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unit 2
Wireless LAN and IEEE 802.
The wired LAN provides reliable service to users, working in a fixed
environment. Once installed, the workstations and the servers of a
wired LAN are fixed in their native locations. For users who are
highly mobile or in a rough terrain, where there is no possibility to
install and lay down the cables of a wired LAN, a good solution is to
install a wireless LAN. Wireless LANs transmit and receive data over
the atmosphere, using radio frequency (RF) or infrared optical
technology, there by, eliminating the need for fixed wired
connections. Wireless LANs provides dual advantage of connectivity
and mobility. Wireless LANs have gained strong popularity in
applications like health-care, retail, manufacturing, warehousing,
and academic. These applications use hand-held
terminals and notebook computers to transmit real-time information
to centralized 'hosts' for processing. Figure shows simple wired and
wireless networks.
Wireless LANs have limitations when compared with wired LANs.
Wireless LANs are slower than wired LAN. Also, they have limitations
with their range of operation. When a station is moved out of its
range, it suffers from noise and error in the received data due to the
poor signal strength.
Need for Wireless LANs
Networking and Internet services are essential requirements for today's business computing. An increasing number of LAN users are becoming mobile. These mobile users require connectivity to a network, regardless of where they are because they want simultaneous access to the network. With wireless LANs, users can access shared information without looking for a place to plug in their systems and do not need network managers to set up networks to install cable and other equipment.
Advantages of WLANs
- They provide clutter free homes, offices and other networked places.
- The LANs are scalable in nature, i.e. devices may be added or removed from the network at a greater ease than wired LANs.
- The system is portable within the network coverage and access to the network is not bounded by the length of the cables.
- Installation and setup is much easier than wired counterparts.
- The equipment and setup costs are reduced.
Fast Installation and Simplicity: Installing a wireless LAN system can
be fast and easy and can eliminate the need to pull cables through
walls, floor, and ceilings.
Disadvantages of WLANs
- Since radio waves are used for communications, the signals are noisier with more interference from nearby systems.
- Greater care is needed for encrypting information. Also, they are more prone to errors. So, they require greater bandwidth than the wired LANs.
- WLANs are slower than wired LANs.
Architecture
2 type
The difference between a portable and mobile station is that a portable station moves from point to point but is only used at a fixed point. Mobile stations access the LAN during movement.
When two or more stations come together to communicate with each other, they form a Basic Service Set (BSS). The minimum BSS consists of two stations. 802.11 LANs use the BSS as the standard building block.
A BSS that stands alone and is not connected to a base is called an Independent Basic Service Set (IBSS) or is referred to as an Ad-Hoc Network. An ad-hoc network is a network where stations communicate only peer to peer. There is no base and no one gives permission to talk. Mostly these networks are spontaneous and can be set up rapidly. Ad-Hoc or IBSS networks are characteristically limited both temporally and spatially.
- Integration
The first three services deal with station mobility. If a station is moving within its own BSS or is not moving, the stations mobility is termed No-transition. If a station moves between BSS's within the same ESS, its mobility is termed BSS-transition. If the station moves between BSS's of differing ESS's it is ESS transition. A station must affiliate itself with the BSS infrastructure if it wants to use the LAN. This is done by Associating itself with an access point. Associations are dynamic in nature because stations move, turn on or turn off. A station can only be associated with one AP. This ensures that the DS always knows where the station is.
Association supports no-transition mobility but is not enough to support BSS-transition. Enter Reassociation. This service allows the station to switch its association from one AP to another. Both association and reassociation are initiated by the station. Disassociation is when the association between the station and the AP is terminated. This can be initiated by either party. A disassociated station cannot send or receive data. ESS- transition are not supported. A station can move to a new ESS but will have to reinitiate connections.
Distribution and Integration are the remaining DSS's. Distribution is simply getting the data from the sender to the intended receiver. The message is sent to the local AP (input AP), then distributed through the DS to the AP (output AP) that the recipient is associated with. If the sender and receiver are in the same BSS, the input and out AP's are the same.
Station services are:
- Authentication
- Deauthentication
- Privacy
- MAC Service Data Unit (MSDU) Delivery.
MAC Frame:
The MAC layer frame consist of 9 fields. The following figure shows the basic
structure of an IEEE 802.11 MAC data frame along with the content of the
frame control field.
Frame Control(FC) –
It is 2 bytes long field which defines type of frame and some control
information. Various fields present in FC are:
1. Version:
It is a 2 bit long field which indicates the current protocol version which
is fixed to be 0 for now.
2. Type:
It is a 2 bit long field which determines the function of frame i.e
management(00), control(01) or data(10). The value 11 is reserved.
3. Subtype:
It is a 4 bit long field which indicates sub-type of the frame like 0000 for
association request, 1000 for beacon.
4. To DS:
It is a 1 bit long field which when set indicates that destination frame is
for DS(distribution system).
5. From DS:
It is a 1 bit long field which when set indicates frame coming from DS.
6. More frag (More fragments):
It is 1 bit long field which when set to 1 means frame is followed by other
fragments.
7. Retry:
It is 1 bit long field, if the current frame is a retransmission of an earlier
frame, this bit is set to 1.
8. Power Mgmt (Power management):
It is 1 bit long field which 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.
9. More data:
It is 1 bit long field which is used to indicates a receiver that a sender
has more data to send than the current frame. This can be used by an
access point to indicate to a station in power-save mode that more
communicating devices using short-range, lower-power, inexpensive wireless radios.
- The project was named Bluetooth after the name of Viking king – Harald Blaatand who unified Denmark and Norway in 10th century.
- Nowadays, Bluetooth technology is used for several computer and non computer application:
- It is used for providing communication between peripheral devices like wireless mouse or keyboard with the computer.
- It is used by modern healthcare devices to send signals to monitors.
- It is used by modern communicating devices like mobile phone, PDAs, palmtops etc to transfer data rapidly.
- It is used for dial up networking. Thus allowing a notebook computer to call via a mobile phone.
- It is used for cordless telephoning to connect a handset and its local base station.
- It also allows hands-free voice comml1nication with headset.
- It also enables a mobile computer to connect to a fixed LAN.
- It can also be used for file transfer operations from one mobile phone to another.
- Bluetoothusesomnidirectionalradio waves that can through wallsor othernon- metalbarriers.
Bluetooth devices have a built-in short range radio transmitter. The rate provided is 1Mbps and uses 2.4 GHz bandwidth.
Bluetooth is that when the device is with in the scope of a other devices automatically start the transfer informationwithout the user noticing. a small network between the devices is created and the user can accessed as if there werecables.
Bluetooth Architecture
Bluetooth architecture defines two types of networks:
- Piconet
- Scattemet
A bluetooth network is called piconet and a collection of interconnected
piconets is call scatternet.
1. Piconet
- Piconet is a Bluetooth network that consists of one primary (master) node and seven active secondary (slave) nodes.
- Thus, piconet can have upto eight active nodes (1 master and 7 slaves) or stations within the distance of 10 meters.
- There can be only one primary or master station in each piconet.
- The communication between the primary and the secondary can be one-to-one or one- to-many.
- All communication is between master and a slave. Salve-slave communication is not possible.
- In addition to seven active slave station, a piconet can have upto 255 parked nodes. These parked nodes are secondary or slave stations and cannot take part in communication until it is moved from parked state to active state. 2. Scatternet
- Scattemet is formed by combining various piconets.
- A slave in one piconet can act as a master or primary in other piconet.
Such a station or node can receive messages from the master in the first piconet and deliver the message to its slaves in other piconet where it is acting as master. This node is also called bridge slave.
- Thus a station can be a member of two piconets.
- A station cannot be a master in two piconets.
defines the physical characteristics of bluetooth transceiver. It defines
two types of physical link: connection-less and connection-oriented.
The Bluetooth radio layer corresponds to the physical layer of OSI model.
1. Baseband Link layer:
It performs the connection establishment within a piconet.
- Baseband layer is equivalent to the MAC sublayer in LANs.
- • Bluetooth uses a form of TDMA called TDD-TDMA (time division duplex TDMA).
- • Master and slave stations communicate with each other using time slots.
- • The master in each piconet defines the time slot of 625 μsec.
- Link Manager protocol layer:
It performs the management of the already established links. It also
includes authentication and encryption processes.
- Logical Link Control and Adaption protocol layer:
It is also known as the heart of the bluetooth protocol stack. It allows
the communication between upper and lower layers of the bluetooth
protocol stack. It packages the data packets received from upper
layers into the form expected by lower layers. It also performs the
segmentation and multiplexing.
It is short for Service Discovery Protocol. It allows to discover the
services available on another bluetooth enabled device.
It is short for Radio Frontend Component. It provides serial interface
with WAP and OBEX.
It is short for Object Exchange. It is a communication protocol to
exchange objects between 2 devices.
It is short for Wireless Access Protocol. It is used for internet access.
It is short for Telephony Control Protocol. It provides telephony
service.
It enables the user to interact with the application.
Advantages:
- (^) Low cost.
- Easy to use.
- It can also penetrate through walls.
- It creates an adhoc connection immediately without any wires.
- It is used for voice and data transfer.
Disadvantages:
- It can be hacked and hence, less secure.
- It has slow data transfer rate: 3 Mbps.
- It has small range: 10 meters.
- Access Code: It is 72 bit field that contains synchronization bits. It identifies the master.
- Header: This is 54-bit field. It contain 18 bit pattern that is repeated for 3 time.
The header field contains following subfields:
(i) Address: This 3 bit field can define upto seven slaves (1 to 7). If the address is zero, it is used for broadcast communication from primary to all secondaries.
(ii)Type: This 4 bit field identifies the type of data coming from upper layers.
(iii) F: This flow bit is used for flow control. When set to 1, it means the device is unable to receive more frames.
(iv) A: This bit is used for acknowledgement.
(v) S: This bit contains a sequence number of the frame to detect retransmission. As stop and wait protocol is used, one bit is sufficient.
(vi) Checksum: This 8 bit field contains checksum to detect errors in header.
- Data: This field can be 0 to 2744 bits long. It contains data or control information coming from upper layers
WiMAX
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
- 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.
The WiMAX architecture framework allows for the flexible decomposition and/or combination of functional entities when building the physical entities. For example, the ASN may be decomposed into base station transceivers (BST), base station controllers (BSC), and an ASNGW analogous to the GSM model of BTS, BSC, and Serving GPRS Support Node (SGSN).
applications
Connectivity for SMBs
Most effective application by WiMAX is SMBs which mean the small
to medium-sized businesses. Due to WiMAX technology the small or
medium sized business progressing day by day because WiMAX
technology offer a connectivity which attract clients and facilitate
them with various types of services like hotspot etc. Therefore a lot
of regional applicant entered into the broadband internet access and
spotlight on this application.
WiMAX Backhaul
The range is the most important application of WiMAX Technology
because a single tower of WiMAX can connect other WiMAX towers
by means of a line-of-sight also known as microwave link. The
connectivity of one tower to another tower referred to as a backhaul.
A backhaul have the ability to cover up 3,000 miles because WiMAX
network offer coverage to rural areas or remote areas.
Nomadic Broadband
WiMAX Technology next application is Nomadic Broadband which is
under the marvelous plan of Wi-Fi. There are lots of medium or small
business companies that might pay for the base station of WiMAX in
key areas for the development of business and commerce. These
business companies permit of facilitate their clients to use them for
free. Wi-Fi also rolled out for similar aims but WIMAX offer enhanced
Quality of Service. WiMAX Technology provide less access point but
very high security. MAN (Metropolitan area network) a wireless
access could supply a solid draw when business leaders attempt to
catch the attention of businesses to their region.
Broadband for Developing Countries
There are many countries such as Asia, Africa, and Eastern Europe
are likely to achieve the most from the fixed wide area wireless
networking technology. The analyst of West Technology Research
Solutions the developing countries have limited cable
transportation, because the expenditure to install a WiMAX station in
concurrence with an accessible cellular tower or yet as a private hub
will be very small in contrast to developing a wired solution. At the
start, computers will require extraordinary add-on WiMAX PC cards.
Though, Intel is preparation to put WiMAX into its Centrino chips. On
the whole Wi-Fi and WiMAX is becoming the same thing with the
option to depend on your preference that which network you
connected to.
Private Networks
Mostly small and medium sized business man pay WiMAX to get
access but big companies having large campuses may finally deploy
and control their own WIMAX networks. Such private networks are
expected to be the very last WIMAX application. All private
networks, Roaming broadband of developing countries are
emphasizing the logical position of WIMAX as the wireless
technology for the Metropolitan Area Network (MAN). The Voice over
IP is the logic behind the design of WiMAX technology and may be
could further force both business and residential clients from
customary mobile operators and copper wire.
WiFi Hotspots
This can allow users to access internet remotely by roaming out side office
and homes. There are several Hotspots and WiMax backhauls which are
providing wireless solutions to wireless networks.
LTE (Long Term Evolution)
LTE (Long Term Evolution) is a standard for 4G wireless broadband
technology that offers increased network capacity and speed to mobile
device users.
communications. LTE supports mixed data, voice, video and messaging traffic.
LTE uses OFDM (orthogonal frequency division multiplexing) and, in later releases, MIMO (multiple input, multiple output) antenna technology similar to that used in the IEEE 802.11n wireless local area network (WLAN) standard. The higher signal-to-noise ratio (SNR) at the receiver enabled by MIMO, along with OFDM, provides improved wireless network coverage and throughput, especially in dense urban areas.
LTE-A Technology
LTE-A stands for LTE-Advanced. It is a standard for mobile communication that is one generation beyond LTE (Long Term Evolution). Whereas LTE was a 3G communication standard, LTE-A is a 4G or fourth generation communication standard.
LTE-A allows for global roaming, smooth handover between networks, and interoperability with existing
wireless standards.
For wireless communication, LTE-A or 4G LTE is the current
state-of-the-art.
LTE-A features
a 4G network offers several advantages over a 3G network. In
order to be classified as 4G, a network must meet certain
criteria, as governed by the International Telecommunications
Union. Requirements for a 4G communication standard
include:
- All-Internet Protocol (IP) packet switched network (for
increased network efficiency)
- Interoperability with existing wireless standards
- Specific nominal data rates for mobile and stationary
users
- Network resources are dynamically shared in order to
support more simultaneous users per cell
- (^) Scalable channel bandwidth up to 40 MHz
- Peak link spectral efficiency of 15 bit/s/Hz for downlink,
and 6.75 bit/s/Hz for uplinks
- Seamless connectivity with smooth handovers across
networks
- Global roaming with universal connectivity
- Service sufficient for multimedia support
LTE and LTE-A comparison
In comparing a 3G LTE network with a 4G LTE-Advanced
network, you will find that there is no comparison. An LTE-A
network offers much faster peak speeds, for both downloads
and uploads, as well as greater reliability, more seamless
handover between networks, and global roaming. If your
laptop is not 4G compatible, its online capabilities are
severely limited. In every objective metric, LTE-A is superior to
3G LTE. Subjectively, a 4G LTE-A network can be expected to
provide a much more fulfilling and rewarding user experience. VoLTE
VoLTE stands for voice over Long Term Evolution. Utilising IMS
technology, it is a digital packet voice service that is delivered over
IP via an LTE access network.
Voice calls over LTE are recognised as the industry-agreed
progression of voice services across mobile networks, deploying LTE
radio access technology.
