Epicentral confidence regions of nuclear test events at teleseismic distances

The accurate location of seismic events is a basic discriminant for underground nuclear test monitoring (Bolt, 1976; Dahlman and Israelson, 1977; Blandford, 1982). Of particular interest are determining epicentral confidence regions and providing constraints on estimated focal depths. In this study, only routine teleseismic P travel-time data are used, as provided by worldwide stations reporting to the International Seismological Centre (ISC). This lessens the need to model the effects of crustal and shallow-mantle velocity variations, as is necessary with seismographic networks operating at regional distances (Blandford, 1981; Evernden et al., 1986)

Venus Interior Structure Mission (VISM): Establishing a Seismic Network on Venus

Magellan radar data show the surface of Venus to contain a wide range of geologic features (large volcanoes, extensive rift valleys, etc.). Although networks of interconnecting zones of deformation are identified, a system of spreading ridges and subduction zones like those that dominate the tectonic style of the Earth do not appear to be present. In addition, the absence of a mantle low-viscosity zone suggests a strong link between mantle dynamics and the surface. As a natural follow-on to the Magellan mission, establishing a network of seismometers on Venus will provide detailed quantitative information on the large scale interior structure of the planet. When analyzed in conjunction with image, gravity, and topography information, these data will aid in constraining mechanisms that drive surface deformation

Distributed slot allocation with centralized power control and beamforming for multicell packet access networks with smart antennas

This paper addresses dynamic resource allocation (DRA) with power control for the downlink of a Spatial Division Multiple Access (SDMA) broadband multicellular wireless packet network with adaptive antennas. The main issue for distributed DRA is how to manage the intercell interference, which is very difficult to handle in an uncoordinated environment, due to packet access and downlink beamforming. The issue of efficiently performing DRA and power control in such environment is still open. In this paper we propose to do the slot allocation distributedly with a rough estimate of the intercell interference, and the power control and beamforming in a centralized manner, after the allocation. This keep the computational effort low with respect to a completely centralized allocation algorithm. We show that the gap between a distributed algorithm with uncoordinated power control and a totally centralized allocation algorithm can be significantly reduced

Nulls preallocation in distributed DRA for multicell SDMA packet access networks

This paper proposes a novel distributed dynamic resource allocation (DRA) algorithm for the downlink of a SDMA broadband wireless packet network with multiple access ports and adaptive antennas. With the new scheme, each access port (AP) independently preallocates some beamforming s toward the most interfered users of the neighbor APs and broadcasts this information to the other APs. Then all APs independently and distributedly perform the allocation of their users using the distributed max-min fit (DMMF) scheme. Simulation results show a significant improvement over the DMMF without s preallocation and a significantly reduced gap between the DMMF and the centralized max-min fit (CMMF) algorithm, which performs the allocation by fully coordinating all the access ports. As a baseline case, the performance of a random slot allocation algorithm is also reported

SIR-Dependent Scheduling and Static Power Preallocation for TDMA-Based Multi-Cell Wireless Packet Network

We introduce here a new class of packet scheduling techniques for TDMA-based (pure or hybrid) cellular packet radio networks with full frequency reuse. These algorithms, which are suited for networks with both centralized and distributed control, assign the available resources according to the SIR predicted at each slot of the frame. Partial prediction of the interference is made possible by the static pre-assignment in each cell of a maximum transmitted power level to each slot of the frame. This technique, also named power shaping, exploits a set of suitably reused power profiles to partially organize the intercell and intersector interference in the available slots. Unlike traditional channel state dependent scheduling techniques, which are not able to deal with quasi-stationary location-dependent radio channel conditions, the proposed method is able to provide channel resources with different levels of SIR inside the frame, even in stationary environments, and to assign them to the packets waiting for service. We show that these techniques are able to increase the capacity of systems with and without centralized resource management control, while maintaining the capability of providing acceptable quality of service to heterogeneous classes of users

Performance Characterization of Digital Transmission Systems with Cochannel Interference

none2This paper presents a general methodology for performance characterization of digital transmission systems in the presence of cochannel interference, as a function of the actual number of interferers (ranging from zero to infinity). The bit error probability in time-invariant channels and outage probability in time-varying quasi-stationary channels are discussed. More precisely, a general approach to an outage probability definition based on the concept of the outage domain is introduced. This allows the discussion of the relation to the other definitions which have appeared in the literature and the proposal of some new more accurate methods for the evaluation of outage probability. A suitable comparison between exact evaluation, the well-known Gaussian approximation, and the other new approaches proposed in this paper, is carried out to evaluate performance, bit error probability is suitably obtained for linearly modulated signals by adopting a semianalytical approach, and for nonlinear (e.g., continuous phase) modulation signals, by means of simulation. Finally, as an example, the different approaches to derive performance discussed in the paper have been applied to a linear microcellular scenariononeTRALLI V.; VERDONE R.Tralli, Velio; Verdone, R

Bit error and outage probability for digital cellular systems with a small number of interferers

This paper proposes a semi-analytical approach to characterise the performance of digital cellular systems when cochannel interference is determined by a small number of interferers. Linearly modulated signals (such as BPSK, QPSK, M-ASK, M-QAM, MSK, O-QPSK, etc.) with linear receivers are investigated by considering the probability density function of the interference at the input of the decision device. Non-linear (Continuous Phase) modulation signals (such as GMSK) and non coherent detection are also investigated by means of simulation. As a consequence, a general approach to outage probability definition considering the protection ratio as a function of the interferers number and useful signal-to-noise ratio is introduced

DCA with power-shaping (PS-DCA) in TDMA and TD/CDMA cellular systems with centralized and distributed control

In this paper we investigate a new dynamic resource allocation technique for TDMA and TD/CDMA cellular radio systems with full frequency reuse. Unlike traditional allocation strategies, that first allocate the time slots and then perform power control, the proposed technique first assigns in advance (static allocation) a maximum power level to each channel and then dynamically performs channel allocation and fine power control. This is done by exploiting a set of suitably reused power profiles that partially organize the intercell and intersector interference in the available slots and make it partially predictable. We show that this technique, originally proposed by the Authors for fixed broadband wireless access systems, where interference is mitigated by the use of highly directional antennas, is able to increase the capacity of systems with and without centralized or partially centralized resource management control. Moreover, it is also able to fill the efficiency gap between centralized and not centralized strategies. In our investigation a greedy algorithm for resource allocation suitable for both centralized and not centralized management is also proposed