Uplink Scrambling Sequence Segmentation for Random Access Interference
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Solution Overview
Problem
In LTE uplink communications, user terminals cannot employ terminal-specific scrambling sequences or reference signals during the initial random access procedure, as they have not yet been assigned these, leading to challenges in randomizing interference and establishing uplink synchronization.
Innovation Solution
A method where user terminals use a general uplink scrambling sequence for initial random access messages, which are then switched to terminal-specific sequences after assignment, allowing for effective interference randomization and channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If user terminals use terminal-specific scrambling sequences during random access, then interference randomization performance is improved, but the system cannot establish uplink synchronization and assign terminal identifiers yet
Solution Approach 1:
The patent segments the scrambling sequence usage into two distinct phases: a first scrambling sequence used during the initial random access procedure before uplink synchronization is established, and a second terminal-specific scrambling sequence used after synchronization is achieved. This segmentation resolves the contradiction by allowing interference randomization during random access without requiring terminal-specific identifiers yet.
Solution Approach 2:
The patent applies preliminary action by using a first scrambling sequence that is prepared and applied before terminal-specific scrambling sequences are assigned. This preliminary scrambling enables interference randomization during the random access phase, allowing the system to proceed with uplink synchronization establishment without waiting for terminal identifier assignment.
2Object-affected harmful factors
If user terminals use general uplink scrambling sequence during random access, then interference randomization is enabled, but terminal-specific channel estimation capability is lost
Solution Approach 1:
The patent segments channel estimation into two phases: during random access, the base station performs channel estimation using the first scrambling sequence; after uplink synchronization is established, the base station performs enhanced channel estimation using the second terminal-specific scrambling sequence. This segmentation enables both interference randomization during random access and precise channel estimation after synchronization.
Solution Approach 2:
The patent applies dynamics by transitioning from a static general scrambling sequence during random access to a dynamic terminal-specific scrambling sequence after synchronization. This dynamic switching enables the system to adapt its channel estimation capabilities based on the operational phase, improving measurement precision when needed while maintaining interference randomization when required.
3Productivity
If user terminals switch to terminal-specific scrambling sequences after random access, then uplink data transmission performance is improved, but scheduling flexibility is reduced
Solution Approach 1:
The patent segments the uplink transmission process into random access phase using first scrambling sequences and data transmission phase using second terminal-specific sequences. This segmentation allows the system to maintain scheduling flexibility during random access while achieving high performance during data transmission, as each phase can be optimized independently for its specific requirements.
Data Source
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AI summary
A method implemented in a user terminal (20) for performing a random access procedure is presented. The method comprises transmitting a first random access request message including a random access preamble to a radio base station (18) using a random access channel, RACH, radio resource and receiving a second random access response message from the radio base station (18). The second random access response message indicates a timing change, an identified radio resource of an uplink shared channel, UL-SCH, and a temporary user terminal identity. The method also comprises adjusting a timing at the user terminal (20) for transmitting signals to the radio base station (18) based on the timing change indicated in the second random access response message and, based on the adjusted timing, transmitting a third message to the radio base station (18) over the identified radio resource of the uplink shared channel. The third message includes a user terminal identity that was assigned to the user terminal before the random access procedure is scrambled using a cell-associated scrambling sequence that is not terminal-specific. Further still, the method comprises receiving a fourth contention resolution message from the radio base station (18) to complete the random access procedure.