Chapter 7: Wireless LAN. What is Wireless LAN? Wireless local area network (LAN) is a local area...

Chapter 7:Wireless LAN

What is Wireless LAN?

Wireless local area network (LAN) is a local area data network without wires.Wireless LAN is also known as WLAN in short.WLAN is a high-speed data networking technology that is being widely deployed in residential network, enterprises, and public areas around the world.A WLAN creates extensions to cabling LAN and reduces the need for wireless connections.It transmits and receives data over electromagnetic waves using radio frequency (RF).

What is Wireless LAN?

With it advantage and lack of wiring, mobile WLAN users can access real-time information and network resources easily.The WLAN ranges approximately 100 meters and is often used in building and on campuses.In short WLAN is a flexible data communication system providing wireless peer-to-peer and point-to-point connectivity within a building or campus.For that different types of technologies used for that which are show in the next slide figure.

Mobile Communication Technology according to IEEE (examples)

Local wireless networksWLAN 802.11

802.11a

802.11b

802.11i/e/…/n/…/z/aa

802.11g

WiFi802.11h

Personal wireless nwWPAN 802.15

802.15.4

802.15.1802.15.2

Bluetooth

802.15.4a/b/c/d/e/f/gZigBee

802.15.3

Wireless distribution networksWMAN 802.16 (Broadband Wireless Access)

[802.20 (Mobile Broadband Wireless Access)]802.16e (addition to .16 for mobile devices)

+ Mobility

WiMAX

802.15.3b/c

802.15.5, .6 (WBAN)

Advantages of WLAN

Flexibility:Within radio coverage, node can communicate without further restriction.Radio waves can penetrate walls, sender and receivers can be placed anywhere.Sometimes wiring is difficult if firewalls separate building.Penetration of a firewall is only permitted at certain points to prevent fire from spreading too fast.

Advantages of WLAN

Planning:Only wireless ad-hoc networks allow for communication without previous planning any wired network needs wiring plans.As long as devices follow the same standard they can communicate.For wired network additional cabling with the right plugs and probably interworking unit have to be provided.

Advantages of WLAN

Design:Wireless networks allow for the design of small, independent devices which can for example be put into a pocket.Cables not only restrict users but also designers of small PDAs, notepads etc.Wireless senders and receivers can be hidden in historic buildings i.e., current networking technology can be introduced without being visible.

Advantages of WLAN

Robustness:Wireless network can survive disaster e.g., earthquakes or users pulling a plug.If the wireless devices survive, people can still communicate.Network requiring a wired infrastructure will usually break down completely.

Advantages of WLAN

Cost:After providing wireless access to the infrastructure via an access point for the first user, adding additional users to a wireless network will not increase the cost.This is, important for e.g. lecture halls, hotel lobbies or gate areas in airports where the numbers using the network may vary significantly.Using fixed network, each seat in a lecture hall should have a plug for the network although many of them might not be used permanently.Wireless connections do not wear out.

Disadvantages of WLAN

Quality of Service:WLANs typically offer lower quality than their wired counterparts.The main reasons for this are the lower bandwidth due to limitation in radio transmission, higher rates due to interference and higher delay/delay variation due to extensive error correction and detection mechanisms.


Proprietary solutions:Due to slow standardization procedures many companies have come up with proprietary solution offering standardized functionality plus many enhanced features.However, these additional features only work in a homogeneous environment i.e. when adapter from same vendors are used for all wireless nodes.At least most components today here to the basic standard IEEE 802.11b or 8.2.11a.


Restrictions:All wireless products have to comply with national regulations.Several government and non-government institutions world wide regulate the operation and restrict frequencies to minimize interference.WLAN are limited to low-power senders and certain license-free frequency bands, which are not the same worldwide.


Safety and Security:Using radio waves for data transmission might interfere with other high-tech equipment in e.g. hospitals.Senders and receivers are operated by laymen and radiation has to be low.Special precautions have to be taken to prevent safety hazards.The open radio interface makes eavesdropping much easier in WLANs than e.g. in the case of fiber optics.


Safety and Security:All standard must offer encryption, privacy mechanisms , support for anonymity etc.Otherwise more and more wireless networks will be hacked into as is the case already.

Design goals for wireless LANs

Global, Faultless 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

Design goals for wireless LANs

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

Types of Transmission TechnologiesToday two different basic transmission technologies can be sued to set up WLANs.Infra red light:This technology use diffuse light reflected at walls, furniture etc. or directed light if an line-of-sight (LOS) exists between sender and receiver.Infrared system are simple in design, therefore it is inexpensive.InfraLAN is an example of wireless LANs using infrared technology.

Types of Transmission TechnologiesRadio way:It is more popular and uses radio transmission in the GHz range.Almost all networks which are used any technology based on radio waves for data transmission.RF systems must used spread spectrum technology in the united states.This spread spectrum technology currently comes in two types : DSSS and FHSS.E.g. GSM at 900,1,800,1,900 MHz etc.

Comparison: infrared vs. radio transmission

Infrared Transmission Advantages

simple, cheap, available in many mobile devices

no licenses needed simple shielding possible

Radio Transmission Advantages

experience from wireless WLAN and mobile phones can be used

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

Comparison: infrared vs. radio transmission

Disadvantages interference by sunlight,

heat sources etc. low bandwidth

Example IrDA (Infrared Data

Association) interface available everywhere

Disadvantages very limited license free

frequency bands shielding more difficult,

interference with other electrical devices

Example Many different products

Modes of Wireless LAN

Wireless works in two different modes:Infrastructure:Ad-hoc Network:

Infrastructure

The infrastructure mode includes one or several interconnected WLAN-cell, which are connected to a fixed net through an access point.Wireless access points can be simply thought to function in a fashion analogous to Ethernet hub and switch are used to allow computers with wireless adapter to participate in a network.All device to device wireless communication goes through the WAP.This is referred to as infrastructure mode.Next slide figure shows actual concept of WLAN modes.

Ad-hoc NetworksThe ad-hoc mode is WLAN-cell interacting without connection to wired networks, i.e. without connection to an access point.However the ad hoc networks work much like the Bluetooth.No access point is needed and the devices might connect to the internet through wired or other wireless techniques.Simple computing device to computing device wireless networking can be accomplished by installing a wireless network adapter (sometimes called wireless NICs) in each device.This is referred to as ad-hoc mode.

Comparison: infrastructure vs. ad-hoc networksinfrastructure network

ad-hoc network

APAP

AP

wired network

AP: Access Point

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 (EES: Extended Service Set) based on several BSS

Distribution System

Portal

802.x LAN

Access Point

802.11 LAN

BSS2

802.11 LAN

BSS1

Access Point

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

802.11 Protocol Architecture

The 802.11 standards cover definitions for both MAC (medium access control) and Physical Layer.The standard currently defines a single MAC while interacts with three PHYs as follow:

Frequency Hopping Spread SpectrumDirect Sequence Spread SpectrumInfrared.

PHY layer one based on infrared and two layers based on radio transmission.

IEEE standard 802.11

mobile terminal

access point

fixedterminal

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

infrastructurenetwork

LLC LLC

IEEE 802.11 Sub layers Architecture and Management

PMD

PLCP

MAC

LLC

MAC Management

PHY Management

PH

YD

LC

Sta

tion

Man

agem

ent

Physical Layer Convergence Procedure (PLCP)Physical Medium Dependent (PMD):

802.11 Protocol Architecture:Physical Layer Architecture

The architecture of the Physical layer comprises of the two sub layers for each station:Physical Layer Convergence Procedure (PLCP):PLCP sub layer is responsible for the Carrier Sense (CS) part of the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol. PLCP layer prepares the MAC Protocol Data Unit (MPDU) for transmission.The PLCP also delivers the incoming frames from the wireless medium to the MAC layer.


PLCP appends fields to the MPDU that contains information needed by the physical layer transmitter and receiver.This frame is called PLCP Protocol Data Unit (PPDU).The structure of PLCP provides for asynchronous transfer of MPDU between stations.The PLCP header contains logical information that allows the receiving stations physical layer to synchronize with each individual incoming packet.


Physical Medium Dependent (PMD):The PMD provides the actual transmission and reception of physical layer entities between stations through the wireless media.This sub layer provides the modulation/demodulation of the transmission.


Frequency Hopping Spread Spectrum (FHSS):In FHSS mode this layer carries the clocking information to synchronize the receiver clock with the clock of the transmitted packet.Bellow figure depicts the FHSS PPDU packet.

synchronization SFD PLW PSF HEC payload

PLCP preamble PLCP header

80 16 12 4 16 variable bits


the fields in the FHSS PLCP are as follows:SYNC:This field is made up of alternate zeroes and ones.This bit pattern is to synchronize the clock of the receiver.Start Frame Delimiter (SFD):This field indicates the beginning of the frame and the content of this field is fixed and always is 0000110010111101.


PLCP Signaling (PSF):This field contains information about the data rate of the fields form whitened PSDU.The PLCP preamble is always transmitted at 1Mbps irrespective of the data rate of the wireless LAN.This field contains information about the speed of the link.For example 0000 means 1 Mbps and 0111 signifies 4.5 Mbps bandwidth.


PSDU Length Word (PLW):This field specifies the length of the PSDU in octets.Header Error Check (HEC):This field contains the CRC (Cyclic Redundancy Check) according to CCITT CRC-16 algorithm.


FHSS PMD is responsible for converting the binary bit sequence into analog signal and transmit the PPDU frame into the air.FHSS PDM does this using the frequency hopping technique.The 802.11 standard defines a set of channels within the ISM band for frequency hopping.Once the hopping sequence is set in the access point, stations automatically synchronize to the correct hopping sequence.


Direct Sequence Spread Spectrum (DSSS):DSSS PLCP is responsible for synchronizing and receiving the data bits correctly.Bellow show a figure depicts the DSSS PPDU packet.

synchronization SFD signal service HEC payload



length

16


The fields in the DSSS PLCP are as following:SYNC:This field is made up of alternate zeroes and ones.This bit pattern is to synchronize the clock of the receiver with the received frame.Start Frame Delimiter (SFD):This field indicates the beginning of the frame and the content of this field is fixed and is always 1111001110100000.


Signal:This field defines the type of modulation the receiver must use to demodulate the signal.When the value of this field is multiplied by 100 Kbps, we get the bandwidth of the transmission,The PLCP preamble and the header are always transmitted at 1 Mbps.The bandwidth defined by this field applies to MPDU field.Service:This field is not used and is usually 0.


Length:This field contains an unsigned 16-bit integer indicating the length of the frame.However, unlike the FHSS this is not in octets.It is rather in microseconds.The receiver will use this to synchronize with the clock to determine the end of frame.Frame Check Sequence:This is a 16-bit checksum based on CCITT CRC-16 algorithm.


DSSS PMD translates the binary digital sequence into analog radio signals and transmits the PPDU frame into the air.DSSS physical layer operates within the ISM band.If we take the 2.4 GHz band then it is between 2.4 GHz and 2.8435 GHz frequency band divided into multiple channels with 22 MHz width.


Infrared:The PHY layer, which is based on infra red (IR) transmission, uses near visible light at 850-950 nm.The standard to require a line-of-sight between sender and receiver.This allows for point-to-multipoint communication.The maximum range is about 10 m if no sunlight or hear source interfere with the transmission,Typically, such a network will only work in buildings, e.g. classrooms, meeting room etc.Today no products are available that offer infra red communication based on 802.11.

802.11 Protocol Architecture:MAC Layer Architecture

The MAC layer has to fulfill several tasks.First of all it has to control medium access, but it can also offer support for roaming, authentication and power conservation.Two basic services provided by the MAC layer: Asynchronous Data Service (mandatory)

exchange of data packets based on “best-effort” support of broadcast and multicast

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

Function)


The following three basic access mechanisms have been defined for IEEE 802.11:DFWMAC-DCF CSMA/CA (Distributed foundation wireless medium access control-Distributed coordination function)- (mandatory)

collision avoidance via randomized „back-off“ mechanism

minimum distance between consecutive packets ACK packet for acknowledgements (not for

broadcasts)


DFWMAC-DCF with RTS/CTS (optional) Distributed Foundation Wireless MAC avoids hidden terminal problem

DFWMAC- PCF (Point coordination function) (optional)

access point polls terminals according to a list


Priorities:The standard defines 4 types of spacing intervals.These are called Inter Frame Spaces (IFS).Bellow show a figure Medium access and inter-frame spacing.

t

medium busySIFS

PIFS

DIFSDIFS

next framecontention

direct access if medium is free DIFS


IFSs are used to defer a station’s access to the medium and provide various levels of priorities:Short Inter Frame Space (SIFS): it is the shortest Inter Frame Space with the highest priority.RTS, CTS & Acknowledge use SIFS intervals.SIFS value is a fixed value per PHY and is calculated in such a way that the transmitting station will be able to switch back to receive mode and be capable of decoding the incoming packet.


Point Coordination IFS (PIFS): It has medium priority to gain access to the medium. It is used for time-bounded service using PCF

Distributed IFS (DIFS): It has lowest priority to gain access to the medium. It is used for asynchronous data service using PCF


Basic DFWMAC-DCF (Distributed foundation wireless medium access control-Distributed coordination function) using 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 an Inter-Frame Space (IFS), the station can start sending (IFS depends on service type)


Basic DFWMAC-DCF using CSMA/CA access method –I:

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)


Basic DFWMAC-DCF using CSMA/CA access method –I:

t

medium busy

DIFSDIFS

next frame

contention window(randomized back-offmechanism)

slot time (20µs)direct access if medium is free DIFS


t

busy

boe

station1

station2

station3

station4

station5

packet arrival at MAC

DIFSboe

boe

boe

busy

elapsed backoff time

bor residual backoff time

busy medium not idle (frame, ack etc.)

bor

bor

DIFS

boe

boe

boe bor

DIFS

busy

busy

DIFSboe busy

boe

boe

bor

bor

bor


Basic DFWMAC-DCF using CSMA/CD access method –II (Sending unicast packets):

t

SIFS

DIFS

data

ACK

waiting time

otherstations

receiver

senderdata

DIFS

contention


Basic DFWMAC-DCF using CSMA/CD access method –II (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


DFWMAC-DCF with RTS/CTS (Sending unicast packets): This access method to solve a hidden Terminal problem. Station can send RTS with reservation parameter after

waiting for DIFS. 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.


DFWMAC-DCF with RTS/CTS (Sending unicast packets): RTS-Request to send, CTS-Clear to send, NAV- net allocation vector

t

SIFS

DIFS

data

ACK

defer access

otherstations

receiver

senderdata

DIFS

contention

RTS

CTSSIFS SIFS

NAV (RTS)NAV (CTS)

DIFS


DFWMAC-DCF with RTS/CTS (Fragmentation):the probability of an erroneous frame is much higher for wireless links assuming the same frame length.One way to decrease the error probability of frames is to use shorter frames.The solution is to use mechanism of fragmenting a user data packet into several smaller parts should be transparent for a user.the IEEE 802.11 standard specifies a fragmentation mode.This michanism show in the next slide figure.


DFWMAC-DCF with RTS/CTS (Fragmentation):

t

SIFS

DIFS

data

ACK1

otherstations

receiver

senderfrag1

DIFS

contention

RTS

CTSSIFS SIFS

NAV (RTS)-frag1NAV (CTS)-frag1

NAV (frag2)NAV (ACK2)

SIFSACK2

frag2

SIFS


DFWMAC- PCF with polling:The two access mechanisms presented so far cannot guarantee a maximum access delay or minimum transmission bandwidth.To provide a time-bounded service the standard specifies a point coordination function (PCF) on top of the standard DCF (control-Distributed coordination function).The point coordinator in the access point splits the access time into super frame periods show in the next slide figure.


DFWMAC- PCF (Point coordination function) -I with polling (optional)

PIFS

stations‘NAV

wirelessstations

point coordinator

D1

U1

SIFS

NAV

SIFSD2

U2

SIFS

SIFS

SuperFramet0

medium busy

t1


DFWMAC- PCF-II with polling

tstations‘NAV

wirelessstations

point coordinator

D3

NAV

SIFSD4

U4

SIFS

SIFSCFend

contentionperiod

contention free period

t2 t3 t4

802.11 Protocol Architecture:MAC Frames

In the next slide figure show the basic structure of an IEEE 802.11 MAC data frame together with content of the frame control field.The first figure fields in the figure refer to the following:Frame control:The first 2 bytes serve several purpose.Like: Protocol version, power management etc.

802.11 Protocol Architecture:MAC Packet Structure

FrameControl

Duration/ID

Address1

Address2

Address3

SequenceControl

Address4

Data CRC

2 2 6 6 6 62 40-2312Field Lenght is in Bytes

Protocolversion

Type SubtypeToDS

MoreFrag

RetryPowerMgmt

MoreData

WEP

2 2 4 1

FromDS

1

Order

Field Lenght is in Bits

1 1 1 1 1 1


Duration/ID:If the field value is less than 32,768 the duration filed contains the value indicating the period of time in which the medium is occupied.It also used for reserved for identifiers.Address 1 to 4:The four address fields contain standard IEEE 802 MAC address (48 bit each).The meaning of each address depends on the Distribution system bits in the frame control field.


Sequence control:Due to the acknowledgement mechanism frames may be duplicated.Therefore a sequence number is used to filter duplicates.Data:The MAC frame may contain arbitrary data which is transferred from a sender to the receiver (s).Checksum (CRC):Finally a 32, bit checksum is used to protect the frame.


The frame control filed shown in the previous slide figure contains the following fields:Protocol version:This 2 bits field indicates the current protocol version and is fixed to 0, If major revisions to the standard make it incompatible with the current version, this value will be increased.Type:the type field determines the function of a frame: management (=00),control(=01),data(=10). Each type has several subtypes as indicated in the following field.


Subtype:Example, subtype for management frames are: 0000 for associated request, RTS us a control frame with subtype 1011, same as CTS coded as 1100.User data is transmitted as data frame with subtype 0000.To DS/From DS:To indicate which Distribution system sender and receiver identification.More fragments:This filed is set to 1 in all data or management frames that have another fragment of the current MAC service data unit (MSDU) to follow.


Retry:If the current frame is a retransmission of an earlier frame, this bit is set to 1.With the help of this bit it may be simpler for receivers to eliminate duplicate frames.Power management:this field indicates the mode of a station after successful transmission of a frame.Set to 1 the field indicates that the station goes into power-save mode.If the field is set to 0 the satiation stay active.


More data:in general, this field is used to indicate a receiver that a receiver that a sender has more data to send that the current frame.This can be used by an access point to indicate to a station in power-save mode that more packets are buffered.Wired equivalent privacy (WEP):This field indicates that the standard security mechanism of 802.11 is applied.Order:If this bit is set to 1 the received frames must be processed in strict order.

802.11 Protocol Architecture:MAC address format

scenario to DS fromDS

address 1 address 2 address 3 address 4

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

0 1 DA BSSID SA -

infrastructurenetwork, to AP

1 0 BSSID SA DA -

infrastructurenetwork, within DS

1 1 RA TA DA SA

DS: Distribution SystemAP: Access PointDA: Destination AddressSA: Source AddressBSSID: Basic Service Set IdentifierRA: Receiver AddressTA: Transmitter Address

802.11 Protocol Architecture:Special Frames: ACK, RTS, CTS

Acknowledgement

Request To Send

Clear To Send

FrameControl

DurationReceiverAddress

TransmitterAddress

CRC

2 2 6 6 4bytes

FrameControl


CRC

2 2 6 4bytes

FrameControl


CRC

2 2 6 4bytes

ACK

RTS

CTS

MAC Management

Synchronization: Try to find a LAN, try to stay within a LAN. Synchronization of inter clocks, generation of

beacon signals etc. Power management:

Functions to control transmitter activity for power conservation e.g. sleep-mode without missing a message, periodic sleep, frame buffering, traffic measurements.

MAC Management

Roaming: roaming, i.e. change networks by changing access

points. scanning, i.e. active search for a network.

MIB - Management Information Base managing, read, write the current status of

wireless station.

MAC Management:Synchronization

Station need to maintain synchronization.This is necessary to keep hopping and other functions like power saving synchronized.On an infrastructure BSS, synchronization is achieved by all the stations updating their clocks according to the AP’s clock.The AP periodically transmits frames called Beacon frames.These frames contain the value of the AP’s clock at the moment of transmission.This is the time when physical transmission actually happens, and not when the packet was put in the queue for transmission.

MAC Management:Synchronization

the receiving stations check the value of their clocks at the moment the signal is received, and correct it to keep in synchronization with the AP’s clock.This prevents clock drifting which would cause loss of synch after a few hours of operations.

Synchronization using a Beacon (infrastructure)

beacon interval(20ms – 1s)

tmedium

accesspoint

busy

B

busy busy busy

B B B

value of the timestamp B beacon frame

Synchronization using a Beacon (ad-hoc)

tmedium

station1

busy

B1

beacon interval

busy busy busy

B1

value of the timestamp B beacon frame

station2

B2 B2

random delay

MAC Management: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

Traffic Indication Map (TIM) list of unicast receivers transmitted by AP

Delivery Traffic Indication Map (DTIM) list of broadcast/multicast receivers transmitted

by AP

MAC Management:Power Management

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

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

d data transmissionto/from the station

Power saving with wake-up patterns (ad-hoc)

awake

A transmit ATIM D transmit data

t

station1

B1 B1

B beacon frame

station2

B2 B2

random delay

A

a

D

d

ATIMwindow beacon interval

a acknowledge ATIM d acknowledge data

MAC Management:Roaming

The characteristic of a mobile network that enables correct call routing when the subscriber move from one network to another or form one cell to another.

Traveling from the range of one access point to another.

The term “handover” or “handoff” as used in the context of mobile or cellular cell.

However, for WLANs roaming is more common.


The steps for roaming between access points are: Scanning

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

Reassociation Request 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 (Wired Equivalent Privacy)

insecure

WLAN: IEEE 802.11b

Connection set-up time Connectionless/always on

Quality of Service Try Best effort, no guarantees (unless polling is

used, limited support in products)

WLAN: IEEE 802.11b

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



length

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)


length

16

96 µs 2, 5.5 or 11 Mbit/s

Long Physical layer converagence protocol (PLCP) PLCP Protocol Data Unit (PPDU) format

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 802.11a 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

WLAN: IEEE 802.11a Frequency

Free 5.15-5.25, 5.25-5.35, 5.725-5.825 GHz ISM-band

Security Limited, WEP insecure

Connection set-up time Connectionless/always on

Quality of Service Try best effort, no guarantees (same as all 802.11

products)

WLAN: IEEE 802.11a 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

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 of 802.11a in Europe

5150 [MHz]5180 53505200

36 44

16.6 MHz

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

channel40 48 52 56 60 64

5220 5240 5260 5280 5300 5320

5470

[MHz]

5500 57255520

100 108

16.6 MHz

channel104 112 116 120 124 128

5540 5560 5580 5600 5620 5640

132 136 140

5660 5680 5700

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 OFDM (Orthogonal FDM) with 52 used sub carriers (64 in total)

48 data + 4 pilot (plus 12 virtual sub carriers)

312.5 kHz spacing

subcarriernumber

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

channel center frequency

312.5 kHzpilot

WLAN: IEEE 802.11 – current developments (06/2009) 802.11c: Bridge Support

Definition of MAC procedures to support bridges as extension to 802.1D

802.11d: Regulatory Domain Update Support of additional regulations related to

channel selection, hopping sequences 802.11e: MAC Enhancements – QoS

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

WLAN: IEEE 802.11 – current developments (06/2009)

Definition of a data flow (“connection”) with parameters like rate, burst, period… supported by HCCA (HCF (Hybrid Coordinator Function) Controlled Channel Access, optional)

Additional energy saving mechanisms and more efficient retransmission

EDCA (Enhanced Distributed Channel Access): high priority traffic waits less for channel access

802.11F: Inter-Access Point Protocol (withdrawn) Establish an Inter-Access Point Protocol for

data exchange via the distribution system

WLAN: IEEE 802.11 – current developments (06/2009) 802.11g: Data Rates > 20 Mbit/s at 2.4 GHz; 54

Mbit/s, OFDM Successful successor of 802.11b, performance

loss during mixed operation with .11b 802.11h: Spectrum Managed 802.11a

Extension for operation of 802.11a in Europe by mechanisms like channel measurement for dynamic channel selection (DFS, Dynamic Frequency Selection) and power control (TPC, Transmit Power Control)

WLAN: IEEE 802.11 – current developments (06/2009) 802.11i: Enhanced Security Mechanisms

Enhance the current 802.11 MAC to provide improvements in security.

TKIP enhances the insecure WEP, but remains compatible to older WEP systems

AES provides a secure encryption method and is based on new hardware

WLAN: IEEE 802.11 – current developments (06/2009) 802.11j: Extensions for operations in Japan

Changes of 802.11a for operation at 5GHz in Japan using only half the channel width at larger range

802.11-2007: Current “complete” standard Comprises amendments a, b, d, e, g, h, i, j

802.11k: Methods for channel measurements 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

WLAN: IEEE 802.11 – current developments (06/2009) 802.11n: Higher data rates above 100Mbit/s

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 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

802.11s: Mesh Networking Design of a self-configuring Wireless

Distribution System (WDS) based on 802.11 Support of point-to-point and broadcast

communication across several hops 802.11T: Performance evaluation of 802.11

networks Standardization of performance measurement

schemes


802.11u: Interworking with additional external networks

802.11v: Network management Extensions of current management functions,

channel measurements Definition of a unified interface

802.11w: Securing of network control 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.

WLAN: IEEE 802.11 – current developments (06/2009) 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

What is Bluetooth? Bluetooth is a new technology that

eliminates the need for cables between electronic devices: PCs, mobile phones, handsets, printers etc.

The technology is based on short-range radio transmission on a globally available frequency.

Bluetooth provides quick, reliable and secure wireless communications aimed at eliminating cables, connectors and adapters.

What is Bluetooth? It is a small design that is inexpensive to

manufacture and install to ensure manufactures will include it in all portable devices.

Bluetooth uses short-range radio which offers an advantage over infrared solution: walls, furniture, pockets or other obstruction no longer impede or compromise data transmission.

Connection are instant and maintained even when devices are no within line of sight.

What is Bluetooth? The range is approximately 10 meters,

which you can extend to 100 meters. Only a few millimeters in size, the

Bluetooth module will revolutionizes the world of wireless voice and data communications.

History of Bluetooth The specification is defined by the Bluetooth

Special Interest Group (SIG) which is made up of over 1000 electronics manufactures in 1994.

Original founding members: Ericsson, Intel, IBM, Nokia, Toshiba.

Added promoters: 3Com, Microsoft, Motorola

Characteristics

2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing Channel 0: 2402 MHz … channel 78: 2480 MHz FSK modulation, 1-100 mW transmit power

FHSS and TDD Frequency hopping with 1600 hops/s Hopping sequence in a pseudo random fashion,

determined by a master Time division duplex for send/receive separation

Characteristics Voice link – SCO (Synchronous Connection Oriented)

FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point, circuit switched

Data link – ACL (Asynchronous ConnectionLess) Asynchronous, fast acknowledge, point-to-

multipoint, up to 433.9 kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched

Topology Overlapping piconets (stars) forming a Scatternet

Piconet

Collection of devices connected in an ad hoc fashion.

One unit acts as master and the others as slaves for the lifetime of the piconet.

Master determines hopping pattern, slaves have to synchronize.

M=MasterS=Slave

P=ParkedSB=Standby

M

S

P

SB

S

S

P

P

SB

Piconet

Each piconet has a unique hopping pattern.

Participation in a piconet = synchronization to hopping sequence.

Each piconet has one master and up to 7 simultaneous slaves (> 200 could be parked).

M=MasterS=Slave

P=ParkedSB=Standby

M

S

P

SB

S

S

P

P

SB

Forming a piconet All devices in a piconet hop together

Master gives slaves its clock and device ID Hopping pattern: determined by device ID (48

bit, unique worldwide) Phase in hopping pattern determined by

clock Assign Addressing

Active Member Address (AMA, 3 bit) Parked Member Address (PMA, 8 bit)

Forming a piconet

SB

SB

SB

SB

SB

SB

SB

SB

SB

M

S

P

SB

S

S

P

P

SB

Scatternet

This is a group of Piconet effectively hubbed via a single Bluetooth device acting as a master in one piconet and a slave in the other piconet.

The Scatternet permits either larger coverage areas or number of devices than a single piconet can offer.

Scatternet

M=MasterS=SlaveP=ParkedSB=Standby

M

S

P

SB

S

S

P

P

SB

M

S

S

P

SB

Piconets(each with a capacity of 720 kbit/s)

Protocol Stack Bluetooth protocol stack can be divided into

bellow specification: Core Specification (Bluetooth 2001a): It contains a software protocol stack similar to the

more familiar Open system Interconnect (OSI) standard reference model for communication protocol stack.

Profile Specification (Bluetooth 2001b) Next slide figure to show Bluetooth Protocol stack

contains the all Core Specification Standard.

Radio

Baseband

Link Manager

Control

HostControllerInterface

Logical Link Control and Adaptation Protocol (L2CAP)Audio

TCS BIN SDP

OBEX

vCal/vCard

IP

NW apps.

TCP/UDP

BNEP

RFCOMM (serial line interface)

AT modemcommands

telephony apps.audio apps. mgmnt. apps.

AT: attention sequenceOBEX: object exchangeTCS BIN: telephony control protocol specification – binaryBNEP: Bluetooth network encapsulation protocol

SDP: service discovery protocolRFCOMM: radio frequency comm.

PPP

Protocol Stack

Protocol Stack The Core protocols of Bluetooth comprise the

following elements: Radio: The radio modulates and demodulates data for

transmitting and receiving over the air. Baseband: It is description of basic connection establishment,

packet formats, timing and basic QoS parameters. Link Manager Protocol: It controls and configures links to the other

devices.

Protocol Stack Logical Link Control and Adaptation Protocol

(L2CAP): It is a multiplexer, adapting data from higher layer

and converting between different packet size (connectionless and connection-oriented services).

Service Discovery Protocol (SDP): These devices discover the services available on

another Bluetooth device.

Protocol Stack Host controller interface (HCL): It between the Baseband and L2CAP layer. It handles communication between host and the module. The standard defines the HCL command packets that the

host uses to control the module. Telephony Control Protocol Specification-binary

(TCS BIN): It describes a bit-oriented protocol that defines call

control signaling for the establishment of voice and data calls between Bluetooth devices.

It also describes mobility and group management function.

Protocol Stack Radio Frequency COMMunication port

(RFCOMM): Which provides an RS232 like serial interface. OBject EXchange (OBEX): Which is responsible for providing interfaces to

other communication protocols.

Radio Layer Specification of the air interface, i.e. frequencies,

modulation and transmit power. There are several limitations had to be taken into

account when Bluetooth’s radio layer was designed.

Bluetooth devices will be integrated into typical mobile devices and rely on battery power.

This requires small, low power chips which can be built into handheld devices.

Bluetooth uses the license-free frequency band at 2.4 GHz allowing for worldwide operation with some minor adaptations to national restrictions.

Radio Layer

The specification highlights three devices power classes possible for Bluetooth radios that are related to the power range of the transmitter base on mile watt:

Class 1: is 100mW and up to about 100m range Class 2: is 2.5mW and up to about 20m range Class 3: is 1mW and up to about 10m range

Baseband Layer

Baseband layer is description of basic connection establishment, packet formats, timing and basic QoS parameters.

Remember that each device participate in a certain piconet hops at the same time to the same carrier frequency (f1) see in the next slide figure.

If for example, the master sends data at fk then a slave may answerer at fk+1 .

S

Frequency selection during data transmission

fk

625 µs

fk+1 fk+2 fk+3 fk+4

fk+3 fk+4fk

fk

fk+5

fk+5

fk+1 fk+6

fk+6

fk+6

MM M M

M

M M

M M

t

t

t

S S

S S

S

Baseband Layer

Next slide figure shows the components of a Bluetooth packet at Baseband layer.

The packet typically consists of the following three fields:

Access code : Channel, device access, e.g., derived from master Packet header: 1/3-FEC, active member address (broadcast + 7

slaves), link type, alternating bit ARQ/SEQ, checksum

Baseband Layer

access code packet header payload

68(72) 54 0-2745 bits

AM address type flow ARQN SEQN HEC

3 4 1 1 1 8 bits

preamble sync. (trailer)

4 64 (4)

Payload: Upto 343 bytes payload can be transferred. The structure of the pay load filed depends on the

type of link.

Baseband Layer :Physical Link

Bluetooth offers two different types of links: Synchronous connection-oriented link (SCO) Asynchronous connection link (ACL)


Synchronous connection-oriented link (SCO) Same access code and header as ACL packets. ARQ (automatic repeat request) and SEQ.

(sequence) flags redundant since flow control and re-transmission do not apply.

Cyclic redundancy code (CRC) field is absent. Payload fixed at 30 bytes, with source data of

10,20 or 30 bytes. Circuit switched. Slot reservation at fixed intervals.

SCO payload types

payload (30)

audio (30)

audio (10)

audio (10)

HV3

HV2

HV1

DV

FEC (20)

audio (20) FEC (10)

header (1) payload (0-9) 2/3 FEC CRC (2)

(bytes)

FEC=forward error correction CRC= Cyclic redundancy code


Asynchronous connection link (ACO) Packet constructed of a 72 bit access code, a 54 bit

packet header, a 16 bit CRC and payload data. Largest data packet is DH5 giving 723.2 kb/s as

highest data rate in one direction. Not time critical data Asynchronous Packet switched Polling access

ACL Payload typespayload (0-343)

header (1/2) payload (0-339) CRC (2)

header (1) payload (0-17) 2/3 FEC

header (1) payload (0-27)


header (2) payload (0-183)


header (2) payload (0-339)DH5

DM5

DH3

DM3

DH1

DM1

header (1) payload (0-29)AUX1

CRC (2)

CRC (2)

CRC (2)

CRC (2)

CRC (2)

CRC (2)

(bytes)

Baseband data ratesPayload User Symmetric AsymmetricHeader Payload max. Rate max. Rate [kbit/s]

Type [byte] [byte] FEC CRC [kbit/s] Forward Reverse

DM1 1 0-17 2/3 yes 108.8 108.8 108.8

DH1 1 0-27 no yes 172.8 172.8 172.8

DM3 2 0-121 2/3 yes 258.1 387.2 54.4

DH3 2 0-183 no yes 390.4 585.6 86.4

DM5 2 0-224 2/3 yes 286.7 477.8 36.3

DH5 2 0-339 no yes 433.9 723.2 57.6

AUX1 1 0-29 no no 185.6 185.6 185.6

HV1 na 10 1/3 no 64.0

HV2 na 20 2/3 no 64.0

HV3 na 30 no no 64.0

DV 1 D 10+(0-9) D 2/3 D yes D 64.0+57.6 D

ACL

1 slot

3 slot

5 slot

SCO

Data Medium/High rate, High-quality Voice, Data and Voice


Next slide figure shows an example transmission between a master and two slaves.

The master always uses the even frequency slots and odd slots are for the slaves.

This example again shows the hopping sequence which is independent of the transmission of packets.

Baseband Layer :Example of data transmission

MASTER

SLAVE 1

SLAVE 2

f6f0

f1 f7

f12

f13 f19

f18

SCO SCO SCO SCOACL

f5 f21

f4 f20

ACLACLf8

f9

f17

f14

ACL


The robustness of Bluetooth data transmission is based on several technologies.

Slow frequency hopping with hopping patterns determined by a master Protection from interference on certain frequencies Separation from other piconets (FH (frequency

hopping)-CDMA) Retransmission

ACL only, very fast Forward Error Correction

SCO and ACL

Baseband Layer :Robustness

MASTER

SLAVE 1

SLAVE 2

A C C HF

G G

B D E

NAK ACK

Error in payload(not header!)

Link Management Protocol

The link manager protocol (LMP) manages various aspects of the radio link between a master and a slave and the current parameter setting of the devices.

LMP enhances Baseband functionality & controlling, but higher layers can still directly access the Baseband.

Link Management Protocol There no. of Baseband states are to controlling

the low power consumption: Sniff state: it puts slaves into a low duty cycle

mode of operation but is still an active member of the piconet and the master can only transmit after a ‘sniff’ interval.

Hold state: it typically used when a master is establishing a link with a new device and requires the other slaves to temporarily halt their transmission. It is just like temporary mode.

Link Management Protocol

Park state: it slaves enter a low duty cycle mode of operation and are no longer active member of the piconet. It is just like slip mode.

In the next slide figure show a major Baseband states of a Bluetooth device.

Baseband states of a Bluetooth devicestandby

inquiry page

connectedAMA

transmitAMA

parkPMA

holdAMA

sniffAMA

unconnected

connecting

active

low power

Standby: do nothingInquire: search for other devicesPage: connect to a specific deviceConnected: participate in a piconetDetach: remove from the piconet

detach

Park: release AMA- Active Member Address, get PMA-Parked Member Address, Sniff: listen periodically, not each slotHold: stop ACL, SCO still possible, possibly

participate in another piconet

Logical link control and adaptation protocol (L2CAP)

Simple data link protocol on top of Baseband. L2CAP to create a channel like:

signaling channel, Connection oriented and connectionless.

Protocol multiplexing used in upper layer: RFCOMM- Radio Frequency COMMunication

port, SDP-Service discovery Protocol, telephony control.

Segmentation & reassembly Up to 64kbyte user data, 16 bit CRC used from

Baseband.

Logical link control and adaptation protocol (L2CAP)

QoS flow specification per channel Follows RFC (request for comment) 1363,

specifies delay, jitter, bursts, bandwidth. Group abstraction handle by L2CAP like:

Create/close group, add/remove member.

L2CAP logical channels

baseband

L2CAP

baseband

L2CAP

baseband

L2CAP

Slave SlaveMaster

ACL

2 d 1 d d 1 1 d 21

signalling connectionless connection-oriented

d d d

d-dynamic allocate channel

L2CAP packet formats

length

2 bytes

CID=2

2

PSM

2

payload

0-65533

length

2 bytes

CID

2

payload

0-65535

length

2 bytes

CID=1

2

One or more commands

Connectionless PDU-protocol data unit

Connection-oriented PDU-protocol data unit

Signalling command PDU-protocol data unit

code ID length data

1 1 2 0

Security

E3

E2

link key (128 bit)

encryption key (128 bit)

payload key

Keystream generator

Data DataCipher data

Authentication key generation(possibly permanent storage)

Encryption key generation(temporary storage)

PIN (1-16 byte)User input (initialization)

Pairing

Authentication

Encryption

Ciphering

E3

E2

link key (128 bit)

encryption key (128 bit)

payload key

Keystream generator

PIN (1-16 byte)

Service Discovery Protocol- SDP

SDP is the process of determining which bluetooth services are available on the devices within radio range.

The connection request are made for a specific service.

If the desired service is the File Transfer Protocol (FTP) and the remote device does not offer that service and the connection will not be allow.

Service Discovery Protocol- SDP

All services the information's as SDP server has about a service is contained in a service record.

At the server contain the Service record format Information about services provided by

attributes Attributes are composed of an 16 bit ID (name)

and a value values may be derived from 128 bit Universally

Unique Identifiers (UUID)

Profiles

Bluetooth started as a very simple architecture for spontaneous ad-hoc communication, many different protocols, components, extensions and many mechanisms used.

Profiles represent default solutions for a certain usage model.

For example Bluetooth v1.1 or v1.2 model has different profiles.

Profiles

Profiles

Pro

toco

ls

Applications

In this figure to mention a protocols can be seen as horizontal layers while profiles are vertical slices.

Bluetooth Profiles

Profiles

Bellow mention no of profiles supported to v1.1 Generic Access Profile Service Discovery Application Profile Intercom Profile Serial Port Profile Headset Profile Dial-up Networking Profile Fax Profile LAN Access Profile File Transfer Profile

Profiles

Additional Profiles Advanced Audio Distribution PAN Audio Video Remote Control Basic Printing Basic Imaging Extended Service Discovery Generic Audio Video Distribution Hands Free Hardcopy Cable Replacement

Bluetooth versions

Bluetooth 1.1 also IEEE Standard 802.15.1-2002 initial stable commercial standard

Bluetooth 1.2 also IEEE Standard 802.15.1-2005 eSCO (extended SCO): higher, variable

bitrates, retransmission for SCO AFH (adaptive frequency hopping) to avoid

interference

Bluetooth versions

Bluetooth 2.0 + EDR (2004, no more IEEE) EDR (enhanced date rate) of 3.0 Mbit/s for ACL

and eSCO lower power consumption due to shorter duty cycle

Bluetooth 2.1 + EDR (2007) better pairing support, e.g. using NFC improved security

Bluetooth 3.0 + HS (2009) Bluetooth 2.1 + EDR + IEEE 802.11a/g = 54 Mbit/s

WPAN: IEEE 802.15.1 – Bluetooth

Data rate Synchronous, connection-oriented:

64 kbit/s Asynchronous, connectionless

433.9 kbit/s symmetric 723.2 / 57.6 kbit/s asymmetric

Transmission range POS (Personal Operating Space) up

to 10 m with special transceivers up to 100

m Frequency

Free 2.4 GHz ISM-band Security

Challenge/response (SAFER+), hopping sequence

Availability Integrated into many products,

several vendors

Connection set-up time Depends on power-mode Max. 2.56s, avg. 0.64s

Quality of Service Guarantees, ARQ/FEC

Manageability Public/private keys needed, key

management not specified, simple system integration

Special Advantages/Disadvantages

Advantage: already integrated into several products, available worldwide, free ISM-band, several vendors, simple system, simple ad-hoc networking, peer to peer, scatternets

Disadvantage: interference on ISM-band, limited range, max. 8 active devices/network, high set-up latency

WPAN: IEEE 802.15 – future developments 1

802.15.2: Coexistance Coexistence of Wireless Personal Area Networks (802.15) and

Wireless Local Area Networks (802.11), quantify the mutual interference

802.15.3: High-Rate Standard for high-rate (20Mbit/s or greater) WPANs, while still low-

power/low-cost Data Rates: 11, 22, 33, 44, 55 Mbit/s Quality of Service isochronous protocol Ad hoc peer-to-peer networking Security Low power consumption Low cost Designed to meet the demanding requirements of portable

consumer imaging and multimedia applications


Several working groups extend the 802.15.3 standard 802.15.3a: - withdrawn -

Alternative PHY with higher data rate as extension to 802.15.3

Applications: multimedia, picture transmission 802.15.3b:

Enhanced interoperability of MAC Correction of errors and ambiguities in the standard

802.15.3c: Alternative PHY at 57-64 GHz Goal: data rates above 2 Gbit/s

Not all these working groups really create a standard, not all standards will be found in products later …


802.15.4: Low-Rate, Very Low-Power Low data rate solution with multi-month to multi-year battery life

and very low complexity Potential applications are sensors, interactive toys, smart badges,

remote controls, and home automation Data rates of 20-250 kbit/s, latency down to 15 ms Master-Slave or Peer-to-Peer operation Up to 254 devices or 64516 simpler nodes Support for critical latency devices, such as joysticks CSMA/CA channel access (data centric), slotted (beacon) or

unslotted Automatic network establishment by the PAN coordinator Dynamic device addressing, flexible addressing format Fully handshaked protocol for transfer reliability Power management to ensure low power consumption 16 channels in the 2.4 GHz ISM band, 10 channels in the 915 MHz

US ISM band and one channel in the European 868 MHz band

Chapter 7: Wireless LAN. What is Wireless LAN? Wireless local area network (LAN) is a local area...

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Transcript of Chapter 7: Wireless LAN. What is Wireless LAN? Wireless local area network (LAN) is a local area...