The application of decay rate analysis for WSN buffer dimensioning

The provisioning of a Quality of Service (QoS) for applications requiring real-time service demands low latency, low Bit Error Rate (BER) and bounded end to end delay guarantees. Facilitating this within a Wireless Sensor Network (WSN) is Guaranteed Time slots (GTS´s) activated using a beacon enabled mode and under the governance of the accepted protocol of the IEEE 802.15.4 standard. However the limitation in design of only seven GTS per superframe duration pre-determines a problem of allocation when requirements by applications in need of good QoS exceed the supply of GTS´s. This results in the QoS aware traffic requiring differentiation of service in the buffer of the Personal Area Network Coordinator (PANC). A question arises as to the true ability of service dimensioning of networks without the prior knowledge of buffer allocation. In some WSN the buffer shares memory with the application and radio stack. This memory requirement will vary depending on the application. This research complements a previous paper in which the application of Decay Rate Analysis in relation to the dimensioning of buffer allocation of the various nodes was analysed using simulation and analytical methodology. The results illustrated the probability of queue occupancy for a specific application namely VoIP. This paper proposes that by employing the decay rate analysis a better understanding of buffer requirements at the PANC can be determined for different sensor applications. This analysis will further enhance the pre-deployment dimensioning of a network for greater operational efficiency and overall cost effectiveness.