IEEE 802 - Technische Universität Ilmenau · 802.11 – DCF with RTS/CTS Extension • Sending...

Integrated Communication Systems GroupIlmenau University of Technology

IEEE 802.11

Summer Semester 2011

Integrated Communication Systems Group

Content

• Characteristics• System Architecture• Protocol Architecture• Physical Layer• MAC Layer

MAC Management Power Management Roaming Current Developments

Advanced Networking (MSCSP) 2


Characteristics of Wireless LANs

• Advantages– very flexible alternative to wired LANs– (almost) no wiring difficulties (e.g. historic buildings, firewalls)– ad-hoc networks without previous planning possible– more robust against disasters, e.g. earthquakes, fire, or users pulling a

plug ...

• Disadvantages– lower bandwidth compared to wired networks – possible interference may reduce bandwidth– no guaranteed service due to license-free spectrum– need to consider security issues– proprietary solutions, especially for higher bit-rates– wireless products have to follow many national restrictions

=> long time to establish global standards like, e.g. IMT-2000 (UMTS)

Advanced Networking (MSCSP)


Design goals for Wireless LANs

global, seamless operation

low power for battery use

no special permissions or licenses needed to use the LAN

robust transmission technology

simplified spontaneous cooperation at meetings

easy to use for everyone, simple management

protection of investment in wired networks

security (no one should be able to read my data), privacy (no one should be able to collect user profiles), safety (low radiation)

transparency concerning applications and higher layer protocols, but also location awareness if necessary



Comparison: Infrared vs. Radio Transmission

•Infrared– uses IR diodes, diffuse light,

multiple reflections (walls, furniture etc.)

•Advantages– simple, cheap, available in many

mobile devices– no licenses needed– simple shielding possible

•Disadvantages– interference by sunlight, heat

sources etc.– many things shield or absorb IR

light – low bandwidth

•Example– IrDA (Infrared Data Association)

interface available everywhere

•Radio– typically using the license free

ISM band at 2.4 GHz •Advantages

– experience from wireless WAN and mobile phones can be used

– coverage of larger areas possible (radio can penetrate walls, furniture etc.)

•Disadvantages– very limited license-free

frequency bands – shielding more difficult,

interference with other electrical devices

•Examples– 802.11a/b/g, HIPERLAN1/2,

Bluetooth, ZigBee



Comparison: Infrastructure vs. Ad-hoc Networks


infrastructurenetwork

ad-hoc network

APAPAP

wired network

AP: Access Point


Distribution System

Portal

802.x LAN

AccessPoint

802.11 LAN

BSS2

802.11 LAN

BSS1

AccessPoint

802.11: Architecture of an Infrastructure Network•Station (STA)

– terminal with access mechanisms to the wireless medium and radio contact to the access point

•Basic Service Set (BSS)– group of stations using the same

radio frequency•Access Point

– station integrated into the wireless LAN and the distribution system

•Portal– bridge to other (wired) networks

•Distribution System– interconnection network to form

one logical network (ESS: Extended Service Set) based on several BSS

STA1

STA2STA3

ESS


802.11: Architecture of an Ad-hoc Network

•Direct communication within a limited range

– Station (STA):terminal with access mechanisms to the wireless medium

– Independent Basic Service Set (IBSS):group of stations using the same radio frequency

802.11 LAN

IBSS2

802.11 LAN

IBSS1

STA1

STA4

STA5

STA2

STA3


IEEE Standard 802.11

mobile terminal

access point

server

fixed terminal

application

TCP

802.11 PHY

802.11 MAC

IP

802.3 MAC

802.3 PHY

application

TCP

802.3 PHY

802.3 MAC

IP

802.11 MAC

802.11 PHY

LLC

infrastructure network

LLC LLC



802.11 – Layers and Functions

•MAC– access mechanisms,

fragmentation, encryption •MAC Management

– synchronization, roaming, MIB, power management

•PLCP (Physical Layer Convergence Protocol)

– clear channel assessment signal (carrier sense)

•PMD (Physical Medium Dependent)– modulation, coding

•PHY Management– channel selection, MIB

•Station Management– coordination of all management

functions


PMD

PLCP

MAC

LLC

MAC Management

PHY Management

PHY

DLC

Stat

ion

Man

agem

ent


802.11 – Physical Layer

• 3 versions: 2 radio (typ. 2.4 GHz), 1 IR– data rates 1 or 2 Mbit/s

• FHSS (Frequency Hopping Spread Spectrum)– spreading, despreading, signal strength, typ. 1 Mbit/s– min. 2.5 frequency hops/s (USA), two-level GFSK modulation

• DSSS (Direct Sequence Spread Spectrum)– DBPSK modulation for 1 Mbit/s (Differential Binary Phase Shift Keying),

DQPSK for 2 Mbit/s (Differential Quadrature PSK)– preamble and header of a frame is always transmitted with 1 Mbit/s, rest

of transmission 1 or 2 Mbit/s– chipping sequence: +1, -1, +1, +1, -1, +1, +1, +1, -1, -1, -1 (Barker code)– max. radiated power 1 W (USA), 100 mW (EU), min. 1mW

• Infrared– 850-950 nm, diffuse light, typ. 10 m range– carrier detection, energy detection, synchonization



FHSS PHY Packet Format

• 802.11 only, not 802.11a/b!• Synchronization

– synch with 010101... pattern• SFD (Start Frame Delimiter)

– 0000110010111101 start pattern• PLW (PLCP_SDU Length Word)

– length of payload incl. 32 bit CRC of payload, PLW < 4096 (octets)• PSF (PLCP Signaling Field)

– data rate of packet (1 or 2 Mbit/s)• HEC (Header Error Check)

– CRC with x16+x12+x5+1


synchronization SFD PLW PSF HEC payload

PLCP preamble PLCP header

80 16 12 4 16 variable bits


DSSS PHY Packet Format

• 802.11 (802.11b)• Synchronization

– synch., gain setting, energy detection, frequency offset compensation

• SFD (Start Frame Delimiter)– 1111001110100000

• Signal– data rate of the packet (0A: 1 Mbit/s DBPSK; 14: 2 Mbit/s DQPSK)

• Service Length– future use, 00: 802.11 compliant length of the payload

• HEC (Header Error Check)– protection of signal, service and length, x16+x12+x5+1


synchronization SFD signal service HEC payload


128 16 8 8 16 variable bits

length

16


802.11 MAC Layer – DFWMAC

• Traffic services– Asynchronous Data Service (mandatory)

• exchange of data packets based on "best-effort"• support of broadcast and multicast• implemented using DCF (Distributed Coordination Function)

– Time-Bounded Service (optional)• implemented using PCF (Point Coordination Function)

• Access methods– DFWMAC-DCF CSMA/CA (mandatory)

• Distributed Foundation Wireless MAC• collision avoidance via randomized "back-off" mechanism• minimum distance between consecutive packets• ACK packet for acknowledgements (not for broadcasts)

– DFWMAC-DCF with RTS/CTS Extension (optional)• avoids hidden terminal problem

– DFWMAC- PCF (optional)• access point polls terminals according to a list



802.11 MAC

• Priorities– defined through different Inter-Frame Spaces (IFSs)– no guaranteed, hard priorities– SIFS (Short Inter-Frame Spacing)

• highest priority, for ACK, CTS, polling response– PIFS (PCF IFS)

• medium priority, for time-bounded service using PCF– DIFS (DCF IFS)

• lowest priority, for asynchronous data service


t

medium busy

DIFSDIFS

next framecontention

direct access if medium is free DIFS

SIFS

PIFS


t

medium busy

DIFSDIFS

next frame

contention window(randomized back-offmechanism)

802.11 – CSMA/CA Access Method

– station ready to send starts sensing the medium (Carrier Sense based on CCA, Clear Channel Assessment)

– if the medium is free for the duration of an Inter-Frame Space (IFS), the station can start sending (IFS depends on service type)

– if the medium is busy, the station has to wait for a free IFS, then the station must additionally wait a random back-off time (collision avoidance, multiple of slot-time)

– if another station occupies the medium during the back-off time of the station, the back-off timer stops (fairness)


slot time

direct access if medium is free DIFS

SIFS

PIFS


802.11 – Competing Stations – Simple Version


t

busy

boe

station1

station2

station3

station4

station5

packet arrival at MAC

DIFS

boe

boe

boe

busy

elapsed backoff time

borresidual backoff time

busy medium not idle (frame, ack etc.)

bor

bor

DIFS

boe

boe

boe bor

DIFS

busy

busy

DIFS

boe busy

boe

boe

bor

bor


802.11 – CSMA/CA Access Method

• Sending unicast packets– station has to wait for DIFS before sending data– receivers acknowledge at once (after waiting for SIFS) if the packet

was received correctly (CRC)– automatic retransmission of data packets in case of transmission

errors


t

SIFS

DIFS

data

ACK

waiting time

otherstations

receiver

sender data

DIFS

contention


Hidden Terminal Problem

– A sends to B, C cannot receive A – C wants to send to B, C senses a “free” medium -> CS fails– collision at B, A cannot receive the collision -> CD fails– A is “hidden” for C

=> Application of RTS/CTS


A B C


802.11 – DCF with RTS/CTS Extension

• Sending unicast packets– station can send RTS with reservation parameter after waiting for DIFS

(reservation determines amount of time the data packet needs the medium)

– acknowledgement via CTS after SIFS by receiver (if ready to receive)– sender can now send data at once, acknowledgement via ACK– other stations store medium reservations distributed via RTS and CTS


t

SIFS

DIFS

data

ACK

defer access

otherstations

receiver

sender data

DIFS

contention

RTS

CTSSIFS SIFS

NAV (RTS)NAV (CTS)

NAV: network allocation vector (implicit in RTS and CTS)


Fragmentation

t

SIFS

DIFS

data

ACK1

otherstations

receiver

sender frag1

DIFS

contention

RTS

CTSSIFS SIFS

NAV (RTS)NAV (CTS)

NAV (frag1)NAV (ACK1)

SIFS

ACK2

frag2

SIFS



802.11 – PCF (Polling)

PIFS

stations‘NAV

wirelessstations

point coordinator

D1

U1

SIFS

NAV

SIFS

D2

U2

SIFS

SIFS

SuperFramet0

medium busy

t1

D1: polling of wireless station 1U1: station 1 responds to polling by sending its dataD2: polling of wireless station 2U2: station 2 responds to polling by sending its data

SuperFrame defines time span for polling of (all) wireless stations by AP (including time to reply)



802.11 – PCF (Polling)

tstations‘NAV

wirelessstations

point coordinator

D3

NAV

PIFSD4

U4

SIFS

SIFSCFend

contentionperiod

contention free period

t2 t3 t4

D3: polling of wireless station 3U3: no data -> no response by station 3 within SIFSD4 (after PIFS): polling of wireless station 4U4: station 4 responds to polling by sending its data

Discussion: unpredictable beacon delays unknown transmission duration of polled

stations=> no QoS guarantees



802.11 – MAC Frame Format

• Types (frame control)– control frames, management frames, data frames

• Sequence number– important against duplicated frames due to lost ACKs

• Addresses– receiver, transmitter (physical), BSS identifier, sender (logical)

• Miscellaneous– duration (NAV), checksum, data


FrameControl

Duration/ID

Address1

Address2

Address3

SequenceControl

Address4 Data CRC

2 2 6 6 6 62 40-2312bytes

Protocolversion Type Subtype To

DSMoreFrag Retry Power

MgmtMoreData WEP

2 2 4 1

FromDS

1

Order

bits 1 1 1 1 1 1


MAC Address Format


scenario to DS from DS

address 1 address 2 address 3 address 4

ad-hoc network 0 0 DA SA BSSID - infrastructure network, from AP

0 1 DA BSSID SA -

infrastructure network, to AP

1 0 BSSID SA DA -

infrastructure network, within DS

1 1 RA TA DA SA

DS: Distribution System AP: Access PointDA: Destination Address SA: Source AddressBSSID: Basic Service Set Identifier RA: Receiver AddressTA: Transmitter Address

FrameControl Duration DA SA BSSID Sequence

Control Frame Body CRC

2 2 6 6 6 2 40-2312bytes

Management frame format


Control Frames: ACK, RTS, CTSAcknowledgement

Request To Send

Clear To Send

FrameControl Duration Receiver

AddressTransmitter

Address CRC

2 2 6 6 4bytes


Address CRC

2 2 6 4bytes


Address CRC

2 2 6 4bytes

ACK

RTS

CTS

Duration is used to determine NAV value



802.11 – MAC Management

• Synchronization– try to find a LAN, try to stay within a LAN– synchronization of internal clocks to coordinate access (e.g. SIFS, PIFS,

etc.), send beacons, etc.

• Power management– sleep-mode without missing a message– periodic sleep, frame buffering, traffic measurements

• Association/Reassociation– integration into a LAN– roaming, i.e. change networks by changing access points – scanning, i.e. active search for a network

• MIB - Management Information Base– managing, read, write



Synchronization Using a Beacon (Infrastructure)


beacon interval

tmedium

accesspoint

busy

B

busy busy busy

B B B

value of the timestamp B beacon frame

• Beacon contains a timestamp and other management information used for power management and roaming

• Beacon sent only by access point• Beacon may be delayed due to busy medium; beacon interval is not influenced by

this!


Synchronization Using a Beacon (Ad-hoc)


tmedium

station1

busy

B1

beacon interval

busy busy busy

B1

value of the timestamp B beacon frame

station2B2 B2

random delay

Beacon may be sent by any station (sending of beacon employs a random delay to avoid collisions)


Power Management

• Idea: switch the transceiver off if not needed• States of a station: sleep and awake

• Timing Synchronization Function (TSF)– stations wake up at the same time

• Infrastructure– AP stores frames intended for sleeping stations– AP transmits indication about stored frames in periodic beacons

(Indication Maps) sent during awake interval• Traffic Indication Map (TIM): List of unicast receivers• Delivery Traffic Indication Map (DTIM): List of broadcast/multicast

receivers

• Ad-hoc– Ad-hoc Traffic Indication Map (ATIM)

• announcement of receivers by stations buffering frames• more complicated - no central AP• collision of ATIMs possible (scalability?)



Power Saving with Wake-up Patterns (Infrastructure)

TIM interval

t

medium

accesspoint

busy

D

busy busy busy

T T D

T TIM D DTIM

DTIM interval

BB

B broadcast/multicast

station

awake

p PS poll

p

d

d

ddata transmissionto/from the station

beacon indicates station that data are available station replies with PS (power save)

poll and continues listening to the medium AP transmits data

station acknowledges the data



Power Saving with Wake-up Patterns (Ad-hoc)

awake

A transmit ATIM D transmit data

t

station1B1 B1

B beacon frame

station2B2 B2

random delay

A

a

D

d

ATIMwindow beacon interval

a acknowledge ATIM d acknowledge data

medium busy busy busy



802.11 – Roaming

• No or bad connection? Then perform:• Scanning

– scan the environment, i.e. listen into the medium for beacon signals or send probes into the medium and wait for an answer

=> time-consuming (scan all channels)• Association Request

– station sends a request to an AP• Association Response

– success: AP has answered, station can now participate– failure: continue scanning

• AP accepts Reassociation Request– signal the new station to the distribution system– the distribution system updates its data base (i.e. location information)– the distribution system may inform the old AP so it can release resources– 802.11f standard (IAPP – Inter AccessPoint Protocol)



WLAN: IEEE 802.11b

•Data rate– 1, 2, 5.5, 11 Mbit/s, depending

on SNR – User data rate max. approx. 6

Mbit/s•Transmission range

– 300m outdoor, 30m indoor– Max. data rate ~10m indoor

•Frequency– Free 2.4 GHz ISM-band

•Security– Limited, WEP insecure, SSID

•Cost– 25€ adapter, 100€ base station

•Availability– Many products, many vendors

•Connection set-up time– Connectionless/always on

•Quality of Service– Typ. best effort, no guarantees

(unless polling is used, limited support in products)

•Manageability– Limited (no automated key

distribution, sym. encryption)•Advantages/Disadvantages

– Advantage: many installed systems, lot of experience, available worldwide, free ISM band, many vendors, integrated in laptops, simple system

– Disadvantage: heavy interference on ISM band, no service guarantees, slow relative speed only



IEEE 802.11b – PHY Frame Formats

synchronization SFD signal service HEC payload


128 16 8 8 16 variable bitslength

16

192 µs at 1 Mbit/s DBPSK 1, 2, 5.5 or 11 Mbit/s

short synch. SFD signal service HEC payload

PLCP preamble(1 Mbit/s, DBPSK)

PLCP header(2 Mbit/s, DQPSK)

56 16 8 8 16 variable bitslength

16

96 µs 2, 5.5 or 11 Mbit/s

Long PLCP PPDU format 8 (corresponds to 802.11)

Short PLCP PPDU format (optional)



Channel Selection (Non-overlapping)

2400[MHz]

2412 2483.52442 2472

channel 1 channel 7 channel 13

Europe (ETSI)

US (FCC)/Canada (IC)

2400[MHz]

2412 2483.52437 2462

channel 1 channel 6 channel 11

22 MHz

22 MHz



WLAN: IEEE 802.11g

•Data rate– 6, 9, 12, 18, 24, 36, 48, 54

Mbit/s, depending on SNR– User throughput (1500 byte

packets): 5.3 (6), 18 (24), 24 (36), 32 (54)

– 6, 12, 24 Mbit/s mandatory•Transmission range

– 150m outdoor, 20m indoor54 Mbit/s up to 6 m

•Frequency– 2.412~2.472GHz (Europe ETSI)– 2.457~2.462GHz (Spain)– 2.457~2.472GHz (France)

•Security– Limited, WEP insecure, SSID

•Cost– 50€ adapter, 200€ base station

•Availability– Some products, some vendors


•Quality of Service– Typ. best effort, no guarantees

(same as all 802.11 products)•Manageability

– Limited (no automated key distribution, sym. encryption)

•Advantages/Disadvantages– Advantage: free ISM band,

compatible with 802.11b standard

– Disadvantage: heavy interference on ISM band, no service guarantees



WLAN: IEEE 802.11a

•Data rate– 6, 9, 12, 18, 24, 36, 48, 54 Mbit/s,

depending on SNR– User throughput (1500 byte packets):

5.3 (6), 18 (24), 24 (36), 32 (54) – 6, 12, 24 Mbit/s mandatory

•Transmission range– 100m outdoor, 10m indoor

e.g. 54 Mbit/s up to 5 m, 48 up to 12 m, 36 up to 25 m, 24 up to 30m, 18 up to 40 m, 12 up to 60 m

•Frequency– Free 5.15-5.25, 5.25-5.35, 5.725-

5.825 GHz ISM-band•Security

– Limited, WEP insecure, SSID•Cost

– 100€ adapter, 200€ base station•Availability

– Some products, some vendors


•Quality of Service– Typ. best effort, no guarantees (same

as all 802.11 products)•Manageability

– Limited (no automated key distribution, sym. encryption)

•Advantages/Disadvantages– Advantage: fits into 802.x standards,

free ISM band, available, simple system, uses less crowded 5 GHz band

– Disadvantage: stronger shading due to higher frequency, no service guarantees



WLAN: IEEE 802.11h – Regulatory Details

• Spectrum Managed 802.11a – power control– dyn. channel/frequency selection

• 4 frequency bands:

5.150 - 5.250 GHz – 4 usable channels (100 MHz)– indoor only – max. 30mW EIRP (.11a)– TPC (Transmit Power Control) max.

60mW EIRP– combined TPC and DCS/DFS

(Dynamic Channel/Frequency Selection) max. 200mW EIRP

– Turbo Mode: combination of two carriers to reach 108 Mbps

5.250 - 5.350 GHz – 4 usable channels– TPC, DCS/DFS mandatory

5.470 – 5.725 GHz – indoor and outdoor– max. 1W EIRP– disallowed in US– not supported by all chipsets

5.725 bis 5.825 GHz – disallowed in Germany


EIRP (Equivalent Isotropic Radiated Power)

Usage in Germany according to the German Federal Regulation (Vorschrift der Regulierungsbehörde für das Telekommunikations- und Postwesen, RegTP, 35/2002)


IEEE 802.11a – PHY Frame Format

rate service payload

variable bits

6 Mbit/s

PLCP preamble signal data

symbols12 1 variable

reserved length tailparity tail pad

616611214 variable

6, 9, 12, 18, 24, 36, 48, 54 Mbit/s

PLCP header



Operating Channels for 802.11a / US U-NII

5150 [MHz]5180 53505200

36 44

16.6 MHz

center frequency = 5000 + 5*channel number [MHz]

channel40 48 52 56 60 64

149 153 157 161

5220 5240 5260 5280 5300 5320

5725 [MHz]5745 58255765

16.6 MHz

channel

5785 5805



OFDM in IEEE 802.11a (and HiperLAN2)

• OFDM with 52 used subcarriers (64 in total) 48 data + 4 pilot (plus 12 virtual subcarriers) 312.5 kHz spacing

channel center frequency

subcarriernumber

1 7 21 26-26 -21 -7 -1

312.5 kHzpilot



IEEE 802.11a/b/g Data Rate

Barker: 11-bits Barker coding sequence (DPSK/DQPSK modulation, fixed code) CCK: Complementary Code Keying (DPSK/DQPSK modulation, switching of the spreadingsequence)PBCC: Packet Binary Convolutional Code (8PSK, complex version of CCK))OFDM: Orthogonal Frequency Division Multiplexing (BPSK, QPSK, 16QAM, 64QAM) Advanced Networking (MSCSP)


WLAN: IEEE 802.11 – Extensions and developments (05/2007)

• 802.11d: Regulatory Domain Update – completed• 802.11e: MAC Enhancements – QoS – completed

– Enhance the current 802.11 MAC to expand support for applications with Quality of Service requirements, and in the capabilities and efficiency of the protocol

• 802.11f: Inter-Access Point Protocol (IAPP) – withdrawn 2006– Establish an Inter-Access Point Protocol for data exchange via the distribution

system• 802.11h: Spectrum Managed 802.11a (DCS, TPC) – completed • 802.11i: Enhanced Security Mechanisms – completed

– Enhance the current 802.11 MAC to provide improvements in security• 802.11j: MAC and PHY Specifications for Operation in 4.9-5 GHz Band in

Japan – completed• 802.11n: Throughput enhancement to 108-320 Mbps – draft

• Study Groups– 5 GHz (harmonization ETSI/IEEE) – closed – Radio Resource Measurements – started– High Throughput – started

• See http://standards.ieee.org/getieee802/802.11.html for an update



WLAN: IEEE 802.11 – Details

802.11d aims to produce versions of 802.11b that work at other frequencies, making it suitable for parts of the world where the 2.4GHz band isn't available. Most countries have now released this band, thanks to an ITU recommendation and extensive lobbying by equipment manufacturers. The only holdout is Spain, which may follow soon.

802.11e add QoS capabilities to 802.11 networks. It replaces the Ethernet-like MAC layer with a coordinated Time Division Multiple Access (TDMA) scheme, and adds extra error-correction to important traffic. The technology is similar to Whitecap, a proprietary protocol developed by Sharewave and used in Cisco's 802.11a prototypes. A standard was supposed to be finalized by the end of 2001, but has run into delays thanks to arguments over how many classes of service should be provided and exactly how they should be implemented.

802.11f tries to improve the handover mechanism in 802.11 so that users can maintain a connection while roaming between two different switched segments (radio channels), or between access points attached to two different networks. This is vital if wireless LANs are to offer the same mobility that cell phone users take for granted.

802.11h attempts to add better control over transmission power and radio channel selection to 802.11a. Along with 802.11e, this could make the standard acceptable to European regulators.

802.11i deals with 802.11's most obvious weakness: security. Rather than WEP, this is an entirely new standard based on the Advanced Encryption Standard (AES), the U.S. government's "official" encryption algorithm.



WLAN: IEEE 802.11 – More Details

• IEEE 802.11 - THE WLAN STANDARD was original 1 Mbit/s and 2 Mb/s, 2.4 GHz RF and IR standard (1997), all the others listed below are Amendments to this standard, except for Recommended Practices 802.11F and 802.11T.

• IEEE 802.11a - 54 Mbit/s, 5 GHz standard (1999, shipping products in 2001) • IEEE 802.11b - Enhancements to 802.11 to support 5.5 and 11 Mb/s (1999) • IEEE 802.11c - Bridge operation procedures; included in the IEEE 802.1D standard (2001) • IEEE 802.11d - International (country-to-country) roaming extensions (2001) • IEEE 802.11e - Enhancements: QoS, including packet bursting (2005) • IEEE 802.11F - Inter-Access Point Protocol (2003) Withdrawn February 2006 • IEEE 802.11g - 54 Mb/s, 2.4 GHz standard (backwards compatible with b) (2003) • IEEE 802.11h - Spectrum Managed 802.11a (5 GHz) for European compatibility (2004) • IEEE 802.11i - Enhanced security (2004) • IEEE 802.11j - Extensions for Japan (2004) • IEEE 802.11k - Radio resource measurement enhancements (proposed - 2007?) • IEEE 802.11m - Maintenance of the standard; odds and ends. (ongoing) • IEEE 802.11n - Higher throughput improvements using MIMO (multiple input, multiple output

antennas) (pre-draft - 2009?) • IEEE 802.11p - WAVE - Wireless Access for the Vehicular Environment (such as ambulances and

passenger cars) (working - 2009?) • IEEE 802.11r - Fast roaming Working "Task Group r" - 2007? • IEEE 802.11s - ESS Extended Service Set Mesh Networking (working - 2008?) • IEEE 802.11T - Wireless Performance Prediction (WPP) - test methods and metrics Recommendation

(working - 2008?) • IEEE 802.11u - Interworking with non-802 networks (for example, cellular) (proposal evaluation - ?) • IEEE 802.11v - Wireless network management (early proposal stages - ?) • IEEE 802.11w - Protected Management Frames (early proposal stages - 2008?) • IEEE 802.11y - 3650-3700 Operation in the U.S. (early proposal stages - ?)



Reference

• Books on 802.11: Franz-Joachim Kauffels: Wireless LANs: Drahtlose Netze planen und verwirklichen, der Standard

IEEE 802.11 im Detail, WLAN-Design und Sicherheitsrichtlinien. 1. Aufl., mitp-Verl., Bonn, 2002 Frank Ohrtman: WiFi-Handbook – Building 802.11b wireless networks. McGraw-Hill, 2003 Jochen Schiller: Mobile Communications (German and English), Kap 7.3, Addison-Wesley, 2002

• Details on 802.11e: Anders Lindgren, Andreas Almquist, Olov Schelén. Quality of service schemes for IEEE 802.11

wireless LANs: an evaluation. Mobile Networks and Applications, Volume 8 Issue 3, June 2003 Daqing Gu; Jinyun Zhang. QoS enhancement in IEEE 802.11 wireless local area networks.

Communications Magazine, IEEE , Volume: 41 Issue: 6, June 2003 Qiu Qiang; Jacob, L., Radhakrishna Pillai, R., Prabhakaran, B.. MAC protocol enhancements for QoS

guarantee and fairness over the IEEE 802.11 wireless LANs. 11th Intl. Conf. on Computer Communications and Networks, Oct. 2002

Mangold S, Choi S, May P, Klein O, Hiertz G, and Stibor L. IEEE 802.11e wireless LAN for quality of service. Proc. Of European Wireless (EW2002), Feb. 2002

• Web Links:• The IEEE 802.11 Wireless LAN Standards• http://standards.ieee.org/getieee802/802.11.html

• Introduction to the IEEE 802.11 Wireless LAN Standard• http://www.wlana.org/learn/80211.htm



Visitors address:Technische Universität IlmenauGustav-Kirchhoff-Str. 1 (Informatikgebäude, Room 210)D-98693 Ilmenau

fon: +49 (0)3677 69 2819 (2788)fax: +49 (0)3677 69 1226e-mail: [email protected]

[email protected]

www.tu-ilmenau.de/ics


Univ.-Prof. Dr.-Ing. Andreas Mitschele-ThielDr. rer. nat. habil. Oliver Waldhorst

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