| 1. |
- AT, Andersen, et al.
(författare)
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A partially-blocking queueing system with CBR/VBR and ABR/UBR arrival streams
- 2002
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Ingår i: Telecommunications Systems. - : Baltzer Academic Publisher. - 1018-4864 .- 1572-9451. ; 19:1, s. 75-99
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we consider an ATM transmission link., to which CBR or VBR and ABR or UBR calls arrive according to independent Poisson processes. CBR/VBR calls (characterized by their equivalent bandwidth) are blocked and leave the system if the available link capacity is less than required at the time of arrival. ABR/UBR calls, however, accept partial blocking, meaning that they may enter service even if the available capacity is less than the specified required peak bandwidth, but greater than the so called minimal accepted bandwidth. Partially blocked ABR/UBR calls instead experience longer service time, since smaller given bandwidth entails proportionally longer time spent in the system, as first suggested in [3] and analyzed in details herein. Throughout the life time of an ABR/UBR connection, its bandwidth consumption fluctuates in accordance with the current load on the link but always at the highest possible value up to their peak bandwidth (greedy sources). Additionally, if this minimal accepted bandwidth is unavailable at the time of arrival, ABR/UBR calls are allowed to wait in a finite queue. This system is modeled by a Continuous Time Markov Chain (CTMC) and the CBR/VBR and ABR/UBR blocking probabilities and the mean ABR/UBR waiting- and service times are derived.
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| 2. |
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| 3. |
- Fodor, Gabor, et al.
(författare)
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Bounding the blocking probabilities in multirate CDMA networks supporting elastic services
- 2007
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Ingår i: IEEE/ACM Transactions on Networking. - : IEEE Press. - 1063-6692 .- 1558-2566. ; 15:4, s. 944-956
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Tidskriftsartikel (refereegranskat)abstract
- Several previous contributions have proposed calculation methods that can be used to determine the steady state (and from it the blocking probabilities) of code-division multiple-access (CDMA) systems. This present work extends the classical Kaufman-Roberts formula such that it becomes applicable in CDMA systems in which elastic services with state-dependent instantaneous bit rate and average-bit-rate-dependent. residency time are supported. Our model captures the effect of soft blocking, that is, an arriving session may be blocked in virtually all system states but with a state dependent probability. The core of this method is to approximate the original irreversible Markov chain with a reversible one and to give lower and upper bounds on the so-called partially blocking macro states of the state space. We employ this extended formula to establish lower and upper bounds on the steady state and the classwise blocking probabilities.
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| 4. |
- Fodor, Gabor, et al.
(författare)
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On the impact of antenna correlation on the pilot-data balance in multiple antenna systems
- 2015
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Ingår i: 2015 IEEE International Conference On Communications (ICC). - : IEEE conference proceedings. - 9781467364324 ; , s. 2590-2596
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Konferensbidrag (refereegranskat)abstract
- We consider the uplink of a single cell single input multiple output (SIMO) system, in which the mobile stations use intra-cell orthogonal pilots to facilitate uplink channel estimation. In such systems, the problem of transmission power balancing between pilot and data is known to have a large impact on the mean square error (MSE) for the received signal and, consequently, on the achievable uplink data rate. In this paper, we derive a closed form expression of the MSE for the received signal as a function of the pilot and data power levels under a per-user sum pilot-data power constraint. As a major contribution, our model is developed for arbitrary channel covariance matrices and it enables us to study the impact of the number of antennas and antenna correlation structures, including the popular 3GPP spatial channel model. Numerical results suggest that the effect of the antenna spacing is limited, but the angle of arrival and angular spread have a strong and articulated impact on the MSE performance. Moreover, as the number of antennas at the base station grows large, we show that a higher percentage of the power budget should be allocated to pilot signals than with a lower number of antennas.
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| 5. |
- Fodor, Gabor, 1964-, et al.
(författare)
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Recent advances in acquiring channel state information in cellular MIMO systems
- 2019
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Ingår i: Infocommunications Journal. - : Scientific Association for Infocommunications. - 2061-2079. ; 11:3, s. 2-12
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Tidskriftsartikel (refereegranskat)abstract
- In cellular multi-user multiple input multiple output (MU-MIMO) systems the quality of the available channel state information (CSI) has a large impact on the system performance. Specifically, reliable CSI at the transmitter is required to determine the appropriate modulation and coding scheme, transmit power and the precoder vector, while CSI at the receiver is needed to decode the received data symbols. Therefore, cellular MUMIMO systems employ predefined pilot sequences and configure associated time, frequency, code and power resources to facilitate the acquisition of high quality CSI for data transmission and reception. Although the trade-off between the resources used for pilot and user data transmission has been known for long, the near-optimal configuration of the available system resources for pilot and data transmission is a topic of current research efforts. Indeed, since the fifth generation of cellular systems utilizes heterogeneous networks in which base stations are equipped with a large number of transmit and receive antennas, the appropriate configuration of pilot-data resources becomes a critical design aspect. In this article, we review recent advances in system design approaches that are designed for the acquisition of CSI and discuss some of the recent results that help to dimension the pilot and data resources specifically in cellular MU-MIMO systems.
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| 6. |
- G, Fodor, et al.
(författare)
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On providing blocking probability and throughput guarantees in a multi-service environment
- 2002
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Ingår i: International Journal of Communication Systems. - : WILEY. - 1074-5351 .- 1099-1131. ; 15:4, s. 257-285
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Tidskriftsartikel (refereegranskat)abstract
- As the Internet evolves from a packet network supporting a single best effort service class towards an integrated infrastructure supporting several service classes-some with QoS guarantees-there is a growing interest in the introduction of admission control and in devising bandwidth sharing strategies, which meet the diverse needs of QoS-assured and elastic services. In this paper we show that the extension of the classical multi-rate loss model is possible in a way that makes it useful in the performance analysis of a future admission control based Internet that supports traffic with peak rate guarantee as well as elastic traffic. After introducing the model, it is applied for the analysis of a single link, where it sheds light on the trade-off between blocking probability and throughput. For the investigation of this trade-off, we introduce the throughput-threshold constraint, which bounds the probability that the throughput of a traffic flow drops below a predefined threshold. Finally, we use the model to determine the optimal parameter set of the popular partial overlap link allocation policy: we propose a computationally efficient algorithm that provides blocking probability- and throughput guarantees. We conclude that the model and the numerical results provide important insights in traffic engineering in the Internet. Copyright (C) 2002 John Wiley Sons, Ltd.
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| 7. |
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| 8. |
- M, Telek, et al.
(författare)
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An effective numerical method to compute the moments of the completion time of Markov reward models
- 1998
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Ingår i: Computers and Mathematics with Applications. - 0898-1221 .- 1873-7668. ; 36:8, s. 59-65
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of Markov Reward Models (MRM) with preemptive resume (prs) policy results in a double transform expression, whose solution is based on the inverse transformations both in time and reward variable domain. We present a symbolic expression of moments of the completion time, from which a computationally effective recursive numerical method can be obtained. (C) 1998 Elsevier Science Ltd. All rights reserved.
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| 10. |
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