Now showing items 21-40 of 75

    • Dual Problems in Power Control 

      Sabharwal, Ashutosh; Rajan, Dinesh; Aazhang, Behnaam (2001-10-20)
      In this paper, we study power control to minimize packet loss for delay-bounded transmission of bursty sources over Gaussian channels and transmission of constant rate sources over time-varying block fading channels. In ...
    • Exploring the effect of food intake and physical activity on body weight 

      Prioleau, Temiloluwa; Heng, Yuqiang; Veeraraghavan, Ashok; Sabharwal, Ashutosh (2017)
      Body weight is an important measurement parameter towards management of obesity, diabetes and overall health. Previous research and society at large has primarily focused on long-term fluctuation in body weight to describe ...
    • Feedback gain in Multiple Antenna Systems 

      Bhashyam, Srikrishna; Sabharwal, Ashutosh; Aazhang, Behnaam (2002-05-20)
      Multiple antenna transmission and reception have been shown to significantly increase the achievable data rates of wireless systems. However, most of the existing analysis assumes perfect or no channel information at the ...
    • Finite Backlog Effects on Downlink Scheduling 

      Ahmed, Nasir; Khojastepour, Mohammad; Sabharwal, Ashutosh; Aazhang, Behnaam (2003-11-20)
      In a multi-user downlink system, the use of channel estimates in the scheduling process can significantly improve the spectral efficiency. Recent work has shown that from a sum rate capacity standpoint, and assuming infinite ...
    • Finite Rate Feedback Design for Multiple Transmit Antennas 

      Mukkavilli, Krishna Kiran; Sabharwal, Ashutosh; Aazhang, Behnaam (2002-10-20)
      Many practical systems employ a feedback channel to convey the channel state information to the transmitter.The capacity of the feedback channels is usually limited to a few bits per frame. We design feedback based ...
    • An FPGA Based Rapid Prototyping Platform for MIMO Systems 

      Murphy, Patrick; Lou, Feifei; Sabharwal, Ashutosh; Frantz, Patrick (2003-11-20)
      There exists a seemingly limitless demand for wireless communications systems capable of higher datarates with lower power consumption. While the demand for improvement in these systems seems limitless, the spectrum ...
    • FPGA in Wireless Communications Applications 

      Amiri, Kiarash; Duarte, Melissa; Cavallaro, Joseph R.; Dick, Chris; Rao, Raghu; Sabharwal, Ashutosh (2012-07-12)
      In the past decade we have witnessed explosive growth in the wireless communications industry with over 4 billion subscribers worldwide. While first and second generation systems focused on voice communications, third ...
    • Generalized Beamforming for MIMO Systems with Limited Transmitter Information 

      Mukkavilli, Krishna Kiran; Sabharwal, Ashutosh; Aazhang, Behnaam (2003-11-20)
      In this work, we investigate the outage performance of beamforming schemes in wireless systems equipped with multiple transmit and receive antennas. In particular, we analyze the outage performance of unit rank beamforming ...
    • Half-Duplex Estimate-and-Forward Relaying: Bounds and Code Design 

      Chakrabarti, Arnab; de Baynast, Alexandre; Sabharwal, Ashutosh; Aazhang, Behnaam (2006-07-01)
      We propose a coding scheme for half-duplex estimate-and-forward relaying. Our first contribution is to present an achievable rate for the estimate-and-forward protocol. We also derive the achievable rate for the special ...
    • Half-Duplex Estimate-and-Forward Relaying:Bounds and Code Design 

      Chakrabarti, Arnab; de Baynast, Alexandre; Sabharwal, Ashutosh; Aazhang, Behnaam (2006-01-01)
      We propose a coding scheme for half-duplex estimate-and-forward relaying. Our first contribution is to present an achievable rate for the estimate-and-forward protocol. We also derive the achievable rate for the special ...
    • Impact of Multiple Access on Uplink scheduling 

      Rajan, Dinesh; Sabharwal, Ashutosh; Aazhang, Behnaam (2001-09-20)
      In this paper, we consider uplink scheduling for bursty traffic. We characterize the achievable rate region for Gaussian multiple access in terms of minimum required powers, with a constraint on average transmission delay ...
    • Improved Achievable Rates for User Cooperation and Relay Channels 

      Khojastepour, Mohammad; Sabharwal, Ashutosh; Aazhang, Behnaam (2004-06-01)
      In this paper, we derive a new achievable rate region for the user cooperation channel, which exceeds the best known result for this channel [Wil83]. Since the user cooperation channel includes many other known channels ...
    • Interference management with mismatched partial channel state information 

      Vahid, Alireza; Aggarwal, Vaneet; Avestimehr, A. Salman; Sabharwal, Ashutosh (2017-08-03)
      Abstract We study the fundamental limits of communications over multi-layer wireless networks where each node has only limited knowledge of the channel state information. In particular, we consider the scenario ...
    • Interference management with mismatched partial channel state information 

      Vahid, Alireza; Aggarwal, Vaneet; Avestimehr, A. Salman; Sabharwal, Ashutosh (2017)
      We study the fundamental limits of communications over multi-layer wireless networks where each node has only limited knowledge of the channel state information. In particular, we consider the scenario in which each ...
    • LDPC Code Design for Half-Duplex Decode-and-Forward Relaying 

      Chakrabarti, Arnab; de Baynast, Alexandre; Sabharwal, Ashutosh; Aazhang, Behnaam (2005-09-01)
      We propose LDPC code designs for the half-duplex relay channel. Our designs mimic the information theoretic random coding scheme for decode-and-forward relaying. An important advantage of our scheme is that it is built ...
    • LDPC Code Design for OFDM Channel: Graph Connectivity and Information Bits Positioning 

      de Baynast, Alexandre; Sabharwal, Ashutosh; Aazhang, Behnaam (2005-07-01)
      We present an optimized channel coding scheme for OFDM transmission. In the future wireless standards such IEEE 802.11n, frame error rates (FER) as low as 0.0001 are targeting. Irregular LDPC codes have excellent performance ...
    • LDPC Code Design for Relay Channel in Time-Division mode 

      de Baynast, Alexandre; Chakrabarti, Arnab; Sabharwal, Ashutosh; Aazhang, Behnaam (2006-06-01)
      We address the problem of LDPC code design for relay channel in time-division mode based on a distributed strategy: In the first time slot, the source transmits part of the codeword. The relay and the destination receive ...
    • LDPC Code-Design for the Relay Channel 

      Chakrabarti, Arnab; de Baynast, Alexandre; Sabharwal, Ashutosh; Aazhang, Behnaam (2006-06-01)
      We propose LDPC code designs for the half-duplex relay channel. Our designs are derived from the information theoretic random coding scheme for decode-and-forward relaying. An important advantage of our scheme is that it ...
    • LDPC Code-Design for the Relay Channel 

      Chakrabarti, Arnab; de Baynast, Alexandre; Sabharwal, Ashutosh; Aazhang, Behnaam (2006-02-01)
      We propose LDPC code designs for the half-duplex relay channel. Our designs are derived from the information theoretic random coding scheme for decode-and-forward relaying. An important advantage of our scheme is that it ...
    • Lower Bounds on the Capacity of Gaussian Relay Channel 

      Khojastepour, Mohammad; Sabharwal, Ashutosh; Aazhang, Behnaam (2004-03-01)
      It has been shown recently that the overall throughput of dense wireless networks can increase significantly when wireless nodes collaborate in transmission of different packets. In this paper, we focus on a simple network ...