Reconfigurable Baseband Processing for Wireless Communications - Adaptive Signal Processing in Wireless Communications - page 460

broadcast has been completely turned of. Additionally, 88% of the United Kingdom is
already covered with DAB.
One common characteristic of the digital radio systems is that they all employ orthog-
onal frequency division multiplexing (OFDM). Although digital radio standards are all
OFDM based, many differences exist. Characteristic OFDM properties vary between
the different standards, but the characteristics of the OFDM receiver can even change
within one standard, because different modes are defined (see Table 15.6 ) . Moreover, for
all digital radio standards different source coding techniques are applied, i.e., MPEG-1
Layer 2 Audio Coding (MP2) or Advanced Audio Coding (AAC).
The identified DSP kernels in digital broadcasting receivers are based on the generic
OFDM receiver framework ( Figure 15.10 ). Mapping digital broadcasting receivers on
the heterogeneous reconfigurable SoC can be done in a manner similar to the Hiper-
LAN/2 implementation approach. The DSP kernels in, e.g., the DAB, DRM, and DVB
receiver are similar to those in the HiperLAN/2 receiver and can be mapped to the SoC
in the same manner as in Figure 15.11 .

15.3.1.5.1 Digital Audio Broadcasting
The Digital Audio Broadcasting standard has been in existence since the early 1980s.
The standard was initiated to replace the analog FM radio services and has already been
adapted by many countries all over the world. DAB is capable of delivering data and
audio services to end users. Data services are performed via packet transfers.
Figure 15.12 depicts the basic DAB receiver structure. After frequency and gain cor-
rection (AFC/AGC) of the DAB signal, the received signal is OFDM demodulated by
means of a fast Fourier transform (FFT) (referred to as inverse OFDM) and differential
quadrature phase shift keying (QPSK) demodulation. Then, the FEC decoding is applied
by means of deinterleaving and Viterbi decoding. In the last stage of the receiver, the
user data are demultiplexed and source decoded using the MP2 codec to audio.

15.3.1.5.2 Digital Radio Mondiale
Digital Radio Mondiale (DRM), approved as an ETSI standard in 2001, is proposed to
replace the analog AM radio service for frequencies below 30 MHz. The DRM system deliv-
ers near-FM quality sound over short-wave, medium-wave, and long-wave radio channels.
Figure 15.13 shows the basic structure of the DRM receiver. In the first stage of the
receiver, the FFT is applied to the received OFDM signal. All separate OFDM carri-
ers are demodulated using the appropriate hierarchical constellation (BPSK, QPSK,

Inverse
OFDM

Differential
de-modulator

Frequency
de-interleaver

AFC
AGC

OFDM
symbols

QPSK
symbol
de-mapper

Time
de-interleaver

Viterbi
decoder

Audio
decoder

FIgure 15.12 DAB receiver structure.