Bit error rate analysis of coded OFDM for digital audio broadcasting system, employing parallel concatenated convolutional turbo codes

This paper describes the bit error rate (BER) performance of the Enhanced Packet Mode (EPM) of the Eureka 147 Digital Audio Broadcast (DAB) system in a mobile environment. The BER performance of DAB-EPM is characterized by computer simulations in frequency selective (typical case) and flat faded (worst case) mobile channels. For each of these channels, simulations are performed at vehicle speeds ranging from very slow (walking speed) to very fast (high speed trains). Simulation results show that, in typical frequency selective mobile environments, the target BER of 10 8 required to deliver adequate packet data service via the EPM is achieved at Carrier to Noise Ratio (C/N) values smaller than the target value of 14 dB used in coverage and frequency planning at most of the vehicle speeds tested. Moreover, the coverage area of packet data services is equivalent to the coverage of audio services delivered with the MPEG Layer 2 audio codec and the Unequal Error Protection Level 3 of DAB.

It is envisioned that all broadcasting systems will be digitalized in future. New services and more information require high data rates for broadcasting systems. There are many digital audio broadcasting standards in the world, such as DAB (Digital Audio Broadcasting) in Band III and Band L, DRM (Digital Radio Mondiale)and HD Radio in AM band and FM band. In this paper, we will present a general purpose SDR (Software Defined Radios) platform to realize digital audio broadcasting systems, including transmission and reception. In the platform, we not only can test novel digital technologies but also experiment with different service modes.

Orthogonal Frequency Division Multiplexing (OFDM) is used to encode digital data at multiple carrier frequencies and has evolved into a very common broadband digital communication scheme. All its subcarriers are orthogonal to each other, reducing the interference among subcarriers. Additionally, inter-symbol interference (ISI) can be reduced by using the Cyclic Prefix (CP). However, the intra-block OFDM symbol still degrades the performance. Bit Error Rate (BER) can be used to analyze OFDM performance. The efficiency of the OFDM system increases as the BER value decreases. The performance of the errors can be enhanced by using forward error correction. This study covers the performance of OFDM with Linear Block Code, Convolutional Code, Cyclic Block Code, Turbo Code, and LDPC across the whole SNR range. There has also been a discussion of the difference between coded and uncoded OFDM. The outcome demonstrates that Cyclic Block Code is superior to Linear Block Code in complex situations., LDPC Code performs better when increasing the data rate than Convolutional Code, and with more code generator polynomials, Turbo Code shows less BER value in comparison with Convolutional Code.

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 BERs. The influence of different spatial and temporal probabilities is investigated. Examples are shown for verification at 230 and 1472 MHz.

Orthogonal frequency division multiplexing (OFDM) is a very attractive technique for high-bit-rate data transmission in a multipath fading environment that causes intersymbol interference (ISI). There are many error-correcting codes applied to OFDM, convolutional codes, Reed-Solomon codes, turbo codes, and so on. Low-density parity-check (LDPC) codes have attracted much attention particularly in the field of coding theory. LDPC codes were proposed by Gallager (1962) and the performance is very close to the Shannon limit with practical decoding complexity like turbo codes. We propose LDPC coded OFDM (LDPC-COFDM) systems to improve the bit error rate (BER) of OFDM. We show that the BER of the LDPC-COFDM is worse than that of the TCOFDM on an AWGN channel, while that of the LDPC-COFDM is better than that of the turbo-coded OFDM (TCOFDM) on a frequency-selective fading channel.

Sending broadcast messages is an efficient means of communicating in emergency situations, especially during serious disasters. This paper focuses on the digital audio broadcast (DAB) system. First, several new techniques are reported to enhance the emergency warning message (EWM) receiving and display functionalities for both personal and public DAB terminals. Then, a novel bidirectional communication method between two DAB transmitters is proposed, to enable the communication to and from the disaster area and the outside. Experiments show that the EWM can be correctly sent to the intended DAB terminals within 0.2–3 s, and the existing public light emitting diode screens can be expanded as DAB EWM terminals without affecting their normal functions. The bidirectional multimedia communication between two DAB transmitters is also successfully demonstrated. The proposed techniques expand upon the DAB’s existing functionality, and can benefit more people during emergencies.

In the orthogonal frequency division multiplexing (OFDM) transmission system, when the digital symbols are transmitted in the wireless channel, it would be affected by a lot of noise interference due to the unsatisfactory condition characteristics of the wireless channel itself, therefore, the symbol error and bit error would be generated. To achieve a certain bit error rate (BER) under the condition of known signal-to-noise ratio (SNR), convolutional channel coding and block interleaver should be utilized to further reduce the BER. Moreover, convolutional code is almost utilized in all wireless communication systems. This paper proposes a convolutional code channel estimation method in multiple-input single-output (MISO)-based OFDM (MISO-OFDM) system with frequency-shift m-sequence (FSMS) as guard interval (GI) for avoiding inter-symbol interference (ISI). The proposed space-frequency block code (SFBC) MISO-OFDM system achieves higher transmit diversity gains and better BER performance. Simulation results verify that the proposed iterative threshold channel estimation (ITCE) method in octal representation generation vector (ORGV) convolutional code 4 × 1 MISO-OFDM system provides good BER and normalized mean squared error (NMSE) performance with significant coding gains in both static and dynamic multipath channels.

In recent years, several implementations have been reported for Digital Audio Broadcasting (DAB) systems. Normally, implementation parameters of these systems are extracted from extensive system level simulations to adjust various parameters while maintaining the required performance. In this paper, the bit-true model of a DAB system is extracted and an accurate model simulation for the system is performed to find the word lengths of various parameters to approach the best trade off between performance and hardware cost. Here, the decimation-in-time algorithm for FFT/IFFT and adaptive LMS algorithm for time equalizer is adopted.

A new rate 1/2 turbo code with short memory 2 is developed in this paper. The proposed turbo code consists of two 4-state parallel concatenated non-punctured systematic rate-2/3 convolutional codes. Using a modified maximum a posteriori (MAP) decoding algorithm working on dual codes, its bit error rate (BER) performance is comparable to that of the classic 16-state turbo code at short block lengths, such as k=1024, while its decoding complexity is less than 1/8 that of the classic 16-state turbo codes; for information block length k=504, its BER performance is better than that of the (1008, 3, 6) LDPC codes with comparable decoding complexity. The dual code decoding algorithm is intrinsically partial parallel and a considerably higher throughput of the turbo decoder can be obtained compared with classic turbo codes consisting of punctured codes. The simulation results show that the proposed turbo code can be a competitive technique for short block length applications.

Since the Eureka-147 DAB (Digital Audio Broadcasting) system was announced in the middle of 1990s, many kinds of applications have been introduced in many countries in the world as well as in Europe. T-DMB (Terrestrial Digital Multimedia Broadcasting), which is developed in Korea, is one of the applications which have emerged from Eureka-147 DAB system. T-DMB system provides mobile multimedia broadcasting services including moving pictures as well as CD quality digital audio services in the VHF band. This paper introduces the Korean T-DMB standard based on Eureka-147 DAB and proposes the architecture of a new T-DMB transmission system, which uses a new device called the Ensemble Remultiplexer, to verify it. Although the proposed T-DMB transmission system is the improved version of the conventional DAB system, it still utilizes the existing devices from the DAB system in many parts. Therefore, it provides a solution with high flexibility and low cost for mobile multimedia broadcasting services. We also verified the Korean T-DMB standard and evaluated the proposed T-DMB transmission system by moving the city surrounded by high buildings in high speed. The T-DMB is transmitted at the broadcasting station site in Kwanak mountain in Korea. From the result of this experiment, we could confirm that the T-DMB keeps good quality pictures without any problem comparing to analog broadcasting. The T-DMB is expected to provide mobile multimedia broadcasting services for users from the middle of 2005 and will be evolved to focus on more intelligent and interactive services in Korea.

A new type of interleaver, block-random interleaver, is proposed and compared with the principal types of interleavers on the basis of the BER (bit error rate) performances of the turbo code. A recursive systematic convolutional code, 1/3 rate, unpunctured turbo code was used. The convolutional code has the constraint length, K=4 with generator matrix [1, 15/13], in octal representation. The MAP algorithm, 12 iterations were used. A log likelihood ratio (LLR) stop criterion was selected. The BER and FER (frame error rate) for different interleaver lengths were obtained.

In this paper, we propose a weighting factor (WF) estimation method for peak power reduction (PPR) based on adaptive flipping of parity carriers in a turbo-coded orthogonal frequency-division multiplexing (OFDM) system. In this PPR scheme, the peak-to-average power ratio of a turbo-coded OFDM signal is reduced with adaptive flipping of the phase of the parity carriers corresponding to the WFs. At the receiver, the WFs are estimated at a turbo decoder by exploiting the redundancy of an error-correcting code using no extra side information. The proposed WF estimation method is based on an iterative decoding of the turbo code, i.e., the turbo decoder provides not only error correction capability but the WF estimation function as well. When the proposed WF estimation method is used for the system using a turbo code with constraint length <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> = 4 and a code rate of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> = 1/2, the instantaneous power of the OFDM signal at the complementary cumulative distribution function of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> can be reduced by about 2.1 dB through the application of the PPR scheme. When the bit error rate (BER) performance is evaluated as a function of the peak signal-to-noise power ratio (PSNR), the proposed method achieves better BER performance than the case without the PPR in an attenuated 12-path Rayleigh fading condition. The improvements in BER performance as a function of PSNR are about 1.1, 2.0, and 2.1 dB at BER = 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> for turbo-coded OFDM signals using QPSK, 16-state quadrature amplitude modulation (QAM), and 64-state QAM schemes, respectively.

A robust in-band on-channel (IBOC) digital audio broadcast (DAB) system for improved performance over existing FM broadcasting is under development by Westinghouse for USA Digital Radio. Both the analog FM and the DAB signals are transmitted simultaneously in the FM hybrid IBOC system. Broadcasters can simultaneously transmit both analog and digital signals within the allocated channel mask, allowing full compatibility with existing analog receivers. It is shown here that the solution is tolerant of interference from adjacent channels, or interference from the co-channel analog transmission, even in a multiple station, strong-signal urban market. Although the primary focus of this paper is to discuss the compatibility issues between the existing FM and the DAB signals, the paper also briefly describes spectral occupancy, power ratios, modulation formats, and coding, as well as the introduction of frequency and time diversity.

This paper studies the performance of ultra-wideband (UWB) radio communications systems employing phase shift keying (PSK) modulation and fully saturated power amplifiers through additive white Gaussian noise (AWGN) channel or Rayleigh fading channel. An impulse response method is provided to analyze the signal-to-noise ratio (SNR) degradation. Both convolutional code and turbo code are employed with the Viterbi decoding and the iterative decoding, respectively. The decoding algorithms are modified for the Rayleigh fading channel. Near optimal bit error rate (BER) performance is achieved when employing either convolutional code or turbo code. The simulation results match the derivation. Therefore, fully saturated power amplifiers can be employed in UWB PSK systems to significantly reduce radio cost, simplify radio circuit, and increase battery life for portable terminals.

Orthogonal frequency division multiplex-single frequency network (OFDM-SFN) has been widely used in the digital audio broadcasting system (DAB) and the terrestrial digital video broadcasting system (DVB-T) as a scheme of downlink broadcasting service. A novel system structure of single frequency cellular network (SFCN) is proposed by applying OFDM-SFN to conventional cellular systems. Transmitter macrodiversity and receiver selective diversity are adopted in the downlink and the uplink respectively. Theoretical analysis and numerical simulation in comparison with conventional cellular systems demonstrate the performance improvement of the proposed system.