## 2 Related Work
Admission control is a crucial element of the PBNM-based management infrastructure as it provides the means to maintain QoS of the flows already present within the network. Several admission control schemes that have been previously studied are mainly classified as either _parameter-based_ or _measurement-based_[17, 18, 19]. While parameter-based approaches may be easier to implement as they are based on estimates of parameters such as peak rate or effective bandwidth usage in the admission request of a new flow rather than actual network measurements, measurement-based approaches provide better network utilization in the presence of bursty traffic patterns as shown in [17]. In [19], the authors focus on evaluating the effectiveness of measurement-based admission control in 3G and 4G wireless networks, where the results of their study highlight the benefits of measurement-based admission control within wireless IP networks. Earlier work [20], proposes a time-window based measurement based admission control scheme for dynamic call admission control in ATM networks using marginal distributions of cell arrivals for aggregate bandwidth estimates. Similarly, [21, 22, 23], have also considered time-window based measurement approaches while [24] offered an implementation-based comparison of various estimators employed in measurement-based admission control schemes and [25] focused on measurement-based scheme with aggregate traffic envelopes. The authors of [26] proposed and evaluated an online measurement-based admission control scheme applied to variable bit-rate video where effective bandwidth is estimated using statistical parameters of the aggregate video traffic. The aforementioned previous works have proposed several effective measurement based methods for admission control in single-class scenarios, but further studies are required to investigate their applicability, scalability and performance to multi-class scenarios in order to support tiered services. Also, given the requirement to rapidly deploy and support dynamic heterogeneous services within today's converging networks, practical PBNM systems should have scalable, extensible and cost-effective multi-class admission control solutions. Hence, in this paper, we considered a fuzzy logic based approach as it provides highly efficient control without requiring crisp measurements which must be available for traditional measurement-based approaches. Not only are monitoring overhead requirements for PBNM systems reduced with a fuzzy-based approach, but also the admission control process is better able to cope with imprecise or incomplete data compared to traditional measurement-based methods. Furthermore, a fuzzy-based approach is more flexible and easily extensible with multiple classes and therefore well suited to tiered services management than traditional measurement-based approaches. Fuzzy logic has also been previously applied to admission control problems in wireless/cellular networks [27, 28, 29, 30, 31, 32]. For instance, in [27], [PERSON], [PERSON] and [PERSON] applied fuzzy logic to adaptive call admission control and bandwidth reservation to alleviate forced termination probability of multimedia handoffs in cellular systems. The authors showed the feasibility of their approach by means of computer simulations which indicated that bandwidth reservation using fuzzy logic system tuned by Particle Swarm Optimization has the potential to improve the admission of new calls whilst reducing forced termination of ongoing calls during handoff. Other papers such as [33, 34] focus mainly on employing fuzzy logic for alleviating wireless/mobile network handoff problems. Although fuzzy logic is becoming more popular for alleviating network resource management problems, to the best of our knowledge we are not aware of existing work in the literature that have experimentally studied its application in a real implementation of a PBNM system.