Abstract

Multiple Input Multiple Output (MIMO) techniques are used to exploit spatial diversity and to achieve high bit rates required for emerging multimedia applications. To achieve this spatial diversity, more than one antenna have to be collocated at the transmitter and/or receiver nodes and the separation between those antenna has to be more than half a wavelength to ensure that the signals will experience different channel fading coefficients. One major drawback of this technique which makes it almost impossible to implement on handheld devices is the dimension of these devices.
Cooperative communication can be used to achieve the diversity gains typical of MIMO without the need for multiple antennas on the mobile units. Diversity is attained through collaboration between nodes in the wireless network. In wireless communications, cooperative diversity improves throughput and reliability. To effectively combat multipath fading in wireless networks, we develop energy efficient protocols that employ some cooperation among receiving nodes.
Motivated by the very promising results of cooperative diversity for both uncoded and coded systems as well as the substantial demand for higher data rates; in this thesis, we investigate the 2-user and 3-user destination cooperation in interference channels. We develop a collaboration protocol for the 2-user and 3-user models which is based on the fact that the information presents at one destination node can help in increasing the chance of correctly decoding the previously not decodable information at another destination node. Furthermore, we introduce network coding in the 3-user model and we show that network coding achieves further substantial gain. We demonstrate that the 2-user case outperforms the baseline scheme using orthogonal channels by far. This is due to the cooperative communication. In the cooperative scheme, the receiver nodes in the first time slot, decode the received information from both sources while in the second time slot they cooperate. The scheme provides both diversity and coding gain. Furthermore, we show that an enhanced scheme which exploits the unused information available at each destination node improves the outage probability.
We present the simulation results of various scenarios that illustrate the efficiency of employing such techniques with and without channel coding. We show how the SNR required for obtaining a certain frame error rate varies with the distance between destination nodes. We also show a comparable analysis between the 2-user and 3-user destination cooperation in interference channels on one hand and the baseline orthogonal scheme on the other hand.