Local Multipoint Distribution System Research Articles

Design, fabrication, and measurement of a miniaturized MIMO antenna applicable for 5G communication

Abstract The design of low-profile Multiple-Input-Multiple-Output (MIMO) antennas for various 5G applications is a topic of huge interest in academia, research, and telecommunication sector. In this aspect, a compact and low-profile 5G MIMO antenna has been designed and analyzed for various 5G applications, specifically for the 24 GHz bands (24.25–24.45 GHz and 25.05–25.25 GHz) and local multipoint distribution system band (27.5–28.35 GHz) of the 5G spectrum. The proposed antenna structure is 20 × 20 × 1 mm3 in dimension. Two spade-shaped radiators composed of Copper (annealed) material are placed orthogonally to improve isolation and maintain signal diversity. Rogers RT 5880 is used as the material for substrate. The antenna exhibits a wide bandwidth of 21.5–28.5 GHz. The mutual isolation |S21| has been maintained ≤29 dB due to the insertion of a T-shaped parasitic strip in between the radiating elements. Novelty in design and superiority in performance has been observed when compared with related antenna categories.

Millimeter-Wave Multi-Beam Waveguide Lens Antenna

A millimeter-wave multi-beam antenna operating dual-band with a 1 GHz bandwidth each, around the 28 and 31 GHz frequencies, is presented. The antenna is designed on the principle of transformation of the cylindrical wavefront to planar to enhance the gain. A metal ridge lens is used for the wavefront transformation by a phase extraction and compensation method. The dual-band operation of the antenna aids in transmitting and receiving at two independent frequencies. An advantage to this is the significant reduction of the number of RF chains due to the use of the shared aperture over the lens. The antenna has been validated for casting the beam in three primary target directions of - 60°, 0°, and 60°, however, other beam directions can be suitably designed. The spatial footprint of the antenna is 170 mm × 150 mm and has a gain varying between 14 and 15 dBi at each of the three ports centered around 28 and 31 GHz. The theoretical simulated results are in good agreement with the measurements. The antenna could potentially be used in 5G small cell deployments of a millimeter-wave local multipoint distribution system (LMDS).

Design of circularly polarised beam‐shaped RAs using a single layer of concentric dual split loops

This study presents the design of circularly polarised beam-shaped reflectarrays (RAs) based on a rotational element. This element is a single layer of concentric dual split-loop structure using multi-resonance technique to improve the unit bandwidth. For accuracy and efficiency, a new multi-step convergence strategy has been used in the intersection approach to avoid local minima. This strategy leads the optimisation to the solution independently of the starting point by gradually varying the target pattern. Two kinds of shaped beams have been calculated. A medium-sized RA has been designed for a local multipoint distribution system application to validate the modified approach. The numerical result suggests good convergence without critical starting point demand for the intersection approach. The other RA is designed, manufactured and tested for quad-beam radiation, and it presents a 12.1% 1 dB bandwidth from 13.1 to 14.8 GHz with the axial ratio <3 dB. All the results suggest the rotational element can be a good solution in beam-shaped RA designs.

Performance of Subcarrier and Power Allocation Orthogonal Frequency-Division Multiplexing on Millimeter Wave

Local multipoint distribution system (LMDS) that operated in millimeter waves can be used to fulfill the need of bit rate higher than 40 Mbps. However it has problem when applied in tropic country such as Indonesia because of the high rainfall. Therefore LMDS system was developed by cross-layer mechanism. In this research we used joint subcarrier and power allocation (JSPA) technique in multi-user cross-layer OFDM. This technique is proposed to increase the performance of telecommunication system even there were disturbance of rain attenuation. The research is discussing the performance of transmission capacity, data rate, utility and fairness of JSPA algorithm that applied in rain attenuation measurement in Surabaya. The result shows the increment of performance system using JSPA technique. For 40 dB rain attenuation, JSPA can achieves respectively average capacity of transmission up to 173,3%, 189,9 % for data rate and 9,6% for fairness system. The application of JSPA technique improve the performance of utility 13,61-15,48 bps/Hz

Systematic Framework for Reflectarray Synthesis Based on Phase Optimization

A new systematic synthesis framework for reflectarray antennas is discussed. Optimization based on the Levenberg-Marquardt algorithm is used to obtain the phase distribution of the reflection coefficients required on the reflectarray surface, in order to achieve the pattern specifications. A Local Multipoint Distribution System (LMDS) base station working in the 24.5–26.5 GHz frequency band has been proposed to evaluate the method. The 3D requirements are defined by the combination of the elevation and templates and considering a maximum acceptable ripple in the beam shaping. Some illustrative results are obtained.

37–38 GHz substrate integrated filtenna for wireless communication application

AbstractThe seamless or incorporate design of RF filter and antenna is very important for size and loss reduction in the design of millimeter wave wireless communication systems.Such antenna is then called as filtenna. In this article, an integrated design of the filter and antenna or filtenna at 37–38 GHz for local‐multipoint‐distribution‐system (LMDS) based on substrate integrated waveguide (SIW) technology is presented. One slot and two‐slot SIW antennas and corresponding filtennas are simulated, fabricated and measured. By comparing the measured return loss and radiation patterns between the filtenna and the original antenna, it is concluded that the performance of the filtenna is kept nearly no change within the working frequency band while the out of band signal is effectively filtered. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:346–351, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26589

A REAL-TIME MULTIMEDIA APPLICATION STUDY IN LMDS NETWORKS USING MPLS

Several wireless networking solutions have been developed to provide different types of services for various end user applications. Due to the success of ATM and IP technology in the information technology area. Local Multipoint Distribution Service (LMDS) is a broadband wireless access (BWA) networking solution. In this paper, an LMDS (Local Multipoint Distribution System) over MPLS (Multi-Protocol Label Switching) network for real-time multimedia applications is introduced. LMDS-MPLS network model is realized and simulated by using OPNET 9.0 simulation package. The simulation results are obtained for sample voice, video, data and non-critical data traffics under varying network load conditions. Analysis of the end-to-end delay results is also presented.

A GCPW CMOS Bandpass Filter for Local Multipoint Distribution Systems

In this paper, an integrated millimeter-wave bandpass filter (BPF) using a standard CMOS process was designed and fabricated successfully for Local multipoint distribution systems (LMDS). Ground coplanar waveguide (GCPW) line, instead of the microstrip line, is used for realizing the proposed filter without extra transition between the CPW and microstrip, reducing the design complex. Moreover, the bandwidth of the proposed filter can be easily tuned by varying the structural parameters. The design procedure, including the electromagnetic (EM) and circuit simulation, is addressed. The measured results of the circuit have a center frequency of 39.6 GHz, an insertion loss of 5.5 dB, and a 3dB bandwidth of 33%. In addition, a transmission zero at 51.49 GHz appears near the passband edge, improving the band selectivity.

Application of ANFIS Power Control for Downlink CDMA-Based LMDS Systems

Rain attenuation and intercell interference are two crucial factors in the performance of broadband wireless access networks such as local multipoint distribution systems (LMDS) operating at frequencies above 20 GHz. Power control can enhance the performance of downlink CDMA-based LMDS systems by reducing intercell interference under clear sky conditions; however, it may damage system performance under rainy conditions. To ensure robust operation under both clear sky and rainy conditions, we propose a novel power-control scheme which applies an adaptive neuro-fuzzy inference system (ANFIS) for downlink CDMA-based LMDS systems. In the proposed system, the rain rate and the number of users are two inputs of the fuzzy inference system, and output is defined as channel quality, which is applied in the power control scheme to adjust the power control region. Moreover, ITU-R P.530 is employed to estimate the rain attenuation. The influence of the rain rate and the number of users on the distance-based power control (DBPC) scheme is included in the simulation model as the training database. Simulation results indicate that the proposed scheme improves the throughput of the DBPC scheme.

Measurements and modelling of cellular interference in local point-to-multipoint distribution systems

Frequency and polarisation reuse for optimum spectral efficiency in local multipoint distribution system (LMDS) networks generate co- and adjacent-channel inter- and intra-cell interference because of the line-of-sight constraints among transmitting and receiving antennas. Such operational constraints limit the system capacity and affect link performance. Measurements at 40 GHz from a number of possible interference scenarios for two different LMDS reuse cellular plans of dual-frequency and dual-polarisation discriminations are presented. An electromagnetic-stochastic propagation model is employed. The model successfully predicts the interference parameters and takes into account the effects of multiple paths and depolarisation caused by reflection and scatter from building surfaces at millimetre-wave frequencies. The probability density function of the signal-to-interference ratio and the statistical channel parameters, such as the average signal strength and the Rician K-factor, are extracted from the measured data and compared with model predictions.

Accurate analysis of printed reflectarrays considering the near field of the primary feed

An analysis technique is proposed for the analysis of reflectarrays placed in the Fresnel zone of the primary feed. The technique is based on the classic analysis of reflectarrays considering local periodicity, improved by considering the near field radiated by the feed horn instead of ideal feed models. The incident field on each reflectarray cell is obtained by applying field transformation to the measured far field (FF) of the horn antenna. The stronger variation of the incident field is considered by increasing the number of samples per reflectarray cell for the incident and reflected waves. This enhanced analysis has been applied to the analysis of a multi-fed and multiple-shaped beam reflectarray placed in the Fresnel zone of the feed horns. The antenna was proposed as a central station antenna for a local multipoint distribution system in the 24.5-26.5-GHz band. The antenna was designed by considering an approximate FF feed model in the radiation pattern synthesis and the reflectarray design. The results obtained through the enhanced analysis are compared with those from measurements of a prototype, validating the proposed analysis procedure and providing a significant improvement with respect to conventional analysis.

Demonstration of a Shaped Beam Reflectarray Using Aperture-Coupled Delay Lines for LMDS Central Station Antenna

A shaped-beam reflectarray based on patches, aperture-coupled to delay lines is demonstrated for local multipoint distribution system (LMDS) central station antennas, in the 10.10-10.70 GHz band. The antenna must cover a 60 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">deg</sup> -sector in azimuth with a squared cosecant pattern in elevation. The design process consists of two steps. First, a phase-only pattern synthesis technique is applied to obtain the required phase-shift distribution on the reflectarray surface which generates the shaped pattern. The second stage consists of determining the length of the delay lines, aperture-coupled to the square patches, in order to achieve the phase distribution synthesized in the previous step. Two reflectarray antennas have been designed, one for vertical (V) and the other for horizontal (H) polarization. A breadboard for V-polarization has been manufactured and tested in an anechoic chamber, showing a good agreement between theoretical and measured radiation patterns.

Multifed Printed Reflectarray With Three Simultaneous Shaped Beams for LMDS Central Station Antenna

A two-layer reflectarray is proposed as a central station antenna for a local multipoint distribution system (LMDS) in the 24.5-26.5 GHz band. The antenna produces three independent beams in an alternate linear polarization that are shaped both in azimuth (sectored) and in elevation (squared cosecant). The design process is divided into several stages. First, the positions of the three feeds are established as well as the antenna geometry to produce the three beams in the required directions. Second, the phase distribution on the reflectarray surface, which produces the required beam shaping, is synthesized. Third, the sizes of the printed stacked patches are adjusted so that the phase-shift introduced by them matches the synthesized phase distribution. Finally, the radiation patterns are computed for the central and lateral beams, showing a shaping close to the requirements. A breadboard has been manufactured and measured in an anechoic chamber, showing a good behavior, which validates the designing methodology.

Analyses of numerical and experimental results for optical signal generation using heterodyne scheme

In this paper, we have proposed a heterodyne technique to generate an optical millimeter-wave signal for ultra-wideband communication. First, we have investigated the characteristics of semiconductor lasers locked to another semiconductor under the RF modulation having many sidebands. The RF-modulated master laser is represented by a series of Bessel functions. This model is then inserted into Lang's rate equations. By numerically solving the resulting rate equations, we have determined the locked laser output characteristics as well as the RF spectrum of the beat signals. The result is that the unselected sidebands can produce undesired beat signals whose power may be comparable to that of the desired beat signal. Furthermore, their strength is affected by the injected ML light power. With reduced ML light, undesired beat signals and the injection-locking bandwidth can be suppressed. Second, we have experimented a new technique for generating millimeter-wave signals from a semiconductor laser. A 32 GHz signal is generated using a multisection semiconductor laser operated under a continuous wave by injecting optical pulses at a repetition rate equal to the fourth subharmonic (8 GHz). The generated millimeter-wave signal exhibits a large subharmonic suppression ratio, a large frequency detuning range, low levels of phase-noise and a large locking range. These simulation results are confirmed by experimental results. The high-frequency signal can be used in the field of ultra-wideband communication employing local multipoint distribution system (LMDS), wireless local loop (WLL) and mobile broadband system (MBS).

Fast automated design of waveguide filters using aggressive space mapping with a new segmentation strategy and a hybrid optimization algorithm

Waveguide filters are key elements present in many microwave and millimeter-wave communication systems. In recent times, ever-increasing efforts are being devoted to the development of automated computer-aided design (CAD) tools of such devices. In this paper, a novel CAD tool based on modal analysis methods, which improves the efficiency and robustness of the classical aggressive space-mapping technique, is presented for those purposes. The use of a new segmentation strategy and the hybridization of a specific combination of several well-known optimization algorithms is proposed. The CAD tool has been successfully validated with the practical design of several H-plane coupled cavity filters in a rectangular waveguide for space and communication applications. A filter prototype for local multipoint distribution systems operating at Ka-band, and two tunable H-plane filters with tuning posts operating at 11 and 13 GHz, have been successfully designed, manufactured, and measured.

Effects of Rain Fading on the Efficiency of the Ka-Band LMDS System in the Taiwan Area

This work presents the effects of rain on the performance of a Ka-band local multipoint distribution system (LMDS) in Taiwan. The rain distribution statistics, from 2-yr measurements with 1-min temporal resolution and 12-yr measurements with a 1-h temporal resolutions, were analyzed. The rain-attenuation model that takes local rain effects is established statistically. These statistical data are used to analyze the performance of the LMDS in terms of its signal-to-interference (S/I) ratio, bit-error rate (BER), and channel capacity at various service distances. From the analysis, it is found that the light rain events induce better S/I for cellular network service, because other base transceiver station (BTS) interference signals around the main BTS are likely to be blocked by rain. The probability that below the nominal value of the channel capacity, when there is rain fading without cellular interference, meets a margin of BER=10/sup -6/ in a 6-km cell using quaternary phase-shift keying (QPSK) modulation. However, when the cellular interference is presented, the effective BTS service distance greatly shrinks to 2-3 km. In summary, in a cellular network environment, as the cell coverage radius is reduced, the effective BTS service range will be correspondingly compressed, suggesting that the cellular interference is even more serious than the rain attenuation itself.

Improving Capacity in LMDS Networks Using Trellis-Coded Modulation

Local multipoint distribution systems (LMDS), which are operating worldwide in the frequency range of 26 to 43GHz, have large bandwidths of 0.1 up to 2 GHz but a limited area coverage of a few kilometers only. This is due to line-of-sight (LOS) constraints for reliable point-to-multipoint links as well as due to large propagation losses. The size of the macrocells illuminated by the base stations, where LOS exists, is approximately 1 to 5 km. As suggested in the CRABS report (1999), the maximal spectral efficiency can be obtained with a dual frequency and polarization reuse plan. This frequency and polarization reuse leads to interference. In this paper, we report a new technique that uses trellis-coded modulation (TCM) for increasing the capacity of LMDS networks. Analytical expressions have been derived for pairwise error probability for both high and low SNR scenarios. Numerical simulations have shown that using the proposed TCM schemes in cochannel cells have resulted in a large decrease in interference, thereby allowing us to reduce the frequency reuse distance. In this paper, we present the strategy using two TCM schemes that allow the frequency reuse factor of unity, without compromising on the QoS caused by increased interference. Design rules for constructing TCM schemes are also proposed in this paper.

Two-Dimensional Line of Sight Interference Analysis of LMDS Networks for the Downlink and Uplink

Local multipoint distribution systems (LMDS), which are operating worldwide in the frequency range of 26 to 43 GHz, have large bandwidths of 0.1 up to 2 GHz, but a very limited area coverage due to line of sight constraints and large propagation losses. As suggested in the Cellular Radio Access for Broadband Services (CRABS) Report , a high spectral efficiency can be obtained for a regular network of squared cells with a dual frequency and polarization reuse scheme. However, this frequency and polarization reuse leads to cochannel and adjacent channel interference. In this paper, we report a systematic two-dimensional study of interference in such a regular LMDS network for the downlink and uplink in order to assess the impact of different geometric and propagation parameters. The paper reports simple formulas to estimate the areas of high interference levels within an LMDS cell as a function of the half-power beamwidth of the customer-site antennas for the downlink. The effect on the carrier-to-interference distribution over a LMDS cell is evaluated by varying the half-power beamwidth of the customer-site antennas, the time percentage of short term enhancement due to atmospheric multipath and focusing effects and the cell dimensions. We also introduce a simple technique by reorientation of the customer-site antennas for interference reduction. The results presented in this paper can be used to carry out system-level design for interference-limited LMDS cells.

PAE improvement and compensation of small‐signal gain drift due to temperature on power amplifiers through active biasing

AbstractPower millimetre‐wave band transmitters are commonly formed by a chain of MESFET or HEMT GaAs MMIC power amplifiers. Under large‐signal conditions the reverse gate output current, which appears at the gate port of those devices due to drain‐gate breakdown mechanisms, causes a drop in the power amplifier's power added efficiency (PAE) figure, thus affecting the entire transmitter reliability. Additionally, it is desirable to obtain a stable performance from the transmitters for different ambient temperatures. In particular, millimetre‐wave wireless systems, such as the local multipoint distribution system (LMDS), require constant small signal gain for a wide range of temperatures. In this paper, an active bias network is used to compensate for both effects. The performance of the active bias network is shown to be superior, in terms of the power amplifier's PAE and the compensation of the power amplifier's small signal gain drifts due to temperature, to a conventional resistive divider when used for biasing the power amplifier. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 389–392, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11069

General coverage prediction algorithm for LMDS

A general algorithm for coverage prediction for local multipoint distribution systems is presented. It is based on area-averaged rainfall statistics and a correction factor dependent on the spatial inhomogeneity of the rainfall medium. A validation of the proposed method based on experimental results concerning Chilbolton, United Kingdom, is made and coverage prediction examples are given.