Introduction
Wireless Access Networks and Physical Media
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Wireless access networks
shared wireless access network connects end system to router
via base station aka “access point”
wireless LANs:
within building (within a few tens of meters of the access point)
IEEE 802.11 b/g/n (WiFi):
11, 54, 450 Mbps shared transmission rate
wide-area wireless access technologies
cellular infrastructure is provided by telco operator, (within few tens of kilometers of the base station)
between 1 and 10 Mbps
3G, 4G: LTE
to Internet
to Internet
IEEE – Institute of Electrical and Electronics Engineers
Physical Media
Physical media
bit: propagates between
transmitter/receiver pairs
physical link: what lies between transmitter & receiver
CATEGORIES
guided media:
signals propagate in solid media: copper, fiber, coax
unguided media:
signals propagate freely, e.g., radio
twisted pair (TP)
two insulated copper wires arranged in a regular spiral pattern
(1 wire pair = communication link)
Category 5: 100 Mbps, 1 Gbps Ethernet
Category 6a: 10Gbps (up to hundred meters)
Data rates depend on the thickness of wire and distance between transmitter and receiver
UTP for computer networks
Twisted pair cabling is a type of wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources;
Common sources of interference include radios, televisions, motors, appliances, radar transmitters, static electricity, and lightning.
Unshielded twisted pair (UTP) is ordinary telephone wire, with no form of electromagnetic shielding around the wire.
Shielded twisted pair (STP) surrounds the wire with a metallic braid or sheathing that reduces interference.
RJ45 is a type of connector commonly used for Ethernet networking. … Since Ethernet cables have an RJ45 connector on each end, Ethernet cables are sometimes also called RJ45 cables. The “RJ” in RJ45 stands for “registered jack,” since it is a standardized networking interface.
Physical media: coax, fiber
coaxial cable:
two concentric copper conductors with special insulation and shielding
bidirectional
broadband:
multiple channels on cable
used as shared medium
fiber optic cable:
thin, flexible glass fiber carrying light pulses, (1 pulse = 1 bit)
high-speed operation:
high-speed point-to-point transmission (e.g., 10’s-100’s Gpbs transmission rate)
low error rate:
repeaters spaced far apart
immune to electromagnetic interference
the preferred long-haul guided transmission media for overseas links
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