2,259 research outputs found
Adaptive medium access control for VoIP services in IEEE 802.11 WLANs
Abstract- Voice over Internet Protocol (VoIP) is an important service with strict Quality-of-Service (QoS) requirements in Wireless Local Area Networks (WLANs). The popular Distributed Coordination Function (DCF) of IEEE 802.11 Medium Access Control (MAC) protocol adopts a Binary Exponential Back-off (BEB) 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 adaptive MAC 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 is investigated and compared to the original DCF using the network simulator NS-2. The performance results reveal that the adaptive scheme is able to achieve the higher throughput and medium utilization as well as lower access delay and packet loss probability than the original DCF
A Dynamic Multimedia User-Weight Classification Scheme for IEEE_802.11 WLANs
In this paper we expose a dynamic traffic-classification scheme to support
multimedia applications such as voice and broadband video transmissions over
IEEE 802.11 Wireless Local Area Networks (WLANs). Obviously, over a Wi-Fi link
and to better serve these applications - which normally have strict bounded
transmission delay or minimum link rate requirement - a service differentiation
technique can be applied to the media traffic transmitted by the same mobile
node using the well-known 802.11e Enhanced Distributed Channel Access (EDCA)
protocol. However, the given EDCA mode does not offer user differentiation,
which can be viewed as a deficiency in multi-access wireless networks.
Accordingly, we propose a new inter-node priority access scheme for IEEE
802.11e networks which is compatible with the EDCA scheme. The proposed scheme
joins a dynamic user-weight to each mobile station depending on its outgoing
data, and therefore deploys inter-node priority for the channel access to
complement the existing EDCA inter-frame priority. This provides efficient
quality of service control across multiple users within the same coverage area
of an access point. We provide performance evaluations to compare the proposed
access model with the basic EDCA 802.11 MAC protocol mode to elucidate the
quality improvement achieved for multimedia communication over 802.11 WLANs.Comment: 15 pages, 8 figures, 3 tables, International Journal of Computer
Networks & Communications (IJCNC
Building Programmable Wireless Networks: An Architectural Survey
In recent times, there have been a lot of efforts for improving the ossified
Internet architecture in a bid to sustain unstinted growth and innovation. A
major reason for the perceived architectural ossification is the lack of
ability to program the network as a system. This situation has resulted partly
from historical decisions in the original Internet design which emphasized
decentralized network operations through co-located data and control planes on
each network device. The situation for wireless networks is no different
resulting in a lot of complexity and a plethora of largely incompatible
wireless technologies. The emergence of "programmable wireless networks", that
allow greater flexibility, ease of management and configurability, is a step in
the right direction to overcome the aforementioned shortcomings of the wireless
networks. In this paper, we provide a broad overview of the architectures
proposed in literature for building programmable wireless networks focusing
primarily on three popular techniques, i.e., software defined networks,
cognitive radio networks, and virtualized networks. This survey is a
self-contained tutorial on these techniques and its applications. We also
discuss the opportunities and challenges in building next-generation
programmable wireless networks and identify open research issues and future
research directions.Comment: 19 page
Providing Dynamic TXOP for QoS Support of Video Transmission in IEEE 802.11e WLANs
The IEEE 802.11e standard introduced by IEEE 802.11 Task Group E (TGe)
enhances the Quality of Service (QoS) by means of HCF Controlled Channel Access
(HCCA). The scheduler of HCCA allocates Transmission Opportunities (TXOPs) to
QoS-enabled Station (QSTA) based on their TS Specifications (TSPECs) negotiated
at the traffic setup time so that it is only efficient for Constant Bit Rate
(CBR) applications. However, Variable Bit Rate (VBR) traffics are not
efficiently supported as they exhibit nondeterministic profile during the time.
In this paper, we present a dynamic TXOP assignment Scheduling Algorithm for
supporting the video traffics transmission over IEEE 802.11e wireless networks.
This algorithm uses a piggybacked information about the size of the subsequent
video frames of the uplink traffic to assist the Hybrid Coordinator accurately
assign the TXOP according to the fast changes in the VBR profile. The proposed
scheduling algorithm has been evaluated using simulation with different
variability level video streams. The simulation results show that the proposed
algorithm reduces the delay experienced by VBR traffic streams comparable to
HCCA scheduler due to the accurate assignment of the TXOP which preserve the
channel time for transmission.Comment: arXiv admin note: substantial text overlap with arXiv:1602.0369
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