Network Node Channel Estimation in Overlapping WLAN Cells
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Solution Overview
Problem
Co-channel interference in dense wireless communications networks, particularly in IEEE 802.11 WLAN standards, leads to reduced signal-to-noise-plus-interference ratios and performance losses due to inadequate interference mitigation in overlapping Basic Service Sets (OBSSs).
Innovation Solution
A method where a network node controls Access Points (APs) to transmit information indicating when a Null Data Packet (NDP) is being transmitted, ensuring associated wireless devices refrain from contending for transmission resources, allowing for improved channel estimation and interference channel estimation towards the second AP without interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If co-channel frequency reuse is implemented in dense deployment scenarios, then network coverage and capacity are improved, but co-channel interference increases compromising QoS
Solution Approach 1:
The system performs preliminary channel assessment and identification of OBSS transmissions before actual data transmission. The AP detects NDP announcements from overlapping BSSs and proactively configures wireless devices to enter sleep mode during these periods, preventing interference before it occurs.
Solution Approach 2:
The patent introduces an intermediary coordination mechanism where the AP acts as a mediator between wireless devices and external interfering BSSs. The AP receives NDP announcements from external BSSs and translates them into coordinated sleep mode commands for its associated devices, enabling indirect interference management.
2Object-affected harmful factors
If coordinated power control is implemented to mitigate interference, then interference reduction is achieved, but transmission scheduling complexity increases
Solution Approach 1:
The patent extracts the complex power control and scheduling decisions from the individual APs and wireless devices, concentrating them in a centralized coordinator. This coordinator manages interference mitigation across multiple BSSs, simplifying the operation of individual nodes while achieving coordinated interference reduction.
Solution Approach 2:
A centralized coordinator acts as an intermediary that receives channel state information from multiple APs and generates coordinated power control commands. This mediator simplifies the overall system complexity by centralizing the decision-making process for interference mitigation.
3Measurement precision
If channel sounding procedures are performed in OBSS environments, then channel estimation is obtained, but interference from contending transmissions degrades estimation accuracy
Solution Approach 1:
The system performs preliminary identification of ongoing NDP transmissions from external BSSs before initiating channel sounding procedures. Based on this preliminary detection, the AP proactively configures its wireless devices to remain silent during the sounding period, ensuring interference-free channel measurements.
Solution Approach 2:
The system implements feedback mechanisms where APs share information about detected NDP announcements and channel sounding schedules. This feedback enables coordinated silence periods across overlapping BSSs, ensuring that channel estimations are performed without interference from contending transmissions.
Data Source
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AI summary
Embodiments herein relate to a method performed by a network node (110, 111, 01) for enabling channel estimation in a wireless communications network (100). The wireless communications network (100) comprises at least a first and a second Access Point, AP, (110, 111) having overlapping cells(115, 116) using contention-based transmission resources of the same frequency. The first network node (110, 111, 101) controls the first AP (110) to transmit information indicating that wireless devices served by the first AP (110) are not to contend for the contention-based transmission resources when the second AP (111) is transmitting a Null Data Packet, NDP. Then, the first network node (110, 111, 101) controlsthe second AP (111) to transmit a NDP. Embodiments of the first network node (110) are also described. Embodiments herein also relate to a method performed by a wireless device(121) for enabling channel estimation in a wireless communications network (100),and embodiments of the wireless device (121, 122).