Mobile Computing | Unit 3 & 4
GGSIPU | B.TECH | 8th Semester | Mobile Computing | Unit 3 & 4
Unit 3
a) Discuss Mobile IP. What are modifications in TCP for Mobile environment?
Mobile IP is a protocol that allows mobile devices to maintain connectivity while moving across different networks. It enables seamless mobility by assigning a unique IP address to the mobile device, which remains constant regardless of its location within the network. Mobile IP consists of three main entities: the mobile node (MN), the home agent (HA), and the foreign agent (FA). The MN is the mobile device itself, while the HA and FA are network entities responsible for managing the movement of the MN. The HA acts as the anchor point for the MN and is responsible for maintaining its permanent IP address, known as the home address. Whenever the MN moves to a foreign network, it registers its temporary care-of address with the FA in that network. The FA then forwards packets destined for the MN to its current care-of address. Now, let's discuss the modifications in TCP (Transmission Control Protocol) for the mobile environment: TCP connection maintenance: In a mobile environment, where the MN may change its network attachment frequently, TCP needs to handle connection disruptions gracefully. To achieve this, modifications have been made to TCP's connection setup, teardown, and reestablishment mechanisms. Handover support: Handover refers to the process of transferring the MN's connection from one network to another. TCP in the mobile environment incorporates mechanisms to minimize service disruption during handovers. These mechanisms include fast retransmit and fast recovery algorithms, which help to recover from packet losses quickly. Congestion control: TCP's congestion control algorithms play a crucial role in maintaining network stability and fairness. In the mobile environment, modifications have been made to TCP's congestion control mechanisms to account for the dynamic nature of wireless networks. These modifications aim to prevent network congestion while ensuring efficient resource utilization. Buffer management: Mobile devices often experience variations in network conditions, such as fluctuating bandwidth and increased latency. To address these challenges, TCP for the mobile environment employs adaptive buffer management techniques. These techniques adjust the size of TCP's congestion window and receive window dynamically, optimizing the overall performance in varying network conditions. Error recovery: The mobile environment introduces additional possibilities of packet loss, such as handover-induced losses or link instabilities. TCP in the mobile environment incorporates error recovery mechanisms, such as selective acknowledgment (SACK) and forward error correction (FEC), to enhance reliability and recover from packet losses effectively.
b) Explain ZigBee protocol for communication.
ZigBee is a wireless communication protocol designed for low-power, low-data-rate applications. It operates on the IEEE 802.15.4 standard and is widely used in applications such as home automation, industrial control, and wireless sensor networks. The ZigBee protocol defines the network, security, and application layers, providing a framework for reliable and energy-efficient communication. At the network layer, ZigBee uses a mesh networking topology, where devices communicate with each other through intermediate devices, called routers or coordinators. This allows for greater network coverage and robustness, as messages can be routed dynamically. The security layer in ZigBee provides mechanisms for secure communication. It includes encryption, authentication, and access control features to protect against unauthorized access and ensure data integrity. The application layer in ZigBee allows for the development of specific profiles tailored to different application domains. These profiles define the functionality and behavior of devices, enabling interoperability between different manufacturers.
Read More : https://www.geeksforgeeks.org/introduction-of-zigbee/
c) What are Advantages and Disadvantages of IrDA.
Read More : https://www.geeksforgeeks.org/irda-infrared-data-association/
d) What is importance of frequency reuse scheme explain with Diagram.
Frequency reuse is a technique used in cellular communication systems to maximize the efficient use of available radio spectrum. It involves dividing the available frequency spectrum into smaller cells and reusing the same frequencies in different cells that are sufficiently far apart to avoid interference. This concept can be explained using a diagram:
In the diagram, we can see a cellular network divided into hexagonal cells. Each cell represents a geographical area served by a base station. The frequency reuse pattern is depicted by the different colors assigned to the cells. The importance of frequency reuse can be understood through the following points:
Efficient spectrum utilization: By reusing the same frequencies in different cells, the available spectrum can be utilized efficiently, allowing more users to be accommodated within a given frequency band.
Increased capacity: Frequency reuse enables the cellular network to support a larger number of simultaneous connections, improving the overall capacity of the system.
Reduced interference: By carefully planning the frequency allocation in each cell, interference between neighboring cells can be minimized. This results in improved signal quality and better overall performance of the network.
Enhanced coverage: Frequency reuse allows for the expansion of cellular coverage areas. As cells are added to the network, they can reuse frequencies from existing cells, extending the reach of the network.
e) What is encapsulation? Explain in detail the various encapsulation techniques in mobile IP.
Encapsulation refers to the process of enclosing data packets within additional headers or wrappers for transmission over a network. In the context of Mobile IP, encapsulation techniques are used to encapsulate IP packets with specific headers to enable seamless routing of packets across different networks. There are two main encapsulation techniques used in Mobile IP: Foreign Agent (FA) Encapsulation: In this technique, when a mobile node (MN) moves to a foreign network, it registers with a foreign agent. The foreign agent encapsulates the IP packets destined for the MN with a foreign agent header. The encapsulated packets are then tunneled to the MN's care-of address (CoA) in the foreign network. The MN decapsulates the packets to retrieve the original IP packets. Co-located CoA Encapsulation: In this technique, the MN obtains a CoA in the foreign network and establishes a direct tunnel with its home agent (HA). The HA encapsulates the IP packets with a home agent header and tunnels them to the MN's CoA. The MN decapsulates the packets to retrieve the original IP packets. This technique eliminates the need for foreign agent involvement.
f) Explain DSR Routing Protocol in detail. Dynamic Source Routing (DSR) is a routing protocol used in mobile ad hoc networks (MANETs). It is a reactive or on-demand routing protocol, which means that it establishes routes only when needed. Here is an explanation of DSR routing protocol: Route Discovery: When a source node wants to send a packet to a destination node for which it does not have a route, it initiates a route discovery process. The source node floods a route request (RREQ) packet throughout the network. Each intermediate node appends its own address to the RREQ packet before forwarding it. The destination node or an intermediate node with a route to the destination responds with a route reply (RREP) packet. Route Maintenance: Once a route is established, the source node includes the route in the packet header. Intermediate nodes use this route information to forward packets. If a link in the established route breaks, the affected nodes use a route error (RERR) packet to inform the source node about the link failure. The source node then initiates a new route discovery process to find an alternative route. Source Routing: DSR utilizes source routing, where the complete route is included in the packet header. Each node along the route processes the packet header and forwards it accordingly. This eliminates the need for maintaining routing tables at intermediate nodes.
g) What is snooping TCP approach in mobile wireless networks? Discuss its advantages.
Snooping TCP is an approach used in mobile wireless networks to enhance the performance of TCP (Transmission Control Protocol) over wireless links. In snooping TCP, an intermediate node, called a snooper, actively monitors the TCP traffic between a mobile node and a correspondent node. It intercepts and modifies the TCP packets to improve efficiency and reduce latency.
Some advantages of snooping TCP are: Congestion Control: Snooping TCP can actively monitor the network conditions and detect congestion. It can modify the TCP congestion window and adjust the sending rate of the mobile node to alleviate congestion and prevent network congestion collapse. Latency Reduction: By intercepting and modifying TCP packets, snooping TCP can reduce the round-trip time (RTT) and overall latency experienced by the mobile node. It achieves this by optimizing the TCP acknowledgment process and reducing unnecessary retransmissions. Buffer Management: Snooping TCP can manage and allocate buffer resources more efficiently. It can prioritize and discard TCP packets based on network conditions and buffer availability, ensuring a fair allocation of resources and reducing packet loss. Error Recovery: In the case of packet loss or errors, snooping TCP can actively recover and retransmit lost packets without relying solely on the mobile node or the correspondent node. This improves the reliability and overall performance of TCP over wireless links.
h) Discuss and detail the differences in topology reorganization in DSDV and DSR routing protocols.
DSDV (Destination-Sequenced Distance Vector) and DSR (Dynamic Source Routing) are two routing protocols used in wireless ad hoc networks. They differ in their approach to topology reorganization: DSDV: DSDV is a proactive routing protocol that maintains a consistent routing table at each node. It relies on periodic updates to exchange routing information between nodes. When a topology change occurs, such as a node failure or link breakage, the affected nodes update their routing tables accordingly. DSDV uses sequence numbers to ensure the freshness of routing information and avoid routing loops. It is based on the distance-vector algorithm and provides loop-free and loop-free paths. DSR: DSR is a reactive or on-demand routing protocol that establishes routes only when needed. It does not maintain a routing table at each node. Instead, it uses source routing, where the complete route is included in the packet header. When a node wants to send a packet, it initiates a route discovery process. Intermediate nodes respond with route replies containing the route information. If a link in the established route breaks, DSR uses route error packets to inform the source node, which initiates a new route discovery process to find an alternative route. In terms of topology reorganization, DSDV requires frequent updates to adapt to changes, even in relatively stable network conditions. DSR, on the other hand, is more efficient in adapting to topology changes as it establishes routes on-demand. DSR avoids maintaining unnecessary routing tables and reduces overhead. However, DSR incurs additional overhead due to route discovery and route maintenance processes, especially in highly dynamic network scenarios.
Unit 4
a) Describe Dynamic Host Configuration Protocol for Wireless Communication.
Dynamic Host Configuration Protocol (DHCP) is a network protocol used to automatically assign IP addresses and network configuration settings to devices on a network. It plays a crucial role in wireless communication by simplifying the process of network configuration and management. Here is a description of DHCP: DHCP works in a client-server architecture. The DHCP server is responsible for managing a pool of available IP addresses and configuration parameters. When a wireless device, acting as a DHCP client, connects to the network, it sends a DHCP discovery message to locate a DHCP server. The DHCP server responds with a DHCP offer message, providing an available IP address and other configuration parameters, such as subnet mask, default gateway, and DNS server addresses. The client can accept the offer by sending a DHCP request message. Upon receiving the request, the DHCP server confirms the allocation of the IP address and sends a DHCP acknowledgment message to the client. The client then configures its network settings accordingly and becomes an active participant on the network.
Read More : https://www.geeksforgeeks.org/dynamic-host-configuration-protocol-dhcp/
b) Explain Advantages and Disadvantages of Indirect TCP and Snooping TCP.
Advantages and Disadvantages of Indirect TCP and Snooping TCP: Indirect TCP and Snooping TCP are variations of TCP (Transmission Control Protocol) used in certain network architectures. Here are their advantages and disadvantages: Indirect TCP:
Advantages: Improved security: Indirect TCP provides a level of security by preventing direct communication between external networks and internal hosts. It acts as an intermediary, protecting internal network resources. Network address translation: Indirect TCP allows for network address translation, enabling the use of private IP addresses internally while communicating with external networks using public IP addresses. Disadvantages: Increased latency: The indirect nature of communication in Indirect TCP introduces additional hops and potential bottlenecks, leading to increased latency in data transmission. Complexity: Implementing and managing Indirect TCP requires additional configuration and infrastructure, increasing the complexity of the network architecture.
Snooping TCP:
Advantages: Improved performance: Snooping TCP optimizes network performance by actively monitoring network traffic and caching frequently accessed data. This reduces the need for repeated data transfers and improves response times. Bandwidth conservation: By caching and reusing data, Snooping TCP helps conserve network bandwidth, especially in scenarios where data patterns are repetitive. Disadvantages: Data staleness: Snooping TCP relies on caching mechanisms, which can lead to data staleness if the cached data is not updated in a timely manner. This can result in outdated information being served to clients. Limited applicability: Snooping TCP is most effective in scenarios with a high degree of data redundancy. In cases where data patterns are dynamic or unique, the benefits of Snooping TCP may be limited.
c) Explain Quality of Service in 3G.
Quality of Service (QoS) in 3G refers to the set of parameters and mechanisms that ensure the desired level of performance and service delivery for mobile communications. It encompasses various aspects such as data transmission rates, reliability, latency, priority handling, and resource allocation. Here is an explanation of Quality of Service in 3G: Data Transmission Rates: 3G networks aim to provide high-speed data transmission rates to support multimedia services. QoS mechanisms ensure that users can experience consistent and reliable data rates based on their subscribed plans and network conditions. Reliability: QoS in 3G ensures reliable data transmission by minimizing packet loss, errors, and disruptions in the network. Techniques like error correction, retransmission, and congestion control algorithms are employed to maintain a high level of reliability. Latency: Latency refers to the delay experienced in transmitting data packets across the network. 3G networks strive to keep latency low to enable real-time applications such as video streaming, online gaming, and voice calls. QoS mechanisms prioritize low-latency traffic and employ techniques like traffic shaping and prioritization to reduce delays. Priority Handling: Different types of data require varying levels of priority. QoS in 3G allows for the differentiation of traffic based on priority levels, ensuring that critical applications receive preferential treatment over less time-sensitive traffic. This prioritization ensures a consistent user experience for applications like voice calls and video conferencing. Resource Allocation: QoS mechanisms in 3G dynamically allocate network resources based on demand and application requirements. This allocation optimizes resource utilization and ensures fair distribution among users. Techniques like admission control, bandwidth reservation, and traffic scheduling are used to efficiently allocate resources. Service Differentiation: QoS in 3G enables service providers to offer different service classes with varying levels of performance guarantees. Users can choose service plans based on their specific requirements, such as high-speed data, low latency for gaming, or reliable voice calls.
d) Compare Pure ALOHA and Slotted ALOHA. Use suitable diagram to explain the difference.
Aloha is a type of Random access protocol it was developed at the University of Hawaii in early 1970, it is a LAN-based protocol this type there are more chances of occurrence of collisions during the transmission of data from any source to the destination, Aloha has two types one Pure Aloha and another Slotted Aloha.
Pure ALOHA and Slotted ALOHA are protocols used for random access in shared communication channels. Here is a comparison of these two protocols: Pure ALOHA:
- In Pure ALOHA, data frames can be transmitted at any time without synchronization.
- Collisions between frames are possible and lead to retransmissions.
- The time to retry transmission after a collision is random, which can result in inefficient channel utilization.
- The throughput of Pure ALOHA is around 18% of the channel capacity.
Slotted ALOHA:
- In Slotted ALOHA, the time is divided into discrete slots, and frames can only be transmitted at the beginning of each slot.
- Collisions can still occur if multiple frames are transmitted in the same slot, but the probability is reduced compared to Pure ALOHA.
- The time to retry transmission after a collision is synchronized with the slots, resulting in better channel utilization.
- The throughput of Slotted ALOHA is around 36% of the channel capacity, which is double that of Pure ALOHA
| Pure Aloha | Slotted Aloha |
|---|---|
| In this Aloha, any station can transmit the data at any time. | In this, any station can transmit the data at the beginning of any time slot. |
| In this, The time is continuous and not globally synchronized. | In this, The time is discrete and globally synchronized. |
| Vulnerable time for Pure Aloha = 2 x Tt | Vulnerable time for Slotted Aloha = Tt |
In Pure Aloha, the Probability of successful transmission of the data packet = G x e-2G | In Slotted Aloha, the Probability of successful transmission of the data packet = G x e-G |
In Pure Aloha, Maximum efficiency = 18.4% | In Slotted Aloha, Maximum efficiency = 36.8% |
| Pure Aloha doesn’t reduce the number of collisions to half. | Slotted Aloha reduces the number of collisions to half and doubles the efficiency of Pure Aloha. |
e) Explain the concept of wireless markup language.
Wireless Markup Language (WML) is a markup language specifically designed for mobile devices and wireless networks. It is based on the Extensible Markup Language (XML) and is used to create content for mobile applications and mobile websites. WML allows the presentation of information in a format suitable for the limited display capabilities and bandwidth constraints of mobile devices. The concept of WML revolves around creating structured and lightweight pages that can be easily rendered on mobile devices. Some key aspects of WML include: Tag-based Structure: WML uses tags, similar to HTML, to define the structure and content of mobile pages. It includes tags for headers, text, links, images, input forms, and other elements commonly used in mobile applications. Card Deck Model: WML uses a card deck model where each card represents a separate screen or page in a mobile application. Users navigate through different cards using links or buttons. Simplified Syntax: WML uses a simplified syntax compared to HTML, reducing the overhead and complexity of rendering pages on mobile devices. It focuses on essential elements and avoids unnecessary features that may be irrelevant or impractical for mobile browsing. Device Independence: WML is designed to be device-independent, allowing content to be rendered on various mobile devices with different screen sizes, input methods, and capabilities. It enables developers to create content once and have it adapt to different mobile devices.
f) Discuss the special features that an operating system for mobile device needs to support compared to the traditional operating system.
Operating systems for mobile devices need to support several special features compared to traditional operating systems due to the unique characteristics of mobile environments. Some of these features include: Power Management: Mobile devices operate on limited battery power, so the operating system needs to implement efficient power management techniques. It includes features like CPU throttling, dynamic voltage scaling, and device sleep modes to optimize power consumption and extend battery life. Memory Management: Mobile devices typically have limited memory compared to desktop computers. The operating system needs to employ effective memory management techniques, such as process prioritization, memory compression, and efficient storage allocation, to ensure optimal usage of available memory resources. Resource Constraints: Mobile devices have limited processing capabilities, storage capacity, and network bandwidth. The operating system should handle these resource constraints efficiently, optimizing performance and ensuring smooth operation of applications while managing resource allocation effectively. Connectivity and Networking: Mobile devices heavily rely on wireless connectivity for communication. The operating system needs to support wireless protocols, such as Wi-Fi, Bluetooth, and cellular networks, providing seamless connectivity and managing network connections effectively. Security and Privacy: Mobile devices store and handle sensitive personal information, making security and privacy critical. The operating system must incorporate robust security measures, including secure authentication, data encryption, secure sandboxing of applications, and protection against malware and unauthorized access. User Interface: Mobile devices have unique input methods and small touchscreens. The operating system should support touch gestures, virtual keyboards, and other mobile-specific input mechanisms. It should provide a user-friendly interface that is optimized for small screens, allowing smooth navigation and interaction with applications. Application Ecosystem: Mobile operating systems need to provide a platform for developers to create and distribute applications easily. This includes app stores, software development kits (SDKs), and frameworks that enable developers to build mobile applications and ensure compatibility across different devices.
g) Compare the features provided by the following operating system: Android, Symbain and Windows phone.
Android: Open-source: Android is an open-source operating system, allowing customization and modifications by device manufacturers and developers.
Wide Device Support: Android is available on a wide range of devices from various manufacturers, providing options for different price ranges and hardware capabilities.
App Ecosystem: Android has a vast app ecosystem through the Google Play Store, offering a wide range of applications and services.
Customizability: Android offers extensive customization options for users, allowing them to personalize their device's look and feel, widgets, launchers, and more.
Integration with Google Services: Android tightly integrates with Google services like Google Maps, Gmail, Google Drive, and Google Assistant.
Multitasking: Android supports multitasking, allowing users to run multiple apps simultaneously and switch between them easily.
Symbian: Legacy System: Symbian was one of the earliest mobile operating systems and was popular in older Nokia devices.
Efficiency: Symbian was known for its efficient resource usage, enabling smooth performance on devices with limited hardware capabilities.
Native Support for Java: Symbian had native support for Java applications, making it easy for developers to create apps using Java.
Customizable User Interface: Symbian provided options for users to customize their device's user interface, including themes and layouts.
Integration with Nokia Services: Symbian devices offered integration with Nokia services like Ovi Store, Nokia Maps, and Nokia Music.
Windows Phone: Modern User Interface: Windows Phone introduced a unique and visually appealing "Metro" user interface with live tiles.
Integration with Microsoft Services: Windows Phone tightly integrated with Microsoft services like Office, Outlook, OneDrive, and Xbox.
Fluid Performance: Windows Phone was optimized for smooth performance and offered consistent user experience across devices.
Limited App Ecosystem: Windows Phone had a smaller app ecosystem compared to Android and iOS, with fewer app choices.
Enterprise-Friendly: Windows Phone emphasized enterprise features, including integration with Microsoft Exchange, ActiveSync, and security features like device encryption.
Integration with Windows PCs: Windows Phone offered integration with Windows PCs, allowing seamless sharing and synchronization of data.
h) Write short note on Data Synchronization
Data synchronization refers to the process of maintaining consistency and coherence of data across multiple devices or platforms. It ensures that the same data is available and up-to-date on different devices or systems. Here are some key points about data synchronization: Purpose: The main purpose of data synchronization is to ensure that data remains consistent and accurate across multiple devices or platforms, allowing users to access the same information regardless of the device they are using. Types of Data: Data synchronization can involve various types of data, including files, documents, emails, contacts, calendars, tasks, and other forms of digital information. Methods: Data synchronization can be achieved through different methods, depending on the devices or platforms involved. Common synchronization methods include manual synchronization, scheduled synchronization, and real-time synchronization. Synchronization Protocols: Synchronization protocols define the rules and procedures for transferring and updating data between devices or platforms. Examples of synchronization protocols include SyncML, CalDAV, CardDAV, and Microsoft ActiveSync. Conflict Resolution: In cases where conflicting changes occur on different devices, conflict resolution mechanisms are used to determine the most appropriate version of the data. Conflict resolution can be automated or require user intervention, depending on the synchronization implementation. Benefits: Data synchronization provides several benefits, including seamless access to up-to-date information across devices, improved productivity, data backup and recovery, and the ability to work offline and synchronize changes later. Examples: Data synchronization is commonly used in various scenarios, such as syncing email across multiple devices, keeping calendars and contacts in sync, sharing files across devices.
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