| 61. |
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| 62. |
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| 63. |
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| 64. |
- Rashidi Avendi, Moslem, 1979, et al.
(författare)
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A NLLS based sub-Nyquist rate Spectrum Sensing for Wideband Cognitive Radio
- 2011
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Ingår i: Fifth IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks 2011(DySPAN 2011). - 9781457701788 ; , s. 545-551
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Konferensbidrag (refereegranskat)abstract
- For systems and devices, such as cognitive radio and networks, that need to be aware of available frequency bands, spectrum sensing has an important role. A major challenge in this area is the requirement of a high sampling rate in the sensing of a wideband signal. In this paper a wideband spectrum sensing method is presented that utilizes a sub-Nyquist sampling scheme to bring substantial savings in terms of the sampling rate. The correlation matrix of a finite number of noisy samples is computed and used by a NLLS estimator to detect the occupied and vacant channels of the spectrum. We provide an expression for the detection threshold as a function of sampling parameters and noise power. Also, a sequential forward selection algorithm is presented to find the occupied channels in a low complexity. The method can be applied to both correlated and uncorrelated wideband multichannel signals. A comparison with conventional energy detection using Nyquist-rate sampling shows that the proposed scheme can yield similar performance for SNR above 4 dB with a factor of 3 smaller sampling rate.
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| 65. |
- Rashidi Avendi, Moslem, 1979, et al.
(författare)
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A Wideband Spectrum Sensing Method For Cognitive Radio Using Sub-Nyquist Sampling
- 2011
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Ingår i: 2011 Digital Signal Processing and Signal Processing Education Meeting, DSP/SPE 2011 - Proceedings. - 9781612842271 ; , s. 30-35
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Konferensbidrag (refereegranskat)abstract
- Spectrum sensing is a fundamental component in cognitiveradio. A major challenge in this area is the requirement of a high sampling rate in the sensing of a wideband signal. In this paper a wideband spectrum sensing model is presented that utilizes a sub-Nyquist sampling scheme to bring substantial savings in terms of the sampling rate. The correlation matrix of a finite number of noisy samples is computed and used by a subspace estimator to detect the occupied and vacant channels of the spectrum. In contrast with common methods, the proposed method does not need the knowledge of signal properties that mitigates the uncertainty problem. We evaluate the performance of this method by computing the probability of detecting signal occupancy in terms of the number of samples and the SNR of randomly generated signals. The results show a reliable detection even in low SNR and small number of samples.
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| 66. |
- Razavi, Aidin, 1982, et al.
(författare)
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Optimal Aperture Distribution for Maximum Power Transfer in Planar Lossy Multilayered Matters
- 2015
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Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856
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Konferensbidrag (refereegranskat)abstract
- We combine array-signal-processing and spectral domain techniques to determine the optimal aperture current distribution that maximizes the power coupling between two antenna apertures which are located on opposing sides of a multilayered lossy structure in the near-field. The resulting optimal distribution can be used as a reference in the design of antennas for near-field applications, such as for the detection of foreign objects in lossy media, wireless charging of implant batteries, or near-field communications with an implant. A MoM approach is formulated to study the performance of the optimal aperture currents in a simulated detection application in the presence of a small PEC patch, and it is shown that the optimal aperture current can improve the system sensitivity and increase the detection probability of the object.
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| 67. |
- Razavi, Aidin, 1982, et al.
(författare)
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Optimal aperture distribution for near-field detection of foreign objects in lossy media
- 2014
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Ingår i: 2014 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, APWC 2014. - 9781467356923 ; , s. 659-662
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Konferensbidrag (refereegranskat)abstract
- We determine the optimal source aperture field distribution to maximize the power transfer through a lossy medium from the transmitter aperture to a receiver aperture located in the near-field region. The optimal distribution is determined by applying array signal processing techniques to aperture field modes. By designing the system to be sensitive to the presence of foreign objects in a homogenous matter, the synthesized optimal aperture distribution increases the detection probability of foreign objects in various near-field applications, such as those that can detect potentially hazardous contaminations in food.
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| 68. |
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| 69. |
- Seifi, Nima, 1981, et al.
(författare)
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An Efficient Signaling for Multi-mode Transmission in Multi-user MIMO
- 2010
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Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. - 9781424442966 ; , s. 3402-3405
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Konferensbidrag (refereegranskat)abstract
- In this paper the downlink of a multi-user MIMO (MUMIMO)system with multi-mode transmission is considered.We propose a low-complexity algorithm for selecting usersand the corresponding number of data streams to each user,denoted as user transmission mode (UTM). The selectionis only based on the average received signal-to-noise ratio(SNR) from the base station (BS) for each user. This reducesthe overall amount of feedback for scheduling, as opposedto techniques that assume perfect instantaneous channelstate information (CSI) from all users. Analytical averagethroughput approximations are derived for each user at different UTMs. Simulation results demonstrate that the proposed algorithm provides performance close to dirty paper coding (DPC) with considerably reduced feedback.
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| 70. |
- Seifi, Nima, 1981, et al.
(författare)
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Coordinated Single-Cell vs Multi-Cell Transmission with Limited-Capacity Backhaul
- 2010
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Ingår i: IEEE Asilomar Conf. on Signals, Systems, and Computers, Pacific Grove, CA, Nov. 2010. - 1058-6393. - 9781424497218 ; , s. 1217-1221
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Konferensbidrag (refereegranskat)abstract
- Base station coordination is an efficient techniqueto transcend the limits on spectral efficiency imposed by intercellinterference. In this paper, we compare the performance ofdifferent coordination strategies with different amount of channelstate information (CSI) and data sharing among the coordinatingbase stations. We focus on the effect of limited backhaul capacityin a two-cell network. Contrary to the common belief, we showthat coordination strategies with no data and only limited CSIsharing is preferred to those with full data and CSI sharing whenthe backhaul capacity is relatively low and the edge SNR is high.
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