پياده سازي يك حلقه ي بي سيم محلي مبتني بر نقطه ي دسترسي GSM

چكيده انگليسي :

A Wireless Local Loop Implementation Based on GSM Access Point Milad Hallajian m hallajian@ec iut ac ir Date of Submission 2011 04 19 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language PersianSupervisor Ali M Doost Hoseini alimdh@cc iut ac irAbstract Software Radio refers to a tendency to increase the proportion of software component in the realizationof a communication system This approach brings some advantages like decrease in the implementationcost ease of modification and upgrading and facilities to support multiple standards in a single system Researchers in this field focus on topics such as development of hardware tools production of multi purpose development kits introducing new software algorithms and implementation techniques proposingstandard communication protocols oriented softwares and realization of the Cognitive radio concept Software Radio as a general field exploits the developments in digital communication and electronicsfileds A Wireless Local Loop or briefly WLL is a communication network that provides wirelesscommunications between internal users and the ability of bidirectional contacts between internal andexternal users A WLL as a general communication network may be based upon various protocols in itsinfrastructure GSM standards have a world wide popularity and GSM compliant user terminals are easilyavailable almost anywhere Then these standards provide an appropriate protocol collection to setup aWLL However some challenges like security and coexistence with licensed operators should beconsidered In this research a general hardware is used to receive and transfer radio signals The receivedsignals are sampled and digitized by hardware and the resultatnt digital symbols are transfered to apersonal computer through a USB2 connector for processing The software is designed on Linux operatingsystem and performs all the processes from physical layer to the highest control layer This softwarecomprises a transceiver a GSM stack and a control layer The functions such as demodulation decoding processing of triple layers of Air interface and predefined transactions of GSM networks are included inthe software in the receive path Equivalent functions are designed for reverse path too In a real GSMnetwork these functions and predefined procedures like Mobile Originating Call MOC MobileTerminating Call MTC Short Message Service Mobile Originated SM MO and Short Message Service Mobile Terminated SM MT are distributed among several parts like Base Transceiver Station BTS Base Station Controller BSC Mobile Switching Center MSC and Short Message Service Center SMSC The designed software realizes needed functions completely in contact with a Back to Back UserAgent B2BUA and uses some VoIP protocols The implemented wireless local loop in this work uses aGSM VoIP infrastructure to provide stable calls between internal mobile stations Internal users cancommunicate to external users through a Public Switched Telephone Network PSTN Thiscommunication may be initiated by either internal or external users Also Short Message Service SMS aVoice Group Call Service VGCS type service and some management commands are added to the system The manager can modify the membership of group call users Furthermore appending the ability ofcognition and completion of SMS features such as supporting Unicode messages and message exchangewith mobile stations from other operators are studied Different software tool kits and hardware devices beyond those directly used in the main implementation have been surveyed to present an outline for similarachievements in academic media Keywords Software Radio GSM VoIP Wireless Local Loop

هلاجيان، ميلاد

پياده سازي يك حلقه ي بي سيم محلي مبتني بر نقطه ي دسترسي GSM

راديو نرم افزاري , VOIP