wimax, wimesh, bluetooth, zigbee, rfid, and other wimesh, bluetooth, zigbee, rfid, and other...
TRANSCRIPT
IEEE 802.16
Standard IEEE 802.16 (http://grouper.ieee.org/groups/802/16/) defines the
air interface, including the MAC layer and multiple PHY layer options,
for fixed Broadband Wireless Access (BWA) systems to be used in a
Wireless Metropolitan Area Network (WMAN) for residential and
enterprise use.
IEEE 802.16 is also often referred to as WiMax. The WiMax Forum strives to ensure
interoperability between different 802.16 implementations - a difficult task due to the
large number of options in the standard.
IEEE 802.16 cannot be used in a mobile environment. For this IEEE 802.16e is being
developed; expected to compete with IEEE 802.20 standard (base standard 2008 –now
in hibernation – lack of activity).
IEEE 802.20 http://grouper.ieee.org/groups/802/20/ or Mobile Broadband
Wireless Access (MBWA) is a proposed IEEE Standard to enable worldwide
deployment of multi-vendor interoperable mobile broadband wireless access
networks
4
WiMax Standards
802.16 802.16a 802.16-2004
802.16e-2005
Date Completed
December 2001
January 2003
June 2004
December 2005
Spectrum 10-66 GHz < 11 GHz < 11 GHz < 6 GHz
Operation LOS Non-LOS Non-LOS Non-LOS and Mobile
Bit Rate 32-134 Mbps Up to 75 Mbps
Up to 75 Mbps
Up to 15 Mbps
Cell Radius 1-3 miles 3-5 miles 3-5 miles 1-3 miles
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IEEE 802.16 standardization
first version of IEEE 802.16 standard completed in 2001.
defined a single carrier (SC) physical layer for line-of-sight
(LOS) transmission in the 10-66 GHz range.
IEEE 802.16a defined three physical layer options (SC, OFDM,
and OFDMA) for the 2-11 GHz range.
IEEE 802.16c contained upgrades for the 10-66 GHz range.
IEEE 802.16d contained upgrades for the 2-11 GHz range.
In 2004, the original 802.16 standard, 16a, 16c and 16d were
combined into the massive IEEE 802.16-2004 standard.
7
WiMax system
• Typically, a WiMAX system consists of two parts:
– A WiMAX Base Station (BS): Base station consists
of indoor electronics and a WiMAX tower. Typically, a base
station can cover up to 10 km radius (Theoretically, a base
station can cover up to 50 km radius or 30 miles, however
practical considerations limit it to about 10 km or 6 miles).
Any wireless node within the coverage area would be able to
access the Internet.
– A WiMAX receiver (Subscriber Station-SS) - The receiver
and antenna could be a stand-alone box or a PCMCIA card
that sits in your laptop or computer. Access to WiMAX base
station is similar to accessing a Wireless Access Point in a
WiFi network, but the coverage is further.
9
How WiMax Works
• WiMax can provide 2 forms of wireless service:
- Non-LOS, Wi-Fi sort of service, where a small antenna on a computer connects to the tower. Uses lower frequency range (2 to 11 GHz).
- LOS, where a fixed antenna points straight at the WiMax tower from a rooftop or pole. The LOS connection is stronger and more stable, so it is able to
send a lot of data with fewer errors. Uses higher frequencies, with ranges reaching a possible 66 GHz.
Through stronger LOS antennas, WiMax transmitting stations would send data to WiMax enabled computers or routers set up within 30 mile radius (3,600 square miles of coverage) .
12
WiMax Spectrum
• Broad Operating Range
• WiMax Forum is focusing on 3 spectrum bands for global deployment: – Unlicensed 5 GHz: Includes bands between 5.25 and
5.85 GHz. In the upper 5 GHz band (5.725 – 5.850 GHz) many countries allow higher power output (4 Watts) that makes it attractive for WiMax applications.
– Licensed 3.5 GHz: Bands between 3.4 and 3.6 GHz have been allocated for Broadband Wireless Access (BWA) in majority of countries.
– Licensed 2.5 GHz: The bands between 2.5 and 2.6 GHz have been allocated in the US, Mexico, Brazil and in some SEA countries.
13
WiMax Uplink / downlink separation
IEEE 802.16 offers both TDD (Time Division Duplexing) and
FDD (Frequency Division Duplexing) alternatives.
Wireless devices should avoid transmitting and receiving at
the same time, since duplex filters increase the cost:
TDD: this problem is automatically avoided
FDD: IEEE 802.16 offers semi-duplex operation as an
option in Subscriber Stations.
(Note that expensive duplex filters are also the reason why
IEEE 802.11 WLAN technology is based on CSMA/CA
instead of CSMA/CD.)
14
IEEE 802.16 basic architecture
BS SS
SS
SS
Point-to-multipoint transmission AP
AP
802.11
WLAN BS = Base Station
SS = Subscriber Station
Fixed network
Subscriber line
replacement
15
ATM
transport
IP
transport
Service Specific Convergence
Sublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer
(MAC CPS)
Privacy sublayer
Physical Layer (PHY)
MA
C
Like IEEE 802.11, IEEE
802.16 specifies the Medium
Access Control (MAC) and
PHY layers of the wireless
transmission system.
The IEEE 802.16 MAC layer
consists of three sublayers.
16
ATM
transport
IP
transport
Service Specific Convergence
Sublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer
(MAC CPS)
Privacy sublayer
Physical Layer (PHY)
MA
C
CS maps data (ATM cells or IP
packets) to a certain
unidirectional connection
identified by the Connection
Identifier (CID) and associated
with a certain QoS.
CS adapts higher layer
protocols to MAC CPS.
May also offer payload header
suppression.
17
ATM
transport
IP
transport
Service Specific Convergence
Sublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer
(MAC CPS)
Privacy sublayer
Physical Layer (PHY)
MA
C
MAC CPS provides the core
MAC functionality:
• System access
• Bandwidth allocation
• Connection control
Note: QoS control is applied
dynamically to every
connection individually.
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ATM
transport
IP
transport
Service Specific Convergence
Sublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer
(MAC CPS)
Privacy sublayer
Physical Layer (PHY)
MA
C
The privacy sublayer provides
authentication, key
management and encryption.
19
ATM
transport
IP
transport
Service Specific Convergence
Sublayer (CS)
IEEE 802.16 protocol layering
MAC Common Part Sublayer
(MAC CPS)
Privacy sublayer
Physical Layer (PHY)
MA
C
IEEE 802.16 offers three PHY
options for the 2-11 GHz band:
• WirelessMAN-SCa
• WirelessMAN-OFDM
• WirelessMAN-OFDMA
20
WiMAX
The WiMax (Worldwide
Interoperability for Microwave Access)
certification program of the WiMax
Forum addresses compatibility of IEEE
802.16 equipment
=>
WiMax ensures interoperability of
equipment from different vendors.
ATM
transport
IP
transport
Service Specific Convergence
Sublayer (CS)
MAC Common Part Sublayer
(MAC CPS)
Privacy sublayer
Physical Layer (PHY)
WiMax
21
22
WiMAX (IEEE 802.16a) in a nutshell
Frequency Spectrum: 2 – 11GHz
Last mile technology (WAN)
Up to 30 miles of range with cell radius: 4-6 miles
Backhaul technology for wireless LANs (802.11)
Shared data rate up to 75 Mbps.
Support 50 customers with T1-rate wireless connections
ISP: http://www.towerstream.com/about.asp
Ref: http://www.intel.com/ebusiness/pdf/wireless/intel/80216_wimax.pdf
IEEE 802.16: WiMax in a nutshell
• The WiMAX wireless metropolitan network standard, IEEE 802.16,
– defines various high speed mechanisms that provide wireless last mile broadband access in Metropolitan Area Networks (MANs) at a cost much lower than traditional cable, DSL or T1 technologies.
• A typical scenario for the use of WiMAX is for it to provide broadband Internet access to various users in one or more buildings via rooftop antennae. – This emerging technology could had provided a very attractive
alternative to the 3G technology which is based on cellular networks. The low cost of WiFi deployment is obtained at the cost of much smaller coverage.
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IEEE 802.16: WiMax in a nutshell
• WiMAX is part of a global standardization effort of the IEEE that involves not only the local WiFi networks (IEEE 802.11) but also regional networks (IEEE 802.22).
• IEEE 802.16 MAC protocol is mainly designed for point-to-multipoint access in wireless broadband applications.
• provides different levels of QoS to provide a multitude of transmission services including data, video and voice over IP.
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IEEE 802.16: WiMax in a nutshell
• WIMAX Forum announced that 802.16 networks now
cover 430m people worldwide and are on a path to nearly
double to 800m pops by end of 2010. prediction!!
• based on almost 460 deployments in 135 countries,
• new roll-outs will be driven by auctions in India and Brazil,
among others.
• “In both emerging markets and mature countries,
companies and governments are deploying 4G WIMAX
networks to help bridge the digital divide,” said Intel’s
Maloney (Feb 2009).
• In early 2011 projections say that only about 5% of the
market will adopt 802.16!!!
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Challenges to Overcome in WiMax
Deployment
• RF Interference: Disrupts a transmission and decreases performance. – Common forms are multi-path interference and attenuation.
Overlapping interference generate random noise.
• Infrastructure Placement: physical structure that houses or supports base station must be RF friendly. – Health and environmental concerns
– High RF activity in the area can cause interference.
– Obstacles such as trees and buildings can block signal paths.
– A metal farm silo, for example, may distort signals, or a tree swaying in the wind may change signal strength.
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Solving the challenges in WiMax
Deployment
• Proper network design and infrastructure
placement are critical for solving the challenges.
- Subscriber Site Survey, Statistics Gathering, coordination
of RF use with neighbouring providers.
- Antennas (Type, Tilt Angles, Array Gain, Diversity Gain)
- Proper design and deployment of the provider’s NOC.
- Well deployed base station or cells with 24/7 access, RF
friendly structure, and shielding from weather elements.
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MBWA: 802.20
• Mobile Broadband Wireless Access (MBWA)
aka Mobile-Fi
– IEEE Standard to enable worldwide deployment of
multi-vendor interoperable mobile broadband wireless
access network
– scope of working group consists of PHY, MAC, LLC
layers. The air interface will operate in bands below 3.5
GHz and with a peak data rate of over 80 Mbit/s.
– The goals of 802.20 and 802.16e, the so-called "mobile
WiMAX", are similar.
– New MAC and PHY with IP and adaptive antennas
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Wireless Mesh Network solution
• ideal for WLAN coverage of large open areas, both indoor and outdoor,
• considered where Ethernet cabling is prohibitive to install or to minimize the requirement for leased backhaul.
• deployment scenarios that are often particularly well suited for Wireless Mesh Network include: – campus environments (enterprises and universities),
manufacturing, shopping centers,
– construction sites
– airports, sporting venues, special events
– military operations, disaster recovery, temporary installations, public safety
– municipalities, including downtown cores, residential areas, and parks
– carrier managed service in public areas or residential communities
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WiMax Mesh Mode
35
• Presented in
(802.16d-2004) as
optional mode
• SS don’t have to
be within the range
of the BS
• Traffic is relayed
by parent nodes to
the BS
Wireless Mesh networks example
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The Wireless Mesh Network is well-suited for providing broadband
wireless access in areas that traditional WLAN systems are unable to cover.
49
IEEE definition of WPAN
Wireless personal area networks (WPANs) are used to convey information over short distances among a private, intimate group of participant devices. connection made through a WPAN involves little or no infrastructure or direct connectivity to the world outside the link (ad-hoc). This allows small, power-efficient, inexpensive solutions to be implemented for a wide range of devices.
• less than 10 m diameter
• replacement for cables
(mouse, keyboard,
headphones)
• ad hoc: no infrastructure
• master/slaves:
– slaves request permission to
send (to master)
– master grants requests
• 802.15: evolved from
Bluetooth specification
– 2.4-2.5 GHz radio band
– up to 721 kbps
50
M radius of
coverage
S
S S
P
P
P
P
M
S
Master device
Slave device
Parked device (inactive) P
802.15: personal area network
52
Bluetooth (IEEE 802.15.1)
Wireless Personal Area Network
Spread Spectrum: Frequency Hopping Spread Spectrum (FHSS)
Frequency Band: 2.4GHz
Very low power consumption
Short distance: < 10m
Relatively low rate: < 1M
Applications: Cellular phone
Peripheral device
Home appliance
Car
www.xilinx.com/esp/bluetooth/tutorials/intro.htm
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Bluetooth ≈ IEEE 802.15.1
A widely used WPAN technology is known as Bluetooth (version 1.2 or version 2.0) The IEEE 802.15.1 standard specifies the architecture and operation of Bluetooth devices, but only as far as physical layer and medium access control (MAC) layer operation is concerned (the core system architecture). Higher protocol layers and applications defined in usage profiles are standardised by the Bluetooth SIG.
54
Piconets
Bluetooth enabled electronic devices connect and communicate wirelessly through short-range, ad hoc networks known as piconets.
Piconets are established dynamically and automatically as Bluetooth enabled devices enter and leave radio proximity.
Up to 8 devices in one piconet (1 master and 7 slave devices). Max range 10 m.
ad hoc => no base station
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Piconet operation
The piconet master is a device in a piconet whose clock and device address are used to define the piconet physical channel characteristics. All other devices in the piconet are called piconet slaves. At any given time, data can be transferred between the master and one slave. The master switches rapidly from slave to slave in a round-robin fashion. Any device may switch the master/slave role at any time.
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Power classes
Bluetooth products are available in one of three power classes:
Class
Class 1
Class 2
Class 3
Power
100 mW
2.5 mW
1 mW
Range
~100 m
~10 m
~10 cm
Industrial usage
Mobile devices
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Data rates
Channel data rates: Bluetooth version 1.2 offers a bit rate of 1 Mbit/s. Bluetooth version 2.0 offers 3 Mbit/s. Achievable user bit rates are much lower, (among others) due to the following reasons:
overhead resulting from various protocol headers
interference causes destroyed frequency bursts => information has to be retransmitted
IEEE 802.15.1 BLUETOOTH (I)
• Bluetooth technology aims at so-called ad hoc piconets, which are local area networks with a very limited coverage and without the need for an infrastructure.
• Needed to connect different small devices in close proximity without expensive wiring or the need for a wireless infrastructure.
• Represents a single-chip, low-cost, radio-based wireless network technology.
58
BLUETOOTH (II)
• No standardization body has set up any specification
regarding Bluetooth.
• The primary goal of Bluetooth is not a complex
standard covering many aspects of wireless
networking, but a quick and very cheap solution
enabling ad hoc personal communication within a
short range in the license-free 2.4 GHz band.
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BLUETOOTH (III)
• Physical layer: – A frequency-hopping\time-division duplex scheme is used
for transmission with a fast hopping rate of 1,600 hops per second. The time between two hops is called a slot, which is an interval of 625μs, thus each slot uses a different frequency.
– On average, the frequency-hopping sequence ´visits´ each hop carrier with an equal probability.
– All devices using the same hopping sequence with the same phase form a Bluetooth piconet.
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BLUETOOTH (IV)
– With transmitting power of up to 100 mW, Bluetooth
devices have a range of up to 10m (or even up to 100m
with special transceivers).
– Having this power and relying on battery power, a
Bluetooth device cannot be in an active transmit mode all
the time.
– Bluetooth defines several low-power states for the device.
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BLUETOOTH (V)
– States of a possible Bluetooth device and possible
transitions:
• Standby mode: Every device which is currently not participating in
a piconet (and not switched off)
– In this mode, a device listens for paging messages.
• Connections can be initiated by any device which becomes the
master.
– This is done by sending page messages if the device already knows
the address of the receiver, or inquiry messages followed by a page
message if the receiver’s address is unknown.
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BLUETOOTH (VI)
• To save battery power, a Bluetooth device can go into one of three low power states if no data is ready to be sent:
– PARK state: The device has the lowest duty cycle, and thus the lowest power consumption. The device releases its MAC address, but remains synchronized with the piconet. The device occasionally listens to the traffic of the master device to resynchronize and check for broadcast messages.
– HOLD state: The power consumption of this state is a little higher. The device does not release its MAC address and can resume sending at once after transition out of the HOLD state.
– SNIFF state: It has the highest power consumption of the low-power states. The device listens to the piconet at a reduced rate.
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BLUETOOTH (VII)
64
STANDBY
inquiry page
connected transmit
PARK HOLD SNIFF
unconnected
connecting
active
low power
BLUETOOTH (VIII)
• MAC layer: – Several mechanisms control medium access in a Bluetooth
system.
– One device within a piconet acts as a master, all other devices (up to seven) act as slaves.
– The master determines the hopping sequence as well as the phase of the sequence.
– All Bluetooth devices have the same networking capabilities, i.e., they can be master or slave. The unit establishing the piconet automatically becomes the master and controls medium access; all other devices will be slaves.
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L2CAP layer
Host Controller Interface
L2CAP layer
Channel Manager
Resource Manager
L2CAP
Control Data Synchronous traffic
The Logical Link Control and Adaptation Protocol (L2CAP) layer handles the multiplexing of higher layer protocols and the segmentation and reassembly (SAR) of large packets. The L2CAP layer provides both connectionless and connection-oriented services.
67
Higher protocol layers (1)
The operation of higher protocol layers is outside the scope of the IEEE 802.15.1 standard (but included in the Bluetooth SIG standards). The usage of these protocols depends on the specific Bluetooth profile in question. A large number of Bluetooth profiles have been defined.
L2CAP layer
RFCOMM
TCP/IP/PPP RS-232 emulation SDP TCS BIN OBEX
68
Higher protocol layers (2)
The radio frequency communication protocol RFCOMM enables the replacement of serial port cables (carrying RS-232 control signals such as TxD, RxD, CTS, RTS, etc.) with wireless connections. Several tens of serial ports can be multiplexed into one Bluetooth device.
L2CAP layer
RFCOMM
TCP/IP/PPP SDP TCS BIN OBEX RS-232 emulation
69
Higher protocol layers (3)
TCP/IP based applications, for instance information transfer using the Wireless Application Protocol (WAP), can be extended to Bluetooth devices by using the Point-to-Point Protocol (PPP) on top of RFCOMM.
L2CAP layer
RFCOMM
TCP/IP/PPP SDP TCS BIN OBEX RS-232 emulation
70
Higher protocol layers (4)
The Object Exchange Protocol (OBEX) is a session-level protocol for the exchange of objects. This protocol can be used for example for phonebook, calendar or messaging synchronisation, or for file transfer between connected devices.
L2CAP layer
RFCOMM
TCP/IP/PPP SDP TCS BIN OBEX RS-232 emulation
71
Higher protocol layers (5)
The telephony control specification - binary (TCS BIN) protocol defines the call-control signalling for the establishment of speech and data calls between Bluetooth devices. In addition, it defines mobility management procedures for handling groups of Bluetooth devices.
L2CAP layer
RFCOMM
TCP/IP/PPP SDP TCS BIN OBEX RS-232 emulation
72
Higher protocol layers (6)
The Service Discovery Protocol (SDP) can be used to access a specific device (such as a digital camera) and retrieve its capabilities, or to access a specific application (such as a print job) and find devices that support this application.
L2CAP layer
RFCOMM
TCP/IP/PPP SDP TCS BIN OBEX RS-232 emulation
73
Usage models
A number of usage models are defined in Bluetooth profile documents. A usage model is described by a set of protocols that implement a particular Bluetooth-based application. Some examples are shown on the following slides:
• File transfer
• LAN access
• Wireless headset
• Cordless (three-in-one) phone.
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File transfer application
Using the file transfer profile:
A Bluetooth device can browse the file system of another Bluetooth device, can manipulate objects (e.g. delete objects) on another Bluetooth device, or - as the name implies - files can be transferred between Bluetooth devices.
SDP
RFCOMM
OBEX
File transfer application
L2CAP
75
LAN access application
Using the LAN profile:
A Bluetooth device can access LAN services using (for instance) the TCP/IP protocol stack over Point-to-Point Protocol (PPP).
Once connected, the device functions as if it were directly connected (wired) to the LAN.
SDP
RFCOMM
PPP
LAN access application
L2CAP
TCP/IP (e.g.)
76
Wireless headset application
Using the headset profile:
According to this usage model, the Bluetooth-capable headset can be connected wirelessly to a PC or mobile
SDP RFCOMM
Headset application
L2CAP
Audio
phone, offering a full-duplex audio input and output mechanism.
This usage model is known as the ultimate headset.
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Cordless (three-in-one) phone
application
Using the cordless telephone profile:
A Bluetooth device using this profile can set up phone calls to users in the PSTN (e.g. behind a PC acting as voice base
SDP TCS BIN
Cordless phone application
L2CAP
Audio
station) or receive calls from the PSTN.
Bluetooth devices implementing this profile can also communicate directly with each other.
802.15.4 vs ZigBee - What's the
difference?
• The Wireless Sensor Network Research group (WSNRG)
has published an article titled 802.15.4 vs ZigBee which
helps people understand and distinguish between all the
communications technologies that are used in the WSN
field: 802.15.4, ZigBee, Mesh protocols, 2.4GHz, 868MHz
and 900MHz bands…
• This document compares both IEEE 802.15.4 and ZigBee
technologies while explaining the main characteristics of
each.
79
See 802.15.4 vs Zigbee doc
802.15.4 vs ZigBee - What's the
difference?
• To summarize 802.15.4 vs ZigBee:
– 802.15.4 is a protocol to get point to point and energy
efficient communications.
– ZigBee defines extra services (star topology routing,
encryption, application services) over 802.15.4.
– ZigBee creates semi-centralized networks where just
the end devices can sleep
– Different completely distributed mesh algorithms are
being used over 802.15.4.
80
See 802.15.4 vs Zigbee doc
IEEE 802.15.4
• a standard which specifies the physical layer and
media access control (MAC) for low-rate wireless
personal area networks (LR-WPANs).
• basis for the ZigBee, ISA100.11a, WirelessHART,
and MiWi specifications, which further extend
standard by developing the upper layers which
are not defined by 802.15.4.
• Alternatively, it can be used with 6LoWPAN and
standard Internet protocols to build a Wireless
Embedded Internet.
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82
IEEE 802.15.4 LR-WPAN (ZigBee
http://www.zigbee.org/)
ZigBee technology is simpler (and less expensive) than Bluetooth.
The main objectives of an LR-WPAN like ZigBee are ease of installation, reliable data transfer, short-range operation, extremely low cost, and a reasonable battery life, while maintaining a simple and flexible protocol.
The raw data rate will be high enough (maximum of 250 kbit/s @ 10 metres) to satisfy a set of simple needs such as interactive toys, etc..., but is also scalable down to the needs of sensor and automation needs (20 kbit/s or below) using wireless communications.
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IEEE 802.15.4 LR-WPAN (ZigBee
http://www.zigbee.org/) Important features include:
• real-time suitability by reservation of guaranteed time slots,
• collision avoidance through CSMA/CA and integrated support for secure communications.
• Devices also include power management functions such as link quality and energy detection
• PHY manages the physical RF transceiver and performs channel selection and energy and signal management functions. Operates on unlicensed frequency bands:
• 868.0-868.6 MHz: Europe, allows 1 communication channel (2003, 2006) 902-928 MHz: North America, up to ten channels (2003), extended to 30 (2006) 2400-2483.5 MHz: worldwide use, up to 16 channels (2003, 2006)
84
ZigBee http://www.zigbee.org/
ZigBee offers basically four kinds of different services:
• Extra Encryption services (application and network keys implement extra 128b AES encryption)
• Association and authentication (only valid nodes can join to the network).
• Routing protocol: AODV, a reactive ad hoc protocol.
• Application Services: An abstract concept called "cluster" is introduced. Each node belongs to a predefined cluster and can take a predefined number of actions. Example: the "house light system cluster" can perform two actions: "turn the lights on", and "turn the lights off".
90
LR-WPAN device types
Two different device types can participate in an LR-WPAN network:
Full-function devices (FFD) can operate in three modes serving as a personal area network (PAN) coordinator, a coordinator, or a device.
Reduced-function devices (RFD) are intended for applications that are extremely simple.
An FFD can talk to RFDs or other FFDs, while an RFD can talk only to an FFD.
91
Network topologies (1)
Two or more devices communicating on the same physical channel constitute a WPAN. The WPAN network must include at least one FFD that operates as the PAN coordinator. The PAN coordinator initiates, terminates, or routes communication around the network. The PAN coordinator is the primary controller of the PAN. The WPAN may operate in either of two topologies: the star topology or the peer-to-peer topology.
92
Network topologies (2)
Star topology
PAN coordinator (always FFD) FFD RFD
In a star network, after an FFD is activated for the first time, it may establish its own network and become the PAN coordinator. The PAN coordinator can allow other devices to join its network.
93
Network topologies (3)
Peer-to-peer topology In a peer-to-peer network, each FFD is capable of communicating with any other FFD within its radio sphere of influence. One FFD will be nominated as the PAN coordinator.
A peer-to-peer network can be ad hoc, self-organizing and self-healing, and can combine devices using a mesh networking topology.
PAN coordinator (always FFD) FFD RFD
94
ZigBee PHY and MAC parameters
Topology Ad hoc (central PAN coordinator)
RF band 2.4 GHz ISM frequency band
RF channels 16 channels with 5 MHz spacing
Spreading DSSS (32 chips / 4 bits)
Chip rate 2 Mchip/s
Modulation Offset QPSK
Access method CSMA/CA (or slotted CSMA/CA)
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Comparison: Bluetooth radio and
baseband parameters
Topology Up to 7 simultaneous links
Modulation Gaussian filtered FSK
RF bandwidth 220 kHz (-3 dB), 1 MHz (-20 dB)
RF band 2.4 GHz ISM frequency band
RF carriers 79 (23 as reduced option)
Carrier spacing 1 MHz
Access method FHSS-TDD-TDMA
Freq. hop rate 1600 hops/s
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Beacon frames
The LR-WPAN standard allows the optional use of a superframe structure. The format of the superframe is defined by the coordinator. Superframe is bounded by network beacons, sent by the coordinator, and is divided into 16 equally sized slots. The beacon frame is transmitted in the first slot of each superframe. If a coordinator does not wish to use a superframe structure, it may turn off the beacon transmissions. The beacons are used to synchronize the attached devices, to identify the PAN, and to describe the superframe structure.
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CSMA/CA operation (1)
Nonbeacon-enabled networks use an unslotted CSMA-CA channel access mechanism. Each time a device wishes to transmit data frames or MAC commands, it shall wait for a random period. If the channel is found to be idle, the device shall transmit its data. If the channel is found to be busy, following the device shall wait for the random backoff before trying to access the channel again.
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CSMA/CA operation (2)
Beacon-enabled networks use a slotted CSMA-CA channel access mechanism, where the backoff slots are aligned with the start of the beacon transmission.
Similar to the unslotted operation, however the device can begin transmitting on the next available slot boundary.
What is 6LoWPAN
• Low-power RF + IPv6 = 6LoWPAN
• Defined by IETF standards – RFC 4919, “IPv6 over Low-Power Wireless
Personal Area Networks (6LoWPANs): Overview, Assumptions, Problem Statement, and Goals”
– RFC 4944, “Transmission of IPv6 Packets over IEEE 802.15.4 Networks”
– draft-ietf-6lowpan-hc and –nd
100 Prepared by Zinon Zinonos
University of Cyprus 6LoWPAN
• simple, low-cost, wireless communication network for
constrained applications with limited power.
• is an adaption layer that allows efficient IPv6 communication
over IEEE 802.15.4.
• turns IEEE 802.15.4 into the next IP-enabled link
• offers wide-scale connectivity, open-system based interoperability,
and interoperability between low-power devices and IP devices
• Leverages well-known IP-based knowledge and practices
• Imports well-known capabilities of IPv6 to low-power devices.
uIPv6 101
Blip,and uIPv6 are implementations of
the 6LoWPAN stack for TinyOS 2.x
and CONTIKI
Benefits of using IP in 6LoWPAN
Technology
The benefits of 6LoWPAN include:
– Open, long-lived, reliable standards
– Transparent Internet integration
– Easy learning-curve
– Established network management tools
– Global scalability
– Established security
– End-to-end data flows
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6LoWPAN architecture
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IPv6
Application Protocols
UDP
IEEE 802.15.4 MAC
IEEE 802.15.4 PHY
6LowPan
IP
HTTP
UDP/TCP
Ethernet MAC
Ethernet PHY
IP Protocol Stack
6LowPAN protocol Stack
6LoWPAN characteristics
As IEEE 802.15.4: – Small MTU size of 127 bytes
– Low data rate of 250kbps
– Operates in 2.4 GHz band
– Short range communication
Efficient header compression
Network autoconfiguration using neighbor discovery
Unicast, multicast and broadcast support
Fragmentation – 1280 bytes IPv6 MTU -> 127 bytes 802.15.4 frames
Support for IP routing (e.g. IETF RPL)
Star and peer-to-peer (mesh) topologies
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Radio-frequency identification (RFID)
• wireless non-contact system that uses radio-
frequency electromagnetic fields to transfer data
from a tag attached to an object, for the purposes
of automatic identification and tracking.
– Passive tags: require no battery and are powered by
the electromagnetic fields used to read them.
– Active tags: use a local power source and emit radio
waves (electromagnetic radiation at radio frequencies).
• RFID tag contains electronically stored information which
can be read from up to several metres away. Unlike a bar
code, the tag does not need to be within line of sight of the
reader and may be embedded in the tracked object.
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Radio-frequency identification (RFID)
• RFID tags are used in many industries: – track its progress through the assembly line of an
automobile
– Pharmaceuticals can be tracked through warehouses.
– Livestock and pets may have tags injected.
– identity cards can give employees access to locked
areas of a building
– RF transponders mounted in automobiles can be used
to bill motorists for access to toll roads or parking.
• Since RFID tags can be attached to
clothing, possessions, or even implanted
within people, the possibility of reading
personally-linked information without
consent has raised privacy concerns.
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Radio-frequency identification (RFID)
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http://en.wikipedia.org/wiki/Radio-frequency_identification
5 D. Sen et al., RFID For Energy and Utility Industries, PennWell Corp., 2009 ISBN 978-1-595370-
105-5, pages 1-48
6 Stephen A. Weis, RFID (Radio Frequency Identification):Principles and Applications, MIT
Radio-frequency identification (RFID)
• SEE SLIDES
• RFID: Cow Jewelry – or – Revolution slides
• By Travis Sparks
• http://www.cs.unc.edu/~sparkst
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Dash7 low-power radio protocol
gains momentum …
• Yet another technology ???? • Goal: The lowest power, longest range wireless
networking technology available anywhere!!!
• DASH7 Alliance is the body responsible for overseeing the development of the
ISO 18000-7 standard for wireless sensor networking, as well as
interoperability certification of DASH7 devices and the licensing of DASH7
trademarks. The DASH7 Alliance is an industry consortium whereas "DASH7"
is the name of the technology.
• http://www.dash7.org/index.php?option=com_content&view=article&id=9&Itemid=11
• See IEEE spectrum article Wireless Networking Dashes in a New
Direction: The Dash7 low-power radio protocol gains momentum, Feb 2010.
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Dash7
• Range: Dynamically adjustable from 10 meters to 10 kilometers
• Power: <1 milliwatt power draw
• Data Rate: dynamically adjustable from 28kbps to 200kbps.
• Frequency: 433.92 MHz (available worldwide)
• Signal Propagation: Penetrates Walls, Concrete, Water
• Real-Time Locating Precision: within 4 meters
• Latency: Configurable, but worst case is less than two seconds
• P2P Messaging: Yes
• IPv6 Support: Yes
• Security: 128-bit AES, public key
• Application Profiles: None
• Standard: ISO/IEC 18000-7
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Dash7 in a nutshell
especially appropriate for such things as radio-frequency
identification (RFID) tags
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Dash7 in comparison
http://www.dash7.org/index.php?option=com_content&view=article&id=148&Itemid=203
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Dash7 in comparison
SEE slides:
DASH7 Capabilities Overview for Seoul
Seoul Briefing of Dec 9th 2009 Slides
http://www.dash7.org/index.php?option=com_content&view
=article&id=192&Itemid=196
WLAN technologies – summary
• The basic goals of all wireless LAN/WAN types (WLAN, WiMAX, WiMesh, BUETOOTH, ZigBee, etc…) are the provision of a much higher flexibility for nodes within a network.
• All WLANs suffer from limitations of the air interface and higher complexity compared to their wired counterparts but allow for a new degree of freedom for their users within rooms, buildings etc, leading to diverse applications, including the Internet-Of-Things
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HIPERLAN –
High Performance LAN (I)
• The European Telecommunications Standards Institute (ETSI) standardized HIPERLAN as a WLAN allowing for node mobility and supporting ad hoc and infrastructure-based topologies.
• It is a wireless LAN supporting priorities and packet life time for data transfer at 23.5 Mbit/s, including forwarding mechanisms, topology discovery, user data encryption, network identification and power conservation mechanisms.
• HIPERLANs operate at 5.1 – 5.3 GHz with a range of 50m in buildings at 1 W transmit power.
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HIPERLAN –
High Performance LAN (II)
• The service offered by a HIPERLAN is compatible
with the standard MAC services known from IEEE
802.x LANs.
• The HIPERLAN Channel Access Control mechanism
was specifically designed to provide channel access
with priorities.
• The CAC contains the access scheme EY-NPMA,
which is unique for HIPERLAN.
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HIPERLAN –
High Performance LAN (III)
• Elimination-yield non-preemptive priority multiple access (EY-NPMA) – not only a complex acronym, but also the heart of the
channel access providing priorities and different access schemes.
– divides the medium access of different competing nodes into three phases:
• Prioritization: Determine the highest priority of a data packet ready to be sent on competing nodes
• Contention: Eliminate all but one of the contenders, if more than one sender has the highest current priority.
• Transmission: Finally, transmit the packet of the remaining node.
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HIPERLAN –
High Performance LAN (IV)
– The contention phase is further subdivided into an elimination phase and a yield phase.
– The purpose of the elimination phase is to eliminate as many contending nodes as possible. The result is a more or less constant number of remaining nodes, almost independent of the initial number of competing nodes.
– The yield phase completes the work of the elimination phase with the goal of only one remaining node.
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