UNIT-VIIIMobile Wireless Short Range Networks

ANDMobile Internet

Wireless Networking & Wireless LAN:• We know that Local Area Network (LAN) means a set of interconnected computers with in a specific area which may include some other computing systems.• To form a LAN, we use the protocol suit IEEE 802.x or 802.1y.• All the units in local area network, has an address, and with the help of address (IP) they can communicate with each other.• Now we discuss about wireless LANs, in which each system may consists of smart sensors, RFID labels, and have short range communication capabilities.

•We know that the wireless LAN devices or computers are using the IEEE 802.11 communication protocol.• The implementation of IEEE802.11 leads to WiFi – Wireless Fidelity. The WiFi is a trademark of WiFi alliance, that certify the products whose functions are based on 802.11 and used in WLANs. Thus interfaces, devices, system and systems which are used in wireless communication are WiFi enabled.• Today a new technology in the market known as “WiFi direct”, which is able to connect with the existing WiFi networks and

gain the transmission speed up to 250Mbps.• The WiFi direct devices may able to advertise their presence and able to discover another WiFi direct device.• Generally establishment of wireless LANs are a bit complex, the following diagram shows an example for WLAN.

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•The following are the some standards recommended for WLAN in mobile communication and for establishing communication between mobile devices, internet or other networks. •2G: It enables digital encoding of voice and enables mobile phone and SMS. It is based on circuit switching.•2.5G: It enables packet switching, Internet and E-mail.•3G: It enables wideband wireless communication, video conferencing, video calls and mobile TV.

• It supports data communication at 384kbps and 3 x 1.2288Mbps when using three carriers of 1.2288Mbps each.• 3.5G: It is a High speed Packet Access Enhanced (HSPA) data communication at 28Mbps uplink and 56Mbps downlink.•Pre-4G: It enables mobile WiMax using IEEE 802.16e standard and very high data rates using Long Term Evolution (LTE).•4G: It enables multimedia news paper, mobile TV of high resolution, IP telephony, and 100Mbps data rates. It also uses mobile WiMax IEEE 802.16m standard and advanced LTE.

WLAN Configuration: Generally WLAN is a peer-to-peer independent network. It connects a set of computing systems, each of which has a wireless interface (adaptors).• Naturally two or more wireless interfaces within the range of each other at an instant.• The WLAN is formed on-demand, it should not require administration and pre-configuration.• There is another kind of configuration in WLANs, which may known as a fixed infrastructure network.

• In fixed infrastructure network, there are multiple access points provide wireless connectivity to the mobile computing systems and also linked with wired networks.• The access point may form a micro cell or PAN, which may have number of wireless computing systems. The computing system’s wireless interface (adaptor) sufficient capabilities to establish connection with the access point within a micro cell.• Generally WLAN follows two types of communication establishment techniques;

a) Spread spectrum.

b) Infrared WLAN.

The following are some important point that should follow during configuration of WLAN.

1. The range or coverage of WLAN may vary from 30m to 125m.

2. A typical data transmission rate (throughput) varies 1Mbps to 50Mbps.

3. It has interoperability with other wireless infrastructure.

4. It also has interoperability with wired infrastructure.

5. The WLAN has interference and coexistence.

6. It should have the scalability.

7. Generally it is a ad-hoc network.

8. The WLAN should support security, integrity and reliability.

9. It should have simplicity and ease of use.

10. It must be cost effective.

Advantages of WLANs:

1.Installation speed of wireless LANs are so speed.

2.It is simple to install WLAN hardware.

3. WLANs has installation flexibility – The WLANs are installed at anywhere, because there is no need of wires and hubs and the dynamic environment of network is extendable.

4. WLANs provide improved services – The WLAN user can interact with the network at any time and able to access the real time information through WiFi enabled handsets.• The WLAN users can access internet instead of expensive cellular services.• Making secure phone call through VoIP service.

• They are able to access local files of an enterprise.

5. WLANs reduce the cost of ownership – The initial investment of WLAN are higher compared to wired LAN, but the cost of maintaining over the whole life is low.

6. WLANs are scalable – We know that, WLAN network is independent or Fixed infrastructure or peer-to-peer network. The WLANs are configured in various topologies depending on need of specific applications.

WLAN Architecture:• An addressable node in WLAN is called a station. The following diagram shows a Basic Service Set (BSS) of a particular station in WLAN architecture.

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• The BSS can have number of computing systems and those are interconnected with access point by using 802.11.• The devices in a station of WLAN may use same frequencies and interconnection of stations done only through access point.• Each node of a station use same frequency band if it is at a tolerable distance from another station or a node may use different frequency bands if its distance not enough from other stations.•

•So a particular node at a station can communicate directly to the access point and to the other node at another station through the access point.• The nodes of a station can communicate among themselves by forming an ad-hoc or any other type of network, using same frequency band by each node.•Independent Basic Service Set (IBSS): An IBSS having no access point for the connectivity of distributed systems. The IBSS has set of nodes those can communicate among themselves within its boundary.

The following diagram shows an IBSS;

• There are several devices at a station, which are networked by using 802.11 protocol.• In the diagram an IBSS has three stations, STAB, STAC, and STAD, the stations in IBSS

does not connected to any access point. Here the devices are communicate directly with one another or communicate among themselves after forming a ad-hoc network.• All the nodes in a particular station can considered as a single addressable unit. The nodes among them are interact through peer-to-peer communication manner.• Here 802.11 protocol does not specify any protocols for communication among the nodes, for data routing, exchanging and support for exchange of network topology information.

• So in IBSS, the exchange of information among the node can use Bluetooth and these are ZigBee devices.

Distributed System: The wireless BSS may or may not provide sufficient service over the specified coverage area. So IEEE 802.11 provides the facility to integrate multiple BSSs which have number of distributed systems.

The following diagram shows distributed systems interconnected by wireless access points;

• The distributed systems provides flexible functionality to the WLAN architecture component. Here the wireless medium 802.11 is logically separates from the distributed system medium (DSM).

• The following are the main functions of the Distributed systems in WLAN.

1.Perform address-to-destination mapping.

2.Seamless integration of multiple mobile devices in the BSS.•An access point in WALN support the following services

1.It physically connects the distributed systems with access point and access those systems.

2.The access point can provide distributed system services.

3. The access point functions as a station within BSS.

4. The access point bridge and extends the services of the network.

5. It provide address for the connectivity.

Extended service set (ESS): The distributed system can create a wireless network of arbitrary size and complexity. It also from a network which defines an extended service set (ESS).

The following diagram shows WLAN access points of distributed systems networked using ESS.

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• Here the access points A, B, C, D, E, F and G networked together and form an ESS. Generally an ESS have an ID known as ESSID.• Suppose to gent the internet I at each WLAN DS, then establish a connection between internet I and ESS.• The ESS access point may exist or implemented at a base station or gateway and the access point may have multi point relay node.•The ESS can able to interconnect with a cellular network.

•At this stage the 802.11 can facilitate only the ESSID, but it not define or provide any protocols that support distributed system.• The protocols used in ESS may or may not be TCP/IT or IPv6, these usage of protocols may depend upon the how the BSS is interoperate in a service provider servicing setup.

IEEE802.11 Protocol Layers:• 802.11 protocol layers means those are the physical and data link layers.• We know that there is a need of multiple layers each of which may consists of various protocols are for establishing communication network.• Generally these protocols can send the bits to the above and bellow layers and some of the layers may communicate with neighboring node layers.

• In open system interconnectivity the order of the layers are, Physical (L1), Data link (L), Network (L3), Transport (L4), Session (L5), Presentation (L6) and Application (L7) layers.• Suppose the transceiver send the signals then the order of the layers are L7 to L1, when it receiving signals, the order is L1 to L7.• But during the communication, the transceiver may not use the services of seven layers and the functions of the layers are also divide among the sub layers.

• Generally the physical layer, does the sequencing and formatting of data bits, it also do multiplexing, modulating and demodulating. Addition and deletion of some control bits are also takes place at physical layer.• The data link layer does the control functions of addressing, access coordination, frame sequencing and logical links.

The following is the description of 802.11 protocol layers

IEEE 802.x: The IEEE 802.x is a set of protocols defined for networking of computers. Here x=1 specifies the bridge between LLC (Logical Link Control) and MAC (Medium Access Control) sub layers and 802.1 also have some management function of layer 1 and 2. If X=2 especially specifies the LLC at the layer 2.• The 802.1 and 802.2 specifications are common for all 802.x standard.

• 802.3 specifies the functionalities of MAC at the layer 2 and physical layer functionalities in wired networks.• In 802.x all upper layers have some common protocols up to 802.10, specifies security mechanisms.

IEEE 802.1y: IEEE 802.1y when y=1 means 802.11 series protocols, which are the specifications for WLANs.• Here each station in WLAN has a logical architecture as per the 802.11 standard and consists of a single MAC and one multiple physical sub layers.

• The 802.11 may include the previous specifications of 802.x (x= 1-10). So the nodes using 802.11 may access the network either wired or through wireless, because the higher layers of 802.11 are identical to 802.x.

The following diagram shows the physical and MAC functions in 802.11

• Here the physical layer, which transmit or receives the signals through wireless communication or through wire, fiber or microwave after formatting, multiplexing, modulating, the following three options of physical layer is called Physical Media Data (PMD).•1The physical layer in 802.11 using Frequency Hopping Spread Spectrum (FHSS) or Direct Sequence Spread Spectrum (DSSS) or using Diffused Infra Red for the signaling.

2. It also using Orthogonal Frequency Division Multiple Access (OFDM), which is capable of multiplexing 6Mbps to 54Mbps.

3. The physical layer may also includes, Physical Layer Convergence Protocol (PLCP) and Complementary Code Keying (CCK) sub layers.

In the diagram, the goal of MAC is to provide access control functions. These functions may be addressing, access coordination, and Frame sequence checking for shared medium in support of LLC layer.

•The following diagram shows the basic protocol layers at the transmitter and receiver in 802.11

• Here MAC service Data Units (MSDUs) are sent between two entities on the network. The 802.11 also specifies the services that required by the LLC.• The following are the general MAC functions supported by 802.11 at layer 2.

1.Station services – which include MSDU delivery, Privacy, Authentication, and de-authentication.

2.Distribution system services – Distribution, Integration, association, disassociation and re-association.

Wireless Application Protocol: We know that wired environment has HTTP for accessing the websites.• The HTTP browser is installed at the client side. The client sends a request to the web server and server responds to the client through the internet.• The following diagram shows web access architecture based on HTTP

• Coming to the wireless environment, packet losses and disconnections has the major problem, so wireless environment require new web access architecture.• WAP is an open international standard, which defines industry oriented specifications for developing the service applications.• Now a days WAP is used in smart phones and in mobile devices for web browsing and supporting innovative applications. So WAP is a powerful framework to support such an applications.

• There are several services are accessed through WAP such as, email, downloading music, sending MMS, receiving news, and other web services.• The WAP transmission physical layer contains, High Speed Circuit Switched Data (HSCSD), SMS, General Packet Radio Service (GPRS), GSM, Cellular Digital Packet Data (CDPD) and 3G bearer services.• The main objective of WAP is to facilitate browsing and used of wired internet, in protocol independent environment.

WAP 1.1 Architecture: We know that WAP defines a set of protocols. There are mainly three protocol layers in WAP which facilitates the wireless data transmission and reception.• These three protocol layers are, Transport, Transaction and Session layers. Here Wireless Datagram Protocol (WDP) is used for transmitting and receiving the datagram over the network.

The following diagram shows functions of Wireless Application Environment (WAE)

• Here WAE at the layer-7, which supports the web services, and Wireless Markup Language (WML). The following are WAE functions at the (client) Mobile computing system.

1.WAP supports WML (Wireless Markup Language) and WML script.

2.It also support WAP binary XML (WBXML).

3.It support Wireless Telephony Applications (WTA).

4.It is able to maintain user agent profiles.

5. It supports the data formats vCard2.1, vCalender1.0, address book, pictogram, and other picture formats (jpg, gif, etc..).

6. It is able to pre configuring the remote service provider.

WAP 1.1 Gateway:• A WAP1.1 gateway is required for protocol conversions between the mobile client and HTTP server.• The gateway converts WAE1.1, WSP, WTP, WTLS and UDP layers encoded data packets into HTTP and Transport Layer Security (TLS) formats.

• The gateway also getting the data from the clients and encoded in UDP format, when device transmit the data to the server. It also decoding in the reverse path that the server sends the data to the client through the gateway.• The WAP gateway is able to access the both wired and wireless networks. Over the wireless networks it builds the cashes to procure the data due frequent disconnections. It also ensures the security in wired and wireless environment.

• We know that the HTTP environment can only provide the PULL mode of services – the client sends the request and pull the data from the server as a response.• The WAP gateway support both PUSH and PULL mode of services.• The WAP gateway also has WML encoder-decoder, so that the application written in WML is converted into HTML, when the client who using WAE, sends a request to HTTP server and response from the server to the client is also decoded into WML formats.

• One more important function of gateway is iWML Script compilation. The script written in Common Gateway Interface (CGI) runs at the HTTP server and then the server generates the HTML responses to the client.

Wireless Datagram Protocol (WDP):• The WDP (wireless datagram protocol) a connectionless protocol over the wireless environment, so the data transmitted by using WDP in connection less way like UDP in wired environment.• The WDP datagram's provide independent and stateless information. That is the data

in one datagram is no way to related to data in another datagram.• WDP supports the multicasting of the datagram's over the network. It also uses the Wireless Control Message Protocol (WCMP) which functions like an ICMP in wired environment.• The WCMP is a connectionless protocol, it is used when sending the messages, to know the queuing information, reporting errors, and for route address advertisement. It also used for route seeking (soliciting) messages.

• The following diagram shows the WDP header

• The WDP can enable the adaptation of datagram's over the wireless environment. The WDP datagram header is received from the upper layers at the client device.• The WDP header consists of source port, destination port, source IP address, destination IP address (it is optional), length of data, and checksum fields.• The WDP datagram may also has error code to report errors to the upper layers at client.

Wireless Transport Layer Security (WTLS):• We know that the Transport Layer Security is used in wired internet for secure networking of transport layer data.• In wired networks the TLS is an optional one and also TLS maps to Secure Socket Layer (SSL) in HTTPS (HTTP with SSL).• In wireless networks also the WTLS is an optional one, which provide security to the networked data getting from the transport layer.

• The following diagrams shows data exchanges by using WTLS

The following are the WTLS services;

1.It assures integrity when data transactions occurs between client and gateway.

2.It ensures the privacy of transactions.

3.It maps SSL to HTTPS.

4.It supports TCP, WDP, and WCMP.

5.It serves as a layer, above the WDP and provide security to datagram's when required.

• Before transmission of the data over the wireless network, a secure session is established between the nodes by using the upper layer protocols, such as WTP, WSP, WAE.• The following specifications can takes place during WTLS establishing secure session;

1.Source device generate a message to create a secure channel consists the following information;

a.Source address and source port number.

b.Destination address and destination port number.

c. Either RSA or ECC algorithms for key exchange.

d. IDEA or DES algorithms for ciphering the data.

e. Compression method used for data compression.

2. The destination side messages for secure channel establishment conformation consists the following information.

a.Sequence number.

b.How many times the key is refreshed and exchanged again

C. Identification of session after establishment of session.

d. RSA or ECC algorithm for key exchange.

e. IDEA or DES algorithm for ciphering of text.

f. A compression method for data compression.

3. After getting the request from the destination the source generates the secure channel public key authentication by a client certificate.

4. Source device generate message to commit the request.

5. The destination generate the message for commit conformation request.

Wireless Transaction & Session Layers:

Introduction:• We know that the TCP getting the problem of loss of packets in wireless environment, so we need Wireless Transaction Protocol (WTP) for sending and receiving of information in wireless environment.• In wired networks, first we establish session (connection) and then transmit the data as per the TCP segment numbers (here the maximum segment number is 232 ),

but the wireless environment has frequent loss of connectivity, so the wireless environment require compressed codes and suitable encoding mechanism. • Here encoding means adding additional bits for error detection and correction.• The Wireless Session Protocol (WSP) can also used compressed binary codes for establishing wireless sessions.

Wireless Transaction Protocol (WTP): • Wireless Transaction Protocol (WTP) is an upper layer of Wireless Transaction Layer Security (WTLS), so it transmits the data to

WTLS for secure transmission. •The WTP has also able to directly transmit the data to Wireless Datagram Protocol (WDP) or to Wireless Control Message Protocol (WCMP) without transmit the information to WTLS.• WTP supports the joining of messages and enables asynchronous data transmissions.• Suppose the transmission is aborted in the middle of transmission, then the WTP facilitates set back the whole transaction to the initial state.• WTP also indicate the success or failure of transactions.

• The WTP act as an interface for reliable transmission and it has three WTP services classes such as 0, 1 and 2.

1.Class-0: Here the source send the messages to destination and it should not expect any response from the destination.

2.Class-1: This class represents reliable data transfer. Here source start the transaction with a request.•Now the destination device obtain the request then generate the conformation of invocation.

• After getting the invocation from the destination, the source responds with data transmission.• Finally the device sends the acknowledgement to the source.• Here the source takes the responsibility to remove the duplicate data, provide retransmission and transaction identifier.• The total process comes under the PUSH service, in which there is no acknowledgement for user’s data except conformation invocation.

3. Class-2: This class also represents the reliable data transmission. Here also the source start the transaction with a request.• Now the destination device gets this request and send back the acknowledgement to the source.• Now the source responds by transmitting the information to the destination. Again the device send the acknowledgement to source.• Here also the source takes the responsibility of removing the duplicate data, retransmission and transmitting transaction ID.

• Here two acknowledgements, one is acknowledgement generated by the user and another is automatic acknowledgement.• The following diagram shows WTP header and WTP invocation

Wireless Session Protocol:• The Wireless Session Protocol support stateless data transfers, so the client browser get the packets in any sequence from the server.• Here Synchronization Markup Language (Sync ML) in WSP is used to connect the particular node to the internet (server). Here the synchronizations can also takes place between the client and server by using Sync ML at WAP application layer.•The WSP transmit the data to the WTP for reliable data transmissions other wise the WSP is also able to transmit the data directly to the WDP or WCMP.

The following diagram shows WSP protocol session, it has establishing connection, receiving and response headers.

• WSP can considered as a compressed binary encoded version and as a extended version HTTP.• The WSP also supports, asynchronous exchange of data, multiple requests from clients, push and pull mechanism of data dissemination, capability negotiation and content encoding.• The following is the session management of WSP.

1. First the session is established by using the functions of agreed common protocols.

2. In WSP, an established session can be suspended and then resumed from the point at which it was suspended.

3. A session can be terminated.• The WSP having the three service classes such as 0,1 and 2.

Class-0: This class indicating the source sending unconfirmed push. It support session suspension, resumption, and management. The messages sent from the source do not get any response from destination.

Class-1: This class represents the source sending the confirmation push.

Class-2: This class represents source support for session invocation, suspension, and resumption.

The following diagram shows WSP invocation and request for results;

Wireless Application Environment:• The Wireless Application Environment consists of the following components;

1.WML

2. WML Script.

3. WBXML – Wireless Binary XML.

4. WTA - Wireless Telephony Application.

5. Data formats.

• The WML is also a XML based language which takes the following mobile devices constraints into account while programming an application for running on the device.• These are the constraints of mobile devices;

1.Narrow band network connection with intermittent loss of connectivity.

2.String parameterization and state management.

3.Limited user input and output facility.

4.Limited computational resources and memory.

WML: We know that XML and how to create applications in XML based languages. Here tags are used to markup the code.• The WML is a webpage markup language for wireless environment internet. There are two versions of WML those are WML2.x and WML1.x . The WML2.x may also include Extensible Hyper Text Markup Language Mobile Profile( XHTML-MP). • Generally, the WAP also has the functions and WML methods at the server for pre configuration of mobile device.

WML Card:• WML is used to create the cards for mobile applications. Here a card represents an interaction between the user and the deck contains the cards.• In WML all the information collected and managed in the form of deck and cards. The WML deck is save with file extension .wml.• Let us consider the deck is a WML file and cards are records with in the file.•In WML a scaled down set of procedural elements are used to control navigation between the cards and WML parser parses the information within deck of cards.

• A WML card has the following features;

1.It provide content – programs, data, commands, strings, or images.

2.It support wide variety of formatting commands and layout commands.

3.It provides user interface for mobile devices with constraints as mentioned in the WML code.

4.Organizing similar deck of cards.• A WML card is first validated against its declared document type by using Document Type definition (DTD) before parsing.

WML Script: • WML script is a scripting language is used in wireless environment. It is similar to CGI script in HTML at server side.• The WML script is used to retrieving the application required data from the server and enables the server response for clients request.• In WML script each line of code is loaded into computer and executed at run time only

• At the client side the WML script is similar to JavaScript and it does not require to communicate with the server by sending a request and waiting for the response.• WML script is embedded markups within WML, WAP browser displays the page having WML script.• The WML script does not require any pre compilation, so it is executed very fast and it is compiled at gateway, only byte code is sent to the client.

WBXML: • The Wireless application protocol provides communication between the client and the gate way by using the WBXML.• General XML and WML data formats are not compact to establish communication between the client and gateway.• WBXML represents any information in binary format, so the data is transmitted to the gateway in compact format.• In WBXML we use a binary number instead to represent a tag.

• The binary codes causes the compact transmission, but there is no change in contents, code functionality, and semantic information.• WBXML also support and keep the structure of elements which are used in XML intact. But metadata information, document type definitions, conditional sections are removed when the XML document is converted into binary format.• The WBXML browser does not take unknown elements or attributes from the gateway.

WTA: • The specific telephonic features are defined by the WAT interface (WATI) by using the WML browser.• A WTA server can push the script and WTA event handler can handle the events, persistent storage can help to data storage on device.• WTA can also provide security interface, only authorized gateway can access the data at the server.

User agent Profile: • User agent is a software used by the user to give inputs using Voice User Interface (VUI) or Graphic User Interface (GUI) and also interact with mini browser.• User agent executes the WMLscript at the client and displays the result. It also displays the responses from the server.• User agent support the small screen device characteristics and profile enhances, such as font, display capabilities, touch characteristics etc.

Data Formats:• The data displayed on mobile devices is in special data format.• vCard2.1 is format for visiting card, vCalendar 1.0 is the format for calendar. The mobile devices also support pictogram, which display small pictures of low resolution.

END OF UNIT VIII