547 research outputs found
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
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