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NETW 360 DeVry Complete iLabs Package

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NETW 360 DeVry Complete iLabs Package

NETW 360 DeVry Complete iLabs Package

NETW360

 

NETW 360 DeVry Week 1 iLab Latest

Week 1 iLab: Basic RF Calculations

The power emitted from wireless devices, especially in unlicensed bands, such as 2.4 GHz and 5 GHz, are regulated by the Federal Communications Commission (FCC). Wireless network professionals must calculate power levels (or RF signal strength) that are being transmitted by wireless devices to make sure their designs are complaint with FCC regulations. They also need to calculate power levels that are being received by wireless devices to make sure the signal is properly received at the destination.

RF power can be measured in two ways: on the linear scale, by the number of watts that are being transmitted; and on a relative scale, by the number of decibels (dBs) instead of watts.

Decibel milliwatt (dBm) is thelogarithmicpower ratio (in dB) of the measured power in milliwatts referenced to one milliwatt (mW). Notice that the reference point is specified as 1 mW = 0 dBm.

3’s and 10’s rules are shortcuts for estimating the increase or decrease of these power levels.

In this lab, students will practice basic RF calculations, including

1. converting from mW to dBm;

2. converting from dBm to mW; and

3. estimating power levels using the 3’s and 10’s rules.

Task 1: Converting between dBm and mW

Applying the 3’s and 10’s rules, the relationship between dBm and mW is estimated as shown in the following (partial) table.

3’s rule 10’s rule
…… ……
0.125 mW = -9 dBm 0.001 mW = -30 dBm
0.25 mW = -6 dBm 0.01 mW = -20 dBm
0.5 mW = -3 dBm 0.1 mW = -10 dBm
1 mW = 0 dBm 1 mW = 0 dBm
2 mW = 3 dBm 10 mW = 10 dBm
4 mW = 6 dBm 100 mW = 20 dBm
8 mW = 9 dBm 1,000 mW = 30 dBm
…… ……

Notice that as the mW value increases or decreased by the factor of 10, the dBm value increases and decrease by adding or subtracting 10. As the mW value doubles or halves, the corresponding dBm value increases and decrease by adding or subtracting 3.

1. Apply 3’s rule to estimate what 16 mWs is in dBm. _____

2. Apply 3’s rule to estimate what 0.0625 mWs is in dBm. _____

3. Apply 10’s rule to estimate what 10,000 mWs is in dBm. _____

4. Apply 10’s rule to estimate what 0.0001 mWs is in dBm. _____

5. Apply 3’s rule to estimate what 15 dBm is in mW. _____

6. Apply 3’s rule to estimate what -15 dBm is in mW. _____

7. Apply 10’s rule to estimate what 50 dBm is in mW. _____

8. Apply 10’s rule to estimate what -50 dBm is in mW. _____

Task 2: Estimating power levels using 3’s and 10’s rules

In cascaded systems with power gain and/or loss along a chain of subsystems, power levels given in dB forms can be directly added or subtracted to calculate the total power.

For instance, a transmitter with a power of 9 dBm, after a cable and connector loss of 3 dB, ends up with a power of 9 dBm ? 3 dB = 6 dBm or 4 mW. Notice that the simple addition and subtraction here doesn’t apply to powers given in mW.

If one were to subtract 3 dB from 8 mW (i.e., mixed measurement units), 8 mW should be converted to 9 dBm first. The result is in dBm which can be converted to mW when needed.

9. Applying the 3’s and 10’s rules, what’s 0.125 mW ? 30 dBm in dBm? _____

10. Applying the 3’s and 10’s rules, what’s 0.125 mW ? 30 dBm in mW? _____

11. Applying the 3’s and 10’s rules, what’s 0.0625 mW ? 40 dBm in dBm? _____

12. Applying the 3’s and 10’s rules, what’s 0.0625 mW ? 40 dBm in mW? _____

13. Applying the 3’s and 10’s rules, what’s 8 mW + 30 dBm in dBm? _____

14. Applying the 3’s and 10’s rules, what’s 8 mW + 30 dBm in mW? _____

15. Applying the 3’s and 10’s rules, what’s 16 mW + 40 dBm in dBm? _____

16. Applying the 3’s and 10’s rules, what’s 16 mW + 40 dBm in mW? _____

The same idea can be applied to conversions from dBm to mW when a dBm value is not readily available in the 3’s and 10’s rules table.

For instance, what is 13 dBm in mW?

First, 13 dBm = 0 dBm + 10 dBm + 3 dBm, where 0 dBm, 10 dBm, and 3 dBm are in the table.

Next, let’s apply the following 3’s and 10’s rules:

a) 0 dBm = 1 mW

b) When the dBm value increases by adding 10, the mW value increases by the factor of 10.

c) When the dBm value increases by adding 3, the mW value increases by the factor of 2.

Finally, we have 13 dBm = 0 dBm + 10 dBm + 3 dBm = 1 mW × 10 × 2 = 20 mW.

17. Applying the 3’s and 10’s rules, what’s 7 dBm in mW (must show steps)?

Answer:

18. Applying the 3’s and 10’s rules, what’s 4 dBm in mW (must show steps)?

Answer:

19. Applying the 3’s and 10’s rules, what’s 9 dBm in mW (must show steps)? Answer: 20. Applying the 3’s and 10’s rules, what’s -7 dBm in mW (must show steps)?

Answer:

NETW 360 Week 1 iLab: Basic RF Calculations

Date:

Student’s Name:

Professor’s Name:

Task 1: Converting between dBm and mW

1. Apply 3’s rule to estimate what 16 mWs is in dBm. _____

2. Apply 3’s rule to estimate what 0.0625 mWs is in dBm. _____

3. Apply 10’s rule to estimate what 10,000 mWs is in dBm. _____

4. Apply 10’s rule to estimate what 0.0001 mWs is in dBm. _____

5. Apply 3’s rule to estimate what 15 dBm is in mW. _____

6. Apply 3’s rule to estimate what -15 dBm is in mW. _____

7. Apply 10’s rule to estimate what 50 dBm is in mW. _____

8. Apply 10’s rule to estimate what -50 dBm is in mW. _____

Task 2: Estimating power levels using 3’s and 10’s rules

9. Applying the 3’s and 10’s rules, what’s 0.125 mW ? 30 dBm in dBm? _____

10. Applying the 3’s and 10’s rules, what’s 0.125 mW ? 30 dBm in mW? _____

11. Applying the 3’s and 10’s rules, what’s 0.0625 mW ? 40 dBm in dBm? _____

12. Applying the 3’s and 10’s rules, what’s 0.0625 mW ? 40 dBm in mW? _____

13. Applying the 3’s and 10’s rules, what’s 8 mW + 30 dBm in dBm? _____

14. Applying the 3’s and 10’s rules, what’s 8 mW + 30 dBm in mW? _____

15. Applying the 3’s and 10’s rules, what’s 16 mW + 40 dBm in dBm? _____

16. Applying the 3’s and 10’s rules, what’s 16 mW + 40 dBm in mW? _____

17. Applying the 3’s and 10’s rules, what’s 7 dBm in mW (must show steps)?

Answer:

18. Applying the 3’s and 10’s rules, what’s 4 dBm in mW (must show steps)?

Answer:

19. Applying the 3’s and 10’s rules, what’s 9 dBm in mW (must show steps)?

Answer:

20. Applying the 3’s and 10’s rules, what’s -7 dBm in mW (must show steps)?

Answer:

NETW 360 DeVry Week 2 iLab Latest

NETW 360 Week 2 iLab: RF Behavior Calculations

In this Lab, students use an online calculator to compute power, cable loss, antenna gain, free space path loss, link budget, and Fresnel zone clearance.

Go to.swisswireless.org/wlan_calc_en.html”>www.swisswireless.org/wlan_calc_en.html and locate the online calculator. If the web page has been moved, try searching for “swiss wireless”, without the double quotation marks, on the Internet to locate the main page.

Task 1: Power calculations

The reference point that relates the logarithmic decibel (dB) scale to the linear milliwatt scale is known as the dBm. This reference point specifies that 1 mW = 0 dBm. Here, 1 mW is a measurement of absolute power, and 0 dBm is a measurement of relative power.

Notice that the calculator expects absolute power in watts. If you are given an absolute power level in milliwatts, which is fairly common on WLANs, you need to convert it to watts before using the calculator. Notice that 1 watt = 1000 milliwatts, and 1 milliwatt = 0.001 watts.

Simply put, dBm reflects the relationship between a given power level and 1 milliwatt. This comparison yields three outcomes:

a) If the given power level is more than 1 milliwatt, the resultant dBm is a positive value.

b) If the given power level is less than 1 milliwatt, the resultant dBm is a negative value. Note that a negative dBm value doesn’t mean there is no power!

c) If the given power level is equal to 1 milliwatt, the resultant dBm is 0.

Use the calculator in the Power section to complete the following steps:

1. On the lower UNII-1 band (i.e., 5.150–5.250 GHz with 100 MHz channels), the maximum output power of the intentional radiator (IR) allowed by the FCC is 50 mW. The IR is also referred to as a wireless transmitter.

Click in the watts box and type 0.05 (50 mW = 0.05 watts). What is the dBm of 50 mW?

Answer:

2. On the middle UNII-1 band (i.e., 5.250–5.350 GHz with 100 MHz channels), the maximum output power of the intentional radiator (IR) allowed by the FCC is 250 mW.

Click in the watts box and type 0.25 (250 mW = 0.25 watts). What is the dBm of 250 mW?

Answer:

3. On the upper UNII-1 band (i.e., 5.725–5.825 GHz with 100 MHz channels), the maximum output power of the intentional radiator (IR) allowed by the FCC is 800 mW.

Click in the watts box and type the given power level in watts. What is the dBm of 800 mW?

Answer:

Scroll down to the Receive Sensitivity section. Review the information regarding receive sensitivity.

4. The receive sensitivity of a LinksysWUSB600N wireless network adaptor at 54 Mbps is -70 dBm. Click in the dBm box and type -70. What are the watts of -70 dBm?

Answer:

5. The receive sensitivity of a LinksysWUSB300N wireless network adaptor at 54 Mbps is -68 dBm. Click in the dBm box and type -68. What are the watts of -68 dBm?

Answer:

6. If you have to choose between these adaptors based on their receive sensitivity at the bit rate of 54 Mbps, which adaptor will potentially perform better in achieving the desired bit rate?

Answer:

Task 2: Cable loss calculations

As an antenna accessary, RF cables introduce loss/attenuation to signals being transmitted on the communications link. Cable manufactures such as Times Microwave Systems (TMS) often provide an attenuation chart to list different types of cables with their signal loss (e.g., in dB per 100 feet) at a specific frequency.

When selecting a coaxial cable for RF communications, note that:

a) The impedance of the cable needs to match that of the antenna and wireless transceiver to avoid signal loss caused by the voltage standing wave ration (VSWR) effect.

b) Not all coaxial cables support the transmission of 2.4 GHz and 5 GHz signals.

c) Given an RF cable with a certain length, signal loss/attenuation in the cable increases with frequency.

d) Given a RF cable and a signal frequency, signal loss/attenuation in the cable increases with distance.

Use the calculator in the Loss in a Coaxial Cable at 2.45 GHz section to complete the following steps:

1. Next to Choose type of cable, select LMR 400. This is a TMS cable that supports both 2.4 GHz and 5 GHz RF signals. 100 feet of such cable used on the 2.5 GHz range decreases the signal strength by about 6.76 dB (that is, 6.76 dB signal loss per 100 feet).

2. Click in the Length (meter) box and type 30.48 (100 feet = 30.48 meters). Click m?dB. What is the loss at this length? _____

3. Click in the Length (meter) box and type 60.92 (200 feet = 30.48 meters). Click m?dB. What is the loss at this length? _____

4. When the cable length doubles, how does the loss change approximately? _____

Task 3: Antenna gain calculations

Antennas are often used to increase the power output of a transmitter. Antennas achieve this by focusing the existing power in a specific direction. Notice that the amount of power provided to the antenna from the transmitter does not change; the signal gain created by antennas is a passive gain.

Antenna gain in dBi or dBd is a parameter that describes the directionality characteristic of an antenna. Given a particular type of antenna, the higher the antenna gain, the more directional the antenna is, and the more focused the existing power is in a specific direction.

Parabolic or dish antennas are an example of highly directional antennas. Due to their relatively high antenna gain, dish antennas are typically used for point-to-point transmission links. The antenna gain of a parabolic antenna is directly related to the diameter of a dish antenna’s reflector and the signal frequency.

Use the calculator in the Antenna section to complete the following steps:

1. Next to frequency band, select 2.41–2.48 GHz.

2. Next to antenna diameter in meters, type 0.1 (0.1 meters = 3.9 inches). This is an optional antenna that could be added to an access point (AP).

3. Click D ? dB. What is the maximum theoretical antenna gain? _____

4. Next to frequency band, select 5.15–5.85 GHz.

5. Next to antenna diameter in meters, type 0.1 (0.1 meters = 3.9 inches)

6. Click D ? dB. What is the maximum theoretical antenna gain? _____

7. Given the same sized reflector, which signals, high-frequency or low-frequency, can be more efficiently focused by parabolic antennas (i.e., result in a higher antenna gain)?

Answer:

8. Next to frequency band, select 5.15–5.85 GHz.

9. Next to antenna diameter in meters, type 0.2 (0.1 meters = 7.8 inches)

10. Click D ? dB. What is the maximum theoretical antenna gain? _____

11. Given the same signal frequency, which dish antennas, large-sized or small-sized, are more efficient at focusing the signal (i.e., result in a higher antenna gain)?

Answer:

Task 4: Free space loss calculations

Free space path loss (FSPL) is the amount of signal loss/attenuation caused by signal dispersion over a distance. As does the light emitted from a flash light, RF signals spread out and weaken when propagating from an antenna. Notice that FSPL occurs regardless of the obstacles that cause reflection, diffraction, etc.; this is indicated by the “free space” phrase in its name.

Use the calculator in the Free space loss section to complete the following steps:

1. Next to frequency band, select 2.41–2.48 GHz.

2. Next to kilometers, type 0.1 (100 meters = 0.1 kilometers).

3. Click dB ? km. What is the free space path loss in dB? _____

4. Change the frequency band to 5.15–5.85 GHz.

5. Next to kilometers, type 0.1 (100 meters = 0.1 kilometers).

6. Click dB ? km. What is the free space path loss in dB? _____

7. How does the free space path loss for 802.11a (operating on the 5 GHz band) compare with 802.11g (operating on the 2.4 GHz band)?

Answer:

8. Next to frequency band, select 2.41–2.48 GHz.

9. Next to kilometers, type 0.02 (20 meters = 0.02 kilometers).

10. Click dB ? km. What is the free space path loss in dB? _____

11. Next to kilometers, type 0.04 (40 meters = 0.04 kilometers).

12. Click dB ? km. What is the free space path loss in dB? _____

13. Next to kilometers, type 0.08 (80 meters = 0.08 kilometers).

14. Click dB ? km. What is the free space path loss in dB? _____

15. When the distance doubles, how does free space path loss in dB change?

Answer:

16. Next to frequency band, select 17.1–17.3 GHz.

17. Next to kilometers, type 1.

18. Click dB ? km. What is the free space path loss in dB? _____

19. Next to kilometers, type 2.

20. Click dB ? km. What is the free space path loss in dB? _____

21. Next to kilometers, type 4.

22. Click dB ? km. What is the free space path loss in dB? _____

23. When the distance doubles, how does free space path loss in dB change?

Answer:

Without the calculator, we could use the 6 dB rule to estimate free space loss: doubling the distance results in a signal loss/attenuation of 6 dB.

Task 5: Link Budget Calculations

The ultimate goal of link budget calculations is to ensure that the received signal strength is above the receive sensitivity of the receiver. A link budget is computed by adding and subtracting gains and losses represented in dB forms from the original power level of the transmitter or IR.

Fade margin is the amount of desired signal (i.e., the received signal) above what is required (i.e., the receive sensitivity). If the receive sensitivity of a receiver is -75 dBm, and the received signal is measured as -75 dBm, a transmission link may or may not be successful. The fact is that the received signal strength cannot be maintained at -75 dBm, due to interference, obstacles, and weather conditions. A 10 dB to 25 dB margin is commonly planned to accommodate received signal strength fluctuations. This range may seem to be wide, but the longer a transmission link (especially outdoors), the higher the margin should be.

Use the calculator in the Link budget section to complete the following steps:

1. Enter the following values for an office WLAN:

Transmit—

Transmit output power: +15 dBm

Cable loss: -6 dB

Antenna gain: +2 dBi

NOTE: the previous values are used to compute effective isotropically radiated power (EIRP): (+15 dBm) + (-6 dB) + (+2 dBi) = 11 dBm. By definition, EIRP is the amount of power an ideal isotropic radiator can generate. In reality, EIRP is the power radiated from an antenna; it is regulated by the FCC.

Propagation—

Free space loss: -81 dB

Reception—

Antenna gain: +2 dBi

Cable loss: -4 dB

Receiver sensitivity: -80 dBm

2. Click Compute. What’s the total remaining margin in dB? _____

3. Is this margin sufficient to accommodate received signal fluctuations? Why?

Answer:

4. Enter the following values for a 10-killometer outdoor transmission link:

Transmit—

Transmit output power: +10 dBm

Cable loss: -3 dB

Antenna gain: +25 dBi

NOTE: the previous values are used to compute effective isotropically radiated power (EIRP): (+10 dBm) + (-3 dB) + (+25 dBi) = 32 dBm. EIRP is regulated by the FCC.

Propagation—

Free space loss: -120 dB

Reception—

Antenna gain: +25 dBi

Cable loss: -3 dB

Receiver sensitivity: -80 dBm

5. Click Compute. What’s the total remaining margin in dB? _____

6. Is this margin sufficient to accommodate received signal fluctuations? Why?

Answer:

Task 6: Link budget calculations

Between two point-to-point antennas, the area that surrounds the visual line of sight path (i.e., the straight line drawn between two antennas) is called the Fresnel zone. If trees, buildings, and other obstacles encroach on this football shaped area, RF signals could experience loss caused by reflection, scattering, and diffraction. This contributes to signal loss fluctuation, and could cause a transmission link to fail.

To determine if a tree or building is obstructing the Fresnel zone, the radius of the Fresnel zone at the location of the potential obstacle is calculated. Actions needed to maintain Fresnel zone clearance include removing the obstacle or raising the antenna. Often, this Fresnel zone clearance is relaxed by 40%, that is, only 60% of the Fresnel zone is clear of obstacles.

Use the calculator in the Fresnel ellipsoid section to complete the following steps:

1. Next to distance “D” between transmitter and receiver [meters], type 114. This is close to the maximum distance of an office WLAN.

2. Next to distance “d” between transmitter and obstacle [meters], type 65. This assumes an obstacle is at the midpoint between two antennas.

3. Click Compute radius. What’s the radius of the Fresnel zone at the middle point? _____

4. Next to distance “D” between transmitter and receiver [meters], type 16000. This refers to an approximately 10-mile outdoor point-to-point transmission link.

5. Next to distance “d” between transmitter and obstacle [meters], type 4800. The obstacle is about 3 miles from one antenna.

6. Click Compute radius. What’s the radius of the Fresnel zone at this specific location?

Answer:

NETW 360 Week 2 iLab: RF Behavior Calculations

Date:

Student’s Name:

Professor’s Name:

Task 1: Power calculations

Use the calculator in the Power section to complete the following steps:

1. On the lower UNII-1 band (i.e., 5.150–5.250 GHz with 100 MHz channels), the maximum output power of the intentional radiator (IR) allowed by the FCC is 50 mW. The IR is also referred to as a wireless transmitter.

Click in the watts box and type 0.05 (50 mW = 0.05 watts). What is the dBm of 50 mW? __________

2. On the middle UNII-1 band (i.e., 5.250–5.350 GHz with 100 MHz channels), the maximum output power of the intentional radiator (IR) allowed by the FCC is 250 mW.

Click in the watts box and type 0.25 (250 mW = 0.25 watts). What is the dBm of 250 mW? __________

3. On the upper UNII-1 band (i.e., 5.725–5.825 GHz with 100 MHz channels), the maximum output power of the intentional radiator (IR) allowed by the FCC is 800 mW.

Click in the watts box and type the given power level in watts. What is the dBm of 800 mW? __________

Scroll down to the Receive Sensitivity section. Review the information regarding receive sensitivity.

4. The receive sensitivity of a LinksysWUSB600N wireless network adaptor at 54 Mbps is -70 dBm.

Click in the dBm box and type -70. What are the watts of -70 dBm? __________

5. The receive sensitivity of a LinksysWUSB300N wireless network adaptor at 54 Mbps is -68 dBm.

Click in the dBm box and type -68. What are the watts of -68 dBm? __________

6. If you have to choose between these adaptors based on their receive sensitivity at the bit rate of 54 Mbps, which adaptor will potentially perform better in achieving the desired bit rate? __________

Task 2: Cable loss calculations

Use the calculator in the Loss in a Coaxial Cable at 2.45 GHz section to complete the following steps:

1. Next to Choose type of cable, select LMR 400. This is a TMS cable that supports both 2.4 GHz and 5 GHz RF signals. 100 feet of such cable used on the 2.5 GHz range decreases the signal strength by about 6.76 dB (that is, 6.76 dB signal loss per 100 feet).

2. Click in the Length (meter) box and type 30.48 (100 feet = 30.48 meters). Click m?dB. What is the loss at this length? __________

3. Click in the Length (meter) box and type 60.92 (200 feet = 30.48 meters). Click m?dB. What is the loss at this length? __________

4. When the cable length doubles, how does the loss change, approximately? __________

Task 3: Antenna gain calculations

Use the calculator in the Antenna section to complete the following steps:

1. Next to frequency band, select 2.41–2.48 GHz.

2. Next to antenna diameter in meters, type 0.1 (0.1 meters = 3.9 inches). This is an optional antenna that could be added to an access point (AP).

3. Click D? dB. What is the maximum theoretical antenna gain? __________

4. Next to frequency band, select 5.15–5.85 GHz.

5. Next to antenna diameter in meters, type 0.1 (0.1 meters = 3.9 inches)

6. Click D? dB. What is the maximum theoretical antenna gain? __________

7. Given the same sized reflector, which signals, high-frequency or low-frequency, can be more efficiently focused by parabolic antennas (i.e., result in a higher antenna gain)? __________

8. Next to frequency band, select 5.15–5.85 GHz.

9. Next to antenna diameter in meters, type 0.2 (0.1 meters = 7.8 inches)

10. Click D? dB. What is the maximum theoretical antenna gain? __________

11. Given the same signal frequency, which dish antennas, large-sized or small-sized, are more efficient at focusing the signal (i.e., result in a higher antenna gain)? __________

Task 4: Free space loss calculations

Use the calculator in the Free space loss section to complete the following steps:

1. Next to frequency band, select 2.41–2.48 GHz.

2. Next to kilometers, type 0.1 (100 meters = 0.1 kilometers).

3. Click dB? km. What is the free space path loss in dB? __________

4. Change the frequency band to 5.15–5.85 GHz.

5. Next to kilometers, type 0.1 (100 meters = 0.1 kilometers).

6. Click dB? km. What is the free space path loss in dB? __________

7. How does the free space path loss for 802.11a (operating on the 5 GHz band) compare with 802.11g (operating on the 2.4 GHz band)? __________

8. Next to frequency band, select 2.41–2.48 GHz.

9. Next to kilometers, type 0.02 (20 meters = 0.02 kilometers).

10. Click dB? km. What is the free space path loss in dB? __________

11. Next to kilometers, type 0.04 (40 meters = 0.04 kilometers).

12. Click dB? km. What is the free space path loss in dB? __________

13. Next to kilometers, type 0.08 (80 meters = 0.08 kilometers).

14. Click dB? km. What is the free space path loss in dB? __________

15. When the distance doubles, how does free space path loss in dB change? ___________________________________

16. Next to frequency band, select 17.1–17.3 GHz.

17. Next to kilometers, type 1.

18. Click dB? km. What is the free space path loss in dB? __________

19. Next to kilometers, type 2.

20. Click dB? km. What is the free space path loss in dB? __________

21. Next to kilometers, type 4.

22. Click dB? km. What is the free space path loss in dB? __________

23. When the distance doubles, how does free space path loss in dB change? ___________________________________

Task 5: Link budget calculations

Use the calculator in the Link budget section to complete the following steps:

1. Enter the following values for an office WLAN:

Transmit—

Transmit output power: +15 dBm

Cable loss: -6 dB

Antenna gain: +2 dBi

NOTE: the previous values are used to compute effective isotropically radiated power (EIRP): (+15 dBm) + (-6 dB) + (+2 dBi) = 11 dBm. By definition, EIRP is the amount of power an ideal isotropic radiator can generate. In reality, EIRP is the power radiated from an antenna; it is regulated by the FCC.

Propagation—

Free space loss: -81 dB

Reception—

Antenna gain: +2 dBi

Cable loss: -4 dB

Receiver sensitivity: -80 dBm

2. Click Compute. What’s the total remaining margin in dB? __________

3. Is this margin sufficient to accommodate received signal fluctuations? Why? _________________________________________

4. Enter the following values for a 10-killometer outdoor transmission link:

Transmit—

Transmit output power: +10 dBm

Cable loss: -3 dB

Antenna gain: +25 dBi

NOTE: the previous values are used to compute effective isotropically radiated power (EIRP): (+10 dBm) + (-3 dB) + (+25 dBi) = 32 dBm. EIRP is regulated by the FCC.

Propagation—

Free space loss: -120 dB

Reception—

Antenna gain: +25 dBi

Cable loss: -3 dB

Receiver sensitivity: -80 dBm

5. Click Compute. What’s the total remaining margin in dB? __________

6. Is this margin sufficient to accommodate received signal fluctuations? Why? ____________________________________________

Task 6: Link budget calculations

Use the calculator in the Fresnel ellipsoid section to complete the following steps:

1. Next to distance “D” between transmitter and receiver [meters], type 114. This is close to the maximum distance of an office WLAN.

2. Next to distance “d” between transmitter and obstacle [meters], type 65. This assumes an obstacle is at the midpoint between two antennas.

3. Click Compute radius. What’s the radius of the Fresnel zone at the middle point? ________

4. Next to distance “D” between transmitter and receiver [meters], type 16000. This refers to an approximately 10-mile outdoor point-to-point transmission link.

5. Next to distance “d” between transmitter and obstacle [meters], type 4800. The obstacle is about 3 miles from one antenna.

6. Click Compute radius. What’s the radius of the Fresnel zone at this specific location?

NETW 360 DeVry Week 3 iLab Latest

NETW 360 Week 3 iLab: Observing RF Activities

Wireless signals are invisible to the human eye. To observe these signals, tools such as a spectrum analyzer are required. Displaying wireless signal strength with respect to its frequency, a spectrum analyzer typically captures activities in a pre-defined range of frequencies. It is often used for layer 1 site survey in WLAN monitoring and planning.

In this lab, students learn how to use a spectrum analyzer to identify potential RF interferences on a wireless LAN. Notice that the analyzer operates on the 2.4 GHz and 5 GHz bands; students will observe RF activities across the 11 WLAN channels of the 2.4 GHz band.

Task 1: Tutorial

Review Tutorial: Using Spectrum Analyzer Wi-Spy located in Appendix A.

1. Name the three default views of Chanalyzer 3.4 that display RF activities from different perspectives. ____________________________________

2. Explain what hardware and software are required in this iLab to capture and visualize RF activities. ____________________________________

Task 2: Observing RF Activities

Students are not required to capture RF activities on the spectrum in this iLab. Four capture files are provided for students to observe and identify RF activities instead.

1. Go to.devry.edu”>http://lab.devry.edu. Enter “Chanalyzer” in the search field on the top right corner to locate and select the Chanalyzer program.

2. Click on the Chanalyzer icon in the window, and launch the program in the Citrix environment. Click on the Cancel button to close the Chanalyzer 3.4 registration window.

3. In the Chanalyzer window, click File and Open Recording… to navigate to G: drive. In the NETW360 folder, locate and open the first capture file: Capture1.wsr. Let the recording run for at least five minutes, and answer the following questions in your lab report.

4. There are three non-overlapping channels on the 2.4 GHz band: 1, 6, and 11. Move the cursor over each of the 11 channels shown on the horizontal axis. What channel(s) currently in use overlap with other channels? _______________________________________

5. To rectify the problem in Step 4, to which channel would you move that overlapping device or access point to? ________________________________________

6. In the Chanalyzer window, open the second capture file: Capture2.wsr. Let the recording run for at least 5 minutes, and answer the following questions in your lab report.

7. Move the cursor over each of the 11 channels shown on the horizontal axis. What channels are being used? ________________________________________

8. Cross-reference the information in the Spectral View, Topographic View, and Planar View windows. Which channel is being used the most? ________________________________________

9. In the Chanalyzer window, open the second capture file: Capture3.wsr. Let the recording run for at least 5 minutes, and answer the following questions in your lab report.

10. Click on the vertical SIGNATURES tab on the right of the Chanalyzer window. Scroll down the list, and compare the signatures to the pattern shown in the Topographic View window. What device most likely generated the RF activities across channels 8 and 9 in the capture file? ________________________________________

11. Click on the vertical INSPECTOR tab on the right of the Chanalyzer window. Move the cursor over the center frequency of the RF pattern in the Topographic View window. Double-click the mouse in any of the three views to generate a vertical referencing line. Double-click again to remove it. What frequency (not channel!) is being used by this device? ________________________________________

12. In the Chanalyzer window, open the fourth capture file: Capture4.wsr.Let the recording run for a few seconds, and answer the following questions in your lab report.

13. Click on the vertical SIGNATURES tab on the right of the Chanalyzer window. Scroll down the list, and compare the signatures to the pattern shown in the Topographic View window. What device most likely generated the RF activities around channel 6 in the capture file? ________________________________________

14. Wait until the capture file stops running. Click on the vertical INSPECTOR tab on the right of the Chanalyzer window. Switch on both the Max and Average formats in the Planar View window. Move the cursor over to the center frequency (i.e., channel 6) of the RF pattern in the Topographic View window. What are the maximum signal strength and average signal strength in dBm recorded in this capture, respectively? _________________________________________

15. In the Chanalyzer window, click File and Exit to close the program.

Appendix A

Tutorial: Using the Spectrum Analyzer Wi-Spy

The hardware used to capture and record the activities on the 2.4 GHz band in this lab is a USB-based spectrum analyzer: Wi-Spy from Metageek (.metageek.net”>www.metageek.net).

The device itself looks like this:

As demonstrated in the following diagram, Chanalyzer is the program that displays what is captured by Wi-Spy and helps visualize the RF activities.

Observing data (required in this iLab)

The red line at the bottom of the diagram indicates the time line of a data capture. In this particular case, the capture has lasted for 29 seconds.

In the Spectral View window on the top of the diagram, a color bar is used to represents signal strength. The colors towards the left side represent weaker signals, with the weakest being -110 dBm. The colors towards the right side represent stronger signals, with the strongest at -54.5 dBm. Vertical stripes in the Spectral View window indicate steady signals around a particular WLAN channel. For instance, a weak but constant signal (i.e., a blue-colored stripe) near channel 8 is shown in the diagram below.

The Topographic View window is in the middle of the diagram; it shows the RF signal patterns with a color coding system similar to that of the Spectral View. The cooler the color, the less often that particular frequency and signal strength pair occurred. The actual signal strength in dBm is shown on the vertical axis.

The Planar View window is on the bottom of the diagram. It illustrates the relationship between the signal strength and frequency in one, two, or all of the three formats: the current signal strength in yellow, the average signal strength in green, and the maximum signal strength in blue. The actual signal strength in dBm is shown on the vertical axis.

In the Planar View window, each of these three formats can be turned on or off by clicking its name in the upper right corner. When looking for RF interferences, it is recommended to turn off the maximum and average signal strength formats and only display the current signal strength in yellow.

Common signal signatures can be accessed by clicking on the vertical SIGNATURES tab on the right side of the diagram. As show in the second diagram below, a selected signature will follow the mouse over to the Topographic View window for one to match/ identify a RF activity pattern.

Capturing data (not required in this iLab)

Capturing data requires a wireless NIC be present in the same system that the USB spectrum analyzer Wi-Spy is connected to. After the hardware is ready, select the vertical Wi-Fi tab in the Chanalyzer window and then click Start Scanning as shown in the diagram below. Once the network list in the SIDE BAR pane is complete, select the ones to be shown in the spectrum display windows.

NETW 360 Week 3 iLab: Observing RF Activities

Date:

Student’s Name:

Professor’s Name:

Task 1: Tutorial

Review Tutorial: Using Spectrum Analyzer Wi-Spy, located in Appendix A.

1. Name the three default views of Chanalyzer 3.4 that display RF activities from different perspectives.

2. Explain what hardware and software are required in this iLab to capture and visualize RF activities.

Task 2: Observing RF Activities

Students are not required to capture RF activities on the spectrum in this iLab. Four capture files are provided for students to observe and identify RF activities instead.

1. From the Course Shell, download Week3iLabCaptureFiles.zip to a working directory of a computer. Right click on the .zip file, click Extract All to unzip its contents into a directory with the same name.

2. Go to.devry.edu”>http://lab.devry.edu, and launch the Chanalyzer program in the Citrix environment.

3. In the Chanalyzer window, click File and Open Recording to locate/open the first capture file: Capture1.wsr. Let the recording run for at least five minutes, and answer the following questions in your lab report.

4. There are three non-overlapping channels on the 2.4 GHz band: 1, 6, and 11. Move the cursor over each of the 11 channels shown on the horizontal axis. What channel(s) currently in use overlap with other channels?

5. To rectify the problem in Step 4, to which channel would you move that overlapping device or access point?

6. In the Chanalyzer window, open the second capture file: Capture2.wsr. Let the recording run for at least five minutes, and answer the following questions in your lab report.

7. Move the cursor over each of the 11 channels shown on the horizontal axis. What channels are being used?

8. Cross-reference the information in the spectral view, topographic view, and planar view windows. Which channel is being used the most? ________________________________________

9. In the Chanalyzer window, open the second capture file: Capture3.wsr. Let the recording run for at least five minutes, and answer the following questions in your lab report.

10. Click on the vertical signatures tab on the right of the Chanalyzer window. Scroll down the list, and compare the signatures to the pattern shown in the topographic view window. What device most likely generated the RF activities across channels 8 and 9 in the capture file?

11. Click on the vertical inspector tab on the right of the Chanalyzer window. Move the cursor over the center frequency of the RF pattern in the topographic view window. Double-click the mouse in any of the three views to generate a vertical referencing line. Double-click again to remove it. What frequency (not channel!) is being used by this device?

12. In the Chanalyzer window, open the fourth capture file: Capture4.wsr. Let the recording run for a few seconds, and answer the following questions in your lab report.

13. Click on the vertical signatures tab on the right of the Chanalyzer window. Scroll down the list, and compare the signatures to the pattern shown in the topographic view window. What device most likely generated the RF activities around channel 6 in the capture file?

14. Wait until the capture file stops running. Click on the vertical inspector tab on the right of the Chanalyzer window. Switch on both the max and average formats in the planar view window. Move the cursor over to the center frequency (i.e., channel 6) of the RF pattern in the topographic view window. What are the maximum signal strength and average signal strength in dBm recorded in this capture, respectively?

15. In the Chanalyzer window, click File and Exit to close the program.

NETW 360 DeVry Week 4 iLab Latest

Week 4 iLab: Observing 802.11 Frames

Date:

Student’s Name:

Professor’s Name:

Task 2: Beacon Frames

2. Record the basic information of the beacon frame below in the lab report document. Afterwards, shrink the header by clicking the – sign to its left.

Type/Subtype of the frame: Source MAC address:

Destination MAC address:

3. Next expand the radiotap header by clicking the + sign to its left. Record the radio information of the beacon frame below in the lab report document. Afterwards, shrink the header by clicking the – sign to its left.

Data rate: Channel frequency:

Channel type:

4. Next expand the IEEE 802.11 wireless LAN management frame section. Expand both the fixed parameters and tagged parameters subsections. Provide the following information in the lab report document. Afterwards, shrink the header by clicking the – sign to its left.

Beacon Interval: SSID:

Supported Rates:

5. What type of address, unicast, multicast, or broadcast is a beacon frame’s destination MAC address? Why?

6. What’s the significance of increasing and decreasing the beacon interval, respectively, on a WLAN?

Task 3: Probe Frames

3. Expand the IEEE 802.11 probe request header by clicking the + sign to its left. Record the following information in the lab report. Afterwards, shrink the header by clicking the – sign to its left.

Type/Subtype: Destination MAC address:

Source MAC Address:

4. Expand the IEEE 802.11 wireless LAN management frame header by clicking the + sign to its left. Record the following information in the lab report.

SSID: Supported Rates:

Extended Supported Rates:

6. Expand the IEEE 802.11 probe request header by clicking the + sign to its left. Record the following information in the lab report. Afterwards, shrink the header by clicking the – sign to its left.

Type/Subtype: Destination MAC address:

Source MAC Address:

7. Expand the IEEE 802.11 wireless LAN management frame header by clicking the + sign to its left. Record the following information in the lab report.

SSID: Supported Rates:

Extended Supported Rates:

8. Is the destination address of the probe response frame the same as the source address of the previous probe request frame?

9. When a wireless client is looking for an access point or network, what frame(s) are involved in the passive scanning process? What frame(s) are involved in the active scanning process?

Task 4: Authentication and Association Frames

3. Expand the IEEE 802.11 authentication and 802.11 wireless LAN management headers. Record the following information in the lab report. If needed, shrink the headers by clicking the – sign to their left.

Type/Subtype: Authentication algorithm:

Authentication SEQ: Status code:

5. Expand the IEEE 802.11 authentication and 802.11 wireless LAN management headers. Record the following information in the lab report. If needed, shrink the headers by clicking the – sign to their left. Type/Subtype:

Authentication algorithm: Authentication SEQ:

Status code:

8. Expand the IEEE 802.11 association request and 802.11 wireless LAN management headers. Record the following information in the lab report. If needed, shrink the headers by clicking the – sign to their left.

Type/Subtype: SSID:

10. Expand the IEEE 802.11 association request and 802.11 wireless LAN management headers. Record the following information in the lab report. If needed, shrink the headers by clicking the – sign to their left.

Type/Subtype: Status code:

Association ID:

NETW 360 DeVry Week 5 iLab Latest

Week 5 iLab: Discovering Access Points and Monitoring Signal Strength

Taking detailed measurements required for the successful installation of a WLAN, site survey programs come in different forms. Some programs use their own hardware, and some work with the host environment, such as a laptop. Some of them are designed to conduct manual site surveys and some are used for predictive site surveys.

InSSIDer from .com/”>metageek.com could be used in the process of a site survey. Once installed, inSSIDer works with a compatible wireless NIC to reveal important information of the WLAN environment it’s in. Aside from detecting various access points or WLAN networks, it can also verify network parameters, find RF shadows, detect rouge access points, and help fine-tune antenna positions.

In this lab, a series of inSSIDer screenshots are evaluated by students. It serves as an example to demonstrate how WLAN professionals, during a site survey process, discover access points and investigate or verify their network parameters. These parameters include network type, security standard, channel, maximum transmission rate, co-channels, and overlapping channels.

Task 1: Discovering Access Points

Once launched, the inSSIDer program displays a list of access points it picked up as demonstrated in the diagram below. Depending on the software version, the following sections are typically included in the inSSIDer window.

· The FILTERS section, on the top of the window, which allows one to display or hide network parameters

·The list of detected access points in the middle section of the window

· The graphical representation section (2.4 GHz Band and 5 GHz Band), on the bottom of the window, where access points and their channels are shown

· The detailed information section, on the right side of the window, displays the information about an individual access point that is highlighted on the list of detected access points

1. Refer to the truncated list of detected access points from the middle section of the inSSIDer window shown below and answer the following questions.

a) Which CHANNEL is used by the “linksys” access point?

b) What’s the MAX RATE of this access point or network?

c) What SECURITY standard is used by this access point or network?

d) What’s its NETWORK TYPE?

2. Refer to the detailed information about the “linksys” access point shown below and answer the following questions.

a) How many Co-Channels are listed here?

b) What does this value mean?

3. When clicking on the CHANNEL column in the inSSIDer window, the access points discovered by the software are sorted based on their channels. The 16 access points operating on channel 6 (including the “linksys” access point itself) are listed in the diagram below.

4. The graphical representation of these 16 access points is shown in the diagram below. Notice that theirtransmission channel width is 20 MHz (5 MHz per channel * 4 channels = 20 MHz).

5. Let’s assume some network parameters of the “linksys” access point have been changed. After several seconds, the information shown in the inSSIDer window is also changed as captured below.

6. Refer to the truncated list of detected access points from the middle section of the inSSIDer window shown below and answer the following questions.

a) Which CHANNEL(s) is (are) used by the “linksys” access point now?

b) What’s the MAX RATE of this access point or network?

c) What SECURITY standard is used by this access point or network?

d) What’s its NETWORK TYPE?

7. Refer to the detailed information about the “linksys” access point shown below and answer the following questions. a) How many Co-Channels are listed here? b) What’s the Overlappingvalue? c) Explain what the Overlapping value means. 8. Refer to the graphical representation of the access points shown in the diagram below and answer the following questions: a) What’s the transmission channel width (in MHz) of the “linksys” access point now? b) If the “linksys” access point is meant to work in harmony with other access points in the same environment, what went wrong with the configuration changes?

Task 2: Monitoring Signal Strength

The amplitude of a wireless signal measured by WLAN and site survey tools is referred to as received signal strength indication (RSSI). Higher RSSI values are often associated with higher data rates and fewer retransmissions. RSSI is typically used by vendors for purposes such as roaming handoff and data rate switching. It could also be used, during a site survey, to mark the coverage boundary of an access point. For instance, Cisco recommends the minimum RSSI of -67 dBm for voice applications.

Notice that RSSI is an indicator of relative signal strength; it could be mapped to the actual signal strength based on each vendor’s specifications. Different vendors’ tools most likely provide different RSSI values in the same environment. Therefore, RSSI values from different vendors should not be directly compared to each other.

Another parameter typically used in site surveys to define the coverage boundary of an access point is the signal-to-noise (SNR) ratio. It is an indicator of how much stronger a measured signal is in relation to the noise level. Higher SNR values typically indicate higher data rates, fewer retransmissions, and better throughput. For instance, Cisco recommends the minimum SNR of 25 dB for voice applications.

The following inSSIDer screenshots demonstrate how the Signal and Link Score values change when the wireless client with inSSIDer installed moves away from the “linksys” access point. As explained in MetaGeek’s quick start guide for the inSSIDer Home software, Signal is “the amplitude level of the wireless network as seen by your computer’s wireless adapter, also known as RSSI.” Link Score is “a grade for each network calculated by its signal strength, channel power, and number of networks competing for airtime.”

1. Refer to the detailed information about the “linksys” access point shown below and answer the following questions.

a) What’s the Signal strength of this access point when the screenshot was taken?

b) What’s the Link Score?

2. The laptop with the insider software installed is moved away from the “linksys” access point for a certain distance in the same room, but hidden underneath a computer table.

Refer to the detailed information about the “linksys” access point shown below and answer the following questions.

a) What’s the Signal strength of this access point when the screenshot was taken?

b) What’s the Link Score?

3. At the same location, position the laptop with inSSIDer installed on top of the computer table.

Refer to the detailed information about the “linksys” access point shown below and answer the following questions.

a) What’s the Signal strength of this access point when the screenshot was taken?

b) What’s the Link Score?

c) What could be the reason that the signal strength is higher, although the distance between the access point and the wireless client (with inSSDIer installed) has not changed?

4. The laptop with the insider software installed is moved further away from the “linksys” access point into a different room across the hall.

Refer to the detailed information about the “linksys” access point shown below and answer the following questions.

a) What’s the Signal strength of this access point when the screenshot was taken?

b) What’s the Link Score?

NETW 360 DeVry Week 6 iLab Latest

Week 6 iLab Evaluating Security-Related WLAN Problems

In this lab, three scenarios are presented as examples of how WLAN security is addressed from different aspects: signal spillage, security standards, and rogue access points. Students are expected to fully understand each scenario, correctly identify the problem(s), and sufficiently justify their recommendations.

Scenario I: Signal Spillage

Signal spillage refers to the reach of Wi-Fi signals that is beyond the perimeter of an intended coverage area. Signals spilling outside the perimeter could be received and potentially be interpreted by outsiders. Given the reciprocal nature of antennas, a high-gain directional antenna can also be used to “amplify” weak Wi-Fi signals on the edge of the perimeter. Although the signal coverage area and physical boundary of a location may not be matched perfectly, signal spillage should be limited to reduce security risks.

Refer to the site survey diagram below. The Wi-Fi signal coverage area overlays with the second-floor physical layout of a campus building. The coverage area is color-coded with the descending signal strength from green, light green, yellow, to orange.

1. Compare the physical boundary of the building to the signal coverage area. Name a couple of locations where the incidents of signal spillage occur (e.g., the northwest corner)?

2. Assume the external antennas being used are all omni-directional with an antenna gain of 2.14 dBi. Given all other conditions remain the same, how would relocating some of the access points to a different part of the floor help reduce the amount of signal spilling outside of the building?

3. Given all other conditions remain the same, how would replacing some of these antennas help reduce the amount of signal spilling outside of the building? What type of antennas would you recommend?

4. Given all other conditions remain the same, how would adjusting the power level of some access points help reduce the amount of signal spilling outside the building? What undesirable outcome, from the signal coverage perspective, will likely be caused by such isolated adjustments?

5. Research a couple of other methods that could help reduce signal spilling outside of a building.

Scenario II: WLAN Security Standards

In addition to securing the perimeter of a network, encrypting the information itself has always been an important component of the security paradigm. This works well for data applications on a WLAN, as you will realize after evaluating Scenario II.

On a Voice over Wi-Fi (VoWiFi) network, however, encryption could pose a negative impact, such as choppy voice and echo problems, on delay-sensitive voice traffic. This is mainly due to 1) the extra encryption/decryption latency and 2) the overhead to Wi-Fi frames (e.g., extra 8 bytes from the WEP/RC4 encryption, extra 20 bytes from the WPA/RC4 encryption, and extra 16 bytes from the WPA2/AES encryption). Encryption, when being applied to real-time traffic, needs to be carefully considered.

Assume that the “Monitor” WLAN as shown below is assigned to a sales department. On a daily basis, sales data, including the credit card/check payment details, are transmitted on the network.

1. Refer to the diagram above. Is the network, as well as the information transmitted on the network, protected from eavesdropping?

2. Among the typical security standards, such as WEP, WPA personal, WPA enterprise, WPA2 personal, and WPA2 enterprise, which one is best suited for the intended use of the “Monitor” network as described in this scenario?

3. Justify your recommendation in the previous question.

Scenario III: Rogue Access Points

Many wireless attacks, for example, man-in-the-middle and Denial-of-Service (DoS), start with a rogue access point. Enterprise WLAN controllers typically have the built-in capability of identifying and even quarantining access points that are not under its management. At times, a WLAN professional is also expected to physically locate and remove the rogue device.

The process of locating a rogue device requires a WLAN tool that measures the received signal strength from the targeted device. An external directional antenna, as compared to the typical omni-directional antennas, could speed up the process by zeroing in the direction of the targeted device.

Refer to the outcome of a recent wireless network sweep as shown below. As part of the security policy, all SSIDs used on this office network should start with “NETW”.

1. Refer to the screenshot. What’s the name of the identified rogue access point?

2. Given the inSSIDer software installed on a laptop, how would one go about physically locating this rogue access point?

NETW360 Week 6 iLab

Evaluating Security-Related WLAN Problems

Date:

Student’s Name:

Professor’s Name:

Scenario I: Signal Spillage

1. Compare the physical boundary of the building to the signal coverage area. Name a couple of locations where the incidents of signal spillage occur (e.g., the northwest corner)?

2. Assume the external antennas being used are all omni-directional with an antenna gain of 2.14 dBi. Given all other conditions remain the same, how would relocating some of the access points to a different part of the floor help reduce the amount of signal spilling outside of the building?

3. Given all other conditions remain the same, how would replacing some of these antennas help reduce the amount of signal spilling outside of the building? What type of antennas would you recommend?

4. Given all other conditions remain the same, how would adjusting the power level of some access points help reduce the amount of signal spilling outside the building? What undesirable outcome, from the signal coverage perspective, will likely be caused by such isolated adjustments?

5. Research a couple of other methods that could help reduce signal spilling outside of a building.

Scenario II: WLAN Security Standards

1. Refer to the diagram above. Is the network, as well as the information transmitted on the network, protected from eavesdropping?

2. Among the typical security standards, such as WEP, WPA personal, WPA enterprise, WPA2 personal, and WPA2 enterprise, which one is best suited for the intended use of the “Monitor” network as described in this scenario?

3. Justify your recommendation in the previous question.

Scenario III: Rogue Access Points

1. Refer to the screenshot. What’s the name of the identified rogue access point?

2. Given the inSSIDer software installed on a laptop, how would one go about physically locating this rogue access point?

NETW 360 DeVry Week 7 iLab Latest

Week 7 iLab Troubleshooting Common WLAN Problems

Four WLAN troubleshooting scenarios are presented in this lab. Students are expected to practice a typical troubleshooting process: understanding the problem, identifying possible causes, verifying the causes, and recommending solutions.

When troubleshooting, there are various ways of categorizing potential WLAN problems. One could look at them as connectivity and throughput issues: First, a wireless device needs to be connected, and next, it requires an acceptable level of throughput. One could also look at them from the perspectives of wireless clients, access points, and wired network segments. For instance, a wireless client that doesn’t support the appropriate authentication protocol won’t be able to connect to a Wi-Fi network. An access point whose network cable is overly stretched or loose could cause intermittent connection issues. If an authentication server malfunctions, a wireless client could lose connection shortly after its initial association.

WLAN spectrum analyzers and packet sniffers are two types of widely-used troubleshooting tools. They support an array of functions, such as passive monitoring, active testing, and traffic analysis.

Below are some examples of common problems related to WLANs.

  1. RF interference is associated to the majority of WLAN problems. In theory, any device that operates on the ISM and UNII bands could potentially interfere with WLAN transmissions. These devices include, but are not limited to, microwave ovens, wireless video cameras, wireless game consoles, cordless phones, and baby monitors. RF interference could either be narrow-band or all-band. An access point can shift to operate on a different channel to avoid narrow-band interference, but it really cannot avoid all-band interference, for example, from older Bluetooth devices.
  2. Co-channel interference occurs when multiple access points in close proximity operate on the same channel. These access points may or may not share the same network or ownership. Such interference could go undetected if the network bandwidth utilization is low or no real-time applications present on the network.
  3. Coverage holes refer to parts of a WLAN coverage area where the actual throughput is much less than expected or there is no connectivity. Even with a proper initial site survey, a WLAN coverage area could change due to new physical obstacles, replacement access points, and different antennas.
  4. The hidden node problem occurs when two wireless clients on the same network cannot detect each other’s transmission. This renders the MAC layer contention avoidance mechanism useless. Their transmission within the same time window causes damaged frames that need to be retransmitted. In a nut shell, collision causes retransmission, which in turn, reduces throughput.
  5. Weather, such as a dense fog or a blizzard, causes air density changes that could worsen the RF signal attenuation. If the link budget is not done with a healthy margin to factor in local weather conditions, an outdoor WLAN link could become unstable or even fail. Wind could also cause antenna misalignment, which contributes to a decreased throughput or zero connectivity.

Scenario I

The Continental Hotel has just completed a major renovation. An elegant thick glass wall, with a water fall running down, has replaced the dry wall between the front desk and the resting area for hotel staff. While patrons in the lobby haven’t experience anything different, the hotel staff has reported an almost nonexistant Wi-Fi connection when they are in the resting area between shifts. The situation hasn’t changed since the renovation.

  1. Among the common WLAN problems described at the beginning of this lab, which do you suspect is most likely the problem?
  2. How would you verify and confirm your educated guess? What WLAN tool(s) would you use, and what information would you look for?
  3. Suggest two possible ways of remedying the identified problem.

Scenario II

Alice, working for an accounting firm in New York City, has recently started to conduct daily web conferences with her colleagues in the CA headquarters at noon. Her west-coast colleagues need her input to start their work day; otherwise, Alice would have spent the hour in the adjacent lunch room where her local colleagues often microwave their lunches.

Alice has recently switched her web conferences to an iPad that’s connected to the Wi-Fi network. She now could sit on the couch during a meeting instead of by her desk the whole hour. However, Alice has noticed frozen video and choppy audio intermittently during the web conferences. All these problems disappear when she joins the meetings using her desktop that’s connected to the wall jack.

  1. Among the common WLAN problems described at the beginning of this lab, which do you suspect is most likely the problem?
  2. How would you verify and confirm your educated guess? What WLAN tool(s) would you use, and what information would you look for?
  3. Suggest two possible ways of remedying the identified problem.

Scenario III

Charles is the owner of a flooring store in a small strip mall. His son comes over whenever there is no school to play online video games on the store’s Wi-Fi network. Since a yogurt business moved in next door last month, his son has been complaining that the lagging network speed is causing his winning record to suffer. Charles does book-keeping and occasionally reads news online on the computer; he hasn’t noticed anything significant. Charles changed the password on his Wi-Fi network and moved his wireless router away from the wall he shared with the yogurt store, but none of these helped.

  1. Among the common WLAN problems described at the beginning of this lab, which do you suspect is most likely the problem?
  2. How would you verify and confirm your educated guess? What WLAN tool(s) would you use, and what information would you look for?
  3. Suggest two possible ways of remedying the identified problem.

Scenario IV

John is temporarily assigned to work with the billing department this week. He is given a user name and password to connect to the Wi-Fi network of the billing department. Although his cubicle has some distance from the rest of the billing department staff, IT ensured him that there is Wi-Fi coverage where his desk is. Soon, John noticed that his Wi-Fi connection is noticeably slower. Other billing staff members didn’t have any problems, except Janice whose cubicle is on the other side of the floor. She started to experience a slow Wi-Fi connection the same day John came on board.

IT moved the access point closer to John, but it didn’t help. They connected John’s computer to a network cable for one day and both John and Janice’s problems disappeared.

  1. Among the common WLAN problems described at the beginning of this lab, which do you suspect is most likely the problem?
  2. How would you verify and confirm your educated guess?
  3. Suggest two possible ways of remedying the identified problem.

NETW360 Week 7 iLab

Troubleshooting Common WLAN Problems

Date:

Student’s Name:

Professor’s Name:

Scenario I

  1. Among the common WLAN problems described at the beginning of this lab, which do you suspect is most likely the problem?
  2. How would you verify and confirm your educated guess? What WLAN tool(s) would you use, and what information would you look for?
  3. Suggest two possible ways of remedying the identified problem.

Scenario II

  1. Among the common WLAN problems described at the beginning of this lab, which do you suspect is most likely the problem?
  2. How would you verify and confirm your educated guess? What WLAN tool(s) would you use, and what information would you look for?
  3. Suggest two possible ways of remedying the identified problem.

Scenario III

  1. Among the common WLAN problems described at the beginning of this lab, which do you suspect is most likely the problem?
  2. How would you verify and confirm your educated guess? What WLAN tool(s) would you use, and what information would you look for?
  3. Suggest two possible ways of remedying the identified problem.

Scenario IV

  1. Among the common WLAN problems described at the beginning of this lab, which do you suspect is most likely the problem?
  2. How would you verify and confirm your educated guess?
  3. Suggest two possible ways of remedying the identified problem.
NETW 360 DeVry Complete iLabs Package

NETW 360 DeVry Complete iLabs Package

ABS,AC,ACC,ACCT,ACT,ADJ,AH,AJS,AMP,ANT,ART,BA,BAM,BBA,BCOM,BIO,BIOS,BIS,BMGT,BPA,BSA,BSE,BSHS,BSOP,BUS,BUSN,CARD,CEIS,CHEM,CIS,CIT,CJA,CJS,CMC,CMGT,COLL,COM,COMM,COMP,CPN1, CRJ,CRMJ,CRT,CS,CWV,DBM,EBUS,ECE,ECET,ECN,ECO,