7 research outputs found
End-to-end Precoding Validation over a Live GEO Satellite Forward Link
In this paper we demonstrate end-to-end precoded multi-user multiple-input
single-output (MU-MISO) communications over a live GEO satellite link. Precoded
communications enable full frequency reuse (FFR) schemes in satellite
communications (SATCOM) to achieve broader service availability and higher
spectrum efficiency than with the conventional four-color (4CR) and two-color
(2CR) reuse approaches. In this scope, we develop an over-the-air test-bed for
end-to-end precoding validations. We use an actual multi-beam satellite to
transmit and receive precoded signals using the DVB-S2X standard based gateway
and user terminals. The developed system is capable of end-to-end real-time
communications over the satellite link including channel measurements and
precompensation. It is shown, that by successfully canceling inter-user
interference in the actual satellite FFR link precoding brings gains in terms
of enhanced SINR and increased system goodput.Comment: Submitted to IEEE Access Journa
Generic Optimization of Linear Precoding in Multibeam Satellite Systems
Multibeam satellite systems have been employed to provide interactive
broadband services to geographical areas under-served by terrestrial
infrastructure. In this context, this paper studies joint multiuser linear
precoding design in the forward link of fixed multibeam satellite systems. We
provide a generic optimization framework for linear precoding design to handle
any objective functions of data rate with general linear and nonlinear power
constraints. To achieve this, an iterative algorithm which optimizes the
precoding vectors and power allocation alternatingly is proposed and most
importantly, the proposed algorithm is proved to always converge. The proposed
optimization algorithm is also applicable to nonlinear dirty paper coding. In
addition, the aforementioned problems and algorithms are extended to the case
that each terminal has multiple co-polarization or dual-polarization antennas.
Simulation results demonstrate substantial performance improvement of the
proposed schemes over conventional multibeam satellite systems, zero-forcing
and regularized zero-forcing precoding schemes in terms of meeting the traffic
demand. The performance of the proposed linear precoding scheme is also shown
to be very close to the dirty paper coding
Massive MIMO Transmission for LEO Satellite Communications
Low earth orbit (LEO) satellite communications are expected to be
incorporated in future wireless networks, in particular 5G and beyond networks,
to provide global wireless access with enhanced data rates. Massive MIMO
techniques, though widely used in terrestrial communication systems, have not
been applied to LEO satellite communication systems. In this paper, we propose
a massive MIMO transmission scheme with full frequency reuse (FFR) for LEO
satellite communication systems and exploit statistical channel state
information (sCSI) to address the difficulty of obtaining instantaneous CSI
(iCSI) at the transmitter. We first establish the massive MIMO channel model
for LEO satellite communications and simplify the transmission designs via
performing Doppler and delay compensations at user terminals (UTs). Then, we
develop the low-complexity sCSI based downlink (DL) precoder and uplink (UL)
receiver in closed-form, aiming to maximize the average
signal-to-leakage-plus-noise ratio (ASLNR) and the average
signal-to-interference-plus-noise ratio (ASINR), respectively. It is shown that
the DL ASLNRs and UL ASINRs of all UTs reach their upper bounds under some
channel condition. Motivated by this, we propose a space angle based user
grouping (SAUG) algorithm to schedule the served UTs into different groups,
where each group of UTs use the same time and frequency resource. The proposed
algorithm is asymptotically optimal in the sense that the lower and upper
bounds of the achievable rate coincide when the number of satellite antennas or
UT groups is sufficiently large. Numerical results demonstrate that the
proposed massive MIMO transmission scheme with FFR significantly enhances the
data rate of LEO satellite communication systems. Notably, the proposed sCSI
based precoder and receiver achieve the similar performance with the iCSI based
ones that are often infeasible in practice.Comment: 31 pages, 4 figure