The MAC Project

Experimental details



Mobility & Peer Estimator is the MAC component which interacts with underlying network interfaces to gather nearby connector set and corresponding RSSIs, applies DFT to RSSI sequences, provides CMob and joint. At the current stage MPE interacts only with IEEE 802.11 devices and provides only CMob. We are currently evolving MPE to provide even IEEE 802.11 ad-hoc peer Joint estimation and to interact even with Bluetooth devices. Connector Evaluator and Connector Selector will be available afterwards. About gathering IEEE 802.11 raw RSSI data, due to the relative novelty and high heterogeneity of wireless technologies, there is currently no standard specification, widely accepted by vendors and available in most common operating systems, of an application-level API to achieve full RSSI visibility. For this reason, we have developed our own portable 80211NetworkInterface component which includes different implementations of RSSI monitoring mechanisms, which are automatically selected depending on the specific characteristics of served client devices. To achieve maximum portability, MobilityEstimator exploits 80211NetworkInterface component. In particular, it provides an original and operating-system-transparent Java API to obtain the list of all APs in current visibility and their related RSSI information. For Linux clients, it gathers those monitoring data via the standardized API provided by the Linux Wireless Extensions. For Windows CE/.NET clients, instead, it transparently binds the same Java API to the monitoring functionality provided by the Microsoft Network Driver Interface Specification User-mode I/O (NDISUIO), which is platform-dependent but portable among different wireless interface implementations. For instance, it exploits the NDISUIO function DeviceIOControl() to query the OID_802_11_BSSID_LIST_SCAN object to retrieve the complete list of currently reachable IEEE 802.11 APs. Moreover, 80211NetworkInterface component is able to interact with our original IEEE 802.11 simulator to make possible, mainly for experimental purposes, the exploitation of MobilityEstimator even if it is not available any actual IEEE 802.11 environment. Mobility and Peer Estimator The following applet provides the capability to actually test our MPE prototype in a simulated environment. The simulated context is depicted by 17 Access Points distributed in an hexagonal manner in a 168x124 meters rectangle area and the mobile node has a Waypoint trajectory with a random thinking pause in the [0, 20] seconds range (so, wait a while after a simulation starts for mobile node movements). In the simple simulated example below the RSSI is not affected by noise. CMob is set to 0 when the first harmonic module is <= 0.1, to 1 when the module is >= 0.45, to a linearly dependent intermediate value otherwise. (note CMob = -1 and State = NotAvailable whenever MPE has not sufficient values to compute the DFT) We have experimentally validated how CMob and Joint depend on RSSI variability and the values used in MAC are the result of these experimental evaluations. At the current stage, For instance, our experiments in IEEE 802.11 test-bed environments suggest us to set CMob to 0 when the first harmonic module is <= 1.3, to 1 when the module is >= 2.3, to a linearly dependent intermediate value otherwise. In the future we want to validate our MPE prototype in wireless scenarios with different AP distributions, different area dimensions, great signal noise. The main objective is to achieve upper and lower bounds for the Still/Motion states, checling their validity in several heterogeneous wireless scenarios. Novel information will be published as soon as possible.

9-nov-09