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 TitleDate AddedCompany
whitepaper ICI Cancellation Based Channel Estimation for OFDM Systems0000-00-00 University of South Florida
  Orthogonal Frequency Division Multiplexing OFDM), which is a multicarrier modulation scheme, splits high data rate information symbols into lower rate parallel data streams and transmits this parallel information on different orthogonal carriers. The loss of orthogonality among subcarriers causes inter-carrier interference (ICI), which affects both channel estimation and detection of OFDM data symbols. Channel estimation error degrades the performance of coherent receiver limiting capacity, data rate and performance of the overall OFDM system. This paper proposes a novel frequency-domain channel estimator, which mitigates the effects of ICI by jointly finding the frequency offset and channel frequency response (CFR).   
whitepaper Intercarrier and Intersymbol Interference Analysis of OFDM Systems on Time-Varying Channels0000-00-00 University of Hannover
  In intersymbol interference (ISI) and intercarrier interference (ICI) for OFDM systems with insufficient guard length was analyzed in the case of time-invariant radio channels. This was carried out by truncating the channel impulse response (CIR) in mathematical analysis into two parts, the so-called truncated channels. The same technique is used in this paper to compute the ISI and ICI components for the case of time-varying channels, where again the WSSUS assumption (wide sense stationary uncorrelated scattering) is applied.   
whitepaper Adaptive Resource Allocation in Multiuser OFDM Systems With Proportional Fairness2004-06-13 University of Texas at Austin
  Multiuser orthogonal frequency division multiplexing (MU-OFDM) is a promising technique for achieving high downlink capacities in future cellular and wireless LAN systems. The sum capacity of MU-OFDM is maximized when each subchannel is assigned to the user with the best channel-to-noise ratio for that subchannel, with power subsequently distributed by water-filling. However, fairness among the users cannot generally be achieved with such a scheme. In this paper, we impose a set of proportional fairness constraints to assure that each user can achieve a required data rate, as in a system with quality of service guarantees. Since the optimal solution to the constrained fairness problem is extremely computationally complex to obtain, this paper proposes a low-complexity suboptimal algorithm that separates subchannel allocation and power allocation.

Tags: Mobile and Wireless, 		  
whitepaper Impact of the Propagation Environment on the Performance of Space-Frequency Coded MIMO-OFDM0000-00-00 ETH Zurich
  Previous work on space-frequency coded MIMOOFDM has been restricted to idealistic propagation conditions. In this paper, using a broadband MIMO channel model taking into account Ricean K-factor, transmit and receive angle spread, and antenna spacing, we study the impact of the propagation environment on the performance of space-frequency coded MIMO-OFDM.   
whitepaper M-QAM OFDM and PCC-OFDM Performance in the Presence of Phase Noise2003-11-10 Monash University
  This paper addresses the issue of OFDM and PCC-OFDM systems impaired by phase noise (PN). PCC-OFDM is a variation of OFDM in which data is mapped onto adjacent subcarrier pairs. As a result intercarrier interference (ICI) in adjacent subcarriers is cancelled. Phase noise in OFDM causes both ICI and common phase error (CPE). PCC-OFDM reduces the ICI component, but the CPE is unchanged. Theoretical and simulations results for bit error rate (BER) are presented for M-QAM OFDM and PCC-OFDM systems over Rayleigh fading channels. The performance with and without CPE correction at the receiver is considered. It is shown that PCC-OFDM has a lower BER in all cases. The theoretical results agree closely with the computer simulations.   
whitepaper Spectral Spreading by Linear Block Codes for OFDM in Powerline Communications2002-08-14 University of Saarland
  Power Line Communication (PLC) uses the highly developed infrastructure of the electrical energy distribution network for data transmission. Measurements are showing that a broadband use of PLC channels is possible. So, PLC is of interest to future broadband communication systems. Such systems will be heterogeneous in several respects, for example relative to the used transmission channel but also relative to the complexity of the participant nodes.

Tags: Mobile and Wireless		   
whitepaper OFDM or Single-Carrier Block Transmissions?2004-03-01 Regents of the University of Minnesota
  This paper compares two block transmission systems over frequency-selective fading channels: orthogonal frequency-division multiplexing (OFDM) versus single-carrier modulated blocks with zero padding (ZP). It first compares their peak-to-average power ratio (PAR) and the corresponding power amplifier backoff for phase-shift keying or quadrature amplitude modulation. Then it studies the effects of carrier frequency offset on their performance and throughput. It further compares the performance and complexity of uncoded and coded transmissions over random dispersive channels, including Rayleigh fading channels, as well as practical HIPERLAN/2 indoor and outdoor channels.   
whitepaper Generalized 8-PSK for Totally Blind Channel Estimation in OFDM0000-00-00 University of Stuttgart
  Channel estimation in OFDM systems can conveniently be done by inserting a stream of pilot symbols at the transmitter and by using FIR interpolation filters at the receiver. Most blind channel estimation approaches are based on higher order statistics and converge slowly, making them unsuitable for mobile environments. Moreover, the channel estimate suffers from a phase blindness, which can only be resolved by pilot symbols. The concept of totally blind channel estimation makes pilots completely unnecessary and even works in rapidly time varying environments. This is achieved by using two different modulation schemes, such as QPSK and 3-PSK, on adjacent subcarriers. This paper develops the concept of totally blind channel estimation by applying a regular 8-PSK and a generalized 8-PSK to achieve totally blind channel estimation without the need for any pilot symbols.   
whitepaper Constant Envelope OFDM Phase Modulation: Spectral Containment, Signal Space Properties and Performance0000-00-00 Regents of the University of California
  A class of constant envelope OFDM phase modulated (OFDM-PM) signals is studied. The motivation behind OFDM-PM is to alleviate the high peak-to-average power ratio of conventional OFDM systems. Power density spectrum plots and fractional out-of-band power curves are given. For small modulation indices, the OFDM-PM signals are shown to be more spectrally contained than conventional OFDM. The signal space is studied by considering the correlation properties of the OFDM-PM signals. A performance bound on the optimum OFDM-PM receiver is compared to simulation results.   
whitepaper OFDM Versus Single Carrier With Cyclic Prefix: A System-Based Comparison0000-00-00 Interuniversity MicroElectronics Center
  In recent years, wireless indoor networks have received a lot of scientific and industrial attention. Most systems rely on the use of Orthogonal Frequency Division Multiplexing (OFDM) because of its capability to elegantly cope with multi-path interference. However, while OFDM provides a nice solution for the digital modem, its front-end requirements should be investigated as well. To that goal, authors have set up a simulation environment, which comprises both the digital modem and the most important front-end non-idealities. This paper shows that for the same data rate, bandwidth and transmit power constraints Single-Carrier with Cyclic Prefix (SC-CP) allows the design of a more power efficient modem than OFDM and is therefore a better candidate for portable wireless terminals.

Tags: Network Management,