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1.
Integration of multicast and unicast data in future radio access networks will be necessary in order to improve the resource
efficiency and provide new services. Such integration requires new and efficient resource sharing mechanisms. These mechanisms
need to be optimized to provide the best possible trade-off between resource efficiency and fairness. In this article, we
consider a case where streaming multicast users are multiplexed together with elastic unicast users on a common time-slotted
channel. We derive a system model to study the performance of various resource allocations strategies under proportional and
resource fairness constraints. Fairness is directly defined in terms of the users’ utilities rather than of the throughputs
they are assigned to. We also describe an extension of the well-known unicast proportional fair scheduler to the multicast
scenario. Through extensive simulations we demonstrate the performance of this scheduler for various traffic loads and multicast
group sizes.
相似文献
Gunnar KarlssonEmail: |
2.
Francesco Chiti Michele Ciabatti Giovanni Collodi Davide Di Palma Romano Fantacci Gianfranco Manes Antonio Manes Ilaria Nelli 《Wireless Personal Communications》2008,47(1):15-26
This paper deals with a novel MAC layer protocol, namely Directive synchronous transmission asynchronous reception (D-STAR),
which is able to logically synchronize a Wireless sensor network (WSN). In this case both sleep and active states together
with integrating directional antennas within the communications framework can be managed, according to a cross-layer design.
D-STAR protocol has been characterized in terms of functional characteristics and the overall performance is presented in
terms of network lifetime gain, set-up latency and collision probability. A remarkable gain is shown with respect to the basic
approach endowed with omnidirectional antennas without increasing the signaling overhead nor affecting the set up latency,
but achieving energy consumption reduction.
相似文献
Francesco ChitiEmail: |
3.
We study online multicasting in WDM networks with shared light splitter bank. Our objective is either to maximize the network
throughput or to minimize the blocking probability. Due to the nature of dynamic requesting for network resources by online
multicast requests, the network usually is unable to allocate the resources needed for each request in advance. Instead, it
either accepts the request by building an economic multicast tree for the request, in terms of the utilization of the network
resources if it has sufficient resources available, or rejects the request, otherwise. It is desirable that the cost of realizing
each multicast request be minimized, and the network throughput will be maximized ultimately through the cost saving on each
individual request. Since optical light splitting and wavelength conversion switching in optical networks is cost expensive
and its fabrication is difficult, it is assumed that only a limited number of light splitters and wavelength converters are
installed at a node, which will be shared by all the incoming signals at the node. In addition, it is further assumed that
only a fraction of nodes in the network are installed with such optical switches. In this article we first propose a cost
model for realizing an online multicast request under such network environments with limited light splitters and wavelength
converters, which models the cost of utilization of network resources, particularly in modeling the light splitting and wavelength
conversion ability at nodes. We then show that finding a cost-optimal multicast tree for a multicast request under the proposed
cost model is NP-complete, and instead devise approximation and heuristic algorithms for it. We finally conduct experiments
to evaluate the performance of the proposed algorithms. The results show that the proposed algorithms are efficient and effective
in terms of network throughput.
相似文献
Weifa LiangEmail: |
4.
Performance assessment of multicast node placement for multicast routing in WDM networks with sparse light splitting 总被引:1,自引:0,他引:1
This article examines all-optical multicast routing for wavelength-routed optical networks with sparse Multicast Capable (MC)
nodes in two phases. The first phase is MC node placement and use of a simple and straightforward Maximum Path Count First
(MPCF) algorithm to obtain candidates for MC nodes. The second phase is multicast routing with MC-based schemes that minimizes
the number of wavelength channels with minimum transmission delay as required by a given multicast session, in that a light-tree
is first constructed to connect MC nodes in a multicast group by using two algorithms, namely, the Pre-computing Minimum Cost
(PMC) tree algorithm and the Pre-computing Shortest Path (PSP) tree algorithm. System performance of the proposed MPCF MC
node placement algorithm is compared with that of the Normalized Cuts (NC) MC node placement algorithm for both PMC and PSP
multicast routing. Furthermore, simulation results compare PMC and PSP multicast routing based on MPCF and NC node placement
with Re-route-to-Source (RTS), Re-route-to-Any (RTA), Member-First (MF), and Member-Only (MO) multicast routing based on a
light forest for a given multicast session in terms of average number of wavelengths needed, average blocking probability,
and mean maximum transmission delay.
相似文献
Tsung-Ching LinEmail: |
5.
Using directional antennas in wireless mobile ad hoc networks can greatly improve the transmission range as well as the spatial
reuse. However, it will also cause some problems such as deafness problem and hidden terminal problem, which greatly impair
the network performance. This paper first proposes a MAC protocol called Selectively Directional MAC (SDMAC) that can effectively
address these problems and significantly improve the network throughput. Then two improvements on SDMAC are proposed. The
first one is to improve the network throughput by scheduling the packets in the queue (a scheme called Q-SDMAC), thus the
head-of-line (HOL) blocking problem can be addressed. The second one is to relax the assumption that each node knows the relative
directions of its neighboring nodes and use caches to buffer those relative directions (a scheme named Q-SDMAC using cache).
Extensive simulations show that: (1) SDMAC can achieve much better performance than the existing MAC protocols using directional
antennas; (2) The network throughput can be significantly improved by scheduling the packets in the queue; (3) Using caches
can still achieve high network throughput when nodes are moving; and (4) Network throughput decreases when directional antennas
have side lobe gain.
相似文献
Yuguang Fang (Corresponding author)Email: |
6.
Jae-Hoon Kim 《Wireless Personal Communications》2008,45(1):121-129
This paper deals with one of the most important cell planning issues in a CDMA based multicast network. In a CDMA based wireless
network, a terminal can significantly reduce the bit error rate via the cohesion of data streams from multiple base stations
that share a common time line and are operated according to it. The cells whose base stations are operated as such are called
soft-combining cells. Therefore, a terminal in a soft-combining cell can take advantage of error rate reduction, if the cell
has at least one neighboring soft-combining cell. However, as soft-combining operation gives heavy burden to the network controller,
the number of soft-combining cells should be limited. Our problem is to find a limited number of soft-combining cells such
that each soft-combining cell has at least one neighboring soft-combining cell and that the sum of traffic demands of the
selected cells is maximized.
相似文献
Jae-Hoon KimEmail: |
7.
The issue of wavelength assignment is one of the most important factors that affect the capacity for the deployment of optical
networks. This issue becomes more critical for multicast connections, especially when the network nodes have no wavelength
conversion capability. Although the wavelength assignment can be more flexible if each node can perform wavelength conversion,
the deployment cost increases accordingly. A compromise is to support a limited portion of conversion nodes in the WDM network.
We propose a systematic approach for the wavelength assignment of multicast connections in WDM networks with sparse wavelength
conversion nodes. The efficiency of the arrangement of wavelength is measured by its influences on the available capacity
of the network and the consumption of wavelengths. By using the proposed approach, the Static Cost Greedy (SCG) algorithm
[8] can be easily extended to be applicable in a Sparse Wavelength Conversion Network (SWCN). In addition, instead of SCG,
the Minimum-Effect-First (MEF) algorithm is proposed to maximize the network capacity during wavelength assignment. We compare
the performance of the proposed MEF methods with the extended SCG scheme through exhaustive simulations. The experimental
results indicate that the proposed MEF schemes demonstrate much better performance than the SCG scheme. We also found that
the performance is not always improved proportionally to the increment of the wavelength conversion nodes. The improvement
reaches saturation when the number of conversion nodes is above 35% of the total number of nodes.
相似文献
I-Hsuan PengEmail: |
8.
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: |
9.
Network survivability is crucial to both unicast and multicast traffic. Up to now, extensive research has been done on unicast
traffic protection. Recently, due to the rapid growth of multicast applications, such as video-conferencing, high definition
television (HDTV), distance learning, and multi-player on-line gaming, the problem of multicast traffic protection has started
to draw more research interests. The preconfigured protection cycle (p-cycle) method proposed by Grover offers fast speed in restoration (because p-cycles are pre-cross-connected) and high efficiency in resource utilization (because p-cycles protect both on-cycle and straddling links). So far p-cycles based protection approaches have been intensively studied for unicast traffic protection, but have been rarely investigated
for multicast traffic. We propose to apply p-cycles to dynamic protection provisioning of multicast traffic, and evaluate the blocking performance in comparison to other
existing multicast protection schemes. We consider three different p-cycle based multicasting protection methods, namely dynamic p-cycle (DpC) design, p-cycle based protected working capacity envelope (PWCE) design, and hybrid DpC and PWCE design. We show that p-cycle-based multicast protection approaches offer much better blocking performance, as compared with other existing multicast
protection schemes. The main reasons for the much better blocking performance are attributed to the facts that (i) the selection
of p-cycles is independent of the routing of the multicast light trees, (ii) there are no path/segment disjoint constraints between
the selected p-cycles and the multicast light trees to be protected, (iii) the selected p-cycles are the most efficient p-cycles.
相似文献
Wen-De ZhongEmail: |
10.
Marc C. Necker 《Mobile Networks and Applications》2009,14(4):539-550
The currently emerging 802.16e (WiMAX) and 3GPP Long Term Evolution (LTE) cellular systems are based on Orthogonal Frequency
Division Multiple Access (OFDMA). OFDMA suffers from heavy inter-cell interference if neighboring base stations use the same
frequency range. One approach to solve this issue is the application of beamforming antennas in combination with interference
coordination (IFCO) mechanisms between base stations. In this paper, we trace the problem of IFCO back to the graph coloring
problem and investigate the achievable resource utilization of the interference coordinated system. We develop a heuristic
that allows the combination of arbitrary scheduling algorithms with the IFCO mechanism. This allows an efficient utilization
of the radio system’s frequency resources while still obeying scheduling constraints, such as Quality of Service requirements.
Finally, we study the tradeoff between fairness and the total system throughput.
相似文献
Marc C. NeckerEmail: |
11.
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: |
12.
The use of multibeam antennas (MBAs) in decentralized wireless networks significantly increases the throughput by improving
spatial reuse and extending coverage compared with single-beam antennas. The throughput performance may, however, degrade
in multipath environments due to the fact that multipath propagation increases the probability of collision among different
users. Based on the probability of collision, accurate analytical expressions are derived for the node throughput gain (NTG)
of a wireless network using MBAs in quasi-stationary multipath environments. The results show that a higher number of propagation
paths cause more frequent collisions and thus yield lower node throughput.
相似文献
Moeness G. AminEmail: |
13.
This paper presents the design and evaluation of a highly efficient on-demand multicast routing protocol for mobile ad hoc
networks (MANETs). The protocol, called Geography-aided Multicast Zone Routing Protocol (GMZRP), eliminates as much as possible
duplicate route queries by using a simple yet effective strategy for propagating the multicast route request (MRREQ) packets.
GMZRP is the first hybrid multicast protocol taking the advantages of both topological routing and geographical routing. It
partitions the network coverage area into small zones and guarantees that each geographic zone is queried only once. GMZRP
maintains a multicast forwarding tree at two levels of granularities, i.e., the zone granularity and the node granularity.
By doing this, it can easily handle route breakage since the zone level information can help recover the link failure at the
node level. The results of the performance evaluation of GMZRP using simulation show that, comparing with the well-known multicast
protocol ODMRP (On-Demand Multicast Routing Protocol), GMZRP has much lower protocol overhead in terms of query packets and,
meanwhile, achieves competing packet delivery ratio and shorter delivery latency.
相似文献
Xiaopeng FanEmail: |
14.
The serial-mode multicasting scheme (SM), which can achieve duplication, buffering, and serial export of optical multicast
packets in Optical Packet Switched (OPS) networks, is experimentally studied in this paper. Based on the experimental results,
several limitations of this scheme, such as the multicast latency and signal impairment, are discussed. In addition, its performance
in OPS networks is investigated by computer simulations. From the simulation results, a conclusion can be drawn that compared
with the parallel-mode multicasting scheme (PM) producing multiple simultaneous copies of the optical packets by an optical
power splitter or other devices, the SM scheme can increase the multicast success ratio and reduce the multicast retransmission
times at the costs of some signal impairments and some extra transmission latency.
相似文献
Yuefeng Ji (Corresponding author)Email: |
15.
We consider two related optimization problems: bin-packing with fragile objects and frequency allocation in cellular networks.
The former is a generalization of the classical bin-packing problem and is motivated by the latter. The problem is as follows:
each object has two attributes, weight and fragility. The goal is to pack objects into bins such that, for every bin, the
sum of weights of objects in that bin is no more than the fragility of any object in that bin. We consider approximation algorithms
for this problem. We provide a 2-approximation to the problem of minimizing the number of bins. We also show a lower bound
of 3/2 on the approximation ratio. Unlike for the classical bin-packing problem, this lower bound holds in the asymptotic
case. We then consider the approximation with respect to fragility and provide a 2-approximation algorithm (i.e., our algorithm
uses the same number of bins as the optimum, but the weight of objects in a bin can exceed the fragility by a factor of 2).
We then consider the frequency allocation problem (which is a special case of bin-packing with fragile objects) and give improved
approximation algorithms for it. Finally, we consider a probabilistic setting and show that our algorithm for frequency allocation
approaches optimality as the number of users increases.
相似文献
Arvind SankarEmail: |
16.
Cognitive Radio with Single Carrier TDCS and Multicarrier OFDM Approach with V-BLAST Receiver in Rayleigh Fading Channel 总被引:1,自引:0,他引:1
This article presents the performance comparison of TDCS and OFDM based cognitive radio for MIMO system using VBLAST receiver
architecture to reconstruct the transmitted data. The interference avoidance performance in terms of BER and bitrate are improved
by adding multiple antennas to the system and the use of V-BLAST technique at the receiver. The results show the most promising
interference avoidance technique combined with MIMO V-BLAST architecture to be applied in the CR system.
相似文献
L. P. LigthartEmail: |
17.
Mohamed Khalaf-Allah 《Wireless Personal Communications》2008,44(3):311-322
This paper investigates a Global Positioning system (GPS)-free positioning method for mobile units (MUs) in outdoor wireless
environments by using the Bayesian filtering formulation. The procedure utilizes simulated inertial measurements, cell-ID
of the serving base station, and pre-determined locations grouped according to cell antennas radio coverage in the experimentation
area. The developed algorithm makes no assumptions on the initial position of the MU. However, the algorithm takes some time
to converge. Experiments show the range of inertial measurement errors that would maintain reliable location information with
accuracy comparable to GPS positioning.
相似文献
Mohamed Khalaf-AllahEmail: |
18.
Liang Yang 《Wireless Personal Communications》2008,45(2):225-230
In this letter, taking into account realistic propagation environments in the presence of double scattering, we analyze the
outage probability of orthogonal space-time block coding (OSTBC) for an arbitrary finite number of transmit and receive antennas.
Closed-form expressions for the outage probability of OSTBC over Rayleigh-fading multiple-input multiple-output (MIMO) channels
with double scattering are presented. Finally we give some numerical results to verify our analysis.
相似文献
Liang YangEmail: |
19.
We present an adaptive antenna algorithm for Gaussian minimum-shift keying (GMSK)-based cellular systems with beamformer weights
that are iteratively computed using re-encoded data to suppress cochannel interference (CCI). Filtered training sequences
are proposed in order to compensate for the effects of timing offsets that occur for asynchronous cochannel signals. Also,
we extend the receiver to include a linear equalizer that mitigates intersymbol interference (ISI). Various multistage receivers
incorporating the proposed beamformer and equalizer algorithms are presented. Their performance is evaluated using simulated
and real time-division multiple-access (TDMA) data, demonstrating that the proposed beamforming algorithms suppress CCI and
significantly improve the performance compared to a conventional GMSK receiver.
相似文献
Richard P. GoochEmail: |
20.
Wireless sensor networks scheduling for full angle coverage 总被引:2,自引:2,他引:0
Kit-Yee Chow King-Shan Lui Edmund Y. Lam 《Multidimensional Systems and Signal Processing》2009,20(2):101-119
Many current studies in tracking and surveillance assume that a target can be monitored by a single sensor. However, there
are situations where a sensor can only monitor a certain portion of the object. Examples include image capturing and coastline
monitoring. In our previous work, we develop the Minimum Cost Cover algorithm to identify a set of sensors which preserve 360° coverage of a target with minimum cost, such that when different
cost functions for the sensors are used, covers with different optimization objectives can be identified. In this work, we
study the scheduling problem to monitor a target continuously with full angle coverage. To increase network lifetime, we develop
several algorithms by adopting different cost functions in selecting the sensors. We evaluate the performance of our schemes
through extensive simulations. The simulation results show that our proposed Conditional Scheduling metric can help to improve
the network lifetime as well as the time to the first node failure.
相似文献
Edmund Y. Lam (Corresponding author)Email: |