Transcript Slide 1

IT351: Mobile & Wireless Computing
Wireless Local Area Networks (WLAN)
Part-1: IEEE802.11
Objectives:
– To provide a detailed study of the WLAN architecture and system operation
Outline
• Wireless LAN main uses, advantages, disadvantages
• Classification of transmission technologies for WLAN
• Classification of WLAN IEEE802.11
– Infrastructure networks
– Ad Hoc networks
• WLAN IEEE802.11
–
–
–
–
–
–
Architecture
Protocols
Physical layer
MAC layer
MAC management
IEEE802.11-a/ b/... n
Overview of the main chapters
Chapter 10:
Support for Mobility
Chapter 9:
Mobile Transport Layer
Chapter 8:
Mobile Network Layer
Chapter 4:
Telecommunication
Systems
Chapter 5:
Satellite
Systems
Chapter 6:
Broadcast
Systems
Chapter 3:
Medium Access Control
Chapter 2:
Wireless Transmission
Chapter 7:
Wireless
LAN
Mobile Communication Technology according to
IEEE
WiFi
Local wireless networks
WLAN 802.11
802.11a
802.11h
802.11i/e/…/n/…/z/aa
802.11b
802.11g
ZigBee
Personal wireless nw
WPAN 802.15
802.15.4
802.15.2
802.15.4a/b/c/d/e/f/g
802.15.5, .6 (WBAN)
802.15.3
802.15.1
Bluetooth
Wireless distribution networks
WMAN 802.16 (Broadband Wireless Access)
WiMAX
+ Mobility
[802.20 (Mobile Broadband Wireless Access)]
802.16e (addition to .16 for mobile devices)
802.15.3b/c
Wireless LAN (WLAN)
• Main uses:
– Extension to existing
LAN
– Cross building
interconnect
– Nomadic access /
‘wireless hotspots’
– Ad Hoc networks
IBSS
BSS1
Distribution System
BSS2
BSS3
• Main Standard is IEEE
802.11
• Wireless extension for
Ethernet
• Wi-Fi, Wireless-Fidelity,
Alliance to certify
products to the IEEE
standard
BSS4
ESS
Characteristics of wireless LANs
• Advantages
– very flexible within the reception area,
– allow for design of small independent devices (e.g. to be put in
pockets)
– Ad-hoc networks without previous planning possible
– (almost) no wiring difficulties (e.g. historic buildings, firewalls)
– more robust against disasters like, e.g., earthquakes, fire - or
users pulling a plug...
– Cost is independent of the number of users
Characteristics of wireless LANs
• Disadvantages
– typically very low bandwidth compared to wired
networks (1-10 Mbit/s) due to shared medium
– high error rates, low quality
– many proprietary solutions, especially for higher bitrates, standards take their time (e.g. IEEE 802.11n)
– products have to follow many national restrictions if
working wireless, it takes a very long time to establish
global solutions
– Safety & security
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 (plug & play)
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
• …
Classifications of transmission technologies:
infrared vs. radio transmission
•
Infrared
– At 900 nm wavelength, uses IR
diodes, diffuse light, multiple
reflections (walls, furniture etc.)
•
•
– typically using the license free
ISM band at 2.4 GHz
•
Disadvantages
– interference by sunlight, heat
sources etc.
– many things shield or absorb IR
light , can not penetrate objects
– low bandwidth (115kbps – 4 Mbps
•
Example
– IrDA (Infrared Data Association)
interface available everywhere
Advantages
– experience from wireless WAN
and mobile phones can be
used
– coverage of larger areas
possible (radio can penetrate
walls, furniture etc.)
Advantages
– simple, cheap, available in many
mobile devices
– no licenses needed
– simple shielding possible
•
Radio
•
Disadvantages
– very limited license free
frequency bands
– shielding more difficult,
interference with other
electrical devices
•
Example
– Many different products
IEEE802.x standards
• 802 standards specify OSI layers 1 & 2
– Physical layer
• Encoding/decoding signals
• Preamble (for synchronization)
• Bit transmission/reception
– Link layer (Medium Access Control (MAC))
•
•
•
•
Manage access to media
Assemble/disassemble frames
Addressing and error detection
Interface with higher layers
ISM Unlicensed Frequency Bands
IEEE 802.11 WLAN
– 802.11 (Legacy, 1997) operates at 1-2
Mbps, with 3 methods
•
•
1 infrared
2 radio access (FHSS, DSSS)
– 802.11a (1999) operates at 54Mbps
(5GHz Freq. Band)
– 802.11b (Wi-Fi 1999) operates at
11Mbps (2.4GHz ISM Freq. Band 2.400 – 2.4835 GHz)
– 802.11g (2003) operates at 54Mbps
(2.4GHz Freq. Band)
– 802.11n (Oct 2009) operates at 540 M
bps (typically 200Mbps) (2.4GHz or
5GHz Freq. Band)
Wireless Communications and Networks, W. Stallings, Prentice Hall, N.J., 2001.
•
Two Modes:
– Infrastructure Mode (LAN
extension)
– Ad Hoc (wireless only)
Classifications of IEEE802.11:
infrastructure vs. ad-hoc networks
infrastructure
network
AP
AP
ad-hoc network
wired network
AP: Access Point
AP
802.11 - System architecture
infrastructure network
•
802.11 LAN
STA1
– terminal with access mechanisms to
the wireless medium and radio
contact to the access point
802.x LAN
•
Portal
•
ESS
•
802.11 LAN
Portal
– bridge to other (wired) networks
•
BSS2
STA2
Access Point
– station integrated into the wireless
LAN and the distribution system
Distribution System
Access
Point
Basic Service Set (BSS)
– group of stations using the same
radio frequency
BSS1
Access
Point
Station (STA)
STA3
Distribution System
– interconnection network to form one
logical network (ESS: Extended
Service Set) based on several BSS
– Each ESS has its own identifier
ESSID
IEEE802.11: System architecture
infrastructure network
• The distribution system is not specified in IEEE802.11.
– It could consist of IEEE LANs, wireless links or any other
networks
– It handles data transfer between different APs
– To participate in a WLAN, you need to know the ESSID
• Stations can select an AP and associate with it
– The AP supports roaming (changing access points)
– APs provide synchronization within a BSS, support
power management, and can control medium access
802.11 – System architecture
Ad-hoc network
• Direct communication within a
limited range
802.11 LAN
– Station (STA):
terminal with access
mechanisms to the wireless
medium
– Independent Basic Service Set
(IBSS):
group of stations using the same
radio frequency
– No specific node for data routing,
or forwarding or exchange of
topology information
STA1
STA3
IBSS1
STA2
IBSS2
STA5
STA4
802.11 LAN
IEEE802.11: Protocol architecture
fixed
terminal
mobile terminal
infrastructure
network
access point
application
application
TCP
TCP
IP
IP
LLC
LLC
LLC
802.11 MAC
802.11 MAC 802.3 MAC
802.3 MAC
802.11 PHY
802.11 PHY
802.3 PHY
802.3 PHY
802.11 – Protocol Architecture
• MAC
• PLCP Physical Layer Convergence Protocol
– access mechanisms,
fragmentation, encryption
– clear channel assessment signal
(carrier sense)
– Service access point (SAP)
• MAC Management
LLC
MAC
MAC Management
PLCP
PHY Management
PMD
• PMD Physical Medium Dependent
– modulation, coding
• PHY Management
– channel selection, MIB maintenance
• Station Management
Station Management
PHY
DLC
– Association/de-association,
synchronization, roaming, MIB
(management Information Base),
power management to save
battery power, authentication
mechanism
– coordination of all management
functions, higher layer functions
(interaction with distribution system)
802.11 - Physical layer (legacy)
• 3 versions: 2 radio (typ. 2.4 GHz ISM), 1 IR
– data rates 1 or 2 Mbit/s
• All physical variants include the provision of the clear channel
assessment (CCA). This is needed for MAC mechanisms.
• The Physical layer a service access point (SAP) with 1 or 2
Mbits/s transfer rate to the MAC layer.
• FHSS (Frequency Hopping Spread Spectrum)
– spreading, despreading using different hopping sequences (79
hopping channels for North America and Europe)
– Frequency Shift Keying (FSK) digital modulation
802.11 - Physical layer (legacy)
• DSSS (Direct Sequence Spread Spectrum)
– Spreading, despreading using 11-chip Barker code
chipping sequence: +1, -1, +1, +1, -1, +1, +1, +1, -1, -1, -1
– Phase Shift Keying (PSK) digital modulation
– max. radiated power 1 W (USA), 100 mW (EU), min. 1mW
– Robust against interference and multipath propagation
– More complex compared to FHSS
• Infrared
– 850-950 nm, diffuse light, typ. 10 m range
– Typically in buildings (classrooms, meeting rooms,..)
– Frequency reuse is simple, a wall is enough for shielding
802.11 - MAC layer - DFWMAC
• The MAC mechanisms are called Distributed Foundation
Wireless Medium Access Control (DFWMAC)
• Functions: medium access, support for roaming,
authentication and power conservation
• Traffic services
– Asynchronous Data Service (mandatory)
• exchange of data packets based on “best-effort” – no delay
bounds
• support of broadcast and multicast
• Implemented using distributed coordination function (DCF)
OR Point Coordination Function (PCF)
• For both infrastructure and ad Hoc
– Time-Bounded Service (optional)
• implemented using PCF (Point Coordination Function)
• Provides delay guarantees
• For infrastructure 802.11 only
MAC Layer
• Asynchronous Data Service access method
– DFWMAC-DCF CSMA/CA (mandatory)
• collision avoidance via randomized „back-off“
mechanism
• minimum distance between consecutive packets
• ACK packet for acknowledgements (not for broadcasts)
– DFWMAC-DCF w/ RTS/CTS (optional)
• avoids hidden terminal problem
– DFWMAC-PCF (optional)
• Time-bounded Service access method
– DFWMAC- PCF (optional)
• access point polls terminals according to a list
802.11 - MAC layer
• Priorities
– defined through different inter frame spaces
– 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, Distributed Coordination Function IFS)
• lowest priority, for asynchronous data service
DIFS
DIFS
medium busy
PIFS
SIFS
direct access if
medium is free  DIFS
contention
next frame
t
802.11 - CSMA/CA access method I
• 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 a DCF Inter-Frame
Space (DIFS), the station can start sending
• 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)
DIFS
DIFS
medium busy
direct access if
medium is free  DIFS
contention window
(randomized back-off
mechanism)
next frame
t
slot time (20µs)
802.11 - competing stations - simple
version
DIFS
DIFS
DIFS
boe bor
station1
DIFS
boe bor
boebusy
boe busy
boebor
boe busy
boebor
boe busy
station2
busy
station3
station4
boe bor
station5
t
busy
medium not idle (frame, ack etc.)
boe elapsed backoff time
packet arrival at MAC
bor residual backoff time
802.11 – CSMA/CA
• The contention window (CW) size affect the
performance of the MAC scheme
• A small CW ensures shorter access delay but the
probability of collision increases (more than one
station can have the same backoff time)
• The contention window starts with a minimum value
then doubles each time a collision occurs up to a
maximum value (e.g. 7, 15, 31,63, 127, 255).
• This is called the exponential backoff algorithm
(already used in CSMA/CD)
802.11 - CSMA/CA
• 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 (The sender has to compete again)
DIFS
sender
data
SIFS
receiver
ACK
DIFS
other
stations
waiting time
data
t
contention
802.11 – DFWMAC with RTS/CTS (method II)
• Sending unicast packets
– To solve the problem of hidden terminal
– 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 in the
NAV (net allocation vector)
DIFS
sender
RTS
data
SIFS
receiver
CTS SIFS
SIFS
DIFS
NAV (RTS)
other
stations
ACK
NAV (CTS)
defer access
data
t
contention
802.11 – DFWMAC with RTS/CTS (cont.)
• The scheme reserves the medium for one user (virtual
reservation scheme)
• RTS/CTS can result in a non-negligible overhead causing a
waste of bandwidth and higher delay
• A threshold based on frame size can be used to determine
when to use the additional mechanism and when to disable it
• To reduce the bit error-rates in transmission, fragmentation can
be used. However, for RTS/CTS scheme all fragments are sent
by one RTS. Each fragment reserve the medium for the next
fragment.
CTS/RTS with Fragmentation
DIFS
sender
RTS
frag1
SIFS
receiver
CTSSIFS
frag2
SIFS
ACK SIFS
SIFS
1
ACK2
NAV (RTS)
NAV (CTS)
other
stations
DIFS
NAV (frag1)
NAV (ACK1)
contention
data
t
DFWMAC-PCF with polling – Method III
(almost never used)
• The two previous methods cannot guarantee a maximum delay
or minimum bandwidth
• PCF provides time-bounded service
• It requires an access point that control medium access and
polls the single nodes
• Ad Hoc network can’t use this function so it provides only besteffort service
• The point coordinator in the access point splits the access time
into super frame periods.
• A super frame comprises an contention-free period and a
contention period
• If only PCF is used and polling is distributed evenly, the
bandwidth is also distributed evenly – static centrally controlled
TDMA with TDD transmission
• Much overhead if nodes have nothing to send.
DFWMAC-PCF (cont.)
t0 t1
SuperFrame
medium busy PIFS
point
coordinator
D1
SIFS
D2
SIFS
SIFS
U1
wireless
stations
stations‘
NAV
SIFS
U2
NAV
t2
point
coordinator
D3
SIFS
D4
t4
CFend
SIFS
U4
wireless
stations
stations‘
NAV
PIFS
t3
NAV
contention free period
contention
period
t
802.11 - Frame format
• Types: control frames, management frames, data frames
• Sequence numbers
– important against duplicated frames due to lost ACKs
• Addresses
– receiver, transmitter (physical), BSS identifier, sender/receiver
(logical)
• Miscellaneous
– Duration (to set the NAV), checksum, frame control, data
bytes
2
Frame
Control
bits
2
2
6
6
6
2
6
0-2312
Duration/ Address Address Address Sequence Address
Data
ID
1
2
3
Control
4
2
4
1
Protocol
To
Type Subtype
version
DS
1
1
From More
DS Frag
1
Retry
1
1
1
1
Power More
WEP Order
Mgmt Data
4
CRC
802.11 - Frame format
• Frame Control
– Protocol version: 2 bits
– Type (management 00, control 01, data 10)
– Subtype (e.g. Management- association 0000, beacon 100
Control – RTS 1011, CTS 1100)
– More fragments: 1 if another fragment to follow
– Retry: 1 if retransmission of an earlier frame
– Power Management: 1 if the station will go to power save mode
– More Data: A sender has more data to send
– Wired Equivalent Privacy (WEP): Standard security mechanism applied
– Order: frame must be processed in strict order
bytes
2
Frame
Control
bits
2
2
6
6
6
2
6
0-2312
Duration/ Address Address Address Sequence Address
Data
ID
1
2
3
Control
4
2
4
1
Protocol
To
Type Subtype
version
DS
1
1
From More
DS Frag
1
Retry
1
1
1
1
Power More
WEP Order
Mgmt Data
4
CRC
MAC address format
scenario
ad-hoc network
infrastructure
network, from AP
infrastructure
network, to AP
infrastructure
network, within DS
to DS from
DS
0
0
0
1
address 1 address 2 address 3 address 4
DA
DA
SA
BSSID
BSSID
SA
-
1
0
BSSID
SA
DA
-
1
1
RA
TA
DA
SA
DS: Distribution System
AP: Access Point
DA: Destination Address
SA: Source Address
BSSID: Basic Service Set Identifier
RA: Receiver Address
TA: Transmitter Address
802.11 - MAC management
MAC management plays a central role in an IEEE802.11 as
it controls all the functions related to system integration,
i.e., integration of a wireless station into a BSS,
formation of an ESS, synchronization of stations,..etc
The major functions are:
• Synchronization
– try to find a WLAN and stay within it
– synchronization of internal clock (timing synchronization
function (TSF)
• For power management
• For coordination of PCF (super frame)
• For synchronization of hopping sequence in FHSS systems
– Generation of beacon signals
802.11 - MAC management (cont.)
• Power management
– To control transmitter activity for power conservation
– sleep-mode without missing a frame
– periodic sleep, frame buffering, traffic measurements
• Association/Re-association
– integration into a WLAN
– roaming, i.e. change networks by changing access
points
– scanning, i.e. active search for a network
• MIB - Management Information Base
– managing, read, write, update
Synchronization using a Beacon (infrastructure)
• Within a BSS, timing is conveyed by the periodic transmission of a
beacon frame
• A beacon contains a timestamp and other management information
(identification of BSS, power management, roaming)
• In infrastructure-based networks, the beacon is sent by the access point
periodically. However, it may be delayed if medium is busy, but beacon
interval is not shifted if one beacon is delayed.
• The time stamp is used by a node to adjust its local clock
beacon interval
(20ms – 1s)
access
point
medium
B
B
busy
busy
B
busy
B
busy
t
value of the timestamp
B beacon frame
Synchronization using a Beacon (ad-hoc)
• Each node maintains its own timer and starts transmission of
a beacon frame after the beacon interval
• Using random backoff algorithm, one beacon only wins
• All other stations adjust their internal clock according to the
received beacon
beacon interval
station1
B1
B1
B2
station2
medium
busy
busy
B2
busy
busy
t
value of the timestamp
B beacon frame
random delay
Power management
• Power-saving mechanisms are crucial for wireless
devices
• Standard WLAN protocols assume that stations are
always ready to receive data. This permanent
readiness consumes much power
• Idea: switch the transceiver off if not needed
• States of a station: sleep and awake
• Timing Synchronization Function (TSF)
– stations wake up periodically at the same time
• Buffering of data at senders
• Senders announce destination during wake periods
• Longer off periods save battery life but reduce
average throughput and increase delay
Power Management
• Infrastructure
– Access point buffers all frames destined for stations operating in powersave mode
– With every beacon sent, a Traffic Indication Map (TIM) is transmitted
• TIM contains a list of unicast receivers transmitted by AP
• Beacon interval = TIM interval
– Additionally, the AP maintains a Delivery Traffic Indication Map (DTIM)
• list of broadcast/multicast receivers transmitted by AP
• DTIM interval = multiple of TIM interval
– The TSF assures that sleeping stations will wake-up periodically and
listen to the beacon and TIM
– If TIM indicates a unicast frame buffered for a station, the station stay
awake to receive it
– Stations always stay awake for muti-cast/ broadcast transmission
– Stations also wake-up when they have frames to be transmitted
Power saving with wake-up patterns
(infrastructure)
TIM interval
access
point
medium
DTIM interval
D B
T
busy
busy
T
d
D B
busy
busy
p
station
d
t
T TIM
D DTIM
B broadcast/multicast
awake
p PS poll
d data transmission
to/from the station
Power saving with wake-up pattern
(Ad hoc)
• 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?)
• APSD (Automatic Power Save Delivery)
– new method in 802.11e replacing above schemes
802.11 - Roaming
• No or bad connection? Then perform:
• Scanning
– scan the environment,
• Passive scanning: listen into the medium for beacon signals
• Active scanning: send probes into the medium and wait for an answer
• Reassociation Request
– Choose best AP (e.g. based on signal strength)
– station sends a request to one or several AP(s)
• Reassociation 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)
– typically, the distribution system now informs the old AP so it can
release resources
• Fast roaming – 802.11r
– e.g. for vehicle-to-roadside networks
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
– DSSS, 2.4 GHz ISM-band
• Security
– Limited, WEP insecure, SSID
(service set identifier)
• 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)
•
Special 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
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
•
– Connectionless/always on
•
•
Frequency
– Free 5.15-5.25, 5.25-5.35, 5.7255.825 GHz ISM-band
•
Security
– Limited, WEP insecure, SSID
•
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)
– 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
Connection set-up time
•
Special 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 QoS
WLAN: IEEE 802.11– current developments
•
802.11j: Extensions for operations in Japan
–
•
802.11-2007: Current “complete” standard
–
•
Changes of PHY and MAC with the goal of 100Mbit/s at MAC SAP
MIMO antennas (Multiple Input Multiple Output), up to 600Mbit/s are currently feasible
However, still a large overhead due to protocol headers and inefficient mechanisms
802.11p: Inter car communications
–
–
–
•
Devices and access points should be able to estimate channel quality in order to be able to
choose a better access point of channel
802.11m: Updates of the 802.11-2007 standard
802.11n: Higher data rates above 100Mbit/s
–
–
–
•
Comprises amendments a, b, d, e, g, h, i, j
802.11k: Methods for channel measurements
–
•
•
Changes of 802.11a for operation at 5GHz in Japan using only half the channel width at larger
range
Communication between cars/road side and cars/cars
Planned for relative speeds of min. 200km/h and ranges over 1000m
Usage of 5.850-5.925GHz band in North America
802.11r: Faster Handover between BSS
–
–
–
Secure, fast handover of a station from one AP to another within an ESS
Current mechanisms (even newer standards like 802.11i) plus incompatible devices from
different vendors are massive problems for the use of, e.g., VoIP in WLANs
Handover should be feasible within 50ms in order to support multimedia applications efficiently
WLAN: IEEE 802.11– current developments
•
802.11s: Mesh Networking
•
802.11T: Performance evaluation of 802.11 networks
•
•
802.11u: Interworking with additional external networks
802.11v: Network management
•
802.11w: Securing of network control
•
•
•
•
•
802.11y: Extensions for the 3650-3700 MHz band in the USA
802.11z: Extension to direct link setup
802.11aa: Robust audio/video stream transport
802.11ac: Very High Throughput <6Ghz
802.11ad: Very High Throughput in 60 GHz
•
Note: Not all “standards” will end in products, many ideas get stuck at working
group level
Info: www.ieee802.org/11/, 802wirelessworld.com,
standards.ieee.org/getieee802/
•
– Design of a self-configuring Wireless Distribution System (WDS) based on 802.11
– Support of point-to-point and broadcast communication across several hops
– Standardization of performance measurement schemes
– Extensions of current management functions, channel measurements
– Definition of a unified interface
– Classical standards like 802.11, but also 802.11i protect only data frames, not the
control frames. Thus, this standard should extend 802.11i in a way that, e.g., no
control frames can be forged.