PDSCH Resource Mapping Around SS/PBCH Blocks in Unlicensed Spectrum
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently mapping physical downlink shared channels (PDSCH) on unlicensed spectrum, particularly in defining UE behavior for rate matching around synchronization signal/broadcast channel (SS/PBCH) blocks within discovery reference signals (DRS), which are compact in time domain and require enhanced resource mapping configurations.
Innovation Solution
The system employs a method where a user equipment (UE) or base station determines a window for SS/PBCH block transmission, using a bitmap and quasi-co-location assumption to identify transmitted or non-transmitted blocks, and adjusts resource mapping to avoid overlap with SS/PBCH blocks, allowing PDSCH transmission on available resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PDSCH transmission is performed on unlicensed spectrum without considering SS/PBCH block locations, then resource utilization is simplified, but interference with synchronization signals occurs and communication reliability deteriorates
Solution Approach 1:
The base station performs preliminary actions by determining the SS/PBCH block transmission window and bitmap before PDSCH resource allocation. The UE uses the ssb-PositionsInBurst bitmap to identify which resource elements are occupied by SS/PBCH blocks in advance, allowing the UE to perform rate matching around these blocks. This preliminary identification and avoidance mechanism ensures reliable communication by preventing interference with synchronization signals while maintaining structured resource mapping.
2Loss of information
If PDSCH resources are allocated without rate matching around SS/PBCH blocks, then resource allocation is simpler, but resource overlap occurs causing interference and loss of information
Solution Approach 1:
The patent extracts the SS/PBCH block resource elements from the available PDSCH resource pool by using the ssb-PositionsInBurst bitmap to identify and exclude these specific resource elements. The UE performs rate matching by removing (taking out) the resource elements corresponding to SS/PBCH blocks from the PDSCH resource allocation, ensuring that PDSCH data is not mapped to these critical synchronization signal resources, thereby preventing information loss and interference.
3Measurement precision
If the SS/PBCH block transmission window is extended to cover all possible blocks, then detection accuracy improves, but false detection of non-transmitted blocks increases
Solution Approach 1:
The base station provides feedback to the UE through the ssb-PositionsInBurst bitmap, which explicitly indicates which SS/PBCH blocks are actually transmitted within the detection window. The UE uses this feedback information to distinguish between transmitted and non-transmitted blocks, avoiding false detections. The bitmap serves as a feedback mechanism that reconciles the extended detection window with accurate transmission status identification, ensuring both detection precision and transmission reliability.
Data Source
AI summary
A method and apparatus in a wireless communication system supporting shared spectrum channel access is provided. The method and apparatus comprises: receiving a set of downlink channels supporting the shared spectrum channel access; identifying, a window for SS/PBCH block transmission, a bitmap for SS/PBCH blocks (ssb-PositionsInBurst), and a parameter for QCL assumption Q; determining, based on the identified window for the SS/PBCH block transmission, the identified bitmap for the ssb-PositionsInBurst, and the identified parameter for the QCL assumption Q, a SS/PBCH block as one of: a first set of SS/PBCH blocks assumed to be transmitted by the BS, or a second set of SS/PBCH blocks not transmitted by the BS; determining a set of resources that is not available for at least one PDSCH as overlapped with the first set of SS/PBCH blocks; and receiving the at least one PDSCH based on resource other than the determined set of resources.