NTSC in-band data broadcasting using orthogonal frequency division multiplexing

This paper presents a new data broadcasting technique for transmitting data using the orthogonal frequency division multiplexing modulation scheme, within the NTSC television signal. The data signal is inserted in the vestigial sideband of the video signal. The advantages of this implementation are that the shape of the data spectrum minimizes the degradation of the picture quality and increases the noise margin of the data signal. Two approaches are taken to evaluate the performance of this system. In the first one, computer simulations are used to determine the available bit rate by varying the number of carriers. Bit error rate measurements are also done to evaluate the performance of the system when the data signal is combined with the NTSC television signal. In the second approach, the perceptual impact is determined, using accepted subjective assessment methodology, when varying levels of OFDM carriers are injected into the NTSC signal. The results show that the proposed system has the potential to offer higher data rate throughput than existing data broadcasting systems, with negligible degradation effects on the NTSC picture quality