DRM+ employs Orthogonal Frequency Division Multiplexing (OFDM) with Quadrature Amplitude Modulation (QAM). Details of the sub-carrier structure and modulation are in Table 1. 1 DRM+ Modulation scheme Modulation COFDM Number of sub-carriers 213 Sub-carrier spacing 444 Hz Modulation (data carriers) 4-QAM or 16-QAM Bandwidth 96 kHz The spectrum emission and transmitter masks for DRM+ are shown in Fig. 1 and Table 2 below. 1 Spectrum mask for DRM+ and FM TABLE 2 Spectrum masks for FM and DRM+ ETSI mask for FM DRM+ mask Offset Rel. level (1 kHz) Offset Rel. Level (1 kHz) Attenuation –400 kHz –85,0 dB –400,00 kHz –85,0 dB –65,0 dB –300 kHz –85,0 dB –300,00 kHz –85,0 dB –65,0 dB –200 kHz –80,0 dB –200,00 kHz –80,0 dB –60,0 dB –100 kHz 0,0 dB –100,00 kHz –70,0 dB –50,0 dB 100 kHz 0,0 dB –70,00 kHz –50,0 dB –30,0 dB 200 kHz –80,0 dB –50,00 kHz –20,0 dB 0,0 dB 300 kHz –85,0 dB 50,00 kHz –20,0 dB 0,0 dB 400 kHz –85,0 dB 70,00 kHz –50,0 dB –30,0 dB 100,00 kHz –70,0 dB –50,0 dB 200,00 kHz –80,0 dB –60,0 dB 300,00 kHz –85,0 dB –65,0 dB 400,00 kHz –85,0 dB –65,0 dB The DRM+ signal can be offsets of multiples of 10 kHz from the nominal centre frequency. This feature can be further exploited by placing two DRM+ signals side by side, offset by –50 kHz and +50 kHz from the classical FM carrier frequency, so as to fill the nominal 200 kHz ETSI FM mask bandwidth. This “double DRM+” mask is shown in Fig. 2 and Table 3 below. FIGURE
Speed (km/h) 0 (static) 55, 100 (driving) 0 (quasi static) Indicated antenna noise @10 kHz BW (dBµV/m) 23.5 23.5 23.5 MA3 – 10kHz Minimum carrier strength Emin (dBµV/m) For receiving PL+PU 36.5 + Lp 36.5 + Lp 36.5 + Lp MA3 – Minimum carrier field strength Emin (dBµV/m) For receiving PL+PU 36.5 + Lp 36.5 + Lp 36.5 + Lp TABLE 22 Minimum Usable Carrier Field Strength for HD Radio All Digital Configuration Secondary Bands Reception based on Noise Level (parametric values) Reception mode FX MO Channel symbol Environment Suburban/Urban Suburban/Urban Speed (km/h) 0 (static) 55, 100 (driving) 0 (quasi static) Indicated antenna noise @10 kHz BW (dBµV/m) 23.5 23.5 23.5 MA3 – 20kHz Minimum carrier field strength Emin (dBµV/m) For receiving SL+SU 36.5 + Ls 36.5 + Ls 36.5 + Ls 4 Laboratory and field testing 4.1 Test program All of the tests were conducted pursuant to laboratory and field test procedures the National Radio Systems Committee developed. Those procedures were designed to assess both the digital performance of the system and the system’s compatibility with existing analogue MF operations. The tests were conducted using receivers the NRSC selected as representative of the range of receiver characteristics in the marketplace. The test receivers are listed in Table 23 below. TABLE 23 List of test receivers Type Manufacturer No. Original Equipment Auto Delphi PN 09394139 Aftermarket Auto Pioneer KEH–1900 Home Hi–Fi Technics SA–EX140 Portable Sony CFD–S22 The objective laboratory performance tests were conducted at the Advanced Television Technology Center (“ATTC”) in Alexandria, Virginia. The objective laboratory compatibility tests were conducted at Xetron Corporation (“Xetron”) in Cincinnati, Ohio. In addition to these objective measurements, the ATTC and Xetron recorded audio samples for both the digital and analogue
mV/m: millivolts per meter (Field Strength) NIF: Night–time Interference Free Contour EXP: Experimental Test Station 43 Station WBCN Daytime Coverage 44 Station WBCN Night–time Coverage Station Freq (kHz) Class TX power D/N (kW) POF day (mi) Pred. contour (mV/m) POF night (mi) NIF (mV/m) OUT TO NIF? WBCN 1660 B 10/1 26–45 0.5–0.1 10–14 5.1 YES 45 Station WNCT Daytime Coverage 46 Station WNCT Night–time Coverage Station Freq (kHz) Class TX power D/N (kW) POF day (mi) Pred. contour (mV/m) POF night (mi) NIF (mV/m) OUT TO NIF? WNCT 1070 B 25/10 25–68 >0.5 4–20 53 YES 47 Station WBT Coverage FIGURE FIGURE FIGURE FIGURE FIGURE
7.1 Field Test Results Testing in Cincinnati evaluated data service coverage in comparison with service coverage. Table 46 summarizes the packet error rate information for various test routes in the market. The results were consistent with the lab testing and support the findings that smaller packet sizes have few effective errors in the mobile environment. The coverage maps provided in Fig. 89 through Fig. 100 compare the service area of the data with the service area of the audio. The results for the Edge conditions highlight the extended coverage area for data applications. TABLE 46 Station WVMX Mobile Data PER Data Packet Size Inner Loop Outer Loop Edge 64 bytes 0.0 % 4.6 % 3.5 % 256 0.0 % 6.4 % 5.5 % 1024 bytes 0.0 % 6.6 % 7.1 % 2048 bytes 0.0 % 9.9 % 8.5 % 89 Station WVMX loop audio coverage 90 Station WVMX inner loop data coverage 64–byte packets 91 Station WVMX outer loop audio coverage 92 Station WVMX outer loop data coverage 64–byte packets
TX Power/ Block Antenna type ERP Antenna height above ground Site height above sea Azimuth Polarization 1000W/ 12D VHF 2 bays 5kW 80m 149m Directive 105° Vertical The predicted field strength at 10m height for the two transmitters (red and black icons) operating in SFN on block 7B is detailed in Fig. 131. Figure 129 predicted field strength @10m for CAG and CVA FIGURE 131 Legend for threshold colors: Fs≥ 90dBV/m Fs≥ 78dBV/m Fs≥ 68dBV/m Fs≥58dBV/m Preliminary measurements of field strength at 10m height in pre–determined fixed points were performed with the following equipment: – Rhode & Schwarz Test Receiver ESPI 3 with pre–selector, RMS detector, bandwidth 1 500 kHz; – Calibrated ground plane antenna built by Vatican Radio; – 10 m pneumatic telescopic mast; – Calibrated RG214 cable. The table below shows the results of the measurements, test points are also detailed in Fig. 131. Test Point Block LAT LON Voltage at the receiver input Eq. field strength dBµV dBµV/m A 7B 41.96342 12.5691 60.6 68.4 B 7B 41.8107 12.58194 71.4 79.2 C 7B 12.54241 72.6 80.4 D 7B 41.89569 12.18185 57.51 65.31 E 7B 41.69453 12.59892 74.75 82.55 F 7B 12.49099 65.5 73.3 The minimum field strength required by ITU–R Rec. BS.1660–6 was reached in all considered points. The measured field strength values were quite close to the predicted ones. 4 Mobile measurements, coverage verification In order to check the performances of the network operating on block 7B, mobile measurements were carried out with the following equipment: