| 1. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
On the Capacity of the Wiener Phase Noise Channel: Bounds and Capacity Achieving Distributions
- 2015
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 63:11, s. 4174-4184
-
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)
-
Improving Bandwidth Efficiency in E-band Communication Systems
- 2014
-
Ingår i: IEEE Communications Magazine. - 0163-6804 .- 1558-1896. ; 52:3, s. 121-128
-
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)
-
Bandlimited Power-Efficient Signaling and Pulse Design for Intensity Modulation
- 2014
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 62:9, s. 3274-3284
-
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)
-
Bandlimited Power-Efficient Signaling for Intensity Modulation
- 2014
-
Ingår i: European Conference on Optical Communication, ECOC 2014; Cannes; France; 21 September 2014 through 25 September 2014. - 9782954944401
-
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
-
Ingår i: 2012 IEEE International Frequency Control Symposium, IFCS 2012, Proceedings. - 9781457718199 ; , s. 508-511
-
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)
-
A Novel Cognitive Modulation Method Considering the Performance of Primary User
- 2010
-
Ingår i: Wireless Advanced (WiAD), 2010 6th Conference on. - 9781424470693 ; , s. 1 - 6
-
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
-
Ingår i: IEEE Transactions on Circuits and Systems I: Regular Papers. - 1549-8328 .- 1558-0806. ; 61:5, s. 1553-1565
-
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
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 63:9, s. 3218-3231
-
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
-
Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. - 9781479903566 ; , s. 4938-4942
-
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
-
Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 17:11, s. 2160-2163
-
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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| 11. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
High-SNR Capacity of Multiple-Antenna Phase-Noise Channels with Common/Separate RF Oscillators
- 2015
-
Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467364324 ; , s. 4012-4017
-
Konferensbidrag (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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| 12. |
- Khanzadi, M Reza, 1983
(författare)
-
Modeling and Estimation of Phase Noise in Oscillators with Colored Noise Sources
- 2013
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The continuous increase in demand for higher data rates due to applications with massive number of users motivates the design of faster and more spectrum efficient communication systems. In theory, the current communication systems must be able to operate close to Shannon capacity bounds. However, the real systems perform below capacity limits, mainly due to channel estimation error and hardware impairments that have been neglected by idealistic or simplistic assumptions on the imperfections. Oscillator phase noise is one of the hardware impairments that is becoming a limiting factor in high data rate digital communication systems. Phase noise severely limits the performance of systems that employ dense constellations. Moreover, the level of phase noise (at a given off-set frequency) increases with carrier frequency which means that the problem of phase noise may be even more severe in systems with high carrier frequency.The focus of this thesis is on finding accurate statistical models of phase noise, as well as the design of efficient algorithms to mitigate the effect of this phenomenon on the performance of modern communication systems. First we derive the statistics of phase noise with white and colored noise sources in free-running and phase-locked-loop-stabilized oscillators. We investigate the relation between real oscillator phase noise measurements and the performance of communication systems by means of the proposed model. Our findings can be used by hardware and frequency generator designers to better understand the effect of phase noise with different sources on the system performance and optimize their design criteria respectively. Then, we study the design of algorithms for estimation of phase noise with colored noise sources. A soft-input maximum a posteriori phase noise estimator and a modified soft-input extended Kalman smoother are proposed. The performance of the proposed algorithms is compared against that of those studied in the literature, in terms of mean square error of phase noise 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 phase noise statistics. The performance improvement is more significant in low-SNR or low-pilot density scenarios.
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| 13. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
On Models, Bounds, and Estimation Algorithms for Time-Varying Phase Noise
- 2011
-
Ingår i: 5th International Conference on Signal Processing and Communication Systems (ICSPCS2011). - 9781457711800 ; , s. Art Nr. 6140897-
-
Konferensbidrag (refereegranskat)abstract
- In this paper, first, a new discrete-time model of phase noise for digital communication systems, which is a more accurate model compared to the classical Wiener model, is proposed based on a comprehensive continuous-time representation of time-varying phase noise, and statistical characteristics of this model are derived. Next, the non-data-aided (NDA) and decision-directed (DD) maximum-likelihood (ML) estimators of time-varying phase noise, using the proposed discrete-time model are derived. To evaluate the performance of the proposed estimators, the Cramer-Rao lower bound (CRLB) for each estimation approach is derived and by using Monte-Carlo simulations it is shown that the mean-square error (MSE) of the proposed estimators converges to the CRLB at moderate signal-to-noise ratios (SNR). Finally, simulation results show that the proposed estimators outperform existing estimation methods as the variance of the phase noise process increases.
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| 14. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
Optimal Modulation for Cognitive Transmission over AWGN and Fading Channels
- 2011
-
Ingår i: 17th European Wireless Conference 2011, EW 2011; Vienna; Austria; 27 April 2011 through 29 April 2011. - 9783800733439 ; , s. 575-580
-
Konferensbidrag (refereegranskat)abstract
- This paper proposes a new modulation method for an uncoded cognitive transmission (secondary user transmission) in presence of a Primary User (PU) for AWGN and time-varying flat-fading channels. Interference symbol of the PU is assumed to be known at the transmitter of the Cognitive User (CU) beforehand. Based on this knowledge and using a symbol by symbol approach, we design a CU modulation which can fulfill the coexistence conditions of the CU and the PU. The proposed method is a low-complexity modulation approach in a single (complex-valued) dimension rather than a high dimensional coding scheme, but still it achieves good performance. The robustness of the method is also investigated in case of having an imperfect knowledge about the PU transmitted symbols. An implementation algorithm for our modulation method is presented and its performance is evaluated by experiments.
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| 15. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
Oscillator Phase Noise and Small-Scale Channel Fading in Higher Frequency Bands
- 2014
-
Ingår i: 2014 IEEE Globecom Workshops, GC Wkshps 2014; Austin; United States; 8 December 2014 through 12 December 2014. - 9781479974702 ; , s. 410-415
-
Konferensbidrag (refereegranskat)abstract
- This paper investigates the effect of oscillator phasenoise and channel variations due to fading on the performance of communication systems at frequency bands higher than 10GHz. Phase noise and channel models are reviewed and technology dependent bounds on the phase noise quality of radio oscillators are presented. Our study shows that, in general, both channel variations and phase noise can have severe effects on the system performance at high frequencies. Importantly, their relative severity depends on the application scenario and system parameters such as center frequency and bandwidth. Channel variations are seen to be more severe than phase noise when the relative velocity between the transmitter and receiver is high. On the other hand, performance degradation due to phase noise can be more severe when the center frequency is increased and thebandwidth is kept a constant, or when oscillators based on low power CMOS technology are used, as opposed to high powerGaN HEMT based oscillators.
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| 16. |
- Khanzadi, M Reza, 1983
(författare)
-
Phase Noise in Communication Systems--Modeling, Compensation, and Performance Analysis
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The continuous increase in demand for higher data rates due to applications with massive number of users motivates the design of faster and more spectrum efficient communication systems. In theory, the current communication systems must be able to operate close to Shannon capacity bounds. However, real systems perform below capacity limits, mainly because of considering too idealistic or simplistic assumptions on the imperfections such as channel estimation errors or hardware impairments. Oscillator phase noise is one of the hardware impairments that is becoming a limiting factor in high data rate digital communication systems. Phase noise severely limits the performance of systems that employ dense constellations. Moreover, the level of phase noise (at a given off-set frequency) increases with carrier frequency, which means that the problem of phase noise may be worse in systems with high carrier frequencies.The focus of this thesis is on: i) finding accurate statistical models of phase noise, ii) designing efficient algorithms to mitigate the effect of this phenomenon, iii) analyzing the Shannon capacity of the single and multiple-antenna communication systems affected by phase noise. First, a new statistical model of phase noise valid for free-running and phase-locked-loop-stabilized oscillators is provided. The new model incorporates white and colored noise sources inside the oscillator circuitry. The new model is used in order to connect the performance of phase-noise affected communication systems, in terms of error-vector-magnitude, with oscillator phase-noise measurements. The results can be used by hardware and frequency generator designers to better understand the impairing effects of phase noise on the system performance and optimize their design criteria respectively. Second, the proposed phase-noise model is employed for estimation of phase noise generated from white and colored noise sources. A soft-input maximum a posteriori phase noise estimator and a modified soft-input extended Kalman smoother are proposed. The performance of the proposed algorithms is compared against that of those studied in the literature, in terms of mean square error of phase noise 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 phase-noise statistics. The performance improvement is more significant in low-SNR or low-pilot density scenarios.Finally, the capacity of single and multiple antenna communication systems affected by phase noise is investigated. For the SISO Wiener phase-noise channel, upper and lower bounds on the capacity are obtained, which are tight for a wide range of SNR values. In addition, a family of input distributions, which result in a tight lower bound are introduced. The high-SNR capacity of single-input multiple-output (SIMO) and multiple-output single-input (MISO) phase-noise channels for two different oscillator configurations is investigated. The provided analysis shows that driving antennas at the base station by separate (independent) local oscillators is beneficial for the SIMO channel compared to driving all the antennas with a common oscillator. In contrast, larger gains are achieved for the MISO channel when a common oscillator is employed.
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| 17. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
Receiver Algorithm based on Differential Signaling for SIMO Phase Noise Channels with Common and Separate Oscillator Configurations
- 2015
-
Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. - 9781479959525
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a receiver algorithm consisting of differential transmission and a two-stage detection for a single-input multiple-output (SIMO) phase-noise channels is studied. Specifically, the phases of the QAM modulated data symbols are manipulated before transmission in order to make them more immune to the random rotational effects of phase noise. At the receiver, a two-stage detector is implemented, which first detects the amplitude of the transmitted symbols from a nonlinear combination of the received signal amplitudes. Then in the second stage, the detector performs phase detection. The studied signaling method does not require transmission of any known symbols that act as pilots. Furthermore, no phase noise estimator (or a tracker) is needed at the receiver to compensate the effect of phase noise. This considerably reduces the complexity of the receiver structure. Moreover, it is observed that the studied algorithm can be used for the setups where a common local oscillator or separate independent oscillators drive the radio-frequency circuitries connected to each antenna. Due to the differential encoding/decoding of the phase, weighted averaging can be employed at a multi-antenna receiver, allowing for phase noise suppression to leverage the large number of antennas. Hence, we observe that the performance improves by increasing the number of antennas, especially in the separate oscillator case. Further increasing the number of receive antennas results in a performance error floor, which is a function of the quality of the oscillator at the transmitter.
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| 18. |
- Krishnan, Rajet, 1982, et al.
(författare)
-
Large-Scale Analysis of Linear Massive MIMO Precoders in the Presence of Phase Noise
- 2015
-
Ingår i: 2015 IEEE International Conference on Communication Workshop. - 9781467363051 ; , s. 1172-1177
-
Konferensbidrag (refereegranskat)abstract
- We study the impact of phase noise on the downlink performance of a multi-user multiple-input multiple-output system, where the base station (BS) employs a large number of transmit antennas $M$. We consider a setup where the BS employs $M_{\mr{osc}}$ free-running oscillators, and $M/M_{\mr{osc}}$ antennas are connected to each oscillator. For this configuration, we analyze the impact of phase noise on the performance of regularized zero-forcing (RZF) precoding, when $M$ and the number of users $K$ are asymptotically large, while the ratio $M/K=\beta$ is fixed. We analytically show that the impact of phase noise on the signal-to-interference-plus-noise ratio (SINR) can be quantified as an effective reduction in the quality of the channel state information available at the BS when compared to a system without phase noise. As a consequence, we observe that as $M_{\mr{osc}}$ increases, the SINR of the RZF precoder degrades as the interference power increases, and the desired signal power decreases. On the other hand, the variance of the random phase variations caused by the BS oscillators reduces with increasing $M_{\mr{osc}}$. Through simulations, we verify our analytical results, and study the performance of the RZF precoder for different phase noise and channel noise variances.
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| 19. |
- Krishnan, Rajet, 1982, et al.
(författare)
-
Linear Massive MIMO Precoders in the Presence of Phase Noise – A Large-Scale Analysis
- 2016
-
Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 65:5, s. 3057-3071
-
Tidskriftsartikel (refereegranskat)abstract
- We study the impact of phase noise on the downlink performance of a multi-user multiple-input multiple-output system, where the base station (BS) employs a large number of transmit antennas M. We consider a setup where the BS employs Mosc free-running oscillators, and M/Mosc antennas are connected to each oscillator. For this configuration, we analyze the impact of phase noise on the performance of the regularized zero-forcing (RZF), when M and the number of users K are asymptotically large, while the ratio M/K=β is fixed. We analytically show that the impact of phase noise on the signal-to-interference-plus-noise ratio (SINR) can be quantified as an effective reduction in the quality of the channel state information available at the BS when compared to a system without phase noise. As a consequence, we observe that as Mosc increases, the SINR performance of all considered precoders degrades. On the other hand, the variance of the random phase variations caused by the BS oscillators reduces with increasing Mosc. Through Monte-Carlo simulations, we verify our analytical results, and compare the performance of the precoders for different phase noise and channel noise variances. For all considered precoders, we show that when β is small, the performance of the setup where all BS antennas are connected to a single oscillator is superior to that of the setup where each BS antenna has its own oscillator. However, the opposite is true when β is large and the signal-to-noise ratio at the users is low.
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| 20. |
- Krishnan, Rajet, 1982, et al.
(författare)
-
Soft metrics and their Performance Analysis for Optimal Data Detection in the Presence of Strong Oscillator Phase Noise
- 2013
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 61:6, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we address the classical problem ofmaximum-likelihood (ML) detection of data in the presence of random phase noise. We consider a system, where the random phase noise affecting the received signal is first compensated by a tracker/estimator. Then the phase error and its statistics are used for deriving the ML detector. Specifically, we derive an ML detector based on a Gaussian assumption for the phase error probability density function (PDF). Further without making any assumptions on the phase error PDF, we show that the actual ML detector an be reformulated as a weighted sum of central moments of the phase error PDF. We present a simple approximation of this new ML rule assuming that the phase error distribution is unknown. The ML detectors derived are also the aposteriori probabilities of the transmitted symbols, and are referred to as soft metrics. Then, using the detector developed based on Gaussian phase error assumption, we derive the symbol error probability (SEP) performance and error floor analytically for arbitrary constellations. Finally we compare SEP performance of the various detectors/metrics in this work and those from literature for different signal constellations, phase noise scenarios and SNR values.
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| 21. |
- Krishnan, Rajet, 1982, et al.
(författare)
-
Variational Bayesian Framework for Receiver Design in the Presence of Phase Noise in MIMO Systems
- 2012
-
Ingår i: IEEE Wireless Communications and Networking Conference, WCNC. - 1525-3511. - 9781467304375 ; , s. 347-352
-
Konferensbidrag (refereegranskat)abstract
- In this work, the problem of receiver design for phasenoise estimation and data detection in the presence of oscillator phase noise in a point-to-point multiple-input multiple-output (MIMO) system is addressed. First, we discuss some interesting and challenging aspects in receiver design for MIMO systems in thepresence of Wiener phase noise. Then, using the variational Bayesian (VB) framework, a joint iterative phase noise estimator and symbol detector are developed based on inverse Gibbs or variational free energy maximization. Further, the symbol error probability (SEP) of the newly proposed iterative scheme is compared with the optimal ML detector with perfect phase information for 16-PSK and 16-QAM modulation schemes.
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| 22. |
- Tahmasebi Toyserkani, Arash, 1978, et al.
(författare)
-
A Complexity Adjustable Scheduling Algorithm for Throughput Maximization in Clusterized TDMA Networks
- 2010
-
Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. - 9781424425198
-
Konferensbidrag (refereegranskat)abstract
- We consider clustered wireless networks, wheretransceivers in a cluster use a time-slotted mechanism (TDMA) to access a wireless channel that is shared among several clusters.Earlier work has demonstrated that a significant increase innetwork throughput can be achieved if all the schedules areoptimized jointly. However, a drawback of this approach is the prohibitive level of computational complexity is required when a network with a large number of clusters and time-slots is to be scheduled. In this paper, we propose a modification to our previously proposed algorithm which allows for the complexityto be adjusted to the available processing power, provided some minimum processing power is available. This is achieved by carefully reducing the number of interfering clusters considered when scheduling a cluster. In addition, we propose and evaluatetwo heuristic methods of discarding the less significant clusters.While the optimality of the obtained schedule is not proven, our results demonstrate that large gains are consistently attainable.
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