The document discusses the key elements and characteristics of wireless networks. It describes the different components of a wireless network including wireless hosts, base stations, wireless links, and the infrastructure and ad hoc modes. It then covers characteristics of wireless links such as decreased signal strength, interference, and multipath propagation that make wireless communication more difficult than wired networks. It also discusses wireless network issues like the hidden terminal problem and signal attenuation.
The document discusses slides that are being made freely available for use in teaching networking concepts. It states that the slides can be modified as needed but requests that their source is credited if used for teaching and their copyright is noted if posted online. The slides are from the textbook "Computer Networking: A Top Down Approach" by Jim Kurose and Keith Ross.
This document discusses the network layer and IP protocol. It begins by explaining the key functions of the network layer, including forwarding, routing, and connection setup in some network architectures. It then explains the differences between virtual circuit and datagram networks, as well as the forwarding and routing processes. The document outlines the chapter and describes the IP datagram format and functions of the IP, ICMP, and routing protocols. It also provides details about router architecture and functions.
This document describes slides for a chapter on the transport layer. It states that the slides can be freely used and modified for educational purposes with proper attribution. It asks users to mention the source if the slides are used for a class and to note any adaptation if slides are posted online. The document also provides copyright information for the material.
This document discusses the link layer and provides an overview of its services and context. It describes how the link layer is implemented in network interface cards and how these cards encapsulate datagrams into frames. It also outlines the topics to be covered, including error detection and correction, multiple access protocols, local area networks, and link virtualization.
This document provides an overview and outline of topics to be covered in a chapter about the link layer and local area networks (LANs). It discusses the goals of understanding link layer services like error detection and correction as well as sharing bandwidth on a broadcast channel. It also outlines the key sections to be covered, including multiple access protocols, LAN addressing, Ethernet, switches, and virtual LANs. Sample slides are provided on topics like link layer services, error detection techniques, and multiple access protocols. The document is intended for educational use and asks that the source be cited if used for teaching.
The document discusses the key aspects of Chapter 7 in a computer networking textbook. It provides an outline of the chapter topics, which cover wireless links and characteristics such as CDMA, IEEE 802.11 wireless LANs, cellular networks and standards, and principles of mobility including Mobile IP and handling mobility in cellular networks. It also includes slides on specific elements and functioning of wireless networks, 802.11 protocols, and capabilities such as rate adaptation.
SOLUTION MANUAL OF COMMUNICATION NETWORKS BY ALBERTO LEON GARCIA & INDRA WIDJAJAvtunotesbysree
The document provides solutions to chapter 1 problems from the textbook "Communication Networks" by Alberto Leon Garcia and Indra Widjaja.
The solutions describe the procedures involved in mailing a letter and sending an email. They are both connectionless services. Procedures for making a telephone call and providing personal communication services are also described. Setting up telephone calls is connection-oriented. Requirements for interactive online games over connection-oriented and connectionless networks are discussed. Networks must support real-time delivery of commands and responses for interactive games and applications.
The document discusses slides that are being made freely available for use in teaching networking concepts. It states that the slides can be modified as needed but requests that their source is credited if used for teaching and their copyright is noted if posted online. The slides are from the textbook "Computer Networking: A Top Down Approach" by Jim Kurose and Keith Ross.
This document discusses the network layer and IP protocol. It begins by explaining the key functions of the network layer, including forwarding, routing, and connection setup in some network architectures. It then explains the differences between virtual circuit and datagram networks, as well as the forwarding and routing processes. The document outlines the chapter and describes the IP datagram format and functions of the IP, ICMP, and routing protocols. It also provides details about router architecture and functions.
This document describes slides for a chapter on the transport layer. It states that the slides can be freely used and modified for educational purposes with proper attribution. It asks users to mention the source if the slides are used for a class and to note any adaptation if slides are posted online. The document also provides copyright information for the material.
This document discusses the link layer and provides an overview of its services and context. It describes how the link layer is implemented in network interface cards and how these cards encapsulate datagrams into frames. It also outlines the topics to be covered, including error detection and correction, multiple access protocols, local area networks, and link virtualization.
This document provides an overview and outline of topics to be covered in a chapter about the link layer and local area networks (LANs). It discusses the goals of understanding link layer services like error detection and correction as well as sharing bandwidth on a broadcast channel. It also outlines the key sections to be covered, including multiple access protocols, LAN addressing, Ethernet, switches, and virtual LANs. Sample slides are provided on topics like link layer services, error detection techniques, and multiple access protocols. The document is intended for educational use and asks that the source be cited if used for teaching.
The document discusses the key aspects of Chapter 7 in a computer networking textbook. It provides an outline of the chapter topics, which cover wireless links and characteristics such as CDMA, IEEE 802.11 wireless LANs, cellular networks and standards, and principles of mobility including Mobile IP and handling mobility in cellular networks. It also includes slides on specific elements and functioning of wireless networks, 802.11 protocols, and capabilities such as rate adaptation.
SOLUTION MANUAL OF COMMUNICATION NETWORKS BY ALBERTO LEON GARCIA & INDRA WIDJAJAvtunotesbysree
The document provides solutions to chapter 1 problems from the textbook "Communication Networks" by Alberto Leon Garcia and Indra Widjaja.
The solutions describe the procedures involved in mailing a letter and sending an email. They are both connectionless services. Procedures for making a telephone call and providing personal communication services are also described. Setting up telephone calls is connection-oriented. Requirements for interactive online games over connection-oriented and connectionless networks are discussed. Networks must support real-time delivery of commands and responses for interactive games and applications.
With statistical multiplexing, the total bandwidth available can be utilized more fully since the links are not idle when only one host is transmitting. The statistical multiplexing allows aggregation of variable bit rate traffic streams.
The document discusses network models including the OSI model and TCP/IP protocol suite. The OSI model has 7 layers - physical, data link, network, transport, session, presentation, and application layers. Each layer has a specific function in communication. Similarly, the TCP/IP protocol suite has 5 layers that correspond to the OSI layers - physical, data link, network, transport, and application. The document also discusses different types of addresses used in networking including physical, logical, port, and specific addresses.
This document discusses protocols for real-time multimedia applications such as voice over IP. It introduces the Real-Time Protocol (RTP) which specifies packet structures for carrying audio and video data. RTP runs on top of UDP, providing functions like payload type identification, sequence numbering, and time stamping. It allows for interoperability between multimedia applications that both implement RTP. The document also discusses the Session Initiation Protocol (SIP) which is used to initialize multimedia sessions and exchange session description and control messages.
Networking interview questions and answersAmit Tiwari
CSMA/CD describes the Ethernet access method where many stations can transmit on the same cable without priority. MAC addresses provide unique identification for devices on a LAN. The three types of LAN traffic are unicast, broadcast, and multicast frames. Unicast frames are intended for a single host, broadcast frames for everyone, and multicast frames for a group. Spanning Tree Protocol (STP) dynamically maintains a loop-free network topology by putting redundant links in a blocking state.
This document provides an introduction to data communications and computer networks. It discusses key topics such as data communication components like data representation and data flow. It also defines networks and describes different network topologies including point-to-point, star, bus, ring and hybrid configurations. The document then provides an overview of the Internet, including its history and role of Internet Service Providers. It concludes with definitions of protocols and standards, which are sets of agreed upon rules, and discusses standards organizations and their role in establishing Internet standards.
Ccn(Data communication and networking) edited solution-manual suitable to be ...Vishal kakade
This document provides solutions to review questions and exercises related to network models and data link control. It begins with solutions to review questions on network models, including definitions of the OSI and Internet models. It then provides solutions to exercises on typical network examples like telephone and cable networks. Finally, it discusses data link control protocols like Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective-Repeat ARQ, and provides solutions to related exercises.
The document describes a set of PowerPoint slides for a networking textbook. It provides instructions for using and modifying the slides, with the only requests being to mention the source and copyright if used for teaching or posted online.
This chapter discusses different techniques for interconnecting networks, including switching, bridging, and routing. It covers store-and-forward switching using switches to connect networks. There are two main approaches for switching - connectionless switching using datagrams and connection-oriented switching using virtual circuits. Connectionless switching forwards each packet independently based on the destination address, while connection-oriented switching establishes paths through the network before transmitting data packets.
This document discusses computer networks and their classification. It defines the goals of computer networks as resource sharing without regard to physical location. It classifies networks into personal, local, metropolitan and wide area networks. The document then discusses how computer networks enable communication and collaboration between employees through technologies like email, video conferencing, desktop sharing and e-commerce. It explains how networks allow businesses to place electronic orders and enhance efficiency.
This document contains questions related to computer networks. It covers topics like network classification and goals, point-to-point subnet topologies, layered network architecture principles, early networks like ARPANET and NSFNET, the OSI model layers and protocols, connection-oriented vs connectionless networks, data link layer services and operation, dynamic channel allocation protocols, error control using Hamming codes, Ethernet frame format, ADSL components and operation, Bluetooth technology and architecture, cable characteristics and types, optical fiber systems and transmission, Ethernet cabling and topologies, modulation techniques, DNS name resolution, email systems, the web architecture, flow control types, sliding window protocols, and CRC error detection.
This document provides an overview of Ethernet and wireless computer networks. It discusses Ethernet standards and protocols including CSMA/CD, frame formats, addressing, and the transmitter algorithm. It also covers wireless networking technologies such as Bluetooth, Wi-Fi (IEEE 802.11), and WiMAX (IEEE 802.16). Key aspects summarized include the use of carrier sensing and collision detection in Ethernet, exponential backoff for retransmission after collisions, and the use of frequency hopping and direct sequence spread spectrum in wireless networks.
This chapter discusses end-to-end transport protocols like UDP and TCP. UDP provides a simple demultiplexing service but does not guarantee delivery. TCP provides a reliable byte-stream service using a sliding window algorithm to ensure reliable, in-order delivery along with flow and congestion control. It establishes connections using a three-way handshake and terminates them gracefully. The chapter covers TCP and UDP headers, connection management, sliding window mechanics, and differences between flow and congestion control.
Data Link Layer, Error correction and detection like LRC, VRC, CRC, checksum and Hamming coding, Data link protocols, stop and wait ARQ, sliding window ARQ, Petrinet models, HDLC, etc
The document provides an overview of networking basics, including:
- The OSI 7-layer model for network communication and the TCP/IP 4-layer Internet model.
- Standardization is needed to allow different network components to communicate through common protocols.
- Real-world networks are more complex than models, using combinations of topologies, media, and hardware like switches, routers, and gateways.
- Key concepts include IP addressing, subnets to extend address space, and the Domain Name System to map names to numbers.
- Configuring a host requires settings like the IP address, subnet mask, default gateway, and DNS servers.
This document provides a course syllabus for the subject "Communication Networks". It includes:
1) An outline of 5 units that will be covered in the course, including fundamentals of data communications, media access and internetworking, routing, transport layer protocols, and application layer.
2) Course objectives to understand network layering and functionality and analyze network solutions.
3) 4 course outcomes related to identifying network components, choosing layer functionality, and tracing information flow.
4) A mapping of course outcomes to 12 program outcomes and 3 program specific outcomes.
Networking Concepts Lesson 06 - Protocols - Eric VanderburgEric Vanderburg
This document summarizes networking concepts related to protocols. It discusses how protocols enable communication by sending data in small packets with headers containing source/destination, sequence numbers, and payload data. Packet types include unicast, broadcast, and multicast. Common protocol suites are described like TCP/IP, IPX/SPX, and AppleTalk. Specific protocols are also outlined at each layer of the OSI model including transport protocols like TCP and network protocols like IPv4. Concepts such as subnetting, supernetting, NAT, DHCP, and IPv6 addresses are also summarized.
Mobile IP allows users to move between networks while maintaining the same IP address. It uses home and foreign agents and care-of addresses. A mobile node can register its care-of address with its home agent to receive packets when away from home. There are three main processes: agent discovery to find foreign agents, registration of the mobile node's care-of address with its home agent, and data transfer either via indirect routing through home and foreign agents or direct routing from correspondent nodes to the mobile node. Mobile IP supports host mobility across networks in a transparent manner without changing IP addresses.
The document discusses network management and the Internet standard framework. It describes the key components of the framework, including the Structure of Management Information (SMI) which defines management objects, the Management Information Base (MIB) which stores the managed objects, and the Simple Network Management Protocol (SNMP) used to communicate between managing and managed devices. The framework also includes security and administration capabilities added in SNMPv3.
With statistical multiplexing, the total bandwidth available can be utilized more fully since the links are not idle when only one host is transmitting. The statistical multiplexing allows aggregation of variable bit rate traffic streams.
The document discusses network models including the OSI model and TCP/IP protocol suite. The OSI model has 7 layers - physical, data link, network, transport, session, presentation, and application layers. Each layer has a specific function in communication. Similarly, the TCP/IP protocol suite has 5 layers that correspond to the OSI layers - physical, data link, network, transport, and application. The document also discusses different types of addresses used in networking including physical, logical, port, and specific addresses.
This document discusses protocols for real-time multimedia applications such as voice over IP. It introduces the Real-Time Protocol (RTP) which specifies packet structures for carrying audio and video data. RTP runs on top of UDP, providing functions like payload type identification, sequence numbering, and time stamping. It allows for interoperability between multimedia applications that both implement RTP. The document also discusses the Session Initiation Protocol (SIP) which is used to initialize multimedia sessions and exchange session description and control messages.
Networking interview questions and answersAmit Tiwari
CSMA/CD describes the Ethernet access method where many stations can transmit on the same cable without priority. MAC addresses provide unique identification for devices on a LAN. The three types of LAN traffic are unicast, broadcast, and multicast frames. Unicast frames are intended for a single host, broadcast frames for everyone, and multicast frames for a group. Spanning Tree Protocol (STP) dynamically maintains a loop-free network topology by putting redundant links in a blocking state.
This document provides an introduction to data communications and computer networks. It discusses key topics such as data communication components like data representation and data flow. It also defines networks and describes different network topologies including point-to-point, star, bus, ring and hybrid configurations. The document then provides an overview of the Internet, including its history and role of Internet Service Providers. It concludes with definitions of protocols and standards, which are sets of agreed upon rules, and discusses standards organizations and their role in establishing Internet standards.
Ccn(Data communication and networking) edited solution-manual suitable to be ...Vishal kakade
This document provides solutions to review questions and exercises related to network models and data link control. It begins with solutions to review questions on network models, including definitions of the OSI and Internet models. It then provides solutions to exercises on typical network examples like telephone and cable networks. Finally, it discusses data link control protocols like Stop-and-Wait ARQ, Go-Back-N ARQ, and Selective-Repeat ARQ, and provides solutions to related exercises.
The document describes a set of PowerPoint slides for a networking textbook. It provides instructions for using and modifying the slides, with the only requests being to mention the source and copyright if used for teaching or posted online.
This chapter discusses different techniques for interconnecting networks, including switching, bridging, and routing. It covers store-and-forward switching using switches to connect networks. There are two main approaches for switching - connectionless switching using datagrams and connection-oriented switching using virtual circuits. Connectionless switching forwards each packet independently based on the destination address, while connection-oriented switching establishes paths through the network before transmitting data packets.
This document discusses computer networks and their classification. It defines the goals of computer networks as resource sharing without regard to physical location. It classifies networks into personal, local, metropolitan and wide area networks. The document then discusses how computer networks enable communication and collaboration between employees through technologies like email, video conferencing, desktop sharing and e-commerce. It explains how networks allow businesses to place electronic orders and enhance efficiency.
This document contains questions related to computer networks. It covers topics like network classification and goals, point-to-point subnet topologies, layered network architecture principles, early networks like ARPANET and NSFNET, the OSI model layers and protocols, connection-oriented vs connectionless networks, data link layer services and operation, dynamic channel allocation protocols, error control using Hamming codes, Ethernet frame format, ADSL components and operation, Bluetooth technology and architecture, cable characteristics and types, optical fiber systems and transmission, Ethernet cabling and topologies, modulation techniques, DNS name resolution, email systems, the web architecture, flow control types, sliding window protocols, and CRC error detection.
This document provides an overview of Ethernet and wireless computer networks. It discusses Ethernet standards and protocols including CSMA/CD, frame formats, addressing, and the transmitter algorithm. It also covers wireless networking technologies such as Bluetooth, Wi-Fi (IEEE 802.11), and WiMAX (IEEE 802.16). Key aspects summarized include the use of carrier sensing and collision detection in Ethernet, exponential backoff for retransmission after collisions, and the use of frequency hopping and direct sequence spread spectrum in wireless networks.
This chapter discusses end-to-end transport protocols like UDP and TCP. UDP provides a simple demultiplexing service but does not guarantee delivery. TCP provides a reliable byte-stream service using a sliding window algorithm to ensure reliable, in-order delivery along with flow and congestion control. It establishes connections using a three-way handshake and terminates them gracefully. The chapter covers TCP and UDP headers, connection management, sliding window mechanics, and differences between flow and congestion control.
Data Link Layer, Error correction and detection like LRC, VRC, CRC, checksum and Hamming coding, Data link protocols, stop and wait ARQ, sliding window ARQ, Petrinet models, HDLC, etc
The document provides an overview of networking basics, including:
- The OSI 7-layer model for network communication and the TCP/IP 4-layer Internet model.
- Standardization is needed to allow different network components to communicate through common protocols.
- Real-world networks are more complex than models, using combinations of topologies, media, and hardware like switches, routers, and gateways.
- Key concepts include IP addressing, subnets to extend address space, and the Domain Name System to map names to numbers.
- Configuring a host requires settings like the IP address, subnet mask, default gateway, and DNS servers.
This document provides a course syllabus for the subject "Communication Networks". It includes:
1) An outline of 5 units that will be covered in the course, including fundamentals of data communications, media access and internetworking, routing, transport layer protocols, and application layer.
2) Course objectives to understand network layering and functionality and analyze network solutions.
3) 4 course outcomes related to identifying network components, choosing layer functionality, and tracing information flow.
4) A mapping of course outcomes to 12 program outcomes and 3 program specific outcomes.
Networking Concepts Lesson 06 - Protocols - Eric VanderburgEric Vanderburg
This document summarizes networking concepts related to protocols. It discusses how protocols enable communication by sending data in small packets with headers containing source/destination, sequence numbers, and payload data. Packet types include unicast, broadcast, and multicast. Common protocol suites are described like TCP/IP, IPX/SPX, and AppleTalk. Specific protocols are also outlined at each layer of the OSI model including transport protocols like TCP and network protocols like IPv4. Concepts such as subnetting, supernetting, NAT, DHCP, and IPv6 addresses are also summarized.
Mobile IP allows users to move between networks while maintaining the same IP address. It uses home and foreign agents and care-of addresses. A mobile node can register its care-of address with its home agent to receive packets when away from home. There are three main processes: agent discovery to find foreign agents, registration of the mobile node's care-of address with its home agent, and data transfer either via indirect routing through home and foreign agents or direct routing from correspondent nodes to the mobile node. Mobile IP supports host mobility across networks in a transparent manner without changing IP addresses.
The document discusses network management and the Internet standard framework. It describes the key components of the framework, including the Structure of Management Information (SMI) which defines management objects, the Management Information Base (MIB) which stores the managed objects, and the Simple Network Management Protocol (SNMP) used to communicate between managing and managed devices. The framework also includes security and administration capabilities added in SNMPv3.
This document discusses public key cryptography and the RSA algorithm. RSA allows two parties to communicate securely without having to share a secret key beforehand. It works by having each party generate both a public and private key. The public key can be used to encrypt messages, while only the private key can decrypt them. RSA relies on the difficulty of factoring large numbers to be secure. The document provides an example of how RSA key generation and encryption/decryption work in practice.
The document discusses the application layer and HTTP protocol. It provides an overview of the HTTP protocol, including that it uses a client-server model with browsers as clients and web servers as servers. It describes how HTTP messages are exchanged over TCP connections and covers non-persistent and persistent HTTP connections. It also provides details on the format of HTTP requests and responses.
FIXED TELEPHONE, MOBILE TELEPHONE AND SATELLITE COMMUNICATION SYSTEMSDr. Ghanshyam Singh
This document provides an overview of different telecommunication systems, including fixed telephone networks, mobile telephone networks, and satellite communication systems. It begins with an introduction explaining how voice and data communications have merged. It then describes basic telephone systems including POTS lines and limitations. It covers components of telephone networks like local loops, central offices, and trunks. It also discusses mobile telephone standards and multiple access techniques. Finally, it provides details on satellite communication systems, orbital parameters, frequency bands, and multiple access methods for satellites.
1G mobile networks used analog signals and FDMA technology which resulted in inefficient spectrum usage. 2G introduced GSM, using digital TDMA technology for improved capacity and security. Key aspects of 2G included encryption, SMS messaging, and SIM cards which enabled roaming and secure authentication. The core network components of 2G like HLR, VLR, and MSC enabled location management and call routing.
Speech biometric is a revolutionary change in the field of security. Speech biometric works on the identity fication of an individual person with the help of intonation in voice. This speech biometric technology breaks down the speech in small packets of data and computer analyze and interpret. The result is extremely high voice recognition accuracy that enables natural, human-like conversations and satisfying mobile interactions. Because of this technology users in India can access any information and transact easily on their phones.
This document provides an overview of UMTS network architecture and components. It describes the key elements of the UMTS Release 99 core network, including the circuit switched and packet switched domains. It also discusses the radio access network (UTRAN) and its components such as the radio network controller (RNC) and Node B. Finally, it summarizes the functions of the mobile switching center (MSC) and media gateway (MGW) in the UMTS network.
Concepts of & cell sectoring and micro cellKundan Kumar
The document discusses concepts related to cellular network sectoring and microcells. It explains that cells can have square or hexagonal shapes, with hexagons providing equidistant antennas. Frequency reuse allows the same frequencies to be used in different cells by controlling base station power to limit interference. Common frequency reuse patterns include reuse factors of 1, 3, 7, etc. Capacity can be increased through methods like frequency borrowing, cell splitting, cell sectoring, and microcells which use smaller cell sizes.
The document discusses key concepts in GSM cellular networks including:
1. An overview of GSM including its definition, phases, specifications, system architecture, network areas, and advantages over analog systems.
2. Cell planning principles such as types of cells, the planning process, and cell clusters.
3. Frequency reuse which allows frequencies to be reused in different cells to improve capacity, with an example shown.
The document discusses the cellular concept in wireless networks. Key points include:
- Cells have a hexagonal shape and neighboring cells reuse frequencies to avoid interference and increase capacity.
- Frequency reuse allows more simultaneous calls by allocating the same set of frequencies to different neighboring cells.
- Cell size is a tradeoff between interference and system capacity - smaller cells mean lower power needs but more cells and handoffs.
Network components include nodes, links, clients, servers, and other devices that connect and allow communication between systems. Key components discussed include network interface cards, hubs, bridges, routers, switches, gateways, and wireless devices. Various media are used to physically transmit data between nodes on a network.
This document provides an overview of the evolution of cellular networks from traditional networks to broadband networks. It discusses early cellular networks including 2G technologies like GSM and CDMA networks. It then covers 3G and 3.5G broadband cellular networks including UMTS, HSPA, HSDPA and HSUPA which enabled higher data speeds. The document reviews the history and development of cellular standards over time from 1G to 4G networks and the increasing data capabilities they provided.
This document provides an overview of cellular networks. It begins with an introduction that defines a cellular network as a radio network composed of radio cells served by base stations. It then discusses how cellular networks work by allowing mobile devices to connect to the nearest base station and hand off connections between stations as the device moves between cells. Finally, it covers benefits like increased network capacity and coverage area as well as examples of cellular technologies used in modern mobile phone networks.
The 3 main components of a cellular communication system are:
1. The Mobile Station (MS), which includes the mobile device and SIM card.
2. The Base Station Subsystem (BSS), which includes the base transceiver station (BTS) and base station controller (BSC).
3. The Network and Switching Subsystem (NSS), which is centered around the Mobile Switching Center (MSC) and also includes the Home Location Register (HLR), Visitor Location Register (VLR), Authentication Center (AuC), Equipment Identity Register (EIR), Gateway MSC (GMSC), and SMS Gateway. The MSC manages calls and tracks the location of mobile users, with help from
cellular concepts in wireless communicationasadkhan1327
The document discusses the concept of frequency reuse in cellular networks. It explains that a limited radio spectrum is used to serve millions of subscribers by dividing the network coverage area into cells and reusing frequencies across spatially separated cells. Each cell is allocated a portion of the total available frequencies, and neighboring cells are assigned different frequencies to minimize interference. The frequency reuse factor is defined as the ratio of the minimum distance between co-channel cells to the cell radius. Larger frequency reuse factors provide better isolation between co-channel cells but reduce network capacity. The document also covers additional topics like different channel assignment strategies, handoff methods, interference calculation and optimization of frequency reuse networks.
This power point presentation discusses cell splitting and sectoring techniques used to increase channel capacity in cellular networks. It explains that a large cellular area is divided into smaller hexagonal cells, each with its own base station and frequency set. To further increase capacity, cells can be split into smaller cells served by additional base stations. Alternatively, directional antennas can be used to sector each cell into three segments to reduce interference and allow frequency reuse over smaller areas. Both techniques aim to add channels by subdividing congested cells.
A computer network is defined as the interconnection of two or more computers. It is done to enable the computers to communicate and share available resources.
Components of computer network
Network benefits
Disadvantages of computer network
Classification by their geographical area
Network classification by their component role
Types of servers
The document is a chapter from a textbook on computer networking that covers wireless and mobile networks. It contains slides used to teach various topics in the chapter, including:
- The basic elements of a wireless network including wireless hosts, base stations, wireless links, and infrastructure vs. ad hoc modes.
- Characteristics of different types of wireless links including data rates and transmission distances.
- An overview of wireless network challenges including signal attenuation, interference, and the hidden terminal problem.
- A description of Code Division Multiple Access (CDMA) used in cellular networks and how it allows multiple users to transmit simultaneously.
- Details on the IEEE 802.11 wireless LAN standard including the standards 8
Wireless networks allow devices to connect to a network without being physically connected with wires. They consist of wireless hosts that communicate over the air with network infrastructure like access points or base stations. There are challenges to wireless communication including signal attenuation, interference, and the hidden terminal problem. Wireless networks can operate in infrastructure mode with access points or in ad hoc mode without infrastructure between devices. Standards like 802.11 (Wi-Fi) and CDMA are used to allow multiple devices to communicate over the same wireless channel. Devices must associate with an access point to connect to the network and protocols like CSMA/CA are used to avoid collisions between transmissions.
This document provides an overview of key topics in chapter 6 on wireless and mobile networks. It begins with background on the growth of wireless networks and defines two main challenges - wireless communication over the wireless link, and handling mobility as users change their point of attachment. The chapter outline is then presented, covering wireless link characteristics, IEEE 802.11 wireless LANs, cellular networks, principles of addressing and routing for mobile users, and handling mobility. Elements of wireless networks like wireless hosts, base stations, and wireless links are defined. Characteristics of different wireless links are summarized and issues like interference, multipath propagation, and the hidden terminal problem are introduced.
This document provides an overview of Chapter 7 from the textbook "Computer Networking: A Top-Down Approach 8th edition" by Jim Kurose and Keith Ross. It discusses the use of the PowerPoint slides from the chapter and provides copyright information. The chapter outline is then presented, covering topics on wireless links and networks, WiFi (802.11), cellular networks, mobility management, and the impact of mobility on higher layer protocols.
This document provides an overview of Chapter 7 from the textbook "Computer Networking: A Top-Down Approach 8th edition" by Jim Kurose and Keith Ross. It includes notes on using the PowerPoint slides freely but asking users to cite the source and copyright. The chapter outline covers wireless links and networks, WiFi (802.11), cellular networks, and mobility management. It provides context on the growth of wireless and mobile networks and examples of wireless link characteristics, protocols, and WiFi frame addressing.
The document provides an overview of wireless and mobile networks. It discusses how wireless networks allow anytime untethered internet access for devices like laptops and phones. It also distinguishes between the challenges of wireless communication over a wireless link and handling mobility as users change their point of attachment. The chapter outline covers wireless link characteristics, wireless standards like 802.11 and CDMA, cellular internet access architectures and standards, principles of addressing and routing to mobile users, and protocols for mobility like Mobile IP.
This document provides an overview of wireless and mobile networks. It begins with background on the growth of wireless networks and devices. The key challenges of wireless communication over wireless links and handling mobility are introduced. The chapter outline covers wireless link characteristics, wireless local area networks (Wi-Fi), cellular networks, and principles of mobility. Elements of wireless networks like base stations, wireless hosts, and infrastructure and ad hoc modes are defined. Characteristics of different wireless links and issues like interference are also summarized.
The document provides an overview of wireless and mobile networks. It discusses key differences between wired and wireless links, including decreased signal strength over distance, interference from other devices, and multipath propagation. It also describes various wireless network characteristics such as signal-to-noise ratio tradeoffs, the hidden terminal problem, and how Code Division Multiple Access (CDMA) works to allow multiple users to transmit simultaneously using unique coding. The chapter outline and sections cover additional topics like IEEE 802.11 wireless networks, cellular network architectures and standards, principles of mobility, and handling mobility in different network types.
The document discusses the components and characteristics of wireless local area networks (WLANs). It describes the basic components of a WLAN including access points, WLAN adapters, and software. It discusses characteristics such as typical ranges of access points, the number of users supported, and how multiple access points can be connected. It also covers topics such as roaming between access points, infrastructure versus ad-hoc network architectures, and standards like IEEE 802.11.
These ppt are the part 2 of mobile computing concepts. These ppt defines the following things
Wireless Networking
Wireless LAN Overview: IEEE 802.11
Wireless applications
Data Broadcasting
Bluetooth
TCP over wireless
Mobile IP
WAP: Architecture, protocol stack, application
environment, applications.
This chapter discusses wireless and mobile networks. It covers wireless link characteristics and multiple access techniques used in cellular networks like FDMA, TDMA, CDMA, and hybrid schemes. Key components of cellular network architecture are base stations, mobile switching centers, and the connections between cells and wired networks. Mobility introduces challenges for addressing, routing, and maintaining ongoing connections. Approaches for mobility include letting the routing handle location updates or having end systems handle it through techniques like Mobile IP with indirect routing through a home agent or direct routing to a care-of address. Registration notifies the home and foreign agents of a user's location.
This document provides a summary of basic wireless networking concepts for new users. It discusses the need for wireless networks and their benefits over wired networks. It then covers fundamental wireless topics like wireless topologies, regulatory bodies, wireless network components, and wireless network types. It also addresses wireless design concepts such as ad-hoc vs infrastructure networks and wireless access point types. The document aims to give new wireless users a high-level understanding of wireless fundamentals and common industry terminology.
Wi-Fi, also known as IEEE 802.11, is a set of standards that allow wireless devices to communicate. It operates in various frequency bands including 2.4GHz and 5GHz. Wi-Fi standards have evolved from 2Mbps with 802.11 to 600Mbps with 802.11n. Wi-Fi networks can operate in ad hoc, mesh, or infrastructure modes. Infrastructure mode with an access point is most common in homes and businesses. Wi-Fi uses techniques like CSMA/CA and frequency hopping/direct sequence spread spectrum to allow multiple devices to share the wireless channel.
The document discusses free computer science eBooks and technology news that are being provided. It includes links to blogs sharing this free content and encourages clicking on advertisements to support their work. It then discusses the topics of wireless technologies and Wi-Fi networks in particular, covering introductions, architectures, elements, how they work, topologies and configurations.
Wireless networking technology uses wireless stations like computers or devices with radios to transmit and receive data without wires. There are two main types of wireless networks: infrastructure networks with an access point that devices connect to and ad-hoc peer-to-peer networks without an access point where devices connect directly. Wireless networks use radio frequencies and transmission methods like frequency hopping spread spectrum or direct sequence spread spectrum to transmit data over the air. Newer standards are developing technologies like MIMO that use multiple antennas to improve wireless network performance and speeds.
Wi-Fi, also known as IEEE 802.11, allows wireless devices to communicate using radio signals in the 2.4 GHz and 5 GHz bands. It uses CSMA/CA to allow multiple devices to share bandwidth and avoid collisions. Devices can connect to each other directly in ad hoc mode or through an access point in infrastructure mode. Access points allow devices to roam between different coverage areas. Security features include authentication to verify devices and encryption to protect data transmissions.
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Very nice Wireless-lan-wlan-selected-topics-selected-topics-introduction-wlan...AssocaKazama
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1. Chapter 6
Wireless and
Mobile Networks
A note on the use of these ppt slides:
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Thanks and enjoy! JFK/KWR
Computer
Networking: A Top
Down Approach
6th edition
Jim Kurose, Keith Ross
Addison-Wesley
March 2012
All material copyright 1996-2012
J.F Kurose and K.W. Ross, All Rights Reserved
Wireless, Mobile Networks
6-1
2. Ch. 6: Wireless and Mobile Networks
Background:
# wireless (mobile) phone subscribers now exceeds #
wired phone subscribers (5-to-1)!
# wireless Internet-connected devices equals #
wireline Internet-connected devices
laptops, Internet-enabled phones promise anytime
untethered Internet access
two important (but different) challenges
wireless: communication over wireless link
mobility: handling the mobile user who changes point of
attachment to network
Wireless, Mobile Networks
6-2
3. Chapter 6 outline
6.1 Introduction
Mobility
Wireless
6.5 Principles: addressing and
routing to mobile users
6.6 Mobile IP
6.7 Handling mobility in
cellular networks
6.8 Mobility and higher-layer
protocols
6.2 Wireless links,
characteristics
CDMA
6.3 IEEE 802.11 wireless
LANs (“Wi-Fi”)
6.4 Cellular Internet Access
architecture
standards (e.g., GSM)
6.9 Summary
Wireless, Mobile Networks
6-3
4. Elements of a wireless network
network
infrastructure
Wireless, Mobile Networks
6-4
5. Elements of a wireless network
wireless hosts
network
infrastructure
laptop, smartphone
run applications
may be stationary (nonmobile) or mobile
wireless does not always
mean mobility
Wireless, Mobile Networks
6-5
6. Elements of a wireless network
base station
network
infrastructure
typically connected to
wired network
relay - responsible for
sending packets between
wired network and
wireless host(s) in its
“area”
e.g., cell towers,
802.11 access points
Wireless, Mobile Networks
6-6
7. Elements of a wireless network
wireless link
network
infrastructure
typically used to connect
mobile(s) to base station
also used as backbone
link
multiple access protocol
coordinates link access
various data rates,
transmission distance
Wireless, Mobile Networks
6-7
9. Elements of a wireless network
infrastructure mode
network
infrastructure
base station connects
mobiles into wired
network
handoff: mobile changes
base station providing
connection into wired
network
Wireless, Mobile Networks
6-9
10. Elements of a wireless network
ad hoc mode
no base stations
nodes can only
transmit to other
nodes within link
coverage
nodes organize
themselves into a
network: route
among themselves
Wireless, Mobile Networks 6-10
11. Wireless network taxonomy
single hop
infrastructure
(e.g., APs)
no
infrastructure
host connects to
base station (WiFi,
WiMAX, cellular)
which connects to
larger Internet
no base station, no
connection to larger
Internet (Bluetooth,
ad hoc nets)
multiple hops
host may have to
relay through several
wireless nodes to
connect to larger
Internet: mesh net
no base station, no
connection to larger
Internet. May have to
relay to reach other
a given wireless node
MANET, VANET
Wireless, Mobile Networks 6-11
12. Chapter 6 outline
6.1 Introduction
Mobility
Wireless
6.5 Principles: addressing and
routing to mobile users
6.6 Mobile IP
6.7 Handling mobility in
cellular networks
6.8 Mobility and higher-layer
protocols
6.2 Wireless links,
characteristics
CDMA
6.3 IEEE 802.11 wireless
LANs (“Wi-Fi”)
6.4 Cellular Internet Access
architecture
standards (e.g., GSM)
6.9 Summary
Wireless, Mobile Networks 6-12
13. Wireless Link Characteristics (1)
important differences from wired link ….
decreased signal strength: radio signal attenuates as it
propagates through matter (path loss)
interference from other sources: standardized wireless
network frequencies (e.g., 2.4 GHz) shared by other
devices (e.g., phone); devices (motors) interfere as
well
multipath propagation: radio signal reflects off objects
ground, arriving ad destination at slightly different
times
…. make communication across (even a point to point)
wireless link much more “difficult”
Wireless, Mobile Networks 6-13
14. Wireless Link Characteristics (2)
SNR: signal-to-noise ratio
10-1
larger SNR – easier to
extract signal from noise (a
“good thing”)
SNR versus BER tradeoffs
given physical layer: increase
power -> increase SNR>decrease BER
given SNR: choose physical layer
that meets BER requirement,
giving highest thruput
• SNR may change with
mobility: dynamically adapt
physical layer (modulation
technique, rate)
10-3
BER
10-2
10-4
10-5
10-6
10-7
10
20
30
40
SNR(dB)
QAM256 (8 Mbps)
QAM16 (4 Mbps)
BPSK (1 Mbps)
Wireless, Mobile Networks 6-14
15. Wireless network characteristics
Multiple wireless senders and receivers create additional
problems (beyond multiple access):
B
A
C
C
A
B
Hidden terminal problem
B, A hear each other
B, C hear each other
A, C can not hear each other
means A, C unaware of their
interference at B
C’s signal
strength
A’s signal
strength
space
Signal attenuation:
B, A hear each other
B, C hear each other
A, C can not hear each other
interfering at B
Wireless, Mobile Networks 6-15
16. Code Division Multiple Access (CDMA)
unique “code” assigned to each user; i.e., code set
partitioning
all users share same frequency, but each user has own
“chipping” sequence (i.e., code) to encode data
allows multiple users to “coexist” and transmit
simultaneously with minimal interference (if codes are
“orthogonal”)
encoded signal = (original data) X (chipping
sequence)
decoding: inner-product of encoded signal and
chipping sequence
Wireless, Mobile Networks 6-16
18. CDMA: two-sender interference
Sender 1
channel sums together
transmissions by sender 1
and 2
Sender 2
using same code as sender
1, receiver recovers sender
1’s original data from
summed channel data!
Wireless, Mobile Networks 6-18
19. Chapter 6 outline
6.1 Introduction
Mobility
Wireless
6.5 Principles: addressing and
routing to mobile users
6.6 Mobile IP
6.7 Handling mobility in
cellular networks
6.8 Mobility and higher-layer
protocols
6.2 Wireless links,
characteristics
CDMA
6.3 IEEE 802.11 wireless
LANs (“Wi-Fi”)
6.4 Cellular Internet Access
architecture
standards (e.g., GSM)
6.9 Summary
Wireless, Mobile Networks 6-19
20. IEEE 802.11 Wireless LAN
802.11b
2.4-5 GHz unlicensed spectrum
up to 11 Mbps
direct sequence spread spectrum
(DSSS) in physical layer
all hosts use same chipping
code
802.11a
5-6 GHz range
up to 54 Mbps
802.11g
2.4-5 GHz range
up to 54 Mbps
802.11n: multiple antennae
2.4-5 GHz range
up to 200 Mbps
all use CSMA/CA for multiple access
all have base-station and ad-hoc network versions
Wireless, Mobile Networks 6-20
21. 802.11 LAN architecture
Internet
wireless host
communicates with base
station
base station = access point
(AP)
hub, switch
or router
Basic Service Set (BSS) (aka
“cell”) in infrastructure
mode contains:
wireless hosts
access point (AP): base
station
ad hoc mode: hosts only
BSS 1
BSS 2
Wireless, Mobile Networks 6-21
22. 802.11: Channels, association
802.11b: 2.4GHz-2.485GHz spectrum divided into 11
channels at different frequencies
AP admin chooses frequency for AP
interference possible: channel can be same as that
chosen by neighboring AP!
host: must associate with an AP
scans channels, listening for beacon frames containing
AP’s name (SSID) and MAC address
selects AP to associate with
may perform authentication [Chapter 8]
will typically run DHCP to get IP address in AP’s
subnet
Wireless, Mobile Networks 6-22
23. 802.11: passive/active scanning
BBS 1
AP 1
BBS 1
BBS 2
1
1
2
BBS 2
1
AP 2
AP 1
2
3
(1) beacon frames sent from APs
(2) association Request frame sent: H1 to
selected AP
(3) association Response frame sent from
selected AP to H1
AP 2
4
H1
H1
passive scanning:
2
3
active scanning:
(1) Probe Request frame broadcast
from H1
(2) Probe Response frames sent
from APs
(3) Association Request frame sent:
H1 to selected AP
(4) Association Response frame sent
from selected AP to H1
Wireless, Mobile Networks 6-23
24. IEEE 802.11: multiple access
avoid collisions: 2+ nodes transmitting at same time
802.11: CSMA - sense before transmitting
don’t collide with ongoing transmission by other node
802.11: no collision detection!
difficult to receive (sense collisions) when transmitting due to weak
received signals (fading)
can’t sense all collisions in any case: hidden terminal, fading
goal: avoid collisions: CSMA/C(ollision)A(voidance)
C
A
B
A
B
C
C’s signal
strength
A’s signal
strength
space
Wireless, Mobile Networks 6-24
25. IEEE 802.11 MAC Protocol: CSMA/CA
802.11 sender
1 if sense channel idle for DIFS then
sender
transmit entire frame (no CD)
2 if sense channel busy then
DIFS
start random backoff time
timer counts down while channel idle
transmit when timer expires
if no ACK, increase random backoff interval,
repeat 2
802.11 receiver
- if frame received OK
receiver
data
SIFS
ACK
return ACK after SIFS (ACK needed due to
hidden terminal problem)
Wireless, Mobile Networks 6-25
26. Avoiding collisions (more)
idea: allow sender to “reserve” channel rather than random
access of data frames: avoid collisions of long data
frames
sender first transmits small request-to-send (RTS) packets
to BS using CSMA
RTSs may still collide with each other (but they’re short)
BS broadcasts clear-to-send CTS in response to RTS
CTS heard by all nodes
sender transmits data frame
other stations defer transmissions
avoid data frame collisions completely
using small reservation packets!
Wireless, Mobile Networks 6-26
27. Collision Avoidance: RTS-CTS exchange
A
B
AP
RTS(B)
RTS(A)
reservation collision
RTS(A)
CTS(A)
CTS(A)
DATA (A)
defer
time
ACK(A)
ACK(A)
Wireless, Mobile Networks 6-27
28. 802.11 frame: addressing
2
2
6
6
6
frame
address address address
duration
control
1
2
3
Address 1: MAC address
of wireless host or AP
to receive this frame
Address 2: MAC address
of wireless host or AP
transmitting this frame
2
6
0 - 2312
seq address
4
control
4
payload
CRC
Address 4: used only in
ad hoc mode
Address 3: MAC address
of router interface to
which AP is attached
Wireless, Mobile Networks 6-28
29. 802.11 frame: addressing
R1 router
H1
Internet
R1 MAC addr H1 MAC addr
dest. address
source address
802.3 frame
AP MAC addr H1 MAC addr R1 MAC addr
address 1
address 2
address 3
802.11 frame
Wireless, Mobile Networks 6-29
30. 802.11 frame: more
frame seq #
(for RDT)
duration of reserved
transmission time (RTS/CTS)
2
2
6
6
6
frame
address address address
duration
control
1
2
3
2
Protocol
version
2
4
1
Type
Subtype
To
AP
6
2
1
0 - 2312
payload
seq address
4
control
1
From More
AP
frag
1
Retry
1
4
CRC
1
Power More
mgt
data
1
1
WEP
Rsvd
frame type
(RTS, CTS, ACK, data)
Wireless, Mobile Networks 6-30
31. 802.11: mobility within same subnet
H1 remains in same
IP subnet: IP address
can remain same
switch: which AP is
associated with H1?
self-learning (Ch. 5):
switch will see frame
from H1 and
“remember” which
switch port can be
used to reach H1
BBS 1
H1
BBS 2
Wireless, Mobile Networks 6-31
32. 802.11: advanced capabilities
Rate adaptation
base station, mobile
dynamically change
transmission rate
(physical layer modulation
technique) as mobile
moves, SNR varies
QAM256 (8 Mbps)
QAM16 (4 Mbps)
BPSK (1 Mbps)
operating point
10-2
10-3
BER
10-1
10-4
10-5
10-6
10-7
10
20
30
SNR(dB)
40
1. SNR decreases, BER
increase as node moves
away from base station
2. When BER becomes too
high, switch to lower
transmission rate but with
lower BER
Wireless, Mobile Networks 6-32
33. 802.11: advanced capabilities
power management
node-to-AP: “I am going to sleep until next
beacon frame”
AP knows not to transmit frames to this node
node wakes up before next beacon frame
beacon frame: contains list of mobiles with APto-mobile frames waiting to be sent
node will stay awake if AP-to-mobile frames to be
sent; otherwise sleep again until next beacon frame
Wireless, Mobile Networks 6-33
34. 802.15: personal area network
less than 10 m diameter
replacement for cables (mouse,
keyboard, headphones)
ad hoc: no infrastructure
master/slaves:
slaves request permission to send
(to master)
master grants requests
802.15: evolved from Bluetooth
specification
2.4-2.5 GHz radio band
up to 721 kbps
P
S
P
radius of
coverage
M
S
P
S
P
M Master device
S Slave device
P Parked device (inactive)
Wireless, Mobile Networks 6-34
35. Chapter 6 outline
6.1 Introduction
Wireless
6.2 Wireless links,
characteristics
CDMA
6.3 IEEE 802.11 wireless
LANs (“Wi-Fi”)
6.4 Cellular Internet access
architecture
standards (e.g., GSM)
Mobility
6.5 Principles: addressing and
routing to mobile users
6.6 Mobile IP
6.7 Handling mobility in
cellular networks
6.8 Mobility and higher-layer
protocols
6.9 Summary
Wireless, Mobile Networks 6-35
36. Components of cellular network architecture
MSC
connects cells to wired tel. net.
manages call setup (more later!)
handles mobility (more later!)
cell
covers geographical
region
base station (BS)
analogous to 802.11 AP
mobile users attach to
network through BS
air-interface: physical
and link layer protocol
between mobile and BS
Mobile
Switching
Center
Public telephone
network
Mobile
Switching
Center
wired network
Wireless, Mobile Networks 6-36
37. Cellular networks: the first hop
Two techniques for sharing
mobile-to-BS radio spectrum
combined FDMA/TDMA:
divide spectrum in frequency
channels, divide each channel
into time slots
CDMA: code division multiple
frequency
access
time slots
bands
Wireless, Mobile Networks 6-37
38. 2G (voice) network architecture
Base station system (BSS)
BTS
MSC
G
BSC
Public
telephone
network
Gateway
MSC
Legend
Base transceiver station (BTS)
Base station controller (BSC)
Mobile Switching Center (MSC)
Mobile subscribers
Wireless, Mobile Networks 6-38
39. 3G (voice+data) network architecture
MSC
G
radio
network
controller
Public
telephone
network
Gateway
MSC
G
SGSN
Key insight: new cellular data
network operates in parallel
(except at edge) with existing
cellular voice network
voice network unchanged in core
data network operates in parallel
Public
Internet
GGSN
Serving GPRS Support Node (SGSN)
Gateway GPRS Support Node (GGSN)
Wireless, Mobile Networks 6-39
40. 3G (voice+data) network architecture
MSC
G
radio
network
controller
Public
telephone
network
Gateway
MSC
G
SGSN
Public
Internet
GGSN
radio interface
(WCDMA, HSPA)
radio access network
Universal Terrestrial Radio
Access Network (UTRAN)
core network
General Packet Radio Service
(GPRS) Core Network
public
Internet
Wireless, Mobile Networks 6-40
41. Chapter 6 outline
6.1 Introduction
Wireless
6.2 Wireless links,
characteristics
CDMA
6.3 IEEE 802.11 wireless
LANs (“Wi-Fi”)
6.4 Cellular Internet Access
architecture
standards (e.g., GSM)
Mobility
6.5 Principles: addressing and
routing to mobile users
6.6 Mobile IP
6.7 Handling mobility in
cellular networks
6.8 Mobility and higher-layer
protocols
6.9 Summary
Wireless, Mobile Networks 6-41
42. What is mobility?
spectrum of mobility, from the network perspective:
no mobility
mobile wireless user,
using same access
point
high mobility
mobile user,
connecting/
disconnecting from
network using
DHCP.
mobile user, passing
through multiple
access point while
maintaining ongoing
connections (like cell
phone)
Wireless, Mobile Networks 6-42
43. Mobility: vocabulary
home network: permanent
“home” of mobile
(e.g., 128.119.40/24)
home agent: entity that will
perform mobility functions on
behalf of mobile, when mobile is
remote
wide area
network
permanent address:
address in home
network, can always be
used to reach mobile
e.g., 128.119.40.186
Wireless, Mobile Networks 6-43
44. Mobility: more vocabulary
permanent address: remains
constant (e.g., 128.119.40.186)
visited network: network in
which mobile currently
resides (e.g., 79.129.13/24)
care-of-address: address
in visited network.
(e.g., 79,129.13.2)
wide area
network
correspondent: wants
to communicate with
mobile
foreign agent: entity in
visited network that
performs mobility
functions on behalf of
mobile.
Wireless, Mobile Networks 6-44
45. How do you contact a mobile friend:
Consider friend frequently
changing addresses, how do you
find her? phone books?
search all
I wonder where
Alice moved to?
call her parents?
expect her to let you
know where he/she is?
Wireless, Mobile Networks 6-45
46. Mobility: approaches
let routing handle it: routers advertise permanent address of
mobile-nodes-in-residence via usual routing table exchange.
routing tables indicate where each mobile located
no changes to end-systems
let end-systems handle it:
indirect routing: communication from correspondent to
mobile goes through home agent, then forwarded to
remote
direct routing: correspondent gets foreign address of
mobile, sends directly to mobile
Wireless, Mobile Networks 6-46
47. Mobility: approaches
let routing handle it: routers advertise permanent address of
not
mobile-nodes-in-residence via usual routing table exchange.
scalable
routing tables indicate where each mobile located
to millions of
no changes to end-systems
mobiles
let end-systems handle it:
indirect routing: communication from correspondent to
mobile goes through home agent, then forwarded to
remote
direct routing: correspondent gets foreign address of
mobile, sends directly to mobile
Wireless, Mobile Networks 6-47
48. Mobility: registration
visited network
home network
2
wide area
network
foreign agent contacts home
agent home: “this mobile is
resident in my network”
1
mobile contacts
foreign agent on
entering visited
network
end result:
foreign agent knows about mobile
home agent knows location of mobile
Wireless, Mobile Networks 6-48
49. Mobility via indirect routing
home agent intercepts
packets, forwards to
foreign agent
foreign agent
receives packets,
forwards to mobile
home
network
3
1
correspondent
addresses packets
using home address of
mobile
visited
network
wide area
network
2
4
mobile replies
directly to
correspondent
Wireless, Mobile Networks 6-49
50. Indirect Routing: comments
mobile uses two addresses:
permanent address: used by correspondent (hence
mobile location is transparent to correspondent)
care-of-address: used by home agent to forward
datagrams to mobile
foreign agent functions may be done by mobile itself
triangle routing: correspondent-home-networkmobile
inefficient when
correspondent, mobile
are in same network
Wireless, Mobile Networks 6-50
51. Indirect routing: moving between networks
suppose mobile user moves to another network
registers with new foreign agent
new foreign agent registers with home agent
home agent update care-of-address for mobile
packets continue to be forwarded to mobile (but
with new care-of-address)
mobility, changing foreign networks transparent: on
going connections can be maintained!
Wireless, Mobile Networks 6-51
52. Mobility via direct routing
correspondent forwards
to foreign agent
foreign agent
receives packets,
forwards to mobile
visited
network
home
network
3
1
correspondent
requests, receives
foreign address of
mobile
2
4
mobile replies
directly to
correspondent
Wireless, Mobile Networks 6-52
53. Mobility via direct routing: comments
overcome triangle routing problem
non-transparent to correspondent: correspondent
must get care-of-address from home agent
what if mobile changes visited network?
1
3
2
4
Wireless, Mobile Networks 6-53
54. Accommodating mobility with direct routing
anchor foreign agent: FA in first visited network
data always routed first to anchor FA
when mobile moves: new FA arranges to have
data forwarded from old FA (chaining)
foreign net visited
at session start
wide area
network
anchor
foreign
agent
1
2
4
5
correspondent
correspondent
agent
3
new foreign
agent
new
foreign
network
Wireless, Mobile Networks 6-54
55. Chapter 6 outline
6.1 Introduction
Wireless
6.2 Wireless links,
characteristics
CDMA
6.3 IEEE 802.11 wireless
LANs (“Wi-Fi”)
6.4 Cellular Internet Access
architecture
standards (e.g., GSM)
Mobility
6.5 Principles: addressing and
routing to mobile users
6.6 Mobile IP
6.7 Handling mobility in
cellular networks
6.8 Mobility and higher-layer
protocols
6.9 Summary
Wireless, Mobile Networks 6-55
56. Mobile IP
RFC 3344
has many features we’ve seen:
home agents, foreign agents, foreign-agent registration,
care-of-addresses, encapsulation (packet-within-apacket)
three components to standard:
indirect routing of datagrams
agent discovery
registration with home agent
Wireless, Mobile Networks 6-56
57. Mobile IP: indirect routing
foreign-agent-to-mobile packet
packet sent by home agent to foreign
agent: a packet within a packet
dest: 79.129.13.2
dest: 128.119.40.186
dest: 128.119.40.186
Permanent address:
128.119.40.186
dest: 128.119.40.186
Care-of address:
79.129.13.2
packet sent by
correspondent
Wireless, Mobile Networks 6-57
58. Mobile IP: agent discovery
agent advertisement: foreign/home agents advertise
service by broadcasting ICMP messages (typefield = 9)
0
type = 9
24
checksum
=9
code = 0
=9
H,F bits: home and/or
foreign agent
R bit: registration
required
16
8
standard
ICMP fields
router address
type = 16
length
registration lifetime
sequence #
RBHFMGV
bits
reserved
0 or more care-ofaddresses
mobility agent
advertisement
extension
Wireless, Mobile Networks 6-58
60. Components of cellular network architecture
recall:
correspondent
wired public
telephone
network
MSC
MSC
MSC
MSC
MSC
different cellular networks,
operated by different providers
Wireless, Mobile Networks 6-60
61. Handling mobility in cellular networks
home network: network of cellular provider you
subscribe to (e.g., Sprint PCS, Verizon)
home location register (HLR): database in home network
containing permanent cell phone #, profile information
(services, preferences, billing), information about
current location (could be in another network)
visited network: network in which mobile currently
resides
visitor location register (VLR): database with entry for
each user currently in network
could be home network
Wireless, Mobile Networks 6-61
62. GSM: indirect routing to mobile
home
network
HLR
2
home MSC consults HLR,
gets roaming number of
mobile in visited network
correspondent
home
Mobile
Switching
Center
1
VLR
3
Mobile
Switching
Center
4
Public
switched
telephone
network
call routed
to home network
home MSC sets up 2nd leg of call
to MSC in visited network
mobile
user
visited
network
MSC in visited network completes
call through base station to mobile
Wireless, Mobile Networks 6-62
63. GSM: handoff with common MSC
VLR Mobile
Switching
Center
old
routing
old BSS
handoff goal: route call via
new base station (without
interruption)
reasons for handoff:
stronger signal to/from new BSS
(continuing connectivity, less
battery drain)
load balance: free up channel in
current BSS
GSM doesnt mandate why to
perform handoff (policy), only
how (mechanism)
new
routing
new BSS
handoff initiated by old BSS
Wireless, Mobile Networks 6-63
64. GSM: handoff with common MSC
VLR Mobile
Switching
Center 2
4
1
8
old BSS
5
7
3
6
new BSS
1. old BSS informs MSC of impending
handoff, provides list of 1+ new BSSs
2. MSC sets up path (allocates resources)
to new BSS
3. new BSS allocates radio channel for
use by mobile
4. new BSS signals MSC, old BSS: ready
5. old BSS tells mobile: perform handoff to
new BSS
6. mobile, new BSS signal to activate new
channel
7. mobile signals via new BSS to MSC:
handoff complete. MSC reroutes call
8 MSC-old-BSS resources released
Wireless, Mobile Networks 6-64
65. GSM: handoff between MSCs
home network
correspondent
Home
MSC
anchor MSC
MSC
PSTN
MSC
MSC
anchor MSC: first MSC
visited during call
call remains routed
through anchor MSC
new MSCs add on to end of
MSC chain as mobile moves
to new MSC
optional path minimization
step to shorten multi-MSC
chain
(a) before handoff
Wireless, Mobile Networks 6-65
66. GSM: handoff between MSCs
home network
correspondent
Home
MSC
anchor MSC
MSC
PSTN
MSC
MSC
anchor MSC: first MSC
visited during call
call remains routed
through anchor MSC
new MSCs add on to end of
MSC chain as mobile moves
to new MSC
optional path minimization
step to shorten multi-MSC
chain
(b) after handoff
Wireless, Mobile Networks 6-66
67. Mobility: GSM versus Mobile IP
GSM element
Comment on GSM element
Mobile IP element
Home system
Network to which mobile user’s permanent
phone number belongs
Home
network
Gateway Mobile
Switching Center, or
“home MSC”. Home
Location Register
(HLR)
Home MSC: point of contact to obtain routable
address of mobile user. HLR: database in
home system containing permanent phone
number, profile information, current location of
mobile user, subscription information
Home agent
Visited System
Network other than home system where mobile Visited
user is currently residing
network
Visited Mobile
services Switching
Center.
Visitor Location
Record (VLR)
Visited MSC: responsible for setting up calls
Foreign agent
to/from mobile nodes in cells associated with
MSC. VLR: temporary database entry in visited
system, containing subscription information for
each visiting mobile user
Mobile Station
Roaming Number
(MSRN), or “roaming
number”
Routable address for telephone call segment
between home MSC and visited MSC, visible
to neither the mobile nor the correspondent.
Care-ofaddress
Wireless, Mobile Networks 6-67
68. Wireless, mobility: impact on higher layer protocols
logically, impact should be minimal …
best effort service model remains unchanged
TCP and UDP can (and do) run over wireless, mobile
… but performance-wise:
packet loss/delay due to bit-errors (discarded packets,
delays for link-layer retransmissions), and handoff
TCP interprets loss as congestion, will decrease congestion
window un-necessarily
delay impairments for real-time traffic
limited bandwidth of wireless links
Wireless, Mobile Networks 6-68
69. Chapter 6 summary
Wireless
wireless links:
Mobility
capacity, distance
channel impairments
CDMA
home, visited networks
direct, indirect routing
care-of-addresses
IEEE 802.11 (“Wi-Fi”)
CSMA/CA reflects wireless
channel characteristics
case studies
mobile IP
mobility in GSM
cellular access
architecture
standards (e.g., GSM, 3G,
4G LTE)
principles: addressing,
routing to mobile users
impact on higher-layer
protocols
Wireless, Mobile Networks 6-69