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We present techniques for simulcasting low-power digital data and analog FM over fading channels. Our methods have strong connections to what are referred to as dirty paper coding techniques in that a low-power digital data signal is modulo-added to the host analog FM signal. Due to the low power levels of the digital data and the suppression capability of analog FM, a standard analog FM receiver can be used to reliably recover the analog audio signal. We develop digital receivers that work reliably over fading channels given imperfect channel state information. Spread-response precoding is exploited to not only provide rate-1 temporal diversity benefits, but also to simplify the design of the modulo-precanceler and the receiver. Our theoretical and simulation-based performance analysis of the digital receivers and our MSE-based analog FM distortion analysis suggest that precoded modulo-precanceling schemes provide substantially higher data rates than existing precanceling strategies at the cost of transmission delay and transmitter and receiver complexity. The systems we present are also readily compatible with conventional channel coding techniques as well as with analog FM postcancelers, which can improve the digital receiver bit-error-rate performance at the expense of receiver complexity. Index Terms--Digital audio broadcasting, digital modulation, dirty paper coding, spread response precoding, simultaneous analog FM and data, HD radio, hybrid IBOC.

With the upcoming fourth generation wireless systems and convergence of multiple radio standards into a single terminal, building blocks are needed that can be configured for computing various algorithms used in different standards. Given these trends and requirements, in our previous paper we successfully proposed a circuit-sharing design for the DAB receiver to integrate the FFT (fast Fourier transform) and IMDCT (inverse modified discrete cosine transform) operations into the same functional circuit. The proposed technique reduces hardware overhead, enhances circuit efficiency and significantly reduces the cost of DAB receivers. To further improve the efficiency of our previous work, this investigation proposes another alternative design named the circuit-sharing pipeline design (CSPD) using a single processor with a pipeline scheme to combine two functions, FFT and IMDCT, into the same circuit. The proposed method reduces the required chip area and cost of DAB receivers. Analyzing the existing relationship among IMDCT, DCT (discrete cosine transform) and FFT, the IMDCT function can be replaced using a FFT function. Therefore, it is not necessary to design an extra circuit for IMDCT. The arithmetic unit in the FFT processor can be significantly reduced due to employing the pipeline scheme. Consequently, the circuit redundancies in the IMDCT and FFT functions can be easily eliminated to allow exploitation of the decreased chip area. Results of this study demonstrate that the proposed design can provide advantages such as low gate count and small memory size in the DAB (digital audio broadcasting) receiver. Index Terms--DAB (digital audio broadcasting), DCT, FFT (fast Fourier transform), IMDCT, OFDM (orthogonal frequency division multiplexing), VLSI.

Commercial terrestrial digital multimedia broadcasting (T-DMB) service was launched on December 1st, 2005, in the Seoul metropolitan area of the Republic of Korea. As the world's first commercial terrestrial mobile multimedia broadcasting service, T-DMB garnered huge attention in the field of mobile broadcasting. This paper presents the history, system, and services of T-DMB. Index Terms--Mobile multimedia broadcasting, T-DMB.

This paper examines the temporal variability in fixed reception of the ground-wave propagated DRM (Digital Radio Mondiale) signal. This field strength analysis in the medium wave band has been performed using the first Spanish DRM field trial. Several fixed reception points located along radial routes provided the field strength sample distributions in rural and suburban areas. Additionally a second measurement campaign was carried out in several dense and open areas of downtown Madrid. The maximum likelihood estimations and logarithmic functions were used to analyse the fit of the experimental data with theoretical statistical distributions. A deep analysis of the most important parameters of the distribution has been carried out in order to characterize the field strength behavior in the different reception situations. It has been taken into account the influence of environment, measurement time interval, distance to the transmitter and the presence of critical reception impairments. The most remarkable result of this study has shown that the time variability of the ground-wave medium wave DRM channel is well approximated by a Log Normal and also by a Nakagami process. The Log Normal distribution is preferred as it is the one considered by the analog medium wave broadcasts for the ground-wave propagation case. Index Terms--Digital AM, digital audio broadcasting, digital radio, DRM, medium wave, statistical distributions, statistical inference, statistical modeling.

This paper presents the results of the first Spanish field trial carried out to analyze a DRM (Digital Radio Mondiale) system in the medium-wave band. A 4-kW average power omni directional ground-wave experimental DRM transmission at a frequency of 1359 kHz was surveyed by means of a measurement vehicle for fixed and mobile reception. Several radial routes starting from the transmitter site provided rural and suburban behavior features of the system. Urban reception trials were performed in several dense and open streets of Madrid, within the expected coverage area. Field strength threshold values were determined for the tested transmission configurations and compared with the AM ground-wave ITU model predictions. Reliability versus distance from the transmitter is stated in this paper for different transmission configurations and the causes of dropouts for different reception conditions are explained. This analysis took into account subjective quality features of each configuration, providing practical planning parameter values. Index Terms--Digital AM, digital audio broadcasting, digital radio, DRM, medium wave.

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.

A hierarchical modulation scheme is proposed to upgrade an existing digital broadcast system, such as satellite TV, or satellite radio, by adding more data in its transmission. The hierarchical modulation consists of a basic constellation, which is the same as in the original system, and a secondary constellation, which carries the additional data for the upgraded system. The upgraded system with the hierarchical modulation is backward compatible in the sense that receivers that have been deployed in the original system can continue receiving data in the basic constellation. New receivers can be designed to receive data carried in the secondary constellation, as well as those in the basic constellation. Analysis will be performed to show the tradeoff between bit rate of the data in secondary constellation and the penalty to the performance of receiving the basic constellation. Index Terms--Backward compatibility, bit rate, constellation mapping, digital broadcast, hierarchical modulation, iterative decoding, local repeaters, penalty analysis, QAM, QPSK, receiver design, system upgrade.

In this paper, we discuss a kind of meander antenna which is designed for digital audio broadcasting (DAB) reception in BAND-III upper band (210-240 MHz). Three resonators in addition to a driven element were constructed on the topside of a printed circuit board. On the backside of it, several coupling stubs were introduced to tune resonant frequencies to the required passband. Resonators with different lengths are resonated at different frequencies and these multiple resonances are responsible for an enhancement in bandwidth. With the help of backside coupling, it is easy to tune multiple frequencies to the required pass-band. It is also found that current density of the associated elements is increased by backside coupling. According to experimental results, the designed antenna reaches a bandwidth around 13.3% (return loss >10 dB) in the range of 210-240 MHz. Index Terms--Meander antenna, resonator, tuning, wide bandwidth.

This paper describes the new world-wide broadcasting system Digital Radio Mondiale[TM] (DRM[TM]) for the long, medium and short wave bands. It is originated by the goal of the consortium members to develop a flexible and efficient audio and data broadcasting standard. Better sound quality, more reliable reception in combination with additional service information make DRM a promising successor to the analogue AM. Achieving good audio quality becomes a challenging task due to the limited bandwidth of 9 or 10 kHz, especially in often strong impaired channels. Many other requirements, which were the basis for the system development, are illustrated. This article gives an overview of the system architecture including the components multiplexing, modulation, channel coding and source coding. Important receiver aspects such as synchronization and channel estimation are also described. Index Terms--Broadcast, digital radio mondiale, DRM.

A method for broadcasting digital audio signals simultaneously with existing analog frequency modulation radio (88-108 MHz) in adjacent channels is presented. The digital transmission is based on continuous phase modulation (CPM) and a proper reduced-state sequence estimator. With the proposed method, the power level and the symbol rate of the transmitter signal is determined in a manner that the interference the CPM signal poses for the analog FM signal in adjacent channels remains below a level according to the radio frequency emission mask defined by international rules. Due to the multipath propagation Of the transmitted signal, the transmission behavior of the radio channel is determined by high dispersion up to 85 [micro]s. With the selected bit rate, the receiver has to cope with a channel memory of up to 17 bits. Since Viterbi detection is not feasible due to the number of channel states, detection is performed by a reduced-state sequence estimator that is able to eliminate the complete channel interferences by decision feedback. Simulation results show that the detector almost achieves the detection quality of the optimum receiver. CPM achieves data rates of up to 200 kb/s inside a 200 kHz FM channel, which is sufficient for transmission of digital compressed audio signals in compact disc quality. Field tests with encouraging results were performed with a real digital transmission system based on a transmitter in a public transmission station afnd a PC based mobile receiver. The results of these field tests will be published in a second paper. Index Terms--CPM, digital audio broadcasting, FM.

This paper proposes a circuit-sharing approach to improve efficiency for the key Digital Audio Broadcasting(DAB) techniques, i.e., MPEG1-audio decoding and orthogonal frequency division multiplexing (OFDM). Because OFDM's Fast Fourier Transform (FFT) requires heavy computational power for implementation, a single butterfly processing element (BPE) is adopted to reduce the chip area required for FFT. Furthermore, by modifying the BPE logical combinational circuit, both IMDCT (Inverse Modified Discrete Cosine Transform) and FFT functions can be obtained simultaneously from a single VLSI chip. Therefore, the proposed technique reduces hardware overhead, enhances circuit efficiency and significantly reduces the cost of DAB receivers. The proposed circuit is simulated as a VLSI prototype chip using a 0.35 [micro]m CMOS process, with a chip area of about 22.09 [mm.sup.2] and a total gate count of approximately 10839 (excluding ROM and RAM). Index Terms--Circuit sharing, COFDM, digital audio broadcasting, IMDCT, VLSI.

We consider simultaneous broadcasting of low-power digital data and analog FM and present reliable receivers for the digital data. Due to the relatively low power level of the digital data and the interference suppression capability of analog FM, standard analog FM receivers can reliably recover the analog FM audio signal. To recover the digital data, an extended Kalman filter front end is developed that exploits the capture capability of analog FM to reconstruct and postcancel the analog FM component from the received composite signal. Simulations are conducted with artificial analog FM signals, suggesting that postcanceling schemes can provide higher data rates than their precanceling counterparts, at a lower transmission delay penalty but higher digital receiver complexity. For analog FM to digital signal power level ratios in the range of 30-50 dB, the postcanceler digital signal recovery appears fairly robust, providing digital signal-to-noise ratios of 2-7.5 dB. The corresponding uncoded bit error rates strongly depend on the power level difference between the host analog FM and the digital data signal. In particular, at 260 kb/s and [E.sub.b]/[N.sub.o] = 10 dB they range between 1% to about 15%, and can be reduced to acceptable levels using standard channel coding techniques. Index Terms--Digital audio broadcasting (DAB), digital modulation, frequency modulation, Kalman filters.

Hybrid In Band on Channel (IBOC) digital audio broadcasting simultaneously with analog amplitude modulation (AM) has been proposed as a hybrid solution to digital audio broadcasting in the AM band. Since the AM band is crowded and since the available bandwidth per program is limited, adding digital transmission is a challenging proposition. To achieve FM like audio quality, an audio coder rate of 32-64 kb/sec may be required. One of the currently proposed hybrid IBOC-AM systems is 30 kHz wide. Severe second adjacent interference may occur in certain geographical areas. This may lead to loss of 40% of the effective transmission audio bit rate. For coping with such harsh transmission conditions, we present a solution based on embedded/multidescriptive audio coding with matched multistream transmission in separate frequency bands. With loss of one frequency band, the embedded system blends to a lower audio coder rate with a much better quality than analog AM. The nonembedded system without multistream transmission fails catastrophically when a little more than one sideband is severely interfered with causing a severe discontinuity in quality while blending directly to analog AM. A number of detailed robust embedded systems are outlined. We also show how multistream transmission schemes can be used with nonembedded audio coders. Both daytime and nighttime scenarios are included. This paper contains a catalog of possible systems for different audio quality levels and interference scenarios, including systems with 20 kHz bandwidth rather than 30 kHz. Index Terms--Amplitude modulation, audio coding, channel coding, digital audio broadcasting, error detection coding, radio broadcasting.

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 the field trials and the coverage measurements carried out in urban areas in the first experimental terrestrial DAB (T-DAB) network at L-Band in Spain. The trials focused on obtaining the parameters that characterize the propagation channel for different urban environments. The results will be discussed taking into consideration recommended parameters and values given by international organizations (ITU-R, ETSI) as well as the ones obtained in former experimental networks worldwide. Index Terms--Digital audio broadcasting (DAB), Eureka 147, L-band, minimum C/N, scale factors CRC, urban areas.

Digital transmissions and digital communications are a reality nowadys and very soon some system of digital MF AM and VHF FM transmission will be a common service in many countries. For this reason it is very important having the proper antenna, specially in the MF AM band where achieving the necessary bandwidth in the antenna impedance is some time a difficult task. This problem is critical in the lower frequencies were the antenna matching to the transmission line generally is very sharp and the best match is obtained only at the carrier frequency with an appreciable power reflection in the lateral frequency bands. This problem is not very important in the classical AM transmissions were the maximum transmitted power is located at the carrier frequency and only a fraction in the upper and lower lateral bands. Of course this produces some distortion in the AM transmission but in this case the quality of the audio is not really of high fidelity, like in an FM transmission, due to a lot of factors, one of them the lack of full audio spectrum. This problem can be corrected with a high fidelity audio transmitters and specially with a digital transmission in order to achieve a CD quality audio and here the transmitting antenna plays an important role. Improvements of the MF AM transmissions is very important specially in a large country, because medium frequency broadcast service can cover a very large area with the proper antenna and transmitted power. Very stable and good quality signals and practically without any multipath problems, specially in the lower frequencies, are achieved. This makes the MF AM system, one of the cheapest systems per radiated power kilowatt relative to the covered area and population.

The worldwide installed analog broadcast networks suffer from problems in quality, power consumption, and waste of frequency spectrum. They will be replaced by digital networks in the next century. For analog networks, the planning parameters for frequency, power, and site assignment are well known. For digital audio broadcasting (DAB) networks, the research of the relevant criteria has just started. This paper presents the derivation of protection ratios and field strength levels under worst case conditions for Eureka 147 orthogonal frequency division multiplex (OFDM)-based digital audio broadcast systems from the bit error rate (BER) of the unprotected propagation channel. The channel is characterized by a three-dimensional (3-D) ray optical wave-propagation model. The peculiarities of the resulting multipath field strength delay spectra in single-frequency networks (SFN's) for the calculation of the signal-to-noise ratio (SNR) and the BER at the receiver are discussed. Different terrain types and frequencies are considered. A statistical analysis of the relationship between the SNR and BER leads to the determination of the cochannel protection ratio. An expansion thereof results in the adjacent-channel protection ratios. The minimum required field strength is derived from the protection ratios and the BER's. The influence of different spatial and temporal probabilities is investigated. Examples are shown for verification at 230 and 1472 MHz. Index Terms - Bit error rate, channel characterization, digital audio broadcasting, protection ratio.

The Digital Audio Broadcasting (DAB) system which was originally designed for high quality audio transmission to mobile receivers is investigated for transmission of compressed digital video and multimedia signals. The bit error performance is considered using various levels of error protection provided by the DAB system. As a result, a net bit rate of about 1.5 Mbit/s can be achieved.With additional error correction coding, a bit error ratio (BER) of less than [10.sup.-10] can be realized. This is the requirement for compressed video signals. The SNR per bit is below 16 dB. The results are demonstrated and compared using computer simulations of the complete system.

A synthetic aperture radar (SAR) is considered, located on a geosynchronous receiver, and illuminated by the backscattered energy of satellite broadcast digital audio or television signals. The principal application of such a passive system could be differential interferometry, since even low spatial resolution coupled to zero baseline would be useful; however, other imaging applications could be envisaged and even some topographic capabilities if a baseline is created by ellipticizing the receiver's orbit. Spatial resolution, link budget, and possible focusing techniques are evaluated. Index Terms - Interferometry, microwave imaging, parasitic, satellite communication, synthetic aperture radar (SAR).

A method for broadcasting digital audio simultaneously with existing analog frequency modulation (FM) radio is presented. The method is based on precomputing the response of the host analog FM signal at the digital receiver and precanceling it at the transmitter. As a result, the digital transmission is free from interference from analog FM. We select the rate and power level of the digital transmission in a manner that the interference the digital data incur on the analog FM signal remains at acceptably low levels. The digital transmission is based on adaptive orthogonal frequency-division multiplexing (OFDM) (adaptive multicarrier). The frequencies and number of carriers of the digital multicarrier modem are judiciously selected in a time-varying fashion so as to cause a negligible distortion in a standard receiver for analog FM. Simulations based on conservative nonoptimized signal design indicate that data rates up to about 130 kb/s inside the 200-kHz FM channel are achievable for acoustic test signals. We present a number of numerical examples where the average digital data use up to 50% of the 200-kHz power spectrum with digital signal power levels 25-35 dB below the analog signal. Due to the resulting variable-rate digital transmission, a control channel is required. A method of precanceling with multiple orthogonal direct-sequence spread-spectrum schemes is also presented. Index Terms - Adaptive precanceling, digital audio broadcasting, FM, simultaneous analog FM and data.

In support of the 1995-1997 DAB (Digital Audio Broadcasting) testing conducted by the NRSC (National Radio Systems Committee), an IBAC (InBand Adjacent-Channel) scheme was developed by AT&T. Although now not considered for use in the United States, bit error rate (BER) system performance under both fading environments and the existing analog FM broadcasting is important to quantify. This is because there may still exist other countries and environments where an IBAC approach to DAB is feasible and economical. Given this situation, an IBAC simulation model has been developed to allow for a performance analysis study within the mobile reception environment, which is dominated by Rayleigh and Ricean fading statistics. This paper presents the simulation results for coherent quadrature phase-shift-keying (QPSK) with nonlinear equalization for both frequency-selective Rayleigh and Ricean slow fading channel environments, along with co-channel, 1st-adjacent and 2nd-adjacent analog FM interference. The results indicate that for a country where spectrum availability dictates an IBAC solution, this approach may perform well under various fading and interference environments.

In this paper, the effects of HPA nonlinearities on the performance of the Eureka 147 DAB system are studied by computer simulation. The performance is determined for three types of HPA: a TWTA, an SSPA and a perfectly linearized amplifier (PLA). Two related performance criteria are used: a) the degradation, resulting from HPA nonlinearitites, in the [E.sub.b]/[N.sub.o] ratio required at the receiver to maintain a bit error rate of [10.sup.-4] and b) the total power degradation. These degradations are measured as a function of the HPA output backoff. The effect, on the [E.sub.b]/[N.sub.o] degradation, of linearizing only the phase or only the amplitude transfer characteristic of the TWTA and the SSPA is also assessed. Correcting the phase distortion alone in both HPA's is found to reduce the [E.sub.b]/[N.sub.o] degradation by less than 0.5 dB. Linearization of the amplitude characteristic alone, on the other hand, can reduce the [E.sub.b]/[N.sub.o] degradation by several dB's at small OBO values (< 2 dB). The optimum output backoff which minimizes the total power degradation is between 2 and 3 dB for both the TWTA and the SSPA in a terrestrial mobile channel and between 1 and 2 dB in an AWGN channel. The optimum output backoff for the PLA is 2 dB in the terrestrial channel and between 1 and 2 dB in the AWGN channel. At the optimal operation point, the power saved by linearizing the amplitude and phase characteristics of the TWTA or the SSPA is about 0.6 dB for the terrestrial mobile channel and 0.4 dB for the AWGN channel.

The interest in software radios has focused on using wide-band analogue-to-digital (ADC) and digital-to-analogue (DAC) converters. Radios can be designed with reusable programmable digital processing hardware, requiring the radio tuning function to be undertaken in an analogue way. The Airadio Division (ARD) of GEC-Marconi Electro-Optics Ltd has been using the technology for airborne communications applications. An overview of hardware and software technologies used in Terrestrial Flight Telephone System (TFTS) products is provided.

In this paper, we present a performance analysis of a Coded Orthogonal Frequency Division Multiplexing DAB systems that is power multiplexed over a commercial FM station. We model the mobile channel with a time-frequency scattering function. Results show that the performance of the FM demodulator is crucial, since the level of the residual FM signal has a strong influence on the BER performance of the COFDM system. As with other mobile communication systems, the use of inter-leaving greatly enhances the performances.

All transmitters in a Single Frequency Network (SFN) simultaneously transmit the same information within the same frequency block. Simulcasting provides a diversity gain which has been shown to yield good coverage. In traditional analysis uncorrelated shadow fading is used. In some cases this assumption does not capture the behaviour of the shadow fading, e.g. when several transmitters are shadowed by a large obstacle. In this paper we investigate the changes in coverage due to correlation among the received signals field strength from different transmitters. A spatial shadow fading correlation model is proposed and validated using the Blomquist-Ladell [13] prediction method on a digital terrain data base. Results for both wide area and local SFN show that the coverage properties depends on the correlation in the shadow fading. This will affect the planning process since strong correlation, due to the structure of the terrain, yields better coverage for high transmitter powers (interference limited systems) and worse coverage for low transmitter powers (noise limited systems).

A compensation technique for nonlinearities is usually necessary in QAM digital satellite links. Analog waveform compensation has the advantage of reducing out-of-band spectral emissions with respect to end-to-end digital predistortion, in addition to its easy realization. Nevertheless, it has been often neglected in the literature because of its lack of adaptivity; we propose making the predistorter fully adaptive. In this paper, different control schemes applied to fifth-order IF predistortion with different optimization criteria have been investigated. A simulation-based analysis shows that adaptive IF compensation achieves excellent performance if compared with static predistortion of the same order. Comparisons with upper bounds related to digital predistortion with memory, moreover, denote that IF analog predistortion can be truly considered an alternative approach, especially for narrow pulse shaping.

This paper describes the performance of COFDM for digital audio broadcasting (DAB) over various multipath mobile radio channels. COFDM is a channel coding and modulation scheme which mitigates the adverse effects of fading by using wideband multicarrier modulation combined with time interleaving and a convolutional error correcting code. A guard interval is inserted at the transition between successive symbols to absorb the intersymbol interference created by the time domain spread of the mobile radio channel. The decoding process is performed using differential demodulation in conjunction with a soft decision Viterbi decoder. The COFDM evaluation is done by means of computer simulations. A parametric study of the proposed COFDM system is done in this first of a series of papers to determine the optimal system parameter values for operation at a radio frequency of 1.5 GHz. The results show that the parameter values proposed in the standard are indeed well suited for operation at 1.5 GHz. Using the set of optimal parameter values found, the COFDM performance is then evaluated in mobile radio channels typical of different geographical environments. Simulation results confirm the benefit that the system gains from frequency diversity found in the urban and hilly terrain areas.

Bandwidth efficiencies that have not been possible in the past are now being achieved using VPSK and VMSK modulation without the loss of signal power that normally accompanies high bandwidth efficiency methods. Theoretically, these two methods do not lose any signal energy with increasing bandwidth compression. Efficiencies up to 15 bits/sec./Hz are now being achieved in usable hardware with C/N ratios better than that obtainable using FM, BPSK or QPSK. This paper explains how this is accomplished and gives a full mathematical analysis of the method.

In this paper we deal with some of the main blocks which consist a stereophonic RDS modulation system. As such we consider the 19 KHz pilot tone of the FM stereo, the 38 KHz subcarrier modulated by the difference of the two stereo channels and the 57 KHz subcarrier of the RDS digital signal. Also, a digital substitute of the biphase signal generator required for coding and shaping of the RDS data preceding the balanced modulator, is considered. The substitution of the balanced modulator by a multiplying DAC is another consideration. The synthesis of the three carriers takes place by a multiplexed (triple) Direct Digital Synthesizer (DDS). The multiplexed synthesizer can be considered independently for the generation of multiple frequencies.

In this paper, we present and analyze a technique for fast acquisition and accurate tracking of the carrier frequency in orthogonal frequency division multiplexing (OFDM) receivers. The scheme is based on a data-aided frequency estimation algorithm recently proposed in the literature by the authors. The presence of known symbol sequences periodically inserted in the OFDM frame allows the data demodulator to rapidly lock onto the carrier frequency during the acquisition phase, even in the presence of frequency offsets up to a few tenths of the overall signaling rate. Once acquisition is over, the circuit switches to a decision-directed mode to perform fine frequency tracking for reliable data demodulation. The algorithm performance is analyzed in terms of width of the lock-in frequency range and of lock-in probability in the acquisition mode, and of mean-square frequency estimation error in the tracking mode. Since OFDM is known to be extremely sensitive to carrier frequency errors, the impact of the carrier frequency synchronizer on the receiver error rate is also investigated.

Within a time frame of three years a DAB SFN transmitter network will be brought into operation in the south-western part of Germany. The network is designed to serve at least three million inhabitants. The network performance is analyzed by means of computer simulations. For that purpose, the power density functions (PDFs) of the contributing partial waves are combined in order to determine the local coverage probability. It is shown that SFNs are superior in comparison to multifrequency FM networks. The advantage is identified as SFN gain. A temptative definition is given. Results of model calculations are presented for VHF- and L-Band assignments. It is shown that guard interval violations cause intersymbol interference (ISI), deteriorating the SFN's performance.

A spectrum analysis technique is described which will measure the quantization noise in a digital audio system with a signal present. An estimate of the power density spectrum will be interpreted to find the signal to quantization noise ratio. Additional information derived from real life spectrum measurements will be explained.

Digital audio broadcasting (DAB) to mobile and fixed users exploiting the latest advances in compression, coding, and transmission techniques represents an appealing application for future satellite systems. This paper introduces coded quasi-orthogonal code division multiplexing (CQO-CDM) as a transmission technique for digital audio broadcasting. The proposed technique performs well over both the L-band satellite fading channel and the terrestrial gap-filler type of transmission. Preliminary link budgets based on extensive computer simulation results are provided. Numerical results show that remarkable overall capacity can be achieved by using a constellation of satellites in highly elliptical orbit (HEO) complemented by a terrestrial gap-filler network. A variety of transmission rates and hence broadcasting services can be realized with the proposed transmission technique. It is shown that a geostationary orbit (GEO) satellite can provide limited service availability to the mobile user, but can also be used for experimental purposes.

The Electronic Industries Association (EIA) DAR Subcommittee is evaluating proposed Digital Audio Radio (DAR) systems for the United States. As a part of that process, the Subcommittee is conducting a 'VHF Radio Channel Characterization Test'. The results of the test will be applied directly to the laboratory testing of the DAR systems and will also find general use within the radio communications industry.

A new digital approach to an FM exciter is presented that provides several advantages over previous analog techniques. This new approach called Direct Digital Frequency Modulation (DDFM) is centered around a Direct Digital Synthesis (DDS) chip which allows true digital generation of the FM signal. The DDS chip is a perfectly linear modulator with superior phase noise characteristics over the current analog VCO approach. The DDS modulator drives a low noise PLL which allows upconversion to any FM channel without manual tuning. The exciter demonstrates superior microphonics immunity by separating the frequency tuning from the modulation path, thus allowing wider PLL bandwidths. The exciter can accept either the existing composite analog format or can interface with digital sources of the future. The DDFM approach will allow better performance in many key areas, while providing the user with compatibility to future digital formats.