Introduction to Communication Theory Lijun Qian Department of Electrical Engineering PVAMU
Figure 1 Elements of a communication system.
Elements of a communication system Transmitter To convert the message signal produced by the source into a form suitable for transmission over the channel. Channel Received signal is a corrupted version of the transmitted signal due to Channel imperfection Added noise and interference Receiver Operate on the received signal to reconstruct a recognizable form of the original message signal.
Analog Communication vs. Digital Communication An analog communication system transfers information from an analog source (which produce messages that are defined on a continuum, for example, the output voltage describes the information in the sound from a microphone) to the sink/destination. A digital communication system transfers information from a digital source (which produce a finite set of possible messages, for example, messages from a typewriter) to the sink/destination.
Advantages and Disadvantages of Digital Communication Advantages Inexpensive digital circuits Privacy by data encryption Noise does not accumulate Use of error correction coding Disadvantages More bandwidth is required than that for analog systems Synchronization is required
Figure 9 Block diagram of digital communication system.
Function blocks in a digital communication system Source coding (source encoder/decoder) Data compaction, reduce the unnecessary redundancy in messages generated by the information source Channel coding (channel encoder/decoder) Introduce controlled redundancy to combat channel imperfection and noise/interference Modulation (modulator/demodulator) a.k.a. MODEM
Figure 10 Elements of a digital communication system. (a) Block diagram of transmitter. (b) Block diagram of channel. (c) Block diagram of receiver.
Communication networks Wireline vs. Wireless communication networks Wirelinenetworks Example: Ethernet, token ring, fiber optic networks, the Internet Wireless networks Example: 3G CDMA cellular and PCS networks, 2G TDMA cellular networks, WLAN (802.11b/a/g), Bluetooth, wireless sensor networks
Communication networks (contd.) Local area networks vs. Wide area networks Local area networks Examples: Ethernet, WLAN (802.11b/a/g), the computer network within PVAMU Wide area networks Examples: Trans-Atlantic fiber optic backbone networks, ATM backbone networks in the U.S., the backbone network connect all computer networks within Texas A&M University System
Figure 4 Communication network.
Figure 5 OSI model; the acronym DLC in the middle of the figure stands for data link control.
Figure 6 An interconnected network of subnets.
Figure 7 Illustrating the network architecture of the Internet.
Global Wireless Standards Evolution CDMA IS-95-A Voice 14.4 kbps CSD & PD 2G 2.5G IS-95-B Voice 64 kbps Packet RF Backward Comp. CDMA2000 1X High Capacity Voice 153 kbps Packet RF Backward Comp. 3GCDMA - IMT-2000 Compliant CDMA2000 1xEV-DO 2.4 Mbps Packet RF Backward Comp. CDMA2000 1xEV-DV Higher Cap Voice/ Data RF Backward Comp TDMA IS-136 Voice 9.6 kbps CSD EDGE (US) EDGE (Europe 384 kbps Packet GSM Voice 9.6 kbps CSD PDC PDC GSM GPRS 114 kbps Packet RF Backward Comp. W-CDMA (Japan) W-CDMA (Europe & US) Voice Voice 9.6 kbps 28.8 kbps RF Backward Comp. 1995 1999 2000 part of this 2001 presentation is from2002 2003+ High Capacity Voice 384+ kbps Packet New RF
Infrastructure backhaul PDSN Internet HLR ANSI-41 network PCN AAA BSC MSC PSTN wireless access BS BS cell