Single Channel Full Duplex Massive MIMO for Wireless Backhaul
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Solution Overview
Problem
Massive MIMO multi-user beamforming (MM-MUBF) systems face significant overhead in channel estimation, especially when dealing with fast-moving User Equipment (UE) and limited frequency resources, particularly at low frequencies, due to the need for frequent channel state information (CSI) updates, which reduces data communication time and interferes with the requirement for in-band wireless backhaul in heterogeneous networks.
Innovation Solution
Implementing Single Channel Full Duplex (SCFD) technology in base stations and small cells using massive MIMO with self-interference cancellation techniques, such as RF filters and digital processing, to enable simultaneous transmission and reception in the same frequency channel, reducing the need for out-band wireless backhaul and leveraging channel reciprocity to minimize channel estimation overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Massive MIMO multi-user beamforming uses a large number of RF chains and antennas to increase spectral efficiency, then throughput is improved, but channel estimation overhead increases significantly
Solution Approach 1:
The patent segments the channel estimation process by separating backhaul channel estimation from access channel estimation. The backhaul channel (BS-SC) is estimated separately from the access channel (SC-UE), allowing independent optimization of each estimation process and reducing overall overhead.
Solution Approach 2:
The patent performs preliminary channel estimation for the backhaul link between BS and SCs before actual data transmission. By pre-obtaining CSI for the BS-SC channel, the system reduces the need for frequent re-estimation and minimizes overhead during active communication phases.
2Reliability
If out-band wireless backhaul is used for communication between BS and SCs, then frequency resources are separated, but precious frequency resources are consumed and line of sight is required
Solution Approach 1:
The patent makes the SC radio universally functional by enabling it to simultaneously handle both access communication (with UEs) and backhaul communication (with BS) using the same frequency band. This multi-functionality eliminates the need for separate out-band resources dedicated solely to backhaul.
Solution Approach 2:
The patent merges the access band and backhaul band into a single frequency band for in-band operation. By combining these previously separate frequency resources into one shared band, the system reduces overall frequency resource consumption while enabling flexible resource allocation.
3Productivity
If a SC uses the same frequency channel for simultaneous transmission and reception (Single Channel Full Duplex), then in-band wireless backhaul is enabled, but self-interference occurs
Solution Approach 1:
The patent converts the harmful self-interference into a beneficial signal by using the transmitted signal itself for channel estimation. The strong transmitted signal, which would normally be interference, is instead utilized to estimate the backhaul channel characteristics, turning a harmful factor into a useful resource.
Solution Approach 2:
The patent introduces digital signal processing techniques as an intermediary to separate the desired received signal from the self-interference. Through digital filtering and interference cancellation algorithms, the system mediates between the transmitted and received signals to extract the useful backhaul information while removing the harmful self-interference component.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases throughput by improving Signal to Interference and Noise Ratio (SINR) and allows for efficient wireless backhaul without wired connections, matching the throughput of wired backhaul systems while reducing inter-cell interference and power consumption.
Implementation Method 1
Implementing Single Channel Full Duplex (SCFD) technology in base stations and small cells using massive MIMO with self-interference cancellation techniques, such as RF filters and digital processing
Implementation Method 2
leveraging channel reciprocity to minimize channel estimation overhead
Data Source
Figure 1(a)
Figure 1(b)
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AI summary
This invention presents a method and apparatuses for wireless networking comprising one or more BS with Nbs antennas; two or more SCs in the range of a BS where a SC has Nsc antennas, uses Nsc1≤Nsc antennas for communication with a BS and uses Nsc2≤Nsc antennas for communication with one or more UEs; at the same time a BS transmitting DL signals to K SCs using multi-user transmit BF in a frequency channel, a SC simultaneously transmitting DL signals to one or more UEs in its range using the same frequency channel; and, at the same time a BS receiving UL signals from K SCs using multi-user receive BF in a frequency channel, a SC simultaneously receiving UL signals from one or more UEs in its range using the same frequency channel. Furthermore, beamforming using antennas on the SCs is performed to reduce the inter-SC interferences.