| 1. |
- Bengtsson, Mats, 1967-, et al.
(författare)
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Recent Advances on MIMO Processing in the SATURN Project
- 2002
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Ingår i: Proc. IST Mobile Communications Summit.
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Konferensbidrag (refereegranskat)abstract
- We highlight some recent results on the theory and algorithmsfor MIMO systems, obtained at the Royal Instituteof Technology (KTH) within the SATURN project.The paper includes a a new approximate expression forthe ergodic channel capacity of a MIMO system with correlatedfading, algorithms for MIMO beamforming underEIRP (equivalent isotropic radiated power) constraintsand a low-complexity algorithm for MIMO channel estimationin OFDM systems. Also, we show how transmitand beamformers can be determined in a decentralizedfashion without explicitly estimating the channel response.
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| 2. |
- Jöngren, George, et al.
(författare)
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Utilizing Partial Channel Information in the Design of Space-Time Block Codes
- 2002
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Ingår i: Proceedings of the 5th International Symposium on Wireless Personal Multimedia Communications (WPMC ’2002). - NEW YORK : IEEE. ; , s. 681-685
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Konferensbidrag (refereegranskat)abstract
- The assumption of no channel knowledge at the transmitter is inherent in the design of classical space-time codes for wireless communication. This work, on the other hand, assumes that non-perfect quantized channel information obtained from a feedback link is available at the transmitter and investigates how such channel knowledge can be incorporated into the design of space-time block codes. Efficient codes are found by means of a gradient search over a continuous alphabet. Simulation results for a Rayleigh fading scenario a system using two transmit antennas and one receive antenna show that significant gains are possible.
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| 3. |
- Klang, Göran, et al.
(författare)
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Space-time interference rejection cancellation in transmit diversity systems
- 2002
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Ingår i: International Symposium on Wireless Personal Multimedia Communications. - NEW YORK : IEEE. ; , s. 706-710
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Konferensbidrag (refereegranskat)abstract
- We consider the use of space diversity methods in conjunction withinterference rejection combining (IRC) to mitigate the impact of interferenceand noise for interference limited scenarios. The use of transmit diversityschemes in a system generally limits the interference rejection capabilities of IRC techniques. We introduce a novel space-time IRC (STIRC) scheme that exploits the spatio-temporal correlation induced by cochannel users employingtransmit diversity in the form of space-time block codes (STBC). Thus, thesystem can draw upon the benefits of interference rejection methods althoughtransmit diversity is being employed. Simulation examples are presented to illustrate the discussion and to highlight the importance of taking both the spatial and temporal structure of the interference into account.
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| 4. |
- Martin, Cristoff, et al.
(författare)
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Analytic Approximations of Eigenvalue Moments and Mean Channel Capacity for MIMO Channels
- 2002
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Ingår i: Proceedings IEEE International Conference on Acoustics, Speech, and Signal Processing. - : IEEE. ; , s. 2389-2392
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Konferensbidrag (refereegranskat)abstract
- Approximate second order moments of the squared singular values of the channel matrix of a multiple input multiple output (MIMO) system are derived. Correlation at both the receiver and the transmitter antenna arrays is allowed. The approximation converges to the true moments as either the number of transmit or receive antennas increases. Simulations indicate that the derived moments may provide a good approximation of the true moments even for realistic array sizes. As an application, an expression for the mean channel capacity is derived. The expression is simple enough to provide insight while offering promising performance when compared with simulated channel capacities.
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| 5. |
- Henriksson, Christian, et al.
(författare)
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Reducing Bluetooth Interference with Diversity Techniques in IEEE 802.11b Networks
- 2002
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Ingår i: Proceedings Nordic Signal Processing Symposium.
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Konferensbidrag (refereegranskat)abstract
- Lately different kinds of wireless networks have become more frequently used. If they occupy the same frequency band they are likely to interfere with each other. In this paper, we examine how spatial diversity can be exploited to suppress Bluetooth interference on a IEEE 802.11b network. Two dual antenna receivers, the maximum ratio combining (MRC) and the interference rejection combining (IRC) methods, have been evaluated and compared to the ordinary single antenna receiver. Simulation results show that adding spatial diversity yields a signicant reduction in biterror rate (BER) and as a consequence the throughput is increased, especially for larger fragment sizes.
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| 6. |
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| 7. |
- Hyberg, Per, et al.
(författare)
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Array Mapping : Optimal Transformation Matrix Design
- 2002
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Ingår i: Proceedings IEEE International Conference on Acoustics, Speech, and Signal Processing. - : IEEE. ; , s. 2905-2908
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Konferensbidrag (refereegranskat)abstract
- Mapping of the data output vector from an existing antenna array onto the data vector of an imaginary array of more suitable configuration is well known in array signal processing. By mapping onto an array manifold of lower dimension or uniform structure for example., processing speed can be improved. Conditions for the retaining of DOA error variance under such mapping have been formulated by several authors but the equally important systematic mapping errors, the bias, has been less treated to date. This paper uses a geometrical interpretation of a Taylor expansion of the DOA estimator cost function to derive an alternative design of the mapping matrix that almost completely removes the bias. The key feature of the proposed design is that it takes the orthogonality between the manifold mapping errors and certain gradients of the estimator cost function into account.
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| 8. |
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| 9. |
- Klang, Göran, et al.
(författare)
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Interference Rejection in Systems Employing Transmit Diversity
- 2002
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Ingår i: European Signal Processing Conference. - : EUSIPCO. - 2219-5491.
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Tidskriftsartikel (refereegranskat)abstract
- Space diversity methods provide excellent means for increasing the robustness against interference and noise in communication systems. This is well known for systems using multiple receive antennas and it holdsforsystems applying transmit diversity as well. In fact, the use of transmit diversity provide two independent means for reducing the impact of interference. Via the diversity gain and via the code rate, both related to the underlying space-time code. In this paper, we are considering the use of space diversity methods in conjunction with interference rejection combining (IRC) to mitigate the impact of interference and noise for interference limited scenarios. Transmit diversity schemes based on space-time block codes (STBC) are assumed. We elucidate the importance of taking into account the spatio-temporal correlation induced by cochannel users employing transmit diversity. A novel space-time IRC (STIRC) scheme is proposed to handle the problem. The STIRC scheme combines the simplicity of conventional IRC while taking the structure of interfering users into account. Simulation examples demonstrate significant gains compared to the use of conventional IRC.
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| 10. |
- Klang, Göran, et al.
(författare)
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Structured Semi-Blind Interference Rejection in Dispersive Multichannel Systems
- 2002
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Ingår i: IEEE Transactions on Signal Processing. - : IEEE Signal Processing Society. - 1053-587X .- 1941-0476. ; 50:8, s. 2027-2036
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Tidskriftsartikel (refereegranskat)abstract
- The impact of interference is one of the most capacity limiting factors in cellular networks today. In order to host more users in existing systems and maximize the capacity of future networks, the use of interference suppression techniques are instrumental. In this paper, we propose a structured semi-blind parameter estimation procedure to support rejection, of unknown cochannel interference (CCI) in systems facing multipath channels with non-negligible delay spread. Employing spatio-temporal processing, the proposed scheme exploits the temporal correlation present in the output signal from an antenna array and the training data of a desired user in order to find parameter estimates that fit the range space of a structured CCI model to the signal subspace of the interfering signals. Simulation results illustrating the behavior of a spatio-temporal receiver using the proposed scheme with respect to both signal-to-noise and signal-to-interference ratios (SNRs and SIRs) are presented. In addition, results highlighting the impact of the training sequence length as well as the impact of the channel model order of the CCI users are also included.
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