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Papers by Constantinos Hilas

Research paper thumbnail of A Game Theoretic Approach to Enhance DCF Performance in Full Duplex Ad-hoc WLANs

Research paper thumbnail of Designing an expert system for fraud detection in private telecommunications networks

Expert Systems With Applications, Nov 1, 2009

Research paper thumbnail of Exploiting Reverse Direction Protocol in Full Duplex WLANs

This paper proposes the application of Reverse Direction (RD) protocol to enhance performance in ... more This paper proposes the application of Reverse Direction (RD) protocol to enhance performance in future Full Duplex (FD) Wireless Local Area Networks (WLANs). Full duplex communications in WLANs will be possible when a receiving node has frames ready for the transmitting node. This requires the receiver to decode the frame header for each and every frame in the Transmission Opportunity (TXOP) of the transmitter, in order to obtain the source and destination addresses. It is shown that, in FD-capable WLANs, this procedure may lead to suboptimal performance, reducing the benefits of FD communications. A simple and effective method, based on the usage of RD protocol, is proposed in order to enhance efficiency in future FD WLANs. The performance of the proposed solution is evaluated and compared to the standard method in terms of maximum achievable throughput.

Research paper thumbnail of A comparative study of Particle Swarm Optimization and Differential Evolution on Radar Absorbing Materials design for EMC applications

Radar absorbing materials (RAM) design for a desired frequency and angle range is presented. We e... more Radar absorbing materials (RAM) design for a desired frequency and angle range is presented. We evaluate the performance of particle swarm optimization (PSO) and differential evolution (DE) regarding their applicability to absorber design. The results show that the DE algorithm outer performs PSO variants.

Research paper thumbnail of On the Performance of DCF in Full Duplex WLANs with Hidden Terminals

Research paper thumbnail of A MAC - centric Approach to Detect and Mitigate EDCA Misbehavior Attacks

Journal of Engineering Science and Technology Review, Oct 1, 2016

Research paper thumbnail of A Dynamic Fuzzy Neural System for Time Series Classification

A dynamic fuzzy neural system is proposed, for time series anomaly detection. The model is entitl... more A dynamic fuzzy neural system is proposed, for time series anomaly detection. The model is entitled BFuzzTiD (Block-diagonal Fuzzy Time-series Detector) and consists of fuzzy rules whose consequent parts are three-layer small recurrent neural networks. The hidden layer of each network has blocks of neurons that feed back to each other. BFuzzTid is trained by the Dynamic Resilient Propagation algorithm. The model learns the dynamics of the time series such that it can classify them by detecting the anomaly points. A comparative analysis is conducted with a series of time series anomaly detection models, in order to investigate the capabilities of the proposed detector.

Research paper thumbnail of CSMA/CA analysis and enhancement for IEEE 802.11ax WLANs operating in STR mode

Electronics Letters, Jun 1, 2018

Research paper thumbnail of Clustering of Telecommunications User Profiles for Fraud Detection and Security Enhancement in Large Corporate Networks: A case Study

Applied Mathematics & Information Sciences, 2015

Research paper thumbnail of To Split or not to Split? A Simulation Study on the Network Convergence Duration of Multi-Area OSPF

2023 46th International Conference on Telecommunications and Signal Processing (TSP)

Research paper thumbnail of Neurofuzzy modelling of lung sounds

Contemporary engineering sciences, 2018

Research paper thumbnail of Short-Term Load Forecasting of the Greek Power System Using a Dynamic Block-Diagonal Fuzzy Neural Network

A block-diagonal fuzzy neural network for short-term load forecasting is proposed. DBD-FELF consi... more A block-diagonal fuzzy neural network for short-term load forecasting is proposed. DBD-FELF consists of fuzzy rules with consequent parts that are neural networks with internal recurrence. These networks have a hidden layer which consists of pairs of neurons with feedback connections between them. The overall fuzzy model partitions the input space in partially overlapping fuzzy regions, where the recurrent neural networks of the respective rules operate. The partition of the input space and determination of the fuzzy rule base is performed by use of Fuzzy C-Means clustering algorithm and the RENNCOM constrained optimization method is applied for consequent parameter tuning. The electric load time-series of the Greek power system is examined, and hourly-based forecasting for the whole year is performed. The performance of DBD-FELF is tested via extensive experimental analysis and the results are promising, since an average percentage error of 1.18% is attained, along with an average ...

Research paper thumbnail of Service development and user characterization in communication and networking technologies

The main task of the dissertation is the modeling of user behavior in a telecommunications networ... more The main task of the dissertation is the modeling of user behavior in a telecommunications network in order to detect fraudulent activities. User behavior characterization is achieved by means of appropriate user profiles. These can be either one- or multi-dimensional structures. One-dimensional user activity representations are actually time-series of a network usage measure, e.g. calls per day or bulk of downloaded data. Multi-dimensional profiles may use more usage characteristics such as calls per day, corresponding duration, cost, hour-of-day, etc. User profiles are analyzed through artificial intelligence, statistical and data mining methods. The dissertation uses both a dofferential and an absolute approach to the problem. Problem heuristics as well as all experimentation and conclusions are based on real worldΗ παρούσα διατριβή ασχολείται με το πρόβλημα της μοντελοποίησης της συμπεριφοράς χρηστών σε τηλεπικοινωνιακά δίκτυα με στόχο τον εντοπισμό περιπτώσεων τηλεπικοινωνιακής...

Research paper thumbnail of Pareto Optimal Design of Dual-Band Base Station Antenna Arrays Using Multi-Objective Particle Swarm Optimization With Fitness Sharing

IEEE Transactions on Magnetics, 2009

Research paper thumbnail of Sharing transmission opportunity in ad-hoc WLANs supporting VoIP

2018 7th International Conference on Modern Circuits and Systems Technologies (MOCAST)

Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enabl... more Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enables modern Wireless Local Area Networks (WLANs) to efficiently exploit network resources. It is essentially a resource allocation technique that enables a contention winning station with multiple backlogged frames belonging to a specific traffic class to transmit a burst of packets for a pre-defined time interval without having to re-content for medium access. However, while multimedia traffic flows are allowed to benefit from TXOP, best effort applications are precluded from utilizing it. In the recent IEEE 802.11ac amendment an enhanced TXOP version allows multiple applications belonging to different traffic classes (including best effort and background traffic) to share the contention-free period and transmit simultaneously. That feature is available only when the Down-Link Multi-User Multiple-Input Multiple-Output (DL-MU-MIMO) is enabled in a Quality of Service (QoS) Access Point (QAP) of a WLAN that operates in infrastructure mode. In this paper, an alternative mechanism is presented that allows the sharing of the TXOP in a sequential manner and can be applied to stations in ad-hoc WLANs with co-existing Voice over IP (VoIP) and non-multimedia flows. The proposed mechanism is analyzed and the results obtained are encouraging.

Research paper thumbnail of Sharing transmission opportunity in ad-hoc WLANs supporting VoIP

2018 7th International Conference on Modern Circuits and Systems Technologies (MOCAST)

Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enabl... more Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enables modern Wireless Local Area Networks (WLANs) to efficiently exploit network resources. It is essentially a resource allocation technique that enables a contention winning station with multiple backlogged frames belonging to a specific traffic class to transmit a burst of packets for a pre-defined time interval without having to re-content for medium access. However, while multimedia traffic flows are allowed to benefit from TXOP, best effort applications are precluded from utilizing it. In the recent IEEE 802.11ac amendment an enhanced TXOP version allows multiple applications belonging to different traffic classes (including best effort and background traffic) to share the contention-free period and transmit simultaneously. That feature is available only when the Down-Link Multi-User Multiple-Input Multiple-Output (DL-MU-MIMO) is enabled in a Quality of Service (QoS) Access Point (QAP) of a WLAN that operates in infrastructure mode. In this paper, an alternative mechanism is presented that allows the sharing of the TXOP in a sequential manner and can be applied to stations in ad-hoc WLANs with co-existing Voice over IP (VoIP) and non-multimedia flows. The proposed mechanism is analyzed and the results obtained are encouraging.

Research paper thumbnail of Sharing transmission opportunity in ad-hoc WLANs supporting VoIP

2018 7th International Conference on Modern Circuits and Systems Technologies (MOCAST)

Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enabl... more Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enables modern Wireless Local Area Networks (WLANs) to efficiently exploit network resources. It is essentially a resource allocation technique that enables a contention winning station with multiple backlogged frames belonging to a specific traffic class to transmit a burst of packets for a pre-defined time interval without having to re-content for medium access. However, while multimedia traffic flows are allowed to benefit from TXOP, best effort applications are precluded from utilizing it. In the recent IEEE 802.11ac amendment an enhanced TXOP version allows multiple applications belonging to different traffic classes (including best effort and background traffic) to share the contention-free period and transmit simultaneously. That feature is available only when the Down-Link Multi-User Multiple-Input Multiple-Output (DL-MU-MIMO) is enabled in a Quality of Service (QoS) Access Point (QAP) of a WLAN that operates in infrastructure mode. In this paper, an alternative mechanism is presented that allows the sharing of the TXOP in a sequential manner and can be applied to stations in ad-hoc WLANs with co-existing Voice over IP (VoIP) and non-multimedia flows. The proposed mechanism is analyzed and the results obtained are encouraging.

Research paper thumbnail of DL MU-MIMO with TXOP Sharing and Suppressed Acknowledgments in IEEE 802.11ac WLANs

2018 41st International Conference on Telecommunications and Signal Processing (TSP), 2018

Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contributio... more Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contribution of the IEEE 802.11ac amendment. It is essentially an enhanced version of the standard TXOP mechanism initially introduced by the IEEE 802.11e amendment, specifically engineered to improve performance of the Downlink Multi-User Multiple-Input-Multiple-Output (DL MU-MIMO) technology. DL MU-MIMO transmissions with TXOP sharing are performed only by the Access Point (AP) allowing multiple frames from multiple traffic classes to be transmitted simultaneously towards multiple users in the downlink. However, in the reverse path, acknowledgments must be transmitted sequentially. The default acknowledgment scheme selected by the IEEE 802.11ac is the Block Acknowledgments (BlockACK) which is a poll-based approach. In this paper, we investigate the application of an acknowledgment-free scheme, known as No Acknowledgment (NoACK), during DL MU-MIMO transmissions in IEEE 802.11ac Wireless Local Area Networks (WLANs). Its impact on the overall achieved throughput is evaluated through an analytical study.

Research paper thumbnail of DL MU-MIMO with TXOP Sharing and Suppressed Acknowledgments in IEEE 802.11ac WLANs

2018 41st International Conference on Telecommunications and Signal Processing (TSP), 2018

Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contributio... more Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contribution of the IEEE 802.11ac amendment. It is essentially an enhanced version of the standard TXOP mechanism initially introduced by the IEEE 802.11e amendment, specifically engineered to improve performance of the Downlink Multi-User Multiple-Input-Multiple-Output (DL MU-MIMO) technology. DL MU-MIMO transmissions with TXOP sharing are performed only by the Access Point (AP) allowing multiple frames from multiple traffic classes to be transmitted simultaneously towards multiple users in the downlink. However, in the reverse path, acknowledgments must be transmitted sequentially. The default acknowledgment scheme selected by the IEEE 802.11ac is the Block Acknowledgments (BlockACK) which is a poll-based approach. In this paper, we investigate the application of an acknowledgment-free scheme, known as No Acknowledgment (NoACK), during DL MU-MIMO transmissions in IEEE 802.11ac Wireless Local Area Networks (WLANs). Its impact on the overall achieved throughput is evaluated through an analytical study.

Research paper thumbnail of DL MU-MIMO with TXOP Sharing and Suppressed Acknowledgments in IEEE 802.11ac WLANs

2018 41st International Conference on Telecommunications and Signal Processing (TSP), 2018

Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contributio... more Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contribution of the IEEE 802.11ac amendment. It is essentially an enhanced version of the standard TXOP mechanism initially introduced by the IEEE 802.11e amendment, specifically engineered to improve performance of the Downlink Multi-User Multiple-Input-Multiple-Output (DL MU-MIMO) technology. DL MU-MIMO transmissions with TXOP sharing are performed only by the Access Point (AP) allowing multiple frames from multiple traffic classes to be transmitted simultaneously towards multiple users in the downlink. However, in the reverse path, acknowledgments must be transmitted sequentially. The default acknowledgment scheme selected by the IEEE 802.11ac is the Block Acknowledgments (BlockACK) which is a poll-based approach. In this paper, we investigate the application of an acknowledgment-free scheme, known as No Acknowledgment (NoACK), during DL MU-MIMO transmissions in IEEE 802.11ac Wireless Local Area Networks (WLANs). Its impact on the overall achieved throughput is evaluated through an analytical study.

Research paper thumbnail of A Game Theoretic Approach to Enhance DCF Performance in Full Duplex Ad-hoc WLANs

Research paper thumbnail of Designing an expert system for fraud detection in private telecommunications networks

Expert Systems With Applications, Nov 1, 2009

Research paper thumbnail of Exploiting Reverse Direction Protocol in Full Duplex WLANs

This paper proposes the application of Reverse Direction (RD) protocol to enhance performance in ... more This paper proposes the application of Reverse Direction (RD) protocol to enhance performance in future Full Duplex (FD) Wireless Local Area Networks (WLANs). Full duplex communications in WLANs will be possible when a receiving node has frames ready for the transmitting node. This requires the receiver to decode the frame header for each and every frame in the Transmission Opportunity (TXOP) of the transmitter, in order to obtain the source and destination addresses. It is shown that, in FD-capable WLANs, this procedure may lead to suboptimal performance, reducing the benefits of FD communications. A simple and effective method, based on the usage of RD protocol, is proposed in order to enhance efficiency in future FD WLANs. The performance of the proposed solution is evaluated and compared to the standard method in terms of maximum achievable throughput.

Research paper thumbnail of A comparative study of Particle Swarm Optimization and Differential Evolution on Radar Absorbing Materials design for EMC applications

Radar absorbing materials (RAM) design for a desired frequency and angle range is presented. We e... more Radar absorbing materials (RAM) design for a desired frequency and angle range is presented. We evaluate the performance of particle swarm optimization (PSO) and differential evolution (DE) regarding their applicability to absorber design. The results show that the DE algorithm outer performs PSO variants.

Research paper thumbnail of On the Performance of DCF in Full Duplex WLANs with Hidden Terminals

Research paper thumbnail of A MAC - centric Approach to Detect and Mitigate EDCA Misbehavior Attacks

Journal of Engineering Science and Technology Review, Oct 1, 2016

Research paper thumbnail of A Dynamic Fuzzy Neural System for Time Series Classification

A dynamic fuzzy neural system is proposed, for time series anomaly detection. The model is entitl... more A dynamic fuzzy neural system is proposed, for time series anomaly detection. The model is entitled BFuzzTiD (Block-diagonal Fuzzy Time-series Detector) and consists of fuzzy rules whose consequent parts are three-layer small recurrent neural networks. The hidden layer of each network has blocks of neurons that feed back to each other. BFuzzTid is trained by the Dynamic Resilient Propagation algorithm. The model learns the dynamics of the time series such that it can classify them by detecting the anomaly points. A comparative analysis is conducted with a series of time series anomaly detection models, in order to investigate the capabilities of the proposed detector.

Research paper thumbnail of CSMA/CA analysis and enhancement for IEEE 802.11ax WLANs operating in STR mode

Electronics Letters, Jun 1, 2018

Research paper thumbnail of Clustering of Telecommunications User Profiles for Fraud Detection and Security Enhancement in Large Corporate Networks: A case Study

Applied Mathematics & Information Sciences, 2015

Research paper thumbnail of To Split or not to Split? A Simulation Study on the Network Convergence Duration of Multi-Area OSPF

2023 46th International Conference on Telecommunications and Signal Processing (TSP)

Research paper thumbnail of Neurofuzzy modelling of lung sounds

Contemporary engineering sciences, 2018

Research paper thumbnail of Short-Term Load Forecasting of the Greek Power System Using a Dynamic Block-Diagonal Fuzzy Neural Network

A block-diagonal fuzzy neural network for short-term load forecasting is proposed. DBD-FELF consi... more A block-diagonal fuzzy neural network for short-term load forecasting is proposed. DBD-FELF consists of fuzzy rules with consequent parts that are neural networks with internal recurrence. These networks have a hidden layer which consists of pairs of neurons with feedback connections between them. The overall fuzzy model partitions the input space in partially overlapping fuzzy regions, where the recurrent neural networks of the respective rules operate. The partition of the input space and determination of the fuzzy rule base is performed by use of Fuzzy C-Means clustering algorithm and the RENNCOM constrained optimization method is applied for consequent parameter tuning. The electric load time-series of the Greek power system is examined, and hourly-based forecasting for the whole year is performed. The performance of DBD-FELF is tested via extensive experimental analysis and the results are promising, since an average percentage error of 1.18% is attained, along with an average ...

Research paper thumbnail of Service development and user characterization in communication and networking technologies

The main task of the dissertation is the modeling of user behavior in a telecommunications networ... more The main task of the dissertation is the modeling of user behavior in a telecommunications network in order to detect fraudulent activities. User behavior characterization is achieved by means of appropriate user profiles. These can be either one- or multi-dimensional structures. One-dimensional user activity representations are actually time-series of a network usage measure, e.g. calls per day or bulk of downloaded data. Multi-dimensional profiles may use more usage characteristics such as calls per day, corresponding duration, cost, hour-of-day, etc. User profiles are analyzed through artificial intelligence, statistical and data mining methods. The dissertation uses both a dofferential and an absolute approach to the problem. Problem heuristics as well as all experimentation and conclusions are based on real worldΗ παρούσα διατριβή ασχολείται με το πρόβλημα της μοντελοποίησης της συμπεριφοράς χρηστών σε τηλεπικοινωνιακά δίκτυα με στόχο τον εντοπισμό περιπτώσεων τηλεπικοινωνιακής...

Research paper thumbnail of Pareto Optimal Design of Dual-Band Base Station Antenna Arrays Using Multi-Objective Particle Swarm Optimization With Fitness Sharing

IEEE Transactions on Magnetics, 2009

Research paper thumbnail of Sharing transmission opportunity in ad-hoc WLANs supporting VoIP

2018 7th International Conference on Modern Circuits and Systems Technologies (MOCAST)

Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enabl... more Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enables modern Wireless Local Area Networks (WLANs) to efficiently exploit network resources. It is essentially a resource allocation technique that enables a contention winning station with multiple backlogged frames belonging to a specific traffic class to transmit a burst of packets for a pre-defined time interval without having to re-content for medium access. However, while multimedia traffic flows are allowed to benefit from TXOP, best effort applications are precluded from utilizing it. In the recent IEEE 802.11ac amendment an enhanced TXOP version allows multiple applications belonging to different traffic classes (including best effort and background traffic) to share the contention-free period and transmit simultaneously. That feature is available only when the Down-Link Multi-User Multiple-Input Multiple-Output (DL-MU-MIMO) is enabled in a Quality of Service (QoS) Access Point (QAP) of a WLAN that operates in infrastructure mode. In this paper, an alternative mechanism is presented that allows the sharing of the TXOP in a sequential manner and can be applied to stations in ad-hoc WLANs with co-existing Voice over IP (VoIP) and non-multimedia flows. The proposed mechanism is analyzed and the results obtained are encouraging.

Research paper thumbnail of Sharing transmission opportunity in ad-hoc WLANs supporting VoIP

2018 7th International Conference on Modern Circuits and Systems Technologies (MOCAST)

Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enabl... more Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enables modern Wireless Local Area Networks (WLANs) to efficiently exploit network resources. It is essentially a resource allocation technique that enables a contention winning station with multiple backlogged frames belonging to a specific traffic class to transmit a burst of packets for a pre-defined time interval without having to re-content for medium access. However, while multimedia traffic flows are allowed to benefit from TXOP, best effort applications are precluded from utilizing it. In the recent IEEE 802.11ac amendment an enhanced TXOP version allows multiple applications belonging to different traffic classes (including best effort and background traffic) to share the contention-free period and transmit simultaneously. That feature is available only when the Down-Link Multi-User Multiple-Input Multiple-Output (DL-MU-MIMO) is enabled in a Quality of Service (QoS) Access Point (QAP) of a WLAN that operates in infrastructure mode. In this paper, an alternative mechanism is presented that allows the sharing of the TXOP in a sequential manner and can be applied to stations in ad-hoc WLANs with co-existing Voice over IP (VoIP) and non-multimedia flows. The proposed mechanism is analyzed and the results obtained are encouraging.

Research paper thumbnail of Sharing transmission opportunity in ad-hoc WLANs supporting VoIP

2018 7th International Conference on Modern Circuits and Systems Technologies (MOCAST)

Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enabl... more Transmission Opportunity (TXOP) is the key Medium Access Control (MAC) layer mechanism that enables modern Wireless Local Area Networks (WLANs) to efficiently exploit network resources. It is essentially a resource allocation technique that enables a contention winning station with multiple backlogged frames belonging to a specific traffic class to transmit a burst of packets for a pre-defined time interval without having to re-content for medium access. However, while multimedia traffic flows are allowed to benefit from TXOP, best effort applications are precluded from utilizing it. In the recent IEEE 802.11ac amendment an enhanced TXOP version allows multiple applications belonging to different traffic classes (including best effort and background traffic) to share the contention-free period and transmit simultaneously. That feature is available only when the Down-Link Multi-User Multiple-Input Multiple-Output (DL-MU-MIMO) is enabled in a Quality of Service (QoS) Access Point (QAP) of a WLAN that operates in infrastructure mode. In this paper, an alternative mechanism is presented that allows the sharing of the TXOP in a sequential manner and can be applied to stations in ad-hoc WLANs with co-existing Voice over IP (VoIP) and non-multimedia flows. The proposed mechanism is analyzed and the results obtained are encouraging.

Research paper thumbnail of DL MU-MIMO with TXOP Sharing and Suppressed Acknowledgments in IEEE 802.11ac WLANs

2018 41st International Conference on Telecommunications and Signal Processing (TSP), 2018

Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contributio... more Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contribution of the IEEE 802.11ac amendment. It is essentially an enhanced version of the standard TXOP mechanism initially introduced by the IEEE 802.11e amendment, specifically engineered to improve performance of the Downlink Multi-User Multiple-Input-Multiple-Output (DL MU-MIMO) technology. DL MU-MIMO transmissions with TXOP sharing are performed only by the Access Point (AP) allowing multiple frames from multiple traffic classes to be transmitted simultaneously towards multiple users in the downlink. However, in the reverse path, acknowledgments must be transmitted sequentially. The default acknowledgment scheme selected by the IEEE 802.11ac is the Block Acknowledgments (BlockACK) which is a poll-based approach. In this paper, we investigate the application of an acknowledgment-free scheme, known as No Acknowledgment (NoACK), during DL MU-MIMO transmissions in IEEE 802.11ac Wireless Local Area Networks (WLANs). Its impact on the overall achieved throughput is evaluated through an analytical study.

Research paper thumbnail of DL MU-MIMO with TXOP Sharing and Suppressed Acknowledgments in IEEE 802.11ac WLANs

2018 41st International Conference on Telecommunications and Signal Processing (TSP), 2018

Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contributio... more Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contribution of the IEEE 802.11ac amendment. It is essentially an enhanced version of the standard TXOP mechanism initially introduced by the IEEE 802.11e amendment, specifically engineered to improve performance of the Downlink Multi-User Multiple-Input-Multiple-Output (DL MU-MIMO) technology. DL MU-MIMO transmissions with TXOP sharing are performed only by the Access Point (AP) allowing multiple frames from multiple traffic classes to be transmitted simultaneously towards multiple users in the downlink. However, in the reverse path, acknowledgments must be transmitted sequentially. The default acknowledgment scheme selected by the IEEE 802.11ac is the Block Acknowledgments (BlockACK) which is a poll-based approach. In this paper, we investigate the application of an acknowledgment-free scheme, known as No Acknowledgment (NoACK), during DL MU-MIMO transmissions in IEEE 802.11ac Wireless Local Area Networks (WLANs). Its impact on the overall achieved throughput is evaluated through an analytical study.

Research paper thumbnail of DL MU-MIMO with TXOP Sharing and Suppressed Acknowledgments in IEEE 802.11ac WLANs

2018 41st International Conference on Telecommunications and Signal Processing (TSP), 2018

Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contributio... more Transmission Opportunity (TXOP) sharing is the main Medium Access Control (MAC) layer contribution of the IEEE 802.11ac amendment. It is essentially an enhanced version of the standard TXOP mechanism initially introduced by the IEEE 802.11e amendment, specifically engineered to improve performance of the Downlink Multi-User Multiple-Input-Multiple-Output (DL MU-MIMO) technology. DL MU-MIMO transmissions with TXOP sharing are performed only by the Access Point (AP) allowing multiple frames from multiple traffic classes to be transmitted simultaneously towards multiple users in the downlink. However, in the reverse path, acknowledgments must be transmitted sequentially. The default acknowledgment scheme selected by the IEEE 802.11ac is the Block Acknowledgments (BlockACK) which is a poll-based approach. In this paper, we investigate the application of an acknowledgment-free scheme, known as No Acknowledgment (NoACK), during DL MU-MIMO transmissions in IEEE 802.11ac Wireless Local Area Networks (WLANs). Its impact on the overall achieved throughput is evaluated through an analytical study.