Indoor Distributed Antenna System Research Articles

Metamaterial-Inspired Electrically Compact Triangular Antennas Loaded with CSRR

In this paper, simulation of two distinct kinds of metamaterial (MTM) antennas are proposed for fifth generation (5G) indoor distributed antenna systems (IDAS). Both antennas operate in the sub-6 GHz 5G band, i.e., 3.5 GHz and to analyze various factors like gain, directivity, return loss, radiation intensity for the frequency of 3.5 GHz. The simulation of this metamaterial antenna is carried out in ANSYS HFSS v2021. Results like return loss, radiation pattern, 3D polar plot, side lobe level, beamwidth, radiated power, accepted power have been obtained using HFSS v2021. This research on metamaterial gives a great view on how it can be designed and used at 3.5GHz frequency has a measured gain/bandwidth characteristic of 100 MHz/2.6 dBi and 700 MHz/2.3 dBi, respectively. The main advantage of this antenna is it can be used as both transmitting and receiving antenna. Key Words: Metamaterial, CSRR, return loss, triangular CSRR

Human Exposure to Non-Ionizing Radiation from Indoor Distributed Antenna System: Shopping Mall Measurement Analysis.

It is crucial to monitor the levels of Non-Ionizing Radiation (NIR) to which the general population may be exposed and compare them to the limits defined in the current standards, in view of the rapid rise of communication services and the prospects of a connected society. A high number of people visits shopping malls and since these locations usually have several indoor antennas close to the public, it is therefore a kind of place that must be evaluated. Thus, this work presents measurements of the electric field in a shopping mall located in Natal, Brazil. We proposed a set of six measurement points, following two criteria: places with great the flow of people and the presence of one or more Distributed Antenna System (DAS), co-sited or not with WiFi access points. Results are presented and discussed in terms of the distance to DAS (conditions: near and far) and flow density of people in the mall (scenarios: low and high number of people). The highest peaks of electric field measured were 1.96 and 3.26 V/m, respectively corresponding to 5% and 8% of the limits defined by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Brazilian National Telecommunication Agency (ANATEL).

Impact of Indoor Distributed Antenna System on RF-EMF Global Exposure

Impact of Indoor Distributed Antenna System on RF-EMF Global Exposure

A Compact Triple-Band UWB Inverted Triangular Antenna with Dual-Notch Band Characteristics Using SSRR Metamaterial Structure for Use in Next-Generation Wireless Systems

A compact triple-band operation ultra-wideband (UWB) antenna with dual-notch band characteristics is presented in this paper. By inserting three metamaterial (MTM) square split-ring resonators (MTM-SSRRs) and a triangular slot on the radiating patch, the antenna develops measured dual-band rejection at 4.17–5.33 GHz and 6.5–8.9 GHz in the UWB frequency range (3–12 GHz). The proposed antenna offers three frequency bands of operation in the UWB range, which are between 3–4.17 GHz (~1.2 GHz bandwidth), 5.33–6.5 GHz (~1.17 GHz bandwidth), and 8.9–12 GHz (~3.1 GHz bandwidth), respectively. The higher resonating frequency band can be tuned/controlled by varying the width of the triangle slot, while the medium operational band can be controlled by adjusting the width of the SSRR slot. Initially, the simulated S-parameter response, 2D and 3D radiation patterns, gain, and surface current distribution of the proposed UWB inverted triangular antenna has been studied using epoxy glass FR4 substrate having parameters εr = 4.3, h = 1.6 mm, and tan δ = 0.025, respectively. In order to validate the simulation results, the proposed UWB antenna with dual-notch band characteristics is finally fabricated and measured. The fabricated antenna’s return-loss and far-field measurements show good agreement with the simulated results. The proposed antenna achieved the measured gain of 2.3 dBi, 4.9 dBi, and 5.2 dBi at 3.5 GHz, 6.1 GHz, and 9.25 GHz, respectively. Additionally, an in-depth comparative study is performed to analyze the performance of the proposed antenna with existing designs available in the literature. The results show that the proposed antenna is an excellent candidate for fifth-generation (5G) mobile base-stations, next-generation WiFi-6E indoor distributed antenna systems (IDAS), as well as C-band and X-band applications.

Passive Intermodulation Measurement: Challenges and Solutions

In modern wireless communication systems, the signal-to-noise ratio (SNR) is one of the most important performance indicators. When the other radio frequency (RF) performance of the components is well designed, passive intermodulation (PIM) interference may become an important factor limiting the system’s SNR. Whether it is a base station, an indoor distributed antenna system, or a satellite system, there are stringent PIM level requirements to minimize interference and enhance network capacity in multicarrier networks. Especially for systems of high power and wide bandwidth such as 5G wireless communication, PIM interference is even more serious. Due to the complexity and uncertainty of PIM, measurement is the most important means to study and evaluate the PIM performance of wireless communication systems. In this review, the current main PIM measurement methods recommended by International Electrotechnical Commission (IEC) and other standard organizations are introduced, and several key challenges in PIM measurement and their solutions (including the design of PIM tester, the location of the PIM sources, the design of compact PIM anechoic chambers, and the evaluation methods of PIM anechoic chambers) are highlighted. These challenges are of great significance to solve PIM problems that may arise during device characterization and verification in real wireless communication systems.

Metamaterial-Inspired Electrically Compact Triangular Antennas Loaded with CSRR and 3 × 3 Cross-Slots for 5G Indoor Distributed Antenna Systems.

In this article, two distinct kinds of metamaterial (MTM) antennas are proposed for fifth-generation (5G) indoor distributed antenna systems (IDAS). Both antennas operate in the sub-6 GHz 5G band, i.e., 3.5 GHz. The antenna’s radiating structure is based on a combination of triangular and rectangular patches, as well as two complementary split-ring resonators (CSRR) unit-cells etched on the top layer. The bottom layer of the first MTM antenna is a complete ground plane, while the bottom layer of the second MTM antenna is etched by a 3 × 3 cross-slot MTM structure on the ground plane. The use of these structures on the ground plane improves the antenna bandwidth. The proposed antennas are designed using two different substrates i.e., a high-end Rogers thermoset microwave materials (TMM4) substrate (h = 1.524 mm/εr = 4.5/tan δ = 0.002) and a low-end flame-resistant (FR4) epoxy glass substrate (h = 1.6 mm/εr = 4.3/tan δ = 0.025), respectively. The antenna designs are simulated using CST microwave studio, and in the end, the antenna fabrication is performed using FR4 substrate, and the results are compared. Furthermore, parametric analysis and comparative studies are carried out to investigate the performance of the designed antennas. The simulated and measured results are presented for various parameters such as return-loss, gain, and radiation pattern. The two MTM antennas have an overall dimension of 18 × 34 mm2, demonstrating that the proposed design is 60 percent smaller than a standard microstrip patch antenna (MPA). The two proposed MTM antenna designs with complete ground plane and 3 × 3 cross-slot MTM on the bottom layer using FR4 substrate have a measured gain/bandwidth characteristic of 100 MHz/2.6 dBi and 700 MHz/2.3 dBi, respectively.

RoF-based indoor distributed antenna system that can simultaneously support 5G mmWave and 6G terahertz services.

The telecommunication society is paving the way toward ultra-high frequency regions, including the millimeter wave (mmWave) and sub-terahertz (sub-THz) bands. Such high-frequency electromagnetic waves induce a variety of physical constraints when they are used in wireless communications. Inevitably, the fiber-optic network is deeply embedded in the mobile network to resolve such challenges. In particular, the radio-over-fiber (RoF)-based distributed antenna system (DAS) can enhance the accessibility of next-generation mobile networks. The inherent benefits of RoF technology enhance the DAS network in terms of practicality and transmission performance by enabling it to support the 5G mmWave and 6G THz services simultaneously in a single optical transport link. Furthermore, the RoF allows the indoor network to be built based on the cascade architecture; thus, a service zone can be easily added on request. This study presents an RoF-based multi-service DAS network and experimentally investigates the feasibility of the proposed system.

A Time Series-Based Study of Correlation, Channel Power Imbalance, and Diversity Gain in Indoor Distributed Antenna Systems at 60 GHz

In this article, we investigate the potential enhancements in signal reliability which can be achieved using a millimeter-wave distributed antenna system (DAS) within an indoor environment. To achieve this, we measured the signal power simultaneously received at nine ceiling-mounted access point (AP) locations likely to be used in future indoor DAS deployments while a mobile user imitated making a voice call on a hypothetical user equipment. Key metrics, associated with the performance of multiple antenna systems, such as the cross correlation coefficient (CCC) and channel power imbalance (CPI) are determined. It was found that line-of-sight (LOS) and quasi-LOS (QLOS) links with the APs typically led to higher CCC values than the non-LOS (NLOS) cases. Similarly, LOS and QLOS links typically produced higher CPI values between APs than the NLOS case. To enable the reproduction of our results, we have successfully applied autoregressive moving average and autoregressive integrated moving average modeling to the CCC and CPI time series. The performance improvement that can be achieved using a DAS instead of a single AP was evaluated using three commonly deployed diversity combining schemes, namely, selection combining , equal gain combining , and maximal ratio combining along with three AP selection mechanisms, namely, per-sample random AP selection , one-shot AP selection , and per-sample optimal AP selection . Finally, we have provided some useful insight into the influence of differing AP numbers on the diversity gain when considering the aforementioned AP selection methods.

Investigation of optical power budget for expanding indoor-mobile coverage in 5G indoor distributed antenna system (DAS) supporting 32 FAs transmission

We experimentally present the maximum optical power budget in the analog IFoF-based indoor distributed antenna system (DAS) link supporting 32 FAs transmission of 5G wireless signals. For maximum optical power budget, we derive the maximum launched optical power and the optimum optical modulation index (OMI)/frequency assignment (FA) based on laser over-modulation. To investigate the effect, we analyze the impacts of nonlinear distortion of the single-mode-fiber (SMF) on the Tx side, and influence of noise and distortions of the analog IFoF-based indoor DAS link. Also, we include the avalanche photodiode (APD) as an optical receiver and the erbium-doped fiber amplifier (EDFA) as an optical power booster in mmWave 5G based indoor DAS link to meet the transmission performance at low received optical power. It is experimentally observed that the optical power budget is improved with using the laser over-modulation by 23 dB in analog IFoF based 5G indoor DAS link for 32 FAs x 100 MHz 5G wireless signals.

A Highly Linear Low-Noise Transimpedance Amplifier for Indoor Fiber-Wireless Remote Antenna Units

This article presents an optimized design of a low-noise transimpedance amplifier (TIA) with high linearity for use in the downlink receiver of a remote antenna unit (RAU). The aim of this design is to be used in a cost-effective indoor distributed antenna system (DAS) for WLAN transmission using a mixed fiber-wireless system. The circuit topology consists of a fully differential shunt–shunt feedback TIA with digitally programmable transimpedance. An open-loop gain compensation technique is used to maintain stability and constant bandwidth (BW). The TIA has been fabricated in 65 nm CMOS technology with a 1.2 V voltage supply. The total power consumption of the TIA is 6 mW. A complete electrical and optical characterization with a 1550 nm PIN photodiode has been performed to demonstrate the reliable 54 Mb/s 802.11a WLAN transmission achieved with an error vector magnitude (EVM) lower than 3% for a 20 dB optical input range.

Power budget improvement of multi-IFoF based analog indoor-distributed antenna system (DAS) with laser over-modulation

Abstract We demonstrate the improvement of the optical power budget in multi-intermediate frequency over fiber (IFoF) based indoor-distributed antenna system (DAS) with 48 IF carriers of LTE-A signal using laser over-modulation. The laser over-modulation can improve the optical power budget by increasing the input RF power to DFB-LD until a limit of nonlinear distortion such as CTB and clipping, when the received optical power is very low. To compensate the decrease of optical power budget in analog optical link, we employ the laser over-modulation, and derive the optimum optical modulation index (OMI)/ch to enhance link budget. To investigate the effect of laser over-modulation, we analyze the noise characteristics associated with the carrier-to-noise ratio (CNR) depending on the received optical power, and compare three different optical receivers (Rx) most often used: i) PIN-photodiode (PD), ii) APD, iii) PIN-PD following an EDFA (EDFA-PIN), respectively. Using the laser over-modulation, it is experimentally observed to achieve optical power budget of 25 dB for PIN-PD, 31 dB for APD, and 33 dB for EDFA-PIN in multi-IFoF based indoor-DAS for 48 x 20 MHz LTE-A signals transmission, respectively.

4 × 4 MIMO architecture supporting IFoF-based analog indoor distributed antenna system for 5G mobile communications.

We demonstrate the analog indoor distributed antenna system (DAS) for 5G mobile communications that supports 4 × 4 multiple-input multiple-output (MIMO) configuration. For this, we exploit a pair of intermediate frequency over fiber (IFoF)-based analog optical links, transporting 32 frequency allocation (FA) 5G mobile signals (effectively ~4 GHz bandwidth). The analog optical link manifests its high fidelity in the measured characteristics: small gain variation (< ± 1 dB for the entire transmission bandwidth), low noise (<-136 dBm/Hz), and large dynamic range (spurious free dynamic range of >106 dB∙Hz2/3), subsequently providing superior error vector magnitude (EVM) performance (~2%) for a wide range of ambient temperatures (-20 ~60°C). Consequently, the IFoF-based 4 × 4 MIMO supporting analog indoor DAS is capable of providing record high peak throughput of 5.3 Gb/s for millimeter wave based 5G mobile communication system.

Gene-Sequencing-Based Indoor Localization in Distributed Antenna System

In the indoor distributed antenna system (DAS), base station transmits signals with even power via the distributed antennas. Thus, single reference signal received power (RSRP) from the receiver will result in accurate localization. In response to this compelling problem, we utilize the pedestrian dead reckoning, which is based on consecutive signals in collected RSRP sequences as the template sequences, to achieve high-performance location estimation. Specifically, the main idea of the proposed localization algorithm is calculating the correlation between the on-site sequence and each pre-constructed template sequence, which is labeled with human movement coordinates. Then, the prediction location is considered as the template sequence label that is with the largest approximation to the on-site sequence. Experiments are conducted with real time division long-term evolution signals in indoor DAS, and the corresponding experimental results demonstrate that the proposed approach can not only solve the problem of positioning in DAS, but also provide satisfactory localization accuracy.

Link-Level Analysis of a Multiservice Indoor Distributed Antenna System [Wireless Corner

In this article, the link-level performance of a multiservice indoor distributed antenna system (MS-IDAS) in an indoor-hotspot scenario is studied. A low-profile broadband antenna is proposed as the access point (AP) antenna, and then it is used as an identical array element for constructing two-and three-port multipleinput, and multiple-output (MIMO) antennas. The proposed MS-IDAS antenna covers various IEEE 802.11 standards within 2-6 GHz, and its link-level simulations are performed at 5 GHz for the 802.11n protocol. The error-rate performances of the three-element MIMO antenna is analyzed in WINNER indoor scenarios by using simulated-channelimpulse response (CIR). In a typical indoor-hotspot room with dimensions of 20 m x 20 m x 10 m, the wallmounted MS-IDAS antenna shows better coverage than the ceilingmounted case. In addition, the proposed MIMO antenna outperforms a uniform linear-dipole array with the same interelement distance in terms of error-rate performance.

Distributed Hybrid Precoding for Indoor Deployments Using Millimeter Wave Band

Distributed Antenna Systems (DAS) are an alternative of network deployment that allows reducing the distance between transmitter and receiver by distributing the antennas throughout the coverage area. Moreover, the performance of the millimeter wave (mmWave) band can be significantly high within short transmitter-receiver distances. In this paper, the potential benefits of DAS deployments in the mmWave band are studied. To this aim, a distributed hybrid precoding (DHP) solution with remote antenna unit (RAU) selection capabilities is proposed and analyzed in an indoor DAS working in mmWaves and compared to two other indoor deployment strategies: a conventional cellular system with colocated antenna arrays and a small cell deployment. The results show that, using DHP, DAS not only brings huge gains to cell-edge users rate but also increases system capacity, becoming the best overall deployment. Further simulations including practical limitations have revealed that DAS using DHP is quite robust to combiner losses, although its performance is significantly degraded by outdated channel reports.

A compact broadband dual‐polarized omnidirectional antenna with high isolations for indoor DAS applications

ABSTRACTA compact broadband horizontally/vertically polarized omnidirectional antenna with high isolations is presented for indoor distributed antenna systems. The antenna is a combination of a horizontally polarized (HP) element and a vertically polarized (VP) element, which are connected by four broadside parallel strips (BPSs). Its HP and VP elements consist of four horizontal and vertical elliptical printed dipoles respectively. The vertical dipoles locate between adjacent horizontal dipoles, which makes the antenna compact in structure. The dual‐polarized antenna obtains a bandwidth of 45.5% from 1.7 to 2.7 GHz, and the port isolations are better than 30 dB without introducing large distance between vertical dipoles and horizontal dipoles. The HP and VP gains are higher than 1.7 and 2 dBi respectively. For both horizontal and vertical elements, the radiation patterns in the horizontal plane are omnidirectional with ripples &lt;2.5 dB, and the cross‐polarization levels are also below −25 dB in the horizontal plane. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:176–180, 2017

A COMPACT BROADBAND SLOT ANTENNA FOR INDOOR DISTRIBUTED ANTENNA SYSTEMS

A compact omnidirectional vertical-polarized broadband slot antenna for indoor distributed antenna systems is presented. The proposed antenna consists of a deformed printed monopole on one side of the substrate and a polygon slot in the circular ground plane on the other side. Due to the utilization of the wideband slot structure, the antenna achieves small electrical dimension of 0.327λ × 0.327λ × 0.0046λ at the lowest operating frequency, and an impedance bandwidth of about 129% (0.66–3.07 GHz) for VSWR ≤ 1.5 is achieved, covering all frequency bands for 2G, 3G, 4G and some Wi-Fi communications. The proposed antenna has stable radiation patterns over the operating bands. The measured gains of the antenna range from 1.5 dBi (lower band) to 5.5 dBi (higher band). Compact planar structure makes the proposed antenna a perfect candidate for ceiling or surface mounted indoor distributed antenna applications.

A Broadband Dipole Antenna for Multiservice Indoor Distributed Antenna System (MS-IDAS)

Multiservice indoor distributed antenna system (MS-IDAS) plays an important role in wireless communications. This letter investigates a broadband antenna for MS-IDAS, which is composed of a loop-loaded dipole, a microstrip feeding line, and a flat reflector. Through the loop-loaded structure, the low frequency band is greatly extended. A prototype with dimensions of $180~\hbox{mm} \times 150~\hbox{mm} \times 50~\hbox{mm}$ is presented to cover the frequency band of 880-2700 MHz. Indoor coverage experiments prove that high quality signals are provided by the antenna within the designed bandwidth, which is a decent candidate for MS-IDAS.

Wideband ceiling mount omnidirectional antenna for indoor distributed antenna system applications

A wideband omnidirectional vertical polarised antenna is presented. By incorporating a shorted coupling top loading structure over two cross-connected monopole antennas, an enhanced impedance bandwidth of 152% is achieved. The prototype antenna operates from 650 to 4500 MHz, with a reflection coefficient <;-15 dB, a 2-6 dBi antenna gain with a very stable vertical radiation pattern and <;3.5 dB horizontal pattern ripples. The proposed antenna can be widely used in indoor distributed antenna systems (DASs), such as GSM900, GSM1800, UMTS2100 and the enhanced TD-LTE (up to 3.5 GHz) bands. The simulated and the measured return loss and radiation pattern results show good agreement.

Experimental Evaluation of Layout Designs for 3 $ \times$ 3 MIMO-Enabled Radio-Over-Fiber Distributed Antenna Systems

This paper experimentally demonstrates that, for two representative indoor distributed antenna system (DAS) scenarios, existing radio-over-fiber (RoF) DAS installations can enhance the capacity advantages of broadband 3 × 3 multiple-input-multiple-output (MIMO) radio services without requiring additional fibers or multiplexing schemes. This is true for both single- and multiple-user cases with a single base station and multiple base stations. First, a theoretical example is used to illustrate that there is a negligible improvement in signal-to-noise ratio (SNR) when using a MIMO DAS with all N spatial streams replicated at N RAUs, compared with a MIMO DAS with only one of the N streams replicated at each RAU for N ≤ 4. It is then experimentally confirmed that a 3 × 3 MIMO DAS offers improved capacity and throughput compared with a 3 × 3 MIMO collocated antenna system (CAS) for the single-user case in two typical indoor DAS scenarios, i.e., one with significant line-of-sight (LOS) propagation and the other with entirely non-line-of-sight (NLOS) propagation. The improvement in capacity is 3.2% and 4.1%, respectively. Then, experimental channel measurements confirm that there is a negligible capacity increase in the 3 × 3 configuration with three spatial streams per antenna unit over the 3 × 3 configuration with a single spatial stream per antenna unit. The former layout is observed to provide an increase of ~ 1% in the median channel capacity in both the single- and multiple-user scenarios. With 20 users and three base stations, a MIMO DAS using the latter layout offers median aggregate capacities of 259 and 233 bit/s/Hz for the LOS and NLOS scenarios, respectively. It is concluded that DAS installations can further enhance the capacity offered to multiple users by multiple 3 × 3 MIMO-enabled base stations. Further, designing future DAS systems to support broadband 3 × 3 MIMO systems may not require significant upgrades to existing installations for small numbers of spatial streams.