Random Access Response Transmission Using RAA Segmentation
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Solution Overview
Problem
In LTE systems, the collision probability of random access preambles increases with the number of user equipment (UEs), reducing the success rate of random access due to shared time-frequency resources, leading to inefficient random access response message transmission.
Innovation Solution
The method involves determining whether user equipment belongs to a central or edge group of random access areas based on the random access preamble, allowing for differentiated random access response message transmission, using specific MAC PDU and PDCCH signaling strategies to reduce collisions and improve success rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If all transmission points share one cell identity in a DAS system, then the system architecture is simplified and easier to operate, but the collision probability of random access preambles increases and the success rate of random access decreases
Solution Approach 1:
The patent segments the cell into multiple random access areas (RAAs), each with its own unique RAA ID. This segmentation allows the base station to differentiate between UEs in different geographic regions even when they use the same preamble sequence, thereby reducing collision probability while maintaining the simplified DAS architecture with shared cell identity.
Solution Approach 2:
The patent applies local quality by assigning different RAA IDs to different geographic regions within the cell. Each RAA has localized identification characteristics that enable the base station to provide region-specific random access response messages, reducing collisions while maintaining overall system simplicity.
2Quantity of substance
If the number of user equipment increases, then the network capacity and coverage are improved, but the collision probability of random access preambles increases due to shared time-frequency resources
Solution Approach 1:
The patent introduces a new dimension for random access resource differentiation by adding RAA ID to the existing preamble sequence and time-frequency resource structure. This creates a multi-dimensional resource space (preamble sequence × RAA ID × time-frequency resource) that can accommodate more UEs simultaneously without increasing collision probability.
3Device complexity
If one RAR message is transmitted for the same random access preamble from different random access areas, then the transmission process is simplified, but the collision probability increases and random access success rate decreases
Solution Approach 1:
The patent changes the parameters of the random access response by incorporating RAA ID into the RAR message content and using different RA-RNTI values for different RAAs. This parameter differentiation allows the system to maintain simplified transmission procedures while avoiding collisions through unique identification of the target RAA in each response message.
Data Source
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AI summary
Disclosed are a method, an eNodeB (eNB) and a User Equipment (UE) for transmitting Random Access Response (RAR) messages. The method comprises: receiving Random Access Preamble (RAP) transmitted by the UE through the Random Access Channel (RACH) (S110); according to the RAP, determining whether the UE belongs to the central group or the edge group of the Random Access Area (RAA) (S120); after determining that the UE belongs to the central group of the RAA, determining the RAA which the UE belongs to (S130); transmitting the first RAR message to the UE according to the RAP, the channel resource information of the RACH, and the RAA (S140). By transmitting the RAR message on the basis of the RAP and the RAA, the method, eNB and UE, provided by the embodiments of the present invention, for transmitting RAR messages enable different RAR messages to be transmitted with respect to identical Random Access (RA) requests of different RAAs, thereby reducing the collision probability during the transmission of the RAR and increasing the success rate of the RA.