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Efficient Utilization of Bandwidth for Ofdm Wsn

Thesis Info

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External Link

Author

Hashmi, Ansar Saeed

Program

PhD

Institute

University of Engineering and Technology

City

Lahore

Province

Punjab

Country

Pakistan

Thesis Completing Year

2018

Thesis Completion Status

Completed

Subject

Electrical Engineering

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/12510/1/Th-08-E-1-ansar-hashmi-final-thesis.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727746336

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Wireless Sensor Networks (WSNs) have gained popularity in a lot of emerging areas since their evolution, like the monitoring of natural phenomena concerning geosciences in various disciplines. Some relevant areas include the monitoring of oil and gas exploration field, earth quake and volcanic eruptions etc. In these processes real time phenomena are monitored in remote fields and after data collection through WSN, it is ported to the far flung research centers for further investigation and decision making. Here 2-tier WSN is considered with lower tier of sensor nodes in WiFi and upper tier of WiMAX as a backhaul for data transportation to distant research facility. However WiMAX has already popularity for applications with main configuration of downlink data delivery direction, like serving internet hot spots and similar amenities. This innovative research work is concerned with previously mentioned phenomena monitoring which needs high data throughput efficiency in the uplink direction. For dense sensor node concentration, in order to transport consolidated output form all sensor nodes in real time phenomena of impulsive nature, sufficient uplink throughput is needed with low latency which forms a bottleneck in these cases for WiMAX backhaul. Real time applications constrain end-to-end delay and hence throughput which severely affect the performance and the accuracy of the monitoring. To the system only fixed bandwidth is available, for which resources of slots have to be shared between downlink and uplink. Here WiMAX OFDM in TDD mode is considered. Initially analysis has been presented to point out main important constituent parameters of WiMAX which contribute to throughput. This research work proposes a solution to enhance uplink bandwidth allocation efficiency for these phenomena through adaptive shift of WiMAX frame ratio. In this regard for WiMAX adaptive ratio shift researchers have used a number of scenarios but all of them are not very efficient and have drawbacks. Some of them are using either fixed margins or some other are using fixed step sizes for upward or downward (increment) without any calculation. If a link (uplink or downlink) is running near full capacity then any kind of sudden appearance of internal system overheads in the form of system message or broadcast may bring the link to fragmentation. And fragmentation successively may contribute to increase the link overheads further, causing either increased delay or some other problem related to packet drop, re-transmission or transmission failure. If problems are induced, this may take relatively longer at a reduced data transfer rate. In order to avoid similar problems, relevant calculations have to be performed to guarantee good QoS values of maximum link throughput while keeping low delay and packet drop, which needs adequately more resources. In fact keeping in view the complex trade-off between QoS parameters and system resources, the optimization problem is formulized to maximize the uplink throughput while keeping the latency and packet drop of downlink to minimum limit, to facilitate the efficient operation of uplink’s momentarily bulky traffic. A novel solution to this problem is obtained through the incorporation of stochastic processes with random variable in finite state space. The analytical and mathematical expressions are contributed for the different analytical models. A MMPP traffic model is formed for OFDMA transmission. This is supported with a DTMC system model for queuing theoretic performance modeling. Analytical and numerical values of performance parameters like throughput, packet delay and probability of packet drop are estimated for resource allocation through mathematical models of stochastic process. First of all to restrict the downlink traffic to minimum level a traffic pattern is defined from downlink to WSN sensor nodes. While considering packet scheduling, two scenarios are taken into account, one is concerned with known MCS distribution and the other is concerned with unknown MCS distribution. In this process mainly affecting factors of frame overheads are also taken into account. Then by using all these analytic and mathematical models, an algorithm is formulated to find out minimum optimal resource requirement on down link after considering these QoS parameters. Through this manipulation rest of the resources can be transferred to facilitate uplink operation. Another DTMC model is designed to check and quantify the uplink frame utilization. When uplink frame utilization is beyond normal, the frame resources have to be incremented to previously calculated maximum limit by adaptively remapping the frame ratio. Also when utilization on uplink reduces below normal, it is remapped to normal frame ratio. The main algorithm is formed by appropriately including all these previous analytical models. This sets the adaptive ratio to the best suitable maximum value, to facilitate the uplink bulky traffic, and saves the link from congestion and slowing down. This also ensures minimization of previously mentioned errors of delay, drop or timeout related problems. This process achieves highest degree of convergence in just one step by providing maximum throughput on uplink without degrading QoS parameters on the downlink operation. In order to prove the results firstly analytical results are obtained from the computations of the algorithm in MATLAB. Secondly intensive simulations are conducted around Rayleigh flat fading channel through models in three steps. One simulation model gives results for downlink minimum traffic, next model is for uplink maximum traffic and another model is for uplink normal ratio traffic. All these results together prove the accuracy and superiority of the algorithm by showing an outstanding uplink bandwidth efficiency enhancement without degrading the downlink operation. Future research directions are to further enhance the analytical models for more states. Also more variations to overhead analysis can be added by more realistic models and with more overhead reduction techniques.
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’’نظامی صاحب بلند پایہ عالم اور ملک کے ممتاز مورخ اور دارالمصنفین کے رکن رکین تھے، ان پر بعض مشہور اہل قلم سے جن کو ان سے گہری واقفیت تھی، مضمون لکھنے کی فرمایش کی گئی ہے، اس مضمون میں ان کی زندگی کے ایک خاص پہلو ہی سے گفتگو کی گئی ہے‘‘۔ (ض)
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نظامی صاحب متوسط قد کے تھے لیکن ان کا جسم ایسا تھا کہ ہر لباس خواہ ہندوستانی ہو یا انگریزی ان پر خوب پھبتا تھا، ان کا رنگ گندمی تھا جس کی وجہ سے ان کے سفید بالوں کی جو قدرے لمبائی لیے ہوئے تھے سپیدی کا احساس بڑھ جاتا تھا۔ ان کی آنکھیں بڑی نہیں تھیں لیکن نہایت روشن تھیں جن میں ایک خاص چمک تھی، ان کے چہرے سے رعب عیاں ہوتا تھا لیکن خوف بالکل نہیں معلوم ہوتا تھا۔
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The enormous and unprecedented spread of English has made it difficult for the so- called ‘Native Speakers of English’ to exercise their control over it. The non-native varieties of English are establishing their niche alongside the standard varieties of English. A paradigm shift can be noticed from ‘EFL, ESL, ENL’ to EIL paradigm. The non-native varieties of English have initiated their codification and description. In this scenario, this research studies Pakistani English as a non-native institutionalized variety and aims at identifying various features of it. The lexico-grammatical features of noun phrase in Pakistani English have been explored from six aspects. A corpus of written Pakistani English (PWE), 2.1 million words, has been compiled as a research tool. PWE comprises 29 text categories to enhance the representativeness of the corpus. PWE has been used to identify the features on the basis of actual instances or corpus evidence. BoE, BNC, Brown, Frown, LOB, and FLOB corpora have been used as reference corpora. This investigation is mainly a corpus driven research and the components of this research are based on corpus evidence observed during the study. One inference can be drawn from all the components of the present research that the differences between Pakistani English and the Standard varieties of English are not so wide as to create any serious problems in mutual intelligibility. But the differences seem wider than those between the British and American Englishes. The chapter 1 introduces the research and chapter 2 explores the theoretical undercurrents related to World Englishes and Pakistani English. It discusses the spread of English and the emergence of non-native varieties, conflicting standards among varieties, role of English in non-native context, the impact of pluricintricity, language policy and which model Pakistani English should follow etc. Chapter 3 is the survey of literature and links the present research with the research already done in the areas of Pakistani English, corpus linguistics, collocations, lexico-grammar, and noun phrase. Chapter 4 discusses the steps taken in the compilation of the corpus and introduces the corpus (PWE). Methodological framework has been kept separate from methodology. Chapter 5 describes the methodological framework of the research and explores the paradigm this research is II aligned with. Due to the complex methodology of the six components of the research, the methodology (a guide for the replication of the research) has been discussed in each component of the noun phrase before analysis in Chapter 6. The sixth chapter comprises six components of research and presents their analysis. The first component deals with mechanics i.e. hyphenated compounds in PWE, and highlights the differences from BNC and also addresses the importance of such issues in the context of Non-native varieties of English. The second component, Urduization, is the study of Urdu words in PWE and tabulates the data in various domains to show how Pakistani English as a non-native variety of English is bound in socio-cultural make up of the community. The third component, Noun Noun Compounds explores nine trends in the noun compounds and reveals hundreds of examples to identify trends in PWE. The fourth component, Modifying Adjectives, uses Yibin Ni’s (2004) model to explore lexico- grammatical and semantic categories of the modifying adjectives of 50 nouns selected on the basis of frequency and detailed consistency. The quantitative differences of this component have been further explored in the fifth component of the research. The same 50 nouns have been used as nodes of concordance lines to study the 1R and 1L collocates. These collocates have been grouped into lexical fields. The results of this component loudly pronounce that the real differences between Pakistani English and other varieties of English are mainly of collocations. One hundred nouns in PWE, which have been identified as vocabulary differences between British and American Englishes by Davies (2005), have been studied in the final component of the research. Chapter 7 concludes the research and shares some observations I made during the research. Chapter 8 is forward looking and introduces various researchable areas the present research has identified. In the light of the detailed discussion on theoretical undercurrents, it can be assumed that the results obtained in the data analysis are significant for description of Pakistani English and establishing the status of Pakistani English. Moreover, the results are insightful in ELT because they can show the difference between what is taught and what is being used. The information obtained as the results of the data analysis can be used in lexicographical activities. A supplement can be added to the already existing dictionaries.