Aeronautical audio broadcasting via satellite

Communications Satellite Corp., Clarksburg, MD.
01/1993; -1:33-38.


A system design for aeronautical audio broadcasting, with C-band uplink
and L-band downlink, via Inmarsat space segments is presented.
Near-transparent-quality compression of 5-kHz bandwidth audio at 20.5
kbit/s is achieved based on a hybrid technique employing linear
predictive modeling and transform-domain residual quantization.
Concatenated Reed-Solomon/convolutional codes with quadrature phase
shift keying are selected for bandwidth and power efficiency. RF
bandwidth at 25 kHz per channel, and a decoded bit error rate at 10(exp
-6) with E(sub b)/N(sub o) at 3.75 dB are obtained. An interleaver,
scrambler, modem synchronization, and frame format were designed, and
frequency-division multiple access was selected over code-division
multiple access. A link budget computation based on a worst-case
scenario indicates sufficient system power margins. Transponder
occupancy analysis for 72 audio channels demonstrates ample remaining
capacity to accommodate emerging aeronautical services.

5 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: This book is written for the design engineer who must build the coding and decoding equipment and for the communication system engineer who must incorporate this equipment into a system. It is also suitable as a senior-level or first-year graduate text for an introductory one-semester course in coding theory. Fundamental concepts of coding are discussed along with group codes, taking into account basic principles, practical constraints, performance computations, coding bounds, generalized parity check codes, polynomial codes, and important classes of group codes. Other topics explored are related to simple nonalgebraic decoding techniques for group codes, soft decision decoding of block codes, algebraic techniques for multiple error correction, the convolutional code structure and Viterbi decoding, syndrome decoding techniques, and sequential decoding techniques. System applications are also considered, giving attention to concatenated codes, coding for the white Gaussian noise channel, interleaver structures for coded systems, and coding for burst noise channels.
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents the configuration of the variable-rate Viterbi decoder which was newly developed based on a concept of punctured convolutional coding, and the performance characteristics of punctured codes of rates 1/2 through 16/17 are clarified by hardware experiments and theoretical calculations. Obtained results indicate that the developed codec will be quite useful for effective use of the power and bandwidth of the digital satellite communication systems.
  • [Show abstract] [Hide abstract]
    ABSTRACT: A low-bit-rate speech encoder must employ bit-saving measures to achieve intelligible and natural sounding synthesized speech. Some important measures are: (a) quantization of parameters based on their spectral-error sensitivities (i.e., coarser quantization for spectrally less sensitive parameters), and (b) quantization of parameters in accordance with properties of auditory perception (i.e., coarser quantization of the higher frequency components of the speech spectral envelope, and finer representation of spectral peaks than valleys). The use of Line-Spectrum Pairs (LSPs) makes it possible to employ these measures more readily than the better known reflection coefficients. As a result, the intelligibility of an LSP-based, pitch-excited vocoder operating at 800 bits/second (b/s) can be made as high as 87 for three male speakers (as measured by the Diagnostic Rhyme Test (DRT)) which is only 1.4 below that of the 2400-b/s LPC. Likewise, the intelligibility of a 4800-b/s nonpitch-excited vocoder is as high as 92.3 which compares favorably with scores from current 9600-b/s vocoders.
    Acoustics, Speech, and Signal Processing, IEEE International Conference on ICASSP '85.; 05/1985
Show more


5 Reads
Available from