Chapter 05 Wireless Design Models, Topologies, Infrastructure, and Wireless LAN Devices
Chapter 7: Wireless LAN
description
Transcript of Chapter 7: Wireless LAN
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.
Disadvantages of WLAN
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.
Disadvantages of WLAN
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.
Disadvantages of WLAN
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.
Disadvantages of WLAN
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.
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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
PLCP preamble PLCP header
128 16 8 8 16 variable bits
length
16
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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.
802.11 Protocol Architecture:Physical Layer Architecture
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)
802.11 Protocol Architecture:MAC Layer Architecture
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)
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Layer Architecture
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.
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Layer Architecture
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)
802.11 Protocol Architecture:MAC Layer Architecture
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)
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Layer Architecture
Basic DFWMAC-DCF using CSMA/CD access method –II (Sending unicast packets):
t
SIFS
DIFS
data
ACK
waiting time
otherstations
receiver
senderdata
DIFS
contention
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Layer Architecture
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.
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Layer Architecture
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.
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Layer Architecture
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.
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Layer Architecture
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
802.11 Protocol Architecture:MAC Frames
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.
802.11 Protocol Architecture:MAC Frames
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.
802.11 Protocol Architecture:MAC Frames
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.
802.11 Protocol Architecture:MAC Frames
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.
802.11 Protocol Architecture:MAC Frames
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.
802.11 Protocol Architecture:MAC Frames
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
DurationReceiverAddress
CRC
2 2 6 4bytes
FrameControl
DurationReceiverAddress
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.
MAC Management:Roaming
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.
MAC Management:Roaming
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
PLCP preamble PLCP header
128 16 8 8 16 variable bits
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)
56 16 8 8 16 variable bits
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
WLAN: IEEE 802.11 – current developments (06/2009)
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
WLAN: IEEE 802.11 – current developments (06/2009)
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
WLAN: IEEE 802.11 – current developments (06/2009)
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)
Baseband Layer :Physical Link
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
Baseband Layer :Physical Link
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 (0-121) 2/3 FEC
header (2) payload (0-183)
header (2) payload (0-224) 2/3 FEC
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
Baseband Layer :Physical Link
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
Baseband Layer :Physical Link
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
WPAN: IEEE 802.15 – future developments 2
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 …
WPAN: IEEE 802.15 – future developments 3
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