A supermarket uses WiFi to enable staff to check inventory levels and to perform

Question

A supermarket uses WiFi to enable staff to check inventory levels and to perform price checks. Staff have complained that the wireless scanners they use to check stock levels do not work reliably in some isles. The supermarket manager has contracted you to diagnose the wireless problems and correct them. The supermarket is 60m by 40m. Assume that the useful range of WiFi within the warehouse will be 15m radius. The access points are organised into a grid with the following channel allocations: i. You have determined that the channel allocations are not optimal, how would you improve upon the current channel allocations? ii. As you are reconfiguring the access points you notice that none of them currently have any security enabled. Is this a problem, and if so, what type of security would you recommend?

Explanation / Answer

i....)

supermarket is 60 * 40..

WiFi range is 15 m radius...

channel is divide into 6 access points....

Ch1 Ch6 Ch1

Ch6 Ch1 Ch6

Ch1 is overlapping with Ch6 and Ch6 is overlapping with Ch1

Proper design helps minimize co-channel and adjacent channel interference, which degrade WLAN performance..

Wireless is a shared medium invisible to the eye. We typically find out about WLAN performance problems from end users and through testing. Two reasons for poor WiFi performance are co-channel Interference (CCI) and

adjacent channel interference (ACI).

A well-thought-out WLAN design can help mitigate the amount of CCI/ACI deployed on implementation.

Visualization tools such as site survey software assist in displaying both effects to an engineer.

After an implementation, validation surveys ensure the wireless network is operating as designed. This includes

verifying the amount of CCI/ACI.

Adjacent channel interference

Adjacent channel interference (ACI) occurs when transmissions are sent on an adjacent or partially overlapping

channel. The channel bleeds over on an overlapping channel, which adds noise and interference. As a result, ACI

is worse than CCI.A station performs clear channel assessment (CCA) to determine if it can transmit on an idle

medium. A received signal may get corrupted by ACI from a nearby transmitter on the overlapping frequency if that

received signal is weak

Ch1 Ch1 Ch6

Ch1 Ch6 Ch6

or

Ch6 Ch6 Ch1

Ch6 Ch1 Ch1

This type of channel allocation reduces the ACI problem..

ii.)

The need for security on any network is apparent: the prevention of eavesdropping and the desire for authentication

has been the main focus of many network administrators. However, the problems that already exist are added to

when you add wireless networking to the equation. As wireless networking becomes more popular, the flawed

security of most of those networks becomes more apparent. Several organizations have devised ways to secure

their wireless networks from intruders. However, there is currently no wireless security...

problems without security and solutions..

Eavesdropping and Authentication:

The security of any network is an important issue. No one likes the idea that the possibility exists that someone

could be intercepting their Internet traffic, reading their email, ordering items with their credit cards, or sending

inappropriate messages to their boss in their name. Security of wired networks is often a primary objective of

system administrators.When considering a network with a Wireless Access Point, or “WAP”, available, new

security concerns come into play. Because wireless is broadcast in nature, anyone within range of a wireless card

can intercept the packets being sent out without interrupting the flow of data between wireless card and base

station. It is because of this that wireless network security is somewhat more concentrated than that of wired

networks. Network administrators with WAP’s tend to focus on the security between the wireless card and the

base station. After packets leave the base station on the wired side, administrators can rely on more conventional

security features already in place on their wired networks to protect the information in question.

There are two main issues that wireless security solutions tend to address. First, since all wireless packets are

available to anyone who listens, security is needed to prevent eavesdropping. Since it is impossible to physically

keep people away from the WAP’s, short of erecting a fence around your building, solutions tend to rely on

encryption in one form or another. Depending on what is implemented, this can include a static shared key, a key

generated from a static key, a dynamically-generated key, or negotiated keys.

One of the solution is...

authentication before you get to connect to anything. All base stations route requests through a central firewall

which sits between the base stations and the rest of the network. Users open a browser and go to the network’s

login page; attempts to open any other page are redirected to the login page, while other connections are denied.

Once on the SSLprotected login site, users are given the opportunity to authenticate against a RADIUS server. If

authentication is successful, their traffic is allowed to pass through to the rest of the network. The firewall queries

their wireless card every few minutes to make sure that the connection is still alive.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.