CHAPTER 3 (WIRELESS PERSONAL AREA NETWORKSPresentation Transcript
A WPAN (Wireless PAN) is a short-distance wireless network specifically designed to support portable and mobile computing devices such as PCs, PDAs, wireless printers and storage devices, cell phones, pagers, set-top boxes, and a variety of consumer electronics equipment.
Bluetooth is an example of a wireless PAN that allows devices within close proximity to join together in ad hoc wireless networks in order to exchange information.
Many cell phones have two radio interfaces-one for the cellular network and one for PAN connections.
WPANs such as Bluetooth provide the bandwidth
and convenience to make data exchange practical
for mobile devices such as palm computers.
Bluetooth overcomes many of the complications
of other mobile data systems such as cellular
packet data systems...
The reach of a PAN is typically a few meters.
A Bluetooth PAN is also called a piconet, and is composed of up to 8 active devices in a master-slave relationship (up to 255 devices can be connected in 'parked' mode).
The first Bluetooth device in the piconet is the master, and all other devices are slaves that communicate with the master.
A piconet typically has a range of 10 meters, although ranges of up to 100 meters can be reached under ideal circumstances.
A wireless PAN consists of a dynamic group of less than 255 devices that communicate within about a 33-foot range.
Unlike with wireless LANs, only devices within this limited area typically participate in the network, and no online connection with external devices is defined.
One device is selected to assume the role of the controller during wireless PAN initialization, and this controller device mediates communication within the WPAN.
The controller broadcasts a beacon that lets all devices synchronize with each other and allocates time slots for the devices.
Each device attempts to join the wireless PAN by requesting a time slot from the controller.
The controller authenticates the devices and assigns time slots for each device to transmit data.
The data may be sent to the entire wireless PAN using the wireless PAN destination address, or it may be directed to a particular device.
The 802.15 working group is defining different versions for devices that have different requirements.
802.15.3 focuses on high-bandwidth (about 55M bit/sec), low-power MAC and physical layers, while 802.15.4 deals with low-bandwidth (about 250K bit/sec), extra-low power MAC and physical layers.
WPAN: smaller area of coverage, ad hoc only topology, plug and play architecture, support of voice and data devices, and low-power consumption.
BodyLAN (DARPA, mid-1990s): inexpensive WPAN with modest bandwidth that could connect personal devices within a range of about 5 feet.
802.11 project initiated a WPAN group in 1997.
In March 1998, the HomeRF group was formed
In May 1998, a Bluetooth special group was formed
In March 1999, 802.15 was approved as a separate group to handle WPAN
IEEE 802.15 WPAN
Development of standards for short distance wireless networks used for networking of portable ad mobile computing devices.
The original functional requirement was published in January 22, 1998, and specified devices with:
Power management: low current consumption
Range: 0 - 10 meters
Speed: 19.2 - 100 kbps
Small size: .5 cubic inches without antenna
Low cost relative to target device
Should allow overlap of multiple networks in the same area
Networking support for a minimum of 16 devices
IEEE 802.15 WPAN
The initial activities in the WPAN group included HomeRF and Bluetooth group.
HomeRF currently has its own website [HomeRFweb]
IEEE 802.15 WPAN has four task groups:
Task group 1: based on Bluetooth. Defines PHY and MAC for wireless connectivity with fixed, portable, and moving devices within or entering a personal operating space.
Task group 2: focused on coexistence of WPAN and 802.11 WLANs.
Task group 3: PHY and MAC layers for high-rate WPANs (higher than 20 Mbps)
Task group 4: ultra-low complexity, ultra-low power consuming, ultra-low cost PHY and MAC layer for data rates of up to 200 kbps.
Universal radio interface for ad-hoc wireless connectivity
Interconnecting computer and peripherals, handheld devices, PDAs, cell phones – replacement of IrDA
Embedded in other devices, goal: 5€/device (2002: 50€/USB Bluetooth)
Short range (10 m), low power consumption, license-free 2.45 GHz ISM
Voice and data transmission, approx. 1 Mbit/s gross data rate
Bluetooth One of the first modules (Ericsson).
History and hi-tech…
1994: Ericsson (Mattison/Haartsen), “MC-link” project
Renaming of the project: Bluetooth according to Harald “Bl åtand” Gormsen [son of Gorm], King of Denmark in the 10 th century
1998: foundation of Bluetooth SIG, www.bluetooth.org
1999: erection of a rune stone at Ericsson/Lund
2001: first consumer products for mass market, spec. version 1.1 released
Special Interest Group
Original founding members: Ericsson, Intel, IBM, Nokia, Toshiba
Common specification and certification of products
… and the real stone Located in Jelling, Denmark, erected by King Harald “Bl åtand” in memory of his parents. The stone has three sides – one side showing a picture of Christ. This could be the “original” colors of the stone. Inscription: “ auk tani karthi kristna” (and made the Danes Christians) Inscription: "Harald king executes these sepulchral monuments after Gorm, his father and Thyra, his mother. The Harald who won the whole of Denmark and Norway and turned the Danes to Christianity." Btw: Blåtand means “of dark complexion” (not having a blue tooth…)
Asynchronous, fast acknowledge, point-to-multipoint, up to 433.9 kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched
Overlapping piconets (stars) forming a scatternet
Bluetooth Protocol Stack Radio Baseband Link Manager Control Host Controller Interface Logical Link Control and Adaptation Protocol (L2CAP) Audio TCS BIN SDP OBEX vCal/vCard IP NW apps. TCP/UDP BNEP RFCOMM (serial line interface) AT modem commands telephony apps. audio apps. mgmnt. apps. AT: attention sequence OBEX: object exchange TCS BIN: telephony control protocol specification – binary BNEP: Bluetooth network encapsulation protocol SDP: service discovery protocol RFCOMM: radio frequency comm. PPP
Frequency Selection During Data Transmission (TDMA/TDD) symmetric asymmetric asymmetric S f k 625 µs f k+1 f k+2 f k+3 f k+4 f k+3 f k+4 f k f k f k+5 f k+5 f k+1 f k+6 f k+6 f k+6 M M M M M M M M M t t t S S S S S
Overall Frame Format of Bluetooth Packets
The 48 bit address unique to every Bluetooth device is used as the seed to derive the sequence for hopping frequencies of the devices.
Four types of access codes:
Type 1: identifies a “M” terminal and its piconet address
Type 2: identifies a “S” identity used to page a specific “S”.
Type 3: Fixed access code reserved for the inquiry process (will be explained)
Type 4: dedicated access code reserved to identify specific set of devices such as fax machines, printers, or cell phones.
Header: 18 bits repeated 3 times with a 1/3 FEC code
ID: occupies half of a slot, and it carries the access code with no data or even a packet type code
NULL: used for ACK signaling, and there is no ACK for it
POLL: similar to the NULL, but is has an ACK
NULL and POLL: have the access code and the header, and so they have packet type codes and status report bits
“ M” terminals use the POLL packet to find the “S” terminals in their coverage area.
FHS (Frequency Hop Synchronization): carries all the information necessary to synchronize two devices in terms of access code and hopping timing. This packet is used in the inquiry and paging process explained later.
Polling-based TDD packet transmission
625µs slots, master polls slaves
SCO (Synchronous Connection Oriented) – Voice
Periodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point
MASTER SLAVE 1 SLAVE 2 f 6 f 0 f 1 f 7 f 12 f 13 f 19 f 18 SCO SCO SCO SCO ACL f 5 f 21 f 4 f 20 ACL ACL f 8 f 9 f 17 f 14 ACL
In the beginning of the formation of a piconet, all devices are in SB mode, then one of the devices starts with an inquiry and becomes the “M” terminal.
During the inquiry process, “M” registers all the SB terminals that then become “S” terminals. After the inquiry process, identification and timing of all “S” terminals is sent to “M” using FHS packets.
The “M” terminal starts a connection with a PAGE message including its timing and ID to the “S” terminal.
When the connection is established, the communication takes place, and at the end, the terminal can be sent back to SB, Hold, park or Sniff states.
Standby: do nothing Inquiry: search for other devices Page: connect to a specific device Connected: participate in a piconet
Hold, Park and Sniff are power-saving modes.
The Hold mode is used when connecting several piconets or managing a low-power device.
In the Hold mode, data transfer restarts as soon as the unit is out of this mode.
In the Sniff mode, a slave listens to the piconet at reduced and programmable intervals according to the applications needs.
In the Park mode a device gives up its MAC address but remains synchronized with the piconet.
A Parked device does not participate in the traffic but occasionally listens to the traffic of “M” to resynchronize and check on broadcast messages.
Park: release AMA, get PMA Sniff: listen periodically, not each slot Hold: stop ACL, SCO still possible, possibly participate in another piconet
Interference Between Bluetooth and 802.11
The WLAN industry specified three levels of overlapping:
Interference: multiple wireless networks are said to interfere with one another if colocation causes significant performance degradation
Coexistence: multiple wireless networks are said to coexist if they can be colocated without significant impact on performance. It provides for the ability of one system to perform a task in a shared frequency band with other systems that may or may not be using the same rules for operation
Interoperation: provides for an environment with multiple wireless systems to perform a given task using a single set of rules
Collection of devices connected in an ad hoc fashion
One unit acts as master and the others as slaves for the lifetime of the piconet
Master determines hopping pattern, slaves have to synchronize
Each piconet has a unique hopping pattern
Participation in a piconet = synchronization to hopping sequence
Each piconet has one master and up to 7 simultaneous slaves (> 200 could be parked)
M=Master S=Slave P=Parked SB=Standby M S P SB S S P P SB
Forming a Piconet
All devices in a piconet hop together
Master gives slaves its clock and device ID
Hopping pattern: determined by device ID (48 bit, unique worldwide)
Phase in hopping pattern determined by clock
Active Member Address (AMA, 3 bit)
Parked Member Address (PMA, 8 bit)
SB SB SB SB SB SB SB SB SB M S P SB S S P P SB
Linking of multiple co-located piconets through the sharing of common master or slave devices
Devices can be slave in one piconet and master of another
Communication between piconets
Devices jumping back and forth between the piconets
M=Master S=Slave P=Parked SB=Standby M S P SB S S P P SB M S S P SB Piconets (each with a capacity of < 1 Mbit/s)
WPAN: IEEE 802.15-1 – Bluetooth
Synchronous, connection-oriented: 64 kbit/s
433.9 kbit/s symmetric
723.2 / 57.6 kbit/s asymmetric
POS (Personal Operating Space) up to 10 m
with special transceivers up to 100 m
Free 2.4 GHz ISM-band
Challenge/response (SAFER+), hopping sequence
50€ adapter, drop to 5€ if integrated
Integrated into some products, several vendors
Connection set-up time
Depends on power-mode
Max. 2.56s, avg. 0.64s
Quality of Service
Public/private keys needed, key management not specified, simple system integration
Advantage: already integrated into several products, available worldwide, free ISM-band, several vendors, simple system, simple ad-hoc networking, peer to peer, scatternets
Disadvantage: interference on ISM-band, limited range, max. 8 devices/network&master, high set-up latency
WPAN: IEEE 802.15 – future developments 1
Coexistence of Wireless Personal Area Networks (802.15) and Wireless Local Area Networks (802.11), quantify the mutual interference
Standard for high-rate (20Mbit/s or greater) WPANs, while still low-power/low-cost
Data Rates: 11, 22, 33, 44, 55 Mbit/s
Quality of Service isochronous protocol
Ad hoc peer-to-peer networking
Low power consumption
Designed to meet the demanding requirements of portable consumer imaging and multimedia applications
WPAN: IEEE 802.15 – future developments 2
802.15-4: Low-Rate, Very Low-Power
Low data rate solution with multi-month to multi-year battery life and very low complexity
Potential applications are sensors, interactive toys, smart badges, remote controls, and home automation
Data rates of 20-250 kbit/s, latency down to 15 ms
Master-Slave or Peer-to-Peer operation
Support for critical latency devices, such as joysticks
CSMA/CA channel access (data centric), slotted (beacon) or unslotted
Automatic network establishment by the PAN coordinator
Dynamic device addressing, f lexible addressing format
Fully handshaked protocol for transfer reliability
Power management to ensure low power consumption
16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz US ISM band and one channel in the European 868 MHz band
A cable replacement technology
1 Mb/s symbol rate
Range 10+ meters
Single chip radio + baseband
at low power & low price point ($5)
Why not use Wireless LANs? - power - cost
IEEE 802.11: Classical WLANs
Replacement for Ethernet
Supported data rates
11, 5.5, 2, 1 Mbps; and recently up to 20+Mbps @ 2.4 GHz
up to 54 Mbps in 5.7 GHz band (802.11 a)
Indoor 20 - 25 meters
Outdoor: 50 – 100 meters
Transmit power up to 100 mW
Chipsets $ 35 – 50
AP $200 - $1000
PCMCIA cards $100 - $150
Which option is technically superior ?
What market forces are at play ?
What can be said about the future ?
Cordless headset IEEE 802.11 Bluetooth LAN AP
802.11b for PDAs
Bluetooth for LAN access
New developments are blurring the distinction
Bluetooth Working Group History
February 1998 : The Bluetooth SIG is formed
promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba
May 1998 : Public announcement of the Bluetooth SIG
July 1999 : 1.0A spec (>1,500 pages) is published
December 1999 : ver. 1.0B is released
December 1999 : The promoter group increases to 9
3Com, Lucent, Microsoft, Motorola
March 2001 : ver. 1.1 is released
Aug 2001 : There are 2,491+ adopter companies
Automatic synchronization of calendars, address books, business cards
Push button synchronization
Multiple device access
Cordless phone benefits
Hands free operation
Usage Scenarios Examples
Data Access Points
Business Card Exchange
A hardware/software/protocol description
An application framework
RF Baseband Audio Link Manager L2CAP SDP RFCOMM Applications Data IP Single chip with RS-232, USB, or PC card interface HCI
Interoperability & Profiles
Represents default solution for a usage model
Vertical slice through the protocol stack
Basis for interoperability and logo requirements
Each Bluetooth device supports one or more profiles
Profiles Protocols Applications
Bluetooth Profiles (in version 1.2 release)
Generic Object Exchange
Bluetooth Radio Specification RF Baseband Audio Link Manager L2CAP Data Control SDP RFCOMM IP Applications
conserve battery power
cost < $10
Data signal x(t) Recovered data signal Goal cost power spectrum Noise, interference
EM Spectrum Propagation characteristics are different in each frequency band AM radio UV S/W radio FM radio TV TV cellular 1 MHz 1 kHz 1 GHz 1 THz 1 PHz 1 EHz infrared visible X rays Gamma rays LF HF VHF UHF SHF EHF MF 902 – 928 Mhz 2.4 – 2.4835 Ghz 5.725 – 5.785 Ghz ISM band 30kHz 300kHz 3MHz 30MHz 300MHz 30GHz 300GHz 10km 1km 100m 10m 1m 10cm 1cm 100mm 3GHz
Baseband RF Baseband Audio Link Manager L2CAP RFCOMM SDP Applications Data Control IP RF Baseband Audio Link Manager L2CAP Data Control SDP RFCOMM IP Applications
Bluetooth Physical Link
Point to point link
master - slave relationship
radios can function as masters or slaves
m s s s m s
Master can connect to 7 slaves
Each piconet has max capacity =1 Mbps
hopping pattern is determined by the master
Inquiry - scan protocol
to learn about the clock offset and device address of other nodes in proximity
Inquiry on Time Axis Slave1 Slave2 Master f1 f2 Inquiry hopping sequence
Page - scan protocol
to establish links with nodes in proximity
Master Active Slave Parked Slave Standby
Bluetooth device address (BD_ADDR)
48 bit IEEE MAC address
Active Member address (AM_ADDR)
3 bits active slave address
all zero broadcast address
Parked Member address (PM_ADDR)
8 bit parked slave address
Piconet Channel m s 1 s 2 625 sec f1 f2 f3 f4 1600 hops/sec f5 f6 FH/TDD
Multi Slot Packets m s 1 s 2 625 µ sec f1 FH/TDD Data rate depends on type of packet f4 f5 f6
Physical Link Types m s 1 s 2
Synchronous Connection Oriented (SCO) Link
slot reservation at fixed intervals
Asynchronous Connection-less (ACL) Link
Polling access method
SCO SCO SCO SCO SCO SCO ACL ACL ACL ACL ACL ACL
Packet Types Control packets Data/voice packets ID* Null Poll FHS DM1 Voice data HV1 HV2 HV3 DV DM1 DM3 DM5 DH1 DH3 DH5
Packet Format 72 bits 54 bits 0 - 2744 bits Access code Header Payload Data Voice CRC No CRC No retries 625 µs master slave header ARQ FEC (optional) FEC (optional)
DC offset compensation
Access code Header Payload 72 bits Purpose X
Channel Access Code (CAC)
Device Access Code (DAC)
Inquiry Access Code (IAC)
Packet type (4)
Flow control (1)
1-bit ARQ (1)
Access code Header Payload 54 bits Purpose Encode with 1/3 FEC to get 54 bits Broadcast packets are not ACKed For filtering retransmitted packets 18 bits total 16 packet types (some unused) Verify header integrity s s m s Max 7 active slaves
Bluetooth Value Chain Radio Silicon Stack providers Software vendors Integrators Wireless Carriers Conspicuously missing
Value to Carriers: Synchronization and Push
More bits over the air
Utilization of unused capacity during non-busy periods
Higher barrier for switching service providers
Value to Carriers: Cell phone as an IP Gateway
More bits over the air
Enhanced user experience
Palmpilot has a better UI than a cell phone
Growth into other vertical markets
Will Pilot and cell phone eventually merge?
Value to Carriers: Call Handoff
More attractive calling plans
Alleviate system load during peak periods
Serve more users with fewer resources
Threat or opportunity? Cordless base
Biggest Challenges facing Bluetooth
Always a challenge for any new technology
Hyped up expectations
Out of the box ease of use
Cost target $5
RF in silicon
Conflicting interests – business and engineering
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