spread fading
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ICI Mitigation for Pilot-Aided OFDM Mobile Systems
White Paper Orthogonal frequency-division multiplexing (OFDM) is robust against frequency selective fading due to the increase of the symbol duration. As delay spread increases, symbol duration should also increase in order to maintain a near-constant channel... [16 May 2008]
Replica Analysis of Large-System CDMA
White Paper It is found that the spectral efficiency of randomly spread CDMA subject to Gaussian noise and flat fading in the large-system limit under arbitrary input distributions. This paper presents some new results on large-system CDMA obtained through the... [10 Apr 2008]
Feasibility of Adaptive Transmission for Multicarrier and Frequency Hopping Mobile Radio Systems
White Paper The paper describes the design and performance of adaptive transmission methods enabled by the Long Range Fading Prediction algorithms (LRP) for Orthogonal Frequency Division Multiplexing (OFDM) and slow Frequency-Hopping Spread Spectrum (FH/SS... [31 Aug 2007]
Feasibility of Adaptive Transmission for Multicarrier and Frequency Hopping Mobile Radio Systems
White Paper The paper describes the design and performance of adaptive transmission methods enabled by the Long Range Fading Prediction algorithms (LRP) for Orthogonal Frequency Division Multiplexing (OFDM) and slow Frequency-Hopping Spread Spectrum (FH/SS... [10 Aug 2007]
Multilevel Codes for OFDM-Like Modulation Over Underspread Fading Channels
White Paper This paper studies the problem of modulation and coding for doubly dispersive, i.e.time and frequency selective fading channels. Using the recent result that under-spread linear systems are approximately diagonalized by biorthogonal Weyl-Heisenberg... [18 Apr 2007]
Asymptotic Performance of Transmit Diversity Via OFDM for Multipath Channels
White Paper The major drawback is that this system only works when a "Flat-fading" model for the channel is assumed; when used in a multipath environment, the system breaks down. Here it shows that when the Alamouti code is placed within an OFDM structure... [13 Apr 2007]
Increasing Time Domain Diversity in OFDM Systems
White Paper Delay- and Doppler spread of multipath fading channels have already been identified as sources of diversity in wireless communications systems. This paper proposes a method for increasing the Doppler spread of the multipath fading channel without... [11 Apr 2007]
Optimum Beamforming for Pre-FFT OFDM Adaptive Antenna Array
White Paper It is well known that Orthogonal Frequency-Division Multiplexing (OFDM) is robust to frequency-selective fading in wireless channels due to the exploitation of a guard interval that is inserted at the beginning of each OFDM symbol. [11 Apr 2007]
Efficient Video Transmission Over Correlated Nakagami Fading Channels for IS-95 CDMA Systems
White Paper This paper deals with the problem of efficient transmission of video signals over generalized fading channels in Direct Sequence-Spread Spectrum (DS-SS) Code Division Multiple Access (CDMA) systems. By integrating the proposed video codec with a... [10 Nov 2006]
Diversity Gain for CDMA Systems Equipped With Antenna Arrays
White Paper In order to achieve the diversity gain, this paper proposes a beamforming method that utilizes two beamforming weight vectors and applies this beamforming technique to Code-Division Multiple-Access (CDMA) systems equipped with antenna arrays under... [21 Feb 2006]
Tradeoff Between Source Coding and Spreading in a Multicarrier DS-CDMA System Operating Over Multipath Fading Channels With Narrow-Band Interference
White Paper For a fixed total bandwidth expansion factor, and for a fixed channel code rate, the authors' consider the problem of optimal bandwidth allocation between the source coder and the spread-spectrum unit for a multicarrier direct-sequence CDMA system... [14 Feb 2006]
The Impact of Frequency-Flat Fading on the Spectral Efficiency of CDMA
White Paper The capacity of the randomly spread synchronous Code-Division Multiple-Access (CDMA) channel subject to frequency- flat fading is studied in the wide-band limit of large number of users. This paper finds the spectral efficiency as a function of the... [12 Jan 2006]
Spectral Efficiency of MC-CDMA: Linear and Non-Linear Receivers
White Paper This paper analyzes the spectral efficiency (total channel capacity per subband) of randomly-spread synchronous MultiCarrier Code-Division Multiple-Access (MC-CDMA) channel subject to frequency-selective fading in the asymptotic regime of number... [12 Jan 2006]
Data-Aided Timing Offset Estimation for Frequency Selective Fading Channels
White Paper A novel algorithm for Timing offset estimation is proposed in this paper for GSM and GPRS handsets, especially for multi-path channels with large delay-spread. The timing offset leads to errors in the channel response estimation with a consequent... [21 Nov 2005]
Increase in Co-Located Simultaneous Transmissions for CDMA Ad Hoc Networks
White Paper This paper shows that this trade off favors CDMA as the density of the network increases both for AWGN and fading channel. The improvement in capacity normalized are quantified by the cost in bandwidth expansion for a spread spectrum ad hoc network... [13 Oct 2005]
