| 1. |
- 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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| 2. |
- Isikman, Arif Onder, 1988, et al.
(författare)
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Joint phase noise estimation and data detection in coded multi-input-multi-output systems
- 2014
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Ingår i: IET Communications. - : Institution of Engineering and Technology (IET). - 1751-8628 .- 1751-8636. ; 8:7, s. 981-989
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Tidskriftsartikel (refereegranskat)abstract
- The problem of joint oscillator phase noise (PHN) estimation and data detection for multi-input multi-output (MIMO) systems using bit-interleaved-coded modulation is analysed. A new MIMO receiver that iterates between the estimator and the detector, based on the expectation-maximisation (EM) framework, is proposed. It is shown that at high signal-to-noise ratios, a maximum a posteriori (MAP) estimator can be used to carry out the maximisation step of the EM algorithm. Moreover, to reduce the computational complexity of the proposed EM algorithm, a soft decision-directed extended Kalman filter-smoother (EKFS) is applied instead of the MAP estimator to track the PHN parameters. The numerical results show that by combining the proposed EKFS-based approach with an iterative detector that employs low-density parity check codes, PHN can be accurately tracked. The simulations also demonstrate that compared to the existing algorithms, the proposed iterative receiver can significantly enhance the performance of MIMO systems in the presence of PHN.
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| 3. |
- Khanzadi, M Reza, 1983, et al.
(författare)
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On Models, Bounds, and Estimation Algorithms for Time-Varying Phase Noise
- 2011
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Ingår i: 5th International Conference on Signal Processing and Communication Systems (ICSPCS2011). - 9781457711800 ; , s. Art Nr. 6140897-
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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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| 4. |
- Krishnan, Rajet, 1982, et al.
(författare)
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Optimal and Approximate Methods for Detection of Uncoded Data with Carrier Phase Noise
- 2011
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Ingår i: IEEE Globecom 2011.
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Konferensbidrag (refereegranskat)abstract
- Previous results in the literature have shown that derivation of the optimum \textit{maximum-likelihood} (ML) receiver for \textit{symbol-by-symbol} (SBS) detection of an uncoded data sequence in the presence of \textit{random phase noise} is an intractable problem, since it involves the computation of the conditional \textit{probability distribution function} (PDF) of the phase noise process. In this paper, we seek to minimize \textit{symbol error probability} (SEP), which is achieved by SBS detection of the sequence based on all received signals. We show that the ML detector for this problem can be formulated as a weighted sum of central moments of the conditional PDF of phase noise. Given that the central moments of the conditional PDF of phase noise can be estimated, this new optimal structure is tractable with respect to the previously known optimal ML receiver. Furthermore, based on the new receiver structure, we propose a simple approximate method for SBS detection and investigate its scope and applicability. Simulation results demonstrate that SEP performance close to optimality can be obtained through the proposed method for scenarios of low phase noise variance and low \textit{signal-to-noise ratio} (SNR).
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| 5. |
- Mehrpouyan, Hani, 1981, et al.
(författare)
-
A New Distributed Approach for Achieving Clock Synchronization in Heterogeneous Networks
- 2011
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Ingår i: IEEE Globecom 2011. - 1930-529X. - 9781424492688 ; , s. 5-
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Konferensbidrag (refereegranskat)abstract
- Heterogeneous networks have the potential to improve coverage, throughput, and energy efficiency of wireless networks through the use of specialized cellular structures, in particular femtocells and macrocells. However, to reduce interference between different cells, ensure smooth hand-offs from cell to cell, and achieve seamless operation the overall network needs to be synchronized. In this paper a new distributed clock synchronization scheme for heterogeneous networks is proposed that employs the clock drift information available at user-equipments (UEs) to achieve synchronization between non-interacting femtocells and macrocells. Simulation results show that the proposed scheme can significantly reduce the clock drift between macrocells and femtocells and result in timing synchronization throughout the network without introducing significant overhead.
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| 6. |
- Mehrpouyan, Hani, 1981, et al.
(författare)
-
A New Distributive Approach for Achieving Timing Synchronization in Heterogenous Networks, (in peer review)
- 2010
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Ingår i: ICC Worksop on Heterogeneous Networks 2011.
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Konferensbidrag (refereegranskat)abstract
- Heterogeneous networks have the potential to improve coverage, throughput, and energy efficiency of wireless networks through the use of specialized cellular structures, i.e., femtocells and macrocells. However, to reduce interference between different cells, ensure smooth hand-offs from cell to cell, and achieve seamless operation the overall network needs to be synchronized. In this paper a new distributive timing synchronization scheme for heterogenous networks is proposed that employs the timing information available at user equipments (UEs) to achieve synchronization between noninteracting femtocells and macrocells. Simulation results show that the proposed scheme can significantly reduce the clock bias between macrocells and femtocells without introducing any significant overhead. When the femtocells are densely deployed the combination of the proposed scheme and gossip algorithms can result in synchronization throughout the network.
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| 7. |
- Mehrpouyan, Hani, 1981, et al.
(författare)
-
Bounds and Algorithms for Multiple Frequency Offset Estimation in Cooperative Networks
- 2011
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Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 10:4, s. 1300-1311
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Tidskriftsartikel (refereegranskat)abstract
- The distributed nature of cooperative networks may result in multiple carrier frequency offsets (CFOs), which make the channels time varying and overshadow the diversity gains promised by collaborative communications. This paper seeks to address multiple CFO estimation using training sequences in space-division multiple access (SDMA) cooperative networks. The system model and CFO estimation problem for cases of both decode-and-forward (DF) and amplify-and-forward (AF) relaying are formulated and new closed-form expressions for the Cramer-Rao lower bound (CRLB) for both protocols are derived. The CRLBs are then applied in a novel way to formulate training sequence design guidelines and determine the effect of network protocol and topology on CFO estimation.Next, two computationally efficient iterative estimators are proposed that determine the CFOs from multiple simultaneously relaying nodes. The proposed algorithms reduce multiple CFO estimation complexity without sacrificing bandwidth and training performance.Unlike existing multiple CFO estimators, the proposed estimators are also accurate for both large and small CFO values. Numerical results show that the new methods outperform existing algorithms and reach or approach the CRLB at mid-to-high signal-to-noise ratio (SNR). When applied to system compensation, simulation results show that the proposed estimators significantly reduce average-bit-error-rate (ABER).
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| 8. |
- Mehrpouyan, Hani, 1981, et al.
(författare)
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Comments on "Timing Estimation and Resynchronization for Amplify-and-Forward Communication Systems
- 2011
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Ingår i: IEEE Transactions on Signal Processing. - 1941-0476 .- 1053-587X. ; 59:8, s. 4047-4048
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Tidskriftsartikel (refereegranskat)abstract
- This correspondence first shows that the Cramer-Rao lower bound (CRLB) derivations in the above paper areincorrect. In addition, contrary to the claims in the abovepaper, the assumptions of perfect timing offset estimation andmatched-filtering at the relays affect the generality of theanalytical results and cannot be justified assumption.
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| 9. |
- Mehrpouyan, Hani, 1981, et al.
(författare)
-
Joint Estimation of Channel and Oscillator Phase Noise in MIMO Systems
- 2012
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Ingår i: IEEE Transactions on Signal Processing. - 1941-0476 .- 1053-587X. ; 60:9, s. 4790-4807
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Tidskriftsartikel (refereegranskat)abstract
- Oscillator phase noise limits the performance of high speed communication systems since it results in timevarying channels and rotation of the signal constellation from symbol to symbol. In this paper, joint estimation ofchannel gains and Wiener phase noise in multi-input multi-output (MIMO) systems is analyzed. The signal modelfor the estimation problem is outlined in detail and new expressions for the Cram´er-Rao lower bounds (CRLBs) forthe multi-parameter estimation problem are derived. A data-aided least-squares (LS) estimator for jointly obtainingthe channel gains and phase noise parameters is derived. Next, a decision-directed weighted least-squares (WLS)estimator is proposed, where pilots and estimated data symbols are employed to track the time-varying phase noiseparameters over a frame. In order to reduce the overhead and delay associated with the estimation process, anew decision-directed extended Kalman filter (EKF) is proposed for tracking the MIMO phase noise throughouta frame. Numerical results show that the proposed LS, WLS, and EKF estimators’ performances are close to theCRLB. Finally, simulation results demonstrate that by employing the proposed channel and time-varying phase noiseestimators the bit-error rate (BER) performance of a MIMO system can be significantly improved.
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| 10. |
- Mehrpouyan, Hani, 1981, et al.
(författare)
-
Time-varying phase noise and channel estimation in MIMO systems
- 2012
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Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. - 9781467309707 ; , s. 560-564
-
Konferensbidrag (refereegranskat)abstract
- Performance of high speed communication systems is negatively affected by oscillator phase noise (PN). In this paper joint estimation of channel gains and Wiener PN in multi-input multi-output (MIMO) systems is analyzed. The signal model for the estimation problem is outlined in detail. In order to reduce overhead, a low complexity data-aided least-squares (LS) estimator for jointly obtaining the channel gains and PN parameters is derived. In order to track PN processes over a frame, a new decision-directed extended Kalman filter (EKF) is proposed. Numerical results show that the proposed LS and EKF based PN estimator performances are close to the CRLB and simulation results indicate that by employing the proposed estimators the bit-error rate (BER) performance of a MIMO system can be significantly improved in the presence of PN.
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