Flexible Subframes for TDD Interference Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Heterogeneous cellular networks face interference issues due to downlink-uplink asymmetry, particularly in macro and pico cell deployments, where macro-to-pico downlink interference prevents pico cell reception, limiting resource reuse and capacity.
Innovation Solution
Introducing flexible subframes in TDD systems that can dynamically switch between uplink and downlink usage based on traffic demand and inter-cell coordination, allowing base stations to exchange information on intended subframe usage to avoid interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed downlink-uplink subframe allocation is used in TDD systems, then network synchronization and interference coordination are simplified, but resource allocation flexibility and capacity in heterogeneous networks are reduced
Solution Approach 1:
The patent applies dynamics by enabling subframes to change their direction (downlink or uplink) dynamically based on traffic demand and network conditions. Specifically, subframes that are normally configured as downlink subframes can be dynamically switched to uplink subframes through DCI format 6/7 signaling, allowing the system to adapt to varying traffic patterns without changing the overall frame structure configuration.
Solution Approach 2:
The patent changes the parameter of subframe direction assignment from static to dynamic. By introducing a new parameter indicator in DCI formats that specifies whether a subframe should be used for downlink or uplink, the system can adjust resource allocation parameters in real-time based on traffic conditions, thereby improving resource utilization flexibility.
2Object-affected harmful factors
If separate frequency bands are used for macro and pico cells, then interference between cells is reduced, but spectrum efficiency and resource reuse are decreased
Solution Approach 1:
The patent implements periodic action by creating alternating uplink-downlink subframe patterns in pico cells. During subframes where macro cells transmit downlink, pico cells are configured to transmit uplink, and vice versa. This periodic switching creates interference-free windows that allow resource reuse on the same frequency without continuous interference.
Solution Approach 2:
The system dynamically adjusts the uplink-downlink configuration of pico cell subframes based on macro cell transmission patterns and traffic demand. This dynamic adaptation allows the pico cell to exploit interference-free periods created by macro cell transmissions, thereby enabling frequency reuse without separate frequency bands.
3Productivity
If downlink subframes are used exclusively for downlink transmission, then downlink throughput is maximized, but uplink capacity and resource reuse are limited
Solution Approach 1:
The patent makes downlink subframes dynamic by allowing them to be reconfigured as uplink subframes when uplink traffic demand is high. Through DCI format 6/7 signaling, the system can switch the direction of normally downlink subframes, thereby increasing uplink capacity without sacrificing overall downlink throughput when traffic conditions require it.
Solution Approach 2:
The patent applies universality by making downlink subframes multi-functional. These subframes can serve as either downlink or uplink subframes depending on traffic conditions and network configuration, thereby increasing the versatility of resource allocation and improving overall system capacity.
4Productivity
If uplink subframes are used exclusively for uplink transmission, then uplink throughput is maximized, but downlink capacity and resource reuse are limited
Solution Approach 1:
The patent enables uplink subframes to dynamically switch to downlink subframes when downlink traffic demand increases. Through the same DCI format 6/7 signaling mechanism, the system can reconfigure uplink subframes for downlink transmission, thereby balancing uplink and downlink capacity according to real-time traffic conditions.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The technology disclosed provides the ability for a subframe to be configured as a "flexible" subframe. As a result, at least three different types of sub frames in a TDD system may be configured: a downlink ("DL") subframe, an uplink ("UL") subframe, and a "flexible" subframe. While the DL and UL subframes are preconfigured for each frame instance, the flexible subframes are dynamically allocated to be an uplink subframe in one instance of a frame and a downlink subframe in another instance of the frame.