This paper presents an error control scheme for transmitting vector-quantized data over noisy channels. First, we review a self-organizing feature map (SOFM)-based approach to construct the mapping from the codebook o...
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This paper presents an error control scheme for transmitting vector-quantized data over noisy channels. First, we review a self-organizing feature map (SOFM)-based approach to construct the mapping from the codebook of the quantizer to the channel signal set of the communication system, This approach is robust with respect to channel noise even if we do not use any error control scheme in the communication system, Afterwards, a new trellis type quantizer, namely, the trellis-coded Kohonen map (TCKM), is presented. The design process of the TCKRM, which is based on the neighborhood structure of SOFM's, is simpler than that of conventional trellis coded vector quantizers (TCVQ's), Simulation results show that the performance of TCKM's is comparable with that of TCVQ's, Last, we introduce the error control scheme based on the concepts of the above two applications of SOFM's. Simulation results show that the proposed error control scheme is more robust with respect to channel noise, The advantage of our approaches mentioned above is that the design processes of transmission systems are predefined before the construction of the codebook, Thus, different codebooks with the same neighborhood structure can share the same design.
In Japan, a new digital satellite broadcasting service is scheduled to start in the year 2000. The technical standard for the transmission system was established in 1998. The system provides an information bit rate of...
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In Japan, a new digital satellite broadcasting service is scheduled to start in the year 2000. The technical standard for the transmission system was established in 1998. The system provides an information bit rate of 52Mbps, which is sufficient for broadcasting two HDTV programs. It can handle multiple MPEG2 Transport Streams. The system supports multiple modulation schemes such as trellis coded eight PSK(TC8PSK), QPSK, and BPSK. These modulation schemes can be selected and/or used simultaneously. Accordingly, broadcasters sharing one satellite channel can select modulation schemes suitable for their own services independently from each other. The configuration and characteristics of the system are described below.
A nonorthogonal binary frequency-shift keying is considered in frequency-hopped multiple-access communication systems with Reed-Solomon coding. The effect of tone spacing on the average number of successfully transmit...
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A nonorthogonal binary frequency-shift keying is considered in frequency-hopped multiple-access communication systems with Reed-Solomon coding. The effect of tone spacing on the average number of successfully transmitted information bits per unit time per unit bandwidth (called normalized throughput) is examined in Rayleigh fading channels. The tradeoff among tone spacing, code rate, and number of frequency slots in maximizing the normalized throughput is examined, keeping the total bandwidth fixed, The optimal tone spacing, code rate, and number of frequency slots in terms of the number of users and (E) over bar(b)/N-0 is also discussed. The throughput gain attained by using the optimal tone spacing becomes more significant as the number of users is increased.
Spread spectrum pulse compression is a signal processing algorithm that enhances critical system performance parameters such as signal-to-noise ratio, peak power requirements, minimum detectable signal, and total dyna...
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Spread spectrum pulse compression is a signal processing algorithm that enhances critical system performance parameters such as signal-to-noise ratio, peak power requirements, minimum detectable signal, and total dynamic range. For this research, a digital, real-time, Barker coded, bi-phase modulator was designed and constructed, as well as a simple ultrasonic test tank containing both synthetic targets and excised goat's liver. Upon reception and demodulation of the spread spectrum ultrasonic echo, cross-correlation with a sidelobe suppression filter was performed. Due to limitations such as narrow bandwidth, and very short minimum ranges, a practical ultrasonic pulse compression system must be restricted to short code lengths. For 13 bit Barker code compression, the expected increase in signal-to-noise ratio of 11 dB was realized, at the same time greater than 30 dB of instantaneous dynamic range was maintained.
We present an enumerative technique for encoding and decoding binary sequences satisfying a constraint defined by a runlength graph. The presented technique enables to implement encoders and decoders of constrained co...
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We present an enumerative technique for encoding and decoding binary sequences satisfying a constraint defined by a runlength graph. The presented technique enables to implement encoders and decoders of constrained codes having code rates very close to channel capacity. As a detailed example, we consider enumerative coding of (0, G/I) constrained sequences as often applied in magnetic hard disk recording systems. Using floating-point notation to express the weight coefficients required to perform encoding and decoding, this technique results in moderate complexity. For (0, G/I) constraints of practical interest, the hardware required to implement such a quasi-optimum coding scheme consists mainly of a ROM of at most 2 kByte. As a remarkable example, a (0,6/8) constrained code can be implemented at rate 256/260 or 512/518 using a ROM of about 2 kByte.
作者：
O'Leary, SRTE
Network Capital Projects Dublin 4 Ireland
The digital terrestrial television standard approved by the European Telecommunications Standards Institute (ETSI) using Coded Orthogonal Frequency Division Multiplexing (COFDM) facilitates the establishment of comple...
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The digital terrestrial television standard approved by the European Telecommunications Standards Institute (ETSI) using Coded Orthogonal Frequency Division Multiplexing (COFDM) facilitates the establishment of complex networks including Single Frequency Networks (SFN) and Multiple Frequency Networks (MFN). RTE and other partners of European Union (EU) sponsored projects such as MOTIVATE and VALIDATE have established and tested these networks in order to understand the important parameters of digital networks. Protection Ratios are needed in order to plan the coverage of digital networks and minimise interference from co-channel transmitters. This paper describes a network established to field test protection ratios and details the measurements performed. Three co-channel UHF transmitters were installed at RTE mainstations in the Dublin area.
The prospects for gray-scale (or multilevel) digital holographic data storage are theoretically and experimentally investigated. A simple signal-to-noise ratio (SNR) partitioning argument shows that when SNR scales as...
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The prospects for gray-scale (or multilevel) digital holographic data storage are theoretically and experimentally investigated. A simple signal-to-noise ratio (SNR) partitioning argument shows that when SNR scales as 1 over the number of holograms squared, five gray levels (log(2) 5 bits/pixel) would be expected to result in a 15% capacity increase over binary data pages. However, the additional signal-dependent noise sources present in practical systems create a baseline SNR that reduces both the optimal number of gray levels and the resulting gain in capacity. To implement gray-scale recording experimentally, we adapt the predistortion technique previously developed for binary page-oriented memories [Opt. Lett. 23, 289 (1998)]. Several new block-based modulation codes for decoding gray-scale data pages are introduced. User capacity is evaluated by an experimental technique using LiNbO3:Fe in the 90 degrees geometry. Experimental results show that a balanced modulation code with three gray levels provides a 30% increase in capacity (as well as a 30% increase in readout rate) over local binary thresholding. (C) 1998 Optical Society of America.
The monitoring purpose of the broadcast transmission system is to provide a means of determining bow the transmission system is performing and where a fault or abnormal condition exists in the transmission chain. This...
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The monitoring purpose of the broadcast transmission system is to provide a means of determining bow the transmission system is performing and where a fault or abnormal condition exists in the transmission chain. This article presents the monitoring system for the digital DBS (Direct Broadcast Satellite). The author describes the monitoring requirements relating to which signals need to be monitored, where to monitor in the transmission chain, and how often each signal needs to be monitored.
This paper is concerning about the demapping method using the pilots inserted in transmitter in COFDM(Coded Orthogonal Frequency Division Multiplexing) system which is the standard transmission system of terrestrial d...
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This paper is concerning about the demapping method using the pilots inserted in transmitter in COFDM(Coded Orthogonal Frequency Division Multiplexing) system which is the standard transmission system of terrestrial digital TV in Europe[1]. We have tested the demapping method of this paper under the standard Rayleigh and Ricean fading channel and obtained better performance than conventional soft decision demapper.
In this paper, a modified equalization target is proposed for the high density magnetic recording channel. This target is a closer match to the channel than the EEPR4 response and hence has better detection performanc...
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In this paper, a modified equalization target is proposed for the high density magnetic recording channel. This target is a closer match to the channel than the EEPR4 response and hence has better detection performance, Based on the dominant error events for this target, a parity-based coding scheme is also proposed to achieve a coding gain with the modified target. The use of the parity code detects the occurrence of the dominant error events while achieving a high code rate. The detection system consists of a Viterbi detector matched to the channel response and a post processor to handle the code constraints. This system is shown to perform well compared to other proposed detection systems through analysis and simulation on a Lorentzian based channel model.
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