OFDM Frame Creation Using Frequency Domain Spreading
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Solution Overview
Problem
The existing OFDM system specifications for Smart Utility Networks, such as IEEE 802.15.4g, face challenges in forming frames due to an unclear relationship between the size of the interleaving structure and frequency domain spreading, leading to difficulties in achieving a high link margin and efficient low-power radio signal transmission.
Innovation Solution
A method and apparatus for creating OFDM frames that determine the number of coded bits, data bits, and padding bits based on the size of the interleaver and coding rate, incorporating frequency domain spreading to maximize the link margin and minimize redundant symbols, using a transmitter configuration that includes an input bit generator, encoder, interleaver, subcarrier modulation mapper, and inverse fast Fourier transform unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency domain spreading is applied to maximize link margin, then reliability is improved, but device complexity increases due to unclear relationship between interleaving structure size and FDS
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships between interleaver size (Ncbps) and frequency domain spreading factor (NF). The invention defines Ncbps as a multiple of NF (Ncbps = k × NF where k is an integer), which standardizes the parameters and resolves the complexity while maintaining high link margin through FDS
Solution Approach 2:
The patent introduces dynamic adaptability by providing multiple frame formation methods that can be selected based on different OFDM options and channel conditions. The system can dynamically adjust the interleaving structure and FDS configuration to optimize performance for varying reliability requirements
2Reliability
If interleaving structure size is increased to support FDS, then reliability is improved, but manufacturing precision becomes difficult due to undefined relationship between interleaver size and FDS
Solution Approach 1:
The patent establishes precise parameter relationships by defining Ncbps as an integer multiple of NF, and specifying exact formulas for calculating the number of coded bits, data bits, and padding bits. This creates a well-defined frame structure that ensures manufacturing precision while supporting the required interleaving size for FDS
Solution Approach 2:
The patent segments the frame formation process into distinct steps: determining coded bits per NF symbols, calculating data bits based on coding rate, determining padding bits, and generating the encoded bit sequence. This segmentation makes the complex frame formation process manageable and precisely definable
3Reliability
If frame formation is optimized for high link margin, then reliability is improved, but energy consumption increases due to redundant symbols
Solution Approach 1:
The patent applies partial action by determining the minimum required number of OFDM symbols based on the ratio of total bits to data bits per symbol (NSYM = ceil(TotalBits / NDBPS)). This ensures that only the necessary number of symbols are transmitted to achieve the required link margin, avoiding excessive energy consumption from redundant symbols
Data Source
AI summary
A method and an apparatus for creating a frame of an orthogonal frequency division multiplexing (OFDM) specification using a frequency domain spreading (FDS). The method and the apparatus determine a number of padding bits based on various FDSs and a size of an interleaver and constitute a frame including a determined number of padding bits, so that there is provided a frame which is adequate for a data transmission rate using various FDSs and which includes a minimal number of redundant OFDM symbol.