Mobile Computing (ITE216) PDF

Mobile Computing (ITE216) BY ANU R AJ  What is Mobile Computing? Mobile Computing Technology is a mobile technology that allows transmission of data of any kind such as written document, voice, picture, video, etc. from one wireless-enabled device to another wireless- enabled...

Mobile Computing (ITE216) BY ANU R AJ  What is Mobile Computing? Mobile Computing Technology is a mobile technology that allows transmission of data of any kind such as written document, voice, picture, video, etc. from one wireless-enabled device to another wireless- enabled device. These wireless-enabled devices can be a computer, laptop, notepad, mobile phone, pager, sensor, embedded controller, etc. “Mobile Computing refers to mobile technology that allows transmission of data, from one wireless- enabled device to another wireless-enabled device without the use of a fixed physical link.” “Mobile computing can be defined as a human and computer communication while a human is mobile. It enables the transmission of text, audio, video, and images, etc. The technology includes mobile communication via mobile hardware and mobile software.” Mobile Computing contd…. The concept of Mobile Computing can be divided into three parts: 1. Mobile Communication 2. Mobile Hardware 3. Mobile Software Mobile Communication Mobile Communication specifies a framework that is responsible for the working of mobile computing technology. In this case, mobile communication refers to an infrastructure that ensures seamless and reliable communication among wireless devices. Fixed and Wired Fixed and Wireless Mobile and Wired Mobile and Wireless  Mobile Communication Fixed and Wired: In Fixed and Wired configuration, the devices are fixed at a position, and they are connected through a physical link to communicate with other devices. For Example, Desktop Computer. Fixed and Wireless: In Fixed and Wireless configuration, the devices are fixed at a position, and they are connected through a wireless link to make communication with other devices. For Example, Communication Towers, WiFi router Mobile and Wired: In Mobile and Wired configuration, some devices are wired, and some are mobile. They altogether make communications with other devices. For Example, Laptops. Mobile and Wireless: In Mobile and Wireless configuration, the devices can communicate with each other irrespective of their position. They can also connect to any network without the use of any wired device. For Example, WiFi Dongle.  Mobile Hardware & Software Mobile hardware It consists of mobile devices or device components that can be used to receive or access the service of mobility.  Examples of mobile hardware can be smartphones, laptops, portable PCs, tablet PCs, Personal Digital Assistants, etc. Mobile Software Mobile software is a program that runs on mobile hardware. This is designed to deal capably with the characteristics and requirements of mobile applications. This is the operating system for the appliance of mobile devices. In other words, you can say it the heart of mobile systems. This is an essential component that operates the mobile device.  Features of Mobile Computing The most important features of mobile computing technology are as follows- Mobility Mobility is a fundamental feature of mobile computing technology. The technology allows transferring data to the user while the user is in a mobile environment means roaming from one place to another place. It not only supports communication with mobile users but also when devices are mobile doesn’t matter the user is the same or different. Wireless Connectivity Wireless connectivity is another essential feature of mobile communication. It means all the mobile devices such as mobile phones, laptops, tablets must have wireless connectivity enabled otherwise no data transfer is possible. These devices must have all the hardware and software that are essential to the Wi-Fi enabled device.  Features of mobile computing contd…. Portability Portability means that the devices used to make mobile computing enabled can be ported from one place to another place without any issue. Mobile phones, laptops, tablets can be ported one location to any other location in any distant area. Interaction Interaction refers to communicate and transfer information from one user to another user using wireless- enabled devices. Users can send textual data, audio, and video files from person to another and one group of people to another group of people. Location Independence Location independence means a user can communicate at any distant location from any location.  Mobile Computing Technology Applications Emergencies and Natural Hazards In situations of emergencies such as accidents, flooding, earthquakes, wars, and natural calamities, etc., wireless mobile technology is the only system that can be survived and can provide services to the victims and facilitators both Entertainment Entertainment is a big industry that is revolutionized with the use of wireless mobile technology. Sports, movies, and games all have become richer with the use of mobile computing technology. Vehicle Vehicles, cars, buses all are equipped with wireless mobile-enabled devices that allow you to be aware by the traffic status and allow you to plan your journey and route accordingly. Business Now, no business can grow and survive without the use of mobile computing technology.  Issues and Challenges in Mobile Computing Technology Disconnection Frequent Connection failure is one of the major challenges. Low bandwidth Mobile internet access is slower than the fixed desktop connection while using GSM and other advanced technologies such as 3G, 4G, and 5G. Local wireless connection offers Mbit/s of speed and wide wireless connection offers only Kbit/s of speed. Lower security When working with mobile people are completely dependent on the public network which can be easily tracked and hacked by hackers. Therefore, to protect the data from eavesdropping there is a need for strongly secured algorithms of authentication and security. Heterogeneous Network Radio transmission cannot be protected therefore there is higher transmission interference due to electric engines, lightening, high buildings, mountains, weather conditions, etc., all this results in a higher loss of data rate and bit errors.  Issues and Challenges in Mobile Computing Technology Bandwidth Variation-High delays, large delay variation A serious problem faced by Internet protocols is variations in link characteristics. In wireless transmission delays of various seconds occur that create so many problems in transmission and communication. Shared medium Radio access is a shared medium because it is just impossible to give dedicated radio access to all the users. However, different techniques are deployed still so many questions are unanswered such as how to provide quality of service to each user sharing radio access. Ad-hoc networking Wireless and mobile computing allow ad-hoc networking without a prior set of infrastructure between senders and receivers. This creates several challenges. Overview of Wireless Telephony - Cellular Concept Wireless Telephony refers to communication systems that transmit voice and data without the use of physical wires, typically using radio waves. Key points: 1. Components Mobile Phones: Primary user devices. Cellular Networks: Use cell towers (base stations) to provide coverage. Radio Spectrum: Specific frequencies are used for transmission, regulated by governments. Core Network: Manages call routing and data transmission.  Overview of Wireless Telephony - Cellular Concept contd… 2. Generations of Wireless Telephony 1G: Analog voice communication (1980s). 2G: Digital voice, SMS, and basic data (1990s). 3G: Mobile internet and multimedia (2000s). 4G: High-speed data, video calls, streaming (2010s). 5G: Ultra-fast speeds, low latency, IoT support (2020s). 3. Types Cellular: Mobile communication across wide areas. Cordless Phones: Short-range, for home/office use. Satellite Phones: Communication in remote areas via satellites. VoIP: Voice over Internet Protocol using Wi-Fi or data networks.  Overview of Wireless Telephony - Cellular Concept contd… Cellular Concepts refers to the use of a group of cells to provide communication from one place to another place when the user is mobile. A cellular system in mobile computing implements space division multiplexing or SDM. Each transmitter in the cellular system is called a base station. Base station The base station covers a specific area that is called a cell. Cell Cell radius can vary from tens of meters in building, hundreds of meters in a city, and tens of kilometers in the country. The shape of a cell depends on the environmental conditions such as type of building, mountains, weather conditions, load, and other conditions. Generally, it is hexagon shape but not an exact hexagon. Cellular Structure Group of Cells  Advantages of Cellular System Mobile computing used cellular system and it has the following advantages: Higher Capacity Cellular system uses SDM. SDM allows frequency reuse. If one transmitter is far away from another transmitter particularly out of the range of the interference area then another transmitter can use the same frequency Mobile systems assign one specific frequency to a certain user and that frequency is blocked for the use by other users. But frequency is a scarce resource therefore for their optimum utilization of the same frequency, the same frequency is used for other users using the technique frequency reuse.  Advantages of Cellular Systems Less Transmission Power Transmission power is not a big issue for the base station but it is important for the mobile receivers. Keeping cell size small facilitates mobile receivers because as they move far from the base station their receiving capacity reduces and due to small cells after a few distances they can again access receiving power from the cell nearby them and the problem of the mobile receiver is solved. Local Interference When the distance is large between the sender and receiver then interference is also more and difficult to manage. There is only local interference when cells are small and that is easy to handle by the base station and the mobile station. Robustness The cellular system is decentralized therefore more robust as compared to when centralized. If any component fails only that specific area affected and the rest of the part remains unaffected and works efficiently. Disadvantages of Cellular System Infrastructure Requirement Cellular system establishment needs complex infrastructure, storage registers to locate mobile users in local areas and roaming, antennas, transmitters, receivers, and amplifiers, etc. that are expensive. Handover Needed The mobile system needs handovers when they change cells. This is quite often which further incur a cost.  Frequency Planning To avoid the interference between transmitters frequencies are planned carefully. Frequency is a limited resource therefore they are distributed intelligently so that they can be reused without any kind of interference. Mobile Computing Architecture – GSM Architecture The full form of GSM is group special mobile (GSM) and later it was named as a global system for mobile communications (GSM). It was founded in 1965. GSM is the most successful and popular mobile telecommunication system. GSM is used by over 800 million people and in over 190 countries. The main aim of GSM was to provide a mobile phone system that allows users to move throughout Europe and allows voice services compatible with the ISDN and PSTN systems. GSM is a particularly second-generation system, a replacement of the first- generation analog system. This system was not capable to give high worldwide data rates as promised by the third generation systems. GSM Architecture GSM consists of three subsystems as given below – 1. Radio Subsystem 2. Network Switching subsystem 3. Operation support subsystem Radio subsystem comprises the entire radio specific entities such as A mobile station (ms) and  Base station subsystem (BSS) RSS and NSS connected with “a” interface and further connected with OSS via the “o” interface GSM Architecture GSM Architecture Air Interface in GSM The Air Interface in GSM refers to the communication link between the mobile station (MS) (the user’s phone) and the Base Transceiver Station (BTS) (the cell tower). It is the radio interface over which all user data (voice, SMS, internet) and signaling information are exchanged. This link operates using a combination of TDMA (Time Division Multiple Access) and FDMA (Frequency Division Multiple Access) to allow multiple users to share the same frequency band without interference. Key Features of the GSM Air Interface: 1.Frequency Bands: 1. GSM 900 MHz: 890–915 MHz (uplink) and 935–960 MHz (downlink). 2. GSM 1800 MHz: 1710–1785 MHz (uplink) and 1805–1880 MHz (downlink). 3. Different countries and regions may use different frequency bands. Subsystems of GSM All the subsystems of GSM are as follows- 1. Base station subsystem – BSS 2. Base transceiver station – BTS 3. Base station controller -BSC 4. Mobile station – ms Subsystems of GSM Base station subsystem – BSS A BSS comprises many base station subsystems. Each BSS is controlled by BSC or base station controller.  A BSS does all functions that are necessary to manage and maintain radio connections to a mobile station, for instance, coding and decoding of voice, and rate adaptation to and from the wireless network. A BSS contains several BSC and BTS. Base transceiver station – BTS The base transceiver comprises all radio entities and equipment such as  Antennas, Signal processing, Amplifiers, etc. necessary for radio transmission A BTS form a radio cell or using sectorized antennas several cells and that are connected to the mobile station via the Um interface (ISDN U Interface for mobile ) and to the BSC via the Abis interface. The Um-interface contains all the entities required for wireless transmission such as TDMA, FDMA, etc. Subsystems of GSM The base transceiver comprises all radio entities and equipment such as Antennas, Signal processing, Amplifiers, etc. necessary for radio transmission A BTS form a radio cell or using sectorized antennas several cells and that are connected to the mobile station via the Um interface (ISDN U Interface for mobile ) and to the BSC via the Abis interface.  The Um-interface contains all the entities required for wireless transmission such as TDMA, FDMA, etc. Base station controller –BSC  The base station controller manages all the BTS.  It reserves radio frequencies, handles handovers, from one BTS to another BTS within the BSS. Mobile station – ms The mobile station comprises user equipment and entities as well as the software required for communication with the GSM network system. The mobile station consists of user-independent hardware and software and subscriber entity module or ‘Sim’ that store all the user-related data that is relevant for the GSM system. Network Switching Subsystem Network and Switching subsystem connects the wireless with the standard public network. NSS performs handovers between different BSS. NSS performs following functions-  Worldwide localization of mobile users Support charging, accounting, and roaming of users between various providers in different countries NSS consists of following switches and databases Mobile services switching center –MSC Home location register – HLR The home location register is the most important database in the GSM system. It stores all the user-specific data such as- Mobile Subscriber ISDN number – MSISDN Information on subscriber services such as forwarding, roaming restrictions, and the international mobile subscriber identity – IMSI Dynamic information is also needed such as the current location area (LA) of the mobile station. As soon as the mobile station leaves its current location area, the information of the HLR is immediately updated. This information is needed to localize the mobile station in the worldwide GSM network. HLR also stores present MSC and VLR. All these user-specific information elements only exist once for each user in a single HLR, that also facilitates charging and accounting. Visitor Location Register – VLR The visitor location register is associated with each MSC.  VLR is dynamic database stores all important information of the mobile user such as its current location area, and current MSC.  Whenever a new user changes its location area and MSC, VLR copies its data from its HLR. VlRs capable to store the data of millions of customers. Operation support Subsystem – OSS OSS is the third subsystem of GSM. It contains all the necessary functions for network operations and maintenance. It contains the following entities-  Operation and Maintenance Center  Authentication Center  Equipment Entity Register Operation and Maintenance Center Operation and Maintenance (OMC) monitors and controls network entities via O interface. OMC management functions are as below- Traffic monitoring Status reporting of network entities Subscriber management Channel Structures in GSM In GSM (Global System for Mobile Communications), the radio spectrum is divided into multiple channels. These channels are structured and classified into two main categories: GSM uses two kinds of channels  Logical Channels  Traffic Channels GSM Traffic Channels – GSM TCH GSM uses traffic channels to transmit voice and fax data. Two types of TCHs have been defined in the GSM. Full-rate TCH – TCH/F Channel Structures in GSM A TCH/F has a data rate of 22.8 kbits/s. Half-rate TCH – TCH/h TCH/h has data rate of 11.4 kbits/s. Voice codecs used in the beginning of GSM standardization consumed 13 kbit/s. Remaining capacity of the TCH/F (22.8 kbit) was used for error correction. Improved codecs give better voice quality in terms of speed and used with TCH/h, however voices quality decreased after the use of improved codecs. The standard codecs system for voice are called full rate or FR,13 kbits/s and half rate or HR, 5.6 kbit/s GSM Control channels – CCH Different control channels are used in the GSM network architecture to control the following – Medium access Allocation of traffic channels Mobility management Three groups of Control channels – CCH are defined and these groups of channels have further sub channels Broadcast control channel – BCCH Common control channel – CCCH Dedicated control channel – DCCH Channel Structures in GSM Broadcast control channel – BCCH A base transceiver system or BTS uses a broadcast control channel to provide information to all mobile stations within a cell. Information transmitted in this channel is as follows- Cell identifier Options present within the cell about frequency hopping Frequency available inside the cell and in the neighboring cells BTS gives frequency correction information via frequency correction channel (FCCH) and also information about time synchronization via synchronization channel (SCH). Channel Structures in GSM Broadcast control channel – BCCH A base transceiver system or BTS uses a broadcast control channel to provide information to all mobile stations within a cell. Information transmitted in this channel is as follows- Cell identifier  Options present within the cell about frequency hopping  Frequency available inside the cell and in the neighboring cells BTS gives frequency correction information via frequency correction channel (FCCH) and also information about time synchronization via synchronization channel (SCH). Channel Structures in GSM Common control channel – CCCH The common control channel exchanged all the information about the connection setup between a mobile station and BTS. If a mobile station wants to set up the connection it uses a random access channel or RACH, to send data to the BTS. RACH implements multiple accesses using slotted Aloha. All the mobile stations within a cell may access RACH channel. If any collision occurs with other mobile stations in a GSM system, the BTS uses the access grant channel or AGCH to signal a mobile station that it can use a TCH or SDCCH for further connection setup. Channel Structures in GSM Dedicated control channel – DCCH Dedicated control channels are bidirectional channels while all other channels mentioned above are unidirectional channels. As long as a mobile station has not set up a TCH with the BTS, the mobile station uses the Standalone dedicated control channel (SDCCH) at a low data rate of 782bit/s for signaling. This includes signaling for authentication, registration or other data required for setup TCH. TCH and SDCCH have a slow associate dedicated control channel (SACCH) also which is used for exchanging system information like system quality and signal power level. If more signaling data required to be shared a GSM uses fast associated dedicated control channel (FACCH). Channel Allocation in GSM Cellular Systems Channel allocation in GSM refers to how the available radio spectrum (frequency channels) is assigned to base stations (BTS) and mobile devices (MS) for communication. Since the radio spectrum is a limited resource, efficient channel allocation is essential to ensure proper coverage, avoid interference, and optimize capacity in the cellular network. There are two main strategies for channel allocation in GSM: Fixed Channel Allocation (FCA) Dynamic Channel Allocation (DCA). Channel Allocation in GSM Cellular Systems 1. Fixed Channel Allocation (FCA) Definition: Channels are pre-assigned to each cell based on a fixed frequency plan. Each cell has a dedicated set of frequencies that can be used for communication. How It Works: A certain number of channels are allocated to each BTS. Channels are reused in other cells that are far enough apart to avoid interference, following the frequency reuse principle. Frequency Reuse: The same frequencies are reused in different cells that are geographically separated to minimize co-channel interference. This is usually done using a frequency reuse pattern, such as a 7-cell reuse pattern Channel Allocation in GSM Cellular Systems 2. Dynamic Channel Allocation (DCA) Definition: Channels are dynamically allocated based on the current demand in the cell. No fixed set of frequencies is reserved for each cell; instead, channels are assigned as needed. How It Works:  The network continuously monitors the traffic load in each cell and allocates available channels accordingly.  If one cell is experiencing high traffic, more channels can be temporarily assigned to that cell, as long as it doesn't cause interference with neighboring cells. Handoffs in GSM Architecture Handoff (or Handover) in GSM (Global System for Mobile Communications) refers to the process of transferring an ongoing call or data session from one cell (base station) to another without interrupting the service. It is a critical feature in GSM to maintain communication when a mobile user moves between different cells. Types of Handoffs in GSM Intra-Cell Handoff: 1. Definition: Occurs when the mobile station (MS) stays within the same cell but switches to a different frequency or channel due to interference or signal quality issues. 2. Purpose: Improves connection quality while staying within the same base station. Handoffs in GSM Architecture Inter-Cell Handoff (Inter-BTS Handoff): 1. Definition: Occurs when the mobile station moves from one cell (Base Transceiver Station, BTS) to another within the same Base Station Controller (BSC) area. 2. Purpose: Ensures continuous communication as the user moves out of the coverage area of the current BTS. Inter-BSC Handoff: 3. Definition: Occurs when the mobile station moves from a cell controlled by one BSC to a cell controlled by another BSC within the same Mobile Switching Center (MSC) area. 4. Purpose: Maintains the call continuity as the user moves between different BSCs. Inter-MSC Handoff: 5. Definition: Occurs when the mobile station moves from a cell in one MSC area to a cell in another MSC area. 6. Purpose: Ensures uninterrupted service as the user moves between different MSCs, often over long distances or across different regions. Types of Handoff Based on Mode: 1.Hard Handoff: 1. Definition: Involves breaking the connection with the current cell before establishing a new connection with the target cell. It is also known as a "break-before-make" handoff. 2. Common in: GSM systems. 3. Challenges: There may be a slight delay during the switch, but it is usually not noticeable by users. 2.Soft Handoff: 1. Definition: Involves simultaneously connecting to more than one cell during the handoff process. The mobile station switches to the target cell without breaking the connection to the current one. 2. Common in: CDMA systems (not GSM). 3. Advantage: Provides a smoother transition and reduces the chances of call drops. CDMA (Code Division Multiple Access) CDMA refers to Code Division Multiple Access. CDMA is cellular technology. In CDMA there are two main systems  Base Station (BS) mobile subscribers or users. In CDMA Unique codes are assigned to the users for communication with BS or base station. CDMA allows multiple transmitters to send data over a single channel simultaneously. This makes it possible to share the same bandwidth by multiple users at the same time. Codes with specific characteristics can be applied to the transmission to enable the use of code division multiplexing (CDM). Code division multiple access (CDMA) systems use exactly these codes to separate different users in code space and to enable access to a shared medium without interference. CDMA (Code Division Multiple Access) In CDMA entire bandwidth is being used by multiple users and each user has their unique codes to recover the data. The system works based on the spread spectrum concept. The main problem is how to find “good” codes and how to separate the signal from noise generated by other signals and the environment. CDMA can be used in combination with FDMA/TDMA access schemes to increase the capacity of a cell  GPRS - General Packet Radio Service – Definition & Architecture GPRS refers to General Packet Radio Service. GPRS provides packet mode data transfer service over cellular network system. GPRS uses the existing network resources more efficiently for packet mode application and also provide quality of service. The main aim of GPRS is to allow more efficient and cheaper packet data transfer service for Internet application that particularly requires packet data transfer. GPRS network providers specially support the system by charging on volume and not on connection time as is used in traditional GSM data services. The main goals of GPRS are as below-  Continuous and consistent Internet Packet service This is a cheaper service as compare to circuit switched network service  It has a open architecture  GPRS service innovations are independent from the infrastructure GPRS Architecture GPRS Services The main advantage of GPRS is the ‘always on’ feature of GPRS. There is no need of any connection set up prior to data transfer. But GPRS needs some additional network components including software and hardware components to transfer the data from source to destination. GPRS provides following services to its users  Instant messaging and presence Multimedia messaging service Point-to-Point and Point-to-Multipoint services SMS messaging and broadcasting Advantages of GPRS Mobility GPRS has the capacity to manage a consistent voice transfer and information interchanges while the user is moving. Cost Efficient Communication via GPRS technology is cheaper than the GSM network system. Availability GPRS allows users to get connectivity whenever they need regardless of the distance, and location. Localization GPRS enables users to receive data at their present location. Easy Billing GPRS packet transmission service provides an easier billing system than that provided by the GSM circuit switched system THANK YOU