The IEEE 802.15.4 Standard and the ZigBee Specications · The IEEE 802.15.4 Standard and the ZigBee...

The IEEE 802.15.4 Standardand the ZigBee SpecificationsCourse T-110.5111 (Computer Networks II – Advanced Topics)Lecture about Wireless Personal Area Networks

Mario Di Francesco

Department of Computer Science and Engineering, Aalto UniversityDepartment of Computer Science and Engineering, University of Texas at Arlington

October 15, 2012

Architecture and objectives

Physical layer

Data link layer

Network layer

Upper layers

IEEE 802.2 LLC

SSCS

Other LLC

IEEE 802.15.4 MACIEEE 802.15.4

868/915 MHz PHYIEEE 802.15.42400 MHz PHY

Architecture

two physical (PHY) layer

MAC layer

ZigBee for the upper layers

Objectives

low-rate

low-power

low-complexity

IEEE 802.15.4 and ZigBee 2/58M. Di Francesco October 15, 2012Aalto University T-110.5111 WPAN Lecture

Components

Full Function Device(FFD)

Implements the entire standardCoordinatormanages (part of) thenetwork

PAN coordinatormanages the whole PAN(unique in the network)

(Regular) Devicecommunicates with FFDsand/or RFDs

Reduced Function Device(RFD)

Implements a reduced portion ofthe standard

cannot be a (PAN)coordinator

only communicates withFFDs


Topology

Star

C

FFD

RFD

PANCoordinator

C

all messages flow throughthe center (hub) of the star

Peer-to-peer

C

neighboring nodes cancommunicate directly

only available to FFDs


Radio and modulation (1 of 2)

Two distinct physical layers

PHY 868/915 MHz

PHY 2400 MHz

Shared features

direct sequence spread spectrum (DSSS)

ISM (Industrial, Scientific and Medical) bands


Radio and modulation (2 of 2)

PHY 868/915 MHz

2 MHz

868.0 868.6 902.0 928.0

Channel 0 Channels 1-10

f (MHz)

868 MHz (Europe)1 channel (20 kbps)

915 MHz (USA)8 channel (40 kbps)

differential encoding(1 sym = 1 bit)

BPSK encoding

PHY 2400 MHz

Channels 11-26

2400.0 2483.5

f (MHz)

5 MHz

16 channels

250 kbps bandwidth

orthogonal encoding(1 sym = 4 bits)

O-QPSK modulation


Format of the PHY frame

PreambleStart-of-frame

delimiterFrame length PHY Service Data Unit (PSDU)

4 bytes 1 byte 1 byte ≤ 127 bytes

Synchronization Header PHY Header

PHY Protocol Data Unit (PPDU)

Header

synchronization preamble

delimiter of the PHY frame

frame length

Payload

is the same as the MSDU

maximum size of 127 bytes


Available primitives

Transceiver modes

RX_ON active in receivemode

TX_ON active in transmitmode

TRX_OFF inactive(idle mode)

Channel Selection

Energy Detection (ED)

Link Quality Indication(LQI)

“quality” of received frames

SNR, ED, or both

Clear Channel Assessment(CCA)

Different modes

1. energy above threshold

2. carrier sense only

3. combination of 1 and 2


Addressing modes

PAN address

PANs can be co-located

16 bits chosen by the PAN coordinator

Device address64-bit IEEE Extended Unique Identifier (EUI-64)

24-bit Organizationally Unique Identifier (OUI)40 bits assigned by the manufacturer

16-bit short addressassigned by the PAN coordinator during association

Overhead reduction

flag in the frame control field


Format of the MAC frame

Framecontrol

Sequencenumber

Addressing fields Payload

2 bytes 1 byte Variable

MAC Header MAC Footer

MAC Protocol Data Unit (MPDU)

≤ 20 bytes

Frame checksequence

2 bytes

MAC Service Data Unit (MSDU)

Header

frame control

sequence number

addressing fields

Frame payload

Footer

frame check sequence(FCS) ITU-T CRC-16


Frame types

Beacon framesynchronization and management of the PAN

list of devices with pending messagessuperframe parameters

Acknowledgment frame

MAC payload

MAC command

command identifier (1 byte)

command payload


Channel access methods

MAC

Non-beacon enabled Beacon enabled

Superframe Structure

Contention free

Reserved time slot

Contention based

Slotted CSMA-CA

Contention based

Unslotted CSMA-CA


Superframe structure

GTS GTS

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

CAP CFP

SD = aBaseSuperFrameDuration*2SO sym

BI = aBaseSuperFrameDuration*2BO sym

Inactive

Active

Beacon Beacon


Active period

Contention Access Period (CAP)

always present in the superframe

immediately follows the beacon

slotted CSMA-CA protocol

Contention Free Period (CFP)

optional

contiguous slots at the end of the superframe

without CSMA-CA

All transactions end within the CAP (CFP)


Superframe parameters

Beacon interval

BI = aBaseSuperFrameDuration· 2BO sym

interval between subsequent beacons

0 ≤ BO ≤ 14, if BO = 15 no beacons

Superframe duration

SD = aBaseSuperFrameDuration· 2SO sym

duration of the active part

0 ≤ SO ≤ BO ≤ 14, if SO = 15 only active period(no duty-cycle)

aBaseSuperFrameDuration = 960 sym ≈ 32 µs (2.4 GHz PHY)


Synchronization

Tracking mode

the device gets the first beacon

then activates the transceiver before the subsequent one

Non tracking mode

the device only gets a single beacon

it has to reactivate the transceiver for at mostaBaseSuperframeDuration· (2BO + 1) sym

Orphaned device

does not detect beacons for aMaxLostBeacons (4) superframes


GTS management

Features of GTSs

unidirectional

at most 7, all in the CFP

each spanning one or more contiguous slots

GTS allocationmanaged by the PAN coordinator

the device requests a GTS to the PAN coordinatorthe PAN coordinator decides whether to assign it or not

advertised in the GTS parameters of the superframenot always possible

no GTS availablecannot reduce the size of the CAP further


Frame spacing

Frames need to be separated by an Inter Frame Space (IFS)

Long frame Another frame

LIFS

Short frame Another frame

SIFS

if pframe ≤ aMaxSIFSFrameSize (18) bytesthen SIFS (Short IFS) ≥ aMinSIFSPeriod (12) sym

if pframe > aMaxSIFSFrameSize bytesthen LIFS (Long IFS) ≥ aMinLIFSPeriod (40) sym


The CSMA-CA algorithm

Common features

wait before transmitting

without RTS/CTS

Two variants

slotted (beacon enabled mode CAP)

unslotted (non-beacon enabled mode)

Features

backoff period slot of 20 sym (6= superframe slot)

slotted variant aligns rx/tx to backoff periods


Initialization

CSMA-CA

NB=0

CW=2

Battery LifeExtension?

BE=min(2,macMinBE)

BE=macMinBE

Yes

No

ParametersNB number of backoffs(i.e., backoff attempts)

CW contention window

BE backoff exponent

macMinBE = 3 (default)

Battery Life Extension

power saving mode


Main loop

Delay for a randombackoff period

∈ [0, 2BE-1]

Perform CCAon backoff period

boundary

Channel idle?

CW=2, NB=NB+1BE=min(BE+1,

aMaxBE)CW=CW-1

NB >macMaxCSMA

Backoffs?CW=0?

SuccessFailure

Yes

No

Yes

No

Yes

No

Slotted modewaiting and CCAsare aligned to backoffperiods

two CCAs before tx

backoff timer stopped at theend of the CAP andreactivated at the beginningof the subsequent one

In both cases

default max backoffs is 4


Channel access example

Slotted CSMA-CA

DataaUnitBackoffPeriod

Backoff

SuperframeSlot

12 13 14 15 0 1 2

B

Backoff Backoff Data

Packetarrival

Backoff

CCA

Backoff timerpaused

C

A

B


Communication reliability

CRC (FCS) check

CRC-16 computed over header and payload

checked against the FCS

Acks and retransmissions

at most aMaxFrameRetries = 3

ack waiting time is macAckWaitDuration (54 sym)


Acks and retransmissions

Ack timing

Frame Ack

tack

Frame

tack

aUnitBackoffPeriodAck

tack = aTurnAroundTime (unslotted)

aTurnAroundTime ≤ tack ≤aTurnAroundTime + aUnitBackoffPeriod (slotted)

tack < SIFS < LIFS, at most aMaxFrameRetries = 3


Sending data

Beacon enabled (CAP)

Coordinator Device

Data

Acknowledgement

Beacon

Non-beacon enabled

Coordinator Device

Data

Acknowledgement


Receiving data (indirect transfer)

Beacon enabled (CAP)

Coordinator Device

Beacon

Data request

Acknowledgement

Data

Acknowledgement

Non-beacon enabled

Coordinator Device

Data request

Acknowledgement

Data

Acknowledgement


Peer-to-peer communications

We have previously considered

star topology

FFD or RFD devices

Peer-to-peer topology

only between FFDs

according to the tx case already seenin the non-beacon enabled mode

synchronization not defined by the standard


Security

Unsecured mode

no security

delegated to the upper layers

ACL mode

based on Access Control Lists

Secured mode

access control

anti-replay protection

confidentiality and integrity of messages


Scanning modes

ED channel scan (only FFDs)

ED of the PHY layer

Active channel scan (only FFDs)

sends a beacon request command

waits for a reply

Passive channel scan

waits for a beacon

Orphan channel scan

resynchronization of orphaned nodes


PAN creation

FFD intending to be a PAN coordinator

starts an active channel scan

selects a (possibly unused) channel

selects a PAN identifier

starts transmitting beacons (in the beacon-enabled mode)

PAN identifier conflict

detection and resolution are supported by the MAC layer


Association

Coordinator Device

Association request

Acknowledgement

Acknowledgement

Data request

Association response

Acknowledgement

Message exchangethe first ack does not implythat the request has beenaccepted

it depends on availableresources

replies obtained as anindirect transmission

maximum waiting timeaResponseWaitTime(30720 sym)


Dissociation

Coordinator Device

Dissociation notification

Acknowledgement

Acknowledgement

Data request

Disassociation notification

Acknowledgement

Spontaneous

Coordinatordriven

Spontaneousdecided by the device

ack not really needed

Forced

decided by the coordinator

indirect transfer

ack not really needed


References

E. Callaway et al., Home Networking with IEEE 802.15.4: ADeveloping Standard for Low-Rate Wireless Personal AreaNetworks, IEEE Communications Magazine, August 2002

IEEE 802.15.4, Part 15.4: Wireless Medium Access Control(MAC) and Physical Layer (PHY) Specifications for Low-RateWireless Personal Area Networks (LR-WPANs), May 2003

Paolo Baronti, Prashant Pillai, Vince W.C. Chook, StefanoChessa, Alberto Gotta, Y. Fun Hu, Wireless sensor networks: Asurvey on the state of the art and the 802.15.4 and ZigBeestandards, Computer Communications, Volume 30, Issue 7, 26May 2007, Pages 1655–1695


The ZigBee consortium

Wireless Control That Simply Works

Objectivesinteroperability betweenplatforms of differentvendors

low-energy

low-cost

high node density

Reference scenarios

industrial and commercial

consumer electronics andPC peripherals

personal healthcare andhome automation


The protocol stack (1 of 2)

IEEE 802.15.4

defined

ZigBeeTM Alliancedefined

End manufacturerdefined

Layerfunction

Layerinterface

Physical (PHY) Layer

Medium Access Control (MAC) Layer

Network (NWK) Layer

-

Application Support Sublayer (APS)

APS Message

BrokerASL Security

Management

APS Security

Management

Reflector

Management

Application

Object 240Application

Object 1

…

Application (APL) Layer

ZigBee Device Object

(ZDO)

Endpoint 240

APSDE-SAP

Endpoint 1

APSDE-SAP

Endpoint 0

APSDE-SAP

NLDE-SAP

MLDE-SAPMLME-SAP

PD-SAP PLME-SAP

NWK Security

Management

NWK Message

Broker

Routing

Management

Network

Management

2.4 GHz Radio 868/915 MHz

di

Security

Service

Provider

ZD

O P

ub

licIn

terfaces

Application Framework

ZD

O M

anagement P

lane

AP

SM

E-S

AP

NL

ME

-SA

P


The protocol stack (2 of 2)

The layers

Application layer (APL)service discoverybinding between devices and servicescommunication modes

Network layer (NWK)network topologyaddressing and routing

physical and MAC layers defined by the IEEE 802.15.4 standard

Other elements

ZDO Management Plane

Security Service Provider


ZigBee device modelType Description Elements

ApplicationDevice Type

Represents the type ofdevice from the userperspective

Motion detection sen-sor, light switch, etc.

ZigBee LogicalDevice Type

Represents the type ofdevice from the net-work perspective

Network coordinator,router, end device

IEEE 802.15.4Device Type

Represents the type ofZigBee hardware (ra-dio) platform

Full Function Device,Reduced Function De-vice

ZigBee products are a combination ofApplication, Logical e Physical Device Types

how to combine the different Device Typesis defined by the vendor or by a profile


The application layer (APL)

Sublayers

Application Framework (AF)contains the higher layer application components(application objects) defined by the vendor

Application Support Layer (APS)links the application layer to the network layer

ZigBee Device Object (ZDO)is a special application object with management purposes


General concepts (1 of 2)

Profile

an agreement over messages, formats and actionsadopted by the applications running on different devicesto create a given distributed application

Component

a physical object and the corresponding application profile

ZigBee device

a (set of) component(s) sharing a ZigBee transceiver

each device has a unique 64-bit IEEE addressand a 16-bit network address


General concepts (2 of 2)

Attribute

an entity representing a physical quantity or state

Endpoint

a specific (sub)component within a ZigBee device

each device supports up to 240 endpointswith distinct addresses

Cluster

container of attributes or a message

has a unique 8-bit address within a certain profile


Sample addressing at the application layer

ZigBee DeviceZigBeeRadio

ZigBee Device

ZigBeeRadio

Home Control Profile

light control (on/off)

dimmer

motion detection

Legend

Endpoint

Link

Cluster


Application Framework (1 of 2)

Features

contains application objectsprovides two data services

key value pair service (KVP)messsage service (MSG)

Observations

exploits services made available by the APS

control and management of application objectsare handled by the ZigBee Device Object (ZDO)


Application Framework (2 of 2)

Key Value Pair (KVP) service

allows to manipulate attributes definedwithin the application objectstakes an approach based on state variables with transitions

get, get response commandsset, event (and eventual response) commands

uses data structures in compressed XML format

Message (MSG) service

allows the application profile to use its own frame format

has more flexibility than the KVP apprach


The application support layer (APS)

Objective

interfacing the application layer (AP) with the network layer

Features

generation of messages at the application layer (APDUs)

binding between devices and services

transport of APDUs between different devices


Message transmission

Message format

Octets: 1 0/1 0/1 0/2 0/1 Variable

Frame control

Destination end-point

ClusterIdentifier

ProfileIdentifier

Source endpointFrame payload

Addressing fields

APS header APS payload

Transmission modes

direct or indirect transmissions

unicast or broadcast transmissions

acknowlegments and (optional) retransmissions


Binding

Definition

creation of a unidirectional link between devices and endpoints

every devices keeps a binding table with entries in the format

(as, es, cs) = {(ad1, ed1), (ad2, ed2), . . . , (adn, edn)}

where

as address of the source device in the link

es endpoint of the source device in the link

cs cluster identifier used in the link

adi the i-th destination device address in the link

edi the i-th destination endpoint address in the link


Features of the NWK layer

Objectives

ensures the proper functioning of the MAC layer

provides an interface to the application level

Major features

services for creating a PAN (ZigBee Coordinator)

services for device association (ZigBee Router and End Devices)

logical address assignment and routing (ZigBee Router)


Network management

Network creation, device association and dissociation

high-level primitives of the IEEE 802.15.4 standard

Additional functions

message filtering

broadcast transmissions

Message format

Octets: 2 2 2 1 1 Variable

Frame Con-trol

Destination Address

SourceAddress

Radiusa

aCCB Comment #125

Sequence Numberb

Frame Payload

Routing Fields

NWK Header NWK Payload


ZigBee devices

ZigBee Coordinator

manages the entire network

PAN coordinator in IEEE 802.15.4 (FFD)

ZigBee Router

manages device association

routes the messages to devices

coordinator in IEEE 802.15.4 (FFD)

ZigBee End Device

regular device in the network

RFD or FFD in IEEE 802.15.4


Network topologies

Tree network

non beacon-enabled mode of IEEE 802.15.4beacon-enabled mode of IEEE 802.15.4

active periods of different superframes should not interfere

Beacon Interval

Inactive Period

Superframe Duration

Beacon CAP

Mesh network

corresponds to the peer-to-peer network of IEEE 802.15.4

devices cannot use IEEE 802.15.4 beacons


Distributed address assignment (1 of 2)

Used in tree networks (nwkUseTreeAddrAlloc = TRUE)

Parameters

Cm max number of children (per parent) nwkMaxChildren

Lm maximum depth of the tree nwkMaxDepth

Rm max number of routers (per parent) nwkMaxRouters

The address block assigned by each parent at level d to their own(child) routers is

Cskip(d) =

1 + Cm · (Lm − d − 1) if Rm = 1

1 + Cm − Rm − Cm · R Lm−d−1m

1− Rmotherwise


Distributed address assignment (2 of 2)

Parent node

accepts children if Cskip(d) > 0

uses Cskip(d) as offset for router childrens

the n-th address An is given by

An = Aparent + Cskip(d) · Rm + n

with 1 ≤ n ≤ (Cm − Rm) and Aparent the parent address

Observations

addresses are sequentially assigneda block of addresses cannot be shared between multiple devices

one parent can run out of addresseswhile another parent has unused addresses


Address assigned by upper layers

Used in the general case (nwkUseTreeAddrAlloc = FALSE)

Layer above the network

picks the block of addresses to assign

next address to assign nwkNextAddress

number of available addresses nwkAvailableAddresses

step used when assigning addresses nwkAddressIncrement

Algorithm

a router accepts associations if nwkAvailableAddresses > 0

the device is assigned the address nwkNextAddress

the router decrements nwkAvailableAddressesand adds nwkAddressIncrement to nwkNextAddress


Hierarchical routing

Finding the descendants

D is a descendant of A (at level d) if

A < D < A + Cskip(d − 1)

Forwarding towards descendants

if D is an End Device1 the next hop is N = D

if D is a Router the next hop is

N = A + 1 +

⌊D − (A + 1)

Cskip(d)

⌋· Cskip(d)

1 I.e., D > A + Rm · Cskip(d)


Table-driven routing

Features

uses a simplified version of theAd Hoc On Demand Distance Vector Routing (AODV) protocol

every device with enough memory resourceskeeps a routing table

Hybrid solution

hierarchical and table-driven routing can be used togetherif the destination is in the routing tablethen the corresponding entry is usedif the destination is not known and the routing table has roomfor a new entry then the device starts route discoveryotherwise messages are routed along the tree


Routing metric (1 of 2)

Definitions

P path of length L, i.e., (D1,D2, . . . ,DL)

(Di ,Di+1) link (sub-path of length 2)

C(Di ,Di+1) cost of the link (Di ,Di+1)

Cost of a link

cost of a link l

[0, 1, . . . , 7] 3 C{l} =

7

min(

7, round(

1p4

l

))

where pl is the probability of delivering a message over link l


Routing metric (2 of 2)

Path cost

path cost

C{P} =L−1∑

i=1

C{(Di ,Di+1)}

Observations

pl can be estimatedthrough the LQI of IEEE 802.15.4use of the metric

route discoveryroute maintenance


References

ZigBee Alliance, ZigBee Specification, Version 1.0, December2004

Don Sturek, ZigBee V1.0 Architecture Overview, ZigBee OpenHouse Presentations, Oslo, June 2005

Ian Marsden, Network Layer Technical Overview, ZigBee OpenHouse Presentations, Oslo, June 2005

Paolo Baronti, Prashant Pillai, Vince W.C. Chook, StefanoChessa, Alberto Gotta, Y. Fun Hu, Wireless sensor networks: Asurvey on the state of the art and the 802.15.4 and ZigBeestandards, Computer Communications, Volume 30, Issue 7, 26May 2007, Pages 1655–1695


Computer Networks II

Advanced Features (T-110.5111)

Bluetooth

Mario Di Francesco, PhD

Postdoctoral Researcher – DCS Research Group

Based on slides previously done by Matti Siekkinen and reused with permission For classroom use only, no unauthorized distribution

Computer networks II – Advanced topics

T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco

http://www.uta.edu/faculty/mariodf

Bluetooth

Originally as cable replacement technology

Follows the main objectives of WPAN technologies – low-cost, low-power, short range

Main features – devices find and connect to each other

via inquiry and paging processes

– pairing for authenticated use of services

– master and slave devices

together form a piconet

– different application profiles (and stacks)

e.g. hands-free, streaming audio and video

– secure data transfer


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Piconets and scatternets

A master and up to 7 active slaves form a piconet

– up to 255 parked nodes in addition

Two piconets can be connected to form a scatternet


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Bluetooth “flavors”

Version 2 + EDR

– a.k.a. Classic

– Enhanced Data Rate (EDR) adds 2 and 3 Mbps rates

– basic rate is still 1 Mbps

Version 3 + HS

– adds alternate MAC + PHY (Wi-Fi)

to provide higher speed data channels

Version 4

– adds Bluetooth low energy

– targets embedded low-power devices

runs up to two years on coin cell battery


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Protocol stack


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Layers

Radio layer

– channel access and modulation

Link control (or baseband)

– framing and management of time slots

Link manager

– establishment of logical channels between devices

Logical link control and adaptation protocol (L2CAP)

– framing of variable-length messages and reliability

Application profiles span almost the whole stack


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Radio layer

License-free ISM band at 2.402 – 2.480 GHz – 79 channels 1 MHz wide

Channel access – Adaptive Frequency-Hopping (AFH) spread spectrum

up to 1600 hops/s

all nodes of piconet hop synchronously

– master dictates timing and decides the pseudorandom hop sequence

dynamically exclude channels with interference

– channel map update

Three modulations – 1-bit symbol per μs for 1Mbps rate

– 2/3-bit symbol per μs (EDR) for 2/3 Mbps rates (respectively)


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Other layers

Link control and timeslot management – time division multiplexing with 625μs slots – master transmission at each even slots and slaves at each odd slot

Link manager and link establishment – secure simple pairing – Synchronous Connection Oriented (SCO) link

master and slave set up a periodic schedule

real time data (e.g., phone calls)

– Asynchronous ConnectionLess (ACL) link master polls, slave responds

packet data, best effort

L2CAP – gets packets and outputs frames for the link manager – (de)multiplexes data for upper layers


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Frame structure

Basic

data rate

Enhanced

data rate

higher rate

modulation

only here

specifies the

master

specifies

the slave


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Establishment of a new connection

Inquiry

– discovers units in range

their device addresses and clocks

Paging

– establishes an actual connection

ID ID FHS ID ID FHS ID POLL NULL

M

S INQUIRY SCAN BACKOFF

INQUIRY

INQUIRY

RESPONSE

PAGE

PAGE

SCAN

MASTER

RESPONSE

SLAVE RESPONSE

CONNECTION

CONN


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Inquiry

Inquiry Scan – performed by device that wants to be discovered

– periodically listens for inquiry packets on a special inquiry hopping sequence of 32 frequencies

Inquiry – sends an inquiry packet with a specific inquiry access code

– the code indicates who should respond

either generic or dedicated to certain type of devices

Inquiry Response – sends a response packet containing the responding device address

after receiving inquiry message during the inquiry scan

– sends to corresponding inquiry hopping response sequence

for each inquiry hop there is a corresponding inquiry response hop


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Paging

Page – Master sends a page message to slave’s address

– Send to special page hopping sequence of 32 frequencies

– Master uses the clock information from slave to be paged

Estimate where in the hop sequence slave is listening in page scan mode

Send to the frequencies just before and after

Page Scan – Slave enters page scan state when it wishes to receive page packets

– Slave listens to packets addressed to its DAC

Page Response – Upon receiving page message, slave enters page response state

– Send back a page response containing its DAC

– Use frequencies from corresponding page response sequence

For each page hop there is a corresponding page response hop


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Pairing

Used to establish a link key

– e.g. to prevent eavesdropping an man-in-the-middle attacks

– PIN code pairing (legacy pairing)

– Secure Simple Pairing

Authentication based on shared secret

Encryption of data based on shared secret

– based on SAFER+ block cipher 5478

5478


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Bluetooth Low Energy

Introduction

History

– Nokia initiated project

– Bluetooth Low End Extension (2004)

– WiBree (2006)

– part of Bluetooth v4.0 (2009)

Characteristics

– very low-power consumption

– cheap

– for small amounts of data

– two implementations

single mode for low-power devices (e.g., sensors)

dual mode for less constrained devices (including Bluetooth Classic)


T-110.5111 – Bluetooth (15.10.2012)

Mario Di Francesco


Bluetooth Low Energy

Technical aspects

Radio characteristics

– same frequency band as Classic but only 40 channels 2 MHz wide

– AFH similar to Classic and raw data rate of 1 Mbps

Simpler stack and protocols

– only L2CAP, link layer, and PHY

– reduced number of states

Standby, Advertising, Scanning, Initiating, and Connection

– low-power achieved through a low duty-cycle mechanism

periodic wake-ups for connection events and then sleep

Market availability

– besides devkits, recently appeared in off-the-shelf smartphones

iPhone 4S and 5, iPad 3rd gen, Samsung Galaxy S3

Computer Networks II – Advanced

Features (T-110.5111)

Mario Di Francesco, PhD

[email protected]


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