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Symbol Detection Techniques in a Spatial Multiplexing System

Thesis Info

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External Link

Author

Khan, Adnan Ahmed

Program

PhD

Institute

University of Engineering and Technology

City

Taxila

Province

Punjab

Country

Pakistan

Thesis Completing Year

2008

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1293

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727424867

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Significant performance gains are achievable in wireless communication systems using a Multi-Input Multi-Output (MIMO) communications system employing multiple antennas. This architecture is suitable for higher data rate multimedia communications. One of the challenges in building a MIMO system is the tremendous processing power required at the receiver side. MIMO Symbol detection involves detecting symbol from a complex signal at the receiver. The existing MIMO detection techniques can be broadly divided into linear, non-linear and exact detection methods. Linear methods like Zero-Forcing offer low complexity with degraded Bit Error Rate (BER) performance as compared to non-linear methods like VBLAST. Non-linear detectors are computationaly not very expansive with acceptable performance. Exact solutions like Sphere Decoder provide optimal performance however it suffers from exponentional complexity under certain conditions. The focus in the early part of this thesis is on non-linear approximate MIMO detectors and an effort has been made to develop a low complexity near-optimal MIMO detector. Computational Swarm Intelligence based Meta-heuristics are applied for Symbol detection in a MIMO system. This approach is particularly attractive as Swarm Intelligence (SI) is well suited for physically realizable, real-time applications, where low complexity and fast convergence is of absolute importance. Application of Particle Swarm Optimization (PSO) and Ant Colony Optimization (ACO) algorithms is studied. While an optimal Maximum Likelihood (ML) detection using an exhaustive search method is prohibitively complex, we show that the Swarm Intelligence optimized MIMO detection algorithms gives near-optimal Bit Error Rate (BER) performance in fewer iterations, thereby reducing the ML computational complexity significantly. In this thesis novel non-conventional MIMO detection approaches based on Swarm-Intelligence techniques have been presented. An effective and practical way to enhance the capacity of MIMO wireless channels is to employ space-time (ST) coding. Space-time block coding (STBC) is a transmit diversity technique in which the data stream to be transmitted is encoded in blocks, which are distributed among multiple antennas and across time. Alamouti’s simple STBC scheme for viwireless communication systems uses two transmit antennas and linear maximum-likelihood (ML) decoder. This system was generalized by Tarokh to an arbitrary number of transmit antennas by applying the theory of orthogonal designs. In the later part of this thesis a simple multi-step constellation reduction technique based decoding algorithm that further simplifies the linear ML detection in Orthogonal Space-Time Block Coded systems is proposed. This approach reduces the computational complexity of these schemes while presenting the ML performance. In addition, Spatial Multiplexing systems using Orthogonal Walsh codes are also studied. This approach has a potential to reduce the search space to allow efficient symbols detection in Spatial Multiplexing systems.
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اردو زبان کا آغاز و ارتقا

موضوع 10:اردو زبان کا آغاز و ارتقا
کسی زبان کے آغاز اور ارتقاء کی داستان کچھ مخصوص تہذیبی اور معاشرتی حالات سے جڑی ہوتی ہے۔ زبان اپنی ترقی یافتہ شکل اختیار کرنے سے پہلے مختلف مراحل سے گزرتی ہے۔ اسے رنگ و روپ دینے اور نکھارنے میں مختلف عوامل کار فرما ہوتے ہیں۔ اردو زبان جو آج کی چند ترقی یافتہ اور کثرت سے بولی جانے والی زبانوں میں سے ایک ہے اسے بھی معرض وجود میں آنے سے قبل مختلف مراحل سے گزرنا پڑا۔ ان مختلف مراحل اور تہذیبی اور معاشرتی عوامل کو سمجھنے کے لئے ہمیں ماضی کی طرف پلٹنا ضروری ہے۔
جیسا کہ تاریخ کے مطالعے سے پتہ چلتا ہے کہ ہندوستان کے قدیم باشندے دراوڑ تھے۔آریا قوم باہر سے آئی اور مقامی باشندوں کو پیچھے دھکیل کر ملک پر قابض ہو گئی۔آریا قوم ملک پر ایک نئی تہذیبی طاقت بن کر ابھری۔ ان کی زبان کو مرکزی حیثیت حاصل ہوئی۔ مقامی باشندوں سے میل جول کی وجہ سے آریاؤں کی زبان متاثر ہونے لگی اور بہت سے الفاظ کا تلفظ کچھ سے کچھ ہو گیا۔ آریاؤں نے اپنی زبان کو محفوظ رکھنے کے خیال سے اسے قواعدی اصولوں سے جکڑ دیا اور اپنی زبان میں صرف ٹکسالی الفاظ باقی رکھے۔مقامی اثرات اس سے پاک و صاف ہو کر ان کی زبان نے اپنا ایک معیار برقرار رکھا اور اسی معیاری زبان کو سنسکرت کا نام دیا گیا۔
اس زبان کو کافی فروغ حاصل ہوا لیکن اس کا رشتہ عوام سے کٹ گیا گیا اور ایک مخصوص دائرے تک سمٹ کر رہ گئی۔ عوام کی زبان مختلف علاقوں میں تھوڑے سے فرق کے ساتھ ایک رسم الخط میں موجود رہیں اس زبان کو پراکرت کا نام دیا گیا۔ پراکرت زبان برابر ترقی کرتی رہی اور مختلف علاقوں میں مختلف روپ اختیار کرتی رہی۔ آگے...

Creation of Pakistan and the Political Orientation of Bengali Muslims: 1940-47

, Officer Incharge/Senior Research Fellow, National Institute of Historical and Cultural Research, Centre of Excellence, Quaid-i-Azam University, Islamabad. Dr , Research Fellow, National Institute of Historical and Cultural Research, Centre of Excellence, Quaid-i-Azam University, Islamabad.

Relationship Between the School Resource Inputs and Academic Achievement of Students at Secondary Level in Pakistan

The study was conducted to investigate the relationship between school resource inputs and academic achievement at secondary level in Pakistan. School resource inputs have a vital role in the education process. The provision and availability of school resource inputs in schools is not important and beneficial until they are actually used efficiently. The focus of the provision and availability, and the use of school resource inputs, is to maximize the academic achievement of students within the limited funds available. School resource inputs include prior achievement, prior academic environment, leadership style, per pupil expenditures, pupil teacher ratio, class size, school facilities, instructional material and teacher quality. . The population of the study comprised all the secondary and higher secondary schools, secondary teachers and secondary students in Punjab. Overall, a total of 288 schools, 5760 students and 2880 teachers were the sample of the study. The study identified the availability and the use of school resource inputs through the ―School profile Proforma‖ and the ―Questionnaire‖. The longitudinal data of academic achievement of the same students from class VI to X were collected through ―Result Sheet‖. The study identified the extent of the use of school resource inputs i.e. leadership style, practical laboratories and instructional material. However, it was assumed that the basic school facilities and teacher quality are used where provided. The data were analyzed at school level and then collectively for the final analysis through Statistical package for social sciences (SPSS). Pearson Correlation Coefficient was used to find out the simple relationship (association) and Stepwise Regression analysis was used to find out the differential impact of school resource inputs on academic achievement. The results of the study show that school resource inputs are, overall, the predictors of academic achievement in their collective function. However, they have the mixed effects on academic achievement in their individual function. The findings of the study show that prior achievement of students is the most important predictor of academic achievement and prior academic environment has some positive impact. Democratic leadership style is the best leadership style; however, it is not properly used. Per student expenditure, most of the basic school facilities and most of the items of instructional material have the mixed effects on academic achievement. Student teacher ratio has positive but larger class size has negative impact. Additionally, the five indicators of teacher quality i.e. academic and professional qualifications, in-service refresher courses/ trainings, teacher experience and teacher salary are not effective. The study also identified that school resource inputs are least provided, misallocated, and inefficiently and deficiently used. These are the main causes of the negative, insignificant and minor impact of some school resource inputs on academic achievement. It is also concluded that fairly allocation and efficient use of school resource inputs leads to the significant impact of school resource inputs on academic achievement. One of the policy implications of this study is that education standards for the provision, allocation and use of school resource inputs may be developed and implemented in Pakistan. This study also guides the policy makers and the educationists by formulating the lines of action how and to what extent the school resource inputs may be provided and used in schools.