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POPS-OFDM: Ping-pong Optimized Pulse Shaping OFDM for 5G Cellular Systems and Beyond By Prof. Mohamed Siala (Sup’Com, Tunis, Tunisia)

  • Class schedule:    Sunday, October 18th, 2015​ from 1:00 to 2:30pm   
  • Location:  Building 1,  Room 3119​

Next generation mobile communication systems will face stringent propagation conditions ranging from large Doppler spreads in frequency to excessive multipath spreads in time, both of which can be of natural or artificial origins.First of all, natural severe Doppler dispersions are to be experienced in next generation mobile communications because of expected high speed mobility as well as the use of new frequency bands beyond those used today.Secondly, slowerloops for time advance and frequency control, needed to alleviate the synchronization overhead burden for very small packet communications, needed in low latency applications of tactile internet, will incur severe synchronization errors especially in the time domain.Last but not least, the use of the CoMP (Coordinated Multi-Point) technique, in its JP (Joint Processing) version, and the MBMS (Multimedia Broadcast Multicast Service) services in LTE, and its SFN (Single Frequency Network) counterpart in DVB-T, will cause severe artificial time dispersions that cannot be tackled by today cyclic prefix OFDM systems. Unfortunately, conventional OFDM with CP (Cyclic Prefix) can no longer cope with these severe and challenging impairments, which will for sure be faced by 5G systems and beyond. The proposed solution, subject of the keynote speech, is to have recourse to pulse shaped (PS) OFDM. The idea behind PS-OFDM is to use non-perfectly orthogonal waveforms, unlike those of conventional OFDM, which can however better stand against time and frequency channel distortions. After presenting an overview of conventional OFDM with guard interval insertion, with both its PC and ZP (Zero Padding) versions, and OFDM/OQAM, we present a new paradigm for simple and systematic pulse shape optimization for any given channel impairments: POPS-OFDM (Ping-pong Optimized Pulse Shaping OFDM). We show how the new waveforms can withstand these impairments, how we benefit from an increased robustness to unexpected time and frequency synchronization errors, and how we can dramatically reduce out of band spurious emissions for a peaceful coexistence of adjacent frequency and power uncoordinated transmissions. We finish the keynote speech by presenting several perspectives for pulse shaping, pertaining to partially equalized OFDM, multi-pulse OFDM and single- and multi-pulse OFDM/OQAM.

Mohamed Siala received his general engineering degree from EcolePolytechnique, Palaiseau, France, in 1988, his specialization engineering degree in telecommunications from Telecom ParisTech, Paris, France, in 1990, and his Ph.D. in digital communications from Telecom ParisTech, Paris, France, in 1995. From 1990 to 1992, he was with Alcatel Radio-Telephones, Colombes, France, working on the GSM physical layer. In 1995, he joined Wavecom, Issy-les-Moulineaux, France, where he worked on advanced multicarrier modulations and channel estimation for low-orbit mobile satellite communications. From 1997 to 2001, he worked at Orange Labs, Issy-les-Moulineaux, France, on the physical layer of 3G systems and participated actively on the standardization of the physical layer of the UMTS system. In 2001, he joined Sup’Com, Tunis, Tunisia, where he is now a full Professor. His research interests are in the areas of digital and wireless communications with special emphasis on OFDM with optimized pulse shaping, channel estimation, efficient synchronization algorithms for OFDM, optimum combination of adaptive modulation and coding and power control, ARQ, MIMO systems, space-time coding, relaying, cooperative networks and cognitive radio with efficient multiband sensing. Mohamed Siala holds around 190 journal and conference research papers and 6 patents on channel estimation for CDMA and OFDM.