MS-initiated handover decision criteria for VoIP over IEEE 802.16e

The emerging mobile WiMAX (IEEE 802.16e) has gained serious attention as a means of providing wireless broadband access to mobile users. 802.16e supports high data rates and QoS for various applications, and is thus a powerful contender for next generation wireless access technology. On the other hand, IEEE 802.11 a/b/g/n have already been widely used to provide high data rates in a limited area. Therefore, in the near future, 802.16e and 802.11 will co-exist and a multi-homed mobile station (MS) will be likely to execute many handovers (HOs) due to free movement among 802.16e´s hotzones and 802.11´s hotspots. Many studies of HO decision criteria for 802.11 have been conducted but, so far, HO decision criteria for 802.16e have not yet been sufficiently studied, in particular that for MS-initiated HO in 802.16e. In this paper, we propose MS-initiated HO decision criteria for VoIP over 802.16e considering wireless link condition and congestion state of the 802.16e network, i.e, CINR and MS queue length. Our simulation results show that the combined use of MS queue length and CINR can be a proper MS-initiated HO decision criterion for VoIP over 802.16e.