Network selection is crucial in improving the performance of heterogeneous wireless access systems.Most of previous work on network selection or radio resource allocation concentrates on the capability of each available network and ignores the time-varying nature of wireless media due to channel fading.However,the channel condition determines the state of each wireless network and plays a vital role in ensuring quality of service in multi-radio access environment.In this article,we propose a network selection policy using stochastic control theory considering the time-varying and stochastic character of wireless channels.The proposed scheme selects one network among different alternatives in each decision epoch according to the channel state of each network,which is modeled as finite-state Markov channel,with the objectives of increasing the data-rate,decreasing the bit error rate and minishing the delay.The procedure of network selection is formulated as a stochastic control problem,which can be solved using linear programming and primal-dual index heuristic algorithm.Simulation results are presented to show that network selection has great impact on the system performance,and the proposed scheme can improve the performance significantly. Network selection is crucial in improving the performance of heterogeneous wireless access systems. Host of previous work on network selection or radio resource allocation concentrates on the capability of each available network and ignores the time-varying nature of wireless media due to channel fading. However, the channel condition determines the state of each wireless network and plays a vital role in assurance quality of service in multi-radio access environment. this article, we propose a network selection policy using stochastic control theory considering the time-varying and stochastic character of wireless channels. proposed scheme selects one network among different alternatives in each decision epoch according to the channel state of each network, which is modeled as finite-state Markov channel, with the objectives of increasing the data-rate, decreasing the bit error rate and minishing the delay. The procedure of network selection is formulated as a stochastic control problem, w hich can be solved using linear programming and primal-dual index heuristic algorithm.Simulation results are presented to show that network selection has great impact on the system performance, and the proposed scheme can improve the performance significantly.