scholarly journals Decoupling-Based Channel Access Mechanism for Improving Throughput and Fairness in Dense Multi-Rate WLANs

2019 ◽  
Vol 12 (1) ◽  
pp. 3 ◽  
Author(s):  
Jianjun Lei ◽  
Ying Wang ◽  
Hong Yun
Keyword(s):  
Data Transmission ◽  
Local Area ◽  
Access Time ◽  
Channel Access ◽  
Distributed Coordination ◽  
Medium Access ◽  
Performance Anomaly ◽  
Network Utilization ◽  
Free Data ◽  
And Performance

Legacy IEEE 802.11 Medium Access Control (MAC) adopts the Distributed Coordination Function (DCF) mechanism, which provides the same access opportunity for all contenders. However, in dense multi-rate Wireless Local Area Networks (WLANs), the pure distributed control mechanism will cause high collision rate and performance anomaly, which results in low network utilization and wasting valuable channel resources. In this paper, we present a decoupling MAC mechanism (DMAC) based on the idea of contention/reservation to reduce collision and realize collision free data transmission. In proposed mechanism, the channel access time is partitioned into channel contention process and data transmission process. The proposed algorithm makes full use of the distributed random channel access mechanism and performs a centralized collision-free data transmission. Wherein, we also design an adaptive algorithm to adjust the length of the contention period to improve the channel utilization. Furthermore, we further propose two airtime fairness algorithms Improve-DMAC1 (I-DMAC1) and Improve-DMAC2 (I-DMAC2) for delay sensitive network and high throughput network scenarios, respectively, to solve the performance anomaly in multi-rate WLANs, based on DMAC. We verify the effectiveness of these decoupling algorithms through extensive simulations. Moreover, the simulation results show that the proposed algorithms achieve better performance than the 802.11 standard and other protocols.

scholarly journals A Novel Synchronous MAC Protocol for Wireless Sensor Networks with Performance Analysis

Sensors ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 5394 ◽  
Author(s):  
Prasan Kumar Sahoo ◽  
Sudhir Ranjan Pattanaik ◽  
Shih-Lin Wu
Keyword(s):  
Wireless Sensor Networks ◽  
Sensor Networks ◽  
Data Transmission ◽  
Mac Protocol ◽  
Wireless Sensor ◽  
Medium Access ◽  
Relay Nodes ◽  
Healthcare Applications ◽  
Mesh Topology ◽  
Free Data

Synchronous medium access control (MAC) protocols are highly essential for wireless sensor networks (WSN) to support transmissions with energy saving, quality services, and throughput in industrial, commercial and healthcare applications. In this paper, a synchronous channel access mechanism is designed, where sensors can reserve the contention free data transmission slots in different available channels. To reduce the delay of data transmission among the nodes in the mesh topology, a linear programming problem (LPP) model is designed to select suitable relay nodes. Moreover, the performance of the proposed MAC is analyzed and our models are validated with simulation and analytical results. The results show that our proposed MAC protocol outperforms the IEEE 802.15.4e MAC mechanism in terms of throughput, reliability, delay, energy, packet drop rate and transmission success rate.

scholarly journals Hybrid Control of Contention Window and Frame Aggregation for Performance Enhancement in Multirate WLANs

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Muhammad Adnan ◽  
Eun-Chan Park
Keyword(s):  
Performance Enhancement ◽  
Hybrid Control ◽  
Transmission Rate ◽  
Local Area ◽  
Contention Window ◽  
Channel Access ◽  
Distributed Coordination ◽  
Frame Aggregation ◽  
Transmission Rates ◽  
Coordination Function

The IEEE 802.11 standard has been evolved to support multiple transmission rates in wireless local area networks (WLANs) to cope with diverse channel conditions and to increase throughput. However, when stations with different transmission rates coexist, the basic channel access mechanism of WLAN, distributed coordination function (DCF), not only fails to assure airtime fairness among competing stations but also decreases overall network throughput, because DCF was designed to provide fair opportunity of channel access, regardless of transmission rate. As an effective solution to this problem, we propose a hybrid control mechanism that integrates contention window control and frame aggregation. The former adjusts the size of contention window and differentiates the channel access opportunity depending on the transmission rates of stations. The latter controls the number of packets in the aggregated frame to tightly assure per-station airtime fairness with the reduced channel access overheads. Moreover, we derive an analytical model to evaluate the performance of the proposed mechanism in terms of throughput and fairness. Along with the analysis results, the extensive simulation results confirm that the proposed mechanism significantly increases the overall throughput by about three times compared to the conventional DCF, while assuring airtime fairness strictly.

scholarly journals The Impact of Dynamic RTS Threshold Adjustment for IEEE 802.11 MAC Protocol

2009 ◽  
Vol 5 (1) ◽  
pp. 5-20 ◽  
Author(s):  
Mostafa Mjidi ◽  
Debasish Chakraborty ◽  
Naoki Nakamura ◽  
Norio Shiratori
Keyword(s):  
Ieee 802.11 ◽  
Data Transmission ◽  
Mac Protocol ◽  
Threshold Value ◽  
Local Area ◽  
Wireless Channel ◽  
Main Element ◽  
Medium Access ◽  
Hidden Terminal ◽  
The Impact

In recent years, wireless technologies and application received great attention. The Medium Access Control (MAC) protocol is the main element that determines the efficiency in sharing the limited communication bandwidth of the wireless channel in wireless local area networks (WLANs). IEEE 802.11 introduced the optional RTS/CTS handshaking mechanism to address the hidden terminal problem as well as to reduces the chance of collision in case of higher node density and traffic. RTS Threshold (RT) determines when RTS/CTS mechanism should be used and proved to be an important parameter for performance characteristics in data transmission. We first investigate to find a meaningful threshold value according to the network situation and determine the impact of using or disengaging the RTS/CTS optional mechanism and dynamically adjust the RTS Threshold to maximize data transmission. The results show a significant improvement over existing CSMA/CA and RTS/CTS schemes. Our adaptive scheme performed even better when data rate increases. We verify our proposed scheme both analytically and with extensive network simulation using ns-2.

Enhanced Distributed Coordination Function of MAC for VoIP Services Using IEEE802.11 Networks

2012 ◽  
Vol 433-440 ◽  
pp. 2304-2309
Author(s):  
B. Suvarna Vignan ◽  
B. Lalu Naick
Keyword(s):  
Mac Protocol ◽  
Local Area ◽  
Contention Window ◽  
Collision Probability ◽  
Network Simulator ◽  
Distributed Coordination ◽  
Medium Access ◽  
Packet Collision ◽  
Distributed Coordination Function ◽  
Coordination Function

Voice over Internet Protocol (VoIP) is an important service with strict Quality-of-Service (QoS) requirements with in wireless local area networks. The popular Distributed Coordination Function (DCF) of IEEE802.11 Medium Access Control (MAC) protocol adopts Multiplicative Increase and linear Decrease procedure to reduce the packet collision probability in WLANs. In DCF, the size of contention window is doubled upon a collision regardless of the network loads. This paper presents an enhanced DCF scheme to improve the QoS of VoIP in WLANs. This scheme applies a threshold of the collision rate to switch between two different functions for increasing the size of contention window based on the status of network loads. The performance of this scheme investigated and compared to the original DCF using the network simulator NS-2. Under the high traffic loads the packet loss probability decreases with the enhanced DCF compared to the original DCF. Some other parameters like throughput and access delay is decreased with the enhanced DCF.

A Markov Model for the IEEE 802.11 DCF under Limit Load

2011 ◽  
Vol 48-49 ◽  
pp. 29-33
Author(s):  
Sheng Guo Gao
Keyword(s):  
Markov Model ◽  
Load Condition ◽  
Packet Delay ◽  
Limit Load ◽  
Local Area ◽  
Distributed Coordination ◽  
Medium Access ◽  
802.11 Dcf ◽  
Significant Research ◽  
Coordination Function

Wireless Local Area Networks (WLANs) have been attracted significant research during the last few years. The primary medium access control (MAC) technique of 802.11 is called distributed coordination function (DCF). DCF is a carrier sense multiple access with collision avoidance (CSMA/CA) scheme with binary slotted exponential backoff. This paper proposes a new Markov model to analyze the CSMA/CA protocol and average packet delay. This model covers the finite load condition and saturation condition. The close agreement between the theoretical results and simulation results using NS-2 under reaffirms the accuracy of the analytical model.

scholarly journals Latency and Jitter Analysis for IEEE 802.11e Wireless LANs

2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Sungkwan Youm ◽  
Eui-Jik Kim
Keyword(s):  
Local Area ◽  
Ieee 802.11E ◽  
Distributed Coordination ◽  
Mac Layer ◽  
Medium Access ◽  
Distributed Coordination Function ◽  
Packet Latency ◽  
Coordination Function ◽  
The Voice

This paper presents a numerical analysis of latency and jitter for IEEE 802.11e wireless local area networks (WLANs) in a saturation condition, by using a Markov model. We use this model to explicate how the enhanced distributed coordination function (EDCF) differentiates classes of service and to characterize the probability distribution of the medium access control (MAC) layer packet latency and jitter, on which the quality of the voice over Internet protocol (VoIP) calls is dependent. From the proposed analytic model, we can estimate the available number of nodes determining the system performance, in order to satisfy user demands on the latency and jitter.

scholarly journals Majority Voting-Based MAC Protocol for Exploiting Link-Layer Diversity in Wireless Networks

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2706
Author(s):  
Jaehyoung Park ◽  
Yonggang Kim ◽  
Gyungmin Kim ◽  
Hyuk Lim
Keyword(s):  
Data Transmission ◽  
Software Defined Radio ◽  
Mac Protocol ◽  
Local Area ◽  
Majority Voting ◽  
Medium Access ◽  
Link Layer ◽  
Error Corrections ◽  
Carrier Sensing ◽  
Interference Signals

In wireless local area networks (WLANs), the effect of interference signals between neighboring nodes increases as the number of wireless nodes using limited radio frequency resources in a limited space increases, which can significantly degrade the reliability of data transmission. In high-density WLANs, there can be several neighboring access points (APs) that can receive uplink transmission from a station. In conventional medium access control (MAC) protocols, uplink data frames containing errors or transmitted from a non-associated station are discarded at APs. Alternatively, we propose a MAC protocol using redundant wireless links between neighboring APs and the non-associated stations. In the proposed MAC protocol, we consider a centralized WLAN with a control node that performs error corrections of erroneous uplink data frames via a majority voting algorithm-based link-layer diversity scheme using uplink data received from multiple APs to increase the reliability of data transmission. In addition, we propose an adaptive carrier sensing ranging mechanism to improve the uplink network throughput in the proposed centralized WLAN system. Further, we conduct simulation studies and software-defined radio-based experiments to evaluate the performance of the proposed MAC protocol in various WLAN scenarios.

scholarly journals Improving WLAN Quality of Services (Qos) Using Opnet

2016 ◽  
Vol 9 (3) ◽  
pp. 204-211
Author(s):  
Ishwar Baidari ◽  
S. P. Sajjan ◽  
Ajeet Singh
Keyword(s):  
Ieee 802.11 ◽  
Local Area Networks ◽  
Local Area ◽  
Wireless Local Area Networks ◽  
Ieee 802.11E ◽  
Distributed Coordination ◽  
Medium Access ◽  
Access Delay ◽  
Coordination Function

Wireless local area networks (WLANs) are in a period of great expansion and there is a strong need for them to support multimedia applications. With the increasing demand and penetration of wireless services, users of wireless networks now expect Quality of Service (QoS) and performance comparable to what is available from fixed networks. Providing QoS requirements like good throughput and minimum access delay are challenging tasks with regard to 802.11 WLAN protocols and Medium Access Control (MAC) functions. This research is done to study, the presently implemented schemes (the Point Coordination Function (PCF) of IEEE 802.11, the Enhanced Distributed Coordination Function (EDCF) of the proposed IEEE 802.11e extension to IEEE 802.11), solves these issues and what can be done to improve them further. The metrics used were Throughput, Data Drop, Retransmission and Medium Access Delay, to analyze the performance of various MAC protocols in providing QoS to users of WLAN. Two scenarios, with same Physical and MAC parameters, one implementing the DCF and other EDCF, were created in the network simulation tool (OPNET MODELER) to obtain the results. The results showed that the performance of EDCF was better in providing QoS for real-time interactive services (like video conferencing) as compared to DCF, because of its ability to differentiate and prioritize various services. Index Terms - Wireless local area networks (WLANs),

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