Interpreting the Total Isotropic Sensitivity and Diversity Gain of LTE-enabled wireless devices from Over The Air Throughput Measurements in Reverberation Chambers

The characterization of the performance of wireless devices is the key to developing new RF products conforming to the latest communications protocols. Traditionally, communication performance tests have focused on the RF performance of the tested devices, e.g., smart phones, pads, laptops, etc. More specifically, the focus has shifted from conducted (i.e., cabled) measurements to more realistic Over-The-Air (OTA) characterization of the RF performance of these devices in transmit or receive mode. For example, the receiver performance of 2G and 3G wireless devices can be measured in terms of the total isotropic sensitivity (TIS) that depends on the antenna and the receiver parts of a wireless device. These measurements can be performed in a reverberation chamber setup. However, standard TIS measurements can be time consuming and do not reflect the actual performance gains of Multiple-Input Multiple- Output (MIMO) antenna systems operating over Orthogonal Frequency Division Multiplexing (OFDM) channels, such as those encountered in 4G Long Term Evolution (LTE) systems. Therefore, in order to meet both time and cost efficiency requirements, we propose here a new method to determine the TIS, as well as the diversity performance, of an LTE device based on throughput measurements. The proposed method shows that the TIS of an LTE device is characterized much faster directly from OTA throughput measurements than from standard TIS measurements and with excellent accuracy

Measured Probabilities of Detection for 1- and 2 Bitstreams of 2-port Car-roof Antenna in RIMP and Random-LOS

Autonomous cars will in a near future drive around in cities and on highways. Antennas will then be needed to secure the wireless connection to these cars. To be able to test the antennas we have defined two edge environments: the Random Line-of-Sight (LOS) and the Rich Isotropic Multipath (RIMP). This paper shows a throughput performance comparison between measurements and simulations of a car-roof (shark-fin) antenna mounted on a ground plane in both of these environments. The comparison is done for both one and two bitstreams in a 22 MIMO system. The analysis is based on probability of detection (PoD) curves representing the throughput performance with digital threshold receivers

Simulations of a planar array arrangement for automotive Random-LOS OTA testing

We present simulations of near-field plane wave synthesis by a planar array. The focus is on minimization of reference signal errors within the test zone for Random Line-Of-Sight Over-The-Air characterization of wireless devices on cars. The analysis considers the output of the ideal digital threshold receiver model of the device under test as a Probability of Detection curve. The dimensions, the interelement spacings and the number of elements in a planar array comprising Huygens sources are investigated to produce an absolute error less than 0.5 dB

Design of a Planar Eleven Antenna for Optimal MIMO Performance as a Wideband Micro Base-station Antenna

A new low-profile planar Eleven antenna is designed for optimal MIMO performance as a wideband MIMO antenna for micro base-stations in future wireless communication systems. The design objective has been to optimize both the reflection coefficient at the input port of the antenna and the 1-bitstream and 2-bitstream MIMO efficiency of the antenna at the same time, in both the Rich Isotropic MultiPath (RIMP) and Random Line-of-Sight (Random-LOS) environments. The planar Eleven antenna can be operated in 2-, 4-, and 8-port modes with slight modifications. The optimization is performed using genetic algorithms. The effects of polarization deficiencies and antenna total embedded efficiency on the MIMO performance of the antenna are further studied. A prototype of the antenna has been fabricated and the design has been verified by measurements against the simulations.Comment: 7 pages, 15 figures, 15 reference

Preparing for GBit/s coverage in 5G: Massive MIMO, PMC packaging by gap waveguides, OTA testing in random-LOS

In this invited presentation I describe how we prepare for 5G in my research division. The background is that we have contributed to 3G and 4G developments with two commercial successes: The hat-fed reflector antenna for backhaul radio links, and Bluetest reverberation chambers for OTA (Oer-The-Air) characterization of devices with MIMO and OFDM. 5G means Gbit/s data rates, for which higher frequencies are needed towards the user terminal, may be up to 30 or 60 GHz. This means that the multipath will be weaker as it gradually diminishes when frequency increases. Therefore, we prepare by introducing a Random-LOS (RLOS) complement to the OTA testing in Rich Isotropic Multipath (RIMP) being provided by Bluetest\u27s reverberation chambers. Further, high gain steerable beams will be needed, requiring new planar packaging solutions for closer integration of antennas and RF chipsets. Therefore, we prepare by research on gap waveguides. Massive MIMO have many technological uncertainties, so others also consider old-fashioned phased arrays, but they will not work in RIMP. The best hardware can only be chosen if we know how to characterize the system performance. The radiation pattern and realized gain cannot be used directly for this purpose due to all the statistical variations caused by the arbitrariness of the user. Therefore, we introduce instead the Probability of Detection (PoD) as a quality metric. This will be different for each desired number of bitstreams. Further, we quantify the difference between different PoD curves in dBiid in RIMP, i.e. in dB relative to the i.i.d. (idependent identically distributed) case, and in dBt in RLOS, i.e. in dB relative to an ideal polarization- and coverage- matched threshold receiver. The presentation will give an overview of this research

Antenna Designs Aiming at the Next Generation of Wireless Communication

Millimeter-wave (mm-wave) frequencies have drawn large attention, specically for the fifth generation (5G) of wireless communication, due to their capability to provide high data-rates. However, design and characterization of the antenna system in wireless communication will face new challenges when we move up to higher frequency bands. The small size of the components at higher frequencies will make the integration of the antennas in the system almost inevitable. Therefore, the individual characterization of the antenna can become more challenging compared to the previous generations.This emphasizes the importance of having a reliable, simple and yet meaningful Over-the-Air (OTA) characterization method for the antenna systems. To avoid the complexity of using a variety of propagation environments in the OTA performance characterization, two extreme or edge scenarios for the propagation channels are presented, i.e., the Rich Isotropic Multipath (RIMP) and Random Line-of-Sight (Random-LoS). MIMO efficiency has been defined as a Figure of Merit (FoM), based on the Cumulative Distribution Function (CDF) of the received signal, due to the statistical behavior of the signal in both RIMP and Random-LoS. Considering this approach, we have improved the design of a wideband antenna for wireless application based on MIMO efficiency as the FoM of the OTA characterization in a Random-LoS propagation environment. We have shown that the power imbalance and the polarization orthogonality plays major roles determining the 2-bitstream MIMO performance of the antenna in Random-LoS. In addition, a wideband dual-polarized linear array is designed for an OTA Random-LoS measurement set-up for automotive wireless systems. The next generation of wireless communications is extended throughout multiple narrow frequency bands, varying within 20-70 GHz. Providing an individual antenna system for each of these bands may not be feasible in terms of cost, complexity and available physical space. Therefore, Ultra-Wideband (UWB) antenna arrays, coveringmultiple mm-wave frequency bands represent a versatile candidate for these antenna systems. In addition to having wideband characteristics, these antennas should offer an easy integration capability with the active modules. We present a new design of UWB planar arrays for mm-wave applications. The novelty is to propose planar antenna layouts to provide large bandwidth at mm-wave frequencies, using simplified standard PCB manufacturing techniques. The proposed antennas are based on Tightly Coupled Dipole Arrays (TCDAs) concept with integrated feeding network

Verification of the Random Line-of-Sight Measurement Setup at 1.5-3 GHz including MIMO Throughput Measurements of a Complete Vehicle

The performance evaluation of wireless systems is crucial for the development of future systems with more connected devices. It is essential to have an easy and relevant method for ensuring the wireless communication performance of the devices. We have recently developed a new random line-of-sight (random-LOS) measurement system for evaluating the communication performance of wireless devices, e.g., transceivers and antennas installed on a vehicle. In the measurement system, a plane wave is generated in the test zone emulating the far-field wave transmitted from a radio base station. In this paper we present both numerical simulations and actual experimental results of the random-LOS over-the-air (OTA) measurement setup operating in the 1.5-3 GHz band. The measurement accuracy is determined by the field variations within the test zone, where a smaller variation gives better measurement accuracy. In this paper the achieved accuracy expressed in terms of standard deviation (STD) was evaluated to be approximately 1 dB of the power within a cylindrical test zone of height 0.4 m and diameter 2 m. The active multiple-input multiple-output (MIMO) performance of antenna systems installed on an actual vehicle was measured and evaluated using the presented setup. A comparison to a theoretical zero forcing (ZF) receiver is also presented

Characterizing Polarization-MIMO Antennas in Random-LOS Propagation Channels

Abstract-In the 5G system, we foresee the use of LOSdominated mm-wave radio links to moving users being subject to slow fading resulting from the users' random locations and orientations. We refer to this as a Random-LOS channel. MIMO processing algorithms will be used in 5G to improve performance in slow fading, similar to how they are used in Rayleigh fading. To this end, we study the probability of detection (PoD) in the Random-LOS channel when there are dual-polarized antennas on both sides of the link. We introduce two polarization deficiencies: the polarization non-orthogonality and the amplitude imbalance between the ports of a two-port antenna. The MIMO efficiency is evaluated as a function of these deficiencies. In the analysis, we consider the MRC algorithm for one bitstream, and the ZF and SVD algorithms for two bitstreams. We also present two analytical formulas for the MIMO efficiency that can be used to determine performance. We use the formulas on two ideally orthogonal dipoles, and show by means of coverage plots how much the 1-and 2-bitstream performances degrade due to the polarization deficiencies in off-boresight directions

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium