10.6 The Spectrum Management Classes

   


Early in the development of the spectrum management standard, a proposal was considered to specify a single 0-to-infinity PSD mask that would apply to all systems. Later it was determined that no such single PSD mask would suffice because it would have to be overly restrictive to protect the basis systems. Thus, it was determined that a family of more narrow- band masks would best way to specify an easy-to-use method of determining spectral compatibility.

The spectrum management standard T1.417 defines a set of nine spectrum management classes, whereby any DSL system that meets the PSD limitations, total average power limitations, longitudinal output voltage, and transverse balance requirements for any one of the spectrum management classes is considered to be spectrally compatible with all of the basis systems if they are deployed according to the applicable deployment guidelines associated with that class. Alternatively, deployment guidelines for a system compliant with any of the spectrum management classes may be computed using the analytical method (Method B). It is worth noting that the spectrum management classes represent an overly conservative estimation of many actual subscriber line transmission systems, for example, 2B1Q and single carrier modulation such as CAP or QAM. In such situations applying the specific system's PSD to the computations of Method B may yield a better deployment guideline than that associated with the compliant spectrum management class.

  • Spectrum management classes are meant to be technology independent.

  • The PSD mask defines the absolute upper bound for spectrum management compliance.

  • The PSD template defines a nominal signal characteristic for modeling margin of, and crosstalk due to, technologies using the PSD in reference.

10.6.1 Class 1: Very-Low-Band Symmetric

Spectrum Management Class 1 is intended to accommodate narrowband symmetric (echo canceled ) transmission systems. Both the upstream and downstream channels use the same spectrum. Definition of this class is driven by the definition of ISDN per the standard T1.601. The shape of this mask was designed to accommodate numerous technologies with symmetric spectra up about 115 kHz, including passband CAP systems up to approximately 70 kBaud. Table 10.2 provides a mathematical definition of the SM Class 1 template. Plots of SM Class 1 are provided in Figure 10.4.

Figure 10.4. Spectrum management class 1 template plots.

graphics/10fig04.jpg

The total average power for a spectrum management class 1 system is 14.0 dBm measured into 135 and frequencies below 115 kHz. Systems complying with SM Class 1 are considered to be spectrally compatible on any nonloaded loop facility. As long as the loop is unloaded, there are no distance limitations.

Table 2. Spectrum Management Class 1 Template Definition

Frequency Band (kHz)

PSD (dBm/Hz)

0 < f 25

-32.5

25 < f 76

graphics/10inl01.gif

76 < f 79

graphics/10inl02.gif

79 < f 85

graphics/10inl03.gif

85 < f 100

graphics/10inl04.gif

100 < f 115

graphics/10inl05.gif

115 < f 120

-53

120 < f 225

graphics/10inl06.gif

225 < f 635

graphics/10inl07.gif

635 < f

graphics/10inl08.gif


10.6.2 Class 2: Low-Band Symmetric

Spectrum Management (SM) Class 2 is intended to accommodate symmetric (echo canceled) transmission systems with bandwidths slightly greater than those of SM Class 1. Both the upstream and downstream channels use the same spectrum. Definition of this class is driven by the transport of 384 kb/s symmetric data using 2B1Q technology. The shape of this mask was designed to accommodate numerous technologies with symmetric spectra up about 238 kHz. In this class passband CAP systems could support symbol rates up to approximately 120 kBaud. Table 10.3 provides a tabular definition of the SM Class 2 template. The template is constructed using linear interpolation of the frequency in kHz and the PSD in dBm/Hz. Plots of SM Class 2 are provided in Figure 10.5.

Figure 10.5. Spectrum Management Class 2 template plots.

graphics/10fig05.jpg

Note : The interpolation formula for computing the PSD(f) values at intermediate frequencies is provided as follows . The PSD(f) has values of PSD 1 at frequency f 1 and PSD 2 at frequency f 2 , then the intermediate PSD(f) values in the frequency range of f 1 f < f 2 is

graphics/10equ01.gif


The total average power for an SM Class 2 system is 14.0 dBm measured into 135 and frequencies below 238 kHz. Systems complying with SM Class 2 are considered to be spectrally compatible on nonloaded loop facilities with an equivalent working length (of 26-gauge wire) of 11.5 kft or less.

Table 10.3. Spectrum Management Class 2 Template Definition

Frequency (kHz)

PSD (dBm/Hz)

-36

25

-36

75

-36.5

100

-39

150

-45

200

-54

230

-64

245

-71

335

-72

390

-76

440

-83

475

-90

500

-98

500 < f

graphics/10inl09.gif


For any subscriber loop implemented with a mixture of 26-gauge and 24-gauge wire, the loop can be expressed with an equivalent working length (EWL) of 26 gauge, which approximates a 26-gauge loop having roughly the same insertion loss as the mixed gauge cable. The EWL is computed by graphics/10inl10.gif ,where L 26 is the total length of 26-gauge wire and L 24 is the total length of 24-gauge wire.

Table 10.4. Spectrum Management Class 3 Template Definition

Frequency (kHz)

PSD (dBm/Hz)

-37

50

-37

125

-38

210

-41

310

-57

370

-73

550

-75

670

-85

750

-97

980

-98

1050

-102.75

1050 < f

graphics/10inl11.gif


10.6.3 Class 3: Mid-Band Symmetric

Spectrum Management Class 3 is intended to accommodate symmetric transmission systems with bandwidths greater than those of SM Classes 1 and 2. Both the upstream and downstream channels use the same spectrum. Definition of this class is driven by the definition of HDSL that transports 784 kb/s symmetric data using 2B1Q technology. The shape of this mask was designed to accommodate numerous technologies with symmetric spectra up about 370 kHz. In this class passband CAP systems could support symbol rates up to approximately 200 kBaud. Table 10.4 provides a tabular definition of the SM Class 3 template. The template is constructed using linear interpolation of the frequency in kHz and the PSD in dBm/Hz. Plots of SM Class 3 are provided in Figure 10.6.

Figure 10.6. Spectrum Management Class 3 template plots.

graphics/10fig06.gif

Table 10.5. Spectrum Management Class 4 Template Downstream Definition

Frequency (kHz)

PSD (dBm/Hz)

Frequency (kHz)

PSD (dBm/Hz)

Frequency (kHz)

PSD (dBm/Hz)

1

-54.2

280

-35.7

1000

-89.2

2

-42.2

375

-35.7

2000

-99.7

12

-39.2

400

-40.2

>3000

-108

190

-39.2

440

-68.2

   

236

-46.2

600

-76.2

   

The total average power for an SM Class 3 system is 14.0 dBm measured into 135 and frequencies below 370 kHz. Systems complying with SM Class 3 are considered to be spectrally compatible on nonloaded loop facilities with an EWL of 9 kft or less.

10.6.4 Class 4: HDSL2

SM Class 4 was included to accommodate HDSL2 (T1.418-2000) “based systems in the spectrum management standard. Because the SM classes are meant to be technology independent, any transmission systems whose spectra meets the Class 4 template would be considered to be spectrally compatible with the basis systems. The downstream spectrum utilizes frequencies up to about 400 kHz and the upstream spectrum utilizes frequencies up to about 300 kHz. Table 10.5 and Table 10.6 provide a tabular definition of the SM Class 4 template. Plots of SM Class 4 are provided in Figure 10.7 and Figure 10.8.

Figure 10.7. Spectrum Management Class 4 downstream template plot.

graphics/10fig07.gif

Figure 10.8. Spectrum Management Class 4 upstream template plot.

graphics/10fig08.jpg

The total average power for the downstream channel of a spectrum management Class 4 system is 17.3 dBm measured into 135 and frequencies below 450 kHz. The total average power for the upstream channel of a spectrum management Class 4 system is 17.0 dBm measured into 135 and frequencies below 350 kHz. Systems complying with SM Class 4 are considered to be spectrally compatible on nonloaded loop facilities with an EWL of 10.5 kft or less.

10.6.5 Class 5: Asymmetric

SM Class 5 is intended to accommodate ADSL (T1.413-1998) in the SM standard. Specifically, Class 5 favors the frequency division duplex (FDD) configuration of ADSL where the upstream and downstream channels use separate frequency bands, but overlap is permitted in the low frequency bands that are common with SM Class 1. The downstream frequency spectrum uses frequencies from about 25 kHz to about 1104 kHz and the upstream frequency spectrum uses frequencies from about 25 kHz to about 138 kHz. Table 10.7 provides a mathematical definition of the SM Class 5 template. Plots of SM Class 5 are provided in Figure 10.9.

Figure 10.9. Spectrum Management Class 5 template plots.

graphics/10fig09.gif

Table 10.6. Spectrum Management Class 4 Template Upstream Definition

Frequency (kHz)

PSD (dBm/Hz)

Frequency (kHz)

PSD (dBm/Hz)

Frequency (kHz)

PSD (dBm/Hz)

1

-64.2

220

-34.4

555

-102.6

2

-42.1

255

-34.4

800

-105.6

10

-37.8

276

-41.1

1400

-108

175

-37.8

300

-77.6

2000

-108


Table 10.7. Spectrum Management Class 5 Template Definition

Frequency Band (kHz)

PSD (dBm/Hz)

0 < f 4

-101, with max power in the in 0 “4 kHz band of + 15 dBm

4 < f 25.875

-96 + 21 x log 2 (f/4)

25.875 < f 81

-40

81 < f 92.1

-40-70 x log 2 (f/81)

92.1 < f 121.4

-53

121.4 < f 138

-53 + 70 x log 2 (f/121.4)

138 < f 1104

-40

1104 < f 3093

-40-36 x log 2 (f/1104)

3093 < f 4545

min(-36.5-36 x log 2 (f/1104),-93.5)

4545 < f 11040

-110


The total average power for the downstream channel of a spectrum management Class 5 system is 20.9 dBm measured into 100 and frequencies between 25 kHz and 1104 kHz. The total average power for the upstream channel of an SM Class 4 system is 13 dBm measured into 100 and frequencies between 25 kHz and 138 kHz. Systems complying with SM Class 5 are considered to be spectrally compatible on any nonloaded loop facilities. As long as the loop is unloaded, there are no distance limitations.

10.6.6 Class 6:Wide-Band Asymmetric

This spectrum management class is intended to accommodate asymmetric VDSL transmission systems that utilize the frequency spectrum up to about 10 “20 MHz. SM Class 6 should be based on the emerging VDSL standards, and at the time of the writing of T1.417, the VDSL standard was not completed. Therefore the template for the SM Class 6 is not yet defined and left as a placeholder for inclusion of the VDSL standard once it is complete.

10.6.7 Class 7: Very-Wide-Band Symmetric

SM Class 7 is another symmetric spectrum, which was designed to accommodate single pair 1.5 Mb/s 2B1Q systems. Both the upstream and downstream channels use the same spectrum. The shape of this mask was designed to accommodate numerous technologies with symmetric spectra up to about 776 kHz. In this class passband, CAP systems could support symbol rates up to approximately 400 kBaud. Table 10.8 provides a tabular definition of the SM Class 7 template. The template is constructed using linear interpolation of the frequency in kHz and the PSD in dBm/Hz. Plots of SM Class 7 are provided in Figure 10.10.

Figure 10.10. Spectrum Management Class 7 template plots.

graphics/10fig10.jpg

The total average power for an SM Class 7 system is 14.0 dBm measured into 135 and frequencies below 776 kHz. Systems complying with SM Class 7 are considered to be spectrally compatible on nonloaded loop facilities with an EWL of 6.5 kft or less.

10.6.8 Class 8: Wide-Band Symmetric

SM Class 8 is yet another symmetric spectrum, which was designed to accommodate single pair 1.1 Mb/s 2B1Q systems. Both the upstream and downstream channels use the same spectrum. The shape of this mask was designed to accommodate numerous technologies with symmetric spectra up about 584 kHz. In this class passband, CAP systems could support symbol rates up to approximately 300 kBaud. Table 10.9 provides a tabular definition of the SM Class 8 template. The template is constructed using linear interpolation of the frequency in kHz and the PSD in dBm/Hz. Plots of SM Class 8 are provided in Figure 10.11.

Figure 10.11. Spectrum Management Class 8 template plots.

graphics/10fig11.jpg

Table 10.8. Spectrum Management Class 7 Template Definition

Frequency (kHz)

PSD (dBm/Hz)

Frequency (kHz)

PSD (dBm/Hz)

-40

775

-77

100

-40

1000

-77

150

-40.5

1100

-80

200

-41.5

1300

-86

300

-42

1500

-102

390

-42

1900

-104

420

-43

2000

-107

500

-51

>2000

graphics/10inl12.gif


The total average power for an SM Class 8 system is 14.0 dBm measured into 135 and frequencies below 584 kHz. Systems complying with SM Class 8 are considered to be spectrally compatible on nonloaded loop facilities with an EWL of 7.5 kft or less.

10.6.9 Class 9: Overlapping Asymmetric

SM Class 9 is intended to accommodate ADSL (T1.413-1998) with overlapping upstream and downstream spectra in the SM standard. The downstream frequency spectrum uses frequencies from about 25 kHz to about 1104 kHz, and the upstream frequency spectrum uses frequencies from about 25 kHz to about 138 kHz. Table 10.10 provides a mathematical definition of the SM Class 9 template. Plots of SM Class 9 are provided in Figure 10.12.

Figure 10.12. Spectrum Management Class 5 or Class 9 upstream template plots.

graphics/10fig12.jpg

The total average power for the downstream channel of an SM Class 9 system is 20.9 dBm measured into 100 and frequencies between 25 kHz and 1104 kHz. The total average power for the upstream channel of an SM Class 4 system is 13 dBm measured into 100 and frequencies between 25 kHz and 138 kHz. Systems complying with SM Class 9 are considered to be spectrally compatible on any nonloaded loop facilities. As long as the loop is unloaded, there are no distance limitations.

Table 10.9. Spectrum Management Class 8 Template Definition

Frequency (kHz)

PSD (dBm/Hz)

Frequency (kHz)

PSD (dBm/Hz)

Frequency (kHz)

PSD (dBm/Hz)

-39

400

-53

1120

-95

60

-39

500

-66

1500

-95

200

-40

550

-75

2000

-107

250

-40.5

750

-76

>2000

graphics/10inl13.gif

315

-41

950

-84

   


   
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DSL Advances
DSL Advances
ISBN: 0130938106
EAN: 2147483647
Year: 2002
Pages: 154

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