A 4-channel V-band beamformer featuring a switchless PALNA for scalable phased array systems. - In: 2021 IEEE/MTT-S International Microwave Symposium, (2021), S. 839-841
This paper presents a 4-channel bidirectional V-band beamformer adopting a switchless PALNA in a SiGe:C 130 nm BiCMOS technology, featuring ft/fmax of 250/340 GHz. Using such technique saves the silicon area occupied by the RF switches avoiding their lossy effect on PAs outputs and LNAs inputs. The designed beamformer contains PAs, LNAs, vector modulators with active balun, passive power dividers/combiners and an integrated SPI interface. On-wafer measurements show that the fabricated beamformer covers the band from 57 GHz to 66 GHz with an average small signal gain of 18 dB and 9 dB all over the channels in both Tx and Rx modes respectively. Furthermore, the beamformer achieves an OP1dB of 10.5 dBm in Tx mode and an IP1dB of -27 dBm in Rx mode. The circuit occupies 11 mm2 and consumes 230 mW and 100 mW per channel in Tx and Rx modes respectively.
https://doi.org/10.1109/IMS19712.2021.9574827
Energy-efficient autonomous resource selection for power-saving users in NR V2X. - In: 2021 IEEE 32nd Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), (2021), S. 972-978
Energy efficiency has recently drawn significant attention in diverse applications, such as vehicle-to-everything (V2X) communications. This paper investigates a joint energy efficiency and sum-rate maximization problem in autonomous resource selection in the 5G new radio (NR) vehicular communication while catering for reliability and latency requirements. An autonomous resource allocation problem is formulated as a ratio of sum-rate to energy consumption, where the objective is to maximize the total energy efficiency of power-saving users subject to the reliability and latency requirements. The energy efficiency problem is a mixed-integer programming optimization problem that is computationally complex when the number of users increases. Therefore, a heuristic algorithm, density of traffic-based resource allocation (DeTRA), is proposed to solve the problem. The traffic density per traffic type is considered a metric to split the radio resources and trigger an appropriate resource selection strategy. The simulation results show that the proposed algorithm outperforms the existing schemes in terms of energy efficiency.
https://doi.org/10.1109/PIMRC50174.2021.9569365
Verification of dual-polarized ultra-wideband channel sounder for THz applications. - In: 2021 IEEE 32nd Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), (2021), insges. 5 S.
The lower THz bands are foreseen as candidates to achieve the data-rates demanded in the sixth generation (6G) of wireless communications. Hence, multiple measurements for characterization of propagation at these frequencies in different scenarios are being conducted all around the world. This also impulses activities on standardization of measurement equipment and methodologies to define common practices and make measurements from different actors comparable. Therefore, in the present paper we investigate the accuracy of a dual-polarized ultra-wideband channel sounder in the time, angular, and polarization domains by means of a verification methodology based on interferometry.
https://doi.org/10.1109/PIMRC50174.2021.9569491
Fully digital and hybrid beamforming design for millimeter-wave MIMO-OFDM two-way relaying systems. - In: 2021 IEEE Statistical Signal Processing Workshop (SSP), (2021), S. 296-300
https://doi.org/10.1109/SSP49050.2021.9513786
Time-instance zero-crossing precoding with quality-of-service constraints. - In: 2021 IEEE Statistical Signal Processing Workshop (SSP), (2021), S. 121-125
https://doi.org/10.1109/SSP49050.2021.9513848
Open source electronic system for controlling of hybrid electromagnetic systems with magnetic flux modulation. - In: 2021 17th Conference on Electrical Machines, Drives and Power Systems (ELMA), (2021), insges. 4 S.
The use of open-source software and hardware systems in engineering applications is constantly growing. In this paper, an open-source system for controlling hybrid electromagnetic system with magnetic modulation is developed and tested. Some results when powering the tested device with pulses of different frequency are shown.
https://doi.org/10.1109/ELMA52514.2021.9503075
Two-step machine learning approach for channel estimation with mixed resolution RF chains. - In: 2021 IEEE International Conference on Communications workshops (ICC workshops), (2021), insges. 6 S.
Massive MIMO is one of the main features of 5G mobile radio systems. However, it often leads to high cost, size and power consumption. To overcome these issues, the use of constrained radio frequency (RF) frontends has been proposed, as well as novel precoders, e.g., a multi-antenna, greedy, iterative and quantized precoding algorithm (MAGIQ). Nevertheless, the best performance of MAGIQ assumes accurate channel knowledge per antenna element, for example, from uplink sounding reference signals. In this context, we propose an efficient uplink channel estimator by applying machine learning (ML) algorithms. In a first step a conditional generative adversarial network (cGAN) predicts the radio channels from a limited set of full resolution RF chains to the rest of the low resolution RF chain antenna elements. A long-short term memory (LSTM) neural network extracts further phase information from the low resolution RF chain antenna elements. Our results indicate that our proposed ML approach is competitive with traditional Unitary Tensor-ESPRIT in scenarios with various closely spaced multipath components (MPCs).
https://doi.org/10.1109/ICCWorkshops50388.2021.9473491
Enable software-defined radios for real-time MIMO channel sounding. - In: To measure is to know, (2021), insges. 5 S.
This paper describes a field-programmable gate array (FPGA)-based implementation of a switched multiple input multiple output (MIMO) channel sounder realization by use of software-defined radio (SDR) hardware (NI USRP-2954, X310 series with UBX 160 daughterboard). Essential basic functionalities are the synchronous switching of the antenna elements at both link ends and an integrated automatic gain control (AGC) at the receiver. To meet the high timing requirements in the switched MIMO setup, an FPGA-based AGC is introduced. The detector of the AGC is based on a sample-by-sample calculation of the average and maximum of the I/Q samples within a sliding window. The used SDR hardware allows a minimum AGC update interval of approx. 14 [my]s and a timing accuracy of the antenna switching of 5 ns. Our setup demonstrates the applicability of state-of-the-art SDRs as a sounding system for continuous acquisition of the time-variant, directional mobile radio channel.
https://doi.org/10.1109/I2MTC50364.2021.9460077
V2V communication performance of conformal plastic-embedded side-mount antennas investigated with field-operational tests. - In: 2021 IEEE 93rd Vehicular Technology Conference (VTC2021-Spring), (2021), insges. 5 S.
Car-to-car communication has wide-ranging applications in the fields of traffic safety and optimization as well as minimization of emissions. For a seamless and reliable communication between the cars and their road environment, as may be evaluated through packet delivery ratio and received power measurements, an appropriate antenna placement is necessary. Accordingly, the field test discussed in this paper compares the performance of three different antenna placements on a test vehicle: 1. Roof-mounted monopole antenna pair contained in a shark fin housing, 2. Patch antenna pair embedded in the front-left B-column, and 3. Combination of two patch antennas with one in the front-left and the other in the front-right B-column. The concurrent use of three V2V modules allowed us to evaluate the performance of the three antenna set-ups simultaneously in a single run through a mixed terrain, allowing for straightforward performance comparisons. The power received by the roof-top monopole antennas was, on average, 8 dBm higher than the front-left/right B-column patch antenna combination and 13 dBm higher than the front-left B-column patch antenna pair. The reasons for these and other differences are appropriately addressed in the paper. While the roof-top monopole antenna combination performed overall better, we argue that using an appropriate amplifier could raise the performance of the B-column antennas to the same or even higher levels.
https://doi.org/10.1109/VTC2021-Spring51267.2021.9448811
Characterization of urban radio channels and base station antenna correlation in the 3.75 GHz band. - In: 2021 IEEE 93rd Vehicular Technology Conference (VTC2021-Spring), (2021), insges. 5 S.
Single side mMIMO channel measurements over 100 MHz bandwidth at 3.75 GHz were performed in two German cities. In dense urban as well as urban/suburban environments, a total track length of about 20 km has been measured. Multipath parameters by means of the high-resolution parameter estimator RIMAX are estimated and subsequently used to derive the statistics of large scale parameters and to allow a comparison to the statistics from standard channel model (3GPP, WINNER). While most of the parameters match quite well, for the angular spread at the base station (BS) partly larger deviations are observed. The correlation properties between the 32 dual polarized antenna patches of the BS antenna are investigated with respect to the antenna patch separation as well as to the distance between the BS and user equipment (UE).
https://doi.org/10.1109/VTC2021-Spring51267.2021.9448718