Random Access Channel Procedure for Reducing Signature Collisions
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Solution Overview
Problem
The existing random access channel (RACH) in LTE networks faces limitations in capacity due to collisions between RACH signatures, leading to high overhead and increased latency, particularly in scenarios where multiple user equipment (UEs) select the same signature, resulting in failed detection and subsequent contention resolution delays.
Innovation Solution
The solution involves providing multiple partially overlapping resource opportunities for the first scheduled transmission, allowing user equipment (UEs) to select one of these resources based on predetermined rules, and employing advanced receivers in eNodeB for blind decoding, which can separate resources using different reference signals, time advances, or sub-carrier allocations, thereby reducing collisions and improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple UEs select the same RACH signature, then collision occurs leading to failed detection, but providing more unique signatures increases overhead
Solution Approach 1:
The patent segments the single RACH signature selection into multiple signature groups (e.g., Group A and Group B). UEs are assigned to different groups based on their uplink timing advance values, dividing the collision-prone single signature space into multiple manageable segments. This reduces collisions within each group while maintaining overall system capacity without increasing total overhead.
Solution Approach 2:
The patent introduces a new dimension for resource differentiation by using uplink timing advance values to assign UEs to different signature groups. Instead of relying solely on the signature index dimension, the system now uses the timing advance dimension to create orthogonal resource allocation, effectively adding another degree of freedom to resolve collisions without increasing overhead.
2Productivity
If traditional RACH procedure is used, then system maintains simplicity, but capacity is limited due to signature collisions
Solution Approach 1:
The patent performs preliminary classification of UEs into different signature groups based on their uplink timing advance values before the actual RACH signature selection. This preliminary action prevents collisions from occurring in the first place, allowing the system to achieve higher capacity while maintaining relatively simple detection procedures at the eNodeB side.
Solution Approach 2:
The patent changes the parameter used for signature group assignment from static to dynamic, using uplink timing advance values (which vary per UE) to determine group membership. This parameter change enables the system to differentiate UEs more effectively, increasing RACH capacity without requiring complex additional signaling or procedures.
3Loss of time
If contention resolution is performed after collision, then detection can be attempted, but latency increases due to additional resolution steps
Solution Approach 1:
The patent applies preliminary anti-action by preventing collisions before they occur through signature group assignment based on uplink timing advance values. By anticipating and preventing the collision condition in advance, the system eliminates the need for subsequent contention resolution procedures, thereby reducing latency while maintaining detection reliability.
Data Source
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AI summary
Systems, methods, apparatuses, and computer program products for an enhanced random access channel (RACH) procedure are provided. One method may include receiving an access request comprising a signature from at least one user equipment. The method may then include providing, to the at least one user equipment, multiple at least partially overlapping resource opportunities for a first scheduled transmission, and performing blind decoding of the first scheduled transmission for the multiple at least partially overlapping resource opportunities