Bluetooth Technology Interview Questions and Answers

Q1. Define IP Spoofing?
Sending messages by intruder to a computer system with an IP address that indicates the message is sent from a trusted host, for gaining unauthorized access to computer systems. The hacker/intruder first utilize a variety of techniques for finding an IP address of a trusted host. Later he modifies the packet headers, in order to give an illusion that the packets are sent from the host

Q2. Define Cabir Worm?
Cabir worm is one of the malicious software, usually referred as malware. It utilizes Bluetooth technology for sending itself to another similarly vulnerable device. As it is self-replicative, is it classified as a worm.
Cabir worms are currently affects mobile phone which uses the Symbian Series 60 User Interface Platform and feature Bluetooth wireless technology.

Q3. Name few applications of Bluetooth?
* Wireless control of and communication between a cell phone and a hands free headset or car kit. This is the most popular use.
* Wireless networking between PCs in a confined space and where little bandwidth is required.
* Wireless communications with PC input devices such as mouses and keyboards and output devices such as printers.
* Transfer of files between devices via OBEX.
* Transfer of contact details, calendar appointments, and reminders between devices via OBEX.
* Replacement of traditional wired serial communications in test equipment, GPS receivers and medical equipment.
* For remote controls where infrared was traditionally used.
* Sending small advertisements from Bluetooth enabled advertising hoardings to other, discoverable, Bluetooth devices.
* Wireless control of a games console, Nintendo’s Wii and Sony’s PlayStation 3 will both use Bluetooth technology for their wireless controllers.
* Sending commands and software to the upcoming LEGO Mindstorms NXT instead of infra red.

Q4. Why can Bluetooth equipment integrate easily in TCP/IP network? 
Because Bluetooth uses wireless LAN standards IEEE for data transmission.

Q5. Is it possible to connect multiple Bluetooth hubs? 
No, only one hub can be used at a time with a computer. USB or Serial devices can be added.

Q6. What are Different Classes in Bluetooth?
Bluetooth is a radio standard and communications protocol primarily designed for low power consumption, with a short range (power class dependent: 1 meter, 10 meters, 100 meters) based around low-cost transceiver microchip in each device.
Bluetooth lets these devices communicate with each other when they are in range. The devices use a radio communications system, so they do not have to be in line of sight of each other, and can even be in other rooms, so long as the received power is high enough.

Q7. What is FCC and how does it relate to Bluetooth? 
FCC is Federal Communication Commission, which issues licenses to the stations for specific frequencies. It also decides who is able to use which frequency for what purpose. Since Bluetooth is using unlicensed spectrum, FCC has no direct involvement with Bluetooth

Q8. What are some of the uses of Bluetooth?
Depending on the Bluetooth profiles included on the device, Bluetooth technology has the capability to wirelessly synchronize and transfer data among devices. The Bluetooth audio capabilities can be used for headset and hands free applications. The exact functionality provided by a Bluetooth enabled device depends on the Bluetooth profiles included.

Q9. How does Bluetooth fit in with WiFi?
The 802.11b (WiFi) standard is commonly used for wireless networking. Bluetooth is not a competitor with 802.11b, but rather a complement to it. While 802.11b is generally a replacement for wired local area networking, Bluetooth is more commonly used as a replacement for cables between individual devices. Bluetooth is designed to link devices within a very short range (up to 33 feet ). Bluetooth is part of the 802.15 standard.

Q10. Under what frequency range does Bluetooth work? 
2.45 GHz is the frequency range.

Q11. Do Bluetooth devices need line of sight to connect to one another? 

Q12. List the differences between Bluetooth and Wi-Fi IEEE 802.11 in networking
Bluetooth technology is to replace cables, while Wi-Fi is utilized for providing wireless, high-speed access to the Internet or a local area network.
Bluetooth is specified for fast transmission speeds of 800 kbps, where as Wi-Fi’s transmission speed is 11 mbps.
Bluetooth is a short-range network specification with 30 feet, where as Wi-Fi is aimed at 300 feet.
Bluetooth allows connecting to printers, notebooks, mobile phone and mobile books, without cables. Wi-Fi allows sharing high-speed internet connections without cables.

Q12. What is Bluetooth SIG?
Bluetooth Special Interest Group (SIG) :Bluetooth wireless technology is revolutionizing personal connectivity by providing freedom from wired connections. It is a specification for a small-form factor, low-cost radio solution providing links between mobile computers, mobile phones, other portable handheld devices and automobiles, as well as connectivity to the Internet. The Bluetooth SIG, comprised of leaders in the telecommunications, computing, automotive and consumer electronics industries, is driving development of the technology and bringing it to market. The Bluetooth SIG includes Promoter member companies Agere, Ericsson, IBM, Intel, Microsoft, Motorola, Nokia and Toshiba, and thousands of Associate and Adopter member companies. The Bluetooth SIG, Inc. headquarters are located in Overland Park, Kansas, U.S.A.

Q13. How many devices can communicate concurrently?
A Bluetooth device playing the role of the “master” can communicate with up to 7 devices playing the role of the “slave”. This network of “group of up to 8 devices” (1 master + 7 slaves) is called a piconet. A piconet is an ad-hoc computer network of devices using Bluetooth technology protocols to allow one master device to interconnect with up to seven active slave devices (because a three-bit MAC address is used). Up to 255 further slave devices can be inactive, or parked, which the master device can bring into active status at any time.

Q14. What is Pairing?
Pairs of devices may establish a trusted relationship by learning (by user input) a shared secret known as a “passkey”. A device that wants to communicate only with a trusted device can cryptographically authenticate the identity of the other device. Trusted devices may also encrypt the data that they exchange over the air so that no one can listen in. The encryption can however be turned off and passkeys are stored on the device’s file system and not the Bluetooth chip itself. Since the Bluetooth address is permanent a pairing will be preserved even if the Bluetooth name is changed. Pairs can be deleted at any time by either device. Devices will generally require pairing or will prompt the owner before it allows a remote device to use any or most of its services. Some devices such as Sony Ericsson phones will usually accept OBEX business cards and notes without any pairing or prompts. Certain printers and access points will allow any device to use its services by default much like unsecured Wi-Fi networks.

Q15. How secure a Bluetooth device is?
Bluetooth uses the SAFER+ algorithm for authentication and key generation. The E0 stream cipher is used for encrypting packets. This makes eavesdropping on Bluetooth-enabled devices more difficult.

Q16. What kind of encryption will be used for Bluetooth security?
The Bluetooth specification 1.0 describes the link encryption algorithm as a stream cipher using 4 LFSR (linear feedback shift registers). The sum of the width of the LFSRs is 128, and the spec says “the effective key length is selectable between 8 and 128 bits”. This arrangement allows Bluetooth to be used in countries with regulations limiting encryption strength, and “facilitate a future upgrade path for the security without the need for a costly redesign of the algorithms and encryption hardware” according to the Bluetooth specification. Key generation and authentication seems to be using the 8-round SAFER+ encryption algorithm. The information available suggests that Bluetooth security will be adequate for most purposes; but users with higher security requirements will need to employ stronger algorithms to ensure the security of their data.

Q17. What is the range of Bluetooth transmitter/receivers?
Bluetooth is designed for very low power use, and the transmission range will only be 10m, about 30ft. High-powered Bluetooth devices will enable ranges up to 100m (300ft). Considering the design philosophy behind Bluetooth, even the 10m range is adequate for the purposes Bluetooth is intended for. Later versions of the Bluetooth spec may allow longer ranges.

Q18. What is the data throughput speed of a Bluetooth connection?
Bluetooth transfers data at a rate of 721 Kbps, which is from three to eight times the average speed of parallel and serial ports, respectively. This bandwidth is capable of transmitting voice, data, video and still images

Q19. What is a Bluetooth dongle? 
A device that hangs outside of a computer, or phone to provide Bluetooth connection.

Q20. What are the other (competing or not) wireless technologies? 
Wi-Fi, IrDa, EDGE, UWB (Ultra Wide Band)

Q21. Which Bluetooth version uses adaptive frequency hopping? Why? 
In Version 1.2 Adaptive frequency hopping method is used, which improves resistance to radio interference, and provides higher transmission speed.

Q22. How many SCO links are there in a piconet?

In a piconet, there can be up to three SCO links of 64,000 bits per second each.

Q23. what is the total number of masters and slaves in a piconet?
1 Master and 7 Slaves.

Q24. Which method is used for Data transfer?
Asynchronous Connectionless (ACL) is Data transfer method in Bluetooth

Q25. What is RJ-45?
RJ-45 stands for Registered Jack – 45. It is an 8-wire connector for connecting computer systems on to a LAN, especially Ethernets. These connections are similar in appearance to the ubiquitous RJ-11, which are used in connecting telephone equipment, with little more width.

Q26. Which technology is used to avoid interference in Bluetooth?
Blue tooth uses frequency hopping technology. In this technology, 79 hop frequencies are transmitted and received from 2402 to 2480 mhz. hopping in a pseudo random sequence at a rate of 1600 times in a second. Guassian frequency shift keying modulation is utilized with a maximum data transfer rate of 721 kbps. Bluetooth protocol stack is developed and TCP/IP imported layers are used in this technology.
Interference is being avoided by utilizing the frequency-hop(FH) spread spectrum technology. It is adaptable for low-power, low-cost radio implementations and also used in certain wireless LAN products.
The major advantage with this technology transmission is the high rate of 1600 hops / ps. Another advantage is, short packet length is also used by Bluetooth.

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