CHAPTE R 16 Wireless Networking - PowerPoint Presentation

Slide1

CHAPTE

R 16Wireless NetworkingTechnologies

CECS 474 Computer Network Interoperability

Notes for Douglas E. Comer, Computer Networks and Internets (5th Edition)

Tracy Bradley Maples, Ph.D.

Computer Engineering & Computer Science

Cal

ifornia

State University, Long Beach

Wireless Network Taxonomy

Wireless communication includes a wide range of network types and sizes.Government regulations that make specific ranges of the electromagnetic spectrum available for communicationA license is required to operate transmission equipment in some parts of the spectrum and other parts of the spectrum are unlicensed

Personal Area Networks (PANs)

A PAN technology provides communication over a short distance.It is intended for use with devices that are owned and operated by a single user. 
IEEE has assigned the number 802.15 to PAN standards.

Bluetooth

 The IEEE 802.15.1a Standard evolved after vendors created Bluetooth technology as a short-distance wireless connection technology.The characteristics of the Bluetooth technology are:Wireless replacement for cables (e.g., headphones or mouse)Uses 2.4 GHz frequency bandShort distance (up to 5 meters, with variations up to

10 or 50 meters)Device is

either master or slave Master grants permission to slave

Data rate is up to 721 Kbps

Wireless LAN

Standards (WiFi)Standards from the first years of WiFi:

Wireless LAN Standards (

WiFi) (cont’d)More recent WiFi standards:802.11ac – Preliminary versions now showing up in new WiFi

Routers. -- WLANs on the 5 GHz frequency bands

-- Final standard approval expected in early 2014 -- Expected total multi-station throughput of 1 Gbps; single link throughput 500 Mbps

-- Extends 802.11n capabilities with: wider RF band & up to 8 MIMO spatial streams

802.11n

–

Standardized in 2009.

-- Extends 802.11b and .11g

-

-

Uses the 2.4 GHz and 5 GHz frequency bands

-

- Expected total multi-station throughput

of 600 Mbps

-- Uses MIMO (Multiple Input Multiple Output) by having multiple antennae at both sender and receiver

-

- Up to 4 more

MIMO spatial

streams

Wireless

Local Area Network (WLAN) Architecture Note: The set of computers within range of a given access point is known as a Basic Service Set (BSS).

Contention and Contention-Free Access

RTS: Request to Send (frame sent to request communication and reserve channel)CTS: Clear to Send (frame sent confirming reserved channel)

ACK: Acknowledgement

DIFS: Distributed Inter

f

rame

S

pace (enough time for the station to sense the medium to see that it is idle)

SIFS

:

S

hort

I

nter

f

rame

S

pace (enough time for the transmitting station to switch back to receive mode)

Note

: More on this will be discussed in the Wireless

Supplement notes.

Wireless MAN Technology and

WiMAX Standardized by IEEE under the category IEEE 802.16.Two main versions of WiMAX are being developed that differ in their overall approach:Fixed WiMAX

refers to systems built using IEEE 802.16-2004 (informally called 802.16d)

does not provide for handoff among access pointsprovides connections between a service provider and a fixed location

Mobile

WiMAX

Standard 802.16e-2005 (informally called 802.16e)

handoffs among Aps

used

for mobile hosts

Wireless MAN Technology and

WiMAX (cont’d) WiMAX offers broadband communication that can be used in a variety of ways:

Wireless MAN Technology and

WiMAX (cont’d)The key features of WiMAX can be summarized as follows:Uses licensed spectrum (i.e., offered by carriers)

Each cell can cover a radius of 3 to 10 KmUses scalable orthogonal FDM

Guarantees quality of services (for voice or video)Can transport 70 Mbps in each direction at short distances

Provides 10 Mbps over a long distance (10 Km)

Cellular Communication Systems

When moving between two cells belonging to the same MSC the switching center handles the change.When a user passes from one geographic region to another, MSCs are involved in the handoff.

Cellular Communication Systems

(cont’d) (a) Perfect cellular coverage occurs if each cell is a hexagon:because the cells can be arranged in a honeycombin practice, cellular coverage is imperfect(b) Most

cell towers use omnidirectional antennas:

transmit in a circular patternobstructions and electrical interference can attenuate a signal or cause an irregular patternin some cases, cells overlap and in others, gaps exist with no coverage

Generations of Cellular Technologies

 Telecommunications industry divides cellular technologies into four generations: 1G, 2G, 3G, and 4G (with intermediate versions labeled 2.5G and 3.5G) Simplified Descriptions:1GBegan in the late 1970s, and extended through the 1980s

Originally called cellular mobile radio telephonesused analog signals to carry voice 

2G and 2.5G

Began in the early 1990s and continues to be

used

One standard: GSM (General System for Communications)

The main distinction between 1G and 2G arises because 2G uses digital signals to carry voice

The label 2.5G is used for systems that extend a 2G system to include some 3G features

Generations of Cellular

Technologies (cont’d) 3G and 3.5GBegan in the 2000sFocuses on the addition of higher-speed data servicesA 3G system offers download rates of 400 Kbps to 2 Mbps, and is intended to support applications such as web browsing and photo sharingIncludes EDGE (Enhanced Data Rates for GSM Evolution) (amongst other approaches)

3G allows a single telephone to roam across the world

 4G and 4G LTE (Long Term Evolution)

Began around 2008

Incompatible with 2G and 3G networks and must be implemented

separatedly

.

Based on GSM/EDGE

Focuses

on support for real-time multimedia

such as a television program or high-speed video

They include multiple connection technologies

such as Wi-Fi and satellite

at any time, the phone automatically chooses the best connection technology available