ارسال صوت با استفاده از كد گذاري چند توصيفي در شبكه اي از چند ارائه دهنده ي GPRS

چكيده انگليسي :

110 Voice Transmission Using Multiple Description Coding in Multi provider GPRS Network Seyyed Mohammadreza Azimi sm azimi@ec iut ac ir Date of Submission 2010 07 24 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Dr Faramarz Hendessi hendessi@cc iut ac ir Abstract Increase in wireless services during recent decade resulted in dedication of more radio resources by service providers so 3G and 4G standards have been emerged These standards are different from previous versions over cases such as dedicated bandwidth multiple access techniques modulation schemes and their constellations adaptive coding rates in different channel conditions resource allocation to users and so on As a result not only the capacity of mobile network namely maximum simultaneous connections has been improved but also each user benefits from higher transmission rate rather than users of traditional standards Existing large number of demands for different applications such as call multimedia communication web browsing etc lead to a need that the mobile network resource should be used effectively It has been assumed that mobile users have been equipped with a new device called Multi Interface Multi Channel MIMC cell phone which makes it possible to communicate with different service providers at the same time and send or receive packets from them The MIMC device uses Multiple Description Coding MDC as source coding in order to overcome one of the major wireless channel impairments namely packet loss With this coding MIMC device benefits from routing diversity or multi path routing which results in robustness against variations in network capacity achieving higher level of statistical multiplexing and also providing better performance for special applications such as video or voice Using MDC MIMC cell phone transmission rate has been adjusted to the conventional users of mobile network As a result network traffic would not increase Frequency planning in each provider remains unchanged and MIMC users such as conventional users use available frequencies and get together To avoid changes in network protocols a new node called Gateway has been used at the edge of network which is responsible of decoding transmitted multi description packets and executing proper coding with respect to receiver in uplink and also decoding transmitted regular packets and executing MDC in downlink direction Therefore proposed architecture will be compatible with current networks For implementation a special case namely VoIP over GPRS has been developed GPRS was previously considered as an infrastructure in order to carry VoIP packets and therefore mobile network capacity had been increased GPRS suffers from high overhead because of inefficient protocol stack it also has low data rate in data link layer As proposed in packing more than one radio block through one packet which caused higher packetization delay and using header compression are two solutions for GPRS impairments However this solution fails in bad channel conditions As described earlier new method which is a combination of MD source coding and multi provider architecture can exploits better voice quality and network performance with introducing cooperation method in uplink and downlink

عظيمي، محمدرضا

ارسال صوت با استفاده از كد گذاري چند توصيفي در شبكه اي از چند ارائه دهنده ي GPRS

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