Anwar Saif - Academia.edu (original) (raw)

Papers by Anwar Saif

The present invention relates to a method for adjusting aggregation size based on Acknowledgement... more The present invention relates to a method for adjusting aggregation size based on Acknowledgement (ACK) bitmap, characterized by the steps of: receiving kth Compressed Block Acknowledgement (CBA); calculating granularity factor (g) by applying Equation (1); determining bit error density (BEDk) for kth CBA by applying Equation (2); receiving (k+1)th CBA; determining bit error density (BED(k+1)) for (k+1)th CBA by applying Equation (2); adjusting the aggregation size based on the value of granularity factor (g), kth bit error density BEDk values and (k+1)th bit error density BEDk+1; wherein if the kth bit error density BEDk is greater than the (k+1)th bit error density BEDk+1, then increasing the aggregation size based on the value of granularity factor (g); wherein if the kth bit error density BEDk is lower than the (k+1)th bit error density BEDk+1 then decreasing the aggregation size based on the value of granularity factor (g); wherein if the kth bit error density BEDk is equal to ...

Saba Journal Of information Technology And Networking (SJITN)-ISSN: 2312-4989, Feb 9, 2021

Control theory & applications, 2016

The tremendous increase in user demands for multimedia applications with its various quality of s... more The tremendous increase in user demands for multimedia applications with its various quality of service (QoS) requirements has become essential for the operators to accommodate the demand for real-time services in WLAN network. One of the challenging issues still open for research in IEEE 802.11 WLAN is the scheduling mechanism to fully support the various QoS requirements. Furthermore, the large contrast in the real-time and non-real-time traffic specification, the insufficient bandwidth allocation and not able to satisfy the latency requirement can lead to degradation or decreases the overall system performance. In this paper, an efficient scheduling scheme is proposed for IEEE 802.11n WLAN to supports small packet size and to guarantee the timing constraint of the real-time traffics. The proposed adaptive bandwidth allocation and latency guarantee for WLAN networks using fuzzy Logic control (ASEF) will provide fair resource allocations for the real-time and non-real-time traffics...

2019 First International Conference of Intelligent Computing and Engineering (ICOICE), 2019

The International Arab Journal of Information Technology, 2011

Handoff is a critical function that enables mobile nodes to stay connected to the wireless networ... more Handoff is a critical function that enables mobile nodes to stay connected to the wireless network by switching the data connection from one WLAN to another. During handoff the communication may be degraded or interrupted due to the high packets loss. To prevent packet loss during handoff, a handoff management scheme that employs a transport protocol has been proposed. It supports multiple connections for Voice Over IP communication and makes handoff decision based on the number of frame retransmission on the MAC layer. Moreover, the handoff scheme uses the multi-scan technique that enables mobile nodes to use two WLAN interfaces for channel scanning and multi-path transmission rather than single WLAN interface. This technique introduces extra network overhead during multi-path transmission. This work optimizes the network overhead and packet loss and keeps VoIP communication at an acceptable level.

International Journal of Computer Network and Information Security, Jul 8, 2018

Wireless Personal Communications, 2012

The main goal of the IEEE 802.11n standard is to achieve a minimum throughput of 100 Mbps at the ... more The main goal of the IEEE 802.11n standard is to achieve a minimum throughput of 100 Mbps at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. A key enhancement at the MAC layer is frame aggregation in which the timing and headers overheads of the legacy MAC are reduced by aggregating multiple frames into a single large frame before being transmitted. Two aggregation schemes have been defined by the 802.11n standard, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). As a consequence of the aggregation, new aggregation headers are introduced and become parts of the transmitted frame. Even though these headers are small compared to the legacy headers they still have a negative impact on the network performance, especially when aggregating frames of small payload. Moreover, the A-MSDU is highly influenced by the channel condition due mainly to lack of subframes sequence control and retransmission. In this paper, we have proposed an aggregation scheme (mA-MSDU) that reduces the aggregation headers and implements a retransmission control over the individual subframes at the MSDU level. The analysis and simulations results show the significance of the proposed scheme, specifically for applications that have a small frame size such as VoIP.

ICST Transactions on Mobile Communications and Applications, Jul 13, 2018

Optimizing the performance of TCP in wireless networks in a changing network condition is a highl... more Optimizing the performance of TCP in wireless networks in a changing network condition is a highly challenging issue. The lack of information at the TCP layer about the link quality will result in inaccurate transmission rate. Therefore, TCP needs to have sufficient information about the environment and the different characteristics of the lower layers to improve the performance. To achieve this goal we proposed a cross-layer scheme which makes use of the information stored in the 802.11n compressed block acknowledged bitmap about the status of the transmitted subframes of the aggregated frame. This information is fed to the TCP transmission mechanism as a new criterion to adjust the TCP transmission rate with accordance to the aggregation level and channel quality. The simulation results show that the proposed scheme improves the TCP performance in term of throughput and packet loss.

Journal of Network and Computer Applications, Jul 1, 2013

The main goal of the IEEE 802.11n standard is to achieve more than 100 Mbps of throughput at the ... more The main goal of the IEEE 802.11n standard is to achieve more than 100 Mbps of throughput at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. One of the MAC enhancements is the frame aggregation in which multiple frames are concatenated into a single large frame before being transmitted. The 802.11n MAC layer defines two types of aggregation, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). The A-MPDU outperforms A-MSDU due to its large aggregation size and the subframes retransmission in erroneous channels. However, in error free channels and under the same aggregation size the A-MSDU performs better than the A-MPDU due to its smaller headers. Thus, adding a selective retransmission capability to the A-MSDU would improve the system performance. In this paper, we have proposed an MSDU frame aggregation scheme that enables selective retransmission at the MSDU level without altering the original MAC header. In this proposed scheme an implicit sequence control mechanism has been introduced in order to keep the frames in sequence and preserve their correct order at the receiver side. The results show that the proposed scheme improves the system performance in terms of throughput and delay even under highly erroneous channels.

The IEEE 802.11n network main feature is to support high throughput of more than 100Mbps at the M... more The IEEE 802.11n network main feature is to support high throughput of more than 100Mbps at the MAC layer. To achieve this, the 802.11n Task Group has introduced frame aggregation technique which reduces the overhead and increases the channel utilization efficiency. Some recent researches have enabled an A-MSDU selective retransmission which makes it robust against error. In this paper, we propose a scheduler based on an A-MSDU aggregation mechanism that supports small size and high sensitivity traffics, and enable prioritization according to the QoS requirements of the traffic classes.

EAI Endorsed Transactions on Cloud Systems

Cloud computing delivers computing resources like software and hardware as a service to the users... more Cloud computing delivers computing resources like software and hardware as a service to the users through a network. Due to the scale of the modern datacentres and their dynamic resources provisioning nature, we need efficient scheduling techniques to manage these resources. The main objective of scheduling is to assign tasks to adequate resources in order to achieve one or more optimization criteria. Scheduling is a challenging issue in the cloud environment, therefore many researchers have attempted to explore an optimal solution for task scheduling in the cloud environment. They have shown that traditional scheduling is not efficient in solving this problem and produce an optimal solution with polynomial time in the cloud environment. However, they introduced sub-optimal solutions within a short period of time. Meta-heuristic techniques have provided near-optimal or optimal solutions within an acceptable time for such problems. In this work, we have introduced the major concepts of resource scheduling and provided a comparative analysis of many task scheduling techniques based on different optimization criteria.

INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY

Nowadays, cloud computing makes it possible for users to use the computing resources like applica... more Nowadays, cloud computing makes it possible for users to use the computing resources like application, software, and hardware, etc., on pay as use model via the internet. One of the core and challenging issue in cloud computing is the task scheduling. Task scheduling problem is an NP-hard problem and is responsible for mapping the tasks to resources in a way to spread the load evenly. The appropriate mapping between resources and tasks reduces makespan and maximizes resource utilization. In this paper, we present and implement an independent task scheduling algorithm that assigns the users' tasks to multiple computing resources. The proposed algorithm is a hybrid algorithm for task scheduling in cloud computing based on a genetic algorithm (GA) and particle swarm optimization (PSO). The algorithm is implemented and simulated using CloudSim simulator. The simulation results show that our proposed algorithm outperforms the GA and PSO algorithms by decreasing the makespan and incre...

International Journal of Engineering & Technology

The tremendous increase in user demands for multimedia applications with its various quality of s... more The tremendous increase in user demands for multimedia applications with its various quality of service (QoS) requirements has become essential for the operators to accommodate the demand for real-time services in IEEE 802.11 WLAN network. Scheduling mechanism is one of the challenging issues still open for research to fully support the various QoS requirements. In this paper, scheduling scheme is proposed to manage the channel access parameter between competitive nodes. An embedded fuzzy expert system is used to dynamically allocation these parameters to the competitive stations. The simulation results show that the proposed algorithm manages to optimize the overall system utilization.

Femtocells are fully customized deployed base stations. They are being deployed in the macrocell ... more Femtocells are fully customized deployed base stations. They are being deployed in the macrocell cellular network in order to improve the indoor coverage and provide better user experience. Nevertheless, the randomly deployed femtocell poses a number of challenges, among the most critical is the interference as the achievable data rates and capacity depends mainly on the interference mitigation by the femtocell network. In this study, a self organizing solution combined with power control mechanism is proposed as the interference mitigation scheme for Long Term Evolution (LTE) femtocell network. The notion is based on adjusting the femtocell's transmission power and based on interference power received at femtocell downlink, in order to reduce the interference between femtocells. The power adjustment is controlled and based on some basic factors such as number of femtocells and distance between the femtocells and subscribers. The performance evaluation of real time services is conducted in terms of Packet Loss Ratio (PLR) and throughput.

2010 International Conference on Computer Applications and Industrial Electronics, 2010

The main goal of the IEEE 802.11n standard is to achieve more than 100Mbps of throughput at the M... more The main goal of the IEEE 802.11n standard is to achieve more than 100Mbps of throughput at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. A key enhancement is frame aggregation which reduces the overheads and increases the channel utilization efficiency. The MAC layer defines A-MSDU and A-MPDU frame aggregations in which MAC overheads are squeezed by aggregating multiple frames into a single large frame before being transmitted. As a consequence of the aggregation, new aggregation headers are introduced and become parts of the transmitted frame. The existence of such headers will have a negative impact on the performance, especially when aggregating frames of small payloads. In this paper, we have analysed the aggregation headers of the 802.11n aggregation schemes and introduced an MSDU frame aggregation that reduces the header's overhead and supports the applications that have a small frame size such as VoIP.

2014 2nd International Conference on Electrical, Electronics and System Engineering (ICEESE), 2014

Procedia Computer Science, 2015

ABSTRACT Frame aggregation is one of the IEEE802.11n wireless networks features. In frame aggrega... more ABSTRACT Frame aggregation is one of the IEEE802.11n wireless networks features. In frame aggregation multiple frames are combined and then sent. However sending a large number of frames in one aggregation frame in an error-prone environment will result in massive frame loss and retransmission. Thus a prior knowledge about the state of the channel will help in selecting the proper aggregation size that would utilize the channel bandwidth and improve the system performance. In this paper, we introduce an algorithm that adjusts the aggregation size based on the ACK bitmap without adding any extra headers or messages for determining the network conditions. Simulation results show that the Acknowledgment Bitmap can be used as an indicator of the network conditions to create adaptive frame aggregation schemes.

The IEEE 802.11n standard is defined to achieve a high throughput at the MAC layer. This high thr... more The IEEE 802.11n standard is defined to achieve a high throughput at the MAC layer. This high throughput is accomplished via many enhancements in both the physical and MAC layers. A key enhancement introduced in the 802.11n standard is frame aggregation. Two types of aggregation defined by the 802.11n standard, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). Frame aggregation reduces both the headers and timing overheads at the MAC layer by aggregating multiple frames into a single large frame before being transmitted. The aggregation headers themselves still have a negative impact on the network performance especially when aggregating frames of small payload. Moreover, the lack of partial retransmission in the A-MSDU aggregation is behind its poor performance in error-prone channels. In this paper we proposed an optimized header A-MSDU frame aggregation (OHA-MSDU) with subframes retransmission capability at the MSDU level. The simulation results show the significance of the proposed scheme, especially for applications that have a small frame size such as VoIP.

The timing and headers overheads of IEEE 802.11 PHY and MAC layers consume a large part of the ch... more The timing and headers overheads of IEEE 802.11 PHY and MAC layers consume a large part of the channel time leading to performance degradation especially at higher data rates. Several enhancements at both the PHY and MAC layers have been proposed in order to reduce these overheads and increase the channel utilization. A key enhancement is frame aggregation in which the timing and headers overheads are reduced by aggregating multiple frames into a single large frame and then transmit it in a single channel access. This paper addresses the frame aggregation techniques that have been proposed for the next generation wireless networks and the aggregation techniques that are adopted by IEEE 802.11n standard. It also highlights the aggregation issues that need to be investigated in order to further enhance the frame aggregation performance.

The present invention relates to a method for adjusting aggregation size based on Acknowledgement... more The present invention relates to a method for adjusting aggregation size based on Acknowledgement (ACK) bitmap, characterized by the steps of: receiving kth Compressed Block Acknowledgement (CBA); calculating granularity factor (g) by applying Equation (1); determining bit error density (BEDk) for kth CBA by applying Equation (2); receiving (k+1)th CBA; determining bit error density (BED(k+1)) for (k+1)th CBA by applying Equation (2); adjusting the aggregation size based on the value of granularity factor (g), kth bit error density BEDk values and (k+1)th bit error density BEDk+1; wherein if the kth bit error density BEDk is greater than the (k+1)th bit error density BEDk+1, then increasing the aggregation size based on the value of granularity factor (g); wherein if the kth bit error density BEDk is lower than the (k+1)th bit error density BEDk+1 then decreasing the aggregation size based on the value of granularity factor (g); wherein if the kth bit error density BEDk is equal to ...

Saba Journal Of information Technology And Networking (SJITN)-ISSN: 2312-4989, Feb 9, 2021

Control theory & applications, 2016

The tremendous increase in user demands for multimedia applications with its various quality of s... more The tremendous increase in user demands for multimedia applications with its various quality of service (QoS) requirements has become essential for the operators to accommodate the demand for real-time services in WLAN network. One of the challenging issues still open for research in IEEE 802.11 WLAN is the scheduling mechanism to fully support the various QoS requirements. Furthermore, the large contrast in the real-time and non-real-time traffic specification, the insufficient bandwidth allocation and not able to satisfy the latency requirement can lead to degradation or decreases the overall system performance. In this paper, an efficient scheduling scheme is proposed for IEEE 802.11n WLAN to supports small packet size and to guarantee the timing constraint of the real-time traffics. The proposed adaptive bandwidth allocation and latency guarantee for WLAN networks using fuzzy Logic control (ASEF) will provide fair resource allocations for the real-time and non-real-time traffics...

2019 First International Conference of Intelligent Computing and Engineering (ICOICE), 2019

The International Arab Journal of Information Technology, 2011

Handoff is a critical function that enables mobile nodes to stay connected to the wireless networ... more Handoff is a critical function that enables mobile nodes to stay connected to the wireless network by switching the data connection from one WLAN to another. During handoff the communication may be degraded or interrupted due to the high packets loss. To prevent packet loss during handoff, a handoff management scheme that employs a transport protocol has been proposed. It supports multiple connections for Voice Over IP communication and makes handoff decision based on the number of frame retransmission on the MAC layer. Moreover, the handoff scheme uses the multi-scan technique that enables mobile nodes to use two WLAN interfaces for channel scanning and multi-path transmission rather than single WLAN interface. This technique introduces extra network overhead during multi-path transmission. This work optimizes the network overhead and packet loss and keeps VoIP communication at an acceptable level.

International Journal of Computer Network and Information Security, Jul 8, 2018

Wireless Personal Communications, 2012

The main goal of the IEEE 802.11n standard is to achieve a minimum throughput of 100 Mbps at the ... more The main goal of the IEEE 802.11n standard is to achieve a minimum throughput of 100 Mbps at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. A key enhancement at the MAC layer is frame aggregation in which the timing and headers overheads of the legacy MAC are reduced by aggregating multiple frames into a single large frame before being transmitted. Two aggregation schemes have been defined by the 802.11n standard, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). As a consequence of the aggregation, new aggregation headers are introduced and become parts of the transmitted frame. Even though these headers are small compared to the legacy headers they still have a negative impact on the network performance, especially when aggregating frames of small payload. Moreover, the A-MSDU is highly influenced by the channel condition due mainly to lack of subframes sequence control and retransmission. In this paper, we have proposed an aggregation scheme (mA-MSDU) that reduces the aggregation headers and implements a retransmission control over the individual subframes at the MSDU level. The analysis and simulations results show the significance of the proposed scheme, specifically for applications that have a small frame size such as VoIP.

ICST Transactions on Mobile Communications and Applications, Jul 13, 2018

Optimizing the performance of TCP in wireless networks in a changing network condition is a highl... more Optimizing the performance of TCP in wireless networks in a changing network condition is a highly challenging issue. The lack of information at the TCP layer about the link quality will result in inaccurate transmission rate. Therefore, TCP needs to have sufficient information about the environment and the different characteristics of the lower layers to improve the performance. To achieve this goal we proposed a cross-layer scheme which makes use of the information stored in the 802.11n compressed block acknowledged bitmap about the status of the transmitted subframes of the aggregated frame. This information is fed to the TCP transmission mechanism as a new criterion to adjust the TCP transmission rate with accordance to the aggregation level and channel quality. The simulation results show that the proposed scheme improves the TCP performance in term of throughput and packet loss.

Journal of Network and Computer Applications, Jul 1, 2013

The main goal of the IEEE 802.11n standard is to achieve more than 100 Mbps of throughput at the ... more The main goal of the IEEE 802.11n standard is to achieve more than 100 Mbps of throughput at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. One of the MAC enhancements is the frame aggregation in which multiple frames are concatenated into a single large frame before being transmitted. The 802.11n MAC layer defines two types of aggregation, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). The A-MPDU outperforms A-MSDU due to its large aggregation size and the subframes retransmission in erroneous channels. However, in error free channels and under the same aggregation size the A-MSDU performs better than the A-MPDU due to its smaller headers. Thus, adding a selective retransmission capability to the A-MSDU would improve the system performance. In this paper, we have proposed an MSDU frame aggregation scheme that enables selective retransmission at the MSDU level without altering the original MAC header. In this proposed scheme an implicit sequence control mechanism has been introduced in order to keep the frames in sequence and preserve their correct order at the receiver side. The results show that the proposed scheme improves the system performance in terms of throughput and delay even under highly erroneous channels.

The IEEE 802.11n network main feature is to support high throughput of more than 100Mbps at the M... more The IEEE 802.11n network main feature is to support high throughput of more than 100Mbps at the MAC layer. To achieve this, the 802.11n Task Group has introduced frame aggregation technique which reduces the overhead and increases the channel utilization efficiency. Some recent researches have enabled an A-MSDU selective retransmission which makes it robust against error. In this paper, we propose a scheduler based on an A-MSDU aggregation mechanism that supports small size and high sensitivity traffics, and enable prioritization according to the QoS requirements of the traffic classes.

EAI Endorsed Transactions on Cloud Systems

Cloud computing delivers computing resources like software and hardware as a service to the users... more Cloud computing delivers computing resources like software and hardware as a service to the users through a network. Due to the scale of the modern datacentres and their dynamic resources provisioning nature, we need efficient scheduling techniques to manage these resources. The main objective of scheduling is to assign tasks to adequate resources in order to achieve one or more optimization criteria. Scheduling is a challenging issue in the cloud environment, therefore many researchers have attempted to explore an optimal solution for task scheduling in the cloud environment. They have shown that traditional scheduling is not efficient in solving this problem and produce an optimal solution with polynomial time in the cloud environment. However, they introduced sub-optimal solutions within a short period of time. Meta-heuristic techniques have provided near-optimal or optimal solutions within an acceptable time for such problems. In this work, we have introduced the major concepts of resource scheduling and provided a comparative analysis of many task scheduling techniques based on different optimization criteria.

INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY

Nowadays, cloud computing makes it possible for users to use the computing resources like applica... more Nowadays, cloud computing makes it possible for users to use the computing resources like application, software, and hardware, etc., on pay as use model via the internet. One of the core and challenging issue in cloud computing is the task scheduling. Task scheduling problem is an NP-hard problem and is responsible for mapping the tasks to resources in a way to spread the load evenly. The appropriate mapping between resources and tasks reduces makespan and maximizes resource utilization. In this paper, we present and implement an independent task scheduling algorithm that assigns the users' tasks to multiple computing resources. The proposed algorithm is a hybrid algorithm for task scheduling in cloud computing based on a genetic algorithm (GA) and particle swarm optimization (PSO). The algorithm is implemented and simulated using CloudSim simulator. The simulation results show that our proposed algorithm outperforms the GA and PSO algorithms by decreasing the makespan and incre...

International Journal of Engineering & Technology

The tremendous increase in user demands for multimedia applications with its various quality of s... more The tremendous increase in user demands for multimedia applications with its various quality of service (QoS) requirements has become essential for the operators to accommodate the demand for real-time services in IEEE 802.11 WLAN network. Scheduling mechanism is one of the challenging issues still open for research to fully support the various QoS requirements. In this paper, scheduling scheme is proposed to manage the channel access parameter between competitive nodes. An embedded fuzzy expert system is used to dynamically allocation these parameters to the competitive stations. The simulation results show that the proposed algorithm manages to optimize the overall system utilization.

Femtocells are fully customized deployed base stations. They are being deployed in the macrocell ... more Femtocells are fully customized deployed base stations. They are being deployed in the macrocell cellular network in order to improve the indoor coverage and provide better user experience. Nevertheless, the randomly deployed femtocell poses a number of challenges, among the most critical is the interference as the achievable data rates and capacity depends mainly on the interference mitigation by the femtocell network. In this study, a self organizing solution combined with power control mechanism is proposed as the interference mitigation scheme for Long Term Evolution (LTE) femtocell network. The notion is based on adjusting the femtocell's transmission power and based on interference power received at femtocell downlink, in order to reduce the interference between femtocells. The power adjustment is controlled and based on some basic factors such as number of femtocells and distance between the femtocells and subscribers. The performance evaluation of real time services is conducted in terms of Packet Loss Ratio (PLR) and throughput.

2010 International Conference on Computer Applications and Industrial Electronics, 2010

The main goal of the IEEE 802.11n standard is to achieve more than 100Mbps of throughput at the M... more The main goal of the IEEE 802.11n standard is to achieve more than 100Mbps of throughput at the MAC service access point. This high throughput has been achieved via many enhancements in both the physical and MAC layers. A key enhancement is frame aggregation which reduces the overheads and increases the channel utilization efficiency. The MAC layer defines A-MSDU and A-MPDU frame aggregations in which MAC overheads are squeezed by aggregating multiple frames into a single large frame before being transmitted. As a consequence of the aggregation, new aggregation headers are introduced and become parts of the transmitted frame. The existence of such headers will have a negative impact on the performance, especially when aggregating frames of small payloads. In this paper, we have analysed the aggregation headers of the 802.11n aggregation schemes and introduced an MSDU frame aggregation that reduces the header's overhead and supports the applications that have a small frame size such as VoIP.

2014 2nd International Conference on Electrical, Electronics and System Engineering (ICEESE), 2014

Procedia Computer Science, 2015

ABSTRACT Frame aggregation is one of the IEEE802.11n wireless networks features. In frame aggrega... more ABSTRACT Frame aggregation is one of the IEEE802.11n wireless networks features. In frame aggregation multiple frames are combined and then sent. However sending a large number of frames in one aggregation frame in an error-prone environment will result in massive frame loss and retransmission. Thus a prior knowledge about the state of the channel will help in selecting the proper aggregation size that would utilize the channel bandwidth and improve the system performance. In this paper, we introduce an algorithm that adjusts the aggregation size based on the ACK bitmap without adding any extra headers or messages for determining the network conditions. Simulation results show that the Acknowledgment Bitmap can be used as an indicator of the network conditions to create adaptive frame aggregation schemes.

The IEEE 802.11n standard is defined to achieve a high throughput at the MAC layer. This high thr... more The IEEE 802.11n standard is defined to achieve a high throughput at the MAC layer. This high throughput is accomplished via many enhancements in both the physical and MAC layers. A key enhancement introduced in the 802.11n standard is frame aggregation. Two types of aggregation defined by the 802.11n standard, aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU). Frame aggregation reduces both the headers and timing overheads at the MAC layer by aggregating multiple frames into a single large frame before being transmitted. The aggregation headers themselves still have a negative impact on the network performance especially when aggregating frames of small payload. Moreover, the lack of partial retransmission in the A-MSDU aggregation is behind its poor performance in error-prone channels. In this paper we proposed an optimized header A-MSDU frame aggregation (OHA-MSDU) with subframes retransmission capability at the MSDU level. The simulation results show the significance of the proposed scheme, especially for applications that have a small frame size such as VoIP.

The timing and headers overheads of IEEE 802.11 PHY and MAC layers consume a large part of the ch... more The timing and headers overheads of IEEE 802.11 PHY and MAC layers consume a large part of the channel time leading to performance degradation especially at higher data rates. Several enhancements at both the PHY and MAC layers have been proposed in order to reduce these overheads and increase the channel utilization. A key enhancement is frame aggregation in which the timing and headers overheads are reduced by aggregating multiple frames into a single large frame and then transmit it in a single channel access. This paper addresses the frame aggregation techniques that have been proposed for the next generation wireless networks and the aggregation techniques that are adopted by IEEE 802.11n standard. It also highlights the aggregation issues that need to be investigated in order to further enhance the frame aggregation performance.