bluuebunny/crossref_metadata_2025_split huggingface dataset:
A PSK group modem based on digital signal processing: Algorithm, hardware design, implementation and performance
Authors: Takahata Fumio , Yasusaga Masayuki , Hirata Yasuo , Ohsawa Tomoki , Namiki Junji 
Published: July 2007

AbstractA PSK group modem which modulates and demodulates multiple PSK signals en bloc will play an important role in cost‐effective satellite communications systems based on the narrow‐band multicarrier PSK/FDMA technique. This paper describes the development of a PSK group modem, including its algorithm, hardware design and implementation. In the algorithm, PSK signals are efficiently filtered by digital signal processing applied to the digital transmultiplexor. Furthermore, in order to compensate for the difference between the operation timing of the PSK group modem and the symbol timing of each input/output data signal, digital signal processing based on a table‐look‐up method using ROM and a rate‐conversion filter with adaptive weighting are proposed for the modulator and demodulator, respectively. An experimental four‐phase PSK group modem has been developed, and experiments have been conducted under various conditions. The measured performance of the developed hardware is also demonstrated.
Frequency diversity and its applications
Authors: Carassa F. , Tartara G. , Matricciani E. 
Published: July 2007

AbstractAdaptive shared resource methods may be the only available effective countermeasure to rain‐induced attenuation in satellite communication systems above 20 GHz. Two of these methods, frequency diversity (FDV) and burst length control (BLC) are examined and compared by using a unified approach. The fundamental statistical relationships between unassisted and assisted conditions are derived, and optimum values are identified. It is found that BLC (which improves power margins) is easier to implement than FDV, but FDV (which improves outage probability and retains most of its advantages at higher frequencies) is more effective in reducing built‐in power margins in ‘unassisted’ conditions. From a large database at 11.6 GHz collected in the Sirio experiment, some realistic FDV results are derived for systems using 20/30 GHz bands for unassisted conditions and 12/14 GHz bands for assisted conditions. As the ESA Olympus satellite will carry both 20/30 GHz and 12/14 GHz transponders, an FDV experiment with Olympus has been proposed by CSTS; the characteristics of the three earth‐stations planned to be built in Italy for the experiment are described.
Up‐link power control of satellite earth‐stations as a fade countermeasure of 20/30 GHz communications systems
Authors: Hörle J. 
Published: July 2007

AbstractAll 20/30 GHz satellite communications systems suffer from atmospheric attenuation in cloudy or rainy weather, particularly if high link availabilities are required. In FDMA systems the power transfer characteristic of each carrier is linear, so any up‐link fade degrades the overall performance on a dB‐by‐dB basis. This, together with the fact that the 30 GHz up‐link attenuation is much greater than the 20 GHz down‐link attenuation, makes adaptive countermeasures of up‐link fades most important. This paper shows how the overall link performance can be improved by applying up‐link power control. It is explained how this improvement depends on the up‐link/down‐link balance, the dynamic range of the up‐link power control, and the up‐link and down‐link atmospheric attenuation.If a small number of carriers can be allocated in an intermodulation‐free frequency plan, the satellite transponder can be operated near saturation in order to optimize the down‐link performance. Computer simulations of up‐link power control for such an FDMA scheme have been performed based on measured three‐carrier characteristics of a transponder TWT. It is shown that the overall link performance in faded conditions can be significantly improved with up‐link power control. This may be utilized to increase the availability of a satellite link or to relax the earth‐station performance in terms of G/T or EIRP if the link margin provided by an earth‐station with fixed EIRP is satisfactory.
Forward error correction applied to intelsat IDR carriers
Authors: Morley S. A. 
Published: July 2007

AbstractForward error correction (FEC) techniques are applied to INTELSAT intermediate data rate (IDR) services to reduce the transmitted power requirements relative to uncoded systems, thereby increasing the satellite transponder capacity. Properly designed FEC systems reduce data errors in the received digital stream with minimal impact to the protocols, operation and equipment involved with the communication system. This paper discusses the overall system impact of the addition of FEC to the IDR service. The appropriateness of the specific application of convolutional encoding combined with Viterbi decoding techniques is discussed. Basic concepts of convolutional encoding and Viterbi decoding are presented in order to provide understanding of the trade‐offs involved in the specification of the coding technique for the IDR service. The details of the IDR FEC specification are presented. The implementation of a system based on a VLSI Viterbi decoder device which conforms to the INTELSAT requirements is described.
New rain rate analyses to assess rain attenuation on satellite ehf communications
Authors: Tattelman Paul 
Published: July 2007

AbstractThis paper provides estimates of the frequency of occurrence, duration and probability of satellite EHF communication outages due to attenuation by rain. These can be used to determine optimum frequencies, power levels and the need for space diversity of terminals or other alternatives to maintain reliable communications. Ten years of 1 min rain rates at each of 12 U.S. cities were used in conjunction with an attenuation model to quantify communication outages at locations representing a variety of climatic regimes. Analyses of the 1 min rain rates and outage estimates at 10, 30 and 45 GHz for elevation angles of 10°, 30°, 50° and 70° are presented.
Asymptotic analysis of unslotted frequency‐hop multiple‐access without side information
Authors: Kim Sang Wu , Kim Sangmun 
Published: July 2007

AbstractIn a packet radio network that employs frequency‐hop transmission and error control coding, the use of side information permits identification and erasure of symbols that have been corrupted by multiple‐access interference, and thus greatly enhances multiple‐access capability. In one approach, side information is generated from an error detecting random code. We investigate the trade‐off between the reliability of side information and the rate of the code, and derive the maximum allowable code rate to achieve a certain reliability of side information. An achievable region and the channel throughput are examined for an unslotted frequency‐hop packet radio network that employs Reed‐Solomon codes and side information generated within the radio by an error detecting code.
Analytical evaluation of average bit error rate for the land mobile satellite channel
Authors: Cygan Daniel 
Published: July 2007

AbstractAn analytical solution is presented showing the average bit error probability for the land mobile satellite channel. The channel is modelled as Rice and Rayleigh—lognormal fading. Modulation schemes under consideration include differentially detected PSK and non‐coherently detected FSK. Results indicate that the receiver performance is highly dominated by the time share of shadowing. The ratio of the BERs in shadowed and unshadowed areas of typical measured channels and an operating point assumed to be at Es/No = 10 dB is of the order of 10−2.
On‐board non‐linear circuitry for Ku‐band active arrays
Authors: Giannini F. , Leuzzi G. , Ruggieri M. 
Published: July 2007

AbstractActive phased arrays will play an important role in future satellite communications, because of the system flexibility and potential reconfigurability that they may provide.Therefore, an investigation of the relationship existing between payload characteristics and the synthesis parameters of this kind of antenna may constitute a helpful tool.To this end, a parametric analysis of the on‐board non‐linear circuitry of the transmitting system (power and up‐converter sections) has been carried out, establishing the dependence of the mass and DC power demand on the number of beams and feeds of the transmitting phased array.The parametric investigation has been, in particular, applied to an active imaging phased array and an active direct radiating phased array whose suitability to provide a multibeam coverage of Western Europe at Ku band has been demonstrated within an ESA/ESTEC contract.This paper describes the parametric approach followed in the investigation of the on‐board non‐linear subsystems of the active transmitting phased arrays.The assumed circuitry configurations are widely commented, and the parametric curves for the case of imaging and direct radiating phased arrays are reported.
Channel coding for satellite mobile channels
Authors: Wong K. H. H. , Hanzo L. , Steele R. 
Published: July 2007

AbstractThe deployment of channel coding and interleaving to enhance the bit‐error performance of a satellite mobile radio channel is addressed for speech and data transmissions. Different convolutional codes (CC) using Viterbi decoding with soft decision are examined with inter‐block interleaving. Reed‐Solomon (RS) codes with Berlekamp‐Massey hard decision decoding or soft decision trellis decoding combined with block interleaving are also investigated. A concatenated arrangement employing RS and CC coding as the outer and inner coders, respectively, is used for transmissions via minimum shift keying (MSK) over Gaussian and Rayleigh fading channels. For an interblock interleaving period of 2880 bits, a concatenated arrangement of an RS(48,36). over the Galois field GF(256) and punctured PCC(3,1,7) yielding an overall coding rate of 1/2, provides a coding gain of 42dB for a BER of 10−6, and an uncorrectable error detection probability of 1–10−9.
Comparison of advanced coding and modulation schemes for multicarrier satellite communication systems
Authors: Benedetto S. , Pent M. , Zhang Z. 
Published: July 2007

AbstractDigital satellite communication systems use coherent quaternary PSK (QPSK) as the preferred modulation scheme. In recent years, however, the search for bandwidth and power‐efficient digital modulation methods has become an active research area. In this paper the performances of combined coding and modulation schemes employing multilevel signal alphabets are considered, in the framework of a system model which reasonably approximates the INTELSAT SCPC system. The main goal of the research was to investigate whether the efficiency of coded modulation schemes and their savings in transmitted power could be maintained in a system environment dominated by interference more than by the additive white Gaussian noise. A second goal was to compare the performance of signals with constant envelope, such as multilevel PSK, with that of signals allowing variations in amplitude, such as multilevel PSK, with that of signals allowing variations in amplitude, such as multilevel QAM. In the paper, we propose a channel model which is reasonably close to the real system, and a method for performance evaluation leading to an estimate of the asymptotic power gain of the modulation systems. The channel model and the method are applied to the analysis of coded 16‐ and 32‐ PSK and QAM.
Coding for the gaussian channel: The promise of weighted‐output decoding
Authors: Battail Gérard 
Published: July 2007

AbstractWe introduce the concept of weighted‐output decoding, which enables us to perform many successive decodings without information loss. The design of a coding system for the additive white Gaussian channel can thus be viewed as a means for combining many simple codes. We illustrate this concept by the example of parity‐check codes which are combined according to Elias' iterated product. Examination of the performance thus obtained leads us to criticize the conventional minimal distance criterion and to propose as a criterion a proximity measure of the weight distribution of the code with respect to the binomial one. According to this point of view, the iterated product of parity‐check codes appears as a means of decimation of the set of n‐tuples.
Low complexity concatenated coding schemes for digital satellite communications
Authors: Brine A. , Farrell P. G. , Harris R. A. 
Published: July 2007

AbstractA study of reduced complexity concatenated coding schemes, for commercial digital satellite systems with low‐cost earth terminals, is reported. The study explored trade‐offs between coding gain, overall rate and decoder complexity, and compared concatenated schemes with single codes. It concentrated on short block and constraint length inner codes, with soft decision decoding, concatenated with a range of Reed‐Solomon outer codes. The dimension of the inner code was matched to the outer code symbol size, and appropriate interleaving between the inner and outer codes was used. Very useful coding gains were achieved with relatively high‐rate, low‐complexity schemes. For example, concatenating the soft decision decoded (9,8) single parity check inner code with the CCSDS recommended standard Reed‐Solomon outer code gives a coding gain of 4.8dB at a bit error probability of 10−5, with an overall rate of 0‐78.
Saw‐based chirp fourier transform and its application to analogue on‐board signal processing
Authors: Bakken Petter M. , Rønnekleiv Arne 
Published: July 2007

AbstractThis paper reports on the work done at ELAB‐RUNIT on surface acoustic wave (SAW) on‐board signal processing. The main processing is done by the analogue chirp Fourier transformer (CFT) and its inverse (ICFT). In a CFT, the input signal is transformed from an FDMA format to a TDM format and at the same time filtered by a filter bank. By multiplying and convolving the signal with chirp waveforms, the CFT is implemented by one bandpass cover filter and one chirp filter. The paper demonstrates that SAW reflector array compressors (RAC) built by ELAB‐RUNIT have suitable chirp responses and adequate precision for digital satellite communication. Two applications are described. An on‐board multicarrier demodulator (MCD) for 9·6 kb/s QPSK carriers and a processor for filtering, routeing and beam steering (FROBE) for flexible transparent repeaters. For MCDs the use of SAW CFTs leads to a power consumption for demultiplexing and A/D conversion of 15 mW per carrier with room for improvements. For transparent paylods, the FROBE leads to more flexibility and narrower guardbands than can be obtained by other analogue processors.
On‐board frequency demultiplexing by magnetostatic wave technologies
Authors: de Santis Pietro V. 
Published: July 2007

AbstractPossible magnetostatic wave (MSW) implementations of variable bandwidth variable centre frequency (VBVCF) on‐board demultiplexers are presented. Hybrid technologies using magnetic thin films in conjunction with gallium arsenide (GaAs) monolithic microwave integrated circuits (MMIC) are introduced. New areas of research to advance the state of the art in this field are identified.
Distance measures for viterbi decoding of coded and bandlimited 8PSK signals
Authors: Cheung S. W. , Clark A. P. 
Published: July 2007

AbstractThe paper studies a digital modem that transmits a convolutionally encoded eight‐phase‐shift keyed (CE8PSK) signal over a satellite channel and employs a near‐maximum‐likelihood decoder at the receiver. Several different earth‐stations are assumed to have simultaneous access to a given transponder in the satellite as an arrangement of frequency‐division multiple access. Adjacent channel interference (ACI) is neglected here. The high‐power amplifier (HPA) at the earth‐station transmitter and the satellite transponder are assumed to be linear. The channel distorts the data signal, through the bandlimiting introduced by the equipment filters, and it adds stationary white Gaussian noise to the data signal at the receiver input. The resulting noisy and distorted data signal is coherently demodulated. Four different bandwidths of the transmitted CE8PSK signal are considered, together with three different demodulation processes. The decoder uses the Viterbi algorithm, together with one of six different distance measures to determine the costs of the stored vectors (survivors).The paper describes the various techniques involved in the modem, and presents the results of an extensive series of computer‐simulation tests to measure the performances of the system with all appropriate combinations of the signal bandwidth, demodulation process and distance measure. The results of the tests are then used to determine the preferred modem design.
Performance study of 16‐ary deqam modem for future satellite communication systems
Authors: Cheung S. W. , Aghvami A. H. 
Published: July 2007

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 CE16QAM modem in a regenerative satellite system
Authors: Cheung S. W. 
Published: July 2007

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.
Selective reject ALOHA/FCFS: An advanced VSAT channel access protocol
Authors: Raychaudhuri D. 
Published: July 2007

AbstractThis paper proposes and evaluates selective reject (SREJ) ALOHA/FCFS, a highly efficient, flexible and robust multiaccess protocol for very small aperture terminal (VSAT) applications. SREJ‐ALOHA with locally synchronous FCFS retransmission scheduling is a ‘semi‐compatible’ enhancement of asynchronous SREJ‐ALOHA, which has earlier been shown to be an attractive satellite channel sharing protocol for low volume bursty terminals with variable length messages. The FCFS retransmission scheduling policy proposed here broadens the applicability of SREJ‐ALOHA by providing higher maximum throughput, particularly in the important source traffic scenario with bimodal message length distributions. Improved channel‐sharing efficiency and delay are achieved by exploiting time‐of‐arrival feedback naturally embedded in an unslotted SREJ‐ALOHA channel to develop an implicit time‐of‐arrival based (FCFS) ordering for conflict‐free, locally synchronous retransmission of most contending messages. An analytical procedure for evaluation of stability, throughput and delay for a general finite source, variable message length traffic model is described. The model is used to demonstrate that random access SREJ‐ALOHA/FCFS typically achieves a maximum throughput in the region of 0·4–0·45 along with excellent stability and delay properties. In addition, a natural extension of the protocol which supports implicit reservation for long messages is described and shown to offer a high maximum throughput (>0·6), comparable to that achieved by highly co‐ordinated slotted systems, for example mixed interactive/file‐transfer traffic scenarios.
A carrier‐phased satellite receiving array
Authors: Brennan P. V. 
Published: July 2007

AbstractThe carrier‐phased array—in which array phasing is derived from the incident modulated signal—is conceptually a very simple means of achieving automatic beam pointing in communications systems. The technique is particularly suitable for satellite reception applications, although careful consideration must be given in a practical design due to problems associated with the low signal levels derived from satellite broadcasts. In this paper, the basic principles of operation of such an array are described and the requirements of a practical system are addressed, resulting in the design and evaluation of an array system suitable for use with BPSK modulated signals from a communications satellite.
Simulation of an on‐board hierarchical multistage digital FDM demultiplexer for mobile scpc satellite communications
Authors: Eyssele Helmut , Göckler Heinz 
Published: July 2007

AbstractThis paper is focused on the finite‐precision time‐domain simulation of the hierarchical multistage method detailed in References 1 and 2 for demultiplexing of an FDM signal being composed ofL= 32 slot signals. This approach to FDM demultiplexing is based on the processing of complex signals by linear‐phase FIR filters, where at any stage of processing the respective signals are always oversampled by a factor of two.The simulation results fully confirm the system performance predicted in Reference 1 by modelling the distortions (spectral foldover and quantization noise) inherent in the system: assuming an ideal FDM signal at the input port of the analogue anti‐aliasing bandpass filter in front of the analogue‐to‐digital converter, a minimum signal‐to‐distortion ratio (S/D) of 30 dB is achieved at allLoutput ports of the demultiplexer with {w,wF,wi} = {11,12,14}, as anticipated in Reference 1. The signal word lengthwapply to the A/D conversion,wFto requantization between the filter stages, andwito filter internal signal processing.
On the digital signal processor based programmable real‐time reed‐solomon coding‐decoding system
Authors: Zheng Ou Yang Jing , Yong Un Ze 
Published: July 2007

AbstractA real‐time high‐speed Reed‐Solomon coding—decoding system has been built based on a low‐cost signal processor TMS 32010. By taking advantage of the TMS 320 16‐bit multiplier and barrel shifter, the evaluation of the sum‐of‐products expression over a prime field can be simplified. Decoding of a (256,228) code with powerful error correcting capability over GF(257) has been implemented in this system, and the information bit rate is at least twice that of the ISDN B‐channel basic rate.