256 QAM Resource Allocation via Dynamic Power Backoff
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Solution Overview
Problem
Current 3GPP LTE systems face challenges in supporting 256 QAM modulation at base stations with higher transmission power due to limitations in transmit error vector magnitude (EVM), which restricts the use of high-order modulation schemes in macro cells with greater coverage areas.
Innovation Solution
A method for dynamically controlling transmit power backoff in downlink subframes, allowing for resource allocation using higher or lower modulation coding schemes based on channel quality information (CQI) to support 256 QAM, involving the use of backoff values and offset calculations to optimize EVM for macro-cell base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-order modulation (256 QAM) is used in base stations with high transmission power, then data transmission rate and spectral efficiency are improved, but transmit error vector magnitude (EVM) limitations cause modulation accuracy to deteriorate
Solution Approach 1:
The patent implements dynamic MCS selection based on real-time CQI feedback and power backoff status. The base station adjusts the modulation coding scheme dynamically between subframes, selecting higher MCS levels when power backoff is applied and lower MCS levels when full power is transmitted, thereby adapting to changing transmission conditions to maintain modulation accuracy while maximizing data rate
Solution Approach 2:
The patent changes the transmission parameter (MCS level) based on the power backoff application status. When power backoff is applied to enable 256 QAM, the system selects appropriate MCS levels from enhanced tables that support higher order modulation. When full power is transmitted, conventional MCS tables are used, ensuring modulation accuracy is maintained despite the fundamental change in power transmission characteristics
2Adaptability or versatility
If power backoff is applied to support 256 QAM in macro cells, then high-order modulation capability is improved, but transmission power and coverage area deteriorate
Solution Approach 1:
The patent segments the transmission time into different subframe types based on power backoff application. Type 1 subframes use full transmission power with conventional MCS tables, while Type 2 subframes apply power backoff and use enhanced MCS tables supporting 256 QAM. This segmentation allows the system to utilize both full-power coverage and high-order modulation capabilities in different time intervals
Solution Approach 2:
The system employs periodic switching between different transmission modes based on the power backoff application pattern. By alternating between full-power transmission and power-backoff-with-256QAM modes in a periodic manner determined by CQI feedback and network configuration, the system achieves both coverage and high-order modulation support over time
3Productivity
If MCS level is increased to utilize available power headroom, then data rate is improved, but reliability and error performance worsen when power backoff is applied
Solution Approach 1:
The patent implements a feedback mechanism where the UE reports CQI based on the actual received power level (accounting for power backoff). The base station uses this CQI feedback to select appropriate MCS levels from enhanced tables that are specifically designed for power-backoff conditions, ensuring that the selected MCS provides both high data rate and reliable error performance under the actual transmission conditions
Solution Approach 2:
The system prepares multiple MCS tables in advance, including enhanced tables specifically designed for power backoff scenarios. These pre-configured tables contain MCS levels optimized for the reduced power conditions, allowing the base station to quickly select appropriate modulation and coding parameters without real-time calculation, thereby maintaining both high data rate and error performance reliability
Data Source
AI summary
One embodiment of the present specification provides a method for allocating resources to user equipment (UE) supporting 256 quadrature amplitude modulation (QAM) demodulation. The resource allocation method can comprise the steps of: receiving a channel quality information (CQI) report from the UE; determining, by the UE, whether a backoff of transmission power has been applied to a downlink subframe from which CQI is measured; determining whether the backoff of the transmission power is to be applied to the downlink subframe which is supposed to allocate the resources; and determining a modulation coding scheme (MCS) level on the basis of the CQI and the results of the determination.