In 188 bytes per frame. The channel encoders consist

In this section, the design of power adaptive DVB-T system that includes DVB-T system block and
the adaptive power control block will be discussed. The main DVB-T system that was used during the
simulation process using Simulink software is shown in Figure 1. As shown in Figure 1, DVB-T transmission system takes the input from file in MPEG2-TS or MPEG2
Transport Stream format. Input data is segmented into frames with the length of 188 bytes per frame. The
channel encoders consist of outer and inner encoders. For outer encoders, Reed Solomon (RS)(255,188) code
was used. This is the reason behind 188 bytes as an input frame length. For the inner encoder, punctured
convolutional code with rate 3/4 was used 8. Outer and Inner interleaver were also used to reduce the impact
of burst errors by improving the performance of forward error correction codes. The modulation scheme used
in the experiment is 64-QAM with 2K-mode Orthogonal Frequency Division Multiplexing (OFDM)
transmitter. Outer and Inner decoders were used in the receiver, where Viterbi decoder was used as the inner
decoder. The channel used during the simulation is adaptive white Gaussian noise (AWGN) channel. The
system block produced 188 bytes of output frame for every 188 bytes of input frame.

As shown in Figure 2, the proposed DVB-T adaptive power control method is presented. The method
consists of picture quality assessment algorithm, feedback channel, and power adaptation scheme. Many different picture quality assessment methods can be used, such as full-reference (a received image is compared
with the original or source picture), reduced-reference (features from the received picture are extracted and
compared with corresponding stored features of the original or source picture), and no-reference (does not
require prior knowledge about the original or source image but performs assessment of the received
image/blind assessment) 9. However, for real-time picture quality monitoring, the no-reference (NR) is the
most suitable method, since no extra information is needed to be communicated to the receiver, as well as no
prior knowledge about the original picture is required. For real implementation, the feedback or return channel
from the receiver to the transmitter for DVB-T system can be based-on general packet radio service (GPRS)
or other suitable methods, since the picture quality data is only a few bits in length. The measurement interval
can be predefined, for example every 50 frames or every 100 frames. The quality will be the average quality
of 50 frames or 100 frames, which will be depended upon the selected predefined interval. Power adaptation
scheme will be based on this quality information. When the quality is below a certain predefined quality
threshold, then the power will be increased. The power will be decreased when the quality is greater or equal
to the threshold. By adapting the power of the transmitter, the picture quality will be maintained in good quality
while at the same time maintaining the power efficiency.

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