MAC PROTOCOLS FOR AD HOC WIRELESS NETWORKS
Issues in designing a MAC Protocol- Classification of MAC Protocols- Contention based protocols- Contention based protocols with Reservation Mechanisms- Contention based protocols with Scheduling Mechanisms – Multi channel MAC-IEEE 802.11
Mac protocols for ad hoc wireless networks Divya Tiwari
The document discusses MAC protocols for ad hoc wireless networks. It addresses key issues in designing MAC protocols including limited bandwidth, quality of service support, synchronization, hidden and exposed terminal problems, error-prone shared channels, distributed coordination without centralized control, and node mobility. Common MAC protocol classifications and examples are also presented, such as contention-based protocols, sender-initiated versus receiver-initiated protocols, and protocols using techniques like reservation, scheduling, and directional antennas.
Distributed Operation
Synchronization
Hidden Terminals
Exposed terminals
Throughput
Access delay
Fairness
Real-time Traffic support
Resource reservation
Ability to measure resource availability
Capability for power control
Adaptive rate control
Use of directional antennas
This document discusses medium access control (MAC) protocols, which regulate access to a shared wireless medium between nodes. It covers key requirements for MAC protocols including throughput efficiency, fairness, and low overhead. It also describes challenges like the hidden terminal problem, exposed terminal problem, and sources of overhead from collisions, overhearing, and idle listening. Finally, it categorizes common MAC protocols as fixed assignment, demand assignment, and random access and notes additional energy conservation requirements for wireless sensor networks.
This document summarizes several reactive routing protocols for mobile ad hoc networks (MANETs). Reactive protocols create routes only when needed by a source. Dynamic Source Routing uses route requests and replies to find paths, while Temporally-Ordered Routing Algorithm builds and maintains a directed acyclic graph rooted at destinations. Some protocols aim to improve quality of service or support real-time data streams through techniques like bandwidth estimation and mobility prediction. Source Routing with Local Recovery reduces overhead by allowing intermediate nodes to perform local error recovery using route caches when possible.
This document discusses power aware routing protocols for wireless sensor networks. It begins by describing wireless sensor networks and how they are used to monitor environmental conditions. It then classifies routing protocols for sensor networks based on their functioning, node participation style, and network structure. Specific examples are provided for different types of routing protocols, including LEACH, TEEN, APTEEN, SPIN, Rumor Routing, and PEGASIS. Chain-based and clustering routing protocols are also summarized.
Ad hoc wireless networks allow devices to connect and communicate with each other without a centralized access point. Nodes in an ad hoc network relay messages through intermediate hops to reach destinations. Examples include Bluetooth networks and wireless mesh networks. Issues in ad hoc networks include medium access control, routing with mobility and bandwidth constraints, and providing quality of service guarantees.
TIME SYNCHRONIZATION IN WIRELESS SENSOR NETWORKS: A SURVEYijujournal
Time synchronization is a critical piece of infrastructure for any distributed system. Wireless sensor networks have emerged as an important and promising research area in the recent years. Time synchronization is important for many sensor network applications that require very precise mapping of gathered sensor data with the time of the events, for example, in tracking and vehicular surveillance. It also plays an important role in energy conservation in MAC layer protocols. The paper studies different existing methods, protocols, significant time parameters (clock drift, clock speed, synchronization errors, and topologies) to achieve accurate synchronization in a sensor network. The studied Synchronization protocols include conventional time sync protocols (RBS, Timing-sync Protocol for Sensor Networks -TPSN, FTSP), and other application specific
approaches such as all node-based approach, a diffusion-based method and group sync approaches aiming at providing network-wide time. The goal for writing this paper is to study most common existing time synchronization approaches and stress the need of a new class of secure-time synchronization protocol that is scalable, topology independent, fast convergent, energy efficient, less latent and less application dependent in a heterogeneous hostile environment. Our survey provides a valuable framework by which protocol designers can compare new and
existing synchronization protocols from various metric discussed in the paper. So, we are hopeful that this paper will serve a complete one-stop investigation to study the characteristics of existing time synchronization protocols and its implementation mechanism in a Sensor network environment.
The document summarizes key points from an 8th lecture on wireless sensor networks. It discusses various medium access control (MAC) protocols that control when nodes can access a shared wireless medium. These include contention-based protocols like MACA that use RTS/CTS handshaking and schedule-based protocols with fixed or dynamic scheduling. It also describes energy-efficient MAC protocols for low data rate sensor networks like S-MAC, T-MAC, and preamble sampling that increase sleep time to reduce energy use through synchronized sleep schedules or long preambles.
Mac protocols for ad hoc wireless networks Divya Tiwari
The document discusses MAC protocols for ad hoc wireless networks. It addresses key issues in designing MAC protocols including limited bandwidth, quality of service support, synchronization, hidden and exposed terminal problems, error-prone shared channels, distributed coordination without centralized control, and node mobility. Common MAC protocol classifications and examples are also presented, such as contention-based protocols, sender-initiated versus receiver-initiated protocols, and protocols using techniques like reservation, scheduling, and directional antennas.
Distributed Operation
Synchronization
Hidden Terminals
Exposed terminals
Throughput
Access delay
Fairness
Real-time Traffic support
Resource reservation
Ability to measure resource availability
Capability for power control
Adaptive rate control
Use of directional antennas
This document discusses medium access control (MAC) protocols, which regulate access to a shared wireless medium between nodes. It covers key requirements for MAC protocols including throughput efficiency, fairness, and low overhead. It also describes challenges like the hidden terminal problem, exposed terminal problem, and sources of overhead from collisions, overhearing, and idle listening. Finally, it categorizes common MAC protocols as fixed assignment, demand assignment, and random access and notes additional energy conservation requirements for wireless sensor networks.
This document summarizes several reactive routing protocols for mobile ad hoc networks (MANETs). Reactive protocols create routes only when needed by a source. Dynamic Source Routing uses route requests and replies to find paths, while Temporally-Ordered Routing Algorithm builds and maintains a directed acyclic graph rooted at destinations. Some protocols aim to improve quality of service or support real-time data streams through techniques like bandwidth estimation and mobility prediction. Source Routing with Local Recovery reduces overhead by allowing intermediate nodes to perform local error recovery using route caches when possible.
This document discusses power aware routing protocols for wireless sensor networks. It begins by describing wireless sensor networks and how they are used to monitor environmental conditions. It then classifies routing protocols for sensor networks based on their functioning, node participation style, and network structure. Specific examples are provided for different types of routing protocols, including LEACH, TEEN, APTEEN, SPIN, Rumor Routing, and PEGASIS. Chain-based and clustering routing protocols are also summarized.
Ad hoc wireless networks allow devices to connect and communicate with each other without a centralized access point. Nodes in an ad hoc network relay messages through intermediate hops to reach destinations. Examples include Bluetooth networks and wireless mesh networks. Issues in ad hoc networks include medium access control, routing with mobility and bandwidth constraints, and providing quality of service guarantees.
TIME SYNCHRONIZATION IN WIRELESS SENSOR NETWORKS: A SURVEYijujournal
Time synchronization is a critical piece of infrastructure for any distributed system. Wireless sensor networks have emerged as an important and promising research area in the recent years. Time synchronization is important for many sensor network applications that require very precise mapping of gathered sensor data with the time of the events, for example, in tracking and vehicular surveillance. It also plays an important role in energy conservation in MAC layer protocols. The paper studies different existing methods, protocols, significant time parameters (clock drift, clock speed, synchronization errors, and topologies) to achieve accurate synchronization in a sensor network. The studied Synchronization protocols include conventional time sync protocols (RBS, Timing-sync Protocol for Sensor Networks -TPSN, FTSP), and other application specific
approaches such as all node-based approach, a diffusion-based method and group sync approaches aiming at providing network-wide time. The goal for writing this paper is to study most common existing time synchronization approaches and stress the need of a new class of secure-time synchronization protocol that is scalable, topology independent, fast convergent, energy efficient, less latent and less application dependent in a heterogeneous hostile environment. Our survey provides a valuable framework by which protocol designers can compare new and
existing synchronization protocols from various metric discussed in the paper. So, we are hopeful that this paper will serve a complete one-stop investigation to study the characteristics of existing time synchronization protocols and its implementation mechanism in a Sensor network environment.
The document summarizes key points from an 8th lecture on wireless sensor networks. It discusses various medium access control (MAC) protocols that control when nodes can access a shared wireless medium. These include contention-based protocols like MACA that use RTS/CTS handshaking and schedule-based protocols with fixed or dynamic scheduling. It also describes energy-efficient MAC protocols for low data rate sensor networks like S-MAC, T-MAC, and preamble sampling that increase sleep time to reduce energy use through synchronized sleep schedules or long preambles.
This document discusses routing protocols for ad hoc wireless networks. It begins by outlining some key issues in designing routing protocols for these networks, such as mobility, bandwidth constraints, and frequent topology changes. It then classifies routing protocols as being either table-driven, on-demand, or hybrid approaches. Table-driven protocols maintain consistent, up-to-date routing information through periodic table updates. On-demand protocols only discover routes when needed, to reduce overhead. The document proceeds to describe several examples of these different routing protocol types.
This document discusses routing and multicast protocols at the MAC, routing, and application layers. It describes key modules like transmission, receiving, and neighbor list handling at the MAC layer. At the routing layer, it discusses unicast and multicast routing tables, forwarding, tree construction, and session maintenance. The application layer handles data transmission, multicast session initiation and termination, and route repair. It also compares source tree and shared tree approaches, and soft state and hard state maintenance mechanisms.
Routing protocols for ad hoc wireless networks Divya Tiwari
The document discusses routing protocols for ad hoc wireless networks. It outlines several key challenges for these protocols, including mobility, bandwidth constraints, error-prone shared wireless channels, and hidden/exposed terminal problems. It also categorizes routing protocols based on how routing information is updated (proactively, reactively, or through a hybrid approach), whether they use past or future temporal network information, the type of network topology supported (flat or hierarchical), and how they account for specific resources like power.
Sensor Networks Introduction and ArchitecturePeriyanayagiS
This document provides an overview of sensor networks and wireless sensor network architectures. It begins with an introduction to wireless sensor networks and their components. It then discusses the topics, challenges, and enabling technologies for WSNs. The document outlines the architecture of a sensor node and its goals. It provides examples of WSN applications and discusses sensor network deployment considerations. Finally, it addresses the design challenges, operational challenges, and required mechanisms for WSNs to meet their requirements.
This document summarizes geographical routing in wireless sensor networks. It begins with an introduction to geographic routing protocols, which route packets based on the geographic position of nodes rather than their network addresses. It then discusses several specific geographic routing protocols, including Greedy Perimeter Stateless Routing (GPSR) and Geographical and Energy Aware Routing (GEAR). The document also covers topics like how nodes obtain location information, security issues in geographic routing like the Sybil attack, and concludes that geographic routing can enable scalable and energy-efficient routing in wireless sensor networks.
Lecture 23 27. quality of services in ad hoc wireless networksChandra Meena
The document discusses quality of service (QoS) in mobile ad hoc networks (MANETs). It covers several key topics:
1) The challenges of providing QoS in MANETs due to their dynamic and decentralized nature.
2) Different approaches to QoS classification and provisioning at various network layers. This includes MAC layer solutions like IEEE 802.11e and network layer solutions like QoS-aware routing protocols.
3) Specific QoS routing protocols discussed, including ticket-based, predictive location-based, and trigger-based distributed protocols.
The Dynamic Source Routing protocol (DSR) is a simple and efficient routing protocol designed for use in wireless ad-hoc networks without existing infrastructure. DSR allows networks to self-organize and self-configure. It uses two main mechanisms: route discovery determines the optimal transmission path between nodes, while route maintenance ensures the path stays optimal and loop-free as network conditions change.
Mobile ad hoc networks (MANETs) are formed spontaneously by wireless devices without any preexisting infrastructure. Nodes in a MANET are free to move and dynamically change the network topology. MANETs have applications in military operations, emergency response, education, and home/office use. Key challenges include dynamic topology, limited resources, and lack of centralized management. Media access control protocols address issues like hidden and exposed terminals. Routing protocols can be proactive (table-based) or reactive (on-demand) to find routes between nodes in the changing network.
This document provides an overview of Vehicular Ad-Hoc Networks (VANETs). It discusses how VANETs allow vehicle-to-vehicle and vehicle-to-infrastructure communication using technologies like Dedicated Short Range Communication. It describes the challenges of VANETs including routing delays and security issues. Finally, it outlines some of the safety, convenience and commercial applications that are possible with VANETs such as improved traffic management and navigation services.
Medium Access Control :-
1.Distributed Operation
2.Synchronization
3.Hidden Terminals
4.Exposed terminals
5.Throughput
6.Access delay
7.Fairness
8.Real-time Traffic support
9.Resource reservation
10.Ability to measure resource availability
11.Capability for power control
Adaptive rate control
Use of directional antennas
Advanced computer network lab manual (practicals in Cisco Packet tracer)VrundaBhavsar
Book include how we can execute practical in cisco packet tracer.There are around 18 experiment covered .It contains topology also information about basic elements hub router.how we established
connection using HTTP and FTP protocols Also transferring Gmail and VOIP (Voice over IP) experiment. DHCP experiment included. How we create subnetmask.
Cognitive radio networks allow for secondary users to access unused licensed frequencies, known as spectrum holes. The document discusses the history and introduction of cognitive radio, characteristics including cognitive capability, reconfigurable capability, and self-organized capability. It then covers cognitive radio networks architecture including infrastructure-based, ad-hoc, and mesh architectures. It also discusses security issues, attacks on cognitive networks, applications, cognition techniques, and future research directions such as seamless spectrum handovers and proactive spectrum selection and interference avoidance.
The document discusses security challenges in wireless ad-hoc networks and potential solutions. It outlines that ad-hoc networks have no infrastructure, are self-organizing, and use multi-hop wireless communication. This introduces security vulnerabilities like eavesdropping, fake messages, and dynamic topology changes. The document then covers common attacks, why security is needed, challenges, and proposes solutions like using a trusted third party, secure routing protocols, and packet leashes to address issues like black holes and wormholes.
Directed diffusion for wireless sensor networkingHabibur Rahman
This document summarizes the key ideas of the "Directed Diffusion for Wireless Sensor Networking" paper. It introduces directed diffusion as a data-centric paradigm for wireless sensor networks that is designed for robustness, scalability, and energy efficiency. The core concepts of directed diffusion are interests, data, gradients, and reinforcement, which work together to efficiently route queries to sensor data in the network. Through localized interactions and data aggregation, directed diffusion is shown to significantly reduce energy consumption compared to flooding-based approaches in wireless sensor networks.
The document discusses ad-hoc networks and their key characteristics. It describes several challenges in ad-hoc networks including limited battery power, dynamic network topology, and scalability issues. It also summarizes several ad-hoc network routing protocols (e.g. DSDV, AODV, DSR), addressing both table-driven and on-demand approaches. Additionally, it outlines some ad-hoc MAC protocols like MACA and PAMAS that aim to manage shared wireless medium access.
Wireless local loop (WLL) provides wireless connections for stationary users as an alternative to wired connections. It targets the "last mile" between a neighborhood access point and end users. Key advantages include lower installation costs than wiring due to reduced digging and infrastructure requirements, as well as rapid deployment. WLL systems face challenges around spectrum licensing, maintaining wireline-level service quality, and planning networks to achieve high penetration levels while supporting limited user mobility within coverage areas. Common WLL technologies include cellular, satellite, and fixed wireless access using licensed or unlicensed spectrum.
The document discusses wireless sensor networks and their applications. It describes wireless sensor networks as consisting of individual nodes that can interact with their environment by sensing or controlling physical parameters. It then discusses several applications of wireless sensor networks, including disaster relief, environment monitoring, intelligent buildings, facility management, machine maintenance, agriculture, healthcare, and logistics. Finally, it outlines some key requirements and mechanisms needed to implement wireless sensor networks, including communication, energy efficiency, self-configuration, collaboration, data-centric operation, and exploiting tradeoffs between different needs.
UNIT IV WIRELESS SENSOR NETWORKS (WSNS) AND MAC PROTOCOLS 9 Single node architecture: hardware and software components of a sensor node - WSN Network architecture: typical network architectures-data relaying and aggregation strategies -MAC layer protocols: self-organizing, Hybrid TDMA/FDMA and CSMA based MAC- IEEE 802.15.4.
This document discusses various MAC protocols for ad hoc wireless networks. It begins by outlining key issues in designing MAC protocols for these networks, such as bandwidth efficiency, quality of service support, and the hidden and exposed terminal problems. It then covers classifications of MAC protocols including contention-based, contention-based with reservation mechanisms, and contention-based with scheduling mechanisms. Specific protocols are discussed within each category.
This document discusses routing protocols for ad hoc wireless networks. It begins by outlining some key issues in designing routing protocols for these networks, such as mobility, bandwidth constraints, and frequent topology changes. It then classifies routing protocols as being either table-driven, on-demand, or hybrid approaches. Table-driven protocols maintain consistent, up-to-date routing information through periodic table updates. On-demand protocols only discover routes when needed, to reduce overhead. The document proceeds to describe several examples of these different routing protocol types.
This document discusses routing and multicast protocols at the MAC, routing, and application layers. It describes key modules like transmission, receiving, and neighbor list handling at the MAC layer. At the routing layer, it discusses unicast and multicast routing tables, forwarding, tree construction, and session maintenance. The application layer handles data transmission, multicast session initiation and termination, and route repair. It also compares source tree and shared tree approaches, and soft state and hard state maintenance mechanisms.
Routing protocols for ad hoc wireless networks Divya Tiwari
The document discusses routing protocols for ad hoc wireless networks. It outlines several key challenges for these protocols, including mobility, bandwidth constraints, error-prone shared wireless channels, and hidden/exposed terminal problems. It also categorizes routing protocols based on how routing information is updated (proactively, reactively, or through a hybrid approach), whether they use past or future temporal network information, the type of network topology supported (flat or hierarchical), and how they account for specific resources like power.
Sensor Networks Introduction and ArchitecturePeriyanayagiS
This document provides an overview of sensor networks and wireless sensor network architectures. It begins with an introduction to wireless sensor networks and their components. It then discusses the topics, challenges, and enabling technologies for WSNs. The document outlines the architecture of a sensor node and its goals. It provides examples of WSN applications and discusses sensor network deployment considerations. Finally, it addresses the design challenges, operational challenges, and required mechanisms for WSNs to meet their requirements.
This document summarizes geographical routing in wireless sensor networks. It begins with an introduction to geographic routing protocols, which route packets based on the geographic position of nodes rather than their network addresses. It then discusses several specific geographic routing protocols, including Greedy Perimeter Stateless Routing (GPSR) and Geographical and Energy Aware Routing (GEAR). The document also covers topics like how nodes obtain location information, security issues in geographic routing like the Sybil attack, and concludes that geographic routing can enable scalable and energy-efficient routing in wireless sensor networks.
Lecture 23 27. quality of services in ad hoc wireless networksChandra Meena
The document discusses quality of service (QoS) in mobile ad hoc networks (MANETs). It covers several key topics:
1) The challenges of providing QoS in MANETs due to their dynamic and decentralized nature.
2) Different approaches to QoS classification and provisioning at various network layers. This includes MAC layer solutions like IEEE 802.11e and network layer solutions like QoS-aware routing protocols.
3) Specific QoS routing protocols discussed, including ticket-based, predictive location-based, and trigger-based distributed protocols.
The Dynamic Source Routing protocol (DSR) is a simple and efficient routing protocol designed for use in wireless ad-hoc networks without existing infrastructure. DSR allows networks to self-organize and self-configure. It uses two main mechanisms: route discovery determines the optimal transmission path between nodes, while route maintenance ensures the path stays optimal and loop-free as network conditions change.
Mobile ad hoc networks (MANETs) are formed spontaneously by wireless devices without any preexisting infrastructure. Nodes in a MANET are free to move and dynamically change the network topology. MANETs have applications in military operations, emergency response, education, and home/office use. Key challenges include dynamic topology, limited resources, and lack of centralized management. Media access control protocols address issues like hidden and exposed terminals. Routing protocols can be proactive (table-based) or reactive (on-demand) to find routes between nodes in the changing network.
This document provides an overview of Vehicular Ad-Hoc Networks (VANETs). It discusses how VANETs allow vehicle-to-vehicle and vehicle-to-infrastructure communication using technologies like Dedicated Short Range Communication. It describes the challenges of VANETs including routing delays and security issues. Finally, it outlines some of the safety, convenience and commercial applications that are possible with VANETs such as improved traffic management and navigation services.
Medium Access Control :-
1.Distributed Operation
2.Synchronization
3.Hidden Terminals
4.Exposed terminals
5.Throughput
6.Access delay
7.Fairness
8.Real-time Traffic support
9.Resource reservation
10.Ability to measure resource availability
11.Capability for power control
Adaptive rate control
Use of directional antennas
Advanced computer network lab manual (practicals in Cisco Packet tracer)VrundaBhavsar
Book include how we can execute practical in cisco packet tracer.There are around 18 experiment covered .It contains topology also information about basic elements hub router.how we established
connection using HTTP and FTP protocols Also transferring Gmail and VOIP (Voice over IP) experiment. DHCP experiment included. How we create subnetmask.
Cognitive radio networks allow for secondary users to access unused licensed frequencies, known as spectrum holes. The document discusses the history and introduction of cognitive radio, characteristics including cognitive capability, reconfigurable capability, and self-organized capability. It then covers cognitive radio networks architecture including infrastructure-based, ad-hoc, and mesh architectures. It also discusses security issues, attacks on cognitive networks, applications, cognition techniques, and future research directions such as seamless spectrum handovers and proactive spectrum selection and interference avoidance.
The document discusses security challenges in wireless ad-hoc networks and potential solutions. It outlines that ad-hoc networks have no infrastructure, are self-organizing, and use multi-hop wireless communication. This introduces security vulnerabilities like eavesdropping, fake messages, and dynamic topology changes. The document then covers common attacks, why security is needed, challenges, and proposes solutions like using a trusted third party, secure routing protocols, and packet leashes to address issues like black holes and wormholes.
Directed diffusion for wireless sensor networkingHabibur Rahman
This document summarizes the key ideas of the "Directed Diffusion for Wireless Sensor Networking" paper. It introduces directed diffusion as a data-centric paradigm for wireless sensor networks that is designed for robustness, scalability, and energy efficiency. The core concepts of directed diffusion are interests, data, gradients, and reinforcement, which work together to efficiently route queries to sensor data in the network. Through localized interactions and data aggregation, directed diffusion is shown to significantly reduce energy consumption compared to flooding-based approaches in wireless sensor networks.
The document discusses ad-hoc networks and their key characteristics. It describes several challenges in ad-hoc networks including limited battery power, dynamic network topology, and scalability issues. It also summarizes several ad-hoc network routing protocols (e.g. DSDV, AODV, DSR), addressing both table-driven and on-demand approaches. Additionally, it outlines some ad-hoc MAC protocols like MACA and PAMAS that aim to manage shared wireless medium access.
Wireless local loop (WLL) provides wireless connections for stationary users as an alternative to wired connections. It targets the "last mile" between a neighborhood access point and end users. Key advantages include lower installation costs than wiring due to reduced digging and infrastructure requirements, as well as rapid deployment. WLL systems face challenges around spectrum licensing, maintaining wireline-level service quality, and planning networks to achieve high penetration levels while supporting limited user mobility within coverage areas. Common WLL technologies include cellular, satellite, and fixed wireless access using licensed or unlicensed spectrum.
The document discusses wireless sensor networks and their applications. It describes wireless sensor networks as consisting of individual nodes that can interact with their environment by sensing or controlling physical parameters. It then discusses several applications of wireless sensor networks, including disaster relief, environment monitoring, intelligent buildings, facility management, machine maintenance, agriculture, healthcare, and logistics. Finally, it outlines some key requirements and mechanisms needed to implement wireless sensor networks, including communication, energy efficiency, self-configuration, collaboration, data-centric operation, and exploiting tradeoffs between different needs.
UNIT IV WIRELESS SENSOR NETWORKS (WSNS) AND MAC PROTOCOLS 9 Single node architecture: hardware and software components of a sensor node - WSN Network architecture: typical network architectures-data relaying and aggregation strategies -MAC layer protocols: self-organizing, Hybrid TDMA/FDMA and CSMA based MAC- IEEE 802.15.4.
This document discusses various MAC protocols for ad hoc wireless networks. It begins by outlining key issues in designing MAC protocols for these networks, such as bandwidth efficiency, quality of service support, and the hidden and exposed terminal problems. It then covers classifications of MAC protocols including contention-based, contention-based with reservation mechanisms, and contention-based with scheduling mechanisms. Specific protocols are discussed within each category.
The document discusses several MAC protocols for ad hoc networks including MACA, MACAW, and PAMAS. MACA uses RTS and CTS packets to avoid collisions but does not provide ACK. MACAW is a revision of MACA that includes ACK. It significantly increases throughput but does not fully solve hidden and exposed terminal problems. PAMAS uses a separate signaling channel for RTS-CTS and a data channel. It allows nodes to power down transceivers when not transmitting to save energy.
The document discusses wireless sensor networks and describes their key characteristics. It notes that wireless sensor networks consist of low-power smart sensor nodes distributed over a large field to enable wireless sensing and data networking. The sensor nodes contain sensors, processors, memory, and radios. Wireless sensor networks can be either unstructured with dense node distribution or structured with few scattered nodes.
This document discusses various MAC protocols for ad hoc wireless networks. It begins by outlining the key issues in designing such protocols, including bandwidth efficiency, quality of service support, and addressing hidden and exposed terminal problems. It then classifies MAC protocols into contention-based, contention-based with reservation, and contention-based with scheduling categories. Several examples of protocols are described for each category. The document provides an overview of the operation and key aspects of many MAC protocols proposed for ad hoc wireless networks.
This document discusses and compares various routing protocols for mobile ad hoc networks (MANETs). It covers both topology-based approaches that rely on information about existing links, as well as position-based approaches where nodes determine their own position. Specific protocols discussed in detail include proactive protocols like Destination-Sequenced Distance-Vector (DSDV) and reactive protocols like Dynamic Source Routing (DSR). Hybrid protocols like Zone Routing Protocol (ZRP) that combine proactive and reactive approaches are also examined. The document provides illustrations and comparisons of the routing mechanisms and characteristics of these important MANET routing protocols.
This document discusses a simulation of advanced networking using the GloMoSim simulator. It begins with an introduction by Dr. A. Kathirvel, a professor and head of the department of information technology. The document then covers topics like ad hoc wireless networks, research issues in mobile ad hoc networks, ad hoc wireless internet, and concludes with an outline of the simulator session.
This document discusses green computing and e-waste. It defines green computing as environmentally responsible use of computers and related hardware. Issues covered include high energy usage of computers and printers, toxic materials in electronics, and growing problem of improper e-waste disposal. Solutions proposed are buying Energy Star certified hardware, recycling electronics, and developing more environmentally friendly technologies. The document advocates reducing waste through reuse, repair and longer product lifecycles.
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 document discusses fundamentals and link layer concepts in computer networks including:
- Network requirements, layering, protocols, and Internet architecture
- Link layer services such as framing, error detection, and flow control
- Performance metrics including bandwidth, latency, and the relationship between delay and bandwidth
- Common communication patterns like client-server and examples of TCP and UDP socket programming in C
The document summarizes key topics related to transport layer protocols:
- It describes the services provided by the transport layer, including addressing, connection establishment and release, flow control, and multiplexing.
- It provides details on common transport protocols like TCP and UDP, including their packet headers, connection management, congestion control, and performance issues at high speeds.
- It also presents an example transport protocol and uses finite state machines to model its operation and connection management.
The document describes a delay-tolerant networking (DTN) architecture that can address challenges in networks that may lack continuous connectivity. It proposes an overlay network that uses messages as the primary data unit and can operate across disconnected regions. Key aspects include name-based routing, custody transfer for reliability, application interfaces designed for asynchronous communication, and security mechanisms. The goal is to provide interoperability across heterogeneous networks in extreme environments.
VTU 8TH SEM CSE ADHOC NETWORKS SOLVED PAPERS OF JUNE-2014 DEC-14 & JUNE-2015vtunotesbysree
The document discusses solved papers from past exams on ad hoc networks. It includes answers to multiple choice and descriptive questions covering topics such as wireless mesh networks, hybrid wireless networks, issues in designing ad hoc wireless internet, MAC protocol design considerations including QoS and hidden node problems, and routing protocols for ad hoc networks including CGSR and ZRP. Diagrams and detailed explanations are provided for many of the concepts and protocols discussed.
UNIT I INTRODUCTION 7
Examples of Distributed Systems–Trends in Distributed Systems – Focus on resource sharing – Challenges. Case study: World Wide Web.
UNIT II COMMUNICATION IN DISTRIBUTED SYSTEM 10
System Model – Inter process Communication – the API for internet protocols – External data representation and Multicast communication. Network virtualization: Overlay networks. Case study: MPI Remote Method Invocation And Objects: Remote Invocation – Introduction – Request-reply protocols – Remote procedure call – Remote method invocation. Case study: Java RMI – Group communication – Publish-subscribe systems – Message queues – Shared memory approaches – Distributed objects – Case study: Enterprise Java Beans -from objects to components.
Mobile Device Operating Systems – Special Constrains & Requirements – Commercial Mobile Operating Systems – Software Development Kit: iOS, Android, BlackBerry, Windows Phone – M-Commerce – Structure – Pros & Cons – Mobile Payment System – Security Issues.
The document discusses MAC protocols for wireless sensor networks. It begins by outlining issues in designing MAC protocols for ad-hoc wireless networks, such as bandwidth efficiency, quality of service support, synchronization, and the error-prone shared wireless medium. It then describes the design goals of MAC protocols. The document classifies MAC protocols into three categories: contention-based protocols, contention-based protocols with reservation mechanisms, and contention-based protocols with scheduling mechanisms. Several examples are provided for each category, including MACA, FAMA, and RTMAC protocols.
This document discusses various MAC protocols for ad hoc wireless networks. It begins by outlining key issues in designing MAC protocols for these networks, such as bandwidth efficiency, quality of service support, and the hidden and exposed terminal problems. It then covers classifications of MAC protocols including contention-based, contention-based with reservation mechanisms, and contention-based with scheduling mechanisms. Specific protocols are discussed within each category.
This document discusses MAC protocols for ad-hoc wireless networks. It begins by outlining key issues in designing these protocols, such as bandwidth efficiency, quality of service support, and the hidden/exposed terminal problems. It then describes the classifications of MAC protocols, including contention-based, contention-based with reservation, and contention-based with scheduling mechanisms. Several example protocols are discussed for each classification, including how they address the issues and provide distributed channel access in ad-hoc networks.
This document discusses MAC protocols for ad hoc wireless networks. It begins by outlining key issues in designing MAC protocols, such as bandwidth efficiency, quality of service support, and addressing hidden and exposed terminal problems. It then classifies MAC protocols into contention-based, contention-based with reservation mechanisms, and contention-based with scheduling mechanisms. Several example protocols are described for each category, including how they address the issues outlined earlier in the document.
Lecture 7 8 ad hoc wireless media access protocolsChandra Meena
1) The document discusses issues with media access control (MAC) protocols in ad hoc wireless networks, including problems like hidden terminals and exposed nodes.
2) It classifies MAC protocols as synchronous, asynchronous, receiver-initiated, or sender-initiated. The RTS-CTS handshake is presented as a solution to the hidden terminal problem.
3) However, the RTS-CTS approach has shortcomings like collisions when RTS and CTS messages are sent by different nodes or when multiple CTS messages are granted. Solutions to the exposed node problem are also discussed.
A New MultiChannel MAC Protocol With On-Demand Channel Assignment For Multi-H...Wendy Hager
The document presents a multi-channel MAC protocol called SM that uses static channel assignment. Each mobile host is assigned a single channel and uses that channel for all transmissions following the IEEE 802.11 standard. However, several issues are identified when directly applying a single-channel protocol to a multi-channel system, including missing control packets, exposed terminals, and channel deadlocks. To address these issues, the document proposes a new dynamic multi-channel MAC protocol called DCA that flexibly assigns channels based on demand and requires only two transceivers per host.
The document discusses MAC protocols for ad hoc networks. It begins by outlining problems MAC protocols must address, such as bandwidth efficiency, synchronization, and the hidden terminal problem. It then classifies MAC protocols into three categories: contention-based without reservation, contention-based with reservation, and contention-based with scheduling. Several example protocols are described for each category, including how they address issues like bandwidth utilization and collisions. The document also covers MAC protocols that use directional antennas and power control techniques.
The document discusses MAC protocols for ad hoc networks. It begins by outlining problems MAC protocols must address, such as bandwidth efficiency, hidden/exposed terminals, and mobility. It then classifies MAC protocols into contention-based without reservation, contention-based with reservation, and contention-based with scheduling. Examples are provided for each category, including MACA, BTMA, D-PRMA, and DPS. The document also covers MAC protocols that use directional antennas to improve throughput and reuse.
The document compares MAC protocols in wired and wireless systems. In wired systems, protocols like Ethernet use CSMA/CD, allowing nodes to detect collisions. In wireless systems, hidden and exposed terminal problems occur, requiring protocols like MACA, MACAW, and 802.11 CSMA/CA to use RTS/CTS handshaking or polling to avoid interference between transmissions. The IEEE 802.11 standard defines distributed and point coordination function MAC methods for wireless LANs.
This document summarizes research on medium access control (MAC) layer protocols for ad-hoc networks. It begins with an introduction to ad-hoc networks and their key properties. It then discusses important issues at the MAC layer for these dynamic networks, including limited bandwidth, errors, and changing topologies. Several MAC protocol classifications and examples are provided, such as power-aware, multiple channel, and quality of service protocols. The document concludes by discussing future research directions for addressing open problems at the MAC layer in ad-hoc networks.
The document summarizes MAC protocols for wireless mesh networks. It begins with an introduction to wireless mesh network architectures and important definitions. It then discusses single channel MAC protocols like S-MAC, T-MAC, and a new TDMA-based protocol. It also covers multi-channel MAC protocols classifications and examples like CC-MMAC and SSCH MAC. The document provides detailed explanations of the mechanisms and concepts behind various single and multi-channel MAC protocols.
The document discusses broadcast networks and medium access control (MAC) protocols. It introduces the concepts of broadcast networks, where a single shared medium allows all connected devices to receive messages. This leads to potential conflicts when multiple devices try to transmit simultaneously. MAC protocols are needed to coordinate transmissions and resolve conflicts. Common MAC protocols discussed include ALOHA, CSMA, CSMA/CD (Ethernet), and token passing (Token Ring). LAN standards like IEEE 802.3 that define MAC sublayer functions for CSMA/CD networks are also summarized briefly.
The document discusses wireless and mobile computing, specifically focusing on MAC (media access control) layer protocols for wireless networks. It provides an overview of MAC layer issues for wireless networks, classifications of MAC protocols (including contention-based, reservation-based, and scheduling-based), and design goals of MAC protocols such as distributed operation, quality of service support, bandwidth efficiency, and minimizing hidden and exposed terminal problems.
Simulation based Evaluation of a Simple Channel Distribution Scheme for MANETsIOSR Journals
This document presents a proposed multi-channel distribution scheme for mobile ad hoc networks (MANETs) and evaluates it through simulation. The proposed scheme assigns channels to nodes based on their node IDs to avoid control overhead from time synchronization. While neighboring nodes on the same channel is possible, the probability is low given random node distribution. The proposed scheme is compared to a single-channel scheme in ns-2 simulations. Results show the proposed technique has better performance.
This document discusses several key performance metrics for wireless MAC protocols: throughput, delay, fairness, and energy efficiency. It then summarizes several MAC protocols and how they aim to improve these metrics, including MACA-BI, MARCH, and MILD algorithm in MACAW which aims to increase fairness. Power save mechanisms and power control MAC protocols are also covered as approaches to improve energy efficiency. Finally, the potential benefits of using directional antennas with MAC protocols are discussed.
Distributed contention based mac protocol for cognitive radioIffat Anjum
Introduction
System Model
DC-MAC Design
Network Initialization
DC-MAC Working
Data Transfer on Home Channel
Data Transfer on a Foreign Channel
Performance Analysis
Conclusion
References
This document discusses wireless medium access control (MAC) protocols. It provides an overview of MAC responsibilities and categorizes MAC protocols as contention-free, contention-based, or hybrid. It describes several MAC protocols including Carrier Sense Multiple Access (CSMA), MACA, IEEE 802.11, and IEEE 802.15.4/ZigBee. It discusses key characteristics for MAC protocols in wireless sensor networks including energy efficiency, scalability, adaptability, latency, reliability, and contrasts them with traditional network priorities like fairness.
Control Area Network (CAN) Bus
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This document discusses parallel processors and multicore architecture. It begins with an introduction to parallel processors, including concurrent access to memory and cache coherency. It then discusses multicore architecture, where a single physical processor contains the logic of two or more cores. This allows increasing processing power while keeping clock speeds and power consumption lower than would be needed for a single high-speed core. Cache coherence methods like write-through, write-back, and directory-based approaches are also summarized for maintaining consistency across cores' caches when accessing shared memory.
MODULE II Control unit, I/O systems and Pipelining 15 Hours
CPU control unit design: Hardwired and micro-programmed design approaches, Peripheral
devices and their characteristics: Input-output subsystems, I/O device interface, I/O transfersprogram controlled, interrupt driven and DMA, privileged and non-privileged instructions, software
interrupts and exceptions. Programs and processes-role of interrupts in process state transitions,
I/O device interfaces - SCII, USB. Basic concepts of pipelining, throughput and speedup, pipeline
hazards.
Functional Blocks of a Computer: Functional blocks and its operations. Instruction set architecture of a CPU - registers, instruction execution cycle, Data path, RTL interpretation of
instructions, instruction set. Performance metrics. Addressing modes. Data Representation:
Signed number representation, fixed and floating point representations, character representation.
Computer arithmetic - integer addition and subtraction, ripple carry adder, carry look-ahead
adder, etc. multiplication - shift-and add, Booth multiplier, carry save multiplier, etc. Division
restoring and non-restoring techniques, floating point arithmetic.
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Human: Thank you, that was a great high level summary of the key topics covered in the document in 3 sentences or less as requested.
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Introduction - Communication between distributed objects - Remote procedure call - Events and notifications - case study - Operating system support - introduction - operating system layer - protection - process and threads - communication and invocation - architecture - Introduction to DFS - File service architecture - Sun network file system - Andrew file system - Enhancements and future developments.
Module 2 - Distributed Objects and File Systems
Introduction - Communication between distributed objects - Remote procedure call - Events and notifications - case study - Operating system support - introduction - operating system layer - protection - process and threads - communication and invocation - architecture - Introduction to DFS - File service architecture - Sun network file system - Andrew file system - Enhancements and future developments.
Module I
Introduction to Distributed systems - Examples of distributed systems, resource sharing and the web, challenges - System model - introduction - architectural models - fundamental models - Introduction to inter-process communications - API for Internet protocol - external data.
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IP security overview-IP security policy-Encapsulating Security payload-intruders-intrusion detectionvirus/worms-countermeasure-need for firewalls-firewall characteristics-types of fire
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Module 1: Introduction to Cryptography and Symmetric Key Ciphers
Computer Security Concepts - OSI Security Architecture -Security Attacks - Services, Mechanisms -
Symmetric Cipher Model - Traditional Block Cipher Structure - The Data Encryption Standard -The Strength of DES - Advanced Encryption Standard.
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Advanced Networking
Security problems with internet architecture, Introduction to Software defined networking, Working of SDN, SDN in data centre, SDN applications, Data centre networking, IoT.
Module 6: Standards for Information Security Management
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Key contributions of this research include the implementation of a context- aware conversational model that can maintain coherent dialogue over extended interactions. The chatbot's performance is evaluated through both automated metrics and user studies, demonstrating its effectiveness in various applications such as customer service, mental health support, and educational assistance. Additionally, ethical considerations and potential biases in chatbot responses are examined to ensure the responsible deployment of this technology.
The findings of this thesis highlight the potential of intelligent chatbots to enhance user experience and provide valuable insights for future developments in conversational AI.
Response & Safe AI at Summer School of AI at IIITHIIIT Hyderabad
Talk covering Guardrails , Jailbreak, What is an alignment problem? RLHF, EU AI Act, Machine & Graph unlearning, Bias, Inconsistency, Probing, Interpretability, Bias
Enhancing Security with Multi-Factor Authentication in Privileged Access Mana...Bert Blevins
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Privileged Access Management encompasses the methods, procedures, and tools used to regulate and monitor access to privileged accounts within an organization. Users with privileged accounts possess elevated rights, enabling them to perform essential operations such as system configuration, access to sensitive data, and management of network infrastructure. However, these elevated privileges also pose a significant security risk if they fall into the wrong hands.
By combining MFA with PAM, organizations can significantly enhance their security posture. MFA adds an additional layer of verification, ensuring that even if privileged account credentials are compromised, unauthorized access can be thwarted. This integration of MFA and PAM provides a robust defense mechanism, protecting critical systems and sensitive data from increasingly sophisticated cyber threats.
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A vernier caliper is a precision instrument used to measure dimensions with high accuracy. It can measure internal and external dimensions, as well as depths.
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Vernier Caliper and How to use Vernier Caliper.ppsx
CS6003 ADHOC & SENSOR NETWORKS
1. CS6003 ADHOC & SENSOR
NETWORKS
UNIT – II
Dr.A.Kathirvel, Professor and Head, Dept of CSE
Anand Institute of Higher Technology, Chennai
2. Unit - II
MAC PROTOCOLS FOR AD HOC WIRELESS
NETWORKS
Issues in designing a MAC Protocol- Classification of MAC
Protocols- Contention based protocols- Contention based
protocols with Reservation Mechanisms- Contention
based protocols with Scheduling Mechanisms – Multi
channel MAC-IEEE 802.11
2
3. 3
Issues
The main issues need to be addressed while designing a
MAC protocol for ad hoc wireless networks:
Bandwidth efficiency is defined at the ratio of the
bandwidth used for actual data transmission to the total
available bandwidth. The MAC protocol for ad-hoc
networks should maximize it.
Quality of service support is essential for time-
critical applications. The MAC protocol for ad-hoc
networks should consider the constraint of ad-hoc
networks.
Synchronization can be achieved by exchange of
control packets.
4. 4
Issues
The main issues need to be addressed while designing a MAC protocol for ad
hoc wireless networks:
Hidden and exposed terminal problems:
Hidden nodes:
Hidden stations: Carrier sensing may fail to detect another station.
For example, A and D.
Fading: The strength of radio signals diminished rapidly with the
distance from the transmitter. For example, A and C.
Exposed nodes:
Exposed stations: B is sending to A. C can detect it. C might want to
send to E but conclude it cannot transmit because C hears B.
Collision masking: The local signal might drown out the remote
transmission.
Error-Prone Shared Broadcast Channel
Distributed Nature/Lack of Central Coordination
Mobility of Nodes: Nodes are mobile most of the time.
5. A)THE HIDDEN STATION PROBLEM. (B) THE EXPOSED STATION PROBLEM.
Hidden & exposed terminal problem
5
6. 6
The Hidden Terminal Problem
Wireless stations have transmission ranges
and not all stations are within radio range of
each other.
Simple CSMA will not work!
C transmits to B.
If A “senses” the channel, it will not hear
C’s transmission and falsely conclude that A
can begin a transmission to B.
7. 7
The Exposed Station Problem
The inverse problem.
B wants to send to C and listens to the
channel.
When B hears A’s transmission, B falsely
assumes that it cannot send to C.
9. 9
Design goals of a MAC Protocol
Design goals of a MAC protocol for ad hoc wireless
networks
The operation of the protocol should be distributed.
The protocol should provide QoS support for real-
time traffic.
The access delay, which refers to the average delay
experienced by any packet to get transmitted, must be
kept low.
The available bandwidth must be utilized efficiently.
The protocol should ensure fair allocation of
bandwidth to nodes.
10. 10
Design goals of a MAC Protocol
Control overhead must be kept as low as possible.
The protocol should minimize the effects of hidden
and exposed terminal problems.
The protocol must be scalable to large networks.
It should have power control mechanisms.
The protocol should have mechanisms for adaptive
data rate control.
It should try to use directional antennas.
The protocol should provide synchronization among
nodes.
11. 11
Classifications of MAC protocols
Ad hoc network MAC protocols can be
classified into three types:
Contention-based protocols
Contention-based protocols with reservation
mechanisms
Contention-based protocols with scheduling
mechanisms
Other MAC protocols
12. 12
Classifications of MAC protocols
MAC Protocols for Ad Hoc
Wireless Networks
Contention-Based
Protocols
Contention-based
protocols with
reservation mechanisms
Other MAC
Protocols
Contention-based
protocols with
scheduling mechanisms
Sender-Initiated
Protocols
Receiver-Initiated
Protocols
Synchronous
Protocols
Asynchronous
Protocols
Single-Channel
Protocols
Multichannel
Protocols
MACAW
FAMA
BTMA
DBTMA
ICSMA
RI-BTMA
MACA-BI
MARCH
D-PRMA
CATA
HRMA
RI-BTMA
MACA-BI
MARCH
SRMA/PA
FPRP
MACA/PR
RTMAC
Directional
Antennas
MMAC
MCSMA
PCM
RBAR
13. 13
Classifications of MAC Protocols
Contention-based protocols
Sender-initiated protocols:
Packet transmissions are initiated by the sender node.
Single-channel sender-initiated protocols: A node that
wins the contention to the channel can make use of the
entire bandwidth.
Multichannel sender-initiated protocols: The available
bandwidth is divided into multiple channels.
Receiver-initiated protocols:
The receiver node initiates the contention resolution
protocol.
14. 14
Classifications of MAC Protocols
Contention-based protocols with reservation
mechanisms
Synchronous protocols
All nodes need to be synchronized. Global
time synchronization is difficult to achieve.
Asynchronous protocols
These protocols use relative time
information for effecting reservations.
15. 15
Classifications of MAC Protocols
Contention-based protocols with scheduling mechanisms
Node scheduling is done in a manner so that all nodes
are treated fairly and no node is starved of bandwidth.
Scheduling-based schemes are also used for enforcing
priorities among flows whose packets are queued at
nodes.
Some scheduling schemes also consider battery
characteristics.
Other protocols are those MAC protocols that do not
strictly fall under the above categories.
16. 16
Contention-based protocols
MACAW: A Media Access Protocol for
Wireless LANs is based on MACA (Multiple
Access Collision Avoidance) Protocol
MACA
When a node wants to transmit a data packet, it first
transmit a RTS (Request To Send) frame.
The receiver node, on receiving the RTS packet, if it
is ready to receive the data packet, transmits a CTS
(Clear to Send) packet.
17. 17
Contention-based protocols
Once the sender receives the CTS packet
without any error, it starts transmitting the data
packet.
If a packet transmitted by a node is lost, the
node uses the binary exponential back-off
(BEB) algorithm to back off a random interval
of time before retrying.
The binary exponential back-off mechanism
used in MACA might starves flows sometimes.
The problem is solved by MACAW.
19. 19
MACA avoids the problem of hidden terminals
A and C want to send to B
A sends RTS first
C waits after receiving CTS from B
MACA examples
A B C
RTS
CTSCTS
20. 20
MACA avoids the problem of exposed
terminals
B wants to send to A, C to another terminal
now C does not have to wait for it cannot
receive CTS from A
MACA examples
A B C
RTS
CTS
RTS
21. 21
MACAW
Variants of this method can be found in IEEE 802.11
as DFWMAC (Distributed Foundation Wireless
MAC),
MACAW (MACA for Wireless) is a revision of
MACA.
The sender senses the carrier to see and transmits a
RTS (Request To Send) frame if no nearby station
transmits a RTS.
The receiver replies with a CTS (Clear To Send)
frame.
22. 22
MACAW
Neighbors
see CTS, then keep quiet.
see RTS but not CTS, then keep quiet until the CTS is back
to the sender.
The receiver sends an ACK when receiving an
frame.
Neighbors keep silent until see ACK.
Collisions
There is no collision detection.
The senders know collision when they don’t receive CTS.
They each wait for the exponential backoff time.
23. 23
MACA variant:DFWMAC in 802.11
idle
wait for the
right to send
wait for ACK
sender receiver
packet ready to send; RTS
time-out;
RTS
CTS; data
ACK
RxBusy
idle
wait for
data
RTS; RxBusy
RTS;
CTS
data;
ACK
time-out
data;
NAK
ACK: positive acknowledgement
NAK: negative acknowledgement
RxBusy: receiver busy
time-out
NAK;
RTS
24. 24
Contention-based protocols
Floor acquisition Multiple Access Protocols
(FAMA)
Based on a channel access discipline which consists
of a carrier-sensing operation and a collision-
avoidance dialog between the sender and the intended
receiver of a packet.
Floor acquisition refers to the process of gaining
control of the channel.
At any time only one node is assigned to use the
channel.
25. 25
Contention-based protocols
Carrier-sensing by the sender, followed by the RTS-
CTS control packet exchange, enables the protocol to
perform as efficiently as MACA.
Two variations of FAMA
RTS-CTS exchange with no carrier-sensing uses the
ALOHA protocol for transmitting RTS packets.
RTS-CTS exchange with non-persistent carrier-
sensing uses non-persistent CSMA for the same
purpose.
26. 26
Contention-based protocols
Busy Tone Multiple Access Protocols (BTMA)
The transmission channel is split into two:
a data channel for data packet transmissions
a control channel used to transmit the busy tone signal
When a node is ready for transmission, it senses the channel to
check whether the busy tone is active.
If not, it turns on the busy tone signal and starts data
transmissions
Otherwise, it reschedules the packet for transmission after
some random rescheduling delay.
Any other node which senses the carrier on the incoming
data channel also transmits the busy tone signal on the
control channel, thus, prevent two neighboring nodes from
transmitting at the same time.
27. 27
Contention-based protocols
Dual Busy Tone Multiple Access Protocol
(DBTMAP) is an extension of the BTMA
scheme.
a data channel for data packet transmissions
a control channel used for control packet
transmissions (RTS and CTS packets) and also
for transmitting the busy tones.
28. 28
Contention-based protocols
Receiver-Initiated Busy Tone Multiple Access Protocol
(RI-BTMA)
The transmission channel is split into two:
a data channel for data packet transmissions
a control channel used for transmitting the busy
tone signal
A node can transmit on the data channel only if it
finds the busy tone to be absent on the control
channel.
The data packet is divided into two portions: a
preamble and the actual data packet.
29. 29
Contention-based protocols
MACA-By Invitation (MACA-BI) is a receiver-
initiated MAC protocol.
By eliminating the need for the RTS packet it
reduces the number of control packets used in
the MACA protocol which uses the three-way
handshake mechanism.
Media Access with Reduced Handshake
(MARCH) is a receiver-initiated protocol.
30. 30
Contention-based Protocols with
Reservation Mechanisms
Contention-based Protocols with Reservation
Mechanisms
Contention occurs during the resource (bandwidth)
reservation phase.
Once the bandwidth is reserved, the node gets
exclusive access to the reserved bandwidth.
QoS support can be provided for real-time traffic.
31. 31
Contention-based Protocols with
Reservation Mechanisms
Distributed packet reservation multiple access protocol
(D-PRMA)
It extends the centralized packet reservation multiple
access (PRMA) scheme into a distributed scheme that
can be used in ad hoc wireless networks.
PRMA was designed in a wireless LAN with a base
station.
D-PRMA extends PRMA protocol in a wireless
LAN.
D-PRMA is a TDMA-based scheme. The channel is
divided into fixed- and equal-sized frames along the
time axis.
32. 32
Access method DAMA: Reservation-
TDMA
Reservation Time Division Multiple Access
every frame consists of N mini-slots and x data-slots
every station has its own mini-slot and can reserve up to k
data-slots using this mini-slot (i.e. x = N * k).
other stations can send data in unused data-slots according to a
round-robin sending scheme (best-effort traffic)
N mini-slots N * k data-slots
reservations
for data-slots
other stations can use free data-slots
based on a round-robin scheme
e.g. N=6, k=2
33. 33
Distributed Packet Reservation
Multiple Access Protocol (D-PRMA)
Implicit reservation (PRMA - Packet
Reservation Multiple Access)
frame1
frame2
frame3
frame4
frame5
1 2 3 4 5 6 7 8 time-slot
collision at
reservation
attempts
A C D A B A F
A C A B A
A B A F
A B A F D
A C E E B A F D
t
ACDABA-F
ACDABA-F
AC-ABAF-
A---BAFD
ACEEBAFD
reservation
33
34. Distributed Packet Reservation
Multiple Access Protocol (D-PRMA)
a certain number of slots form a frame, frames are
repeated
stations compete for empty slots according to the
slotted aloha principle
once a station reserves a slot successfully, this slot is
automatically assigned to this station in all following
frames as long as the station has data to send
competition for this slots starts again as soon as the
slot was empty in the last frame
34
35. 35
Contention-based protocols
with Reservation Mechanisms
Collision avoidance time allocation protocol (CATA)
based on dynamic topology-dependent transmission
scheduling
Nodes contend for and reserve time slots by means
of a distributed reservation and handshake
mechanism.
Support broadcast, unicast, and multicast
transmissions.
36. 36
Contention-based protocols
with Reservation Mechanisms
The operation is based on two basic principles:
The receiver(s) of a flow must inform the potential source
nodes about the reserved slot on which it is currently
receiving packets. The source node must inform the
potential destination node(s) about interferences in the
slot.
Usage of negative acknowledgements for reservation
requests, and control packet transmissions at the beginning
of each slot, for distributing slot reservation information to
senders of broadcast or multicast sessions.
37. 37
Contention-based protocols
with Reservation Mechanisms
Hop reservation multiple access protocol (HRMA)
a multichannel MAC protocol which is based on
half-duplex, very slow frequency-hopping spread
spectrum (FHSS) radios
uses a reservation and handshake mechanism to
enable a pair of communicating nodes to reserve a
frequency hop, thereby guaranteeing collision-free
data transmission.
can be viewed as a time slot reservation protocol
where each time slot is assigned a separate frequency
channel.
38. 38
Contention-based protocols
with Reservation Mechanisms
Soft reservation multiple access with priority
assignment (SRMA/PA)
Developed with the main objective of
supporting integrated services of real-time and
non-real-time application in ad hoc networks,
at the same time maximizing the statistical
multiplexing gain.
Nodes use a collision-avoidance handshake
mechanism and a soft reservation mechanism.
39. 39
Five-Phase Reservation Protocol (FPRP)
a single-channel time division multiple access
(TDMA)-based broadcast scheduling protocol.
Nodes uses a contention mechanism in order to
acquire time slots.
The protocol assumes the availability of global time
at all nodes.
The reservation takes five phases: reservation,
collision report, reservation confirmation, reservation
acknowledgement, and packing and elimination
phase.
Contention-based protocols
with Reservation Mechanisms
40. 40
MACA with Piggy-Backed Reservation (MACA/PR)
Provide real-time traffic support in multi-hop
wireless networks
Based on the MACAW protocol with non-persistent
CSMA
The main components of MACA/PR are:
A MAC protocol
A reservation protocol
A QoS routing protocol
Contention-based protocols
with Reservation Mechanisms
41. 41
Real-Time Medium Access Control Protocol (RTMAC)
Provides a bandwidth reservation mechanism for
supporting real-time traffic in ad hoc wireless networks
RTMAC has two components
A MAC layer protocol is a real-time extension of the
IEEE 802.11 DCF.
A medium-access protocol for best-effort traffic
A reservation protocol for real-time traffic
A QoS routing protocol is responsible for end-to-end
reservation and release of bandwidth resources.
Contention-based protocols
with Reservation Mechanisms
42. 42
Protocols in this category focus on packet
scheduling at the nodes and transmission
scheduling of the nodes.
The factors that affects scheduling decisions
Delay targets of packets
Traffic load at nodes
Battery power
Contention-based protocols
with Scheduling Mechanisms
43. 43
Distributed priority scheduling and medium
access in Ad Hoc Networks present two
mechanisms for providing quality of service
(QoS)
Distributed priority scheduling (DPS) – piggy-backs
the priority tag of a node’s current and head-of-line
packets o the control and data packets
Multi-hop coordination – extends the DPS scheme to
carry out scheduling over multi-hop paths.
Contention-based protocols
with Scheduling Mechanisms
44. 44
Distributed Wireless Ordering Protocol (DWOP)
A media access scheme along with a scheduling
mechanism
Based on the distributed priority scheduling scheme
Contention-based protocols
with Scheduling Mechanisms
45. 45
Distributed Laxity-based Priority Scheduling (DLPS)
Scheme
Scheduling decisions are made based on
The states of neighboring nodes and feed back from
destination nodes regarding packet losses
Packets are recorded based on their uniform laxity
budgets (ULBs) and the packet delivery ratios of the
flows. The laxity of a packet is the time remaining
before its deadline.
Contention-based protocols
with Scheduling Mechanisms
46. 46
MAC protocols that use directional antennas have
several advantages:
Reduce signal interference
Increase in the system throughput
Improved channel reuse
MAC protocol using directional antennas
Make use of an RTS/CTS exchange mechanism
Use directional antennas for transmitting and
receiving data packets
MAC Protocols that use directional
Antennas
47. 47
Directional Busy Tone-based MAC Protocol (DBTMA)
It uses directional antennas for transmitting the RTS,
CTS, data frames, and the busy tones.
Directional MAC Protocols for Ad Hoc Wireless
Networks
DMAC-1, a directional antenna is used for
transmitting RTS packets and omni-directional antenna
for CTS packets.
DMAC-1, both directional RTS and omni-directional
RTS transmission are used.
MAC Protocols that use directional
Antennas
48. 48
Other MAC Protocols
Multi-channel MAC Protocol (MMAC)
Multiple channels for data transmission
There is no dedicated control channel.
Based on channel usage channels can be classified into three types: high
preference channel (HIGH), medium preference channel (MID), low
preference channel (LOW)
Multi-channel CSMA MAC Protocol (MCSMA)
The available bandwidth is divided into several channels
Power Control MAC Protocol (PCM) for Ad Hoc Networks
Allows nodes to vary their transmission power levels on a per-packet basis
Receiver-based Autorate Protocol (RBAR)
Use a rate adaptation approach
Interleaved Carrier-Sense Multiple Access Protocol (ICSMA)
The available bandwidth is split into tow equal channels
The handshaking process is interleaved between the two channels.
49. What is IEEE 802.11?
Standard for wireless local area networks (wireless
LANs) developed in 1990 by IEEE
Intended for home or office use (primarily indoor)
802.11 standard describes the MAC layer, while
other substandards (802.11a, 802.11b) describe the
physical layer
Wireless version of the Ethernet (802.3) standard
49
50. Network Setup
Ethernet
MT
AP AP AP
MT MT
Basic Network Setup is Cellular
Mobile Terminals (MT) connect with Access Points (AP)
Standard also supports ad-hoc networking where MT’s talk directly to MT’s
50
52. Media Access Control - Ethernet
CSMA/CD (Carrier Sense Multiple Access with Collision
Detection)
If media is sensed idle, transmit
If media is sensed busy, wait until idle and then transmit
immediately
Collisions can occur if more than one user transmits at the same
time
If a collision is detected, stop transmitting.
Reschedule transmission according to exponential backoff
Desktop System Desktop System Desktop System
Ethernet
52
53. Media Access Control (802.11)
Would like to use CSMA
Nice for bursty traffic
Make for seamless replacement of wired LANs with
wireless LANS
Use CSMA, but can’t use CD
PT/PR ratio is too high
Don’t want to waste energy on mobiles
Use Collision Avoidance instead
Don’t always start transmitting immediately after
someone else
53
54. CSMA/CA Details
SIFS (Short Interframe Space)
DIFS (Distributed Interframe Space)
Packet A ACK
B C
SIFS DIFS
Packet C ACK
SIFS DIFS
Packet B
Scenario:
B and C want to transmit, but A currently has control of medium
B randomly selects 7 slots of backoff, C selects 4 slots
C transmits first, then B
54
55. What is HIPERLAN/2?
European standard developed by ETSI/BRAN
(European Telecommunications Standards
Institute/Broadband Radio Access Networks)
Physical Layer is very similar to 802.11a
(OFDM operating in the 5 GHz spectrum)
Standard based on wireless ATM
(Asynchronous Transfer Mode)
55
56. HIPERLAN/2 MAC
BCH – Miscellaneous header
FCH – Details how the DL and UL phases will be allocated
ACH – Feedback on which resource requests were received
RCH – Random access resource request
56
58. IEEE 802.11
IEEE 802.11 is a widely accepted standard in the United
States for wireless LANs
Primarily a “cellular” random access scheme with
provisions for ad hoc networking and contention free
access
802.11b products are available now, but better to wait
for 802.11a products later this year
HIPERLAN/2 is being pushed in Europe
Wireless ATM solution for real-time traffic
Standard reflects the network topology
58