Hari Krishna Garg

National University of Singapore

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Arumugam Nallanathan

Queen Mary University of London

Mehul Motani

National University of Singapore

Ying‐Chang Liang

University of Electronic Science and Technology of China

Xin Kang

University of Science and Technology of China

Wai‐Choong Wong

National University of Singapore

Yonghao Zhao

Hohai University

Himal A. Suraweera

University of Peradeniya

Hanshen Xiao

Nvidia (United States)

Rui Zhang

Chinese University of Hong Kong, Shenzhen

Tianyi Feng

Shandong Provincial QianFoShan Hospital

Cooperative Institutions

National University of Singapore

Institute for Infocomm Research

Agency for Science, Technology and Research

University of Electronic Science and Technology of China

Tsinghua University

Xidian University

Shanghai Jiao Tong University

Chinese Academy of Sciences

Nanyang Technological University

University of Hong Kong

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Characterization of ultra-wideband channels for outdoor office environment

IEEE Wireless Communications and Networking Conference (2005)

C.W. Kim Xuebin Sun L.C. Chiam B. Kannan F.P.S. Chin

We present a statistical model for the characterization of ultra-wideband (UWB) channels for the outdoor office environment. The bandwidth is from 3-6 GHz and measurements are done for the line-of-sight (LOS) and non-line-of-sight (NLOS) cases. Small scale effects are modeled by the Saleh-Valenzuela (S-V) model with modifications on the ray arrival times and amplitude statistics to fit the empirical data. The ray arrival times are described by a mixture of Poisson processes while the amplitude statistics are follow a Nakagami distribution with the m parameter following a lognormal distribution. The parameters for the cluster and ray power-decay time constants, cluster and ray arrival times, mean excess delay and RMS excess delay are also extracted to define the channel model completely.

Non-line-of-sight propagation

Nakagami distribution

Wideband

Log-normal distribution

Power delay profile

Narrowband

Time of arrival

10.1109/wcnc.2005.1424636

Cite

Citations (47)

An Adaptive Filtering Algorithm for Direct-Conversion Receivers: Architecture and Performance Analysis

IEEE Transactions on Circuits and Systems I Regular Papers (2008)

Yuanjin Zheng Mingzheng Cao Evelyn Teo Hari Krishna Garg

An adaptive filtering algorithm is proposed in this paper to remove mismatch, dc offsets, flicker noise, and intersymbol interference (ISI) simultaneously in a direct-conversion receiver. mismatch is cancelled by a real valued adaptive mismatch canceller, and dc offsets are removed with one complex tap. In addition, flicker noise is modeled as a complex autoregressive (AR) random process so the system to be identified transforms to an ARX model. After estimating the coefficients in the model during the training period, the desired signal can be estimated using the decision feedback method. To accelerate the convergence of the algorithm and to reduce the estimation variance, an internal iterative algorithm is introduced. The convergence analysis of the proposed algorithm is also given, and the closed form of the minimum mean square error of the proposed algorithm is derived. Simulation results are provided to verify the superior performance of the proposed algorithm.

Adaptive algorithm

10.1109/tcsi.2008.916419

Cite

Citations (2)

A new family of polyphase sequences for CDMA with good odd and even correlation properties

Yonglan Zhu T.T. Tjhung Hari Krishna Garg

In this paper, we propose and investigate a new signature sequence family for use in asynchronous direct-sequence code-division multiple-access (DS-CDMA) communication systems. The new sequence family offers good correlation properties in both even and odd correlation. This can result in good performance on system capacity, acquisition and demodulation in DS-CDMA systems. The correlation properties of the new sequence family are presented. Based on the measure described in this paper, the correlation properties of the new sequence set are compared to those of the well-known conventional PN sequence sets.

Polyphase system

Sequence (biology)

Gold code

Signature (topology)

Code (set theory)

10.1109/spawc.1999.783053

Cite

Citations (4)

Performance Analysis of Partial Relay Selection With Feedback Delay

IEEE Signal Processing Letters (2010)

Himal A. Suraweera Madushanka Soysa Chintha Tellambura Hari Krishna Garg

We analyze the impact of outdated channel state information due to feedback delay on the performance of amplify-and-forward relays with the $k$th worst partial relay selection scheme. In our analysis, new expressions for the system's outage probability and the average bit error rate are derived. The effects of the rank of the relay chosen, the average SNR imbalance, and the correlation between the delayed and current signal-to-noise ratio (SNR) on the system performance are investigated. Additionally, simple and accurate outage and average BER approximations are also derived to quantify the performance at high SNR. We also give simulation results to support the theoretical study.

Outage Probability

Channel state information

Rank (graph theory)

10.1109/lsp.2010.2045544

Cite

Citations (132)

Joint Channel Estimation and Data Detection for MIMO-OFDM Two-Way Relay Networks

The-Hanh Pham Ying‐Chang Liang Hari Krishna Garg Arumugam Nallanathan

In this paper, we consider multi-input multi-output (MIMO) two-way relay networks with orthogonal frequency-division multiplexing (OFDM) modulation scheme. The networks consist of two end users exchanging their information via a relay. One information exchange between two end users is divided into two Phases. In Phase 1, two users send their information to the relay. The relay then amplifies and broadcasts its received signals to the two users in Phase 2, i.e., the relay works in the amplify-and-forward (AF) mode. By doing so, two-way relay networks require half as many time slots to accomplish one information exchange as the traditional one-way relay networks. We propose at each end user an iterative algorithm to jointly estimate the channel information and detect the data transmitted from the other user. The channel information consists of the \textit{composite} channels which are the combinations of individual channels in the networks and noise covariance matrices resulting from the AF working mode of the networks. We apply the Expectation Conditional Maximization (ECM) algorithm to estimate the necessary channel information for detection. Simulation results show that the performance of our proposed iterative algorithm is close to that given by the perfect channel information.

10.1109/glocom.2010.5684080

Cite

Citations (16)

On Achievable Rates for Relay Channels

Hon-Fah Chong Mehul Motani Hari Krishna Garg

In previous work, we presented two different generalized decoding strategies for the relay channel, called SeqBack and SimBack decoding, that make use of regular encoding and backward decoding. In this paper, we show that the rates achievable by SeqBack and SimBack decoding are equal. Furthermore, we show that regular encoding/sliding window decoding can achieve the same rate as regular encoding/backward decoding.

List decoding

Sliding window protocol

10.1109/ita.2007.4357615

Cite

Citations (5)

<title>Simulation of distortion in multicarrier subcarrier-multiplexed optical communication systems employing direct intensity modulation of semiconductor lasers</title>

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (1996)

Manas K. Haldar Hari Krishna Garg K.B. Chia F.V.C. Mendis

Direct intensity modulation of semiconductor lasers in subcarrier multiplexed (SCM) optical fiber communication systems is of interest because of its simplicity and the possibility of integration of the drive electronics with the laser diode. Direct modulation also produces distortion which degrades system performance. In this paper, we extend a static numerical simulation method for multi-carrier SCM systems to a dynamic simulation employing rate equations. We first show that the results of our simulation agree with analytical results for multi-carrier SCM systems obtained from perturbation theory in the absence of optical reflection into the semiconductor laser. We proceed with the calculation of distortion in the presence of weak reflections. We show that the distortion is lower than what is expected from previous analytical considerations for two subcarriers. Our simulation can also take into account the effect of overmodulation in a dynamic manner. However, our simulation does not take into account the distortion due to device imperfections.

Subcarrier multiplexing

Overmodulation

Distortion (music)

Modulation (music)

Laser diode

10.1117/12.256369

Cite

Citations (0)

The Capacity Region of a Class of Deterministic Interference Channels with Common Information

Jinhua Jiang Yan Xin Hari Krishna Garg

In this paper, we establish the capacity region of a class of deterministic interference channels with common information. For such a class of channels, each sender needs to transmit not only the private information but also certain common information to the corresponding receiver. Moreover, the channel outputs are deterministic with respect to given channel inputs.

Communication source

10.1109/icassp.2007.366771

Cite

Citations (3)

Capacity Theorems for the Gaussian Zigzag Channel

Hon Fah Chong Mehul Motani Hari Krishna Garg

We consider the two-user Gaussian zigzag channel, where there are two senders and two receivers. One of the senders transmits information to its intended receiver (without interfering with the unintended receiver) while the other sender transmits information to both receivers. We first establish achievable rates for the discrete memoryless zigzag channel under strong interference which can be extended to the Gaussian zigzag channel with strong and very strong crossover link gain (a ² ges 1). We also determine an outer bound for the Gaussian zigzag channel under strong and very strong crossover link gain (a ² ges 1). Moreover, we establish the capacity of the Gaussian zigzag channel under (strictly) strong crossover link gain (1 les a ² les 1 + P ₁ )

Zigzag

Communication source

10.1109/isit.2006.262031

Cite

Citations (5)

A generalized ICA algorithm for extraction of super and sub Gaussian source signals from a complex valued mixture

W. V. D. Wijesinghe Roshan Godaliyadda M. P. B. Ekanayake Hari Krishna Garg

Extraction of unknown independent source signals from a noisy mixture is a fundamental problem in most signal processing applications. The existing independent component analysis (ICA) algorithms have tackled this problem for complex and real valued mixtures for both super and sub Gaussian sources. However in reality super and sub Gaussian sources exist collectively in a mix. It was observed when examining the kurtosis surface behavior for a super-sub Gaussian collective mixture the implications of a positive region implies the existence of at least one super Gaussian source while a statement cannot be made about the existence or non-existence of a sub-Gaussian source. The same observation holds for the reverse case where a negative valued kurtosis surface exists. Thus a modified sign update equation is proposed for source extraction for a super-sub Gaussian mixture in that spirit. The update equation takes into account the existence of a positive/negative region to conclude on the existence of a super/sub Gaussian source and employs an ascent/descent approach accordingly. The technique is analyzed for both real and complex valued mixtures.

Kurtosis

10.1109/iciinfs.2013.6731971

Cite

Citations (4)