Non-Scheduled Network Access with Collision-Aware Retransmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In cellular networks, the distributed nature of random-access algorithms leads to collisions among multiple terminal devices using the same resources, especially when the number of users is high, resulting in inefficiencies and increased latency due to the inadequacy of existing back-off techniques to de-correlate transmissions.
Innovation Solution
Implementing a distributed tree algorithm for resource selection and a hybrid automatic repeat request (HARQ) mechanism to manage collisions by ensuring terminal devices select different physical random access channel occasions and adjust back-off times based on feedback, creating a coordinated set of resources to minimize collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional random access methods are used, then terminal devices can access the network independently, but collisions occur frequently when many devices access simultaneously
Solution Approach 1:
The patent changes the parameter of back-off time from a fixed or simple random value to a dynamically adjusted value based on collision detection. When collisions are detected, the back-off time is increased for subsequent access attempts, transforming the access pattern from purely random to adaptively controlled, thereby reducing collision probability while maintaining self-initiated transmission capability
Solution Approach 2:
The patent introduces a feedback mechanism where terminal devices monitor the random access channel for collision indicators (such as NACK signals or detection of simultaneous transmissions). This feedback information is used to adjust the back-off time parameter, creating a closed-loop control system that reduces collisions without requiring centralized scheduling
2Reliability
If back-off techniques are applied to reduce collisions, then transmission de-correlation is attempted, but the technique is insufficient when too many users collide initially
Solution Approach 1:
The patent makes the back-off time dynamic rather than static. The back-off parameter is adjusted based on the detected collision severity and the number of collision events. This dynamic adjustment allows the system to adapt to varying traffic conditions, applying stronger de-correlation when needed while minimizing unnecessary delays when collisions are rare
Solution Approach 2:
The patent applies preliminary randomization to the back-off time calculation before the actual retransmission. By pre-calculating and randomizing the back-off duration based on collision history, the system prepares diverse transmission schedules in advance, preventing synchronized re-collisions before they can occur
3Reliability
If random decisions are made to break user correlation, then uniform decision over a range is achieved, but the same users may collide again with the same technique
Solution Approach 1:
The patent applies preliminary randomization to the back-off time parameter before retransmission attempts. This preliminary random decision ensures that even if users maintain the same access pattern otherwise, their retransmission times are diversified, preventing systematic re-collisions while maintaining overall pattern consistency for non-colliding users
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A terminal device selects are source indicator to be used for non-scheduled access and transmits it to an access device of the network in the non-scheduled access. If it determines based on a response to the non-scheduled access, that it has selected the same resource indicator as another terminal device, it keeps the resource indicator but selects different physical random access channel occasions by setting a time offset for a retransmission with the selected resource indicator. An initial waiting time may be determined by the access device (e.g. based on a traffic amount on the access channel) and transmitted to the terminal device for setting the time offset.Also, a layer (2) error caused by a random access channel resource collision of terminal devices may be determined at the access device and a feedback indicating a non-acknowledgement for layer (2) may be transmitted to colliding terminal devices.