OFDM Frame Structure Partitioning for Unicast and Broadcast Coexistence
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Solution Overview
Problem
Current OFDM wireless communication systems face challenges in efficiently supporting both unicast and multicast transmissions due to differences in guard intervals and propagation delays, leading to interference and reduced spectral efficiency.
Innovation Solution
The method involves partitioning OFDM frames into unicast and broadcast mode portions with synchronized transmission, using a common sampling frequency and FFT size, and adjusting guard intervals to accommodate varying propagation delays, ensuring efficient coexistence of unicast and broadcast modes in the same frame structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different guard intervals are used for unicast and multicast OFDM symbols, then transmission reliability is improved, but frame structure complexity increases
Solution Approach 1:
The frame is segmented into distinct unicast mode portion and multicast mode portion, with each portion using appropriate guard interval lengths for its specific transmission requirements. This segmentation allows different reliability mechanisms to coexist without requiring a completely different frame structure for each mode.
Solution Approach 2:
The frame structure is designed to be dynamic, allowing the boundary between unicast and multicast portions to be flexible while maintaining synchronization. The system can adaptively allocate resources between unicast and multicast modes while preserving the orthogonality and timing relationships required for reliable transmission.
2Object-generated harmful factors
If synchronized transmission is implemented for multiple transmitters, then interference is reduced, but coordination complexity increases
Solution Approach 1:
Multiple transmitters are synchronized to transmit at the same timing instances, creating equipotential transmission conditions where all transmitters operate on the same time grid. This synchronization eliminates inter-cell interference while the patent reduces coordination complexity by using common sampling frequencies and FFT sizes that simplify the synchronization protocol.
3Productivity
If common sampling frequency and FFT size are used for both modes, then spectral efficiency is improved, but adaptability to different transmission requirements decreases
Solution Approach 1:
The patent applies common sampling frequency and FFT size globally across both unicast and multicast modes to maximize spectral efficiency, while allowing local variations in guard interval lengths and portion allocations to adapt to specific transmission requirements. This local quality adjustment maintains orthogonality without sacrificing the spectral efficiency gains from standardized parameters.
Data Source
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AI summary
In some embodiments of the present invention there is provided a frame structure for transmitting an integer number of OFDM symbols in which some of the OFDM symbols are to be transmitted in a unicast format and some of the OFDM symbols are to be transmitted in a broadcast format. The frame structure includes partitioning of a frame into at least two portions to accommodate both unicast and broadcast modes in the frame. The frame structure is used for transmitting multiple frames in a serial manner from at least one transmitter. The unicast mode supports transmission of OFDM symbols from a single transmitter to a single receiver. The broadcast mode supports transmission of OFDM symbols from multiple transmitters to all receivers within range of the multiple transmitters. The multicast mode supports transmission of OFDM symbols from multiple transmitters to multiple receivers within range of the multiple transmitters.