信息通信Chapter 08.pptVIP

* * Chapter 8 Multiplexing Chapter 8 Multiplexing  8.1 Many to One /One to Many 8.2 Types of Multiplexing 8.3 Multiplexing application: the telephone system 8.4 Summary 8.1 Many to One /One to Many Multiplexing(复用) is the set of techniques that allows the simultaneous transmission of multiple signals across a single data link. MUX(复用器): many to one; DEMUX(解复用器): one to many path(通路): the physical link channel (通道): a portion of a path that carries a transmission between a given pair of device. eg. super highway DEMUX directs data stream to their intended devices. 8.1 Many to One /One to Many 8.1.1 Frequency-division Multiplexing (FDM) analog multiplexing; BW of a link ∑(BW of signals) channels must be separated by strips of unused bandwidth (guard bands警戒频带) to prevent signals from overlapping(重叠) . 频分复用 时分复用 statistical TDM or concentrator (集中器) 8.2 Types of Multiplexing 8.1.2.1 the FDM Process 8.1.2.2 Demultiplexing Fig 8.3 8.2 Types of Multiplexing Fig 8.4 Fig 8.5 AM:调幅 band-pass filter 8.2 Types of Multiplexing f1 f2 f3 f1 f2 f3 guard band demodulator Fig.8.3 Fig.8.6 Three times the bandwidth to accommodate the necessary channels , allow for guard bands. The demultiplexer uses a series of filters to decompose the multiplexed signal into its constituent component signals. The individual signals are then passed to a demodulator that separates them form their carriers. 8.1.2.3 Example: Cable Television Bandwidth of the coaxial cable is 500MHz, an individual television channel requires about 6 MHz. 83 WDM (wavelength division multiplexing 波分复用): visible light spectrum 8.2 Types of Multiplexing 8.1.2 Time-Division Multiplexing (TDM) digital multiplexing; data rate of transmission medium data rate required by the sending and receiving devices. Multiplexing transmission can occupy a single link by subdividing(细分) them and interleaving(交织) the portions. eg. ski lift 滑雪 8.2 Types o