Nov . 2025
How do radios transmit and receive simultaneously? We will examine this intricate phenomenon, and you will grasp the essentials. We will explore multi user full duplex communication. We will also highlight the major challenges and demonstrate MIMO solutions. Finally, we will present the applications and benefits.
MIMO systems are the best for this specific function. These systems use multiple antennas for each data stream. This use greatly enhances multi user full duplex communication. Classical duplex systems encounter many limitations. I remember working on an early network setup where classical duplexing was a constant bottleneck. MIMO technology, by contrast, takes advantage of the spatial domain.
This process forms independent pathways for users. This process, known as Spatial Efficiency, is the reason why systems can function with 8 users or more. The interference level is much lower, and the data transmission is also much faster. This capability is crucial for 5G systems.
Let us get into the fundamentals. You will appreciate how this technology works.
This is the primary feature. TX means transmit, and RX means receive. In a phone call, a person can send out words and simultaneously receive the words of the other person. The old duplex telegraphy was an early example of this. Modern systems require advanced signal processing. Another vital component is echo cancellation, which stops your signal from occluding the inputs.
A good number of systems support 8 channels. This support means 8 users can transmit simultaneously. This ability is extremely beneficial to teams. An example of this includes modules such as the SA618F30. Complex scenes, like firefighting or film crews, become easier to manage. When more users can receive unlimited signals, the teamwork becomes smoother. Have you ever tried to coordinate a team in a loud environment with laggy Walkie-Talkies? It’s nearly impossible. The immediate, simultaneous feedback from a multi user full duplex communication setup is a game-changer.
This acronym means Full Duplex Multi User MIMO. You need to understand both sides of the term. So, what is full duplex communication? The "Full-duplex" part answers this question. It means TX and RX happen simultaneously. Multi User MIMO means that many users can participate at the same time. This is an advantage to the network because it doubles the bandwidth and capacity. This technology is important to the 5G and IoT systems and the future of multi user full duplex communication.
This part illustrates the scope of what is full duplex and half duplex communication. HD, or Half-Duplex, is different. One data stream moves one way at a time. Take a Walkie-Talkie, for example. You press a button to talk (PTT). You cannot talk and listen at the same time. This method can cause delays. Faster communication is called full-duplex communication.
MIMO is the key enabler. This is how the parts come together.
MIMO systems use multiple antennas, which defines "Multiple-Input Multiple-Output" systems. Older wireless half duplex systems had only one. The more antennas there are, the more signals you can catch. The more signals you catch, the more data you can send. The more data you send, the more paths you create. This process is critical for user separation. This design also aids in self-interference cancellation. Two antennas are the minimum needed.
Beamforming is a smart antenna manipulation that concentrates a wireless signal. It aims the signal at a specific user, which is best described as a spotlight. This technique prevents signal spreading. It also reduces interference, which means the signal is stronger. The range is also wider. You can get 6 km to 7 km in tests. According to researchers at Springer, the Signal-to-Leakage-and-Noise-Ratio (SLNR) precoding approach is key, as it "realizes a better trade-off between performance and complexity." This advanced processing is what makes beamforming so effective in a real-world multi user full duplex communication environment.
The portion of the world that a device occupies is the ‘spatial domain'. For a MIMO device, this domain is a resource space. It can send a different stream of data over the same frequency across different spatial paths. This technique is known as spatial multiplexing. This provides the advantage of connecting multiple users while mitigating the risk of overlapping channels. This is how 8 users can connect simultaneously.
5G networks use MIMO systems, making them one of the finest full duplex communication examples. 5G networks have a high need for speed with low latency. FD-MU-MIMO caters to this need, which helps simultaneously serve multiple devices and enables the Internet of Things. Smart cities and self-driving cars are supported by this technology. This support, in turn, makes MIMO systems priceless for 5G networks.
Technology | Core Principle | Mechanism | Primary Benefit | Performance Metric | Relevance to FD-MU |
Multiple Antennas | Multiple-Input Multiple-Output | Create multiple data paths | User separation | 2+ antennas (min) | Self-interference cancellation |
Beamforming | Smart antenna manipulation | Concentrates signal (spotlight) | Reduces interference | 6 km - 7 km range | SLNR precoding trade-off |
Spatial Domain | Physical area as resource | Spatial multiplexing (same freq) | Mitigates channel overlap | 8+ simultaneous users | Connects multiple users |
5G Networks | MIMO system application | FD-MU-MIMO implementation | Serves multiple devices | High speed / Low latency | Enables IoT / Smart cities |
Technical Enablers for Multi-User Full-Duplex (FD-MU) Communication!
This technology, while groundbreaking, faces some key issues that need to be addressed.
SI is problem number one on the list. Your own transmitter signal is too loud and leaks into the receiver. This signal drowns the receiver, making it impossible to hear. It is similar to how one tends to shout while trying to listen. The old telephone duplex coil system tried to fix this. More modern systems prefer SI cancellers which can bring SI down by 100 dB.
Multi-user interference (MUI) is a phenomenon where multicasting users experience disruption to their signals due to proximity. This is largely problematic within confined spaces. Their signal quality within an area decreases significantly. This directly affects their data transfer rates. Beamforming helps deal with MUI problems. MUI problems can also be solved with exclusivity using other multi-user techniques. This helps in assuring and maintaining signal clarity. We often see this in dense apartment buildings where dozens of Wi-Fi signals are competing for the same space.
Co-channel interference (CCI) is the disruption caused to users in close vicinity by overlapping signals using the same frequency channel. This is mostly observed in duplex system communication. CCI functions like a dominant noise and elevates the noise level in the capture area. This makes the reception of faint signals harder. This is the phenomenon that consumers face in day-to-day communication. If you want to mitigate and eliminate CCI, you must use duplex frequency coordination and CCI management.
Signal leakage is the direct and unintentional emission of covert power. Leaked signals by one user within a signal path interfere with the signal path of another user. This, in a way, reduces the signal-to-interference-and-noise-ratio level. This is what has an effect on the SINR, which is also lowered by signal leakage. User performance is maximized by managing unused SINR residual interference and leakage. But how do you practically manage this leakage without sacrificing signal power? This is the central challenge for engineers.
Below is a compilation of 4 MIMO techniques that use advanced beamforming to resolve interference. Users can optimize interference using these four beamforming techniques.
- SLNR (Proposed): SLNR signifies Signal-to-Leakage-and-Noise Ratio. This is a method still being improved. It is especially proficient for multi user full duplex communication. It sets a balance between two objectives. It optimizes the user’s signals. It also minimizes leakage to other users. SLNR provides a closed-form solution. It sometimes prevails over other algorithms.
- ZF (Zero-Forcing): Zero-Forcing is ZF for short. This precoding method is less complex. It attempts to force MUI, or multiple user interference, to zero. This works to a useful extent in some duplex systems. However, ZF is deficient in one aspect. It does not consider noise. In areas of low signal-to-noise ratio, ZF does poorly. In fact, ZF tends to enhance the noise, making it a poor choice for robust multi user full duplex communication.
- BD (Block-Diagonalization): Block-Diagonalization is popularly known as BD. It is another common method. Also, it is an extension of ZF. It offers improvements for users having multiple antennas. BD cancels user group interference completely. However, the base station dominantly needs a ZF antenna. This tends to increase the cost of the system.
- PCA (Whitening): PCA is Principal Component Analysis. It can also be described as a whitening filter. It is used predominantly at the receiver. This works to diminish the interference by changing the CCI-plus-noise matrix or the SI-plus-noise matrix. This is a cleaning filter. It reinforces the performance of the SLNR precoder.
Spectral Efficiency is the term used to quantify the usefulness of a given system. It is also the most important metric. So, let’s get to the numbers.
§ Doubling Capacity: Within a system, the full-duplex capability can double the spectral efficiency. This is a very important performance metric compared to a half-duplex system. This is the core benefit of multi user full duplex communication.
§ 64.4% Gain: It is very important to understand the basis of the difference and the associated gains, as measured in differently constructed systems. Tests have shown that in Full Duplex systems, the spectral gain in efficiency over a half-duplex system is 64.4%. This is a tremendous improvement. A 2023 study in Scientific Reports noted that this gain "is observable due to dimensional restrictions" being overcome by the new methods. This shows the theoretical promise of multi user full duplex communication is being met in practice.
§ SE Improvement (More Antennas): The spectral efficiency of a system increases with the number of antennas used. In this case, there is a definite increase in the gain with more users and more antennas in the system.
§ SLNR Outperforms: Of the proposed schemes, the SLNR (Signal-to-Leakage-and-Noise Ratio) with additional antennas performs the best. This method achieves higher spectral efficiency compared to Zero-Forcing and Block-Diagonalization techniques.
Of the many systems proposed, there are several that one can practice. In this case, let us look at four.
This is one of the most important fields. Compressed multi user full duplex communication is a very useful tool. Firefighters communicate with one another in real time. This is a great improvement to the old system of duplexed telegraphic communication. Instead of just receiving messages from a commander, rescuers can also respond. This increases safety and coordination in tight spaces with Mesh networking.
Like other organizational environments, these also have a lot of noise. Full-duplex communication is much better than the old system of using hand radios, which is half-duplex. This allows for workers to communicate freely without the constraint of needing to press a button. This communication allows for the real-time correction of many processes. A significant number of accidents are averted, which increases the output from the production line. 1W of power can also be supplied for each system, giving a strong and effective signal for multi user full duplex communication.
Film sets can be quite hectic. The director needs to communicate, and the camera crew needs to respond. Full duplex systems make this possible. They use intercom systems. This helps in eliminating the need to scream. Plus, it helps to save a great deal of time. For instance, the 16K sampling rate helps in the overall audio clarity. This is very important for professionalism. We at G-NiceRF have seen a huge uptake in our full-duplex audio modules, like the SA618F30, for exactly this purpose. The clarity and lack of delay are essential.
The Internet of Things, or IoT, is a system consisting of many interrelated devices and requires many interconnections. The 5G network assists in providing the needed speed. The FD-MU-MIMO system provides the needed capacity. This provides for the use of smart sensors. It assists in smart agriculture as well as devices in smart cities. This is where our LoRa modules play a part. It helps in the construction of the IoT, especially for long-range, low-power applications that feed data back into the high-speed 5G network.
The next major step is energy. We need to make this technology as efficient as possible.
EE means the Energy Efficiency of a system, which we measure in terms of Bit/Hz/Joule. This is a significant metric. It signifies the amount of energy used. The goal is to reduce energy consumption. This is essential for devices that run on batteries. It aids in the longevity of IoT sensors.
Understanding the device's power consumption is important. This is what power models are used for. The model has in it the transmit power (Tx) and also the circuit power. Tx is the power that is needed to send the data. The circuit is the one that runs the device. Both elements must be optimized. This improves the efficiency of the overall system.
Circuit power is a large factor. It comprises static and dynamic power. In full-duplex, extra circuits are needed for SI cancellation. This unit is far more sophisticated than the one used in the old telephone, which was the more common telephone duplex coil. All these circuits consume energy. The growing need for advanced circuits is to develop low-power consuming circuits. This is the area that needs more focus.
Studies also indicate it is possible that FD can be better. Full-duplex has the potential of having a higher EE with the right design of a precoder. The nature of the system is that it sends data quicker, which improves overall energy. Because less energy is used to complete the task, the system becomes more efficient in communication for duplex systems. As noted by IEEE Transactions on Signal Processing, "Precoding for full duplex multiuser MIMO systems: Spectral and energy efficiency maximization" is the next frontier. This proves that with smart design, higher performance in multi user full duplex communication does not have to mean higher power consumption.
MU-MIMO is Multi-User Multiple-Input Multiple-Output. A base station can communicate to a multitude of users simultaneously. It uses multiple antennas. This remains unlike single-user MIMO, which employs spatial multiplexing to discern the users. This is crucial to have for Wi-Fi 6 and is also crucial for 5G. Do you see how this is different from just having multiple antennas for one user?
This answers what is full duplex and half duplex communication. FDD is Frequency Division Duplex. It assigns 2 separate frequencies. One for Tx, and one for Rx. TDD, Time Division Duplex, uses 1 frequency but splits the time. Tx and Rx alternate. FDD is full-duplex, while TDD is half-duplex.
Self-interference (SI) is a big 5G problem. Every full-duplex radio has it. The radio has its own transmitter signal that ‘leaks’ into its receiver. 5G signals are high power, and the leakage is very strong, being 100 dB stronger than the signal. This also requires advanced digital cancellation.
This is one of the most popular questions. No, LoRa is not full-duplex. It is half-duplex. This is also true for LoRaWAN. Devices are unable to transmit and receive simultaneously. It is not the same as full duplex communication examples, such as with 5G. Some custom systems can, however, employ two modules to replicate full-duplex audio.
Rician fading is one channel model. It explains the way a signal is transmitted. It has a dominant direct path, which is a Line-of-Sight (LOS) path. It also has several weaker paths. These are diffuse paths. This is typical in wide open spaces. This model is different than Rayleigh fading. Rayleigh fading has no direct LOS path.
MIMO systems additionally increase speed to the system while tackling difficult interference problems. You learned precoding methods and saw multicell full duplex systems. This technology is low-power. Ready to build your system? Find professional RF solutions at G-NiceRF for your multi user full duplex communication needs.
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