1. Physical layer concepts

2. Distorsion

3. Effect of attenuation, distortion, and noise on transmitted signal.

4. Point-to-point communication
Layer 6 2 1 7
Mikrofon
Högtalare
Source coding
Source decoding
Digitalizating compression
0110
Error management
Error control .
Bit error
NACK
Flow control
ACK
Modulation
Demodulation

5. Digital modulation methods
Binary signal
ASK = Amplitude Shift Keying (AM)
FSK = Frequency Shift Keying (FM)
PSK = Phase Shift Keying (PSK)

6. 8QAM example:
Below you find eight symbols used for a so called 8QAM modem (QAM=Quadrature Amplitude Modulation). The symbols in the first row represent the messages 000, 001, 011 and 010 respectively (from left to right). The second row representents 100, 101, 111 and 110.

7. Example 2 cont.

8. Bit rate vs baud rate Bit rate in bit/s:
Where M is the number of symbols and fs is the symbol rate in baud or symbols/s.

9. Bit and baud rate comparison ASK, FSK, 2-PSK Bit 1 N 4-PSK, 4-QAM
Modulation
Units
Bits /symbol
Baud rate
Bit Rate
ASK, FSK, 2-PSK
Bit 1 N
4-PSK, 4-QAM
Dibit 2 2N
8-PSK, 8-QAM
Tribit 3 3N
16-QAM
Quadbit 4 4N
32-QAM
Pentabit 5 5N
64-QAM
Hexabit 6 6N
128-QAM
Septabit 7 7N
256-QAM
Octabit 8 8N

10. Sine wave example
Complex representation
5 Volt
л/2 radians = 90º I

11. Figure 5.14 The 4-QAM and 8-QAM constellations
Q (Quadrature phase)
Q (Quadrature phase)
I (Inphase)
I (Inphase)

12. Figure 5.11 The 4-PSK characteristics

13. Figure 5.12 The 8-PSK characteristics

14. Figure 5.16 16-QAM constellations

15. Figure 5.20 The V.32 constellation and bandwidth

16. Spectrum of ASK, PSK and QAM signal

18. Figure ADSL modem

19. Figure DSLAM

20. Other DSL Technologies
SDSL (Symmetric DSL) divides frequencies evenly
HDSL (High-rate DSL) provides DS1 bit rate in both directions
Short distances
Four wires
VDSL (Very high bit rate DSL) provides up to 52 Mbps
Very short distance
Requires Optical Network Unit (ONU) as a relay