Unit 3

UNIT III WIRELESS NETWORKS
Wireless LANs and PANs – IEEE 802.11 Standard – Architecture – Services – Blue Tooth- Wi-Fi – WiMAX
WIRELESS NETWORKS
WIRELESS LANs
The increased demands for mobility and flexibility in our daily life are
demands that lead the development from wired LANs to wireless LANs (WLANs).
WLANS use electromagnetic radio waves to transport data between
computers in a Local Area Network (LAN), without the limitations set by ―hard
wired network cable or phone wire connection‖. Whilst simple optical links are
commercially available, radio is presently more useful since it is not strictly
restricted to line-of-sight paths.
Radio waves are often called radio carriers when they are used to
carry information. The data to be transported is superimposed on the radio carrier
by various modulation techniques which allow the data to be faithfully
reconstructed at the receiving end. Once data is superimposed (modulated) onto the
radio carrier, this combined ―radio channel‖ now occupies more than a single
frequency since the frequency components or spectra of the modulating data add
frequency bandwidth to the basic carrier (in direct proportion to its information
content or bit rate). The frequency range which is needed to accommodate a radio
signal with any given modulation bandwidth is called a channel. Radio receiver
techniques can select one radio channel while efficiency rejecting signals on other
frequencies. Many radio signals to and from many users can thereby co-exist in the
same place and time without interfering with each other if the radio waves are
transmitted at minimum necessary power within different radio channels.
ADVANTAGES OF WLAN OVER WIRED LAN
Flexibility : With in radio coverage nodes can communicate without
further restriction.

Planning : Wireless ad hoc network allow communication without
planning whereas wired network needs wiring plans.
Design : Wireless Network allows for the design of small
independent devices.
Robustness : Wireless network can survive disaster. If the wireless
devices survive people can communicate.
Cost : Adding additional users to a wireless network will be increase the
cost. But where as with fixed network addition of an user will lead into
unplugging and plugging. Wireless communications do not wear out.
DISADVANTAGES
QOS:
Wireless offers lower quality than that of wired. The reasons are
The lower bandwidth due to limitations in radio transmission.
High error rate due to interference.
Higher delay due to error correction and detection mechanisms.
PROPRIETARY SOLUTION :
Many companies have comeup with proprietary solutions offering
standardized functionality.

This is due to slow standardization procedures.
RESTRICTION :
The wireless products need to comply with national regulations.
WLAN are limited to low power senders and certain license free frequency hand
which are not same world wide.
SAFETY AND SECURITY :
The radio waves are used for data transmission. They will interfere with
other equipment. Precaution have to be taken to prevent safety hazards.i
 As it is via radio transmissions eaves dropping is possible.
DESIGN GOALS
Global operation : While the product is being sold in all the
countries, national and international frequency regulations should be
considered. 

Low Power : Devices communicating via WLAN are also wireless
devices. These devices run on battery power – while designing a WLAN
these aspects should also be considered. 


License free Operation : The equipment must operate in a license free
band such as 2.4 GHz ISM Band 

Robust Transmission Technology : WLAN operate under difficult
conditions. As they are radio transmission many other electrical devices can
interfere with them. 

Simplified Spontaneous Co-operation : WLAN should not
require complicated startup routines , but should run spontaneously after
power up. 

Easy to use : WLAN‘s are mad for simple use. They should be like plug
and play. 

Protection of Investment : For transmission from wired to wireless,
simple bridging should be enough to interoperate. 

Safety and Security : WLAN should be safe to operate. When low
radiation are used. The network should consider user privacy and
security. 


Transparency : Existing applications should continue to run over
WLAN with trade off to higher delay and lower bandwidth.
IEEE 802.11 STANDARD
The IEEE standard 802.11 (IEEE, 1999) specifies the most famous family of
WLANs in which many products are available. As the standard‘s number indicates,
this standard belongs to the group of 802.x LAN standards, e.g., 802.3 Ethernet or
802.5 Token Ring. This means that the standard specifies the physical and medium
access layer adapted to the special requirements of wireless LANs, but offers the
same interface as the others to higher layers to maintain interoperability. The
primary goal of the standard was the specification of a simple and robust WLAN
which offers time-bounded and asynchronous services.
SYSTEM ARCHITECTURE
Wireless networks can exhibit two different basic system
architectures as infrastructure-based or ad-hoc. Figure shows the components of an
infrastructure and a wireless part as specified for IEEE 802.11. Several nodes,
called stations (STAi), are connected to access points (AP). Stations are terminals
with access mechanisms to the wireless medium and radio contact to the AP. The
stations and the AP which are within the same radio coverage form a basic service
set (BSSi). The example shows two BSSs – BSS1 and BSS2 – which are connected
via a distribution system. A distribution system connects several BSSs via the AP
to form a single network and thereby extends the wireless coverage area. This
network is now called an 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. The distribution system connects the wireless
networks via the APs with a portal, which forms the interworking unit to other

The architecture of the distribution system is not specified further in IEEE 802.11.
It could consist of bridged IEEE LANs, wireless links, or any other networks.
However, distribution system services are defined in the standard 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, support power management, and can
control medium access to support time-bounded service. In addition to
infrastructure-based networks, IEEE 802.11 allows the building of ad-hoc
networks between stations, thus forming one or more independent BSSs (IBSS) as
shown in Figure 7.4. In this case, an IBSS comprises a group of stations using the
same radio frequency. Stations STA1, STA2, and STA3 are in IBSS1, STA4 and
STA5 in IBSS2. This means for example that STA3 can communicate directly with
STA2 but not with STA5. Several IBSSs can either be formed via the distance
between the IBSSs or by using different carrier frequencies (then the IBSSs could
overlap physically). IEEE 802.11 does not specify any special nodes that support
routing, forwarding of data or exchange of topology information as, e.g.,
HIPERLAN 1 or Bluetooth.

SERVICES
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. 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 asynchronous service supports
broadcast and multi-cast packets, and packet exchange is based on a ‗best effort‘
model, i.e., no delay bounds can be given for transmission. The following three
basic access mechanisms have been defined for IEEE 802.11: the mandatory basic
method based on a version of CSMA/CA, an optional method avoiding the hidden
terminal problem, and finally a contention- free polling method for time-bounded
service. The first two methods are also summarized as distributed
coordination function (DCF), the third method is called point coordination
function (PCF). DCF only offers asynchronous service, while PCF offers both

asynchronous and time-bounded service but needs an access point to control
medium access and to avoid contention. The MAC mechanisms are also
called distributed foundation wireless medium access control(DFWMAC). For
all access methods, several parameters for controlling the waiting time before
medium access are important. Figure 7.9 shows the three different parameters that
define the priorities of medium access. The values of the parameters depend on the
PHY and are defined in relation to a slot time. Slot time is derived from the
medium propagation delay, transmitter delay, and other PHY dependent
parameters. Slot time is 50 μs for FHSS and 20 μs for DSSS. The medium, as
shown, can be busy or idle (which is detected by the CCA). If the medium is busy
this can be due to data frames or other control frames. During a contention phase
several nodes try to access the medium.
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. For DSSS SIFS is 10 μs and for FHSS it is 28 μs.
PCF inter-frame spacing (PIFS):
A waiting time between DIFS and SIFS (and thus a medium
priority) is used for a time-bounded service. An access point polling other nodes

only has to wait PIFS for medium access. PIFS is defined as SIFS plus one slot
time.
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 period. DIFS is defined as SIFS plus two slot times.
BLUETOOTH
INTRODUCTION
Bluetooth is a wireless technology standard for exchanging data over short
distances (using short-wavelength radio transmissions in the ISM band from 2400–
2480 MHz) from fixed and mobile devices, creating personal area networks
(PANs) with high levels of security. Different type of network is needed to
connect different small devices in close proximity (about 10 m) without expensive
wiring or the need for a wireless infrastructure .Bluetooth is a new standard
suggested by a group of electronics manufacturers that will allow any sort of
electronic tools from computers and cell phones to keyboards and headphones to
make its own connections, without wires, cables or any direct action from a user. A
key distinction with other offered wireless technologies is that bluetooth enables
combined usability models based on functions provided by different devices.
Bluetooth was invented in1994 by L.M.Ericson of Sweden. The name is attributed
to Harald Bluetooth was king of Denmark around the turn of the last millennium.
Choosing this name for the standard indicates how important companies from the
Baltic region (nations including Denmark, Sweden, Norway and Finland) are to the
communications industry.

As famous as the name is the bluetooth symbol. Bluetooth icon can
be recognized by all. The main strength of bluetooth is its ability to simultaneously
handle both data and voice transmissions. It is capable of supporting one
asynchronous data channel and up to three synchronous voice channels, or one
channel sup-porting both voice and data. This ability combined with ad hoc device
connection and automatic service discovery make it a superior solution for mobile
devices and Internet applications. This grouping allows such novel solutions as a
mobile hands-free headset for voice calls, print to fax capability, and automatically
synchronizing PDA, laptop, and cell phone address book applications.
BLUETOOTH FEATURE:
It is Wireless and automatic
Bluetooth is inexpensive (< $5 per unit) It Handles both data and voice
Signals are omni-directional and can pass through walls and briefcases
Bluetooth uses frequency hopping at rate of 1600 Lops/sec

It operates on 79 channels in 2.4GHZ band with 1MHZ carrier spacing Pi-
conet is the important terminology
NETWORK TOPOLOGY
Piconet:
A set of bluetooth devices sharing a common channel is called piconet. A
piconet is a collection of devices connected via Bluetooth technology in an ad hoc
fashion. A piconet starts with two connected devices, and may grow to eight
connected devices. All Bluetooth devices are peer units and have identical
implementations. However, when establishing a piconet, one unit will act as
a Master and the other(s) as slave(s) for the duration of the piconet
connection. Master is a Bluetooth device that sets the frequency hopping sequence.
The Slave synchronizes to the Masters in time and frequency by following the
Master‘s frequency hoping sequence. Every Bluetooth device has a unique
Bluetooth device address and a 28-bit Bluetooth clock. The baseband part of
the Bluetooth System uses a special algorithm, which calculates the frequency hop
sequence from the masters clock and device address. In addition to controlling the
frequency hop sequence, the Master controls when Slaves are to transmit using
Time Division Multiplexing (TDM).
When there is just one Master and one Slave the system is called a Point
to Point connection. When many Slaves are connected to one Master, the system
is called a Point to Multipoint. Both these types are referred to as a Piconet and
all follow the frequency hopping sequence of the Master. The Slaves in the Piconet
only have links to the Master and no direct links between Slaves.

Formation of piconet:
Two parameters are needed for the formation of piconet
Hopping pattern of the radio it wishes to connect.
Phase within the pattern i.e. the clock offset of the hops.
The global ID defines the hopping pattern. The master shares its global ID and its
clock offset with the other radios which become slaves. The global ID and the
clock parameters are exchanged using a FHS (Frequency Hoping Synchronization)
packet.

There is no difference between terminals and base stations, two or more
devices can form a piconet. The unit establishing the piconet repeatedly becomes
the master, all other devices will be slaves. The hopping pattern is determined by
the device ID, a 48-bit worldwide unique identifier. The phase in the hopping
pattern is determined by the master‘s clock. After altering the interior clock
according to the master a device may take part in the piconet. All active devices
are assigned a 3-bit active member address (AMA). All parked devices use an 8-
bit parked member address (PMA). Devices in stand-by do not need any address.
All users within one piconet have the same hopping sequence and share the same 1
MHz channel. As more users join the piconet, the throughput per user drops
quickly.
Scatternet :
Bluetooth defines a structure called scatternet to facilitate inter piconet
communication. A scatternet is formed by interconnecting multiple piconet. A
group of piconet is called scatternet.
If a device wants to take part in more than one piconet, it has to coordinate to the
hopping sequence of the piconet it wants to take part in. If a device acts as slave in
one piconet, it just starts to synchronize with the hopping sequence of the piconet it
wants to join. After synchronization, it acts as a slave in this piconet and no longer
participates in its former piconet. To permit synchronization, a slave has to know

the uniqueness of the master that determines the hopping sequence of a piconet.
Before leaving one piconet, a slave informs the current master that it will be
unavailable for a certain amount of time.
The left over devices in the piconet continue to communicate normal.
A master can also go away from its piconet and act as a slave in another piconet. It
is obviously not possible for a master of one piconet to act as the master of another
piconet as this would direct to identical behavior. As soon as a master leaves a
piconet, all traffic within this piconet is balanced until the master returns.

Communication between different piconets takes place by devices jumping back
and forth between these nets. If this is done occasionally, for instance, isochronous
data streams can be forwarded from one piconet to another. On the other hand,
scatternets are not yet supported by all piconet.
BLUETOOTH PROTOCOL STACK
The Bluetooth protocol stack can be divided into:
Core Specification -Deals with the lower layers of the architecture
and describes how the technology works. It describe the protocol from
physical to data link layer along with management functions.
Profile Specification -Focuses on how to build interoperating devices
using the core technology.
Bluetooth Radio : specifics details of the air interface, including
frequency, frequency hopping, modulation scheme, and transmission power.

Baseband: concerned with connection establishment within a
piconet, addressing, packet format, timing and power control.
Link manager protocol (LMP): establishes the link setup
between Bluetooth devices and manages ongoing links, including security
aspects (e.g. authentication and encryption), and control and negotiation of
baseband packet size
Logical link control and adaptation protocol (L2CAP): adapts upper
layer protocols to the baseband layer. Provides both connectionless and
connection-oriented services.
Service discovery protocol (SDP): handles device information, services,
and queries for service characteristics between two or more Bluetooth
devices.
Host Controller Interface (HCI): provides an interface method
for accessing the Bluetooth hardware capabilities. It contains a command
interface, which acts between the Baseband controller and link manager
TCS BIN (Telephony Control Service): bit-oriented protocol that
defines the call control signaling for the establishment of voice and data
calls between Bluetooth devices.
OBEX(OBject EXchange) : Session-layer protocol for the exchange
of objects, providing a model for object and operation representation
RFCOMM: a reliable transport protocol, which provides emulation of
RS232 serial ports over the L2CAP protocol
WAE/WAP: Bluetooth incorporates the wireless application
environment and the wireless application protocol into its architecture.

Physical links
Different types of links can be established between master and slave. Two link
types have been defined they are:
Synchronous Connection-Oriented (SCO) link. Asynchronous Connection-Less
(ACL) link.
1.Synchronous Connection Oriented (SCO): It Support symmetrical, circuit-
switched, point-to-point connections . It is typically used for voice traffic. The
Data rate is 64 kbit/s.
2.Asynchronous Connection-Less (ACL): It Support symmetrical
and asymmetrical, packet-switched, point-to-multipoint connections. It is typically
used for data transmission .Up to 433.9 kbit/s are used in symmetric or 723.2/57.6
kbit/s are used in asymmetric. The master uses polling. A slave may answer if it
has used the preceeding slot.
Connection establishment states:
Standby : The State in which Bluetooth device is inactive, radio not switched
on, enable low power operation.
Page : The Master enters page state and starts transmitting paging messages
to Slave using earlier gained access code and timing information.
Page Scan : The Device periodically enters page state to allow paging devices
to establish connections.

Inquiry: The State in which device tries to discover all Bluetooth enabled
devices in the close vicinity.
Inquiry scan : Most devices periodically enter the inquiry scan state to
make themselves available to inquiring devices.
Slave connection state modes:
Active –It participates in piconet It Listens, transmits and receives frames
Sniff – It only listens on specified slots
Hold –It does not support ACL frames. It has reduced power status. It May
still participate in SCO exchanges
Park – It does not participate on piconet and it Still retained as part of piconet
Bluetooth security:
There are three modes of security for Bluetooth access between two devices.
 Non-secure 

 Service level enforced security  Link level enforced security
The following are the three basic security services specified in the Bluetooth
standard:
Authentication : It verify the identity of communicating devices.
User authentication is not provided natively by Bluetooth.

Confidentiality : It prevent information compromise caused by eavesdropping
by ensuring that only authorized devices can access and view data.
Authorization :It allow the control of resources by ensuring that a device
is authorized to use a service before permitting it to do so.
WI-FI-WIRELESS FIDELITY
Wireless Fidelity is commonly known as Wi-Fi, developed on IEEE
802.11 standards, is commonly used technology development in wireless
communication. As the names indicate, WI-FI provides wireless access to
applications and data across a radio network. WI-FI sets up many ways to build
up a connection between the transmitter and the receiver such as DSSS, FHSS,
IRInfrared and OFDM.
Wi-Fi provide its users with the authorization of connecting to the Internet from
any place such as their home, office or a public place without the hassles of
plugging in the wires. Wi-Fi is faster than the conventional modem for accessing
information over a huge network. With the help of different amplifiers, the users
can easily alter their location without interference in their network access. Wi-Fi
devices are yielding with each other to grant well-organized access of information
to the user. Wi-Fi location, the users can attach to the wireless network is called a
Wi-Fi hotspot. Through the Wi-Fi hotspot, the user can evenimprove their home
business as accessing information through Wi-Fi is easy Accessing a wireless
network through a hotspot in some cases is free of cost while in some it may carry
extra charges. Many set of Wi-Fi devices such as PCI, miniPCI, USB, Cardbus and
PC card, ExpressCard make the Wi-Fi experience suitable and enjoyable for the
users. Distance from a wireless network can decrease the signal strength to quite an
extent; some devices such as Ermanno Pietrosemoli and EsLaRed of Venezuela
Distance are used for amplifying the signal power of the network. These devices
create embedded systems that communicate with any other node on the Internet.
Wi-Fi uses radio networks to broadcast data between its nodes. Such networks are
made up of cells that grant coverage across the network. The further the number of
cells, the larger and stronger is the coverage on the radio network. The radio

technology is a absolute package deal as it offers a secure and reliable
connectivity. Radio bands such as 2.4GHz and 5GHz depend on wireless hardware
such Ethernet protocol and CSMA. Originally, Phase Shift Keying (PSK), a
modulation method for transmission of data was used, but now it has been replaced
with CCK. Wi-Fi uses many spectrum such as FHSS and DSSS. The most
accepted Wi-Fi technology such as 802.11b operates on the range of 2.40 GHz up
to 2.4835 GHz band. This provides a complete platform for operating Bluetooth
strategy, cellular phones, and other scientific equipments. While 802.11a
technology has the range of 5.725 GHz to 5.850 GHz and provides up to 54 Mbps
in speed. 802.11g technology is even enhanced as it cover three non-overlapping
channels and permit PBCC. 802.11e technology takes a pale lead by providing
outstanding streaming quality of video, audio, voice channels etc.
Wi-Fi communication devices are extended forms of radios used for cell
phones and walkie-talkies: they simultaneously transmit and receive radio waves
and convert 1s to 0s into the radio waves along with reconverting the radio waves
into 1s and 0s, however the Wi-Fi radios enjoy some exceptional features.
Advantages
Wi-Fi allows cheaper deployment of local area networks (LANs). Also
spaces where cables cannot be run, such as outdoor areas and historical buildings,
can host wireless LANs.

Manufacturers are building wireless network adapters into most laptops. The
price of chipsets for Wi -Fi continues to drop, making it an economical networking
option included in even more devices.
Different competitive brands of access points and client network-interfaces
can inter-operate at a basic level of service. Products designated as "Wi-Fi
Certified" by the Wi-Fi Alliance are backwards compatible. Unlike mobile phones,
any standard Wi-Fi device will work anywhere in the world.
Wi-Fi Protected Access encryption (WPA2) is considered secure, provided a
strong passphrase is used. New protocols for quality-of-service (WMM) make Wi-
Fi more suitable for latency-sensitive applications (such as voice and video).
Power saving mechanisms (WMM Power Save) extend battery life.
Limitations
Spectrum assignments and operational limitations are not consistent
worldwide: most of Europe allows for an additional two channels beyond those
permitted in the US for the 2.4 GHz band (1–13 vs. 1–11), while Japan has one
more on top of that (1–14). As of 2007, Europe is essentially homogeneous in this
respect.
A Wi-Fi signal occupies five channels in the 2.4 GHz band. Any two channel
numbers that differ by five or more, such as 2 and 7, do not overlap. The oft-
repeated adage that channels 1, 6, and 11 are the only non-overlapping channels is,
therefore, not accurate. Channels 1, 6, and 11 are the only group of three non-
overlapping channels in the U.S. In Europe and Japan using Channels 1, 5, 9, and
13 for 802.11g and 802.11n is recommended.
Equivalent isotropically radiated power (EIRP) in the EU is limited to 20 dBm
(100 mW). The current 'fastest' norm, 802.11n, uses double the radio
spectrum/bandwidth (40 MHz) compared to 802.11a or 802.11g (20 MHz). This
means there can be only one 802.11n network on the 2.4 GHz band at a given
location, without interference to/from other WLAN traffic. 802.11n can also be set
to use 20 MHz bandwidth only to prevent interference in dense community.

WIFI NETWORK SERVICES:
2. Distribution and integration
3. Association, re-association, and disassociation
4. Authentication and deauthentication
5. Providing privacy
Distribution:
This service is used by mobile stations in an infrastructure network every
time they send data. Once a frame has been accepted by an access point, it
uses the distribution service to deliver the frame to its destination. Any
communication that uses an access point travels through the distribution
service, including communications between two mobile stations associated
with the same access point.
Integration:
Integration is a service provided by the distribution system; it allows the
connection of the distribution system to a non-IEEE 802.11 network. The
integration function is specific to the distribution system used and therefore
is not specified by 802.11, except in terms of the services it must offer.
Association:
Delivery of frames to mobile stations is made possible because mobile
stations register, or associate, with access points. The distribution system can
then use the registration information to determine which access point to use
for any mobile station.

Re-association:
When a mobile station moves between basic service areas within a single
extended service area, it must evaluate signal strength and perhaps switch
the access point with which it is associated. Reassociations are initiated by
mobile stations when signal conditions indicate that a different association
would be beneficial; they are never initiated by the access point. After the
reassociation is complete, the distribution system updates its location records
to reflect the reachability of the mobile station through a different access
point.
Disassociation:
To terminate an existing association, stations may use the disassociation
service. When stations invoke the disassociation service, any mobility data
stored in the distribution system is removed. Once disassociation is
complete, it is as if the station is no longer attached to the network.
Disassociation is a polite task to do during the station shutdown process. The
MAC is, however, designed to accommodate stations that leave the network
without formally disassociating.
Authentication/deauthentication:
Physical security is a major component of a wired LAN security solution.
Wired network‘s equipment can be locked inside offices. Wireless networks
cannot offer the same level of physical security, however, and therefore must
depend on additional authentication routines to ensure that users accessing
the network are authorized to do so. Authentication is a necessary
prerequisite to association because only authenticated users are authorized to
use the network. (In practice, though, many access points are configured for
"open-system" mode and will authenticate any station.)

Deauthentication terminates an authenticated relationship. Because
authentication is needed before network use is authorized, a side effect of
deauthentication is termination of any current association.
WIFI SECURITY
WiFi hotspots can be open or secure. If a hotspot is open, then anyone
with a WiFi card can access the hotspot. If it is secure, then the user needs to know
a WEP key to connect. WEP stands for Wired Equivalent Privacy. WEP is an
encryption system for the data that 802.11 sends through the air. Encryption
system prevents any non-authorized party from reading or changing data.
Specifically, it is the process of encoding bit stream in such a way that only the
person (or computer) with the key (a digital sequence) can decode it.
WI-MAX
Wi-MAX (Worldwide Interoperability for Microwave Access) unites the
technologies of wireless and broadband to provide high-speed internet access
across long distances. The name was christened by WiMAX Forum that promotes
interoperability and conformity of the standard. The forum defines the technology
as "a standards-based technology enabling the delivery of last mile wireless
broadband access as an alternative to cable and DSL". With the guarantee of
WiMAX Forum the vendors are authorized to sell their WiMAX certified products
so they can enjoy operability with other products of same type. It is a
telecommunication protocol capable of providing internet access to fixed and
mobile users. For an outstanding performance like Wi-Fi networks along with
QOS (Quality of Service) and coverage this Wireless Broadband Access (BAS)
technology is assembled around IP (internet protocol). Currently it offers 40 Mbit/s
but expected to offer 1 Gbit/s speed for fixed users.
WI-MAX ARCHITECTURE
There are three main components of WiMax network architecture.

 The first component is the mobile stations which are used as a source of network
connection for end user.
 The second network is an access service network which is formed of more than
two or three base stations. It also contains ASN gateways which build the radio
access at the end.
 The third component is connectivity service network which is responsible for
providing IP functions. The base station provides the air interface for the mobile
stations. The base stations also provide mobile management functions, triggering
and tunnel establishment, radio resource management, dynamic host control
protocol proxy, quality of service enforcement and multicast group management.
ASN is responsible for radio resource management, encryption keys, routing to the
selected network and client functionality. Connectivity service network is
responsible for internet connections, corporate and public networks and many other
user services.
Standard WiMax Architecture
The WiMax network is based on three four basic components they are:
 AS gateway,  CSN and  MS.

The basic network has a inner IP core which is bounded by an ASN
gateway, which is associated to service network or CSN. The main IP core is
attach to the internet backbone for aid and coverage. The WiMax network which
is also part of the ISP network is recognized as access service gateway. This ASN
handles the micro and macro base stations, which offer WiMax access to end
users. The connectivity examine network or CSN is an important part of WiMax
architecture which provides the verification to the user devices.
CSN is in charge for providing roaming among the network service
providers. It is CSN which is accountable for user security and quality for service
for this reason it uses several protocols. The IP address management is also
handled by CSN. IP core is in the middle of CSN and ASN. CSN provides the
internet and telecommunications connectivity. ASP communicates to the base
stations and the mobile stations. At the users end the WiMax architecture may
additionally contain firewall for security. WiMax architecture provides discretion
at user end to make possible amendments.
Two Dimensions of WiMax Network
WiMax network is composed of two parts the 1. WiMax tower 2. WiMax
receiver.
WiMax tower is associated straightly to the internet backbone using a wired
connection such as optical fiber. It can be linked to the WiMax tower using a line
of sight link or a non line of sight link. The line of site communiqué involves the
use of fixed antenna or dish. This antenna is unchanging or deployed on the roof
top or the tower of the building. Line of sight connection is measured as more
strong and stable connection. Thus it sends lot of error free data over the network.
It uses a frequency range of 66Ghz. Higher frequency reduces the possibility of
signal flaw and interference and provides extra bandwidth. On the other hand the
non line of sight link provides you connectivity with the fixing of small antenna in
your PC. This mode provides lower frequency range from 2 GHz to 11 GHz. The
lower band signals are not prone to obstacles like trees and walls. Hence the
signal

strength is more and the user receives the quality of service. For every WiMax
connectivity and architecture it is significant to connect to an internet backbone via
swift wired connection.
L2CAP-LOGICAL LINK CONTROL AND ADAPTION PROTOCOL:
The L2CAP is a data link control protocol.The L2CAP link layer
operates over an ACL link provided by the baseband. A single ACL link, set up by
the link manager using LMP, is always available between the master and any
active slave. This provides a point-to-multipoint link supporting both asynchronous
and isochronous data transfer. L2CAP provides services to upper-level protocols
by transmitting data packets over L2CAP channels. Three types of L2CAP
channels exist: bidirectional signaling channels that carry commands; connection-
oriented channels for bidirectional point-to-point connections; and unidirectional
connectionless channels that support point-to multipoint connections, allowing a
local L2CAP entity to be connected to a group of remote devices.
Functions:
It Performs 4 major functions
 Managing the creation and termination of logical links for each
connection through ―channel‖ structures
 Enforcing and defining QoS requirements
 Adapting Data, for each connection, between application (APIs)
and Bluetooth Baseband formats through Segmentation and
Reassembly (SAR)
 Performing Multiplexing to support multiple concurrent
connections over a single common radio interface.
Channels:

L2CAP CHANNELS
The above figure shows L2CAP entities with various types of
channels between them. Every L2CAP channel includes two endpoints referred to
by a logical channel identifier (CID). Each CID may represent a channel endpoint
for a connection oriented channel, a connectionless channel, or a signaling channel.
Since a bi-directional signaling channel is required between any two L2CAP
entities before communication can take place, every L2CAP entity will have one
signaling channel endpoint with a reserved CID of 0x0001. All signal channels
between the local L2CAP entity and any remote entities use this one endpoint.
Each connection-oriented channel in an L2CAP entity will have a local CID that is
dynamically allocated. All connection-oriented
CIDs must be connected to a single channel, and that channel must be configured
before data
transfer can take place. Note that the channel will at that point be bound to a
specific upper level

protocol. In addition, a quality of service (QoS) agreement for the channel will be
established
between the two devices. QoS is negotiated for each channel during configuration
and includes data flow parameters such as peak bandwidth, as well as the
transmission type: best effort, guaranteed, or no traffic. Connectionless channels
are unidirectional and used to form groups. A single outgoing connectionless CID
on a local device may be logically connected to multiple remote devices.
The devices connected to this outgoing endpoint form a logical group. These
outgoing CIDs are dynamically allocated. The incoming connectionless CID,
however, is fixed at 0x0002. Although multiple outgoing CIDs may be created to
form multiple logical groups, only one incoming connectionless CID is provided
on each L2CAP entity. All incoming connectionless data arrives via this endpoint.
These channels do not require connection or configuration. Therefore, any required
configuration information, such as upper-level protocol, is passed as part of the
data packet.
Functional requirement:
Protocol multiplexing distinguishes between upper-layer protocols like SDP,
RFCOMM. It Segments larger packets from higher layers into smaller baseband
packets. It allows QoS parameters to be exchanged during connection
establishment and it also allows efficient mapping of protocol groups to piconets.
L2CAP Operation:
L2CAP channel end-points are represented by channel identifiers
(CIDs). An L2CAP channel is uniquely defined by 2 CIDs and device addresses.
Reserved CIDs
0x0001: Signaling channel

0x0002: Connection-less reception
0x0003-0x003F: Reserved for future use
Operation between layers:
It transfers data between higher layer protocols and lower layer protocols. It
Signal with peer L2CAP implementation. L2CA layer should be able to
accept events from lower/upper layers. L2CA layer should be able to take
appropriate actions in response to these events.
L2CAP Format
L2CAP Frame field for connectionless service:
Length – It indicates length of information payload, PSM fields Channel ID
– 2, indicating connectionless channel
Protocol/service multiplexer (PSM) – identifies higher-layer recipient for
payload

Not included in connection-oriented frames Information payload – higher-
layer user data
Signaling frame payload:
It Consists of one or more L2CAP commands, each with four fields Code –
identifies type of command
Identifier – used to match request with reply
Length – length of data field for this command
Data – additional data for command, if necessary
L2CAP signaling command codes:

Unit 3

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Unit 3