baisa 03/28/01 1 ieee orange county computer society joint meeting with ieee oc comsig chapter...
TRANSCRIPT
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Baisa 03/28/01
IEEE Orange County Computer Society Joint Meeting with
IEEE OC ComSig ChapterWireless LAN
Instrumentation, Scientific, Medical BandDwight Borses
MTS, Field Applications EngineeringNational Semiconductor, Irvine,CA
Feb 25, 2002
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• The IEEE ("eye-triple-E") The Institute of Electrical and Electronics Engineers, Inc., helps advance global prosperity by promoting the engineering process of creating, developing, integrating, sharing, and applying knowledge about electrical and information technologies and sciences for the benefit of humanity and the profession.
• Local volunteers needed!
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Points to Ponder
• Standards - so many to choose from
• Cellular/PCS - both a competitor and a
complement to WLAN
• DECT – up-banded applications for
proprietary applications
• UWB – yet another contender
• FSO – Light based wireless
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Wireless Technologies: Short Distance
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802.11 InfraredA real standard that sort of died
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Wireless Technologies: Long Distance
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19991999 20002000 20012001 20022002 20032003 20042004 20052005 20062006
2 M2 M
384 K384 K
144 K144 K
64 K64 K
14.4 K14.4 K
9.6 K9.6 K 1GAnalogue Cellular
1GAnalogue Cellular
2GIS-95-A
Circuit Switched + QNC
2GIS-95-A
Circuit Switched + QNC
2.5GIS-95B
Packet Data
2.5GIS-95B
Packet Data
3G Phase IIS-2000 Rel 0 (1XRTT)
Packet Data
3G Phase IIS-2000 Rel 0 (1XRTT)
Packet Data
3G Phase IIIS-2000 Rel A (3XRTT)
Packet Data / Voice / Video
3G Phase IIIS-2000 Rel A (3XRTT)
Packet Data / Voice / Video
3GFixed access at 2Mbps
3GFixed access at 2Mbps
Subs
crib
er D
ata
Rat
eData Migration Path to 3G WWAN
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2.4GHz ISM Band
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ISM Band Inhabitants (Besides 802.11) Frequency & Modulation Spec’s
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Comparing Different WLAN Technologies
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5 GHz Unlicensed National Information Infrastructure
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IEEE 802 Framework
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802.11 StandardsOverview
IEEE 802.11
802.11a
802.11b
802.11i
802.11h
802.11d
802.11e
802.11f
802.11g
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802.11 Standards
• Original 802.11, circa 1999– FHSS, DSSS, IR– 1 & 2 Mbps– Wired Equivalent Privacy (WEP)– SNMP v2 for remote management
• 802.11b (shortly after 802.11)– DSSS– 1, 2, 5.5 & 11 Mbps, Complementary Code
Keying (CCK)
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802.11 Standards
• 802.11a (Approved same time as .11b)– 6, 9, 12, 18, 24, 36, 48, 54 Mbps– Only 6, 12, 24 Mbps support is mandatory– 5 GHz UNII band (not universally free)
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802.11 Standards
• 802.11c (completed, subsumed into d)– Bridge operation
• 802.11d (ongoing)– Specs for other regulatory domains
• 802.11e (ongoing)– QoS (Security moved to 802.11i (May 2001))
• 802.11f (ongoing)– Inter Access Point interoperability
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802.11 Standards
• 802.11g (ongoing)– High-speed extension to 802.11b, > 20Mbps
– Just approved!
• 802.11h (ongoing)– improvement to 802.11a, w.r.t. power and
spectrum management
• 802.11i (ongoing)– Security enhancements
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Wireless Data Standards Technology Comparison
TechnologyStandardsBody/Proponent
PHYLayer
DataRate
Range(Meters)
Frequency(5GHz)
TechnologyAimed For
IEEE802.11b
IEEE DSSS 11 100 2.4
IEEE802.11a
IEEE OFDM 54 TBD 5
HiperLAN2HiperLAN2
Global ForumOFDM 54 50 5
MMACHiSWAN
MMAC OFDM 54 50 5
Wireless Lan
IEEE802.11g
IEEE DSSS-OFDM
54 50 2.4
OfficeEnvironmentscommunication&
Home SpaceMultimediaDistribution(Video/Audio)
SWAP 1.1HomeRFWorkingGroup
FHSS 1.6 100 2.4 Home RF
HomeRF2 HomeRFWorkingGroup
FHSS 10 100 2.4Home Space
IEEE 802.15(Bluetooth)
BluetoothSIG
FHSS 1 10 2.4Bluetooth
IEEE 802.15(high-rate)
BluetoothSIG
FHSS 2+ TBD 2.4/5
Consumer,Short-RangeWirelessPersonal AreaNetworkCommunication
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PANs, LANs, and Bluetooth
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EHF
(milli-w
ave)SH
F(m
icro-wave)
VHF
UH
F
UH
FW
ired LA
N
Middle Speed 2.4GHz Range LAN
High Speed5GHz Range LAN
Very High Speed60 GHz Range LAN
4Mbps/16MbpsToken RingIEEE 802.5
10MbpsEthernet
IEEE 802.3
25/52/100MbpsATM-LAN
(ATM Forum)
100MbpsFast EthernetIEEE 802.3u
156/622 MbpsATM-LAN
(ATM Forum)
1000MbpsGigabit Ethernet
IEEE 802.3z, 802.3ab
Bandwidth
Frequency
IEEE802.111Mbps/2Mbps
IEEE802.11b5.5Mbps/11Mbps
(1)IEEE 802.11a 6/12/24Mbps
(2)HIPERLAN (ETSI BRAN)Type ½: 23.5/25Mbps
(3)WATM (ATM Forum) 25Mbps
19GHz range LAN10Mbps (ARIB)
(1) 156MbpsMMAC(Japan)
(2) 156MbpsMEDIAN (German)
300GHz
30GHz
3GHz
300MHz
1GHz
Full Range of Wireless LANs
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Data Rates and Range by Technology
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802.11 – Infrastructure Architecture
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802.11 - Layers and Functions
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Binary Phase Shift KeyingQuadrature Phase Shift Keying
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Quadrature Modulation
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Quadrature Amplitude Modulatoion
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IEEE 802.11 Direct Sequence Spread Spectrum DSSS
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Frequency Hopping Spread Spectrum (FHSS)
Freq.
f1
f2
f3
f4
f5
f6
f7
Timet1 t2 t3 t4 t5 t6
AU 1
AU 2
AU 4
AU 3
•Transmitted signal is “spread” over a wide range of frequencies (ISM 2.4-2.4835 GHz)•Transmission hops 8 to 30 times per second
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Complementary Code Keying
This sequence 1 has 4 pairs of like elements with a separation of 1 and 3 pairs of unlike
elements with a separation of 1
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Complementary Code Keying
This sequence has 4 pairs of unlike elements with separation of 1 and 3 pairs of like
elements.
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802.11 Modulation Set
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Binary Phase Shift Keying
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IEEE 802.11a OFDM
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IEEE 802.11 DSSS
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CSMA/CD
• CSMA/CD– Carrier Sense, Multiple Access/Collision
Detection• For wire communication• No control BEFORE transmission
– Generates collisions• Collision Detection
– How?
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CSMA/CA
• CSMA/CA– Carrier Sense, Multiple Access/Collision
Avoidance• For wireless communication• Collision avoidance BEFORE transmission
– Pre-avoidance of collision• Why avoidance on wireless?
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Collision Detection On Wireless?
• Difference on energy/power for transmit and receive– At maximum, transmission power is a million
times larger than receiving– Very hard to detect because of this difference
• Energy often matter on wireless environment– Portable devices/terminals with batteries
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Backoff
• Decrease the possibility of contention/collision
• Backoff window– Time to wait ot avoid collision
• Random backoff– Use random length of time to wait
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IFS – Inter Frame Spacing
• Defined length of time for control• To assure the control of multiple access
– DIFS – Distributed Inter Frame Spacing– PIFS – Point Inter Frame Spacing– SIFS – Short Inter Frame Spacing
• DIFS (MAX) > PIFS > SIFS (MIN)
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Basic Access Method: CSMA/CA
• Backoff Time = Random() x aSlotTime
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802.11 - Competing Stations - Simple Version
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RTS/CTS
• RTS : Request To Sent.• CTS : Clear To Sent• Duration/ID fields that define the period of ti
me that the medium is to be reserved to transmit the actual data frame and the returning ACK frame
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Network Allocation Vector NAV
• The NAV maintains a prediction of future traffic on the medium based on duration information that is announced in RTS/CTS frames prior to the actual exchange of data
• The duration information is also available in the MAC header of all frames sent during the CP other than PS-Poll Control frames
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RTS/CTS/Data/ACK and NAV
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Security
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Basic Security Concerns
• Impractical to stop RF signals from propagating beyond your premises
• “Parking lot” attack, war-driving• Poorly configured networks can be woefully
exposed• Hackers can be highly stealthy, guerilla
warfare style• That’s the reason for WEP
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Baseline Security Features
• Wired Equivalent Privacy– Shared 40/128 bit key– Static, i.e. not designed to change often– RC4 stream cipher
• Any AP/client can be configured to handle up to 4 keys
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Baseline Security Features
• Mutual authentication– Open, i.e. null– Shared key (if WEP is enabled), MS-CHAP style
challenge and response• Access control list at AP
– based on MAC addresses of WLAN cards• Access Control List can be easily bypassed
– MAC addresses can be sniffed from the air– client’s MAC address can be easily spoofed
• Service set ID (SSID)– “secret” word that identifies a WLAN segment
• SSID is not a security feature– transmitted in the clear in beacon frames– clients can set as null string
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Basic Security Concerns
• Sniffing tools are easily available• Freeware
– Ethereal + Prism II card– Now can capture raw encrypted packets
• Commercial tools– WildPacket Airopeek (~$2.5K)– NAI Sniffer Wireless (~ $20K)– Others are available FREE on the web
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Basic Security Concerns
• Besides WEP key, no other credentials required to access WLAN network
• Difficult to manage shared WEP key in large deployments– Keys are seldom changed, manual process
• If a WLAN card is stolen, have to reconfigure all other WLAN cards configured with that same WEP key
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The End of WEP?
• Undeniable fact: WEP in its current form is not secure
• Security issues are now better understood– No false sense of security => a good thing
• Vendors have always advocated higher level security is needed anyway– e.g. VPN, IPSec
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IPSec
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IPSec Sessions
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802.11g
• Newest standard provides for up to 54 Mbps data transfers within the 2.4 GHz band.
• 802.11g devices will be backwards compatible with 802.11b.
• Potentially enables 2.4 GHz-based 802.11b networks to easily upgrade to future 802.11g networks
• Consumers confusion with 802.11a and 802.11g standards entering the market simultaneously
• Cellular phone service providers are considering augmenting their "3G" third generation digital cellular networks with support of the unlicensed WLAN devices, particularly in peak usage areas in downtown cities and at airports
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Something for Everyone
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HomeRF Roadmap
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Bluetooth: Bluetooth: Lose the Cable!Lose the Cable!
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Overview of Bluetooth
Bluetooth is:– Short-range radio technology
• Class 1 (100 m) +20dBm max to 0 dBm w/ power control
• Class 2 ( 30 m) + 4 dBm to -6 dBm• Class 3 ( 10 m) 0 dBm max
– Connections without cables• Laptops, Cell phones, PDA’s, Printers, etc
– Royalty-free– IEEE Standard through 802.15 (PAN)
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Overview of Bluetooth
Bluetooth Applications:– Internet and email bridge
– Ad Hoc network via access point
– Home networking
– Hidden computing
– Wireless wallet
– Laptop and PDA to cell phone modem
– Headset
– Digital camera
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Who Was Bluetooth?
Harald Blaatand “Bluetooth” II– King of Denmark 940-981– Son of Gorm the Old (King of Denmark) and
Thyra Danebod (daughter of King Ethelred of England)
This is one of two Runic stones erected in his capitol city of Jelling (central Jutland)
– This is the front of the stone depicting the chivalry of Harald.
– The stone’s inscription (“runes”) say:• Harald Christianized the Danes• Harald controlled Denmark and Norway• Harald thinks notebooks and cellular phones
should seamlessly communicate
Source: Jim Kardach, Intel
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•Typically used for voice.
•Guaranteed bandwidth
•No re-transmission.
•Typically used for data.•Point to multi-point.•Reliable data (error correction / re-transmission)•No guaranteed bandwidth (best effort).
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Mutual Interference Problems
• IEEE 802.11 and Bluetooth both operate in same 2.4 GHz ISM Band
• Bluetooth enabled devices likely to be portable and need to operate in IEEE 802.11 WLAN environment
• There will be some level of mutual interference
Source: [John Barr] Company [Motorola]IEEE 802.15 Report at BT DevCon
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Coexistence Mechanisms
• Collaborative Mechanisms– Communication between the WLAN and
WPAN – Provide fair sharing of medium through link
• Non-Collaborative Mechanisms– No communication between WLAN and
WPAN – Techniques minimize effects of mutual
interference
Source: [John Barr] Company [Motorola]IEEE 802.15 Report at BT DevCon
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Impact of Bluetooth on 802.11b:
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National Semiconductor Wireless Solutions for 802.11 and Bluetooth
• First to market with BT 1.O compliance
• 802.11a/b/g solution
– Expect to meet all mandatory parts of 802.11g
• Complete solutions– Development boards for Radio and Baseband
– Reference boards for MiniPCI and PCMCIA
– Drivers and utilities
• Bluetooth PC Card, Compact Flash, and Printer Adapters solutions shipping now
