Flat-top beam designs are essential for uniform power distribution over a wide angular sector for applications such as 5G/6G networks, beaconing, satellite communications, radar systems, etc. Low sidelobe levels with steep transitions allow negligible cross sector illumination. Active array designs requiring amplitude taper suffer from poor power amplifier utilization. Phase only designs, e.g., Zadoff-Chu or generalized step chirp polyphase sequence methods, often require large active antenna arrays which in turns increases the hardware complexity and reduces the energy efficiency. In our recently proposed novel array-fed reflective intelligent surface (RIS) architecture, the small (2×2) active array has uniform (principal eigenmode) amplitude weighting. We now present a pragmatic flat-top pattern design method for practical array (RIS) sizes, which outperforms current state-of-the-art in terms of design superiority, energy efficiency, and deployment feasibility. This novel design holds promise for advancing sustainable wireless technologies in next-generation communication systems, including applications such as beaconing, broadcast signaling, and hierarchical beamforming, while mitigating the environmental impact of high-energy antenna arrays.

We present numerical results with a focus on power transfer between two standard linear antenna arrays placed in the near field, where a much smaller active multi-antenna feeder (AMAF) space feeds a far larger passive array referred to as a reflective intelligent surface (RIS). The interest is in the regime of focal length to diameter ratio (F/D) less than unity. We address the question of center feed vs. end feed for array fed array antenna architectures and present the following novel findings and contributions: 1. In the regime of$F$/$D$ratio less than one, the AMAF-RIS power transfer deviates from the classical inverse square law. Furthermore, the behavior of the power transmission coefficient is more sensitive to the$F$/$D$ratio than to a particular RIS size. 2. For an end feed, non-eigenmodes provide better beam shapes than the eigenmodes, which are still inferior to beam shapes from the center feed eigenmodes. 3. The center feed provides more power gain than an end feed. This clearly illustrates that the center feed configuration should be used for array fed arrays, in contrast to the classical parabolic geometry.

We present a novel and hardware-efficient space-fed antenna system that exploits the eigenmodes of the over-the-air propagation matrix from a small active multi-antenna feeder (AMAF) to a large reflective intelligent surface (RIS), both configured as standard linear arrays and placed in the near-field of each other. We demonstrate the flexibility of the proposed architecture by showing that it is capable of generating beam shapes for multiple applications, such as very narrow beams with low side lobes for space division multiple access communications, flat-top wide-angle patterns for short-range automotive sensing and sectorial beaconing, and monopulse-like patterns for radar angular tracking. A key parameter in our designs is the AMAF-RIS distance which must be optimized and it is generally much less than the Rayleigh distance. For a given AMAF array size, the optimal AMAF-RIS distance increases as a function of RIS size. The AMAF-RIS loss is almost exactly compensated by the larger aperture gain of the RIS, resulting in an almost constant RIS gain for increasing RIS sizes. This allows different beam angle selectivities to be selected for the same center beam gain. Active RF amplification is done at the AMAF only, thus resulting in a much lower hardware complexity than conventional active phased arrays for the same beamforming performance.

In this paper, we empirically study the behavior of the near-field over-the-air (NF-OTA) propagation matrix between two antenna arrays, with applications to reflective intelligent surface (RIS) based over-the-air beamforming antenna for very high carrier frequencies (mmWaves and sub-THz) and very large signal bandwidth. The NF-OTA propagation matrix T is a deterministic complex matrix which depends on the feeder array and the RIS array sizes and their geometry. We conduct numerical investigations of the rank of T and its left singular vectors, which play an important role in determining the OTA beamforming capability of the whole architecture.

We present mean communication rate loss (MCRL) values due to the beam cusping phenomenon inherent to grid of beams based wireless systems, which are widely used/proposed in millimeter-wave and sub-THz bands. We consider array antenna elements with non-zero aperture and axisymmetric radiation pattern with a certain directivity, unlike the ideal isotropic antenna elements widely considered in theoretical papers on array processing and RF beamforming. The array antenna elements have a half power beam width of ninety degrees in this work which is typical of commonly used microstrip patch antenna elements. We perform Monte Carlo numerical experiments to obtain MCRL values for different spatial dimensions of multiple input multiple output (MIMO) systems, different angular fields of view, and different beamforming codebook sizes. We show that increasing the beam grid density beyond a certain threshold does not help and therefore a certain cusping loss is unavoidable even for continuous beam steering with directive antenna elements. Further, we also show the quantitative impact on the MCRL values as the axisymmetric radiation pattern directivity of the modelled antenna element is increased.

In this paper, we investigate the mean communication rate loss (MCRL) due to beam cusping with respect to multiple input multiple output (MIMO) spatial dimensions, beamforming codebook sizes, and beam scan spaces for beamforming operations controlled by the medium access control (MAC) layer beamforming protocol. The intractability of the analytical investigation for a closed-form expression leads to the usage of Monte Carlo numerical experiments. For discrete Fourier transform (DFT) beamforming codebooks, the MCRL increases with an increase in the MIMO dimensions while it decreases with an increase in the beam scan space from the array broadside. The MCRL becomes negligible as the number of beams for selection is increased to four times the number of DFT beams. These results will be helpful for determination of MIMO configuration, angular coverage zone, codebook size, and phase-shifter resolution for a minimal MCRL. This is especially relevant for sparse MIMO channels of millimetre-wave (mmWave) and terahertz (THz) wireless systems in the fifth generation (5G) and beyond mobile networks.

This paper presents novel radio frequency (RF) beam training algorithms for sparse multiple-input multiple-output (MIMO) channels using unitary RF beamforming codebooks at transmitter (Tx) and receiver (Rx). The algorithms leverage the statistical knowledge from memory-based past beam training data for expedited massive MIMO channel-learning with statistically-minimal training overheads. Beams are tested in the order of their ranks based on their probabilities for providing a communication link. For low beam entropy scenarios, statistically-ranked beam search performs excellent in reducing the average number of beam tests per Tx-Rx beam pair identification for a communication link. For high beam entropy cases, a hybrid RF beam training algorithm involving both memory-assisted statistically-ranked (MarS) beam search and multi-level (ML) beam search is also proposed. Savings in training overheads increase with decrease in relative beam entropy and increase in MIMO channel dimensions. A novel mathematical operation of multiplying the elements of a Kronecker product with their respective position numbers in the Kronecker product vector is also brought out which may find further applications in the future.

MOTIVATION: One of the major bottlenecks in building systems biology models is identification and estimation of model parameters for model calibration. Searching for model parameters from published literature and models is an essential, yet laborious task. RESULTS: We have developed a new service, BioModels Parameters, to facilitate search and retrieval of parameter values from the Systems Biology Markup Language models stored in BioModels. Modellers can now directly search for a model entity (e.g. a protein or drug) to retrieve the rate equations describing it; the associated parameter values (e.g. degradation rate, production rate, Kcat, Michaelis-Menten constant, etc.) and the initial concentrations. Currently, BioModels Parameters contains entries from over 84,000 reactions and 60 different taxa with cross-references. The retrieved rate equations and parameters can be used for scanning parameter ranges, model fitting and model extension. Thus, BioModels Parameters will be a valuable service for systems biology modellers. AVAILABILITY AND IMPLEMENTATION: The data are accessible via web interface and API. BioModels Parameters is free to use and is publicly available at https://www.ebi.ac.uk/biomodels/parameterSearch. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

In this paper, we obtain and study typical beam entropy values for millimetre-wave (mm-wave) channel models using the NYUSIM simulator for frequencies up to 100 GHz for the fifth generation (5G) and beyond 5G cellular communication systems. The beam entropy is used to quantify sparse MIMO channel randomness in beamspace. Lower relative beam entropy channels are suitable for memory- assisted statistically-ranked (MarS) and hybrid radio frequency (RF) beam training algorithms. High beam entropies can potentially be advantageous for low overhead secured radio communications by generating cryptographic keys based on the channel randomness in beamspace, especially for sparse multiple-input multiple- output (MIMO) channels. Urban microcell (UMi) and urban macrocell (UMa) cellular scenarios have been investigated in this work for 28, 60, 73, and 100 GHz carrier frequencies and the rural macrocell (RMa) scenario for 3.5 GHz.