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1. 2. Mobile networks This lecture covers cellular data technologies It does not cover:

2. 2.1. History of Mobile Data Networks Remember that phones were originally designed for calls

3. Wireles Application Protocol(WAP) Architecture

4. 2.2.Cellular Network Basics There are many types of cellular services Cellular network/telephony is a radio -based technology; radio waves are electromagnetic waves that antennas propagate. Most signals are in the 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz frequency bands Cell phones operate in this frequency range (note the logarithmic scale)

5. 2.2.1. Cellular Network Generations It is useful to think of cellular Network/telephony in terms of generations : 0G : Briefcase-size mobile radio telephones 1G : Analog cellular telephony 2G : Digital cellular telephony EDGE (Enhanced Data Rate For GSM Evolution) provides a higher rate of data transmission than normal GSM. 3G : High-speed digital cellular telephony (including video telephony ) UMTS (Universal Mobile Telecommunications Service) Long Term Evolution ( LTE: 4G): IP-based “anytime, anywhere” voice, data, and multimedia telephony at faster data rates than 3G

6. Evolution of Cellular Networks 1G 2G 3G 4G 2.5G

7. 2.2.2. Cellular Network Base stations transmit to and receive from mobiles at the assigned spectrum Multiple base stations use the same spectrum (spectral reuse) The service area of each base station is called a cell Each mobile terminal is typically served by the ‘closest’ base stations Handoff when terminals move

8. “Simplified” view of 3G NodeB & Base Station Controller: Converts RF to wired Mobile switching center: Analog to digital Serving GPRS Support Node: Move IP packets to/from radio network Gateway GPRS Support Node: Route to/from the Interet

9. Packet switched vs circuit switched 3G and earlier maintains two data paths Circuit switched: Phone calls (8kbps) and SMS/MMS Packet switched: All IP data

10. LTE u ses “all in one” approach Everything over IP, including voice S-GW (Serving Gateway) replaced SGSN, Packet Gateway( P-GW) replaces Gateway GPRS Support Node(GGSN)

11. LTE Key Features Uses Multi-input Multi- output ( MIMO) for enhanced throughput Reduced power consumption. Higher RF power amplifier efficiency (less battery power used by handsets ). Lower latency to get access to the medium. Performance sometimes better than WiFi.

12. 2.3. The Multiple Access Problem In satellite telecommunication, a downlink is the link from a satellite down to one or more ground stations or receivers, and an uplink is the link from a ground station up to a satellite. In mobile communication the base stations serve many mobile terminals at the same time (both downlink and uplink) All mobiles in the cell need to transmit to the base station interference among different senders and receivers So it need multiple access scheme

13. Multiple Access Schemes Frequency Division Multiple Access (FDMA) Time Division Multiple Access (TDMA) Code Division Multiple Access (CDMA) 3 orthogonal Schemes:

14. 2.3.1.Frequency Division Multiple Access Each mobile is assigned a separate frequency channel for a call G uard band is required to prevent adjacent channel interference Usually, one downlink band and one uplink band Different cellular network protocols use different frequencies Frequency is precious and scare – we are running out of it Cognitive radio frequency

15. 2.3.2.Time Division Multiple Access Time is divided into slots and only one mobile terminal transmits during each slot Like during the lecture, only one can talk, but others may take the floor in turn Each user is given a specific slot. No competition in cellular network Unlike Carrier Sensing Multiple Access (CSMA) in WiFi Guard time – signal transmitted by mobile terminals at different locations do no arrive at the base station at the same time

16. TDMA structure of the voice+data system 1 2 57 58 59 ... hyperframe 1 2 15 16 17 ... multiframe 1 2 3 slot 509 frame 14.17 ms 56.67 ms 1.02 s 61.2 s CF Control Frame

17. 2.3.3.Code Division Multiple Access Use of orthogonal codes to separate different transmissions Each symbol of bit is transmitted as a larger number of bits using the user specific code – Spreading Bandwidth occupied by the signal is much larger than the information transmission rate But all users use the same frequency band together Orthogonal among users

18. 2.4. Mobile Computing Services Short Message Service (SMS) A service that supports the sending and receiving of short text messages on mobile phones Enhanced Messaging Service (EMS) An extension of SMS that can send simple animation, tiny pictures, sounds, and formatted text Multimedia Messaging Service (MMS) The emerging generation of wireless messaging; MMS is able to deliver rich media E-payments Electronic payments for purchase amounts.

19. Location-based services global positioning system (GPS) A worldwide satellite-based tracking system that enables users to determine their position anywhere on the earth Voice-support services interactive voice response (IVR) A voice system that enables users to request and receive information and to enter and change data through a telephone to a computerized system Voice portal A Web site with an audio interface that can be accessed through a telephone call

20. 3.Mobile Computing Architecture What is Mobile Computing Architecture? 3-Tier Architecture of Mobile Computing Mobile Computing Architecture Layers Characteristics of mobile computing architecture

21. Mobile computing is enabled with three-tier architecture that has three major layers contains the user interface or the presentation tier, the process management or the application tier and the data management tier. 3.1. Three -Tier Architecture of Mobile Computing Presentation Layer (UI): This layer lets users to face device handling and rendering. Application Layer (AL): It allows executing business logic and rules. Data Access Layer (DM): It lets to get access and management data. Mobile Computing Architecture

22. 1-Tier Presentation Layer This presentation layer lets to execute all applications on the client devices and provide complete user interfaces. It has main responsibility is to present information to edge-user. Users are able to grab all information via speakers, vibration, screens, etc. Users can sent the information with helping of input devices like pen drives, mouse, keyboard, touch screens and so on. This layer is enabled with WAP browsers, customized client programs, web browsers, etc. Presentation layer allows accomplishing via client-side data source, Dynamic HTML and data cursors. Presentation layer must be context aware and device-independent. In General: Responsible for presenting the information to the end user Run on the client device and offer all the user interfaces Includes web browsers, WAP browsers and client programs

23. 2-Tier Application Layer In the application layer, business logic performs all tasks as server for client requests from workstations. It works as business rules fetch or enter data through the Data Layer. It is enabled with few technologies such as PHP, .Net services, JSP, Java and so on. Presentation and database-independent This layer identifies that which types of data is required and performs as client in relation to a third tier or programming that may be situated on a mainframe computer or locally. It takes decision on rendering, network management, security, data store access, need for many types of middlewares.

24. Their components are not linked to certain client, so they can be implemented by all applications and can be proceed to other locations, as responding time frame and other needed rules. Independent of presentation and database management Handles functions related to middleware Middleware layer of software sitting between the operating System and user facing software Many types of middleware: Message Oriented Middleware, Transaction Processing Middleware, Communication Middleware, Distributed Objects and Components, Transcoding Middleware, Web Services, etc.

25. 3-Tier Data Access Layer This layer is implemented to keep store data that is required by application and work as repository for both temporary and permanent data. Data access layer is built up of DBMS that offers all data for above two layers. This layer is also known as ‘DBMS Access Layer’ All data is stored into many format like as text files or relational DB.

26. Used to store data needed by the application and acts as a Repository for both temporary and permanent data Can use XML (Extensible Markup Language) for interoperability of data with other systems And data sources Might incorporate the use of Database Middleware and Sync ML (Machine Language) ’ Database Middleware : interfaces application programs and the database Database Middleware : helps business logic run independent and transparent from database technology and database vendor

27. Physical layer modulation/demodulation generation of the physical channel structure with a guaranteed throughput controlling of radio transmission channel assignment on request of the MAC layer detection of incoming signals sender/receiver synchronization collecting status information for the management plane MAC layer maintaining basic services, activating/deactivating physical channels multiplexing of logical channels e.g., C: signaling, I: user data, P: paging, Q: broadcast segmentation/reassembly error control/error correction 3.2. Mobile Layered Network Architecture

28. Data link control layer creation and keeping up reliable connections between the mobile terminal and basestation two DLC protocols for the control plane (C-Plane) connectionless broadcast service: paging functionality Lc+LAPC protocol: in-call signaling (similar to LAPD within ISDN), adapted to the underlying MAC service several services specified for the user plane (U-Plane) null-service: offers unmodified MAC services frame relay: simple packet transmission frame switching: time-bounded packet transmission error correcting transmission: uses FEC, for delay critical, time-bounded services bandwidth adaptive transmission „Escape“ service: for further enhancements of the standard

29. Network layer similar to ISDN (Q.931) and GSM (04.08) offers services to request, check, reserve, control, and release resources at the basestation and mobile terminal resources necessary for a wireless connection necessary for the connection of the DECT system to the fixed network main tasks call control: setup, release, negotiation, control call independent services: call forwarding, accounting, call redirecting mobility management: identity management, authentication, management of the location register

30. Characteristics of mobile computing architecture It allowing the enhancing the performance Maintainability Flexibility Re-usability and Scalability to architecture, It also helps to invisible complexity of distributed processing from the user.