Meteor Burst Channel Research Articles

An Adaptive State Assignment Mechanism Based on Joint Data Detection and Channel Estimation on Fading Meteor Channel

Integrating adaptive modulation and coding techniques into time-varying meteor burst channels with joint data detection and channel estimation at the receiver can greatly increase the average throughput of a meteor burst communication system (MBCS). Although the per-survivor processing algorithm (PSPA) based on joint data and channel estimation provides superior performance and robustness for MBCS, it is very difficult to implement it into practice due to the extremely high computational complexity. An adaptive state reduction scheme using a dimension-down PSPA (ADPSP) with few states in the trellis diagram is proposed based on the slow-fading characteristic of the meteor burst channel. It has the advantages of the dimension-down PSPA (D-PSPA) and the adaptive state reduction scheme based on PSPA proposed in our previous work. The scheme is proposed to reduce the computation complexity and memory size for exponentially decaying meteor burst channels and make the maximum likelihood sequence detection available for adaptive data transmission. Based on the estimation of parameters of the meteor burst channel, the adaptive threshold is obtained in order to decrease the computation compleixty of PSPA, where the states close to the correct one in the trellis is selected. Simulation results are presented to validate the theoretical analysis. It is shown that the proposed adaptive state reduction scheme using a D-PSPA can obtain a good tradeoff between the achievable performance and its dynamically computation complexity, as well as provide reliable data transmission for MBCS using adaptive coding and modulation.

Simulation and Analysis for Meteor Burst Communications Based on OPNET

Meteor burst communication is an important communication mode for a number of possible civilian and military applications. This paper proposes a channel modeling and simulation based on OPNET for meteor burst communications. Analyzing the characteristics of underdense meteor burst channel, the multi-layer node models of master station and slave station are presented to create practical simulation scenario of meteor burst communications. The simulation processes of half-duplex communication as well as full-duplex communication are designed to execute simulation. The results demonstrated that the channel model based on OPNET is consisted with meteor burst communication very well, and full-duplex communication is better than full-duplex communication in effectiveness.

Reseach of digital modulation methods for meteor data telecommunication system

The theme of this paper is a research of digital modulation methods for further use in a digital data transmission system (DDTS). The paper is just a stage in the DDTS development, and the next step is selecting and grounding a method, an encoding and a decoding algorithms. Usually in modern publications modulation and coding are considered together, which makes it difficult to select and validate the method of modulation in the specific conditions of the meteor burst channel. The goal of the research is to make a complete description of the modulation and demodulation algorithms as well as their parameters and characteristics determination. The method of investigation is a detailed mathematical description and computer simulation. The problem to be solved is considered in terms of the overall system. The main results of the work are a generalization and analysis of existing algorithms, recommendations for the grounded choice of the modulation method and algorithm for its further use in the DDTS. Curves of bit error rates against the signal to noise ratio for the modulation methods under consideration are given

Proposal of Go-Back-i-symbol ARQ Scheme and its Performance Evaluation in Meteor Burst Communications

In this paper, we propose a new automatic repeat request (ARQ) scheme, named Go-Back-i-symbol (GBi) ARQ scheme, suitable to Meteor Burst Communications (MBC). The scheme realizes symbol-wise ARQ by using the Viterbi decoding algorithm for convolutional codes. We also propose a practical transmission protocol for applying the GBi-ARQ scheme to packet communications over time varying short burst channels such as meteor burst channels. Fundamental performances of the GBi-ARQ scheme in MBC are evaluated by computer simulations. Effectiveness of the GBi-ARQ scheme is shown by comparing the performance with that of a conventional block-wise ARQ scheme.

An adaptive receiver of joint data and channel estimation for meteor burst communications

AbstractIn view of the characteristics of the meteor burst channel, the variable rate data transmission should be adopted to improve the system average throughput, which results in channel tracing and equalization problems at the receiver. Although the joint data and channel estimation of maximum likelihood sequence detection performing the principle of per‐survivor processing (PSP) is considered as an optimal detection scheme, its great computational complexity is a major problem and can hardly agree with the decreasing of the meteor channel. Based on the estimation of the system parameters, an adaptive state reduction of the PSP (ASRP) algorithm with only a few states in the trellis diagram is employed, while these states are chosen by the time‐varying threshold according to the exponential decay of meteor channels. It is shown that, ASRP can make a good tradeoff between the performance and the computational complexity, and provides reliable data transmission for adaptive modulation and coding of the meteor burst communication system. Computer simulation results and performance analysis are also included to support our developments. Copyright © 2010 John Wiley & Sons, Ltd.

Information protection based on nanosecond synchronization of time scales in meteor burst channel

The work is dedicated to metrological validation of meteor-based method of information protection--new technique for distant encryption key generation which might be capable of providing thorough security. The method is based on high-precision phase measurements of radio signal propagation time performed simultaneously in both forward and backward directions. These measurements are possible only if the communicants' time scales are synchronized with nanosecond precision, which is shown to be possible by meteor time transfer. In order to account for short-term instability of quantum frequency standards, considering irregularity and variable precision of meteor measurements, we use optimal linear filtration and experimental measurement analogue, based on the results of meteor synchronization experiment conducted on the Mendeleevo(Moscow)-Kazan radio path. The possibility of using a meteor channel in two modes for remote time scale synchronization and encryption key generation is shown together with estimates for the capacity of this procedure.

Impulse response measurements on a 500‐km meteor burst link

Using a wideband chirp sounder technique, the impulse response characteristics of a 500‐km meteor burst channel were investigated for the purpose of studying the fine structure of meteor trails giving rise to multipath propagation, determining the channel delay spread statistics, and examining the correlation between multipath phenomena and meteor trail duration. To date, an analysis of these data has revealed that most of the time only a single dominant path exists between the transmitter and receiver. However, when multipath conditions are encountered, many paths varying in both strength and duration may exist and can adversely affect communications. Fortunately, multipath conditions were observed in only about 30% of all echoes and, while seen in both short‐ and long‐duration trails, were found to occur most frequently during trails of longer temporal extent. In 90% of all measurements considered, the rms delay spread was found to be less than 100 ns.

Optimal signaling for meteor burst channels

We examine the design of modulation systems for meteor burst communications. In particular, we present a technique which allows the designer to determine the signal set size and the signaling rate which maximize the throughput per meteor burst. The technique, which involves the capacity and cutoff rate from information theory, is applied to a variable coding rate scheme and a variable signaling rate scheme, for both coherent MPSK (M=2, 4, 8) and noncoherent MFSK (M=2, 4, 8, 16, 32). As a fringe benefit, the method proposed also provides estimates on achievable throughputs.

Meteor Burst Channel Simulator

This paper describes the hardware implementation of meteor burst channel simulator using the reported data of meteoric burst channel parameters. The look-up table approach along with Pseudo Random Binary Sequence (PRBS) generator is adopted for simulation of the diurnal variation in the channel. The exponential decay for underdense and specular overdense meteors have been simulated. The simulated channel parameters are compared with the reported data of real meteoric burst channel.

Spatial diversity in meteor scatter radio links

Meteor burst communication links rely on radiowave scattering from ionized trails left in the wake of meteors. Because of the significant path loss, on the order of 50 dB, associated with the trail‐scattering process, many means have been sought to improve link performance. Adaptive beam control algorithms and variable burst rate modems have been developed to achieve better use of the meteor burst (MB) channel. In addition to these techniques it is the contention of this paper that link performance may be further improved by making use of the spatial diversity inherent in meteor trails. Given the limited geographic extent of trail‐scattered signal footprints, adequately spaced receive sites can use different propagation paths associated with independent meteor trails from a single transmit site. The assumption here is that these receive sites are linked by a local communications network. The effective performance from the transmit site to any of the receive sites is significantly improved. Of course, this improvement is a function of receive site spacing and the performance of the short‐range network. This paper describes the meteor scatter phenomena that impact spatial diversity, details an approach for predicting the associated link performance improvement, and presents a sensitivity study based on computer model predictions.

Performance analysis of an ARQ transmission scheme for meteor burst communications

Packet error probability is the key parameter in evaluating the performance of ARQ schemes, in terms of waiting time to receive a data packet, and system throughput. The authors present an analysis of the packet error probability for two modulation schemes, BFSK and BPSK, when uncoded packets are transmitted over the meteor burst channel using a fixed data rate. They show that the optimum transmission rate, minimizing the waiting time to receive a packet correctly, is independent of the initial SNR of the trail and the modulation used. The results were derived analytically, and are in excellent agreement with exact numerical calculations. They also present simple approximations to the exact calculations, and lower bounds on the packet error rate which are tight in the neighborhood of the optimum transmission rate.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Evaluating the performance of a message transmission system on meteor burst channel

AbstractThis paper evaluates the performance of the two‐way message transmission system on the meteor burst channel developed and tested by the authors. First, the usual channel model is simplified and then the system is analyzed. It is shown through simulations that the errors introduced by the new channel model and by the approximated analysis method are negligible and the proposed method can be used to design and evaluate the system.The performance of the system having packets with subblocks is compared to that of one with usual packets. It is shown that, by using packets with subblocks, robustness of the system performance against changes of channel parameters as well as a shorter time needed to transmit a message can be obtained. The method of performance evaluation shown in this paper has adequate generality and is also applicable to many other meteor burst communication (MBC) systems.

Adaptive trellis-coded modulation for bandlimited meteor burst channels

The throughput performances of three adaptive information rate techniques on the bandlimited meteor burst channel are investigated. Closed-form expressions for throughput are derived based on the channel model commonly used in the literature. The throughput performance is compared to the conventional fixed information rate modem and upper bounds on throughput improvement over the fixed rate modem are derived. It is shown that an adaptive technique that uses trellis-coded modulation (TCM) with three phase-shift keyed (PSK) signal sets can increase throughput over the conventional fixed rate modem by more than a factor of 3. Data from the US Air Force High Latitude Meteor-Scatter Test Bed confirm the superiority of the adaptive TCM technique. A practical implementation is suggested that uses a single rate 1/2 convolutional code for all three PSK signal sets. The use of this single code, versus the three best Ungerboeck codes, results in a throughput loss of less than 2%. An expression for the theoretical information capacity of the bandlimited meteor burst channel is derived. >

Efficient communications using the meteor-burst channel

This work presents the results of a theoretical study of the meteor-burst channel which illustrates its time-varying bursty nature. In addition, the authors describe an innovative approach to data transmission over meteor-burst systems, i.e. the use of the feedback adaptive variable rate (FAVR) system which allows the maximum amount of information to be transmitted over each meteor-burst channel. For underdense meteor channels the FAVR performance is compared to an optimum system, i.e. a system capable of changing its bit rate instantaneously to channel conditions so as to maintain a constant SNR in each bit, and to a constant optimum rate/burst system. It is shown that when compared to an optimum rate per burst system, FAVR can result in a throughput increase exceeding a factor of 10. It is also shown that FAVR can approach the optimum system performance, although for practical purposes, it appears that 83-88% of optimum is attainable.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Coding for meteor burst communications

The use of error correction coding for meteor burst communications is discussed. The cutoff rate is derived for a meteor burst channel model which assumes that the received signal amplitude decays exponentially. The message error rate of a coded system, obtained by means of computer simulation, is compared to that of an uncoded system. A tight upper bound on the performance of the coded system is presented. It is shown that coding can reduce the signal-to-noise ratio (SNR) required for reliable communications via meteor bursts by many decibels. The coding gain is larger at shorter communication ranges where meteor trails, decay faster. It is also shown that the additional improvement achieved by providing the decoder with side information on the instantaneous level of the received signal is small.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Probability density function of amplitude decay constant on meteor burst communication channel

Lack of accurate characterisation for the amplitude decay constant on the meteor burst channel makes most existing analytical methods of systems on this channel approximate. It is shown that the probability density function of the amplitude decay constant can be approximated by the log-normal density. An expression for the density of the burst duration is also given. These results will allow for a more in depth analysis of meteor burst communication systems.

High Data Rate Meteor-Burst Communications

The meteor burst communications channel offers a largely untapped means of communications that can alleviate congestion in many existing communications systems. It also provides some interesting advantages over other beyond-line-of-sight systems, including lower susceptibility to atmospheric perturbations, a limited footprint, and relatively low cost. Past system applications have been quite limited, however, due to the random nature of the meteor burst phenomenon which has resulted in relatively low throughput and lengthy wait-times.This paper presents the results of an experimental study of the meteor burst channel which illustrates its time-varying bursty nature. In addition, the authors describe an innovative approach to data transmission over meteor burst systems, ie, the use of the Feedback Adaptive Variable Rate (FAVR) system which allows the maximum amount of information to be transmitted over each meteor burst channel.For underdense meteor channels the FAVR performance is compared to an optimum system, ie, a system capable of changing its bit rate instantaneously to channel conditions so as to maintain a constant SNR in each bit, and to a constant optimum rate/burst system. It is shown that for such a system FAVR can result in a throughput increase exceeding a factor of 10.

Error correction coding for a meteor burst channel

The time-varying signal-to-noise ratio (SNR) model for the meteor burst (MB) channel is reviewed. Bounds on the capacity of the channel are derived for both a constant SNR model and a time-varying SNR model. These bounds show that there is a significant throughput improvement to be gained by using forward error correction. Two methods are given for determining the performance of an MB system when packets of information are encoded with an (n,k) linear block code. Numerical results are generated using high-rate BCH codes, and it is found that about 25% improvement over uncoded systems can be obtained by choosing the code rate properly. In addition, some suggestions for techniques that provide further improvement are given. >

Message waiting time performance for meteor-burst communication systems

The performance is investigated of the meteor-burst channel in terms of the waiting time required to reliably transmit a message of length N bits. Two modulation techniques are considered. The first is the traditional fixed-rate modulation scheme where the modem operates at a constant bit rate whenever the channel is available for message traffic. The second is an adaptive modulation method where the channel symbol rate varies continuously to match the time-varying signal-to-noise ratio at the receiver. Upper and lower bounds on waiting time for the general case are derived using probabilistic arguments. Novel closed-form expressions for waiting time and optimal bit rate are derived for the fixed-rate modem. Bounds on mean waiting time are derived for the adaptive-symbol-rate modem. It is shown that for fixed-rate modems operating at the optimal bit rate and for adaptive modems operating at a minimum bit rate equal to this rate, the improvement in mean waiting time can never exceed a factor of two.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An investigation of ARQ and hybrid FEC-ARQ on an experimental high latitude meteor burst channel

A computer investigation of error-control-coding techniques and bit error patterns recorded on an experimental Northern latitude meteor burst link is presented. Automatic repeat request (ARQ) and hybrid forward error correction (FEC) with ARC are examined from the standpoint of probability of message delivery and encountered message delivery delays. It is demonstrated that FEC will yield substantial improvement in the number of messages deliverable within a specified time constraint. Potential gains in extending the usable time duration of a meteor burst channel are on the order of factors of four with successful message delivery percentages increased by factors of 50. >