CPET/ECET 355

9/26/20045. Analog Transmisison - Lin1

CPET/ECET 355CPET/ECET 3555. Analog Transmission

Data Communications and NetworkingFall 2004

Professor Paul I-Hai LinElectrical and Computer Engineering TechnologyIndiana University-Purdue University Fort Wayne

www.ecet.ipfw.edu/~lin

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Analog Transmission - OutlinesAnalog Transmission - Outlines1. Modulation of Digital Data

Bit rate and Baud rate Carrier signal Amplitude Shift Keying (ASK) Frequency Shift Keying (FSK) Phase Shift Keying (PSK) Quadrature Amplitude Modulation (QAM)

2. Telephone Modems Modem Standards: V.32, V.32bis, V.34bis,

V.90, V.92

3. Modulation of Analog Signals: AM, FM, PM

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5.1 Modulation of Digital Data5.1 Modulation of Digital Data Modulation: converting binary data

to analog signals

From p. 116, Figure 5.1 of Data Communications and Networking, Forouzan, McGrawHill

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5.1 5.1 Modulation of Digital Signals Modulation of Digital Signals (cont.)(cont.)

Four Modulation Methods– Amplitude Shift Keying– Frequency Shift Keying– Phase Shift Keying– Quadrature Amplitude Modulation

From p. 116, Figure 5.2 of Data Communications and Networking, Forouzan, McGrawHill

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5.1 5.1 Modulation of Digital Signals Modulation of Digital Signals (cont.)(cont.)

Bit rate– No. of bits transmitted per second

Baud rate– No. of signal units per second that are required to

represent those bits– Baud rate is less than or equal to the bit rate

Example 1– Question: An analog signal carries 4-bit in each signal

unit. If 1000 signal units are sent per second, find the baud rate and the bit rate

– Answer: Baud rate = number of signal units per second = 1000

bauds/sec Bit rate = baud rate x No. of bits per signal unit = 4000

bps

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5.1 5.1 Modulation of Digital Signals Modulation of Digital Signals (cont.)(cont.)

Example 2

– Question: The bit rate of a signal is 9600. If each signal unit carries 8-bits, what is the baud rate?

– Answer:Baud rate = number of signal units

per second = 1000 bauds/sec, or Baud rate = bit rate/no. of bits per

signal unit = 9600/8 = 1200 bauds

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5.1 5.1 Modulation of Digital Signals Modulation of Digital Signals (cont.)(cont.)

Carries Signal

– A high frequency signal that acts as a basis for the information signal

– Digital information modulates the carrier signal by modifying one or more of its characteristics: Amplitude, Frequency, or Phase

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5.1 Amplitude Shift Keying 5.1 Amplitude Shift Keying (cont.)(cont.)

From p. 118, Figure 5.3 of Data Communications and Networking, Forouzan, McGrawHill

• Frequency & Phase remains constant • 1 – higher magnitude• 0 – smaller magnitude• Disadvantage – noise interference

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5.1 5.1 Modulation of Digital DataModulation of Digital Data (cont.)(cont.)

Bandwidth of ASK– BW = (1 +d) * Nbaud

Where d: modulation factor, Nbaud = baud rate If d = 0, BW = Nbaud

– Bit rate = baud rate

From p. 119, Figure 5.4 of Data Communications and Networking, Forouzan, McGrawHill

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5.1 5.1 Modulation of Digital DataModulation of Digital Data (cont.)(cont.)

Example 3– Find the min BW for an ASK signal

transmitting at 2000 bps. The transmission mode is half-duplex.

– Ans: BW = Nbaud = 2000 Hz Example 4

– Given a bandwidth of 5000 Hz for an ASK signal, what are the baud rate and bit rate?

– Ans: In ASK, Bit rate = Baud rate = 5000 bps

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5.1 5.1 (cont.)(cont.) Example 5

– Given a BW of 10,000 Hz (1000 to 11,000 Hz), draw the full-duplex ASK diagram of the system. Find the carriers and the BWs in each direction. Assume there is no gap between bands in the two directions.

– Ans: BW = 10,000/2 = 5000 Hz Carrier Frequency 1 = 1000 + 5000/2 = 3500 Hz Carrier Frequency 2 = 11000 – 5000/2 = 8500Hz

From p. 119, Fig 5.5, Data Communications and Networking, Forouzan, McGrawHill

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5.1 Frequency Shifting Keying 5.1 Frequency Shifting Keying (FSK)(FSK) Varying frequency of carrier signal to

represent 1 or 0 Amplitude and phase remain

constant

From p. 120, Fig 5.6, Data Communications and Networking, Forouzan, McGrawHill

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5.1 FSK 5.1 FSK (cont.)(cont.)

Bandwidth = Fc1 – Fc0 + Nbaud

From p. 121, Fig. 5.7, Data Communications and Networking, Forouzan, McGrawHill

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5.1 FSK 5.1 FSK (cont.)(cont.)

Example 6: Find the min BW for an FSK signal transmitting at 2000 bps. Transmission is in half-duplex mode, and the carriers are separated by 3000 Hz.– Ans:

BW = Nbaud + Fc1 – Fc0 = 2000 + 3000 = 5000 Hz Example 7: Find the maximum bit rates for an

FSK signal if the BW of the medium is 12kHz and difference between the two carriers is 2000 Hz. Transmission is in full-duplex mode.– Ans:

BW = baud rate + Fc1 – Fc0

Baud rate – BW – (Fc1 – Fc0) = 6000 – 2000 = 4000 bps

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5.1 Phase Shift Keying (PSK)5.1 Phase Shift Keying (PSK)

From p. 121, Fig 5.8, Data Communications and Networking, Forouzan, McGrawHill

• Varying phase of the carrier to represent 1 or 0

• 0 degree = 0, 180 degree = 1

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5.1 PSK Constellation5.1 PSK Constellation

From p. 122, Fig. 5-9, Data Communications and Networking, Forouzan, McGrawHill

• Not susceptible to the noise degradation (ASK)

• No bandwidth limitation (FSK)

•1 –bit: two variations (0 and 180)

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5.1 PSK Constellation 5.1 PSK Constellation (cont.)(cont.)

From p. 123, Fig. 5.10, Data Communications and Networking, Forouzan, McGrawHill

• The 4 PSK or Q-PSK method

• 2-bit variation of 4 phases: 00 – 0 deg.; 01 – 90 deg.; 10 – 180 deg.; 11 – 270 deg.

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From p. 123, Fig. 5.11 Data Communications and Networking, Forouzan, McGrawHill

5.1 4 PSK Constellation 5.1 4 PSK Constellation (cont.)(cont.)

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From p. 124, Fig. 5.12, Data Communications and Networking, Forouzan, McGrawHill

5.1 8 PSK Constellation (cont.)5.1 8 PSK Constellation (cont.)

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BW = Baud rate

From p. 124, Fig. 5.13 Data Communications and Networking, Forouzan, McGrawHill

5.1 BW of PSK5.1 BW of PSK

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From p. 125, Fig. 5.14, Data Communications and Networking, Forouzan, McGrawHill

5.1 5.1 Quadrature Amplitude. ModulationQuadrature Amplitude. Modulation• QAM - combining both ASK and PSK; same BW as ASK or PSK

• 4-QAM – 1 amplitude, 4 phases; 8-QAM – 2 amplitude, 4 phases

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Time Domain Signal for 8-QAMTime Domain Signal for 8-QAM

From p. 126, Fig. 5.15, Data Communications and Networking, Forouzan, McGrawHill

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16-QAM Constellations16-QAM Constellations

From p. 126, Fig. 5.16, Data Communications and Networking, Forouzan, McGrawHill

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Bit/Baud ComparisonBit/Baud Comparison

FSK – If over voice-grade line with 1200 bps– Requires 1200 signal units to send 1200

bits: 1200 baud8-QAM

– 3-bit signal units– Bit rate: 1200 bps– Baud rate: 400 bauds

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Bit/Baud ComparisonBit/Baud Comparison

From p. 127, Fig. 5.17, Data Communications and Networking, Forouzan, McGrawHill

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Table 5.1 Bit and Baud Rate Table 5.1 Bit and Baud Rate ComparisonComparison

From p. 127, Table 5.1, Data Communications and Networking, Forouzan, McGrawHill

ModulationModulation UnitsUnits Bits/BaudBits/Baud Baud rateBaud rate Bit Rate

ASK, FSK, 2-PSKASK, FSK, 2-PSK Bit 1 N N

4-PSK, 4-QAM4-PSK, 4-QAM Dibit 2 N 2N

8-PSK, 8-QAM8-PSK, 8-QAM Tribit 3 N 3N

16-QAM16-QAM Quadbit 4 N 4N

32-QAM32-QAM Pentabit 5 N 5N

64-QAM64-QAM Hexabit 6 N 6N

128-QAM128-QAM Septabit 7 N 7N

256-QAM256-QAM Octabit 8 N 8N

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5.2 Telephone Modems5.2 Telephone Modems

Figure 5.18 Manchester Encoding,

From p. 129, Data Communications and Networking, Forouzan, McGrawHill

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5.2 Telephone Modems 5.2 Telephone Modems (cont.)(cont.)

Figure 5.19, From p. 129, Data Communications and Networking, Forouzan, McGrawHill

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5.2 Telephone Modems 5.2 Telephone Modems (cont.)(cont.)

Figure 5.20, From p. 130, Data Communications and Networking, Forouzan, McGrawHill

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5.2 Telephone Modems 5.2 Telephone Modems (cont.)(cont.)

Figure 5.21, From p. 131, Data Communications and Networking, Forouzan, McGrawHill

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5.2 Telephone Modems 5.2 Telephone Modems (cont.)(cont.)

Figure 5.22, From p. 132, Data Communications and Networking, Forouzan, McGrawHill

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5 5 (cont.)(cont.)

Figure 4.10 Manchester Encoding,

From p. 92, Data Communications and Networking, Forouzan, McGrawHill

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5 5 (cont.)(cont.)

Figure 4.10 Manchester Encoding,

From p. 92, Data Communications and Networking, Forouzan, McGrawHill

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5 5 (cont.)(cont.)

Figure 4.10 Manchester Encoding,

From p. 92, Data Communications and Networking, Forouzan, McGrawHill

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5 5 (cont.)(cont.)

Figure 4.10 Manchester Encoding,

From p. 92, Data Communications and Networking, Forouzan, McGrawHill

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5 5 (cont.)(cont.)

Figure 4.10 Manchester Encoding,

From p. 92, Data Communications and Networking, Forouzan, McGrawHill

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5 5 (cont.)(cont.)

Figure 4.10 Manchester Encoding,

From p. 92, Data Communications and Networking, Forouzan, McGrawHill

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5 5 (cont.)(cont.)

Figure 4.10 Manchester Encoding,

From p. 92, Data Communications and Networking, Forouzan, McGrawHill

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5 5 (cont.)(cont.)

Figure 4.10 Manchester Encoding,

From p. 92, Data Communications and Networking, Forouzan, McGrawHill

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5 5 (cont.)(cont.)

Figure 4.10 Manchester Encoding,

From p. 92, Data Communications and Networking, Forouzan, McGrawHill

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SummarySummary

Questions?