SIB Multicast Scheduling for Category 0 UE Coverage
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Solution Overview
Problem
In LTE networks, Category 0 devices with limited capabilities, such as those with only one antenna, face challenges in receiving System Information Blocks (SIBs) due to coverage limitations, and existing methods like increasing transmit power can negatively impact network spectral efficiency and do not guarantee improved performance.
Innovation Solution
The solution involves identifying a location within a transmission subframe for multicast messages based on a physical cell identifier (PCI) and transmission subframe information, allowing for efficient scheduling of SIBs on orthogonal resources, reducing inter-cell interference, and selectively boosting PDCCH power to ensure reliable coverage for special UEs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transmit power of PDSCH and PDCCH carrying SIBs is increased, then coverage of SIBs is improved, but network spectral efficiency deteriorates due to transmit power limitation on resources used for regular UEs
Solution Approach 1:
The patent segments the SIB transmission into multiple repetitions across different subframes. Instead of transmitting the entire SIB in one high-power burst, the system divides the SIB into multiple parts transmitted sequentially, allowing regular UE resources to remain available while providing cumulative coverage enhancement for Category 0 devices.
Solution Approach 2:
The patent implements periodic repetition of SIB transmissions at configured intervals. The SIB is transmitted repeatedly over multiple subframes with a defined periodicity, allowing Category 0 UEs to accumulate signal energy across repetitions while regular UEs can access resources in between repetitions without interference.
2Reliability
If transmit power of PDSCH and PDCCH carrying SIBs is increased, then coverage of SIBs is improved, but signal to interference levels are not improved when surrounding cells also increase transmit power
Solution Approach 1:
The patent changes the temporal distribution parameter of SIB transmissions by introducing repetition across multiple subframes with different timing offsets. This transforms the interference scenario from simultaneous high-power transmissions (poor SIR) to distributed low-power transmissions (better SIR), as Category 0 UEs can accumulate signal while interference varies over time.
Solution Approach 2:
The network pre-configures repetition patterns and timing offsets for SIB transmissions before actual transmission. This preliminary setup ensures that repetitions are distributed in a manner that avoids simultaneous interference with other cells, optimizing the signal-to-interference ratio before the transmission actually occurs.
3Reliability
If SIB transmission resources are allocated for Category 0 devices, then coverage for special UEs is improved, but resource allocation for regular UEs is reduced
Solution Approach 1:
The patent makes the PDSCH resources universal by configuring them to serve both Category 0 devices and regular UEs. The same PDSCH resources carry SIB repetitions that benefit Category 0 UEs while maintaining compatibility with regular UE reception requirements, eliminating the need for separate dedicated resources.
Solution Approach 2:
The SIB repetition mechanism is self-serving for both UE types. The repeated transmissions inherently provide coverage enhancement for Category 0 UEs while the distributed timing pattern allows regular UEs to access the same resources without conflict, making the system self-organizing without additional overhead.
Data Source
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AI summary
A network node may identify a location to be allocated for a multicast message within a transmission subframe based on at least information identifying the transmission subframe, and then transmit the multicast message at the identified location in the transmission subframe. A network node may also identify a transmission subframe in which to transmit a multicast message, allocate transmission resources in the transmission subframe for the multicast message, and transmit information indicating a location of the allocated transmission resources in the transmission subframe in a control signal message having a transmission power adjusted based on at least one of information identifying the transmission subframe and a code redundancy version of the multicast message.