Ch 7. Wireless Personal Area Networks

1
Ch 7. Wireless Personal Area Networks

• Myungchul Kim
• mckim_at_icu.ac.kr

2
Wireless Personal Area Networks

• WPANs
• Bluetooth
• Home Networking
• UWB Overview
• Wireless Sensor Networks

3
WPANs

• Short range networks (lt 10 meters)
• Used in homes, cars, small offices
• Can be interconnected to form large networks
• IEEE 802.15 is the main standards environment
• Many active areas of work Bluetooth, UWB,
  Wireless sensor networks, Zigbees

4
Bluetooth Wireless LANs

• Overview
• Applications and Examples
• Piconets and Scatternets
• Standards Overview
• Core standards

5
Bluetooth Overview

• Founders Ericsson, IBM, Intel, Nokia, Toshiba
  May 98
• Currently Over 1000 companies
• Low-cost, short range radio link between mobile
  PCs, phones and other portable devices
• 2.4 GHz ISM band (unlicensed) Short packets,
  fast-hopping, and FEC limits impacts of
  interference
• Software for service and device discovery
• Typical application cellular phone to PDA or
  earphone
• Supports open-ended list of applications
• Data, audio, graphics, video
• Many products from Nokia, Motorola, Apple, etc.
• Bluetooth.com and palowireless.com/bluetooth have
  great deal of info

6
Bluetooth
PSTN
Access Point
Cellular Network
Wired LAN
Bluetooth Piconet (1 Mbps, 10 meters)
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Bluetooth Application Areas

• Cable replacement
• Eliminates need for numerous cable attachments
  for connection (e.g., RS232)
• Data and voice access points
• Real-time voice and data transmissions
• Ad hoc networking
• Device with Bluetooth radio can establish
  connection with another when in range

8
Piconets and Scatternets

• Piconet
• Basic unit of Bluetooth networking
• Master and one to seven slave devices
• Master determines channel and phase
• Scatternet
• Device in one piconet may exist as master or
  slave in another piconet
• Allows many devices to share same area
• Makes efficient use of bandwidth

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Bluetooth Configurations
Master
A
B
Slave/Master
E
C
D
Slave
Slave
Slave
F
H
G
Slave
Slave
Slave

• 2.4 GHZ ISM band supports around 80 physical
  channels with 1 MHz. bandwidth
• These 80 channels are managed through piconets
  and scatternets
• All radios in a scatternet share the same
  frequency hopping (FHSS)

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Bluetooth Piconets
PC
Slave
Master
PC
Master
Slave
Piconet2 (Cubicle2)
PC
printer
Slave /Master
Ear Phone
Cellular Phone
PC
Slave
Slave
printer
Piconet1 (Cubicle 1)
Slave
Slave
PC
Piconet3 (Cubicle3)
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Bluetooth versus Wi-Fi
Table 7-2 Bluetooth versus Wi-Fi
 
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State Transitions in Bluetooth
Standby
Disconnected State
Page
Inquire
Connecting State
Active
Active State
Park, Sniff, Hold-
Low-Power States

• Typical Scenario
• Devices initially in standby mode
• Issue an inquire (I am available, does someone
  need me)
• Devices scan the inquire list and then page the
  ones they want to invite
• Devices go into an active transfer mode (Piconet)
  
• If too many in a piconet, go into park-sniff-hold
  mode
• After transfer go into standby mode

13
Bluetooth Standards Documents

• Standards specifications
• Details of various layers of Bluetooth protocol
  architecture (more than 1500 pages)
• Bluetooth is a layered protocol architecture
• Core protocols (5 layer) - required
• Cable replacement and telephony control protocols
• Adopted protocols (PPP, WAP,,) .
• Profile specifications
• Use of Bluetooth technology to support various
  applications

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Protocol Architecture

• Core protocols
• Radio layer - Bluetooth transceiver operating in
  the 2.4 GHz
• Baseband layer -Bluetooth Link Controller (LC)
  low-level link routines (complex).
• Link Manager Protocol (LMP) is used by the Link
  Managers (on both side) for link
• Host Controller Interface (HCI) a command
  interface to access to hardware status and
  control registers.
• Logical Link Control and Adaptation Protocol
  (L2CAP) supports higher level protocol
  multiplexing
• Service Discovery Protocol (SDP) applications to
  discover which services are provided by a
  Bluetooth device

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Bluetooth Stack
Legend
Core
TCS Bin
AT- Commands
WAE
vCard/vCal
SDP
Cable replacement

OBEX
WAP
Telephony control
TCP UDP
IP
Adopted
PPP
Audio
RFCOMM
Logical Link Control and Adaptation Protocol (
L2CAP)
Host Controller Interface
Link Management Protocol (LMP)
Baseband
Bluetooth Radio
Shaded areas (see legend) represent different
families of Bluetooth Protocols
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Protocol Architecture (cont.)

• Cable replacement protocol provides emulation of
  serial ports over the L2CAP protocol (e.g.,
  emulates EIA RS232 communications over the
  Bluerooth baseband layer.
• Telephony control protocols (TCS BIN) defines
  the signalling and control sequences needed for
  telephone conversations over Bluetooth.
• Adopted protocols minimize new by Bluetooth
• PPP used to transport IP packets over
  point-to-point links such as dial-up lines.
• TCP/UDP/IP. foundation protocols for the Internet
  
• OBEX The object-exchange protocol developed for
  the exchange of objects (similar to HTTP, vCard
  and vCalendar)
• WAE/WAP The Wireless Application Protocol and
  Wireless Application environment are included in
  Bluetooth.

17
Usage Models

• File transfer to transfer files over Bluetooth.
  protocols used can be SDP or OBEX.
• Internet bridge (Dial-Up networking) to
  wirelessly connect a PC with a cordless modem or
  a cellular phone uses PPP and AT protocols
• LAN access connect a piconet device to access a
  LAN. uses SDP and PPP-IP protocols.
• Synchronization synchronize device-to-device
  PIM (personal information management) information
  such as calendars and phone books. The model uses
  OBEX and IrMC (infrared mobile communications)
  
• Three-in-one phone Telephone headsets and
  handsets can be used in this model as audio input
  and output devices. This model uses Audio, SDP,
  and AT commands.

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Usage Models
File Transfer Application
Modem Emulation or Driver Application
PPP
OBEX
AT Commands
SDP
SDP
RFCOMM
RFCOMM
L2CAP
L2CAP
a) File Transfer
b) Dial-Up Networking
LAN Access Application
Synchronization Application
IP
IrMC
SDP
SDP
PPP
OBEX
RFCOMM
RFCOMM
L2CAP
L2CAP
c) LAN Access
c) LAN Access
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Radio Specification

• 2.4 GHZ ISM band that can support around 80
  physical channels with 1 MHz. bandwidth
• These 80 channels are managed through piconets
  and scatternets.
• Several classes of transmitters
• Class 1 Outputs 100 mW for maximum range
• Power control mandatory
• Provides greatest distance
• Class 2 Outputs 2.4 mW at maximum
• Power control optional
• Class 3 Nominal output is 1 mW
• Lowest power
• Much less powerful than cellular phones (GSM
  operates at 1 to 3 Watts)

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Baseband Specification

• Very complicated
• Specifies
• Frequency hopping
• Physical Links
• Bluetooth Packet Fields
• Error correction
• Logical Channels
• Bluetooth Audio
• Bluetooth Security

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Baseband Specification

• Frequency Hopping in Bluetooth. FH occurs by
  jumping from one channel to another (80). (all
  devices on a piconet share same).
• Physical Links between Master and Slave.
• Synchronous connection oriented (SCO).
  point-to-point connection of master and slave.
  Mainly for voice
• Asynchronous connectionless (ACL).
  Point-to-multipoint link between master and all
  slaves is also supported.
• Bluetooth Packet Fields. Single slot multiple
  slot
• consist of three fields
• Access code used for timing synchronization,
  offset compensation, paging, and inquiry
• Header used to identify packet type and carry
  protocol control information
• Payload contains user voice or data and payload
  header, if present

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Baseband Specification (cont.)

• Error Correction Schemes. different types of
  error correction codes that includes ARQ.
• Logical Channels and Channel Control Bluetooth
  defines five types of channels for different
  types of payload such as Link control (LC), Link
  manager (LM), User asynchronous (UA), User
  isochronous (UI), and User synchronous (US).
• Bluetooth Audio. choice of two
• pulse code modulation (PCM)
• continuously variable slope delta (CVSD)
  modulation.(variable step)
• The choice is made by link manager
• Bluetooth Link Security. includes Authentication,
  Encryption (privacy) and Key management.

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Link Management Protocol (LMP)

• LMP manages the radio links between Bluetooth
  masters and slaves.
• LMP specifies exchange of LMP PDUs
• PDUs supported by the LMP
• General response
• Security Service
• Authentication
• Pairing establish a key between authenticated
  pairs
• Change link key
• Change current link key
• Encryption

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L2CAP

• Provides a link-layer protocol between entities
  with a number of services
• Similar to LLC
• Relies on lower layer for flow and error control
• Makes use of ACL links, does not support SCO
  links
• Provides two alternative services to upper-layer
  protocols
• Connection service
• Connection-mode service

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Cordless Systems and Wireless Local Loop

• Cordless networks
• Wireless MANs (Wireless Local Loops)

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Cordless Phone
Public Switched Telephone Network (PSTN)
Base Unit
Handset

• Basically a cellular phone with no location
  services
• Typical coverage is 100-300 meters
• User owns handset and base unit -- no initial
  need for standards

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Cordless System Operating Environments

• Residential a single base station can provide
  in-house voice and data support
• Office
• A single base station can support a small office
• Multiple base stations in a cellular
  configuration can support a larger office
• Telepoint a base station set up in a public
  place, such as an airport

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Time Division Duplex (TDD)

• Also known as time-compression multiplexing
• Data transmitted in one direction at a time, with
  transmission between the two directions
• Simple TDD Bit stream is divided into equal
  segments, compressed in time to a higher
  transmission rate, and transmitted in bursts
• Wireless TDD typically used with TDMA
• A number of users receive forward channel signals
  in turn and then transmit reverse channel signals
  in turn, all on same carrier frequency
• TDMA/TDD used more often
• Improved ability to cope with fast fading (base
  station can detect strongest signals and send at
  the same)
• Improved capacity allocation (can assign more
  slots to forward channel for improved forward
  traffic)

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TDD
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Cordless Standards

• DECT (Digital Enhanced Cordless
  Telecommunications) developed in Europe
• PWT (Personal Wireless telecomm) developed in US
• DECT is most commonly used standard (mainly
• DECT Architecture (suited for voice)
• Physical layer data transmitted in TDMA-TDD
  frames over one of 10 RF carriers
• Medium access control (MAC) layer selects
  establishes/releases connections on physical
  channels supports three services
• Broadcast
• Connection oriented
• Connectionless
• Data link control layer provides for the
  reliable transmission of messages using
  traditional data link control procedures

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Home R/F
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Home R/F Specification
150 feet, 10 Mbps www.homerf.org
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How SWAP (Shared Wireless Application Protocol)
Supports Voice and Data
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UWB -- Overview

• Ultra Wideband (UWB) is emerging as a new
  wireless personal area network technology.
• Originally developed in the 1960s for the
  military.
• FCC approved the commercial implementation of UWB
  in February 2002, within limits.
• UWB provides high data rates (around 50 Mbps) in
  very short distances (10 meters).
• UWB is a radio system that uses narrow pulses
  (millions of pulses per second) for communication
  and sensing by using short-range radar.
• UWB radio sends data in millions of pulses across
  a wide frequency band
• Legal in the US as long as it uses less power
  than normal radio frequency leakage.

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Wireless Sensor Networks (Overview)

• WSNs typically consist of small, low-powered
  devices (sensors)
• Sensors can be developed to measure temperature,
  humidity, motion, color changes in a painting, or
  any other measurable thing.
• Most WSNs consist of millions of tiny processors
  communicating over slow wireless networks,
• WSNs may consist of devices with a wide range of
  computation, communication, and sensing
  capabilities.
• The WSNs may use Bluetooth or IEEE 802.11
  networks
• ZigBee IEEE 802.15.4

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Sensor Node (Mote)
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WSN Hierarchy
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WSN Design
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WSN Protocol Stack
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Summary

• WPANs
• Bluetooth
• Home Networking
• UWB Overview
• Wireless Sensor Networks