排序方式: 共有14条查询结果,搜索用时 15 毫秒
1.
Antenna downtilting is often mentioned in the literature as a powerful method for improving network performance in cellular systems. The antenna elevation angle on a number of GSM EDGE radio access network (GERAN) cells has been modified to quantify the impact of this method in a real network. In addition, a novel approach to prioritizing the cells to be tilted, which uses network statistics only, has been tested. Trial results indicate that downtilting can improve certain performance aspects, especially those related to signal quality, but not all of them on every cell. 相似文献
2.
Analysis of Heuristic Graph Partitioning Methods for the Assignment of Packet Control Units in GERAN
Matías Toril Iñigo Molina-Fernández Volker Wille Chris Walshaw 《Wireless Personal Communications》2011,60(4):611-633
Over the last few years, graph partitioning has been recognized as a suitable technique for optimizing cellular network structure.
For example, in a recent paper, the authors proposed a classical graph partitioning algorithm to optimize the assignment of
cells to Packet Control Units (PCUs) in GSM-EDGE Radio Access Network. Based on this approach, the quality of packet data
services in a live environment was increased by reducing the number of cell re-selections between different PCUs. To learn
more about the potential of graph partitioning in cellular networks, in this paper, a more sophisticated, yet computationally
efficient, partitioning algorithm is proposed for the same problem. The new method combines multi-level refinement and adaptive
multi-start techniques with algorithms to ensure the connectivity between cells under the same PCU. Performance assessment
is based on an extensive set of graphs constructed with data taken from a live network. During the tests, the new method is
compared with classical graph partitioning approaches. Results show that the proposed method outperforms classical approaches
in terms of solution quality at the expense of a slight increase in computing time, while providing solutions that are easier
to check by the network operator. 相似文献
3.
Fredrik B. Brekke Bård Waldum Amin Amro Tone B. H. Østhus Toril Dammen Helga Gudmundsdottir Ingrid Os 《Hemodialysis international. International Symposium on Home Hemodialysis》2014,18(1):87-94
Sleep complaints are prevalent and associated with poor health‐related quality of life (HRQoL), depression and possibly mortality in dialysis patients. This study aimed to explore possible associations between sleep quality, daytime sleepiness and mortality in dialysis patients. In this study, 301 dialysis patients were followed up to 4.3 years. HRQoL was evaluated at baseline with the Kidney Disease and Quality of Life—Short Form (KDQoL‐SF), depression with Beck Depression Inventory (BDI), sleep quality with Pittsburgh Sleep Quality Index and daytime sleepiness with Epworth Sleepiness Scale. The single item “on a scale from 0–10, how would you evaluate your sleep?” in the sleep subscale in KDQoL‐SF was used to identify poor (0–5) and good sleepers (6–10). A total of 160 patients (53.3%) were characterized as poor sleepers. They were younger (r = 0.241, P < 0.001), had more depression (BDI: 8.72 ± 6.79 vs. 13.60 ± 8.04, P < 0.001), a higher consumption of hypnotics and antidepressants and reduced HRQoL (Mental Component Summary score: 45.4 ± 11.0 vs. 50.0 ± 10.4, P < 0.001. Physical Component Summary score: 35.0 ± 9.9 vs. 38.5 ± 10.5, P = 0.004). In multivariate analyses, poor sleepers had nearly a twofold increase in mortality risk (hazard ratio [HR] 1.92, confidence interval [CI] 1.10‐3.35, P = 0.022). Daytime sleepiness was not related to mortality (HR 1.01, CI 0.95‐1.08, P = 0.751). Sleep complaints predicted increased mortality risk in dialysis patients and should therefore be routinely assessed. Further studies are needed to find suitable treatment options for poor sleep in dialysis patients as it may affect both HRQoL and survival. 相似文献
4.
Optimization of Handover Parameters for Traffic Sharing in GERAN 总被引:1,自引:1,他引:0
Cellular network traffic is unevenly distributed both in time and space, which greatly complicates network dimensioning. As
a result, some cells in the network are permanently congested, while others are underutilized. In a previous paper, the authors
showed that this problem can be effectively solved in GSM/EDGE Radio Access Networks (GERAN) by modifying handover boundaries.
However, several drawbacks prevent operators from fully exploiting the potential of this technique. This paper investigates
the limitations of current traffic-sharing approaches with tight frequency reuses in GERAN. To deal with such limitations,
an algorithm is proposed to jointly optimize handover margins and signal-level constraints based on network statistics for
traffic sharing in GERAN. A complementary algorithm is proposed to adjust cell (re)selection offsets to minimize the number
of handovers. Simulation results show that the proposed method achieves a significant reduction in call blocking without excessive
call quality impairment or increase of network signaling load when compared to the current approaches. More traffic can thus
be handled without the need for any hardware upgrades, providing a cost-effective means to increase network capacity.
相似文献
Volker WilleEmail: |
5.
Why Are “Others” So Polarized? Perceived Political Polarization and Media Use in 10 Countries 下载免费PDF全文
JungHwan Yang Hernando Rojas Magdalena Wojcieszak Toril Aalberg Sharon Coen James Curran Kaori Hayashi Shanto Iyengar Paul K. Jones Gianpietro Mazzoleni Stylianos Papathanassopoulos June Woong Rhee David Rowe Stuart Soroka Rodney Tiffen 《Journal of Computer-Mediated Communication》2016,21(5):349-367
This study tests the associations between news media use and perceived political polarization, conceptualized as citizens' beliefs about partisan divides among major political parties. Relying on representative surveys in Canada, Colombia, Greece, India, Italy, Japan, South Korea, Norway, the United Kingdom, and the United States, we test whether perceived polarization is related to the use of television news, newspaper, radio news, and online news media. Data show that online news consumption is systematically and consistently related to perceived polarization, but not to attitude polarization, understood as individual attitude extremity. In contrast, the relationships between traditional media use and perceived and attitude polarization is mostly country dependent. An explanation of these findings based on exemplification is proposed and tested in an experimental design. 相似文献
6.
Toxic effects of aluminium (Al) on Picea abies (L.) Karst. (Norway spruce) trees are well documented in laboratory-scale experiments, but field-based evidence is scarce. This paper presents results on fine root growth and chemistry from a field manipulation experiment in a P. abies stand that was 45 years old when the experiment started in 1996. Different amounts of dissolved aluminium were added as AlCl3 by means of periodic irrigation during the growing season in the period 1997-2002. Potentially toxic concentrations of Al in the soil solution were obtained. Fine roots were studied from direct cores (1996) and sequential root ingrowth cores (1999, 2001, 2002) in the mineral soil (0-40 cm). We tested two hypotheses: (1) elevated concentration of Al in the root zone leads to significant changes in root biomass, partitioning into fine, coarse, living or dead fractions, and distribution with depth; (2) elevated Al concentration leads to a noticeable uptake of Al and reduced uptake of Ca and Mg; this results in Ca and Mg depletion in roots. Hypothesis 1 was only marginally supported, as just a few significant treatment effects on biomass were found. Hypothesis 2 was supported in part; Al addition led to increased root concentrations of Al in 1999 and 2002 and reduced Mg/Al in 1999. Comparison of roots from subsequent root samplings showed a decrease in Al and S over time. The results illustrated that 7 years of elevated Al(tot) concentrations in the soil solution up to 200 microM are not likely to affect root growth. We also discuss possible improvements of the experimental approach. 相似文献
7.
Salvador Luna-Ramírez Matías Toril Volker Wille 《Wireless Personal Communications》2011,60(2):215-235
GERAN (GSM-EDGE Radio Access Network) operators have traditionally used the Erlang B formula to estimate the number of signalling
channels on a per-cell basis. Thus, it is assumed that the network behaves as a loss system with Poisson arrivals. However,
the presence of automatic retrial mechanisms and correlated arrivals in these channels suggests that these assumptions might
not be valid. This paper presents a performance analysis of the Stand-alone Dedicated Control CHannel in GERAN. Preliminary analysis shows that the Erlang B formula underestimates congestion and blocking on this channel. To
address this issue, a queueing model with retrials and correlated arrivals is proposed, where correlation between arrivals
is modelled by a simple Markov-Modulated Poisson Process. The proposed model can be tuned on a per-cell basis by statistics
in the Network Management System. Model assessment is based on performance statistics from a live GERAN system. Results show
that a simple retrial queueing model fails to explain blocking in cells with a large number of channels. These limitations
are overcome by adding correlated arrivals in the retrial model. 相似文献
8.
Acedo-Hernández R. Toril M. Luna-Ramírez S. Fernández-Segovia J. A. Úbeda C. 《Wireless Personal Communications》2018,98(1):629-649
Wireless Personal Communications - In Long Term Evolution (LTE) systems, the physical cell identity (PCI) assigned to a cell during network planning determines the set of sequences used by... 相似文献
9.
In GSM/EDGE Radio Access Networks (GERAN), the number of neighbor cells defined per cell for handover purposes is limited.
Due to the large number of cells and, consequently, neighbor cells in the system, neighbor cell management proves a complex
and time-consuming process during network operation. Hence, it is very likely that, on some cells, important neighbor cells
are missing. This paper outlines a new approach for determining these missing neighbors, based only on information from the
network management system. Thus, the need for propagation data from network planning tools is circumvented, which makes the
method especially suitable for the operational stage of an existing network. Results from the application of the method in
a live network show its capability to spot such missing neighbors. Although performance benefits from the method are rather
limited for the entire network, significant benefits can be obtained on individual cells. 相似文献
10.
Self-management is essential for Beyond 3G (B3G) systems, where the existence of multiple access technologies (GSM, GPRS,
UMTS, WLAN, etc.) will complicate network operation. Diagnosis, that is, fault identification, is the most difficult task
in automatic fault management. This paper presents a probabilistic system for auto-diagnosis in the radio access part of wireless
networks, which comprises a model and a method. The parameters of the model are thresholds for the discretization of Key Performance
Indicators (KPIs) and probabilities. In this paper, some techniques are proposed for the automatic learning of those model
parameters. In order to support the theoretical concepts, experimental results are examined, based on data from a live network.
It has been proven that calculating parameters from network statistics, instead of being defined by diagnosis experts, highly
increases the performance of the diagnosis system. In addition, the proposed techniques enhance the results obtained with
continuous diagnosis models previously exposed in the literature. 相似文献