© 2009 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved. © The McGraw-Hill Companies, Inc.
Wireless Network Technologies
Asst. Prof. Chaiporn Jaikaeo, Ph.D. [email protected]
http://www.cpe.ku.ac.th/~cpj Computer Engineering Department
Kasetsart University, Bangkok, Thailand
Adapted from the notes by Lami Kaya
2
Electromagnetic Spectrum
Government regulations make specific ranges of the electromagnetic spectrum available for communication
A license is required to operate transmission equipment in some parts of the spectrum
and other parts of the spectrum are unlicensed
RF range
3
ISM Bands
Industrial, Scientific, and Medical frequency band
Can operate without FCC licenses
Tx output power 1 watt
Eliminate cost and time consuming for licenses
26 MHz
902 MHz
928 MHz
915 MHz*
100 MHz
2.40 GHz
2.50 GHz
2.45 GHz
150 MHz
5.725 GHz
5.875 GHz
5.8 GHz
* Region 2 only
4
Taxonomy of Wireless Networks
5
Wireless LANs and Wi-Fi
IEEE provides most of the standards
which are categorized as IEEE 802.11
A group of vendors who build wireless equipment formed the Wi-Fi Alliance
A non-profit organization that tests and certifies wireless equipment using the 802.11 standards
Alliance has received extensive marketing
Most consumers associate wireless LANs with the term Wi-Fi
6
IEEE 802.11 Standards
Standard Max Speed Frequency
Band
Original 802.11 1-2 Mbps 2.4 GHz
802.11a 54 Mbps 5 GHz
802.11b 11 Mbps 2.4 GHz
802.11g 54 Mbps 2.4 GHz
802.11n 600 Mbps 2.4 GHz and
5 GHz
802.11ac 1.3 Gbps 5 GHz
7
Wireless LAN Modes
Ad hoc Wireless hosts
communicate amongst themselves without a base station
Infrastructure based A wireless host only
communicates with an access point, and the access point relays all packets
AP
8 8
Wireless LAN Architecture
The three building blocks of an infrastructure wireless LAN are:
Access Points (AP)
An interconnection mechanism
Such as a switch or router used to connect access points
A set of wireless hosts
Also called wireless nodes or wireless stations
9
Wireless LAN Architecture
BSS – Basic Service Set
10
Overlap and Association
If a pair of APs are too far apart
A dead zone will exist between them
If a pair of APs are too close together
An overlap will exist
A wireless host is required to associate with a single AP
WiFi Channels
Channels in 2.4 GHz band are largely overlapping
11
Source: Wikipedia
12
Wireless MAN - WiMAX
IEEE 802.16 standards for wireless Metropolitan Area Network (WMAN)
A group of companies formed WiMAX Forum to promote use of the technology
Two main versions
Fixed WiMAX
Mobile WiMAX
WiMAX = Worldwide Interoperability for Microwave Access
13
WiMAX Overview ISP
Internet
Backbone
Line of sight
transmission
Non line of sight
transmission
Home WLAN
Cell-like WiMAX towers
14
Wireless WAN – Cellular Systems
Originally designed to provide voice services to mobile customers
Currently being used to provide data services and Internet connectivity
Source: Wikipedia
15
Cellular Coverage
Perfect cellular coverage occurs if each cell is a hexagon
because the cells can be arranged in a honeycomb
In practice, cellular coverage is imperfect
Ideal Realistic
16
Frequency Reuse
Each cell in a given shape is assigned a unique frequency
Not assign the same frequency to any pair of adjacent cells
17
Evolution of Cellular Systems
1G – analog cellular networks Began in the late 1970s, and extended through the 1980s Originally called cellular mobile radio telephones
used analog signals to carry voice
2G – digital cellular networks Began in the early 1990s Uses digital signals to carry voice Standard: GSM (Global System for Mobile
Communications) Circuit-switched voice communications Packet-switched data communications
GPRS – General Packet Radio Services EDGE – Enhanced Data rates for GSM Evolution
Source: Wikipedia
18
Evolution of Cellular Systems
3G – high-speed mobile broadband
Began in the 2000s
Focuses on the addition of higher-speed data services
Standards:
UMTS/HSPA Europe and most of Asia
CDMA2000 North America and South Korea
4G – high-speed all-IP-based mobile broadband
Began around 2008
Standards:
LTE (3GPP Long-Term Evolution)
WiMAX Source: Wikipedia
19
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 between a wireless headset and a cell phone
between a computer and a nearby wireless mouse or keyboard
among appliances in home
E.g., Bluetooth (IEEE 802.15.1), ZigBee (IEEE 802.15.4)
