Abstract
Cache-enabled small base stations (SBS) are capable of relieving the heavy burden of the backhaul link and reducing the transmission latency. The hit probability depends on the coverage probability and caching placement probabilities. However, the interference in the small-cell networks may significantly degrade the coverage probability. In this paper, for MIMO small-cell networks consisting of SBS and users, where both of them are equipped with multiple antennas, a joint interference alignment (IA) and probabilistic caching (JIA-ProbC) scheme is proposed. Using tools from stochastic geometry, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> -th order Voronoi cells are constructed to form clusters, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> SBSs cooperatively serve users within each of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> -th order Voronoi cells. Then, the IA scheme for MIMO interference channel (IC) is employed to cancel the intra-cluster interference within each <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> -th order Voronoi cell. By exploiting the advantage of multiples antennas at users, the IA scheme can simultaneously support more users interference-free than both the zero forcing (ZF) based interference cancellation scheme for MISO systems and SISO systems without interference management, as more interference can be canceled. Furthermore, the coverage probability is analytically approximated by the a closed-form expression. Moreover, the optimal caching placement probability is analytically derived. Numerical Simulation results show that the proposed JIA-ProbC can significantly outperform the existing joint ZF and probabilistic caching (JZF-ProbC) scheme for MISO systems and SISO probabilistic caching (SISO-ProbC) scheme as well as the joint IA and most popular caching (JIA-MPC) caching scheme.
Highlights
The demand of communication content-oriented services has been ever increasing [1]–[4]
In order to relieve the heavy burden of the backhaul link and reduce the transmission latency, cache-enabled base stations (BSs) have been proposed as a promising solution, where the popular contents are cached at BSs [2], [4]
Our main contributions are as following: 1) We propose one novel joint interference alignment (IA) and probabilistic caching (JIA-ProbC) scheme for MIMO small-cell networks which consists of small base stations (SBS) and users, and both of them are equipped with multiple antennas
Summary
The demand of communication content-oriented services has been ever increasing [1]–[4]. For multiple-input single-output (MISO) small cell networks, joint zero forcing (ZF) and probabilistic caching scheme was proposed to maximize the hit probability, where ZF based interference cancellation was exploited to suppress the intra-cluster interference [22]. For MIMO networks, interference alignment (IA) has been being widely proposed as a promising interference management scheme, which can effectively remove the interference and improve degrees of freedom (DoF) of networks [25]–[32] Against this background, in this paper, we investigate joint interference management and caching placement for MIMO systems to enhance the hit probability. Our main contributions are as following: 1) We propose one novel joint IA and probabilistic caching (JIA-ProbC) scheme for MIMO small-cell networks which consists of SBSs and users, and both of them are equipped with multiple antennas. The operator (·)H denotes Hermitian transpose of a vector or matrix, ∥·∥ is the standard Euclidean norm and A\B denotes a set in set A while not in set B
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