Indian Journal of Radio & Space Physics

Total visitors: 92 since 02-11-07

(CODEN : IJRSAK        ISSN : 0367-8393)

VOLUME 36

NUMBER 5

OCTOBER 2007

 

CONTENTS

 

Preface

 

357

Guest Editorial: Schumann Resonance – Its different aspects and latest wonders

        S S De*

359

 

Propagation studies at Ku-band over an earth-space path at Kolkata

        Animesh Maitra*, Kaustav Chakravarty, Sheershendu Bhattacharya & Srijibendu Bagchi

363

 

Scintillation and depolarisation models for satellite communications in the 20-50 GHz band

        Danielle Vanhoenacker-Janvier, Claude Oestges* & Antonio Martellucci

 

369

 

Cloud attenuation and cloud noise temperature over some Indian eastern stations for satellite communication

        Anil Kumar & S K Sarkar*

 

375

 

Estimation of cross-polarization due to rain over some stations in India

        R Sen Jaiswal*, P Geetha & S Uma

379

 

Remote sensing of radio ducts using wind profilers

        N Sengupta* & I A Glover

383

GPS radio occultation on-board the OCEANSAT-2 mission: An Indian (ISRO) – Italian (ASI) collaboration

        Giovanni Perona*, Riccardo Notarpietro & Marco Gabella

 

386

 

Ionospheric studies for the implementation of GAGAN

        Rajat Acharya*, Neha Nagori, Nishkam Jain, Surendra Sunda, Sawarmal Regar M R Sivaraman & Kalyan Bandopadhyay

394

Significance of instrumental biases and dilution of precision in the context of GAGAN

        Quddusa Sultana, Dhiraj Sunehra, D Venkata Ratnam, P V D Somasekhar Rao &
A D Sarma*

405

Propagation channel, capacity and error probability for dual-polarized wireless transmissions

        Claude Oestges*

 

411

 

Studies on radio frequency propagation characteristics for underground coalmine communications

        L K Bandyopadhyay*, P K Mishra, S Kumar, D Selvendran & S K Chaulya

 

418

 

Application of classical two-ray and other models for coverage predictions of rural mobile communications over various zones of India

        M V S N Prasad*, K Ratnamala, M M Gupta & S K Sarkar

 

423

A novel multiple access scheme for mobile communications systems

        Poonam Singh*, R V Raja Kumar & T S Lamba

430

Search for radio signal associated with UHE cosmic ray air showers in VLF range

        N M Saikia*, B Tiru, P K Boruah & K Boruah

436

 

 

Obituary

441

___________

*Authors for correspondence

 

 

 

Indian Journal of Radio Space Physics

Vol. 36, October, 2007, pp. 363-368

 

 

 

Propagation studies at Ku-band over an earth-space path at Kolkata

Animesh Maitra1, Kaustav Chakravarty2, Sheershendu Bhattacharya1 & Srijibendu Bagchi1

1Institute of Radio Physics and Electronics, University of Calcutta, Kolkata 700 009

E-mail: animesh.maitra@gmail.com

2S K Mitra Centre for Research in Space Environment, University of Calcutta, Kolkata 700 009

Received 19 June 2007; accepted 28 August 2007

Propagation measurements at Ku-band over an earth-space path have been carried out at Kolkata (22°34¢ N, 88°29¢ E) by receiving a signal at 11.172 GHz from the satellite NSS-6 (geostationary at 95°E). The amplitudes of the co-polar signal and the cross-polar component have been monitored along with the measurements of rain rate and drop size distribution by an optical raingauge and a Joss-type disdrometer, respectively. Three phenomena studied with the experimental data are rain attenuation, depolarization and scintillation. The rain attenuation observed experimentally tallies well with the values obtained from the point rain rate using a simple attenuation model, if the rain rate is low (less than 20 mm/h). The depolarization, indicated by an enhancement of the cross-polar component of the signal, is well correlated with the rain attenuation. The presence of large rain drops is found to have a more dominant role in determining the extent of depolarization than affecting the co-polar attenuation. The scintillation observations associated with the rain events indicate that the standard deviation of fast fluctuations increases with rain attenuation following a power-law.

Keywords: Earth-space propagation, Ku-band, Rain attenuation, Depolarization, Scintillation

PACS No.: 84.40.Ua; 92.60.Ta; 94.10 Gb

 

 

 

Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 369-374

 

 

 

Scintillation and depolarisation models for satellite communications
in the 20-50 GHz band

 

Danielle Vanhoenacker-Janvier1, Claude Oestges1 & Antonio Martellucci2

1Microwave Laboratory, Université catholique de Louvain, Louvain-la-Neuve, Belgium

2TOS-EEP, ESA, ESTEC, Keplerlaan 1, PB 299, NL-2200 AG Noordwijk, The Netherlands

Email: vanhoenacker@emic.ucl.ac.be

Received 19 June 2007; accepted 14 September 2007

This paper presents improved methods for the prediction of cumulative distribution of scintillation variance, using radiosonde data. This method has the advantage of being usable all around the world and its accuracy is improved with respect to classical methods based only on ground measured data. The second part presents a two-layer depolarisation model separating rain and ice effects for better scalability.

Keywords: Tropospheric scintillation, Satellite communications, Depolarisation

PACS No.: 84.40. Ua

 

 


Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 375-378

 

 

Cloud attenuation and cloud noise temperature over some
Indian eastern stations for satellite communication

 

Anil Kumar & S K Sarkar

Radio and Atmospheric Sciences Division, National Physical Laboratory, New Delhi 110012, India

e-mail: sksarkar@mail.nplindia.ernet.in

Received 19 June 2007, accepted 20 July 2007

In this paper, cloud characteristics in relation to radio wave propagation over some selected locations in different geographical region in eastern India have been presented. It is seen that low cloud occurrence over Patna, Bhubaneswar and Ranchi is quite significant. The performance of radio systems deteriorates due to cloud attenuation as well as due to cloud noise temperature. Based on the cloud attenuation results, the total atmospheric noise temperature including the noise contribution from cloud for different months during different times for different cloud thicknesses at 10 GHz, 18 GHz, 32 GHz, 44 GHz and 70 GHz has been determined for the aforesaid stations. The results, presented here are useful to design future earth- space communication links over these aforesaid locations in India.

Keywords: Cloud attenuation, Noise temperature, Microwave and millimeter wave bands, Indian stations

PACS No.: 92.60. Ta; 92.60.Jq ; 84.40.Ua

IPC Code: G01 S1/00

 

 

 

Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 379-382

 

 

Estimation of cross-polarization due to rain over some stations in India

R Sen Jaiswal, P Geetha & S Uma

Department of Physics, Sona College of Technology, Salem 636 005, Tamilnadu

Email: senoritta_in@yahoo.co.in

Received 19 June 2007; accepted 5 September 2007

In this paper an attempt has been made to compute cross-polarization of millimeter waves in the 30-35 GHz frequency range due to rain. Laws and Parson’s drop size distributions for oblate spheroid drops at 20°C ITU-R (2002) model has been used to predict cross-polarization discrimination (XPD) for circular polarization. The study includes a number of earth stations in India, namely, Ahmedabad, Calcutta, Delhi, Gangtok and Jodhpur. Variations of co-polar attenuation with XPD have been shown. Cumulative time distribution of XPD has also been presented. The study reveals that cross-polarization depends on frequency, co-polar attenuation and rainfall rate. Comparison with measurement does not show good agreement although the two show the same trend. Extensive work on cross-polarization is required in the millimeter wave frequency range over a large number of earth stations in India using different drop size distributions and different polarizations.

Keywords: Rainfall rate, Attenuation, Cross-polarization, Rain height

PACS No: 41.20.Jb

 

 


Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 383-385

 

Remote sensing of radio ducts using wind profilers

N Sengupta* & I A Glover

Institute for Communications & Signal Processing, Department of Electronic & Electrical Engineering, University of Strathclyde, Royal College Building, 204 George Street, Glasgow G1 1XW, UK

E-mail: ian.glover@eee.strath.ac.uk

Received 19 June 2007 ; accepted 14 August 2007

A case study is presented of refractivity gradient height-profile retrieval using a 915 MHz wind profiler operated by the UK Meteorological Office at Camborne, UK. The retrieved gradient compares well with that obtained from concurrent radiosonde data gathered at the same location, thus demonstrating the potential of such profilers for the investigation of duct dynamics and the collection of unbiased duct statistics.

Keywords: Radio ducts, Refractivity gradient, Radiosonde, Wind profiler

PACS No.:  92.60.Ta; 92.60.Gn; 92.70.Gt

 

 

 

 

Indian Journal of Radio Space Physics

Vol. 36, October, 2007, pp. 386-393

 

 

GPS radio occultation on-board the OCEANSAT-2 mission: An Indian
(ISRO) – Italian (ASI) collaboration

Giovanni Perona, Riccardo Notarpietro & Marco Gabella

Politecnico di Torino, Electronics Dept., Corso Duca degli Abruzzi, 24 – I-10129 Torin, Italy

Email: giovanni.perona@polito.it

Received 19 June 2007; accepted 14 September 2007

In the first quarter of 2008, the Indian satellite OCEANSAT-2 will be launched. The Italian Space Agency (ASI) signed a Memorandum of Understandings with the Indian Space Research Organization (ISRO) in which it is agreed to put on-board the OCEANSAT-2 satellite the Italian GNSS receiver devoted to Radio Occultation (ROSA–Radio Occultation Sounder of the Atmosphere). The ROSA receiver has been developed with a new-concept hardware configuration with respect to that normally characterizing a GNSS receiver: it will track the GPS “occulted” signal both just before its setting and just after its rising from the local horizon using an open loop technique, and it will automatically switch from (or to) the standard closed loop approach when the signal crosses higher atmospheric regions. Observations from ROSA will be downloaded both to the Indian and the Italian receiving stations where they will be processed by the ROSA Ground Segment, developed by Italian universities and research centres. In particular, the first version of the processing software will be integrated in a ground segment installed in Matera (Italy) and mirrored at Hyderabad (India). Its second version will be installed in a distributed ground segment implemented by connecting, on a web-based GRID, hardware and software infrastructures installed at the research centres and universities involved in its development.

Keywords: Global positioning system (GPS), Radio occultation, Oceansat-2, Radio occultation sounder of the atmosphere (ROSA)

PACS No: 92.60.Hp

 

 


Indian Journal of Radio Space Physics

Vol. 36, October, 2007, pp. 394-404

 

Ionospheric studies for the implementation of GAGAN

Rajat Acharya, Neha Nagori, Nishkam Jain, Surendra Sunda, Sawarmal Regar

M R Sivaraman & Kalyan Bandopadhyay

Systems & Applications Group, Satcom & IT Applications Area
Space Applications Centre, Ahmedabad 380 015, India

e-mail: rajat_acharya@sac.isro.gov.in

Received 19 June 2007; accepted 30 September 2007

Satellite Based Augmentation System (SBAS), being developed by Indian Space Research Organization (ISRO) in collaboration with Airports Authority of India (AAI) is known as “GPS Aided GEO Augmented Navigation” (GAGAN). It is expected to offer better accuracy and integrity of navigation service than with GPS alone by providing correction terms to the GPS signals. This is achieved by modelling a Near Real Time Grid Based Ionospheric Delay Model for correcting propagation delay at 1575.42 MHz (L1) using measurements at 1575.42 and 1227.6 MHz (L2). Existing algorithms are replaced by Kriging based model to meet the requirement of correction with 0.5 m maximum residue over Indian region. Details of the data collection and pre-processing, including estimation of the Total Electron Content (TEC), which is a measure of ionospheric delay, has been described. Kriging algorithm and some preliminary results of studies are also presented in this paper. This includes the spatial decorrelation of the stochastic random field over the deterministic variation of ionospheric TEC. Its variation with time and locations are investigated and a temporal dependence found to exist. Large scale ionospheric irregularities and depletions that cause severe amplitude and phase scintillations are also studied. Their impacts on GAGAN are also shown. Some major scientific studies required to be carried out over Indian region to improve the GAGAN performance is discussed.

Keywords: GPS, Equatorial ionosphere, SBAS, GAGAN, Ionospheric Large scale model, Kriging, scintillation

PACS No.: 94.20.Bb

 

 

Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 405-410

 

Significance of instrumental biases and dilution of precision in the
context of GAGAN

 

Quddusa Sultana1, Dhiraj Sunehra, D Venkata Ratnam, P V D Somasekhar Rao2 & A D Sarma

Research and Training Unit for Navigational Electronics, Osmania University, Hyderabad 500 007, India

E-mail: ad_sarma@yahoo.com

1Deccan College of Engineering and Technology, Hyderabad 500 001, India

2UGC-ASC, Jawaharlal Nehru Technological University, Hyderabad 500 072, India

Received 19 June 2007; accepted 4 September 2007

The positional accuracy of the GPS Aided GEO Augmented Navigation (GAGAN) system is basically dependent on ranging errors and the satellite constellation geometry. This paper focuses on enhancing the performance of the system through the estimation of instrumental biases and augmentation of GAGAN using pseudolites (pseudo-satellites). The line-of-sight ionospheric measurements derived from the Global Positioning System (GPS) observables are corrupted by the instrumental biases present in both the GPS satellites and the receivers. The instrumental bias and Total Electron Content (TEC) results (Hyderabad GAGAN station (78.47°E, 17.45°N)) obtained using the Kalman filter technique are presented in this paper. It is found that the estimated biases are almost stable during the observation period and show close proximity with other reported values in the open literature. For some strategic applications further augmentation of GAGAN with pseudolites is necessary. Five configurations comprising GPS/geostationary satellites and pseudolites are considered for optimizing the Dilution of Precision (DOP). It is found that the pseudolite-system with properly located pseudolites can augment GAGAN and improves the positional accuracy of the user.

Keywords: GPS aided GEO augmented navigation (GAGAN), Geometric dilution of precision (GDOP), Global positioning system (GPS), Instrumental biases, Pseudolites, Total electron content (TEC).

PACS No.: 94.80+g


Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 411-417

 

 

 

Propagation channel, capacity and error probability for dual-polarized wireless transmissions

Claude Oestges

Microwave Laboratory, 3 place du Levant, Université catholique de Louvain, 1348 Louvain-la-Neuve, Belgium

Email: oestges@emic.ucl.ac.be

Received 19 June 2007; accepted 21 August 2007

Use of dual-polarized arrays in multiple-input multiple-output (MIMO) systems is addressed in this paper. A new and simple analytical model of dual-polarized Rayleigh and Ricean fading channels is taken, which relies on a limited number of physical parameters, such as the spatial correlations, the co-polar gain imbalance and the cross-polar discrimination. Then, the multiplexing advantage of dual-polarized transmissions is investigated through the evaluation of the ergodic mutual information. Finally, the performance of two space-time coding schemes (Alamouti O-STBC and un-coded Spatial Multiplexing) is evaluated via a detailed analysis of the pair-wise error probability (PEP).

Keywords: Multiple-input multiple-output (MIMO), Dual-polarized transmission, Space-time coding

PACS No.: 84.40.Ba

 

 

 

Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 418-422

 

 

 

Studies on radio frequency propagation characteristics for underground coalmine communications

L K Bandyopadhyay, P K Mishra, S Kumar, D Selvendran & S K Chaulya

Central Institute of Mining & Fuel Research, Dhanbad 826 001, India

email: laxmikb@yahoo.com

Received 19 June 2007; accepted 27 July 2007

A basic understanding of the behaviour of electromagnetic wave propagation through strata is the fundamental requirement to design a suitable wireless communication system for underground mines. Background information on radio propagation and its limitations, in a particular confined space can be known only after the measurement. Both electromagnetic propagation studies and modelling of propagation coverage, ultimately help in selecting the best suitable frequency and designing appropriate wireless communication system for underground mine. The paper discusses different aspects for propagation modelling and the experiment conducted in the laboratory to understand the propagation characteristics through coal. It is found that 6 MHz frequency is the best suitable frequency for propagation of electromagnetic wave through coal.

Keywords: Transceivers, Miner, Radio frequency wave, Directional antenna, Underground coal mine

PACS No.: 84.40.Ba; 84.40.Ua; 41.20.Jb

 

 


Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 423-429

 

 

Application of classical two-ray and other models for coverage predictions of rural mobile communications over various zones of India

M V S N Prasad, K Ratnamala, M M Gupta & S K Sarkar

National Physical Laboratory, Radio & Atmospheric Sciences Division, New Delhi 110 012.

e-mail: mvprasad@mail.nplindia.ernet.in

Received 19 June 2007; accepted 30 July 2007

The development of various prediction tools requires the comparison of radio measurements with prediction methods. For a country like India where diverse terrain conditions exist, same prediction method might not hold good in all the regions. To identify the methods suitable to rural zones an attempt is made to compare the measured results with classical two-ray, Hata and ITM methods. Their efficacies have been evaluated in terms of statistical parameters like error distribution functions,etc.

Keywords: Rural mobile communications, Classical two-ray theory, Hata’s model, ITM model

PACS No: 41.20.Jb

  

 

 

Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 430-435

 

 

A novel multiple access scheme for mobile communications systems

 

Poonam Singh, R V Raja Kumar & T S Lamba

Department of Electronics & Electrical Communication Engineering, Indian Institute of Technology,
Kharagpur 721 302 (WB), India

{psingh, rkumar, tsl} @ece.iitkgp.ernet.in

Received 19 June 2007; accepted 30 August 2007

This paper presents a novel multiple access scheme for future mobile communications using Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA). The proposed system can support different classes of users each with different data rates and can provide very high spectral and system efficiency for the uplink and downlink. It is able to meet the demands on flexibility in data rate and provides scalability with respect to bandwidth using variable time slots, spreading factors and number of subcarriers. It exploits the advantages given by the combination of the spread spectrum technique with multicarrier modulation as well as TDMA.

Keywords:   Code division multiple access (CDMA), Orthogonal frequency division multiplexing (OFDM), Multi carrier CDMA, Multi-carrier direct sequence code division multiple access (MC-DS-CDMA)

PACS No: 84.40 Ua

 

 

Indian Journal of Radio & Space Physics

Vol. 36, October 2007, pp. 436-439

 

Search for radio signal associated with UHE cosmic ray air showers in VLF range

N M Saikia1, B Tiru1, P K Boruah2 & K Boruah1

1Department of Physics, Gauhati University, Guwahati (Assam) 781 014, India

2Department of Instrumentation and USIC, Gauhati University, Guwahati (Assam) 781 014, India

E-mail: nayan075@yahoo.co.in

Received 19 June, accepted 29 August 2007

Experimental studies on the possibilities of detection of radio emission from ultra high energy cosmic ray (UHECR) extensive air shower (EAS) are done with the help of loop antenna system in the LF/VLF region. The signals from the loop for different orientations are analyzed off-line. The antenna is operated in coincidence with the particle detectors of mini-array to select the radio pulses originated from UHECR EAS. The experimental arrangement and important conclusion are discussed in the paper.

Keywords: EAS, VLF, Radio emission

PACS No.: 96.40.Pq

IPC Code: H01Q 7/00