The Internet Encyclopedia (Volume 3)

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CELLULARPHONEGENERATION 819

Table 1Comparison of Wireless and Wired Network Systems

Wireless network Wireline network

Transmission media Radio, microwave, infrared and millimeter

waves, lightwave/laser transmission

Twisted pair, coaxial cable, fiber optics

Standard Wireless LAN: IEEE802.11 IEEE802.3 (based on Ethernet

specification)

Wireless MAN: IEEE802.16 IEEE 802.5

Reference model IEEE 802 reference model: OSI reference model:

Physical layer Physical layer

Data link layer (MAC sublayer, LLC sublayer) Date link layer (MAC sublayer, LLC

sublayer)

Upper layer protocols Network layer

Transport layer

Session layer

Presentation

Application layer

Physical layer Wireless LAN: Infrared, FHSS, DSSS, OFDM,

HRDSSS, OFDM

Thick coax, Thin coax, Twisted pair,

Fiber optics

Wireless MAN: QPSK, QAM-16, QAM-64

Data rate 1–54 Mbps Classical Ethernet: 10 Mbps

Fast Ethernet: 100 Mbps

Gigabit Ethernet: 1–10 Gbps

Fiber channel: 100 Mbps–3.2 Gbps

MAC sublayer protocol CSMA/CA (combines CSMA and MACAW) CSMA/CD

Random

Contention

MAC frame format 3 classes of frame: data, control, management

Data frame format: frame control, duration,

address1, address2, address3, seq., address4,

data, checksum

Preamble (8 bytes), destination address

(6 bytes), source address (6 bytes),

type (2 bytes), data, pad (0–46

bytes), checksum (4 bytes)

Logical link control (LLC) Run on top of Ethernet and other IEEE802

protocols. Hides the differences between the

various kinds of 802 networks by providing a

single format and interface to the network

layer

Internet protocol Mobile IP—Enable computer to maintain

Internet connectivity while moving from one

Internet attachment point to another

Ipv4, Ipv6

Mobile IP basic ability—Discovery, registration,

tunneling

Discovery Use ICMP by adding the appropriate extensions

to the ICMP header

ICMP

Routing algorithm For mobile host: use foreign agent and home

agent

Shortest path routing, distance vector

routing, link state routing, etc.

In ad hoc network: AODV (ad hoc on-demand

distance vector) routing algorithm

Congestion control algorithm Poor performance. Since transmission link is

unreliable, packets are lost all the time. The

algorithm uses the wrong assumption (that

timeout is caused by congestion) for

congestion control.

Good performance Assume that

timeout is caused by congestion, not

by packet loss

Transport layer protocol Poor performance using TCP Solution: Indirect

TCP; makes modification to the network

layer code in the base station

TCP

Datagram protocol Performance is far from perfect using UDP.

Since the transmission link is unreliable

UDP

WDP (wireless datagram protocol)