802.15*802.15.1 (Bluetooth)

*802.15.4 (ZigBee)

*802.15.6

Overview

• Cable replacement technology.• Connect devices such as phone handsets, headsets, computer peripherals,

etc.

• Industry standard.• Allows wireless communication between devices.

APPLICATIONS:

• Cable Replacement

• Synchronization

• Cordless Headset

• Conference table.

• Cordless computer.

• Instant photo transmission.

• Cordless phone

Bluetooth Origins

• Study by Ericsson Mobile Communications in 1994.

– Alternatives to cables connecting mobile phones to accessories.

– Use of radio links instead of infrared.

• Why?

– Transmission of data and voice.

• Result: Bluetooth spec.

– Named after Harald Blatand (Danish for Bluetooth).

– 10th century Viking king who united Denmark and Norway.

Bluetooth SIG History

• Early 1998: Bluetooth SIG is formed.

– Promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba.

– Goal: develop license-free technology for universal wireless

connectivity.

– Target: handheld market.

– Bluetooth spec: defines RF wireless communication interface and

protocols.

Goals

• Open spec.

• Low cost.

– In order to replace cables, should have similar cost.

– Cell phone cable is ~ $10.

• Power efficiency.

• Lightweight and small form factor.

• Easy to use.

• Reliable and resilient to failures.

The Bluetooth Standard

• Defines a protocol stack to enable heterogeneous devices to

communicate.

• The Bluetooth stack includes protocols for the radio layer all

the way up to device discovery, service discovery, etc.

Bluetooth Protocol Stack

RF

Baseband

Link Manager

L2CAP

RFCOMM/SDP

Applications

Link Controller

Host Controller Interface

PHY

Data Link Layer

Network Layer

Transport Layer

Session Layer

Presentation Layer

Application

OSI/ISO

Bluetooth Layers

• Radio: physically transmits/receives data.

• Baseband/Link Controller: controls PHY uses 2.4 GHz unlicensed ISM band and frequency hopping.

• Link Manager: controls links to other devices.

• Host Controller:e2e communication.

• Logical Link Control: multiplexes/demultiplexes data from higher layers.

• RFCOMM: RS323-like serial interface.

• SDP: allows service discovery among Bluetooth devices.

Master and Slaves

• Communicating devices must agree on hopping sequence.

• BT devices can operate as masters or slaves.

• Master node defines sequence to be used.

• Slave units use master id to pick sequence.

• Master also controls when devices are allowed to transmit.

– Master allocates slots to slaves.

– Allocates total available bandwidth among slaves.

Piconets

• BT communication takes place over piconets.

• Piconet formation initiated by master.

• All other participants are slaves.

• Number of participants limited to 8 (1 master and 7 slaves).

– Channel capacity and addressing overhead.

– Each slave assigned a locally unique ID.

• Master/slave roles last for the duration of the piconet.

• On a piconet, slaves only have direct links to master.

• Point-to-point or point-to-multipoint connections.

BT States

. Initially, all nodes in standby.. Node (master) can begininquiry to find nearbydevices.. Piconet is then formed.. Devices join by paging.

Inquiry

• Device discovery• Listeners respond with

their address.

Paging

• Device enters paging to invite others to join its piconet.

• Establishes links with nodes in proximity.

• Paging message unicast to selected receiver.

• Receiver sends ACK.

• Sender becomes master, receiver slave.

Bluetooth Link Formation

• Point-to-point link:– Master-slave relationship.

• Piconet:• 8 units: channel capacity.

• Master (establishes piconet) can connect to up to 7 slaves.

• Master/slave relationship lasts while link/piconet lasts.

• No slave-to-slave communication.

Error Control

• Supports both FEC and retransmission.

• FEC for SCO packets.

• ARQ for ACL traffic.

– If no ACKs, retransmit.

– Stop-and-wait ARQ.

• Fast-ARQ: ACK included in RX slot immediately following the TX

slot in which packet was sent.

– CRC to check for errors.

Packet Format

• Access Code: Address of piconet master.• Packet header contains link control (LC) information- 3-bit slave address (active member address)- 4-bit packet type code to define 16 different payload types- 1-bit flow control, 1-bit ack. indication and 1-bit seq.no.- 8-bit header error check

Scatternets

• Interconnection of multiple piconets.

802.15.4 (ZigBee)

802.15.4 market feature

Low power consumption

Low cost

Low offered message throughput

Supports large network orders (<= 65k nodes)

Low to no QoS guarantees

Flexible protocol design suitable for many applications

General characteristics• Data rates of 250 kbps , 20 kbps and 40kpbs.

• Star or Peer-to-Peer operation.

• Support for low latency devices.

• CSMA-CA channel access.

• Dynamic device addressing.

• Fully handshaked protocol for transfer reliability.

• Low power consumption.

• Channels:

• 16 channels in the 2.4GHz ISM band,

• 10 channels in the 915MHz ISM band

• 1 channel in the European 868MHz band.

• Extremely low duty-cycle (<0.1%)

IEEE 802.15.4 basics

802.15.4 is a simple packet data protocol for lightweight wireless networks

Channel Access is via Carrier Sense Multiple Access with collision avoidance and optional time slotting

Message acknowledgement

Optional beacon structure

Target applications

Long battery life, selectable latency for controllers, sensors, remote monitoring and portable electronics

Configured for maximum battery life, has the potential to last as long as the shelf life of most batteries

IEEE 802.15.4 Device Types

• There are two different device types :• A full function device (FFD)

• A reduced function device (RFD)

• The FFD can operate in three modes by serving as

• Device

• Coordinator

• PAN coordinator

• The RFD can only serve as:

• Device

FFD vs RFD

Full function device (FFD)

Any topology

Network coordinator capable

Talks to any other device

Reduced function device (RFD)

Limited to star topology

Cannot become a network coordinator

Talks only to a network coordinator

Very simple implementation

Star topology

Peer to peer topology

PHY Frame Structure

• PHY packet fields• Preamble (32 bits) – synchronization • Start of packet delimiter (8 bits) – shall be formatted as “11100101”• PHY header (8 bits) –PSDU length• PSDU (0 to 127 bytes) – data field

CSMA/CA

Routing Algorithm

• AODV(Ad-hoc on demand distance vector routing) is used as routing algorithm in ZigBee.

• Reactive or on Demand

• Descendant of DSDV

• Uses bi-directional links

• Route discovery cycle used for route finding

• Maintenance of active routes

• Sequence numbers used for loop prevention

• and as route freshness criteria

• Provides unicast and multicast

• communication

AODV continues…

The basic message set consists of:

• RREQ – Route request

• RREP – Route reply

• RERR – Route error

• HELLO – For link status monitoring

Two phases:

• Route Discovery

• Route maintenance

Each node maintains a routing table with knowledge about the network.

AODV deals with route table management.

Route information maintained even for short lived routes – reverse pointers.

RREQ Broadcasting

RREP Unicasting

802.15.6 (WBAN)

INTRODUCTION

• WBAN (wireless body area network) is RF based wireless networking technology that interconnects tiny nodes with sensors in, on, or around a human body.

• A typical WBAN consists of a number of inexpensive, lightweight, miniature sensor platforms, each featuring one or more physiological sensors like

– Motion Sensors– ECG (Electrocardiograms)– Sp02– Breathing Sensors– Blood pressure– EMG (Electromyograms)– EEG(Electro-encephalograms)– Blood Glucose Sensors

CONTINUE…

• Network size of WBAN– Application dependent

( up to 256 devices)

• WBAN Sensors could be located on– The body as intelligent patches– Integrated into clothing– Implanted below the skin– Embedded deeply in tissues

Major MAC Protocol Approaches

• Contention Based (CSMA/CA)• Nodes need to perform CCA before transmission of data• If the channel is busy, the node defers its transmission till it becomes idle.

• Its infrastructure-free

• Ad hoc feature

• Good adaptability to traffic fluctuation

• Schedule Based(TDMA)

• Channels are divided into fixed/variable time slots which are assigned to nodes that transmit during its slot period

• Free of idle listening, overhearing and packet collisions because of the lack of medium competition,

• But require tight time synchronization.

802.15.6 Superframe Format

The EAP is Emergency Access Period. -> In this period only devices with emergency traffic can contend.

The RAP(Random Access Period) can be used by any device both emergency and non-emergency. -> The data that are accumulated in the device buffers have a priority assigned to them. Each of the devices have to contend with backoff windows according to their priority.

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