IEEE 802.11e standard is proposed to support Quality of Service (QoS) in wireless local area networks (WLANs). The distributed access method of 802.11e, Enhanced Distributed Channel Access (EDCA), prioritizes traffic generated by delay-sensitive applications by increasing probability to access medium for this type of traffic. EDCA resets the CONTENTION WINDOW (CW) of mobile stations to a minimum value after each successful transmission. This static behavior is not adapted to dynamic conditions of wireless network as it degrades network performance when channel access requests increases. Several mechanisms focusing on network adaptation have been proposed to improve the performance of IEEE 802.11e standard. The main limitation for these approaches is slow adaptation to the network state when the channel experiences bursty traffic.In this paper, we propose a new dynamic approach for CONTENTION WINDOW adjustement for each Access Category (AC) according to the traffic and network conditions. We compare our proposal with the IEEE 802.11e EDCA standard as well as some other mechanisms in the literature.Simulation results show that our proposed approach outperforms EDCA of 802.11e as well as some other enhancement to the standard present in the literature.

Transmission opportunity and CONTENTION WINDOW are two important parameters in media access in IEEE 802. 11e-based networks. and determine how to access the channel, as well as the length of time the channel is used. In these networks, each wireless station determines its media access probability by adjusting its CONTENTION WINDOW size. After winning in the CONTENTION, with respect to the duration of its transmission opportunity, transmits its data packets without re-CONTENTION. In multi hop networks, because of long distances between the source nodes and the destination nodes, the middle nodes are used to relay the data. Therefore, the middle nodes, in their transmission and receiving range, see more nodes as neighboring nodes, which makes it possible to increase traffic intensity and higher collision rates than other nodes. In this paper, the length of the queue, data arrival rate and the amount media access delay are exploited in order to a dynamic setting of the transmission opportunity and CONTENTION WINDOW to reduce the rate of packet loss and end to end delay. Simulation results show the proposed method improves media access and reduce the amount of packet loss and delay.

IEEE 802. 11e is standardized to enhance real-time multimedia applications’ Quality of Service. This standard introduces four access categories for different types of applications. Each access category has four adjustable parameters: Arbitrary Inter-Frame Space Number, minimum Size of CONTENTION WINDOW, maximum size of CONTENTION WINDOW, and a Transmission Opportunity limit. A Transmission Opportunity limit is the time interval, in which a wireless station can transmit a number of frames consecutively, without releasing the channel and any further CONTENTION with other wireless stations. Transmission Opportunity improves network throughput as well as service differentiation. Proper Transmission Opportunity adjustment can lead to better bandwidth utilization and Quality of Service provisioning. This paper studies the dynamic adjustment of Transmission Opportunity in IEEE 802. 11e using a game-theory based approach called Game Theory Based Dynamic Transmission Opportunity. Based on the proposed method, each wireless node chooses its appropriate Transmission Opportunity according to its queue length and media access delay. Simulation results indicate that the proposed approach improves channel utilization, while preserving efficiency in WLANs and minimizing selfishness behaviors of stations in a distributed environment.

Considering globalization and very intense competition between the main ports of the world, this paper tries to assess re-engineering processes using new servicing techniques in some of the most important regional and international ports. Today, traditional practices are considered as barriers to growth and expansion of the ports. High speed transportation and cargo handling requires new strategies and technologies. Regarding the intense competition to attract the customers, it is very necessary for Iranian ports to offer new services that satisfy customers. Using Information Technology (IT) and being adherence to international organizations like UN/CEFACT (United Nations Centre for Trade Facilitation and Electronic Business) are some of these practices. Many ports have boomed with increasing global trade and therefore have faced new opportunities. Single WINDOW is one of the technologies that ports use to handle the high volume of goods and cargoes.

Close encounters with the Western culture and art starts under the Qajar rule. In this period, art elements of the West find their way in the Persian art and architecture. This paper reports the results of a survey of WINDOW-guards extant form the Qajar period in Hamadan City. Of an initial sample of 68 WINDOWs, 26 samples were selected for not being a repetition of other designs. These show a gradual evolution in technique and style of using wrought iron in four phases.In the first phase, a pattern formed with S-shaped elements covers the rectangular area of a WINDOW, while the semicircular area under the spanning arch is usually blocked. In the second phase, by modifying the ‘S’ element, all the WINDOW area is covered. In the third phase, the S element is further modified, its tips become convoluted and its proportions are freely changed to fill rectangular areas. In the fourth phase, the WINDOW-guard is treated as a decorative architectural element. Therefore, in addition to the S element, other decorative spiral elements are used.

"Demographic WINDOW" refers to a particular period, in the demographic history of a population, in which age-dependency ratio falls to an unprecedented low level. This period is short, the beginning and end of it can be estimated, and it lasts about three to four decades.The Demographic WINDOW of Iran began at the threshold of 2006 census and is expected to end by 2046. Therefore, it is expected to last for almost 4 decades. Thereafter, the population of Iran moves towards becoming old, to an unprecedented level in its history.In the demographic history of each country, demographic WINDOW opens once, and during the time it is open, it provides an exceptional opportunity for the development of the country. However, it is not automatic. It should be activated and guided. Demographic WINDOW becomes a demographic bonus only with appropriate preparation: policy-making, planning and correct implementation of programs.Several years, apparently unnoticed, passed since Iran entered its demographic WINDOW. Time is moving fast and this short time span becomes shorter. Therefore, it seems urgent to conduct required studies for the appropriate utilization of this unrepeatable opportunity for the development of the country.