On Secure Communication over Wireless Erasure Networks (2009)
Andrew Mills, Brian Smith, T. Charles Clancy, Emina Soljanin, Sriram Vishwanath
Abstract — This paper studies the secrecy capacity of unicast communication in a wireless erasure network setting in the presence of a wire-tapper. From an information-theoretic setting of perfect...
On Degrees of Freedom Region of MIMO Networks without CSIT (2009)
Huang, Chiachi, Jafar, Syed A., Shamai, Shlomo, Vishwanath, Sriram
In this paper, we study the effect of the absence of channel knowledge for multiple-input-multiple-output (MIMO) networks. Specifically, we assume perfect channel state information at the receivers,...
Algebraic Traceback for Dynamic Networks (2009)
Das, Abhik K., Agarwal, Shweta, Vishwanath, Sriram
This paper introduces the concept of incremental traceback for determining changes in the trace of a network as it evolves with time. A distributed algorithm, based on the methodology of algebraic...
Hybrid Coding for Gaussian Broadcast Channels with Gaussian Sources (2009)
Soundararajan, Rajiv, Vishwanath, Sriram
This paper considers a degraded Gaussian broadcast channel over which Gaussian sources are to be communicated. When the sources are independent, this paper shows that hybrid coding achieves the...
On the Secrecy Rate of Interference Networks using structured codes (2009)
Agrawal, Shweta, Vishwanath, Sriram
This paper shows that structured transmission schemes are a good choice for secret communication over interference networks with an eavesdropper. Structured transmission is shown to exploit channel...
On Models of Multi-user Gaussian Channels with Fading (2009)
Haddad, Rony EL, Smith, Brian, Vishwanath, Sriram
An analytically tractable model for Gaussian multiuser channels with fading is studied, and the capacity region of this model is found to be a good approximation of the capacity region of the...
Ramya Bhagavatula, Robert W. Heath, Sriram Vishwanath
Abstract — In this paper, the feasibility of multiple-input multiple-output (MIMO) systems in aircraft is examined for the specific application of seatback entertainment, using an approach built...
Ergodic Interference Alignment (2009)
Nazer, Bobak, Gastpar, Michael, Jafar, Syed A., Vishwanath, Sriram
Consider a K-user interference channel under a block fading model. At any particular time, each receiver will see a signal from most transmitters. The standard approach to such a scenario results in...
Pilot Contamination Problem in Multi-Cell TDD Systems (2009)
Jose, Jubin, Ashikhmin, Alexei, Marzetta, Thomas L., Vishwanath, Sriram
This paper considers a multi-cell multiple antenna system with precoding used at the base stations for downlink transmission. To enable precoding, channel state information (CSI) at the base stations...
On the Stability Region of Cooperative Relay Networks with Fading States (2008)
Jose, Jubin, Ying, Lei, Vishwanath, Sriram
This paper considers an amplify-and-forward relay network and determines its maximum stable throughput. Amplify-and-forward (and other forwarding schemes) form the core mechanism for enabling...
Relay Subset Selection in Wireless Networks Using Partial Decode-and-Forward Transmission (2008)
Caleb K. Lo, Sriram Vishwanath, Robert W. Heath
This paper considers the problem of selecting a subset of nodes in a two-hop wireless network to act as relays in aiding the communication between the source-destination pair. Optimal relay subset...
Communicating the Difference of Correlated Gaussian Sources Over a MAC (2008)
Soundararajan, Rajiv, Vishwanath, Sriram
This paper considers the problem of transmitting the difference of two jointly Gaussian sources over a two-user additive Gaussian noise multiple access channel (MAC). The goal is to recover this...
Scheduling and Precoding in Multi-User Multiple Antenna Time Division Duplex Systems (2008)
Jose, Jubin, Ashikhmin, Alexei, Whiting, Phil, Vishwanath, Sriram
The downlink transmission in multi-user multiple antenna wireless communication systems is generally studied assuming channel state knowledge and the topic of determining this channel knowledge is...
On the Capacity of One-sided Two user Gaussian Fading Broadcast Channels (2008)
Jafarian, Amin, Vishwanath, Sriram
In this paper, we investigate upper and lower bounds on the capacity of two-user fading broadcast channels where one of the users has a constant (non-fading) channel. We use the Costa entropy power...
A Layered Lattice Coding Scheme for a Class of Three User Gaussian Interference Channels (2008)
Sridharan, Sriram, Jafarian, Amin, Vishwanath, Sriram, Jafar, Syed A., Shamai, Shlomo
The paper studies a class of three user Gaussian interference channels. A new layered lattice coding scheme is introduced as a transmission strategy. The use of lattice codes allows for an...
Capacity of Symmetric K-User Gaussian Very Strong Interference Channels (2008)
Sridharan, Sriram, Jafarian, Amin, Vishwanath, Sriram, Jafar, Syed A.
This paper studies a symmetric K user Gaussian interference channel with K transmitters and K receivers. A "very strong" interference regime is derived for this channel setup. A "very strong"...
Adaptive Mode Switching in the MIMO Broadcast Channel (2008)
Chulhan Lee, Chan-byoung Chae, Sriram Vishwanath, Robert W. Heath
Abstract — This paper proposes an adaptive mode switching between single user and multi-user multiple input multiple output (MIMO) transmissions for Gaussian MIMO broadcast channels with partial...
Rate Bounds for MIMO Relay Channels Using (2008)
Caleb K. Lo, Sriram Vishwanath, Robert W. Heath
Abstract — Relay channels will play a central role in nextgeneration multihop wireless systems. This paper considers the MIMO relay channel where multiple antennas are employed by each terminal....
Relay Subset Selection in Wireless Networks Using Partial Decode-and-Forward Transmission (2008)
Caleb K. Lo, Sriram Vishwanath, Robert W. Heath
Abstract — This paper considers the problem of selecting a set of relay nodes to assist a transmitting node in a two-hop wireless network. Throughput-maximizing relay subset selection is a...
Network With Costs: Timing and Flow Decomposition (2008)
Shreeshankar Bodas, Jared Grubb, Sriram Sridharan, Tracey Ho, Sriram Vishwanath
Abstract — This paper analyzes a capacitated network with costs from an information theoretic point of view. Specifically, it accomplishes the following for a series-parallel single...
Communication Through Jamming over a Slotted ALOHA Channel (2008)
Bhadra, Sandeep, Bodas, Shreeshankar, Shakkottai, Sanjay, Vishwanath, Sriram
This work derives bounds on the jamming capacity of a slotted ALOHA system. A system with n legitimate users, each with a Bernoulli arrival process is considered. Packets are temporarily stored at...
Relay-Assisted User Scheduling in Wireless Networks with Hybrid-ARQ (2008)
Lo, Caleb K., Hasenbein, John J., Vishwanath, Sriram, Heath Jr, Robert W.
This paper studies the problem of relay-assisted user scheduling for downlink wireless transmission. The base station or access point employs hybrid automatic-repeat-request (HARQ) with the...
An Energy-Based Comparison of Long-Hop and Short-Hop Routing in MIMO Networks (2008)
Lo, Caleb K., Vishwanath, Sriram, Heath Jr, Robert W.
This paper considers the problem of selecting either routes that consist of long hops or routes that consist of short hops in a network of multiple-antenna nodes, where each transmitting node employs...
Generalized Degrees of Freedom of the Symmetric Gaussian $K$ User Interference Channel (2008)
Jafar, Syed A., Vishwanath, Sriram
We characterize the generalized degrees of freedom of the $K$ user symmetric Gaussian interference channel where all desired links have the same signal-to-noise ratio (SNR) and all undesired links...
Wei Wu, Sriram Vishwanath, Ari Arapostathis
This paper is motivated by a sensor network on a correlated field where nearby sensors share information, and can thus assist rather than interfere with one another. We consider a special class of...
Secrecy Capacity of Semi-deterministic Wire-tap Channels (2008)
Jared Grubb, Sriram Vishwanath, Yingbin Liang, H. Vincent Poor
Abstract — This paper studies secrecy capacity in a semideterministic setting, in which the channel between legitimate users (called Alice and Bob) is deterministic, while that between Alice and...
Covert Communication over Slotted ALOHA Systems (2008)
Eep Bhadra, Sanjay Shakkottai, Sriram Vishwanath
This paper uses jamming legitimate transmissions over a slotted ALOHA system as a means of covert communication. The resulting covert channel is found to be source dependent, and to have infinite...
Opportunistic Relay Selection with Limited Feedback (2008)
Caleb K. Lo, Robert W. Heath, Sriram Vishwanath
Abstract — It has been shown that a decentralized relay selection protocol based on opportunistic feedback from the relays yields good throughput performance in dense wireless networks. This...
HYBRID-ARQ IN MULTIHOP NETWORKS WITH OPPORTUNISTIC RELAY SELECTION (2008)
Caleb K. Lo, Robert W. Heath, Sriram Vishwanath
This paper develops a contention-based opportunistic feedback technique towards relay selection in a dense wireless network. This technique enables the forwarding of additional parity information...
Adaptive Sum Power Iterative Waterfilling for MIMO Cognitive Radio Channels (2008)
Soundararajan, Rajiv, Vishwanath, Sriram
In this paper, the sum capacity of the Gaussian Multiple Input Multiple Output (MIMO) Cognitive Radio Channel (MCC) is expressed as a convex problem with finite number of linear constraints, allowing...
Random access over multiple access channels: a queuing perspective (2008)
Bodas, Shreeshankar, Vishwanath, Sriram, Subramanian, Vijay G.
This paper investigates a slotted random access system where packet capture is modeled using communication theoretic techniques. It is shown that the optimum rates and attempt probabilities depend on...
On the Capacity of a Class of MIMO Cognitive Radios (2007)
Sridharan, Sriram, Vishwanath, Sriram
Cognitive radios have been studied recently as a means to utilize spectrum in a more efficient manner. This paper focuses on the fundamental limits of operation of a MIMO cognitive radio network with...
Space-time turbo codes: decorrelation properties and performance analysis for fading channels (2007)
Sriram Vishwanath, Wei Yu, Rohit Negi, Andrea Goldsmith
Abstract|This paper studies the decorrelation property of the constituent codes in Space-Time Turbo Codes (STTCs), where dierent constituent codes are transmitted over different antennas. We show...
Optimum Resource Allocation for Multiple Access Fading Channels (2007)
Sriram Vishwanath, Andrea Goldsmith
We obtain the (Shannon) optimal power and rate allocation strategies for the uplink on single cell systems. For an N user system, we show that successive decoding which is independent of channel...
Adaptive resource allocation in composite fading environments (2007)
Sriram Vishwanath, Syed Ali Jafar, Andrea Goldsmith, David Packard, Electrical Engineering
Abstract | We obtain optimal resource allocation policies for a single user single-carrier system and a multipleaccess multi-carrier-CDMA system when the transmitter adapts to the variations in the...
1 Space-Time Turbo Codes: Decorrelation Properties (2007)
Sriram Vishwanath, Wei Yu, Andrea Goldsmith, Rohit Negi
This letter studies the decorrelation property of the constituent codes in Space-Time Turbo Codes (STTCs), where dierent constituent codes are transmitted over dierent antennas. We show that the time...
Throughput Maximization with Multiple Codes and Partial Outages (2007)
Syed Ali Jafar, Sriram Vishwanath, Andrea Goldsmith
Abstract--- We provide an information theoretic perspective on the problem of throughput maximization in a block flat fading wireless data system with codeword lengths restricted to be less than the...
1 Adaptive Turbo Coded Modulation for Flat Fading Channels (2007)
Sriram Vishwanath, Andrea Goldsmith
This paper considers dierent adaptive modulation techniques for at fading channels when turbo codes are used as channel codes. The optimal adaptive TuCM scheme is determined subject to various system...
On the Existence of a General Multiple-Access/Broadcast Channel Duality (2007)
Nihar Jindal, Sriram Vishwanath, Andrea Goldsmith
We investigate expanding the recently established Gaussian multiple-access/broadcast channel duality to a duality between discrete memoryless broadcast and multiple-access channels. More...
Relay Subset Selection in Wireless Networks Using Partial Decode-and-Forward Transmission (2007)
Lo, Caleb K., Vishwanath, Sriram, Heath Jr, Robert W.
This paper considers the problem of selecting a subset of nodes in a two-hop wireless network to act as relays in aiding the communication between the source-destination pair. Optimal relay subset...
Scheduling and Pre-Conditioning in Multi-User MIMO TDD Systems (2007)
Jose, Jubin, Ashikhmin, Alexei, Whiting, Phil, Vishwanath, Sriram
The downlink transmission in multi-user multiple-input multiple-output (MIMO) systems has been extensively studied from both communication-theoretic and information-theoretic perspectives. Most of...
Lo, Caleb K., Heath Jr., Robert W., Vishwanath, Sriram
This paper presents a decentralized relay selection protocol for a dense wireless network and describes channel feedback strategies that improve its performance. The proposed selection protocol...
Rate Bounds for MIMO Relay Channels (2007)
Lo, Caleb K., Vishwanath, Sriram, Heath Jr, Robert W.
This paper considers the multi-input multi-output (MIMO) relay channel where multiple antennas are employed by each terminal. Compared to single-input single-output (SISO) relay channels, MIMO relay...
Gustavo De Veciana, Sanjay Shakkottai, Lili Qiu, Sriram Vishwanath
program at the Wireless Networking and Communications Group (WNCG) at the University
On the capacity of a class of MIMO cognitive radios (2007)
Sriram Sridharan, Sriram Vishwanath
Cognitive radios have been studied recently as a means to utilize spectrum in a more efficient manner. This paper focuses on the fundamental limits of operation of a MIMO cognitive radio network with...
Robust Methods for Locating Multiple Dense Regions (2006)
Joydeep Ghosh Supervisor, Lizy Kurian John, Edward Marcotte, Raymond Mooney, Sriram Vishwanath
To my dear wife Sandrine, my son Neil, and my parents.
Gustavo De Veciana, Vijay K. Garg, Harrick Vin, Sanjay Shakkottai, Sriram Vishwanath, Shailesh Patil, ...
Dedicated to my parents, who have always encouraged me.
Communication Through Jamming Over a Slotted ALOHA Channel (2005)
Eep Bhadra, Sanjay Shakkottai, Sriram Vishwanath
This work derives bounds on the jamming capacity of a slotted ALOHA system. A system with n legitimate users, each with a Bernoulli arrival process is considered. Packets are temporarily stored at...
Gaussian Interference Networks with Feedback: Duality, Sum capacity and Dynamic Team Problems (2005)
Wei Wu, Sriram Vishwanath, Ari Arapostathis
This paper utilizes and extends the existing control-information theoretic interdisciplinary framework for analyzing multi-user systems with feedback. The results derived in this paper using this...
Sum power iterative water-filling for multi-antenna Gaussian broadcast channels (2005)
Nihar Jindal, Wonjong Rhee, Sriram Vishwanath, Syed Jafar, Andrea Goldsmith
In this paper we consider the problem of maximizing sum rate of a multiple-antenna Gaussian broadcast channel. It was recently found that dirty paper coding achieves the sum capacity of this channel....
This thesis is dedicated to my mother and the greatest influence on my life, Late Mrs. (2005)
Vishal Monga, Brian L. Evans, Ross Baldick, Wilson S. Geisler, John E. Gilbert, Joydeep Ghosh, ...
I would like to begin by thanking my parents, albeit I understand any amount of gratitude shown to them is woefully inadequate. My father’s unconditional support is largely the reason that this PhD...
On the Duality of Gaussian Multiple-Access and Broadcast Channels (2004)
Nihar Jindal, Student Member, Sriram Vishwanath, Andrea Goldsmith, Senior Member
We define a duality between Gaussian multiple-access channels (MACs) and Gaussian broadcast channels (BCs). The dual channels we consider have the same channel gains and the same noise power at all...
On the duality of Gaussian multiple-access and broadcast channels (2004)
Nihar Jindal, Sriram Vishwanath, Andrea Goldsmith
We define a duality between Gaussian multiple-access channels and Gaussian broadcast channels. The dual channels we consider have the same channel gains and the same noise power at all receivers. We...
Fundamental Capacity of MIMO Channels (2003)
Andrea Goldsmith, Syed Ali Jafar, Nihar Jindal, Sriram Vishwanath
broadcast channels. We provide an overview of the extensive recent results on the Shannon capacity of single-user and multiuser multiple-input multiple-output (MIMO) channels. Although enormous...
Capacity Limits of MIMO Channels (2003)
Andrea Goldsmith, Syed Ali Jafar, Nihar Jindal, Sriram Vishwanath
We provide an overview of the extensive recent results on the Shannon capacity of single-user and multiuser multiple-input multiple-output (MIMO) channels. Although enormous capacity gains have been...
Capacity Limits of MIMO Channels (2003)
Andrea Goldsmith, Senior Member, Syed Ali Jafar, Nihar Jindal, Sriram Vishwanath, Student Member, ...
Abstract—We provide an overview of the extensive recent results on the Shannon capacity of single-user and multiuser multiple-input multiple-output (MIMO) channels. Although enormous capacity gains...
Adaptive turbo-coded modulation for flat-fading channels (2003)
Sriram Vishwanath, Andrea Goldsmith, Senior Member
Abstract—In this paper, we consider a turbo-coded system employed on a flat-fading channel where the transmitter and receiver adapt the encoder, decoder, modulation scheme, and transmit power to...
Duality, achievable rates, and sum-rate capacity of Gaussian MIMO broadcast channels (2003)
Sriram Vishwanath, Nihar Jindal, Andrea Goldsmith
We consider a multiuser multiple-input multiple-output (MIMO) Gaussian broadcast channel (BC), where the transmitter and receivers have multiple antennas. Since the MIMO BC is in general a...
Duality, Achievable Rates and Sum-Rate Capacity of Gaussian MIMO Broadcast Channels (2003)
Sriram Vishwanath, Nihar Jindal, Andrea Goldsmith
We consider a multi-user multiple input multiple output (MIMO) Gaussian broadcast channel (BC), where the transmitter and receivers have multiple antennas. Since the MIMO broadcast channel is in...
Fundamental Capacity of MIMO Channels (2003)
Andrea Goldsmith, Syed Ali Jafar, Nihar Jindal, Sriram Vishwanath
broadcast channels. We provide an overview of the extensive recent results on the Shannon capacity of single-user and multiuser multiple-input multiple-output (MIMO) channels. Although enormous...
On the capacity of multiple input multiple output broadcast channels (2002)
Sriram Vishwanath, Nihar Jindal, Andrea Goldsmith
Abstract | We consider a two-user multiple input multiple output (MIMO) Gaussian broadcast channel (BC), where the transmitter has t transmit antennas and receivers have r1; r2 antennas respectively....
On the Duality of Gaussian Multiple-Access and Broadcast Channels (2002)
Nihar Jindal, Sriram Vishwanath, Andrea Goldsmith
We show that the Gaussian multipleaccess channel (MAC) and broadcast channel (BC) are duals. The dual channels we consider have the same channel gains and the same noise power at all receivers. We nd...
On the Capacity of Multiple Input Multiple Output Broadcast Channels (2002)
Sriram Vishwanath, Nihar Jindal, Andrea Goldsmith
We consider a multi-user multiple input multiple output (MIMO) Gaussian broadcast channel (BC), where the transmitter and receivers have multiple antennas. Since the MIMO broadcast channel is in...
Space-Time Multiple Access: Linear Growth in the Sum Rate (2002)
Bertrand Hochwald, Sriram Vishwanath
It is known that some of the spectacular capacity gains of using multiple antennas on a point-to-point rich scattering channel, namely linear growth with the number of antennas, can also be obtained...
On the capacity of multiple input multiple output broadcast channels (2002)
Sriram Vishwanath, Nihar Jindal, Andrea Goldsmith
Abstract — We consider a multi-user multiple input multiple output (MIMO) Gaussian broadcast channel (BC), where the transmitter and receivers have multiple antennas. Since the MIMO broadcast...
Optimum Power and Rate Allocation Strategies for Multiple Access Fading Channels (2001)
Sriram Vishwanath, Syed Ali Jafar, Andrea Goldsmith, David Packard, Electrical Engineering
We obtain the (Shannon) optimal power and rate allocation strategies for the uplink on single cell systems. For an N user system, we show that successive decoding which is independent of channel...
Syed Ali Jafar, Sriram Vishwanath, Andrea Goldsmith
Abstract—We consider the capacity of a narrowband point to point communication system employing multiple-element antenna arrays at both the transmitter and the receiver with covariance feedback....
Optimum Power and Rate Allocation Strategies for Multiple Access Fading Channels (2001)
Sriram Vishwanath, Syed Ali Jafar, Andrea Goldsmithdavid, Packard Electrical Engineering
Abstract We obtain the (Shannon) optimal power and rate allo-cation strategies for the uplink on single cell systems. For an N user system, we show that successive decoding whichis independent of...
On the Duality of Multiple-Access and Broadcast Channels (2001)
Nihar Jindal, Sriram Vishwanath, Andrea Goldsmith
We show that the Gaussian multiple-access channel and the Gaussian broadcast channel are fundamentally related and are essentially duals of each other. The dual channels we consider have the same...