S-MAC is an energy-efficient MAC protocol for wireless sensor networks where nodes follow a listen-sleep cycle. Nodes synchronize their schedules by broadcasting SYNC messages. A node can be a synchronizer that independently chooses a schedule, or a follower that adopts the schedule of its neighbors. Adaptive listening is proposed to reduce latency by allowing nodes to wake up briefly after overhearing transmissions. Later protocols like DW-MAC and AS-MAC use scheduled wake-ups to improve energy efficiency while allowing variable length transmissions. Q-MAC and R-MAC incorporate routing by dynamically adjusting schedules for query and data transmissions between multiple hops to the destination.
Many energy-efficient Receiver Initiated Asynchronous Duty-Cycle MAC protocol for wireless sensor
networks (WSNs) have been proposed. Most nodes suffer from significant performance Degradation for burst traffic,
due to randomly waking up to communicate with each other. The proposed protocol is new receiver initiated
asynchronous duty-cycle MAC protocol for burst traffic . By adaptively adjusting beacon time of the receiver and it
schedules the sender listening time based on scheduled period, by this high energy efficiency and low end-to-end packet
delivery latency for burst traffic is achieved. We have evaluated the performance of MAC through detailed ns- 2
simulation. The simulation results show that this protocol reduce end-to-end packet delivery latency and energy
consumption under various data rates in different topologies compared with RI-MAC.
Keywords— Wireless sensor networks, duty-cycle, receiver-initiated, low latency, energy-efficient
Comparison of TCP congestion control mechanisms Tahoe, Newreno and VegasIOSR Journals
The widely used reliable transport protocol TCP, is an end to end protocol designed for the wireline
networks characterized by negligible random packet losses. This paper represents exploratory study of TCP
congestion control principles and mechanisms. Modern implementations of TCP contain four intertwined
algorithms: slow start, congestion avoidance, fast retransmit, and fast recovery. In addition to the standard
algorithms used in common implementations of TCP, this paper also describes some of the more common
proposals developed by researchers over the years. We also study, through extensive simulations, the
performance characteristics of four representative TCP schemes, namely TCP Tahoe, New Reno and Vegas
under the network conditions of bottleneck link capacities for wired network
Many energy-efficient Receiver Initiated Asynchronous Duty-Cycle MAC protocol for wireless sensor
networks (WSNs) have been proposed. Most nodes suffer from significant performance Degradation for burst traffic,
due to randomly waking up to communicate with each other. The proposed protocol is new receiver initiated
asynchronous duty-cycle MAC protocol for burst traffic . By adaptively adjusting beacon time of the receiver and it
schedules the sender listening time based on scheduled period, by this high energy efficiency and low end-to-end packet
delivery latency for burst traffic is achieved. We have evaluated the performance of MAC through detailed ns- 2
simulation. The simulation results show that this protocol reduce end-to-end packet delivery latency and energy
consumption under various data rates in different topologies compared with RI-MAC.
Keywords— Wireless sensor networks, duty-cycle, receiver-initiated, low latency, energy-efficient
Comparison of TCP congestion control mechanisms Tahoe, Newreno and VegasIOSR Journals
The widely used reliable transport protocol TCP, is an end to end protocol designed for the wireline
networks characterized by negligible random packet losses. This paper represents exploratory study of TCP
congestion control principles and mechanisms. Modern implementations of TCP contain four intertwined
algorithms: slow start, congestion avoidance, fast retransmit, and fast recovery. In addition to the standard
algorithms used in common implementations of TCP, this paper also describes some of the more common
proposals developed by researchers over the years. We also study, through extensive simulations, the
performance characteristics of four representative TCP schemes, namely TCP Tahoe, New Reno and Vegas
under the network conditions of bottleneck link capacities for wired network
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Abstract The data can get lost, reordered or duplicated due to the presence of routers and buffer space over the unreliable channel in the conventional networks. The data link layer deals with frame formation, flow control, error control, and addressing and link management. All such functions will be performed only by data link protocols. The sliding window protocol will detect and correct error if the received data have enough redundant bits or repeat a retransmission of data. The paper shows the working of this duplex protocol of data link network. Keywords: ACK, GOBACK, ARQ, NACK.
Synchronization Pradeep K Sinha
Introduction
Issues in Synchronization
Clock synchronization
Event Ordering
Mutual Exclusion
Deadlock
Election algorithms
Clock Synchronization
How Computer Clocks are Implemented
Drifting of Clocks
Types of Clock Synchronization and issues in them
Clock Synchronization Algorithms
Distributed and Centralized Algorithms
Case Study
Event Ordering
Happened Before Relation
Logical Clocks Concept and Implementation
Mutual Exclusion
Centralized Approach, Distributed Approach, Token Passing Approach
Deadlocks
Election algorithms
Fault tolerant wireless sensor mac protocol for efficient collision avoidancegraphhoc
In sensor networks communication by broadcast methods involves many hazards, especially collision. Several MAC layer protocols have been proposed to resolve the problem of collision namely ARBP, where the best achieved success rate is 90%. We hereby propose a MAC protocol which achieves a greater success rate (Success rate is defined as the percentage of delivered packets at the source reaching the destination successfully) by reducing the number of collisions, but by trading off the average propagation delay of transmission. Our proposed protocols are also shown to be more energy efficient in terms of energy dissipation per message delivery, compared to the currently existing protocol.
This ppt covers different aspects about timing issues and various algorithms involved in having better sync between different systems in a distributed environment
To transmit the data from one node to another, data link layer combines framing, flow control & error control schemes.
We divide the discussion protocols into those that can be used for noiseless(error free) channels and those that can be used for noisy (error creating) channels.
this presentation explains chapter 3 of the distributed operating system book for Andrew S.tanenbaum in addition to other related topics in the synchronization of the distributed operating system
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Abstract The data can get lost, reordered or duplicated due to the presence of routers and buffer space over the unreliable channel in the conventional networks. The data link layer deals with frame formation, flow control, error control, and addressing and link management. All such functions will be performed only by data link protocols. The sliding window protocol will detect and correct error if the received data have enough redundant bits or repeat a retransmission of data. The paper shows the working of this duplex protocol of data link network. Keywords: ACK, GOBACK, ARQ, NACK.
Synchronization Pradeep K Sinha
Introduction
Issues in Synchronization
Clock synchronization
Event Ordering
Mutual Exclusion
Deadlock
Election algorithms
Clock Synchronization
How Computer Clocks are Implemented
Drifting of Clocks
Types of Clock Synchronization and issues in them
Clock Synchronization Algorithms
Distributed and Centralized Algorithms
Case Study
Event Ordering
Happened Before Relation
Logical Clocks Concept and Implementation
Mutual Exclusion
Centralized Approach, Distributed Approach, Token Passing Approach
Deadlocks
Election algorithms
Fault tolerant wireless sensor mac protocol for efficient collision avoidancegraphhoc
In sensor networks communication by broadcast methods involves many hazards, especially collision. Several MAC layer protocols have been proposed to resolve the problem of collision namely ARBP, where the best achieved success rate is 90%. We hereby propose a MAC protocol which achieves a greater success rate (Success rate is defined as the percentage of delivered packets at the source reaching the destination successfully) by reducing the number of collisions, but by trading off the average propagation delay of transmission. Our proposed protocols are also shown to be more energy efficient in terms of energy dissipation per message delivery, compared to the currently existing protocol.
This ppt covers different aspects about timing issues and various algorithms involved in having better sync between different systems in a distributed environment
To transmit the data from one node to another, data link layer combines framing, flow control & error control schemes.
We divide the discussion protocols into those that can be used for noiseless(error free) channels and those that can be used for noisy (error creating) channels.
this presentation explains chapter 3 of the distributed operating system book for Andrew S.tanenbaum in addition to other related topics in the synchronization of the distributed operating system
Kennis en ervaring hebben veel waarde. Deze waarde kan omgezet worden in nieuwe opdrachten. Xperwise is dé B2B portal waar bedrijven en organisaties hun kennis publiceren en delen om in aanmerking te komen voor nieuwe opdrachten
El Catàleg de paisatge de les Comarques Gironines. Els paisatges de la GarrotxaPere Sala i Martí
Presentació a Olot, el 7 d'abril de 2015, organitzat per l'Ajuntament d'Olot i l'Observatori del Paisatge de Catalunya.
Presentación en Olot, el 7 de abril de 2015, organizado por el Ayuntamiento de Olot y el Observatorio del Paisaje de Cataluña.
Presentation in Olot, 7 April 2015, organized by the Council of Olot and the Landscape Observatory of Catalonia.
Las Coplas y Rimas para Niños MATERIAL PARA IMPRIMIR
Las Coplas y Rimas para Niños son composiciones poéticas, generalmente tienen estrofas de cuatro versos, por lo general se utiliza en las canciones populares.
Esta poesía se compone de cuatro estrofas también pueden ser de redondilla, seguidilla o de cuarteta de romance.
La Redondilla
Es una Estrofa de cuatro versos,
En las coplas se narran historias muy apasionadas, que pueden ser desde muy alegres hasta muy tristes como el desamor o la muerte.
Las coplas a parte de usarlas para cuentos o historias, también se pueden utilizar para narrar echos históricos o costumbres.
que-son-las-coplas-y-ejemplos
que-es-una-copla-ejemplos
ejemplos-de-coplas-para-ninos
satellite communication jntuh
Earth Station Technology: Introduction, Transmitters, Receivers, Antennas, Tracking Systems,
Terrestrial Interface, Primary Power Test Methods.
Consider the TCP multiple acknowledgement scheme. A base station (BS.pdfkalerottnerheissst52
Consider the TCP multiple acknowledgement scheme. A base station (BS) may receive an out of
sequence packet that was buffered at an earlier point in time. How can such a situation arise in
the network? (3 marks) Actions taken by the BS will depend upon the sequence number of the
received packet from the sender (in the wired segment) and sequence number of the last
unacknowledged packet (at the BS). Based on these sequence number values, explain the
different responses the BS can generate to bring the system to a consistent state. (6 marks)
Solution
Here TCP may be defined as the transmission control protocol where each nodes has to depend
on acknowledgment and sequence number from sender to receiver. Basically as we look at the
OSI model this TCP protocol lies in transport layer of OSI model, which is connection oriented
protocol. In this type of connection every data is divided into segments and each segment is
given a sequence number and on that basis data is being completely sent one by one in segments.
Since this type of protocol waits for the acknowledgment from the receiver so it is considered a
slow connection. But has got capability of fast data recovery and error control as well flow
control and congestion control.
In multiple acknowledgments we can denote that RTT would be for end to end round trip time
and similarly RTT (w) would be denoted as the round trip for base station and wireless node.
Here sender tries to re send the segments after waiting some time from end to end
acknowledgement until it receives an acknowledgment from the receiver thus establishes a
proper connection when a sender holds a ACK from the base station, then apparently sender gets
to know that base station has received the packets until S-1 but has got a difficulty to send it to
the wireless nodes/hosts, since it has not received the ACK from the wireless host even waiting
for some time.
When a base station receives a packet from the node sender, it keeps a timer and then again
sends to the sender. If suppose the timer get over from the base station it then sends ACKp
towards the sender and then next sequence number is being attached and sends back to the sender
which further sends to the wireless hosts.
Similarly if base station receives a packet which is out of sequence then it will send this packet to
the wireless node and if it doesn’t get received within time given then, then it will send early
packet to the sender by the base station upon which it sends ACKp to the sender..
To Get any Project for CSE, IT ECE, EEE Contact Me @ 09666155510, 09849539085 or mail us - ieeefinalsemprojects@gmail.com-Visit Our Website: www.finalyearprojects.org
To Get any Project for CSE, IT ECE, EEE Contact Me @ 09666155510, 09849539085 or mail us - ieeefinalsemprojects@gmail.com-Visit Our Website: www.finalyearprojects.org
GPS Signal Components, Purpose, Properties and Power level,
Signal Acquisition and Tracking, Navigation Information Extraction, Pseudo Range Estimation, Frequency Estimation, GPS Satellite Position Calculation, Signal Structure, Anti Spoofing (AS), Selective Availability, Difference between GPS and GALILEO Satellite Construction.
RTH-RSS Mac: Path loss exponent estimation with received signal strength loca...IOSR Journals
Abstract: Nowadays , Wireless Sensor Networks (WSNs) succed in domain of technology trends; new
require’sare continuously have more complex challenging, such as the real time location. The MAC layer
plays a crucial role in these networks; it controls the communication module and manages the medium sharing.
In this work, we integrate the received signal strength path-loss exponent estimation (RSS PLE) based on
location technique in Real Time Hybrid MAC (RTHMAC) protocol in goal to minimize the delay phase’s and
get more life time node’s. It combinesalso the advantages of both TDMA and FDMA in order to give a soft real
time communication for WSN.
Keywords: Duty cycle, RSS, PLE ,FDMA,TDMA, WSN ,Cluster
To Get any Project for CSE, IT ECE, EEE Contact Me @ 09849539085, 09966235788 or mail us - ieeefinalsemprojects@gmail.com-Visit Our Website: www.finalyearprojects.org
To Get any Project for CSE, IT ECE, EEE Contact Me @ 09849539085, 09966235788 or mail us - ieeefinalsemprojects@gmail.co¬m-Visit Our Website: www.finalyearprojects.org
DOTNET 2013 IEEE MOBILECOMPUTING PROJECT Optimal multicast capacity and delay...IEEEGLOBALSOFTTECHNOLOGIES
To Get any Project for CSE, IT ECE, EEE Contact Me @ 09849539085, 09966235788 or mail us - ieeefinalsemprojects@gmail.com-Visit Our Website: www.finalyearprojects.org
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
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1. Sensor-MAC(S-MAC)
In S-MAC , the sensor node follows the schedule as listen-sleep mode.
Each node maintains a schedule table
that stores the schedules of all its
known neighbors.
The node first listens for a certain
amount of time. If it does not hear a schedule from another node, it randomly
chooses a time to go to sleep and immediately broadcasts its schedule in a SYNC
message, indicating that it will go to sleep after t seconds. We call such a
node a synchronizer, since it chooses its schedule independently and other
nodes will synchronize with it.
If the node receives a schedule from a neighbor before choosing its own
schedule, it follows that schedule by setting its schedule to be the same. We call
such a node a follower. It then waits for a random delay td and rebroadcasts this
schedule, indicating that it will sleep in t- td seconds. The random delay is for
collision avoidance.
If a node receives a different schedule after it selects and broadcasts its own
schedule, it adopts both schedules (i.e., it schedules itself to wake up at the
times of both is neighbor and itself). It broadcasts it own schedule before going
to sleep.
In listen/sleep scheme, for listen
period a node send a SYNC packet
includes the address of the sender
and the time of its next sleep due to
update schedule.
Receivers will adjust their timers
immediately after they receive the
SYNC packet.
For receiver, The listen interval is
divide into two parts; SYNC and RTS
listening.
if a sender wants to send a SYNC packet, it starts carrier sense when the
receiver begins listening. It randomly selects a time slot to finish its carrier
sense. If it has not detected any transmission by the end of the time slot, it wins
the medium and starts sending its SYNC packet at that time.
CS stands for carrier sense. sender 1 only sends a SYNC packet. Sender 2 only
wants to send data. Sender 3 sends a SYNC packet and a RTS packet.
2. Each node periodically broadcasts SYNC packets to its neighbors even if it has
no followers. This allows new nodes to join an existing neighborhood. The new
node follows the same procedure in the above subsection to choose its
schedule.
S-MAC Adaptive listening(2004)
S-MAC proposes an important technique, called adaptive listen, to improve the
latency caused by the periodic sleep of each node in a multihop network.
The basic idea is to let the node who overhears its neighbor’s transmissions
(ideally only RTS or CTS) wake up for a short period of time at the end of
the transmission.
In this way, if the node is the next-hop node, its neighbor is able to immediately
pass the data to it instead of waiting for its scheduled listen time.
If the node does not receive anything during the adaptive listening, it will go back
to sleep until its next scheduled listen time.
Synchronous channel polling(SCP-MAC)(2006)
To send a packet, the sender adds
a preamble before the packet.
This preamble is effectively a
wake-up signal, informing other
nodes a data packet is about to be
transmitted.
The preamble must be at least as
long as the channel polling period to ensure all receivers will detect it.
The performance of LPL is sensitive to the channel polling period, since longer
periods reduce receiver costs but increase sender costs.
3. unlike LPL, SCP-MAC synchronizes the polling times (schedules) of all neighboring
nodes.
a short wake-up tone is
required for senders to
guarantee rendezvous.
A sends to node B. When B
receives a packet during the first
regular polling.
it adds n high frequency poll in
the same frame, immediately following its regular poll. (We define n below)
If A has more packets to send, it sends them in these adaptive polling times.
Spacing of adaptive slots is determined by the longest packet length that the
physical layer supports.
If B finds none of its additional polls useful (such as if A had no additional data to
send) it transitions back to its regular, low-duty cycle polling period.
If any of B’s additional slots were successfully used, B extends the adaptive polling
with n slots, allowing A to continue transmission.
It also automatically plans an additional n in the next frame.
If the duration of the traffic burst is shorter than one regular polling period, such
process repeats at each hop, and the whole data can be transferred over N hops
using N polling periods.
Disadvantage:
Q-MAC(Query based network)(2006)
In Q-MAC two types of sleep planning to suit query processing in a multi hop
network. It follows a (1) static sleep schedule when there is no query and (2)
dynamic sleep schedule when a query is transmitted.
When there is no query, the nodes follow a static sleep schedule.
The active time
period of the nodes
at different regions
are synchronized such
that the next hop
node is made active
before the current
node’s active period
is over.
4. When the destination is
unknown to the sink, but it
may know the appropriate
region (e.g. temperature of a
node in north).In this case, the
sink can send the query to the
cluster head and the cluster
head can send it to the
destination.
The node which forwards
the query packet will change
the sleep schedule as fully ‘on’
(sink)till it gets the data packet.
When the destination node E
sends the data packet, the
intermediate nodes will change their radio to their usual schedule, after
forwarding the data packet. This dynamic schedule avoids the delay in
transmission.
If the destination is known (i.e. how many hops away from a node), the schedule
can be changed dynamically based on the arrival time of the data.
The intermediate nodes calculate the time at which they have to forward the
data using the following details:
The time at which the
query packet is forwarded,
The distance of the
destination node,
Time taken to transmit the
data packet for one hop
distance.
The accurate wake up time
is hard to estimate and
each node is activated at
the reserved time and is
kept active for a timeout
period.
If the packet is not
received within the
timeout period, the node
will switch off the radio.
The sleep schedule if data
should be collected from
multiple destinations. In
this case, a multicast query
is sent to the destination
sensor nodes.
5. There may be many number of packets to the sink for a single query, since
many nodes send the sensed information.
The radio of the intermediate nodes is made on, after a particular period of
time.
After all the data packets are transmitted, a control packet is sent towards the
sink, so that the intermediate nodes switch off the radio.
The radio remains on until a control packet is received. The cluster head or a
special node is responsible to send this control packet.
Disadvantage:
DW-MAC(demand wakeup mac)(2008)
DW-MAC assumes that
a separate protocol used
to synchronize the clocks
in sensor nodes during the
Sync period with required
precision.
The basic concept of DW-
MAC is to wake up nodes
on demand during the
Sleep period of a cycle in
order to transmit or
receive a packet.
In DW-MAC, medium access control and scheduling are fully integrated.
DW-MAC sets up a one-to-one mapping between a Data period and the
following Sleep period.
An SCH carries no timing information, and the transmission of an SCH simply
replaces RTS/CTS for medium access control thus minimize schedule overhead.
Node A first contends for channel access and transmits an SCH during the Data
period.
Transmission of the SCH starts T1time units after the beginning of the Data
period. Based on T1 and the duration of the SCH transmission,T3, nodes A and
B will both schedule their wakeup time toT2 from the beginning of the
following Sleep period, and will agree on a maximum wakeup duration of T4,
based on the ratio between TData and TSleep.
T2=T1*Tsleep/Tdata
where T2 defines after how much time from the beginning of the sleep the
6. sender and receiver will wake up.
Disadvantage:
• In DW-MAC, Data period and Sleep period are fixed, which results in that the
• system cannot dynamically adapt to different traffic loads.
• At the beginning of the sleep period , the initial data transmission takes too
long time to transmit .
• the interval between the two nodes data transmission may long interval to
transmit.
AS-MAC(Adaptive scheduling-MAC)(2010)
AS-MAC is the enhance and modified format of DW-MAC scheme.
In DW-MAC the durations of the Data period and Sleep period are static, but
AS-MAC designs a flexible Reserved Active Time (RAT) within the fixed
Adaptive Scheduling (AS) period, so that nodes can change the length of the
RAT in each operational cycle and be adaptive to the variable traffic load.
A timer is employed to decide moment the nodes should sleep. The timer
expires when there is no transmission of SCH frames or transmission/collision in
its neighborhood for a period of time,T0
T0 indicates maximum continuing amount of idle listening in the AS period.
.In 1st operation cycle(average traffic load case): after AS-Period starts, two
events occur. After the 2nd event, there is no new event within timeout T0
period. Thus node enters Sleep period after two events plus T0 time, thus early
enter to Sleep period. For this case,T0<RAT<preset AS-Period.
In 2nd operation cycle (high traffic load case): node keeps sensing five events in
succession, and the interval of any two events in succession is shorter than the
timeout T0 period. Thus node keeps Active mode till its full AS-Period. For this
case, RAT = pre-set AS-Period.
7. In 3rd operation cycle (low traffic load case): after AS-Period starts, there is no
single event. Thus after timeoutT0 period, node immediately enters Sleep mode.
For this case, RAT=T0
if the node has not sensed event happened inT0, it will go to sleep, staying awake
only for the period of TSYNC +T0 ,Since T0<<TDATA
In AS-MAC, The SCH frame also have added two parameters in the header of the
SCH compare to DW-MAC SCH.
The SCH also preserve the number of times the SCH has been sent as RTS
or/and CTS. The two parameters are RTS_RetryNo and CTS_RetryNo.
The purpose to introduce the two parameters, RTS_RetryNo and CTS_RetryNo, is
to avoid duplicate data transmission, thus reducing latency and energy
consumption.
Assume A needs to send a data packet to D through B and C as shown in fig.
A sends an SCH (RTS) successfully to B and sets a timer to wait for SCH (CTS)
from B. Upon receiving the SCH (RTS) from A, B sends an SCH (CTS) to A which
at the same time serves as SCH (RTS) to C.
However, A might lost the SCH (CTS) from B before the SCH (CTS) timer timeout
and interprets that its SCH (RTS) transmission failed.
A sends another SCH (RTS) to B. In the mean time, after receiving the SCH (RTS)
from B, C will continue the forwarding to D.
If the 2nd SCH (RTS) succeeds and A also receives SCH (CTS) from B, the DW-
MAC uses the 2nd time SCH (RTS) to schedule the data transmission.
The advantages of SCH frame with tracked retry numbers are in three-folds:
o end-to-end delivery latency will be reduced as the 1st successful RTS is used
for mapping the data transmission.
o energy consumption can be reduced due to the avoidance of unnecessary
SCH frames transmission and
o improvement of the delivery latency and energy conservation will not
introduce perceivable overhead.
8. Disadvantage:
Though the receiver don't know the data size when variable length data can
be transmit by sender then how it can calculate the wakeup time in sleep
period.
R-MAC(Routing Enhancement MAC protocol)(2007)
An operational cycle of a sensor node in RMAC can be divided
into three stages:
SYNC, DATA, and
SLEEP.
SYNC period,
synchronizes the
clocks on sensor
nodes with the
required precision.
When a data packet is
to be sent to a destination node that is multiple hops away, a control frame
PION is sent during the DATA period to initiate the communication with the
downstream nodes.
The dual function of a single PION frame is to confirm receipt of a PION from its
upstream node and to simultaneously request communication from a
downstream node.
Node S first picks a random period from the contention window and waits for
the medium to be quiet for that period and an additional DIFS period (as in IEEE
802.11) before sending a PION to the next-hop node A.
A gets the next-hop address for this destination from its own network layer. A
then waits a SIFS period before transmitting its own PION.
The PION contains three addresses, apart from the final destination address: its
own address, the previous-hop address (S), and the new next-hop address(e.g B)
This PION from A serves both as a CTS to S and as an RTS to B.
when S receives A’s PION, S does not send its data frame immediately but waits
for the start of the SLEEP period to transmit the data frame.
9. Node A stays awake to receive the data frame at the start of the SLEEP period,
and after node A receives the data frame, it sends an ACK frame to S. After
receiving the ACK, node S goes to sleep mode.
If node A earlier received the confirmation PION from its next hop B in the DATA
period, A immediately relays the data frame to B. This data frame relaying
process continues at each hop until the final destination is reached.
Disadvantage:
• In SYNC period how the sensor node synchronize themselves that are not
clearly explained.
10. Node A stays awake to receive the data frame at the start of the SLEEP period,
and after node A receives the data frame, it sends an ACK frame to S. After
receiving the ACK, node S goes to sleep mode.
If node A earlier received the confirmation PION from its next hop B in the DATA
period, A immediately relays the data frame to B. This data frame relaying
process continues at each hop until the final destination is reached.
Disadvantage:
• In SYNC period how the sensor node synchronize themselves that are not
clearly explained.