Code Multiplexing for Full Duplex TDD Interference
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Solution Overview
Problem
In wireless telecommunications networks, overlapping frequencies between neighboring access nodes can lead to increased interference due to differing Time Division Duplexing (TDD) schedules, especially in scenarios where access nodes operate on the same frequency band, affecting communication efficiency and bandwidth utilization.
Innovation Solution
A method and system that set an overlap threshold to determine the extent of overlap between TDD allocations of neighboring access nodes using the same frequency band, and in cases where the overlap exceeds this threshold, instruct one access node to multiplex its downlink communication signals with an orthogonal code before transmission, mitigating interference by distinguishing between overlapping communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If TDD allocations are used for full duplex communication, then bandwidth is doubled, but interference increases when neighboring access nodes have overlapping TDD schedules on the same frequency band
Solution Approach 1:
The patent applies code multiplexing by changing the parameter of signal modulation, specifically using orthogonal codes (such as Walsh-Hadamard codes) to multiplex downlink and uplink signals in the code domain. This allows simultaneous transmission on the same frequency without time division, thereby maintaining full bandwidth utilization while eliminating TDD schedule overlap interference through orthogonal signal separation.
Solution Approach 2:
The patent transitions from time-division multiplexing (TDD) to code-division multiplexing by adding a code domain dimension. Instead of separating uplink and downlink in time slots, the invention separates them using orthogonal codes, effectively moving the separation mechanism from the time dimension to the code dimension, thereby eliminating TDD alignment requirements while maintaining full duplex capability.
2Productivity
If FDD is used for full duplex communication, then simultaneous uplink and downlink are achieved, but spectrum efficiency is reduced due to frequency division
Solution Approach 1:
The patent changes the fundamental parameter of signal separation from frequency division (FDD) to code division. By using orthogonal codes to separate uplink and downlink signals in the code domain rather than frequency domain, the system achieves simultaneous full-duplex communication while utilizing the entire available bandwidth for both directions, thereby improving spectrum efficiency compared to FDD.
3Quantity of substance
If TDD is used with high overlap between neighboring nodes, then bandwidth is maximized, but directional transmission rate is halved due to time slot allocation
Solution Approach 1:
The patent eliminates the time slot allocation constraint by moving from time-division to code-division multiplexing. This dimensional change allows continuous transmission without alternating time slots, thereby achieving full bandwidth utilization while maintaining maximum transmission rates in both uplink and downlink directions simultaneously, rather than halving the rate due to time sharing.
Data Source
AI summary
Systems, methods, and processing nodes for managing duplex communications in a network perform and/or comprise: setting an overlap threshold; comparing a first time division duplex (TDD) allocation corresponding to a first access node with a second TDD allocation corresponding to a second access node which neighbors the first access node and which utilizes a same frequency band as the first access node, thereby to determine a overlap amount; and in response to a determination that the overlap amount exceeds the overlap threshold, instructing the first access node to multiplex a downlink communication signal with an orthogonal code prior to transmitting the downlink communication signal.