Core Concepts
By jointly optimizing the positions and weights of movable antennas in a satellite-mounted array, the beam coverage can be dynamically adjusted to minimize interference leakage while ensuring the minimum beamforming gain over the desired coverage area.
Abstract
The paper proposes utilizing movable antenna (MA) arrays to enhance the dynamic beam coverage and interference mitigation for low-earth orbit (LEO) satellite communications. The key insights are:
Conventional fixed-position antenna (FPA) arrays have limited degrees of freedom in beamforming to adapt to the time-varying coverage requirement of terrestrial users. MA arrays can reconfigure the array geometry via antenna movement, providing more flexibility in beamforming.
Given the satellite orbit and coverage requirement, the antenna position vector (APV) and antenna weight vector (AWV) of the satellite-mounted MA array are jointly optimized over time to minimize the average signal leakage power to the interference area, subject to constraints on the minimum beamforming gain, antenna movement feasibility, and constant modulus of AWV.
The continuous-time optimization problem is transformed into a discrete-time form, and an alternating optimization (AO)-based algorithm is developed by iteratively optimizing the APV and AWV using the successive convex approximation technique.
A low-complexity MA scheme is proposed by using an optimized common APV over all time slots, significantly reducing the antenna movement overhead while achieving comparable interference mitigation performance.
Simulation results validate that the proposed MA array-aided beam coverage schemes can substantially decrease the interference leakage compared to conventional FPA-based schemes, while the low-complexity MA scheme can achieve a performance close to the continuous-movement MA scheme.
Stats
The path loss between the satellite and a point (Θ, Φ) on the earth surface is given by ρ(Θ, Φ, t) = ρ0(‖k̄e(Θ, Φ, t)‖2)−γ.
The effective channel gain between the satellite and point (Θ, Φ) is given by h(Θ, Φ, q(t), w(t), t) = ρ(Θ, Φ, t)|a(k(Θ, Φ, t), q(t))Hw(t)|2.
The average beamforming gain over the coverage area at time t is given by G(q(t), w(t), t) = ∫∫(Θ,Φ)∈Ae h(Θ, Φ, q(t), w(t), t)dΘdΦ / ∫∫(Θ,Φ)∈Ae ρ(Θ, Φ, t)dΘdΦ.
The average signal leakage power to the interference area within time interval (0, T] is given by I(q(t), w(t)) = 1/T ∫t∈(0,T] ∫∫(Θ,Φ)∈Ai(t) h(Θ, Φ, q(t), w(t), t)dΘdΦ / ∫∫(Θ,Φ)∈Ai(t) ρ(Θ, Φ, t)dΘdΦ dt.
Quotes
"By jointly optimizing the antenna position vector (APV) and antenna weight vector (AWV), more flexible beamforming can be achieved by MA arrays as compared to traditional FPA arrays such that the interference leakage of satellites can be more effectively suppressed."
"The superiority of MA arrays over FPA arrays in terms of flexible beamforming has been validated in existing literatures."