The limited number of logic elements makes the implementation of signal processing chains on low-cost FPGAs a challenging task. In order to allow the implementation of complex designs on devices with limited resources, we propose the subpartitioning of a processing chain into several modules, which are loaded and executed in a round-robin fashion using dynamic partial reconfiguration (DPR) of FPGAs. The DPR architecture requires input data pre-buffering which introduces delay. These circumstances are first considered in a theoretical analysis and later applied to a broadcast receiver chain, where the benefits and drawbacks of the architecture are highlighted.
The performance of a DRM+ broadcast system using a modified Digital Video Broadcasting (DVB-T2/S2) Low Density Parity-Check (LDPC) code is compared against the standardized system, which uses convolutional coding. By using this modified LDPC code the datarate can be increased by 33 % at a similar bit error rate (BER) performance. Alternatively, the broadcast coverage can be increased. For the purpose of integration, a signaling scheme is proposed, which enables the broadcaster to decide between convolutional coding and LDPC coding without affecting the compatibility of the system. The presented approach allows for using existing DVB-T2/S2 LDPC codec implementations inside a DRM+ broadcast chain.Index Terms-DRM+, LDPC codeword puncturing, LDPC channel coding, VHF channel simulation, DVB-T2/S2 I. MOTIVATION DRM+ is a new standard for digital audio broadcasting in the very high frequency (VHF) domain. In 2004 the design of the system was initiated in order to supplement FM radio and Digital Audio Broadcasting (DAB) in the VHF band. The DRM+ system specification was published by the European Telecommunications Standards Institute (ETSI) in 2009 [1].Like most of the existing digital audio broadcasting standards DRM+ uses a punctured convolutional channel code, which can optionally be combined with a Reed Solomon code for packet data transmissions. Albeit having a moderate decoding complexity, the coding performance of convolutional codes is rather limited compared to state-of-the-art channel coding schemes.In contrast to DRM+, the second generation of Digital Video Broadcasting (DVB) standards use enhanced Forward Error Correction (FEC) mechanisms like LDPC coding for both satellite DVB-S2 [2] as well as terrestrial DVB-T2 broadcasting [3] in order to increase the system performance.In the following sections we will show that by using these LDPC codes inside a DRM+ transmission chain, a significant gain in coding performance can be achieved without violating the framing of the system.
II. PRIOR ARTConvolutional channel coding in DRM+ is almost equal to channel coding in DRM30, the short wave counterpart of DRM+. In [4] the performance of a punctured turbo-code was compared against the performance of the convolutional code using a 16 QAM alphabet for DRM30. In [5] the applicability of turbo codes for DRM30 was evaluated using iterative decoding techniques in a diversity reception scenario.Our work targets the performance of LDPC codes within the DRM+ specific VHF channel environment.
III. DIGITAL RADIO MONDIALE PLUSIn order to provide a basic understanding of the DRM+ system architecture, the key-parameters of the transmission chain are depicted in the subsequent sections.
A. OFDM FramingThe OFDM framing in DRM+ is strictly hierarchical. The top level framing unit is the transmission super frame (TSF) which contains a sequence of N TF = 4 transmission frames (TF) as shown in Figure 1. Each TF wraps N s = 40 OFDM symbols. With an OFDM symbol duration of T s = 2.5 ms, the transmission duration of a TF is T s · N s = 100 ...
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