An assessment of propagation models for digital television broadcast network in the Ashanti Region of Ghana

Abstract

In radio communication, signal losses are major factor in transmission. To this end, various propagation models have been used in the field of transmission engineering to minimised transmission losses. With the introduction of Digital Terrestrial Transmission (DTT) and the subsequent migration from analogue to digital transmission, it is worthwhile to define which propagation model would best fit this digital migration in any area. Using Ashanti Region of Ghana as a case study, this project examined the behaviour of digital transmission by analysing three signal propagation models – Free Space, the ITU_R P.370 propagation prediction and the Extended COST 231 HATA models. Plots of graphs showed that the ITU-R P370 prediction propagation model predicted relatively poor signal strength as compared to the ideal Free Space path loss propagation model. The study also observed that there was a large disparity between the deviations of the ITU-R P370 model and Free Space path loss model. Results obtained from the investigations, indicated that the Extended COST 231 Hata model delivers a more consistent received power and loss prediction as compared to REC ITU-R P.370. The REC ITU-R P.370 propagation prediction model had limitation since it was developed for limited kinds of land. The study therefore concluded that the Extended COST 231 HATA model performed better than the REC ITU-R P.370 model. The study recommended that for a good reception of the digital terrestrial transmission in Ashanti region, there is the need for gap-filler. This can be achieved by siting repeaters and boosters at convenient locations to maintain or improve the transmitting power. It further recommended the use of a geographical information system to store geographical locations points for every 10 m 2 and their corresponding categories.