Aerosol number-to-volume-relationship and relative humidity in the eastern Atlantic

J. Geophys. Res ., 105, 1987-1995.Measurementsa cquiredf rom the Office of Naval Research( ONR) Pelican research aircraftd uringt he secondA erosolC haracterizationE xperiment( ACE 2) are analyzedt o derive valuesf or the dry (RH = 40%) aerosonl umber-to-volumrea tio in the submicrons izer ange. This ratioi s foundto ber elativelyc onstanwt,i tha meanv alueo f 168_ +2 1 gm- 3,i n agreemenwti th previouss tudiese lsewhere.T he impacto f ambientr elativeh umidity (RH) on the dry number-to-volumies alsoq uantifieda nd a procedurefo r estimatingth e dry from the ambientr atio established.F inally, the feasibilityo f a remoter etrievalo f the aerosoln umberc oncentrationin the submicrons izer ange,e ssentiallyth e cloudc ondensation ucleusc oncentrationa ctive at a nominal0 .2% supersaturationis, partially assessed

Stochastically Consistent Caching and Dynamic Duty Cycling for Erratic Sensor Sources

We present a novel dynamic duty cycling scheme to maintain stochastic consistency for caches in sensor networks. To reduce transmissions, base stations often maintain caches for erratically changing sensor sources. Stochastic consistency guarantees the cache-source deviation is within a pre-specified bound with a certain confidence level. We model the erratic sources as Brownian motions, and adaptively {\it predict} the next cache update time based on the model. By piggybacking the next update time in each regular data packet, we can dynamically adjust the relaying nodes' duty cycles so that they are awake before the next update message arrives, and are sleeping otherwise. Through simulations, we show that our approach can achieve very high source-cache fidelity with low power consumption on many real-life sensor data. On average, our approach consumes 4-5 times less power than GAF~\cite{gaf}, and achieves 50\% longer network lifetime

Relative Span weighted localization of uncooperative nodes in wireless networks

Increasingly ubiquitous wireless technologies require novel localization techniques to pinpoint the position of an uncooperative node, whether the target be a malicious device engaging in a security exploit or a low-battery handset in the middle of a critical emergency. Such scenarios necessitate that a radio signal source be localized by other network nodes efficiently, using minimal information. We propose two new algorithms for estimating the position of an uncooperative transmitter, based on the received signal strength (RSS) of a single target message at a set of receivers whose coordinates are known. As an extension to the concept of centroid localization, our mechanisms weigh each receiver's coordinates based on the message's relative RSS at that receiver, with respect to the span of RSS values over all receivers. The weights may decrease from the highest RSS receiver either linearly or exponentially. Our simulation results demonstrate that for all but the most sparsely populated wireless networks, our exponentially weighted mechanism localizes a target node within the regulations stipulated for emergency services location accuracy

Pilot-aided estimation and equalisation of a Radio-over-Fibre system in Wideband Code Division Multiple Access

In this study, the impact of a Radio-over-Fibre (RoF) subsystem on the capacity performance of wideband code division multiple access is evaluated. This study investigates the use of pilot-aided channel estimation to compensate for the optical subsystem non-linearities for different channel conditions, estimation intervals and coding schemes. The results show that pilot-aided channel estimation is an effective method for compensating the composite impairments of the optical subsystem and the radio frequency (RF) channel. It is found that there is always a suitable pilot power level which maximises the system capacity performance regardless of coding scheme and channel condition. Also, the peak capacity is only slightly affected by a decrease in the estimation interval