Dynamic Contention Window Adjustment for 5G NR Random Access
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Solution Overview
Problem
In 3GPP 5G new radio (NR) networks, the Random Access Channel (RACH) procedure lacks a mechanism to adjust the contention window size effectively, leading to unfair coexistence with other transmission nodes using unlicensed channels, as New Data Indication (NDI) is not included in RACH messages, resulting in potential collisions and inefficient resource allocation.
Innovation Solution
The proposed solution involves an apparatus and method that adjust the contention window value based on the receipt of messages within the random access procedure, increasing it if a response is not received within a time duration or if a message is re-transmitted, and setting it to an initial value if received, thereby ensuring fair coexistence and efficient resource allocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contention window size is increased to avoid collisions, then collision avoidance is improved, but channel access efficiency deteriorates
Solution Approach 1:
The contention window size is dynamically adjusted based on the detection of retransmitted RACH messages. The base station monitors whether received RACH messages are retransmissions and adapts the contention window size accordingly, making the parameter flexible rather than fixed to balance collision avoidance and channel access efficiency
Solution Approach 2:
The base station implements a feedback mechanism by detecting retransmitted RACH messages and using this information to adjust the contention window size. This closed-loop approach allows the system to learn from past collisions and adapt the contention window to current channel conditions, improving both reliability and efficiency
2Productivity
If the contention window size remains unchanged to maintain channel access efficiency, then channel access efficiency is improved, but collision avoidance deteriorates
Solution Approach 1:
The system transitions from a static contention window size to a dynamic one that changes based on observed retransmission patterns. When retransmissions are detected, the contention window is increased to prevent further collisions; when no retransmissions occur, it returns to initial values to maximize channel access efficiency
Solution Approach 2:
The contention window size parameter is changed adaptively based on the state of the random access procedure. The base station modifies this parameter in response to detecting retransmitted messages, allowing the system to optimize the balance between collision avoidance and channel access efficiency under different operating conditions
3Device complexity
If the contention window is not adjusted during RACH procedure to maintain simplicity, then device complexity is reduced, but fairness in coexistence deteriorates
Solution Approach 1:
The base station performs self-service by autonomously detecting retransmitted RACH messages and adjusting the contention window size without requiring complex external coordination or additional signaling protocols. The system uses its existing monitoring capabilities to implement fairness in coexistence
Solution Approach 2:
The existing RACH message monitoring function is extended to serve a dual purpose: both maintaining the random access procedure and detecting retransmissions for contention window adjustment. This multi-functionality approach avoids adding separate complex mechanisms while achieving fairness in coexistence
Data Source
AI summary
An apparatus comprises a transmitter for transmitting a first message to a communication device, where the first message is a message within a random access procedure; a receiver for receiving a second message from the communication device in response to the first message; and a processor that increases a contention window value if the second message is not received in a time duration after the first message is transmitted; and that sets the contention window value to an initial value if the second message is received in the time duration after the first message is transmitted.