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Introduction

Tripleplay-Data, voice and video services over an integrated or converged network is much talked about these days. However, most existing networks have been designed with data applications in mind. Data applications are non-real time. It makes a little difference to the user if the data is minimally delayed, or is received with varying latencies, or was dropped due to congestion or corruption. A frame which has been dropped can be retransmitted later. Similarly, the wireless LAN MAC protocol defined in the standard IEEE 802.11 was designed for data networks. The basic access mechanism remained the same in the 802.11 a/b/g protocol, which is also referred to as the legacy 802.11 protocol.

Networks designed for non-real time traffic, like data, are today being used to support real-time applications like VOIP (or VoWLAN) and streaming video, which are inherently different from data traffic. Real-time applications have every different requirement, as delayed frames are as good as dropped frames for real-time traffic. Jitter is another important parameter, since it indicates the variation in the delay and requires buffering to smooth the jitter. Finally, throughput or bandwidth requirements have to be kept in mind; unlike data which can use the available bandwidth at any instant, real-time applications require guaranteed and periodic bandwidth. The legacy 802.11 protocol was enhanced with various Quality of Service (QoS) mechanisms to serve the requirements of real-time traffic like voice and video.

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