| 1. |
- Blom, Jonas, et al.
(författare)
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Pole Placement Design of Power Control Algorithms
- 1999
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Ingår i: Proceedings of the 49th IEEE Vehicular Technology Conference. - Linköping : Linköping University Electronic Press. - 0780355652
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Konferensbidrag (refereegranskat)abstract
- Time delays reduces the performance of any controlled system. If neglected in the design phase, the system may even become unstable when using the designed controller. Several power control strategies have been proposed in order to improve the capacity of cellular radio systems, but time delays are usually neglected. Here, it is shown that the problems can be handled by considering the time delays in the design phase in order to choose the appropriate parameter values. Most popular algorithms can be seen as special cases of an integrating controller. This structure is extended first to a proportional integrating (PI)-controller and then further on to a general linear controller of higher orders. Corresponding design procedures are outlined based on techniques, such as pole placement, from the field of automatic control. The PI-controller is a very appealing choice of structure, with better performance compared to an I-controller and less complex than a higher order controller. The benefits are further illuminated by network simulations.
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| 2. |
- Fischer, Sven, et al.
(författare)
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System performance evaluation of mobile positioning methods
- 1999
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Ingår i: 1999 IEEE 49TH VEHICULAR TECHNOLOGY CONFERENCE. - : IEEE. - 0780355652 ; , s. 1962-1966
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Konferensbidrag (refereegranskat)abstract
- This paper presents a simulation methodology for evaluating the performance of location techniques for cellular systems. The simulation tool developed enables quantification of the final system performance for various choices of components such as measurement techniques, channel models and position computation methods. Positioning performance of a GSM and IS-136 cellular system is shown for a specific choice of measurements and algorithms in various radio environments. The variation in performance with the choices of system parameters such as number of measurements made per position computation is shown.
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| 3. |
- Flament, Maxime, et al.
(författare)
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An Approach to Fourth Generation Wireless Infrastructures - Scenarios and Key Research Issues
- 1999
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Ingår i: Vehicular Technology Conference, 1999 IEEE 49th. - : IEEE. - 0780355652 ; , s. 1742-1746, s. 1742-1746
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Konferensbidrag (refereegranskat)abstract
- Studying the feasibility and viability of various future infrastructure architectures and potential road-maps of their deployment is the focus of the 4th Generation Wireless Infrastructures (4GW) project within the strategic Personal Computing and Communication (PCC) program (Molin 1998). In attempting to realize the PCC vision “mobile multimedia to all at today's prices for fixed telephony”, a difficult problem arises. In contrast to the process of solving engineering and business problems in current or imminent wireless systems, where system concepts, requirements and markets are reasonably well known, very little is known about these things over a 10 year horizon. The approach used in the project to tackle this problem, is to use various scenario techniques. Plausible scenarios which describe the telecommunication scene in 2010 and which are used to determine potential technological and other bottlenecks in order to find key areas for research in this field are a very important element in these studies. Some of these scenarios are presented in this paper, together with some implications regarding bottlenecks and key research issues. The results are presented in terms of working assumptions (WAs) used with the project. The WAs are also proposed to provide a framework for interrelating different research activities within PCC.
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| 4. |
- Gunnarsson, Fredrik, et al.
(författare)
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Estimation of the Carrier-to-Interference Ratio in Cellular Radio Systems
- 1999
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Ingår i: Proceedings of the 49th IEEE Vehicular Technology Conference. - Linköping : Linköping University Electronic Press. - 0780355652 ; , s. 1312-1316 vol.2
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The problem to track time-varying parameters in cellular radio systems is studied. The focus is on estimation based only on the signals that are readily available. Previous work has demonstrated very good performance relying on analog measurement. In a real system most of the information is lost due to quantization and sampling at a rate that might be as low as 2 Hz (GSM case). Therefore a different approach is required and for that matter a maximum likelihood estimator has been designed and exemplified in the case of GSM. The needed probability functions of the measurements cannot be described analytically. Instead point-mass approximations can be obtained from Monte-Carlo simulations for each point in a grid covering the interesting parameter space. The proposed algorithm can be tuned to track both slowly and fast varying parameters individually. Since most computations take place in the base stations, the estimator is ready for implementation in a second generation wireless system. No update of the software in the mobile stations is needed.
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| 5. |
- Gunnarsson, Fredrik, et al.
(författare)
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Improved Performance Using Nonlinear Components in Power Control Algorithms
- 1999
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Ingår i: Proceedings of the 49th IEEE Vehicular Technology Conference. - Linköping : Linköping University Electronic Press. - 0780355652 ; , s. 1276-1280 vol.2
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Konferensbidrag (refereegranskat)abstract
- When employing power control algorithms in real systems there are anumber of problems that have to be considered, of which some are addressed in this work. It is probably impossible to solve the problems using a linear controller, and as an extension, various nonlinear components and their applicability are discussed. Problems due to hardware and external constraints have been identified in previous work, and here anti-reset windup techniques are reviewed and employed. Previous proposals can be seen as special cases. Sometimes it is desirable to employ several algorithms in parallel, and then use a device to state priorities, i.e., to switch between the algorithms. The applicability of switches and selectors are described and exemplified as proposed solutions to the low interference problem, where a C/I balancing algorithm causes a user to use a too low a power. The benefits of using the proposed nonlinear components are further illustrated by network simulations.
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| 6. |
- Hokfelt, Johan, et al.
(författare)
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A survey on trellis termination alternatives for turbo codes
- 1999
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Ingår i: Proc. IEEE Vehicular Technology Conference. - 0780355652 ; 3, s. 2225-2229
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Konferensbidrag (refereegranskat)abstract
- Numerous strategies and methods for trellis termination of turbo codes have been presented and proposed in the literature. In this paper the most common trellis termination methods are compared and their relative performances are investigated. An important observation is that the performance of a termination method is highly dependent on the particular interleaver choice. Conclusions should thus be drawn for the combination of interleaver and termination method, and not for the termination method alone. Another important conclusion is that the particular choice of termination method is not crucial for the error correcting performance, as long as certain precautions are taken regarding the choice of interleaver
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| 7. |
- Hokfelt, Johan, et al.
(författare)
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Turbo codes: Correlated extrinsic information and its impact on iterative decoding performance
- 1999
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Ingår i: Proc. IEEE Vehicular Technology Conference. - 0780355652 ; 3, s. 1871-1875
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Konferensbidrag (refereegranskat)abstract
- The performance of a turbo code is dependent on two properties of the code: its distance spectrum and its suitability to be iteratively decoded. The performance of iterative decoding depends on the quality of the extrinsic inputs; badly correlated extrinsic inputs can deteriorate the performance. While most turbo coding literature assumes that the extrinsic information is uncorrelated, we investigate these correlation properties. An iterative decoding suitability measure is presented, intended to serve as an indication on the degree of correlation between extrinsic inputs. The suitability measure can be used as a complement to the weight distribution when ranking interleavers
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| 8. |
- Karlsson, Robert S.
(författare)
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Sharing radio resources in hierarchical cell structures utilizing slow frequency hopping
- 1999
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Ingår i: Vehicular Technology Conference, 1999 IEEE 49th. - New York : IEEE. - 0780355652 ; , s. 412-416
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Konferensbidrag (refereegranskat)abstract
- One way to decrease total system cost and improve efficiency in future mobile communication systems is a structure with cells covering the same area. This is often referred to as a hierarchical cell structure, HCS. We investigate the novel option of using slow frequency hopping, SFH, to combat interference between layers in an HCS where the same spectrum is used in all layers to avoid trunking losses and frequency planning between layers. We compare, in terms of capacity, the alternative of splitting the available bandwidth in separate parts. Results show that SFH manages to handle the inter-layer interference of an HCS if adequate admission and power control is used, but splitting the spectrum gives higher capacity.
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| 9. |
- Malm, Peter, et al.
(författare)
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Optimum data rate in cellular systems
- 1999
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Ingår i: Proc. IEEE Vehicular Technology Conference. - 0780355652 ; 3, s. 1856-1860
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Konferensbidrag (refereegranskat)abstract
- The spectrum efficiency in a cellular radio system is affected by the data rates used in the system. High data rates may result in low spectrum efficiency if the frequency reuse is low. The spectrum efficiency may be enhanced by using adaptive modulation with carefully chosen data rates. We present an analytical method, based on a lower bound on the BER, for finding the best data rates. The method results in the best code rates to be used with QPSK, 8-PSK, and 16-QAM in an adaptive fashion. The general conclusion is that a large number of carefully chosen data rates enhances the spectrum efficiency
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| 10. |
- Pettersson, Stefan
(författare)
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A Comparison of Radio Resource Management Strategies in Bunched Systems for Indoor Communication
- 1999
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Ingår i: Vehicular Technology Conference, 1999 IEEE 49th. - New York : IEEE. - 0780355652 ; , s. 402-406
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate the performance of different channel selection strategies in a 3-dimensional indoor environment. The selection strategies are part of a locally centralized or bunched radio communication system using the SIR as a basis for the channel selection decisions. We evaluate the capacity and the complexity of the system for the different strategies. In the performance evaluation, Fixed Channel Assignment (FCA) is used as a reference. The result show that the capacity is more than five times higher in the bunched system compared with the FCA system for the LNF (Lowest Number First) strategy. We also investigate the impact power control has on the system performance.
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