The relationship between RSSI (Received Signal Strength Indication) values and distance is the foundation and the key of ranging and positioning technologies in wireless sensor networks. Log-normal shadowing model (LNSM), as a more general signal propagation model, can better describe the relationship between the RSSI value and distance, but the parameter of variance in LNSM is depended on experiences without self-adaptability. In this paper, it is found that the variance of RSSI value changes along with distance regu- larly by analyzing a large number of experimental data. Based on the result of analysis, we proposed the relationship function of the variance of RSSI and distance, and established the log-normal shadowing model with dynamic variance (LNSM-DV). At the same time, the method of least squares(LS) was selected to es- timate the coefficients in that model, thus LNSM-DV might be adjusted dynamically according to the change of environment and be self-adaptable. The experimental results show that LNSM-DV can further reduce er- ror, and have strong self-adaptability to various environments compared with the LNSM
The focus of the paper is on the analysis of performance effects of different security solutions modeled as aspects in UML. Aspect oriented modeling (AOM) allows software designers to isolate and separately address solutions for crosscutting concerns, which are defined as distinct UML aspect models, then are composed with the primary UML model of the system under development. For performance analysis we use techniques developed previously in the PUMA project, which take as input UML models annotated with the standard UML Profile for Schedulability, Performance and Time (SPT), and transform them first into Core Scenario Model (CSM) and then into different performance models. The contribution of this paper is in performing the composition of the aspects with the primary model at the CSM level. The input is represented by the primary model and a number of aspect models in UML+SPT, which are processed as follows: a) converted separately to CSM; b) composed into a single CSM model; c) transformed into a Layered Queueing Networks (LQN) model and d) analyzed. The proposed approach is illustrated with a case study based on two standards, TPC-W and SSL.
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