4 GHZ ISM BAND. SOME OF THE ITEMS THAT NEED TO BE EVALUATED INCLUDE

2. - CWTS CERTIFIED WIRELESS TECHNOLOGY SPECIALIST OFFICIAL STUDY GUIDE EXAM PW0 070 PHẦN 4 PPS 2. - CWTS CERTIFIED WIRELESS TECHNOLOGY SPECIALIST OFFICIAL STUDY GUIDE EXAM PW0 070 PHẦN 4 PPS 2. - CWTS CERTIFIED WIRELESS TECHNOLOGY SPECIALIST OFFICIAL STUDY GUIDE EXAM PW0 070 PHẦN 4 PPS
CWTS CERTIFIED WIRELESS TECHNOLOGY SPECIALIST OFFICIAL STUDY GUIDE EXAM PW0 070 PHẦN 4 PPS
2.4 GHz ISM band. Some of the items that need to be evaluated include:Are any devices limited to 802.11b/g capability only?

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Does the network require backward compatibility to 802.11b/g?Does the network need to support guest access?What impact would a network using only 5 GHz 802.11a have on the business?

Summary

In this chapter, we looked at access methods used to get data from one device to another.

These access methods consist of collision avoidance and collision detection with multiple

users sharing the medium. These two access methods are:

CSMA/CD

CSMA/CA

WLANs have no way of detecting collisions; therefore they must use collision avoidance

or CSMA/CA. Wireless LANs use half-duplex communication, which decreases the perfor-

mance of the communication data transfer.

This chapter also looked at the various spread spectrum technologies used with WLANs

and the differences among them. The IEEE standard and various amendments use different

spread spectrum technologies and unlicensed radio spectrum allowing for data rates up to

300 Mbps. The spread spectrum technologies include:

FHSS—For data rates of 1 and 2 Mbps

DSSS—For data rates of 1 and 2 Mbps

HR/DSSS—For data rates of 5.5 and 11 Mbps

OFDM—For data rates up to 54 Mbps

HT-OFDM—Currently, for data rates of up to 300 Mbps

Even though FHSS is considered legacy technology when it comes to WLANs, it is still

important to understand some of the basics of this technology since it is still in use today in

many industries in different types of wireless technologies.

Some of the spread spectrum technologies discussed in this chapter are more susceptible

to interference than others. This can make installations in some industries challenging. We

also looked at co-location of HR/DSSS and ERP-OFDM systems and some of the challenges

it can pose. Finally, this chapter also discussed the coexistence of WPANs and WLANs and

the various devices and technology that can cause interference when working in the same

RF space.

Exam Essentials 151

Exam Essentials

Know the frequencies and channels HR/DSSS and OFDM use.

Understand that HR/DSSS

operates in the 2.4 GHz ISM band and can use 14 channels depending on the country/

location used. Be familiar with the fact that ERP-OFDM is used for the 2.4 GHz band

and OFDM is used for the 5 GHz band. Know the three UNII bands OFDM uses for the