The Media Access Delay Information Technology Essay

The Media Access Delay Information Technology Essay OPNET Modeller is the network development software. OPNET permits design and learn communication networks, devices, protocols, and application. OPNETs object-oriented modelling stylishness and graphical user interface (GUI) let easy of developing models from the real world network, hardware devices, and protocols. Modeller supports all major network forms and technologies, permitting you to design and test various situations. (Opnet) Introduction I have deliberated various Medium Access Control (MAC) protocols for Wireless local Area (WLAN) Networks. To choose the best one surrounded by the existing protocols, it is necessary to have a network model scenario and some performance metrics on the basis of which they can be assessed. In this paper, various metrics for comparing the performance of MAC protocols and a network model to carry out simulation is discussed. At the end of this chapter, results obtained from the simulation in the form of graphs will be presented. DCF EDCF Metrics Picking the correct metrics or parameters in the evaluation of the QoS (Quality of Service) mechanisms is vital to the result and rationality of the evaluation. The metrics used are Throughput, Access Delay, and End to End Delay in case of real-time multimedia traffic like VoIP, Video streaming (Video conferencing), response time in case of Telnet or Remote Login; type applications which cannot tolerate delay and loss of data. Retransmission Attempts in case a station does not get a chance due to internal collision. The following list below is the item of metrics used: Throughput The Throughput for different priority levels shows how well the QoS schemes can provide service differentiation between the various priorities. The Throughput of all stations shows the utilization of the wireless medium. Wireless bandwidth is a scarce resource, so efficient use of it is vital. Media Access Delay We measure access delay as the time from when the data reaches the MAC layer until it is successfully transmitted out on the wireless medium. The reason for studying average access delay is that many real-time applications have a maximum tolerable delay, after which the data will be useless. Therefore, it is important to provide low delay for real-time flows. Retransmission Attempts Total number of Retransmission Attempts by all Wireless Local Area Network MACs in the network until either packet is successfully transmitted or it is discarded as a result of reaching short or long retry limit. For 802.11e-capable MACs, the Retransmission Attempt counts recorded under this statistic also include retry count increments due to internal collisions. This factor plays important role in Performance of WLAN. Data Dropped Data Dropped due to unavailability of access to medium. This factor largely affects the reliability of WLAN. Simulation Scenario Creating a simulation scenario that is corresponding to real world scenario is the first step of simulation. In this simulation, the wireless topology consisted of several wireless stations and one base station in the wireless LAN. The base station was connected to a wired node (Figure 2.1) which serves as a sink for the flows from the wireless domain. All wireless stations are located such that every station is able to detect a transmission from any other station, and there is no mobility in the system. This means our results will not be impacted by mobility and phenomenon such as the hidden node problem. Figure 2.1 Wi-Fi network models The simulation experiments are carried out using OPNET Simulator version 9.1 on Windows XP SP3. For this simulation, a data rate of 11 Mbps is chosen. Various MAC and PHY (Physical Layer of OSI) parameter values used in our experiment are according to IEEE 802.11e default values given in Table 2.1. We have run the simulation for 5 minutes for each scenario, and then compared the results obtained from them. Figure 2.1 shows a network model for the experiment. Table 2.1: MAC and PHY parameter values used in Experiment ATTRIBUTE VALUE Physical Characteristics Direct Sequence Data Rate (bps) 11 Mbps Transmit Power (W) 0.005 Buffer Size (bits) 256000 BSS Identifier Auto Assigned Channel settings Auto Assigned Roaming Capability Disabled AP Beacon Interval (secs) 0.02 Large Packet Processing Drop Simulation Method To compare the performance of DCF (Distributed Coordination Function) and EDCF (Enhanced Distributed Coordination Function) two scenarios were created; medium access in first scenario was supported by DCF and in second, EDCF protocol was used at the MAC layer. Network environment factors which were used as a benchmark configured same for both scenarios. Detailed specifications are given in the Table 2.1 showing the MAC and PHY parameters used in experiment. The performance evaluation is done by simulating both scenarios one by one in OPNET simulator and then comparing the graphs obtained. Results After choosing metrics, the simulation is done for 5 minutes for a scenario. Then results were gathered. Analysis of EDCF In case of EDCF, all four traffic classes were fed into the MAC layer from higher layer, which are corresponding to AC (0), AC (1), AC (2) and AC (3) respectively to check how efficient the new protocol is to provide service differentiation required for real time application. (Note that DCF does not support service differentiation, so no provision of Access category). For this, in the application profile of scenario (for EDCF protocol) different application was configured for different access category. Details are shown in the Table 4.1. Table 4.1 Access Category corresponding to an application ACCESS CATEGORY APPLICATION CONFIGURED DESIGNATION AC(0) HTTP (LIGHT) BACKGROUND AC(1) REMOTE LOGIN (HEAVY) EXCELLENT EFFORT AC(2) VIDEO CONFERENCING INTERACTIVE MULTIMEDIA AC(3) VOIP INTERACTIVE VOICE In the profile configuration, a profile for clients was configured that uses all the four applications. In simulation scenario, 15 stations were configured to use these services randomly. In the simulation, we assumed that each traffic class has the equal portion of the total data traffic in terms of the average number of packets generated per unit time. The results obtained are as follows: Throughput of Different Access Categories Figure 4.2 Throughputs of Different Access Categories It is observed from figure 4.2 that the Throughput of Access category 3 is way high than the Access category 0 and 1. Throughput for Access category 2 lies in between 3 and 1. It means that Throughput for applications like Voice over IP and Video conferencing, EDCF provides maximum Throughput by providing them more priority over the other services like simple HTTP. Media Access Delay for Different Access Categories Figure 4.3 Wireless LAN Media Access Delay It is observed from figure 4.3 that the Media Access Delay for Access category 3 is at minimum among all Access categories. Media Access Delay for Access category 2 is just 3 to 4 seconds more than AC (3). It means that the medium is assigned to the application according to the priority. Thus, EDCF provides lesser Medium Access Delay for real-time applications. Comparative Analysis of DCF and EDCF Next step is to check the performance of both protocols in terms of Throughput, Media Access Delay, Retransmission Attempts and Data Dropped. These four metrics are determining factors in terms of overall performance of both the protocols. Throughput Figure 4.4 Throughput of DCF vs. EDCF It is observed from figure 4.4 that in the first 30 seconds of simulation, Throughput of both DCF and EDCF is high, but then after that, it decreases with time and stabilizes for both protocols. Throughput in first 30 seconds is high due to less number of Retransmission Attempts (less number of backoffs). From Graph analysis, one fact is clearly visible, that curve of DCF is marginally higher than that of EDCF. We can conclude that DCFs overall Throughput is somewhat more than the EDCF. Retransmission Attempts Figure 4.5 Retransmission Attempts of DCF vs. EDCF It is observed from figure 4.5 that in the first 30 seconds of simulation, Retransmission Attempts for both DCF and EDCF are less, but then after that, it decreases with time and stabilizes for both protocols. Retransmission Attempts in first 30 seconds are less due to less number of backoffs assigned to wireless stations. There is a small noticeable difference between curves of Retransmission Attempts of DCF and EDCF protocol. That small difference implies that the overall Retransmission Attempts made in DCF protocols are a bit lesser than EDCF protocol. Media Access Delay Figure 4.6 Media Access Delay of DCF vs. EDCF In Figure 4.6, for the first minute of simulation the Medium Access Delay for both protocols increases at equal pace, and then after that, DCF suffers somewhat lesser Access Delay than EDCF. The increase in the Medium Access Delay for both protocols is due to increase in the number of nodes competing to gain access of medium. Data Dropped Figure 4.7 amount of Data Dropped of DCF vs. EDCF It is observed from figure 4.7 that the first 30 seconds of simulation, DCF suffers a sudden high Data Drop, but Data Drop in EDCF increases gradually. The reason of varying Data Drop gradually in EDCF is the service differentiation which provides priority based scheme to handle different kind of data. After 2.5 minutes of simulation, curves of Data Dropped of DCF and EDCF remain same for both protocols, EDCF finishes at less Data Dropped than DCF. Conclusions Conclusion The results obtained from simulation shows that Enhanced Distribution Coordination Function provides efficient mechanism for service differentiation and hence provides quality of service to the Wireless LAN. However, this improvement comes at a cost of a decrease in quality of the lower priority traffic up to the point of starvation. The acquisition of the radio channel by the higher priority traffic is much more aggressive than for the lower priority. Higher priority traffic benefited, while lower priority traffic suffered. In terms of overall performance (under the used simulation conditions in this particular study of QoS of Wireless LAN), DCF performs marginally well than EDCF. This happens due to reason that in EDCF mechanism, each AC function acts like a virtual station for medium access, so more collision will be expected for EDCF scenario. But in terms of Quality of Service for real-time applications (like Video conferencing) EDCF outperforms DCF. EDCF has been purposed as the medium access control protocol for IEEEs upcoming standard IEEE 802.11e. Presently, all of the wireless devices use DCF as the default MAC protocol and PCF as the optional functionality.

Girl Child Essay

The International Day of the Girl Child initiative began as a project of Plan International, a non-governmental organization that operates worldwide. The idea for an international day of observance and celebration grew out of Plan International’s Because I Am a Girl campaign, which raises awareness of the importance of nurturing girls globally and in developing countries in particular. Plan International representatives in Canada approached the Canadian federal government to seek support for the initiative.[1] A coalition of supporters raised awareness of the initiative internationally. International Day of the Girl Child was formally proposed as a resolution by Canada in the United Nations General Assembly. Rona Ambrose, Canada’s Minister for the Status of Women, sponsored the resolution; a delegation of women and girls made presentations in support of the initiative at the 55th United Nations Commission on the Status of Women. On December 19, 2011, the United Nations General Assembly voted to pass a resolution adopting October 11, 2012 as the inaugural International Day of the Girl Child.[2] The resolution states that the Day of the Girl recognizes The empowerment of and investment in girls, which are critical for economic growth, the achievement of all Millennium Development Goals, including the eradication of poverty and extreme poverty, as well as the meaningful participation of girls in decisions that affect them, are key in breaking the cycle of discrimination and violence and in promoting and protecting the full and effective enjoyment of their human rights, and recognizing also that empowering girls requires their active participation in decision-making processes and the active support and engagement of their parents, legal guardians, families and care providers, as well as boys and men and the wider community

Post Freudian theorists and their theories Essay

As indicated earlier, key personality developmental theories that were developed after Freud’s psychoanalytic theory were either directly derived of it or aimed at criticizing some of its major components. a) Erik Erickson i) Stages of development Barbara (2008) and Lieberman (2007) agree that the work of Eric Erickson was a direct derivative of Freudian considerations in human development. Eric Erickson theory of psychosocial development concurred with Freudian view that life, development and challenges develop in stages. Psychosocial theory further builds the notion of the ‘ego’ which was largely brought out by Freud as external reality inculcation to one’s mind. Particularly, the stages of Erickson psychosocial development strongly cohere with Sigmund’s work. Clara et al (2008) explain that stage one of Erickson’s theory of psychosocial development is reflected through ‘trust versus mistrust’ largely because the child is entirely dependent on the caregivers. Like Freud mentioned the pleasure a child derives from oral stimulation, Erickson emphasized on the resulting intimacy as a platform in propelling the child to the next stages. Therefore, Erickson’s first stage borrows the concept of external environment in creating enough force for the next stage. In the second stage of psychosocial development, Erickson equally borrows from Freud’s ‘anal stage’ which is a critical training factor. Nelson-Jones (2005) explains that from a higher consideration, Erickson argued that learning to go to the toilet gave a strong sense of control and therefore great independence. As Freud clearly brought out the notion of the ego, Erickson’s third stage of initiative versus guilt emphasizes the assertion of power and control which plays an important role in the later stages development. Erickson indicated that many children seek to assert their superiority among others but with careful considerations of the existing repercussions (Marrie and Janneke-van, 2007). Notably, Erickson agrees with Freud that parents and caretakers must step in to facilitate the needed reassurance and therefore avoid guilt to their young ones. It is however worth noting that Erickson strongly differed with Freud on how long development persists in an individual’s life. While Freud postulated that personality development only lasted to the genital stage when an individual starts getting interested in sexual relationship with those of the opposite sex, Erickson postulated that developed progressed to the old age (Busch, 2009). However, scholars appear to be strongly divided with one group considering the latter Erickson’s work to be based on criticism of the Freud’s work and therefore its advancement (Barbara, 2008). ii) The notion of fixation One resilient notion of Freud’s work is the notion of succession between different stages. Though they do not necessary cohere on time and expected repercussions, both theorists agree that people at different stages must go through them successfully or get fixated (Hayes, 2004). Fixation as Henry (2009) point out denotes the inability to progress since latter stages are entirely dependent on the previous stages success. Erickson argued that all stages present an individual with two negating outcomes; positive and negative. For example between year five to eleven, Erickson indicated that a successful individual will become industrious while the unsuccessful ones will suffer inferiority (Laura and Pam, 2007). b) Lacanian theory In his work, largely referred to as the return of Freud, Emile Lacan’s concepts appear to be fully defined by the former (Adam, 2008). Though Lacan strongly criticized the Freud’s separation of the conscious (ego) and unconscious (id), he largely employed the same concepts in his work. Lacan argued that the conscious and unconscious considerations of the mind were not different, but operated from a highly sophisticated and complex outline compared to Freud’s consideration. Locan mirror as Brickman (2009) and Gottdiener (2008) conclusions suggest is formative and a derivative of the experience an individual gets during development. Therefore, the paradigm of the imagery to be effective during the younger years as opposed to the old age which is more subjective fits the Freudian connotation of development persisting only to the genital stage.

The Life of Miss Emily Grierson in Faulkners A Rose for...

In William Faulkner’s â€Å"A Rose for Emily† is a short unpleasant story. Everybody faces difficult hardships, relationships, and family matters, such as life and death of loved ones. While going through those difficult times people end up having a difficult time by letting go of loved ones. After reading â€Å"A Rose for Emily†, Miss Emily Grierson had to experience difficult times in her life. She could not date anybody, her father passed away, she met a soon to be great guy, poisoned him, and end up being alone. The story began when Miss Emily Grierson’s father passed away. Miss Emily’s father was a very difficult person to do deal with. He was difficult because he seemed hard to get along with. He never seemed like he would be a person that†¦show more content†¦They all began to remember all of the men that were interested in Miss Emily, but knew he dad chased them off because he was the only person for her, in his mind. Miss Emilyâ₠¬â„¢s father was a deceptive person and played a good role in all of Miss Emily’s actions. After her father’s death, she realized that she had the house to herself. She was actually excited because she felt free. She did not have anybody trying to tell her what to do or have somebody stopping her from meeting any possible boyfriends or husbands. People in the community were also a little excited about her being home alone also, because they could know persuade her to tell what the body of her father was. Miss Emily was a little antisocial and did not want to socialize with the people in her community. Not long after he father passed away some ladies from the community were preparing to call her house and offer aid. According to the text, â€Å"Miss Emily met them at the door, dressed as usual and with no trace of grief on her face. She told them that her father was not dead. She did that for three days† (Faulkner 123). 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