Question

Give 2 page summary on Bluetooth and show diagrams to illustrate interaction of devices within constructed network.

Answer 1

Bluetooth Technology:

Introduction:

Bluetooth technology is high speed low power wireless technology link that is designed to connect phones or other portable equipments together. It uses 2.4GHz ISM band to establish communication between various devices with bandwidth of 1Mhz. It can connect upto 8 devices simulateneously and has a range of connection upto 10 meters.
Bluetooth has many versions depending on which its data transfer spped is determined. Gaussian Frequency Shift Keying (GFSK) is used as modulation up to Bluetooth 1.2, while Differential Quadrature Phase Shift Keying (DQPSK) and eight‐phase differential phase shift keying (8DPSK) are used for EDR packets. Bluetooth is also known as IEEE 802.15 standard.

Bluetooth Architecture:

The architecture of bluetooth defines two types of networks:
1. Piconet 2. Scatternet
A bluetooth network is called piconet and a collection of interconnected piconets is called scatternet.

Piconet :
A piconet consists of one master device, which establishes the connection, and up to seven slave devices.Each device can be a master or a slave of a piconet. The device that initiates a new piconet becomes the master device while remaing become slaves. The master of a piconet controls the order and the duration of slave data transfers over the piconet channel. To grant the channel to a slave device for a certain period of time, the master sends a data packet to the slave. The slave is identified by a 3‐bit address in the header of the data packet, which has been assigned to the device at connection establishment. The data packet of the master can have a length of one to five slots depending on the amount of data that has to be sent to the slave. If no data needs to be sent to the slave, an empty one‐slot packet is used. Sending a packet to a slave device implicitly assigns the next slot to the slave, regardless of whether the packet contains user data. The slave can then use the next one to five slots of the channel to return a packet. As a slave cannot anticipate when a new packet from a master will arrive, it is not able to establish a connection to additional devices. Therefore, in some cases it is necessary that master and slave change their roles during the lifetime of the piconet.

Scatternet:
It is formed by using various piconets. A slave that is present in one piconet can be act as master or we can say primary in other piconet. This kind of node can receive message from master in one piconet and deliver the message to its slave into the other piconet where it is acting as a slave. This type of node is refer as bridge node. A station cannot be master in two piconets.

Bluetooth Protocol Stack:

Protocols in the Bluetooth Protocol Stack

• Core protocols − This includes Bluetooth radio, Baseband, Link Manager Protocol (LMP), Logical Link Control and Adaptation Protocol (L2CAP), and Service Discovery Protocol (SDP).

• Cable Replacement Protocol − This includes Radio Frequency Communications (RFComm) protocol. It is short for Radio Frontend Component. It provides a serial interface with WAP.

• Adopted Protocols − These are the protocols that are adopted from standard models. The commonly adopted protocols used in Bluetooth are Point-to-Point Protocol (PPP), Internet Protocol (IP), User Datagram Protocol (UDP), Transmission Control Protocol (TCP), and Wireless Application Protocol (WAP).

• AT Commands − Attention command set.

The following diagram shows the Bluetooth protocol stack −

Functions of the Core Protocols:

• Radio − This is a physical layer equivalent protocol that lays down the physical structure and specifications for transmission of radio waves. It defines air interface, frequency bands, frequency hopping specifications and modulation techniques.

• Baseband − This protocol takes the services of radio protocol. It defines the addressing scheme, packet frame format, timing, and power control algorithms.

• Link Manager Protocol (LMP) − LMP establishes logical links between Bluetooth devices and maintains the links for enabling communications. The other main functions of LMP are device authentication, message encryption, and negotiation of packet sizes.

• Logical Link Control and Adaptation Protocol (L2CAP) − L2CAP provides adaption between upper layer frame and baseband layer frame format. L2CAP provides support for both connection-oriented as well as connectionless services.

• Service Discovery Protocol (SDP)− SDP takes care of service-related queries like device information so as to establish a connection between contending Bluetooth devices.

Bluetooth Security:

There are three basic means of providing Bluetooth security:

• Authentication:   In this process the identity of the communicating devices are verified. User authentication is not part of the main Bluetooth security elements of the specification.
• Confidentiality:   This process prevents information being eavesdropped by ensuring that only authorised devices can access and view the data.
• Authorisation:   This process prevents access by ensuring that a device is authorised to use a service before enabling it to do so.

Adavantages:
a. It creates adhoc connection immediately without any wires. Connection establishment is very quick. User only need to pair the bluetooth PAN connection between two devices.
b. It has low power consumption.
c. It can pass through walls.
d. It has range better than Infrared communication.

Disadvantages:
a. One of the big disadvantages of bluetooth is security. Bluejacking and bluebugging are common issues with bluetooth.
b. As HomeRF technology operates on same frequency, It has interference from it.
c. The bandwidth is lower compared to WiFi.
d. Battery usage is more compare to the condition when bluetooth is powered OFF. The new technology known as BLE or bluetooth low energy or bluetooth smart is developed to enhance the battery life further.

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