Download
1 / 10
110 likes | 258 Vues
Chapter 8 delves into the contrast between fiber-optic and copper media in data transmission. Fiber-optic cables, using light pulses through glass, offer higher bandwidth and longer distances without signal enhancement, making them ideal for backbone connections. They are immune to electrical interference, enhancing reliability. Conversely, wireless media transmit data through electromagnetic signals, facing challenges like interference from physical objects. Key wireless standards such as Wi-Fi (IEEE 802.11), Bluetooth (IEEE 802.15), and WiMAX (IEEE 802.16) are explored, along with the implications of each for modern networking.
E N D
OSI Physical Layer Network Fundamentals – Chapter 8
Fiber Media • Copper uses electrical voltage to represent data. • Fiber-optic cable uses light pulses conducted through special glass conductors to carry data. • Fiber has greater bandwidth and can run much farther than cable without needing a signal enhanced, • but the higher cost of fiber-optic cable and connectors, + special training required for installing + handling fiber.
Fiber Media • Because fiber does not carry voltage and current = immune to the earth ground and lightning concerns. • Usually considered the best choice for backbone connections between floors and wiring closets in large buildings and for connections between buildings on a campus.
Fiber Media • Fiber-optic cable starts with a core strand of glass or special plastic on which the light signal travels. • Around the glass is cladding, a special material that reflects escaping light into the core. • Outer layers protect and strengthen the vulnerable center core from moisture and damage.
Fiber Media • There are two basic types of fiber-optic cable: • single-mode - most commonly used by telephone companies and in data installations as backbone cable. • multimode - usually the fiber-optic cable used with networking applications such as FDDI and ATM
Wireless Media • Wireless media carry electromagnetic radio signals that represent the binary data of the data-link frame. • Transmit and receive signals through the medium of the open atmosphere = open areas are best • Within buildings, interference occurs from physical objects such as • walls, metal air ducts, • and floors and • machinery. • + subject to degradation • microwave ovens, • fluorescent lighting, • phones and Bluetooth devices.
Wireless Media • Four common data communications standards that apply to wireless media: • ■ Standard IEEE 802.11: Commonly referred to as Wi-Fi, 802.11 is a wireless LAN (WLAN) technology that uses a contention or nondeterministic system with a carrier sense multiple access/collision avoid (CSMA/CA) media access process. • ■ Standard IEEE 802.15:Wireless Personal-Area Network (WPAN): Commonly known as Bluetooth, 802.15 uses a device-pairing process to communicate over distances from 1 to 100 meters. • ■ Standard IEEE 802.16: Commonly known as WiMAX (Worldwide Interoperability for Microwave Access), 802.16 uses a point-to-multipoint topology to provide wireless broadband access. • ■ Global System for Mobile Communication (GSM): Includes physical layer specifications that enable the implementation of the Layer 2 General Packet Radio Service (GPRS) protocol to provide data transfer over mobile cellular telephony networks.
