Kalyan Bandyopadhyay

Comparison of Rain Fade Mitigation Techniques Using CRC and Embedded Pilot Methods in Ka-Band Satellite Links

The large bandwidth available in Ka-band of the satellite channel is one of the prime motivations for broadband communication via satellite. In tropical regions where there are heavy rains, the link availability due to rain fade is a major concern in the Ka-band. Rain fade mitigation techniques are required to address the problem. Methods for Adaptive Modulation and Coding (AMC) controlled from the application layer, which can be applied to any typical modem which supports multiple data rates, in order to maintain link availability is presented in this work. Algorithms for estimating the link quality, from the application layer, which is essential for successful implementation of AMC is also detailed in this work.

Comparison of rain attenuation prediction models with Ku-band beacon measurement for satellite communication system

The bulk of beacon signal attenuation or fading is due to clear-air gaseous absorption (oxygen, water vapour) and stronger attenuation in hydrometeor events (rain, snow, clouds). In this paper, the results of the measurements of rain-induced attenuation in the Radio Wave signal propagating at 11.6995 GHz is presented. This paper also gives the comparison of the measurement result with several models, like ITU-R Model, Crane Global Model, SAM Model, Korea Model and others.

Generalized mechanism of SOTDMA and probability of reception for satellite-based AIS

Satellite based ‘Automatic Identification System’ (AIS) for global maritime applications is of current interest. The challenge of the system mainly lies in the detection capability of the receiver due to multiple transmissions from different ships received at the satellite simultaneously. To estimate the performance of the receiver proper modeling of the channel access scheme is important. In this paper we propose a generalized methodology of the Self Organized Time Division Multiple Access (SOTDMA) in an extended observation area for satellite based AIS. The performance of the proposed scheme is compared with an existing model and more realistic reception performance by a satellite based receiver is shown.

Enhanced transmission control protocol for space network: A COTS implementation

Use of standardized, common and commercial off the shelf (COTS) protocols for space communications increases interoperability and reduces cost of space systems. Most of the existing space transport protocols follow new approaches which are not drawn from the long standing, successful, and robust internet TCP. In this paper, we propose a performance enhanced transport layer protocol for deep space communication named Transport layer for Inter-Planetary Network (T-IPN) using the common standard terrestrial TCP. We have modified the data sending approach of existing TCP so that it can maintain a constant and high rate throughput throughout the transmission. Moreover, T-IPN opens multiple parallel TCP connections so as to transfer a number of TCP segments simultaneously over a single physical link. We develop theoretical models to understand the performance of T-IPN considering error free and erroneous link. Through simulations we evaluate our proposed T-IPN considering RTT values typically seen in Mars Exploration Networks under different conditions of packet error rates and show that the proposed T-IPN is error resistant and delay resilient.

Design and simulation of a Maximum Likelihood Estimator based Ka-band beacon receiver

Tropospheric effect of Ka-band signals are significant and to study that a beacon receiver is designed and its digital signal processing section is implemented in Simulink. The design is based on Maximum Likelihood Estimator to determine both the amplitude and phase of the signal. The implemented receiver is different from commonly used fast Fourier transform based ones and appears simpler. The implemented receiver is tested with the simulated signal, taken from a RF generator and shown to give desired performance.

Beam scanning for reception performance improvement of satellite-based AIS

Satellite based automatic identification system (AIS) is currently being investigated as a remote traffic monitoring system for global maritime surveillance. Because of it being a TDMA based communication system, large number of ships using same communication channel comes under the big field of view (FOV) of the satellite leading towards collisions of the transmissions. This causes the reception performance to drop down drastically. Performance improvement of satellite based AIS receiver is therefore an urgent need to providing more efficient surveillance to a large number of ships. A novel dual channel dual antenna based beam scanning mechanism, the first of its kind is developed to improve the reception capacity of satellite based AIS. 37% more number of ships is received using beam scanning compared with large single beam antenna. The improvement in the number of correct burst reception is also obtained as a part of the major claim of this scheme.