| 1. |
- Andersson, Sören, et al.
(författare)
-
A Study of Adaptive Arrays for Mobile Communication Systems
- 1990
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The application of adaptive antenna techniques to increase the channel capacity in mobile radio communication is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting mode. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction finding following by optimal combination of the antenna outputs. Comparisons to a method based on reference signals are made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements.
|
|
| 2. |
- Andersson, Sören, et al.
(författare)
-
An adaptive array for mobile communication systems
- 1991
-
Ingår i: IEEE Transactions on Vehicular Technology. - Toronto, Ont, Can : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9545 .- 1939-9359. ; 40:1 pt 2, s. 230-236, s. 3289-3292
-
Tidskriftsartikel (refereegranskat)abstract
- The use of adaptive antenna techniques to increase the channel capacity is discussed. Directional sensitivity is obtained by using an antenna array at the base station, possibly both in receiving and transmitting modes. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction-finding followed by optimal combination of the antenna outputs. Comparison with a method based on reference signals is made. Computer simulations are carried out to test the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting cochannel interference, albeit at the expense of high computational requirements.
|
|
| 3. |
|
|
| 4. |
- Carlsson, Christina
(författare)
-
Vehicle Size and Orientation Estimation Using Geometric Fitting
- 2000
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Over the years imaging laser radar systems have been developed for both military and civilian applications. Among the applications we note collection of 3D data for terrain modelling and object recognition. One part of the object recognition process is to estimate the size and orientation of the object.This thesis concerns a vehicle size and orientation estimation process based on scanning laser radar data. Methods for estimation of length and width of vehicles are proposed. The work is based on the assumption that from a top view mos tvehicles’ edges are approximately of rectangular shape. Thus, we have a rectangle fitting problem.The first step in the process is sorting of data into different lists containing object data and data from the ground closest to the object. Then a rectangle with minimal area is estimated based on object data only. We propose an algorithm for estimation of the minimum rectangle area containing the convex hull of the object data. From the rectangle estimate, estimates of the length and width of the objectcan be retrieved.The first rectangle estimate is then improved using least squares methods based on both object and ground data. Both linear and nonlinear least squares methods are described. These improved estimates of the length and width are less biased compared to the initial estimates.Three algorithms are evaluated; a minimum rectangle estimator proposed by the author, the mixed LS-TLS algorithm and a quasi-Newton algorithm. The algorithms are applied to both simulated and real laser radar data.The thesis ends with a discussion of the assumptions that this work is based on and some suggestions of future work.
|
|
| 5. |
- Ericsson, Anders, et al.
(författare)
-
Fast Power Control to Counteract Rayleigh Fading in Cellular Radio Systems
- 1996
-
Ingår i: Proceedings of Radiovetenskaplig Konferens 1996. ; , s. 365-369
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In urban areas, cellular radio signals are subject to Rayleigh fading, which results in rapid changes in the channel gain. For TDMA-systems without the possibility of frequency hopping, this can cause severe problems for slowly moving cellular phones.This thesis studies the possibility to use fast power control to counteract the problems introduced by Rayleigh fading in the up link. Simulations with two mobiles, with restrictions of power levels and rate of power change are made.A two mode power control algorithm basing its control decisions on channel gain predictions is investigated. An important part of the thesis deals with the problem of modeling the gain of a Rayleigh fading channel using regression models, subspace models, and neural network models. Subspace models show the best performance in the noise free case but are very sensitive to noise. Combined with the power control algorithm, the choice of models seems to be of little importance when the noise level is low. The bit-error-rate in simulations is significantly reduced for low noise levels compared to a balanced strategy giving both mobiles equal Carrier-to-Interference-ratio. A comparison with the optimal solution, derived with dynamic programming under the power constraints, indicates that the algorithm is reasonably robust with respect to low noise levels. For higher noise levels, recursive autoregression models of low orders seem to be the most robust ones while subspace models and neural network models are the least robust.
|
|
| 6. |
- Ericsson, Anders
(författare)
-
Fast Power Control to Counteract Rayleigh Fading in Cellular Radio Systems
- 1995
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In urban areas, cellular radio signals are subject to Rayleigh fading, which results in rapid changes in the channel gain. For TDMA-systems without the possibility of frequency hopping, this can cause severe problems for slowly moving cellular phones.This thesis studies the possibility to use fast power control to counteract the problems introduced by Rayleigh fading in the up link. Simulations with two mobiles, with restrictions of power levels and rate of power change are made.A two mode power control algorithm basing its control channel gain predictions is investigated. An important part deals with the problem of modeling the gain of a Rayleigh fading channel using regression models, subspace models, and neural network models. Subspace models show the best performance in the noise free case but are very sensitive to noise. Combined with the power control algorithm, the choice of models seems to be of little importance when the noise level is low. The bit-error-rate in simulations is significantly reduced for low noise levels compared to a balanced strategy giving both mobiles equal Carrier-to-Interference-ratio. A comparison with the optimal solution, derived with dynamic programming under the power constraints, indicates that the algorithm is reasonably robust with respect to low noise levels. For higher noise levels, recursive autoregression models of low orders seem to be the most robust ones while subspace models and neural network models are the least robust.
|
|
| 7. |
- Forsman, Krister, et al.
(författare)
-
Merging 'Reasoning' and Filtering in a Bayesian Framework : Some Sensitivity and Optimality Aspects
- 1989
-
Ingår i: Proceedings of the 28th Conference on Decision and Control. - Linköping : Linköping University. ; , s. 1427-1429
-
Konferensbidrag (refereegranskat)abstract
- It is shown how to incorporate symbolic or logical knowledge into a conventional framework of noisy observations in dynamical systems. The idea is based on approximating the optimal solution that could, theoretically, be computed if a complete Bayesian framework were known (and infinite computational power were available). The nature of the approximations, the deviations from optimality and the sensitivity to ad hoc parameters are specifically addressed.
|
|
| 8. |
- Forsman, Krister, et al.
(författare)
-
Merging 'Reasoning' and Filtering in a Bayesian Framework - Some Sensitivity and Optimality Aspects
- 1991
-
Ingår i: International journal of adaptive control and signal processing (Print). - : Wiley. - 0890-6327 .- 1099-1115. ; 5:2, s. 93-106
-
Tidskriftsartikel (refereegranskat)abstract
- An approach is described how to incorporate knowledge of symbolic/logic character into a conventional framework of noisy observations in dynamical systems. The idea is based on approximating the optimal solution that could theoretically be computed if a complete Bayesian framework were known (and infinite computational power were available). The nature of the approximations, the deviations from optimality and the sensitivity to ad hoc parameters are specifically addressed. This merging of logic and numerics is essential in many problems of adaptation in control and signal processing.
|
|
| 9. |
- Grönwall, Christina, et al.
(författare)
-
Ground Target Recognition using Rectangle Estimation
- 2005
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We propose a ground target recognition method based on 3-D laser radar data. The method handles general 3-D scattered data. It is based on the fact that man-made objects of complex shape can be decomposed to a set of rectangles. The ground target recognition method consists of four steps; 3-D size and orientation estimation, target segmentation into parts of approximately rectangular shape, identification of segments that represent the target's functional/main parts, and target matching with CAD models. The core in this approach is rectangle estimation. The performance of the rectangle estimation method is evaluated statistically using Monte Carlo simulations. A case study on tank recognition is shown, where 3-D data from four fundamentally different types of laser radar systems are used. Although the approach is tested on rather few examples, we believe that the approach is promising.
|
|
| 10. |
- Grönwall, Christina, et al.
(författare)
-
Ground Target Recognition using Rectangle Estimation
- 2006
-
Ingår i: IEEE Transactions on Image Processing. - Linköping : IEEE Signal Processing Society. - 1057-7149 .- 1941-0042. ; 15:11, s. 3400-3408
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a ground target recognition method based on 3-D laser radar data. The method handles general 3-D scattered data. It is based on the fact that man-made objects of complex shape can be decomposed to a set of rectangles. The ground target recognition method consists of four steps; 3-D size and orientation estimation, target segmentation into parts of approximately rectangular shape, identification of segments that represent the target's functional/main parts, and target matching with CAD models. The core in this approach is rectangle estimation. The performance of the rectangle estimation method is evaluated statistically using Monte Carlo simulations. A case study on tank recognition is shown, where 3-D data from four fundamentally different types of laser radar systems are used. Although the approach is tested on rather few examples, we believe that the approach is promising.
|
|
