Cellular Mobile System Capacity influenced by Handoff protection strategies The WritePass Journal

Cellular Mobile System Capacity influenced by Handoff protection strategies ABSTRACT: Cellular Mobile System Capacity influenced by Handoff protection strategies ABSTRACT:INTRODUCTION:1. BACKGROUNDS:1.1 PROBLEM DESCRIPTION:2. Current status and development of research:2.1 Literature survey:2.2 EVALUVATION:2.3 OUTLOOK:REFERENCES:Related ABSTRACT: Today, there   is a large number of mobile user groups and In that, the need of   service of mobile user group   plays a great dispute on the utilization of bandwidth. The radio frequency spectrum is an inadequate resource, to improve service quality and system capacity radio spectrum should be carefully planned. Research is carried out to improve system capacity and service quality. Admission capability is highlighted by the system capacity and the service quality relates to the connection continuity. This proposal reveals the impact of protection, which is used to improve   the strength of the   capacity of cellular mobile systems. Traffic model is established by using the mobility characteristics of the real world. The relation between admission capability and channel reservation is given by the markov’s approach. The proposed dynamic reservation scheme is proposed to provide handoff coordination between the service quality and system capacity. INTRODUCTION: The evolution of cellular mobile systems began with the first generation (1G) cellular systems introduction, and pass on through second generation (2G) and continuing third generation (3G ), featuring the development into the fourth generation (4G) systems. This generation systems are divided based upon the coding, modulation, and multiple access techniques which are used. First public mobile telephone system (MTS) began operation in 25 American cities. In this system contains an efficient transmitter on tall building with in the city and the   permanent single channel is assigned to mobile cellular phone   for sending and receiving data through the concept of push-to-talk. Late 1960s, improved MTS(IMTS) implemented and dual channels for sending and receiving the data. In the starting of   cellular mobile systems there very few number of users. In New York, 12 calls only simultaneously supported over 1000 square mile area. In 1968, Bell laboratories demonstrated the concept of   cellular system. In the cellular concept contains 2-way communication. This type of communication used hexagonal , N-cell frequency reuse pattern by using the intracellular mobile stations (MS), which are controlled by a base station (BS). The factors which improve the capacity of cellular system are handoff, frequency reuse and sectorization . By decreasing the power of BS in the cell, in another BS the particular frequency can be reused which is remotely far away. Handoff between stations intensively increases the flexibility provided to the customer. This in turn improves the capacity and user access area is also expanded. signal processing technology   and very large scale integration (VLSI) were   developed in 1980s, which paved the route for the digital era. In this generation digital signal processor are used for the 2G cellular. ASICs are used, which reduced the size of mobile phones and new signal processing   features. Second generation systems are of digital nature, which offered   elementary data services and improved voice quality compared to that of previous generation. 2G systems were designed for the improvement of communication. In 1G radio signals are analog where as in 2G systems radio signals are digital. 2G systems are mainly developed into the CDMA and TDMA systems based on the type of multiplexing is used. in less popular areas digital signals are not reaching the tower. In digital signal call completely fails to connect when the signal strength is less, where as in analog systems it used to gradually drop. 3G is the generation of mobile phones and telecommunications. In 3G different countries used different types of radio interfaces. Mainly used radio interface is W-CDMA, FDMA is also used in this generation. 3G has various application such as mobile tv, video demand, video conferencing etc. In this generation the users increased enormously, the demand for channels also increased. The main impact on the system capacity and quality of service provided by the service provider. Researches where conducted to increase the system capacity and to decrease the call failing during the handoff. The main issue of the mobile system is the design. Radio spectrum is limited, which must be shared by several users. Each is cell is allocated with the portion of the total frequency of the spectrum. Users in the particular cell can use the channel allocated to that cell. Different cells can use the same channel separated by the minimum distance between the cells because to reduce the co-channel interference. There are three types of channel allocation techniques, they are fixed channel allocation, dynamic channel allocation, hybrid channel allocation. 1. BACKGROUNDS: In cellular systems, the number of mobile systems under a base station is random and time varying. The users of mobile systems move between cells, so there will be variations in the number of users under the particular base station. So there are lots of variations which causes the traffic and handoff of mobile systems. In the third generation mobile communication systems there is lot of research work is carrying. The objective of the research is to offer personalized and integrated services for the mobile users with the service quality than that of fixed users. In the third generation there is lot of demand for the personal communication, there is explosive growth of the user community because its available for affordable price. Increase in the   mobile customers and the   need   of   diversity   will be a great challenge to utilize the bandwidth. The radio spectrum is limited it should be carefully planned for the usage. The research work on radio channel allocation mainly focuses on the admission capability and connection continuity. It gives out the compressed channel exploitation , which in turn maximizes the number of channels. If there is any special variation in requirement of the service, full admission capacity can’t   be achieved by fixed channel allocation [1]. We are considering the dynamic channel allocation (DCA)[2]due to this service request imbalance. In DCA, channels are allocated according to the service requests distribution and load sharing also improve the   user admission capacity. 1.1 PROBLEM DESCRIPTION: The initial connection requests to start new calls are considered to improve the user accommodation capability. Accommodation capacity is based upon the admission capability of new user. Since the user moves around, its needed to establish the connection many number of times with in a single call duration. The user accommodation capacity also depends upon the connection continuity. Impulsive call break takes place when a cellular mobile user transfers from its serving cell into a new one [8], but it is not sure that channel is assigned in the different cell to remain in connection. Protecting the connection continuity is studied extensively. The basic techniques which are used to establish connection continuity for mobile users include guard channel[3], predictive channel reservation and handoff queuing. The other techniques of   handoff   protection are subrating, channel sharing and channel carrying [4]. Handoff protection strategy acquire pessimistic effect on the new user admission. The intake of new users in to the system are reduced by the priority based handoff protection schemes   such as guard channel, handoff queuing, and predictive channel reservation. particular portion of the available channels are confined to only the new users by the Guard channel , so guard channel elimination on the new user admission is apparent. Smaller impact on the new user admission is the advantage of handoff queuing over the guard channel. Assume, both handoff queuing and guard channel techniques contains the equal number of   nominal channels, the over lapping cell structure infatuated by handoff queuing, which   leads to the higher   channel density than guard channel. So the minimum impact of the channel queuing can be attributed to the increase number of nominal channels. To differentiate   these   techniques, let us observe the case   which is   similar channel set is deploy ed to envelop the same service area with implementation of   the two strategies respectively. The cell Overlapping layout demands a huge amount of the reuse factor in order to continue the co-channel interference distance, compared to that of guard channel strategy   only fewer nominal channels per cell present in the handoff queuing strategy, since the other technique does not need   the cell overlapping structure. Both the number of guard channels and non-guard channels may be equal. Equal level of handoff protection can be achieved by substituting guarded channels for handoff queuing. Due to exchange problems in handoff queuing , new call admission capability and handoff protection cont be realized. though reservation channels are not properly used, new users are blocked by the predictive channel reservation. New user admission capability consists of some   disadvantages because of handoff protection. In order to over come these constrains researches investigated chances for better providing handoff protection. In [5] Oh and Tcha introduced the division of nominal channels to protect and unprotect channel sets in order to minimize the handoff failure. Therefore a predefined grade of service satisfies the expected results for the   above proposed division of nominal channels. The functioning of handoff protection and new user admission is affected due to adding or removing the guard channels. If the handoff requests are less then the new users access guard channel because of dynamic channel allocation[7]. 2. Current status and development of research: 2.1 Literature survey: If   an user being engaged in a call connection, then he said to be active. The   number of   factors influence the active time that include walking or driving, speed, impediment and delay at street intersections, traffic density around, shopping intensions and so on. For this dwelling time   negative exponential function is good approximation to the probability distribution   through the assumption of various factors. when an active mobile user   found to be approaching cell boundary, then the   Channel reservation for handoff   is conducted. The speed and position of active mobile user are monitored to calculate the remaining time left connection with the particular current cell. If the remaining time falls below threshold is known as channel reservation interval ( CRI). After confirming the the intention of transfer of the call to the new cell, target cell receives the request for the channel reservation. if there is any ideal channel in the target cell then it is reserved and it is known as locked which means temporarily it cont be used by any other. If in the target cell does not contain any free channels then the reservation request will be in a queue. After   channel is emptied   in the target cell, the request queue searches   to find any requests which are to be processed. The   request   leaves the queue by assigning it to the free channel. A released channel remains to be free until next channel requests for it when an queue is empty. After sending the reservation request the mobile user can end this current call connection. In this situation the target cell receives reservation cancellation request from the user. After receiving a cancellation request the locked channel will be released by the the target cell after processing corresponding reservation request. We assume CRI to be accurate enough that call completion is the single account for a mobile user not to show up at ending of the CRI. If channel has been reserved to take it over or blocked for mobile user, then the target cell handoff will be successful. Whereas in the previous cases the mobile user continues its call on the new channel until leaving or call completion while in the later on into termination [8], since new call is not prioritized, if a free channel exists then new user will be accepted or else it is blocked and cleared from the system. The follo wing figure describes the working process of reservation admission in the flowchart. Markov Approach   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   A markov model is implemented for analysis of the some of active channels and the number of reservation requests which are to be processed. Consider   for each cell C   number of channels are allocated   and buffer size limit for requesting queue is S. The transition rates of the neighbouring channels are obtained as follows. Before channel reduction new calls and handoff calls are entertained, consider the gross arrival rate as the transition rate.   When a handoff call reserves one channel for later use, immediately new call takes one channel for the later use. Whenever all channels have been occupied new call is rejected and reservation request is queued upto maximum length of S, which in result get a transition rate equal to the arrival rate of the channel reservation requests only. Reservation of a channel extends the channel holding time from channel utilization interval(CUI) to channel occupation interval (COI). COI is also assumed that it is exponentially distributed, the mean value of which is obtained by[8] The expected value of the inactive period of a reserved channel before the   utilization of channel is known as the dormant period, dormant period is stated dependent that longer dormancy can be expected and written as [8] The average dormant time on state n is given as [8] Let Fx(t) is considered as the cpd (Cumulative probability distribution ) of the time interval before the ( X + 1)th channel release. The Fx(t) can be written as Fx(t) [8] We   canapproximate the sojurn of a request in the queue, which has   to be exponentially distributed to give out a time independent request. The   living rate that has the value equal to 1/Tcri. The state probabilities are given by 2.2 EVALUVATION: Traffic model supports assures mobility properties and certain geometry in real-world cell plan. Where as manhattan model considers a classic city scenario which is regarded as by the   association of buildings, big structures with streets. In the manhattan model the connection distracts, when a mobile user roams in the streets, a street corner and suffers a sharp signal strength path loss. Handoff protection with prudent channel usage decreases the user accommodation capacity. In the markov approach, accommodation capacity is evaluvated by using the single over the entire system. 2.3 OUTLOOK: In this paper, we have discussed the impact of   on capacity of the cellular mobile systems by the channel reservation. A user should receive un disrupted service through out the life time   after admission which is known as capacity. By using the handoff protection, capability of new user admission increases to that of connection continuity. user accommodation capacity is weakened by handoff protection. Which indicates system capacity and service quality are conflicting objectives. So tradeoff is cont be eliminated. Our further research to be carried out on channel reservation with out degrading the system capacity REFERENCES: [1] S.Jordan and A.Khan, â€Å"A Performance bound on dynamic channel allocation in cellular systems: equal load†. [2] D.Everitt and N. MacFayden, â€Å"analysis of multicellular mobile radio telephone systems with loss.† [3] K. Yeung and T.S. Yum, â€Å"Compact pattern based dynamic channel assignment for cellular mobile systems.† [4] â€Å"channel carrying: A novel handoff scheme for mobile cellular networks.† [5] S. H. Oh and D. W. Tcha, â€Å"prioritized channel assignment in a cellular radio network.† [6] F. A. Cruz-Perez, D. Lara-Rodriguez and M. Lara â€Å" fractional channel reservation in mobile communication systems.† [7] Y. C. Kim, D. E. Lee, B. J. Lee, Y. S. Kim, and B. Mukherjee, â€Å"Dynamic channel reservation based on mobility in wireless ATM networks.† [8] Yi Xu, Quan Long Ding, Chi Chung Ko, â€Å"impact of handoff protection strategies on cellular mobile system capacity.†

Biography of Curtis LeMay, U.S. Air Force General

Biography of Curtis LeMay, U.S. Air Force General Curtis LeMay (November 15, 1906NOctober 1, 1990) was a U.S. Air Force general who became famous for leading a bombing campaign in the Pacific during World War II. After the war, he served as the leader of the Strategic Air Command, the U.S. military division responsible for most of the countrys nuclear weapons. LeMay later ran as George Wallaces running mate in the 1968 presidential election. Fast Facts: Curtis LeMay Known For: LeMay was an important U.S. Army Air Corps leader during World War II and led the Strategic Air Command during the early years of the Cold War.Born: November 15, 1906 in Columbus, OhioParents: Erving and Arizona LeMayDied: October 1, 1990 at March Air Force Base, CaliforniaEducation: Ohio State University (B.S. in Civil Engineering)Awards and Honors: U.S. Distinguished Service Cross, French Legion of Honour, British Distinguished Flying CrossSpouse: Helen Estelle Maitland (m. 1934–1992)Children: Patricia Jane LeMay Lodge Early Life Curtis Emerson LeMay was born on November 15, 1906, in Colombus, Ohio, to Erving and Arizona LeMay. Raised in his hometown, LeMay later attended Ohio State University, where he studied civil engineering and was a member of the National Society of Pershing Rifles. In 1928, after graduating, he joined the U.S. Army Air Corps as a flying cadet and was sent to Kelly Field, Texas, for flight training. The following year, LeMay received his commission as a second lieutenant in the Army Reserve. He was commissioned as a second lieutenant in the regular army in 1930. Military Career First assigned to the 27th Pursuit Squadron at Selfridge Field, Michigan, LeMay spent the next seven years in fighter assignments until he was transferred to bombers in 1937. While serving with the 2nd Bomb Group, LeMay participated in the first mass flight of B-17s to South America, which won the group the Mackay Trophy for outstanding aerial achievement. He also worked to pioneer air routes to Africa and Europe. A relentless trainer, LeMay subjected his aircrews to constant drills, believing this was the best way to save lives in the air. His approach earned him the nickname Iron Ass. World War II Following the outbreak of World War II, LeMay, then a lieutenant colonel, set about training the 305th Bombardment Group and led them as they deployed to England in October 1942 as part of the Eighth Air Force. While leading the 305th in battle, LeMay helped develop key defensive formations such as the combat box, which was used by B-17s during missions over occupied Europe. Given command of the 4th Bombardment Wing, he was promoted to brigadier general in September 1943 and oversaw the units transformation into the 3rd Bomb Division. Known for his bravery in combat, LeMay personally led several missions including the Regensburg section of the August 17, 1943 Schweinfurt-Regensburg raid. LeMay led 146 B-17s from England to their target in Germany and then onto bases in Africa. As the bombers were operating beyond the range of escorts, the formation suffered heavy casualties, with 24 aircraft lost. Due to his success in Europe, LeMay was transferred to the China-Burma-India theater in August 1944 to command the new XX Bomber Command. Based in China, the XX Bomber Command oversaw B-29 raids on Japan. After the capture of the Marianas Islands, LeMay was transferred to the XXI Bomber Command in January 1945. Operating from bases on Guam, Tinian, and Saipan, LeMays B-29s routinely struck targets in Japanese cities. After assessing the results of his early raids from China and the Marianas, LeMay found that high-altitude bombing was proving ineffective over Japan, largely due to poor weather. As Japanese air defenses precluded low- and medium-altitude daylight bombing, LeMay ordered his bombers to strike at night using incendiary bombs. Following tactics pioneered by the British over Germany, LeMays bombers began firebombing Japanese cities. As the predominant building material in Japan was wood, the incendiary weapons proved very effective, frequently creating firestorms that reduced entire neighborhoods. The raids struck 64 cities between March and August 1945 and killed around 330,000 people. Although they were brutal, LeMays tactics were endorsed by Presidents Roosevelt and Truman as a method for destroying the war industry and preventing the need to invade Japan. Berlin Airlift After the war, LeMay served in administrative positions before being assigned to command U.S. Air Forces in Europe in October 1947. The following June, LeMay organized air operations for the Berlin Airlift after the Soviets blocked all ground access to the city. With the airlift up and running, LeMay was brought back to the U.S. to head up the Strategic Air Command (SAC). Upon taking command, LeMay found SAC in poor condition and consisting of only a few undermanned B-29 groups. LeMay set about transforming SAC into the USAFs premier offensive weapon. Strategic Air Command Over the next nine years, LeMay oversaw the acquisition of a fleet of all-jet bombers and the creation of a new command and control system that allowed for an unprecedented level of readiness. When he was promoted to full general in 1951, LeMay became the youngest to attain the rank since Ulysses S. Grant. As the United States principal means of delivering nuclear weapons, SAC built numerous new airfields and developed an elaborate system of midair refueling to enable their aircraft to strike at the Soviet Union. While leading SAC, LeMay began the process of adding intercontinental ballistic missiles to SACs inventory and incorporating them as a vital element of the nations nuclear arsenal. Chief of Staff for the US Air Force After leaving SAC in 1957, LeMay was appointed Vice Chief of Staff for the U.S. Air Force. Four years later, he was promoted to chief of staff. In this role, LeMay made policy his belief that strategic air campaigns should take precedence over tactical strikes and ground support. As a result, the Air Force began procuring aircraft suited for this type of approach. During his tenure, LeMay repeatedly clashed with his superiors, including Secretary of Defense Robert McNamara, Secretary of the Air Force Eugene Zuckert, and Chairman of the Joint Chiefs General Maxwell Taylor. In the early 1960s, LeMay successfully defended the Air Forces budgets and began to utilize satellite technology. Sometimes a controversial figure, LeMay was seen as a warmonger during the 1962 Cuban Missile Crisis when he loudly argued with President John F. Kennedy and Secretary McNamara regarding air strikes against Soviet positions on the island. LeMay opposed Kennedys naval blockade and favored invading Cuba even after the Soviets withdrew. In the years after Kennedys death, LeMay began to voice his displeasure with President Lyndon Johnsons policies in Vietnam. In the early days of the Vietnam War, LeMay had called for a widespread strategic bombing campaign directed against North Vietnams industrial plants and infrastructure. Unwilling to expand the conflict, Johnson limited American air strikes to interdictive and tactical missions, for which U.S. aircraft were poorly suited. In February 1965, after dealing with intense criticism, Johnson and McNamara forced LeMay into retirement. Later Life After moving to California, LeMay was approached to challenge incumbent Senator Thomas Kuchel in the 1968 Republican primary. He declined and elected instead to run for the vice presidency under George Wallace on the American Independent Party ticket. Though he had originally supported Richard Nixon, LeMay had become concerned that Nixon would accept nuclear parity with the Soviets and would take a conciliatory approach to Vietnam. LeMays association with Wallace was controversial, as the latter was known for his strong support of segregation. After the two were defeated at the polls, LeMay retired from public life and declined further calls to run for office. Death LeMay died on October 1, 1990, after a long retirement. He was buried at the U.S. Air Force Academy at Colorado Springs, Colorado. Legacy LeMay is best remembered as a military hero who played a major role in the modernization of the U.S. Air Force. For his service and achievements he was awarded numerous medals by the U.S. and other governments, including those of Britain, France, Belgium, and Sweden. LeMay was also inducted into the International Air Space Hall of Fame.