECEIVER X 2 N 2 -IDFT Filtering F 2 DAC ADC Cyclic- Prefix Removal 2N-DFT Filtering/ Channel Equalization Estimated Bits X B N B -IDFT Filtering F B TRANSMITTER A good compromise: UFMC þ Better control of sidelobe levels/interference þ Robustness to syncronization sensitivity: Carrier Frequency Offset/Timing Offset IEEE 5G GREECE SUMMIT 9
SDR Testbed IEEE 5G GREECE SUMMIT 10
Measurement Results IEEE 5G GREECE SUMMIT 11
Sidelobe levels (1/2) IEEE 5G GREECE SUMMIT 12
Sidelobe levels (2/2) 20 0 32 Subcarriers OFDM DFT-s-OFDM UFMC PSD (dbw/hz) -20-40 -60-80 -100-05 -04-03 -02-01 0 01 02 03 04 05 Normalized frequency IEEE 5G GREECE (a) SUMMIT 13
Further Improvements Figure 51 : Block diagram of the transmitter implementation X 1 X 2 X B Zero Padding Zero Padding Zero Padding Precoding M 1 -DFT Precoding M 2 -DFT Precoding M B -DFT N 1 -IDFT N 2 -IDFT N B -IDFT TRANSMITTER Filtering F 1 Filtering F 2 Filtering F B Figure 51 : Block diagram of the transmitter implementation DAC ADC 32 Subcarriers ZP-DFT-s-UFMC 20 This step can be represented as PSD (dbw/hz) Synchronization 0-20 i th subband before -40 the M-DFT operation Then to complete ZP-DFT-s-UFMC symbol -60-80 Cyclic- Prefix Removal 2N-DFT Filtering/ Channel Equalization ML Detection Figure 52 : Block diagram of the receiver implementation ZP-DFT-s-OFDM ZP-DFT-s-UFMC Estimated Bits supported with zero-padding, zeros are added into data symbols in order to implement ũ i [m]= RECEIVER ( 0, m = 0,1,,Z 1 u i [m], m = Z,Z + 1,,M 1, (51) where Z is the number of added zero symbols, M is the length of DFT, i = 1,2,,B is the index of the subband where total number of subbands is B, u i is the data symbols at generation, spreading with DFT-precoding can be implemented Lets assume that the output of this operation is X i [k], where k = 0,1,,K 1 is the subcarrier index with total number of subcarriers K If spreading version of UFMC is not considered, then weighted correlative coding operation can be applied to X i [k] as [28] p -100-05 -04 2-03 -02-01 0 01 02 03 04 05 ˆX i [k]= 2 (e jq X i [k]+x i [k + 1]), k = 1,2,,K 1, (52) Normalized frequency 51 Figure 52 : Block diagram of the receiver implementation IEEE 5G GREECE SUMMIT 14
Summary 1 OFDM & OFDMA are proven techniques 2 Dense networks may require more flexible waveform design 3 UFMC is a good op;on in terms of its flexibility IEEE 5G GREECE SUMMIT 15
Selected References: [SIOHAN, 2002] P Siohan, C Siclet and N Lacaille, "Analysis and design of OFDM/ OQAM systems based on filterbank theory," in IEEE Transactions on Signal Processing, vol 50, no 5, pp 1170-1183, May 2002 [FETTWEIS, 2009] G Fettweis, M Krondorf and S Bittner, "GFDM - Generalized Frequency Division Multiplexing, IEEE 69th Vehicular Technology Conference, Barcelona, 2009, pp 1-4 [ABDOLI, 2015] J Abdoli, M Jia and J Ma, "Filtered OFDM: A new waveform for future wireless systems," 2015 IEEE 16th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Stockholm, 2015, pp 66-70 [BERARDINELLI, 2013] G Berardinelli, F M L Tavares, T B Sørensen, P Mogensen and K Pajukoski, "Zero-tail DFT-spread-OFDM signals," 2013 IEEE Globecom Workshops (GC Wkshps), Atlanta, GA, 2013, pp 229-234 [VAKILIAN, 2013] V Vakilian, T Wild, F Schaich, S ten Brink and J F Frigon, "Universalfiltered multi-carrier technique for wireless systems beyond LTE," 2013 IEEE Globecom Workshops (GC Wkshps), Atlanta, GA, 2013, pp 223-228 IEEE 5G GREECE SUMMIT 16
Questions? Thank you for you a"en;on! gkurt@ituedutr IEEE 5G GREECE SUMMIT 17