Nodes Scheduling Scheme Of Virtual Mimo In Wireless Network

With the development of wireless communication, high speed communication becomes more common. As the frequency resource is limited, it is important to improve frequency spectrum efficiency. Multiple input multiple output (MIMO) can achieve space diversity gain and space multiplexing gain by using degree of space freedom, and effectively improve frequency spectrum efficiency. Distance between neighboring antennas should be bigger than half wavelength in ideal MIMO system. However, it is difficult to install multiple antennas in mobile equipment for the limit of volume and cost. Therefore, virtual MIMO (VMIMO) arises. VMIMO can bring space diversity gain and space multiplexing gain to users with single antenna. For flat fading, VMIMO can efficiently improve system throughput performance and service quality.Nodes scheduling scheme is important for VMIMO to work well and improve system performance. In this paper, nodes scheduling scheme for space diversity application and space multiplexing application of VMIMO is studied.As a typical VMIMO application of space multiplexing, uplink VMIMO in cell system is studied here. With the development of4G technology such as LTE and WiMax, uplink VMIMO is drawing more attention. In practical system, channel state information (CSI) obtained by the base station is imperfect for channel fading and interference. Moreover, power allocation for pairing users has significant impact on implementation of user pairing algorithm, and power allocation is conducted based on paired users. Therefore, in this paper, a low-complex joint user pairing and power allocation algorithm (JUPPA) in uplink VMIMO with imperfect CSI is proposed. When Lagrangian dual problem solution is applied to solve the optimization problem proposed in this paper, a dynamic power allocation with inter user interference (IUI) threshold is obtained to provide a watering algorithm with multiple water levels. With the introduction of aggressive discrete stochastic optimization algorithm, the user pairing strategy can converge to the optimal pairing users subset while maintaining low complexity compared with the exhaustive search algorithm. Simulation results show that the proposed algorithm can achieve better system throughput performance than conventional user pairing strategies, and efficiently restrict IUI.The typical application studied in this paper for space diversity application of VMIMO is wireless sensor networks (WSNs). Energy efficiency is a critical issue in WSNs. VMIMO technology can effectively reduce energy consumption per bit under specified bit error rate (BER). Existed studies for VMIMO in WSNs concentrate on improving energy efficiency. However, clustering scheme and data aggregation can affect the performance of VMIMO. And the cooperative characteristic introduced by VMIMO can help to balance energy consumption throughout the whole network. Therefore, in this paper, a systematic energy-balanced VMIMO cooperative nodes selection scheme (SEBC) for VMIMO in WSNs is proposed in this paper. This scheme studies energy efficiency in systematic view. For three main steps, namely nodes clustering, data aggregation and cooperative transmission, corresponding measures are put forward to save energy. These measures are well designed and tightly coupled to achieve optimal VMIMO transmission performance. Simulation results show that, compared with other traditional schemes, the proposed scheme can efficiently distribute the energy dissipation evenly throughout the network and achieve longer network lifetime span.