Wenhao Shan Pingzhi Fan Yi Pan Performance Evaluation of a Hierarchical Cellular System with Mobile Velocity-Based Bidirectional Call-Overflow Scheme. 72-83 2003 14 IEEE Trans. Parallel Distrib. Syst. 1 http://computer.org/tpds/td2003/l0072abs.htm db/journals/tpds/tpds14.html#ShanFP03