KEYWORDS: Internet, Computer simulations, Lutetium, Local area networks, Standards development, Iterated function systems, Electronics engineering, Collision avoidance, Data centers
Nowadays IEEE 802.11 Wireless Local Area Networks (WLANs) become pervasive driven by huge demands for portable access to the Internet. Meanwhile, Voice over Internet Protocol (VoIP) is one of the fastest growing Internet applications because of its high resource utilization and low cost. This paper focuses on the combination of these two technologies. Aiming to support more voice calls in IEEE 802.11 infrastructure networks, voice capacity in IEEE 802.11 WLAN is studied. Through simulation, it is found that Access Point (AP) is a bottleneck that limits the number of concurrent voice calls. This is because in infrastructure networks, all frames must go through the AP so that the AP has much more traffic, but the AP has no advantage on accessing the medium. In this paper an enhanced DCF protocol is proposed to give AP higher priority to access wireless medium and mitigate AP bottleneck effect. In proposed scheme, AP's priority is adjusted dynamically by changing some Distributed Coordination Function (DCF) parameters according to the length of the AP queue. Simulations in various scenarios well verify the improvement achieved with increased voice capacity and decreased access delay.
Since the packages from different nodes collide with each other frequently in Ad Hoc networks, it is hard to guarantee QoS of Real-Time multimedia services if only adopting traditional multi-channel MAC protocols such as DCA, MMAC, etc. In this paper, a new multi-channel MAC technology called MAC-MC is proposed. Under MAC-MC protocol, the wireless channel is divided into one control sub-channel and N service sub-channels. The nodes in Ad Hoc network exchange RTS/CTS messages in the control sub-channel to reserve the service sub-channel for dada package. The access mechanism in the control sub-channel is designed basing on DIFFSERV mode. The parameters value of the Real-Time service package CW is different to that of Best-Effort service packages, so that the Real-Time service packages can obtain the higher priority to access the control sub-channel. In addition, a bi-dimension Markov mode is presented to analyze the performances of MAC-MC protocol theoretically. The results via simulation show that: Compared with MMAC protocol, the transfer delay of Real-Time service package is decreased greatly under the MAC-MC protocol; the networks throughput under MAC-MC protocols is larger than the networks throughput under IEEE 802.11 EDCF protocols.
ASON is new type of optical network which can offer the flexibility for bandwidth allocation and fast provision of the new service. However, until now there still are many non-ASON optical networks. It is a challenging issue to reconstruct them into ASON smoothly. In this paper, we propose a new reconstructing technology. This technology performs the function of the control plane such as link management, path management and interface management by an embedded top-set-box (ETSB). The ETSB is located between EMS and the traditional NE such as DWDM, WDM, SDH, etc. By this technology the hardware module of the existing optical network element (NE) need not modification. Thus, compared with other reconstructing technologies, the cost and the risk of this reconstructing technology are smaller.
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