Electromagnetic Modeling of High-Frequency Links With High-Resolution Terrain Data

Al-Daher, Zaid; Ivrissimtzis, L.P.; Hammoudeh, Akram

doi:10.1109/lawp.2012.2226135

“…υ = 2, our proposed channel estimation scheme with ZF precoding can achieve a considerable high sum rate performance due to its interference suppression capability. In Figure 5b, the achievable rate performance gap between the fully digital system and the hybrid system decreases with the increasing Rician K-factor, which is predicted by Equation (30). In particular, with a sufficiently large Rician K-factor, the achievable rates of these two systems will coincide.…”

Section: Corollary 2 In the Large Numbers Of Antennas Regime The Asym...mentioning

confidence: 70%

“…Yet, in recent field tests, especially in the urban microcell environments, both a strong line-of-sight (LOS) component and non-negligible scattering components may exist in mmWave propagation channels [13], [23], [29]. Therefore, for the urban short-distance propagation environment, mmWave channels are more suitable to be modeled by non-sparse Rician fading and with a large Rician K-factor [13], [23], [30]. On the other hand, for the suburban long-distance propagation environment, mmWave channels can be modeled by a sparse channel model.…”

Section: System Modelmentioning

confidence: 99%

Multi-User Precoding and Channel Estimation for Hybrid Millimeter Wave Systems

Zhao

¹

,

Ng

²

,

Yuan

³

2017

IEEE J. Select. Areas Commun.

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In this paper, we develop a low-complexity channel estimation for hybrid millimeter wave (mmWave) systems, where the number of radio frequency (RF) chains is much less than the number of antennas equipped at each transceiver. The proposed mmWave channel estimation algorithm first exploits multiple frequency tones to estimate the strongest angle-of-arrivals (AoAs) at both base station (BS) and user sides for the design of analog beamforming matrices. Then all the users transmit orthogonal pilot symbols to the BS along the directions of the estimated strongest AoAs in order to estimate the channel. The estimated channel will be adopted to design the digital zero-forcing (ZF) precoder at the BS for the multi-user downlink transmission. The proposed channel estimation algorithm is applicable to both nonsparse and sparse mmWave channel environments. Furthermore, we derive a tight achievable rate upper bound of the digital ZF precoding with the proposed channel estimation algorithm scheme. Our analytical and simulation results show that the proposed scheme obtains a considerable achievable rate of fully digital systems, where the number of RF chains equipped at each transceiver is equal to the number of antennas. Besides, by taking into account the effect of various types of errors, i.e., random phase errors, transceiver analog beamforming errors, and equivalent channel estimation errors, we derive a closedform approximation for the achievable rate of the considered scheme. We illustrate the robustness of the proposed channel estimation and multi-user downlink precoding scheme against the system imperfection.

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“…According to recent field measurements, e.g. [18], [35], [36], [62], [63], the typical values of the power ratios of the strongest cluster power over the other scattered paths' power ς l,k and ς l,k for U l,k and H T l,k are in [0, 5], respectively.…”

Section: System Modelmentioning

confidence: 99%

Multi-Cell Hybrid Millimeter Wave Systems: Pilot Contamination and Interference Mitigation

Zhao

¹

,

Wei

²

,

Ng

³

et al. 2018

IEEE Trans. Commun.

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In this paper, we investigate the system performance of a multi-cell multi-user (MU) hybrid millimeter wave (mmWave) communications in a multiple-input multiple-output (MIMO) network. Due to the reuse of pilot symbols among different cells, the performance of channel estimation is expected to be degraded by pilot contamination, which is considered as a fundamental performance bottleneck of conventional multicell MU massive MIMO networks. To analyze the impact of pilot contamination to the system performance, we first derive the closed-form approximation of the normalized mean squared error (MSE) of the channel estimation algorithm proposed in [2] over Rician fading channels. Our analytical and simulation results show that the channel estimation error incurred by the impact of pilot contamination and noise vanishes asymptotically with an increasing number of antennas equipped at each radio frequency (RF) chain at the desired BS. Furthermore, by adopting zero-forcing (ZF) precoding in each cell for downlink transmission, we derive a tight closed-form approximation of the average achievable rate per user. Our results unveil that the intra-cell interference and inter-cell interference caused by pilot contamination over Rician fading channels can be mitigated effectively by simply increasing the number of antennas equipped at the desired BS.

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“…However, in recent field tests, both a strong line-of-sight (LOS) component and non-negligible scattering component may exist in mmWave propagation channels [12], [19], [21], especially in the urban area. In particular, mmWave channels can also be modeled by non-sparse Rician fading and with a large Rician K-factor 1 (approximately ≥ 5 dB) [12], [19], [22].…”

Section: System Modelmentioning

confidence: 99%

Multiuser precoding and channel estimation for hybrid millimeter wave MIMO systems

Zhao

¹

,

Ng

²

,

Yuan

³

2017

2017 IEEE International Conference on Communications (ICC)

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In this paper, we develop a low-complexity channel estimation for hybrid millimeter wave (mmWave) systems, where the number of radio frequency (RF) chains is much less than the number of antennas equipped at each transceiver. The proposed channel estimation algorithm aims to estimate the strongest angle-of-arrivals (AoAs) at both the base station (BS) and the users. Then all the users transmit orthogonal pilot symbols to the BS via these estimated strongest AoAs to facilitate the channel estimation. The algorithm does not require any explicit channel state information (CSI) feedback from the users and the associated signalling overhead of the algorithm is only proportional to the number of users, which is significantly less compared to various existing schemes. Besides, the proposed algorithm is applicable to both non-sparse and sparse mmWave channel environments. Based on the estimated CSI, zero-forcing (ZF) precoding is adopted for multiuser downlink transmission. In addition, we derive a tight achievable rate upper bound of the system. Our analytical and simulation results show that the proposed scheme offer a considerable achievable rate gain compared to fully digital systems, where the number of RF chains equipped at each transceiver is equal to the number of antennas. Furthermore, the achievable rate performance gap between the considered hybrid mmWave systems and the fully digital system is characterized, which provides useful system design insights. I. INTRODUCTIONHigher data rates, large bandwidth, and higher spectral efficiency are necessary for the fifth-generation (5G) wireless communication systems to support various emerging applications [1]. The combination of millimeter wave (mmWave) communication [2]-[5] with massive multiple-input multipleoutput (MIMO) [6]-[8] is considered as one of the promising candidate technologies for 5G communication systems with many potential and exciting opportunities for research [7], [9]- [13]. For example, the trade-offs between system performance, hardware complexity, and energy consumption [2], [14] are still unclear. From the literature, it is certain that the conventional fully digital MIMO systems, in which each antenna connects with a dedicated radio frequency (RF) chain, are impractical for mmWave systems due to the prohibitively high cost, e.g. tremendous energy consumption of high resolution analog-to-digital convertors/digital-to-analog convertors (ADC/DACs) and power amplifiers (PAs). Therefore, several mmWave hybrid systems were proposed as compromised solutions which strike a balance between hardware complexity and system performance [11], [15]-[18]. Specifically, the use

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Electromagnetic Modeling of High-Frequency Links With High-Resolution Terrain Data

Cited by 7 publications

References 6 publications

Multi-User Precoding and Channel Estimation for Hybrid Millimeter Wave Systems

Multi-User Precoding and Channel Estimation for Hybrid Millimeter Wave Systems

Multi-Cell Hybrid Millimeter Wave Systems: Pilot Contamination and Interference Mitigation

Multiuser precoding and channel estimation for hybrid millimeter wave MIMO systems

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