39- infrared - bluetooth systems

8/3/2019 39- Infrared - Bluetooth Systems

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1

Wireless Networks



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3

Bluetooth Systems

• Piconet: Basic unit is a Piconet, consisting of a master and from

one to seven active slave devices.

•Scatternet: A device in one piconet may also exist as part of

another piconet and may function as either a slave or master in

each piconet and this form of overlapping is called a scatternet.



4

Bluetooth Systems- Fundamentals



5

Bluetooth Systems

• A slave may only communicate with the master and may only

communicate when granted permission by the master.

•The advantage of the piconet/scatternet scheme is that it allows

many devices to share the same physical area and make efficient

use of the bandwidth.



6

Bluetooth Systems

• Bluetooth uses the Industrial, Scientific and Medical (ISM)

band, which is free to use in most countries.

•Two main methods are used for spreading out the power:

Direct Sequence Spread Spectrum (DSSS): Transmission across

a wide range of frequencies at low power.

Frequency-Hopping Spread Spectrum FHSS): Uses a smallbandwidth but changes (or hops) frequency after each packet.



7

Bluetooth Systems

• Bluetooth uses FHSS.

•There are 79 channels of 1MHz each; after each transmit or

receive, devices hop to a new channel.

•A Bluetooth system uses a frequency-hopping scheme with a

carrier spacing of 1 MHz. Typically, up to 79 different

frequencies are used, for a total bandwidth of 80 MHz.

•At any given time, the bandwidth available is 1 MHz, with a

maximum of eight devices sharing the bandwidth. Different

logical channels (different hopping sequences) can

simultaneously share the same 80 MHz bandwidth.



8

Bluetooth Systems

• It is possible for a device to take part in two different Piconetsby swapping between two different frequency-hopping

sequences.

• So, Collisions will occur when devices in different piconets, on

different logical channels, happen to use the same hop frequencyat the same time.

•As the number of piconets in an area increases, the number of

collisions increases, and performance degrades.

In summary,

• The physical area and total bandwidth are shared by the

Scatternet.

•The logical channel and data transfer are shared by a Piconet.



9

Bluetooth Systems

•It is not possible to be a master of two different piconets.

•This is because a piconet is a group of devices all synchronized

on a hopping sequence set by the master.

•By definition, any devices that share a master must be on thesame piconet.

•A device that is present on two different piconets must visit each

piconet often enough to keep the link supervision timeout fromelapsing.

•Obviously, Scatternets are not the most efficient way to use

Bluetooth bandwidth. The problem arises because the piconets

that make up scatternets aren't synchronized.



10

Bluetooth Architecture



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Bluetooth Systems

1. RF Layer:•At the lowest level, the radio layer of the core specification

defines the wireless interface.

•

FHSS occurs in the 2.4 GHz ISM band using either 79 radiofrequencies in countries with restrictions in the ISM band.

2. Baseband Layer:

•The Baseband specifies how the radio layer should be

employed to facilitate communication between Bluetoothdevices.

•This layer defines the concept of a piconet, which is BT_s

fundamental logical topology for organising group-wise

communication, under decentralisation.



14

Bluetooth Systems

•At this point, homogeneous devices are distinguished by theirBluetooth device address which is a unique 48-bit address, hard-

coded into the Bluetooth chip.

•

The first device to initiate the formation of a Piconet becomesthe master. Every other device in range is assigned a locally

unique active member address - Slaves within the master_s

piconet.

•At most seven active slaves participate in each Piconet, butadditional slaves can be registered with the master and sustain

the parked mode. Devices outside of any piconet sustain the

stand-by mode.



15

Bluetooth SystemsDevice Admission / Bluetooth Link Formation

The link formation process specified in the Bluetooth Baseband

specification consists of Four processes:

• Inquiry: This process consists of broadcasting inquiry packets,

which do not contain the senders identity or other any

information.

• Inquiry scan: In this state, devices listen for inquiry packets,

and upon detection of an inquiry packet, the device broadcastsan inquiry response packet.

This contains the devices identity and clock of the device

in inquiry scan mode.



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Bluetooth Systems

Device Admission / Bluetooth Link Formation

Page : Under this process, a device tries to establish a connection

with a device whose identity and clock are known. Page packets

are sent, which contain the sending devices address and clock for

synchronisation.

The packets sent can only be received by those devices

with particular identities.

• Page scan: In this state, a device listens for a page packet.

Receipt is acknowledged and synchronisation between the page

and page scan devices is established.



17

Bluetooth Systems


The goal of the Inquiry process is for a master node to discover

the existence of neighboring devices and to collect enough

information about the low-level state of those neighbors

(primarily related to their native clocks) to allow it to establish a

frequency hopping connection with a subset of those neighbors.

The goal of the Page process is to use the information gathered in

during the Inquiry process to establish a bi-directional frequencyhopping communication channel.



18

Bluetooth Systems




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Bluetooth Systems

3. MAC Layer

•Bluetooth uses baseband packets that can span 1, 3, or 5 time-

slots.

•The capacity of a frequency hopping channel is 1 Mbps.

•Each Bluetooth packet is sent at a different frequency.

•For packets that span multiple time-slots, however, thefrequency is not changed until the packet is fully transmitted.

•Bluetooth uses TDD (Time Division Duplex) scheme is as the

duplexing method to provide two-way communication.



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Bluetooth Systems

3. MAC Layer

•For packets that span multiple time-slots, however, the

frequency is not changed until the packet is fully transmitted.

•Bluetooth uses baseband packets that can span 1, 3, or 5 time-

slots.

Multi-Slot Packets



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Bluetooth Systems

3. MAC Layer

In a Piconet there are two possible links:• Synchronous Connection-Oriented (SCO) link

•The SCO link is like a circuit-switched connection.

•An SCO link is established using reserved time slots at regular

time intervals.

•Designed for time-critical connections – voice packets.

•A node (either master or slave) can support at most three SCO

links.

•It is Point-Point connection. There is no broadcast option with

SCO links.



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Bluetooth Systems

3. MAC Layer

In a Piconet there are two possible links:• Asynchronous Connection-Less (ACL) link

•The ACO link is like a packet-switched connection.

•An ACO link is established using unreserved time slots at regular

time intervals.

•Designed for Non time-critical connections – data packets.

•A node (either master or slave) can support at most ONE ACL

link.

•It is a Point-Multi Point connection. There is broadcast option

with ACL links.



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Bluetooth Systems

3. MAC Layer

Reservation of Slots

Polling by master is the declaration of the slave node that will

use the next time slot for sending data.

Polled node is stated by its AM ADDR in the header of the

polling message sent by the master node.

In the next slot that is assigned to a slave, the slave can send

either a data packet or a NULL packet.

If no slave is addressed in a packet sent the master node, i.e.

AM ADDR is set to zero, that packet is a broadcast packet to

all slaves in the piconet.



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Bluetooth Systems

3. MAC Layer


Polling in Piconet



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Bluetooth Systems

3. MAC Layer


• Scheduling by master node for polling and sending data has

impact on performance of intra-piconet data traffic.

•

In even numbered time-slots, a master node sends data to itsslaves and polls them.

•In odd numbered time-slots, polled slaves start sending their

data packets.

•Multi-slot packet is in transmission, the frequency carrier

that is used by the first slot is also used by the other slots

that multi-slot packet occupies.



26

Bluetooth Systems

3. MAC Layer

Packet Format

•Three parts: Access Code, Header, and Payload.

•Each of these three parts also have sub-fields.

•Packets are send in Little-Endian format.



27

Bluetooth Systems

3. MAC Layer

Packet Format – ACCESS CODE

Three types:

• Channel Access Code (CAC): The access code used as part

of data packets during data transmission. It is 72 bits long.

• Device Access Code (DAC): The access code used during

piconet formation processes. It is 68 bits.

• Inquiry Access Code (IAC): The access code used during

inquiry process, as an identification of a single node that

wants to join the piconet. It is 68 bits long.



28

Bluetooth Systems

3. MAC Layer

Packet Format – ACCESS CODE

Three fields:

• Preamble: Fixed zero-one pattern (0101 or 1010) to indicate the

beginning of a packet and facilitate the reception of the packet.

• Sync word: The field that is used for identification purposed. The

value of this field is derived from the hardware (Bluetooth) address

of either the master or a slave. In CAC type of access codes, the

value is derived from the hardware address of the master of the

piconet. In DAC and IAC type of access codes, which is usedduring inquiry and page procedures, it is derived from the

hardware address of the slave node that will join to the piconet.

• Trailer: Fixed zero-one pattern to indicate the end of the access

code.



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Bluetooth Systems

3. MAC Layer

Packet Format – HEADER

• Header defines

• target node

•

ordering• acknowledging information

• Length is shown as 18 bits. With error coding 54 bits long.



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Bluetooth Systems

3. MAC Layer

Packet Format – HEADER

Header is composed of Six fields:

• AM ADDR: Active member address of the target node.

• Type: Defines the type of the packet that is sent. Type value indicates

the number of slots that the packet will occupy and also the type of

the data (SCO or ACL data) that is carried inside the payload field.

•

Flow: Defines the receive buffer availability of the receiver.

• ARQN: Used for acknowledgment of previously received packets.

• SEQN: Used for numbering of streamed packets

• HEC: Used to check header integrity.



31

Bluetooth Systems

3. MAC Layer

Packet Format – PAYLOAD

Payload is composed of Two fields:

• Payload Header:

The payload header stores information about the length of the

data that is stored in the payload part.

May have two different sizes depending on the size of the

packet in terms of time-slots that it occupies.

For single-slot packets, payload header is one byte long.

For multi-slot packets, payload header length is two bytes

long.

• Data: Actual Information



32

Bluetooth Systems

Power Management

Different Modes of operation for minimizing power consumption.

Idle mode: The device performs the scan operation for less than

1% of the time.

Park mode: Reduces device activity further, but can only be

applied to slave devices after a piconet has been

formed.

In park mode, devices remain synchronised with the

master but do not return a packet with a payload.

Park mode permits more than seven slaves to

participate in a piconet.



33

Bluetooth Systems

Power Management

Different Modes of operation for minimizing power consumption.

Sniff mode: The slave does not scan in every master – slave time

slot, but has a low duty cycle.

Effectively the device only wakes up periodically to

communicate with the master.

Hold mode: Used to put devices to sleep.

This is used to suspend intra-piconet communication

while the master searches for new devices to admit to

the piconet.



34

Infrared Systems

What is the difference between Infrared and Bluetooth?

• Bluetooth operates using radio waves while infra-red communication works

on fast pulses of light.

•Sensors of both the devices must be in each other's immediate line of sight.

If something comes in the way of the two mobiles devices, the message or

data will not pass through.

• Bluetooth technology however can pass through walls. You can send

messages, data files, audio- files, video-files etc from your mobile to the other

person in the next room, as long as the other mobile is within the radius of 10meters.

•Infrared also only works between two devices at a time while Bluetooth can

work with as many as mobile devices as you want.

http://www.blurtit.com/q836749.html







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Infrared Systems



36

Infrared Systems

Components of IrDA Architecture:

IrDA has defined a group of short-range, high speed, bidirectional

wireless infrared protocols, generically referred to as IrDA.

IrDA allows a variety of devices to communicate with each other.

Cameras, printers, portable computers, desktop computers, andpersonal digital assistants (PDAs) can communicate with compatible

devices using this technology.



37

Infrared Systems

Components of IrDA Architecture: IrDA has Three layers:

IrPHY - Infrared Physical Layer

IrLAP - Infrared Link Access Protocol

IrLMP - Infrared Link Management Protocol

Serial Infrared (SIR) supporting speeds up to 115.2 Kbps

Medium Infrared (MIR) supporting 0.576 Mbps and 1.152 Mbps

Fast Infrared (FIR) supporting a 4.0 Mbps data rate

Very Fast Infrared (VFIR) supporting 16.0 Mbps.

In addition to the base standards, IrDA has specified several optional layers

such as Tiny TP, IrCOMM, and IrOBEX.



38

Infrared Systems



39

Infrared Systems

Components of IrDA are:

Winsock: Winsock is an API that allows Windows-based

applications to access the transport protocols. The IrDA protocol

stack is made available to applications by using Winsock.

IrTran-P: IrTran-P is a bidirectional image transfer protocol. Manycameras have digital ports and can beam infrared data to a receiving

computer. That data is then placed in a user-specified (or default)

directory.

IrDA Print Monitor: IrDA Print Monitor is a software component

that interfaces with an IrDA-connected printer.

IrXfer: IrXfer is an IrDA file transfer application. IrXfer has

bidirectional transfer capabilities.



40

Infrared Systems


Tiny TP: Tiny TP is a flow control mechanism for IrDA. Tiny TP

acts as a regulator to control the rate of data input or output. This

prevents an overflow of data from occurring and creating data errors.

IrDA.sys: IrDA.sys is the transport protocol stack that supportsIrDA. It provides support for applications through Winsock to the

NDIS layer.

IrCOMM: IrCOMM is a software component that supports IrTran-

P. The IrTran-P server must be disabled if other applications need to

use the IrCOMM port.

IrLPT: IrLPT is the protocol support that is used by IrDA Print

Monitor. IrLPT enables printing directly from IrDA devices to IrDA

printers.



41

Infrared Systems


IrLMP: Infrared Link Management Protocol is used to multiplex

various connections over one IrDA link.

IrLAP: Infrared Link Access Protocol is a media access control

software component that determines which component can access themedia during each time slice.

FIR Driver: A Fast Infrared driver (FIR) is a miniport driver

provided by a hardware vendor to link hardware devices on the lower

side of the protocol stack to the transport protocol above, such as

TCP/IP or IPX/SPX.

FIR devices can exchange data up to 4 megabytes (MB) per

second. All FIR devices are also required to support serial

transmission using Serial Infrared driver (SIR).



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Infrared Systems


IrSIR.sys: Serial Infrared driver is a Microsoft-provided miniport

driver. It is an alternate driver to the Fast Infrared driver and can be

used only in combination with Serial.sys. The maximum data transfer

rate is 115.2 kilobytes per second (Kbps).

Serial.sys: Serial.sys is used to connect infrared devices to the

IrSIR.sys driver above in the protocol stack and the hardware device

below. It is a software driver that sends and receives data from a

hardware device and presents it to the IrSIR.sys driver in a format

that conforms to the requirements of IrSIR.sys.

39- infrared - bluetooth systems

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