Abstract
In recent years, there has been rapid progress on understanding Gaussian networks with multiple unicast connections, and new coding techniques have emerged. The essence of multi-source networks is how to efficiently manage interference that arises from the transmission of other sessions. Classically, interference is removed by orthogonalization (in time or frequency). This means that the rate per session drops inversely proportional to the number of sessions, suggesting that interference is a strong limiting factor in such networks. However, recently discovered interference management techniques have led to a paradigm shift that interference might not be quite as detrimental after all. The aim of this paper is to provide a review of these new coding techniques as they apply to the case of time-varying Gaussian networks with multiple unicast connections. Specifically, we review interference alignment and ergodic interference alignment for multi-source single-hop networks and interference neutralization and ergodic interference neutralization for multi-source multi-hop networks. We mainly focus on the “degrees of freedom” perspective and also discuss an approximate capacity characterization.
Highlights
Characterizing the capacity of Gaussian networks is a fundamental problem in network information theory. (Unless otherwise specified, we assume Gaussian networks having a single antenna at each node throughout the paper.) even for the simplest setting of a single source and a single destination with a single relay, the capacity is not completely characterized for general channel parameters [1]
The degrees of freedom characterizes the capacity to within o(log signal-to-noise ratio (SNR)) bits/sec/Hz, this gap can be dominant depending on the operational regime of a network. (For positive functions f (x) and g(x), f (x) = o(g(x)) means that for every positive constant ε there exists a constant x0 such that f (x) ≤ εg(x) for all x ≥ x0 .) When channel coefficients are varying over time, ergodic pairing of particular channel states and encoding over this paired channel states make interference aligned or neutralized in a finite SNR regime, which are referred to as ergodic interference alignment [15] and ergodic interference neutralization [19,20,21], respectively
To describe the ergodic interference alignment and ergodic interference neutralization schemes, we find it convenient to introduce the notation H ≃ G to indicate that the two matrices H and G are almost equal, in the following sense: Consider a long sequence of matrices H[t], drawn i.i.d. according to a certain probability density function
Summary
Characterizing the capacity of Gaussian networks is a fundamental problem in network information theory. (Unless otherwise specified, we assume Gaussian networks having a single antenna at each node throughout the paper.) even for the simplest setting of a single source and a single destination with a single relay, the capacity is not completely characterized for general channel parameters [1]. Characterizing the capacity of Gaussian networks is a fundamental problem in network information theory. (Unless otherwise specified, we assume Gaussian networks having a single antenna at each node throughout the paper.) even for the simplest setting of a single source and a single destination with a single relay, the capacity is not completely characterized for general channel parameters [1]. Pairs (which we will refer to as multiple “sessions”), and the capacity characterization appears to be much more challenging for these networks. Exact capacity results being notoriously difficult to obtain, many researchers have recently studied approximate capacity characterizations in the shape of so-called “degrees of freedom” for multi-source networks. The aim of this paper is to review recent achievements relating to the capacity characterization of multi-source networks
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call