EC8004 WIRELESS NETWORKS - SNS Courseware · 2020. 2. 11. · Simon Haykin , Michael Moher, David...

EC8004WIRELESS NETWORKS

EC8004/WIRELESS NETWORKS/RAJKUMAR.K.K

TEXT BOOKS:

1. Jochen Schiller, ”Mobile Communications”, Second Edition, Pearson Education 2012.(Unit I,II,III)

2. Vijay Garg, “Wireless Communications and networking”, First Edition, Elsevier 2007.(Unit IV,V)

REFERENCES:

1. Erik Dahlman, Stefan Parkvall, Johan Skold and Per Beming, "3G Evolution HSPA and LTE for Mobile

Broadband”, Second Edition, Academic Press, 2008.

2. Anurag Kumar, D.Manjunath, Joy kuri, “Wireless Networking”, First Edition, Elsevier 2011.

3. Simon Haykin , Michael Moher, David Koilpillai, “Modern Wireless Communications”,

First Edition, Pearson Education 2013


UNIT I WIRELESS LAN


INTRODUCTIONWireless means transmitting signals using radio waves as the medium instead of wires.

Wireless technologies are used for tasks as simple as switching off the television or as complex as supplying the sales force with information from an automated enterprise application while in the field.

Now cordless keyboards, mice and cellular phones have become part of our daily life.


Some of the inherent characteristics of wireless communications systems which

make it attractive for users, are given below −

Mobility − A wireless communications system allows users to access information

beyond their desk and conduct business from anywhere without having a wire

connectivity.

Reachability − Wireless communication systems enable people to be stay

connected and be reachable, regardless of the location they are operating from.

Simplicity − Wireless communication system are easy and fast to deploy in

comparison of cabled network. Initial setup cost could be a bit high but other

advantages overcome that high cost.EC8004/WIRELESS NETWORKS/RAJKUMAR.K.K

Maintainability − In a wireless system, you do not have to spend too much cost

and time to maintain the network setup.

Roaming Services − Using a wireless network system, you can provide service any

where any time including train, buses, aero planes etc.

New Services − Wireless communication systems provide various smart services

like SMS and MMS.


WIRELESS NETWORK TOPOLOGIESThere are basically three ways to set up a wireless network

POINT-TO-POINT BRIDGEAs you know, a bridge is used to connect two networks. A point-to-pointbridge interconnects two buildings having different networks. For example, a wirelessLAN bridge can interface with an Ethernet network directly to a particular accesspoint.


POINT-TO-MULTIPOINT BRIDGEThis topology is used to connect three or more LANs that may be located on different floors in abuilding or across buildings


MESH OR AD HOC NETWORKThis network is an independent local area network that is not connected to a wired infrastructureand in which all stations are connected directly to one another


WIRELESS TECHNOLOGIES

Wireless technologies can be classified in different ways depending on their range. Each wireless

technology is designed to serve a specific usage segment. The requirements for each usage segment

are based on a variety of variables, including Bandwidth needs, Distance needs and Power.

Wireless Wide Area Network (WWAN)

This network enables you to access the Internet via a wireless wide area network (WWAN) access

card and a PDA or laptop. These networks provide a very fast data speed compared with the data

rates of mobile telecommunications technology, and their range is also extensive. Cellular and mobile

networks based on CDMA and GSM are good examples of WWAN.

Wireless Personal Area Network (WPAN)

These networks are very similar to WWAN except their range is very limited.


WIRELESS LOCAL AREA NETWORK (WLAN)

This network enables you to access the Internet in localized hotspots via a wireless local area

network (WLAN) access card and a PDA or laptop.

It is a type of local area network that uses high-frequency radio waves rather than wires to

communicate between nodes.

These networks provide a very fast data speed compared with the data rates of mobile

telecommunications technology, and their range is very limited. Wi-Fi is the most widespread

and popular example of WLAN technology.

WIRELESS METROPOLITAN AREA NETWORK (WMAN)

This network enables you to access the Internet and multimedia streaming services via a

wireless region area network (WRAN).

These networks provide a very fast data speed compared with the data rates of mobile

telecommunication technology as well as other wireless network, and their range is also

extensive.


ISSUES WITH WIRELESS NETWORKS

There are following three major issues with Wireless Networks.

Quality of Service (QoS): One of the primary concerns about wireless data delivery is that, unlike the

Internet through wired services, QoS is inadequate. Lost packets and atmospheric interference are recurring

problems of the wireless protocols.

WLANs typically offer lower quality than their wired counterparts. The main reasons for this are the

lower bandwidth due to limitations in radio transmission (e.g., only 1–10 Mbit/s user data rate instead of 100–

1,000 Mbit/s)

Security Risk: This is another major issue with a data transfer over a wireless network. Basic network

security mechanisms like the service set identifier (SSID) and Wireless Equivalency Privacy (WEP); these

measures may be adequate for residences and small businesses, but they are inadequate for the entities

that require stronger security.


Reachable Range: Normally, wireless network offers a range of about 100 meters or less. Range is

a function of antenna design and power. Now a days the range of wireless is extended to tens of

miles so this should not be an issue any more.

Proprietary solutions: Due to slow standardization procedures, many companies have come up

with proprietary solutions offering standardized functionality plus many enhanced features. At least

most components today adhere to the basic standards IEEE 802.11b or (newer) 802.11a


Design goals have to be taken into account for WLANs to ensure their commercial success

Global operation: WLAN products should sell in all countries so, national and international frequency

regulations have to be considered.

Low power: Devices communicating via a WLAN are typically also wireless devices running on

battery power. The LAN design should take this into account and implement special power-saving

modes and power management functions.

License-free operation: LAN operators do not want to apply for a special license to be able to use the

product. The equipment must operate in a license-free band, such as the 2.4 GHz ISM band.


Robust transmission technology: Compared to their wired counterparts, WLANs operate under difficult

conditions. If they use radio transmission, many other electrical devices can interfere with them (vacuum

cleaners, hairdryers, train engines etc.).

Easy to use: In contrast to huge and complex wireless WANs, wireless LANs are made for simple use. They

should not require complex management, but rather work on a plug-and-play basis.

Protection of investment: A lot of money has already been invested into wired LANs. The new WLANs should

protect this investment by being interoperable with the existing networks. This means that simple bridging

between the different LANs should be enough to interoperate, i.e., the wireless LANs should support the same

data types and services that standard LANs support.

Transparency for applications: Existing applications should continue to run over WLANs


IN FR A S T R UC T UR E A N D A D - H O C

N E T W O R KS

M a n y W L A N s of t o d a y n e e d a n i n fr a s tru c t u r e n et w ork . I nfr a str u ct ur e

n e t w ork s n ot o n l y pr o v i d e a c c e s s t o ot h er n e t w ork s , b ut a l s o i n c l u d e f or w ar d i n g

fu n c tio n s , m e d iu m a c c e s s c o n tro l e tc .

I n t h e s e i nfr a str u ct ure - b a s e d w ir e l e s s n etw ork s , c o m m u n i c ati o n ty p i c a l ly t a k e s

p l a c e o n l y b et w e e n th e w ir e l e s s n o d e s a n d t h e a c c e s s p o i nt , b u t n ot d ir e ctly

b e tw e e n th e wire le s s n o d e s .


In fra s tru c tu re - b a s e d wire le s s n e tw o rks


T h e a c c e s s p o in t d o e s n o t ju s t c o n tro l m e d iu m a c c e s s , b u t a ls o a c ts a s a b rid g e to o th e r w ire le s s o r w ire d

n e tw o rk s .

S e v e ra l w ire le s s n e tw o rk s m a y fo rm o n e lo g ic a l w ire le s s n e tw o rk , s o th e a c c e s s p o in ts to g e th e r w ith th e fixe d

n e tw o rk in b e tw e e n c a n c o n n e c t s e v e ra l w ire le s s n e tw o rk s to fo rm a la rg e r n e tw o rk b e y o n d a c tu a l ra d io

c o v e ra g e . D e s ig n o f in fra s tru c tu re - b a s e d w ire le s s n e tw o rk s is s im p le r.

T h is s tru c tu re is re m in is c e n t o f s w itc h e d E th e rn e t o r o th e r s ta r- b a s e d n e tw o rk s , w h e re a c e n tra l e le m e n t (e . g . ,

a s w itc h ) c o n tro ls n e tw o rk flo w.

T y p ic a l c e llu la r p h o n e n e tw o rks a re in fra s tru c tu re - b a s e d n e tw o rk s fo r a w id e a re a . A ls o s a te llite - b a s e d c e llu la r

p h o n e s h a v e a n in fra s tru c tu re – th e s a te llite s


Ad-h o c w ire le s s n e tw o rk s , h o w e v e r, d o n o t n e e d a n y in fra s tru c tu re to w o rk . E a c h n o d e c a n c o m m u n ic a te

d ire c tly w ith o th e r n o d e s , s o n o a c c e s s p o in t c o n tro llin g m e d iu m a c c e s s is n e c e s s a ry.

N o d e s w ith in a n a d - h o c n e tw o rk c a n o n ly c o m m u n ic a te if th e y c a n re a c h e a c h o th e r p h y s ic a lly, i . e . , if th e y a re

w ith in e a c h o th e rs ra d io ra n g e o r if o th e r n o d e s c a n fo rw a rd th e m e s s a g e .

I n a d - h o c n e tw o rk s , th e c o m p le x ity o f e a c h n o d e is h ig h e r b e c a u s e e v e ry n o d e h a s to im p le m e n t m e d iu m

a c c e s s m e c h a n is m s

ad-hoc wireless networks


E XA M PL E :

I E E E 8 0 2 . 1 1 a n d H ip e rL A N 2 a re ty p ic a lly in fra s tru c tu re - b a s e d n e tw o rk s , w h ic h a d d itio n a lly s u p p o rt

a d - h o c n e tw o rk in g . B lu e to o th is a typ ic a l w ire le s s a d - h o c n e tw o rk .


W L A N T E C H N O L O G I E S :

INFRARED

UHF(Narrow band)

SPREAD SPECTRUM


1. Infrared Technology:

Infrared is an invisible band of radiation that exists at lower end of visible electromagnetic

spectrum.

There are two types of infrared WLAN solutions:

• Direct beam (or line-of-sight)

• Diffused beam (uses reflected rays)

Direct beam WLANs offer faster data rates while diffused beam technology achieves lower data

rates in 1-2 Mbps range.

The advantage of using this technology is that there are no government regulations on its use and

also it is immune to EM and RF interference.

The disadvantage is that it is a short range technology (30-50 ft radius under ideal conditions).Also,

it requires line-of-sight. The signal gets affected by solid objects like doors, walls, etc. The signal is

also affected by fog, dirt, ice, snow.


2. UHF Narrowband technology:

The frequency range is 430 to 470 MHZ and rarely segments in 800 MHZ range.

The portion 430-450 MHZ is unlicensed while 450-470 MHZ band is licensed.

The term narrow band is used because RF signal is sent in a very narrow band width,

typically 12.5 KHz or 25 KHz.

There are two systems: Synthesized and Un-synthesized system uses crystal controlled

frequency operation. There can be frequency drift problem in crystal.

The synthesized uses single, standard crystal. Multiple frequencies are achieved using

dividing the crystal frequency and then multiplying it to desired channel frequency.

The advantage of this technology is that it has longest range and its low cost for large

sites.

The disadvantages of this include the need of license, no multivendor inter operability

and interference potential.


3.Spread Spectrum Technology:

In this technique, the entire allotted bandwidth is shared instead of dividing itinto discrete private parts.

The spread spectrum spreads the transmission power over entire usable spectrum.Thus, though bandwidth efficiency decreases; reliability, integrity and securityincrease.

In commercial applications, spread spectrum techniques currently offer data ratesup to 2Mbps.

Two modulation schemes are used to encode spread spectrum signals : frequencyhopping spread spectrum (FHSS) and direct sequence spread spectrum (DSSS)

FHSS uses a narrowband carrier that changes frequency in a pattern known to bothtransmitter and receiver. To some other receiver, FHSS appears to be a short-duration impulse noise. Thus, the data security increases.

Similarly, DSSS generates redundant bit pattern for every bit to be transmitted,known as spreading code, known only to transmitter and receiver. To some otherreceiver, DSSS appears as low-power, wideband noise and is rejected.


802.11 Wi-Fi Wireless LAN Media Access Control and Physical Layer specification. 802.11a,b,g,etc.are amendments to the original 802.11 standard. Products that implement 802.11standards must pass tests and are referred to as "Wi-Fi certified."

IEEE 802.11

Additional features of the WLAN should include the support of power

management to save battery power, the handling of hidden nodes, and the

ability to operate worldwide.

The 2.4 GHz ISM band, which is available in most countries around the world,

was chosen for the original standard.


../IEEE 802 standards.docx

IEEE 802.11:

• System architecture

• Protocol architecture

• Physical layer

• MAC layer

• 802.11b

• 802.11a


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

STA2 STA3

ESS

System architectureWireless networks can exhibit two different basic system architectures infrastructure-based or ad-hoc.

Infrastructure-based


Extended Service Set (ESS) and has its own identifier, the ESSID. The ESSID is the ‘name’ of a network and

is used to separate different networks. Without knowing the ESSID (and assuming no hacking) it should not be

possible to participate in the WLAN.

Stations can select an AP and associate with it. The APs support roaming (i.e., changing access points), the

distribution system handles data transfer between the different APs. APs provide synchronization within a BSS.

In addition to infrastructure-based networks, IEEE 802.11 allows the building of ad-hoc networks


802.11 LAN

IBSS2

802.11 LAN

IBSS1

STA4

STA5

STA2

STA3

STA1

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 stationsusing the same radio frequency

In this case, an IBSS comprises a group of stations using the same radio frequency.

This means for example that STA3 can communicate directly with STA2 but not with STA5.


PROTOCOL ARCHITECTUREApplications should not notice any difference apart from the lower bandwidth

and perhaps higher access time from the wireless LAN. The WLAN behaves like a slow wired LAN.The higher layers (application, TCP, IP) look the same for wireless nodes as for wirednodes.

An IEEE 802.11 wireless LAN

connected to a switched IEEE 802.3

ethernet via a bridge.


The IEEE 802.11 standard only covers the physical layer PHY and medium access layer MAC like the other

802.x LANs do.

The physical layer is subdivided into the physical layer convergence protocol (PLCP) and the

physical medium dependent sublayer PMD

The basic tasks of the MAC layer comprise medium access, fragmentation of user data, and encryption.

PLCP sublayer provides a carrier sense signal, called clear channel assessment (CCA), and provides a

common PHY service access point (SAP) independent of the transmission technology. Finally, the PMD

sublayer handles modulation and encoding/decoding of signals.

The main tasks of the PHY management include channel

tuning and PHY MIB maintenance.


PHYSICAL LAYER:

IEEE 802.11 supports three different physical layers: One layer based on infra redTwo layers based on radio transmission

The PHY layer offers a service access point (SAP) with 1 or 2 Mbit/s transfer rate to the MAC layer.

THREE VERSIONS OF PHY LAYER:

1. Frequency Hopping Spread Spectrum

2. Direct Sequence Spread Spectrum

3. Infra Red

} Radio Transmission


Frequency Hopping Spread Spectrum

Frequency hopping spread spectrum (FHSS) is a spread spectrum technique which allows for the

coexistence of multiple networks in the same area by separating different networks using different

hopping sequences.

The original standard defines 79 hopping channels for North America and Europe, and 23 hopping

channels for Japan.

The selection of a particular channel is achieved by using a pseudo-random hopping pattern.

The standard specifies Gaussian shaped FSK (frequency shift keying), GFSK, as modulation for the FHSS

PHY. For 1 Mbit/s a 2 level GFSK is used (i.e., 1 bit is mapped to one frequency), a 4 level GFSK for 2 Mbit/s

(i.e., 2 bits are mapped to one frequency).

While sending and receiving at 1 Mbit/s is mandatory for all devices, operation at 2 Mbit/s is optional.

This facilitated the production of low-cost devices for the lower rate only and more powerful devices for

both transmission rates in the early days of 802.11.


Format of an IEEE 802.11 PHY frame using FHSS

Synchronization: This pattern is used for synchronization of potential receivers and signal detection by the CCA.

Start frame delimiter (SFD): The following 16 bits indicate the start of the frame and provide frame synchronization.

PLCP_PDU length word (PLW): This first field of the PLCP header indicates the length of the payload in bytes

PLCP signalling field (PSF): This 4 bit field indicates the data rate of the payload following.

Header error check (HEC): Finally, the PLCP header is protected by a 16 bit checksum


Direct sequence spread spectrum

Direct sequence spread spectrum (DSSS) is the alternative spread spectrum method separating

by code and not by frequency.

In the case of IEEE 802.11 DSSS, spreading is achieved using the 11-chip Barker sequence (+1, –1,

+1, +1, –1, +1, +1, +1, –1, –1, –1). The key characteristics of this method are its robustness against

interference and its insensitivity to multipath propagation.

However, the implementation is more complex compared to FHSS.

The system uses differential binary phase shift keying (DBPSK) for 1 Mbit/s transmission and

differential quadrature phase shift keying (DQPSK) for 2 Mbit/s as modulation schemes.


Format of an IEEE 802.11 PHY frame using DSSS

Synchronization: The first 128 bits are not only used for synchronization, but also gain setting, energy detection

(for the CCA), and frequency offset compensation.

Start frame delimiter (SFD): This 16 bit field is used for synchronization at the beginning of a frame

Signal: Only two values have been defined for this field to indicate the data rate of the payload. The value 0x0A

indicates 1 Mbit/s (and thus DBPSK), 0x14 indicates 2 Mbit/s (and thus DQPSK).

Service: This field is reserved for future use

Length: 16 bits are used in this case for length indication of the payload in microseconds.

Header error check (HEC): Signal, service, and length fields are protected by this checksum.EC8004/WIRELESS NETWORKS/RAJKUMAR.K.K

Infra Red

The PHY layer, which is based on infra red (IR) transmission, uses near visible light at 850–950 nm.

The standard does not require a line-of-sight between sender and receiver, but should also work with

diffuse light. This allows for point-to-multipoint communication.

The maximum range is about 10 m if no sunlight or heat sources interfere with the transmission.

Typically, such a network will only work in buildings, e.g., classrooms, meeting rooms etc.

Today, no products are available that offer infra red communication based on 802.11.

Proprietary products offer, e.g., up to 4 Mbit/s using diffuse infra red light. Alternatively, directed infra red

communication based on IrDA can be used (IrDA, 2002).


Medium access control layer

It has to control medium access, but it can also offer support for roaming, authentication, and power

conservation.

The basic services provided by the MAC layer are the mandatory asynchronous data service and an optional

time-bounded service.

While 802.11 only offers the asynchronous service in ad-hoc network mode, both service types can be

offered using an infrastructure-based network together with the access point coordinating medium access.


The following three basic access mechanisms have been defined for IEEE 802.11:

1. The mandatory basic method based on a version of CSMA/CA

2. An optional method avoiding the hidden terminal problem

3. A contention-free polling method for time-bounded service.

DCF only offers asynchronous service, while PCF offers both asynchronous and time-bounded.

The MAC mechanisms are also called distributed foundation wireless medium access control

(DFWMAC).

} distributed coordination function (DCF)

point coordination function (PCF).


Medium access and inter-frame spacing

Short inter-frame spacing (SIFS): The shortest waiting time for medium access (so the highest priority)

is defined for short control messages, such as acknowledgements of data packets or polling responses.

PCF inter-frame spacing (PIFS): A waiting time between DIFS and SIFS (and thus a medium priority) is

used for a time-bounded service.

DCF inter-frame spacing (DIFS): This parameter denotes the longest waiting time and has the lowest

priority for medium access. This waiting time is used for asynchronous data service within a contention

periodEC8004/WIRELESS NETWORKS/RAJKUMAR.K.K

1.Basic DFWMAC-DCF using CSMA/CA

• Station ready to send starts sensing the medium (carrier sense based on CCA, clear channelassessment)

• If the medium is free for the duration of an inter-frame space (IFS), the station can startsending (IFS depends on service type)

• If the medium is busy, the station has to wait for a free IFS, then the station mustadditionally wait a random back-off time (collision avoidance, multiple of slot-time) CW = 7,15, 31, 63, 127

• If another station occupies the medium during the back-off time of the station, the back-offtimer stops (fairness)


802.11 - competing stations - simple version (no RTS/CTS)

t

busy

boe

station1

station2

station3

station4

station5

packet arrival at MAC

DIFS

boe

boe

boe

busy

elapsed backoff time

borresidual backoff time

busy medium not idle (frame, ack etc.)

bor

bor

DIFS

boe

boe

boe bor

DIFS

busy

busy

DIFS

boe busy

boe

boe

bor

bor


802.11 - CSMA/CA access method IISending unicast packets

Station has to wait for DIFS before sending data

Receivers acknowledge at once (after waiting for SIFS) if the packet was received correctly (CRC)

Automatic retransmission of data packets in case of transmission errors

t

SIFS

DIFS

data

ACK

waiting time

other

stations

receiver

senderdata

DIFS

contention


2. 802.11 – DFWMAC (Distributed Foundation Wireless MAC)

Sending unicast packets• Station can send RTS with reservation parameter after waiting for DIFS (reservation determines

amount of time the data packet needs the medium) • Acknowledgement via CTS after SIFS by receiver (if ready to receive)• Sender can now send data at once, acknowledgement via ACK• Other stations store medium reservations distributed via RTS and CTS

t

SIFS

DIFS

data

ACK

defer access

other

stations

receiver

senderdata

DIFS

contention

RTS

CTSSIFS SIFS

NAV (RTS)NAV (CTS)

NAV – Network Allocation Vector


The RTS packet includes the receiver of the data transmission to come and the duration of the whole

data transmission.

This duration specifies the time interval necessary to transmit the whole data frame and the

acknowledgement related to it.

Every node receiving this RTS now has to set its net allocation vector (NAV) in accordance with the duration

field.


Fragmentation

t

SIFS

DIFS

data

ACK1

other

stations

receiver

senderfrag1

DIFS

contention

RTS

CTSSIFS SIFS

NAV (RTS)NAV (CTS)

NAV (frag1)NAV (ACK1)

SIFSACK2

frag2

SIFS


3. 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 mechanisms.

Using PCF requires an access point that controls medium access and polls the single nodes. Ad-hoc

networks cannot use this function.


DFWMAC-PCF

PIFS

stations‘

NAV

wireless

stations

point

coordinator

D1

U1

SIFS

NAV

SIFS

D2

U2

SIFS

SIFS

SuperFramet0

medium busy

t1

contention free period


DFWMAC-PCF II (cont.)

t

stations‘

NAV

wireless

stations

point

coordinator

D3

NAV

PIFSD4

U4

SIFS

SIFSCFend

contention

period

contention free period

t2 t3 t4

CFend - contention free period end


MAC frames

Frame control: The first 2 bytes serve several purposes. They contain several sub-fields as explained after the

MAC frame.

Duration/ID: The duration field contains the value indicating the period of time in which the medium is occupied

(in μs).

Address 1 to 4: The four address fields contain standard IEEE 802 MAC addresses (48 bit each), as they are

known from other 802.x LANs.

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 (max. 2,312 byte), which is transferred transparently from a

sender to the receiver(s).EC8004/WIRELESS NETWORKS/RAJKUMAR.K.K

Checksum (CRC): Finally, a 32 bit checksum is used to protect the frame as it is common practice in all 802.x

networks.

Protocol version: This 2 bit field indicates the current protocol version and is fixed to 0 by now.

Type: The type field determines the function of a frame: management (=00), control (=01), or data (=10). The

value 11 is reserved

Subtype: Example subtypes for management frames are: 0000 for association request, 1000 for beacon.

More fragments: This field is set to 1 in all data or management frames that have another fragment of the

current.

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 station stays active.

More data: In general, this field is used to indicate a receiver that a sender has more data to send than the

current frame.

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.EC8004/WIRELESS NETWORKS/RAJKUMAR.K.K

802.11 - MAC management• Synchronization

• try to find a WLAN, try to stay within a WLAN• timer etc.

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

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

• MIB - Management Information Base• managing, read, write (SNMP)


Synchronization using a Beacon (infrastructure)

beacon interval

tmedium

access

point

busy

B

busy busy busy

B B B

value of the timestamp B beacon frame (BSSID, Timestamp)


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


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

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

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


Power saving with wake-up patterns (infrastructure)

TIM interval

t

medium

access

pointbusy

D

busy busy busy

T T D

T TIM D DTIM

DTIM interval

BB

B broadcast/multicast

station

awake

p PS poll

p

d

d

ddata transmission

to/from the station

PS – Power SavingTraffic Indication Map (TIM)

Delivery Traffic Indication Map (DTIM)-for multicast data transmission


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

ATIM

window beacon interval

a acknowledge ATIM d acknowledge data


Scanning• Scanning involves the active search for a BSS. IEEE 802.11 differentiates

between passive and active scanning.

• Passive scanning - listening into the medium to find other networks, i.e.,receiving the beacon of another network issued by access point.

• Active scanning - sending a probe on each channel and waiting for aresponse. Beacon and probe responses contain the information necessaryto join the new BSS.


Active Scanning


802.11b

Some companies offered proprietary solutions with 11 Mbit/s.

This standard describes a new PHY layer and is by far the most successful version of IEEE 802.11 available

today.

All the MAC schemes, management procedures etc. are still same.

Depending on the current interference and the distance between sender and receiver 802.11b systems offer

11, 5.5, 2, or 1 Mbit/s. Maximum user data rate is approx. 6 Mbit/s. The lower data rates 1 and 2 Mbit/s use

the 11-chip Barker sequence

The standard defines several packet formats for the physical layer. The mandatory format interoperates with

the original versions of 802.11. The optional versions provide a more efficient data transfer



long PLCP PPDU:

One difference is the rate encoded in the signal field this is encoded in multiples of 100 kbit/s.

0x0A represents 1 Mbit/s

0x14 is used for 2 Mbit/s

0x37 for 5.5 Mbit/s

0x6E for 11 Mbit/s.

Short PLCP PPDU:

The short synchronization field consists of 56 scrambled zeros instead of scrambled ones.

The length of the overhead is only half for the short frames (96 μs instead of 192 μs).


Channel plan for IEEE 802.11b


IEEE 802.11b non-overlapping channel selection

The spacing between the center frequencies should be at least 25 MHz

This results in the channels 1, 6, and 11 for the US/Canada or 1, 7, 13 for Europe, respectively.

It may be the case that, e.g., travellers from the US cannot use the additional channels (12 and 13) in

Europe as their hardware is limited to 11 channels.EC8004/WIRELESS NETWORKS/RAJKUMAR.K.K

802.11a

• Initially aimed at the US 5 GHz U-NII (Unlicensed National Information Infrastructure) bands IEEE 802.11a

offers up to 54 Mbit/s using OFDM.

• ETSI (Europe) defines different frequency bands for Europe: 5.15–5.35 GHz and 5.47–5.725 GHz

• It requires two additional mechanisms for operation: dynamic frequency selection (DFS) and transmit power

control (TPC)

• Japan allows operation in the frequency range 5.15–5.25 GHz and requires carrier sensing every 4 ms to

minimize interference.

• To be able to offer data rates up to 54 Mbit/s IEEE 802.11a uses many different technologies.

• The system uses 52 subcarriers (48 data + 4 pilot) that are modulated using BPSK, QPSK, 16-QAM, or 64-

QAM. To mitigate transmission errors, FEC is applied using coding rates of 1/2, 2/3, or 3/4.

• To offer a data rate of 12 Mbit/s, 96 bits are coded into one OFDM symbol. These 96 bits are distributed

over 48 subcarriers and 2 bits are modulated per sub-carrier using QPSK


WLAN: IEEE 802.11 – developments

• 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 Servicerequirements, and in the capabilities and efficiency of the protocol

• Definition of a data flow (“connection”) with parameters like rate, burst, period…

• Additional energy saving mechanisms and more efficient retransmission

• 802.11f: Inter-Access Point Protocol

• Establish an Inter-Access Point Protocol for data exchange via the distribution system

• 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 dynamicchannel selection (DFS, Dynamic Frequency Selection) and power control (TPC, Transmit Power Control)


WLAN: IEEE 802.11– developments• 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

• 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

• 802.11k: 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 standards

• 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


WLAN: IEEE 802.11– future developments

• 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.


HIPERLAN(High Performance Local Area Network)


WLAN allowing for node mobility and supporting ad-hoc and infrastructure-based topologies

Names have changed and the former HIPERLANs 2, 3, and 4 are now called HiperLAN2, HIPERACCESS,

and HIPERLINK.

The current focus is on HiperLAN2, a standard that comprises many elements from ETSI’s BRAN

(broadband radio access networks) and wireless ATM activities.

Neither wireless ATM nor HIPERLAN 1 were a commercial success.


Historical: HIPERLAN 1

Wireless LAN supporting priorities and packet life time for data transfer at 23.5 Mbit/s, including forwarding

mechanisms, topology discovery, user data encryption, network identification and power conservation

mechanisms. HIPERLAN 1 should operate at 5.1–5.3 GHz with a range of 50 m in buildings at 1 W transmit

power.

The service offered by a HIPERLAN 1 is compatible with the standard MAC services known from IEEE 802.x

LANs.

For power conservation, a node may set up a specific wake-up pattern. This pattern determines at what time

the node is ready to receive, so that at other times, the node can turn off its receiver and save energy. These

nodes are called p-savers and need so-called p-supporters that contain information about the wake-up

patterns of all the p-savers they are responsible for. A p-supporter only forwards data to a p-saver at the

moment the p-saver is awake.


Elimination-yield non-preemptive priority multiple access (EY-NPMA)

It is a heart of the channel access providing priorities and different access schemes. EY-NPMA divides

the medium access of different competing nodes into three phases:

Prioritization: Determine the highest priority of a data packet ready to be sent by competing nodes.

Contention: Eliminate all but one of the contenders, if more than one sender has the highest current priority.

Transmission: Finally, transmit the packet of the remaining node.

prioritization contention transmissiontransmission

synchro

niz

atio

n

prio

rity

dete

ctio

n

prio

rity

assert

ion

t

user

data

elim

ina

tio

n b

urs

t

elim

ina

tio

n s

urv

iva

l

ve

rifica

tio

n

yie

ld lis

tenin

g

IYSIPS IPA IES IESV

The contention phase

is further subdivided

into an elimination

phase and a yield

phase.


EY-NPMA (Elimination Yield Non-preemptive Priority Multiple Access)

3 phases: priority resolution, contention resolution, transmission

Finding the highest priority

• Every priority corresponds to a time-slot to send in the first phase, the higher the priority the earlier the

time-slot to send

• Higher priorities can not be preempted

• If an earlier time-slot for a higher priority remains empty, stations with the next lower priority might send

• After this first phase the highest current priority has been determined


Several terminals can now have the same priority and wish to send

CONTENTION PHASE

Elimination Burst: all remaining terminals send a burst to eliminate contenders

(11111010100010011100000110010110, high bit- rate)

Elimination Survival Verification: contenders now sense the channel, if the channel is free they can continue,

otherwise they have been eliminated

Yield Listening: contenders again listen in slots with a nonzero probability, if the terminal senses its slot idle it is free to

transmit at the end of the contention

DATA TRANSMISSION

The winner can now send its data (however, a small chance of collision remains).if the channel was idle for a longer

time a terminal can send at once without using EY-NPMA

synchronization using the last data transmission


Wireless ATM

(Wireless Asynchronous Transfer Mode)


WATM: sometimes also called wireless, mobile ATM, wmATM

IEEE WLANs originate from the data communication community, many WATM aspects come

from the telecommunication industry

Motivation for WATM:

1. The need for seamless integration of wireless terminals into an ATM network.

2. ATM networks scale well from LANs to WANs – and mobility is needed in local and wide area

applications.

3. For ATM to be successful, it must offer a wireless extension.

4. WATM could offer QoS for adequate support of multi-media data streams.


Wireless ATM working group:

ATM Forum formed the Wireless ATM Working Group in 1996, which aimed to develop a set of specifications that

extends the use of ATM technology to wireless networks.

The following more general extensions of the ATM system also need to be considered for a mobile ATM:

Location management: Similar to other cellular networks, WATM networks must be able to locate a wireless terminal

or a mobile user.

Mobile routing: Even if the location of a terminal is known to the system, it still has to route the traffic through the

network to the access point currently responsible for the wireless terminal. Each time a user moves to a new access

point, the system must reroute traffic.

Handover signalling: The network must provide mechanisms which search for new access points

QoS and traffic control: In contrast to wireless networks offering only best effort traffic, and to cellular networks

offering only a few different types of traffic, WATM should be able to offer many QoS parameters. To maintain these

parameters, all actions such as rerouting, handover etc. have to be controlled.

Network management: All extensions of protocols or other mechanisms also require an extension of the

management functions to control the networkEC8004/WIRELESS NETWORKS/RAJKUMAR.K.K

WATM services:

1. Office environments

2. Universities, schools, training centre

3. Industry

4. Hospitals

5. Home

6. Networked vehicles


Generic reference model

WATM

terminal

adapter

MATM

termi-

nal

RASEMAS

-E

EMAS

-N

ATM-

Switch

fixed

end

system

radio segment fixed network segment

A mobile ATM (MATM) terminal uses a WATM terminal adapter to gain wireless access to a WATM RAS

(Radio Access System).

MATM terminals could be represented by, e.g., laptops using an ATM adapter for wired access plus

software for mobility.

The WATM terminal adapter enables wireless access, i.e., it includes the transceiver etc., but it does not

support mobility.

The RAS with the radio transceivers is connected to a mobility enhanced ATM switch (EMAS-E), which in

turn connects to the ATM network with mobility aware switches (EMAS-N)

Finally, a wired, non-mobility aware ATM end system may be the communication partner in this example.


HANDOVER:

The main problem for WATM during the handover is rerouting all connections and maintaining connection quality.

Different requirements have been set up for handover

Handover of multiple connections:

Handover in WATM must support more than one connection.

This results in the rerouting of every connection after handover.

However, resource availability may not allow rerouting of all connections or forces QoS degradation.

The terminal may then decide to accept a lower quality or to drop single connections.

Handover of point-to-multi-point connections:

WATM handover should also support these types of connection.

However, due to the complexity of the scheme, some restrictions might be necessary.

QoS support:

Handover should aim to preserve the QoS of all connections during handover.

However, due to limited resources, this is not always possible.


LOCATION MANAGEMENT

As for all networks supporting mobility, special functions are required for looking up the current position of a mobile

terminal, for providing the moving terminal with a permanent address, and for ensuring security features such as

privacy, authentication, or authorization.

MOBILE QUALITY OF SERVICE

Wired QoS: The infrastructure network needed for WATM has the same QoS properties as any wired ATM network.

Wireless QoS: The QoS properties of the wireless part of a WATM network differ from those of the wired part.

Channel reservation and multiplexing mechanisms at the air interface strongly influence cell delay variation.

Handover QoS: A new set of QoS parameters are introduced by handover. For example, handover blocking due to limited

resources at target access points, cell loss during handover


Hard handover QoS: While the QoS with the current RAS may be guaranteed due to the current

availability of resources, no QoS guarantees are given after the handover.

Soft handover QoS: Even for the current wireless segment, only statistical QoS guarantees can be

given, and the applications also have to adapt after the handover.


BRANBroadband Radio Access Networks


The main motivation behind BRAN is the deregulation and privatization of the telecommunication

sector in Europe.

Many new providers experience problems getting access to customers because the telephone

infrastructure belongs to a few big companies.

One possible technology to provide network access for customers is radio. The advantages of radio

access are high flexibility and quick installation.

BRAN standardization has a rather large scope including indoor and campus mobility, transfer

rates of 25–155 Mbit/s, and a transmission range of 50 m–5 km.


BROADBAND NETWORK TYPES

HIPERLAN/2• short range (< 200 m), indoor/campus, 25 Mbit/s user data rate

• access to telecommunication systems, multimedia applications, mobility (<10 m/s)

HIPERACCESS• wider range (< 5 km), outdoor, 25 Mbit/s user data rate

• fixed radio links to customers (“last mile”), alternative to xDSL or cable modem, quick installation

• Several (proprietary) products exist with 155 Mbit/s plus QoS

HIPERLINK – currently no activities• intermediate link, 155 Mbit/s

• connection of HIPERLAN access points or connection between HIPERACCESS nodes


HiperLAN2


This wireless network works at 5 GHz and offers data rates of up to 54 Mbit/s including QoS support and

enhanced security features.


Reference model and configurations

2

3

1

AP

APT APC Core

Network

(Ethernet,

Firewire,

ATM,

UMTS)APT

APT

APC

AP

MT4

MT3

MT2

MT1

Sector handover (Inter sector): If sector antennas are used for an AP, which is optional in the standard, the AP

shall support sector handover. This type of handover is handled inside the DLC layer so is not visible outside the

AP

Radio handover (Inter-APT/Intra-AP): As this handover type, too, is handled within the AP, no external interaction

is needed. In the example of Figure the terminal MT3, moves from one APT to another of the same AP. All context

data for the connections are already in the AP

Network handover (Inter-AP/Intra-network): This is the most complex situation: MT2 moves from one AP to

another. In this case, the core network and higher layers are also involved. This handover might be supported by

the core network


Centralized vs. direct mode

MT1

AP/CCAP

MT2

data

control control

MT1 MT2data

control

Centralized Direct

MT1 MT2 +CCdata

control


HiperLAN2 protocol stackHigher layers

Convergence layer

Data link control -

basic data

transport functionScope of

HiperLAN2

standards

DLC control

SAP

DLC user

SAP

Radio link control sublayer

Physical layer

Radio

resource

control

Assoc.

control

DLC

conn.

control

Error

controlRadio link control

Medium access control


Physical layer reference configuration

scrambling FEC coding interleaving

mapping OFDMPHY bursts

(PPDU)

PDU train from DLC

(PSDU)

radio

transmitter

1. Scrambling of all data bits with the generator polynomial for DC blocking and whitening of the

spectrum.

2. FEC coding for error protection

3. For mitigation of frequency selective fading interleaving is applied.

4. mapping process first divides the bit sequence in groups of 1,2, 4, or 6 bits depending on the modulationscheme (BPSK, QPSK, 16-QAM, or 64-QAM).

5. The OFDM modulation step converts these symbols into a baseband signal with the help of the inverse FFT.

6. Creation of PHY bursts Each burst consists of a preamble and a payload.

7. radio transmission shifts the baseband signal to a carrier frequency depending on the channel numberEC8004/WIRELESS NETWORKS/RAJKUMAR.K.K

Operating channels of HiperLAN2 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


Basic structure of HiperLAN2 MAC frames

MAC frame MAC frame MAC frame MAC frame

2 ms 2 ms 2 ms 2 ms

broadcast phase downlink phase uplink phaserandom

access phase

. . .

TDD,

500 OFDM

symbols

per frame

variable variable variable

LCH PDU typesequence

numberpayload CRC

UDCH transfer syntax

(long PDU)

54 byte

2 10 396 24 bit

LCH PDU type payload CRC

2 406 24

LCH transfer syntax

bit


Valid configurations of HiperLAN2 MAC frames

MAC frame MAC frame MAC frame MAC frame

2 ms 2 ms 2 ms 2 ms

BCH FCH ACH DL phase DiL phase UL phase RCHs

. . .

BCH FCH ACH DiL phase UL phase RCHs

BCH FCH ACH DL phase UL phase RCHs

BCH FCH ACH UL phase RCHs

BCH FCH ACH DL phase DiL phase RCHs

BCH FCH ACH DiL phase RCHs

BCH FCH ACH DL phase RCHs

BCH FCH ACH RCHs

Valid

combinations

of MAC frames

for a single

sector AP

broadcast downlink uplink

random

access


Mapping of logical and transport channelsBCCH FCCH RFCH LCCH RBCH DCCH UDCH UBCH UMCH

BCH FCH ACH SCH LCH

downlink

UDCH DCCH LCCH ASCH

SCHLCH RCH

uplink

UDCH UBCH UMCH

LCH

DCCH RBCH

SCH

LCCH

direct link


BluetoothIdea

• Universal radio interface for ad-hoc wireless connectivity

• Interconnecting computer and peripherals, handheld devices, PDAs, cell phones –replacement of IrDA

• Embedded in other devices, goal: 5€/device (2005: 40€/USB bluetooth)

• Short range (10 m), low power consumption, license-free 2.45 GHz ISM

• Voice and data transmission, approx. 1 Mbit/s gross data rate

One of the first modules (Ericsson).


Bluetooth• History

• 1994: Ericsson (Mattison/Haartsen), “MC-link” project• Renaming of the project: Bluetooth according to Harald “Blåtand” Gormsen [son of Gorm],

King of Denmark in the 10th century• 1998: foundation of Bluetooth SIG, www.bluetooth.org• 1999: erection of a rune stone at Ercisson/Lund ;-)• 2001: first consumer products for mass market, spec. version 1.1 released• 2005: 5 million chips/week

• Special Interest Group• Original founding members: Ericsson, Intel, IBM, Nokia, Toshiba• Added promoters: 3Com, Agere (was: Lucent), Microsoft, Motorola• > 2500 members• Common specification and certification of products

(was: )


http://www.bluetooth.org/

History and hi-tech…

1999:

Ericsson mobile

communications AB

reste denna sten till

minne av Harald

Blåtand, som fick ge

sitt namn åt en ny

teknologi för trådlös,

mobil kommunikation.


…and the real rune stoneLocated in Jelling, Denmark,

erected by King Harald “Blåtand”

in memory of his parents.

The stone has three sides – one side

showing a picture of Christ.

This could be the “original” colors

of the stone.

Inscription:

“auk tani karthi kristna” (and

made the Danes Christians)

Inscription:

"Harald king executes these sepulchral

monuments after Gorm, his father and

Thyra, his mother. The Harald who won the

whole of Denmark and Norway and turned

the Danes to Christianity."

Btw: Blåtand means “of dark complexion”

(not having a blue tooth…)


Characteristics

2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing• Channel 0: 2402 MHz … channel 78: 2480 MHz• G-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

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

• 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)

• 3 bit address is used by Bluetooth device. M=Master

S=Slave

P=Parked

SB=Standby

M

S

P

SB

S

S

P

P

SB


Forming a piconetAll 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

Addressing• Active Member Address (AMA, 3 bit)

• Parked Member Address (PMA, 8 bit)

SB

SB

SB

SB

SB

SB

SB

SB

SB

M

S

P

SB

S

S

P

P

SB


ScatternetLinking of multiple co-located piconets through the sharing of common master or slave devices

• Devices can be slave in one piconet and master of another

Communication between piconets• Devices jumping back and forth between the piconets

M=Master

S=Slave

P=Parked

SB=Standby

M

S

P

SB

S

S

P

P

SB

M

S

S

P

SB

Piconets

(each with a

capacity of

720 kbit/s)


Bluetooth protocol stack

Radio

Baseband

Link Manager

Control

Host

Controller

Interface

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 modem

commands

telephony apps.audio apps. mgmnt. apps.

AT: attention sequence

OBEX: object exchange

TCS BIN: telephony control protocol specification – binary

BNEP: Bluetooth network encapsulation protocol

SDP: service discovery protocol

RFCOMM: radio frequency comm.

PPP


Radio layer

Power class 1: Maximum power is 100 mW and minimum is 1 mW (typ. 100 m range without obstacles). Power control is mandatory.

Power class 2: Maximum power is 2.5 mW, nominal power is 1 mW, and minimum power is 0.25 mW (typ. 10 m range without obstacles). Power control is optional.

Power class 3: Maximum power is 1 mW.


BasebandPiconet/channel definition

Low-level packet definition• Access code

• Channel, device access, e.g., derived from master address (48-bit)

• Packet header• 1/3-FEC, active member address (broadcast + 7 slaves), link type, alternating bit

ARQ/SEQ, checksum

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)


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


SCO payload typespayload (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)


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 link types• Polling-based TDD packet transmission

• 625µs slots, master polls slaves

• SCO (Synchronous Connection Oriented) – Voice • Periodic single slot packet assignment, 64 kbit/s full-duplex, point-to-point

• ACL (Asynchronous ConnectionLess) – Data • Variable packet size (1,3,5 slots), asymmetric bandwidth, point-to-multipoint

MASTER

SLAVE 1

SLAVE 2

f6f0

f1 f7

f12

f13 f19

f18

SCO SCO SCO SCOACL

f5 f21

f4 f20

ACLACL

f8

f9

f17

f14

ACL


Robustness• Slow frequency hopping with hopping patterns determined by a master

• Protection from interference on certain frequencies

• Separation from other piconets (FH-CDMA)

• Retransmission• ACL only, very fast

• Forward Error Correction• SCO and ACL

MASTER

SLAVE 1

SLAVE 2

A C C HF

G G

B D E

NAK ACK

Error in payload

(not header!)


Baseband states of a Bluetooth devicestandby

inquiry page

connected

AMA

transmit

AMA

park

PMA

hold

AMA

sniff

AMA

unconnected

connecting

active

low power

Standby: do nothing

Inquire: search for other devices

Page: connect to a specific device

Connected: participate in a piconet

detach

Park: release AMA, get PMA

Sniff: listen periodically, not each slot

Hold: stop ACL, SCO still possible, possibly

participate in another piconet


Example: Bluetooth/USB adapter (2002: 50€)


L2CAP - Logical Link Control and Adaptation Protocol• Simple data link protocol on top of baseband

• Connection oriented, connectionless, and signalling channels

• Protocol multiplexing• RFCOMM, SDP, telephony control

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

• QoS flow specification per channel• Follows RFC 1363, specifies delay, jitter, bursts, bandwidth

• Group abstraction• 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


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

Connection-oriented PDU

Signalling command PDU

code ID length data

1 1 2 0


Security

E3

E2

link key (128 bit)

encryption key (128 bit)

payload key

Keystream generator

Data Data

Cipher 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)


SDP – Service Discovery Protocol

• Inquiry/response protocol for discovering services• Searching for and browsing services in radio proximity• Adapted to the highly dynamic environment• Can be complemented by others like SLP, Jini, Salutation, …• Defines discovery only, not the usage of services• Caching of discovered services• Gradual discovery

• 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)


Additional protocols to support legacy protocols/apps.• RFCOMM

• Emulation of a serial port (supports a large base of legacy applications)• Allows multiple ports over a single physical channel

• Telephony Control Protocol Specification (TCS)• Call control (setup, release)• Group management

• OBEX• Exchange of objects, IrDA replacement

• WAP• Interacting with applications on cellular phones


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 devices/network&master, high set-up latency


WPAN: IEEE 802.15

• 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:• 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

• Basis of the ZigBee technology – www.zigbee.org


Emerging Technologies

WiMAX


Current ScenarioThink about how you access the Internet today. There are basically three different options:

Broadband access - In your home, you have either a DSL or cable modem. At the office,your company may be using a T1 or a T3 line.

WiFi access - In your home, you may have set up a WiFi router that lets you surf the Webwhile you lounge with your laptop. On the road, you can find WiFi hot spots in restaurants,hotels, coffee shops and libraries.

Dial-up access - If you are still using dial-up, chances are that either broadband access isnot available, or you think that broadband access is too expensive.


Current Scenario The main problems with broadband access are that it is pretty expensive and it doesn't

reach all areas. The main problem with WiFi access is that hot spots are very small, socoverage is sparse.

What if there were a new technology that solved all of these problems? This newtechnology would provide:

The high speed of broadband service.

Wireless rather than wired access, so it would be a lot less expensive than cable or DSL

and much easier to extend to suburban and rural areas.

Broad coverage like the cell phone network instead of small WiFi hotspots.


Wireless Broadband

This system is actually coming into being right now, and it is called WiMAX. WiMAX is short for

Worldwide Interoperability for Microwave Access, and it also goes by the IEEE name 802.16.

Also known as Wireless Metropolitan Area Network (Wireless MAN).

Offers an alternative to high bandwidth wired access networks like fiber optic, cable modems and

DSL.

Provides network access to buildings through exterior antennas communicating with radio base

stations.

Networks can be created in just weeks by deploying a small number of base stations on buildings or

poles to create high capacity wireless access systems.


WiMax Vs. WiFi WiMAX operates on the same general principles as WiFi - it sends data from one computer to another via

Radio signals.

A computer (either a desktop or a laptop) equipped with WiMAX would receive data from the WiMAX

transmitting station, probably using encrypted data keys to prevent unauthorized users from stealing access.

The fastest WiFi connection can transmit up to 54 megabits per second under optimal conditions.

WiMAX should be able to handle up to 70 megabits per second.

Even once that 70 megabits is split up between several dozen businesses or a few hundred home users, it

will provide at least the equivalent of cable-modem transfer rates to each user.


WiMax Vs. WiFi

The biggest difference isn't speed; it's distance. WiMAX outdistances WiFi by miles. WiFi's range is about

100 feet (30 m). WiMAX will blanket a radius of 30 miles (50 km) with wireless access.

The increased range is due to the frequencies used and the power of the transmitter.

Of course, at that distance, terrain, weather and large buildings will act to reduce the maximum range in

some circumstances, but the potential is there to cover huge tracts of land.

WiMax is not designed to clash with WiFi, but to coexist with it.

WiMax specifications also provides much better facilities than WiFi, providing higher bandwidth and high

data security by the use of enhanced encryption schemes.


WiMAX is not Wi-Fi


Overview of IEEE 802.16


Sub-standards of IEEE 802.16

IEEE 802.16.1 - Air interface for 10 to 66 GHz

IEEE 802.16.2 - Coexistence of broadband wireless access systems

IEEE 802.16.3 - Air interface for licensed frequencies, 2 to 11 GHz


Basics of IEEE 802.16

IEEE 802.16 standards are concerned with the air interface between a subscriber’s transceiver station and a base transceiver station

The Physical Layer

MAC Layer

Convergence Layer


IEEE 802.16 Protocol Architecture


Physical Layer

Specifies the frequency band, the modulation scheme, error-correction techniques,synchronization between transmitter and receiver, data rate and the multiplexing structure

Both TDD and FDD alternatives support adaptive burst profiles in which modulation andcoding options may be dynamically assigned on a burst-by-burst basis

Three physical layer for services: Wireless MAN-SC2, Wireless MAN-OFDM and WirelessMAN-OFDMA


Medium Access Control Layer

Designed for point-to-multipoint broadband wireless access

Addresses the need for very high bit rates, both uplink (to the base station) anddownlink (from the base station)

Services like multimedia and voice can run as 802.16 MAC is equipped to accommodateboth continuous and bursty traffic


Convergence Layer

Provides functions specific to the service being provided

Bearer services include digital audio/video multicast, digital telephony, ATM, Internetaccess, wireless trunks in telephone networks and frame relay


Reference Network Model

• The IEEE 802.16e-2005 standard provides the air interface for WiMAX but does not define the full end-to-

end WiMAX network. The WiMAX Forum's Network Working Group (NWG), is responsible for

developing the end-to-end network requirements, architecture, and protocols for WiMAX, using IEEE

802.16e-2005 as the air interface.

• The WiMAX NWG has developed a network reference model to serve as an architecture framework for

WiMAX deployments and to ensure interoperability among various WiMAX equipment and operators.

• The network reference model envisions a unified network architecture for supporting fixed, nomadic, and

mobile deployments and is based on an IP service model.



• The overall network may be logically divided into three parts:

1. Mobile Stations (MS) used by the end user to access the network.

2. The access service network (ASN), which comprises one or more base stations and oneor more ASN gateways that form the radio access network at the edge.

3. Connectivity service network (CSN), which provides IP connectivity and all the IP corenetwork functions.





• The network reference model developed by the WiMAX Forum NWG defines a number of functional

entities and interfaces between those entities. Fig below shows some of the more important functional

entities.

1) Base station (BS): The BS is responsible for providing the air interface to the MS. Additional functions that

may be part of the BS are micromobility management functions, such as handoff triggering and tunnel

establishment, radio resource management, QoS policy enforcement, traffic classification, DHCP (Dynamic

Host Control Protocol) proxy, key management, session management, and multicast group management.



2) Access service network gateway (ASN-GW): The ASN gateway typically acts as a

layer 2 traffic aggregation point within an ASN. Additional functions that may be part of

the ASN gateway include intra-ASN location management and paging, radio resource

management and admission control, caching of subscriber profiles and encryption keys,

establishment and management of mobility tunnel with base stations, QoS and policy

enforcement, foreign agent functionality for mobile IP, and routing to the selected CSN.



3) Connectivity service network (CSN): The CSN provides connectivity to the Internet, ASP, other public

networks, and corporate networks.

The CSN is owned by the NSP and includes AAA servers that support authentication for the devices, users,

and specific services. The CSN also provides per user policy management of QoS and security.

The CSN is also responsible for IP address management, support for roaming between different NSPs, location

management between ASNs, and mobility and roaming between ASNs.


Advanced Features of WiMAX

An important and very challenging function of the WiMAX system is the support of various advanced

antenna techniques, which are essential to provide high spectral efficiency, capacity, system performance, and

reliability.

Two Type of Services:

WiMAX can provide two forms of wireless service:

1) Non-line-of-sight: service is a WiFi sort of service. Here a small antenna on your computer connects to the

WiMAX tower. In this mode, WiMAX uses a lower frequency range -- 2 GHz to 11 GHz (similar to WiFi).

2) Line-of-sight: service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or

pole. The line-of-sight connection is stronger and more stable, so it's able to send a lot of data with fewer

errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz.



• Very high peak data rates:

WiMAX is capable of supporting very high peak data rates. In fact, the peak PHY data rate can be as high as

74Mbps when operating using a 20MHz wide spectrum.

More typically, using a 10MHz spectrum operating using TDD scheme with a 3:1 downlink-to-uplink ratio,

the peak PHY data rate is about 25Mbps and 6.7Mbps for the downlink and the uplink, respectively.



• Scalable bandwidth and data rate support:

WiMAX has a scalable physical-layer architecture that allows for the data rate to scale easily with available

channel bandwidth.

For example, a WiMAX system may use 128, 512, or 1,048-bit FFTs (fast fourier transforms) based on

whether the channel bandwidth is 1.25MHz, 5MHz, or 10MHz, respectively.



• Quality-of-service support:

The WiMAX MAC layer has a connection-oriented architecture that is designed to support a variety of

applications, including voice and multimedia services.

WiMAX system offers support for constant bit rate, variable bit rate, real-time, and non-real-time traffic

flows, in addition to best-effort data traffic.

WiMAX MAC is designed to support a large number of users, with multiple connections per terminal, each

with its own QoS requirement.



• Robust security:

WiMAX supports strong encryption, using Advanced Encryption Standard (AES), and has a robust privacy and

key-management protocol.

The system also offers a very flexible authentication architecture based on Extensible Authentication Protocol

(EAP), which allows for a variety of user credentials, including username/password, digital certificates, and

smart cards.

• Support for mobility:

The mobile WiMAX variant of the system has mechanisms to support secure seamless handovers for delay-

tolerant full-mobility applications, such as VoIP.


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