Regenerative Satellite Research Articles

Outage Performance for Satellite-Assisted Cooperative NOMA Systems With Coordinated Direct and Relay Transmission

In this letter, the outage performance of a satellite-assisted cooperative non-orthogonal multiple access (NOMA) system is studied, where a terrestrial source communicates with one terrestrial destination directly while the other terrestrial destination is assisted by a regenerative satellite. We consider the satellite channels and the terrestrial channels undergo shadowed-Rician fading and Nakagami- $m$ fading, respectively. Based on this, we derive the exact closed-form expressions for the outage probabilities. In addition, the asymptotic expressions at high signal-to-noise ratio are provided to gain further insights. Simulation results validate the accuracy of the analytical results and show the superiority over other conventional schemes.

Net‐centric satellite mesh architecture for emergency communication

AbstractThis paper introduces a net‐centric architecture based on ETSI and TIA Regenerative Satellite Mesh‐A (RSM‐A) standard that uses satellites with on‐board packet switching. An Internet Engineering Task Force (IETF) IP protocol family‐based extension of RSM‐A for enhanced user interoperability, combined with multiple spot beam satellite implementation facilitates higher capacity, easy deployment and full mesh terminal‐to‐terminal operation that is required for managing emergency situations. This Net‐centric Satellite Mesh (NSM) architecture adequately addresses the current and evolving networking needs for emergency‐management information systems that can generate high data rate and real‐time multi‐media traffic. The NSM architecture supports the evolving IETF Emergency Telecommunications Service standards with packet flow‐level admission control for guaranteed packet quality‐of‐service needed by real‐time unicast and multicast traffic over satellite networks. The multi‐plane architectural discussion is supported with measurements of selected end‐to‐end application behavior that validate the technical capabilities of NSM by using a pioneering Ka band satellite system, based on RSM‐A, which has recently been deployed in North America. Copyright © 2010 John Wiley & Sons, Ltd.

An integrated FEC coding scheme for ATM transmission over regenerative satellite networks

The application of asynchronous transfer mode (ATM) on both wireless and satellite networks requires system adaptation. This adaptation has to improve the overall system's performance, and achieve high quality-of-service classes approaching that for fibre-optic communications. In this paper, a new integrated forward-error-correction (FEC) coding scheme is introduced for ATM transmission over regenerative satellite networks. The proposed FEC scheme is a concatenation of two Reed–Solomon codes tailored for the header and payload parts of the ATM cell. This integrated coding scheme is shown to significantly improve the cell loss ratio as compared to the standard CRC code used in the ATM cell header. We obtain both upper and lower performance bounds for the concatenated code and check their accuracy when compared to exact system's performance. Both analytical and simulation results show that a cell loss ratio and bit-error rate (BER) of 10−25 and 10−7 can be, respectively, achieved with minimum delay requirements on the SATCOM link. Finally, an approximation for the system's throughout is obtained. It is shown that using a hybrid selective-repeat automatic-repeat-request (SR-ARQ) with the RS code, a large throughput of approximately 0.843 can be achieved at BERs lower than 10−7 for data services. Copyright © 2005 John Wiley & Sons, Ltd.

Modulation techniques for on-board processing satellite communications

The uplink channel from a terminal to a regenerative satellite repeater is considered in which a digital transmultiplexer (TMUX) is used as a frequency-division multiple-access (FDMA) to time-division-multiplexed (TDM) converter for group demodulation. Linear modulation techniques were considered to determine which would make the most efficient use of this on-board processing (OBP) satellite system. The modulation techniques examined were quadrature phase-shift keying (QPSK), /spl pi//4-QPSK, and offset QPSK (OQPSK), all with Nyquist pulse shaping, and minimum-phase keying (MSK). The search for the optimum linear modulation technique took into account the performance criteria of power efficiency, bandwidth efficiency, and especially the complexity of the TMUX algorithm for OBP.

Flight 2 version of in‐orbit test transponder (IOTT2) for on‐board regenerative satellites

AbstractThis paper presents the design and realization of regenerative satellite on‐board bypass test equipment. Furthermore, two particular examples of an in‐orbit test transponder (IOTT) are discussed in detail. The IOTT1, developed for the first 30/20 GHz ITALSAT satellite (F1), was launched in January of 1991. IOTT1 has been a useful tool during satellite assembly, integration and pre‐launch tests. IOTT1 was successfully used to fully characterize the multibeam ITALSAT satellite in orbit.In general, the IOTT functions to bypass the demodulator, the baseband switchboard and the modulator of the multibeam package of the ITALSAT spacecraft payload, providing the ability to fully characterize the satellite's transponders using well‐established IOT test techniques.This paper describes and compares the design, fabrication and test of both ITALSAT in‐orbit test RF bypass transponders (IOTT1 and IOTT2) mounted on board the ITALSAT multibeam spacecraft, (F1) and (F2), respectively. The IOTT1 contains the first MMIC circuitry ever launched into space on a communications satellite. The improved IOTT2, fabricated for the second 30/20 GHz ITALSAT satellite (F2), is schedule for launch in early 1996.These fully space‐qualified designs incorporate COMSAT Laboratories' designed and fabricated MMIC Ku‐band amplifiers, lightweight waveguide Ku‐band channel filters and electronic power conditioner (EPC) and combined IOTT telemetry/command (T&C) circuitry.

Performance of a circular signal set in a regenerative satellite system employing TWTA or SSPA

AbstractThis paper presents the results of a computer‐simulation study of a (4,12) circular signal set for use over regenerative satellite links. The signal has a 16‐ary symbol alphabet. The satellite transponders and each of the earth‐stations use either travelling‐wave‐tube amplifiers (TWTAs) or solid‐state power amplifiers (SSPAs) for high‐power amplification. Several different earth‐stations are assumed to have simultaneous access to a given regenerative satellite, in an arrangement of frequency division mulitple access (FDMA). Thus, adjacent‐channel‐interference (ACI) can be introduced into the wanted signal by the immediately adjacent channels. The performances of the signal are compared to those of a 16‐ary differentially encoded‐quadrature‐amplitude‐modulated (16‐ary DEQAM) signal with a rectangular signal set and the results are used to determine the preferred signal set for spectrally efficient transmission over satellite links. It has been shown that, with TWTAs used for high‐power amplification and in the absence of ACI, the circular signal set has an advantage of about 3 dB over the rectangular signal set, at the bit error rate of 10−4. While in the presence of the ACI, the advantage is 2 dB. With SSPAs, the respective advantages become 0·7 and 0·5 dB.

Influence of signal constellation on the performance of 16‐ary deqam transmission through a regenerative satellite link

AbstractThe paper presents the results of a series of computer‐simulation tests to determine the effects of non‐linear distortion and adjacent channel interference (ACI), on the tolerance to additive white Gaussian noise (AWGN) of a digital satellite modem. The modem transmits a 16‐ary differentially encoded quadrature‐amplitude‐modulated (16‐ary DEQAM) signal over a regenerative satellite link, where the high‐power amplifier (HPA) at the transmitter may introduce AM‐AM and AM‐PM conversion effects into the 16‐ary DEQAM signal. Three signal constellations are used at the transmitter, namely (1) a conventional 16‐ary DEQAM signal constellation, (2) a predistorted 16‐ary DEQAM signal constellation and (3) a prerotated 16‐ary DEQAM signal constellation. An equivalent baseband model of the transmission system is used to determine the performance of the modem under the various conditions studied, and the results are used to select the preferred modem design.

Performance of a rate-3/4 coded signal, incorporated with a circular signal set for regenerative satellite transmissions

The paper studies a digital modem that transmits a rate-3/4 convolutionally encoded 16-ary amplitude and phase modulated (CE16APM) signal, over a regenerative satellite link. The signal uses a (4, 12) circular signal constellation set and has a coding gain of about 4 dB at a bit error rate of 10-4, over an uncoded eight-phase-shift keyed (8PSK) signal. Several different earth stations are assumed to have simultaneous access to a given regenerative satellite using frequency division multiple access. Thus, the CE16APM signals that occupy the immediately adjacent frequency bands can introduce adjacent-channel interference (ACI) into the transmitted CE16APM signal. The high-power amplifier (HPA) at each of the earth-station transmitters or on board the satellite transmitter may introduce nonlinear AM-AM and AM-PM conversion effects into the CE16APM signal. Results of a series of computer-simulation tests are presented. These evaluate the effects of bandlimiting, nonlinear distortion and ACI on the performance of the modem. The HPA are tested with different values of output backoff (OBO). The performances of the preferred system arrangements are compared with those of a rate-3/4 convolutionally encoded 16-ary quadrature-amplitude-modulated (CE16Q AM) signal, using a rectangular signal constellation set, and of an uncoded 8PSK signal. It has shown that the CE16APM signal performs better than the CE16QAM and 8PSK signals over nonlinear channels.

Performance of a CE16QAM modem in a regenerative satellite system

AbstractThis paper studies a digital modem for use over a regenerative satellite link. The modem transmits a convolutionally encoded 16‐ary quadrature‐amplitude‐modulated (CE16QAM) signal. The convolutional code has a three‐bit constraint length and a coding rate of 3/4. The high power amplifier (HPA) on board the satellite transmitter and at each station may introduce non‐linear distortion into the CE16QAM signal, but only a single‐link transmission is considered. Several different earth‐stations are assumed to be used in an arrangement of frequency division multiple access. Thus adjacent‐channel interference (ACI) can be introduced into the signal by the signals that occupy the immediately adjacent frequency bands.Extensive computer‐simulation tests have been carried out to determine the effects of bandlimiting, non‐linear distortion and ACI, on the tolerance to additive white Gaussian noise of the modem, using an equivalent baseband model of the transmission system. The results are used to select the preferred system arrangement. It has been shown that, with 4 dB output back‐off (OBO) in the HPA, a bandwidth efficiency of 2·4 b/s Hz can be achieved, with an improvement in perforamnce of 2·5 dB, relative to that of an ideal uncoded eight‐phase‐shift keyed (8PSK) signal, at a bit‐error rate of 10·4.

Performance study of 16‐ary deqam modem for future satellite communication systems

AbstractThis paper investigates the effects of additive white Gaussian noise (AWGN), adjacent‐channel interference (ACI) and co‐channel interference (CCI) combined with flat fading on the performance of bandlimited 16‐ary differentially encoded quadrature amplitude modulation (16‐ary DEQAM) signalling transmitted through a non‐linear high‐power amplifier (HPA). It is assumed that the HPA exhibits both AM‐AM and AM–PM conversion distortions. This situation may be applied to the up‐link or down‐link of a regenerative satellite system where the HPA is the earth‐station travelling‐wave tube (TWT) or the on‐board TWTA, respectively. The signal‐to‐noise ratio (SNR) degradations at a specific bit error rate (BER) are evaluated by means of a series of computer simulation tests for various values of channel roll‐off factor α (channel bandwidth) and different degrees of output backoff (OBO) of the HPA in the presence of various combinations of the channel impairments. It is shown that by employing a baseband or RF predistortion technique for the HPA and selecting the best arrangement of channel roll‐off factor, OBO value of the HPA and channel spacing, a good performance can be achieved regarding the most efficient use of bandwidth together with a minimum SNR degradation due to the presence of channel impairments. Thus, the use of 16‐ary DEQAM for satellite communications is feasible in the near future.

Performance of a 16-ARY DEQAM modem employing a baseband or RF predistorter over a regenerative satellite link

The paper presents the results of a series of computer-simulation tests that determine the effects of bandlimiting (nonlinear distortion with and without predistortion) on the tolerance to additive white Gaussian noise of a digital modem. The modem transmits a 16-ary differentially encoded quadrature amplitude modulation (16-ary DEQAM) signal over a regenerative satellite link, where the high power amplifier (HPA) on board the satellite transmitter may introduce AM-AM and AM-PM conversion effects into the 16-ary DEQAM signal. Four different bandwidths of the transmitted signal are tested, together with different levels of output back-off in the HPA at the transmitter. The arrangements achieving the most efficient use of the power are selected. There sults show that a surprisingly good improvement in performance can be achieved by using predistortion of the 16-ary DEQAM signal to reduce the nonlinear distortion of the high power amplifier.

14/11 GHz, 120 Mbit/s regenerative satellite transponder

This paper describes the design, implementation and performance of an experimental 14/11 GHz, 120 Mbit/s regenerative satellite transponder for possible use in the European communications satellite (ECS) system. Quarternary DPSK and CPSK are applied on the uplink and downlink, respectively. Demodulation and modulation are performed directly at RF. Specific components of the regenerative transponder, which are the pulse shaping filter, the differential demodulator, the baseband regenerator, the modulator and the output filter, were developed. Using the developed components, a laboratory model of the transponder was completed and evaluated. Bit-error-rate measurements were carried out with a test equipment simulating the earth terminals.

Performance of an IJF-OQPSK Modem in Cascaded Nonlinear and Regenerative Satellite Systems

The probability of error (P e ) performance of an intersymbol-interference and jitter-free-offset QPSK (IJF-OQPSK) modem in conventional and regenerative satellite channels is studied and compared to that of a QPSK modem using computer simulation techniques. The results show that the IJF-OQPSK modem performs better than QPSK in both cascaded nonlinear channels and regenerative satellite links, especially with saturated earth station HPA and transponder TWTA.

Performance of IJF-OQPSK and Partial Response (PR) IJF-OQPSK Modems in a Nonlinearly Amplified and Adjacent-Channel Interference Satellite Environment

The performance of intersymbol-interference and jitterfree offset-QPSK (IJF-OQPSK) and partial-response (PR) IJFOQPSK modems in a nonlinearly amplified multichannel environment is studied and compared to that of conventional QPSK and OQPSK modems. Power efficiency is maximized by operating the high-power amplifier (HPA) in full saturation. The effect of adjacent-channel interference and flat fade on the performance of illustrative nonlinear satellite systems is investigated. Simulation and measurement results are reported. It is shown that both IJF-OQPSK and PR-IJF-OQPSK modems exhibit a significant performance improvement compared to QPSK and OQPSK modems, in illustrative SCPC and on-board regenerative satellite systems, they provide an improvement of more than 4 dB compared to QPSK.

Performance Analysis of a DCPSK Up-Link for a Regenerative Satellite Repeater

A mixed analytic and simulation method is described for the study of a DCPSK up-link used in a regenerative satellite transmission system. A great variety of impairments is considered and their effects on error probability are evaluated, thus emphasizing the performance evaluation in a real situation. A case study is worked out in detail to stress the design-oriented approach.

11-GHz MIC QPSK Modulator for Regenerative Satellite Repeater

An 11-GHz MIC QPSK modulator for a 14/11-GHz, 120-Mbit/s regenerative satellite repeater is described. The modulator consists of cascaded 90° and 180° phase switches, realized with circulators and PIN diodes. The static and the dynamic behavior are presented. It is shown how the bit-error-rate performance is deteriorated by slow switching transients and timing errors.

K-Band Satellite Regenerative Relay Systems Using Multihorn Antenna with Variable Power Combiners/Dividers

The effects on CNR improvements are described for a K -band PCM-TDMA regenerative satellite relay system, using a multihorn antenna, whose horn powers are combined/divided with variable power combiners (VPCs)/dividers (VPDs). In conclusion, when the VPCs combination/VPDs division ratios are controlled according to the criterion maximizing the sum of uplink/downlink rain margins, both efficient on-board RF power utilization and regenerative effect enhancement can be accomplished remarkably.

On increasing the down-link capacity of a regenerative satellite repeater in point-to-point communications

A suggestion is presented for increasing the down-link capacity in a satellite communication system by using a regenerative satellite repeater. This idea is based on Shannon's work on the capacity of two-way communication channels. A possible implementation of the idea is outlined, based on TDMA operation, demodulation and storage at the satellite, and modulo 2 addition of the baseband binary streams.