| 1. |
- Khanzadi, M Reza, 1983, et al.
(författare)
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On the Capacity of the Wiener Phase Noise Channel: Bounds and Capacity Achieving Distributions
- 2015
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 63:11, s. 4174-4184
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the capacity of the additive white Gaussian noise (AWGN) channel, affected by time-varying Wiener phase noise is investigated. Tight upper and lower bounds on the capacity of this channel are developed. The upper bound is obtained by using the duality approach, and considering a specific distribution over the output of the channel. In order to lower-bound the capacity, first a family of capacity-achieving input distributions is found by solving a functional optimization of the channel mutual information. Then, lower bounds on the capacity are obtained by drawing samples from the proposed distributions through Monte-Carlo simulations. The proposed capacity-achieving input distributions are circularly symmetric, non-Gaussian, and the input amplitudes are correlated over time. The evaluated capacity bounds are tight for a wide range of signal-to-noise-ratio (SNR) values, and thus they can be used to quantify the capacity. Specifically, the bounds follow the well-known AWGN capacity curve at low SNR, while at high SNR, they coincide with the high-SNR capacity result available in the literature for the phase-noise channel.
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| 2. |
- Mehrpouyan, Hani, 1981, et al.
(författare)
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Improving Bandwidth Efficiency in E-band Communication Systems
- 2014
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Ingår i: IEEE Communications Magazine. - 0163-6804 .- 1558-1896. ; 52:3, s. 121-128
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Tidskriftsartikel (refereegranskat)abstract
- The allocation of a large amount of bandwidth by regulating bodies in the 70/80 GHz band, i.e., the E-band, has opened up new potentials and challenges for providing affordable and reliable Gigabit per second wireless point-to-point links. This article first reviews the available bandwidth and licensing regulations in the E-band. Subsequently, different propagation models, e.g., the ITU-R and Cane models, are compared against measurement results and it is concluded that to meet specific availability requirements, E-band wireless systems may need to be designed with larger fade margins compared to microwave systems. A similar comparison is carried out between measurements and models for oscillator phase noise. It is confirmed that phase noise characteristics, that are neglected by the models used for narrowband systems, need to be taken into account for the wideband systems deployed in the E-band. Next, a new multi-input multi-output (MIMO) transceiver design, termed continuous aperture phased (CAP)-MIMO, is presented. Simulations show that CAP-MIMO enables E-band systems to achieve fiber-optic like throughputs. Finally, it is argued that full-duplex relaying can be used to greatly enhance the coverage of E-band systems without sacrificing throughput, thus, facilitating their application in establishing the backhaul of heterogeneous networks.
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| 3. |
- Czegledi, Cristian Bogdan, 1988, et al.
(författare)
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Bandlimited Power-Efficient Signaling and Pulse Design for Intensity Modulation
- 2014
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 62:9, s. 3274-3284
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a new method for power-efficient intersymbol interference-free transmission over the bandlimited intensity-modulation direct-detection channel is proposed. A new time-varying bias signal is added to the transmitted signal to make it nonnegative and provide a more power-efficient transmission than the previously considered constant bias. To exploit the benefits of the new signaling method, Nyquist and root-Nyquist pulses suitable for the use with this kind of bias are designed using two different methods. In the first method, new pulses are obtained by adding Nyquist pulses in the time domain with different combining coefficients, whereas in the second method, the pulses are obtained by the design of their frequency response. Analytical expressions for the asymptotic optical power efficiency and symbol error rate of the proposed schemes are derived and evaluated. At a spectral efficiency of 1~b/s/Hz, using on-off keying modulation and the proposed bias signal and pulses, up to 0.628 dB gains in asymptotic power efficiency can be achieved compared to the previously best known signaling scheme, which is based on squared sinc pulse shaping.
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| 4. |
- Czegledi, Cristian Bogdan, 1988, et al.
(författare)
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Bandlimited Power-Efficient Signaling for Intensity Modulation
- 2014
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Ingår i: European Conference on Optical Communication, ECOC 2014; Cannes; France; 21 September 2014 through 25 September 2014. - 9782954944401
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Konferensbidrag (refereegranskat)abstract
- A new, power-efficient signaling method for intersymbol interference-free transmission over the bandlimited intensity-modulation direct-detection channel is proposed. The method utilizes pulse-amplitude modulation with a sinusoidal bias function and is more power-efficient than previously known methods.
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| 5. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
A model-based analysis of phase jitter in RF oscillators
- 2012
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Ingår i: 2012 IEEE International Frequency Control Symposium, IFCS 2012, Proceedings. - 9781457718199 ; , s. 508-511
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Konferensbidrag (refereegranskat)abstract
- The closed-form autocorrelation function of the phase jitter accumulation process in presence of 1/f 3 and 1/f 2 shape noises is derived from the single-sideband (SSB) phase noise (PN) measurements. Exploiting the calculated autocorrelation function, a lower bound for the minimum achievable mean square error (MSE) of the PN prediction in a typical single-input singleoutput communication system is computed. This bound links the performance of a communication system suffering from the PN directly to the SSB PN measurements.
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| 6. |
- Khanzadi, M Reza, 1983, et al.
(författare)
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A Novel Cognitive Modulation Method Considering the Performance of Primary User
- 2010
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Ingår i: Wireless Advanced (WiAD), 2010 6th Conference on. - 9781424470693 ; , s. 1 - 6
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a new modulation method foran uncoded cognitive transmission (secondary user transmission)in presence of a Primary User (PU) for the AWGN channel.Interference of the PU is assumed to be known at the transmitterof Cognitive User (CU) non-causally. Based on this knowledge,for the design of the modulator and demodulator of the CU,a symbol by symbol approach is studied which can fulfill thecoexistence conditions of the CU and the PU of the band. In thisscheme, the modulator and demodulator of CU are designedjointly by solving an optimization problem to mitigate theinterference of the PU and minimize the symbol error probability(Pe) in CU’s communication link without increasing the symbolerror probability (Pe) of the PU. The proposed method is amodulation approach in a single (complex-valued) dimensionrather than a high dimensional coding scheme. Although thisone-dimensional method is not capacity achieving, we show it stillhas a remarkable performance with low amount of complexity.An implementation algorithm for our modulation method is alsopresented and the performance of this method is evaluated byexperimental results.
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| 7. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
Calculation of the Performance of Communication Systems from Measured Oscillator Phase Noise
- 2014
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Ingår i: IEEE Transactions on Circuits and Systems I: Regular Papers. - 1549-8328 .- 1558-0806. ; 61:5, s. 1553-1565
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Tidskriftsartikel (refereegranskat)abstract
- Oscillator phase noise (PN) is one of the major problems that affect the performance of communication systems. In this paper, a direct connection between oscillator measurements, in terms of measured single-side band PN spectrum, and the optimal communication system performance, in terms of the resulting error vector magnitude (EVM) due to PN, is mathematically derived and analyzed. First, a statistical model of the PN, considering the effect of white and colored noise sources, is derived. Then, we utilize this model to derive the modified Bayesian Cramer-Rao bound on PN estimation, and use it to find an EVM bound for the system performance. Based on our analysis, it is found that the influence from different noise regions strongly depends on the communication bandwidth, i.e., the symbol rate. For high symbol rate communication systems, cumulative PN that appears near carrier is of relatively low importance compared to the white PN far from carrier. Our results also show that 1/f^3 noise is more predictable compared to 1/f^2 noise and in a fair comparison it affects the performance less.
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| 8. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
Capacity of SIMO and MISO Phase-Noise Channels with Common/Separate Oscillators
- 2015
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 63:9, s. 3218-3231
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Tidskriftsartikel (refereegranskat)abstract
- In multiple antenna systems, phase noise due to instabilities of the radio-frequency (RF) oscillators, acts differently depending on whether the RF circuitries connected to each antenna are driven by separate (independent) local oscillators (SLO) or by a common local oscillator (CLO). In this paper, we investigate the high-SNR capacity of single-input multiple-output (SIMO) and multiple-output single-input (MISO) phase-noise channels for both the CLO and the SLO configurations.Our results show that the first-order term in the high-SNR capacity expansion is the same for all scenarios (SIMO/MISO and SLO/CLO), and equal to 0.5ln(SNR), where SNR stands for the signal-to-noise ratio. On the contrary, the second-order term, which we refer to as phase-noise number, turns out to be scenario-dependent. For the SIMO case, the SLO configuration provides a diversity gain, resulting in a larger phase-noise number than for the CLO configuration. For the case of Wiener phase noise, a diversity gain of at least 0.5ln(M) can be achieved, where M is the number of receive antennas. For the MISO, the CLO configuration yields a higher phase-noise number than the SLO configuration. This is because with the CLO configuration one can obtain a coherent-combining gain through maximum ratio transmission (a.k.a. conjugate beamforming). This gain is unattainable with the SLO configuration.
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| 9. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
Effect of Synchronizing Coordinated Base Stations on Phase Noise Estimation
- 2013
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Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. - 9781479903566 ; , s. 4938-4942
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Konferensbidrag (refereegranskat)abstract
- In this paper, we study the problem of oscillator phase noise (PN) estimation in coordinated multi-point (CoMP) transmission systems. Specifically, we investigate the effect of phase synchronization between coordinated base stations (BSs) on PN estimation at the user receiver. In this respect, the Bayesian Cramer-Rao bound for PN estimation is derived which is a function of the level of phase synchronization between the coordinated BSs. Results show that quality of BS synchronization has a significant effect on the PN estimation.
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| 10. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
Estimation of Phase Noise in Oscillators with Colored Noise Sources
- 2013
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Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 17:11, s. 2160-2163
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Tidskriftsartikel (refereegranskat)abstract
- In this letter we study the design of algorithms for estimation of phase noise (PN) with colored noise sources. A soft-input maximum a posteriori PN estimator and a modified soft-input extended Kalman smoother are proposed. The performance of the proposed algorithms are compared against those studied in the literature, in terms of mean square error of the PN estimation, and symbol error rate of the considered communication system. The comparisons show that considerable performance gains can be achieved by designing estimators that employ correct knowledge of the PN statistics.
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