كارايي سيستمهاي مخابرات همكارانه با وجود ابهام در مورد اطلاعات كانال

چكيده انگليسي :

Performance of Cooperative Communication Systems with Imperfect Channel Information Mehdi Basiri Abarghouei m basiriabarghooei@ec iut ac ir Apr Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan Iran Degree M Sc Language Persian Supervisor A M Doost Hosseini alimdh@cc iut ac ir Abstract In conventional point to point wireless communications if the channel link is blocked or inactivated the receiver is not able to get the transmitted information and therefore reliable communication is not guaranteed Diversity is a powerful technique of combating random behavior of wireless channels Among various diversity schemes in time frequency and space domains spatial diversity has attracted higher attention in recent years However due to the size and cost limitations multiple antennas may not be used in many circumstance In such cases cooperative diversity as a new way of realizing spatial diversity has been introduced in which single antenna terminals in a multi terminal scenario may share their facilities in a manner to create a virtual multiple input multiple output MIMO system The basic idea is that in addition to the direct transmission from the transmitter to the receiver there are other nodes to relay the source signal to the destination Each user s data information is broadcasted not only by the source but also by cooperating users Thus information transmission reliability is enhanced since from statistical point of view the chance that all independent links to the destination fade is low Various practical schemes have been proposed to exploit the benefits of cooperation among nodes These schemes are usually classified into two categories amplify and forward AF and decode and forward DF In the former scheme a relay node simply scales and retransmits the waveform received from a source In DF the received source signal is demodulated and decoded initially before new encoding and modulation DF can be switched to non cooperative mode in the case of decoding error revealed by a failed cyclic redundancy check CRC Performance of cooperative communication networks can be analyzed under various criteria Outage probability symbol or bit error rate and capacity are examples In this thesis symbol error rate SER performance of uncoded cooperation systems with either DF or AF cooperation protocol with perfect and imperfect channel state information CSI is considered We use a simple relay channel with MQAM signals and a total power constraint In this analysis a modified model of the channel coefficient with estimation error is proposed on the basis of the general model for the cooperative transmission The channel estimation errors are assumed to be circularly symmetric Gaussian distributed and independent from the channel estimates A study of the MRC receiver structure and the corresponding conditional symbol error probability closed form symbol error rate approximations optimal and suboptimal power allocation methods for the decode and forward and amplify and forward schemes as well as providing a new adaptive approach with regard to the channel coefficients estimation errors comprise the objectives of this work The fundamental concept of cooperative diversity can also be applied in multicarrier systems such as orthogonal frequency division multiplexing OFDM In this thesis after reviewing the main concept in these systems the role of resource allocation with power constraints on individual subcarriers is also addressed Keywords Cooperative Communication Imperfect Channel Information Power Allocation Symbol Error Rate Multicarrier Communication Subcarrier Cooperation

بصيري ابرقوئي، مهدي

كارايي سيستمهاي مخابرات همكارانه با وجود ابهام در مورد اطلاعات كانال

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