Ali S. Sadri

Highly Directional Steerable Antennas: High-Gain Antennas Supporting User Mobility or Beam Switching for Reconfigurable Backhauling

Modern millimeter-wave (mmWave) communication systems for large indoor areas and most outdoor scenarios require high-gain antennas with beam-steering ability to support user mobility or beam switching for reconfigurable backhauling. In this article, two new concepts for the development of highly directional steerable mmWave antennas are proposed and analyzed. The first one is modular antenna array (MAA) technology, which allows the creation of large-aperture, high-gain adaptive antenna arrays in a cost-effective and scalable manner. Two MAA configurations based on the existing phased subarray module are considered and analyzed for mmWave small-cell access and backhauling. The second prospective technology that fulfills the required antenna parameters for mmWave smallcell flexible backhauling is the lens-array antenna (LAA). The combination of the dielectric lens for aperture increasing with only one subarray module with beam-steering capabilities may provide 25-30-dBi total antenna gain with azimuth sector sweeping ±45°.

Study of coexistence between 5G small-cell systems and systems of the fixed service at 39 GHz band

This paper presents simulation results in 39 GHz small cells through analysis of required frequency rejection. We calculate two types of interference amounts collected at a fixed service (FS) receiver, i.e., the aggregation of interference into an FS receiver occurred by every transmission (i) from base stations (BSs) to their associated mobile stations (MSs); (ii) from MSs and their associated BSs. The results determine how much interference rejection would be needed to protect FS operation.

Numerical Simulation Study for Frequency Sharing Between Micro-Cellular Systems and Fixed Service Systems in Millimeter-Wave Bands

This paper presents numerical simulation results to study the impact of the co-existence between a fixed service (FS) system and 5G small cell networks at 28-, 38-, and 60-GHz millimeter-wave (mmWave) frequency bands. For this paper, two scenarios are considered: aggregation of interference from small cells into an FS receiver from base stations (BSs) to their associated user equipment (UE) (downlink) and the aggregation of cellular interference at the FS receiver from UEs to their associated BSs (downlink). Moreover, mmWave-specific propagation characteristics and attenuation factors are considered for a more precise simulation study. The simulation results determine how much interference rejection is required to protect the operation of FS. In addition, currently available mmWave modular antenna array (MAA) architectures are introduced. Based on the information, additionalmmWave frequency sharing study is performed using the realistic MAA radiation patterns. Last, we compare and analyze the performance differences between ITU standard models and MAA solutions.

Partially adaptive arrays application for MU-MIMO mode in a MmWave small cells

In this paper we provide detailed system level performance analysis of MU-MIMO mode in the millimeter wave (mmWave) small cells (Wi-Fi hotspots) environment. Traditional way of MIMO implementation assumes a single RF chain per antenna element, with all spatial processing done in the baseband. To overcome high pathloss in the mmWave bands, the large-aperture, very high gain arrays with a large number of elements (several hundreds) are required. Therefore we introduce partially adaptive arrays with reduced number of degrees of freedom which are implemented based on the modular antenna arrays (MAA) architecture. The scalable practical design of MAA allows creation of large-aperture, high-power antenna arrays with reduced number of RF chains at cost of decreasing the adaptability. Employing recently proposed quasi-deterministic (Q-D) model for millimeter-wave channels, it was shown that partially adaptive MAA have very small degradation in comparison with ideal fully adaptive array (FAA) in a realistic scenarios. It was shown that application of MU-MIMO mode in a mmWave small cells allows achieving up to 15-30 Gbps total throughput per cell in a multipath environment (university campus scenario) with practical antenna array design.

Practical LOS MIMO Technique for Short-Range Millimeter-Wave Systems

The widespread availability and use of digital multimedia content has created a need for faster wireless connectivity that current commercial standards cannot support. For example, new generation of display and input-output (IO) interfaces require data rates well in excess of 10 Gbps. The large amount of spectrum in the unlicensed 60 GHz millimeter-wave (mmWave) band offers the most promising approach to meet this challenge, but existing standards operating in this band are limited to data rates below 7 Gbps. Therefore, in this paper we propose a practical mmWave technique that combines the benefits of multi-input, multi-output (MIMO) transmissions and a line-of-sight (LOS) communication channel, hereby referred to as LOS MIMO. Different implementations for LOS MIMO using various options for stream separation techniques including separation in the radio front-end (RF), in the baseband, or by polarization are also discussed. The performance of these LOS MIMO implementations is evaluated by simulations. We show that LOS MIMO systems based on low-power phased antenna arrays can operate at the distances up to several meters and achieve data rates above ten Gbps, thus meeting the requirement of the new generation high-speed interfaces.

60 GHz Frequency Sharing Study between Fixed Service Systems and Small-Cell Systems with Modular Antenna Arrays

This paper presents numerical simulation results in order to identify how much interference can be generated to a fixed service (FS) receiver from nearby small cell networks when the FS systems and small-cell systems are sharing a 60 GHz mmWave frequency band. For this 60 GHz frequency sharing study, two different scenarios are considered, i.e., the aggregation of interference into an FS receiver occurred by every transmission (i) from base stations (BSs) to their associated user elements (UEs); (ii) from UEs and their associated BSs. Moreover, 60 GHz mmWave specific propagation characteristics and attenuation factors are considered for more precise simulation study. The simulation results determine how much interference rejection is required to protect the operation of FS.

Enhanced Next Generation Millimeter-Wave Multicarrier System with Generalized Frequency Division Multiplexing

Orthogonal Frequency Division Multiplexing (OFDM) is a popular multicarrier technique used to attain high spectral efficiencies. It also has other advantages such as multipath tolerance and ease of implementation. However, OFDM based systems suffer from high Peak-to-Average Power Ratio (PAPR) problem. Because of the nonlinearity of the power amplifiers, the high PAPR causes significant distortion in the transmitted signal for millimeter-wave (mmWave) systems. To alleviate the high PAPR problem, this paper utilizes Generalized Frequency Division Multiplexing (GFDM) which can achieve high spectral efficiency as well as low PAPR. In this paper, we show the performance of GFDM using the IEEE 802.11ad multicarrier frame structures. IEEE 802.11ad is considered one of the most successful industry standards utilizing unlicensed mmWave frequency band. In addition, this paper indicates the feasibility of using GFDM for the future standards such as IEEE 802.11ay. This paper studies the performance improvements in terms of PAPR reduction for GFDM. Based on the performance results, the optimal numbers of subcarriers and subsymbols are calculated for PAPR reduction while minimizing the Bit Error Rate (BER) performance degradation. Moreover, transmitter side ICI (Intercarrier Interference) reduction is introduced to reduce the receiver load.

60 GHz Modular Antenna Array Link Budget Estimation with WiGig Baseband and Millimeter-Wave Specific Attenuation

This paper provides practical 60 GHz link budget estimation results with IEEE 802.11ad standard-defined parameters and 60 GHz specific attenuation factors. In addition, the parameters from currently developing modular antenna arrays (MAAs) are adopted for estimating the actual link budgets of our 60 GHz integrated MAA platforms. Based on the practical link budget analysis results, we can estimate fundamental limits in terms of achievable data rates over 60 GHz millimeter-wave wireless links.

Defining the future of multi-gigabit mmWave wireless communications

The widespread availability and use of digital multimedia content has created a need for multi-gigabit wireless connectivity that current commercial standards cannot support. This has driven demand for a single standard that can support advanced applications such as wireless display and docking, as well as more established usages such as network access.. In this talk, we introduce the Wireless Gigabit (WiGig) Alliance, which was formed to meet this need by establishing a unified specification for wireless communication at multi-gigabit speeds. The WiGig Alliance has produced a specification designed to drive a global ecosystem of interoperable products, defining PHY, MAC, and protocol adaptation layers for wireless communication in 60 GHz frequency band