This document summarizes a formal specification, verification, and simulation of the MACAW wireless LAN protocol. The specification formally models MACAW using communicating finite state machines and shared variables. The verification analyzes basic configurations of 2, 3, and 4 machines to check for errors like deadlocks, but does not verify all possible configurations. The simulation provides further insight into MACAW's performance and suggests areas for improvement. In summary, the work formally specifies MACAW, verifies parts of its behavior, and simulates its performance to evaluate and potentially enhance the protocol.
A DDRESSING T HE M ULTICHANNEL S ELECTION , S CHEDULING A ND C OORDINATION...pijans
We discuss a new multichannel coordination and sche
duling challenge called the Multichannel Scheduling
Cost (MSC). It is caused by the inability of the co
ntrol channel to schedule simultaneous transmission
s
resulting in data channels lying idle and their ban
dwidth underutilized. As a result, wasted bandwidth
increases as the number of data channels increases.
To address this challenge, a cyclic scheduling
Algorithm (CSA) is proposed. It employs one dedicat
ed signaling channel and 4 data channels. It is
premised on a proactive channel reservation scheme
which reduces the idleness of channels. The scheme
ensures that data channels are reserved while they
are still busy. The data channels are reserved whil
e
their remaining transmission duration is equal to t
he virtual carrier sensing duration. This gives the
next
pair sufficient time to reserve the current data ch
annel before it becomes available, limiting the MSC
to the
first cycle. The simulation results show a performa
nce benefit of the CSA scheme in addressing the eff
ects
of the MSC
The three-way need for higher data rates, good quality of service and ubiquity in a converged all IP
communication cloud drives research in wireless communication. Wireless access networks are envisaged
candidates of the next generation wireless networks. The various access networks will be integrated with
other technologies including the wired backbone. The major issues in an all IP and converged networks
are: quality of service, seamless handover and network capacity. Emerging research seeks to address these
open research issues; for example the implementation of multi-channel and multi radio MAC protocols in
WMN. In this paper we analyze and evaluate the effectiveness of multi-channel and multi radio techniques
in WMN. The shortcomings of these schemes are highlighted and possible solutions are suggested. The
signalling delay metric is used for evaluation purposes. The focus is on the performance of the control
channel identified as the critical performance metric of multi-channel MAC protocols.
Some of the key driving forces behind the transition from the UMTS based cellular system to the Long Term Evolution Advanced (LTE-A) are to improve the mean and the cell-edge throughput, improve the user fairness, and improve the quality of service (QoS) satisfaction for all users. In the latter system, relays appear as one of the most prominent enabler for improving the cell-edge user experience while increasing the system’s fairness.
In this white paper, we present the basics of relay deployments in LTE-A networks. Moreover, we analyze resource allocation problem for Relay Nodes (RN) deployments and present some of the solutions for improvement in system resource usage and QoS satisfaction. Afterwards, we introduce the capabilities of NOMOR’s LTE-A system level simulator and evaluate the performance of LTE-A relay systems under the described solutions.
A DDRESSING T HE M ULTICHANNEL S ELECTION , S CHEDULING A ND C OORDINATION...pijans
We discuss a new multichannel coordination and sche
duling challenge called the Multichannel Scheduling
Cost (MSC). It is caused by the inability of the co
ntrol channel to schedule simultaneous transmission
s
resulting in data channels lying idle and their ban
dwidth underutilized. As a result, wasted bandwidth
increases as the number of data channels increases.
To address this challenge, a cyclic scheduling
Algorithm (CSA) is proposed. It employs one dedicat
ed signaling channel and 4 data channels. It is
premised on a proactive channel reservation scheme
which reduces the idleness of channels. The scheme
ensures that data channels are reserved while they
are still busy. The data channels are reserved whil
e
their remaining transmission duration is equal to t
he virtual carrier sensing duration. This gives the
next
pair sufficient time to reserve the current data ch
annel before it becomes available, limiting the MSC
to the
first cycle. The simulation results show a performa
nce benefit of the CSA scheme in addressing the eff
ects
of the MSC
The three-way need for higher data rates, good quality of service and ubiquity in a converged all IP
communication cloud drives research in wireless communication. Wireless access networks are envisaged
candidates of the next generation wireless networks. The various access networks will be integrated with
other technologies including the wired backbone. The major issues in an all IP and converged networks
are: quality of service, seamless handover and network capacity. Emerging research seeks to address these
open research issues; for example the implementation of multi-channel and multi radio MAC protocols in
WMN. In this paper we analyze and evaluate the effectiveness of multi-channel and multi radio techniques
in WMN. The shortcomings of these schemes are highlighted and possible solutions are suggested. The
signalling delay metric is used for evaluation purposes. The focus is on the performance of the control
channel identified as the critical performance metric of multi-channel MAC protocols.
Some of the key driving forces behind the transition from the UMTS based cellular system to the Long Term Evolution Advanced (LTE-A) are to improve the mean and the cell-edge throughput, improve the user fairness, and improve the quality of service (QoS) satisfaction for all users. In the latter system, relays appear as one of the most prominent enabler for improving the cell-edge user experience while increasing the system’s fairness.
In this white paper, we present the basics of relay deployments in LTE-A networks. Moreover, we analyze resource allocation problem for Relay Nodes (RN) deployments and present some of the solutions for improvement in system resource usage and QoS satisfaction. Afterwards, we introduce the capabilities of NOMOR’s LTE-A system level simulator and evaluate the performance of LTE-A relay systems under the described solutions.
Dynamic Power Allocation for Mc-Cdma System Using Iterative Water Filling Alg...inventionjournals
ABSTRACT : Power control in Multi Carrier Code Division Multiple Access ( MCCDMA) based wireless cellular network is of great importance. The power allocation methodology to enhance the performance of the MCCDMA system by limiting interference noise is at the expense of signaling overhead due to sharing of Channel State Information (CSI). The distributed algorithms that manage the power level based on the user’s SINR requirements needs the complete knowledge of Channel State Information (CSI) .Since the CSI is subjected to the errors because of the imperfect channel estimation/measurement due to the time varying nature of the channels, the distributed power control algorithm is not globally optimum. The water filling algorithm is used to allocate proper power for every sub channel in order to improve channel capacity. The water filling algorithm distributes power among all users with the help of SINR that is received by the transmitter instead of getting full Channel State Information (CSI).
Simulation and Performance Analysis of Long Term Evolution (LTE) Cellular Net...ijsrd.com
In the development, standardization and implementation of LTE Networks based on Orthogonal Freq. Division Multiple Access (OFDMA), simulations are necessary to test as well as optimize algorithms and procedures before real time establishment. This can be done by both Physical Layer (Link-Level) and Network (System-Level) context. This paper proposes Network Simulator 3 (NS-3) which is capable of evaluating the performance of the Downlink Shared Channel of LTE networks and comparing it with available MatLab based LTE System Level Simulator performance.
Managing Instantly Dense Hot Spot Regions in Wireless Cellular Communication ...Eswar Publications
In a wireless communication cellular network, call activity can be more intensive in some regions than others. These high-traffic regions are called hot spot regions. In typical deployments of wireless cellular networks, traffic hot spots can arise from the non-uniform geographic distribution of the mobile users, and the heavy-tailed nature of their network usage patterns. These hot spots of activity can degrade system performance, by increasing network utilization, wireless interference, call blocking, and even call dropping from failed handoffs for mobile users. In this paper, a hierarchical cellular communication wireless network is characterized by overlapping the service area for managing the new calls users having different mobility speed. The overlapping property of the hierarchical-network provides the advantages that share the traffic load to improve the performance of wireless
cellular networks in the highly populated area where both slow speed users and high speed users are available.
Picocells are created that are underlaid to two-tier networks for handling the slow or staying speed visitor (outside registered) users. The hierarchical-networks with picocells, microcells and macrocells provide the secondary resource, which provide the services to new calls as well as handoff calls with guard channels by overflow the slow speed visitor users in picocells, slow speed local users in macrocell by sharing the frequency in
vertical as well as in horizontal directions. The picocell is installed on four wheeler vehicle may be moved at any place as per necessity and may be utilized to create picocell to handle the load of hot spot area. Such kind of picocell is known as Portable-Picocell (P-Picocell/ P2cell). The call loss probability of new calls is developed through numerical analysis. The proposed schemes are compared with the existing schemes of CAC. Results show that new proposed schemes are more efficient and handle more visitor calls by redirecting calls and sharing of load in P2cell.
A Cross Layer Based Scalable Channel Slot Re-Utilization Technique for Wirele...csandit
Due to tremendous growth of the wireless based application services are increasing the demand
for wireless communication techniques that use bandwidth more effectively. Channel slot reutilization
in multi-radio wireless mesh networks is a very challenging problem. WMNs have
been adopted as back haul to connect various networks such as Wi-Fi (802.11), WI-MAX
(802.16e) etc. to the internet. The slot re-utilization technique proposed so far suffer due to high
collision due to improper channel slot usage approximation error. To overcome this here the
author propose the cross layer optimization technique by designing a device classification
based channel slot re-utilization routing strategy which considers the channel slot and node
information from various layers and use some of these parameters to approximate the risk
involve in channel slot re-utilization in order to improve the QoS of the network. The simulation
and analytical results show the effectiveness of our proposed approach in term of channel slot
re-utilization efficiency and thus helps in reducing latency for data transmission and reduce
channel slot collision.
A Survey of Various Routing and Channel Assignment Strategies for MR-MC WMNsijsrd.com
One fundamental problem of WMNs with a limited number of radio interfaces and orthogonal channels is that the performance degrades significantly as the network size grows. This results from increased interference between nodes and diminished spatial reuse over the network. A WMN node needs to share a common channel with each of its neighbours in the communication range, requiring it to set up a virtual link. Moreover, to reduce network interference, a node should minimize the number of neighbours that it shares a common channel with. The objective of a channel assignment strategy is to ensure efficient utilization of the available channels (e.g., by minimizing interference) while maximizing connectivity in the network. However, since these two requirements are conflicting with each other, the goal is to achieve a balance between these two. The major constraints which need to be satisfied by a channel assignment scheme include fixed number of channels in the network, limited number of radios in mesh nodes, common channel between two communicating nodes, and limited channel capacity. Also, a channel assignment scheme should take the amount of traffic load supported by each mesh node into consideration.
Heterogeneous LTE Networks and Inter-Cell Interference Coordination - Dec 201...Eiko Seidel
Initial deployments of LTE networks are based on so-called homogeneous networks consisting of base stations providing basic coverage, called macro base stations. The concept of heterogeneous networks has recently attracted considerable attention to optimize performance particularly for unequal user or traffic distribution. Here, the layer of planned high-power macro eNBs is overlaid with layers of lower-power pico or femto eNBs that are deployed in a less well planed or even entirely uncoordinated manner. Such deployments can achieve significantly improved overall capacity and cell-edge performance and are often seen as the second phase in LTE network deployment.
This paper discusses the concept of heterogeneous networks as compared to homogeneous networks. It demonstrates the need for inter-cell interference coordination (ICIC) and outlines some ICIC methods that are feasible with release 8 /9 of the LTE standard. System-level simulation results illustrate the benefits of the various features discussed in the following.
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
we find out various power aware and data packet rate control with-collision-avoidance (CSMA/CA)-based ad hoc wireless network communication. And identifies that CSMA
Multi-layer heterogeneous network layout including small cell base stations are considered to be the key to further enhancements of the spectral efficiency achieved in mobile communication networks. It has been recognized that inter-cell interference has become the limiting factor when trying to achieve not only high average user satisfaction, but a high degree of satisfaction for as many users as possible. Therefore, inter-cell interference coordination (ICIC) lies in the focus of researchers defining next generation mobile communication standards, such as LTE-A.
Building upon [1], this paper provides an overview over the background calling for ICIC in heterogeneous LTE-A networks. It outlines techniques standardized in Rel. 10 of LTE-A, discusses them showing their benefits and limitations by means of system-level simulations and motivates the importance of self optimizing network (SON) procedures for ICIC in LTE-A.
Efficient and Fair Bandwidth Allocation AQM Scheme for Wireless NetworksCSCJournals
Heterogeneous Wireless Networks are considered nowadays as one of the potential areas in research and development. The traffic management’s schemes that have been used at the fusion points between the different wireless networks are classical and conventional. This paper is focused on developing a novel scheme to overcome the problem of traffic congestion in the fusion point router interconnected the heterogeneous wireless networks. The paper proposed an EF-AQM algorithm which provides an efficient and fair allocation of bandwidth among different established flows. Finally, the proposed scheme developed, tested and validated through a set of experiments to demonstrate the relative merits and capabilities of a proposed scheme
Investigation of Clock Synchronization Techniques and its Performance Impact ...ijctet
Mobile ad hoc Network (MANET) is an assortment of mobile nodes that area unit needed to transmit packets on behalf of every alternative. The mobile nodes maintain the topology data during a dynamic network among a selected vary. All nodes should remember of its neighbors that area unit directly approachable. The every node in network maintained next hop data of close neighbor nodes. The routing protocols area unit routed knowledge packets in between sender and receiver during a specific time instant. The time synchronization is maintained the communication clock cycle between the nodes. Time synchronization is an important element of a MANET. Time synchronization during a network aims at providing a typical duration for local clocks of nodes within the network. Since all hardware clocks area unit imperfect, local clocks of nodes could alienate from one another in time, thus determined time or durations of your
Dynamic Power Allocation for Mc-Cdma System Using Iterative Water Filling Alg...inventionjournals
ABSTRACT : Power control in Multi Carrier Code Division Multiple Access ( MCCDMA) based wireless cellular network is of great importance. The power allocation methodology to enhance the performance of the MCCDMA system by limiting interference noise is at the expense of signaling overhead due to sharing of Channel State Information (CSI). The distributed algorithms that manage the power level based on the user’s SINR requirements needs the complete knowledge of Channel State Information (CSI) .Since the CSI is subjected to the errors because of the imperfect channel estimation/measurement due to the time varying nature of the channels, the distributed power control algorithm is not globally optimum. The water filling algorithm is used to allocate proper power for every sub channel in order to improve channel capacity. The water filling algorithm distributes power among all users with the help of SINR that is received by the transmitter instead of getting full Channel State Information (CSI).
Simulation and Performance Analysis of Long Term Evolution (LTE) Cellular Net...ijsrd.com
In the development, standardization and implementation of LTE Networks based on Orthogonal Freq. Division Multiple Access (OFDMA), simulations are necessary to test as well as optimize algorithms and procedures before real time establishment. This can be done by both Physical Layer (Link-Level) and Network (System-Level) context. This paper proposes Network Simulator 3 (NS-3) which is capable of evaluating the performance of the Downlink Shared Channel of LTE networks and comparing it with available MatLab based LTE System Level Simulator performance.
Managing Instantly Dense Hot Spot Regions in Wireless Cellular Communication ...Eswar Publications
In a wireless communication cellular network, call activity can be more intensive in some regions than others. These high-traffic regions are called hot spot regions. In typical deployments of wireless cellular networks, traffic hot spots can arise from the non-uniform geographic distribution of the mobile users, and the heavy-tailed nature of their network usage patterns. These hot spots of activity can degrade system performance, by increasing network utilization, wireless interference, call blocking, and even call dropping from failed handoffs for mobile users. In this paper, a hierarchical cellular communication wireless network is characterized by overlapping the service area for managing the new calls users having different mobility speed. The overlapping property of the hierarchical-network provides the advantages that share the traffic load to improve the performance of wireless
cellular networks in the highly populated area where both slow speed users and high speed users are available.
Picocells are created that are underlaid to two-tier networks for handling the slow or staying speed visitor (outside registered) users. The hierarchical-networks with picocells, microcells and macrocells provide the secondary resource, which provide the services to new calls as well as handoff calls with guard channels by overflow the slow speed visitor users in picocells, slow speed local users in macrocell by sharing the frequency in
vertical as well as in horizontal directions. The picocell is installed on four wheeler vehicle may be moved at any place as per necessity and may be utilized to create picocell to handle the load of hot spot area. Such kind of picocell is known as Portable-Picocell (P-Picocell/ P2cell). The call loss probability of new calls is developed through numerical analysis. The proposed schemes are compared with the existing schemes of CAC. Results show that new proposed schemes are more efficient and handle more visitor calls by redirecting calls and sharing of load in P2cell.
A Cross Layer Based Scalable Channel Slot Re-Utilization Technique for Wirele...csandit
Due to tremendous growth of the wireless based application services are increasing the demand
for wireless communication techniques that use bandwidth more effectively. Channel slot reutilization
in multi-radio wireless mesh networks is a very challenging problem. WMNs have
been adopted as back haul to connect various networks such as Wi-Fi (802.11), WI-MAX
(802.16e) etc. to the internet. The slot re-utilization technique proposed so far suffer due to high
collision due to improper channel slot usage approximation error. To overcome this here the
author propose the cross layer optimization technique by designing a device classification
based channel slot re-utilization routing strategy which considers the channel slot and node
information from various layers and use some of these parameters to approximate the risk
involve in channel slot re-utilization in order to improve the QoS of the network. The simulation
and analytical results show the effectiveness of our proposed approach in term of channel slot
re-utilization efficiency and thus helps in reducing latency for data transmission and reduce
channel slot collision.
A Survey of Various Routing and Channel Assignment Strategies for MR-MC WMNsijsrd.com
One fundamental problem of WMNs with a limited number of radio interfaces and orthogonal channels is that the performance degrades significantly as the network size grows. This results from increased interference between nodes and diminished spatial reuse over the network. A WMN node needs to share a common channel with each of its neighbours in the communication range, requiring it to set up a virtual link. Moreover, to reduce network interference, a node should minimize the number of neighbours that it shares a common channel with. The objective of a channel assignment strategy is to ensure efficient utilization of the available channels (e.g., by minimizing interference) while maximizing connectivity in the network. However, since these two requirements are conflicting with each other, the goal is to achieve a balance between these two. The major constraints which need to be satisfied by a channel assignment scheme include fixed number of channels in the network, limited number of radios in mesh nodes, common channel between two communicating nodes, and limited channel capacity. Also, a channel assignment scheme should take the amount of traffic load supported by each mesh node into consideration.
Heterogeneous LTE Networks and Inter-Cell Interference Coordination - Dec 201...Eiko Seidel
Initial deployments of LTE networks are based on so-called homogeneous networks consisting of base stations providing basic coverage, called macro base stations. The concept of heterogeneous networks has recently attracted considerable attention to optimize performance particularly for unequal user or traffic distribution. Here, the layer of planned high-power macro eNBs is overlaid with layers of lower-power pico or femto eNBs that are deployed in a less well planed or even entirely uncoordinated manner. Such deployments can achieve significantly improved overall capacity and cell-edge performance and are often seen as the second phase in LTE network deployment.
This paper discusses the concept of heterogeneous networks as compared to homogeneous networks. It demonstrates the need for inter-cell interference coordination (ICIC) and outlines some ICIC methods that are feasible with release 8 /9 of the LTE standard. System-level simulation results illustrate the benefits of the various features discussed in the following.
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
we find out various power aware and data packet rate control with-collision-avoidance (CSMA/CA)-based ad hoc wireless network communication. And identifies that CSMA
Multi-layer heterogeneous network layout including small cell base stations are considered to be the key to further enhancements of the spectral efficiency achieved in mobile communication networks. It has been recognized that inter-cell interference has become the limiting factor when trying to achieve not only high average user satisfaction, but a high degree of satisfaction for as many users as possible. Therefore, inter-cell interference coordination (ICIC) lies in the focus of researchers defining next generation mobile communication standards, such as LTE-A.
Building upon [1], this paper provides an overview over the background calling for ICIC in heterogeneous LTE-A networks. It outlines techniques standardized in Rel. 10 of LTE-A, discusses them showing their benefits and limitations by means of system-level simulations and motivates the importance of self optimizing network (SON) procedures for ICIC in LTE-A.
Efficient and Fair Bandwidth Allocation AQM Scheme for Wireless NetworksCSCJournals
Heterogeneous Wireless Networks are considered nowadays as one of the potential areas in research and development. The traffic management’s schemes that have been used at the fusion points between the different wireless networks are classical and conventional. This paper is focused on developing a novel scheme to overcome the problem of traffic congestion in the fusion point router interconnected the heterogeneous wireless networks. The paper proposed an EF-AQM algorithm which provides an efficient and fair allocation of bandwidth among different established flows. Finally, the proposed scheme developed, tested and validated through a set of experiments to demonstrate the relative merits and capabilities of a proposed scheme
Investigation of Clock Synchronization Techniques and its Performance Impact ...ijctet
Mobile ad hoc Network (MANET) is an assortment of mobile nodes that area unit needed to transmit packets on behalf of every alternative. The mobile nodes maintain the topology data during a dynamic network among a selected vary. All nodes should remember of its neighbors that area unit directly approachable. The every node in network maintained next hop data of close neighbor nodes. The routing protocols area unit routed knowledge packets in between sender and receiver during a specific time instant. The time synchronization is maintained the communication clock cycle between the nodes. Time synchronization is an important element of a MANET. Time synchronization during a network aims at providing a typical duration for local clocks of nodes within the network. Since all hardware clocks area unit imperfect, local clocks of nodes could alienate from one another in time, thus determined time or durations of your
The IP Landscape: Intellectual Property in Theme Parks and Attractions Jack Rouse Associates
JRA CEO/Owner Keith James discusses why attractions use intellectual property, as well as the design opportunities and challenges inherent in recreating cherished IP characters, themes and environments. As presented at the International Association of Amusement Parks and Attractions' 2015 Euro Attractions Show in Liseberg, Gothenburg Sweden on 7 October 2015. For more information, contact Shawn McCoy, VP of Marketing and Business Development, at smccoy@jackrouse.com, and for a transcript, visit www.jackrouse.com/blog.
A privacy preserving framework for managing mobile ad requests and billing in...LeMeniz Infotech
A privacy preserving framework for managing mobile ad requests and billing information
Do Your Projects With Technology Experts
To Get this projects Call : 9566355386 / 99625 88976
Visit : www.lemenizinfotech.com / www.ieeemaster.com
Mail : projects@lemenizinfotech.com
A CROSS-LAYER BASED SCALABLE CHANNEL SLOT RE-UTILIZATION TECHNIQUE FOR WIRELE...cscpconf
Due to tremendous growth of the wireless based application services are increasing the demand for wireless communication techniques that use bandwidth more effectively. Channel slot reutilization in multi-radio wireless mesh networks is a very challenging problem. WMNs have been adopted as back haul to connect various networks such as Wi-Fi (802.11), WI-MAX (802.16e) etc. to the internet. The slot re-utilization technique proposed so far suffer due to high collision due to improper channel slot usage approximation error. To overcome this here the author propose the cross layer optimization technique by designing a device classification based channel slot re-utilization routing strategy which considers the channel slot and node information from various layers and use some of these parameters to approximate the risk involve in channel slot re-utilization in order to improve the QoS of the network. The simulation and analytical results show the effectiveness of our proposed approach in term of channel slot re-utilization efficiency and thus helps in reducing latency for data transmission and reduce
channel slot collision.
A MAC PROTOCOL WITH DYNAMIC ALLOCATION OF TIME SLOTS BASED ON TRAFFIC PRIORIT...ijaia
In a wireless body area network (WBAN), wireless biomedical sensors are placed around, on, or inside the human body. Given specific requirements, WBANs can significantly improve healthcare, diagnostic monitoring, and other medical services. However, the existing standards such as IEEE 802.11 and IEEE 802.15.4 have some limitations to meet all the requirements of WBANs. Many medium access control (MAC) protocols have been studied so far, most of which are derived from the IEEE 802.15.4 superframe structure with some improvements and adjustments. However, the MAC protocols do not provide the required quality of service (QoS) for various types of traffic in a WBAN. In this paper, a traffic-aware MAC (TA-MAC) protocol for WBANs is proposed, in which time slots are dynamically allocated on the basis of traffic priority, providing the required QoS. According to the performance evaluation results, the proposed TA-MAC is better than IEEE 802.15.4 MAC and the conventional priority-based MAC in terms of transmission time, system throughput, energy efficiency, and collision ratio.
A MAC PROTOCOL WITH DYNAMIC ALLOCATION OF TIME SLOTS BASED ON TRAFFIC PRIORIT...IJCNCJournal
In a wireless body area network (WBAN), wireless biomedical sensors are placed around, on, or inside the human body. Given specific requirements, WBANs can significantly improve healthcare, diagnostic monitoring, and other medical services. However, the existing standards such as IEEE 802.11 and IEEE 802.15.4 have some limitations to meet all the requirements of WBANs. Many medium access control (MAC) protocols have been studied so far, most of which are derived from the IEEE 802.15.4 superframe structure with some improvements and adjustments. However, the MAC protocols do not provide the required quality of service (QoS) for various types of traffic in a WBAN. In this paper, a traffic-aware MAC (TA-MAC) protocol for WBANs is proposed, in which time slots are dynamically allocated on the basis of traffic priority, providing the required QoS. According to the performance evaluation results, the proposed TA-MAC is better than IEEE 802.15.4 MAC and the conventional priority
PERFORMANCE ANALYSIS OF CHANNEL ACCESS MODEL FOR MAC IN RANDOMLY DISTRIBUTED ...IJCNCJournal
Medium Access control (MAC) is one of the fundamental problems in wireless sensor networks. The performance of wireless sensor network depends on it. The main objective of a medium access control method is to provide high throughput, minimize the delay, and conservers the energy consumption by avoiding the collisions. In this paper, a general model for MAC protocol to reduce the delay, maximize throughput and conserve the energy consumption in channel accessing in high density randomly distributed wireless sensor network is presented. The proposed model is simulated using MATLAB. The simulation results show that the average delay for sensors with sufficient memory is lower than sensors without
memory. Further, the throughput of the channel access method with memory is better than without memory.
SLOTTED CSMA/CA BASED ENERGY EFFICIENT MAC PROTOCOL DESIGN IN NANONETWORKSijwmn
Devices in a beacon-enabled network use slotted CSMA/CA to contend for channel usage. Each node in the network competes for the channels when ready to transmit data. The slotted CSMA/CA mechanism based on the super-frame structure fairly provides communication chance for each node and makes a reasonable usage of the available energy in beacon-enabled Zigbee networks. When wireless nano-sensor nodes are implanted into the target human body area for detecting disease symptoms or virus existence, each node also requires a similar characteristic in channel sharing and in the transmission of event-driven data with a short length. In this paper, we suggest a wireless network model with nano-sensor nodes for the in-body application. We propose a novel MAC protocol derived from an existing Zigbee MAC protocol scheme and analyze the performance of energy usage with variable super-frame durations and packet sizes.
SLOTTED CSMA/CA BASED ENERGY EFFICIENT MAC PROTOCOL DESIGN IN NANONETWORKSijwmn
Devices in a beacon-enabled network use slotted CSMA/CA to contend for channel usage. Each node in the
network competes for the channels when ready to transmit data. The slotted CSMA/CA mechanism based
on the super-frame structure fairly provides communication chance for each node and makes a reasonable
usage of the available energy in beacon-enabled Zigbee networks. When wireless nano-sensor nodes are
implanted into the target human body area for detecting disease symptoms or virus existence, each node
also requires a similar characteristic in channel sharing and in the transmission of event-driven data with
a short length. In this paper, we suggest a wireless network model with nano-sensor nodes for the in-body
application. We propose a novel MAC protocol derived from an existing Zigbee MAC protocol scheme and
analyze the performance of energy usage with variable super-frame durations and packet sizes.
Performance of Vehicle-to-Vehicle Communication using IEEE 802.11p in Vehicul...IJNSA Journal
Traffic safety applications using vehicle-to-vehicle (V2V) communication is an emerging and promising area within the ITS environment. Many of these applications require real-time communication with high reliability. To meet a real-time deadline, timely and predictable access to the channel is paramount. The medium access method used in 802.11p, CSMA with collision avoidance, does not guarantee channel
access before a finite deadline. The well-known property of CSMA is undesirable for critical communications scenarios. The simulation results reveal that a specific vehicle is forced to drop over 80% of its packets because no channel access was possible before the next message was generated. To overcome this problem, we propose to use STDMA for real-time data traffic between vehicles. The realtime properties of STDMA are investigated by means of the highway road simulation scenario, with promising results.
Channel Aware Mac Protocol for Maximizing Throughput and FairnessIJORCS
The proper channel utilization and the queue length aware routing protocol is a challenging task in MANET. To overcome this drawback we are extending the previous work by improving the MAC protocol to maximize the Throughput and Fairness. In this work we are estimating the channel condition and Contention for a channel aware packet scheduling and the queue length is also calculated for the routing protocol which is aware of the queue length. The channel is scheduled based on the channel condition and the routing is carried out by considering the queue length. This queue length will provide a measurement of traffic load at the mobile node itself. Depending upon this load the node with the lesser load will be selected for the routing; this will effectively balance the load and improve the throughput of the ad hoc network.
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.
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.
Elastic hybrid MAC protocol for wireless sensor networks IJECEIAES
The future is moving towards offering multiples services based on the same technology. Then, billions of sensors will be needed to satisfy the diversity of these services. Such considerable amount of connected devices must insure efficient data transmission for diverse applications. Wireless sensor network (WSN) represents the most preferred technology for the majority of applications. Researches in medium access control (MAC) mechanism have been of significant impact to the application growth because the MAC layer plays a major role in resource allocation in WSNs. We propose to enhance a MAC protocol of WSN to overcome traffic changes constraints. To achieve focused goal, we use elastic hybrid MAC scheme. The main interest of the developed MAC protocol is to design a medium access scheme that respect different quality of services (QoS) parameters needed by various established traffic. Simulation results show good improvement in measured parameters compared to typical protocol.
Bulk Projects For sale
IEEE 2009-10-11-12-13 PAPERS AVILABLE.
We are providing low cost project for final year student projects.
Solved 2010 -2011 -2012 - 2013 IEEE in all the domain
Mobile : 8940956123
E-Mail : ambitlick@gmail.com,
INNOVATIVE TITLES ARE ALSO WELLCOME TO DO WITH US
For All BE/BTech, ME/MTech, MSC/MCA/MS , and diplamo graduates
PROJECT SUPPORTS & DELIVERABLES
•Project Abstract
•IEEE Paper
•PPT / Review Details
•Project Report
•Working Procedure in Video
•Screen Shots
•Materials & Books in CD
•Project Certification
The Indian economy is classified into different sectors to simplify the analysis and understanding of economic activities. For Class 10, it's essential to grasp the sectors of the Indian economy, understand their characteristics, and recognize their importance. This guide will provide detailed notes on the Sectors of the Indian Economy Class 10, using specific long-tail keywords to enhance comprehension.
For more information, visit-www.vavaclasses.com
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Extraction Of Natural Dye From Beetroot (Beta Vulgaris) And Preparation Of He...SachinKumar945617
If you want to make , ppt, dissertation/research, project or any document edit service
DM me on what's app 8434381558
E-mail sachingone220@gmail.com
I will take charge depend upon how much pages u want
This presentation provides an introduction to quantitative trait loci (QTL) analysis and marker-assisted selection (MAS) in plant breeding. The presentation begins by explaining the type of quantitative traits. The process of QTL analysis, including the use of molecular genetic markers and statistical methods, is discussed. Practical examples demonstrating the power of MAS are provided, such as its use in improving crop traits in plant breeding programs. Overall, this presentation offers a comprehensive overview of these important genomics-based approaches that are transforming modern agriculture.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Basic Civil Engineering Notes of Chapter-6, Topic- Ecosystem, Biodiversity Green house effect & Hydrological cycle
Types of Ecosystem
(1) Natural Ecosystem
(2) Artificial Ecosystem
component of ecosystem
Biotic Components
Abiotic Components
Producers
Consumers
Decomposers
Functions of Ecosystem
Types of Biodiversity
Genetic Biodiversity
Species Biodiversity
Ecological Biodiversity
Importance of Biodiversity
Hydrological Cycle
Green House Effect
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
Power-sharing Class 10 is a vital aspect of democratic governance. It refers to the distribution of power among different organs of government, levels of government, and social groups. This ensures that no single entity can control all aspects of governance, promoting stability and unity in a diverse society.
For more information, visit-www.vavaclasses.com
UNIT – IV_PCI Complaints: Complaints and evaluation of complaints, Handling o...
Specifica‘tion, verification and simulation of a wireless lan
1. SPECIFICA‘TION, VERIFICATION AND SIMULATION OF A WIRELESS LAN
PROTOCOL: MACAW
G M Lundy, M. Almquist, T. Oruk
U S Naval Postgraduate School
Monterey, CA 93943
ABSTRACT able to make some suggestions as to how it can be
A formal specification and verification of a wireless improved, and to give a fairly accurate indication of how
LAN protocol is given, and a simulation of the much the improvements will help performance.
protocol’s performance is also described. The
verification is a partial verification in that it does not MACAW -- Multiple Access, Collision Avoidance,
include a general verification of all possible Wireless -- was designed as an improvement upon an
configurations of the protocol; however; it does cover earlier protocol, called MACA [Karl. MACAW is based
the expected usage of ihe protocol, which is for a small on the same principle as is the cellular radio network for
number of users sharing a cell. The simulation provides automobiles. A set of base stations, which are ail
further insight into the protocol, especially concerning connected by a wired system, communicate via radio
its performance. Ba,sea! on the verification and signals with the user stations. The difference is that with
simulation, some sug,gestions are made which can MACAW, the base stations are connected by a local area
improve the protocol’s performance. network -- such as CSMACD -- rather than a telephone
type network covering a large area. The area around
I. INTRODUCTION each base station is called a cell; and the users
Wireless communications in various forms has been the communicate with the nearest base station. Another
subject of much attention and research in recent years. difference is in the cell size; here we are using cells
Wireless communications include the broadcast radio which are only a few meters in diameter, rather than
medium; terrestrial microwave[Mili]; satellite microwave miles across. A third difference is that the :stations are
in all its forms [Ha,Ree]; and the International Amateur not mobile, as are autos. The signals are relatively weak,
Radio Network, or “Ham Radio”[Bi]. Additionally , so that they should not penetrate beyond the “cell,” or
wireless communications includes acoustical (sound) its local area. However it is possible that some
communications, used by submarines for many years, interference between adjacent cells may occur. Other
and also for data communications, at least protocols for wireless and broadcast networks exist, and
experimentally [Rei]; and optical (visible) light have been in use for years; these are discussed in the
communications, which are still used by maritime references.
vessels. More recent fioms of wireless communications
includes wireless telephones; cellular telephones; air MACA (medium accessicollision avoidance) Karl,
phones, which enable the passenger aboard an airliner to MAC‘4W’s predecessor, used a sequence of three basic
connect to the long distance telephone system; and messages: request-to-send, clear-to-send, and DATA.
wireless computer networks. Pagers and remote control MACX used binary exponential backoff aligorithm to
devices might also be included, though these are very resolve collisions, the same type used in CSMA/CIl.
“low bandwidth” communications devices. Studies showed that the MACA protocol was not fair to
all stations on the network, and the throughput was not
In this paper we discuss a protocol suggested for wireless very high under conditions of imperfect channels [BD].
!oca1 computer networks, known as MACAW [BD]. This
protocol was suggested as an improved means to enable MACAW (MACA-wireless) improved upon IMACA by
computers in a local area to communicate with each adding to this message sequence. The request-to-send
other. The protocol is intended for a single channel (KTS) message from the sending station is followed by
packet radio network. This means that all stations use the the clear-to-send (CTS) from the receiver, as with
same channel (frequency), so that should more than one MACA; but the DATA is preceded by a short data-send
transmit at a time the signals may interfere. (DS) packet, which serves to alert the nearby stations that
a data packet is about to be transmitted, reducing the
Next we briefly describe MACAW. In section 2 , the probability of a collision. This is followed by an ACK
formal specification is summarized. Section 3 discusses packet from the receiver, through which reliability is
averification of the protocol.Further study of the enhanced. This means that MACAW is able to provide
protocol was carried out through a series of simulations; reliability at the MAC layer, where MACA co’uld not.
this is described in section 4. As a result of this work -
what we have learned through the formal specification MACAW also uses a different backoff algorithm than
process, the verification, and the simulation -- we are MACA. MACAW’S developers felt that the MACA
U.S. Government work not protected 565
by U S . copyright.
2. backoff algorithm oscillated too rapidly. Instead the predicate. The full specification is given in [All.
value of the backoff counter is increased by a factor of
1.5 (rather than 3) for each collision, and decreased by 111. VERIFICATION OF MACAW
1 for each success. This provided a gentler fluctuation A major benefit of formal specification of protocols or
in the backoff counter. computer programs is the potential for automated
generation and analysis. This automated analysis was
In this paper we show that MACAW is a reasonable conducted using the program developed in [Bu]. The
protocol for its intended purpose, however that it can be analysis is done by constructing a directed graph of
slightly refined and impioved. Our contributions states and the transitions between states.
include the formalizing of the protocol specification, its
verification, additional knowledge of its performance, Three basic configurations were analyzed with the
and suggested improvements. automated analysis. The number of machines was vaned
by using three input files with two, three and four
ECIFIC~~IO~ OF MACAW machines. Though it is possible to have more than four
MACAW is formally specified and analyzed using a machines in a single cell, this is unusual; a cell is only a
model called systems of communicating machines. This few meters in diameter. So, while our verification does
model, originally defined by Lundy and Miller[LM] has not cover all cases, it does cover the majority of
been used to analyze several communications protocols. practical cases.
Each machine is defined as a finite state machine with
variables. Communication between machines is done All of the the possible specified transitions of MACAW
through the use of shared variables. Local variables are were not always executed by all machines; in fact, for
used to maintain the state information for each machine, some cases, all transitions were not executed by any
and a predicate-action table serves to unify the state machines. At first glance this appeared as a protocol
machines and the variables. The goal of formal error -- an unexecutable transition but in fact was not.
specification is to determine if the protocol is free from It was simply a case in which the transition in question
errors, such as deadlock or unexecutable transitions, was not needed. For example, in the two machine
and if it possesses “liveness,” which is defined as the analysis, none of the quiet stare transitions were
ability to make positive progress. An additional benefit executed for the simple reason that there was no other
is identification of ambiguities in the protocol. machine causing interference.
A formal specification of MACAW was developed in With two machines: Machine 1 and machine 2 were run
[All, which includes a set of local variables, a set of in the two machine analysis. Both began in the IDLE
shared variables, used for communication, a finite state state and machine 1 had a message to send to machne
machine, and a predicate-action table. 2. Once machne 3 received the DATA message from
machine 1 it sent a DATA message to machinel.
The shared variables are channel.type, channel.DA, esn, (Machine 3’s action upon receiving a DATA message
channel-my-backoff, channel-local-backofS, and included writing a DATA type message to its own output
channel-retry-amount. These are used for buffer). No deadlock occurred and the total number of
communication between the nodes, and the names are system state generated was 69. The corresponding
descriptive of their uses global state analysis generated 275 states. One artificial
deadlock occurred in the global state analysis upon
The 1oca1 variables are inbuffer, outbuffer, backof, receipt by machine 2 of the ACK message from
my-backoff, local-backoff. Again, the names of the machinel. The deadlock happened as a result of
variables are descriptive of their uses. clearing the output buffers when an ACK message was
received. Essentially, both machines received their
The finite state machine diagram has 10 major states. respective DATA messages and no more data remained
These states are named IDLE, CONTEND, XMIT, to be transferred, thus causing a deadlock.
WFCTS, WFACK, WFDS, Q U E , WFDATA,
FCONTEND, CQNTEND2. Simulabons with 3 and 4 machines, which generated
many more states, are reported in [All.
The names of the states are descnptive; in IDLE, the
node has nothing to transmit. In CONTEND, the station IV. SIMULATION AND ANALYSIS OF MACAW
has a message to transmit and is trying to get the The purpose of the simulation is to determine the
channel; XMIT, is sending; “WF” signifies “Waiting behavior of the protocol under different operational
for,” as in WFACK, “waiting for acknowledgment.” conditions. Therefore, operational conditions are first
The initials CJTS signify “clear to send.” determined as test cases and simulations are performed
with these test cases. The results are analyzed and some
The predicate-action table unifies the finite-state suggestions to improve the protocol are given.
diagram with the local and shared variables. Each
transition in the diagram has an entry in the table, and The simulation model of the protocol was built using
for each entry there is an action and an enabling OPNET 2 . k from M I D , Inc. The OPNET design
566
3. environment greatly eiased the simulation process. These cases are also tested from 10% to 100% of the
total offered overlapping channel loads. An
A.Test Cases. The behaviors that we are interested in overlapping channel is the intersection of transmission
are the utilization of the channel and packet mean ranges of two (or more) non-communicating nodes
queue delay time. The usual performance measure for a where one’s transmission interferes with the other. .A
protocol is network utilization, but this does nut consider brief explanation of each case follows:
users of the network. ‘Therefore, mean queue delay time
is also considered as a performance measure of the Hidden node: While A is sending to B, C attempts to
protocol. These measures are related to the send to B also. In this scenario A and C are not aware of
Communication channel load. The load of the channel each other but affected from each other’s transmission,
depends on the number of the nodes that are sharing the so they are hidden from each other. &)osed node:
same transmission media (channel) and their (internal) While B is sending to C, , attempts to send 1.0 B. Here B
4
packet arrival rates. Besides these, the performance of is aware of A, thus B is exposed to -4’s transmissions.
the radio networks is greatly affected by hidden- Hidden and exposed nodes: While A and B are mutually
exposed nodeicell conditions [Karl. exchangmg data, C attempts to send to R. Here A and C
are hidden from each other and B is exposed to both A
With these consideratiions in mind, the test cases are and C. Hidden Cell: B and C are in different cells but
separated into two groups known as “load cases” and they can hear each other. Node . is not aware of the
4
“hidden-exposed nodei’cell cases.” In the load cases, it communication going on in the adjacent cell since it
is also determined whether the protocol acts in favor of cannot hear anything from that cell, it is hid’den from A,
any specific communication topology. For each test the same is true for node D. Exmsed Cell B and C are
case, communication scenarios are determined and, for in different cells but each can hear the other’s
each scenario, test cases are generated with different transmissions while they are communicating with other
numbers of nodes and packet arrival rates. nodes in their cells (A and D respectively). So they are
exposed to each other’s transmissions. ]Hidden and
With each load case, networks of up to four transmitting Exposed Cells: Node A does not hear any tiansmissions
nodes are built and each of these cases is tested from from the other cell xwhle node C is hearing node B. So
10% to 100% of the total offered channel loads. Having the adjacent cell is, hidden for A and exposed for C. All
up to four transmitting nodes for each load case in one: Heavy communication in both cells.
provided enough information about the behavior of .the
protocol under these conditions. Sample load case B. Performance Measure Criteria. As mentioned
scenarios are shown in Figure 1. The load case above, the performance measure also includes the mean
topologies of interest are as follows: delay time in addition to utilization. The resultant
formula is:
{a) reporting nodes with two, three and four transmitting
nodes; (b)one-wav communicating nodes with two, Total-Performance = utilization I mean-queue-delay
three and four transmitting nodes; (c)=
communicating nodes with one and two pairs mutually According to this formulation, if two utdizations are
communicating nodes; (d)ring communication with equal then the one with lesser mean delay time will have
three and four nodes. a better performance measure. For example, suppose
we have measured an utilization of 54% with a mean
delay time of 9 sec and for another case 54% Utilization
with a mean delay of 3 sec. Just looking at the
utilizations does not say anything about which one is
better. But when delay times are considcrcd, the first
case will have a performance measure of 0.54/9=0.06
while the second case will have a prformaiuce measure
of 0.%/3=0.18. This clearly shows that the second case
is better.
A performance measure should be independent of
transmission speed of the network in order to be used to
compare different protocols. Thus, delaiy time is
Figure 1: Sample load cases from each communication topology normalized to data packet length. This me.ans we can
tested. For all cases above, all nodes are in one cell, that is all can compare the performance of the protocol for networks
hear each other and arrows show the direction data streams. (a) four with different transmission speeds.
reporting nodes, (b) two 1-way nodes, (c) two pairs cmss-
communicating nodes, (d) ring communication with four nodes. C. Test Results. For all cases the Poisson distribution
function is used for the packet arrival distnbution. The
Hidden-exposed nodeicell cases are shown in [Or]. first test case, our base case, is chosen to determine the
567
4. maximum performance of the node that is running network increases, since per node utilization and data
MACAW protocol for a given arrival rate. This test is mean queue delay times does not change.
conducted with a network of one transmitter and one
receiver, and utilization is calculated. Data mean queue Hidden and Exposed Node/Cell Case Results In the
delay times are collected by OPNE3”s built-in utilities. hidden node case, due to the rapid increase of the
OPNEX calculates the delay times of the packets that backoff value of node B, performance is poor above
arrive to the queue during one unit of time and uses its 1 % of overlapping channel loads (load over node B).
0
mean (middle) value as a mean delay time of this time Channel access is fair, because both transmitters are
period. The simulation result of this base case and the using the same backoff value as in reporting nodes case
other cases are shown in detailed tables in [Or]. of load cases.
As seen from the table, the performance decreases In the exposed node case performance is fairly high
rapidly beyond 80% offered channel loads due the high compared to the hidden node case. However, above 80%
mean delay times. Maximum utilization observed for of offered overlapping channel loads, the behavior of
the protocol with given packet sizes (30B for control the network becomes similar to thc one way
packets, 520B for data packets), packet arrival communicating node cases of the load cases. The
distribution function and backoff limits is 66%. These “lucky” node gets the channel and keeps it.
results will be a base case to use in comparison with test
results. In the hidden and exposed node case , the hidden node
behavior is dominant. Due to the high delay times, the
Load Case Results For the load cases, channel performance decreases dramatically above 4%of
utilization almost never exceeds 50% for all simulations overlapping channel loads .
(the maximum utilization observed for the protocol was
66% with current parameters). The exceptions are the In the hidden cell case channel access of transmitter
base case and “one pair mutually communicating” nodes (node -4 and D) are always fair because the
network case. In the base case there is no interfering congestion levels at the receivers are similar. But due to
node against the transmitting node, so we should get the congestion at the receiver side data packet delay
“the most” from the protocol. The reason that one pair times in the transmitters are h g h so performance is low
mntually communicating network has high utilization for cell loads above 25%. Its behavior is the same as the
and low backoff values than the other simulation cases is hidden node case.
it has a slower rate of backoff increase for its remote
backoff values. Modified Protocol Simulations During the simulations it
was observed that the backoff increase rate is one of the
For high loads, one-way communicating nodes cases key factors that affects the performance of the MACAW
always violate the fairness of channel access. The protocol under moderate and high loads (40% and
backoff algorithm dictates that each node keeps track above). To further investigate, the same set of
of the congestion of the channel between itself and the simulations were run with a lower backoff increase rate.
neighboring nodes via backoff values. When a node As a result, for load cases with a small number of
attempts to communicate with one of its neighboring transmitting nodes, significant performance gains were
nodes, it uses the associated backoff value. These observed. These gains are due to the lower mean delay
backoff values are mutually exclusive. In a one way times rather than increased utilization. But as the
communicating network scenario when a “lucky” node number of the transmitting nodes increased, the
reaches the channel quicker than the others for a couple performance gain achieved by this modification
of consecutive times it gets and keeps the channel by degraded. No significant performance change was
h o w i n g other nodes have very high backoff values. observed in hidden-exposed nodeicell cases.
Reporting and ring cases have similar results. They both Another factor that affects the performance of the
have fair channel access during the simulations. But protocol is the nodes’ inability to determine whether the
both have high backoff values. To have high backoff channel is busy. According to the MACAW protocol,
value causes larger delay times on average therefore nodes behave purely in accordance with the received
reporting and ring cases have lower performance packet information. The keyword here is “received.”
measures. The MAC layer that runs the MACAW protocol does not
know that it is receiving a packet until the entire packet
The best performance measures observed during the has been transmitted. The probability of collision of two
simulations are around 20% channel load conditions for transmitting nodes is the probability of transmission of
three and four transmitting nodes cases. A s the number one node without recognizing (or before recognizing)
of transmitting nodes in the network increases, the effect that another node is transmitting. The transmission
of having high backoff values decreases (for low loads), probability of a node when it assumes that the channel is
because when the channel is free, the chance that there is available is based on the distribution function and its
a node ready to transmit is high. So idle times of the parameter value (in this case Poisson distribution with
channel are used and total performance measure of the
568
5. arrival rate value). The “recognition” period in the observed, which was caused by the rapid iiocrease of the
original MACAW protocol is the time that it takes for backoff increase rate for the small number of
control packet transmission plus propagation delay. transmitting nodes cases. 4 relation between the backoff
Thus, we haw a sample space of increase rate and the number of transmitting nodes was
time_slot+propugatic,n_clelay for a transmission event observed (but this needs to be investigated more
that may cause a collision. When carrier sensing is thoroughly). So, instead of using a linear increase rate
introduced to the protocol, this sample space shrinks to use of dynamic or exponential increase rates may give
one propagarion-delay ( assuming time-slot >> better results. The dynamic increase can bind to the
propagation delay). So, carrier sensing will decrease the number of transmitting nodes. For the fairness problem
probability of c:ollisions by a factor of in one-way communicating nodes cases more
time-slotlpropagatioi~z_delay. This is also what is fundamental changes should be made to the algorithm.
observed during the simulations of the MACAW That is, the backoff algorithm needs to be thoroughly
protocol with carrier sensing capability. Significant analyzed.
performance measure: increases observed for SO% and
above common channel loads. The source of gain is It is also observed that the channel acquisition with
lower mean delay times. While the greatest performance carrier sensing is superior to the original MACAW
gain is achieved in the hidden node case (for SO% protocol policy. This is quite significant for medium
offered load), no change was observed in the hidden cell and high loads. This contradicts the reasoning of the
case. In hidden cell case carrier sensing provides no help original MACAW protocol specification which says
to the network to improve its performance, because “...carrier sensing is inappropriate” [13D]. This
transmitters are out of range from each other (the only simulation is discussed in more detail in [Or] , as well as
time that a transmitter utilizes carrier sensing in this the remainder of the simulations which are omitted here
topology is to sense its receiver’s RRTS packet). due to lack of space.
.4nother improvement achieved by carrier sensing is V. CONCLUSIONS
fairer channel access of the transmitting nodes Uk described the: specification, verification, and
(compared to the original network) in the “hidden- simulation of MACAW. The specification uncovered
exposed cell” and “aill-in-one” network topologies. some ambiguities in the original specilfication. The
verification showed the protocol to be free of deadlocks,
In “hidden-exposed cell” network node C cannot get for most practical cases. Simulations gave further
the common channel1 as frequently as in the origmal confidence in the protocol and showed further possible
protocol. Now C should wait B to send a11 its packet and improvements in performance. We showed that the
act accordingly (nod,e C must understand what B is backoff algorithm is of major importance to the
“saying”). ’Ihis increases the performance of node A performance of the protocol, and topology is also
slightly, because backoff values are dominant for the critical. The protocol can also be improvled by adding
performance and here there is a big difference between carrier sensing. Simulations suggest that this could
congestion levels of the receivers (especially for high improve utilization under heavy load by about 5%.
loads).
REFERENCES
In “all-in-one” case fairness is achieved between inner [All Almquist, Marty, Formal Spec$cation and Analysis ~7f a
Wireless Media Access Protocol, MS Thesis, Department of
nodes. In the originail protocol for high loads (go%), Computer Science, Naval Postgraduate Schcol, Monterey, CA,
one of the inner noldes has much higher performance 1995.
measure than the other. Now with carrier sensing both [BDl Bharghavan, V., Demer;, A.. Sbenker. S. and Zhang, L.
“MACAW A Media Access Protocol for Wireless LAN’s,”
have similar performances. The performance difference Proceedings of ACM SIGCOMM 94, pp. 212-25, ACM, 1994.
between inner and outer nodes are still great because of [BUI Bulbul, B. AProtocol Validator,for the SCM and CFSMModels,
MS Thesk, Naval Postgraduate School, 1993.
the congestion levels at the receivers. CEPl Epstein, M., et al, “Application of Commercial Wireless LAN
Technology to Forward Area Mobile Communication,“
Simulation Summary. It was determined that the Proceedings, Military Communications Conference,
(MILCOM), 19%.
backoff algorithm has a significant importance for the [Gel Geier, Jim, Wireless Networking Handbook, New Riders, 1996.
Performance of the protocol, where performance is l I E l l-
- l IEEE P802.11, Drafl Standard for Wirei’ess LAN Medium
defined in terms of channel utilization and transmitter Access Contrvl (MAC) and Physical Luyer Specifiraation
(PHY), 19 J d y 1996.
mean delay times. [Karl Karn P., “ M C A - A New Channel Access Method for Packet
Radio,” ARRLICRRL, Amateur Radio Yth Computer Networkmg
Conference, September 22, 1990.
Backoff is the measure of the congestion at the location [Kat] Katz, R, “Adaptation and Mobility in Wireless Information
of the node. Distribution of this information throughout System,”IEEE Personal Communications, First Quarter 1994.
the network provides fair access to this node by other &MI Lundy, G., and Miller, R, “Specification ancl analysis of a data
transfer protocol using systems of communicating machines,”
nodes since each node keeps track of the other node’s Distributed Computing, May 1991.
congestion information in the network. But this does not D l Oruk, Tufon. Simulation and Analysis o a Wireless MAC
f
Protocol: MACAW, MS Thesis, Department of Computer
help in the situations like one way communicating nodes Science, Naval Postgraduate Schml, 1996.
cases. Also some performance degradation was
569