Signaling E-RACH Resources via Offset from R99 RACH
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Solution Overview
Problem
Current methods for signaling resources available for Enhanced Random Access Channels (E-RACH) in mobile networks like UMTS WCDMA result in high overhead and potential increased collision probability, and existing solutions either increase broadcast signaling or disturb legacy terminal operations.
Innovation Solution
Defining E-RACH resources efficiently by indicating a predetermined difference from R99 RACH resources, using a combination of signaling and predetermination, such as different scrambling codes or inverted bit maps, to minimize additional BCH loading and maintain compatibility with legacy systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If E-RACH resources are signaled using the same method as R99 RACH resources, then legacy terminal compatibility is maintained, but the amount of broadcast signaling increases significantly
Solution Approach 1:
Instead of signaling E-RACH resources directly, the patent inverts the approach by signaling the difference or offset from the known R99 RACH resources. The base station transmits an offset value that indicates how E-RACH resources differ from R99 RACH resources, allowing terminals to derive E-RACH resources through calculation rather than direct signaling.
Solution Approach 2:
The patent changes the parameter being signaled from absolute resource values to relative offset values. By signaling the difference in parameters (such as signature index offset, scrambling code offset, or time slot offset) rather than complete resource descriptions, the signaling overhead is reduced while maintaining the ability to define distinct E-RACH resources.
2Reliability
If separate resource sets are defined for E-RACH and R99 RACH, then collision probability is reduced, but device complexity increases
Solution Approach 1:
The patent establishes a predetermined relationship between R99 RACH and E-RACH resources in advance, defined through offset values that are configured and stored beforehand. This preliminary definition allows terminals to automatically derive separate resource sets without complex real-time calculations, reducing both collision probability and operational complexity.
3Adaptability or versatility
If complete E-RACH resource information is broadcast, then resource allocation flexibility is improved, but information transmission overhead increases
Solution Approach 1:
The patent extracts only the essential differential information needed to define E-RACH resources from the complete resource description. Instead of broadcasting full resource allocation details, only the offset or difference parameters are extracted and transmitted, allowing terminals to reconstruct complete E-RACH resource information by combining the offset with known R99 RACH resource configurations.
Data Source
AI summary
In UMTS WCDMA a new RACH-based uplink is being discussed. The resources defined for this new “E-RACH” need to be signalled to the UE. This should avoid disturbing the signalling to existing terminals, i.e. that are not aware of E-RACH. This could be done for E-RACH by repeating the kind of signalling defined for R99 RACH and transmitted on the BCH (Broadcast Control Channel). However, this would imply a significant extra load on the BCH, which is undesirable.The invention is based on the recognition that E-DCH resources can be defined efficiently at least partly with reference to the R99 RACH resources. This can be done in such a way that no additional signalling is required on the BCH.