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Wireless Local Area Network (WLAN) has enabled greater communication capabilities compared to LAN counterpart. However, when it comes to quality of service (QoS), WLAN has lower reliability, where it has higher latency and packet-loss, especially for real-time streaming applications such as voice over internet protocol (VoIP) and multimedia. Thus, improving QoS in WLAN is a major research challenge,...
This paper introduces concept and merits and demerits of wireless local area network (WLAN), analyzes the IEEE 802.11 series standards of WLAN. Based on simulation platform OPNET, the network model, node model and process model of distributional WLAN are constructed. The network performances of WLAN under 802.11 series standards are studied. The results indicate that setting different network parameters...
The IEEE 802.11 standard based Wireless Local Area Networks (WLANs) are widely deployed and have gained greater popularity. It is anticipated that WLAN will play an important rule in the future wireless communication systems in order to provide several gigabits data rate. However, it has been a challenging problem to support the IEEE 802.11 WLAN devices to fully exploit the high throughput gains offered...
Minimizing energy consumption is becoming more and more crucial in today's mobile terminals communications. Reducing its use pass necessarily by exploiting low power design techniques and by adopting novel energy-aware applications and protocols. The focus in this paper mainly concerns the Voice over IP over Wireless Local Area Network (VoWLAN) application, which is beyond doubt the most popular application...
Energy consumption is a major issue in the wide deployment of Voice-over-IP (VoIP) over IEEE 802.11 wireless LAN. This energy can be conserves by staying in sleep mode during VoIP call over WLAN. To this end, researchers have conducted extensive simulation and analytical studies to determine the consumed energy during VoIP call in different WLANs. These previous works, however, assume stations are...
This work presents a study in progress about voice broadcasting on WLAN networks based on IP protocol (VoIP). This study proposes a latency analysis of these networks to broadcast VoIP considering implemented and non-implemented WDS (Wireless Distribution System) environments. In this context the study aims to identify mainly the problems that affect voice transmission on IP networks. VoIP sample...
The communication based train control (CBTC) system is an advanced train control system. It uses high accuracy of train locating, realizes a continuous automatic train control system. DCS system plays an important role in the information interaction between ground equipment and vehicle equipment in CBTC. Based on OPNET simulation console, this paper designs a DCS network, simulates its communication...
In this paper we evaluated performances of IEEE 802.11s networks. In that purpose, we simulated competition for the medium based on EDCA (Enhanced Distributed Channel Access) and MCCA (Mesh Coordination Function Coordinated Channel Access) mechanisms, using programming language C. We analysed and presented achieved simulation results (average throughput for different traffic categories and average...
Load balance is a key technology in future heterogeneous wireless networks due to its merits like improving resource utilization, enlarging system capacity and providing QoS for users. This paper presents a load balancing scheme which is composed of QoS-based and load-related admission control and dynamic vertical handover. The scheme can provide better QoS and jointly optimize resource utilization...
With the development of railway transit wireless communication technology, the existing test platforms about comprehensive test are facing new challenge of real-time problems. Aiming at the demand for Doppler Effect testing of domestic railway transit WLAN equipment and in consideration of the flaw of small bandwidth and relatively large delay of the channel emulator, this paper proposes a novel approach...
Wireless local area network (WLAN) has become more popular in recent years. With increase in demand users are expecting quality of service (QoS) for multimedia services in WLAN. The legacy protocol IEEE 802.11 and IEEE 802.11e does not provide QoS and fairness for converging traffic in WLAN, so efficient management of protocols are required to provide acceptable QoS for real time traffic and fairness...
In wireless local area networks (WLANs), there could be several available access points (APs) around a Station (STA). How to select the most appropriate AP among those available APs has become a hot research topic. The conventional selection policy, which selects one AP with the best RSSI, makes the loads among APs be distributed unevenly and degrades resource utilization rate. Recently, several AP...
Reduction of power consumption is one of an important issue in wireless communications because most mobile devices are battery-driven. There are many power saving techniques for use in a wireless LAN (WLAN) environment at the hardware level and at the MAC protocol level. Their common strategy for power saving is to stay in sleep mode, which consumes very little energy, for as long as possible when...
Cellular networks coupled with wireless local area networks would be very common in the next- generation wireless environments. This integration would be made possible by employing techniques of vertical handover across different radio access networks. Finding precise timing to carry out vertical handover is an important problem and is the topic of this research work. We propose a hybrid vertical...
Being reliable and real-time, are the two most challenging requirements of wireless sensor and actuator networks (WSAN) due to the shared, error-prone and nondeterministic behaviour of wireless communication medium. In this paper, an adaptive data-rate and space-time coding (STC) scheme has been proposed for the IEEE 802.11-based Soft-Real-Time WSAN's utilizing Enhanced Distributed Channel Access...
The 802.11 Wireless Standard defines methods for improving reliability and security on Wireless Local Area Networks (WLANs). Two methods that are especially desirable to enterprise networks are handoff and Remote Authentication Dial-In User Service (RADIUS). Handoff allows seamless mobility on a wireless network, thus providing users with the ability to roam among enterprise wireless access points...
Due to the rapid and independent developments of systems, heterogeneity has become a common feature of current networks. In order to harmonize two different networks and close the gap between their technologies, we need to develop a good mechanism for network selection, and access that best satisfy user requirements. Many public areas (collages, airports, hotels...etc) have different systems for providing...
When multicasting through wireless multihop networks, frame losses at the wireless link cause data losses at the application layer because of no ACK (Acknowledgment) at both data link layer and transport layer. The authors propose a novel multicast scheme to reduce data losses at the application layer and to improve reliability. The scheme incorporates a retransmission mechanism into the data link...
In wireless communication, the discovery of the surrounding access points is crucial to provide seamless connectivity to mobile users. In IEEE 802.11, this discovery process is performed by passive and active scanning functions. For both, timers are usually constant (within the 802.11 driver) and their configuration affects the two main scanning performance metrics, i.e., scanning latency and scanning...
IP reconfiguration using DHCP is the usual approach followed by mobile nodes (MNs) when they roam from one network to another one. However, DHCP is too slow for cooping with fast handover requirements. This article describes a cross-layer approach for accelerating DHCP-based IP reconfigurations in a mobility scenario across 802.11 access points (APs). DHCP transactions are initiated by neighboring...
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