19.6 Open Issues
Although this chapter presents a survey of analytical models for cellular/WLAN
interworking that have been proposed in the literature, there are several open issues that
need to be addressed and require further investigations. We briefly summarize some of
them:
??? The modeling of traffic. In the case of Internet data traffic, its self-similar and fractal
nature need to be considered. In the case of IP multimedia traffic, its variable
bandwidth requirements need to be addressed for admission control and resource
management. Such considerations further complicate the analytical models.
??? The modeling of QoS in cellular/WLAN. The different approaches to deal with
guaranteed QoS in each network need to be considered. In the cellular network due to
the resource reservation it can be done, but for the WLAN using contention-based
A Survey of Analytical Modeling for Cellular/WLAN Interworking 464
MAC there is no guaranteed QoS. To solve this, modeling of the IEEE 802.11e with
QoS support is required.
??? The modeling of joint network operations. Although for the case in that each
network is operated by a different operator (i.
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