Research On Cross-layer Resource Allocation In Multiuser MIMO-OFDM Systems

In recent years,the contradiction between the users' growing business demand for Quality of Service(Qo S)and the cable wireless spectrum resources becomes more prominent,so that the future wireless communication is facing severe challenges.The cross-layer resource allocation technology can combine the information of two or more wireless network layers to design the resource allocation method,so that the system resources can be used more rationally and efficiently to improve the system spectral efficiency.Therefore,the study of cross-layer resource allocation technology with higher spectral efficiency has important practical significance and value.Aiming at the problem of unreasonable resource allocation due to the incomplete information of hierarchical design in the downlink of multi-user MIMO-OFDM system,this paper proposes a cross-layer resource allocation algorithm which implements joint carrier and power allocation under the users' minimum rate constraint,this algorithm combines the Qo S requirements of the Media Access Control(MAC)layer with the dynamic resource allocation of the physical layer.The algorithm first models the user MAC layer cache queue into a finite state Markov chain,and uses its steady-state distribution to analyze the Qo S requirements of different users(maximum packet loss requirement),and then transform it into the lowest rate constraint of the user's physical layer condition,then under the condition of user's minimum rate constraint and the total transmit power limit,the algorithm implements joint carrier and power allocation to maximize the system throughput.The algorithm prioritizes the user with the most power required to achieve the minimum rate constraint to allocate the carrier and power,so that the total power required by all users in the system to achieve the minimum rate constraint is as little as possible,so the system will have as much residual power as possible to allocate to the carriers in the best way.The simulation results show that compared with the existing algorithms,the proposed algorithm not only can meet the Qo S requirements of different users,but also can improve the system throughput to a large extent.For a MIMO-OFDM cognitive radio system in which a plurality of primary users and a plurality of cognitive users exist,this paper proposes a cross-layer resource allocation algorithm based on duality decomposition theory.It can maximize system throughput under the conditions of meeting the interference thresholds allowed by all the primary users,the Qo S requirements of all cognitive users,and the total transmit power limit of all cognitive users.The algorithm first transforms the Qo S requirements(the maximum packet loss requirement)of all cognitive users into users' minimum rate constraint,then according to the theory of duality decomposition,the dual problem which is transformed from the original problem is decomposed into several simple sub-problems that are easy to solve,finally,the optimal Lagrangian factors are obtained by using the sub-gradient method,so the optimal solution of carrier and power distribution is obtained.The simulation results show that compared with the traditional algorithm,the algorithm can not only meet the Qo S requirements of different cognitive users,but also can improve the total rate of all cognitive users to a large extent.