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Electrical and Computer Engineering

Selected Works

Siddhartan Govindasamy

2012

Articles 1 - 10 of 10

Full-Text Articles in Engineering

Spectral-Efficiency Of Multi-Antenna Links In Ad-Hoc Networks With Limited Tx Csi, Siddhartan Govindasamy, Daniel Bliss, David Staelin Dec 2012

Spectral-Efficiency Of Multi-Antenna Links In Ad-Hoc Networks With Limited Tx Csi, Siddhartan Govindasamy, Daniel Bliss, David Staelin

Siddhartan Govindasamy

An asymptotic expression is derived for the mean spectral efficiency of multi-antenna links randomly distributed on a plane in a uniform manner where transmitters (Tx) have Channel-State-Information (CSI) of the channels between themselves and their target receivers while receivers (Rx) have CSI between themselves and all transmitters. The mean per-link spectral efficiency in the network is found to increase if nodes transmit using a subset of their strongest channel modes instead of the link-optimal strategy of water-filling on all channel modes (Farrokhi et al.). For reasonable parameters, this system which requires limited Tx CSI, has approximately double the mean spectral …

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Spectral Efficiency In Single-Hop Ad-Hoc Wireless Networks With Interference Using Adaptive Antenna Arrays, Siddhartan Govindasamy, Daniel Bliss, David Staelin Dec 2012

Spectral Efficiency In Single-Hop Ad-Hoc Wireless Networks With Interference Using Adaptive Antenna Arrays, Siddhartan Govindasamy, Daniel Bliss, David Staelin

Siddhartan Govindasamy

Receivers with N antennas in single-hop, ad-hoc wireless networks with nodes randomly distributed on an infinite plane with uniform area density are studied. Transmitting nodes have single antennas and transmit simultaneously in the same frequency band with power P that decays with distance via the commonly-used inverse-polynomial model with path-loss-exponent (PLE) greater than 2. This model applies to shared spectrum systems where multiple links share the same frequency band. In the interference-limited regime, the average spectral efficiency of a representative link E[C] (b/s/Hz/link) is found to grow as log(N) and linearly with PLE, and its variance decays as 1/N. The …

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Cdf Of The Spectral-Efficiency Of A Simple Distributed Channel Assignment Algorithm In Spatially Distributed Wireless Networks, Siddhartan Govindasamy, Raghu Rangan, Elena Koukina, Ashley Lloyd Dec 2012

Cdf Of The Spectral-Efficiency Of A Simple Distributed Channel Assignment Algorithm In Spatially Distributed Wireless Networks, Siddhartan Govindasamy, Raghu Rangan, Elena Koukina, Ashley Lloyd

Siddhartan Govindasamy

The Cumulative-Distribution-Function (CDF) of the spectral efficiency of links in spatially distributed networks with orthogonal channels and a simple channel assignment algorithm is presented for constant link-lengths and nearest-neighbor links. Transmitters are randomly distributed on the plane with uniform probability, and receivers are either randomly distributed or at hexagonal lattice sites. This result includes random channel assignments as a special case. The CDF is used to find the spectral efficiency for a given, small outage probability which is used to optimize the number of channels to maximize the spectral efficiency. The optimum number of channels represents the best trade off …

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On The Spectral Efficiency Of Links With Multi-Antenna Receivers In Non-Homogenous Wireless Networks, Siddhartan Govindasamy, Daniel Bliss Dec 2012

On The Spectral Efficiency Of Links With Multi-Antenna Receivers In Non-Homogenous Wireless Networks, Siddhartan Govindasamy, Daniel Bliss

Siddhartan Govindasamy

An asymptotic technique is developed to find the Signal-to-Interference-plus-Noise-Ratio (SINR) and spectral efficiency of a link with N receiver antennas in wireless networks with non-homogeneous distributions of nodes. It is found that with appropriate normalization, the SINR and spectral efficiency converge with probability 1 to asymptotic limits as N increases. This technique is applied to networks with power-law node intensities, which includes homogeneous networks as a special case, to find a simple approximation for the spectral efficiency. It is found that for receivers in dense clusters, the SINR grows with N at rates higher than that of homogeneous networks and …

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The Performance Of Linear Multiple-Antenna Receivers With Interferes Distributed On A Plane, Siddhartan Govindasamy, Filip Antic, Daniel Bliss, David Staelin Dec 2012

The Performance Of Linear Multiple-Antenna Receivers With Interferes Distributed On A Plane, Siddhartan Govindasamy, Filip Antic, Daniel Bliss, David Staelin

Siddhartan Govindasamy

We find an asymptotic expression for the average signal to interference ratio (SIR) between a transmitter with a single isotropic antenna and a multi-antenna linear receiver in the presence of interferers with single isotropic transmit antennas distributed uniformly on an infinite plane. The channels are modeled as complex Gaussian random variables with average received power dependent on the distance separating nodes. We find that in large networks, the average SIR for a representative link depends primarily on the ratio of the number of receive antenna elements to the area density of interferers. Furthermore for our network model, the SIR grows …

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Minimizing Hidden-Node Network Interference By Optimizing Siso And Mimo Spectral Efficiency, Daniel Bliss, Siddhartan Govindasamy Dec 2012

Minimizing Hidden-Node Network Interference By Optimizing Siso And Mimo Spectral Efficiency, Daniel Bliss, Siddhartan Govindasamy

Siddhartan Govindasamy

In this paper, the optimal spectral efficiency (data rate divided by the message bandwidth) that minimizes the probability of causing disruptive interference for ad hoc wireless networks or cognitive radios is investigated. Two basic problem constraints are considered: a given message size, or fixed data rate. Implicitly, the trade being optimized is between longer transmit duration and wider bandwidth versus higher transmit power. Both single-input single-output (SISO) and multiple-input multiple-output (MIMO) links are considered. Here, a link optimizes its spectral efficiency to be a “good neighbor.” The probability of interference is characterized by the probability that the signal power received …

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Linear Mmse Receivers For Random Cdma In Wireless Networks With Equal Transmit Powers, Siddhartan Govindasamy, David Staelin Dec 2012

Linear Mmse Receivers For Random Cdma In Wireless Networks With Equal Transmit Powers, Siddhartan Govindasamy, David Staelin

Siddhartan Govindasamy

The performance of single-hop links in ad-hoc wireless systems using direct-sequence (DS) code-division-multiple-access (CDMA) with random signature sequences and linear minimum-mean-square-error (MMSE) receivers is investigated. Expressions for the average signal-to-interference-plus-noise-ratio (SINR) and spectral efficiency (b s-1 Hz-1 link-1) were derived for a representative link in the presence of interferers distributed randomly on a plane with uniform area density p interferers m-2. Nodes transmit with equal power P, which decays with distance r as r-alpha. An expression for the optimum spreading factor given system parameters is also provided. It is found that for …

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Asymptotic Spectral Efficiency Of Multiantenna Links In Wireless Networks With Limited Tx Csi, Siddhartan Govindasamy, Daniel Bliss, David Staelin Dec 2012

Asymptotic Spectral Efficiency Of Multiantenna Links In Wireless Networks With Limited Tx Csi, Siddhartan Govindasamy, Daniel Bliss, David Staelin

Siddhartan Govindasamy

An asymptotic technique is presented for finding the spectral efficiency of multiantenna links in spatially distributed wireless networks where transmitters have channel-state-information (CSI) corresponding to their target receiver. Transmitters are assumed to transmit independent data streams on a limited number of channel modes which limits the rank of transmit covariance matrices. An approximation for the spectral efficiency in the interference-limited regime as a function of link-length, interferer density, number of antennas per receiver and transmitter, number of transmit streams, and path-loss exponent is derived. It is found that targeted-receiver CSI, which can be acquired with low overhead in duplex systems …

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Spectral Efficiency Of Wireless Networks With Multi-Antenna Base Stations And Spatially Distributed Nodes, Siddhartan Govindasamy, Daniel Bliss, David Staelin Dec 2012

Spectral Efficiency Of Wireless Networks With Multi-Antenna Base Stations And Spatially Distributed Nodes, Siddhartan Govindasamy, Daniel Bliss, David Staelin

Siddhartan Govindasamy

We analyze networks with wireless nodes distributed randomly in space, transmitting simultaneously in the same channel to their nearest base-stations using a simple power control algorithm. Base-stations are on a hexagonal grid and have N optimally-phased antennas. We derive the asymptotic mean upstream spectral efficiency(validated by simulation) as a function of N, wireless-node density, base-station separation, and path-loss-exponent which controls signal attenuation with distance. These results indicate that mean per-link spectralefficiency is constant if the number of receive antennas or density of base-stations is increased linearly withwireless node density. They also improve our understanding of systems like city-wide wireless Internet …

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Performance Of Multi-Antenna Mmse Receivers In Non-Homogeneous Poisson Networks, Junjie Zhu, Siddhartan Govindasamy Jun 2012

Performance Of Multi-Antenna Mmse Receivers In Non-Homogeneous Poisson Networks, Junjie Zhu, Siddhartan Govindasamy

Siddhartan Govindasamy

A technique to compute the Cumulative Distribution Function (CDF) of the Signal-to-Interference-plus-Noise-Ratio (SINR) for a wireless link with a multi-antenna, Linear, Minimum-Mean-Square-Error (MMSE) receiver in the presence of interferers distributed according to a non-homogenous Poisson point process on the plane, and independent Rayleigh fading between antennas is presented. This technique is used to compute the CDF of the SINR for several different models of intensity functions, in particular, power-law intensity functions, circular-symmetric Gaussian intensity functions and intensity functions described by a polynomial in a bounded domain. Additionally it is shown that if the number of receiver antennas is scaled linearly …

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