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1.
This paper presents a novel methodology for capturing the coupling between the different cells in both the uplink and downlink
directions in a Wideband Code Division Multiple Access (WCDMA) scenario. It is based on the definition and computation of
the gradient of the uplink cell load factor and the downlink transmitted power, which are the two main parameters that reflect
the actual cell load in the two link directions. The paper shows that the gradient is able to capture the relevant information
about the spatial distribution of traffic, which has an impact on cell performance. The proposed methodology is also used
as the basis for defining and evaluating new Radio Resource Management (RRM) strategies that operate at a multi-cell level.
相似文献
Ramon AgustíEmail: |
2.
Saralees Nadarajah 《Wireless Personal Communications》2009,49(4):575-585
The quantization error for MIMO (multiple-input multiple-output) downlink channels is known to be the minimum of independent
and identically distributed beta random variables. In this note, an exact expression is derived for the average quantization
error. Computational issues relating to its correctness, usage and approximations are discussed.
相似文献
Saralees NadarajahEmail: |
3.
In this article, we study an asynchronous optical packet switch equipped with a number of wavelength converters shared per
node. The wavelength converters can be full range or circular-type limited range. We use the algorithmic methods devised for
Markov chains of block-tridiagonal type in addition to fixed-point iterations to approximately solve this relatively complex
system. In our approach, we also take into account the finite number of fiber interfaces using the Engset traffic model rather
than the usual Poisson traffic modeling. The proposed analytical method provides an accurate approximation for full range
systems for relatively large number of interfaces and for circular-type limited range wavelength conversion systems for which
the tuning range is relatively narrow.
相似文献
Carla RaffaelliEmail: |
4.
In this paper, we propose a new differentiated service model, referred to as Differentiated Service-EDCA (DS-EDCA), for the
Enhanced Distributed Channel Access (EDCA) of IEEE 802.11e wireless local area networks (WLANs). With DS-EDCA, both strict
priority and weighted fair service can be provided. The strict priority service is provided for high priority traffic through
carefully setting the EDCA parameter sets of lower priority traffic; the proportional fairness service is enabled by determining
the backoff intervals according to the distributed scheduling discipline (DFS). We also propose a hierarchical link sharing
model for IEEE 802.11e WLANs, in which AP and mobile stations are allocated different amounts of link resource. The performance
of DS-EDCA and EDCA is compared via ns-2 simulations. The results show that DS-EDCA outperforms the original EDCA in terms
of its support for both strict priority and weighted fair service. More importantly, DS-EDCA can be easily implemented, and
is compatible to the IEEE 802.11 Standard.
相似文献
Meng Chang ChenEmail: |
5.
Ashraf S. Hasan Mahmoud 《Wireless Personal Communications》2008,46(4):413-427
The optimal utilization of network resources and the capacity to fulfill quality of service requirements are key requirements
for 3rd G networks operations. Several burst admission and transmission rate scheduling algorithms are proposed in the literature.
In this study, we develop an analytical framework for the downlink transmission rate scheduling problem for CDMA networks
employing discrete service bit rates. The framework uses the average downlink transmit power as the system state and develops
a K-dimensional Markov chain representing all possible states in the system. In addition, the transition probabilities due to
arrivals of burst requests are made a function of the power utilization and the average power required to support the new
burst taking into account the path loss model. The study assumes a transmission rate assignment scheme where the maximum possible
system bit rate is assigned given the current system state and the subscriber’s eligibility profile for particular system
service rates. The analytical model provides performance metrics such as system throughput, average power utilization, average
number of simultaneous transmissions, burst request blocking probability, and mean burst service time. While the developed
model is applicable for a general CDMA based network with arbitrary discrete system service bit rates, the model is evaluated
for the example of a cdma2000 1xRTT network. A comparison between simulation and analytic results to assess the accuracy of
the model is provided.
相似文献
Ashraf S. Hasan MahmoudEmail: |
6.
This paper describes a framework for fixed- length frame scheduling in all-photonic networks with large propagation delays.
We introduce the Fair Matching Algorithm a novel scheduling approach that results in weighted max-min fair allocation of extra
slots, achieves zero rejection for admissible demands, and minimizes the maximum percentage rejection of any connection. We
also propose the Minimum Rejection Algorithm, which minimizes total rejection but treats non-critical connections in a fair
manner. Finally, we introduce a feedback control system based on Smith’s principle that reduces the effect of prediction errors
and increases the speed of the response to the sudden changes in traffic arrival rates. Simulations performed using OPNET
Modeler explore the performance of the scheduling and control algorithms we propose.
相似文献
M. J. CoatesEmail: |
7.
Providing differentiated services in IP/MPLS over WDM networks has attracted a lot of recent attention. This article extends
the Path Inflation Control (PIC) policy recently proposed by us to provide differentiated services in IP/MPLS over WDM networks
with traffic grooming. Three different algorithms are considered for provisioning differentiated services. The simulation
results show that, with two of the three algorithms, the network cannot only provide differentiated services when the traffic
load is high but also gives significantly lower blocking for the lower priority class traffic and for the overall traffic
at low traffic loads.
相似文献
Sanjay K. BoseEmail: |
8.
This paper presents the evaluation of the average spectral efficiencies provided by the adaptive use of a set of LDPC-coded
QAM modulations in an OFDMA downlink scheme over mobile radio channels, considering a joint modeling of the channel and user-access
method. It discusses the selection of the set of coded modulations, briefly describes the joint modeling of the channel and
access method employed, and derives the average spectral efficiency provided by this approach in non-ARQ or H-ARQ environments.
Some comments about the effects of the system’s parameters upon its performances are also included.
相似文献
Vasile BotaEmail: |
9.
It is well known that adding more antennas at the transmitter or at the receiver offers larger channel capacity in the multiple-input
multiple-output communication systems. In this letter, a simple proof is presented for the fact that the channel capacity
increases with an increase in the number of receive antennas. The proof is based on the famous capacity formula of Foschini
and Gans and uses matrix theory.
相似文献
J. F. HayesEmail: |
10.
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: |
11.
Bart Puype Didier Colle Mario Pickavet Piet Demeester 《Photonic Network Communications》2009,18(2):150-159
Multilayer traffic engineering (MLTE) serves to provide cross-layer online network optimization techniques to cope with rapid
variations and short-term evolutions in traffic patterns. MLTE extends traffic engineering as it exists in IP/MPLS-based technology
toward the multilayer IP/MPLS-over-optical transport network. In addition to the IP/MPLS traffic routing, MLTE exposes much
larger adaptation flexibility by building on next-generation automatic switched optical transport networks. These offer fast
setup and teardown of end-to-end multi-hop optical connections (lightpaths), which are offered to the IP/MPLS layer as dynamically
provisioned capacity. This dynamic nature leads to an IP/MPLS logical topology that can be reconfigured on the fly, and IP/MPLS
link capacity that can be up- or downgraded as client traffic demand varies. These MLTE techniques are generally used to increase
perceived network performance in terms of throughput or QoS. As such, a MLTE-managed network offers a better than best-effort
service. Many types of traditional and novel services are shifting toward IP/MPLS technology. Consequentially, MLTE algorithms
and strategies should be conceived with the characteristics of such services in mind. We present a MLTE strategy that can
be implemented in a robust and distributed way. This strategy is then taken as the starting point in a study which evaluates
its suitability to such services. We show how the strategy can be adapted considering service performance metrics such as
end-to-end delay, traffic loss, and routing stability, and how such service optimizations impact general MLTE objectives such
as IP/MPLS logical topology mesh size reduction.
相似文献
Bart PuypeEmail: |
12.
Heesook Choi William Enck Jaesheung Shin Patrick D. McDaniel Thomas F. La Porta 《Wireless Networks》2009,15(4):525-539
Nodes forward data on behalf of each other in mobile ad hoc networks. In a civilian application, nodes are assumed to be selfish
and rational, i.e., they pursue their own self-interest. Hence, the ability to accurately measure traffic forwarding is critical
to ensure proper network operation. These measurements are also often used to credit nodes based on their level of participation,
or to detect loss. Past solutions employ neighbor monitoring and reporting on traffic forwarding of nodes. These methods are
not applicable in civilian networks in which neighbor nodes lack the desire or ability to perform the monitoring function.
Such environments occur frequently in which neighbor hosts are resource constrained, or in networks where directional antennas
are used and reliable eavesdropping is difficult or impossible. In this article, we propose a protocol that uses nodes on
the data path to securely produce packet-forwarding reports. Reporting nodes are chosen randomly and secretly so that malicious
nodes cannot modify their behavior based upon the monitoring point. The integrity and authenticity of reports are preserved
through the use of secure link layer acknowledgments and monitoring reports. The robustness of the reporting mechanism is
strengthened by forwarding the report to multiple destinations (source and destination). We explore the security, cost, and
accuracy of our protocol.
相似文献
Thomas F. La PortaEmail: |
13.
Theodore Drivas Polychronis Koutsakis Michael Paterakis 《Wireless Personal Communications》2009,50(3):291-303
In recent work (Koutsakis et al., IEEE Trans Veh Technol 54(5):1863–1874, 2005), we have introduced multimedia integration
multiple access control protocol (MI-MAC). The protocol was shown to achieve superior performance in comparison to other protocols
of the literature when integrating various types of multimedia traffic over wireless cellular networks. In this work we enhance
the scheduling scheme of MI-MAC by adding three important parameters into its study. These are: (a) the handling of handoff
traffic, (b) per user varying channel conditions in the uplink and downlink channels and (c) video sources’ contention for
channel resources. These parameters are added in order to evaluate the protocol under a significantly more realistic wireless
cellular network scenario. New scheduling ideas are proposed in order to efficiently incorporate the new parameters into the
scheme. The evaluation, conducted by comparing the enhanced MI-MAC with another efficient protocol of the literature and with
an “ideal” MAC protocol, focuses on the efficient transmission of MPEG-4 video traffic and shows that our scheme achieves
excellent performance results.
相似文献
Michael PaterakisEmail: |
14.
M. R. M. Rizk M. I. Dessouky Sami A. El-Dolil Mohammed Abd-Elnaby 《Wireless Personal Communications》2009,48(4):551-568
The major issue related to the realization of wireless multimedia system is the design of suitable medium access control (MAC)
protocol. The design challenge is to maximize the utilization of the limited wireless resources while guaranteeing the various
quality of service requirements for all traffic classes especially for the stringent real-time constraint of real time variable
bit rate (rt-VBR) video service. In this paper a novel resource allocation algorithm for video traffic is proposed. The proposed
allocation algorithm aims to provide fair delay for video packets by minimizing the delay difference among transmitted video
packets. At the same time it adaptively controls the allocated resources (bandwidth) for video traffic around the corresponding
average bit rate, and has the ability of controlling the quality of service (QoS) offered for video traffic in terms of packet
loss probability and average delay. A minimized control overhead of only two bits is needed to increase the utilization efficiency.
Simulation results show that the proposed algorithm achieves very high utilization and provides nearly fair delay among video
packets. Its efficiency is also investigated under traffic integration condition with voice and data traffic to show that
the QoS offered to video traffic does not change in the presence of the highest priority voice traffic while data traffic
increases the channel utilization to 98% by using the remaining bandwidth after voice and video traffic while a good QoS is
offered to voice and data traffic.
相似文献
Mohammed Abd-Elnaby (Corresponding author)Email: |
15.
Muhammad Imadur Rahman Ragnar Reynisson Daniel Figueiredo Ramjee Prasad 《Wireless Personal Communications》2009,50(1):83-97
This article proposes a novel way of grouping users in an orthogonal frequency division multiplexing (OFDM) communication
link based on predefined criteria. The total available spectrum is divided into a number of bands equal to the number of groups.
For efficient time-frequency resource allocation, sub-carrier and band hopping are used simultaneously. Under some constraints,
sub-carriers can also be assigned to different users based on known channel characteristics using dynamic sub-carrier allocation.
Sub-carrier and band hopping are used for mitigating the frequency selectivity of the wireless channel and for minimizing
and avoiding interference in the system. The proposed scheme is equally applicable to both downlink and uplink.
相似文献
Ramjee PrasadEmail: |
16.
Bazil Taha-Ahmed Miguel Calvo-Ramón Leandro de Haro-Ariet 《International Journal of Wireless Information Networks》2008,15(2):90-97
In this paper, the capacity and the interference statistics of the sectors of the cigar-shaped WCDMA microcells are studied
using the hybrid model of propagation. A model of nine microcells in a metro tunnel is used to analyze the uplink capacity
and the interference statistics. The capacity and the interference statistics of the microcells in metro tunnels are studied
in this work for different propagation parameters, antenna side lobe levels, sector ranges and bends losses.
相似文献
Bazil Taha-AhmedEmail: |
17.
Pedro Reviriego Anna Maria Guidotti Carla Raffaelli Javier Aracil 《Photonic Network Communications》2008,16(1):61-70
Loss modeling of asynchronous optical burst switches with shared wavelength converters is considered. An exact analysis based
on continuous time Markov chains is proposed and validated by comparison with simulation for balanced and unbalanced traffic.
A computationally efficient approximated analysis is also proposed and compared with the exact model to find applicability
conditions. Approximate loss performance evaluation is presented for ranges of values which are not tractable either by simulation
or exact analysis.
相似文献
Javier AracilEmail: |
18.
Xianyi Rui 《Wireless Personal Communications》2009,50(2):133-142
The effect of co-channel interference (CCI) is considered in multiple-input multiple-output (MIMO) systems employing maximal
ratio combining (MRC) under independent and identically distributed Rayleigh fading. Closed-form capacity and symbol error
rate expressions are presented to evaluate the performance without any numerical integrations or statistical simulations.
The analytical results are compared with Monte Carlo simulations and the good agreement is obtained.
相似文献
Xianyi RuiEmail: |
19.
In terms of the growth rate, network capacity is slower than network traffic. To solve the mismatch between them, utilization
of available capacity can be maximized to provide “best-fit” service for emerging applications (e.g., eBanking, Peer-to-Peer
(P2P) file exchanges, etc.). To satisfy such a requirement, we propose a three-dimensional label scheduling algorithm (TD-LSA),
which is a distributed scheduling approach powered by central databases. In the proposal, all connections are provisioned
in three dimensions (i.e., space, time and wavelength) in a distributed way and uniquely identified by three-dimensional labels.
And in this way a three-dimensional connection is more robust than a single-dimensional connection because the three-dimensional
approach can avoid potential scheduling conflicts as much as possible by using central databases in a network. Thus, the central
databases can reduce bandwidth consumption and offer “best-fit” service for three-dimensional connections. Furthermore, in
order to further reduce bandwidth consumption and to match with a priority of traffic, K-least hop first path (K-LHPF) and a rescheduling mechanism are applied to our proposal. Simulation experiments demonstrate that our proposal achieves
the expected performance gain against existing alternates.
相似文献
Anshi XuEmail: |
20.
In this paper, a novel beamforming technique is proposed for the high altitude platforms (HAPs) mobile communications to generate
adaptive radio coverage worm-shaped cells to cover the main highways. This technique is based on pattern summation of individual
low-sidelobe narrow beams—which constitute the desired cell pattern—weighted by an adaptive amplitude correcting function.
The new shaped cell differs from the conventional hexagonal or elliptical cells as it follows the curvatures of the highway
for long distances up to 100 km, therefore it has an important role in reducing the frequent handoff and signaling traffic
of location updating from moving users over long highways.
相似文献
Yasser AlbagoryEmail: |