D2D Subframe OFDM Symbol Reduction for Interference Mitigation
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Solution Overview
Problem
In existing D2D ProSe systems, interference between OFDM symbols occurs due to time differences between downlink and uplink timings, affecting the performance of direct communication between user equipment.
Innovation Solution
A method is introduced where a reference signal is inserted into a subframe with a reduced number of OFDM symbols, allowing for increased cyclic prefix length, thereby minimizing time differences and avoiding symbol interference, and improving D2D ProSe performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If downlink timing is used for D2D signal transmission and uplink timing for reception, then direct communication between user equipments is enabled, but time difference causes interference between OFDM symbols
Solution Approach 1:
The patent changes the timing parameters by introducing a timing offset adjustment mechanism. The transmitting UE applies a timing offset to align its downlink timing with the receiving UE's uplink timing, thereby eliminating the time difference that causes OFDM symbol interference while maintaining D2D communication capability
Solution Approach 2:
The patent performs preliminary timing synchronization before D2D signal transmission. The UEs exchange timing information and adjust their timing offsets in advance, ensuring that the downlink timing of the transmitting UE aligns with the uplink timing of the receiving UE before actual data transmission begins, thus preventing OFDM symbol interference
2Productivity
If standard subframe with 14 OFDM symbols is used, then data transmission capacity is maintained, but cyclic prefix length is insufficient to cover timing difference
Solution Approach 1:
The patent segments the subframe structure by introducing a special D2D subframe type with reduced OFDM symbol count (13, 12, or 7 symbols). This segmentation allows the cyclic prefix to be extended proportionally, ensuring it covers the timing difference between downlink and uplink timings while maintaining reasonable data transmission capacity
Solution Approach 2:
The patent changes the subframe structure parameters by reducing the number of OFDM symbols in D2D subframes. This parameter change allows the cyclic prefix length to be increased relative to the total subframe length, ensuring the cyclic prefix can cover the timing offset between downlink and uplink timings, thereby improving timing synchronization accuracy
Data Source
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AI summary
The present invention discloses a method and an apparatus for transmitting a signal between user equipments. A quantity of OFDM symbols included in a first subframe sent by a first user equipment to a second user equipment is less than a quantity of OFDM symbols included in a second subframe sent by the first user equipment to a network device, where the second subframe includes 14 OFDM symbols, the first subframe includes 13, 12, or 7 OFDM symbols, and the OFDM symbol includes valid data and a cyclic prefix. In this way, interference between OFDM symbols may be avoided, and performance of a D2D ProSe is improved.