Telecommunications in India has evolved greatly in the last two decades, and the number of lines has grown to over 100 million. However, these lines are disproportionate in the urban areas and are mainly low bandwidth wireless access links. Thus there is double challenge we are facing, namely how to take the Telecom revolution to the rural areas and how to take broadband to both the urban and rural parts of India. This article discusses these issues and how the TeNeT group at IIT Madras is trying to tackle some of the problems. Copyright © 2006 by the IETE.

Harishankar Ramachandran

Department of Electrical Engineering

K. Giridhar

Ashok Jhunjhunwala

Bandwidth

Broadband networks

Problem solving

Rural areas

Telecommunication links

Wireless telecommunication systems

TELECOM REVOLUTION

Urban areas

WIRELESS ACCESS LINKS

Telecommunication lines

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Convergence and India—The Tenet Group Perspective

IETE Technical Review (Institution of Electronics and Telecommunication Engineers, India)

In this paper, a novel method to enhance license plate numbers of moving vehicles in real traffic videos is proposed. A high-resolution image of the number plate is obtained by fusing the information derived from multiple, subpixel shifted, and noisy low-resolution observations. The image to be superresolved is modeled as a Markov random field and is estimated from the observations by a graduated nonconvexity optimization procedure. A discontinuity adaptive regularizer is used to preserve the edges in the reconstructed number plate for improved readability. Experimental results are given on several traffic sequences to demonstrate the robustness of the proposed method to potential errors in motion and blur estimates. The method is computationally efficient as all operations can be implemented locally in the image domain. © 2007 IEEE.

IEEE Transactions on Intelligent Transportation Systems

Superresolution of license plates in real traffic videos

We present an overview of multiple-input multiple-output (MIMO) wireless communication systems followed by some of the new techniques proposed by us to enhance performance. Firstly, some of the popular transmit and receive diversity schemes available in the literature are discussed and issues like diversity, rate, power distribution, decoding complexity, decoding delay, amount of feedback and feedback delay and their tradeoffs to achieve reliable and cost effective communications are described. We then analyze the merits and demerits of some of the open-loop (no feedback) and closed-loop (with feedback) schemes, and discuss various methods proposed by us recently to improve the performance of such schemes. The symbol error rate (SER) performance of the various schemes are compared through computer simulations. © 2005 Taylor & Francis Group, LLC.

IETE Journal of Research

Open-loop and closed-loop transmit diversity techniques—overview and new results

Space-time trellis codes (STTCs) have been designed for quasi-static Rayleigh channels. When these codes are directly used for additive white Gaussian noise (AWGN) channels or Ricean channels with a high K factor, their frame error-rate (FER) performance is no longer optimal. We propose open-loop (no feedback) preprocessing methods for improving the error-rate performance of these codes when used in channels with a high K. For K = 0 (Rayleigh channels), these open-loop schemes generally do not alter the FER performance of the STTCs. The preprocessing operation at the transmitter is either to rotate the constellation points in one of the transmit antennas relative to the other by some angle, or suitably divide (unequally) the total power between the two transmit antennas. The angle of rotation and power division is optimized by maximizing the dfree of the STTCs. Simulation results show that for AWGN or Ricean fading channels with a large K, the FER performance can be significantly improved by doing either rotation or power division at the transmitter. While the FER performance is nearly unchanged for quasi-static Rayleigh channels, the improvement in performance is between 1 to 3 dB for Ricean or AWGN channels. © 2005 IEEE.

IEEE Transactions on Vehicular Technology

Performance enhancement of space-time trellis codes when encountering AWGN and ricean channels

Multiple antennas are useful in orthogonal frequency division multiplexing (OFDM) systems for providing transmit and receive diversity to overcome fading. Typically, these designs require considerable separation between the antennas. Spatial correlation is introduced when antennas are not well separated, and it often leads to performance degradation in a flat fading environment. However, in frequency selective fading channels with rich multipath diversity, OFDM receivers can overcome this performance degradation due to antenna correlation. This is due to transformation of a highly spatially correlated channel impulse response to a less spatially correlated channel frequency response inherently by an OFDM system in the presence of rich multipath diversity. We illustrate this for a simple receive diversity OFDM system and hence introduce the concept of space sampling at the receiver where antennas are placed relatively close to each other. The minimum separation required between the antennas under such circumstances is derived analytically, and it is shown that even with a separation of only 0.44λ, the required spatial correlation in the channel frequency response becomes sufficiently low. Simulated performance results with such spacing for various multiple antenna OFDM systems corroborate the analytical results. © 2005 IEEE.

Exploiting multipath diversity in multiple antenna OFDM systems with spatially correlated channels

Open-loop (no feedback) pre-processing methods for improving the error-rate performance of space-time trellis codes in additive white Gaussian noise (AWGN) and Ricean channels which nearly preserve the performance in Rayleigh channels are proposed in [1]. The rotation based pre-processing preserves the Rayleigh channel performance, whereas there is a small degradation in performance in the power division based pre-processing. This degradation depends on the trellis complexity, and is more pronounced for the lower state trellis codes. In this letter, we propose a one-bit feedback method, that improves the performance of the power division method in Rayleigh channels. Simulation results for a 2 × 1 system show that this improvement is significant for the higher state trellis codes. The one-bit feedback is used to determine which of the two channels has a higher gain, and the higher power is assigned to the corresponding transmitter. © 2005 IEEE.

Journal	IETE Technical Review (Institution of Electronics and Telecommunication Engineers, India)
Publisher	Medknow Publications
ISSN	02564602
Open Access	No