30 research outputs found
Target Localization in MIMO OFDM Radars Adopting Adaptive Power Allocation among Selected Sub-Carriers
Multiple-input multiple-output (MIMO) radar has been introduced to enhance the performance of classical radar systems. Nevertheless, radar cross sections (RCS) fluctuations remains a known problem in radars. Target localization using narrowband signal produces reduced accuracy due to RCS fluctuations. One of the solution to this problem is utilization of frequency diversity of wideband signal. This paper presents target localization in MIMO radars using an adaptive orthogonal frequency division multiplexing (OFDM) waveform for effective frequency diversity utilization. Each transmitting antenna transmits an OFDM signal in different time slots and received by the each receiving antenna in the receiver array. A joint direction-of-departure (DOD) and direction-of-arrival (DOA) estimation scheme is applied to each of the OFDM sub-carrier using two-way multiple signal classification (MUSIC) algorithm. The estimation results at each sub-carrier are combined based on majority decision using angle histogram (non-parametric approach) to formulate the final wideband angle estimation. In addition, an adaptive power allocation among the sub-carriers is implemented, where the system evaluates the signal quality at each sub-carrier and consequently formulates a feedback to the MIMO transmitting side. The following transmission will comprise of OFDM waveform that focuses the transmit power at selected sub-carriers only. The sub-carrier selection is based on singular values obtained from singular value decomposition operation at each of the sub-carrier. The performance of the proposed scheme is evaluated through numerical simulations as well as validation by experiments in a radio anechoic chamber. It was demonstrated that the usage of larger number of sub-carriers improves the angle estimation accuracy
Massive MIMO is a Reality -- What is Next? Five Promising Research Directions for Antenna Arrays
Massive MIMO (multiple-input multiple-output) is no longer a "wild" or
"promising" concept for future cellular networks - in 2018 it became a reality.
Base stations (BSs) with 64 fully digital transceiver chains were commercially
deployed in several countries, the key ingredients of Massive MIMO have made it
into the 5G standard, the signal processing methods required to achieve
unprecedented spectral efficiency have been developed, and the limitation due
to pilot contamination has been resolved. Even the development of fully digital
Massive MIMO arrays for mmWave frequencies - once viewed prohibitively
complicated and costly - is well underway. In a few years, Massive MIMO with
fully digital transceivers will be a mainstream feature at both sub-6 GHz and
mmWave frequencies. In this paper, we explain how the first chapter of the
Massive MIMO research saga has come to an end, while the story has just begun.
The coming wide-scale deployment of BSs with massive antenna arrays opens the
door to a brand new world where spatial processing capabilities are
omnipresent. In addition to mobile broadband services, the antennas can be used
for other communication applications, such as low-power machine-type or
ultra-reliable communications, as well as non-communication applications such
as radar, sensing and positioning. We outline five new Massive MIMO related
research directions: Extremely large aperture arrays, Holographic Massive MIMO,
Six-dimensional positioning, Large-scale MIMO radar, and Intelligent Massive
MIMO.Comment: 20 pages, 9 figures, submitted to Digital Signal Processin