现代通信新技术导论
第五章 小覆盖无线网络
Chapter 5 Wireless Networks with Narrow Coverage
电控学院 电子工程学科部
司鹏搏 综合楼825室
sipengbo@bjut.edu.cn
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
–
–
–
–
–
–
–
5.1.1 Wireless Networks
5.1.2 IEEE 802.11 Overview
5.1.3 Components
5.1.4 Services
5.1.5 MAC Layer
5.1.6 Physical Layer
5.1.7 IEEE 802.11 Protocols
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
–
–
–
–
–
–
–
5.2.1 Introduction to Bluetooth
5.2.2 Protocol Stack
5.2.3 Network Topology
5.2.4 Packet Structure
5.2.5 Connection States
5.2.6 Security
5.2.7 Technology Comparison and Target Markets
• 5.3 Wireless Body Area Networks (WBANs)
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
–
–
–
–
–
–
–
5.3.1 Introduction to WBAN
5.3.2 Three-Tier Architecture
5.3.3 Comparison with Other Networks
5.3.4 Designing WBANs
5.3.5 Physical Layer Considerations
5.3.6 MAC Layer Considerations
5.3.7 Network Layer Considerations
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
–
–
–
–
–
–
–
5.1.1 Wireless Networks
5.1.2 IEEE 802.11 Overview
5.1.3 Components
5.1.4 Services
5.1.5 MAC Layer
5.1.6 Physical Layer
5.1.7 IEEE 802.11 Protocols
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.1 Wireless Internetworking Overview
Residential/
Premise/ Campus
Fixed
Mobile
Broadband Multiservice
IEEE
802.11
BLUE
TOOTH
MMDS
LMDS
2G+
Cellular
3G
Cellular
Data
Services
Packet
Data/Voice
GPRS
Mobile IP
UMTS
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.1 Standardization of Wireless Networks
• Wireless networks are standardized by IEEE.
• Under 802 LAN MAN standards committee.
Application
ISO
OSI
7-layer
model
Presentation
Session
Transport
IEEE 802
standards
Network
Logical Link Control
Data Link
Medium Access (MAC)
Physical
Physical (PHY)
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
–
–
–
–
–
–
–
5.1.1 Wireless Networks
5.1.2 IEEE 802.11 Overview
5.1.3 Components
5.1.4 Services
5.1.5 MAC Layer
5.1.6 Physical Layer
5.1.7 IEEE 802.11 Protocols
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.2 IEEE 802.11 Overview
• Goals
–
–
–
–
To deliver services in wired networks
To achieve high throughput
To achieve highly reliable data delivery
To achieve continuous network connection
• Adopted in 1997.
• Defines
– MAC sublayer
– MAC management protocols and services
– Physical (PHY) layers
• IR
• FHSS
• DSSS
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
–
–
–
–
–
–
–
5.1.1 Wireless Networks
5.1.2 IEEE 802.11 Overview
5.1.3 Components
5.1.4 Services
5.1.5 MAC Layer
5.1.6 Physical Layer
5.1.7 IEEE 802.11 Protocols
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.3 Components
• Station
• BSS - Basic Service Set
– IBSS : Independent BSS
• ESS - Extended Service Set
– A set of infrastructure BSSs
– Connection of APs
– Tracking of mobility
• DS – Distribution System
– AP communicates with another
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.3 BSS
• A set of stations controlled by a single “Coordination
Function”
– = the logical function that determines when a station can
transmit or receive
• Similar to a “cell” in pre IEEE terminology
• A BSS can
– Have an Access-Point (both in standalone networks and in
building-wide configurations),
– Or can run without and Access-Point (in standalone
networks only)
• Diameter of the cell is approximately twice the coveragedistance between two wireless stations
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5.1.3 BSS
BSS
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.3 IBSS
• A Basic Service Set (BSS) which forms a selfcontained network in which no access to a
Distribution System is available
• A BSS without an Access-Point
• One of the stations in the IBSS can be
configured to “initiate” the network and
assume the Coordination Function
• Diameter of the cell determined by coverage
distance between two wireless stations
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.3 IBSS
IBSS
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5.1.3 ESS and DS
• Extended Service Set (ESS):
– A set of one or more Basic Service Sets interconnected by a
Distribution System (DS)
– Traffic always flows via Access-Point
– Diameter of the cell is double the coverage distance between
two wireless stations
• Distribution System (DS):
– A system to interconnect a set of Basic Service Sets
• Integrated; A single Access-Point in a standalone network
• Wired; Using cable to interconnect the Access-Points
• Wireless; Using wireless to interconnect the Access-Points
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5.1.3 ESS, Single BSS with Integrated DS
BSS
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5.1.3 ESS, BSSs with Wired DS
BSS
BSS
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5.1.3 ESS, BSSs with Wireless DS
BSS
BSS
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5.1.3 SSID and BSSID
• Service Set Identifier (SSID):
–
–
–
–
“Network name”
32 octets long
Similar to “Domain-ID” in the pre-IEEE WaveLAN systems
One network (ESS or IBSS) has one SSID
• Basic Service Set Identifier (BSSID)
–
–
–
–
–
“cell identifier”
6 octets long (MAC address format)
Similar to NWID in pre-IEEE WaveLAN systems
One BSS has one SSID
Value of BSSID is the same as the MAC address of the radio in the
Access-Point
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
–
–
–
–
–
–
–
5.1.1 Wireless Networks
5.1.2 IEEE 802.11 Overview
5.1.3 Components
5.1.4 Services
5.1.5 MAC Layer
5.1.6 Physical Layer
5.1.7 IEEE 802.11 Protocols
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.4 Services
• Station services:
–
–
–
–
Authentication
De-authentication
Privacy
Delivery of data
• Distribution Services (A thin layer between MAC and LLC)
–
–
–
–
–
Association
Disassociation
Reassociation
Distribution
Integration
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现代通信新技术导论 第五章 小覆盖无线网络
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
–
–
–
–
–
–
–
5.1.1 Wireless Networks
5.1.2 IEEE 802.11 Overview
5.1.3 Components
5.1.4 Services
5.1.5 MAC Layer
5.1.6 Physical Layer
5.1.7 IEEE 802.11 Protocols
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Medium Access Control
• Functionality
– Reliable data delivery
– Fairly control access
– Protection of data
• Deals
–
–
–
–
–
–
Noisy and unreliable medium
Frame exchange protocol - ACK
Overhead to IEEE 802.3
Hidden Node Problem – RTS/CTS
Participation of all stations
Reaction to every frame
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Medium Access Control
• Retry Counters
– Short retry counter
– Long retry counter
– Lifetime timer
• Basic Access Mechanism
– CSMA/CA
– Binary exponential back-off
– NAV – Network Allocation Vector
• Timing Intervals: SIFS, Slot Time, PIFS, DIFS, EIFS
• DCF Operation
• PCF Operation
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Hidden Node Problem
A
B
C
• A and C cannot see each other, B can
see both
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 CSMA/CA
• Sender sends Request to Send (RTS)
• Receiver sends Clear to Send (CTS)
• Sender transmits for required time
CTS
RTS
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 DCF Operation
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 PCF Operation
• Poll – eliminates contention
• PC – Point Coordinator
– Polling List
– Over DCF
– PIFS
• CFP – Contention Free Period
– Alternate with DCF
•
•
•
•
Periodic Beacon – contains length of CFP
CF-Poll – Contention Free Poll
NAV prevents during CFP
CF-End – resets NAV
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Frame Types

Upper layer data

2048 byte max

256 upper layer
header
NAV information
Or

FC
2
Short Id for PS-Poll
Duration Address Address Address Sequence Address
/ID
1
2
3
Control
4
2
6
6
•
Protocol Version

•
Frame Type and Sub
Type

•
To DS and From DS
•
More Fragments
•
Retry
•
Power Management
•
More Data
•
WEP

•
Order






6
IEEE 48 bit
address
Individual/Group
Universal/Local
46 bit address
2



MSDU
Sequence
Number
Fragment
Number
6
DATA
0-2312

FCS
4
bytes
CCIT CRC-32
Polynomial
BSSID –BSS
Identifier
TA - Transmitter
RA - Receiver
SA - Source
DA - Destination
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Frame Control Field
Bytes:
2
2
Frame
Control
6
Duration
ID
Addr 1
6
Addr 2
6
2
Sequence
Control
Addr 3
6
0-2312
Frame
Body
Addr 4
4
CRC
802.11 MAC Header
Bits: 2
Protocol
Version
2
4
Type
SubType
1
To
DS
1
1
1
1
1
1
1
From
DS
More
Frag
Retry
Pwr
Mgt
More
Data
WEP
Rsvd
Frame Control Field
MAC Header format differs per Type:
– Control Frames (several fields are omitted)
– Management Frames
– Data Frames
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Address Field
Bits: 2
Protocol
Version
2
4
Type
SubType
1
To
DS
1
1
1
1
1
1
1
From
DS
More
Frag
Retry
Pwr
Mgt
More
Data
WEP
Rsvd
Frame Control Field
To DS
From DS
Address 1
Address 2
Address 3
Address 4
0
0
DA
SA
BSSID
N/A
0
1
DA
BSSID
SA
N/A
1
0
BSSID
SA
DA
N/A
1
1
RA
TA
DA
SA
Addr. 1 =
All stations filter on this address.
Addr. 2 =
Transmitter Address (TA), Identifies transmitter to address the ACK frame to.
Addr. 3 =
Dependent on To and From DS bits.
Addr. 4 =
Only needed to identify the original source of WDS (Wireless Distribution System)
frames
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Type Field
Bits: 2
Protocol
Version
2
4
Type
SubType
1
To
DS
1
1
1
1
1
1
1
From
DS
More
Frag
Retry
Pwr
Mgt
More
Data
WEP
Rsvd
Frame Control Field
Type and subtype identify the function of the frame:
Type=00 Management Frame
Beacon
(Re)Association
Probe
(De)Authentication
Power Management
Type=01 Control Frame
RTS/CTS
ACK
Type=10 Data Frame
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 MAC Management Frames
• Beacon
– Timestamp, Beacon Interval, Capabilities, SSID, Supported Rates,
parameters
– Traffic Indication Map
• Probe
– SSID, Capabilities, Supported Rates
• Probe Response
– Timestamp, Beacon Interval, Capabilities, SSID, Supported Rates,
parameters
– Same as Beacon except for TIM
• Association Request
– Capability, Listen Interval, SSID, Supported Rates
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 MAC Management Frames
• Association Response
– Capability, Status Code, Station ID, Supported Rates
• Re-association Request
– Capability, Listen Interval, SSID, Supported Rates, Current AP
Address
• Re-association Response
– Capability, Status Code, Station ID, Supported Rates
• Dis-association
– Reason code
• Authentication
– Algorithm, Sequence, Status, Challenge Text
• De-authentication
– Reason
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Frame Subtypes
CONTROL
DATA
•
RTS

•
CTS

•
ACK
•
PS-Poll
•
CF-End & CF-End
ACK






Data
Data+CF-ACK
Data+CF-Poll
Data+CF-ACK+CFPoll
Null Function
CF-ACK (nodata)
CF-Poll (nodata)
CF-ACK+CF+Poll
MANAGEMENT








Beacon
Probe Request & Response
Authentication
Deauthentication
Association Request &
Response
Reassociation Request &
Response
Disassociation
Announcement Traffic
Indication Message (ATIM)
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Other MAC Operations
• Fragmentation
– Sequence control field

WEP Details

– In burst
– Medium is reserved
– NAV is updated by ACK

Privacy





WEP bit set when encrypted.
Only the frame body.
Medium is reserved
NAV is updated by ACK
Symmetric variable key



Two mechanism
 Default keys
 Key mapping
WEP header and trailer
 KEYID in header
 ICV in trailer
dot11UndecryptableCount
 Indicates an attack.
dot11ICVErrorCount
 Attack to determine a
key is in progress.
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 MAC Management and Authentication
•
MAC Management
– Interference by users that have no concept of data communication. Ex: Microwave
– Interference by other WLANs
– Security of data
– Mobility
– Power Management
•
Authentication
– Prove identity to another station.
– Open system authentication
– Shared key authentication
• A sends
• B responds with a text
•
Security Problem
– A rogue AP
• SSID of ESS
• Announce its presence with
beaconing
• An active rogue AP reaches higher
layer data if unencrypted
• A encrypt and send back
• B decrypts and returns an authentication management frame.
– May authenticate any number of station
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Association
•
•
•
•
Transparent mobility
After authentication
Association request to an AP
After established, forward data
–
–
–
–
To BSS, if DA is in the BSS.
To DS, if DA is outside the BSS.
To AP, if DA is in another BSS.
To “portal”, if DC is out of the ESS.
• New AP after reassociation, communicates with the
old AP.
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Power Management
• Independent BSS
–
–
–
–
Distributed
Data frame handshake
Wake up every beacon.
Awake a period of ATIM after each
beacon.
– Send ACK if receive ATIM frame
& awake until the end of next
ATIM.
– Estimate the power saving station,
and delay until the next ATIM.
– Multicast frame : No ACK :
optional
• Overhead
– Sender
• Announcement frame
• Buffer
• Power consumption in
ATIM
– Receiver
• Awake for every Beacon
and ATIM
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Power Management
• Infrastructure BSS
– Centralized in the AP
– Greater power saving
– Mobile Station sleeps for a number of beacon
periods.
– Awake for multicast indicated in DTIM in Beacon.
– AP buffer, indicate in TIM
– Mobile requests by PS-Poll
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Synchronization
• Timer Synchronization in an Infrastructure BSS
– Beacon contains TSF
– Station updates its with the TSF in beacon.
• Timer Synchronization in an IBSS
– Distributed. Starter of the BSS send TSF zero and
increments.
– Each Station sends a Beacon
– Station updates if the TSF is smaller
– Take into account the contention time
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Scanning & Joining
• Scanning
– Passive Scanning : only listens for Beacon and get
info of the BSS. Power is saved
– Active Scanning: transmit and elicit response from
APs. If IBSS, last station that transmitted beacon
responds. Time is saved
• Joining a BSS
– Synchronization in TSF and frequency : Adopt
PHY parameters : The BSSID : WEP : Beacon
Period : DTIM
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Operational Process
• Association
– To establish relationship with Access-Point
– Stations scan frequency band to and select Access-Point with best
communications quality
• Active Scan (sending a “Probe request” on specific channels and assess
response)
• Passive Scan (assessing communications quality from beacon message)
– Access-Point maintains list of associate stations
• Record station capability (data-rate)
• To allow inter-BSS relay
– Station’s MAC address is also maintained in bridge learn table
associated with the port it is located on
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Operational Process
• Authentication
– To control access to the infrastructure via an
authentication
– Stations identify themselves to other stations (or AccessPoints) prior to data traffic or association
– Open System Authentication
• Uses null authentication algorithm
• Default
– Shared Key Authentication
• Uses WEP privacy algorithm
• Optional
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Operational Process
• Starting an ESS
– The infrastructure network is identified by its ESSID
– All Access-Points will have been set according to this
ESSID
– Wireless stations will be configured to set their desired
SSID to the value of ESSID
– On power up stations will issue Probe Requests and will
locate the Access-Point that they will associate with:
• “Best” Access-Point with matching ESSID
• “Best” Access-Point if the “desired SSID” has been set to “ANY”
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Operational Process
• Starting an IBSS
– Station configured for IBSS operation will:
• “look” for Beacons that contain a network name (SSID) that matches the
one that is configured
• When Beacons with matching Network Name are received and are issued
by an AP, Station will associate to the AP
• When Beacons with matching Network Name are received and are issued
by another Station in IBSS mode, the station will join this IBSS
• When no beacons are received with matching Network Name, Station will
issue beacons itself.
– All Stations in an IBSS network will participate in sending beacons.
• All stations start a random timer prior to the point in time when next
Beacon is to be sent.
• First station whose random timer expires will send the next beacon
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5.1.5 Operational Process
Free access when medium
is free longer than DIFS
DIFS
Contention Window
PIFS
DIFS
Busy Medium
SIFS
Backoff-Window
Next Frame
Slot time
Defer Access
Select Slot and Decrement Backoff as long as medium is idle.
• Inter-Frame Spacing
– Inter frame spacing required for MAC protocol traffic
• SIFS = Short interframe space
• PIFS = PCF interframe space
• DIFS = DCF interframe space
– Back-off timer expressed in terms of number of time slots
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Operational Process
DIFS
Src
Data
SIFS
ACK
Dest
DIFS
Contention Window
Next MPDU
Other
Defer Access
Backoff after Defer
• Data Frames and their ACK
– Acknowledgment are to arrive at within the SIFS
– The DCF interframe space is observed before medium is
considered free for use
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.5 Operational Process
• Traffic Flow
——Inter BSS
Bridge learn
table
STA-1
STA-2
2
2
AP-1000 or AP-500
Wireless PC-Card
Association table
STA-1
STA-2
BSS-A
Inter-BSS
Relay
Associate
ACK
STA-1
Packet for STA-2
Associate
ACK
Packet for STA-2
STA-2
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5.1.5 Operational Process
• Traffic Flow ——ESS Operation
Bridge learn
table
Bridge learn
table
STA-2
1
STA-1
2
AP-1000 or AP-500
STA-2
2
STA-1
1
AP-1000 or AP-500
Avaya Wireless PC-Card
Association table
Avaya Wireless PC-Card
STA-2
Association table
STA-1
Packet for STA-2
Packet for STA-2
ACK
ACK
BSS-B
STA-1
BSS-A
STA-2
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5.1.5 Operational Process
• Traffic Flow ——WDS Operation
Bridge learn
table
Bridge learn
table
STA-2
2
STA-1
2
AP-1000 or AP-500
STA-2
2
STA-1
2
AP-1000 or AP-500
Avaya Wireless PC-Card
Association table
Avaya Wireless PC-Card
STA-2
Association table
STA-1
WDS
Relay
WDS
Relay
Packet for STA-2
ACK
Packet for STA-2
Packet for STA-2
ACK
ACK
BSS-B
STA-1
BSS-A
STA-2
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
–
–
–
–
–
–
–
5.1.1 Wireless Networks
5.1.2 IEEE 802.11 Overview
5.1.3 Components
5.1.4 Services
5.1.5 MAC Layer
5.1.6 Physical Layer
5.1.7 IEEE 802.11 Protocols
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
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现代通信新技术导论 第五章 小覆盖无线网络
5.1.6 Physical Layer
• Direct Sequence Spread Spectrum (DSSS) PHY
– 2.4 GHz : RF : 1 – 2 Mbps
• The Frequency Hopping Spread Spectrum (FHSS) PHY
– 110KHz deviation : RF : PMD controls channel hopping : 2 Mbps
• Infrared (IR) PHY
– Indoor : IR : 1 and 2 Mbps
• The OFDM PHY – IEEE 802.11a
– 5.0 GHz : 6-54 Mbps
• High Rate DSSS PHY – IEEE 802.11b
– 2.4 GHz : 5.5 Mbps – 11 Mbps
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5.1.6 FHSS and DSSS in Physical Layer
• Preamble Sync, 16-bit Start Frame Delimiter, PLCP Header including
16-bit Header CRC, MPDU, 32-bit CRC
• FHSS
– 2 & 4GFSK
– Data Whitening for Bias Suppression
• 32/33 bit stuffing and block inversion
• 7-bit LFSR scrambler
– 80-bit Preamble Sync pattern
– 32-bit Header
• DSSS
–
–
–
–
DBPSK & DQPSK
Data Scrambling using 8-bit LFSR
128-bit Preamble Sync pattern
48-bit Header
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5.1.6 Other Issues in Physical Layer
• Antenna Diversity
–
–
–
–
Multipath fading a signal can inhibit reception
Multiple antennas can significantly minimize
Spatial Separation of Orthoganality
Choose Antenna during Preamble Sync pattern
• Presence of Preamble Sync pattern
• Presence of energy
– RSSI - Received Signal Strength Indication
• Combination of both
• Clear Channel Assessment
– Require reliable indication that channel is in use to defer
transmission
– Use same mechanisms as for Antenna Diversity
– Use NAV information
57
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
–
–
–
–
–
–
–
5.1.1 Wireless Networks
5.1.2 IEEE 802.11 Overview
5.1.3 Components
5.1.4 Services
5.1.5 MAC Layer
5.1.6 Physical Layer
5.1.7 IEEE 802.11 Protocols
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
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5.1.7 IEEE 802.11 Protocols
• IEEE 802.11a
– 1999 : PHY Standard : 8 channels : 5 GHz : 54 Mbps
• IEEE 802.11b
– 1999 : PHY Standard : 3 channels : 2.4 GHz : 11 Mbps
• IEEE 802.11d
– MAC Standard : operate in variable power levels :
ongoing
• IEEE 802.11e
– 2002 : MAC Standard : QoS support
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5.1.7 IEEE 802.11 Protocols
• IEEE 802.11f
– Inter-Access Point Protocol : 2nd half 2002
• IEEE 802.11g
– 2000 : PHY Standard: 3 channels : OFDM and PBCC : 54
Mbps
• IEEE 802.11h
– 2002 : Supplementary MAC Standard: TPC and DFS
• IEEE 802.11i
– 2004 : Supplementary MAC Standard: Alternative WEP
• IEEE 802.11n
– 2009 : MIMO OFDM : 600 Mbps? 100 Mbps?
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5.1.7 IEEE 802.11e
•
•
•
•
•
•
EDCF - Enhanced DCF
HCF - Hybrid Coordination Function
QBSS
HC – Hybrid Controller
TC – Traffic Categories
TXOP – Transmission Opportunity
– Granted by EDCF-TXOP or HC- poll TXOP
• AIFS – Arbitration Interframe Space
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5.1.7 Operational Process of 802.11e
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5.1.7 IEEE 802.11e Backoff
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5.1.7 IEEE 802.11i
Description
Enhancements to the 802.11 MAC standard to increase the security; addresses
new encryption methods and upper layer authentication
Importance
High: weakness of WEP encryption is damaging the 802.11 standard perception
in the market
Related standards
This applies to 802.11b, 802.11a and 802.11g systems.
802.1x is key reference for upper layer authentication
Status +
Roadmap
Enhanced encryption software will replace WEP software; This is on a
recommended best practice /voluntary basis; development in TgI: first draft Mar
2001; next draft due Mar 2002; stable draft: July 2002; final standard: Jan 2003
Products affected
Client and AP cards (Controller chip, Firmware, Driver)
AP kernel, RG kernel, BG kernel
Agere’s activity
Actively proposing WEP improvement methods, participating in all official/interim
meetings
Key players
Agere/Microsoft/Agere/Cisco/Atheros/Intel/3Com/Intersil/Symbol/Certicom/RSA/F
unk
Key issues
Mode of AES to use for encryption (CTR/CBC [CBC MIC] or OCB [MIC and
Encryption function])
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
–
–
–
–
–
–
–
5.2.1 Introduction to Bluetooth
5.2.2 Protocol Stack
5.2.3 Network Topology
5.2.4 Packet Structure
5.2.5 Connection States
5.2.6 Security
5.2.7 Technology Comparison and Target Markets
• 5.3 Wireless Body Area Networks (WBANs)
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5.2.1 What is Bluetooth?
• Bluetooth is a short-range wireless network
originally intended to replace the cable(s)
connecting portable and/or fixed electronic devices.
Such a network is also sometimes called a PAN
(Personal Area Network)
• Bluetooth is supposed to got it’s name from Harald
“Bluetooth” II, King of Denmark 940-981
• The concept was first patented by Ericsson.
Currently the Bluetooth trade mark is owned by the
Bluetooth SIG, a consortium of companies having
stake in Bluetooth
• Key features are robustness, low power, and low
cost.
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5.2.1 What can Bluetooth Do?
Landline
Cable
Replacement
Data/Voice
Access Points
Personal Ad Hoc Networks
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5.2.1 What can Bluetooth Do?
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5.2.1 What can Bluetooth Do?
69
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5.2.1 What can Bluetooth Do?
In the Office
At Home
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5.2.1 Bluetooth Overview
Connection Type
Spread Spectrum (Frequency Hopping)
MAC Scheme
FH-CDMA
Spectrum
2.4 GHz ISM
Modulation
Gaussian Frequency Shift Keying
Transmission Power
1 mw – 100 mw
Aggregate Data Rate
1 Mbps
Range
30 ft (~9 m)
Supported Stations
8 devices
Voice Channels
3
Data Security- Authentication Key
128 bit key
Data Security-Encryption Key
8-128 bits (configurable)
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
–
–
–
–
–
–
–
5.2.1 Introduction to Bluetooth
5.2.2 Protocol Stack
5.2.3 Network Topology
5.2.4 Packet Structure
5.2.5 Connection States
5.2.6 Security
5.2.7 Technology Comparison and Target Markets
• 5.3 Wireless Body Area Networks (WBANs)
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5.2.2 Protocol Stack——Transport Protocol Group
Composed of protocols to allow
Bluetooth devices to locate each
other and to create, configure and
manage both physical and logical
links that allow higher layer
protocols and applications to pass
data through these transport
protocols
Applications
IP
SDP
Data
Audio
Transport Protocol Group
RFCOMM
L2CAP
Link Manager
Baseband
RF
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5.2.2 Transport Protocol Group
• Radio Frequency (RF)
– Sending and receiving modulated bit streams
•
Baseband
– Defines the timing, framing
– Flow control on the link.
• Link Manager
– Managing the connection states.
– Enforcing Fairness among slaves.
– Power Management
• Logical Link Control &Adaptation Protocol
– Handles multiplexing of higher level protocols
– Segmentation & reassembly of large packets
– Device discovery & QoS
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5.2.2 Protocol Stack——Middleware Protocol Group
Additional transport protocols to allow
existing and new applications to operate
over Bluetooth. Packet based telephony
control signaling protocol also present.
Also includes Service Discovery
Protocol.
Applications
IP
SDP
RFCOMM
Data
Middleware
MiddlewareProtocol
ProtocolGroup
Group
Audio
L2CAP
Link Manager
Baseband
RF
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5.2.2 Middleware Protocol Group
• Service Discovery Protocol (SDP)
– Means for applications to discover device info,
services and its characteristics.
• TCP/IP
– Network Protocols for packet data communication,
routing
• RFCOMM
– Cable replacement protocol, emulation of serial
ports over wireless network
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5.2.2 Protocol Stack——Application Group
Applications
Application Group
IP
SDP
Consists of Bluetooth aware as well as
un-aware applications.
RFCOMM
Data
Audio
L2CAP
Link Manager
Baseband
RF
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
–
–
–
–
–
–
–
5.2.1 Introduction to Bluetooth
5.2.2 Protocol Stack
5.2.3 Network Topology
5.2.4 Packet Structure
5.2.5 Connection States
5.2.6 Security
5.2.7 Technology Comparison and Target Markets
• 5.3 Wireless Body Area Networks (WBANs)
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5.2.3 Network Topology
• Master
– Device in Piconet whose clock and hopping sequence are used to
synchronize all other devices (slaves) in the Piconet.
– It also carries out Paging procedure and also Connection
Establishment.
• Slaves
– Units within the piconet that
are synchronized to the
master via its clock and
hopping sequence.
– After connection
establishment, Slaves are
assigned a temporary 3 bit
member address to reduce the
no. of addressing bits required
S
P
M
sb
M
P
S
P
sb
S
S
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5.2.3 Network Topology
• Point to Point Link
– Master - slave relationship
– Bluetooth devices can function as masters or
slaves
m
s
• Piconet
– It is the network formed by a Master and one
or more slaves (max 7).
– Each piconet is defined by a different hopping
channel to which users synchronize to.
– Each piconet has max capacity (1 Mbps).
– Hopping pattern is determined by the master.
m
s
s
s
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5.2.3 Physical Link Types
• Synchronous Connection Oriented (SCO)
–
–
–
–
Point to Point Full Duplex between Master & Slave
Established once by master & kept alive till released by Master
Typically used for Voice connection ( to guarantee continuity )
Master reserves slots used for SCO link on the channel to preserve
time sensitive information
• Asynchronous Connection Link (ACL)
–
–
–
–
It is a momentary link between master and slave.
No slots are reserved.
It is a Point to Multipoint connection.
Symmetric & Asymmetric links possible
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
–
–
–
–
–
–
–
5.2.1 Introduction to Bluetooth
5.2.2 Protocol Stack
5.2.3 Network Topology
5.2.4 Packet Structure
5.2.5 Connection States
5.2.6 Security
5.2.7 Technology Comparison and Target Markets
• 5.3 Wireless Body Area Networks (WBANs)
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5.2.4 Packet Structure
54 bits
72 bits
Access
Code
Header
Voice
No CRC
No retries
FEC (optional)
0 - 2744 bits
Payload
Data
CRC
ARQ
FEC (optional)
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5.2.4 Access Code
• Purpose
–
–
–
–
Synchronization
DC offset compensation
Identification
Signaling
• Types
– Channel Access Code (CAC)
• Identifies a piconet.
– Device Access Code (DAC)
• Used for signalling procedures like paging and response paging.
– Inquiry Access Code (IAC)
• General IAC is common to all devices, Dedicated IAC is for a dedicated group of
Bluetooth devices that share a common characteristic.
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5.2.4 Packet Header
•
•
•
•
•
•
•
AM_ADDR: 3 bits: address of slave in piconet.
TYPE: One of 16 possible packet types
FLOW: Used to stop flow on ACL link.
ARQN: Positive or negative acknowlegement.
SEQN: Inverted for each new transmitted packet.
HEC: Header-error check.
The entire header is protected by 1/3 rate FEC.
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
–
–
–
–
–
–
–
5.2.1 Introduction to Bluetooth
5.2.2 Protocol Stack
5.2.3 Network Topology
5.2.4 Packet Structure
5.2.5 Connection States
5.2.6 Security
5.2.7 Technology Comparison and Target Markets
• 5.3 Wireless Body Area Networks (WBANs)
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5.2.5 Connection State Machine
Inquiry
Page
Standby
Connected
Transmit data
Park
Hold
Sniff
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5.2.5 Connection State Machine
• Inquiry Scan
– A device that wants to be discovered will periodically enter
this mode and listen for inquiry packets.
• Inquiry
– Device sends an Inquiry packet addressed to GIAC or DIAC
– Transmission is repeated on the inquiry hop sequence of
frequencies.
• Inquiry Response
– When an inquiry message is received in the inquiry scan
state, a response packet (FHS) containing the responding
device address must be sent after a random number of slots.
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5.2.5 Connection State Machine
• Page
– The master uses the clock information, about the slave to be paged,
to determine where in the hop sequence, the slave might be
listening in the page scan mode.
– The master sends a page message
• Page Scan
– The page scan substate can be entered by the slave from the
standby state or the connection state. It listens to packets addressed
to its DAC.
• Page Response
– On receiving the page message, the slave enters the slave page
response substate. It sends back a page response consisting of its ID
packet which contains its DAC, at the frequency for the next slot
from the one in which page message was received.
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5.2.5 Power Control Modes
• Sniff Mode
– This is a low power mode in which the listening activity of the slave
is reduced.
– In the sniff mode, the slave listens for transmissions only at fixed
intervals Tsniff, at the offset slot Dsniff for Nsniff times. These
parameters are given by the LMP in the master when it issues the
SNIFF command to the slave.
• Hold Mode
– Slave temporarily (for Thold sec) does not support ACL packets on
the channel (possible SCO links will still be supported).
– By this capacity can be made free to do other things like scanning,
paging, inquiring, or attending another piconet.
– The slave unit keeps its active member address (AM_ADDR).
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5.2.5 Power Control Modes
• Park Mode
– This is a very low power mode with very little activity.
– The slave however, stays synchronized to the channel.
– The parked slaves regularly listen for beacon signals at intervals
decided by the beacon structure communicated to the slave during
the start of parking.
– The parked slave has to be informed about a transmission in a
beacon channel which is supported by the master to keep parked
slaves in synchronization and send them any other information.
– Any message to be sent to a parked member are sent over the
broadcast channel.
– It also helps the master to have more than seven slaves.
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
–
–
–
–
–
–
–
5.2.1 Introduction to Bluetooth
5.2.2 Protocol Stack
5.2.3 Network Topology
5.2.4 Packet Structure
5.2.5 Connection States
5.2.6 Security
5.2.7 Technology Comparison and Target Markets
• 5.3 Wireless Body Area Networks (WBANs)
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5.2.6 Security
• Security Measures
–
–
–
–
–
Limited/Restricted Access to authorized users.
Both Link Level Encryption & Authentication.
Personal Identification Numbers (PIN) for device access.
Long encryption keys are used (128 bit keys).
These keys are not transmitted over wireless. Other parameters are
transmitted over wireless which in combination with certain information
known to the device, can generate the keys.
– Further encryption can be done at the application layer.
• Security values
–
–
–
–
Device Address-Public
Authentication Key(128 bits)-Private
Encryption Key(8-128 bits)-Private
Random Number
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
–
–
–
–
–
–
–
5.2.1 Introduction to Bluetooth
5.2.2 Protocol Stack
5.2.3 Network Topology
5.2.4 Packet Structure
5.2.5 Connection States
5.2.6 Security
5.2.7 Technology Comparison and Target Markets
• 5.3 Wireless Body Area Networks (WBANs)
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5.2.7 Bluetooth v.s. IrDA
•
Bluetooth Advantages
–
–
–
–
–
–
•
Point to Multipoint
Data & Voice
Broadcast
Easier Synchronization due to omnidirectional and no LOS requirement
Devices can be mobile
Range 10 m
IrDA
–
–
–
–
–
–
–
–
Point to point
Intended for Data Communication
Currently 16 Mbps
Ample security and very less interference
Already ubiquitous & Low cost
Infrared, LOS, serial data comm.
Simple to configure and use
Both devices must be stationary, for synchronization
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5.2.7 Bluetooth Target Markets
• The first wave
–
–
–
–
–
–
–
PC, Notebooks
Organizers & Palm Computers
Headsets
Cellular/ PCS
Cordless phones
Automotive cellular
Digital cameras
• The second wave
–
–
–
–
Printers
Photo printers
Fax machines
Industrial, musical and vertical industries
products
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
–
–
–
–
–
–
–
5.3.1 Introduction to WBAN
5.3.2 Three-Tier Architecture
5.3.3 Comparison with Other Networks
5.3.4 Designing WBANs
5.3.5 Physical Layer Considerations
5.3.6 MAC Layer Considerations
5.3.7 Network Layer Considerations
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5.3.1 What is WBAN
• Wireless Body Area Network
– Consists of a set of mobile and compact
intercommunicating sensors, either wearable or implanted
into the human body, which monitor vital body parameters
and movements
– These devices, communicating through wireless technologies,
transmit data from the body to a home base station, from
where the data can be forwarded to a hospital, clinic or
elsewhere, real-time
– Still in its primitive stage and is being widely researched
– Is expected to be a breakthrough invention in healthcare
• IEEE 802.15.6 is the task group for BAN.
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5.3.1 Motivations of WBAN
• Goal: ubiquitous and affordable healthcare
• Opportunities:
– Ambulatory (流动的) health monitoring
– Computer-assisted rehabilitation (康复)
– Augmented reality systems
• Long-term benefits:
– Promote healthy lifestyle
– Seamless integration of data into personal medical
records and research databases
– Knowledge discovery through data mining
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
–
–
–
–
–
–
–
5.3.1 Introduction to WBAN
5.3.2 Three-Tier Architecture
5.3.3 Comparison with Other Networks
5.3.4 Designing WBANs
5.3.5 Physical Layer Considerations
5.3.6 MAC Layer Considerations
5.3.7 Network Layer Considerations
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5.3.2 Three-Tier Architecture of WBAN
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5.3.2 Tier 1: WBAN
• Consisted of intelligent nodes
–
–
–
–
Sensing
Sampling
Processing
Communicating
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5.3.2 Body Sensors
Signal Conditioning
Finger Probe
RS232 Interface
Programmable Logic
Microcontroller
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5.3.2 Tier 2: Personal Server
• As the interface of WBAN sensor nodes through Zigbee
or Bluetooth.
• Connected with the medical server through mobile
telephone networks (2G, GPRS, 3G) or WLANs—
Internet
• Implemented regularly at cell phone
• Functions
– Register type and number sensor node .
– Manages the network channel sharing, time synchronization,
and processing data.
– Send data to MS
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5.3.2 Tier 3
• Function:
– Authenticate the users
– Save patient data into medical records
– Analyze the data
– Recognize serious health cases in order to
contact emergency care givers
– Forward new instruction to user
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Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
–
–
–
–
–
–
–
5.3.1 Introduction to WBAN
5.3.2 Three-Tier Architecture
5.3.3 Comparison with Other Networks
5.3.4 Designing WBANs
5.3.5 Physical Layer Considerations
5.3.6 MAC Layer Considerations
5.3.7 Network Layer Considerations
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5.3.3 Comparison with Other Networks
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5.3.3 Comparison with Other Networks
“Self-awareness”
People shift between different
roles in participating different
groups, using multiple devices
with different modalities over
different networks
BAN – Body Area Network
• Bluetooth, RFID, sensors, …
•
Local environment
•
Automatic configuration
arrangement of devices, services,
and local connectivity
•
Automatic and multi-modal
interfaces
“Group-awareness”
PAN – Personal Area Network
• Bluetooth, WLAN, …
•
Context and presence support
•
Novel privacy and trust models
“World-awareness”
•
WAN – Wide Area Network
•
3G, B3G, WLAN, *DSL, …
Communication Spheres
Automatic support for seamless
access to and delivery of services
across different domains
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5.3.3 Data Rate v.s. Power Consumption
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
–
–
–
–
–
–
–
5.3.1 Introduction to WBAN
5.3.2 Three-Tier Architecture
5.3.3 Comparison with Other Networks
5.3.4 Designing WBANs
5.3.5 Physical Layer Considerations
5.3.6 MAC Layer Considerations
5.3.7 Network Layer Considerations
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5.3.4 Designing WBANs
• Types of Devices
– Wireless sensor node
• A device that responds to and gathers data on physical stimuli, processes
the data if necessary and reports this information wirelessly. It consists of
several components: sensor hardware, a power unit, a processor, memory
and a transmitter or transceiver.
– Wireless actuator node
• A device that acts according to data received from the sensors or through
interaction with the user. The components of an actuator are similar to the
sensor's: actuator hardware, a power unit, a processor, memory and a
receiver or transceiver.
– Wireless personal device
• A device that gathers all the information acquired by the sensors and
actuators and informs the user via an external gateway, an actuator or a
display/LEDS on the device. The components are a power unit, a processor,
memory and a transceiver. This device is also called a Body Control Unit,
body-gateway or a sink. In some implementations, a PDA or smart phone
is used.
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5.3.4 Data Rate Issue
• Examples of Medical Applications
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5.3.4 Other Issues
• Energy Issue
– Restricted by battery capacity
• Sensing
• Communication (most power consuming)
– RF radiation
• Data processing
• QoS Issue
– Data loss rate
– Delivery time delay
• Security and Privacy Issue
– Data safety
– Should be accessible when the user is not capable of giving the pwd
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5.3.4 Positioning WBAN
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
–
–
–
–
–
–
–
5.3.1 Introduction to WBAN
5.3.2 Three-Tier Architecture
5.3.3 Comparison with Other Networks
5.3.4 Designing WBANs
5.3.5 Physical Layer Considerations
5.3.6 MAC Layer Considerations
5.3.7 Network Layer Considerations
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5.3.5 Physical Layer Considerations
• RF Communications
– Minimize the transmit power
– In the body
• Channel losses are mainly due to the absorption in the tissue, very high
compared to the free space propagation, related to heat
• Specific absorption rate is defined
– Along the body
• LOS
• NLOS, multi-hop
• Movement of the Body
• Non-RF Communications
– Body-coupled communication
– Transfer data by capacitive and galvanic coupling
– Low frequency (10 kHz to 10 MHz) and low data rate (5 bps)
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
–
–
–
–
–
–
–
5.3.1 Introduction to WBAN
5.3.2 Three-Tier Architecture
5.3.3 Comparison with Other Networks
5.3.4 Designing WBANs
5.3.5 Physical Layer Considerations
5.3.6 MAC Layer Considerations
5.3.7 Network Layer Considerations
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5.3.6 MAC Layer Considerations
• Non-Specific MAC protocols designed for WBAN Yet
• Requirement
– Simple
– Low cost
• Applicable MAC Protocols
– CSMA/CA
– Bluetooth MAC protocol
– 802.15.4
• QoS guarantee, but not scalable in terms of power consumption
– 802.15.6
• Designed for WBAN, under standardization
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现代通信新技术导论 第五章 小覆盖无线网络
Main Contents
• 5.1 Wireless Local Area Networks (WLANs)
• 5.2 Wireless Personal Area Networks (WPANs)
• 5.3 Wireless Body Area Networks (WBANs)
–
–
–
–
–
–
–
5.3.1 Introduction to WBAN
5.3.2 Three-Tier Architecture
5.3.3 Comparison with Other Networks
5.3.4 Designing WBANs
5.3.5 Physical Layer Considerations
5.3.6 MAC Layer Considerations
5.3.7 Network Layer Considerations
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5.3.7 Network Layer Considerations
• Temperature Routing
– Thermal aware routing algorithm
– Adaptive least temperature routing
– Least total route temperature
• Cluster Based Routing
– Protocols based on LEACH
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A Brief Review
• WLAN
– Coverage: office, airport, building, …
– Wi-Fi, IEEE 802.11
– CSMA/CA, DCF/PCF/PSM/…
• WPAN
– Coverage: personal devices
– Bluetooth
– MAC/PHY
• WBAN
– Coverage: body sensors
– Medical applications
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