Amer Catovic

The Cramer-Rao bounds of hybrid TOA/RSS and TDOA/RSS location estimation schemes

The Cramer-Rao bound (CRB) on location estimation accuracy of two different hybrid schemes, time of arrival/received signal strength (TOA/RSS) and time difference of arrival/received signal strength (TDOA/RSS), is computed. For short-range networks, the hybrid schemes offer improved accuracy with respect to conventional TOA and TDOA schemes, particularly in the proximity of the reference devices.

A hybrid location estimation scheme (H-LES) for partially synchronized wireless sensor networks

Heterogeneity is the key distinguishing characteristic of wireless sensor networks (WSN) as compared to wireless cellular networks (WCN). It may appear in the form of communication ranges of sensor devices, synchronization, and signal processing capabilities. In this article, we develop a hybrid location estimation scheme for heterogeneous WSN with unsynchronized short-range simple relays and mobile sensors nodes, and synchronized stations. Our scheme employs combination of time difference of arrival (TDOA) and received signal strength (RSS) measurements, whereby the TDOA is used to filter out the clock offset that appears due to the lack of synchronization. We quantify the estimation accuracy of the scheme by deriving the Cramer-Rao bound (CRB), and discuss the performance trade-off between the number of synchronized and non-synchronized devices involved.

Power efficiency of user cooperation in multihop wireless networks

In this paper we analyze the power efficiency of a user cooperation scheme for multihop wireless networks. In this scheme, the signals are jointly transmitted by two mobile terminals (MTs), emulating transmit macro diversity. We derive the optimal transmit power assignments for the two transmitting MTs and quantify the power efficiency of the scheme. The results indicate that macro diversity by way of user cooperation can substantially reduce the total consumed power in multihop wireless networks for wide range of topologies of MTs and their distances.

Impact of SIB Scheduling on the Standby Battery Life of Mobile Devices in UMTS

The UMTS standard for third generation wireless communications specifies several parameters that play a role in the tradeoff between the performance and the battery life of mobile devices. There are also other, non-standardized, implementation-specific mechanisms that affect both the performance as well as the battery life. In this paper, we focus on the scheduling of system information blocks (SIB) broadcasts on the network side and the inter-SIB sleep management on the mobile device side. We analyze the impact of these mechanisms on the standby battery life of mobile devices in three commercial networks.