Meteor Burst Communication Systems Research Articles

Технология построения системы метеорной радиосвязи с кодовым разделением каналов

Технология построения системы метеорной радиосвязи с кодовым разделением каналов

Концепция построения перспективной системы метеорной радиосвязи

Концепция построения перспективной системы метеорной радиосвязи

A Broadband Horizontally Polarized Omnidirectional Antenna for VHF Application

A novel broadband horizontally polarized (HP) omnidirectional antenna is proposed for meteor-burst communication system in VHF. The proposed antenna is composed of three bowtie dipoles, which are concentrically placed to form a loop antenna. The bowtie dipole is shorted at the terminal by folded elements in order to reduce antenna size. The bowtie dipoles are fed by a three-way power divider. A slotted line balun is employed to achieve broadband impedance matching and realize balanced-to-unbalanced transformation. The designed HP omnidirectional antenna exhibits a fractional bandwidth of 24.7% with VSWR < 2 ranging from 39 to 50 MHz. Uniform omnidirectional radiation patterns in the azimuth plane with HP have been obtained. The loop antenna provides a relatively low gain of no more than 1.5 dBi. Therefore, a two-element HP antenna array is developed to enhance its gain. In order to reduce longitudinal dimension of the array, the two loop antenna elements are placed in reverse and employ differential feeding method to realize in-phase current. Both the simulation and measured results are used to verify the design approach.

On the possibility of creating a hybrid meteor-burst communication system

The possibility of using a meteor-burst communication for one-way transmission of short text messages is considered. The method for organizing a meteor-burst communication, which fully realizes its stealthiness and low power consumption, is proposed. According to the proposal, the meteoric radio channel is used to information transfer only from the base station to the peripheral one, and the sending of acknowledgments is via the Internet connection. The simulation results show that the proposed method can be used to transfer up to 1.5 Mbit per day.

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.

Analysis and Simulation of Channel Nonreciprocity in Meteor-Burst Communications

This paper addresses the problem of nonreciprocity of propagation conditions in meteor-burst communication systems (MBCSs). In prior publications, this problem has not gained appropriate attention. The channel nonreciprocity may have a significant impact on such advanced communication systems as meteor synchronization systems with nanosecond precision and meteor key distribution systems intended to securely create two identical copies of a shared secret key at both channel sides. These systems are based on the processing of phase characteristics of meteor radio reflections that need to be accurately modeled. We propose a new MBCS simulation model that is based on a rigorous solution to the problem of oblique diffraction of radio waves on ionized meteor trails. Our diffraction approach allows more accurate simulation of the amplitude and phase characteristics of oppositely propagating signals that makes possible detailed investigation of the channel nonreciprocity effects. Using this approach, we present some preliminary simulation results on the channel nonreciprocity at meteor-burst propagation that prove satisfactory immunity of MBCS to ionospheric disturbances even while operating in severe conditions of polar regions.

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 &amp; Sons, Ltd.

Novel mobile terminal antenna for meteor burst communication systems

AbstractThe possibility of establishing a communication channel using meteor burst has been known for decades. In recent years there has been a renewed interest on the subject as a way to offer new wireless services at a low cost. This Letter proposes a novel mobile terminal antenna that fits the stringent size requirements demanded while retaining good gain and polarization purity. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 80–83, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10378

Erasure generation and interleaving for meteor-burst communications with fixed-rate and variable-rate coding

Erasure generation techniques are investigated in conjunction with symbol interleaving as methods to improve the performance of meteor-burst communication systems. Erasure generation via Viterbi's (1982) ratio-threshold test (RTT) and a Bayesian scheme are both considered. It is found that a system using fixed-rate coding, interleaving, and erasure generation can significantly outperform more complex variable-rate coding schemes which do not use erasures.

Relative impact of meteor scatter and other long‐distance high‐latitude propagation modes on VHF communication systems

We have analyzed the duty cycle, due to ionospheric propagation, of very high frequency sounding signals for both polar cap and auroral paths. We find that at 35 and 45 MHz the propagation is often sustained by sporadic E layers and other nonmeteoric modes rather than by meteor scatter. At the higher frequencies of 65 and 85 MHz we find that the path is generally dominated by meteor scatter modes. These results have important ramifications for frequency reuse and security in meteor burst communications systems and for the development of extended frequency range HF systems (above 30 MHz) with a capability to operate on any available propagation mode. The diurnal, seasonal, and geomagnetic variations of the nonmeteoric duty cycle have been examined. A polar cap path model is presented for the nonmeteoric duty cycle as a function of geomagnetic activity.

Recent studies of meteors in South Africa

Recent meteor research in South Africa, arising largely from the development of forward and back scatter observing systems, is briefly reviewed. The main areas of investigation have been the use of single station radars to deduce meteor radiant structures, the study of upper atmospheric wind patterns, and research into the factors which influence the performance of meteor burst communication systems.

On the effect of overlapping trails on the performance of a meteor burst communication system

A model based on some results from queueing theory is developed which takes into account the possibility of overlapping bursts in a meteor-burst (MB) communication system. Application of this model to a simple broadcast MB system shows that for meteor arrival rates that correspond to times of slowest meteor activity the assumption of non-overlapping bursts is justified, while for arrival rates corresponding to times of highest meteor activity the problem of overlapping trails may cause significant performance degradation. >

Meteor burst communication without feedback

Traditional meteor burst communication (MBC) systems are duplex (or half-duplex) systems. These systems provide the transmitter with feedback information for the detection of usable meteor trails. To achieve this feedback, a high power transmitter is required also at receive-only sites. In this paper, however, we discuss the application of channel coding to construct a true broadcast-type MBC system that allows for the simultaneous reception of messages at several receiving sites. Furthermore, MBC-systems without feedback allow for simple low power receivers that are impossible to to detect. Suitable codes, system performance and implementation complexity aspects are considered. Simulations with actual field trial data show that these systems are feasible and provide reliable, low-cost transmission of broadcast data. >

Use of antenna nulling with broadcast meteor burst communications

An antenna nulling system exploiting the duty cycle difference between the interference and the meteor burst signal was developed for combating interference experienced in broadcast meteor burst communications. Using an existing experimental broadcast meteor burst communication system, the impact of antenna nulling on communication statistics was measured both against an intentionally generated interference signal and against the benign or co-channel interference environment experienced at the reception site. >

Measured performance of meteor burst systems using antenna beam steering

This paper describes the use of antenna beam steering to improve performance of meteor burst communications systems. Various techniques used to achieve antenna beam steering are described and compared. Measured comparisons of meteor burst performance with and without antenna beam steering are given. To demonstrate an application of beam steering, a meteor burst system with 10 times the throughput performance of any previous meteor burst system, and with sufficient capacity to provide interactive voice communication, is also described. >

Analysis of meteor burst communication systems with n pairs of stations

AbstractIn the two‐way beyond line‐of‐sight communication using meteor burst, several station pairs can operate on the same frequency band. To date, however, no quantitative studies have been carried out to determine how many station pairs can use a given frequency band.In this paper, the characteristics are analyzed quantitatively in the case where n station pairs commonly use the same frequency band. As the simplest system, a meteor burst system with full‐duplex station pairs is considered. The throughput, optimum number of station pairs, and channel utilization are analyzed.First, an ideal case is studied in which neither the overhead by the header nor the loss of division into blocks is considered. Next, the case with a header and then the case with constant block size are considered. In each case, the relationship of the number of the station pairs to the throughput and channel utilization is derived. Some numerical results for practical models are presented. It is shown that such a configuration is useful for improving the utilization of frequency band.

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.

Performance analysis for a convolutionally coded DPSK meteor-burst communication system

The performance analysis of a convolutionally encoded DPSK MBC system is based on the time-varying SNR model, and the statistical nature of the burst duration and the decaying time constant. The performance is evaluated in terms of the average bit error rate, the throughput, the average waiting time, and the, system complexity. The average bit error rate is stressed, whereas only maximum acceptable BER is used as a parameter in earlier literature. The results obtained by this method are more accurate than that obtained by the classical methods. The new results are about 1 dB more optimistic in terms of minimum SNR. The performance of the convolutional coding-DPSK combination is compared with that of a Reed-Solomon coding-DPSK combination. The comparison shows that,for similar performance, the CC-DPSK combination has a much smaller system complexity, and for similar complexity the soft-decision decoded-CC-DPSK has a much better performance.

Spaced antenna diversity in temperate latitude meteor burst systems operating near 40 MHz: Variation of signal cross‐correlation coefficients with antenna separation

We have studied 37‐MHz signals received over an 800‐km temperate latitude path using 400‐W continuous wave transmissions. Signals collected during a 9‐day period in February 1990 on two antennas at separations of 5λ, 10λ, and 20λ were analyzed. Three signal categories were identified (overdense, underdense, and not known (NK)) and cross‐correlation coefficients between the signals received by the two antennas were calculated for each signal category. No spatial variation, and in particular no decrease, in average cross‐correlation coefficient was observed for underdense or NK signals as the antenna spacing was increased from 5λ to 20λ. At each antenna separation the cross‐correlation coefficients of these two categories were strongly dependent on time. Overdense signals, however, showed no cross‐correlation time dependency at 5λ and 10λ, but there was a strong time dependency at 20λ. Recommendations are made in regard to the optimum antenna spacing for a meteor burst communication system using spaced antenna diversity. Our measurements support the views of Bartholomé and Vogt [1968], who suggested that a 4λ spaced antenna diversity configuration contributed to the exceptional signal throughput of the COMET meteor burst communication system.

Performance of short- and long-range meteor burst communication systems with different antennas

The performance of meteor burst communication at different ranges for a number of antenna configurations is analyzed. Characteristics of ideal antenna patterns for short- and long-range meteor scatter communication are described. An ideal antenna configuration matches its illumination pattern to the spatial arrival pattern of meteor trails. The analysis is used to compare the performance of several commonly used antenna configurations. It will be demonstrated that the characteristics of antennas which perform well at short ranges are different than those that perform well at long ranges. >