Maryam Najmafshar

  Abstract

  As information and communication technology develops, the demand for ubiquitous communication networks with fast and high quality grows. Next wireless networks, are so dynamic in terms of their performance. One of the most fundamental characteristics of wireless channels is fading. Since the current view on multipath fading recognizes that random fading increases the number of degrees of freedom available for communication, these degrees of freedom and also broadcasting nature of wireless signals need to be exploited in the emerging standards. By using multihop transmission besides these characteristics we can enhance the performance of wireless connection without any increase in device complexity (unlike MIMO technology).

  In this research, we provide a performance analysis of a two-hop OFDM based network with fixed relays under MQAM modulation, in terms of average throughput and probability of outage. Although using relays has the benefits of multihop systems, this increases the complexity of analysis because of an increase in the number of paths which can carry a symbol.

  Referring to the analytical calculations and simulation results we have shown that using selective OFDMA relaying scheme makes more improvement in system performance which is an increase in throughput for a boundary user up to 60 percent in comparison with single hop system. Moreover, this method leads to a dramatically reduce in probability of outage in all reviewed cases. For example we need more than 20 dB less power in transmitter by using selective OFDMA relaying method to achieve outage probability equal to .

  Date: Saturday 89/4/26 Time: 17 PM

  Location: Room 205 Electrical Engineering department