Decentralized control mechanism suppressing delay fluctuation in wireless LANs

Real-time applications, such as phone, videoconference, multimedia streaming, typically require relatively small delay and small delay fluctuation. To meet the QoS requirements of these applications, network infrastructures should have the ability to accommodate real-time traffic. IEEE 802.11 wireless LANs, fundamentally based on CSMA/CA, have been widely used as parts of network infrastructures, so QoS support in wireless LANs becomes important. Several existing centralized control mechanisms can support constant small real-time traffic delays in a wireless LAN. However, they require a centralized controlled coordinator, and cannot be utilized in all cases. So, a decentralized control mechanism supporting real-time traffic is an important alternative solution. EDCF (enhanced distributed coordination function) is a typical decentralized control mechanism. It provides relatively small real-time traffic delay, but cannot achieve small delay fluctuation. We propose a decentralized control mechanism suppressing delay fluctuation in CSMA/CA networks, called DDFC (decentralized delay fluctuation control), and examine the performance of DDFC by simulation. The simulation results confirm that we can achieve not only small delay but also small delay fluctuation in EDCF-based wireless LANs by controlling real-time traffic according to DDFC.