Wireless home networks (11)


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Wireless home networks (11)

  1. 1. Wireless Home NetworksA home network or home area network (HAN) is a local area network (LAN)used in residential areasfor communication between digital devices, but it it is used to connect small numbers of digitaldevices, computers laptops , tablets, pdas,mobile phones and printers. An important and the mostcommon function is the sharing of Internet access. If an ISP have only one IP address, a router isused it has network address translation (NAT), proxy server software and a network firewall, thisallows several computers and other electronic devices to share the IP address.NetworkA network is defined as a system that is used to connect multiple electronic devices together, sothey can exchange the information with each other. Thenetwork are not just established foroffices but is also used for homes because in many homes there is more than one pc.Any kind of data can be shared on network either files, photos videos or music, and the mosteffective use is if u have broadband service at your home then many computers can be connectedto one single connection through wireless network which was not possible earlier or few years back.http://technet.microsoft.com/en-us/library/cc757419(v=ws.10).aspxThere are two types of network: wired or wirelessWired Network:As it is obvious from the name that in wired networks devices are connected with physical wires orcables on wired network each device should have an Ethernet (RJ-45) port. Each computer thenconnects to the router with the help of Ethernet cable or there are few other ways to connectdevices in wired network.Wireless home network:Because of this wireless technology the wireless home networks have become friendlierthenit used to be, it means you no longer have to carry yards of cables from room to room to getconnected.In wireless we just need a wireless router and an adapter that is usually installed onall modern devices or PCs that you want to connect. Mostly in modern devices the wirelessadapter is built in .Also wireless networking devices dont need to have ports, but just need antennas, which aremostly now a days hidden inside the device itself. To have a Wi-Fi connection, an accesspoint is needed and a Wi-Fi client.Access Point: In order to broad cast the Wi-Fi signal for Wi-Fi clients an An Access point(AP) is used . For each wireless network, you need an access point. Although an AP can bepurchased separately, and can be connected to a router or a switch to add Wi-Fi support to awired network, but now a days the routers available in shops has a built-in AP. Some routerseven come with more than one access point and are called dual-band AP.We can think of a Wi –Fi network as a device that has an invisible network port and invisiblecable and the length of this unseen cable is equal to the range of the Wi-Fi.
  2. 2. Wi-Fi client:A Wi-Fi client we means that it includes devices that detects the signal broadcast by an AP,and they also maintain the connection.A Wi-Fi connection in which AP is used is called theInfrastructure mode.All laptops, smartphones, and tablets on the market come have built-inWi-Fi capability. But if any device doesn’t have its easy to upgrade by using USB or eitherby PCIE Wi-Fi adapter.Difference between Router and Access PointTo connect computer or other devices on to the networkwe need Hub , switches, routers, andaccess points, although the all used to connect the different devices to a network but each ofthem have different functions.RoutersComputer communicates using router and the information exchanged between two networksby using router for eg between home network and the Internet. Routers can be wireless orwired. For connecting just computers we can use hub and switches but if you want to connectall your computers to the internet using one modem we need to use router or modem withbuilt-in router. Routers provide built-in security, it has a a firewall. Routers are moreexpensive than hubs and switches.Access pointsAccess point is used to provide wireless access to a wired Ethernet network. An access pointis connected into a hub, switch, or router and then sends the wireless signals. This enablescomputers and devices to connect to a wired network wirelessly. By using Access pointsyou can move from one place to another and have wireless access to a network. If you wantto give wirless connection to your computers and you have a router that enables wirelesscapability, you dont need an access point. There is no buitin technology in Access points forsharing Internet connections. To share an Internet connection, you must have an access pointinto a router or a modem with a built-in router.As we know that wireless network offers two modes of configuration Adhoc and infrastructure modeAd hoc mode:In adhoc mode it is not centralizedall computer are connected to each other in peer to peerconnection , Adhoc mode is ok for few devices to connect but for more connections itbecomes complicated and its difficult to manage.In Adhoc mode the network has no structure and fixed node.No access point is needed in thismode it is useful for short duration network for small group of people.
  3. 3. Infrastructure Mode:The connections made by infrastructure mode is centralised . For infra structure mode weneed a wireless access point (AP).In order to make the connection to the the WLAN, wemust configure the AP and all wireless clients to use the same SSID. The AP is thenconnected to the wired network inorder to establish a wireless clients access. Additional APscan be added to increase the coverage area and support more clients.The access point haseither one or more antennas that is used to connect u to the wireless nodes.Frequency bands: These bands are the radio frequencies used by the Wi-Fi standards:2.4GHz and 5GHz. The 2.4GHz band is currently the most popular, meaning, its used bymost existing network devices. That plus the fact that home appliances, such as cordlessphones, also use this band, makes its signal quality generally worse than that of the 5GHzband due to oversaturation and interference.IEEE 802.11It is a standard and was found in 1987 to start the standardization of spread spectrum WLANthat is used in ISM band, and is used for the communication between computers usingWLAN in the 2.4, 3.6, 5 and 60 GHz frequency bands. They are established by the IEEELAN/MAN Standards Committee (IEEE 802). Initially it was released in 1997 and had to gothrough various changes. It is used by devices To establish wireless networks.
  4. 4. IEEE Frequency/Medium Speed Modes Transmission SpreadStandard Range Spectrum802.11 2.4GHz RF 1 to Ad 20-60 feet DSSS 2Mbps hoc/infrastructure indoors. FSSS802.11a 5GHz Up to Ad 35 to 115 feet OFDM 54Mbps hoc/infrastructure indoors.802.11b 2.4GHz Up to Ad 35 to 115 feet DSSS 11Mbps hoc/infrastructure indoors.802.11g 2.4GHz Up to Ad 38 to 125 feet OFDM, 54Mbps hoc/infrastructure indoors. DSSS802.11n 2.4GHz/5GHz Up to Ad 70 TO 130 feet OFDM 600Mbps hoc/infrastructure indoors.FHSS, DSSS, OFDM, and 802.11 StandardsThe standard set by the 802.11 had given two standards of spread spectrum DSSS and FSSS,there isno difference in terms of the speed but only use different technologies.DSSS It operates at the radio frequency band of 2.4 GHz and has a data rate of 1 0r 2 Mbps. There is alsoan option for fall back which is 1Mbps this is for just in case if the environment is crowded.FSSS:The 802.11 standard also used DSSS and had a data rate of 2Mbps this has a fall back i.e 1Mbps for acrowded environment .This shows that the data rate is same for both schemes the only difference is in their spread spectrumtechnology.Below all the details are summed up in the following table.IEEE Standard RF Used Spread Spectrum Data Rate (in Mbps)802.11 2.4GHz DSSS 1 or 2802.11 2.4GHz FHSS 1 or 2802.11a 5GHz OFDM 54802.11b 2.4GHz DSSS 11802.11g 2.4Ghz DSSS 54802.11n 2.4/5GHz OFDM 600 (theoretical) < Back Page 4 of 14 Next >
  5. 5. As seen above that there are different wireless standards set be IEEE 802.11 and it depends on these standards that how devices communicate inThere are several different wireless standards that control how devices communicate. The main ones are IEEE 802.11b and IEEE 802.11g – ‘b’ and ‘g’ for short.The major difference between these two devices is speed.A wireless ‘b’ device can transfer data at a maximum speed of 11Mbps, while the newer ‘g’standard can reach speeds of up to 54Mbps.Now adays most common wireless equipmentnow available is 802.11g. Although the two standards are compatible with each other,but an802.11g network may run more slowly if it is connectedto a 802.11b.Although 802.11 operates at 2.4GHz ISM band no licence is required. and the maximumdata rate is 54 Mbits/s and the net throughput for this is 19 Mbits/s.Modulation Scheme:The modulation scheme used in 802.11 is OFDM(Orthogonal Frequency DivisionMultiplexing)Data rate is 54Mbps but it can do automatic rate selection (with fallback to 48, 36, 24, 12, 11,6, 5.5, 2, 1Mbps).*They operate in both point-to-access point (infrastructure mode)point-to-point (ad hoc mode, peer-to-peer networking).IEEE 802.11N:IT is also compatible with IEEE 802.11 b/g802.11g is the third modulation standard for wLANs. It has a frequency range of about 2.4GHz band (like 802.11b) but operates at a data rate of 54 Mbit/s, or the net throughput isabout 19 Mbit/s which is similar to 802.11a core, except for some additional legacy overheadwhich are there for backward compatibility. The hardware of 802.11g is backwardscompatible with 802.11b hardware. Details of making b and g work well together occupiedmuch of the lingering technical process. In an 802.11g network, because of the presence of alegacy 802.11b participant the overall speed of 802.11g network will be reduced.The modulation scheme used in 802.11g is orthogonal frequency-division multiplexing(OFDM) copied from 802.11a with data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbit/s,and reverts to CCK (like the 802.11b standard) for 5.5 and 11 Mbit/s andDBPSK/DQPSK+DSSS for 1 and 2 Mbit/s. Even though 802.11g operates in the samefrequency band as 802.11b, it can achieve higher data rates because of its heritage to802.11aWireless Channelswireless nodes communicate with each other by using radio frequency signals in theISM (Industrial, Scientific, and Medical) band between 2.4 GHz and 2.5 GHz. Eachneighbouring channel is 5MHz from next channel inorder to avoid interference. due to thespread spectrum effect of the signals, a nodeThe original 802.11 had two standards DSSS and FSSS, although they both offers the same speed but
  6. 6. use different spread spectrum. The first one used used the 2.4GHz radio frequency band and operated ata 1 or 2Mbps data rate. Since this original standard, wireless implementations have favored DSSS.The second 802.11 standard used DSSS and had a data rate of 2Mbps peak data rate with an option offallbacki.e 1Mbps if the environment is noisy. 802.11, 802.11b, and 802.11g use DSSS. This means thatthe underlying modulation scheme is similar between each standard, all DSSS systems to have 2, 11, and54Mbps 802.11 standardsIf we send signals using a particular channel it will utilize frequency spectrum which is12.5MHz above center channel frequency and 12.5MHZ below the center frequency. If twodifferent wireless network use neighbouring channel e.g channel 1 and channel 2 it willcause iinterference with each other. So inorder to avoid interference use two differentchannels that has a difference in frequency range for example channel 1 and channel 6 it willreduce the cross-talk and give better performance.IEEE 802.11 Protocols and Technologies:*The IEEE802.11-related protocols and technologies are briefly defined here :•802.11. The IEEE 802.11 wireless standard had specify the defination of both es the physicallayer and the media access control (MAC) layer.•Wi-Fi Protected Access (WPA). WPA is an interim standard which was used until the IEEE802.11i standard was officialy approved. These standards, were used to be a replacement forthe WEP standard, they use various method of data encryption and network authentication.•Wireless Auto Configuration. The Wireless Auto Configuration feature was introduced inWindows XP and Windows Server 2003 had an ability to detect the wireless network towhich a connection has to be established, it is based on configured preferences or defaultsettings.802.11 ProtocolThe IEEE 802 standards committee defines two separate layers, the Logical Link Control(LLC) and media access control, for the Data-Link layer of the OSI model. The IEEE 802.11wireless standard defines the specifications for the physical layer and the media accesscontrol (MAC) layer that communicates up to the LLC layer, as shown in the followingfigure.802.11 and OSI Model
  7. 7. The components in the 802.11 architecture lie in the MAC sublayer of data-link layer orthe physical layer.802.11 MAC Frame802.11 MAC Frame FormatFrame Control FieldThe Frame Control field, actually contains the control information which is used to definethe type of 802.11 Mac frame . the number in the following figure represents the no of bitsfor each field.Frame Control FieldProtocol Version It gives the current version of the 802.11 protocol that is used. When STAs receive thisvalue they use it to determine if the frame that has been received its version protocol issupported.TypeThere are three type of frame fields they are control, data, and management.
  8. 8. Subtype There are different number of subtype fields for each frame type . Each typeperform certain function and for each type their subtype also perform the specific function.To DS and From DSIt is only used in data type frames of STAs that belongs to an AP itsfunction I sthat it indicates whether the frame is going to or leaving from the DS (distributedsystem.More Fragmentsused to give information if more fragments of the frame are still have tocome they can be data or management type..Retry It basically takes the decision whether data or management frame needs to beretransmitted or not.Power ManagementThis indicates the mode of sending STA which could be either inactive mode or power-save mode.More DataWhen STA is in power save mode it indicates STA the there are more frames tosend by AP. It is also used for APs to show that there are broadcast/multicast frames arestillthere to send.WEPrepresents if encryption and authentication are used in the frame. for all data framesand management frames it has to be set.Ordershow that frames received has to be processed in order.Duration/ID FieldThis is used for control type frames,but should not be used with those who have a subtype ofpower save Poll.Address FieldsThere are different address fields depending upon the the frame type, the four address fieldshas a combination of the following address types: BSS Identifier (BSSID). BSSID uniquely identifies each BSS. When the frame is from an STA in an infrastructure BSS, the BSSID is the MAC address of the AP. When the frame is from a STA in an IBSS, the BSSID is the randomly generated, locally administered MAC address of the STA that initiated the IBSS. Destination Address (DA) It is the MAC address of the destination. Source Address (SA). It is the MAC address of the original source . Receiver Address (RA). RA shows the MAC address of the next STA to receive the frame on the wireless medium.
  9. 9. Transmitter Address (TA). The fram transmitted by STA its transmitted address is represented by TA.Sequence ControlIt is divided into two subfields, the fragment number field and the sequence number field.Sequence Control Field Sequence Number shows the sequence number of individual frame. Fragment Number when each frame of a segmented frame is sent it represent the sequence number of each frame.Frame BodyThe frame body holds the data or information which is present in either management type ordata type frames.Frame Check SequenceOn all fields of MAC header and the frame body field the cyclic redundancycheck(CRC) is performed by the transmitting STA to generate the FCS value.Then this same CRC calculation to determine the values of FCS field to verify ifthere is any error occurred in the frame during transmission.802.11 PHY SublayerIEEE 802.11 At the physical (PHY) sublayer, defines a different encoding and transmissionschemes for wireless communications, the most commonly used transmission schemes arethe Frequency Hopping Spread Spectrum (FHSS), Direct Sequence Spread Spectrum (DSSS),and Orthogonal Frequency Division Multiplexing (OFDM).Standards for 802.11 at the PHY Layer
  10. 10. 802.1X ProtocolThe IEEE 802.1X this standard was designed for wired Ethernet networks, it has beenadapted to 802.11 wireless LANs.Components of 802.1X {{{{{{{{{{{*Port access entity. A LAN port, also known as port access entity (PAE), is the logical entity that supports the IEEE 802.1X protocol that is associated with a port. A PAE can adopt the role of the authenticator, the supplicant, or both. Authenticator. For wireless connections,for wireless AP’s it acts as the logical LAN port, through this Authenticator wireless clients in infrastructure mode gain access to other wireless clients in the network and the wired network. *Supplicant. For wireless connections, the supplicant is the logical LAN port on a wireless LAN network adapter that requests access to the other wireless clients and the wired network by associating with and then authenticating itself to an authenticator. Whether for wireless connections or wired Ethernet connections, the supplicant and authenticator are connected by a logical or physical point-to-point LAN segment. **Authentication server. To verify the credentials of the supplicant, the authenticator uses an authentication server, which checks the credentials of the supplicant on behalf of the authenticator and then responds to the authenticator, indicating whether or not the supplicant is authorized to access the authenticators services.}}The following figure shows these components for a wireless LAN network.Components of IEEE 802.1X Authentication
  11. 11. The authentication server can be the following: A component of the access point. In this case, the AP must be configured with the sets of user credentials corresponding to the supplicants that will be attempting to connect (it is typically not implemented for wireless APs). A separate entity. In this case, the AP forwards the credentials of the connection attempt to a separate authentication server. Typically, a wireless AP uses the Remote Authentication Dial-In User Service (RADIUS) protocol to send a connection request message to a RADIUS server.
  12. 12. BLUETOOTH AND PERSONAL AREA NETWORK:After the boom of Wireless technology for past 2 decades the ,manufacturers realized that it would be great for consumer to implementthe wireless technology for removing the cumbersome wire that connectsthe devices, as consumer find it irritating to move along wire it providepeople mobility within small range these included devices like (wirelessmouse, keyboard, printers, scannners, head phones ) this wireless givesthese devices invisible short distance connection.Bluetooth is an standard it is used by most of the electronic appliancesmanufacturers. In order to communicate devices in Bluetooth it use thatad-hoc –Mode approach and allow the communication within the range of10 m.It is designed to have communication over short distance It supports alarge number of channels and power levels.Bluetooth radio interface basicsThe bluetooth operates in the 2.4 GHz ISM band, Bluetooth uses Frequency Hopping SpreadSpectrum (FHSS) techniques with the carrier modulated using Gaussian Frequency ShiftKeying (GFSK).Since there is interference that has to be avoided by bluetooth the reason for this is thedevices like microwave and corless telephone or baby monitors these are operated on ISMband . As we discussed above Bluetooth transmission use FHSS so it remains on onefrequency only for a short period of time as the frequency keep on hopping on differentfrequency channels , but if incase any error occurs in transmission it has to resend the dataagain , and at this time it might be using a difeerent channel which is more likely interferencefree. The hopping rate is standardized that is of 1600 hops per second, and the system hopsover all frequencies that are available by using a pre-determined pseudo-random hopsequence it depends on the Bluetooth address of the master node in the network.Bluetooth channels and frequenciesThe Bluetooth channels are spaced 1 MHz apart, it startsfrom 2 402 MHz to 2 480 MHz.wecan determine this as 2401 + n, where n varies from 1 to 79.Bluetooth channels is arranged in such a way that Bluetooth channels gives a guard band of2 MHz at the bottom of the band and 3.5 MHz at the top.
  13. 13. Bluetooth pairingTo establish a connectivity between two devices by using a bluetooth a scheme calledbluetooth pairing I sused. Once Bluetooth pairing has established two devices maycommunicate with each other.Bluetooth pairing is simple is done manuallyonce u activate the bluetooth on your devicethen bluetooth link can be seen on the phone and other devices within range is also seen andconnect to any device that is known to you that you wanted to connect on.The Bluetooth pairing process is typically triggered automatically the first time a devicereceives a connection request from a device with which it is not yet paired. In order thatBluetooth pairing may occur, a password has to be exchanged between the two devices. Thispassword or "Passkey" as it is more correctly termed is a code shared by both Bluetoothdevices. It is used to ensure that both users have agreed to pair with each other..