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1 Physical Layer Performance Enhancement Solutions for the IEEE 802.11a and 802.16a Systems Dr S Srikanth AU-KBC Research Centre M.I.T.Campus of Anna University Chromepet, Chennai-600 044

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Physical Layer Performance Enhancement Solutions for the IEEE 802.11a and 802.16a Systems

Dr S Srikanth AU-KBC Research Centre

M.I.T.Campus of Anna University Chromepet, Chennai-600 044

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LIST OF ABBREVIATIONS

3G WCDMA - Third Generation Wideband Code Division Multiple Access

4G - Fourth Generation Wireless System

AGC - Automatic Gain Control

ATM - Asynchronous Transfer Mode

BER - Bit-Error Rate

BWA - Broadband Wireless Access

CDMA - Code Division Multiple Access

DS-CDMA - Direct Sequence Code Division Multiple Access

DSP - Digital Signal Processors

FDMA - Frequency Division Multiple Access

FFT - Fast Fourier Transform

IF - Intermediate Frequency

IFDMA - Interleaved Frequency Division Multiple Access

IFFT - Inverse Fast Fourier Transform

MAC - Medium Access Control

MC-CDMA - Multi-Carrier Code Division Multiple Access

MIMO - Multiple Input Multiple Output

OFDM - Orthogonal Frequency Division Multiplexing

PAPR - Peak-to-Average Power Ratio

PER - Packet Error Rate

PHY Layer - Physical Layer

SNR - Signal-to-Noise Ratio

TDMA - Time Division Multiple Access

WLANs - Wireless Local Area Networks

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Project Summary

This applied research project shall focus on innovative physical layer techniques for improving performance of systems which use 2 key wireless standards. The IEEE 802.11a standard has become a popular WLAN standard and the IEEE 802.16a standard is expected to become popular for BWA applications. Both standards are based on multicarrier solutions (OFDM) and our research focus will be on physical layer solutions for improving the performance of both these systems. The solutions can enable improved spectral efficiencies, error performance, etc. leading to higher popularity of wireless applications. The following deliverables are expected from the project:

?? New PHY. layer solutions to improve performance in the 802.11a and 802.16a systems. ?? Analytical investigations of new solutions and comparison with existing solutions. ?? Simulation modules with documentation. ?? Scaled-down hardware demonstrator. ?? Research publications, courses, theses, seminars, tutorials, and other academic outputs.

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1. Broad Subject Area of the Proposal:

Engineering Sciences. 2. Specialization: Communications Engineering. 3. Title of the Proposed Project:

Physical Layer Performance Enhancement Solutions for the IEEE 802.11a and 802.16a Systems.

4. Name and Address of the Investigator:

Dr. S. Srikanth, AU-KBC Research Centre, MIT Campus, Anna University, Chennai –600 044. Email: [email protected] Phone: 44-2223-2711, 44-2223-4885. Fax: 44-2223-1034

5. Details of the Proposed Project to be Undertaken: Origin of the Proposal: Wireless communications systems are generally considered as the one of the highest growth areas in the communications industry [Spectrum]. The popularity of cellular phones, WLANs, and the possibilities portrayed by many studies indicate the enormous market potential for technologies which can solve key problems so as to enable widespread proliferation of wireless communications. Some of the challenges that need to be tackled are improvement in spectral efficiency, BER/PER performance enhancements, reduction in transmit power, range increase, complexity reduction, flexibility, and security enhancements among many other things [Chuang]. Improvements in many layers of the network can have an impact on performance. Our focus is on developing PHY. layer solutions to improve performance of the IEEE 802.11a standard which pertains to WLANs and the IEEE 802.16a standard which pertains to BWA systems. The key common feature in both systems is the use of OFDM transmission techniques and hence certain overlap is there with respect to the transmission techniques used. Research efforts have been underway all over the world for improving the physical layer performance of wireless systems. However, many of the new ideas cannot be applied to the standards due to various reasons. Consequently, there is a clear need for direct investigation of solutions which will be applicable to the standards based systems; this is the focus of this proposal. We believe that there will be sufficient interest in such solutions as it could be potentially used in commercial systems.

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Present Research Work: I have been working on multicarrier communications technologies for the past 18 months. The work started in the context of powerline communications as multicarrier technologies (like OFDM) were considered to be suitable candidates under the severe frequency selective fading environments [Isplc]. We designed a OFDM based multiple access system for a low-voltage powerline access system based on standard channel models and carried out extensive simulation studies to study the performance. Based on this work, we developed a OFDM based wireless multiple access system for indoor wireless systems and the results indicated that it performed better than the existing OFDM-TDMA and OFDM-FDMA systems and variants of this. These results are published in conferences [Arun] and a journal paper has been has been accepted [Venk]. A patent has been filed based on these investigations and we are discussing with various agencies about the possibilities of leveraging the ideas for commercial purposes [Sri]. I have worked in various aspects of space-time technologies both in academia and in the industry. The topics addressed were interference suppression for CDMA based indoor wireless systems and capacity enhancement of CDMA based cellular systems. I am involved in studying the various aspects of multicarrier and space-time technologies for various wireless systems. These include some theoretical analysis, simulation studies, and the study of standards based on multicarrier techniques. I have been following the work in the IEEE publications, annual OFDM Workshop Proceedings, WWRF studies, standards, and academic theses from different parts of the world [OFDMWS] [WWRF] [Klaus]. I am guiding groups of students working on different aspects of OFDM, MC-CDMA, and MIMO systems and several papers are being prepared based on these projects. I was also part of a team constituted by the Department of Information Technology to look into the suitability for developing suitable wireless initiatives to suit the Indian market. I am also in touch with some key researchers in this area both here and outside the country. In particular, there has been strong interaction with the TeNet team (IIT Madras), Dr. Seshaiah Ponnekanti (Fujitsu, UK) and Mr. Ram Asokan (Ericsson, USA). I have also visited Prof. Rohling’s group in Technical University of Hamburg, Germany and the Interuniversity Microelectronics Centre (IMEC) in Belgium. Both teams are leaders in the development of OFDM solutions and I have been in constant touch with these groups. Project Objective: The goal of the project is to investigate and develop PHY. layer performance enhancement solutions for the 802.11a and 802.16a standards. The key deliverables from this project will be: ?? New PHY. layer solutions to improve performance in IEEE 802.11a and IEEE 802.16a

systems. ?? Simulation modules with documentation to enable clear understanding of the

innovations for use by other organisations. ?? A reduced-speed low-cost hardware demonstrator to verify the innovations.

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?? Research papers, theses, tutorials, and seminars to benefit industry and academia. Review of R&D Work in the Proposed Area: In the IEEE 802.11a area, the Hiperlan2 enhancements group constituted by the ETSI has specifically mentioned a few areas which are suitable for research [Brain]. These include adaptive modulation techniques, space-time techniques, turbo coding, and some protocol related issues. Preliminary work done by the group has yielded some promising results in the area and is a strong motivation for our work. A block adaptive modulation technique has been proposed for performance enhancement in [Brain]. In another work from researchers at IBM, the performance of adaptive modulation techniques on the different data rate modes has been investigated. The interplay of the coding rate and adaptive modulation mode has also been investigated along with the PAPR when adaptive modulation is introduced. In [Imec1,Imec2], the adaptive modulation idea has been extended for a SDMA based WLAN so as to improve spectral efficiency. The effects of introducing adaptive modulation techniques on the signaling aspects has been discussed in [Hanzo1]. Extensive theoretical results on adaptive modulation have been investigated in [Andrea]. The effects of adaptive modulation on the BWA systems have been presented in several recent publication in the IEEE Communications Magazine. Results presented indicate that the adaptive modulation techniques can result in a significant performance enhancement. The challenges for achieving these gains has also been outlined in detail. The use of the OFDMA mode in the BWA standard with the flexibility to employ different modulation and coding techniques has been discussed in [802.16a]. The various issues of signaling associated with adaptive modulation techniques has been discussed in [Hanzo1]. We have presented some initial results on the effectiveness of block adaptive modulation schemes for 802.11a systems [Bamod]. The potential of the diversity and S-T coding systems for achieving performance enhancements in wireless systems has been mentioned in several publications. In Imec1,Imec2], ideas have been presented for achieving a SDMA solution for a WLAN system. The effect of receive diversity systems on the performance of 802.11a systems has been discussed in [Brain]. The application of popular S-T block coding systems for OFDM systems has been outlined in [Giann]. New channel estimation schemes have been outlined when S-T systems are used in the 802.11a systems. Combined synchronization and channel estimation techniques for multiple-antenna OFDM systems are discussed in [Apurva]. The interplay between spatial domain correlation and subcarrier level correlation in S-T OFDM systems has been discussed recently and is relevant to both 802.11a and 802.16a systems. New multi-antenna orthogonal S-T block codes have been proposed recently which can be applied in WLAN systems. We have proposed an enhanced interference cancellation approach which can be applied to 802.11a and 802.16a systems [Deep].

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Work Plan: The objective of the project is to study and develop physical layer solutions for enhancing the performance of the IEEE 802.11a and 802.16a systems which employ OFDM transmission techniques. We plan to investigate the following schemes: a. Adaptive modulation techniques b. MIMO solutions c. Channel estimation techniques d. Synchronization schemes e. Hardware related effects a. Adaptive modulation techniques for multicarrier systems: A key feature of multicarrier communications systems is the advantage that can be realised by using different modulation modes on the different subcarriers. This is particularly suitable for frequency-selective channels and in the presence of interference. For instance, the present WLAN standard IEEE 802.11a which is based on OFDM technology does not incorporate adaptive modulation in the individual subcarriers [802.11a]. There is flexibility in the selection of modulation modes to achieve different data rates but the real advantage of OFDM systems lies in the ability to perform adaptive modulation at subcarrier level [Cioffi]. Our focus will be on the incorporation of adaptive modulation in the IEEE 802.11a systems and the study of the various issues associated with it. We shall investigate the various methods that can be used for adaptive modulation in 802.11a system. The performance benefits for the different modes and the different channel conditions shall be studied in detail. The effects of block adaptive modulation, the effect of the adaptive modulation schemes on the PAPR of the signal etc. shall be studied. The complexity of the different techniques shall be outlined. Initial results from our investigation suggests that adaptive modulation techniques can enable improved performance for 802.11a systems which can translate into various benefits [Bamod]. In the 802.16a system 2 modes have been specified; one is the standard OFDM mode while the other is the OFDMA mode. In the OFDM mode, it has been specified that the modulation and coding methods can be flexible while in the other mode the problem is related to allocating subcarriers and modulation mode to multiple users. We have done some prior related work which forms a good base for investigating solutions in the 802.16a system [Venki]. In a multicellular application as in the case of BWA, the effects of interference on the performance can be alleviated by adaptive modulation techniques. In general, the incorporation of adaptive modulation in both systems necessitates the consideration of various factors. These include:

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- Developing algorithms for choosing modulation modes based on power, data rate, and performance considerations.

- Development of techniques for SNR estimation on all the subcarriers. - Development of signaling schemes for conveying SNR estimates from receiver to the

transmitter. - Developing signaling schemes for conveying the chosen modulation modes. - Develop adaptive modulation schemes to suit multiple users and multiple antennas. - Investigation of block adaptive modulation and its effects on performance, signaling ,

and other parameters. - Investigation of the effects of adaptive modulation techniques on the PAPR of the

transmitted signal.

Our investigations shall follow the steps mentioned above for the 2 standards that we have mentioned. Detailed analytical modules shall be presented along with detailed simulation studies. b. MIMO Solutions: It is clear from various studies that MIMO systems which enable the use of space and time processing both at the transmitter and at the receiver are key to achieving enhanced performance for wireless systems [Sesh]. They can contribute in improving spectral efficiency, error performance, interference management, etc. . Several MIMO concepts have been outlined in the literature, however, the suitability of them for specific applications and standards has not been studied. Our objective is to investigate and develop MIMO solutions for the 802.11a and 802.16a systems. This means that MIMO-OFDM systems are the target of the investigations and we are planning the following activities: - Comparison of various diversity and S-T coding schemes for the 2 OFDM based

standards. - Investigation of new solutions for improving performance as well as enabling multiple

access. - Investigation of space-time solutions combined with adaptive modulation techniques. - Investigation of the effects of MIMO solutions on the distortions introduced due to the

PAs. c. Channel Estimation: One of the key receiver tasks in the 2 systems that are being investigated is a good channel estimator which can enable improved equalizer performance. Standard preamble sequences and pilots are defined in the 2 standards. The challenge is to design a robust channel estimator which can perform well in the presence of noise and interference and other effects like timing and frequency offset. In addition, the channel estimator has to take the signaling structure of the standards based systems into account. The problem of channel estimation when MIMO systems are employed becomes even more tougher because of the need for multiple channel estimates. However, if preamble lengths and structures are not changed, then this task has to be accomplished with the existing preambles. This will be one of the

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focus areas of our channel estimation work. The work in this part will be organised along the following lines:

- Study of existing channel estimation schemes for OFDM transmission schemes - Suitability of existing and new channel estimation schemes for the 2 standards. - Developing new channel estimation schemes and supporting it with analytical and

simulation studies. - Performance evaluation of the schemes using simulations in the 2 standards.

Channel models for the 2 standards which will be studied have been presented in [H2channel, Hari]. The effects of the different channel modes outlined will also be a crucial part of study. e. Timing and Frequency Synchronization schemes: One of the key challenges in any OFDM system is the effect of synchronization errors on performance. In particular, the effect of timing and residual frequency offset are of interest. It is well known that frequency offset can degrade the performance of OFDM systems in a significant manner. In addition there are other synchronization related issues like carrier phase offset, phase noise, and carrier feedthrough which can affect performance in a similar manner. Typically, the preamble structure of the standard is used in baseband schemes which can estimate the offset. The effect of the synchronization errors will be different for the different channel conditions and the data rate modes. There will be interplay between the channel estimation and the synchronization schemes as they will share the same preamble sequences to achieve the estimation. Residual offsets will have to be taken care of using tracking schemes which will have to use the pilots embedded in the data symbols. Both standards have their own preamble and pilot structures and schemes will have to be developed taking this into account. When MIMO systems are employed, then synchronization schemes also have to be modified taking the possibly changed preamble structure into account. The work in this area will be organised as follows:

- Review and modeling of various synchronization effects. - Simulation testing of new and existing synchronization schemes for OFDM systems. - Application of synchronization schemes to the 2 standards. - Interplay between channel estimation and synchronization in the 2 standards. - Impact of MIMO systems on synchronization schemes.

f. Development of low-speed hardware demonstrator: As mentioned earlier, the goal of the project is to investigate and develop physical layer performance enhancement solutions for the 2 high-speed wireless systems (802.11a and 802.16a). Most of the presentation so far has focussed on analytical and simulation oriented evaluations. We also plan to develop a low-speed hardware demonstrator to verify the PHY. layer ideas. The motivation for this comes from the work of [Klaus] where such a low-speed demonstrator was used for a high-speed OFDM system. The justification for this was that a small team and a relatively low budget would hamper any high-speed hardware

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development which will be needed if we work with the exact specifications of the 2 standards mentioned. Consequently, the use of audio-DSP cards and upconversion to IF using standard modulators was recommended to test the various algorithms which will be investigated for the 2 standards. The proposed idea is illustrated in the block diagram given in Fig. 1.

The transmitter, receiver, and the appropriate channel model for the 2 standards will be emulated using audio sampling rate DSP cards. Standard analog components will be used for modulation, demodulation, analog-to-digital and digital-to-analog conversion The performance of the system will be recorded and will be compared with the pure simulation studies. This will enable us to understand some of the degradations which arise due to hardware imperfections which are difficult to model using a pure software simulation setup. The issues that we plan to address here are:

- Study of the effects of hardware oscillators on system performance. - Study of effects of sampling clocks on system performance. - Study of other hardware effects like PAPR, converters. - Develop a setup to demonstrate multicarrier signals to enable students and researchers to

obtain a real-world feel of these signals. We hope that this will be a starting phase towards a full-scale hardware demonstrators for demonstrating innovative ideas. We plan to use this testbed to then involve commercial organisations in the development of full-scale hardware solutions. As has been reported in [Klaus], this low-cost low-speed testbed can be a very valuable tool for students in understanding concepts and for testing new solutions related to the PHY. layer.

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host PC RS232 audio

audio

Host PC

Transmitter

I/Q Channel

IQ

I/Q

Receiver

host PC

(data source)

RS232 DSP board 1

(analog)

DSP

board 2

I/Q

Mod.

IF Dmo

d.

I/Q

DSP

Board 3

RS232

(data sink)

Channel Simulator

Provide coded

data blocks Decoding; bit and

packet error rate

Time-variant Transversal filter for multipath channel simulation; channel noise estimation

Interleaving : symbol mapping: pilot insertion : IFFT; guard intery : windowing ; training sequence

I/Q modulation and Demodulation to Simulate frequency Synchronization; Phase noise; etc.

AGC, frequency and Time synch; FFT; pilot extraction; channel est.; symbol de-mapping; de-interleaving

Fig. 1 OFDM air-interface emulator

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Project Schedule

T7 T6 T5 T4 T3

T2 T1

0 6 12 18 24 30 36

months

T1-Literature survey

T2-Solutions for 802.11a.

T3-Solutions for 802.16a.

T6-HW. Demonstrator development

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Future Plans: I plan to continue on with my research in the communications area. I am planning to interact with the wireless group at IIT Madras (TeNet) and the companies which have been spun-off from that group. In the technical side I am planning to work on the overall network effects of innovative technologies. This will involve understanding of the application requirements and then devising suitable technologies to suit the end-application's needs. I plan to work in the mathematical techniques which are impacting communications. The AU-KBC Research Centre offers a good opportunity for me to pursue this goal because of the interdisciplinary mandate of the centre and due to the presence of researchers working in different areas. I plan to continue teaching and research guidance in Anna University. Research Funding received in the past: I was part of a team which was awarded an industrial research partnership (IRAP) project by the Govt. of Canada while I was working with Harris Corporation, Canada. The work was in space-time processing and was jointly done with Queen’s University, Canada. I worked in this project from 1998-99. (Approx. 150K Canadian Dollars). I am also part of the team at the AU-KBC Research Centre which is working on a Ministry of Information Technology project on Powerline Communications. I have been coordinating most of the technical activities of the project. (Approx. 50 lakhs, Mar. 2000, Sept. 2002). 6. Institution where the proposal will be executed: I shall be working at the AU-KBC Research Centre, Anna University, Chennai for executing this research proposal. Presently, I am employed as a Member, Research Staff in honorary capacity at this institution. I have been working with this Centre for the past 2 years.

7. Facilities at the host institute: The AU-KBC Research Centre is an autonomous interdisciplinary centre which has been endowed by Mr. K. B. Chandrasekhar who is a successful alumni of Anna University and is the founder of Exodus Communications and Jamcracker Inc. (both in U.S.). The centre has been endowed with the main purpose of enabling world-class research to happen in India which will result in produts, patents, and companies (www.au-kbc.org). It is an unique opportunity for a public-private initiative to carry out world-class research in India. The centre has modern facilities and has a conducive environment for carrying out research. It also attracts high-quality human resources in the form of bright students from many campuses of Anna University (College of Engineering, Guindy, and Madras Institute of Technology are 2 well-known institutions). Extensive computer network, internet access, and communications lab facilities are available. We also have video/audio conferencing facility which will be very useful in keeping in touch with

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experts in this area. Several of the alumni of Anna University who are well-positioned in the communications industry are also keen to contribute to our research efforts and are interacting with us extensively to help us be in touch with the latest developments. We have visitors from all around the world and we have benefitted by the interactions (please see www.au-kbc.org). In addition, the faculty working in different areas contribute to each other’s research through interdisciplinary activities. In particular, I shall be interacting with Dr. Gurumurthi Ramanan who has extensive expertise in the mathematical techniques underpinning communications. The centre also sponsors research and summer fellowships for attracting bright students to aid the faculty in their research work. I plan to work with many groups of students (part-time and full-time) in the research topics outlined in the proposal. 8. Addresses of Indian experts working in the area: Dr. K. Giridhar – Associate Professor, IIT Madras, Chennai, 600 036 Email: [email protected], Phone: 44-257-8386 Dr. Surendra Prasad, Department of Electrical Engineering, Indian Institute of Technology, New Delhi Email: [email protected]

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9. Financial Details:

S.No. Head I Year II Year III Year

TOTAL

1. Fellowship @ 15K p.m.

1.8 lakhs 1.8 lakhs 1.8 lakhs 5.4 lakhs

2. Consumables 5K 5K 5K 15K 3. Travel within India 13K 13K 14K 40K 4. Contingency 20K 25K 25K 70K 5. Minor equipment

(under 5 lakhs) 3.35 lakhs - - 3.35

lakhs 5.53 lakhs 2.23 lakhs 2.24 lakhs 10 lakhs 6. Overhead costs-20% 1.106 0.446 0.448 2 lakhs Total 6.636 2.676 2.688 12 lakhs

S. No. 5 – Minor Equipment Agilent 1.8 GHz Spectrum Analyser – Rs. 2.75 lakhs. ADSP 2061 EZKIT-LITE Evaluation Cards with Software (3 Nos.) – Rs. 30K Max 2450 Evaluation Kits (2 Nos.) - Rs. 10K. Temperature Controlled Crystal Oscillators (4 nos.) – Rs. 10K Printed Circuit board making – Rs. 10K. Total: Rs.3.35 lakhs

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10. Have you applied for schemes under the young investigator schemes: Yes. The earlier proposal was not recommended and I was asked to submit a focussed revised proposal. In the earlier proposal, I had not concentrated on the 2 standards which were relevant. Here, all my research focus will only be on PHY. layer solutions for the 2 OFDM based standards. 11. Any Other Information in Support of the Proposed Project: The AU-KBC Research Centre attracts talented students from Anna University and other institutions and consequently, the research work shall reach the students as they will be involved in some of the simulations and hardware-related work. We expect that student projects and theses shall arise out of the planned investigations. We also feel that the dissemination of the research results will enable the academic community to be in tune with some of the latest concepts. We have been interacting with a large number of industry groups who have interests in the related areas and we plan to share the research findings for possible use.

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References:

[Spectrum]. IEEE Spectrum Magazine, August 2000.

[802.11a]. IEEE Std 802.11a/D7.0-1999, Part11: Wireless LAN Medium Access Control

(MAC) and Physical Layer (PHY) specifications: High Speed Physical Layer in the 5GHz

Band.(www.ieee.org)

[H2channel]. J. Medbo and P. Schramm. Channel Models for HIPERLAN/2. ETSI/BRAN

document no. 3ERI085B, 1998 (www.etsi.org).

[Rapp]. T.Rappaport, Wireless Communications. Prentice Hall, 1996.

[Prasad]. R.van Nee, R. Prasad, OFDM for Mobile Multimedia Communications, Boston:

Artech House, Dec.1999.

[OFDMWS]. Proceedings of the 5 th International OFDM-workshop, Hamburg, Germany,

September 2000 and 2001.

[Chuang]. Justin Chuang, Nelson Sollenberger, “Beyond 3G: wideband wireless data access

based on OFDM and dynamic packet assignment”, IEEE Communications Magazine,

July 2000..

[Giann]. Zhengdao Wang and Georgios B. Giannakis, Signal Processing Advances in

Wireless and Mobile Communications, Trends in Single – and Multi – User systems,

(Volume – II) Prentice Hall PTR, Upper Saddle River, NJ 07458

[Sesh]. Ayman F. Naguib, Nambi Seshadri and A. R. Calderbank, “Increasing data rates

over wireless channels”, IEEE Signal Processing Magazine, pp. 76-92, vol. 17, no. 3, May

2000.

[Hanzo1] L. Hanzo, W. Webb and T. Keller, Single and Multi Carrier Quadrature

Amplitude Modulation, John Wiley & Sons, 2001.

[Imec1]. S. Theon, L. Van de Perre, B. Gyselinckx, M. Engels and H. De Man, “Adaptive

loading in the downlink of OFDM/SDMA - based Wireless Local Networks”, VTC 2000

spring.

[Imec2]. S. Theon, L. Van de Perre, B. Gyselinckx, M. Engels, H. De Man and

P.Vandenameele, “Adaptive loading strategy for a high speed OFDM-based WLAN”,

Globecom Nov ’98.

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[Cioffi]. John M. Cioffi, “A multicarrier primer”.

http://www.isl.stanford.edu/people/cioffi/pdf/multicarrier.pdf

[Hk]. Cheong Yui Wong, Roger S. Cheng, Khaled Ben Letaif and Ross D. Murch,

“Multiuser OFDM with adaptive subcarrier, bit and power allocation,” IEEE Journalon

selected areas in communications, Vol. 17, No. 10, pp. 1747-1758, October 1999.

[Venk]. R. Venkatesh, S. Karthikeyan and S.Srikanth, “ Downlink performance of an

OFDM based multiple access system for indoor wireless communication” Submitted to

Wireless Personal Communications, Kluwer, Netherlands, Aug. 2001.

[Arun]. P. Arun, R. Venkatesh, S. Karthikeyan and S.Srikanth “Multiple access schemes for

OFDM based indoor wireless systems” Proceedings of eighth National Conference on

Communications, pp. 488-492, IIT Bombay, Jan. 2002.

[Linnartz]. N. Yee, J. P. Linnartz and G. Fettweis, " Multi-Carrier CDMA in indoor

wireless networks". PIMRC 1993, Yokohama, Japan, pp109-133.

[Mccdma]. Khaled Fazel, Gerhard P. Fettweis, Multi-Carrier Spread Spectrum, Kluwer

Academic publishers, Netherlands.

[Moen]. H. Steendam and M. Moeneclaey , “ Analysis and optimization of the performance

of OFDM on frequency-selective and time-selective fading channels,” IEEE Transactions

on Communications, vol. 47, no. 12, pp. 1811-1819, Dec. 1999.

[Klaus]. K. Witrisal, OFDM air-interface design for multimedia communications, Ph. D.

Thesis, Delft University of Technology, 2002.

[Isplc]. Proceedings of the International Symposium on Powerline Communications, 1999-

2002.

[WWRF]. World Wireless Research Forum (www.wireless-world.research.org)

[802.16]. Wireless Human Project (www.wirelessman.org).

[Andrea]. S. T. Chung and A. Goldsmith, “Degrees of freedom in adaptive modulation; An

unified view,” To appear in IEEE Transactions on Communication.

[Hanzo2]. L. Yang and L. Hanzo, “Software-Defined-Radio-AssistedAdaptive Broadband

Frequency Hopping Multicarrier DS-CDMA”, IEEE Communications Magazine, pp.174-

184, March 2002.

[Alpat]. Alamouti et al., Transmitter Diversity Technique for wireless communications

Patent Number US 6,185,258 B1, Feb 6,2001.

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[Seshpat]. Calderbank ,et al., Generalized orthogonal designs for space-time codes for

wireless communication, Patent number US6,430,231, August 6,2002.

[Sundarpat] Sundarrajan et.al., Co-ordinate Interleaved Orthogonal Design for Four

Antenna Transmission, Patent filed in India, 2002.

[Giles]. Marvin Sánchez 1 , Tim Giles, Jens Zander, “ CSMA/CA with Beam Forming

Antennas in Multi-hop Packet Radio”, Report, Radio Communication Systems Lab.Dept. of

Signals, Sensors and Systems, Royal Institute of Technology , SE-100 44 Stockholm,

Sweden.

[Rohling]. Rohling et. al. “OFDM based air-interface design for 4G mobile communications

systems”, Proceedings of the OFDM Workshop, Sept. 2001.

[Apurva]. A. Mody and G. Stuber, “ Synchronization sequences for MIMO OFDM

sytems”, Proceedings of the OFDM Workshop, Sept. 2001.

[Hari]. K. V. S. Hari et. al “ Channel Models for broadband wireless access systems”, IEEE

802.16.3 Contribution, 2002.

[Brain]. Brain Enhancements to Hiperlan2 standard, (www.etsi.org).

[802.16a] I. Koffman and V. Roman, “ Broadband wireless access solutions based on

OFDM access in IEEE 802.16 ”, IEEE Communications Magazine, April 2002.

[Bamod]. P.Arun, S.Thiyagarajan, S.Srikanth, "Performance of block adaptive modulation schemes for OFDM based WLAN systems", Proc. IEEE International Conference On Personal Wireless Communications (ICPWC-2002), pp. 6-10, New Delhi, India, Dec 15-17, 2002.

[Deep]. D.Varshney, C.Arumugam, V.Vijayaraghavan, S.Srikanth, " Improved multiuser

detection algorithm with space-time block coded transmission", pp.378-382 , Proc. 9th

National conference on communications, Chennai, India, Jan 31 - Feb 2, 2003.

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Detailed Bio-Data

Name: Dr. S. Srikanth Mailing Address: Member, Research Staff,

AU-KBC Research Centre,

MIT Campus, Anna University,

Chromepet, Chennai.

600 044 Email: [email protected] Phone: 44-2223-2711, 2223-4885 Fax: 44-2223-1034

Date of Birth: 20th Feb. 1969. Education:

?? Ph. D., Electrical Engineering, University of Victoria, Canada, August 1997, (8.0/9/0, GPA).

?? M. A. Sc, Electrical Engineering, University of Victoria, Canada, May 1993, (8.0/ 9.0, GPA).

?? B. E., Electronics and Communication Engineering, Anna University, India, 1990, (First Class with Distiniction).

Work Experience:

?? July 2000 – Present, Member, Research Staff, AU-KBC Research Centre, Chennai.

?? Nov. 1999 - Jul. 2000 – UGC Visiting Professor, College of Engineering,

Anna University. ?? July. 1997 - Sept. 1999 – DSP Engineer, Harris Corporation, Calgary,

Canada. ?? Sept. 1990 - June 1997: Graduate Teaching Fellow, Research and

Teaching Assistant, University of Victoria, Canada.

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Research: Multicarrier Communications Systems for Wireless and

Powerline Communications, Space-time Processing and coding for wireless systems.

Teaching: Elective on Wireless Communications, Advanced Digital Signal Processing

Accomplishments:

?? Design and simulation of baseband signal processing schemes for basestation transceivers in the second generation U.S. Digital Cellular systems. (Harris Corporation)

?? Analysis and simulation of capacity enhancing mechanisms in CDMA

systems using antenna arrays. (Harris Corporation)

?? Evaluation of digital/software radio schemes for basestation applications: concept understanding and hardware experiments. (Harris Corporation)

?? Development of a new resource allocation algorithm for OFDM based

multiple access systems. (AU-KBC Research Centre)

?? Development of powerline communications channel model and low-data rate communications sytems for campus power network. (AU-KBC Research Centre)

?? Adaptive signal processing techniques for HDSL systems. (Micronet,

Centres of Excellence, Victoria, Canada)

?? Space-time processing and equalization for CDMA based indoor wireless sytems. (Micronet, Centres of Excellence, Victoria, Canada)

Patents Filed:

“Power efficient Multiuser Indoor wireless Systems based on OFDM” March, 2002. (AU-KBC Research Centre)

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Selected Publications: [1]. S. Subramanian, D. J. Shpak, and A. Antoniou, “ Performance of a Multiple-Antenna-

Multiple-Equalizer System for Indoor Wireless Communications,’’ Wireless Personal Communications, Kluwer Academic Publishers, 2000.

[2]. R. Venkatesh, S. Karthikeyan and S.Srikanth, “ Downlink performance of an OFDM

based multiple access system for indoor wireless communication” Accepted for Publication Wireless Personal Communications, Kluwer, Netherlands, 2002.

[3] S. Sundaresan, S. Srikanth, and C. N. Krishnan, "Distributed MAC Protocols and

Priority Oriented Scheduling for a PLC Access Network", Accepted, Special Issue on Powerline Communications of the International Journal of Communication Systems.

[4].P.Arun, S.Thiyagarajan, S.Srikanth, "Performance of block adaptive modulation

schemes for OFDM based WLAN systems", Proc. IEEE International Conference On Personal Wireless Communications (ICPWC-2002), pp. 6-10, New Delhi, India, Dec 15-17, 2002.

[5]. V.Rajendran, , K.Sundaresan, S.Srikanth, "Power efficient resource allocation scheme

for multiuser ODFM", Proc. IEEE International Conference On Personal Wireless Communications (ICPWC-2002), pp. 224-228, New Delhi, India, Dec 15-17, 2002.

[6]. N.R.Karthikeyan, Manisridhar, G.Praveenkumar, K.Ramakrishnan, R.Jayaparvathy,

S.Srikanth, " Priority oriented scheduling in cellular systems with dynamic packet assignment", pp. 294-298, Proc. 9th National conference on communications, Chennai, India, Jan 31 - Feb 2, 2003.

[7]. D.Varshney, C.Arumugam, V.Vijayaraghavan, S.Srikanth, " Improved multiuser

detection algorithm with space-time block coded transmission", pp.378-382 , Proc. 9th National conference on communications, Chennai, India, Jan 31 - Feb 2, 2003.

[8]. S.Rajesh, K.Vijayalakshmi, S.Srikanth, V.Vaidehi, " Capacity and Qos enhancement

of adhoc networks with intermittant smart directional nodes", pp. 35-39, Proc. 9th National conference on communications, Chennai, India, Jan 31 - Feb 2, 2003.

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[9]. S. Sundaresan, S. Anand, S. Srikanth and C.N.Krishnan, “Performance of a distributed MAC for OFDM based power line communication networks” Proceedings of eighth National Conference on Communications, pp. 238-243, IIT Bombay, Jan. 2002.

[10] P. Arun, R. Venkatesh, S. Karthikeyan and S.Srikanth “Multiple access schemes for

OFDM based indoor wireless systems” Proceedings of eighth National Conference on Communications, pp. 488-492, IIT Bombay, Jan. 2002.

[11]. S. Subramanian and P. J. Mclane, `` Erlang Capacity of CDMA systems with Adaptive

Array,’’ Proc. Of IEEE Vehicular Technology Conference, Boston, Sept. 2000. [12]. T. V. Prasad, S. Srikanth, C. N. Krishnan, and P. V. Ramakrishna, ``Wideband

Characterization of low-voltage powerline network in India,’’ Proc. Int. Symp. On Powerline Communications, Malmo, Sweden, April 2001.

Fellowships and Awards :

?? Graduate Teaching Fellowship, Department of Electrical Engineering, University of Victoria, Victoria, Canada, 1994-1997.

?? Project Guide for the best student project award winners, College of Engineering, Guindy, 2001.

?? Citation and cash award from KBCRF Pvt. Ltd. for research work leading to patentable results, May 2002.

Other Information:

?? Presented a tutorial on OFDM and 802.11a standard at the National Conference on Communications to be held at IIT Madras, Chennai, Jan. 2003.

?? Member of a 4-person team which was nominated to look into the various

issues related of a wireless systems initiative suitable for India. This Initiative has been coordinated by the Ministry of Communications and Information Technology, Govt. of India. A report has been submitted to the Minsitry.