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 TitleDate AddedCompany
whitepaper Cross-Layer Optimization for Scheduling in OFDM-TDMA Transmission2004-10-15 ETH Zurich
  In the integrated project My personal Adaptive Global NET (MAGNET) of the European Union, advanced adaptive and scalable air interface concepts for personal area networks (PANs) are being studied. The activities are grouped in clusters dealing with different data rates in the physical layer. This paper gives an overview of some initial activities in the air interface design considered in the orthogonal frequency-division multiplexing (OFDM) time-division multiple access (TDMA) cluster.

Tags: Components, Mobile and Wireless		   
whitepaper Pilot-to-Data Power Ratio for Maximizing the Capacity of MIMO-OFDM2004-11-22 Institute of Electrical and Electronics Engineers
  Orthogonal frequency division multiplexing (OFDM) can be used with a multiple-input multiple-output (MIMO) system to improve communication quality and capacity. Pilot-symbol-aided or decision-directed channel estimation must be used to track the variations of the channel. However, while pilot symbols facilitate channel estimation, they reduce the transmit energy for data symbols per OFDM symbol under a fixed total transmit power constraint. This paper analyzes the effects of pilot-symbol-aided channel estimation on the lower bound of the system capacity in MIMO-OFDM systems with three different types of pilot patterns: independent, scattered, and orthogonal.

Tags: Mobile and Wireless, Components, 		  
whitepaper Multiuser Interference Cancellation for OFDM Systems With Frequency Offset2003-07-15 University of Florence
  This paper proposes a method to counteract the effect of different frequency offsets of the users in a OFDMA uplink system with frequency selective Rayleigh fading channel. The multiple access interference is reduced by reconstructing and removing the interfering signals. This is done by accomplish Successive or Selective Cancellation. The paper analyzes the performance of these cancellation schemes assuming either ideal or estimated frequency offsets.

Tags: Components, Mobile and Wireless		   
whitepaper UWB Coexistence and Cognitive Radio: How Multiband-OFDM Leads the Way2004-09-15 Alereon
  The recent history of Ultrawideband communications technology has seen great debate over whether these UWB cause unacceptable interference to existing users of the same and nearby bands. Building on the IEEE 802.15.2 Recommended Practice and the framework developed by IEEE 802.19, researchers are developing techniques to separate UWB signals for others using time, frequency, power, space, and coding, the five techniques available to minimize interference and maximize capacity. This paper explores general methods for using these parameters either to eliminate interference, or to achieve graceful, deterministic degradation.

Tags: Mobile and Wireless, Mobile and Wireless		   
whitepaper Design of a Multiband OFDM System for Realistic UWB Channel Environments2004-09-01 Institute of Electrical and Electronics Engineers
  There are many differences between real-world behavior of narrow-band and UWB systems. All wireless systems must be able to deal with the challenges of operating over a multipath propagation channel, where objects in the environment can cause multiple reflections to arrive at the receiver (RX). For narrow-band systems, these reflections will not be resolvable by the RX when the narrow-band system bandwidth is less than the coherence bandwidth of the channel. The large bandwidth of UWB waveforms, instead, significantly increases the ability of the RX to resolve the different reflections in the channel. The UWB channel model developed by the IEEE 802.15.3a standard body is described in this paper.

Tags: Components, Mobile and Wireless		   
whitepaper A MIMO-OFDM Prototype for Next-Generation Wireless WANs2004-12-01 Institute of Electrical and Electronics Engineers
  Coupled with a robust and efficient OFDM air interface, MIMO technologies lead to a very compelling high-speed data downlink solution for future wireless systems. This paper presents Nortel Networks' MIMO-OFDM concept prototype and measured performance results. This prototype has been developed in the framework of a Nortel Networks system concept for 3G evolution systems and next-generation wide area wireless networks.

Tags: Components, Mobile and Wireless		   
whitepaper Orthogonal Frequency Division Multiplexing (OFDM)2001-05-22 Helsinki University of Technology
  OFDM is a promising candidate for achieving high data rate transmission in mobile environment. The application of OFDM to high data rate mobile communication system is being investigated by many researchers. Also the introduction of Digital Audio Broadcasting (DAB) based on OFDM, successful test on OFDM for Digital Television Terrestrial Broadcasting (dTTb) and research on OFDM for HIPERLAN type II and Wireless ATM projects have increased the interested towards OFDM.

Tags: Mobile and Wireless, Components, 		  
whitepaper Space-Frequency Bit-Interleaved Coded Modulation for MIMO-OFDM/OFDMA Systems2004-11-04 Institute of Electrical and Electronics Engineers
  This paper proposes space-frequency bit-interleaved coded modulation (SF-BICM), which provides both frequency diversity and spatial diversity by interleaving coded bits across transmit antennas and frequency tones. Performance of the proposed SF-BICM is compared to spatial multiplexing (F-BICM) using 802.16e-like coding and modulation over ITU channel models. Performance is demonstrated with minimum mean squared error (MMSE) spatial receivers per tone.

Tags: Components, Mobile and Wireless		   
whitepaper Point-to-Point Transmission Over MIMO Channels With Intersymbol Interference: Comparison of Single- and Multicarrier Modulation2004-09-07 Friedrich-Alexander University Erlangen-Nuremberg
  In MIMO orthogonal frequency division multiplexing, temporal equalization is performed by applying OFDM, which decomposes the MIMO ISI channel into a set of independent flat fading MIMO channels. For each of this parallel channels (the carriers), spatial equalization, e.g., via V-BLAST, is performed individually. Conversely, in MIMO decision-feedback equalization both types of interferences are treated jointly. The advantages and disadvantaged of both strategies are enlightened, and results from numerical simulation are shown in this paper. The paper reveals under which conditions both strategies exhibit the same performance.

Tags: Mobile and Wireless, Mobile and Wireless		   
whitepaper Orthogonal Frequency Division Multiplexing Based on Offset QAM0000-00-00 ETH Zurich
  One of the factors determining the performance of wireless Orthogonal Frequency Division Multiplexing (OFDM) systems is time-frequency localization of the transmitter and receiver pulse shaping filters. OFDM based on offset quadrature amplitude modulation (OFDM/OQAM) bypasses a major disadvantage of OFDM based on ordinary QAM, namely the fact that time-frequency well-localized pulse shaping filters are prohibited in the case of critical time-frequency density where spectral efficiency is maximal. This paper studies the problem of pulse shaping filter design for OFDM/OQAM systems and establishes relations between OFDM/OQAM and Wilson and Gabor expansions.

Tags: Components, Mobile and Wireless