| 1. |
- Dely, Peter, 1982-, et al.
(författare)
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Measuring One-Way Delay in Wireless Mesh Networks : An Experimental Investigation
- 2009
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Ingår i: Proceedings of the 4th ACM workshop on Performance monitoring and measurement of heterogeneous wireless and wired networks. - New York : ACM. - 9781605586212
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Konferensbidrag (refereegranskat)abstract
- Wireless Mesh networks are multi-hop networks mostly based on IEEE 802.11 technology and are considered as a viable alternative for providing broadband wireless Internet access. As a consequence, they require support for Quality of Service or advanced mechanisms for selecting Internet gateways. One important requiredinformation is the one-way delay between different nodes. In this paper, we have developed, implemented, and evaluated an one-way delay estimation technique for wireless mesh networks which is based on estimating intra node queuing and inter node forwarding delay. An IP-header option field is used to accumulate the per hop delay estimate to provide an end-to-end estimate. We also outline problems with the implementation and compare results with real one-way delays obtained from a 14 node mesh testbed.We show how estimation accuracy depends on network load and provide insights into further improvements
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| 2. |
- Pioro, Michal, et al.
(författare)
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On max-min fair flow optimization in wireless mesh networks
- 2014
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Ingår i: Ad hoc networks. - : Elsevier. - 1570-8705 .- 1570-8713. ; 13, s. 134-152
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Tidskriftsartikel (refereegranskat)abstract
- The paper is devoted to modeling wireless mesh networks (WMN) through mixed-integer programming (MIP) formulations that allow to precisely characterize the link data rate capacity and transmission scheduling using the notion of time slots. Such MIP models are formulated for several cases of the modulation and coding schemes (MCS) assignment. We present a general way of solving the max-min fairness (MMF) traffic objective for WMN using the formulated capacity models. Thus the paper combines WMN radio link modeling with a non-standard way of dealing with uncertain traffic, a combination that has not, to our knowledge, been treated so far by exact optimization models. We discuss several ways, including a method based on the so called compatible or independent sets, of solving the arising MIP problems. We also present an extensive numerical study that illustrates the running time efficiency of different solution approaches, and the influence of the MCS selection options and the number of time slots on traffic performance of a WMN. Exact joint optimization modeling of the WMN capacity and the MMF traffic objectives forms the main contribution of the paper.
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| 3. |
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| 4. |
- Bayer, Nico, et al.
(författare)
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VoIP service performance optimization in pre-IEEE 802.11s Wireless Mesh Networks
- 2008
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Ingår i: Proceedings of the IEEE International Conference on Circuits andSystems for Communications (ICCSC) 2008. - : IEEE conference proceedings. - 9781424417070 ; , s. 75-79
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Konferensbidrag (refereegranskat)abstract
- 802.11-based wireless mesh networks are seen as a means for providing last mile connections to next generation networks. Due to the low deployment cost and the mature technology used, they are scalable, easy to implement and robust. With an increasing coverage of wireless networks, VoIP becomes a cheaper alternative for traditional and cellular telephony. In this paper, we carry out a feasibility study of VoIP in a dual radio mesh environment. Heading towards 802.11s, we present the design of a mesh testbed and methodology for performing the measurements. Additionally, we address the problem that small voice packets introduce a high overhead leading to a low voice capacity of 802.11 based mesh networks. In order to alleviate this problem and increase the voice capacity, a novel packet aggregation mechanism is presented and evaluated using the ns-2 simulator.
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| 5. |
- Bellalta, Boris, et al.
(författare)
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On the performance of packet aggregation in IEEE 802.11ac MU-MIMO WLANs
- 2012
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Ingår i: IEEE Communications Letters. - Piscataway, N.J. : IEEE Press. - 1089-7798 .- 1558-2558. ; 16:10, s. 1588-1591
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Tidskriftsartikel (refereegranskat)abstract
- Multi-user spatial multiplexing combined with packet aggregation can significantly increase the performance of Wireless Local Area Networks (WLANs). In this letter, we present and evaluate a simple technique to perform packet aggregation in IEEE 802.11ac MU-MIMO (Multi-user Multiple Input Multiple Output) WLANs. Results show that in non-saturation conditions both the number of active stations (STAs) and the queue size have a significant impact on the system performance. If the number of STAs is excessively high, the heterogeneity of destinations in the packets contained in the queue makes it difficult to take full advantage of packet aggregation. This effect can be alleviated by increasing the queue size, which increases the chances of scheduling a large number of packets at each transmission, hence improving the system throughput at the cost of a higher delay. © 1997-2012 IEEE.
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| 6. |
- Bellalta, Boris, et al.
(författare)
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Performance analysis of CSMA/CA protocols with multi-packet transmission
- 2013
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Ingår i: Computer Networks. - Amsterdam : Elsevier. - 1389-1286 .- 1872-7069. ; 57:14, s. 2675-2688
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Tidskriftsartikel (refereegranskat)abstract
- Wireless objects equipped with multiple antennas are able to simultaneously transmit multiple packets by exploiting the channel's spatial dimensions. In this paper, we study the benefits of such Multiple Packet Transmission (MPT) approach, when it is used in combination with a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol for fully interconnected networks, addressing the interactions between the two mechanisms and showing the performance gains that can be achieved. To this end, a very simple Media Access Control (MAC) protocol that captures the fundamental properties and tradeoffs of a CSMA/CA channel access protocol supporting MPT is introduced. Using this protocol as a reference, a new analytical model is presented for the case of non-saturated traffic sources with finite buffer space. Simulation results show that the analytical model is able to accurately characterize the steady-state behavior of the reference protocol for different number of antennas and different traffic loads, providing a useful tool for understanding the performance gains achieved by MAC protocols supporting MPT. © 2013 Elsevier B.V. All rights reserved.
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| 7. |
- Dely, Peter, 1982-
(författare)
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Cross-Layer Optimization of Voice over IP in Wireless Mesh Networks
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireless Mesh Networks (WMNs) have emerged as a promising network technology, which combines the benefits of cellular networks and Wireless Local Area Networks (WLANs). In a WMN mesh routers wirelessly relay traffic on behalf of other mesh routers or clients and thereby provide coverage areas comparable to cellular networks, while having the low complexity and low costs of WLANs. As Voice over IP (VoIP) is a very important Internet service, it is critical for the success of WMNs to support high quality VoIP. However, currentWMNs are not adapted well for VoIP. The capacity and scalability of single-radio WMNs is low, especially for small packet transmissions of VoIP calls, because the MAC and PHY layer overhead for small packets is high. The scalability of multiradio/multi-channel WMNs is usually higher, since fewer nodes contend for a channel. However channel scheduling might be required, which can lead to excessive delay and jitter and result in poor VoIP quality. In this thesis we investigate how to deliver high quality VoIP in single radio and multi-radio networks by using cross-layer optimization. For single radio WMNs, we consider the use of IP packet aggregation and IEEE 802.11e transmission opportunities. We conclude that IP packet aggregation greatly improves the capacity and thereby the scalability of WMNs. We show that the key for providing good quality is to artificially delay packets prior to aggregation. We propose a distributed cross-layer optimization system, which, based on Fuzzy Logic Inference, derives an aggregation delay that enhances the capacity and quality. For multi-radio/multi-channel WMNs, we demonstrate the importance of qualityof- service-aware channel scheduling. We develop a quality-of-serviceaware channel scheduler that compared to a basic round-robin scheme significantly reduces jitter and in that way increases VoIP quality. Our analysis shows that there is a trade-off between the jitter of high priority VoIP traffic and the throughput of background TCP traffic. The proposed optimizations significantly increase the capacity of singleradio and multi-radio WMNs. This allows network operators to serve more users with an existing mesh infrastructure or provide better service delivery to existing users.
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| 8. |
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Selected Lectures on Multiple Access and Queueing Systems : Revised Selected Papers from International Workshop on Multiple Access Communications - MACOM-2008 (16-17 June 2008, Saint-Peterburg)
- 2008
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Proceedings (redaktörskap) (refereegranskat)abstract
- Claude Shannon established the foundation for the discipline now known as "multi-user information theory" in his pioneering paper "Two-way Communication Channels" in 1961 and later Norman Abramson published his paper “The Aloha System – Another Alternative for Computer Communications” in 1970 which introduced the concept of multiple access using a shared commonchannel. After more than 40 years of study, numerous elegant theories and algorithms have beendeveloped for multiple access techniques.In recent years, broadband wireless data networks (for instance, IEEE 802.11 Wi-Fi, IEEE802.16 WiMAX) are driving the development of the telecommunication industry and Beyond 3G(B3G) wireless systems are expected to provide a variety of multimedia services in a wide range of wireless and mobile environments. To use the scarce bandwidth resource of the wireless channel, it isnecessary to design channel access control techniques for a large population of users (potentiallyhundreds of mobile stations).The aim of these collected articles is to give an overview of the state-of-the-art results inmulti-user communications theory, multiple access techniques, queuing theory and standardizationactivities in areas mostly related to PHY and MAC layer protocols for contemporary wirelessnetworks and their interactions.
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| 9. |
- Staehle, Dirk, et al.
(författare)
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Performance evaluation and parameterization of the IEEE 802.16 contention-based CDMA bandwidth request mechanism for the OFDMA physical layer
- 2009
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Ingår i: MSWiM '09. - New York : Association for Computing Machinery (ACM). - 9781605586168 ; , s. 374-383
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Konferensbidrag (refereegranskat)abstract
- The IEEE 802.16 standard specifies two contention-based mechanisms for the OFDMA physical layer to transmit bandwidth requests from subscriber station to base station: the standard mechanism is based on Slotted Aloha with a truncated binary exponential backoff; the alternative one is based on CDMA. This paper describes the CDMA-based contention mechanism and presents an analytic model to compute its performance in terms of delay and consumed resources. The tunable parameters for the CDMA-based random access procedure are the number of ranging subchannels, the number of codes per ranging subchannels, and the detection threshold. An optimal configuration is derived for a given load in terms of the request arrival rate.
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| 10. |
- Vinel, Alexey, 1983-, et al.
(författare)
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Capacity analysis of reservation-based random access for broadband wireless access networks
- 2009
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Ingår i: IEEE Journal on Selected Areas in Communications. - Piscataway, N.J. : IEEE Press. - 0733-8716 .- 1558-0008. ; 27:2, s. 171-181
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we propose a novel model for the capacity analysis on the reservation-based random multiple access system, which can be applied to the medium access control protocol of the emerging WiMAX technology. In such a wireless broadband access system, in order to support QoS, the channel time is divided into consecutive frames, where each frame consists of some consequent mini-slots for the transmission of requests, used for the bandwidth reservation, and consequent slots for the actual data packet transmission. Three main outcomes are obtained: first, the upper and lower bounds of the capacity are derived for the considered system. Second, we found through the mathematical analysis that the transmission rate of reservationbased multiple access protocol is maximized, when the ratio between the number of mini-slots and that of the slots per frame is equal to the reciprocal of the random multiple access algorithm's transmission rate. Third, in the case of WiMAX networks with a large number of subscribers, our analysis takes into account both the capacity and the mean packet delay criteria and suggests to keep such a ratio constant and independent of application-level data traffic arrival rate. © 2006 IEEE.
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