A system and machine-implemented method are described for performing precoding interpolation in a DIDO system which employs orthogonal frequency-division multiplexing (OFDM) and DIDO precoding to communicate with a plurality of distributed-input-distributed-output (DIDO) clients. For example, a system according to one embodiment of the invention comprises: selecting a first subset of ODFM tones to determine a first subset of precoding weights; deriving a second subset of precoding weights for a second subset of ODFM tones by interpolating between the first subset of precoding weights; and using a combination of the first subset of precoding weights and the second subset of precoding weights to precode a data stream prior to transmitting the data stream to a DIDO client.

System and method for DIDO precoding interpolation in multicarrier systems

A system and method are described which enable planned evolution and obsolescence of multiuser wireless spectrum. One embodiment of such a system includes one or multiple centralized processors and one or multiple distributed nodes that communicate via wireline or wireless connections. The distributed nodes may share their identification number and other reconfigurable system parameters with the centralized processor. The information about all distributed nodes may be stored in a database that is shared by all centralized processors. The reconfigurable system parameters may comprise power emission, frequency band, modulation/coding scheme. The distributed nodes may be software defined radios such as FPGA, DSP, GPU and/or GPCPU that run algorithms for baseband signal processing and may be reconfigured remotely by the centralized processor. A cloud wireless system may be used wherein the distributed nodes are reconfigured periodically or instantly to adjust to the evolving wireless architecture.

System and methods for planned evolution and obsolescence of multiuser spectrum

A system and methods are described which compensate for the adverse effect of Doppler on the performance of DIDO systems. One embodiment of such a system employs different selection algorithms to adaptively adjust the active BTSs to different UEs based by tracking the changing channel conditions. Another embodiment utilizes channel prediction to estimate the future CSI or DIDO precoding weights, thereby eliminating errors due to outdated CSI.

System and methods to compensate for Doppler effects in multi-user (MU) multiple antenna systems (MAS)

Propagation Of Radio Waves

A machine-implemented system and method are described for removing interference between adjacent distributed-input-distributed-output (DIDO) clusters comprising. For example, a method according to one embodiment comprises: detecting signal strength at a first client from a main DIDO cluster; detecting interference signal strength at the first client from an interfering DIDO cluster; if the signal strength from the main DIDO cluster reaches a specified value relative to the value of the interference signal strength from the interfering DIDO cluster, then generating channel state information (CSI) defining channel state between one or more antennas of the first client and one or more antennas of the interfering DIDO cluster; transmitting the CSI from the first client to a base transceiver station (BTS) in the interfering DIDO cluster; and implementing DIDO precoding with inter-DIDO-cluster interference (IDCI) cancellation at the BTS in the interfering DIDO cluster to avoid RF interference at the first client.

System and method for adjusting DIDO interference cancellation based on signal strength measurements

[1] Array processing usually operates on identical sensors. In this paper an investigation is made to apply the direction finding algorithm MUSIC to an antenna array with nonidentical elements (heterogeneous array). This original solution is polarization-sensitive though it resorts to only one sensor at each point of the spatial sampling. As a major consequence of its structure, the computation of the MUSIC algorithm is based on an expression of the steering vector that integrates the spatial response of each sensor. This concept is then validated in the special context of HF radio direction finding, for which a deterministic model of the polarization at the exit of the ionospheric channel is derived. A multichannel radio receiving system has been developed and experimented using transmitters located more than 1000 km from the receiving site.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2002RS002860

HF radio direction finding operating on a heterogeneous array: Principles and experimental validation

Multiple input multiple output (MIMO) systems utilize multiple antennas at both the transmitter and the receiver. This paper describes some recent experimental work that has been carried out in order to investigate the feasibility of applying MIMO techniques within the high frequency (HF) band. It is a significant development because the potential increase in data rates will benefit not only the existing HF radio systems but also open this band to new low cost communication applications. The capacity estimates for systems employing multiple antennas at the transmitter and receiver in the HF band are computed. Specifically a comparison is made between MIMO configurations employing homogenous antenna arrays and collocated antenna arrays in terms of their envelope correlation and capacity. The results indicate that the HF band can be used for MIMO applications and that compact collocated antennas can replace large homogenous arrays to provide potential capacity gains.

/pdf/capacity-estimation-of-hf-mimo-systems-3k87yy15do.pdf

Capacity estimation of HF-MIMO systems

This paper presents an original method of direction finding operating on an array of collocated antennas. At first, we derive the classical MUSIC algorithm for an heterogeneous array, i.e. made up of different sensors: their complex directional responses, which are supposed to be well known, are integrated in the normalized steering-vectors. We underline (the advantages induced by this technique in the field of radio direction finding, especially as two types of polarization are received (right or left circular polarization in the VHF range, ordinary or extraordinary polarization in the HF range). Then, we show that the diversity of the sensors can replace to some extent the space diversity usually provided by classical arrays. Actually, the array manifold does not only depend on the geometry but also on the directivity functions of the sensors. In these conditions, it becomes feasible to find the directions of arrival with a small array aperture, and possibly with collocated sensors. Finally, we present experimental validations in the HF (3-30 MHz) range.

A method of direction finding operating on an array of collocated antennas

[1] The concept of multiple input multiple output (MIMO) has become a productive area of research in the field of wireless communications with the aim of delivering increased data throughput. However, to date, MIMO research has focused primarily on short-range communications within the VHF, UHF, and SHF bands, and very little research has been conducted toward exploiting MIMO techniques for long-range communications within the HF band. Between September 2007 and September 2008, several experimental campaigns were conducted to investigate the feasibility of applying MIMO techniques within the HF band. The results of measurements over a 255 km path from Durham to Leicester within the United Kingdom are presented in this paper with particular emphasis on the use of heterogeneous antenna arrays at the transmitter and receiver.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008RS004075

Investigations into the feasibility of multiple input multiple output techniques within the HF band: Preliminary results

The aim of this paper is to present a high data rate transmission system through the ionospheric channel in the HF-band (3-30 MHz). The applications expected in this study are image transmitting and real-time videoconferencing. Very high rates are required compared to the standard modems.
Therefore, an array processing is performed with a set of antennas whose spatial response differs from one another arranged in a circular array or in a collocated sensor. Synchronization (Zero Crossing
Detector) and source separation (LMS algorithm) resort to classical well-tested techniques involving training sequences. Experimental results are presented for both antenna configurations. These techniques improve data rate, reaching 20 kbits/s within the 6 kHz bandwidth (QAM 64) without
coding or interleaving.

/pdf/a-way-to-increase-the-bit-ratein-ionospheric-radio-links-18bglb1goi.pdf

Louis Bertel

Papers

HF radio direction finding operating on a heterogeneous array: Principles and experimental validation

Capacity estimation of HF-MIMO systems

A method of direction finding operating on an array of collocated antennas

Investigations into the feasibility of multiple input multiple output techniques within the HF band: Preliminary results

A way to increase the bit ratein ionospheric radio links