Digitally encoded speech or digital data is transmitted in four sub-channels at a 4 kHz rate using M-ary symbols mapped to predetermined fixed magnitude and phase components within 1 of 3 constellations associated with a particular modulation scheme.

Figure 6-2 illustrates symbol mapping to one of the four QPSK sub-channels constellations. Figure 6-3 illustrates symbol mapping to one of the four-16QAM sub-channels constellation. Figure 6-4 illustrates symbol mapping to one of the four-64QAM sub-channels constellation.

For Quad-QPSK modulation, this mapping adjusts the amplitude and phase variations of the baseband signal to one of 4 points on the constellation. For Quad-16QAM modulation, this mapping adjusts the amplitude and phase variations of the baseband signal to one of 16 points on the constellation. For Quad-64QAM modulation, this mapping adjusts the amplitude and phase variations of the baseband signal to one of 64 points on the constellation.

The bandwidth of the modulating signals is limited by the pair of modulation limiting low pass filters within the modem block function of U801 (see Figure 4-2 in Exhibit 4.3). These filters serve to limit out-of-band and spurious emissions due to modulation.

The necessary bandwidth of the sub-channels is limited to 4.8 kHz by the pair of modulation limiting low pass filters. The transfer response of these filters is depicted in Figure 6-1 where the filter excess bandwidth coefficient of 0.2 is shown. This excess bandwidth leads to the necessary bandwidth calculation of (1 + 0.2) x (4 kHz) = 4.8 kHz. Since the sub-channels are spaced 4.5 kHz apart, the necessary bandwidth of the composite 4 sub-channel symbol streams is 4.8 + (3 x 4.5) = 18.3 kHz.

Figure 6-1: Modulation Low Pass Filter Response

The modulation low pass filter response is characterized by a root raised cosine function with an alpha (α) of 0.2. The filter's transfer function H(f) is defined as:

• For |f| < 2ω-ω: H(f) = 1
• For 2ω-ω < |f| < ω: H(f) = cos²(π/4 ([f] + ω-2)/(ω-ω))
• For |f| > ω: H(f) = 0

Where ω = 2000 and ω = (1+α) = 2400Hz.

Figure 6-2: Symbol Mapping onto One of Four QPSK Constellations

This diagram illustrates the process from data source to complex symbol stream for QPSK modulation. The data source feeds into a QPSK encoder, which is then interleaved. The interleaved data is processed by a Subchannel Formatter and then sent to the Modem Interface. The output is a complex symbol stream, described as QAM baseband output ready for impression onto a particular subcarrier.

Figure 6-3: Symbol Mapping onto One of Four 16-QAM Constellations

This diagram shows the symbol mapping for 16-QAM modulation. Similar to QPSK, data flows from a Data Source to a 16QAM Encoder, followed by an Interleaver. The output is then combined in a Real to Complex Combiner and processed by a Subchannel Formatter before reaching the Modem Interface. The resulting complex symbol stream is the QAM baseband output ready for impression onto a particular subcarrier.

Figure 6-4: Symbol Mapping onto One of Four 64-QAM Constellations

This diagram depicts the symbol mapping for 64-QAM modulation. The data path includes a Data Source, a 16QAM Encoder (note: this appears to be a typo in the original diagram and should likely be 64QAM Encoder for consistency), an Interleaver, and a Subchannel Formatter. A Real to Complex Combiner processes the signal before it goes to the Modem Interface. The output is a complex symbol stream, which is the QAM baseband output ready for impression onto a particular subcarrier.

Emission Mask

6.3 Emission Mask -- Pursuant 47 CFR 2.1049(h) & 90.210(m)

The method described in paragraph 7.2 was employed with the following conditions:

For Quad-QPSK Modulation:

• 32K Bits Per Second Pseudo-Random Digital Modulation.
• Vertical division: 10 dB/div.
• Carrier Reference: Carrier Reference 0 dB corresponds to maximum and minimum peak output power settings, respectively.

For Quad-16QAM Modulation:

• 64K Bits Per Second Pseudo-Random Digital Modulation
• Vertical: 10 dB/div
• Carrier Reference: Carrier Reference 0 dB corresponds to maximum and minimum peak output power settings, respectively.

For Quad-64QAM Modulation:

• 96K Bits Per Second Pseudo-Random Digital Modulation
• Vertical: 10 dB/div
• Carrier Reference: Carrier Reference 0 dB corresponds to maximum and minimum peak output power settings, respectively.

In Figures 6-5 through Figure 6-22, one trace was used to capture transmitter performance, measured using a resolution bandwidth of 300 Hz, while the reference level was obtained by another trace, using a resolution bandwidth of 30 kHz. A third trace shows the applicable emission mask.

6.3.1 800 MHz Band Operation Measured Data

FCC Limits

Per 47CFR90.210(g)

Per EA SMR GMASK Emission Mask, 47CFR90.691(a)

Figure 6-5: Quad-QPSK Modulation performance relative to GMASK 47 CFR 90.210(g) (MAXIMUM POWER SETTING)

This figure displays the measured Quad-QPSK modulation performance against the GMASK 47 CFR 90.210(g) emission mask at maximum power setting. The trace shows the signal's spectral content, with markers indicating key measurements such as peak power (4.45 dBm) at 820.98760020 MHz. The resolution bandwidth (RBW) was 300 Hz, and the video bandwidth (VBW) was 1 kHz. The reference level was set at 5 dBm.

Figure 6-6: Quad-QPSK Modulation performance relative to GMASK 47 CFR 90.210(g) (MINIMUM POWER SETTING)

This figure shows the measured Quad-QPSK modulation performance against the GMASK 47 CFR 90.210(g) emission mask at minimum power setting. The trace indicates the signal's spectral characteristics, with a marker showing a peak power of -30.45 dBm at 820.98770040 MHz. The RBW was 300 Hz, VBW was 1 kHz, and the reference level was -30 dBm.

Figure 6-7: Quad-QPSK Modulation performance relative to EA-mask 47 CFR 90.691. (MAXIMUM POWER SETTING)

This figure presents the Quad-QPSK modulation performance relative to the EA-mask 47 CFR 90.691 at maximum power. The spectral plot shows the signal's adherence to the mask, with a peak power of 4.45 dBm at 820.98760020 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was 5 dBm.

Figure 6-8: Quad-QPSK Modulation performance relative to EA-mask 47 CFR 90.691. (MINIMUM POWER SETTING)

This figure illustrates the Quad-QPSK modulation performance relative to the EA-mask 47 CFR 90.691 at minimum power. The spectral plot shows the signal's characteristics, with a marker indicating a peak power of -30.45 dBm at 820.98770040 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was -30 dBm.

Figure 6-9a: Quad-16QAM Modulation performance relative to G-Mask 47 CFR 90.210(g) (MAXIMUM POWER SETTING)

This figure displays the measured Quad-16QAM modulation performance against the G-Mask 47 CFR 90.210(g) at maximum power. The spectral plot shows the signal's compliance with the mask, with a peak power of -30.76 dBm at 820.98739980 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was -30 dBm.

Figure 6-10a: Quad-16QAM Modulation performance relative to G-Mask 47 CFR 90.210(g) (MINIMUM POWER SETTING)

This figure illustrates the measured Quad-16QAM modulation performance against the G-Mask 47 CFR 90.210(g) at minimum power. The spectral plot shows the signal's characteristics, with a peak power of -30.45 dBm at 820.98770040 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was -30 dBm.

Figure 6-11a: Quad-16QAM Modulation performance relative to EA-mask 47 CFR 90.691. (MAXIMUM POWER SETTING)

This figure presents the Quad-16QAM modulation performance relative to the EA-mask 47 CFR 90.691 at maximum power. The spectral plot shows the signal's adherence to the mask, with a peak power of 4.45 dBm at 820.98760120 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was 5 dBm.

Figure 6-12a: Quad-16QAM Modulation performance relative to EA-mask 47 CFR 90.691. (MINIMUM POWER SETTING)

This figure illustrates the Quad-16QAM modulation performance relative to the EA-mask 47 CFR 90.691 at minimum power. The spectral plot shows the signal's characteristics, with a peak power of -30.45 dBm at 820.98770040 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was -30 dBm.

Figure 6-13: Quad-64QAM Modulation performance relative to G-mask 47 CFR 90.210(g) (MAXIMUM POWER SETTING)

This figure displays the measured Quad-64QAM modulation performance against the G-mask 47 CFR 90.210(g) at maximum power. The spectral plot shows the signal's compliance with the mask, with a peak power of 4.45 dBm at 820.98760020 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was 5 dBm.

Figure 6-14: Quad-64QAM Modulation performance relative to G-mask 47 CFR 90.210(g) (MINIMUM POWER SETTING)

This figure illustrates the measured Quad-64QAM modulation performance against the G-mask 47 CFR 90.210(g) at minimum power. The spectral plot shows the signal's characteristics, with a peak power of -30.45 dBm at 820.98770040 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was -30 dBm.

Figure 6-15: Quad-64QAM Modulation performance relative to EA-mask 47 CFR 90.691. (MAXIMUM POWER SETTING)

This figure presents the Quad-64QAM modulation performance relative to the EA-mask 47 CFR 90.691 at maximum power. The spectral plot shows the signal's adherence to the mask, with a peak power of 4.86 dBm at 896.01890020 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was 5 dBm.

Figure 6-16: Quad-64QAM Modulation performance relative to EA-mask 47 CFR 90.691. (MINIMUM POWER SETTING)

This figure illustrates the Quad-64QAM modulation performance relative to the EA-mask 47 CFR 90.691 at minimum power. The spectral plot shows the signal's characteristics, with a peak power of -30.45 dBm at 896.01900040 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was -30 dBm.

6.3.2. 900 MHz Band Operation Measured Data

FCC Limits

Per 47 CFR 90.669(a)

Figure 6-17: Quad-QPSK Modulation performance relative to EA-mask 47 CFR 90.669(a) (MAXIMUM POWER SETTING)

This figure displays the measured Quad-QPSK modulation performance against the EA-mask 47 CFR 90.669(a) at maximum power. The spectral plot shows the signal's compliance with the mask, with a peak power of 4.86 dBm at 896.01890020 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was 5.5 dBm.

Figure 6-18: Quad-QPSK Modulation performance relative to EA-mask 47 CFR 90.669(a) (MINIMUM POWER SETTING)

This figure illustrates the measured Quad-QPSK modulation performance against the EA-mask 47 CFR 90.669(a) at minimum power. The spectral plot shows the signal's characteristics, with a peak power of -31.20 dBm at 896.01900040 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was -31 dBm.

Figure 6-19a: Quad-16QAM Modulation performance relative to EA-mask 47 CFR 90.669(a) (MAXIMUM POWER SETTING)

This figure presents the measured Quad-16QAM modulation performance against the EA-mask 47 CFR 90.669(a) at maximum power. The spectral plot shows the signal's adherence to the mask, with a peak power of 4.86 dBm at 896.01890020 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was 5.5 dBm.

Figure 6-20a: Quad-16QAM Modulation performance relative to EA-mask 47 CFR 90.669(a) (MINIMUM POWER SETTING)

This figure illustrates the measured Quad-16QAM modulation performance against the EA-mask 47 CFR 90.669(a) at minimum power. The spectral plot shows the signal's characteristics, with a peak power of -31.20 dBm at 896.01900040 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was -31 dBm.

Figure 6-21: Quad-64QAM Modulation performance relative to EA-mask 47 CFR 90.669(a) (MAXIMUM POWER SETTING)

This figure displays the measured Quad-64QAM modulation performance against the EA-mask 47 CFR 90.669(a) at maximum power. The spectral plot shows the signal's compliance with the mask, with a peak power of 4.86 dBm at 896.01890020 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was 5.5 dBm.

Figure 6-22: Quad-64QAM Modulation performance relative to EA-mask 47 CFR 90.669(a) (MINIMUM POWER SETTING)

This figure illustrates the measured Quad-64QAM modulation performance against the EA-mask 47 CFR 90.669(a) at minimum power. The spectral plot shows the signal's characteristics, with a peak power of -31.20 dBm at 896.01900040 MHz. RBW was 300 Hz, VBW was 1 kHz, and the reference level was -31 dBm.