Characterising University WLANs within Eduroam Context

The eduroam initiative is assuming an ever growing relevance in providing a secure, worldwide roaming access within the university WLAN context. Although several studies have focused on educational WLAN traffic characterisation, the increasing variety of devices, mobility scenarios and user applications, motivate assessing the effective use of eduroam in order to sustain consistent network planning and deployment. Based on recent WLAN traffic traces collected at the University of Minho (Portugal) and University of Vigo (Spain), the present work contributes for identifying and characterising patterns of user behaviour regarding, for instance, the location and activity sector of users. The results of data analysis quantify the impact of network access location on the number of associated users, on the number and duration of sessions and corresponding traffic volumes. The results also illustrate to what extent users take advantage of mobility in the WLAN. Complementing the analysis on a monthly basis, a fine grain study of WLAN traffic is provided through the identification of users' behaviour and patterns in small timescales

Multiple preemptive EDCA for emergency medium access control in distributed WLANs

The increasingly use of wireless local area networks (WLANs) in public safety and emergency network services demands for a strict quality of service (QoS) guarantee especially a large number of users report an emergency for immediate channel access. Unfortunately, the traditional IEEE 802.11e-based enhanced distributed channel access (EDCA) does not support a strict QoS guarantee for life saving emergency traffic under high loads. Previous studies have attempted to enhance the performance of EDCA called the Channel Preemtive EDCA (CP-EDCA) which is a promising idea to support emergency traffic in WLANs. However, CP-EDCA supports a single emergency traffic only (i.e. no emergency service differentiation) with high delays for increased traffic loads. To overcome this problem, we propose a class of EDCA protocol called Multiple Preemption EDCA (MPEDCA) as a candidate to support multiple emergency traffics under high loads. Each MP-EDCA node can support up to four emergency traffics (life, health, property and environment) with different priorities in addition to support background (non-emergency) traffic. The proposed protocol privileged the high priority life-saving emergency traffic to preempt the services of low priority ones without much starvation in the network to maintain a strict QoS guarantee. The paper evaluates the performance of MPEDCA through an extensive analysis of simulation outcome. The results obtained show that MP-EDCA outperforms CP-EDCA in achieving lower medium access control and emergency node delays