Research On The Physical-layer Security Methods For The Wireless Multicast Systems

Due to the broadcasting nature of the wireless channel, wireless multicast is an effectivetechnique to serve multiple users and multiple groups at the same time, and it is becomingpopular in the next generation wireless communication networks. The wireless multicastphysical-layer security methods focus on the wireless physical-layer channel to secure thecommunication, which is irrelevant to the application-layer, therefore they are adapted to thewireless multicast sceneries. There are a few more questions to be investigated. Firstly, when thenumber of receivers’ antenna is more than that of the base station, the artificial noise method isno longer applicable to the multicast system. Secondly, issues about the resource allocation andinterference elimination methods of the multi-group multicasting systems are worthy to beinvestigated. Based on the National Nature Science Foundation of China, this paper investigatesthe physical layer security methods for the wireless multicast systems.Wireless multicast can serve multiple groups at the same time, taking this character intoconsideration, this paper first focuses on the physical layer security methods of signal-groupmulticast system, and then we investigate the physical layer security method for the multi-groupmulticast systems. The detailed research is on the following part:1. A multicarrier-based physical layer security method is proposed. Firstly a multicarrierbased multicast system secure communication model is established, then the subcarriers areallocated while ensure the sending antenna redundancy, so that the artificial noise can be addedinto the null space, depressing the eavesdropper’s SNR. To maximize the secrecy rates, a K-Tcondition based power allocation method is proposed. Simulation results indica te that theproposed method is unlimited by the amount of sender antennas, while the simulations areperformed over64multicarrier, with the SNR of the eavesdropper is15dB and the SNR of legaluser is25dB, the proposed method improves the secrecy rates by1bit/s/Hz than the averagepower allocation method.2. A cluster-based physical layer security method for the signal group multicast system isproposed. Based on the opportunistic multicast scheduling method, the base station divides theuses of the same group into different clusters, so that the sending antenna redundancy ispromised. Then the artificial noise can be added into the null space, depressing theeavesdroppers’ SNR. To maximize the secrecy rates, a cluster-based power allocation method isalso proposed. By introducing artificial noise to the clusters, secure transmission is ensured, andthe secrecy rates improves by3bit/s/Hz than the average power allocation method. 3. A multi-group multicast physical layer security method is proposed. Under themulticarrier communication scenes, an improved subcarrier allocation method is proposed toensure that more subcarrier is allocated to the groups with less users, so that the subcarrier can bereasonable utilized. Under the signal frequency communication scenes, a cluster-based physicallayer security for the multi-group multicast systems is proposed. In order to serve the users ofdifferent groups at the same time, a user-number based cluster-dividing method is proposed.Considering the interference among different groups, a cluster-based multicast beam formingmethod is also proposed. Our simulations are performed over128multicarrier, with the SNR ofthe eavesdropper is15dB and the SNR of legal user is25dB, and simulation result indicates thatthe proposed multicarrier allocation method improves the secrecy rates by10bit/s/Hz. Under thesignal-frequency communication scene, when the base station serves the groups at the same time,the secrecy rates improves6bit/s/Hz more than that when the groups are served independently.