4 Home task

1. Give the answers the key questions.

4.2 Solve the following problem.

a) Determine the near-end crosstalk attenuation ratio A₀ (f_e) between pairs on the estimated frequency f_e for a given their relative positions in the TП cable with layer core construction (twisted construction of the core).

Table 4.1 – Initial data for 1-st problem

Variant	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
Relative positions of pairs	Over a 1 pair in lay		Over 2 pairs in lay		Over 3 pairs in lay		Over 4 pairs in lay		Over a one layer		Over a 2 layers		Over a 3 layers		Over a 4 layers
fe, МHz	0,25	0,5	0,75	1,25	1,5	1,75	2	0,2	0,4	0,6	0,8	1,2	1,4	1,6	1,8	0,1

b) Determine the far end crosstalk attenuation A_{l SL} (f_e) between pairs on the estimated frequency f_e for a given it relative positions in the TП cable with layer core building of the length l.

Table 4.2 – Initial data for 2-nd problem

Variant	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
Relative positions of pairs	Over a one layer		Over a 2 layers		Over a 3 layers		Over a 4 layers		Over a 1 pair in lay		Over 2 pairs in lay		Over 3 pairs in lay		Over 4 pairs in lay
fe, МHz	0,2	0,3	0,4	0,5	0,6	0,7	0,8	0,9	1,2	1,3	1,4	1,5	1,6	1,7	1,8	1,9
l, m	560	840	1120	1400	560	840	1120	1400	560	840	1120	1400	560	840	1120	1400

4.3 Prepare a record form in accordance with laboratory task.

5 Laboratory task

5.1 Get acquainted with the program interface of the "xDSL-Lіner".

5.2 In accordance with the brigade number choose the type of xDSL transmission system.

Table 5.1 – Transmission system variant

№ brigade	1, 5	2, 6	3, 7	4, 8
Transmission system type (technology) xDSL	ADSL	ADSL2+	VDSL A	VSDL B

5.3 Research of the crosstalk levels at the near (p_n ) and far end (p_f) dependence, the signal/noise ratio at the receiver input SNR and transmission rate in a downstream R_D and in the upstream R_U directions in a pair of number 29 from the location of a affecting pair in 50-pair cable ТПП – 0,64 layer twist if the power spectrum density (PSD) of white noise minus 140 dBm/Hz and a cable length 1 km. Calculations are made on the subscriber side of the line.

Put the results in the table 5.2. Make explanations.

For the relevant (or appropriate) calculations necessary to choose the tab "Graphs":

"Near end crosstalk": p_n equal to the integral power at the near end;

"Far end crosstalk": p_f is an integral power at the far end;

"SNR at the receiver input»: SNR is defined as the maximum SNR on graph;

"Transmission rate (or bitrate) and the carriers loading»: R_D and R_U.

Table 5.2 – Dependence of the crosstalk levels, maximum value of SNR and bitrate from pair cable position which is effect on a given pair

№ of pair, exposed to effect	№ effect pair	30	31	32	33	34	14	4	0
29	pn, dBp
	pf, dBp
	SNR, dB
	RD, Мbit/s
	RU, Мbit/s

5.4 The calculations of p. 5.3 to determine the best and worst case position of the affect pair in the cable and for those variants to calculate the dependence of the crosstalk level at the near- and the far-end, the maximum signal/noise ratio and bitrate in the downstream R_D and in the upstream R_U direction of cable length l for the PSD of white noise of minus 140 dBm/Hz.

The results write in the table 5.3. Build the graphs depending on cable length l, crosstalk level, the maximum signal/noise ratio SNR (see Appendix to the lab), transmission rate (bitrate) in the downstream R_D and in the upstream R_U directions for the best and worst location variants of the affects pairs in the cable (each pair graphics (for better and worse choices) is represented in one coordinate system for visual comparison).

Table 5.3 – Dependence of the crosstalk levels, maximum value of SNR and biterate on pair cable position which is effect and on a cable length

№ of pair, exposed to effect	№ effect pair	l, km* (1,2,5,6) (3,4,7,8)	0,5 0,3	1 0,5	1,5 0,7	2 1	2,5 1,2	3 1,5	3,5 2
29		pn, dBp
		pf, dBp
		SNR, dB
		RD, Мbit/s
		RU, Мbit/s
		pn, dBp
		pf, dBp
		SNR, dB
		RD, Мbit/s
		RU, Мbit/s

^*Note. For variants 1, 2, 5, 6 (ADSL & ADSL2 technology) cable length is from 0,5 km to 3,5 km, and for variants 3, 4, 7, 8 (VDSL A & VDSL B technology) - from 0,3 km to 2 km.

5.5 For best and worse variants p. 5.3 to take the dependence of the maximum signal/noise ratio at the receiver input SNR and transmission rate in a downstream R_D and in the upstream R_U directions when the cable length l₁ from the PSD of white noise. The results write in the Table. 5.4. Make explanations.

According to the results of calculations to build the graphs depending from the PSD of white noise of maximum signal/noise ratio at the receiver input SNR, the transmission rate in the downstream R_D and in the upstream R_U directions for the best and worst location variants of the effects pairs in the cable (each pair of graphs (for better and worse variants) is described in one coordinate system for visual comparison).

Table 5.4 – Dependence of the maximum value of SNR at the receiver input and bitrate on the PSD of white noise on a cable length l₁ **

№ of pair, exposed to effect	№ effect pair	PSD noise, dBp/Hz	–140	–130	–120	–110	–100	–90
29		SNR, dB
		RD, Мbit/s
		RU, Мbit/s
		SNR, dB
		RD, Мbit/s
		RU, Мbit/s

^**Comment. For variants 1, 2, 5, 6 (ADSL & ADSL2 technology) cable length is from l₁ = 1 km, and for variants 3, 4, 7, 8 (VDSL A & VDSL B technology) – l₁ = 0,5 km.

5.6 After finishing work to draw conclusions about the crosstalk level dependence, the maximum signal/noise ratio at the receiver input and the transmission rate in the parallel operation of transmission systems xDSL on the relative position digital subscriber line xDSL in multi-pair cable, the length of subscriber lines and the PSD of white noise.