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ABSTRACT: In the IEEE 802.11 MAC protocol, access points (APs) are given the same authority as wireless terminals (WTs) in terms of acquiring the wireless link, even though they aggregate several downlink flows. This feature leads to a serious throughput degradation of downlink flows, compared with uplink flows. In this paper, we propose a dynamic contention window control scheme for the IEEE 802.11e EDCA-based WLANs, in order to achieve fairness between uplink and downlink TCP flows while guaranteeing QoS requirements for real-time traffic. The proposed scheme first determines the minimum contention window size in the best-effort access category at APs, based on the number of TCP flows. It then determines the minimum and maximum contention window sizes in higher priority access categories, such as voice and video, so as to guarantee QoS requirements for these real-time traffic.
Vehicular Technology Conference, 2009. VTC Spring 2009. IEEE 69th; 05/2009
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ABSTRACT: This paper considers (p, q )-Epidemic Routing, a class of store-carry-forward routing schemes, for sparsely populated mobile ad hoc networks. Our forwarding scheme includes Two-Hop Forwarding and the conventional Epidemic Routing as special cases. In such forwarding schemes, the original packet is copied many times and its packet copies spread over the network. Therefore those packet copies should be deleted after a packet reaches the destination. We analyze the performance of (p, q)-Epidemic Routing with VACCINE recovery scheme. Unlike most of the existing studies, we discuss the performance of (p, q)-Epidemic Routing in depth, taking account of the recovery process that deletes unnecessary packets from the network.
IEEE Journal on Selected Areas in Communications 07/2008; · 3.41 Impact Factor
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ABSTRACT: This paper proposes a proactive contention avoidance scheme with dedicated wavelength assignment in optical burst switching networks. Using dedicated wavelengths, we construct several routes from each ingress node in the following way. We first construct spanning trees at respective ingress nodes and assign dedicated wavelengths to them, based on the amount of lost traffic. Further, using unused wavelengths in each link, we construct partial trees at each ingress node, again based on the amount of lost traffic. By this way, contention at intermediate core nodes is completely eliminated, and contention is localized at each ingress node, which can be resolved by means of electric buffers. Through simulation experiments, we show that the proposed scheme can achieve the burst loss performance superior to that in the shared wavelength scheme with full wavelength conversion and shortest-path routing.
Wireless and Optical Communications Networks, 2007. WOCN '07. IFIP International Conference on; 08/2007
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ABSTRACT: This paper considers a fairness issue between uplink and downlink flows in IEEE 802.11 wireless LANs, where uplink flows dominate over downlink flows in terms of wireless bandwidth usage. As a solution to this unfairness, the authors propose modifying the IEEE 802.11 MAC protocol at access points (APs). Our scheme dynamically controls the minimum contention window size at APs and provides an ample opportunity for them to acquire the transmission right. Because the control is based only on the number of downlink flows, APs can easily find the optimal window size to achieve per-flow fairness. Note that the proposed scheme does not require any modifications in the MAC protocol at wireless terminals. Through simulation experiments with UDP flows, the authors show that the proposed scheme can achieve fairness between uplink and downlink flows.
Wireless Communications and Networking Conference, 2007.WCNC 2007. IEEE; 04/2007
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ABSTRACT: This paper proposes an analytical model for a delayed reservation scheme, which can be exactly analyzed. By applying it to a server-based QoS management network, we can obtain the related blocking probability and the waiting time distribution of requests, and discuss its performance by means of numerical results. The numerical results show that the delayed scheme can improve the blocking probability by about two orders of magnitude compared with the conventional reservation scheme even with a small acceptable waiting time (e.g. 20% of average flow duration). We can conclude that the delayed reservation scheme can lead to significant improvement in a server-based QoS management network performance.
Advanced Information Networking and Applications, 2003. AINA 2003. 17th International Conference on; 04/2003
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ABSTRACT: For a statistical perspective of global traffic flows on a large network, the authors have proposed a method for inferring unobservable arrival rate statistics of individual flows based solely on measurements of aggregated-flow rates, which can be easily measured at network links such as router interfaces. The above method, while having potential for inferring arrival rate statistics of various kinds of flows without the need to identify the flow to which each packet belongs, originally had limited practical applicability. Therefore, to extend the range of application of the method, the following improvements are proposed: i) finding the minimum effective rate of each flow and inferring a statistic of the difference between minimum effective rate and the flow rate itself, ii) quantizing rate values into bins with an appropriate bin size; and iii) inferring rate statistics of flows indirectly from those of other "well inferable" flows. Simulations are performed, and the proposed improvements are shown to allow the mean rate inference of each flow in cases that previous methods have been unable to treat.
Applications and the Internet, 2003. Proceedings. 2003 Symposium on; 02/2003
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ABSTRACT: In the Internet, a statistical perspective of global traffic flows
has been considered as an important key to network management.
Nonetheless, it is expensive or sometime difficult to measure statistics
of each flow separately. Therefore, it is of practical importance to
infer unobservable statistical characteristics of individual flows from
characteristics of the aggregated-flows that are easily measured at some
links (router interfaces) in the network. We propose a new approach to
such inference problems, and provide some examples of inferring
unobservable arrival rates of packets on each flow from measurement of
the aggregated-flows. Our method is applicable to cases not covered by
the existing methods for the OD traffic matrix inference. We also show
simulation results, which indicate the potential of our approach
Applications and the Internet, 2002. (SAINT 2002). Proceedings. 2002 Symposium on; 02/2002
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ABSTRACT: As the Internet is shifting towards a reliable QoS-aware network,
accurately synchronized clocks distributed on the Internet are becoming
more significant. The network time protocol (NTP) is broadly deployed on
the Internet for clock synchronization among distributed hosts, but is
weak in asymmetric paths, i.e., it cannot accurately estimate the clock
offset between two hosts when the forward and backward paths between
them have different one-way delays. In this paper, we focus on
estimating the offset and skew of a clock from one-way delay measurement
between two hosts, and propose an idea for improvement of such
estimations, which reduces estimation errors when the forward and
backward paths have different bandwidths, a major factor in asymmetric
delays
Applications and the Internet (SAINT) Workshops, 2002. Proceedings. 2002 Symposium on; 02/2002
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ABSTRACT: We examine the delay performance of packets from constant-bit-rate (CBR) traffic whose delay is affected by non-real-time traffic. The delay performance is analyzed by solving the nD/D/1 queue with vacations. We obtain an exact and closed form solution, hence obviating the need of any approximations or numerical Laplace inversions. We then provide various numerical results for low-bit-rate transmission links, in which packets can experience large delay. From our quantitative evaluation, we conclude that there exists an optimum packet size for a given delay bound. In extremely slow links, such as modem links, transmission control protocol (TCP) packets should be segmented to reduce the CBR delay. We therefore investigate the delay impact of TCP packet sizes as well
IEEE/ACM Transactions on Networking 05/2001; 9(2):177-185. · 2.03 Impact Factor
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ABSTRACT: In the Internet, because of huge scale and distributed
administration, it is of practical importance to infer network-internal
characteristics that cannot be measured directly. We propose a general
method of determining characteristics of links from given
characteristics of end-to-end paths. Our method can be applied to an
arbitrary path-topology. Furthermore we show the general conditions that
the link characteristics to be inferred must satisfy. Packet loss and
queuing delay time are shown to satisfy them. Case studies which our
method can treat are also provided
Communications, 2001. ICC 2001. IEEE International Conference on; 02/2001
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ABSTRACT: Real-time communications services over the Internet need a new
architecture to meet their required quality. From a viewpoint of quality
of service provisioning architecture, the Internet can mainly be divided
into three types of subnetworks: domain networks, access networks, and
stub networks. In this article we focus on issues arising in the former
two networks for end-to-end QoS provisioning. First, the access networks
are of rather low-speed links, so delay is still of major concern. We
examine the statistical delay bound through numerical results derived
from our analysis. Schemes to reduce delay are proposed, and their
performance is evaluated. Next, domain networks are likely to be of very
high-speed links, which can accommodate a huge number of voice flows of
low bit rates. Thus, effective flow management will be of major concern
because per-flow management is a very costly proposition. Therefore, we
pay attention to a flow aggregation scheme, and evaluate its performance
by analyzing its blocking probability
IEEE Communications Magazine 05/2000; · 3.79 Impact Factor
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ABSTRACT: The layer3 switch enables us to fast transmit IP datagrams using
the cut-through technique. The current layer3 router would become a
bottleneck in terms of delay performance, as the amount of traffic
injected into high speed networks gets relatively large. Thus, the
layer3 switch should be an important element in constructing the next
generation Internet backbone. We analyze the cut-through rate, the
datagram waiting time and the mis-ordered rate of a layer3 switch in
case of flow-driven connection setup. In the analysis, by using a
3-state Markov modulated Bernoulli process (MMBP), we model the arrival
process of IP flow and IP datagram from each source. Furthermore, we
investigate impacts of the arrival rate and the average datagram length
on performance
Internet Workshop, 1999. IWS 99; 02/1999
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ABSTRACT: In cellular mobile communication networks, a proper modeling of
call behavior is essential for network planning. Due to the increase of
calls and network complexity, the retrial phenomenon may have a
significant impact on the network performance. We focus on the effect of
the call retrial phenomenon in a cellular mobile network. We formulate
the dynamics of each cell as a three-dimensional Markov chain, and from
which we approximately construct a one-dimensional Markov chain by
aggregating auxiliary states to obtain numerically feasible formulas for
performance measures. In numerical experiments, we show the analytical
results are fairly accurate by comparing simulation results. We come to
the conclusion that the proposed performance evaluation method is useful
for cellular network planning
Personal Wireless Communication, 1999 IEEE International Conference on; 02/1999
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ABSTRACT: The conventional Internet has only provided the best-effort
service, which does not offer any QoS (quality-of-service) guarantees.
However, previous developments of multimedia applications require QoS
guarantees for real-time transfers, which eventually introduced
reservation-based protocols. However, it is pointed out that
reservation-based protocols such as RSVP have several drawbacks such as
a scalability problem. We introduce user's utility to quantify QoS, and
it is used to compare the best-effort and reservation-based services to
discuss which service gives a better solution for real-time applications
and data applications. By extending our previous results, we discuss the
worst utility that the user experiences during the connection in this
paper. The tandem network model is also treated to investigate the
effect of multiple link systems on both services
Communications, 1999. APCC/OECC '99. Fifth Asia-Pacific Conference on ... and Fourth Optoelectronics and Communications Conference; 02/1999
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ABSTRACT: QoS routing is essential for future multimedia telecommunication
services. In this paper, we propose how to design network maps which are
functional databases to manage all network information and to be bases
for QoS routing
Communications, 1999. APCC/OECC '99. Fifth Asia-Pacific Conference on ... and Fourth Optoelectronics and Communications Conference; 02/1999
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ABSTRACT: Flow aggregation will be a key technology for offering real-time
communication services in large scale networks, because it can greatly
reduce the flow management cost. In this paper, we exactly analyze the
performance of flow aggregation of constant bit rate type traffic,
especially the call blocking probability at the ingress routers. Through
our numerical results, we have shown the characteristics of flow
aggregation. As a result, although the flow aggregation scheme, in fact,
needs more capacity than the per-flow management to achieve the same
blocking probability, it enables us to manage a great number of flows of
relatively small bandwidth requirements, e.g., voice flows in high speed
backbone networks without much redundant capacity. Our analysis is so
general that it can treat various kinds of heterogeneous cases, and
helps to determine the capacity allocation to different kinds of
aggregated flows
Global Telecommunications Conference, 1999. GLOBECOM '99; 02/1999
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ABSTRACT: ABT (ATM block transfer) is expected for effectively transferring highly bursty data traffic in ATM networks. In the past work, ABT/IT has been shown to be robust in that its performance is not much affected by the propagation delay when compared with ABT/DT. However, when the traffic load becomes heavy and/or when the number of hop counts of the connection becomes large, the throughput of ABT/IT is drastically decreased. We propose a new protocol, buffered ABT/IT, which makes reservation on the buffer as well as the bandwidth. The approximate analysis method is then developed for buffered ABT/IT. Through numerical examples, we show that it can much improve the performance even in the above conditions by comparison with the exiting ABT protocols
ATM Workshop Proceedings, 1998 IEEE; 06/1998
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ABSTRACT: We consider a priority cell scheduling in the following scenario.
High-speed cell networks accommodate constant bit rate (CBR) streams
from real-time sources and unspecified bit rate (UBR) streams from non
real-time sources. The real-time traffic requires guarantees of its
delay time. On the other hand, the non real-time traffic is relatively
tolerable to its delay time. We obtain the queueing delay distribution
of cells from CBR streams. Further the average queueing delay of cells
from UBR streams is obtained in some special cases. We provide some
numerical results and discuss the effectiveness of quality-of-service
(QoS) guarantees based on the statistical bound and the influence of UBR
streams on the system performance
Global Telecommunications Conference, 1998. GLOBECOM 98. The Bridge to Global Integration. IEEE; 02/1998
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ABSTRACT: This paper provides upper bounds on the end-to-end delay and the
required buffer size at the leaky bucket and packet switches in the
context of the deterministic bandwidth allocation method in integrated
services packet networks. Based on that formulation, a connection
admission control (CAC) method is proposed to guarantee the bounded
end-to-end delay and loss-free packet transmissions. GOP-CBR MPEG-2 and
is considered as an example application. Tighter bounds are also shown
for its slightly modified coding method. Numerical results show that the
loose upper bounds can also achieve more utilization even in the context
of deterministic bandwidth allocation compared with the peak bandwidth
allocation strategy
Global Telecommunications Conference, 1998. GLOBECOM 98. The Bridge to Global Integration. IEEE; 02/1998
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ABSTRACT: In the integrated service networks, the real-time traffic and the
non-real-time traffic share the network resources so that one can affect
the quality of another and vice versa. In this context, it is very
crucial to develop some mechanism to guarantee the quality-of-service
(QoS) required by the real-time traffic. In this paper, we analyze the
delay time of CBR packets from real-time sources when CBR packets have
the priority over UBR packets in a manner that UBR packets are serviced
only if no CBR packets are waiting in the buffer. There are two types of
CBR packets; i.e., they are different in their transmission rate and/or
packet length. In this sense, the case treated is called the
heterogeneous case. We obtain various numerical results on the
statistical bound on delay time such as the 99.9-percentile delay and
compare it with the deterministic bound. By the comparison, we show that
call admission control (CAC) based upon the statistical bound is very
effective in using the network resources efficiently when CBR packets
can tolerate some loss due to late arrival. We also examine whether the
delay time distribution in the heterogeneous case can be approximated by
that of some homogeneous cases
Global Telecommunications Conference, 1998. GLOBECOM 98. The Bridge to Global Integration. IEEE; 02/1998
