E-HICH Signature Sequence Assignment for TD-SCDMA
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Solution Overview
Problem
In the TD-SCDMA system, the assignment of signature sequences for E-HICH channels leads to an unbalanced situation where some UEs have good HSUPA transmission performance while others have poor performance due to varying cross-correlation characteristics, resulting in an unequal false detection rate for feedback information.
Innovation Solution
A method is introduced where a logical signature sequence index is converted into a time-varying physical signature sequence index using a random permutation function known to both the Node B and UEs, ensuring the signature sequences used on the E-HICH channel change pseudo-randomly, thereby equalizing detection performance across UEs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed signature sequence assignment method is used for E-HICH channels, then the system complexity is low and implementation is simple, but the detection performance becomes unbalanced across different UEs with high false detection rates
Solution Approach 1:
The patent applies dynamics by making the signature sequence index time-varying through a permutation function. Instead of using a fixed signature sequence assignment, the system dynamically selects different signature sequences at different time instances based on the permutation of the original signature sequence indices. This dynamic approach equalizes the detection performance across different UEs while maintaining manageable system complexity through the use of pre-defined permutation functions.
2Ease of operation
If signature sequences are assigned based on UE-specific PHY channel parameters, then each UE can identify its own signature sequence, but the cross-correlation characteristics cause unbalanced false detection rates among UEs
Solution Approach 1:
The patent applies parameter changes by transforming the signature sequence index through a permutation function. The original signature sequence index (determined by UE-specific parameters) is permuted to generate a new time-varying index. This parameter transformation maintains the ease of identification (UEs can still determine their signature sequences) while equalizing the cross-correlation characteristics and reducing unbalanced false detection rates across different UEs.
3Productivity
If the same signature sequence is used for multiple UEs, then the system resource utilization is efficient, but the feedback information detection becomes unreliable due to interference
Solution Approach 1:
The patent applies dynamics by introducing time-varying signature sequence assignment through permutation. At different time instances, different UEs are assigned different signature sequences based on the permuted indices, reducing mutual interference while maintaining efficient resource utilization. The dynamic nature ensures that the same signature sequence is not continuously used by multiple UEs, improving feedback information detection reliability.
Data Source
AI summary
A method for assigning signature sequences for E-HICH channel which may avoid the unbalanced situation brought about by the codeword assignment is provided, wherein the use of User Equipment (UE) signature sequences on Enhanced Dedicated Channel Hybrid Automatic Repeat Request Acknowledgement Indicator Channel (E-HICH) is equalized, so as to drive the average detection performance toward equity for different UEs to detect their respective signature sequences on E-HICH channel, and to reduce the average false detection rate for the respective UE on the feedback information transmitted thereto. The method includes: firstly, assigning a E-HICH logical signature sequence index r for each UE; then, converting the logical signature sequence index r into a physical signature sequence index r′ varying with time by using a random permutation function; and after that, assigning a signature sequence corresponding to the physical signature sequence index r′ to the respective UE.