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| 2. |
- Gudmundson, Mikael
(författare)
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Analysis of Handover Algorithms
- 1991
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Ingår i: IEEE 41st Vehicular Technology Conference, 1991. Gateway to the Future Technology in Motion. - : IEEE. - 0879425822 ; , s. 537-542
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Konferensbidrag (refereegranskat)abstract
- Handover algorithms are analyzed for a simple channel model. Three performance measures are defined: the probability of lost calls, the probability of unnecessary handover, and the probability of handover. In the design of a handover algorithm, a tradeoff between these measures has to be made since they cannot be minimized simultaneously. A particular class of algorithms, linear handover algorithms, is introduced. Performance bounds are derived, and expressions for the performance measures for linear algorithms are given. In particular, a lower bound for the probability of lost calls is derived. This bound is valid as long as the signal model is correct and is not limited to the class of linear algorithms.
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| 4. |
- Gudmundson, Mikael
(författare)
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Cell Planning in Manhattan Environments
- 1992
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Ingår i: IEEE 42nd Vehicular Technology Conference. - : IEEE. - 0780306732 ; , s. 435-438
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Konferensbidrag (refereegranskat)abstract
- Using microcells is one way to meet the demand for high capacity in future mobile communication systems. In large cities, small cells can be achieved by placing base station antennas at approximately street level, using the surrounding buildings as propagation obstacles. Cell planning strategies for microcells are quite different from the cell planning strategies used for macrocells. However, as shown, the terrain structure allows a more efficient channel reuse. A simple model of a large city consisting of square blocks with streets in between (Manhattan model) is used. Efficient strategies for street microcells are suggested. Results show that for fixed planning in a microcellular system, a very small number of channel groups will suffice to achieve acceptable signal-to-interference ratios.
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| 5. |
- Gudmundson, Mikael
(författare)
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Correlation Model for Shadow Fading in Mobile Radio Systems
- 1991
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Ingår i: Electronics Letters. - : IEEE. - 0013-5194 .- 1350-911X. ; 27:23, s. 2145-2146
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Tidskriftsartikel (refereegranskat)abstract
- A simple autocorrelation model for shadow fading in mobile radio channels is proposed. The model is fitted to both large cells and microcells. Results show that the model fit is good for large to moderate cell sizes. It is however shown that the model does not provide adequate results for microcells.
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| 6. |
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| 7. |
- Gudmundson, Mikael
(författare)
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Generalized frequency hopping in mobile radio systems
- 1993
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Ingår i: IEEE Vehicular Technology Conference. - : IEEE. - 0780312678 ; , s. 788-791
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Konferensbidrag (refereegranskat)abstract
- An alternative multiple access scheme for cellular radio systems, generalized frequency hopping, is proposed. Contrary to conventional frequency hopping systems, this scheme allows for simultaneous transmission on several frequencies. The choice of frequencies is made randomly with the constraint that each frequency is not used more than once in each cell. With this random channel allocation both frequency planning and intra-cell interference are avoided. Other advantages are frequency diversity, and a very small delay. Frequency spreading and de-spreading may be implemented in digital form. The performance of this system is compared with other proposals for future mobile radio systems.
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| 9. |
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| 10. |
- Johnson, Mikael, et al.
(författare)
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Broad-band transient recording and characterization of acoustic emission events in composite laminates
- 2000
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Ingår i: Composites Science And Technology. - 0266-3538 .- 1879-1050. ; 60:15, s. 2803-2818
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Tidskriftsartikel (refereegranskat)abstract
- Acoustic emission (AE) transients due to different kinds of microdamage, such as matrix cracking, fiber breakage and local delaminations, have been recorded in glass/epoxy composite laminates. Different stacking sequences, [0 degrees, 90(2)degrees](S), [90(2)degrees, 0 degrees](S), [+45 degrees, -45 degrees](S) and [0(4)degrees], were used in order to trigger different crack mechanisms during tensile testing. The AE transients were recorded as functions of time by the use of broad-band AE transducers. In the experiments, it was observed that different types of cracks generated acoustic emission signals varying in amplitude, duration time and frequency content. It was also seen that the same type of crack produced signals with different characteristics depending on the layer in which the crack appeared and its orientation compared to the location of the transducer. The majority of signals from the tests could be divided into a few main groups. Typical signals and characteristics representing these groups are presented in the paper. The observations show that there is a potential in future development of quantitative methods for identification of damage development in composite laminates.
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