1,721,047 research outputs found
Nulls preallocation in distributed DRA for multicell SDMA packet access networks
No full textThis 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
No full textWe 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
Distributed slot allocation with centralized power control and beamforming for multicell packet access networks with smart antennas
No full textThis 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
Allocation and Adaptation Techniques for Protocol Performance Improvement in Multicellular Wireless Packet Networks with MIMO links
No full textWith the aim of optimizing the performance of a data protocol, we investigate the effects and the role played by distributed resource allocation and rate/power adaptation in a wireless SDMA/TDMA network where multiple antenna elements are used at both transmitter and receiver side, and perfect channel state information (CSI) is available at the receiver only. We consider the uplink of a multiple cell system, throughput-driven allocation and adaptation algorithms, and address the issues related to the management of intercell interference. We find that the capacity of the network is heavily affected by the presence of interference and it is important to exploit a part of the receiving antennas to mitigate strong interference and to have an estimation of the interference covariance matrix to tune allocation and adaptation algorithms. The results show that the joint use of distributed best-fit allocation algorithms with adaptive antenna selection allow substantial improvement with respect to the basic case of random access. Moreover, simple stream control strategies prevent capacity degradation when the offered load exceeds the maximum capacity
Downlink scheduling with adaptive antennas in multicell SDMA packet access networks
No full textThis paper investigates the performance of scheduling on a SDMA multicellular packet access systems. Scheduling with spatial division multiple access (SDMA) has been considered on the uplink of a single cell with an ad-hoc scheduling algorithm [Hujun Yin et al., 2002]. Here we consider the downlink of a multicell network and we first apply wireless fair queuing scheduling to SDMA, in the new multicellular environment. We consider the issues related to beamforming, intercell interference and fairness among users. We take into account heterogeneous traffic classes with different QoS requirements and we show that the proposed scheme is feasible in the new multicellular SDMA environment. It increases system capacity for delay sensitive users and achieve better per user QoS performance with respect to the known earliest due date (EDD) strategy and the baseline case of first-come first-served (FCFS), in the same environmen
Power Shaped Advanced Resource Assignment (PSARA) for Fixed Broadband Wireless Access
No full textWe propose and investigate a new resource allocation technique for the downlink of time-division multiple access (TDMA)-based fixed broadband wireless access systems (FBWA) with full frequency reuse. This technique, named power-shaped advanced resource assignment exploits an appropriate set of power profiles which limit (or shape) the power transmitted in each slot of the frame and are suitably reused among the cells, in order to efficiently distribute the intercell and intersector interference inside the frame and to make it partially predictable. In systems where base stations assign radio resources in an uncoordinated fashion, this allows the allocation algorithm to assign time slots to users on the basis of the power required to fulfill a predefined carrier-to-interference ratio, since worst case interference can be suitably estimated; moreover, different degrees of protection against interference are provided across the slots to efficiently accommodate users with different location-dependent channel conditions. Simulation results for a typical cellular FBWA system show that this technique significantly improves the capacity with respect to other techniques recently proposed, e.g., the enhanced staggered resource assignment, even when they use power control. Moreover, an analytical framework useful to understand the concept of power shaping and to discuss some guidelines for the design of power profiles is provided
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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