Smart Home Technologies

Networking

Networking for Smart Homes Requirements Network Topologies Technologies

Networking Service Discovery

Requirements Noise Rejection

Network has to allow for reliable communication Requires preservation of data and synchronization of

data lines Bandwidth

Smart Homes can contain many sensors and actuators Sensor data can be generated at different rates

Connectivity Sensors have to be connected to processing units

Integration Network structures have to be integrated into

buildings Privacy and Security

Smart Home networks will transfer private and sensitive data

Bandwidth Requirements Example

Camera (15) – 320x240, 8-bit color Motion (15) – distance, direction, velocity Temperature (12) Humidity (12) Light (12) – frequency, intensity Microphone (12) – 8000 Hz Gas (4) Pressure (100)

Bandwidth RequirementsSensor Number Bits/sec (1) Bits/sec (total)

Camera (320x240) 8-bit color

15 184,320 2,764,800

Motion (dir/dis/vel)

15 48 720

Temperature 12 16 192

Humidity 12 16 192

Light (inten/freq) 12 32 384

Microphone (8KHz)

12 64,000 768,000

Gas 4 16 64

Pressure 100 16 1600

Total 182 248,464 3,535,952

Other Bandwidth Requirements Audio

Phones (16 kHz, 8 bit) Radios (44 kHz, 16 bit) TVs (44 kHz, 16 bit) Media players (44 kHz,

16 bit) Monitoring (16 kHz, 8

bit) 2.4 Mbits/sec (one

each)

Internet, control, …

Video Phones (30fps,

320x240, 8-bit color) TVs (60 fps, 1024x768,

24-bit color) Video players (60 fps,

1024x768, 24-bit color) Monitoring (30 fps,

320x240, 8-bit color) ~6.9 Gbits/sec (one

each)

Other Bandwidth Requirements

Other Network Requirements Worst-case throughput: 10

Gbits/sec Maximum throughput: 5 Gbits/sec Quality of Service (QoS)

Audio, video Plug and play (service discovery)

Network Topologies Infrastructure-Based Networks

Pre-defined routes through the network Nodes can directly address each other and routers

forward packets appropriately Addition of nodes changes the routing pattern

Point-To-Point Networks Every node has a connection to every other node Communication is directly between the nodes High overhead setting up the connections for new nodes

Ad-Hoc Networks Routes are determined “on the fly” and can change Nodes forward signals for other nodes Addition of nodes can be handled relatively

straightforwardly

Topologies (Point-to-Point) Every device is connected to

every other device Good points

simplest approach no addressing needed everyone is your neighbor you can always talk to your neighbor

Bad points number of ports/lines grow relatively

quickly with the number of devices

A B

C D

Topologies (Hierarchy) Devices are connected via hubs to

other devices If everyone is connected to a single hub,

it is called a Star topology Good points

fewer connections devices can have neighborhoods

Bad points you need an address you may have to wait to talk to a

neighbor asymmetric communication with some

devices

A

B

C

D

Topologies (Broadcast) All of the devices are connected to

a single wire Good points

single wire everyone is your neighbor

Bad points you need an address you may have to wait to talk to anyone collisions can occur communication times become

statistical

A

B

C

D

Physical Addresses If more than two devices are on the same wire

(bus), you will need an address to send and receive data

Approaches separate vs. combined data/address lines hardwired vs. selectable address

Issues as the number of devices increase, the address

space (size of the address) must increase hardwired addresses may tell you nothing about

the network topology addresses will be used up by devices that might

not be on-line so your address space may be too big, causing too

much overhead

A

B

C

D

0001

1111

1000

1100

Virtual Addresses A solution to some physical address

problems is a virtual address the address space (size of the address) can be

reduced by only giving addresses to on-line devices

addresses can be set up to support network topology

Approaches fixed vs. run-time addresses universal vs. p-to-p addresses

Issues how to assign them their relationship to the physical address

A

B

C

D

00

01

10

11

Network Technologies

Wired Phone Line Power Line New Wire

Wireless RF Infrared

Wired Network Technology Examples Phone line

Home Phoneline Networking Alliance (HomePNA) Power line

X10 Consumer Electronics Bus (CEBus) HomePlug LonWorks

New wire Ethernet (coax, twisted pair, optical fiber) Universal Serial Bus (USB) IEEE 1394 Firewire

Home Audio Video Interoperability (HAVi) Specialty: audio, video

Phoneline Networking Home Phoneline Networking Alliance

(HomePNA) www.homepna.org

IEEE 802.3 (Ethernet) Carrier Sense Multiple Access with Collision

Detect (CSMA/CD) 10 Mbps (HPNA 2.0) Length: 500 feet

HomePNA Packet

HomePNA Frequencies Standard voice (POTS): 20Hz - 3.4kHz UADSL: 25kHz - 1.1MHz Home network: 5.5MHz - 9.5MHz

Phoneline Network Issues Random wiring topologies & signal

attenuation Home phoneline wiring system is a random

“tree” topology Simply plugging in the phone or

disconnecting the fax changes the tree This topology can cause signal attenuation

Signal noise Appliances, heaters, air conditioners,

consumer appliances & telephones can introduce signal noise onto the phone wires

Powerline Networking Ubiquity of power lines 10+ Mbps Technologies

X10 Consumer Electronics Bus (CEBus) HomePlug LonWorks

X10 X10 controllers send signals over

existing AC wiring to receiver modules

X10 technology transmits binary data using the Amplitude Modulation (AM) technique

www.x10.com

X10 To differentiate the data symbols, the

carrier uses the zero-voltage crossing point of the 60Hz AC sine wave on the cycle’s positive or negative transition

Synchronized receivers accept the carrier at each zero-crossing point

X10 uses two zero crossings to transmit a binary digit so as to reduce errors

X10 Every bit requires a full 60 Hertz cycle

and thus the X10 transmission rate is limited to only 60 bps

Usually a complete X10 command consists of two packets with a 3 cycle gap between each packet Each packet contains two identical

messages of 11 bits (or 11 cycles) each A complete X-10 command consumes 47

cycles that yields a transmission time of about 0.8s

Consumer Electronics Bus (CEBus) Open standard providing separate physical

layer specification for communication on power lines and other media Electronic Industries Association (EIA-600) www.cebus.org

Data packets are transmitted by the transceiver at about 10 Kbps

Carrier Sense Multiple Access/Collision Detect (CSMA/CD)

Employing spread spectrum technology (100Hz-400 Hz)

OSI and CEBus (EIA-600)

Spread Spectrum Modulation Frequency spectrum of a data-signal is

spread using a code uncorrelated with that signal

Sacrifices bandwidth to gain signal-to-noise performance

HomePlug HomePlug Powerline Alliance

www.homeplug.org Spread-spectrum technology

HomePlug Speed

Support file transfers at 10BaseT-like rates Either node-to-node file transfer or

scenarios with multiple nodes performing simultaneous file transfers

HomePlug 1.0 (14 Mbps) Voice over IP (VoIP)

Maintain adequate QoS while supporting multiple, simultaneous VoIP calls while other nodes are transferring files and during multiple media streams

HomePlug Interoperability

Interoperate with other networking technologies Co-exist with existing powerline networking

technologies such as X-10, CEBus and LonWorks

Security Contain strong privacy features Support multiple logical networks on a single

physical medium Be applicable to markets in North America,

Europe and Asia

LonWorks Local Operation Networks (LonWorks) Developed by Echelon Corporation

www.echelon.com Provides a peer-to-peer communication

protocol, implementing Carrier Sense Multiple Access (CSMA) techniques

1.25 Mbps Works for other wired and wireless media

LonWorks A common message-based

communications protocol LonTalk protocol implements all

seven layers of the OSI model using a mixture of hardware and firmware on a silicon chip

Protocol can be run as fast as 20 MHz

Powerline Network Issues Noise

Switching power supplies Wound motors

Vacuum cleaners, kitchen appliances, drills

Dimmers Security Signal attenuation

New Wire Networking Ethernet (coax, twisted pair, optical

fiber) Universal Serial Bus (USB) IEEE 1394 Firewire

Home Audio Video Interoperability (HAVi) Specialty: audio, video

Ethernet IEEE 802.3

CSMA/CD Up to 1 Gbps

IEEE 802.3ae 10GBase-X, 10 Gps Lengths up to 40 km

www.ethermanage.com/ethernet

IEEE 802.3

Universal Serial Bus (USB) www.usb.org 480 Mbps Plug and Play Hot pluggable Up to 127 devices simultaneously Powered bus 5m maximum cable length

IEEE 1394 Firewire (i.LINK) Digital interface

No need to convert digital data into analog and tolerate a loss of data integrity

Transferring data @ 100, 200, 400 Mbps

Physically small The thin serial cable can replace larger

and more expensive interfaces

IEEE 1394 Firewire No need for terminators or device

IDs Hot pluggable

Users can add or remove 1394 devices with the bus active

Scaleable architecture May mix 100, 200, and 400 Mbps

devices on a bus

IEEE 1394 Firewire It can connect up to 63 devices @

transfer rate of 400Mbps Up to 16 nodes can be daisy-

chained through the connectors Standard cables up to 4.5 m in length

for a total standard cable length of 72 m

IEEE 1394 Firewire Flexible topology

Support of daisy chaining and branching for true peer-to-peer communication

Non-proprietary

IEEE 1394b 1394b is a significant enhancement to

the basic 1394 specification that enables: Speed increases to 3.2 Gbps Distances of 100 meters on UTP-5, plastic

optical fiber and glass optical fiber Significantly reduces latency times by using

arbitration Fully backwards compatible with the

current 1394 and 1394a specifications

I2C (Inter-Integrated Circuit)

One of the oldest controller buses Philips (1980s)

Low-cost chip-to-chip communication link uses two wires to form a clocked serial bus

one called Clock (SCL) and the other Data (SDA) the SDA carries address, selection, control,

and data Overview

multi-master bus (up to 1024 devices) can run at speed up to 3.4 Mbps can be used as a SAN

but normal ranges are on the order of 14 cm

Home Audio Video Interoperability (HAVi) HAVi is a digital Audio Video

networking initiative that provides a home networking software specification Seamless interoperability among

home entertainment products Designed to meet the particular

demands of digital audio and video www.havi.org

HAVi Defines operating-system-neutral

middleware that manages: Multi-directional AV streams Event schedule Registries

Takes advantage of chips built into modern audio and video appliances Provides the management function of a

dedicated audio-video networking system IEEE 1394 (i. LINK or FireWire) has been

chosen as the interconnection medium

Specialty Wiring Audio

Coax RCA Speaker wire

Video Coax RCA VGA

~100m maximum cable lengths

Automotive Inspired Busses

LIN (Local Interconnect Network) Designed for European cars (still

used) Very simple

single wire single mastered bus

Overview 1 master, up to 16 Slaves uses a message-based protocol maximum distance of 40 m Two data rates

9,600 and 19.2 Kbps

CAN(Controller Area Network )

CAN was designed to support emission control system in European cars

but became a general automation control bus Capable of

high-speed (1 Mbits/s) data transmission over short distances (40 m)

low-speed (5 kbits/s) transmissions at lengths of up to 10,000 m

Overview a multi-master bus highly fault tolerant

Built-in support for error detection and handling

MOST(Media Oriented System Transport)

An inexpensive automotive and appliance network 25 Mbps fiber-

optic bus for real-time data

transfer used in surround-

sound systems and CD and DVD players

FlexRay Designed to replace LIN, CAN and MOST

as a ‘by wire’ solution for future cars It is a fiber-optic bus (like MOST) Current speed

10 Mbps But it is designed to go much higher

could run faster than 100 Mbps But remember

that is faster than most current micro-controller’s internal bus speed

Wireless Network Technologies

Digital Enhanced Cordless Telecommunications (DECT)

HomeRF Bluetooth IEEE 802.11 HiperLAN2 Infrared

General Wireless

Narrow band Spread spectrum

Direct Sequence (DSSS) Frequency Hopping (FHSS)

Orthogonal Frequency Division Multiplexing (OFDM)

DECT Digital Enhanced Cordless

Telecommunications (DECT) www.dectweb.com Digital radio technology Dynamic channel selection Encryption, authentication, identification 500 Kbps – 2 Mbps Cordless phones

HomeRF www.homerf.org Shared Wireless Access Protocol

(SWAP) IEEE 802.11 for data DECT for voice

HomeRF Specifications

2.4 GHz band FHSS 1.6 Mbps (10 Mbps with SWAP 2.0) 50m range 127 nodes

Bluetooth www.bluetooth.com Ericsson, the principal inventor,

borrowed the name from Harald Bluetooth (son of Gorm) The King of Denmark circa 900AD United Denmark and Norway

Bluetooth Specifications

2.4 GHz FHSS (79 channels)

1600 hops per second Error correction

1 Mbps capacity, 780 Kbps throughput 10m distance Low power (1 mW)

Bluetooth Personal Area Networks (PANs) Piconet

Collection of up to 8 devices using same hopping sequence

Scatternet Collection of piconets, each with

different hopping sequence

IEEE 802.11

Standard Frequency

PHY Layer

Data Rate

Distance*

802.11a 5 GHz OFDM 54 Mbps 50m

802.11b 2.4 GHz DSSS 11 Mbps 100m

802.11e,MAC layer

Offers QoS and backwards compatibility(in committee)

802.11g 2.4 GHz OFDM 54 Mbps ?

* Data rate degrades with distance.

HiperLAN2 www.hiperlan2.com 5 GHz 54 Mbps OFDM Automatic frequency allocation TDMA/TDD (Time Division) QoS support

Infrared www.irda.org Directed – line of sight

1m range Diffuse – reflective

Limited to room size Speed

4 Mbps available 16 Mbps coming 50 Mbps possible

Wireless Networking

Wireless Issues Distance 2.4 GHz interference

Microwave ovens Cordless phones

Security Not a backbone solution

Wireless Personal Area Networks (WPAN) 802.15.X

Intended for low cost, low distance, low power personal networks

Often intended for mesh networking E.g. ZigBee (build on 802.11.4)

Ad-Hoc Mesh Networks Ad-Hoc networks of wireless sensors

and devices Benefits:

Easy to build (require no infrastructure to be available)

Dynamic and mobile Fault tolerant (usually no single point of failure)

Challenges: Choice of routing to optimize performance

QoS Power consumption

Synchronization and collision avoidance

Service Discovery Self-configuring devices Device becomes aware of network,

network services and other devices Automatic, as opposed to manual

(e.g., DHCP, DNS, LDAP) Several incompatible protocols

Service Discovery Protocols Salutation Service Location Protocol (SLP) Jini Universal Plug and Play Zero-Configuration Networking

Salutation www.salutation.org Architecture for looking up,

discovering and accessing services and information

Salutation Abstractions for devices, applications,

and services Current definitions

Printers Fax machines Document storage devices Address book Schedule Voice message answer, send, storage More coming (e.g., display, OS)

Salutation Capabilities exchange protocol Service request protocol “Personalities” (standardized

protocols for common services) APIs for information access and

session management

Service Location Protocol (SLP)

Developed by Internet Engineering Task Force (IETF)

Applies existing Internet standards to service discovery problem

www.srvloc.org www.openslp.org

SLP Agents User Agent (UA)

The SLP User Agent is a software entity that is looking for the location of one or more services.

Service Agent (SA) The SLP Service Agent is a software entity that

provides the location of one or more services. Directory Agent(DA)

The SLP Directory Agent is a software entity that acts as a centralized repository for service location information.

SLP Messages Service Request (SrvRqst)

Message sent by UAs to SAs and DAs to request the location of a service.

Service Reply (SrvRply) Message sent by SAs and DAs in reply

to a SrvRqst.  The SrvRply contains the URL of the requested service.

SLP Messages (cont.) Service Registration (SrvReg)

Message sent by SAs to DAs containing information about a service that is available.

Service Deregister (SrvDeReg) Message sent by SAs to inform DAs that a

service is no longer available. Service Acknowledge (SrvAck)

A generic acknowledgment that is sent by DAs to SAs as a reply to SrvReg and SrcDeReg messages.

SLP Messages (cont.) Attribute Request (AttrRqst)

Message sent by UAs to request the attributes of a service.

Attribute Reply (AttrRply) Message sent by SAs and DAs in reply

to a AttrRqst.  The AttrRply contains the list of attributes that were requested.

SLP Messages (cont.) Service Type Request (SrvTypeRqst)

Message sent by UAs to SAs and DAs requesting the types of services that are available.

Service Type Reply (SrvTypeRply) Message by SAs and DAs in reply to a

SrvTypeRqst.  The SrvTypeRply contains a list of requested service types.

SLP Messages (cont.) DA Advertisement (DAAdvert)

Message sent by DAs to let SAs and UAs know where they are.

SA Advertisement (SAAdvert) Message sent by SAs to let UAs know

where they are.

Unicast or multicast messaging

Jini Service discovery for networks of

Java-enabled devices www.sun.com/jini www.jini.org

Jini

Jini Services Lookup Communications

Java-RMI, CORBA, … Security Leasing Events

Universal Plug and Play Microsoft’s service discovery

approach IP-based discovery protocols

XML www.upnp.org Examples

Universal Plug and Play Devices

Containers for services XML description

Services Actions (i.e., methods)

Control server Event server

State (i.e., variables) XML description

Universal Plug and Play Control points

Retrieve the device description and get a list of associated services.

Retrieve service descriptions for interesting services.

Invoke actions to control the service. Subscribe to the service’s event source.

Anytime the state of the service changes, the event server will send an event to the control point.

UPnP Protocols Protocols

UDP, TCP/IP, HTTP, XML Simple Service Discovery Protocol

(SSDP) Generic Event Notification Architecture

(GENA) Send/receive event notifications using

HTTP over TCP/IP and multicast UDP Simple Object Access Protocol (SOAP)

XML and HTTP for remote procedure calls

UPnP Protocol StackUPnP Vendor Defined

UPnP Forum Working Committee Defined

UPnP Device Architecture Defined

HTTPMU(Discovery)

HTTPU(Discovery)

SOAP(Control)

HTTP(Description)

UDP TCP

SSDP GENA SSDP

IP

HTTP

GENA(Events)

Zero-Configuration Networking Zeroconf (www.zeroconf.org) IETF standard Objectives

Allocate addresses without a DHCP server Translate between names and IP addresses

without a DNS server Find services, like printers, without a directory

server Allocate IP Multicast addresses without a

MADCAP server Multicast Address Dynamic Client Allocation Protocol

Zeroconf Protocols Address autoconfiguration

Configure interfaces with unique addresses

Determine which subnet mask to use Detect duplicate address assignment Cope with collisions

Name-to-address translation Multicast DNS Decentralized

Zeroconf Protocols Service discovery

Service Location Protocol (SLP) DNS Service Resource Record

Use expanded DNS for service requests Multicast address allocation

Zeroconf Multicast Address Allocation Protocol (ZMAAP)

Allocate unique addresses and maintain them over time

Prevent reallocation of assigned addresses Be notified of multicast allocation collision