Interference Cancellation via Spatial Alignment
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Solution Overview
Problem
Full-duplex wireless systems face challenges in scaling spectral efficiency due to uplink-downlink interference (UDI) when using multiple users and antennas, particularly in enabling full-duplex communication with half-duplex clients, which limits the potential for doubling spectral efficiency.
Innovation Solution
The implementation of spatial interference alignment (IA) between clients, specifically requiring four half-duplex clients to align interfering signals, allowing for 2N streams at an N transceiver access point, and an efficient media access control (MAC) design to handle heterogeneous antenna capabilities and reduce overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full-duplex communication is enabled with multiple half-duplex clients, then spectral efficiency can be doubled, but uplink-downlink interference (UDI) occurs that limits scalability
Solution Approach 1:
The patent applies interference alignment to convert the harmful uplink-downlink interference into a beneficial effect. By aligning the interference subspaces of multiple half-duplex clients, the interference is directed away from the access point's receive antennas, allowing full-duplex operation to scale with multiple users without the usual interference penalties.
2Productivity
If spatial interference alignment is implemented to eliminate UDI, then 2N streams can be enabled at an N transceiver access point, but system complexity increases due to alignment requirements
Solution Approach 1:
The patent employs preliminary action by having half-duplex clients perform interference alignment in advance before full-duplex communication begins. The access point schedules alignment phases where clients pre-compute and apply precoding matrices to align their interference subspaces, enabling subsequent full-duplex operation without real-time alignment computations during data transmission.
3Productivity
If multiple antennas are used for full-duplex communication, then spectral efficiency improves, but hardware complexity and cost increase due to separate RF chains required for each antenna
Solution Approach 1:
The patent applies universality by enabling the access point to serve multiple half-duplex clients simultaneously in full-duplex mode. The access point's multiple antennas are used universally for both uplink reception and downlink transmission across different clients, eliminating the need for separate RF chains for each antenna while maintaining spectral efficiency gains through multi-user multiplexing and interference alignment.
Data Source
AI summary
A method implemented in a wireless communications system including a first uplink (UL) client device, a second UL client device, a first downlink (DL) client device, and an access point (AP) is disclosed. The method comprises the following steps in this order: a) determining interference alignment (IA) solution between the first and second UL client devices and the first device; and b) determining, according to the IA solution, receive filter U0 for the AP and precoder V0 for the AP to improve a UL stream rate and a DL stream rate. Other methods, systems, and apparatuses also are disclosed.