Wireless Personal Area Networks

CS4422 Wireless and Broadband Networking

Dilum Bandara

Dilum.Bandara@uom.lk

Some slides extracted from ZigBee by J. Dohl, F. Diehm, & P. Grosa and

ZigBee by E. Ünal CSE 401 Special Topics In Computer Networks

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Outline Bluetooth ZigBee Ultra-Wideband

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OSI Stack

Source: http://walkwidnetwork.blogspot.com/2013/04/physical-layer-osi-model.html

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OSI vs. TCP/IP

Source: http://blog.anuesystems.com/category/span-and-taps/

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Bluetooth – IEEE 802.15.1 Developed by Ericson Now managed by Bluetooth Special Interest Group 2.4 – 2.48 GHz ISM band Range – 10 m Bandwidth – 2.1 Mbps (shared) (version 2.0)

Version 4.0 Includes Classic Bluetooth, Bluetooth high speed & Bluetooth low

energy protocols Bluetooth high-speed based on Wi-Fi Classic Bluetooth based on legacy Bluetooth protocols

Low power consumption Found in mobile phones, laptops, computer peripherals,

printers, etc.

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Bluetooth Applications Cable replacement

Phone to PC connection Connecting computing devices Digital imaging Smart car systems

Multiparty data exchange Exchange business cards, calendar events Share presentation material Synchronize information between multiple terminals Play multi-player games

Personal trusted device Reliable e-commerce transactions Local value added services Locking & access control

Stick N Find

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Bluetooth Piconet

Through master No slave-to-slave communication Up to 7 active slaves 255 parked slaves

Source: www.techrepublic.com/article/secure-your-bluetooth-wireless-networks-and-protect-your-data/6139987

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Bluetooth Scatternet By connecting 2+

piconets No direct support at

Baseband Layer

Source: www.techrepublic.com/article/secure-your-bluetooth-wireless-networks-and-protect-your-data/6139987

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Bluetooth Protocol Stack

Source: http://withfriendship.com/user/sathvi/bluetooth-stack.php

Protocols & Usage Models

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PPP

RFCOMM

TCP/IP

Baseband

L2CAP

OBEX

IrMC

TCS-BIN

Audio

SyncDial-up

net.

Usage Models

FileTransfer

AT-commands

Fax HeadsetLAN

AccessCordlessPhone

SDP

LMP

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Bluetooth Protocol Stack (Cont.)

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Bluetooth Applications/Profiles Set of application protocols Definitions of possible applications & specify general

behaviors Resides on top of Bluetooth core specification &

(optionally) additional protocols Example profiles

Hands-Free Profile (HFP) Basic Printing Profile (BPP) Audio/Video Remote Control Profile (AVRCP) File Transfer Profile (FTP) Human Interface Device Profile (HID) Personal Area Networking Profile (PAN) Generic Object Exchange Profile (GOEP)

OBEX

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Other Key Layers Link Management Protocol (LMP)

Set-up & control of radio link between 2 devices Logical Link Control & Adaptation Protocol (L2CAP)

Multiplex multiple logical connections between 2 devices using different higher-level protocols

Provides segmentation & reassembly of on-air packets Service Discovery Protocol (SDP)

Allows a device to discover services offered by other devices, & their associated parameters

Baseband layer Physical layer Manages physical channels & links Error correction, data whitening, hop selection, & security

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Physical Channel Required to use spread spectrum technology as

it’s in ISM band 79 RF channels spaced 1 MHz apart

Channel – frequency range in which communication occurs

Frequency hoping Channel represented by a pseudo-random hopping

sequence hopping through 79 channels Piconet – all devices use same channel

Hopping sequence is unique for the piconet & is determined by device address (BD_ADDR) of master

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Physical Channel (Cont.) Traffic controlled by master Master clock used for all timing & scheduling activities Master transmissions at even slots, slaves always at odd

slots Packet start aligned with slot start Packet extended over up to 5 slots

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Packets

Access code Used for timing synchronization, offset compensation, paging &

inquiry Header

Contains information for packet acknowledgement, packet numbering for out-of-order packet reordering, flow control, slave address, & error check for header

Payload Can contain either voice field, data field, or both

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ZigBee IEEE 802.15.4 covers physical layer & MAC

layer of low-rate WPAN ZigBee adds network construction, application

services, & more on top of IEEE 802.15.4 Star networks, peer-to-peer/mesh networks, &

cluster-tree networks By ZigBee Alliance

Very low power consumption long battery life Low data rate Low complexity circuits & small size low cost

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ZigBee Applications

Telecom Services

m-commerceinfo servicesobject interaction (Internet of Things)

ZigBeeWireless Control that

Simply Works

TVVCRDVD/CDremote

securityHVAClighting controlaccess controlirrigation

PC& Peripherals

asset mgtprocess control

environmentalenergy mgt

Personal Health Care

securityHVACAMR

lighting controlaccess control

patient monitoring

fitness monitoring

Source: http://zigbee.org/

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IEEE 802.15.4 Devıce Types LR-WPAN devices defined by IEEE 802.15.4

1. Full Functional Device (FFD) Can work as a PAN coordinator, as a coordinator, or

as a simple device Can communicate with either another FFD or a RFD

2. Reduced Functional Device (RFD) For applications that don’t need to transmit large

volumes of data & have to communicate only with a specific FFD

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IEEE/ZigBee Topologies

Source: http://wireless.arcada.fi/MOBWI/material/PAN_5_2.html

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ZigBee Topologies (Cont.)

1. Star Topology Pros

Easy to synchronize Low latency

Cons Small scale

2. Mesh/P2P Topology Pros

Robust multi-hop communication

Multi-path communication Flexible network Lower latency

Cons Route discovery is costly Needs to store routing

table

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ZigBee Topologies (Cont.)

3. Cluster Tree Topology Pros

Low routing cost Multi-hop communication Scalable

Cons Route reconstruction is costly Latency may be quite long Root not becomes a single point of failure

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ZigBee Protocol Stack

Source: www.sena.com/products/industrial_zigbee/zigbee_summary.php

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Physical Layer Defined in 802.15.4 2 different services

Data service Controls radio

Management service Energy detection in the channel Clear channel assesment before sending messages Link Quality Indication (LQI) for received packets

Bands

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ZigBee Frequency Bands

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PHY Protocol Data Unit (PPDU)

Preamble for chip & symbol synchronization Contains either data or data acknowledgement Packet size 8-127 Octets Contains MAC Protocol Data Unit (MPDU)

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MAC Layer 2 services

Data service Tx & Rx MPDUs

Management service If coordinator

Manages network beacons, PAN association & disassociation, frame validation, & acknowledgment

CSMA/CA for channel access

Support device security

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Traffic-Modes – Device to PAN Coordinator

Beacon mode Beacon send periodically Coordinator & end device

can go to sleep Lowest energy

consumption Precise timing needed Beacon period (ms-min)

Source: IEEE 802.15.4 Standard (2006)

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Traffic-Modes – Device to PAN Coordinator (Cont.)

Non-Beacon mode Coordinator/routers have

to stay awake Heterogeneous network Asymmetric power

Source: IEEE 802.15.4 Standard (2006)

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Data Transfer From PAN Coordınator

Source: IEEE 802.15.4 Standard (2006)

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MAC Layer – Managing PANs

Channel scanning Active, passive

PAN ID conflict detection & resolution Starting a PAN Sending beacons Device discovery Device association/disassociation Synchronization (beacon/nonbeacon) Orphaned device realignment

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MAC Layer – Frame Security Provided security features

Access control Data encryption Frame integrity Sequential freshness

Available security modes Unsecured mode ACL mode Secured mode

Available security suites AES-CTR AES-CCM AES-CBC-MAC

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Network Layer

Distributed address assignment Tree structure or self managed by higher layer 16-bit network space divided among child routers Child routers divide their space again for their children Depends on

Maximum child count per parent Maximum child-routers per parent Maximum network depth

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Network Layer (Cont.)

Route discovery Find or update route between specific source &

destination Started if no active route present in routing table Broadcast routing request (RREQ) packets Generates routing table entries for hops to source Endpoint router responds with Routing response

(RREP) packet Routes generated for hops to destination Routing table entry generated in source device

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Route DiscoveryRREQRREP

1 2 3

4

2

1

5

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Network Layer (Cont.)

Routing Check if routing table entry exists Initiate route discovery if possible Hierarchical routing as fallback

Route maintenance Track failed deliveries to neighbors Initiate route repair when threshold reached Careful with network load! In case of total connectivity loss

Orphaning procedure Re-association with network

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ZigBee Profiles

Describes a common language for exchanging data

Defines offered services Device interoperability across different

manufacturers Standard profiles available from the ZigBee

Alliance Profiles contain device descriptions Unique identifier (licensed by the ZigBee Alliance)

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ZigBee vs. BluetoothFeature(s) Bluetooth ZigBee

Power Profile days years

Complexity complex Simple

Nodes/Master 7 64000

Latency 10 seconds 30 ms – 1s

Range 10m 70m ~ 300m

Extendibility no Yes

Data Rate 1 Mbps 250 Kbps

Security 64bit, 128bit 128bit AES & Application Layer

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ZigBee vs. BluetoothS

HO

RT

<

R

AN

GE

>

L

ON

G

LOW < DATA RATE > HIGH

PAN

LAN

Text Graphics

Internet Hi-fi Audio

StreamingVideo

DigitalVideo

Multi-channelVideo

802.15.1Bluetooth1

802.15.1Bluetooth 2

802.15.4ZigBee

802.11b

802.11a/HL2 & 802.11g

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Ultra-Wideband Short-range technology for high-speed WPANs

3.1 – 10.6 GHz, 15 MHz channels (up to 5) 10 m

Applications – Cell phones, HDTV, DVD players, audio players, etc.

Source: www.ice.rwth-aachen.de/index.php?id=630&tx_felogin_pi1[forgot]=1&tx_iceprojects_pi1[uid]=155

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Ultra-Wideband (Cont.) Emit large no of very-short pluses over a wide

bandwidth Few nanoseconds or less

Gains few 100s of Mbps Channel capacity proportional to used bandwidth

No specific frequency allocation Operate on frequency band allocated to other

technologies Secure

Like other spread spectrum technologies

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Protocol Stack

Wireless USB, Wireless IP, Bluetooth over UWB, & IEEE1394 over UWB can be operated over a common radio platform

Source: http://research.nokia.com/page/244

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Summary Bluetooth

Spread Spectrum Moderate rate, short-range (10 m – 100 m)

ZigBee Low rate, low power, short range (10 m – 100 m)

Ultra-Wideband High rate, very-short range