Bluetooth Interview Questions - An interviewhelper.org blog

What is Frequency-Hopping Spread Spectrum (FHSS)

2009-03-07T00:14:00.000-08:00

Question :What is Frequency-Hopping Spread Spectrum (FHSS)?
Answer :Frequency-Hopping Spread-Spectrum (FHSS) is a spread spectrum modulation scheme that uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver. Properly synchronized, they maintain a single logical channel. To an unintended receiver, FHSS appears as short-duration impulse noise. More simply, the data is broken down into packets and transmitted to the receiver of other devices over numerous “hop frequencies” (79 total) in a pseudo random pattern. Only transmitters and receivers that are synchronized on the same hop frequency pattern will have access to the transmitted data. The transmitter switches hop frequencies 1,600 times per second to assure a high degree of data security

Will other RF (Radio Frequency) devices interfere with Bluetooth Devices

2009-03-07T00:10:00.000-08:00

Question :Will other RF (Radio Frequency) devices interfere with Bluetooth Devices?
Answer :No. Bluetooth radios operate on the unlicensed 2.4 GHz (Industrial, Scientific and Medical) frequency band that is shared among other devices (microwave ovens, cordless phones, garage door openers, etc. ). Bluetooth radios switch frequencies at such a rapid pace (1,600 times per second) and the data packets are so small that interference from other RF sources is highly unlikely. Bluetooth is a robust communication system.

Will Bluetooth and Wireless LAN (WLAN) interfere with each other

2009-03-07T00:09:00.000-08:00

Question :Will Bluetooth and Wireless LAN (WLAN) interfere with each other?
Answer :No, both Bluetooth and WLAN can co-exist. Since Bluetooth devices use Frequency Hopping and most WLANs use Direct Sequence Spreading techniques they each appear as background noise to the other and should not cause any perceivable performance issues.

What is the data throughput speed of a Bluetooth connection

2009-03-07T00:07:00.000-08:00

Question :What is the data throughput speed of a Bluetooth connection?
Answer :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

What is the range of Bluetooth transmitter/receivers

2009-03-07T00:06:00.000-08:00

Question :What is the range of Bluetooth transmitter/receivers?
Answer :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.

What kind of encryption will be used for Bluetooth security

2009-03-07T00:05:00.000-08:00

Question :What kind of encryption will be used for Bluetooth security?
Answer :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.

Is Bluetooth practical for use with mobile devices

2009-03-07T00:04:00.000-08:00

Question :Is Bluetooth practical for use with mobile devices?
Answer :Yes. One concern for mobile computing users is power consumption. Bluetooth radios are very low power, drawing as little as 0.3mA in standby mode and 30mA during sustained data transmissions. Bluetooth radios alternate among power-saving modes in which device activity is lowered to maximize the mobile power supply.

Is it possible to connect multiple Bluetooth hubs

2009-03-07T00:02:00.000-08:00

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

What is Link Manager Protocol

2009-03-07T00:00:00.001-08:00

Question :What is Link Manager Protocol?
Answer :The link manager protocol is responsible for link set-up between Bluetooth devices. This includes setting up of security functions like authentication and encryption by generating, exchanging and checking of link and encryption keys and the control and negotiation of baseband packet sizes. Furthermore it controls the power modes and duty cycles of the Bluetooth radio device, and the connection states of a Bluetooth unit in a piconet.

What is Service Discovery Protocol

2009-03-06T23:59:00.000-08:00

Question :What is Service Discovery Protocol?
Answer :Discovery services are crucial part of the Bluetooth framework. These services provide the basis for all the usage models. Using SDP, device information, services and the characteristics of the services can be queried and after that, a connection between two or more Bluetooth devices can be established. SDP is defined in the Service Discovery Protocol specification.

Do you Know about OBEX Protocol

2009-03-06T23:57:00.000-08:00

Question :Do you Know about OBEX Protocol?
Answer :IrOBEX (shortly OBEX) is a session protocol developed by the Infrared Data Association (IrDA) to exchange objects in a simple and spontaneous manner. OBEX, which provides the same basic functionality as HTTP but in a much lighter fashion, uses a client-server model and is independent of the transport mechanism and transport API, provided it realizes a reliable transport base. Along with the protocol itself, the “grammar” for OBEX conversations between devices, OBEX also provides a model for representing objects and operations. In addition, the OBEX protocol defines a folder-listing object, which is used to browse the contents of folders on remote device. In the first phase, RFCOMM is used as sole transport layer for OBEX.

How is Bluetooth used

2009-03-06T23:55:00.000-08:00

Question :How is Bluetooth used?
Answer :Bluetooth can be used to wirelessly synchronize and transfer data among devices. Bluetooth can be thought of as a cable replacement technology. Typical uses include automatically synchronizing contact and calendar information among desktop, notebook and palmtop computers without connecting cables. Bluetooth can also be used to access a network or the Internet with a notebook computer by connecting wirelessly to a cellular phone.

What is the future direction of the Bluetooth standard

2009-03-06T23:53:00.000-08:00

Question :What is the future direction of the Bluetooth standard?
Answer :At this time, we anticipate the Bluetooth SIG to evolve the Bluetooth technology to provide greater bandwidth and distances, thus increasing the potential platforms and applications used in the emerging personal area networking marketplace.

How secure is a Bluetooth network

2009-03-06T23:52:00.000-08:00

Question :How secure is a Bluetooth network?
Answer :Bluetooth is extremely secure in that it employs several layers of data encryption and user authentication measures. Bluetooth devices use a combination of the Personal Identification Number (PIN) and a Bluetooth address to identify other Bluetooth devices. Data encryption (i.e., 128-bit) can be used to further enhance the degree of Bluetooth security. The transmission scheme (FHSS) provides another level of security in itself. Instead of transmitting over one frequency within the 2.4 GHz band, Bluetooth radios use a fast frequency-hopping spread spectrum (FHSS) technique, allowing only synchronized receivers to access the transmitted data

What is Frequency-Hopping Spread Spectrum (FHSS)

2009-03-06T23:51:00.000-08:00

Why is Bluetooth called a cable replacement technology

2009-03-06T23:50:00.000-08:00

Question :Why is Bluetooth called a cable replacement technology?
Answer :Bluetooth technology allows the creation of Personal Area Networks without cables or wires that are usual in home networks.

How does Bluetooth use frequency hopping for security

2009-03-06T23:47:00.000-08:00

Question :How does Bluetooth use frequency hopping for security?
Answer :Bluetooth picks a random frequency out of 79 and then hops around the range about 1600 times per second.

What are Bluetooth profiles

2009-03-06T23:45:00.000-08:00

Question :What are Bluetooth profiles?
Answer :A profile is a description of how to use a specification to implement a particular function. The International Standards Organization (ISO) first came up with the idea of profiles. In Bluetooth, there are several profiles available and they are arranged in a hierarchical fashion. For example, in order to use the headset profile, a device must also include the lower level profiles such as the serial port and general access profiles.

Give a generic description of Bluetooth

2009-03-06T23:44:00.002-08:00

Question :Give a generic description of Bluetooth?
Answer :Bluetooth is a low-cost, short-range (RF) links between mobile PCs, mobile phones and other portable devices. Bluetooth can transmit through solid, non-metal objects.

Which method is used for Data transfer

2009-03-06T23:44:00.001-08:00

Question :Which method is used for Data transfer?
Answer :Asynchronous Connectionless (ACL) is Data transfer method in Bluetooth

Why can Bluetooth equipment integrate easily in TCP/IP network

2009-03-06T23:43:00.000-08:00

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

What is a Bluetooth dongle

2009-03-06T23:42:00.000-08:00

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

What is Piconet

2009-03-06T23:41:00.000-08:00

Question :What is Piconet?
Answer :A collection of devices connected through Bluetooth technology in an ad hoc fashion.

What is the frequency range used for Bluetooth in Japan

2009-03-06T23:40:00.000-08:00

Question :What is the frequency range used for Bluetooth in Japan?
Answer :2472 to 2497 MHz is the frequency range used for Bluetooth in Japan.

What is the frequency range used for Bluetooth in Europe and United States

2009-03-06T23:39:00.000-08:00

Question :What is the frequency range used for Bluetooth in Europe and United States?
Answer :2402 MHz to 2480 MHz are the frequency ranges used in USA and Europe

Under what frequency range does Bluetooth work

2009-03-06T23:38:00.000-08:00

Question :Under what frequency range does Bluetooth work?
Answer :2.45 GHz is the frequency range.

What is the total number of masters and slaves in a piconet

2009-03-06T23:36:00.000-08:00

Question :What is the total number of masters and slaves in a piconet?
Answer :1 Master and 7 Slaves.

What is the range of Bluetooth transmitter/receivers

2009-03-06T23:33:00.000-08:00

What is it - a technology, a standard, an initiative, or a product

2009-03-06T23:32:00.000-08:00

Question :What is it - a technology, a standard, an initiative, or a product?
Answer :Bluetooth wireless technology is a de facto standard, as well as a specification for small-form factor, low-cost, short range radio links between mobile PCs, mobile phones and other portable devices. The Bluetooth Special Interest Group is an industry group consisting of leaders in the telecommunications, computing, and networking industries that are driving development of the technology and bringing it to market

What is the history of Bluetooth

2009-03-06T23:31:00.000-08:00

Question :What is the history of Bluetooth?
Answer :Bluetooth was initiated by Ericsson, IBM, Intel, Nokia and Toshiba in early 1998. These companies later formed a special interest group known as the Bluetooth SIG. The Bluetooth 1.0 specifications were released on July 26, 1999, but the technology has only recently become inexpensive enough for widespread use.

How does Bluetooth fit in with WiFi

2009-03-06T23:27:00.000-08:00

Question :How does Bluetooth fit in with WiFi?
Answer :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.

What are some of the uses of Bluetooth

2009-03-06T23:26:00.000-08:00

Question :What are some of the uses of Bluetooth?
Answer :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.

What are Different Classes in Bluetooth

2009-03-06T23:25:00.002-08:00

Question :What are Different Classes in Bluetooth?
Answer :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.

What are the problems with older versions (1.0 and 1.0 B)

2009-03-06T23:25:00.001-08:00

Question :What are the problems with older versions (1.0 and 1.0 B)?
Answer :Versions 1.0 and 1.0 B had numerous problems and the various manufacturers had great difficulties in making their products interoperable. 1.0 and 1.0B also had mandatory Bluetooth Hardware Device Address (BD_ADDR) transmission in the handshaking process, rendering anonymity impossible at a protocol level, which was a major setback for services planned to be used in Bluetooth environments, such as Consumerism.

How secure a Bluetooth device is

2009-03-06T23:24:00.000-08:00

Question :How secure a Bluetooth device is?
Answer :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.

What is Pairing

2009-03-06T23:22:00.000-08:00

Question :What is Pairing?
Answer :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.

How many devices can communicate concurrently

2009-03-06T23:21:00.000-08:00

Question :How many devices can communicate concurrently?
Answer :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.

What kind of encryption will be used for Bluetooth security

2009-03-06T23:17:00.000-08:00

Question :What kind of encryption will be used for Bluetooth security?
Answer :: 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.

Name few applications of Bluetooth

2009-03-06T23:15:00.000-08:00

Question :Name few applications of Bluetooth?
Answer :* 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.

Why is Bluetooth 2.0 better

2009-03-06T23:14:00.000-08:00

Question :Why is Bluetooth 2.0 better?
Answer :The main features of Bluetooth Core Specification Version 2.0 + EDR are:• 3 times faster transmission speed (up to 10 times in certain cases)• Lower power consumption through reduced duty cycle• Simplification of multi-link scenarios due to more available bandwidth• Backwards compatible to earlier versions• Further improved BER (Bit Error Rate) performance

What is Bluetooth SIG

2009-03-06T23:13:00.001-08:00

Question :What is Bluetooth SIG?
Answer :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

What is Bluetooth SIG

2009-03-06T23:13:00.000-08:00

What is the future direction of the Bluetooth standard

2009-03-06T23:09:00.001-08:00

What is FEC in Bluetooth

2009-03-06T23:07:00.000-08:00

Question :What is FEC in Bluetooth?
Answer :Forward Error Correction is a method by which Bluetooth increases its noise immunity. FEC is a method that enables a receiver to not only detect, but also correct errors in a transmission

What is FCC and how does it relate to Bluetooth

2009-03-06T23:06:00.001-08:00

Question :What is FCC and how does it relate to Bluetooth?
Answer :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

How is Bluetooth used

2009-03-06T23:05:00.001-08:00

What is it - a technology, a standard, an initiative, or a product

2009-03-06T23:03:00.000-08:00

Why is the technology called Bluetooth

2009-03-06T23:01:00.000-08:00

Question :Why is the technology called Bluetooth?
Answer :The heart of the Bluetooth brand identity is the name, which refers to the Danish king Harald "Bluetooth" Blaatand who unified Denmark and Norway. In the beginning of the Bluetooth wireless technology era, Bluetooth was aimed at unifying the telecom and computing industries.

What is Bluetooth

2009-03-06T22:56:00.000-08:00

Question :What is Bluetooth?
Answer :Bluetooth is the name for a short-range radio frequency (RF) technology that operates at 2.4 GHz and is capable of transmitting voice and data. The effective range of Bluetooth devices is 32 feet (10 meters). Bluetooth transfers data at the rate of 1 Mbps, which is from three to eight times the average speed of parallel and serial ports, respectively.