2011 YÜksek lisans tez özetleri

Timing Synchronization in Cooperative Communication Systems

In this thesis, timing synchronization problem of cooperative communication systems is investigated and a joint estimator is proposed as a solution to this problem.

In the first chapter, wireless communication systems are very briefly introduced. The purpose of this chapter is to fast mention the improvements and related problems in contemporary wireless communication systems.

In the second chapter, channel models in wireless communication systems are first introduced in general without providing many details. These models are categorized into two groups as large-scale fading and small-scale fading. In addition to them, white Gaussian noise is also introduced. Afterwards, multiple-input and multiple-output (MIMO) systems are given short and the reason, why we should consider cooperative communication systems as an alternative to MIMO systems, is explained.

After that receive diversity methods that are crucial for both MIMO and cooperative communications systems are given. Particularly, maximum ratio combining method, which is quite popular nowadays, is introduced in detail. Furthermore, the reason as to why it is the best method is also analytically shown. Afterwards, cooperative communication systems are introduced in general. Since in this thesis amplify-and-forward protocol is used, there are more details about it than decode-and-forward protocol.

In this chapter, synchronization is also defined and explained in general as to how maintain it in wireless communication systems. Because in this thesis it is aimed at obtaining symbol synchronization, this part is given a special attention. In order to implement this synchronization interpolation method is successively introduced. At the end of this chapter, expectation-and-maximization (EM) algorithm is introduced in detail.

At the beginning of the third chapter, the system model under consideration is given comprehensively. Then a joint estimator that can estimate both propagation delay and wireless channel is analytically obtained by means of EM algorithm. In order to show performance of this joint estimator algorithm, joint Cramer-Rao bound for both parameters, propagation delay and the channel, is found and its mathematical details are given in Appendices chapter.

In the last chapter, the performance results of the designed system obtained on MatLab software by means of Monte Carlo method are given and discussed.

ÖZTÜRK Berrak

Danışman : Prof.Dr. Mukden UĞUR

Anabilim Dalı : Elektrik-Elektronik Mühendisliği Anabilim Dalı

Mezuniyet Yılı : 2011

Tez Savunma Jürisi : Prof.Dr. Mukden UĞUR

Prof.Dr. Özcan KALENDERLİ

Prof.Dr. Aydın AKAN

Y.Doç.Dr. Aysel ERSOY YILMAZ

Y.Doç.Dr. Erkan ATMACA