Band Limited Signals Observed Over Finite Spatial and Temporal Windows: An Upper Bound to Signal Degrees of Freedom

The study of degrees of freedom of signals observed within spatially diverse broadband multipath fields is an area of ongoing investigation and has a wide range of applications, including characterising broadband MIMO and cooperative networks. However, a fundamental question arises: given a size limitation on the observation region, what is the upper bound on the degrees of freedom of signals observed within a broadband multipath field over a finite time window? In order to address this question, we characterize the multipath field as a sum of a finite number of orthogonal waveforms or spatial modes. We show that (i) the "effective observation time" is independent of spatial modes and different from actual observation time, (ii) in wideband transmission regimes, the "effective bandwidth" is spatial mode dependent and varies from the given frequency bandwidth. These findings clearly indicate the strong coupling between space and time as well as space and frequency in spatially diverse wideband multipath fields. As a result, signal degrees of freedom does not agree with the well-established degrees of freedom result as a product of spatial degrees of freedom and time-frequency degrees of freedom. Instead, analogous to Shannon's communication model where signals are encoded in only one spatial mode, the available signal degrees of freedom in spatially diverse wideband multipath fields is the time-bandwidth product result extended from one spatial mode to finite modes. We also show that the degrees of freedom is affected by the acceptable signal to noise ratio (SNR) in each spatial mode.Comment: Submitted to IEEE Transactions on Signal Processin

Scaling laws of multiple antenna group-broadcast channels

Broadcast (or point to multipoint) communication has attracted a lot of research recently. In this paper, we consider the group broadcast channel where the users' pool is divided into groups, each of which is interested in common information. Such a situation occurs for example in digital audio and video broadcast where the users are divided into various groups according to the shows they are interested in. The paper obtains upper and lower bounds for the sum rate capacity in the large number of users regime and quantifies the effect of spatial correlation on the system capacity. The paper also studies the scaling of the system capacity when the number of users and antennas grow simultaneously. It is shown that in order to achieve a constant rate per user, the number of transmit antennas should scale at least logarithmically in the number of users

Capacity bounds and estimates for the finite scatterers MIMO wireless channel

We consider the limits to the capacity of the multiple-input–multiple-output wireless channel as modeled by the finite scatterers channel model, a generic model of the multipath channel which accounts for each individual multipath component. We assume a normalization that allows for the array gain due to multiple receive antenna elements and, hence, can obtain meaningful limits as the number of elements tends to infinity. We show that the capacity is upper bounded by the capacity of an identity channel of dimension equal to the number of scatterers. Because this bound is not very tight, we also determine an estimate of the capacity as the number of transmit/receive elements tends to infinity which is asymptotically accurate

Designing Broadband over Power Lines Networks Using the Techno-Economic Pedagogical (TEP) Method – Part I: Overhead High Voltage Networks and Their Capacity Characteristics

This pair of papers proposes the techno-economic pedagogical (TEP) method that is suitable for designing Broadband over Power Lines (BPL) networks in transmission and distribution power grids. During the presentation of TEP method, a review of the recent research efforts concerning BPL networks across transmission and distribution power grids is given.In this first paper, TEP method demonstrates to undergraduate electrical and computer engineering (ECE) students the interaction between two apparently irrelevant fields of their ECE program: Microwave Engineering and Engineering Economics. On the basis of a set of linear simplifications and suitable techno-economic metrics concerning transmission and capacity properties of overhead High Voltage Broadband over Power Lines (HV/BPL) networks, TEP method reveals the broadband potential of overhead HV/BPL networks to ECE students when different overhead HV/BPL topologies, electromagnetic interference (EMI) regulations and noise conditions are considered.  Citation: Lazaropoulos, A.G. (2015). "Designing Broadband over Power Lines Networks Using the Techno-Economic Pedagogical (TEP) Method – Part I: Overhead High Voltage Networks and Their Capacity Characteristics." Trends in Renewable Energy, 1(1), 16-42. DOI: 10.17737/tre.2015.1.1.00