Cooperative communications is an emerging technique that has spatial diversity inherent in wireless multiuser communication systems without multiple antennas at each node. Most studies in the literature assume that users acting as the relays are normally operated and trustworthy, which, however, may not always be true in practice. This thesis considers the design of robust cooperative communication in physical layer for combating relay misbehaviors. This thesis considers both models in which the cooperative communications is with direct path (WDP) and without direct path (WODP). Two signal-correlation-detection rules for both WDP and WODP are proposed, respectively. Utilizing the proposed signal-correlation-detection mechanism, the destination identifies the misbehaving relays within the cooperative communication network and then excludes their transmitting messages when performing the diversity combining to infer the symbols of interest sent by the source. The proposed signal-correlation-detection rules are optimally designed in accordance with either the criterion of the minimization of the probability of misbehavior misidentification or the criterion of the maximum generalized likelihood detector. In addition, this thesis also provides the BER analysis of the cooperative communications employing the proposed misbehaving relay detectors. The simulation result demonstrates that the proposed schemes have excellent robust performance when the relay misbehavior is present in the cooperative communication networks.

In this thesis, we investigate the problem of channel estimation in the amplify-and-forward cooperative communication systems when the networks could be in the presence of selfish relays. The information received at the destination will be detected and then used to estimate the channel. In previous studies, the relays will deliver the information under the prerequisite for cooperation and the destination can receive the information sent from the source without any possible selfish relay. Therefore, the channel will be estimated under this over idealistic assumption. Unfortunately, the assumption does not make sense in real applications. Currently, we don¡¦t have a mechanism to guarantee the relays will always be cooperative. The performance of channel estimation will be significantly degraded when the selfish relays present in the network. Therefore, this thesis considers an amplify-and-forward cooperative communication system with direct transmission and proposes a detection mechanism to overcome the misbehaving relay problem. The detection mechanism employed estimation is based on likelihood ratio test using both direct transmission and relayed information. The detection result will then be used to reconstruct the codeword used for estimating product channel gain of the source-to-relay and relay- to-destination links. The mathematical derivation for the considered problem is developed and numerical simulations for illustration is also carried out in the thesis. The numerical simulation results verify that the proposed method is indeed able to achieve robust channel estimation.

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In the cooperative communications, the users relay each other¡¦s signal and thus forming multiple transmission paths to the destination and therefore the system can achieve spatial diversity gain. Decode-and-forward and amplify-and-forward are the most popular relaying strategies in the literature due to their simplicity. However, in practice, cooperative users acting as relays may not always normally operated or trustworthy. When the relay misbehavior is present in the cooperative networks, the communication performance may degrade dramatically and the users may be even better off without cooperation. Therefore, it is necessary for the destination to determine the misbehaving relays and to take appropriate actions to ensure that cooperative advantages are preserved. In this thesis, we focus on developing a misbehaving relay detection method to detect whether or not the system is in the presence of some misbehaving relays. After performing misbehaving relay detection, the destination removes the signals from the un- reliable paths and then uses maximal ratio combing to achieve spatial diversity. The simulation results conducted by the thesis show that the proposed method is more robust as compared with those without employing misbehaving relay detection when the system is in the presence of some misbehaving relays.

In the cooperative communications, the users relay each other's signal and thus form multiple transmission paths to the destination and therefore the system can achieve spatial diversity gain. Most studies in the literature assumed that cooperative users acting as the relays are normally operated and trustworthy. However, this may not always be true in practice. When the relay misbehaviors are present in the cooperative communications, the communication performance may degrade dramatically and the users may be even better off without cooperation. Therefore, it is necessary for the destination to determine the misbehaving relays and to take appropriate actions to ensure that cooperative advantages are preserved. This thesis considers both models in which the cooperative communications are with direct path (WDP) and without direct path (WODP). Utilizing the proposed Kolmogorov-Smirnov test mechanism, the destination identifies the misbehaving relays within the cooperative communications and then excludes their transmitting messages when performing the diversity combining to infer the symbols of interest sent by the source. In addition, this thesis provides the bit error rate (BER) analysis of the cooperative communications employing the proposed misbehaving relay detectors. The simulation results demonstrate that the proposed methods have robust performance when the relay misbehaviors are present in the cooperative communications.

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This research considers the place of media in society by means of a Foucaudian genealogy of welfare and neo-liberal discourse surrounding youth misconduct in two Toronto newspapers. It was found that the overall “mode of talking” about youth misconduct has shifted from welfare to neo-liberal discourse, and that resistance or critical thought surrounding current neo-liberal discourse emerges in The Globe and Mail. I explore the role of newspapers in the process of governance by analyzing these discourses in terms of Foucault’s three rationalities for “the art of government” and also by analyzing the knowledge produced or titillated and the power outcomes or effects of these discourses. It is argued that newspapers can benefit governance by reflecting, validating and perhaps even rendering current neo-liberal governmentalities more efficient, by encouraging non-government groups to assist in the management of youth misconduct.

This research considers the place of media in society by means of a Foucaudian genealogy of welfare and neo-liberal discourse surrounding youth misconduct in two Toronto newspapers. It was found that the overall “mode of talking” about youth misconduct has shifted from welfare to neo-liberal discourse, and that resistance or critical thought surrounding current neo-liberal discourse emerges in The Globe and Mail. I explore the role of newspapers in the process of governance by analyzing these discourses in terms of Foucault’s three rationalities for “the art of government” and also by analyzing the knowledge produced or titillated and the power outcomes or effects of these discourses. It is argued that newspapers can benefit governance by reflecting, validating and perhaps even rendering current neo-liberal governmentalities more efficient, by encouraging non-government groups to assist in the management of youth misconduct.

This research considers the place of media in society by means of a Foucaudian genealogy of welfare and neo-liberal discourse surrounding youth misconduct in two Toronto newspapers. It was found that the overall “mode of talking” about youth misconduct has shifted from welfare to neo-liberal discourse, and that resistance or critical thought surrounding current neo-liberal discourse emerges in The Globe and Mail. I explore the role of newspapers in the process of governance by analyzing these discourses in terms of Foucault’s three rationalities for “the art of government” and also by analyzing the knowledge produced or titillated and the power outcomes or effects of these discourses. It is argued that newspapers can benefit governance by reflecting, validating and perhaps even rendering current neo-liberal governmentalities more efficient, by encouraging non-government groups to assist in the management of youth misconduct.

This research considers the place of media in society by means of a Foucaudian genealogy of welfare and neo-liberal discourse surrounding youth misconduct in two Toronto newspapers. It was found that the overall “mode of talking” about youth misconduct has shifted from welfare to neo-liberal discourse, and that resistance or critical thought surrounding current neo-liberal discourse emerges in The Globe and Mail. I explore the role of newspapers in the process of governance by analyzing these discourses in terms of Foucault’s three rationalities for “the art of government” and also by analyzing the knowledge produced or titillated and the power outcomes or effects of these discourses. It is argued that newspapers can benefit governance by reflecting, validating and perhaps even rendering current neo-liberal governmentalities more efficient, by encouraging non-government groups to assist in the management of youth misconduct.