WPAN and WLAN Technologies: Standards and Security

Posted on Jan 3, 2025 in Geology

TI3501 Questionnaire Test 2

Unit 2: WPAN and WLAN

1. WPAN

  1. Few bands to define ITU ISM and many areas actually used in WLAN and WPAN.
    R: 7 bands, 2 bands of 1, VF, UF 2, 2nd, and the ones which 1 DUF (2.4 GHz) is used in WPAN and WLAN and 1st DSF (5 GHz) is used in WLAN.
  2. Mention the 4 technologies seen in class and WPAN, which are used and stand in the current development.
    R: Oxygen project (MIT), IrDA, Bluetooth, Zigbee, used in WPAN IrDA, Bluetooth, and Zigbee in development Bluetooth Zigbee.
  3. Which IEEE WPAN group studies are used today, and the specific subgroups?
    R: IEEE 802.15 group, its subgroups:
    802.15.1 (Bluetooth)
    802.15.2 (Bluetooth)
    802.15.3 (Bluetooth)
    802.15.3a (Bluetooth)
    802.15.3b (Bluetooth)
    802.15.4 (Zigbee)
    802.15.4a (Zigbee)
    802.15.4b (Zigbee)
    802.15.4c (Zigbee)
    802.15.4d (Zigbee)
  4. Mention the characteristics of IrDA (scope, speed, radio operation).
    R: Maximum reach 1m, speed around 4Mbps, radio operation of 30°.
  5. What is the technical standard used in IrDA called?
    R: IEEE 802.11 legacy
  6. Which layers of IrDA define the link? Does it fit the OSI model?
    R: Physical Layer: Infrared Signal (IR, infrared). Link layer: IrLAP (link access protocol (infrared) layer protocol), IrLMP (link manager protocol), IAS (information access service) or access module to application information, which, preferentially, the information is subdivided into 2 or 1 layer. The model fails OSI.
  7. Who are the developers, organizations, and manufacturers of Bluetooth, when it was created, and who drives it?
    R: Bluetooth SIG (Special Interest Group of Bluetooth)
  8. What classes of Bluetooth exist, and how do they differ based on the power used?
    R: 3 classes, according to the maximum range and the maximum power level issued:
    Class 1: up to 100mW (20dBm), maximum 100 m
    Class 2: up to 2.5 mW (4dBm), maximum 10m
    Class 3: around 1mW (0dBm), max. 1m
  9. What versions of Bluetooth exist, and what is the current maximum speed allowed?
    R: Bluetooth version v / s IEEE standard:
    IEEE 802.15.1 Bluetooth up to v.1.1 – 720kbps
    IEEE 802.15.2 Bluetooth up to v.1.2 – 1Mbps
    v.2.0 Bluetooth IEEE 802.15.3, around 3Mbps
    Bluetooth v.2.2 (Media2 2009), from 53Mbps
  10. What radio technique does Bluetooth use, how many channels does it use, and how are they dispersed? In which band are these channels?
    R: FHSS, 79 channels, 1,600 changes per second.
  11. What is the current Bluetooth network architecture, how many devices can be connected, and how are they related?
    R: Piconet, up to 8 devices per piconet simultaneously, where 1 is the master and the others are slaves.
  12. Does the Bluetooth architecture comply with the ISO OSI model? Why?
    R: It fails the ISO OSI model. The link layer functions are divided into several information parts, preferentially transmitted, before reaching the application layer directly.
  13. In the Bluetooth plot, how are the destination addresses of the devices handled? What does this imply?
    R: 3 bits for destination addresses, at the header of the plot, which means that only up to 8 devices can be addressed with the plot.
  14. How many times is the Bluetooth header repeated in each plot, and how much data can be sent per plot?
    R: In the Bluetooth security plot, the header is repeated 3 times, sending 18 bits, thus the plot header uses 54 bits. On the other hand, the frame can carry up to 2744 data bits.

2. WLAN

  1. What are the radio techniques defined for WLAN 802.11?
    R: FHSS, DSSS, OFDM
  2. What differences exist between these 3 techniques in terms of scope, frequencies, and speeds?
    frequencies and speeds.
    R: FHSS: 150m, DSSS: 30m, OFDM: 5m
  3. What are the 2 spread spectrum techniques, which one is currently used, and why?
    R: FHSS-DSSS, DSSS is used because it offers better speed, better interference, and noise solution.
  4. Why did OFDM technology stop being used?
    R: Because in 802.11g, DSSS appeared with the same speed but with better scope (54k).
  5. With FHSS and DSSS, how many times does the channel change per second, and what bandwidth does each channel use? In which band do they work?
    R: Both at 2.4 GHz, FHSS (1 MHz), DSSS (22 MHz). The DSSS channel does not change, the channel switch is 50 times per second.
  6. Why is it said that DSSS has better cancellation?
    R: It disperses all the power in 1 MHz of power.
  7. There are 14 defined DSSS channels, how many are used in America, and what is the separation between each channel?
    R: 14 channels in America, but only 11 are used, with a separation of 5 MHz.
  8. Which channels are defined as non-overlapping in America?
    R: Channels 1-6-11
  9. What is more affected by interference, FHSS or DSSS, and what about multipath (reflections)?
    R: FHSS is more affected by multipath than DSSS.
  10. How is the interference problem solved with DSSS multipath?
    R: A second antenna is added, and the best reception is chosen.
  11. What are DCF and PCF?
    R: DCF: Ethernet in the air, PCF: Token ring in the air.
  12. What are the 2 inconveniences that DCF must address, and what are the 3 techniques?
    R: Hidden station problem and high error rate. The techniques are: positive acknowledgment (division of the plot), clean channel, and reserved channel.
  13. What protocol is used in the MAC layer?
    R: CSMA/CA collision avoidance.
  14. What are the 3 types of times that appear in a DCF communication?
    R: SIFS – DIFS – EIFS.
  15. What message does the receptor emit after a communication is finished, and how long does it wait before transmitting?
    R: 1 ACK and waits 10 milliseconds.
  16. How is the problem of high interference in a channel solved?
    R: By fragmenting the plot.
  17. How is the problem of collisions due to hidden stations solved?
    R: By generating RTS messages, so the receptor knows when to start receiving.
  18. What is known to occur with the performance when using virtual carrier fragmentation and sensing?
    R: The performance is low, between 50 and 60%.
  19. How many address fields does a WiFi plot use, and how many bytes are in each one? What does this mean?
    R: 4 address fields, each one of 6 bytes, which means that millions of devices can be addressed.
  20. What does roaming or handover refer to?
    R: It refers to the possibility of moving from one communication station to another automatically without interrupting the communication.
  21. What are the 3 basic wireless LAN network architectures, and what do they consist of?
    R: IBSS (ad hoc), BSS (with an AP), and ESS (extended connection).

3. Security

  1. Mention 3 points of vulnerability in a LAN + wireless system.
    R: AP enabled, firewalls, intruders, and enabled ad-hoc communications.
  2. What are the 3 classes of security applied to WLAN access?
    R: WEP, WPA, WPA2
  3. What other elements can support security besides encryption keys (mention 5)?
    R: MAC filtering, access keys, blocking WAN pings, not broadcasting SSID, access key to the router, and using a firewall.
  4. What type of security is WEP, and what does it consist of?
    R: 64 and 128-bit key, and it takes the first encrypted.
  5. How many types of WPA security exist (encryption), and what process do WiFi routers use for encryption?
    R: TKIP, and it re-encrypts the key from time to time.
  6. What does WPA2 allow, and how does it complement security?
    R: It allows working with an external RADIUS server.
  7. What are the 3 functionalities that define WPA security as more robust than WEP?
    R: It implements mutual authentication mechanisms between the client and the access point, uses new algorithms to replace RC4 WEP, and uses new pairs to ensure message integrity.
  8. What does 802.1x security standard consist of?
    R: It allows port-based access control.

4. Design and Configuration

  1. What are the 3 basic configurations that must be set to schedule an AP or WiFi router?
    R: LAN, Wireless, and WAN.
  2. What is the SSID, and how is it related to the beacon?
    R: Beacon: the number of times per second the SSID is emitted.
  3. What precaution should be taken if more than one router is connected in the same coverage area, attending to users?
    R: Watch for overlapping channels.
  4. How are routers connected to provide WiFi service in a multi-story building? How are they programmed?
    R: They are connected in cascade as a gateway.
  5. What is the name of a network with a hotspot on a PC, and how is it built?
    R: Ad-hoc.
  6. How is a router programmed as a repeater?
    R: All routers with the same name, same key, and same channel.
  7. How is a router programmed to allow roaming?
    R: Same SSID, same password, same subnetwork, different channel.
  8. What physical space condition must exist between 2 antennas for a point-to-point link?
    A: The horizontal separation must be met, and the center of the link must comply with Fresnel.
  9. In which case is a parabolic antenna, a Yagi antenna, and an omnidirectional antenna used?
    R: Point to point (parabolic), Yagi (radio operation links with an aperture of 60-70 degrees), omnidirectional (to connect devices in an environment – scope).
  10. What is the real difference in scope between a WiFi link and a link with parabolic antennas?
    R: Parabolic antennas reach more than 3 km.