Uplink Contention Window Size Update in LAA Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current wireless communication systems face inefficiencies in updating uplink contention window sizes during the Listen Before Talk (LBT) procedure, leading to false alarms and missed detections, which affect throughput and scheduling alignment in Licensed Assisted Access (LAA) technologies, especially in LTE advanced systems.
Innovation Solution
A method and device for updating the uplink contention window size based on information received from a base station, where a reference scheduled burst is transmitted and decoded, allowing the base station to reset or increase the contention window size based on successful or unsuccessful transmission blocks, and the wireless communication device adjusts accordingly, using HARQ process IDs and uplink grant messages to synchronize the contention window size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the uplink contention window size is updated based on downlink transmission status, then the base station can control the contention window size, but the base station may be unaware of the actual uplink contention window size due to false alarms and missed detections
Solution Approach 1:
The patent implements a feedback mechanism where the wireless communication device sends feedback information to the base station about its uplink contention window size. This feedback includes indicators such as whether a transmission occurred in a reference subframe and the outcome of LBT procedures. The base station uses this feedback to accurately determine and track the actual contention window size being used by the device, eliminating the information loss that occurs when relying solely on downlink transmission status.
Solution Approach 2:
The wireless communication device autonomously manages its own uplink contention window size based on its local observations of transmission outcomes and LBT procedure results. The device independently determines when to reset or increase the contention window size and communicates this self-determined state to the base station through feedback messages, rather than having the base station control it directly through downlink transmissions.
2Reliability
If the contention window size is adjusted based on collision detection, then transmission reliability improves, but false alarms and missed detections reduce throughput
Solution Approach 1:
The patent defines a reference subframe that occurs before the uplink grant message is sent, establishing a predetermined time window for observing transmission outcomes. The wireless communication device performs LBT procedures and attempts transmissions in this reference subframe, and the outcome (whether transmission occurred, whether it was successful) is captured before the base station sends the uplink grant. This preliminary observation allows accurate collision detection without requiring additional post-transmission monitoring that would delay throughput.
Solution Approach 2:
The patent replaces the traditional mechanical approach of continuous channel monitoring and collision detection with an information-theoretic approach using feedback messages. Instead of the base station actively monitoring each transmission outcome, the system substitutes this with the wireless device reporting its transmission status and LBT outcomes through structured feedback information, reducing false alarms and missed detections while maintaining reliability.
3Measurement precision
If the base station monitors each transmission to update contention window size, then accurate control is achieved, but scheduling complexity and processing time increase
Solution Approach 1:
The patent extracts the complex monitoring and decision-making function from the base station and relocates it to the wireless communication device. The device independently monitors its own transmission outcomes, performs LBT procedures, determines contention window size adjustments, and communicates only the essential result (feedback information) to the base station. This extraction eliminates the need for the base station to monitor each transmission individually, reducing scheduling complexity while maintaining control accuracy.
Solution Approach 2:
The patent establishes a reference subframe with a predetermined time relationship to the uplink grant message, allowing the wireless communication device to complete transmission observations and determine contention window status before the base station needs to make scheduling decisions. This preliminary action provides the base station with ready-to-use feedback information, eliminating the need for complex real-time monitoring and reducing processing time.
Data Source
AI summary
Updating an uplink contention window size in a listen before talk process in a wireless communication system such as LTE may be done by the eNB if transport blocks contained in the starting subframe of a reference scheduled burst transmitted by a User Equipment are successfully decoded at the eNB. Otherwise, the User equipment adjusts the contention window size depending on information supplied by the eNB. This information identifies the first subframe in the burst whose transport block the base station was able to successfully decode. Depending on whether the User Equipment was first transmitting before or on the identified subframe, the User Equipment can either increase or reset the contention window size.