This document provides an overview of queuing theory models used to analyze the performance of IEEE 802.11 wireless networks. It discusses how queuing models can measure metrics like throughput, delay, and packet loss. It also reviews the IEEE 802.11 standard, including the distributed coordination function (DCF) used for medium access control and quality of service enhancements in 802.11e. The goal is to identify the most accurate queuing or probability models for designing wireless LANs that consider performance and meet QoS requirements.
A Survey on Cross Layer Routing Protocol with Quality of ServiceIJSRD
Wireless is playing the wide role in today’s industrial application. Central idea of this paper is to enhance quality of service (QoS) for multimedia transmission over ad-hoc network. This paper describes the operational of different QoS routing protocols, their properties and various parameters advantages and disadvantages. Also describes the use of QoS in Cross layer routing protocol. Finally, it concludes by study of all these cross layer QoS routing protocols.
Adjustment Delay Scheme to Improve Performance IEEE 802.15.4 NetworksTELKOMNIKA JOURNAL
The challenges of CSMA/CA as following: first, when the device nodes detect the channel in busy
condition, the device nodes have to increase the value of backoff exponent which cause range of blind
backoff process also increase. Second, the blind backoff process will cause lower channel utilization and
more energy consumptions. This article proposes a scheme to improve IEEE 802.15.4 medium access
control, called adjustment delay scheme (ADES). This article also presents a comprehensive Markov chain
analysis to predict the probability of successful transmission, network goodput, bandwidth utilization and
total network energy consumption. The validity of the model analysis is proven by precisely matching the
simulation experiments. ADES performs better than those of other algorithms in term of the probability of
successful packet transmission, network goodput, bandwidth utilization as well as energy consumption in
the networks.
EFFECTS OF MAC PARAMETERS ON THE PERFORMANCE OF IEEE 802.11 DCF IN NS-3ijwmn
This paper presents the design procedure of the NS-3 script for WLAN that is organized according to the
hierarchical manner of TCP/IP model. We configure all layers by using NS-3 model objects and set and
modify the values used by objects to investigate the effects of MAC parameters (access mechanism, CWmin,
CWmax and retry limit) on the performance metrics viz. packet delivery ratio, packet lost ratio, aggregated
throughput, and average delay. The simulation results show that RTS/CTS access mechanism outperforms
basic access mechanism in saturated state, whereas the MAC parameters have no significant impact on
network performance in non-saturated state. A higher value of CWmin improves the aggregated throughput
in expense of average delay. The tradeoff relationships among the performance metrics are also observed
in results for the optimal values of MAC parameters. Our design procedure represents a good guideline for
new NS-3 users to design and modify script and results greatly benefit the network design and
management.
General Model for Single and Multiple Channels WLANs with Quality of Service ...ijwmn
In this paper we develop an intergraded model for request mechanism and data transmission in the uplink phase in the presence of channel noise. This model supports quality of service. The wireless channel is prone to many impairments. Thus, certain techniques have to be developed to deliver data to the receiver. We calculated the performance parameters for single and multichannel wireless networks, like the requests throughput, data throughput and the requests acceptance probability and data acceptance probability. The proposed model is general model since it can be applied to different wireless networks such as IEEE802.11a, IEEE802.16e, CDMA operated networks and Hiperlan\2.
A Survey on Cross Layer Routing Protocol with Quality of ServiceIJSRD
Wireless is playing the wide role in today’s industrial application. Central idea of this paper is to enhance quality of service (QoS) for multimedia transmission over ad-hoc network. This paper describes the operational of different QoS routing protocols, their properties and various parameters advantages and disadvantages. Also describes the use of QoS in Cross layer routing protocol. Finally, it concludes by study of all these cross layer QoS routing protocols.
Adjustment Delay Scheme to Improve Performance IEEE 802.15.4 NetworksTELKOMNIKA JOURNAL
The challenges of CSMA/CA as following: first, when the device nodes detect the channel in busy
condition, the device nodes have to increase the value of backoff exponent which cause range of blind
backoff process also increase. Second, the blind backoff process will cause lower channel utilization and
more energy consumptions. This article proposes a scheme to improve IEEE 802.15.4 medium access
control, called adjustment delay scheme (ADES). This article also presents a comprehensive Markov chain
analysis to predict the probability of successful transmission, network goodput, bandwidth utilization and
total network energy consumption. The validity of the model analysis is proven by precisely matching the
simulation experiments. ADES performs better than those of other algorithms in term of the probability of
successful packet transmission, network goodput, bandwidth utilization as well as energy consumption in
the networks.
EFFECTS OF MAC PARAMETERS ON THE PERFORMANCE OF IEEE 802.11 DCF IN NS-3ijwmn
This paper presents the design procedure of the NS-3 script for WLAN that is organized according to the
hierarchical manner of TCP/IP model. We configure all layers by using NS-3 model objects and set and
modify the values used by objects to investigate the effects of MAC parameters (access mechanism, CWmin,
CWmax and retry limit) on the performance metrics viz. packet delivery ratio, packet lost ratio, aggregated
throughput, and average delay. The simulation results show that RTS/CTS access mechanism outperforms
basic access mechanism in saturated state, whereas the MAC parameters have no significant impact on
network performance in non-saturated state. A higher value of CWmin improves the aggregated throughput
in expense of average delay. The tradeoff relationships among the performance metrics are also observed
in results for the optimal values of MAC parameters. Our design procedure represents a good guideline for
new NS-3 users to design and modify script and results greatly benefit the network design and
management.
General Model for Single and Multiple Channels WLANs with Quality of Service ...ijwmn
In this paper we develop an intergraded model for request mechanism and data transmission in the uplink phase in the presence of channel noise. This model supports quality of service. The wireless channel is prone to many impairments. Thus, certain techniques have to be developed to deliver data to the receiver. We calculated the performance parameters for single and multichannel wireless networks, like the requests throughput, data throughput and the requests acceptance probability and data acceptance probability. The proposed model is general model since it can be applied to different wireless networks such as IEEE802.11a, IEEE802.16e, CDMA operated networks and Hiperlan\2.
An Implementation and Analysis of RTS/CTS Mechanism for Data Transfer in Wire...iosrjce
In this paper, the implementation and analysis of RTS/CTS mechanism for data transfer in wireless
network is being studied. The Request-To-Send (RTS) and Clear-To-Send (CTS) mechanism is widely used in
wireless networks to avoid collisions due to hidden nodes by reserving the channel for transmitting data from
source to destination. The collisions caused by the hidden nodes reduce the network throughput and efficiency.
In RTS/CTS mechanism, RTS/CTS packets set the timer for the neighboring nodes so that these nodes defer their
transmission for the entire data packet transmission period. But there may be the case when the intended
transmission completes before the expiration of this timer, so a kind of delay has been developed. To reduce this
delay, the proposed methodology in this paper provides RTR (Ready-To-Receive) packets along with RTS/CTS
packets. The receiving node sends RTR packets to notify all the neighboring nodes that the intended
communication has finished. The results show that this method improves the data transfer rate resulting in
higher throughput and network efficiency and the system will be more efficient. This will reflect in the overall
information transfer time.
Improving Performance of TCP in Wireless Environment using TCP-PIDES Editor
Improving the performance of the transmission
control protocol (TCP) in wireless environment has been an
active research area. Main reason behind performance
degradation of TCP is not having ability to detect actual reason
of packet losses in wireless environment. In this paper, we are
providing a simulation results for TCP-P (TCP-Performance).
TCP-P is intelligent protocol in wireless environment which
is able to distinguish actual reasons for packet losses and
applies an appropriate solution to packet loss.
TCP-P deals with main three issues, Congestion in
network, Disconnection in network and random packet losses.
TCP-P consists of Congestion avoidance algorithm and
Disconnection detection algorithm with some changes in TCP
header part. If congestion is occurring in network then
congestion avoidance algorithm is applied. In congestion
avoidance algorithm, TCP-P calculates number of sending
packets and receiving acknowledgements and accordingly set
a sending buffer value, so that it can prevent system from
happening congestion. In disconnection detection algorithm,
TCP-P senses medium continuously to detect a happening
disconnection in network. TCP-P modifies header of TCP
packet so that loss packet can itself notify sender that it is
lost.This paper describes the design of TCP-P, and presents
results from experiments using the NS-2 network simulator.
Results from simulations show that TCP-P is 4% more
efficient than TCP-Tahoe, 5% more efficient than TCP-Vegas,
7% more efficient than TCP-Sack and equally efficient in
performance as of TCP-Reno and TCP-New Reno. But we can
say TCP-P is more efficient than TCP-Reno and TCP-New
Reno since it is able to solve more issues of TCP in wireless
environment.
Abstract - The Transmission Control Protocol (TCP) is
connection oriented, reliable and end-to-end protocol that support
flow and congestion control, with the evolution and rapid growth
of the internet and emergence of internet of things IoT, flow and
congestion have clear impact in the network performance. In this
paper we study congestion control mechanisms Tahoe, Reno,
Newreno, SACK and Vegas, which are introduced to control
network utilization and increase throughput, in the performance
evaluation we evaluate the performance metrics such as
throughput, packets loss, delivery and reveals impact of the cwnd.
Showing that SACK had done better performance in terms of
numbers of packets sent, throughput and delivery ratio than
Newreno, Vegas shows the best performance of all of them.
Implementing True Zero Cycle Branching in Scalar and Superscalar Pipelined Pr...IDES Editor
In this paper, we have proposed a novel architectural
technique which can be used to boost performance of modern
day processors. It is especially useful in certain code constructs
like small loops and try-catch blocks. The technique is aimed
at improving performance by reducing the number of
instructions that need to enter the pipeline itself. We also
demonstrate its working in a scalar pipelined soft-core
processor developed by us. Lastly, we present how a superscalar
microprocessor can take advantage of this technique and
increase its performance.
Abstract
The rapid growth in the Internet of Things (IoTs)
has change our life to be more intelligent and smart,
the development in the Wireless Sensors Networks
(WSNs), besides the wide use of the embedded devices
in different area like industry, home automation,
transport, agriculture and health care, which was led
the Routing Over Low-power and Lossy-network
(ROLL) working group to introduce the IPv6 Routing
Protocol for Low-Power and Lossy Networks (RPL),
therein the RPL nodes have organized topology as a
Directed Acyclic Graph (DAG) and terminated at one
root to form the Destination Oriented DAGs
(DODAGs). In this paper by using InstantContiki3.0
and CoojaGUI we analyze the DODAG formations,
the RPL control messages that are send downward
and upward routes to construct and maintain
DODAG and the Rank computation by Objective
Function (OF) for inconsistency and loop detection,
also we evaluate the performance of the RPL based
on the Expected Transmission Count (ETX) OF that
enable RPL to select and optimize routes within RPL
instance, as well as we evaluate the following metrics:
The ETX Reliability Object (ETX), Radio Duty Cycle
(RDC), energy consumption, the received packets by
the motes and neighbor count. The simulation results
show that the RPL control messages flow in consistent
manner, the DODAG root able to connect to all of the
neighbor motes, also Rank illustration shows no loops
and DODAG topology consistent, as well as the ETX
can essentially take control over DODAG formations
and it has an effects in the RDC ratio, furthermore
most of the motes show reasonable low power
consumption, also the motes show acceptable number
of the received packets.
Abstract— Internet of things (IoT) is a new networks paradigm,
that billions of internet things can be connected at anytime and
anyplace, and it’s expected to include billions of smart devices,
these devices characterized by small memory, low transfer rate
and low energy, internet protocol version 6 (IPv6) it was
introduced to offer huge address space, however it doesn’t
compatible with capabilities of the constrained device, therefore
IPv6 over low power Wireless Personal Area network
(6LoWPAN) adaptation layer was introduced to carry IPv6
datagram over constrained links, in this paper, we first provide
intensive analysis of 6LoWPAN specifications that includes IPv6
encapsulation, frame format, 6LoWPAN header compression,
fragmentation of the payload datagram and encoding of user
datagram protocol UDP, in addition to the implementation of the
6LoWPAN in the NS-3 using different payload size, then we
evaluate the following metrics throughput, packets loss, delay
and jitter, the results showed that the fragmentation effects the
network throughput and increase the delay and the number of
lost packets, moreover, when payload fit within a single frame the
network show better performance , there are no packets lost as
well as minimum values of the delay and the jitter, and in the
two cases 6LoWPAN shows reasonable packets delivery ratio.
Differentiated Classes of Service and Flow Management using An Hybrid Broker1IDES Editor
Recently, mobile networks have been overloaded
with a considerable amount of data traffic. The current paper
proposes a management service for mobile environments,
using policies and quality metrics, which ensure a better usage
of network resources with a more fine-grained management
based on flows with different classes of service and
transmission rates. This management of flows is supported
through a closed innovative control loop among a flexible
brokerage service in the network, and agents at the mobile
terminals. It also allows the terminals to make well-informed
decisions about their connections to enhance the number of
connected flows per technology and the individual service level
offered to each flow. Our results indicate that the proposed
solution optimizes the usage of available 4G network resources
among a high number of differentiated flows in several
scenarios where access technologies are extremely overloaded
whilst protecting, through a low complexity scheme, the flows
associated to users that have celebrated more expensive
contracts with their network operators.
EFFECTS OF MAC PARAMETERS ON THE PERFORMANCE OF IEEE 802.11 DCF IN NS-3ijwmn
This paper presents the design procedure of the NS-3 script for WLAN that is organized according to the hierarchical manner of TCP/IP model. We configure all layers by using NS-3 model objects and set and modify the values used by objects to investigate the effects of MAC parameters (access mechanism, CWmin, CWmax and retry limit) on the performance metrics viz. packet delivery ratio, packet lost ratio, aggregated throughput, and average delay. The simulation results show that RTS/CTS access mechanism outperforms basic access mechanism in saturated state, whereas the MAC parameters have no significant impact on network performance in non-saturated state. A higher value of CWmin improves the aggregated throughput in expense of average delay. The tradeoff relationships among the performance metrics are also observed in results for the optimal values of MAC parameters. Our design procedure represents a good guideline for new NS-3 users to design and modify script and results greatly benefit the network design and management.
An Accurate Performance Analysis of Hybrid Efficient and Reliable MAC Protoco...IJECEIAES
Vehicular Ad Hoc Networks (VANETs) is a technology supporting two types of applications, safety and service applications with higher and lower priorities respectively. Thereby, Medium Access Control (MAC) protocol is designed to provide reliable and efficient data broadcasting based on prioritization. Different from the IEEE 1609.4 (legacy), HER-MAC protocol is a new multi-channel MAC proposed for VANETs, offering remarkable performance with regards to safety applications transmission. This paper focuses on the analysis of packet delivery ratio of the HER-MAC protocol under non-saturated conditions. 1-D and 2-D Markov chains have been developed for safety and non-safety applications respectively, to evaluate mathematically the performance of HER-MAC protocol. The presented work has taken into account the freezing of the backoff timer for both applications and the backoff stages along with short retry limit for non-safety applications in order to meet the IEEE 802.11p specifications. It highlights that taking these elements into consideration are important in modeling the system, to provide an accurate estimation of the channel access, and guarantees that no packet is served indefinitely. More precise results of the system packet delivery ratio have been yield. The probability of successful transmission and collisions were derived and used to compute the packet delivery ratio. The simulation results validate the analytical results of our models and indicate that the performance of our models outperformed the existing models in terms of the packet delivery ratio under different number of vehicles and contention window.
PERFORMANCE ANALYSIS OF OLSR PROTOCOL IN MANET CONSIDERING DIFFERENT MOBILITY...ijwmn
A Mobile Ad Hoc Network (MANET) is created when an independent mobile node network is connected
dynamically via wireless links. MANET is a self-organizing network that does not rely on pre-existing
infrastructure such as wired or wireless network routers. Mobile nodes in this network move randomly,
thus, the topology is always changing. Routing protocols in MANET are critical in ensuring dependable
and consistent connectivity between the mobile nodes. They conclude logically based on the interaction
between mobile nodes in MANET routing and encourage them to choose the optimum path between source
and destination. Routing protocols are classified as proactive, reactive, or hybrid. The focus of this project
will be on Optimized Link State Routing (OLSR) protocol, a proactive routing technique. OLSR is known as
the optimized variant of link state routing in which packets are sent throughout the network using the
multipoint relay (MPR) mechanism. This article evaluates the performance of the OLSR routing protocol
under condition of changing mobility speed and network density. The study's performance indicators are
average packet throughput, packet delivery ratio (PDR), and average packet latency. Network Simulator 2
(NS-2) and an external patch UM-OLSR are used to simulate and evaluate the performance of such
protocol. As a result of research, the approach of implementing the MPR mechanism are able to minimise
redundant data transmission during the normal message broadcast. The MPRs enhance the link state
protocols’ traditional diffusion mechanism by selecting the right MPRs. Hence, the number of undesired
broadcasts can be reduced and limited. Further research will focus on different scenario and environment
using different mobility model
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
An Implementation and Analysis of RTS/CTS Mechanism for Data Transfer in Wire...iosrjce
In this paper, the implementation and analysis of RTS/CTS mechanism for data transfer in wireless
network is being studied. The Request-To-Send (RTS) and Clear-To-Send (CTS) mechanism is widely used in
wireless networks to avoid collisions due to hidden nodes by reserving the channel for transmitting data from
source to destination. The collisions caused by the hidden nodes reduce the network throughput and efficiency.
In RTS/CTS mechanism, RTS/CTS packets set the timer for the neighboring nodes so that these nodes defer their
transmission for the entire data packet transmission period. But there may be the case when the intended
transmission completes before the expiration of this timer, so a kind of delay has been developed. To reduce this
delay, the proposed methodology in this paper provides RTR (Ready-To-Receive) packets along with RTS/CTS
packets. The receiving node sends RTR packets to notify all the neighboring nodes that the intended
communication has finished. The results show that this method improves the data transfer rate resulting in
higher throughput and network efficiency and the system will be more efficient. This will reflect in the overall
information transfer time.
Improving Performance of TCP in Wireless Environment using TCP-PIDES Editor
Improving the performance of the transmission
control protocol (TCP) in wireless environment has been an
active research area. Main reason behind performance
degradation of TCP is not having ability to detect actual reason
of packet losses in wireless environment. In this paper, we are
providing a simulation results for TCP-P (TCP-Performance).
TCP-P is intelligent protocol in wireless environment which
is able to distinguish actual reasons for packet losses and
applies an appropriate solution to packet loss.
TCP-P deals with main three issues, Congestion in
network, Disconnection in network and random packet losses.
TCP-P consists of Congestion avoidance algorithm and
Disconnection detection algorithm with some changes in TCP
header part. If congestion is occurring in network then
congestion avoidance algorithm is applied. In congestion
avoidance algorithm, TCP-P calculates number of sending
packets and receiving acknowledgements and accordingly set
a sending buffer value, so that it can prevent system from
happening congestion. In disconnection detection algorithm,
TCP-P senses medium continuously to detect a happening
disconnection in network. TCP-P modifies header of TCP
packet so that loss packet can itself notify sender that it is
lost.This paper describes the design of TCP-P, and presents
results from experiments using the NS-2 network simulator.
Results from simulations show that TCP-P is 4% more
efficient than TCP-Tahoe, 5% more efficient than TCP-Vegas,
7% more efficient than TCP-Sack and equally efficient in
performance as of TCP-Reno and TCP-New Reno. But we can
say TCP-P is more efficient than TCP-Reno and TCP-New
Reno since it is able to solve more issues of TCP in wireless
environment.
Abstract - The Transmission Control Protocol (TCP) is
connection oriented, reliable and end-to-end protocol that support
flow and congestion control, with the evolution and rapid growth
of the internet and emergence of internet of things IoT, flow and
congestion have clear impact in the network performance. In this
paper we study congestion control mechanisms Tahoe, Reno,
Newreno, SACK and Vegas, which are introduced to control
network utilization and increase throughput, in the performance
evaluation we evaluate the performance metrics such as
throughput, packets loss, delivery and reveals impact of the cwnd.
Showing that SACK had done better performance in terms of
numbers of packets sent, throughput and delivery ratio than
Newreno, Vegas shows the best performance of all of them.
Implementing True Zero Cycle Branching in Scalar and Superscalar Pipelined Pr...IDES Editor
In this paper, we have proposed a novel architectural
technique which can be used to boost performance of modern
day processors. It is especially useful in certain code constructs
like small loops and try-catch blocks. The technique is aimed
at improving performance by reducing the number of
instructions that need to enter the pipeline itself. We also
demonstrate its working in a scalar pipelined soft-core
processor developed by us. Lastly, we present how a superscalar
microprocessor can take advantage of this technique and
increase its performance.
Abstract
The rapid growth in the Internet of Things (IoTs)
has change our life to be more intelligent and smart,
the development in the Wireless Sensors Networks
(WSNs), besides the wide use of the embedded devices
in different area like industry, home automation,
transport, agriculture and health care, which was led
the Routing Over Low-power and Lossy-network
(ROLL) working group to introduce the IPv6 Routing
Protocol for Low-Power and Lossy Networks (RPL),
therein the RPL nodes have organized topology as a
Directed Acyclic Graph (DAG) and terminated at one
root to form the Destination Oriented DAGs
(DODAGs). In this paper by using InstantContiki3.0
and CoojaGUI we analyze the DODAG formations,
the RPL control messages that are send downward
and upward routes to construct and maintain
DODAG and the Rank computation by Objective
Function (OF) for inconsistency and loop detection,
also we evaluate the performance of the RPL based
on the Expected Transmission Count (ETX) OF that
enable RPL to select and optimize routes within RPL
instance, as well as we evaluate the following metrics:
The ETX Reliability Object (ETX), Radio Duty Cycle
(RDC), energy consumption, the received packets by
the motes and neighbor count. The simulation results
show that the RPL control messages flow in consistent
manner, the DODAG root able to connect to all of the
neighbor motes, also Rank illustration shows no loops
and DODAG topology consistent, as well as the ETX
can essentially take control over DODAG formations
and it has an effects in the RDC ratio, furthermore
most of the motes show reasonable low power
consumption, also the motes show acceptable number
of the received packets.
Abstract— Internet of things (IoT) is a new networks paradigm,
that billions of internet things can be connected at anytime and
anyplace, and it’s expected to include billions of smart devices,
these devices characterized by small memory, low transfer rate
and low energy, internet protocol version 6 (IPv6) it was
introduced to offer huge address space, however it doesn’t
compatible with capabilities of the constrained device, therefore
IPv6 over low power Wireless Personal Area network
(6LoWPAN) adaptation layer was introduced to carry IPv6
datagram over constrained links, in this paper, we first provide
intensive analysis of 6LoWPAN specifications that includes IPv6
encapsulation, frame format, 6LoWPAN header compression,
fragmentation of the payload datagram and encoding of user
datagram protocol UDP, in addition to the implementation of the
6LoWPAN in the NS-3 using different payload size, then we
evaluate the following metrics throughput, packets loss, delay
and jitter, the results showed that the fragmentation effects the
network throughput and increase the delay and the number of
lost packets, moreover, when payload fit within a single frame the
network show better performance , there are no packets lost as
well as minimum values of the delay and the jitter, and in the
two cases 6LoWPAN shows reasonable packets delivery ratio.
Differentiated Classes of Service and Flow Management using An Hybrid Broker1IDES Editor
Recently, mobile networks have been overloaded
with a considerable amount of data traffic. The current paper
proposes a management service for mobile environments,
using policies and quality metrics, which ensure a better usage
of network resources with a more fine-grained management
based on flows with different classes of service and
transmission rates. This management of flows is supported
through a closed innovative control loop among a flexible
brokerage service in the network, and agents at the mobile
terminals. It also allows the terminals to make well-informed
decisions about their connections to enhance the number of
connected flows per technology and the individual service level
offered to each flow. Our results indicate that the proposed
solution optimizes the usage of available 4G network resources
among a high number of differentiated flows in several
scenarios where access technologies are extremely overloaded
whilst protecting, through a low complexity scheme, the flows
associated to users that have celebrated more expensive
contracts with their network operators.
EFFECTS OF MAC PARAMETERS ON THE PERFORMANCE OF IEEE 802.11 DCF IN NS-3ijwmn
This paper presents the design procedure of the NS-3 script for WLAN that is organized according to the hierarchical manner of TCP/IP model. We configure all layers by using NS-3 model objects and set and modify the values used by objects to investigate the effects of MAC parameters (access mechanism, CWmin, CWmax and retry limit) on the performance metrics viz. packet delivery ratio, packet lost ratio, aggregated throughput, and average delay. The simulation results show that RTS/CTS access mechanism outperforms basic access mechanism in saturated state, whereas the MAC parameters have no significant impact on network performance in non-saturated state. A higher value of CWmin improves the aggregated throughput in expense of average delay. The tradeoff relationships among the performance metrics are also observed in results for the optimal values of MAC parameters. Our design procedure represents a good guideline for new NS-3 users to design and modify script and results greatly benefit the network design and management.
An Accurate Performance Analysis of Hybrid Efficient and Reliable MAC Protoco...IJECEIAES
Vehicular Ad Hoc Networks (VANETs) is a technology supporting two types of applications, safety and service applications with higher and lower priorities respectively. Thereby, Medium Access Control (MAC) protocol is designed to provide reliable and efficient data broadcasting based on prioritization. Different from the IEEE 1609.4 (legacy), HER-MAC protocol is a new multi-channel MAC proposed for VANETs, offering remarkable performance with regards to safety applications transmission. This paper focuses on the analysis of packet delivery ratio of the HER-MAC protocol under non-saturated conditions. 1-D and 2-D Markov chains have been developed for safety and non-safety applications respectively, to evaluate mathematically the performance of HER-MAC protocol. The presented work has taken into account the freezing of the backoff timer for both applications and the backoff stages along with short retry limit for non-safety applications in order to meet the IEEE 802.11p specifications. It highlights that taking these elements into consideration are important in modeling the system, to provide an accurate estimation of the channel access, and guarantees that no packet is served indefinitely. More precise results of the system packet delivery ratio have been yield. The probability of successful transmission and collisions were derived and used to compute the packet delivery ratio. The simulation results validate the analytical results of our models and indicate that the performance of our models outperformed the existing models in terms of the packet delivery ratio under different number of vehicles and contention window.
PERFORMANCE ANALYSIS OF OLSR PROTOCOL IN MANET CONSIDERING DIFFERENT MOBILITY...ijwmn
A Mobile Ad Hoc Network (MANET) is created when an independent mobile node network is connected
dynamically via wireless links. MANET is a self-organizing network that does not rely on pre-existing
infrastructure such as wired or wireless network routers. Mobile nodes in this network move randomly,
thus, the topology is always changing. Routing protocols in MANET are critical in ensuring dependable
and consistent connectivity between the mobile nodes. They conclude logically based on the interaction
between mobile nodes in MANET routing and encourage them to choose the optimum path between source
and destination. Routing protocols are classified as proactive, reactive, or hybrid. The focus of this project
will be on Optimized Link State Routing (OLSR) protocol, a proactive routing technique. OLSR is known as
the optimized variant of link state routing in which packets are sent throughout the network using the
multipoint relay (MPR) mechanism. This article evaluates the performance of the OLSR routing protocol
under condition of changing mobility speed and network density. The study's performance indicators are
average packet throughput, packet delivery ratio (PDR), and average packet latency. Network Simulator 2
(NS-2) and an external patch UM-OLSR are used to simulate and evaluate the performance of such
protocol. As a result of research, the approach of implementing the MPR mechanism are able to minimise
redundant data transmission during the normal message broadcast. The MPRs enhance the link state
protocols’ traditional diffusion mechanism by selecting the right MPRs. Hence, the number of undesired
broadcasts can be reduced and limited. Further research will focus on different scenario and environment
using different mobility model
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Express delivery typically involves a time specific constraint, traditionally on a 24-hour, 48-hour or 72-hour basis or particular window of time that the customer chooses.
#Small Package Industry Before FedEx
1.In 1973, 1.5 ton of freight shipped in US by surface transport and 2% of total shipped by aircraft.
2.High cost of Airfreight down the clients demand.
3.Cargo freight carried by passenger planes which increased operational coast which is uneconomical.
## FedEx
--Founded in 1971 by Frederick W. Smith and started their operation in 1973.
--Smith Finds Major Difference Between Package and Passengers.
--Smith’s aim was to build a system that could achieve next-day delivery of small-package airfreight.
Established a Hub and Spoke route System.
--After 1973 FedEx quickly build up volume.
--By 1976 it had an average daily volume of
19,000 packages, a fleet of 32 aircraft, 500
Delivery vans and 2,000 employees.
--It had initiated service in 75 cities.
Profit $3.7 million on revenue of $75
Million .
##Industry Evaluation,1980-1986
#New Products and Industry Growth.
--Introduce Letter Service which Guaranteed overnight Delivery Service.
--Direct competition with USPS Priority mail.
---Within 3 month their growth is 17000 letters per day.
--1980s yearly growth is 30%.
--Increasing Price Competition.
--Entry of UPS in 1982 in overnight delivery market.
--UPS purchase some freighters(Boeing 727-100s,DC-8) from flying tigers.
--Introduce Next day air service in September 1982.
--Cut the price at roughly half the price Federal Express was charging.
--Federal Express announce overnight delivery at 10.30am.
--In 1983 most of the major carriers include FedEx cut their price following UPS.
--Three new services introduced by Purolator, Emery, and Gelco also offer lower price.
--Between 1983 and 1984 Federal Express’s average revenue per package fall nearly 14% ,Emery 15%.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Performance evaluation of the IEEE 802.11n random topology WLAN with QoS appl...IJECEIAES
The IEEE 802.11n supports high data rate transmissions due its physical layer Multiple Input Multiple Output (MIMO) advanced antenna system and MAC layer enhancement features (frame aggregation and block acknowledgement). As a result this standard is very suitable for multimedia services through its Enhanced Distributed Channel Access (EDCA). This paper focuses on evaluating the Quality of Service (QoS) application on the performance of the IEEE 802.11n random topology WLAN. Three different number of nodes (3, 9 and 18) random topology with one access point are modeled and simulated by using the Riverbed OPNET 17.5 Modular to investigate the Wireless Local Area Network (WLAN) performance for different spatial streams. The result clarified the impact of QoS application and showed that its effect is best at the 18 node number topology. For a 4x4 MIMO, when QoS is applied and with respect to the no QoS application case, simulation results show a maximum improvement of 86.4%, 33.9%, 52.2% and 68.9% for throughput, delay, data drop and retransmission attempts, respectively.
General Model for Single and Multiple Channels WLANs with Quality of Service...ijwmn
In this paper we develop an intergraded model for request mechanism and data transmission in the uplink
phase in the presence of channel noise. This model supports quality of service. The wireless channel is prone
to many impairments. Thus, certain techniques have to be developed to deliver data to the receiver. We
calculated the performance parameters for single and multichannel wireless networks, like the requests
throughput, data throughput and the requests acceptance probability and data acceptance probability. The
proposed model is general model since it can be applied to different wireless networks such as IEEE802.11a,
IEEE802.16e, CDMA operated networks and Hiperlan\2.
Quality of Service for Video Streaming using EDCA in MANETijsrd.com
Mobile Ad-hoc network(MANET) is a collection of wireless terminals that are able to dynamically form a temporary network. To establish such a network no fixed infrastructure is required. Here, it is the responsibility of network nodes to forward each other's packets and thus these nodes also act as routers. In such a network resources are limited and also topology changes dynamically. So providing Quality of service(QoS) is also necessary. QoS is more important for real time applications for example Video Streaming. IEEE 802.11e network standard supports QoS through EDCA technique. This technique does not fulfill the requirements of QoS. So, in this project modified EDCA technique is proposed to enhance QoS for Video Streaming application. This technique is implemented in NS2 and compared with traditional EDCA.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
A MODIFIED IEEE 802.15.6 MAC SCHEME TO ENHANCE PERFORMANCE OF WIRELESS BODY A...ijwmn
The recently released IEEE 802.15.6 standard specifies several physical (PHY) layers and medium access
control (MAC) layer protocols for variety of medical and non-medical applications of Wireless Body Area
Networks (WBAN). Themedical applications of WBAN hasseveral obligatory requirements and constrains
viz. high reliability, strict delaydeadlines and low power consumption.The standard IEEE 802.15.6 MAC
scheme is not able to fulfil the all requirements of medical applications of WBAN. To address this issue we
propose anIEEE 802.15.6-based MAC schemethat is the modification of superframe structure, user
priorities and access mechanism of standard IEEE 802.15.6 MAC scheme. The proposed superframe has
three access phases: random access phases (RAP), manage access phases (MAP) and contention access
phase (CAP). The proposed four user priorities nodes access the channel during RAP using CAMA/CA
mechanism with a large value of contention window. The proposed MAC scheme uses RTS/CTS access
mechanism instead of basic access mechanism to mitigate the effect of hidden and expose terminal
problem. Moreover, we develop an analytical model to evaluate the performance of proposed MAC scheme
and solve the analytical model using Maple. The results show that the modified IEEE802.15.6 MAC
scheme achieve the better performance in terms of reliability, throughput, average access delay, energy
consumption, channel utilization and fairness compared to standard IEEE 802.15.6 MAC scheme in Ehealth applications.
A MODIFIED IEEE 802.15.6 MAC SCHEME TO ENHANCE PERFORMANCE OF WIRELESS BODY A...ijwmn
The recently released IEEE 802.15.6 standard specifies several physical (PHY) layers and medium access
control (MAC) layer protocols for variety of medical and non-medical applications of Wireless Body Area
Networks (WBAN). Themedical applications of WBAN hasseveral obligatory requirements and constrains
viz. high reliability, strict delaydeadlines and low power consumption.The standard IEEE 802.15.6 MAC
scheme is not able to fulfil the all requirements of medical applications of WBAN. To address this issue we
propose anIEEE 802.15.6-based MAC schemethat is the modification of superframe structure, user
priorities and access mechanism of standard IEEE 802.15.6 MAC scheme. The proposed superframe has
three access phases: random access phases (RAP), manage access phases (MAP) and contention access
phase (CAP). The proposed four user priorities nodes access the channel during RAP using CAMA/CA
mechanism with a large value of contention window. The proposed MAC scheme uses RTS/CTS access
mechanism instead of basic access mechanism to mitigate the effect of hidden and expose terminal
problem. Moreover, we develop an analytical model to evaluate the performance of proposed MAC scheme
and solve the analytical model using Maple. The results show that the modified IEEE802.15.6 MAC
scheme achieve the better performance in terms of reliability, throughput, average access delay, energy
consumption, channel utilization and fairness compared to standard IEEE 802.15.6 MAC scheme in Ehealth applications.
Wireless Evolution: IEEE 802.11N, 802.11AC, and 802.11AX Performance Comparisonpijans
The widespread adoption of IEEE 802.11 WLANs is attributed to their inherent mobility, flexibility, and
cost-effectiveness. Within the IEEE 802 working group, a dedicated task group is diligently advancing
WLAN technologies, particularly tailored for dense network scenarios. Amidst these advancements, the
802.11ac protocols have emerged as a preferred choice, delivering superior data transfer rates compared
to the preceding 802.11n standard. Significantly, the sixth-generation wireless protocol, IEEE 802.11ax,
has been introduced, showcasing enhanced performance capabilities that outpace its fifth-generation
predecessor, 802.11ac.In this pioneering investigation, we engage in an in-depth simulation-based scrutiny
of prominentWLAN protocols—namely, IEEE 802.11n, IEEE 802.11ac, and the cutting-edge IEEE
802.11ax. Our exhaustive analyses traverse a spectrum of critical metrics, encompassing throughput,
coverage, spectral efficiency, Tx/Rx gain, and Tx/Rx power.In a single-user and SISO scenario, both
802.11ac and 802.11ax outperform 802.11n. Significantly, 802.11ax surpasses the previous 802.11n/ac
standards, highlighting substantial advancements in wireless performance.
IEEE 802.11n Based Wireless Backhaul Enabled by Dual Channel IPT (DCH-IPT) Fo...CSCJournals
Wireless backhaul has received much attention as an enabler of future broadband mobile communication systems because it can reduce deployment cost of pico-cells, an essential part of high capacity system. A high throughput with a minimum delay network is highly appreciated to sustain the increasing proliferation in multimedia transmissions. In this paper, we propose a backhaul network using the Multi-Input Multi-Output (MIMO) IEEE 802.11n standard in conjunction with the Dual Channel Intermittent Periodic Transmit IPT (DCH-IPT) packets forwarding protocol. By using these two techniques (IEEE 802.11n + DCH-IPT), wireless backhaul nodes can meet more demanding communication requirements such as higher throughput, lower average delay, and lower packet dropping rate than those achieved by the currently used backhaul. The current backhaul is based upon Single-Input Single-Output (SISO) IEEE 802.11a,b,g standards in conjunction with Single Channel Conventional (SCH-Conv) relaying protocol in which packets are transmitted continuously from source nodes using single channel. The proposed backhaul will accelerate introduction of picocell based mobile communication systems.
Design and Evaluation of MAC Protocol Strategies Techniques in Wireless Ad Ho...ijtsrd
Wireless communication has become a core part of modern communication technology. The Infrastructure less wireless network, commonly referred to as Ad Hoc networks, has attracted extensive research interest for past 30 years. In this work, the focus is on IEEE 802.11 network performance analysis of Multihop hop Ad Hoc networks under non-saturated network conditions. To meet the increasing demand of multimedia, it is necessary to provide the quality of service in such networks. The current work presents the development of an analytical model for network performance analysis. The medium access mechanism in multihop wireless networks should minimize collisions, and take care of the hidden and exposed node problems. The IEEE 802.11 MAC with Distributed Coordination Function DCF does not scale well in such networks. We introduce Point Coordination Function PCF in the region of high traffic areas, and discuss its effect on network performance. To improve network scalability and throughput, we propose the design of a new MAC called Dual MAC. This work discusses architecture and working of the dual MAC in detail. Performance results of the network using dual MAC are presented, and compared with that of pure DCF operation. Prince Kumar | Rashmi Raj "Design and Evaluation of MAC Protocol Strategies Techniques in Wireless Ad Hoc Network" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-6 , October 2018, URL: http://www.ijtsrd.com/papers/ijtsrd18446.pdf
Comparative study of various voip applications in 802.11 a wireless network s...ijmnct
Today, Voice over Wireless Local Area Network (VOWLAN) is the most accepted Internet application.
There are a large number of literatures regarding the performance of various WLAN networks. Most of
them focus on simulations and modeling, but there are also some experiments with real networks. This
paper explains the comparison of performance of two different VOIP (Voice over Internet Protocol)
applications over the same IEEE 802.11a wireless network. Radio link standard 802.11a have maximum
transmission rate of 54Mbps. First protocol is session initiation protocol (SIP) and second is H.323
protocol. First one has an agent called SIP proxy. Second have a gateway reflects the characteristics of a
Switched Circuit Network (SCN). With this comparison we have required to obtain a better understanding
of wireless network suitability for voice communication in IP network.
Distributed Priority based channel access for VANET (DPBCA)Editor IJMTER
IEEE 802.11p vehicular network supports various applications with different
transmission priorities and QoS requirements. It classifies the access categories into four priority
levels to ensure the successful transmission of higher priority traffic compared to lower priority
traffic in a vehicle. But the external collision between traffic of same priority from different vehicles
is not considered. Based on such consideration, this paper proposes a distributed priority based
channel access scheme. In this proposed work, the priority of each vehicle is calculated based on its
stature on the road and access category. The proposed approach can ensure successful transmission
reducing collision leading to overall throughput improvement.
A STUDY OF QOS 6LOWPAN FOR THE INTERNET OF THINGSijscmcj
6LowPAN was introduced by the IETF as a standard protocol to interconnect tiny and constrained devices
across IPv6 clouds. 6LowPAN supports a QoS feature based on two priority bits. So far, little interest has
been granted and this QoS feature and there are no implementations of such feature in real networks. In
this paper,we evaluate the capacity to provide QoS of these priority bits in various scenarios. We show that
under very heavy or very low network load, these bits have a limited effect on the delay
1. A brief review of an application of queuing theory for
the performance and QoS analysis of IEEE 802.11
Panth Shah1
Graduate Student of Computer Engineering
Illinois Institute of Technology
Chicago, Illinois, U.S.A.
pshah80@hawk.iit.edu
Abstract— IEEE 802.11 is a standardized protocol for the
development of Wireless LAN with MAC and PHY specification
which was a major breakthrough to develop a best effort service
model for wireless technology. Distributed Coordination function
(DCF) is the primary technique for medium access control
(MAC) of 802.11. For IEEE 802.11 to meet the QoS
requirements, it is very much important to analyze the
performance metrics such as throughput or delay in both
saturated and non-saturated case. A required improvisation in
performance can be obtained by reserving bandwidth, analyzing
number of nodes and packet size distribution, and packet arrival
pattern for IEEE 802.11 based WLAN. A comprehensive study is
been conducted in this research paper regarding the
performance analysis for IEEE 802.11 protocol by measuring the
throughput, mean frame delay, packet loss rate, queuing delay
and channel busyness. In this paper, I have also studied different
probability and queuing models and conducted a generalized
survey to compare those models to analyze the performance of
IEEE 802.11 WLAN for different cases. An analytical study is
been conducted to check the results supporting important QoS
requirements for IEEE 802.11 MAC and Physical layer protocol
for WLAN supporting multimedia application.
Index Terms—IEEE 802.11, queuing analysis, service time,
QoS, throughput analysis, DCF, RTS/CTS, wireless local area
network (WLAN)
INTRODUCTION:
In recent years, communication on wireless medium has
always been a field of research for various researchers to
develop a sustainable and compatible infrastructure which can
support a multi user access service using broadband
bandwidth capability with layered architecture. Cellular
phones, wireless internet access and home network based on
wireless technology are the practical development of proposed
Wireless communication model. By the time, a standard has
been set up by IEEE 802.11 for the development of Wireless
LAN which is IEEE 802.11. IEEE 802.11 protocol is
developed with the support specification of Multiple Access
Control (MAC) and Physical layer Infrastructure. For WLAN,
it is architectures conducting an Access Point (AP) in the
middle and multiple users to access the same AP. In IEEE
802.11, the mechanism used for multiple access to the medium
by multiple users is Distributed Coordinated Function (DCF)
which is based on CSMA/CA protocol.
As a major technique for multiple access in IEEE 802.11,
DCF is has been researched and analyzed by many researchers
to obtain the optimum performance in accessing channel by
avoiding packet collision and providing sufficient amount of
random back off time for the retransmission. Two way hand
shacking and four way hand shacking are the two techniques
for basic access mechanisms associated with DCF. In two way
hand shacking mechanism, an ACK is sent by the receiver to
the sender to give feedback for the received packet. While in
four way hand shacking mechanism, RTS/CTS method is
used. There is a reserved slot for the transmission of RTS/CTS
before packet transmission and after packet reception. But, for
this RTS/CTS mechanism Hidden Terminal problem is one
major performance issue.
For the analysis of the performance of IEEE 802.11 DCF
mechanism, Binachi [1] proposes a model based on Markov
chain model with the assumption of ideal channel and having
a finite number of terminals in the system. In addition to this,
analyze the behavior of IEEE 802.11 in saturation and non-
saturation condition is also an extensive study topic for many
researchers. Researchers Zhai, Chen and Fang [2] came up
with the study of maximum IEEE 802.11 protocol capacity for
DCF based WLAN under non-saturated case and resulted that
protocol supports strict QoS requirements under unsaturated
traffic condition. In [3], researchers have developed an
analytical model based on discrete time G/G/1 queuing to
check the performance of the IEEE 802.11 MAC protocol with
respect to delay and queue length. Here, each node in the
network is been studied and modeled as a G/G/1 queue to
determine number of connections in the case of delay and to
evaluate the efficiency of delay reduction techniques for the
given network in multiple access protocols. While evaluating
the performance of an IEEE 802.11 MAC layer, position of
nodes in reference to Access Point (AP) is also a metric to
calculate the saturation throughput of the medium. In [4],
researcher had developed a model to calculate the saturation
throughput conditioning the station position with respect to the
other stations. In this paper, assumption that all stations are to
be placed at the same distance taken by Bianchi in [1] to
compute the performance of IEEE 802.11 MAC layer using
discrete time Markov chain is extended.
In this paper, various IEEE 802.11 QoS schemes are studied
and demonstrated with their respective techniques used for the
analysis of the performance metrics of DCF based WLAN
developed based on IEEE 802.11 protocol. Main aim of this
2. paper is to provide a survey of the different performance
issues examined so far, and possible solution for those
problems. The intended purpose of this brief review is to find
out the most accurate probability and/or queuing model for
designing Wireless LAN system with IEEE 802.11 protocol by
taking all the performance and design issues into
consideration. Also, the new features added into IEEE
802.11e standard is also described and evaluated for its
performance [5].
REVIEW OF IEEE 802.11 STANDARD:
IEEE 802.11 is a protocol developed as a Wireless
Communication standard with optimized Physical Layer
(PHY) and Medium Access Control (MAC) sublayers. For
multiple channel access support, IEEE 802.11 protocol uses
DCF mechanism with CSMA/CA with complexity
consideration in wireless environment. While developing
wireless LAN using this protocol, station can't listen the
collision while transmitting. In this standard, two types of
network configuration modes [5] are provided: one is
infrastructural mode and the other on is ad-hoc mode. In
infrastructural mode, stations are connected with access point
for transmission and reception. Whereas, in ad-hoc mode
stations can communicate with each other without any Access
Point.
A. Distribution Coordination Function(DCF) in IEEE
802.11 standard:
In wireless communication system developed on this
standard, when a station is ready to transmit a new packet,
station checks whether the channel is idle or busy. This is very
much important to avoid the collision of packets after
transmission. DCF uses Carrier sense multiple access with
collision avoidance (CSMA/CA) technique with binary
exponential back off for collision free packet transmission
between stations. DCF defines two methods to access the
channel: two way hand shacking and four way hand shacking.
Before initiating a packet transmission, each station senses the
medium/channel and generates a binary exponential back off.
DCF interface space is a time interval defined as an interval
for which the medium is idle. A slotted back off time is
generated randomly from a contention window (CW) size
which is defined as Back off time = rand [0; CW] ⋅ slot time
[5]
. Contention window size changes according to each
successful or unsuccessful transmission of packets. Initially,
for the first transmission CW is set to minimum value and the
size doubled after each unsuccessful transmission. After
successful transmission, CW sets to minimum value.
By checking the current channel status, back off time is
been set up and only when back off time reaches to zero,
station can access the channel. To notify the successful
transmission, a positive acknowledgement (ACK) signal is
sent back from receiver to sender station. Shortest Interface
Space (SIFS) is defined as a time duration between data frame
and ACK received for that frame. This two way handshaking
technique for the packet transmission can be stated as a basic
access mechanism. Another method for reliable transmission
is to use four way handshaking scheme in which RTS/CTS
signals are used to send a transmission request from sender to
receiver and a clear transmission request from receiver to
sender. This is the way where a system performance can
significantly be improvised when there is a hidden terminal
issue. RTS and CTS are the frames which carries the
information of length of the packet which is transmitted.
Receiver than using this information about packet updates the
Network Allocation Vector (NAV) to determine the time for
which channel will be busy. RTS/CTS mechanism is efficient
for system containing large packets, as it reduces the length of
frames in the contention process. Also, in RTS/CTS collision
can only occur on the RTS frame and is detected when CTS
response lacks.
Figure 1. Operational diagram of IEEE 802.11[7]
Figure 2. Functionality of CSMA/CA and RTC/CT[8]
B. IEEE 802.11e EDCA:
The IEEE 802.11e uses the EDCA mechanism which is an
extension of mechanism DCF used by IEEE 802.11. The
extension is required to add QoS requirement into
conventional IEEE 802.11 standard. In this mechanism, a
concept of Access Category (AC) with parameters such as
inter frame space duration, minimum contention window size,
maximum contention window size and so on is presented
which is the category in which stations separates it's arrival
traffic into. Each Access Category is numbered from 0 to 3
and having its predefined parameters mentioned. Arbitration
Inter-Frame Space in EDCA is defined as SIFS + AIFSN(AC)
x Tslot
[6]
.
A trace of backoff counter is important for the packet
transmission as when backoff counter reaches to zero, a packet
is transmitted until and unless there no other packet from a
higher priority category is ready for the transmission. In this
case, if there is any lower priority packet ready to be
transmitted, it experiences a virtual collision with the higher
3. priority packet intended to get transmitted.
LITERATURE REVIEW:
Examination of the properties and performance of IEEE
802.11 has been researched and analyzed by different
researchers based on various performance metrics. There has
been a various models proposed to analyze the saturation
throughput and packet delay or packet loss for IEEE 802.11
DCF protocol.Authors and Affiliations
Performance analysis: To characterize the behavior of
802.11and analyzing the performance of the system based on
this protocol, Binchi [1] proposed a Markov chain based model
for the back off window size analysis. Binchi's model is very
simple and easily understandable using the concepts of
Queuing theorem. Packet transmission probability and
throughput is been observed and formulated by using the
stochastic process representing the back off time counter for
the given node. Back off time counter decreases at the
beginning of the each time slot and this decrement stopes when
the channel is sensed busy. The value of the back off time
counter for each node in the system depends on its transmission
history, the stochastic process is non-Markovian. Let s(t) be
the stochastic process representing the back off stage (0,….,m)
of the station at time t. But, the major approximation in the
given model is that, at each transmission regardless of the
number of retransmission suffered, each packet may collide
with constant probability of p which is also independent to the
probability of the other node. The assumption also made up
here is that every node/station in the system is at the same
distance from the Access Point (AP) in the wireless system.
In [4], a Distance Aware Model is proposed where the
assumption taken by Binchi[1] is been eliminated. The model
proposed here considers the interference from the other station
in WLAN and also packet loss is computed by the background
noise. This model is called as DAW (Distance Aware) model.
In this model, the distance dk is been taken into consideration
which is the distance of Station to Access Point. Packet loss for
this model is a subject to this distance denoted by pk(dk). For
this model, fixed and random topologies are taken into
consideration for the analytical purpose and to calculate the
throughput of the system. By this model, it is concluded that
the model achieved more realistic results compare to the model
which doesn't consider the condition where the station is
moving with reference to Access Point.
In [2], the authors have conducted a comprehensive study
to analyze the performance of the network with respect to
maximum protocol capacity, throughput, and delay and packet
loss rate. But in this paper, researchers have taken non-
saturated case into consideration apart from just a saturated
case for the network a maximum protocol capacity according
to this paper can only be achieved in non-saturated case. The
author in this paper has tried to simulate their study around the
non-saturated case and tune the 802.11 to work on the
maximum throughput, minimum loss rate and packet delay
rate. In this paper, authors assumed that the traffic is uniformly
distributed among the stations where the total number of
nodes taken here is n and also the transmission probability for
each node in any time slot is also given as pt. The probability
of back off time slot to be idle, probability of one successful
transmission and collision probability is explained as follows:
Figure 3. Markov Chain Model proposed for the back off
window size [1]
Here, the impact of fading channel is also discussed with
the assumption that the channel is perfect. The condition
where the faded channel can affect the performance of the
system can be observed from packet losses. In here, it is
considered that channel fading is not a serious problem in
WLAN which takes low node movement and stable channel
into consideration. If the channel is faded, than packet loss in
not only a subject of collision, but packet loss can also be
done because of channel fading. From the analytical model
presented here, the normalized throughput decreases with the
service time increases and mean and variation of delay
increases along with the service time increment. Also packet
loss rate is also increased. From the results simulated and
analyzed in this paper, network QoS parameters such as
throughput, delay and packet loss can be tuned to get the
optimum performance of the network. Also, using channel
busyness ratio network utilization can accurately be
monitored.
In [7], the author has discussed about different scenario
where IEEE 802.11 protocol shows serious performance
issues. The author has summarized different performance
issues extracted and possible solution for those issues. Also,
the classification of issues has been extended to help
designing MAC protocol for ad-hoc network apart from
WLAN. In this paper, author has classified the issues into
three main categories which are: Configuration with long term
fairness issue. Configuration with short-term fairness issue
and Configuration that results in overall throughput
4. decrement. At the end it is concluded that cross layer protocol
design is one of the best and effective solution for the
problems encountered into complex systems which isolated
MAC layer into its design.
ANALYTICAL MODEL PROPOSED FOR IEEE 802.11
DCF:
Back off counter value is a fair representation of a state of
IEEE 802.11 DCF based wireless network and the back off
stage the station is situated in currently. While using the
concept of queuing theory and properties of probability model
into consideration to observe the performance of DCF
mechanism, MAC buffer is taken as a queue and number of
packets currently present in the queue is taken as a
performance metric for the consideration of queuing theorem.
Here, we have modeled a behavior of typical wireless station
and also includes the effect of other stations on the
performance of that station at the time of packet transmission.
Here by comparing the entire WLAN system with customer-
server model to analyze the behavior of the system using
queuing theory. In this case, we are modeling the behavior of
every wireless station present into a wireless system where
back off stage is mapped on a queue and every single wireless
node is articulated as a single customer. This is the reason, the
proposed system is closed queuing network. While designing
this model on the current network system, two dimensional
array of queues are taken where each queue is modeled on
(k, i)th position in which i represents current back off stage
and k represents the number of packets currently in the MAC
buffer.
Figure 4. IEEE 802.11 DCF modeled on Queuing network
modeling [6]
As, there is only one customer in the system modeled on
queuing network, Queuing system is considered M/G/inf.
According to the model proposed, traffic equation for the
given queuing network is given as follows:
A. Model for Saturation Throughput and Packet Delay
analysis for IEEE 802.11 DCF with channel fading:
For WLAN developed using this protocol, station's
transmission probability for packet transmission can be
evaluated using the modified Markov chain model presented
here. This modified Markov chain includes the analysis of
back off window size for each station that takes frame-error
into consideration and maximum allowable number of
retransmission attempts are also be analyzed by taking each
station as a queue. The frame error rate has a significant
impact on the evaluation of throughput, mean frame delay and
discarding probability. For the analysis purpose, transmission
probability of each station is taken in a randomly chosen time
slot and so the Modified Markovian chain is analyzed as in
fig. 5. Moreover, this model is extended by taking error free
probability Pf into consideration. Finite number of
retransmission attempts (m + f + 1) which is the number after
which the frame is discarded from the transmission queue with
an addition of a new frame in the queue. A current state (i, k)
of a station is determined by the current value of the back off
timer k after which it will start suffering unsuccessful
transmission attempts.
From the analysis, it is observed that the saturation
throughput decreases with increment in number of stations in
basic access mode while others are stable with RTS/CTS
access mode. While comparing the ratio between the length of
the useful frames for transmission and RTS frames, the
difference is not major. This is because of the frame delay in
each station which is originated from the back off defer period
in the station queues significantly. Impact of frame error rate
over the performance of the protocol is observed using the
following result shown in fig. 6. The transmission probability,
saturation throughput, frame discard probability and mean
delay after analyzing this model is obtained as follows:
Transmission probability:
5. Saturation Throughput:
Frame Discard Probability:
Mean Delay:
Average duration of a renewal cycle Trc:
Figure 5. Fading channel analysis for IEEE 802.11 DCF using
finite-state station model [9]
While considering the frame-error rate Pf on the overall
performance measure of the system under fading channel
condition, this parameter will effect on saturation throughput,
delay rate and discard probability of the system/model
proposed here. In the result shown below, increasing frame-
error rate from 0.01 to 1, throughput degrades towards zero
and by increasing discard probability towards 100%.
Saturation mean delay also increases with the increment in
frame-error rate.
(a)
(b)
(c)
Figure 6. Frame-error rate impact over the performance: (a)
saturation throughput, (b) Delay, (c) Discard probability [9]
6. QOS ANALYSIS BASED ON PERFORMANCE PARAMETERS AND
MECHANISM:
While designing wireless links using given protocol, a
major challenge associated with the QoS of the system is the
performance of upper layer application. In conventional IEEE
802.11 protocol, there is an isolated MAC layer which can't
support the QoS specification of upper layer applications as
the analysis of upper layer application performance won't help
evaluating the QoS of MAC layer. The specified
characteristics observed for all the layers of this protocol are
high loss rates, burst or frame loss, high latency rate and jitter.
QoS mechanism for 802.11 can be classified into three
categories given as: Service differentiation, Admission control
and bandwidth reservation and Link adaption. In WLAN
environment, except relatively low data rate and higher error
caused due to RF characteristics like multi-path fading due to
channel fading, CSMA/CA proposed in IEEE 802.11 DCF
also trapped into a problem with different layers.
Though, there are different QoS mechanism applied to
every layer of the network, various ideas are applied based on
the queuing models to analyze the 4 major performance
parameters of the system for QoS.
A. Differentiation Serving Model System:
Different requirements of different application are served
using different layers from the proposed model. For IEEE
802.11, there are two methodologies used. 1. Priority Based
and 2. Fair Scheduling based service. This classification
mechanism replicates the traffics into various flows. So, each
flow can be handled according to specific requirement they
should be handled. Priority based service always serves those
traffics with the highest priority out of the total traffic.
Whereas, second service model schedules the bandwidth on
the basis of weight of each traffic flow. The specified service
differentiation mechanisms are [8]
:
1. Enhanced DCF (EDCF)
2. Persistent Factor DCF (P-DCF)
3. Distributed Weighted Fair Queue (DWFQ)
4. Distributed Fair Scheduling (DFS)
5. Distributed Deficit Round Robin (DDRR)
Figure 7. Differentiation Serving Model System for IEEE
802.11
B. QoS Mechanism for Admission Control (CAC):
To obtain optimized output under heavy traffic load
condition, Differentiation Serving Model is not a correct
choice. For any multimedia application in IEEE 802.11 to be
analyzed for its performance, saturation delay is a critical
parameter to be considered. When the saturation delay is
large, it leads to a failure to support multimedia application.
Also, bandwidth provisioning in contention based CSMA/CA
channel access mechanism is an impossible case. So, for this
case, admission control and bandwidth reservation is an
important considerations for guaranteed QoS By considering
broader approach of wireless communication, admission
control scheme is extended into measurement based and
calculation based scheme. A concept of delay sensitive traffic
is a critical methodology of observing WLAN traffic using
Queuing models developed. This option assumes that the
traffic entering into WLAN is pre shaped and is given a
deterministic bound because of the limited capacity of a
wireless medium. So to maintain QoS of a wireless system
based on IEEE 802.11 it is very much important to analyze the
traffic type and whether it may violate the QoS of the system
or not. For this decision to be taken, CAC algorithm [10] is
developed.
CONCLUSION AND FUTURE WORK ON AN OPEN ISSUE
So far, it has been surveyed in this paper about the models
researchers had proposed by the time for the performance
analysis and relational issues related to the performance of
IEEE 802.11 protocol under different considerations. In this
article, I have represented a Queuing theory based probability
analysis model for packet transmission and packet lost analysis
to find the maximum throughput of the system. Also, for both
saturated and non-saturated environment, a model based on
Markovian chain is been studied in this paper to find the
effectiveness and essentiality of packet loss rate to measure the
performance of the system using performance metrics such as
throughput, packet loss rate, packet arrival timing and so on.
Also, from the research obtained it has been devised that
RTS/CTS mechanism in channel access is superior in most of
the cases and while using this mechanism, performance is only
partially dependent on the system parameters.
Also, a hidden terminal problem associated with
CSMA/CA is also discussed in this article and how QoS
parameters are added into IEEE 802.11e, which is an
improvised version of IEEE 802.11. Discussion about the
choice of EDCF over DCF is also obtained to check how QoS
is important to analyze while working with multimedia
applications in IEEE 802.11 protocol.
It is also concluded from the study that isolated MAC
layer is not a correct choice as information from the lower
layer is important to analyze the performance of the upper
layers.
Also, it has been discussed in the paper that QoS is been
guaranteed in IEEE 802.11 WLANs by classifying QoS
approaches into two schemes: One is Differentiation Serving
7. Model System and the other one is QoS mechanism for
Admission Control (AC).
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