6 Bandwidth example Data transmission If a periodic signal is decomposed into five sine waves with frequencies of 100, 300, 500, 700, and 900 Hz, what is the bandwidth?B = Fh - FlB =B = 800 Hz
7 Bandwidth example Data transmission A signal has a bandwidth of 20 Hz. The highest frequency is 60 Hz. What is the lowest frequency?B = Fh - Fl20 = 60 - FlFl = = 40 Hz
8 Bandwidth example Data transmission A signal has a spectrum with frequencies between 1000 and 2000 Hz (Bandwidth of 1000 Hz). A medium can pass frequencies from 3000 to 4000 Hz (a bandwidth of 1000 Hz). Can this signal faithfully pass through this medium?AnswerThe answer is definitely no. Although the signal can have the same bandwidth (1000 Hz), the range does not overlap. The medium can only pass the frequencies between 3000 and 4000 Hz, the signal is totally lost.
9 Telephone line Bandwidth Data transmissionTelephone line Bandwidth
10 Digital signal and Analog signal Data transmissionDigital signal and Analog signal
11 Bit rate and Bit interval Data transmissionBit rate and Bit interval
12 The bit interval is the inverse of the bit rate. Data transmissionBandwidth exampleA digital signal has a bit rate of 2000 bps. What is the duration of each bit (bit interval)The bit interval is the inverse of the bit rate.Bit interval = 1/2000 s = s = x 106 ms = 500 ms
13 Summary Data transmission The analog bandwidth of a medium is expressed in hertz (Hz); the digital bandwidth, in bits per second (bps).
14 Summary Data transmission Bit rate is the number of bits per second. Baud rate is the number of signal units
15 Summary Data transmission Baud rate is the number of signal units. Baud rate is less than or equal to the bit rate.
16 Baud rate = 1000 bauds per second (baud/sec) Data transmissionExampleAn analog signal carries 4 bits in each signal unit. If 1000 signal units are sent per second, find the baud rate and the bit rate.Baud rate = 1000 bauds per second (baud/sec)Bit rate = 1000 x 4 = 4000 bps
17 Analog transmission Data transmission Digital/Analog Modulation Techniques1. Amplitude – Shift Keying (ASK)2. Frequency – Shift Keying (FSK)3. Phase – Shift Keying (PSK)(1) + (3) – Quadrature amplitude modulation (QAM)
23 Bit and Baud rate comparison Data transmissionBit and Baud rate comparisonModulationUnitsBits/BaudBaud rateBit RateASK, FSK, 2-PSKBit1N4-PSK, 4-QAMDibit22N8-PSK, 8-QAMTribit33N16-QAMQuadbit44N32-QAMPentabit55N64-QAMHexabit66N128-QAMSeptabit77N256-QAMOctabit88N
31 Analog transmission Data transmission Analog/Analog Modulation Techniques1. Amplitude Modulation (AM)2. Frequency Modulation (FM)
32 Analog transmission Data transmission Modulation กรรมวิธีในการรวมกันของสัญญาณ (สัญญาณพาหะ + สัญญาณข้อมูล)Demodulation กรรมวิธีในการแยกคลื่นสัญญาณข้อมูลออกจากคลื่นสัญญาณพาหะCarrier Frequency สัญญาณพาหะที่ทำหน้าที่ในการนำพาข้อมูลไปยังปลายทาง