LTE Shared Data Channel MCS Adjustment for Variable OFDM Symbols
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Solution Overview
Problem
The LTE system's existing modulation and coding scheme adjustment method is inadequate when the actual number of OFDM symbols deviates from the assumed 11 symbols, leading to sub-optimal code rates and reduced data throughput due to excessive code rates or unusable modulation and coding schemes.
Innovation Solution
The method modifies the modulation order determination by using index offsetting, increasing the modulation order when the actual number of OFDM symbols is less than 11 and decreasing it when more than 11, based on a factor or nonlinear function to ensure suitable code rates, thereby adjusting the modulation and coding scheme for the LTE shared Data Channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the LTE system uses a fixed assumption of 11 OFDM symbols for modulation and coding scheme selection, then the system design is simplified, but the code rate becomes sub-optimal and data throughput is reduced when the actual number of OFDM symbols deviates from 11
Solution Approach 1:
The patent applies dynamics by making the modulation order determination adaptive rather than fixed. The base station dynamically adjusts the modulation order based on the actual number of OFDM symbols available for data transmission. When NOS < 11, the modulation order is increased to compensate for fewer symbols, and when NOS > 11, the modulation order is decreased, ensuring optimal code rates and data throughput for each transmission scenario.
Solution Approach 2:
The patent changes the modulation order parameter based on the actual number of OFDM symbols. By modifying the modulation order (Qm) according to the relationship between actual and assumed OFDM symbols, the system adjusts the code rate to remain optimal. This parameter change allows the system to maintain high data throughput regardless of whether the actual OFDM symbol count is less than or greater than the assumed 11 symbols.
2Device complexity
If the LTE system uses a fixed assumption of 11 OFDM symbols for MCS selection, then the scheduling algorithm is simpler, but the number of unusable MCSs increases and scheduling flexibility is reduced
Solution Approach 1:
The patent makes the scheduling algorithm dynamic by adjusting the modulation order based on actual OFDM symbol count. This dynamic adjustment enables the system to utilize a broader range of MCSs that would otherwise be unusable with a fixed 11-symbol assumption. The base station can flexibly select from more MCS options by adapting the modulation order to match the actual transmission resources available.
Solution Approach 2:
By changing the modulation order parameter according to actual OFDM symbols, the patent expands the set of usable MCSs. This parameter adjustment allows the scheduling algorithm to select from a larger pool of valid MCS combinations, increasing scheduling flexibility and adaptability to different channel conditions and resource allocations without significantly increasing algorithmic complexity.
3Loss of time
If the actual number of OFDM symbols is less than 11, then the transmission time is reduced, but the code rate becomes excessively high and transmissions fail requiring retransmissions
Solution Approach 1:
When the actual number of OFDM symbols is less than 11, the patent increases the modulation order to compensate for the reduced time resources. This parameter change adjusts the code rate to an optimal level, preventing excessively high code rates that would cause transmission failures. By adapting the modulation order, the system maintains transmission reliability even with fewer OFDM symbols available.
4Quantity of substance
If the actual number of OFDM symbols is more than 11, then the available transmission resources are increased, but the code rate becomes sub-optimal and data throughput is reduced
Solution Approach 1:
When the actual number of OFDM symbols exceeds 11, the patent dynamically decreases the modulation order to maintain optimal code rates. This dynamic adjustment ensures that the system fully utilizes the additional transmission resources by selecting appropriate MCSs with lower modulation orders, thereby maximizing data throughput rather than leaving capacity unused due to sub-optimal code rates.
Data Source
AI summary
A system, method and node for modulation and coding scheme adjustment for a Long Term Evolution (LTE) shared Data Channel. The method determines an actual number of orthogonal frequency division multiplexing (OFDM) symbols, NOS utilized for the shared Data Channel. A modulation order for transmission of data on the shared Data Channel is increased when the actual number of OFDM symbols NOS is less than 11 and decreased when NOS is more than 11. A modulation and coding scheme field (IMCS) of a downlink control information of the shared Data Channel may also be determined. If 0≦IMCS+11−NOS≦28, the modulation order is modified by utilizing a factor of (IMCS+11−NOS) in a standardized modulation scheme. If it is determined that IMCS+11−NOS<0, the modulation order is set to Quadrature Phase Shift Keying (QPSK). If it is determined that IMCS+11−NOS>28, the modulation order is set to 64 Quadtrative Amplitude Modulation (64QAM).