UNIT-1 Mobile computing (2).pptx for notes

Notes of unit 1

1. UNIT-1 Introduction Mobile Computing is a technology that provides an environment which allow users to transmit data from one device to another device without the use of any physical link or cables . It is a human–computer interaction in which a computer is transported during normal use and allow for transfer of data, which include voice and video transmissions. It facilitates the users to move from one physical location to another during communication.

2. : Mobile communication can be divided in the following four types

3. 1.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 . Example, Desktop Computer. 2.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. Example , Communication Towers, WiFi router 3.Mobile and Wired: In Mobile and Wired configuration, some devices are wired, and some are mobile. They altogether make communication with other devices. Example, Laptops. 4.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. Example, WiFi Dongle.

4. Three major elements of mobile computing are mobile communication, mobile hardware, and mobile software .   Mobile Communication :  It refers to the communication infrastructure set in place, including wireless network infrastructure, protocols, data formats, bandwidths, and portals necessary to ensure seamless connectivity and communication.   Mobile Hardware:   The hardware is the mobile computing devices and supporting devices, with the capabilities required to perform their required operations and connect to networks.   Mobile Software :  The most important software component is the operating system, which is the brain of any computing system. For a laptop, this may be Windows, Linux or macOS , and for a smartphone, it may be Android or iOS .

5. Issues in Mobile Computing Hardware Challenges 1.Limited Battery Life and Power Management: The battery life of a mobile device can be one of the biggest challenges for users . Users often need to charge their devices multiple times per day, which is inconvenient and reduces productivity. Mobile devices use different applications that run in the background, which can drain the battery quickly. 2.Small Form Factor and Limited Processing Power Mobile devices are typically smaller than desktop computers or laptops, which limits their processing power. 3.Compatibility Issues with Different Devices and Operating Systems Compatibility issues between different devices and operating systems is another important hardware challenge in mobile computing.

6. Software Challenges 1.Security Concerns and Data Protection Mobile devices store large amounts of critical personal information such as banking details, passwords, emails, contacts and other sensitive data. This makes them prime targets for hackers who exploit security vulnerabilities in mobile operating systems to gain unauthorized access to this valuable data . 2.Network Connectivity Issues Mobile devices rely on wireless networks for internet connectivity. However, these networks are susceptible to interference from other wireless signals causing connection stability issues. 3.Small Screen Size and Touch Screen Limitations The small screen size of mobile devices can limit the amount of information that can be displayed at any given time. 4.Limited Input Options such as Keyboard or Mouse Mobile devices typically have limited physical input options such as a keyboard or mouse. This can be challenging for applications that require precise input or complex interactions

7. Overview of Wireless Telephony Wireless telephony refers to technology which operates on transmission of information through space; there is no physical or fixed connection between sender and receiver devices . By using wireless telephony people can be transceivers information from driving cars, and walking in garden. Wireless telephony come in two basic varieties: Cordless phones Mobile phones (cell phones). Most modern mobile telephone services use a cellular network architecture, and therefore mobile telephones are also called cellular telephones or cell phones.

8. Cellular Concept Mobile Computing Technology It refers to the use of a group of cells to provide communication from one place to another 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 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.

9. Mobile computing used cellular system and it has the following advantages : 1.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. 2.Less Transmission Power Keeping cell size small facilitate 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. 3.Local Interference . There is only local interference when cells are small and that is easy to handle by the base station and the mobile station. 4.Robustness If any component fails only that specific area affected and the rest of the part remains unaffected and works efficiently.

10. Cellular System or having small cells have the following disadvantages. 1. 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 . 2. Handover Needed The mobile system needs handovers when they change cells. This is quite often which further incur a cost . 3. 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.  

11. GSM (Global System for Mobile Communications) is a set of mobile communications standards and protocols governing second-generation or 2G networks, first developed and deployed in Europe. GSM is a digital cellular communication standard that is universally accepted. The European Telecommunications Standards Institute created the GSM standard to define the procedures for second-generation digital mobile networks that are used by devices such as mobile phones. It is a wide-area communications technology program that utilizes digital radio channeling to bring forth audio, information, and multimedia communication systems.

12. Three subsystem BSS, NSS and OSS are connected with each other via some interfaces. Total three interfaces are there : Air Interface :  Air interface is also known as UM interface. Interface  between MS and BTS is called as UM interface because it is mobile analog to the U interface of ISDN . Abis Interface :  It is a BSS internal interface linking with BTS and BSC . A interface :  It provides communication between BSS and MSC. .

13.   Location Management Location management is a two-stage process : T he first stage is to discover the current attachment point of the mobile user for call delivery T he second one is call delivery . The associated protocol deals with querying and storing information in location databases and sending paging signals to locate the user within the network. Key research areas are the design of database architecture to reduce query traffic, streamlining location update signaling, and terminal paging scheme .

14. Home Location Register (HLR) The HLR is a database used for storage and management of subscriptions. It is considered the most important database, as it stores permanent data about subscribers, including a subscriber's service profile, location information, and activity status. When an individual buys a subscription in the form of SIM, then all the information about this subscription is registered in the HLR of that operator . Mobile Services Switching Center (MSC ) The MSC performs the switching of calls between the mobile and other fixed or mobile network users, as well as the management of mobile services such as registration, authentication, location updating, handovers, and call routing to a roaming subscriber. Visitor Location Register (VLR) The VLR is a database that contains temporary information about subscribers that is needed by the MSC in order to service visiting subscribers .. When a mobile station roams into a new MSC area, the VLR connected to that MSC will request data about the mobile station from the HLR. Later, if the mobile station makes a call, the VLR will have the information needed for call setup without having to interrogate the HLR each time.

15. How are the HLR and VLR used ? Each mobile network has its own HLRs and VLRs. When a MSC detects a mobile user’s presence in the area covered by its network, it first checks a database to determine if the user is in his/her home area or is roaming, i.e., the user is a visitor . o User in Home Area: HLR has the necessary information for initiating, terminating, or receiving a call . o User is Roaming: VLR contacts the user’s HLR to get the necessary information to set up a temporary user profile. The user’s location is recorded in the HLR, and in case the user roaming, it is also recorded in the VLR. Suppose that the user wants to make a call: o User in Home Area: MSC contacts the HLR prior to setting up the call. o User is Roaming: MSC contacts the VLR prior to setting up the call. Suppose that there is a call for the user (call goes to the home MSC): o User in Home Area: Home MSC delivers the call immediately. o User is Roaming: Home MSC contacts the VLR to determine the appropriate switch in the roaming area to handle the arriving call and then transfers the call to the roaming area MSC.

16. Hand-off Process of transferring a mobile telephone call from one cell to another without dropping the call. Cellular users may traverse several cells during a conversation, sometimes requiring a high-speed handoff in a moving vehicle. A soft handoff entails establishing a second radio link with the mobile device before the first link is severed It is the process of transferring an active call or data session from one cell in a cellular network or from one channel to another.

17. Hard Handoff  − In a hard handoff, an actual break in the connection occurs while switching from one cell to another. The radio links from the mobile station to the existing cell is broken before establishing a link with the next cell. It is generally an inter-frequency handoff. It is a “break before make” policy . Soft Handoff  − In soft handoff, at least one of the links is kept when radio links are added and removed to the mobile station. This ensures that during the handoff, no break occurs. This is generally adopted in co-located sites. It is a “make before break” policy.

18. Channel Allocation in Cellular System Channel allocation deals with the allocation of channels to cells in a cellular network. Once the channels are allocated, cells may then allow users within the cell to communicate via the available channels.  Channels in a wireless communication system typically consist of time slots, frequency bands and/or CDMA pseudo noise sequences   There are three major categories for assigning these channels to cells (or base-stations). They are Fixed Channel Allocation ,  Dynamic Channel Allocation Hybrid Channel Allocation (which is a combination of the first two methods). Fixed Channel Allocation (FCA) systems allocate specific channels to specific cells. This allocation is static and can not be changed. For efficient operation, FCA systems typically allocate channels in a manner that maximizes frequency reuse Dynamic Channel Allocation In DCA systems, no set relationship exists between channels and cells. Instead, channels are part of a pool of resources. Whenever a channel is needed by a cell, the channel is allocated

19. Hybrid Channel Allocation Schemes This category of channel allocation methods includes all systems that are hybrids of fixed and dynamic channel allocation systems.  Channel Borrowing is one of the most straightforward hybrid allocation schemes. Here, channels are assigned to cells just as in fixed allocation schemes. If a cell needs a channel in excess of the channels previously assigned to it, that cell may borrow a channel from one of its neighboring cells given that a channel is available and use of this channel won't violate frequency reuse requirements.

20. CDMA - Technology Code Division Multiple Access (CDMA) is a form of multiplexing that facilitates various signals to occupy a single transmission channel. It optimizes the use of available bandwidth. The technology is commonly used in ultra-high-frequency (UHF) cellular telephone systems, bands ranging between the 800-MHz and 1.9-GHz. A CDMA network assigns every user a code that  encodes  and decodes wireless signals sent to and from their device. Multiple users can communicate with the network's transmission towers using the entire width of the frequency spectrum . Each device decodes only the signals that use their personal code, with signals meant for other users appearing as noise that the receiver can safely discard. By not limiting each user's frequency range, CDMA provides more  bandwidth  when compared to the TDMA method used by GSM networks. CDMA also allows more simultaneous users to use the same frequency spectrum without negatively affecting network performance .

21. Advantages of CDMA :  1. CDMA channel is not easily decodable hence it offers increases cellular communication securities 2. Call quality is better with more consistent sound as compared to GSM 3. Less interference due to hand off features reduces call dropping 4 . Gives better coverage and needs few antenna sites and also consumes less power Disadvantages of CDMA : 1. Time synchronization is required 2. It can't offer international roaming, a large GSM advantage 3. The CDMA system performance degrades with an increase in the number of users

22. General Packet Radio Service (GPRS) is the packet and data transfer service on the 2G and 3G wireless networks used for the global communications in the mobile systems . It allows the continuous connections of the Internet to mobile phones and handheld devices. It is based on the GSM services which used existing services such as the SMS and circuit-switched phone networks and connections . Features of GPRS GPRS operates at an extremely slow speed. It downloads the data at the deficient range and even uploads the data at the range lower than the download range. Its features are as follows: • Short messaging service: it is the communication protocol which specially designed for text messaging. So, it is a special-purpose communication protocol. • Multimedia messaging service: It has done an extension to SMS, i.e., now we can transmit videos along with the text also. • Wireless application protocol: it is a special-purpose communication protocol which used for mobile browsers.

23. Advantages of GPRS are as follows : • High-speed : GPRS offers us the speed which is 3 times quicker than the data transfer speed of fixed telecommunication networks. Also, the speed of GPRS is 10 times faster than the GSM services. GPRS gives the speed of 171.2 kbps. • Instant connection and immediate data transfer: GPRS provide us the instant connections. It can send data wherever and whenever the data is required. • Cost-effective solution: The cost of using GPRS is less. That’s why there is an increase in the penetration of data services. The disadvantages of GPRS are as follows: • The data rate supported by GPRS is slower than the data rate of the latest wireless standards like LTE, LTE-advanced, etc., • We cannot troubleshoot the error in case any issue appears in front of us. • The problem of congestion also occurs , which means that if multiple users of GPRS are utilizing the services of GPRS in the same area at the same time, then slower data connection there .