Fast gain switching on TwinRX USRPs. - In: 16th European Conference on Antennas and Propagation, (2022), insges. 5 S.
In this paper, we investigate the gain switching performance of the software-defined radio (SDR) universal software radio peripheral (USRP) X310 with the TwinRX daughterboard and propose a method to optimize it for fast transitions. This receiver uses a complex structure of two switchable amplifiers and two digital step attenuators to realize the wide gain setting range of up to 92 dB. Our measurements of the settling time show that the bulk of transitions between two gain settings take below 1.5 µs, but some require more than 50 µs, caused by the power-up of the switchable amplifiers. Based on this knowledge, we propose a modified switching regime, in which the amplifiers are not toggled in time-critical phases, e.g., during a running measurement, so that a transition time of 1.5 µs can be reliably realized. Thus, a gain switching range of 62 dB is achieved, within which, for example, a fast automatic gain control can be realized.
https://doi.org/10.23919/EuCAP53622.2022.9769488
Open sub-granting radio resources in overlay D2D-based V2V communications. - In: EURASIP journal on wireless communications and networking, ISSN 1687-1499, Bd. 2022 (2022), 46, S. 1-29
Richtiger Name des Verfassers: Dariush Mohammad Soleymani
Capacity, reliability, and latency are seen as key requirements of new emerging applications, namely vehicle-to-everything (V2X) and machine-type communication in future cellular networks. D2D communication is envisaged to be the enabler to accomplish the requirements for the applications as mentioned earlier. Due to the scarcity of radio resources, a hierarchical radio resource allocation, namely the sub-granting scheme, has been considered for the overlay D2D communication. In this paper, we investigate the assignment of underutilized radio resources from D2D communication to device-to-infrastructure communication, which are moving in a dynamic environment. The sub-granting assignment problem is cast as a maximization problem of the uplink cell throughput. Firstly, we evaluate the sub-granting signaling overhead due to mobility in a centralized sub-granting resource algorithm, dedicated sub-granting radio resource (DSGRR), and then a distributed heuristics algorithm, open sub-granting radio resource (OSGRR), is proposed and compared with the DSGRR algorithm and no sub-granting case. Simulation results show improved cell throughput for the OSGRR compared with other algorithms. Besides, it is observed that the overhead incurred by the OSGRR is less than the DSGRR while the achieved cell throughput is yet close to the maximum achievable uplink cell throughput.
https://doi.org/10.1186/s13638-022-02128-0
Make some noise: energy-efficient 38 Gbit/s wide-range fully-configurable linear feedback shift register. - In: SMACD / PRIME 2021, (2021), S. 384-387
https://ieeexplore.ieee.org/document/9547997
Every clock counts - 41 GHz wide-range integer-N clock divider. - In: SMACD / PRIME 2021, (2021), S. 388-391
https://ieeexplore.ieee.org/document/9547998
Positioning with medium frequency R-Mode. - In: Navigation, ISSN 2161-4296, Bd. 68 (2021), 4, S. 829-841
R-Mode is a terrestrial navigation system under development for the maritime domain that provides backup in case of a GNSS outage. This paper describes the first test results for real-time positioning on board a ship using medium frequency R-Mode signals. The estimation and positioning algorithms used are described in detail and it is shown how they are integrated into the R-Mode receiver developed by the German Aerospace Center. Moreover, during two daytime experiments with lower and higher dynamic movements of a ship in the Baltic Sea, we were able to achieve a 95% horizontal positioning accuracy of better then 12 m in the center of three R-Mode transmitters. This demonstrates the first time that the medium frequency R-Mode has provided positioning at sea.
https://doi.org/10.1002/navi.450
Frequency subsampling of ultrasound nondestructive measurements: acquisition, reconstruction, and performance. - In: IEEE transactions on ultrasonics, ferroelectrics, and frequency control, ISSN 1525-8955, Bd. 68 (2021), 10, S. 3174-3191
In ultrasound nondestructive testing (NDT), a widespread approach is to take synthetic aperture measurements from the surface of a specimen to detect and locate defects within it. Based on these measurements, imaging is usually performed using the synthetic aperture focusing technique (SAFT). However, SAFT is suboptimal in terms of resolution and requires oversampling in the time domain to obtain a fine grid for the delay-and-sum (DAS). On the other hand, parametric reconstruction algorithms give better resolution, but their usage for imaging becomes computationally expensive due to the size of the parameter space and a large amount of measurement data in realistic 3-D scenarios when using oversampling. In the literature, the remedies to this are twofold. First, the amount of measurement data can be reduced using state-of-the-art sub-Nyquist sampling approaches to measure Fourier coefficients instead of time-domain samples. Second, parametric reconstruction algorithms mostly rely on matrix-vector operations that can be implemented efficiently by exploiting the underlying structure of the model. In this article, we propose and compare different strategies to choose the Fourier coefficients to be measured. Their asymptotic performance is compared by numerically evaluating the Cramér-Rao bound (CRB) for the localizability of the defect coordinates. These subsampling strategies are then combined with an l1-minimization scheme to compute 3-D reconstructions from the low-rate measurements. Compared to conventional DAS, this allows us to formulate a fully physically motivated forward model matrix. To enable this, the projection operations of the forward model matrix are implemented matrix-free by exploiting the underlying two-level Toeplitz structure. Finally, we show that high-resolution reconstructions from as low as a single Fourier coefficient per A-scan are possible based on simulated data and measurements from a steel specimen.
https://doi.org/10.1109/TUFFC.2021.3085007
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
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
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