Adaptive Modulation Coding SC-FDMA Resource Allocation
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Solution Overview
Problem
Current SC-FDMA transmission schemes in 3GPP-LTE systems are limited by the inability to adaptively allocate frequency resources based on channel quality, leading to spectral inefficiencies and throughput degradation, especially for high-rate users who experience variable pathloss and SINR across the allocated bandwidth.
Innovation Solution
The method involves splitting the input data stream into sub-streams, processing each through separate DFTs, and allocating them to frequency resource blocks based on channel quality estimates, allowing for adaptive modulation and coding schemes to be chosen for each sub-stream, enabling independent power control and increased spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single DFT is used for all allocated frequency resources in SC-FDMA, then PAPR is reduced and implementation is simplified, but channel-adaptive resource allocation cannot be performed leading to spectral inefficiency
Solution Approach 1:
The invention divides the single DFT operation into multiple separate DFTs, one for each frequency resource block. This segmentation allows independent channel quality assessment and AMC scheme selection for each block, enabling spectral efficiency improvement while keeping each individual DFT operation simple and manageable
Solution Approach 2:
The invention applies different AMC schemes (modulation and coding combinations) to different frequency resource blocks based on their local channel quality conditions. Each resource block receives optimized treatment according to its specific SINR characteristics, achieving local optimization without requiring complete system redesign
2Productivity
If AMC scheme is adapted per sub-carrier or group of sub-carriers as in OFDM, then spectral efficiency is improved, but PAPR increases and implementation complexity increases
Solution Approach 1:
The invention segments the frequency spectrum into discrete resource blocks and applies separate DFTs to each, enabling AMC adaptation at the resource block level rather than requiring per-subcarrier adaptation. This achieves spectral efficiency improvement with significantly lower complexity and PAPR compared to full OFDM AMC
Solution Approach 2:
The invention changes the granularity of AMC adaptation from fine-grained (per sub-carrier) to coarse-grained (per resource block), and changes the signal processing approach from OFDM to SC-FDMA with multiple DFTs. This parameter change maintains spectral efficiency benefits while reducing PAPR and implementation complexity
3Device complexity
If channel quality is not considered in resource allocation, then implementation is simpler, but throughput degradation occurs especially for high-rate users with variable pathloss
Solution Approach 1:
The invention implements feedback-based resource allocation where channel quality indicators (CQI) are measured and reported for each frequency resource block. The base station uses this feedback information to select appropriate AMC schemes and allocate resources optimally, achieving throughput improvement through informed decision-making
Solution Approach 2:
The invention changes the resource allocation approach from uniform/simplified allocation to quality-aware allocation based on channel conditions. By introducing channel quality as a decision parameter, the system achieves better throughput performance while maintaining manageable complexity through standardized CQI measurement and reporting mechanisms
Data Source
AI summary
A method and a system for transmitting data by a transmitter over a channel having a predetermined channel quality estimate, comprises the steps of splitting (S2P) input data stream (S40, S60, S80) to be transmitted into a plurality of data sub-streams (S40a, S40b, S40c); processing (SYM1, SYM2, SYMj) each of the plurality of data sub-streams (S40a, S40b, S40c) into a plurality of symbol subsets (S41, S42, S43) by selecting a certain scheme of coded-modulation (BPSK, QPSK, 16-QAM); processing, separately, each of the plurality of symbol subsets (S41, S42, S43), via a plurality of separate Discrete Fourier Transforms (DFT1, DFT2, DFT3), herein after denoted as DFTs, to obtain a plurality of DFT-precoded data sub-streams (S44, S45, S46); allocating each DFT-precoded data sub-stream (S44, S45, S46) in a frequency resource block (RB1, RB2, RB3), via a sub-carrier mapping module (SCM), so that for each data sub-stream (S40a, S40b, S40c) the selected scheme of coded-modulation (BPSK, QPSK, 16-QAM) is chosen in dependence of the values of the channel quality estimate at the frequencies of its own allocated frequency resource block (RB1, RB2, RB3).