Search

We introduce new methods for increasing the performance of multiprogram digital audio broadcast systems, e.g., satellite digital audio broadcasting. Joint multiprogram encoding is an attractive possibility for parallel broadcasting of a large number of programs. Joint coding extended over multiple audio frames in time give further improvements. The benefits of this kind of statistical multiplexing yield improved audio quality and/or higher capacity in terms of number of programs. We describe the new Joint Multiple Program Encoding Technique in the context of the perceptual audio coding (PAC) type of algorithms. We also describe methods for multi-program transmission including Equal Error Protection (EEP) as well as Unequal Error Protection (UEP) and improved error concealment for multiple program transmission. Some of the techniques described in this paper, are currently being used in satellite digital audio broadcasting in the United States. Index Terms--Digital audio, digital audio broadcasting, source coding, statistical multiplexing.

High peak-to-average power ratio (PAPR) of the transmitted signal is a major drawback of orthogonal frequency division multiplexing (OFDM). In this paper, we propose a modified selective mapping (SLM) technique for PAPR reduction of coded OFDM signal. In this technique, we embed the phase sequence, which is used to lower the PAPR of the data block, in the check symbols of the coded OFDM data block. It is shown that we can achieve both PAPR reduction from the SLM technique as well as error performance improvement from the channel coding with no loss in data rate from the transmission of side information. In addition, approximate expression for the complementary cumulative distribution function (CCDF) of the PAPR of the modified SLM technique is derived and compared with the simulation results.

In this paper, design and implementation of a DAB transmitter prototype is proposed. The system architecture, ensemble multiplexer, channel encoder, OFDM (Orthogonal Frequency Division Multiplexing) modulator and other digital baseband parts are described. The prototype is fully compatible with ETS 300 401 and other related standards. It supports different services with various data formats and provides a convenient pc-based user interface. All I/Os and core parts are based on modular design with a universal internal interface, hence the prototype can be flexibly configured to adapt different requirements. Compared with existing products, the proposed transmitter prototype offers higher flexibility and lower cost. Index Terms--Digital audio broadcasting, modulator, multiplexing, transmitters.

This paper presents a new databroadcasting technique for transmitting data using the Orthogonal Frequency Division Multiplexing modulation scheme, within the NTSC television signal. The data signal is inserted in the vestigial sideband of the video signal. The advantages of this implementation are that the shape of the data spectrum minimizes the degradation of the picture quality and increases the noise margin of the data signal. Two approaches are taken to evaluate the performance of this system. In the first one, computer simulations are used to determine the available bit rate by varying the number of carriers. Bit error rate measurements are also done to evaluate the performance of the system when the data signal is combined with the NTSC television signal. In the second approach, the perceptual impact is determined, using accepted subjective assessment methodology, when varying levels of OFDM carriers are injected into the NTSC signal. The results show that the proposed system has the potential to offer higher data rate throughput than existing databroadcasting systems, with negligible degradation effects on the NTSC picture quality.

A multiplexers available several purposes such as for mobile communications, CATV systems and multimedia systems in future, are propped and trially made by authors. This paper present the results the design concept and experimental results. The design principle was based on the theoretical concept proposed by us.

A time-domain based channel estimation for OFDM system with pilot-data multiplexed scheme is investigated. As an approximation to linear minimum mean square estimator (LMMSE), a time-domain based channel estimation is proposed where intra-symbol time-averaging and most significant channel taps selection are applied. The relation and differences of the proposed method to DFT-based LMMSE methods are discussed. The performances of the proposed method, DFT-based LMMSE method [15] and the methods of [16] and [17] are evaluated in multipath fading channels. The simulation results show that proposed method achieves almost the same performance as DFT-based LMMSE method and better BER performance than the other methods while keeping less complexity. Index Terms--Channel estimation, intra-symbol time-averaging, linear minimum mean square error estimator, most significant taps selection, orthogonal frequency division multiplexing (OFDM).

The feasibility of terrestrial Digital Video Broadcast (DVB) to mobile receivers is studied and turbo coded performance enhancements are proposed. Initially, the MPEG-2 codec is subjected to a rigorous bit error sensitivity investigation, in order to assist in designing various error protection schemes for wireless DVB transmission. The turbo codec is shown to provide Signal-to-Noise Ratio (SNR) performance advantages in excess of 5-6 dB over conventional convolutional coding both in terms of bit error rate and video quality. Our experiments suggested that--despite our expectations--multi-class data partitioning did not result in error resilience improvements, since a high proportion of relatively sensitive video bits had to be relegated to the lower integrity subchannel, when invoking a powerful low-rate channel codec in the high-integrity protection class. Nonetheless, DVB transmission to mobile receivers is feasible, when using turbo-coded OFDM transceivers at realistic power-budget requirements under the investigated highly dispersive fading channel conditions. It is interesting to note furthermore that the 5-6 dB SNR improvement due to turbo coding allows us to invoke for example the double-throughput 16-level Quadrature Amplitude Modulation (16-QAM) mode instead of the standard convolutional-coded 4-QAM mode. This facilitates doubling the bit rate and hence improving the video quality. Index Terms--DVB, DVB-T, error sensitivity, hierarchical video transmission, mobile video broadcast, MPEG-2, OFDM, QAM, terrestrial video broadcast, wireless video broadcast.