RACH Contention Resolution Channel for Collision Detection
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Solution Overview
Problem
In communication systems, collisions during Random Access Channel (RACH) transmission lead to delays in initial access as UEs may select and transmit the same preamble, causing failures in RRC CONNECTION REQUEST message transmission, resulting in prolonged waiting times for retransmissions or timer restarts.
Innovation Solution
Implementing a Contention Resolution (CR) channel for collision detection, where UEs select and transmit a CR channel along with their connection request message, allowing the Evolved Node B (E-NB) to detect collisions and send a collision indicator, enabling UEs to initiate a new RACH procedure without restarting timers or waiting for maximum retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UEs transmit RRC CONNECTION REQUEST messages without collision detection, then the procedure is simple, but collisions cause delays and require prolonged waiting for retransmissions
Solution Approach 1:
The patent introduces a CR channel as an intermediary mechanism between UEs and the network for collision detection. The CR channel carries collision indication information from the network to UEs, enabling collision detection without requiring complex changes to the basic RACH procedure. This intermediary approach allows reliable collision detection while maintaining procedural simplicity.
Solution Approach 2:
The patent implements feedback through the CR channel, where the network provides collision indication information back to UEs after receiving RRC CONNECTION REQUEST messages. This feedback mechanism allows UEs to detect collisions and adjust their behavior accordingly, improving reliability without significantly increasing complexity.
2Productivity
If UEs wait for timer expiration or maximum retransmissions before attempting new RACH, then the procedure is simple, but access delay increases
Solution Approach 1:
The CR channel provides immediate feedback to UEs about collision status, allowing them to know whether they need to retry or can proceed to the next step. This feedback enables faster decision-making and reduces unnecessary waiting time, thereby decreasing access delay and improving system access efficiency.
Solution Approach 2:
The patent performs collision detection before the UE needs to wait for timer expiration or reach maximum retransmissions. By detecting collisions early through the CR channel, the system can take preliminary actions to resolve conflicts, reducing the overall time required for initial access and improving productivity.
3Loss of information
If no collision indicator is transmitted, then the network response is simple, but UEs cannot determine if collision occurred causing prolonged waiting
Solution Approach 1:
The CR channel serves as an intermediary that carries collision information from the network to UEs. This intermediary mechanism transmits collision indication information without requiring complex changes to the network response structure, thereby reducing information loss while maintaining response simplicity.
Solution Approach 2:
The patent extracts collision detection functionality from the main RACH procedure and places it in a separate CR channel. This extraction allows collision information to be transmitted independently and simply, without complicating the overall network response mechanism. The CR channel carries only the necessary collision indication information, minimizing data transmission complexity.
Data Source
AI summary
A method and apparatus for transmitting/receiving a Random Access Channel (RACH) signal in a communication system. A User Equipment (UE) selects one of Contention Resolution (CR) channels allocated for collision detection, and transmits the selected CR channel and a connection request message to an Evolved Node B (E-NB), and receives a response signal from the E-NB. The UE transmits the RACH signal, if a collision indicator is included in the response signal. The E-NB receives from each of UEs a connection request message and a CR channel, decodes the connection request message, and detects a collision between the UEs using the CR channel. The E-NB generates a response signal to the connection request message according to the decoding result, generates a collision indicator according to the collision detection result, and transmits to the UEs at least one of the generated response signal, the generated collision indicator, and a unique ID of a corresponding UE.