Sub-carrier Allocation in MIMO OFDM Systems
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Solution Overview
Problem
Current sub-carrier allocation methods in MIMO OFDM mobile communication systems face challenges in efficiently allocating sub-carriers to multiple users and antennas, leading to increased peak to average power ratio (PARR) and complexity, while also requiring complex algorithms and inducing overhead due to feedback information.
Innovation Solution
An apparatus and method for allocating sub-carriers in a MIMO OFDMA system that determines the number of sub-carriers based on channel information and allocates them to each user and antenna, using a closed-loop transmit diversity scheme with an adaptive sub-carrier allocation algorithm to reduce PARR and improve frequency utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional sub-carrier allocation methods are used in MIMO OFDM systems, then sub-carriers can be allocated to multiple users and antennas, but the peak to average power ratio (PARR) increases and system complexity increases
Solution Approach 1:
The patent segments the sub-carrier allocation process into distinct stages: channel information collection from multiple antennas, determination of optimal sub-carrier counts per antenna based on channel quality, and sequential allocation to users. This segmentation simplifies the overall allocation complexity while maintaining efficiency by breaking down the complex MIMO allocation problem into manageable sub-tasks that can be processed independently.
2Productivity
If complex allocation algorithms are used to optimize sub-carrier distribution, then allocation efficiency improves, but overhead due to feedback information increases
Solution Approach 1:
The patent extracts and utilizes existing channel information that is already available at the receiver for other purposes (such as channel estimation and equalization) and feeds it back to the transmitter for sub-carrier allocation decisions. By reusing this existing feedback information rather than requesting additional dedicated feedback for allocation, the system improves allocation efficiency without increasing feedback overhead.
3Productivity
If more sub-carriers are allocated to improve data transmission, then transmission capacity increases, but PARR increases causing signal distortion
Solution Approach 1:
The patent applies local quality by allocating different numbers of sub-carriers to different antennas based on their individual channel qualities. Antennas with better channel conditions receive more sub-carrier allocations, while antennas with poorer conditions receive fewer allocations. This localized, adaptive approach maximizes data transmission capacity while controlling PARR by concentrating sub-carrier resources on the most favorable transmission paths rather than uniformly distributing them across all antennas.
Data Source
AI summary
An apparatus and a method capable of effectively allocating sub-carriers for a plurality of users and transmitting the sub-carriers to users through multiple antennas in an orthogonal frequency division multiplexing (OFDMA) mobile communication system are provided. A sub-carrier allocation method reduces transmission power by taking a desired bit rate and power budget into consideration. The sub-carriers are optimally allocated to each antenna, so that peak to average power ratio (PARR) is reduced and Quality of Service (QoS) is improved. The apparatus and the method are adaptable for multi-users and obtain space diversity gain through multiple antennas.