Semi-Persistent Grant Handling in LTE Wireless Systems

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Solution Overview

Problem

In the LTE system, semi-persistent scheduling leads to radio resource misusing and interference due to the inability of the C-RNTI to indicate whether an uplink or downlink grant is accompanied, causing issues like unsuccessful decoding of system information and interference with other UE's transmissions.

Innovation Solution

The method involves performing data transmission according to semi-persistent grants when no non-semi-persistent grants are found on the physical channel, and stopping transmissions when non-semi-persistent grants collide with semi-persistent grants in frequency allocation, using processes that differentiate between semi-persistent and non-semi-persistent grants based on cell and system information identifiers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If semi-persistent scheduling is used to reduce control information overhead, then control channel overhead is reduced, but radio resource misusing and interference occur due to inability to distinguish grant types

Engineering Contradiction:

Improvecontrol information overheadVSAvoidradio resource allocation accuracy

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent segments the grant identification process into two distinct parts: first checking for C-RNTI (cell-specific identifier), then checking for SPS C-RNTI (semi-persistent scheduling specific identifier). This segmentation allows the system to maintain low overhead while accurately distinguishing between dynamic and semi-persistent grants, preventing resource misallocation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary identification mechanism using two different RNTI types as mediators. The C-RNTI serves as the first-level identifier for dynamic grants, while the SPS C-RNTI serves as the second-level identifier for semi-persistent grants. This intermediary system resolves the ambiguity in grant type identification without increasing overall control overhead.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If C-RNTI is used for scheduling identification, then unique UE identification is provided, but it cannot indicate whether uplink or downlink grant is accompanied causing resource misuse

Engineering Contradiction:

ImproveUE identificationVSAvoidgrant type information

Core Design Contradiction:

Ease of operationVSLoss of information

Solution Approach 1:

The identification system is segmented into two distinct identifier types: C-RNTI for dynamic grants and SPS C-RNTI for semi-persistent grants. Each identifier type is specifically designed for its intended grant type, ensuring that the UE can easily identify the grant type through the identifier used, without losing grant type information.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The RNTI mechanism serves multiple functions: it provides unique UE identification (original function) and simultaneously indicates the grant type (new function). By having two RNTI variants (C-RNTI and SPS C-RNTI), the system achieves multi-functionality where the identifier itself conveys both UE identity and scheduling type information.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Loss of energy

If semi-persistent resources are allocated without PDCCH control information, then control overhead is reduced, but interference with other UE transmissions and system information decoding occurs

Engineering Contradiction:

Improvecontrol channel overheadVSAvoidinterference and decoding errors

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by having the UE check for the presence and type of RNTI before performing any data transmission or decoding operations. The UE first checks for C-RNTI, then checks for SPS C-RNTI in advance of actual data processing. This preliminary identification prevents interference and decoding errors by ensuring the correct transmission mode is used before data operations commence.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements feedback through the RNTI identification mechanism that provides real-time information to the UE about the type of grant received. Based on which RNTI is detected (C-RNTI or SPS C-RNTI), the UE adjusts its transmission behavior accordingly, creating a feedback loop that prevents interference and ensures correct system information decoding.

Inventive Principle:

Principle #23Feedback

Data Source

PatentEP2403308B1Method of performing data transmission corresponding to semi-persistent resources in wireless communications system

Publication Date: 2014.01.15 HTC CORP

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AI summary

A method of performing data transmission or reception corresponding to semi-persistent resources for a user equipment of a wireless communication system (10) includes performing a data transmission or reception process according to a uplink or downlink grant in a transmission opportunity of the semi-persistent grant when a uplink or grant and a cell identifier of the UE are found on a physical channel for the transmission opportunity.