An improved method of peak-to-average power ratio reduction for FM+IBOC broadcast transmission

The roll out of HD Radio broadcasting is at a crucial crossroads in the history of this digital audio broadcasting standard. Before widespread adoption of the standard can be anticipated among broadcasters and listenership, the transmission of the HD Radio signal must be strengthened to deliver solid HD Radio reception to a population base comparable to that of the established FM service. Various broadcasters have noted a significant shortfall in the HD Radio coverage area with the HD Radio signal as it is presently defined. A proposal to increase the power in the HD Radio signal has been presented to the FCC and is awaiting approval. The technical challenges associated with this power increase are detailed in this report.;The proposed power increase significantly impacts a station's HD Radio conversion costs and continued cost of listenership unless creative solutions are found that address the technical challenges associated with the HD Radio power increase. Common amplification of the hybrid IBOC and FM waveform with elevated HD Radio power levels develops instantaneous power peaks of 4 dB to 4.5 dB above the average power level of the hybrid waveform. This requires broadcast transmitters to provide additional amplifier capacity of 150% to 180% above the average power level, increasing initial transmitter installation costs and decreasing amplifier efficiency.;The improved method of peak-to-average power reduction presented in this report demonstrates that a 15% to 30% reduction in peak power requirements can be obtained by modifying the standard peak power reduction method, which only operates on the HD Radio signal, to operate on the combined hybrid waveform of both the FM and HD Radio broadcast signals. Through the improved DSP algorithm, the reduction in peak power drops the additional amplifier capacity to around 105% compared to the 50% additional capacity required at present HD Radio power levels. About 5% in transmitter efficiency can be re-claimed, but specific measurments have yet to be taken. Hence, the proposed peak reduction method can ease the transition to elevated HD Radio power levels by decreasing HD Radio conversion costs and cost of listenership. This report also demonstrates that the receivability of the proposed peak reduced signal is comparable to the standard HD Radio signal as shown in AWGN bit error tests and on-air test results. Additional gains in peak reduction may yet be achieved by investigating the advanced concepts listed as future work items.;The report recommends to proceed with full productization of the proposed PAPR reduction method in order to aid the transition to elevated carrier levels and increase HD Radio coverage.