| 1. |
- Geijer Lundin, Erik, et al.
(författare)
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Adaptive Filtering Applied to an Uplink Load Estimate in WCDMA
- 2003
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Ingår i: Proceedings of the 57th IEEE Semiannual Vehicular Technology Conference. - Linköping : Linköping University Electronic Press. - 0780377575 ; , s. 452-456
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Konferensbidrag (refereegranskat)abstract
- In the uplink of a WCDMA system, a natural choice of resource quantity is the uplink noise rise, i.e., total received power over noise power. Unfortunately this quantity is hard to measure and estimates are often noisy. This paper focuses on relative load which is closely related to the noise rise. Model-based signal processing with change detection techniques is herein used to suppress noise and minor oscillations while being alert on fast load changes. The time varying model identified in the process can also be used for prediction of future values, something which resource management algorithms can benefit from.
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| 2. |
- Geijer Lundin, Erik, et al.
(författare)
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Characterizing Uplink Load : Concepts and Algorithms
- 2004
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Ingår i: Wireless Communications Systems and Networks. - Boston : Springer US. - 0306481901 - 0306486423 ; , s. 425-441
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Bokkapitel (refereegranskat)abstract
- The maximum capacity of a CDMA cellular system’s radio interface depends on the time varying radio environment. This makes it hard to establish the amount of currently available capacity. The received interference power is the primarily resource in the uplink. Ability to predict how different resource management decisions affect this spatial quantity is therefore of utmost importance. The uplink interference power is related to the uplink load through the pole equation. In this chapter, we discuss both theoretical and practical aspects of uplink load estimation.
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| 3. |
- Geijer Lundin, Erik, et al.
(författare)
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Uplink Load Estimates in WCDMA with Different Availability of Measurements
- 2003
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Ingår i: Proceedings of the 57th IEEE Semiannual Vehicular Technology Conference. - Linköping : Linköping University Electronic Press. - 0780377575 ; , s. 1198-1202 vol.2
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Konferensbidrag (refereegranskat)abstract
- In the uplink of a WCDMA system, a natural choice of resource management control quantity is the uplink noise rise, i.e., total received power over noise power. Unfortunately this quantity is hard to measure. In this paper, we propose and evaluate a number of noise rise estimates which all rely on path gain measurements. These measurements can be made available either periodically or event-driven as described in 3GPP (Release 99). Simulations show that event-driven measurements yield comparable performance to periodic measurements, but with much fewer measurement reports. Despite severely limited path gain knowledge due to that some users report to another RNC, we still manage to estimate the uplink noise rise reasonably well.
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| 4. |
- Geijer Lundin, Erik, et al.
(författare)
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Uplink Load Estimation in WCDMA
- 2003
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Ingår i: Proceedings of the 2003 IEEE Wireless Communications and Networking. - 0780377001 ; , s. 1669-1674 vol.3
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Konferensbidrag (refereegranskat)abstract
- All cellular radio systems have radio resource management algorithms which rely on some sort of resource quantity. In the uplink of a WCDMA system, a natural choice of such a quantity is the uplink noise rise, i.e., total received power over noise power. Unfortunately this quantity is hard to measure. In this paper, we propose and evaluate four different noise rise 711 estimates. The best performing estimate provides an average error of less than 1 dB for practical load levels. Due to low standard deviation of single estimates it is possible to apply a simple error correction algorithm.
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| 5. |
- Geijer Lundin, Erik
(författare)
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Uplink Load in CDMA Cellular Systems
- 2003
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cellular mobile systems designed to handle multimedia services are currently being developed. The primary goal for any mobile system is to provide a satisfactory quality of service, both to operators and customers. Providing good quality of service while maintaining system stability requires accurate knowledge of the system load. In particular, it is important to be able to predict how a resource management decision will affect the stability of the network. This thesis addresses the problem of characterizing and estimating the uplink load in a cellular system using CDMA (Code Division Multiple Access) in the radio interface.Uplink load can be related directly to the uplink power control problem of finding transmitter powers to support the users' quality of service requirements. This yields a rather theoretical view. Another way of looking at uplink load is to relate it to the total received power users induce in the base station antennas. Both of these views are handled and relations between them are established in this thesis.The literature survey on uplink load provided in this work concludes that practical estimates of the uplink load are generally what can be referred to as decentralized estimates; they use information gathered only in the immediate vicinity of the estimates' host node. As an alternative to these estimates, a number of centralized estimates based on information readilyavailable to the system are proposed. The usage of information from several cells makes them more sensitive to the soft capacity inherent in all CDMA cellular systems.Extensive simulations in an advanced WCDMA (Wideband Code Division Multiple Access) simulator show that the estimates statistically perform well and the performance is insensitive to non uniform traffic load.In the time domain, the load approximation can be described as oscillations superimposed on a slowly varying bias. If occasional high loads can be accepted, a non-oscillative signal representing the uplink load can be used to further increase the utilization of the resources. An algorithm is proposed to estimate the bias and a prediction of it.
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| 6. |
- Gunnarsson, Fredrik, et al.
(författare)
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Admission Control in Cellular Radio Systems Based on Relative Load Estimates
- 2001
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Ingår i: Proceedings of the Third Conference on Computer Science and Systems Engineering. - Linköping : Linköping University Electronic Press. ; , s. 163-168
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- When operating a cellular radio system nearly at full capacity, admitting yet another user may jeopardize the stability of the system as well as the performance of the individual users. Therefore, proper admission control is crucial. The core idea in this work is to predict the relative load of the system, given that a user is admitted. Then, the user will be admitted if the predicted load in the specific cell, and in its neighbors, is below some threshold. This provide an interesting alternative to algorithms based on hard capacity, which might be utilizing the resources inefficiently in order to be robust. The proposed uplink admission control algorithm utilizes measurements readily available in the system. Simulations indicate performance improvements. Furthermore, multi-services are naturally handled, and availability of high data-rate services are automatically limited with respect to coverage, compared to services of lower data-rate.
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| 7. |
- Gunnarsson, Fredrik, et al.
(författare)
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Uplink Admission Control in WCDMA Based on Relative Load Estimates
- 2002
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Ingår i: Proceedings of the 2002 IEEE International Conference on Communications. - Linköping : Linköping University Electronic Press. - 0780374002 ; , s. 3091-3095 vol.5
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Konferensbidrag (refereegranskat)abstract
- When operating a cellular radio system at nearly full capacity, admitting yet another user may jeopardize the stability of the system as well as the performance of the individual users. Therefore, proper admission control is crucial. Prior art includes algorithms which are limiting the number of users or the uplink interference per cell. Both are known to yield roughly the same performance, but the former is difficult to configure, and the latter is based on a quantity, which is hard to measure accurately. The core idea in this work is to predict the relative load of the system directly, given that a user is admitted. Then, the user will be admitted if the predicted load in the specific cell, and in its neighbors, is below some threshold. The proposed uplink relative load estimate is focused on WCDMA. It utilizes measurements readily available in that system, either periodically scheduled or from handover events. Multi-services are naturally handled, and availability of high data-rate services are automatically limited with respect to coverage, compared to services of lower data-rate. Simulations indicate that the admission control operates satisfactory in different traffic situations with a universal parameter setting. Furthermore, the reporting overhead with periodical measurements can be avoided, since handover event-driven measurements yield roughly the same performance.
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| 8. |
- Gunnarsson, Fredrik, et al.
(författare)
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Uplink Transmission Timing in WCDMA
- 2003
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Ingår i: Proceedings of the 58th IEEE Vehicular Technology Conference. - Linköping : Linköping University Electronic Press. - 0780379543 ; , s. 1688-1692 vol.3
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Konferensbidrag (refereegranskat)abstract
- In wireless network uplink communications, there is a trade off between transmission coordination to avoid overload situations, and distributed transmission decisions to adapt to fast channel variations. Here, uplink transmission timing (UTT) is proposed as a scheme to allow some load control support, while transmitting mainly when the channel is favorable. It utilizes channel state feedback in the form of power control commands, which already are available in the system. Simulations illustrate the transmission timing behavior, and also indicate that UTT is a power and intercell interference efficient scheme to transport data compared to traditional dedicated channels with continuous transmissions and to schemes where transmission decisions are random.
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| 9. |
- Gustafsson, Fredrik, et al.
(författare)
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Transmission Timing - A Control Approach to Distributed Uplink Scheduling in WCDMA
- 2004
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Ingår i: Proceedings of Reglermöte 2004. - Linköping : Linköping University Electronic Press. ; , s. 1667-1672 vol.2
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Centralized control and coordination of the connections in a wireless network is not possible in practice. To keep the delay from measure-ment instants to actuating the decisions, distributed control is required. This paper focuses on the uplink (from mobiles to base stations) and dis-cusses distributing the decision of when and when not to transmit data (distributed scheduling) to the mobiles. The scheme, uplink transmission timing, utilizes mobile transmitter power control feedback from the base station receiver to determine whether the channel is favorable or not compared to the average channel condition. Thereby, the battery consumption and disturbing power to other connections are reduced. The algorithm can be described as a feedback control system. Some transient behaviors are analyzed using systems theory, and supported by wireless network simulations of a system with a WCDMA (Wideband Code Division Multiple Access) radio interface as in most 3G systems.
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| 10. |
- Gustafsson, Fredrik, et al.
(författare)
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Uplink Load and Link Budget with Stochastic Noise Rise Levels in CDMA Cellular Systems
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The limiting factor in the uplink of all CDMA cellular systems is the relation between uplink noise rise and intended coverage. In link budgets, noise rise is usually simply handled as a constant contribution to the background noise in logarithmic scale, often referred to as interference margin. In practice, however, it is not constant. We model the uplink noise rise as a lognormal distribution, and investigate the impact to link budgets. Simulations and numerical calculations show that the uplink noise rise variance does not critically affect the uplink capacity and coverage. System feasibility and its relation to the uplink load is also discussed. It is shown that approximative load expressions provides an upper bound on the uplink load and therefore they can be used to imply system feasibility. Furthermore, the uplink load expressions provide accurate approximations of the load given that the load is within the practical limits given by the link budgets.
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