My Articles

1-Voice over IP (VoIP)

ANALYSIS AND EVALUATION OF EFFECT OF QUEUNING TECHNIQUES QUALITY OF SERVICE OF VOICE OVER INTERNET PROTOCOL

Voice Over Internet Protocol (VoIP) is the transmission of voice over completely IP based Networks, instead of today‟s circuit switching phone networks. VoIP is a technology that enables the transport of data packets on t he Internet. VoIP technology obtains low cost, easy and flexible structure that can be developed, such factors as ease of setup anduse. For real VoIP implementations analog signals has to be packetized. The process goes through sampling and coding. There are many different codecs providing different features and voice quality. Also there are many mechanisms developed to avoid degradation of the voice quality and improve the voice quality after it is processed. Some of these mechanisms are voice activity detection, silence suppression, comfort noise generation, packet loss concealment, echo cancellation and others. Delay is one of the biggest issues with voice quality. Buffers and QoS mechanisms like classification and prioritization of packets are developed to avoid delay affect. However, there are also many issues that need to be carefully resolved before availability of whole IP based VoIP can be a reality.

The aim of this thesis, the sound quality and uninterrupted transmission of voice over Internet Protocol to transmit the impact on the quality of service queuing techniques realized with simulator analysis. In the first chapter of this thesis, general information on Voice over Internet Protocol (IP) is provided. The second chapter examines the general structure of the Voice over IP technology, the protocols and architectures used, the call scenario examples, factors affecting voice quality , encoding techniques and voice codecs.

In the third chapter, the current voice and data traffic in a real Local Area Network were simulated by forming three different scenarios with the Opnet Modeler simulation program. The first scenario is a real campus data network traffic is simulated with FIFO queuing. The second scenario was simulated with this data traffic queuing PQ. The third scenario was also simulated with the WFQ queuing. The fourth chapter, the third section focuses in detail on the simulation results. The fifth chapter, the simulation results and parameters affecting the quality of service are examined and presented recommendations to improve these factors.

PS: This article is abstract of my thesis at Marmara University.

June,2011

PS: You can reach to full version of thesis via http://www.belgeler.com/blg/3h5f/analysis-and-evaluation-of-effect-of-queuning-techniques-quality-of-service-of-voice-over-internet-protocol-with-an-simulator

2-Wireless and Mobile Networks

ANALYSIS OF PERFORMANCES OF DIFFERENT SERVICES IN WIRELESS NETWORKS

One or more computers and peripherals connected to each other in order to discover other network devices form computer network. Computer networks offer an environment that users can make sharing information and data between computers. The main purpose of computer networks for connected users is to provide and to reach resources and to have contact with other users.

Through the use of computer networks people save time and resources. Users can Access each other’s hard disks and data, software or hardware through share options. Shared peripherals (printer, scanner, CD-ROM, modems, etc.) can be used by all computers on the same network.

With the spread of internet on worldwide in all areas, the internet has become a need. Data traffic, as well as requirements of multimedia applications, such as transfer between different concepts of speed and quality of service become very importante. Dynamic business life in the intensive tempo, resource sharing without being tied to an office or people, led to the need to benefit from services such as Internet access. Despite the use of Ethernet in broad application areas, wireless LAN technology has started to become increasingly common at offices, airports, and other public areas.

Usage of wireless network systems is through enterprise applications such as Health, Education, Manufacturing and Service sectors. In the field of health in order to facilitate patient, follow-up patients is used for ensuring their access to information anytime and anywhere in hospitals. The patient bedside or bracelet-like device information can be transmitted wirelessly to the desired location. In some hospitals are installed for physician practices wireless controlled robot. In this way, the doctor can make remote consultation with the patient. In the field of education, teachers and students are provided with access in order to ensure access to the internet in any place in the campus such as dormitories, libraries and cafes. Production facilities, Home apliences, automobile and other manufacturing plants are used in wireless computer networks. In addition, wireless control devices are used in control systems. The service sector, in daily life especially in the restaurant and retail stores have become used in the wireless communication. Restaurants; orders, fast tracking, large warehouses and stores, merchandise offers tremendous ease of monitoring of inputs and outputs.

Today, free wireless access points are set up and people from the train stations, hotels, airports, can provide internet access at these places.

There are many different standards for wireless LAN systems. Different protocols and physical infrastructure should be used in different frequency bands. Using the different frequencies and standards gives better results depending on the distance, needs and purpose of use. Developing new technologies, developing with each other and complement each other rather than to replace. Diversity of existing wireless applications is inevitable. Due to this diversity, publication of standards resulting confusion is prevented.

Worldwide, the establishment of standards for the purpose of conducting studies in various organizations. These organizations provides information and classifies technology related to in many areas such as introduction of systems, equipment compatibility approvals, access areas, should be provided services, security policies.

WLAN standardization activities, the IEEE (Institute of Electrical and Electronics Engineers-Institute of Electrical and Electronics Engineers), ETSI (European telecomunications Institute – European Telecommunications Institute), MMAC (Multimedia Mobile Access Communication-Multi-Media Mobile Communication) is carried out by the three main organizations.  Practices and standards developed tremendously raises some problems in practice. Difficult to determine and implement the most appropriate standard and there are compliance issues arising from the use of a combination of different standards. During the preparation of the application of a network there are certain criteria that should be considered. As an example of these criteria, the data type of the application to be moved, the service will be provided the number of users, the physical dimensions of the field.

PS: This article is abstract of my thesis at International University of Sarajevo.

June,2013

PS: You can reach to full version of thesis via http://www.belgeler.com/blg/4rnf/analysis-of-performance-of-different-services-in-wireless-technologies