PRACH Link Budget via Multiple Transmission Combining
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Solution Overview
Problem
Wireless communication systems face challenges in establishing reliable communication links between user equipment (UE) and base stations due to the limited geographic area served by directional beams, leading to frequent handover procedures and poor link budget for Physical Random Access Channel (PRACH) transmissions.
Innovation Solution
The method involves combining multiple PRACH transmissions to form a combined PRACH control message, which includes identifying failed transmissions, determining a fixed timing between them, and extracting common data to improve the link budget by retransmitting at higher power levels and using multiple communication resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple PRACH transmissions are combined to improve link budget, then reliability of communication links is improved, but device complexity increases due to multiple transmission coordination and combining operations
Solution Approach 1:
The patent combines multiple PRACH transmissions (first PRACH transmission and second PRACH transmission) into a single combined PRACH control message. The base station receives multiple PRACH transmissions from the UE and combines them to form one consolidated control message, which improves link budget and reliability while managing complexity through standardized combining operations.
Solution Approach 2:
The patent establishes fixed timing relationships between multiple PRACH transmissions before they are actually transmitted. The UE is configured with predetermined timing offsets for subsequent PRACH transmissions based on the first reception time, allowing the base station to prepare combining operations in advance and reducing real-time processing complexity.
2Reliability
If multiple PRACH transmissions are used to enhance link budget, then successful decoding probability increases, but loss of time occurs due to multiple transmission attempts and combining operations
Solution Approach 1:
The patent employs periodic PRACH transmissions with fixed timing intervals. The UE transmits PRACH messages at predetermined periodic intervals (first PRACH transmission, second PRACH transmission) based on configured timing offsets, allowing the base station to accumulate signals systematically without requiring continuous monitoring or adaptive scheduling.
Solution Approach 2:
The base station configures the UE with predetermined timing offsets for multiple PRACH transmissions before the actual random access procedure begins. This preliminary configuration allows the UE to transmit at exact predetermined times without requiring real-time timing adjustments, reducing processing delays and enabling efficient combining operations.
3Ease of manufacture
If fixed timing is determined between PRACH transmissions to enable combining, then extraction of common data becomes more efficient, but adaptability decreases due to rigid timing requirements
Solution Approach 1:
The patent uses fixed timing parameters (timing offsets T1, T2, T3) that can be configured through higher-layer signaling. These parameters allow the system to adapt to different channel conditions and deployment scenarios by changing timing values without altering the fundamental combining mechanism, thus maintaining extraction efficiency while providing flexibility.
Solution Approach 2:
The fixed timing mechanism serves multiple functions: it enables efficient signal combining at the base station, provides implicit synchronization for the UE, and allows the same PRACH procedure to be used in various scenarios (contended and non-contended random access). The universal timing framework adapts to different operational modes without requiring separate procedures.
Data Source
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AI summary
Techniques are described herein to improve a link budget of physical random access channel (PRACH) transmissions used during a random access (RACH) procedure. The link budget of a PRACH transmission associated with the RACH procedure may be improved by transmitting multiple PRACH transmissions. The multiple PRACH transmissions may be combined to achieve some combining gain. Each retransmission of a PRACH transmission may be done at a higher power level than the previous PRACH transmission. If UE receives an indication that a target base station failed to successfully decode the PRACH transmission, the UE may retransmit the PRACH transmission but at a higher power level than the initial PRACH transmission. PRACH transmissions may be distributed across multiple slots. PRACH transmissions may be distributed across multiple frequency sub-bands in the same slot or across frequency sub-bands in the different slots.