The problem of power allocation in cognitive radio networks plays an important role to improve the efficiency of spectrum utilization. However, most of previous works focus on the power allocation for secondary users in spectrum sharing overlay or spectrum sharing underlay, which needs to frequently handoff between the idle spectrum bands or considers the interference constraints in all spectrum bands respectively. In order to reduce the handoff and fully utilize the spectrum resource, we propose a new spectrum sharing paradigm which not only can just need to adjust the transmit power in spectrum bands instead of frequently handoff between idle spectrum bands, but can fully utilize the spectrum resource as we only consider the interference power constraints in active spectrum bands rather than in all spectrum bands. Then based on this new spectrum sharing paradigm and the constraint conditions, we study the distributed power allocation for secondary users and formulate the optimization problem as a non-cooperative game problem, after that the variational inequality approach is used to solve this game problem and a Nash equilibria solution is got, finally simulation results are illustrated to demonstrate the performance of the proposed scheme.
Quality of service(QoS)routing algorithms have been hardly discussed in the scientific community,most previous work on QoS routing concentrates on the performance of the single route.Cognitive packet network(CPN)has been designed for providing QoS routing.In this paper,to balance the loads among networks,we present a multi-path routing algorithm based on load-balance(MPRLB),which is carried out in two steps.The algorithm with low computational complexity is firstly applied to establish multi path routing for each source and destination node pairs(SD-pair)nodes in the network.Then,we propose the hopfield neural network algorithm,which is applied to improve the efficiency of the flow deviation method for fast flow allocation among the links of the network based on load balance.Extensive simulation results demonstrate that the proposed scheme significantly improves the performance compared with the existing scheme that ignores load balancing.
For cooperative relay multicast networks,the general cross-layer optimization approaches converge to the global optimal value slowly because of the large quantity of relay terminals.However,the mobility of relay terminals requires quick converging optimization strategies to refresh the relay links frequently.Based on the capacity analysis of multiple relay channels,an improved cross-layer optimization scheme is proposed to resolve this problem,in which the bound of the relay selecting region is determined as a pre-processing.Utilizing the primal-dual algorithm,a cross-layer framework with pre-processing optimizes both the relay terminal selection and power allocation with quick convergence.The simulation results prove the effectiveness of the proposed algorithm.
Within a cell of cellular system,cooperative relay technique can improve the performance of multicast efficiently,but it can cause the stream frequent interruptions because of the mobility of relay terminals.A video layered cooperative relay strategy is proposed to guarantee the continuity of multicast stream and retain high-bandwidth of the cooperative relay channel.Based on the capacity analysis for layered relay channel in the strategy,the optimal power allocation is studied to maximize capacity.After analyzing and optimizing the capacity in abstract models,the study is extended to a non-fading and a Gaussian wireless channel model to satisfy the scenario of cellular system.Giving the relay nodes position or distribution of noise power,the obtained results can determine the optimal power allocation among the transmitter and relay nodes.At last,the simulation results show that the strategy and its optimal power allocation have a significant improvement on the performance.
Multiple-input multiple-output (MIMO) wireless communication systems can significantly improve the spectrum efficiency or transmission reliability through spatial multiplexing or diversity respectively.Most of previous works mainly have focused on the multiplexing-diversity tradeoff or switching between multiplexing and diversity without considering the property of heterogeneous QoS provisioning.In this paper,switching between multiplexing and diversity in MIMO system with the heterogeneous QoS provisioning is studied.Firstly the QoS provisioning for users are classified into two classes:users with real time service requirement and users with non-real time service requirement respectively.Then based on the heterogeneous QoS Provisioning for users,two different switching criterions are proposed,switching based on the Euclidean distance for users with real time service to minimize the probability of symbol error and capacity-based switching criterion for users with non-real time service to maximize the transmission capacity respectively.Finally,numerical simulation results are illustrated to demonstrate the performance of proposed scheme.
