Now showing items 1-20 of 134

  • Achievable Rates for Arbitrary Network Topologies with â Cheapâ Nodes 

    Khojastepour, Mohammad; Sabharwal, Ashutosh; Aazhang, Behnaam (2003-05-01)
    In this paper, we derive achievable rates for arbitrary network topologies consisting of â cheapâ nodes. A node is labeled â cheapâ if its radio can only operate in TDD mode when transmitting and receiving in the ...
  • All-optical CDMA with bipolar codes 

    Nguyen, Lim; Aazhang, Behnaam; Young, James F. (1995-03-20)
    A method for the transmission and detection of bipolar sequences in a unipolar system is presented. It allows all-optical implementation, in noncoherent optical CDMA systems, of the bipolar codes that have been developed ...
  • Analysis of Decision-Feedback Based Broadband OFDM Systems 

    de Baynast, Alexandre; Sabharwal, Ashutosh; Aazhang, Behnaam (2005-11-01)
    In wireless communications, about 25% of the bandwidth is dedicated to training symbols for channel estimation. By using a semi-blind approach, the training sequence length can be reduced while improving performance. The ...
  • Antenna Packing in Low Power Systems: Communication Limits and Array Design 

    Muharemovic, Tarik; Sabharwal, Ashutosh; Aazhang, Behnaam (2005-01-01)
    In this paper, we study design of transceiver antenna arrays and its impact on spectral efficiency of low-power systems. Our primary motivation is construction of practical and portable multi-antenna configurations with a ...
  • An Approach to Capacity Analysis of Coarsely Coordinated Low Power Multiple Access Systems 

    Muharemovic, Tarik; Sabharwal, Ashutosh; Aazhang, Behnaam (2004-07-01)
    We consider multiaccess problem in low power systems, where we allow each user to select its own data rate and transmit power locally and independently from other users. Here, every user has a set of low power codebooks, ...
  • Bayesian Blind PARAFAC Recievers forDS-CDMA Systems 

    de Baynast, Alexandre; Declercq, David; De Lathauwer, Lieven; Aazhang, Behnaam (2003-10-01)
    In this paper an original Bayesian approach for blind detec-tion for Code Division Multiple Access (CDMA) Systems in presence of spatial diversity at the receiver is developed. In the noiseless context, the blind ...
  • 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 ...
  • BER of optical communication system using fiber source 

    Nguyen, Lim; Aazhang, Behnaam; Young, James F. (1995-11-20)
    We analyze the bit-error rate (BER) of an optical communication system using the superfluorescent fiber source (SFS). The counting statistics of thermal light give improved performance relative to the Gaussian statistics ...
  • Blind PARAFAC Receivers for Multiple Access-Multiple Antenna Systems 

    de Baynast, Alexandre; De Lathauwer, Lieven; Aazhang, Behnaam (2003-10-01)
    In this paper, we present a new blind receiver for multiple access channel with multiple transmit antennas per user and multiple receive antennas (MIMO channel). After being multiplied by a spreading sequence, each user s ...
  • Bounds on Achievable Rates for General Multi-terminal Networks with Practical Constraints 

    Khojastepour, Mohammad; Aazhang, Behnaam; Sabharwal, Ashutosh (2003-04-20)
    We consider the problem of communication in a general multi-terminal network where each node of the network is a potential sender or receiver (or both) but it cannot do both functions together. The motivation for this ...
  • Broadcast Space-Time Coding 

    Memarzadeh, Mahsa; Sabharwal, Ashutosh; Aazhang, Behnaam (2001-08-20)
    In this paper, we study transmission techniques for broadcast channels with a single transmitter and multiple receivers. The transmitter is assumed to be equipped with multiple antennas. Further, each receiver is interested ...
  • The Capacity of Average and Peak Power Constrained Fading Channels with Channel Side Information 

    Khojastepour, Mohammad; Aazhang, Behnaam (2004-03-01)
    We derive the ergodic capacity of discrete-time fading channel with additive Gaussian noise subject to both peak and average power constraint. The average power can be interpreted as the cost that we incur to achieve a ...
  • 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 ...
  • Computationally Efficient Multiuser Detectors 

    Das, Suman; Cavallaro, Joseph R.; Aazhang, Behnaam (1997-09-20)
    CDMA is becoming an increasingly popular multiplexing scheme in wireless communications and this has necessitated the development of efficient detection techniques. The exponential complexity of the optimal detector on ...
  • Constellations for Imperfect Channel State Information at the Receiver 

    Borran, Mohammad Jaber; Sabharwal, Ashutosh; Aazhang, Behnaam (2002-10-20)
    We consider the problem of digital communication in a Rayleigh flat fading environment using a multiple antenna system. We assume that the transmitter doesn't know the channel coefficients, and that the receiver has only ...
  • Contraction, Smoothness, and Low-Pass Filtering 

    Khojastepour, Mohammad; Aazhang, Behnaam; Baraniuk, Richard G. (2004-05-01)
    We introduce a generalized definition for "low-pass" filters that covers time-varying and nonlinear systems under the same umbrella. We show that the qualitative concept of signal smoothing can be made precise through the ...
  • Cooperative Communications in the Fading Channel 

    Ahmed, Nasir; Aazhang, Behnaam (2005-03-01)
    Cooperative coding is a communication paradigm that pools distributed resources of different nodes in a network, such that the nodes act like a collaborative system instead of greedy adversarial participants. Cooperation ...
  • COOPERATIVE COMMUNICATIONS: Fundamental Limits and Practical Implementation 

    Chakrabarti, Arnab; Sabharwal, Ashutosh; Aazhang, Behnaam (2006-01-01)
    This chapter summarizes theoretically achievable gains and the construction of practical codes for user-cooperation. Most of these results relate to the relay channel, which is a three-terminal channel that captures the ...
  • Cut-set Theorems for Multi-state Networks 

    Khojastepour, Mohammad; Aazhang, Behnaam; Sabharwal, Ashutosh (2003-10-01)
    We derive new cut-set bounds on the achievable rates in a general multi-terminal network with finite number of states. Multiple states are common in communication networks in the form of multiple channel and nodes' states. ...