A comparison of wi-fi and wimax with case studies - Florida State ...
A comparison of wi-fi and wimax with case studies - Florida State ...
A comparison of wi-fi and wimax with case studies - Florida State ...
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3.1. The background <strong>of</strong> IEEE 802.11<br />
CHAPTER THREE<br />
3. IEEE 802.11, Wireless LAN<br />
When, IEEE published the st<strong>and</strong>ard 802.11Wireless Local Area Network protocol in 1997, it<br />
caused a revolution in methods <strong>of</strong> communication. People started to get rid <strong>of</strong> the constraint <strong>of</strong><br />
<strong>wi</strong>res <strong>and</strong> began to enjoy the freedom <strong>of</strong> unlimited space for getting information. It changed the<br />
way that people entertain themselves, get information, communicate <strong>and</strong> so on. IEEE 802.11 has<br />
many members in its family, <strong>and</strong> there are some <strong>of</strong> them that are <strong>wi</strong>dely used such as 802.11 a,<br />
802.11b, <strong>and</strong> 802.11g. The newest incoming st<strong>and</strong>ard is 802.11n. The other name for 802.11 is<br />
called Wi-Fi. [01] - [03][22]<br />
The <strong>fi</strong>rst practical st<strong>and</strong>ard in the 802.11 family is 802.11b <strong>and</strong> it came out in 1999. The<br />
earlier st<strong>and</strong>ard 802.11 was too slow. Due to its sluggish speed, users could not experience the<br />
advantages <strong>of</strong> <strong>wi</strong>reless communication. However, 802.11b was still very successful. Its speed<br />
may be only 5.5 Mbps <strong>and</strong> 11 Mbps [04]-[06], but it was fast enough to satisfy the basic<br />
requirement for browsing the Internet. In the past two years, this st<strong>and</strong>ard has become extremely<br />
popular. As a result, a PC which can support this protocol becomes a fundamental requirement.<br />
Approximately around the same time when 802.11b came out, IEEE published another<br />
st<strong>and</strong>ard, 802.11a. These two st<strong>and</strong>ards used different operation b<strong>and</strong>s <strong>and</strong> were not compatible.<br />
[07][08] 802.11a can reach the speed 54 Mbps <strong>and</strong> has more channels in its b<strong>and</strong> to improve the<br />
b<strong>and</strong><strong>wi</strong>dth capacity for users. However, because <strong>of</strong> higher cost <strong>and</strong> the shorter transmission<br />
distance, this st<strong>and</strong>ard was only used by certain groups. [09][15]<br />
The st<strong>and</strong>ard 802.11g was developed based on 802.11b <strong>and</strong> combined <strong>wi</strong>th OFDM<br />
(Orthogonal Frequency Division Multiplexing, used in 802.11a). Theoretically, its speed could<br />
reach 54 Mbps. This st<strong>and</strong>ard was published in the summer <strong>of</strong> 2003.. [10][20] Compared to the<br />
previous two st<strong>and</strong>ards, it was faster than 802.11b <strong>and</strong> had longer transmission distance <strong>and</strong><br />
lower cost than 802.11a. It had the advantages <strong>of</strong> 802.11a <strong>and</strong> had backward compatibility <strong>wi</strong>th<br />
802.11b. [09][11][15]<br />
In the business <strong>fi</strong>eld, rebuilding is always the last choice. 802.11b has existed in the market<br />
for a long time making it un<strong>wi</strong>se to replace 802.11b <strong>wi</strong>th 802.11g. Therefore, the best method is<br />
to produce a device which can support both st<strong>and</strong>ards. Because they are compatible <strong>and</strong> operate<br />
in the same b<strong>and</strong>, this is a more cost ef<strong>fi</strong>cient option. For example Intel’s “Centrino” <strong>and</strong><br />
“Sonoma” uses this type <strong>of</strong> production. [12] – [14] Meanwhile, the 802.11a has its unique<br />
advantages <strong>and</strong> was still used in certain areas. A device that supports a/b/g st<strong>and</strong>ards is also<br />
currently available. [08][09]<br />
10