Chapter Preview In this chapter, we will study: The basic components of a telecomm system The technologies used in telecomm systems Various ways.
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Chapter Preview In this chapter, we will study: The basic components of a telecomm system The technologies used in telecomm systems Various ways to configure networks Various ways that businesses use networks today
Telecommunications The transmission of different forms of data (such as text, audio, video, images, graphics) from one set of electronic devices over media to another set of geographically separated electronic devices.
The Telecommunications System The hardware and software that transmits information from one location to another Components include: Hardware Media Networks Software Data comm providers Protocols Applications
Telecommunication Signals Analog signals Continuous waves Information conveyed by changing wave characteristics (amplitude and frequency) Digital signals Discrete pulses Information conveyed in binary form (on or off pulses) Easily understood by computer
Communication Processors Hardware devices utilized in data transmission and reception Modem - device that converts analog signals to digital (and vice versa); enables signal transmission over telephone system Multiplexor - device that transmits multiple signals over single medium Front-end processor – specialized computer dedicated to managing communication tasks
The Five Characteristics of Channels Characteristics Description Transmission rate Rate at which channel carries data from one computer to another. Volume or capacity of data that a channel can carry. Ways by which data are transmitted. Two ways include asynchronous (one byte at a time) and synchronous (blocks of bytes). Three directions for transmitting data include simplex, half duplex, and full duplex. Information travels as analog or digital signals. Bandwidth Transmission mode Transmission direction Transmission signals
Wire-based Communication Channels Twisted-pair wire (telephone wire) Cheap and easy to work with Slow; subject to interference; low security Coaxial cable Carries more data; shielded from interference More expensive; harder to work with; low security
Wire-based Communication Channels (continued) Fiber-optic cable Transmit information as light waves through glass fiber Fast; high-capacity; secure; not subject to interference Hard to work with
Wireless Communication Channels Microwave High capacity; inexpensive relative to wire Requires line of sight transmission towers; subject to environmental interference Satellite Very high capacity; large coverage area Expensive; propagation delay; requires encryption for security
Wireless Communication Channels (continued) Radio Suitable for short distance communication; inexpensive; easy to install; high speed Interference problems; insecure Cellular radio technology Infrared
Understanding Communication Media Transmission speed Bandwidth – the range of frequencies available in a channel More bandwidth, more channel capacity Transmission mode Character by character (asynchronous) Streams of characters (synchronous) Transmission accuracy Accuracy controls added to messages Error detection and correction required
Telecomm Carriers and Services Telecomm carriers – provide telecomm technology and services for data communication Common carriers – long-distance phone companies Value-added carriers – provide private telecomm systems and services for a fee
Telecomm Carriers and Services (continued) Telecomm services Switched lines – transmission is routed along path to destination Dedicated lines – continuous connection is established Wide-area Telecomm Service (WATS) – lower cost long distance telephone service Integrated Services Digital Network (ISDN) – high speed data transmission over existing phone lines Digital Subscriber Lines (DSL) - high speed digital transmission over existing phone lines
Network Basics Network – the communication devices, media, and software needed to connect two or more computer systems. Local area networks (LANs) – a network that spans a relatively small geographic distance Wide area networks (WANs) – network that spans a large geographic distance
Network Topology There are three popular network topologies: Bus topology Ring topology Star topology
Bus Topology A network configuration in which all computers on the network are connected through a single circuit, such as twisted-pair cable. Messages are transmitted to all computers on the network, although only the targeted device responds to the message.
Ring Topology A network configuration in which computers are arranged in the form of a ring using twisted-wire, coaxial cable, or fiber optics. Messages are transmitted in one direction to all devices between the sending node and the receiving node.
Star Topology A topology in which a central host computer receives all messages and then forwards the message to the appropriate computer on the network.
Local Area Networks Connect computers and other devices enabling resource sharing Variety of topologies can be used, each with performance strengths and weaknesses Several LANs can be connected via bridges LANs can be connected to external networks via gateways