Advanced antenna systems play a crucial role in modern communication. They ensure seamless connectivity in both ground-to-ground and ground-to-air communication systems. And in the ever-evolving landscape of antennas used for communication, demands for improved performance are exponentially increasing. Advancements in communication antennas and the expansion of the usable electromagnetic spectrum have paved the way for improved signal speed, increased network capacity, and enhanced coverage. This article explores cutting-edge advanced antenna system technologies like MIMO and distributed antenna systems (DAS) that enable the modern era of wireless communication in aerospace and ground-to-ground applications.
Antenna systems rely on MIMO technology
Gone are the days of single, extendable antennas on the back of a portable radio. Today, many modern antenna systems employ Multi-input Multi-Output (MIMO) technology. MIMO involves using multiple antennas at both the transmitter and receiver to enhance the data throughput of the signal and improve its reliability. By leveraging spatial multiplexing, MIMO allows the simultaneous transmission of multiple data streams over the same frequency band. Standard MIMO typically uses 2 to 6 transmitter- and receiver-antennas to send and receive data.
Satellite and aerospace systems with multiple antennas can utilize MIMO techniques to enhance ground-to-air communication data rates and quality. MIMO is particularly useful for satellite internet access, video streaming, and data-intensive communication applications.
Massive MIMO (referred to in shorthand as mMIMO) significantly expands the scale of the previous generation MIMO. For example, modern mMIMO network antennas from Ericsson, such as the AIR 6476 product, feature 64 transmitter and 64 receiver branches.
mMIMO technology is a key enabler of 5G networks. It can deploy many antennas at a radio base station, increasing network capacity and providing better coverage. Advanced antenna software can control these massive MIMO arrays to sense interference, intelligently shape the network distribution cell, and reduce intercell interference.
Multiplexing increases signal strength
Multiplexing is a technique commonly used in MIMO systems to transmit multiple unique information ‘streams’ operating at the same or different frequencies from different antennas. These data streams are then received by independent antennas, where each signal is recombined to form the original signal. Given that each signal will have its own channel distortion as it travels between antennas, the receiving MIMO antenna must adjust the individual signal streams for distortion using advanced digital signal processing to rebuild the original signal.
Multiplexing techniques, such as quadrature amplitude modulation (QAM), can increase overall signal strength and ramp data transfer rates between antenna assemblies. QAM can transmit data over multiple antenna channels simultaneously, furthering the total channels that the total antenna system can transmit. QAM is particularly useful in satellite communication systems, such as Starlink, as the limited frequency spectrum must be effectively utilized to accommodate multiple users and high data rates.
Individual antennas have a fixed amount of data they can transmit per second per Hertz. By being able to split a single large signal into smaller ‘streams’ that fit within the capacity of a single antenna, large data signals can be transmitted via a dynamic series of many smaller antennas. QAM is designed to break up a single antenna signal into multiple smaller streams. Multiple antennas can increase the bandwidth by adding additional channels of the same signal frequency, and increase accuracy by beamforming.
Multiplexing capabilities were originally developed for 4G LTE and now play a crucial role in 5G by enabling high-speed data transmission while maintaining antenna and spectral efficiency.
Spatial diversity helps signals cover long distances
Wireless signals that cover large distances can suffer from fading phenomena or interference from obstacles or electromagnetic interference. Spatial diversified encoding techniques can be thought of as redundant multi-channel communication. These techniques are used to send multiple copies of the same signal through several physically separated transmit antennas (even if already multiplexed).
Additionally, multiple antennas that are physically separated from each other receive those duplicative signals, even though it is likely that these signals are corrupted. Given the differing signal path, however, each individually corrupted signal can be combined, reducing the impact of the path-fading phenomenon and restoring the signal reliability.
Given the nature of long-distance communication needs in aerospace applications, spatial diversity techniques effectively minimize signal fading and interference for aerospace communication.
Beamforming sends signals efficiently
Commonly found in applications with multiple antennas, such as MIMO and distributed antenna systems, beamforming is an advanced antenna-network optimization technique that focuses radio signals in a specific direction to increase the coverage and capacity of a wireless network. Antenna patterns are intelligently adjusted to create positive interference of the individual electromagnetic waves with each other in a very specific direction. This strategy enables targeted signal amplification, reduced interference, and maximum signal quality.
Beamforming is achieved by adjusting the phase and gain of a single RF signal output through multiple antennas. In MIMO applications, each antenna can send different signals that can be combined, with each weighted with its own gain and phase to create a multi-channel beamform. This type of beamforming can send entirely different signals in many directions using a single MIMO antenna array.
Beamforming is highly relevant in aerospace communication systems, especially for air-to-ground communication, where power efficiency is essential. Beamforming techniques allow satellites or aircraft to focus their transmissions toward specific locations, such as ground stations or other aircraft, to maximize signal quality and minimize interference.
Distributed antenna systems spread coverage evenly
While modern individual antenna assemblies are excellent at increasing capacity, single antenna systems may not be operable in all environments. In large buildings with poor signal penetration or large interferences, distributed antenna systems (DAS) can provide necessary network coverage. DAS consists of a network of antennas distributed throughout a building and designed to coordinate to maximize connectivity and minimize wasted signals.
DAS networks are designed to complement network base stations, such as 4G and 5G cell towers, by extending networks into buildings where a single antenna may not provide reliable coverage. Distributed Antenna Systems generally support all major network carriers and can conceptually be compared to Wi-Fi range extenders, but for cellular networks.
DAS can vary in size to support buildings ranging from small 10,000 square-foot office spaces with 2-4 cellular repeater systems to huge 500,000+ square-foot high-rise buildings. Outdoor distributed antenna systems can cover large, densely populated areas, including busy city streets, zoos, and event venues. In aerospace applications, DAS systems are commonly utilized within large aircraft to provide uniform wireless coverage and capacity.
Communication antenna technology for aerospace applications
Advanced antenna technologies play a vital role in ground-to-air and ground-to-ground communication systems. Reliable and high-performance wireless connectivity solutions are increasingly essential for aerospace applications, including satellite, aircraft-to-aircraft, aircraft-to-ground, and in-flight passenger communication. As the aerospace industry evolves, these antenna solutions will be instrumental in ensuring the growing communication demands are met with efficient, reliable, and secure coverage.
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