Question

a Describe how nodes exchange wireless signals

b explain us characteristics of popular WLAN transmission methods, including 802.11 a/b/g/n/ac

c Recognize potential obstacles to successful wireless transmission and their repercussions, such as interference and reflection

Answer 1

a. Wireless signals are carried through air by electromagnetic waves which is used for data and voice communication.The nature of atmosphere provides no fixed path on which signals can transmit or travel without guidance. so the nodes exchange wireless signal with the help of antenna.Just as with wired signals ,wireless signals originate from electrical current travelling along a conductor.These signals travels from transmitter to the antenna. the antenna then emits the signal as a series of electromagnetic waves to the air.Then the signal travels through the atmosphere so that it reaches the specified destination.At the defined destination another antenna accepts the sent signal and a receiver converts it back to current. So in this way the node exchanges wireless signals as there was a lack of fixed path which was required to transmit wireless signal . That's why antenna is used here to do the same and it can be used for both transmission and reception of wireless signals.

b. WLAN: Wireless Local Area Network are the networks that helps to transmit signals through the atmosphere via radio frequency waves . It supports the same protocols and OS as wired LANs.

The most popular wireless standards used on LANs are the ones which are developed by IEEE’s 802.11 committee. The IEEE 802.11 standard specifies communication between two wireless nodes or stations and between a station and access point.There are four best known standards ,they are as follows:

• 802.11b
• 802.11a
• 802.11g
• 802.11n

• 802.11b : It is unique among 802.11 standards in its use of direct sequence spread spectrum(DSSS) signalling.It uses the 2.4-2.4835-GHz frequency range and separates it into 22-MHz channels. It is least expensive of all 802.11 WLAN technologies.It provides a max of 11-Mbps throughput.

• 802.11a : It was released after 802.11b. It differs from the first as it uses channels in the 5-GHz band .It provides a max theoretical throughput of 54 Mbps. 802.11a signals are less likely to suffer interference from microwave ovens ,motors & other wireless WLAN signals.It is the least used.

• 802.11g : It is designed just to be affordable as 802.11b, it's max theoretical throughput is increased from 11 Mbps to 54 Mbps through different data modulation techniques.the antenna having 802.11g has geographic range of 100 meters. It's effective throughput ranges from 20 to 25 Mbps.

• 802.11n : It is the newest 802.11 standard by IEEE. It may use either the 2.4Ghz or 5 GHz frequency range. 802.11n employs the same data modulation techniques which are used by 802.11a and 802.11g. but it differs from the other three standards in respective of how it manages frames ,channels and encoding and so these differences allow 802.11n to have high throughput by including channel bonding and MIMO(multiple-input multiple-output)

c.Interference weakens wireless signals and therefore is an important consideration when working with wireless networking. Physical objects,radio frequency interference ,electrical interference, environmental factors some of the factors which causes interference.