The advancement in multimedia system triggers the development of the digital television system. Anumber of standards have been proposed, such as Digital Video Broadcasting (DVB), Digital MultimediaBroadcasting (DMB), Integrated Service Digital Broadcasting (ISDB), and Advanced Television SystemsCommittee (ATSC) 1.
Although there are many available standards, most of the countries around the worldadopted DVB system for their national television system standard. DVB is a suite of internationally acceptedopen standards for digital television. DVB standards are maintained by the DVB Project, an internationalindustry consortium with more than 270 members, and are published by a Joint Technical Committee (JTC) ofthe European Telecommunications Standards Institute (ETSI), European Committee for ElectrotechnicalStandardization (CENELEC) and European Broadcasting Union (EBU). DVB system consists of a number ofapproaches in delivering the broadcast content, such as DVB-T/T2 (terrestrial), DVB-S/S2 (satellite), DVB-C/C2 (cable), DVB-H/SH (handheld). DVB-T was selected in this research due to the free-to-air scheme andit is still widely used by many operators around the world, although DVB-T2 has been introduced. The DVB-T system uses MPEG-2 Transport Stream (MPEG-2 TS) as the input stream. This streamis transmitted over the channel through DVB-T system. During transmission, the stream might be affected bychannel impairments, such as noise, which may decrease the video quality that received by the end user.
Thisproblem must be able to be detected and identified by the DVB-T system in order to maintain the picture qualityin a good condition. One of the solutions in combating such situation is to increase power. However, increasing power without monitoring channel condition might lead to power inefficiency. As the channel condition changeover time, thus power adaptation is required in order to maintain power efficiency. Adaptive power control ispart of link adaptation strategy, particularly explicit link adaptation. Link adaptation techniques have gainedincreasing attention for improving the quality of wireless multimedia communication schemes 2-4. In explicitlink adaptation, transmission parameters such as the signal power, the modulation constellation, or the amountof redundancy provided for error control are explicitly adjusted to compensate for the variations in channelconditions. For these purposes, channel state information (CSI) needs to be estimated at the receiver and thencommunicated back to the transmitter 2.
This feedback enables the transmitter to adapt transmissionparameters on a regular basis in response to the CSI at the time. In this research, adaptive power control wasselected since it has lower complexity than adaptive modulation and adaptive coding. Adapting the power of the transmit signal in order to account for signal fades that are caused bymultipath propagation or other channel impairments, results in the channel being used more efficiently.
Thiscan be achieved by controlling the power in such a way that it takes advantage of favorable channel conditions5. The overall objective of power control is to conserve as much transmit power as possible while at the sametime maintaining satisfactory link quality for a wide range of channel conditions. The advantages of powercontrol include longer battery life 6 and high resolution with respect to adapting to small variations in thechannel quality. On the other hand, power control techniques may result in an undesirable increase of co-channel interference. Although power control schemes can be classified in many different ways, the focus ofthis research is on metrics that are used to initiate the power control algorithm. There are four differentmeasurements that can be used to indicate link quality and hence can be deployed with power controlalgorithms. These are referred to as strength-based 6, signal-to-interference-ratio (SIR) based 6, BER-based6 and perceptual quality (PQ) based power control 7.
This paper is organized as follows. In Section 2, research methods, which contain research approachand design, are discussed. Section 3 presents experiment setup, results from the experiments, and analysis ofthe results. Finally, concluding remarks and future works are given in Section 4.