Now showing items 1-17 of 17

  • Beamformer Design with Feedback Rate Constraints : Criteria and Constructions 

    Mukkavilli, Krishna Kiran; Sabharwal, Ashutosh; Erkip, Elza; Aazhang, Behnaam (2003-07-20)
    In this work, we provide a geometrical framework for the analysis and design of beamformer codebooks with finite number of beamformer vectors. We present a design criterion for good beamfomer codebooks and show the equivalence ...
  • A comparative study of multiple accessing schemes 

    Erkip, Elza; Aazhang, Behnaam (1997-11-20)
    We compare the performance of different accessing schemes (frequency division, time division and code division) for the uplink in a wireless communication system. We assume an additive white Gaussian noise channel with ...
  • Computationally Efficient Iterative Multiuser Detection and Decoding 

    Das, Suman; Erkip, Elza; Aazhang, Behnaam (1998-11-20)
    We describe an iterative detection and decoding scheme for the uplink in a convolutionally coded direct sequence code division multiple access (DS-CDMA) system. We consider maximum-a-posteriori (MAP) decoding and reduce ...
  • Distorted Channel Capacity: A Geometrical Approach 

    Das, Suman; Cavallaro, Joseph R.; Erkip, Elza; Aazhang, Behnaam (2000-06-20)
    Shannon's capacity result has often been used as a benchmark to compare the performance of practical codes. Shannon's theorem helps us to calculate the maximum rate at which data can be transferred without making any errors. ...
  • Increasing uplink capacity via user cooperation diversity 

    Sendonaris, Andrew; Erkip, Elza; Aazhang, Behnaam (IEEE, 1998-08-20)
    Mobile users' capacity is limited by the fact that within the duration of any given call, they experience severe variations in signal attenuation, thereby necessitating the use of some type of diversity. We are proposing ...
  • Iterative Multiuser Detection and Decoding 

    Das, Suman; Erkip, Elza; Cavallaro, Joseph R.; Aazhang, Behnaam (1998-11-20)
    An iterative detection and decoding algorithm is explored for a convolutionally coded DS-CDMA system. The optimum decoding strategy is to consider the trellises of all the users simultaneously, but this has exponential ...
  • Low Complexity Iterative Multiuser Detection and Decoding for Real-Time Applications 

    Das, Suman; Erkip, Elza; Cavallaro, Joseph R.; Aazhang, Behnaam (IEEE, 2005-07-01)
    This paper presents a low-complexity multiuser decoding technique that can be implemented in real time for a convolutionally coded direct sequence code division multiple access (DS-CDMA) system. The main contribution, ...
  • Maximum Weight Basis Decoding of Convolutional Codes 

    Das, Suman; Erkip, Elza; Cavallaro, Joseph R.; Aazhang, Behnaam (IEEE, 2002-11-01)
    In this paper we describe a new suboptimal decoding technique for linear codes based on the calculation of maximum weight basis of the code. The idea is based on estimating the maximum number locations in a codeword which ...
  • Maximum Weight Basis Decoding of Convolutional Codes 

    Das, Suman; Erkip, Elza; Cavallaro, Joseph R.; Aazhang, Behnaam (2000-06-20)
    The effectiveness of the convolutional code increases with the constraint length of the code. Unfortunately the decoding complexity of Viterbi algorithm grows exponentially with the constraint length. In this paper we ...
  • Multiple access schemes over multipath fading channels 

    Erkip, Elza; Aazhang, Behnaam (1998-10-20)
    We compare the performance of different accessing schemes for communication over an additive white Gaussian noise multiple access channel with multipath fading. We assume that only the receiver can track the channel ...
  • New Spread Spectrum Techniques for Multiple Antenna Transmit Diversity 

    Rajan, Dinesh; Erkip, Elza; Aazhang, Behnaam (1999-12-20)
    We propose a new scheme for multiple antenna transmission in the context of spread spectrum signaling. The new scheme consists of using shifted Gold sequences to modulate independent information on the multiple atennas. ...
  • On Beamforming with Finite Rate Feedback in Multiple Antenna Systems 

    Mukkavilli, Krishna Kiran; Sabharwal, Ashutosh; Erkip, Elza; Aazhang, Behnaam (2003-10-20)
    In this paper, we study a multiple antenna system where the transmitter is equipped with quantized information about instantaneous channel realizations. Assuming that the transmitter uses the quantized information for ...
  • On Channel State Information in Multiple Antenna Block Fading Channels 

    Sabharwal, Ashutosh; Erkip, Elza; Aazhang, Behnaam (2000-11-20)
    Motivated by large capacity gains in multiple antenna systems when perfect channel state information is available at both receiver and transmitter, we examine the achievable rates of channel measurement based techniques. ...
  • Performance limits on beamforming with finite rate feedback for multiple antenna systems 

    Mukkavilli, Krishna Kiran; Sabharwal, Ashutosh; Erkip, Elza; Aazhang, Behnaam (2002-11-20)
    In this work, we address the problem of evaluating the outage performance of beamformers designed for multiple transmit and single receive antenna systems when quantized channel state information is available at the ...
  • Spreading and Power Allocation for Multiple Antenna Transmission using Decorrelating receivers 

    Rajan, Dinesh; Erkip, Elza; Aazhang, Behnaam (2003-05-20)
    We propose a new scheme for multiple antenna transmission in the context of spread spectrum signaling. The new scheme consists of using shifted Gold sequences to modulate independent information on the multiple antennas. ...
  • User Cooperation Diversity--Part I: System Description 

    Sendonaris, Andrew; Erkip, Elza; Aazhang, Behnaam (2003-11-20)
    Mobile users' data rate and quality of service are limited by the fact that, within the duration of any given call, they experience severe variations in signal attenuation, thereby necessitating the use of some type of ...
  • User Cooperation Diversity--Part II: Implementation Aspects and Performance Analysis 

    Sendonaris, Andrew; Erkip, Elza; Aazhang, Behnaam (2003-11-20)
    This is the second in a two-part series of papers on a new form of spatial diversity, where diversity gains are achieved through the cooperation of mobile users. Part I described the user cooperation concept and proposed ...