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.

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.

Improving WLAN Performance by Modifying an IEEE 802.11 Protocol

2013 ◽  
pp. 15-32
Author(s):  
Nurul I. Sarkar
Keyword(s):  
Ieee 802.11 ◽  
Ad Hoc ◽  
Packet Delay ◽  
Distributed Coordination ◽  
Bandwidth Utilization ◽  
Medium Access ◽  
802.11 Dcf ◽  
802.11 Networks ◽  
Distributed Coordination Function ◽  
Coordination Function

One of the limitations of the IEEE 802.11 distributed coordination function (DCF) protocol is its low bandwidth utilization under medium-to-high traffic loads resulting in low throughput and high packet delay. To overcome performance problems, traditional IEEE 802.11 DCF (“DCF”) protocol is modified to the buffer unit multiple access (BUMA) protocol. The BUMA protocol achieves a better system performance by introducing a temporary buffer unit at the medium access control (MAC) layer to accumulate multiple packets and combine them into a single packet (with a header and a trailer) before transmission. This paper provides an in-depth performance evaluation (by simulation) of BUMA for multiuser ad hoc and infrastructure networks. Results obtained show that the BUMA is more efficient than that of DCF. The BUMA protocol is simple and its algorithm (software) can be upgraded to 802.11 networks requiring no hardware changes. The BUMA protocol is described and simulation results are presented to verify the performance.

ANALISIS PERBANDINGAN KINERJA TRANSPORT PROTOCOL PADA WIRELESS LAN DENGAN MENGGUNAKAN METODE DCF DAN DCF

2016 ◽  
Vol 8 (2) ◽  
Author(s):  
I Gusti Ngurah Dwi Mulyartha ◽  
Nurain Silalahi ◽  
Nyoman Bogi A. K.
Keyword(s):  
Ad Hoc Network ◽  
Wireless Lan ◽  
Ad Hoc ◽  
Transport Protocol ◽  
Distributed Coordination ◽  
Mac Layer ◽  
Medium Access ◽  
Distributed Coordination Function ◽  
Infrastructure Network ◽  
Coordination Function

EEE 802.11 adalah protokol standar yang digunakan pada wireless LAN dan memiliki Medium Access Control (MAC) layer yang mendukung pengiriman data tak sinkron (asynchronous) untuk jaringan wireless baik pada infrastructure network dan ad hoc network. MAC menggunakan dua metode akses yaitu Point Coordination Function (PCF) dan Distributed Coordination Function (DCF), dimana DCF dikembangkan menjadi DCF+. Penelitian ini mensimulasikan ad hoc Network menggunakan perangkat bantu Borland Delphi dan dari hasil simulasi dianalisa performansi dari MAC dengan membandingkan parameter Throughput, Delay, Goodput dan Fairness antara metode DCF dan DCF+.

scholarly journals Enhancing MAC performance of DCF protocol for IEEE 802.11 wireless LANs

2017 ◽  
Vol 68 (1) ◽  
pp. 83-86
Author(s):  
Woo-Yong Choi
Keyword(s):  
Access Control ◽  
Medium Access Control ◽  
Ieee 802.11 ◽  
Wireless Lans ◽  
Medium Access Control Protocol ◽  
Distributed Coordination ◽  
Medium Access ◽  
Distributed Coordination Function ◽  
802.11 Wireless Lans ◽  
Coordination Function

Abstract The DCF (Distributed Coordination Function) is the basic MAC (Medium Access Control) protocol of IEEE 802.11 wireless LANs and compatible with various IEEE 802.11 PHY extensions. The performance of the DCF degrades exponentially as the number of nodes participating in the DCF transmission procedure increases. To deal with this problem, we propose a simple, however efficient modification of the DCF by which the performance of the DCF is greatly enhanced.

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 TSCH Multiple Slotframe Scheduling for Ensuring Timeliness in TS-SWIPT-Enabled IoT Networks

Electronics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 48
Author(s):  
Dongwan Kim ◽  
Jung-Hyok Kwon ◽  
Eui-Jik Kim
Keyword(s):  
Mac Protocol ◽  
Access Point ◽  
Energy Utilization ◽  
Distributed Coordination ◽  
Medium Access ◽  
Sensor Device ◽  
Channel Hopping ◽  
Transmission Period ◽  
A Cell ◽  
Coordination Function

This paper presents a time-slotted channel hopping (TSCH) multiple slotframe scheduling (TMSS) protocol to ensure the timeliness of energy harvesting and data transmission for sensor devices with different transmission periods in Internet of Things (IoT) networks enabled with time-switching simultaneous wireless information and power transfer (TS-SWIPT). The TMSS uses a modified three-step 6P transaction to allocate power and data cells within the slotframe. The sensor device sets the slotframe length equal to the transmission period and estimates the number of power and data cells for allocation in the configured slotframe and requests cell allocation to the hybrid access point (HAP). Upon request from a sensor device, the HAP executes a cell-overlapping prevention (COP) algorithm to resolve the cell-overlapping problem and responds to the sensor device with a candidate cell list. Upon receiving the response from HAP, the sensor device determines its power and data cells by referring to the cell list. We conducted experimental simulations and compared the TMSS performance to that of the legacy TSCH medium access control (MAC) with a single slotframe and the harvest-then-transmit-based modified enhanced distributed coordination function (EDCF) MAC protocol (HE-MAC). The results showed that TMSS outperforms legacy TSCH MAC and HE-MAC in terms of delay, effective throughput and energy utilization.

scholarly journals Hybrid MAC protocol for IEEE 802.11 wireless LANs with hidden node problem

2018 ◽  
Vol 69 (4) ◽  
pp. 323-325
Author(s):  
Woo-Yong Choi
Keyword(s):  
Ieee 802.11 ◽  
Mac Protocol ◽  
Wireless Lans ◽  
Distributed Coordination ◽  
Medium Access Control Protocols ◽  
Medium Access ◽  
Hidden Node ◽  
802.11 Wireless Lans ◽  
Coordination Function ◽  
Node Problem

Abstract Combining the IEEE 802.11 basic MAC (medium access control) protocols, which are the DCF (distributed coordination function) and the PCF (point coordination function), we propose a hybrid MAC protocol to improve the performance of IEEE 802.11 wireless LANs and mitigate the hidden node problem.

On the Logarithmic Backoff Algorithm for MAC Protocol in MANETs

2009 ◽  
pp. 174-184 ◽  
Author(s):  
Saher S. Manaseer ◽  
Mohamed Ould-Khaoua ◽  
Lewis M. Mackenzie
Keyword(s):  
Ad Hoc ◽  
Mac Protocol ◽  
Window Size ◽  
Local Area ◽  
Collision Probability ◽  
Medium Access ◽  
Available Bandwidth ◽  
Binary Exponential Backoff ◽  
Backoff Algorithm ◽  
Communication Environments

In wireless communication environments, backoff is traditionally based on the IEEE binary exponential backoff (BEB). Using BEB results in a high delay in message transmission, collisions and ultimately wasting the limited available bandwidth. As each node has to obtain medium access before transmitting a message, in dense networks, the collision probability in the MAC layer becomes very high when a poor backoff algorithm is used. The Logarithmic algorithm proposes some improvements to the backoff algorithms that aim to efficiently use the channel and to reduce collisions. The algorithm under study is based on changing the incremental behavior of the backoff value. The Binary Exponential Backoff (BEB) is used by the Local Area Networks standards, IEEE 802.11, Medium Access Control (MAC). BEB uses a uniform random distribution to choose the backoff value; this often leads to reducing the effect of window size increment. This paper carries out a deeper study and analysis of the logarithmic backoff algorithm that uses logarithmic increment instead of exponential extension of window size to eliminate the degrading effect of random number distribution. Results from simulation experiments reveal that the algorithm subject to study achieves higher throughput and less packet loss when in a mobile ad hoc environment.

scholarly journals An Adaptive Contention Window Scheme for 802.11ah WLANs

2018 ◽  
Vol 17 ◽  
pp. 01016
Author(s):  
Renzheng Gao ◽  
Xiaoying Lei ◽  
Qiang Hu
Keyword(s):  
Wireless Local Area Network ◽  
Local Area Network ◽  
Mac Protocol ◽  
Rapid Development ◽  
Window Size ◽  
Local Area ◽  
Contention Window ◽  
Collision Probability ◽  
Sleep Mode ◽  
Area Network

In order to cope with the rapid development of the Internet of things, IEEE working group has proposed a new wireless network technology, 802.11ah. IEEE 802.11ah operates at sub 1GHz band, and can provide long transmission range, wide coverage, while supporting more than 6,000 of station to be connected. In order to alleviate the high collision probability, 802.11ah MAC protocol involves in the RAW (restricted access window) mechanism combined with grouping mechanism. However, in 802.11ah WLAN (wireless local area network), most of the stations operate at sleep mode, and it is expected that at the start of a BI, the network suffers much higher collision probability than at the latter period of the BI. In order to improve these drawbacks, we propose an adaptive contention window scheme based on which an optimum contention window size is adapted at the start of the BI, and then gradually halved when the transmission completes successfully. Through conducting simulations, we prove that our proposed protocol can enhance the performance of 802.11ah WLAN.

A MAC Throughput in the IEEE 802.11ac over Error-Prone Channel

2014 ◽  
Vol 631-632 ◽  
pp. 801-805 ◽  
Author(s):  
Ha Cheol Lee
Keyword(s):  
Wireless Lan ◽  
Transmission Rate ◽  
Mac Protocol ◽  
Transmission Probability ◽  
Packet Error Rate ◽  
Distributed Coordination ◽  
Medium Access ◽  
Ieee 802.11Ac ◽  
Coordination Function ◽  
Control Layer

This paper analyzes a MAC (Medium Access Control) layer throughput over error-prone channel in the IEEE 802.11ac-based wireless LAN with DCF (Distributed Coordination Function) protocol and A-MPDU (MAC Protocol Data Unit Aggregation) scheme, using theoretical analysis method. The MAC saturation throughput is evaluated by using a PER (Packet Error Rate) on the condition that the number of station, transmission probability, the number of parallel beams and the number of frames in each A-MPDU are variables. When the PER is 10-2 and the number of aggregated MPDUs in each A-MPDU is 20, it is identified that the MAC layer throughput of IEEE 802.11ac can be maximally attained up to a 92.8% of physical transmission rate.

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