A Seamless Handoff With Multiple Radios in IEEE 802.11 WLANs

It is obvious that a seamless handoff should be pursued for better service. For this reason, we design a novel and feasible 802.11 handoff scheme for 802.11 wireless local area networks (WLANs). In the proposed handoff scheme, the 802.11 access points (APs) have multiple radios. One of the multiple radios is exclusively reserved for scanning purposes. It certainly helps the 802.11 mobile stations (STAs) to easily search neighboring APs. Moreover, the reserved exclusive channel is available for data frame exchanges. Consequently, STAs can be serviced with minimized data frame losses while they are performing the proposed handoff. For practical observations, we implement the proposed handoff scheme. Then, we evaluate handoff performances by comparing the packet losses between the proposed handoff scheme and the existing handoff schemes. Based on the evaluation, we have built analytical models to estimate overall packet losses while an STA moves from an AP to another AP in an indoor environment. The analytical results show that the proposed handoff significantly reduces packet losses compared with existing 802.11 handoff schemes.