RACH Response Control via CCE Allocation
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Solution Overview
Problem
In evolved universal terrestrial radio access (E-UTRA) and long-term evolution (LTE) wireless communications, the existing systems face challenges in efficiently managing random access responses due to the large size of transport blocks needed for signaling all responses in one transport block per random access-radio network temporary identity (RA-RNTI), which reduces scheduling flexibility and increases bandwidth usage.
Innovation Solution
The solution involves configuring multiple control channel elements (CCEs) in the RACH Response to provide unique location information for each wireless transmit/receive unit (WTRU), allowing them to blind decode their intended RACH Response control signal, with the starting location set to CCE-0 and optionally spread across a subset of CCEs, reducing the need for explicit signaling of resource allocations and improving scheduling flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If all random access responses are signaled in one transport block per RA-RNTI, then complete response information is provided to all WTRUs, but the transport block size increases reducing scheduling flexibility and increasing bandwidth usage
Solution Approach 1:
The patent divides the random access response signaling into multiple separate transport blocks, each associated with a different RA-RNTI. Instead of sending all responses in a single large transport block, the base station segments the responses and sends them individually through multiple smaller transport blocks. This segmentation maintains complete response information delivery while improving scheduling flexibility and reducing bandwidth usage requirements.
2Productivity
If multiple CCEs are configured for RACH Response, then WTRUs can locate their responses more efficiently, but the control channel complexity increases
Solution Approach 1:
The patent assigns different numbers of CCEs to different WTRUs based on their specific needs and the amount of response information they require. Instead of using a uniform CCE allocation for all WTRUs, the system applies local quality by tailoring the CCE resources to each WTRU's requirements. This approach improves response location efficiency for each individual WTRU while managing overall control channel complexity through selective resource allocation.
Data Source
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AI summary
A method and apparatus for supporting a random access using a random access channel (RACH) are disclosed. Each of a plurality of wireless transmit/receive units (WTRUs) sends a random access request to a base station on an uplink RACH preamble. A RACH Response (Access Indication Channel, AICH, message), sent by the base station, is received by each WTRU. The received RACH response signal comprises a control portion (Physical downlink control channel, PDCCH), and a data portion QO (Physical downlink shared channel, PDSCH). The control signal portion of the RACH Response indicates the location of the RACH Response message portion. The RACH Response control signal comprises multiple control channel elements (CCE), where each Q WTRU is allocated a respective CCE to provide its unique RACH Response control signal. The WTRU is configured to locate its intended CCE from among the multiple CCEs sent by the base station. Blind decoding.