4 Home task

ADSL equipment by the action of uniformly distributed noise in the spectrum is adapted to new conditions of the transmission. This equipment automatically changes the modulation QAM-64 to the QAM-64 at all used carriers. Calculate the transmission rate for the given type of DSL in the upstream and downstream directions before and after adaptation.

Variant for the calculation is chosen of the table. 4.1.

Comment: The frequency of information frames (symbols) is 4000Hz.

Table. 4.1 – Input data for home work

№ of brigade	Variant of xDSL transmission system and ITU-T recommendation	Quantity of used carriers in one direction (pcs)
		From a subscriber/to a subscriber
1	ADSL (G.992.1)	26/224
2	ADSL (G.992.1)	18/176
3	ADSL G.Lite (G.992.2)	26/52
4	ADSL G.Lite (G.992.2)	15/35
5	ADSL2+ (G.992.5)	26/289
6	ADSL2+ (G.992.5)	13/395
7	ADSL2+ (G.992.5)	26/480
8	ADSL2+ (G.992.5)	22/317

For example, given type of transmission system is ADSL (G.992.1); quantity of carriers is 20 in the upstream direction and 200 in the down stream direction.

Than the calculation of transmission rate is:

In the upstream direction:

Before adaptation 20 х 4000 Hz х 6 bit = 480 кbit/s

After adaptation 20 х4000 Hz х 2 bit = 160кbit/s

In the downstream direction:

Before adaptation 200 х 4000 Hz х 6 bit = 4800 кbit/s

After adaptation 200 х4000 Hz х 2 bit = 1600 кbit/s

5 Laboratory task

5.1 DSL variant studied (cable core diameter of ТПП type and the type SP) is selected from the table.

Table 5.1 – Variants of researching DSL

№ brigade	Linear and station DSL equipment		Note
	Cable	Type of TS xDSL
	core diameter, d1 и d2, mm
1	0,32; 0,5	ADSL	-
2		ADSL2+	-
3	0,4; 0,64	VDSL А	frequency plan А
4		VDSL B	frequency plan B
5	0,32; 0,4	ADSL	-
6		ADSL2+	-
7	0,5; 0,64	VDSL A	frequency plan А
8		VDSL B	frequency plan B

5.2 Calculate and research amplitude-frequency (AFC) and phase-frequency (PFC) characteristics graphs of a cable pair with 1 km length for core cable diameter using the software (SW) xDSL-Liner and according to the table. 5.1.

Construct frequency and phase response sketches for various diameters of cable in the workbook in the same coordinate system. Write down the conclusions about the sketches.

Attention! In order to establish units kHz or MHz on the horizontal axis, it is necessary in the main window click on "View" button and "Calibration of the X-axis" press "Frequency, kHz" or "Frequency, MHz".

5.3 Research of the data transfer rate (bitrate) dependence for a given variant of the DSL (Table 5.1) on the line length and core cable diameter if the power spectrum density (PSD) of white (uniform over the spectrum) noise is equal to minus 120 dBm / Hz. The research results should be recorded in the Table. 5.2.

Table 5.2-Transfer rate (bitrate) dependence on DSL length and core cable diameter

core diameter	DSL length, km		0,5	1	1,5	2	2,5	3	3,5
d1	Bitrate, Мbit/s	RU (from subscriber)
		RD (to subscriber)
d2		RU (from subscriber)
		RD (to subscriber)

Build the following sketches of the bitrate dependence on the line length according to the research (see application to LR):

1) transition rate series dependency in the uplink direction RU (Mbit/s) on the DSL length L (km) for various core cable diameter;

2) transition rate series dependency in the downward direction RD (Mbit/s) on the DSL length L (km) for various core cable diameter.

Write down the conclusions about the results of completed researches in Section 5.3.

5.4 Research the bitrate dependence on power spectrum density (PSD) noise, cable length and core cable diameter which is given by version of TS xDSL, table 5.3-5.5.

Attention! SPD noise value in the line must be installed on the station as well as on the subscriber side, for each calculation, carried out by software xDSL-Liner.

Table 5.3 – The bitrate dependence on power spectrum density (PSD) noise for 1 km cable length of DSL with various core cable diameters

Core diameter, mm	SPD noise, dBp/Hz		–140	–130	–120	–110	–100	–90
d1	Bitrate, Мbit/s	RU (from subscriber)
		RD (to subscriber)
d2	Bitrate, Мbit/s	RU (from subscriber)
		RD (to subscriber)

Table 5.4 – The bitrate dependence on power spectrum density (PSD) noise for 2 km cable length of DSL with various core cablediameters

Core diameter, mm	SPD noise, dBp/Hz		–140	–130	–120	–110	–100	–90
d1	Bitrate, Мbit/s	RU (from subscriber)
		RD (to subscriber)
d2	Bitrate, Мbit/s	RU (from subscriber)
		RD (to subscriber)

Table 5.5 – The bitrate dependence on power spectrum density (PSD) noise for 3 km cable length of DSL with various core cablediameters

Core diameter, mm	SPD noise, dBp/Hz		–140	–130	–120	–110	–100	–90
d1	Bitrate, Мbit/s	RU (from subscriber)
		RD (to subscriber)
d2	Bitrate, Мbit/s	RU (from subscriber)
		RD (to subscriber)

According to calculations, build three following charts (see application to LR) which are in the table. 5.3 - 5.5:

1) R_U and R_D dependence (Mbit/s) on PSD noise for 1 km length of DSL, at different core cable diameters;

2) R_U and R_D dependence (Mbit/s) on PSD noise for 2 km length of DSL, at different core cable diameters;

3) R_U and R_D dependence (Mbit/s) on PSD noise for 3 km length of DSL, at different core cable diameters.

Write down conclusions about the results of completed researches in Section 5.4.

5.5 For the researched xDSL technology in laboratory work, define transmission rate in the forward and reverse directions for a teacher’s given DSL length, core cable diameters and the PSD noise. To do this, use of graphics, built in carrying out Sections 5.3 and 5.4.