The latest mobile devices such as smartphone, laptop, and tablet PC have supported IEEE 802.11 interfaces for broadband wireless data services. To extend the coverage in medium or large-scale areas such as office buildings, airports, campuses, or convention center, multiple access points (APs) need to be deployed. When a mobile station (MS) moves an AP to another, it typically experiences a long delay time for reconnection and communications to an AP due to the four sequential phases such as detection, channel scanning, authentication and reassociation. Consequently, the traditional WLAN is not adequate for mobile multimedia services such as real-time video conferences, augmented reality (AR), virtual reality (VR), etc., especially, in a mobile environment where requires to deploy several APs. This paper proposes a new handoff scheme where the channel scanning is completely omitted by having active MSs hold the channel consistently which is acquired at an initial connection stage to an AP even when it moves to a neighboring AP. Each AP changes its own channel periodically in a predetermined order while providing the orthogonality between the channels of the neighboring APs to mitigate interference. Therefore, seamless mobility can be supported for multimedia services by eliminating link layer handoff in the IEEE 802.11 WLAN. Moreover, any IEEE 802.11-based mobile devices can roam seamlessly without any modification. In other words, the proposed scheme can maintain backward compatibility with the legacy DCF and only requires the modification of APs. By adopting the periodic channel switching scheme, additionally, the proposed scheme can uniformly distribute all the MSs over the entire channels. This distribution can also reduce collision probability by decreasing the number of competing MSs over the same channel. Performance evaluation shows that the proposed scheme can provide low handoff latency and enhance throughput performance due to the decrease of collision probability.
