Gong, Zhigang2020-09-022020-09-022003-05-22https://hdl.handle.net/11299/215567This thesis focuses on the design and application of approximation algorithms in computer and communication systems. Many problems in these computer and communication systems are known as NP-hard in combinatorial computation complexity theory. Several of them can be solved approximately using a common approximation theory approach: the combination of greedy, linear programming and randomization. We first extended the known approximation techniques and then applied the technique to several chosen problems.en-USReport