关键词: 认知无线电, 多目标遗传算法, 二级用户链接（SUL）维持问题, 冗余子信道模型, 基于多目标遗传算法的SUL维持算法（SULEA）

Abstract: When some primary users re-emergence，the secondary users must immediately give up the spectrum belonging to the primary users.At this point there is a problem on how to maintain the existence of the Secondary Users’Link（SUL）.The redundant sub channels model based on CORVUS system use another X redundant sub channels besides the original N sub channels for the communications among secondary users.As long as the interfered sub channels during the transmission are less than X，the receiver can restore the correct information from the N+X sub channels，thus solving the SUL maintaining problem.However so far，there is no effective way to solve the optimal N and X.This paper models the SUL maintaining problem as a multiobjective optimization problem，develops a new SUL maintaining algorithm called SULEA based on a multiobjective evolutionary algorithm.SULEA can dynamically select the fitness functions according to the user’s different service need，so as to solve the optimal N and X，and the results of Matlab simulation experiment testify the validity of SULEA.

Key words: cognitive radio, multiobjective evolutionary algorithm, Secondary Users’Link（SUL） maintaining problem, redundant sub channels model, SUL Maintaining Algorithm Based on Multiobjective Evolutionary Algorithm（SULEA）