DUALMAC: 安全無線區域網路中即時通訊之軟換手機制

Abstract

近幾年來，無線區域網路被廣泛地佈建於私人及公眾場合，已成為最重要的無線存取技術之一。然而在無線存取點之間進行切換的換手過程中，將造成通訊的中斷而對即時通訊服務的服務品質產生嚴重的影響，因此有相當多的研究已經著力於減少此換手延遲時間。然而目前現存的解決方案中，大部分的方法都未考慮在安全的無線網路下進行換手或是需要仰賴後端骨幹網路的支援，對於現階段的已佈建好的無線區域網路環境來說，作全面的更新以及升級將會有其難度。 在這篇研究中，我們提供了一個創新的設計，僅需要在使用者端做更新而不仰賴後端網路的方法。我們使用兩個媒體存取控制位址， 以分時雙工的方式同時進行即時通訊服務以及換手的連線步驟。在模擬結果中，在安全控制開啟的無線網路中，使用我們的方法可以在不影響原先即時通訊的原則下，進行無缝式的換手。

WLAN has been widely deployed over public and private areas in recent years and has become one of the most popular access technologies for mobile Internet services. Handoffs between WLAN access points (APs) that introduce packet loss and delay during a network session is one of the critical issues for real-time communication services. Unfortunately, most of the previous studies in reducing handoff latency and packet loss in WLANs rely on WLAN infrastructure upgrades, and those solutions suffer from deployment problems in the well-established WLAN hotspots. In this work, a pure station (STA)-side approach which only requires the firmware or software upgrade on WLAN STAs without the enhancements of the WLAN standards and infrastructures is presented. The proposed mechanism developed from a time division duplex concept maintains both connections with the serving and target AP simultaneously using two different medium access control (MAC) addresses. Thus, an STA can perform WLAN association, authentication, security key handshake procedures with the target AP, or further acquires an IP address in a new subnet while transmitting and receiving real-time packets through the serving AP at the same time. Simulation results demonstrate that seamless handoffs for real-time communications in secured WLANs can be easily achieved by the proposed mechanism.