A Novel Local and Hyper-Local Multicast Services Transmission Scheme for Beyond 5G Networks

The efficiency of the broadcast network is impacted by the different types of services that may be transmitted over it. Global services serve users across the entire network, while local services cater to specific regions, and hyper-local services have even narrower coverage. Multimedia Broadcast over a Single-Frequency Network (MBSFN) is typically used for global service transmission while existing literature extensively discusses schemes for transmitting local or hyper-local services with or without Single Frequency Network (SFN) gain. However, these schemes fall short when network-wide requests for only local and hyper-local services are made, leading operators to scale down to either Single Cell-Point to Multipoint (SCPtM) or Multi-Frequency Network (MFN). SCPtM is highly susceptible to interference, and MFN requires substantial amounts of valuable spectrum. They both employ the Least Channel Gain (LCG) strategy for transmitting hyper-local services without SFN gain. Our proposed Local and Hyper-Local Services (LHS) transmission scheme utilizes the knowledge of user distribution and their corresponding radio link channel quality to schedule single or multi-resolution, local or hyper-local services within a three-cell cluster and aims to enhance spectral efficiency and maximize system throughput. It leverages Scalable Video Coding (SVC) in conjunction with Hierarchical Modulation (HM) for transmitting multi-resolution multimedia content to address the problem of heterogeneity amongst the multicast group users. The proposed scheme also employs macro-diversity combining with optimal HM parameters for each gNB catering to a local service area in order to minimize the service outage. System-level simulation results testify to the better performance achieved by the proposed LHS transmission scheme with respect to SCPtM.Comment: 12 pages, 18 figures, 2 tables, 3 algorithm

Variable stars in the globular cluster NGC 7492. New discoveries and physical parameters determination

We have performed a photometric V, R, I CCD time-series analysis with a baseline of ~8 years of the outer-halo globular cluster NGC 7492 with the aim of searching for new variables and using these (and the previously known variables) to determine the physical parameters of interest for the cluster (e.g. metallicity, absolute magnitude of the horizontal branch, distance, etc.). We use difference image analysis (DIA) to extract precise light curves in the relatively crowded star field, especially towards the densely populated central region. Several approaches are used for variability detection that recover the known variables and lead to new discoveries. We determine the physical parameters of the only RR0 star using light curve Fourier decomposition analysis. We find one new long period variable and two SX Phe stars in the blue straggler region. We also present one candidate SX Phe star which requires follow-up observations. Assuming that the SX Phe stars are cluster members and using the period-luminosity relation for these stars, we estimate their distances as ~25.2+-1.8 and 26.8+-1.8 kpc, and identify their possible modes of oscillation. We refine the periods of the two RR Lyrae stars in our field of view. We find that the RR1 star V2 is undergoing a period change and possibly exhibits the Blazhko effect. Fourier decomposition of the light curve of the RR0 star V1 allows us to estimate the metallicity [Fe/H]_ZW-1.68+-0.10 or [Fe/H]_UVES-1.64+-0.13, log-luminosity ~1.76+-0.02, absolute magnitude ~0.38+-0.04 mag, and true distance modulus of ~16.93+-0.04 mag, which is equivalent to a distance of ~24.3+-0.5 kpc. All of these values are consistent with previous estimates in the literature.Comment: 12 pages, 13 figures, 6 tables, accepted for publication in A&

Interference-Managed Local Service Insertion for 5G Broadcast

Broadcast of localized TV content enables tailored content delivery catering to the requirements of regional user base. 5G multicast-broadcast service (MBS) requires a spectrally efficient broadcast solution that enables the change of content from one local service area (LSA) to another. A frequency reuse factor of unity between two adjacent LSAs causes their boundary region to become saturated with co-channel interference (CCI). Increasing the reuse factor will reduce the CCI at the cost of degrading the spectral efficiency. This paper addresses the frequency and transmit power planning which manages the CCI at the LSA boundary to achieve a satisfactory trade-off between spectral efficiency and broadcast coverage.Comment: Newer version of our unpublished wor

Using DCFT for Multi-Target Detection in Distributed Radar Systems with Several Transmitters

In distributed radar systems, when several transmitters radiate simultaneously, the reflected signals need to be distinguished at the receivers to detect various targets. If the transmit signals are in different frequency bands, they require a large overall bandwidth. Instead, a set of pseudo-orthogonal waveforms derived from the Zadoff-Chu (ZC) sequences could be accommodated in the same band, enabling the efficient use of available bandwidth for better range resolution. In such a design, special care must be given to the 'near-far' problem, where a reflection could possibly become difficult to detect due to the presence of stronger reflections. In this work, a scheme to detect multiple targets in such distributed radar systems is proposed. It performs successive cancellations (SC) starting from the strong, detectable reflections in the domain of the Discrete Chirp-Fourier Transform (DCFT) after compensating for Doppler shifts, enabling the subsequent detections of weaker targets which are not trivially detectable. Numerical simulations corroborate the efficacy and usefulness of the proposed method in detecting weak target reflections