BlueTooth Interview Questions and Answers
Question - 31 : - What is a Bluetooth dongle?
Answer - 31 : - A device that hangs outside of a computer, or phone to provide Bluetooth connection.
Question - 32 : - What is the data throughput speed of a Bluetooth connection?
Answer - 32 : - 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
Question - 33 : - What is the range of Bluetooth transmitter/receivers?
Answer - 33 : - 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.
Question - 34 : - What kind of encryption will be used for Bluetooth security?
Answer - 34 : - 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.
Question - 35 : - How secure a Bluetooth device is?
Answer - 35 : - 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.
Question - 36 : - What is Pairing?
Answer - 36 : - 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.
Question - 37 : - How many devices can communicate concurrently?
Answer - 37 : - 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.
Question - 38 : - What is Bluetooth SIG?
Answer - 38 : - 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.
Question - 39 : - Do Bluetooth devices need line of sight to connect to one another? List the differences between Bluetooth and Wi-Fi IEEE 802.11 in networking.
Answer - 39 : -
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.
Question - 40 : - How many SCO links are there in a piconet?
Answer - 40 : - In a piconet, there can be up to three SCO links of 64,000 bits per second each.