LTE Carrier Bandwidth Extension via Increased Subcarrier Spacing
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Solution Overview
Problem
LTE systems face performance degradation at higher carrier frequencies due to increased path loss, sensitivity to user equipment velocity, and increased intercarrier interference, limiting their ability to support wider bandwidths and higher data rates.
Innovation Solution
The method involves T-F scaling, which increases subcarrier spacing by factors such as 2, 4, 5, or 8, allowing for wider bandwidths while maintaining compatibility with LTE by adjusting symbol and cyclic prefix lengths, thereby enhancing flexibility and supporting higher carrier frequencies with minimal changes to the system architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LTE systems operate at higher carrier frequencies, then data rates and bandwidth can be increased, but path loss increases and link performance degrades
Solution Approach 1:
The patent changes the subcarrier spacing parameter from the standard 15 kHz to larger values (30 kHz, 60 kHz, or 120 kHz) to adapt LTE systems for higher carrier frequencies. This parameter change reduces the duration of each OFDM symbol, which reduces the impact of phase noise and Doppler effects, thereby maintaining link performance while enabling operation at higher frequencies that support wider bandwidths and higher data rates
2Productivity
If subcarrier spacing is increased to support wider bandwidths, then carrier bandwidth can be extended, but system compatibility with existing LTE specifications deteriorates
Solution Approach 1:
The patent introduces dynamic subcarrier spacing that can be configured based on the carrier frequency range. The system can dynamically select from multiple subcarrier spacing values (15 kHz, 30 kHz, 60 kHz, 120 kHz) depending on the operating conditions, allowing it to maintain LTE compatibility at lower frequencies while extending bandwidth capability at higher frequencies through larger subcarrier spacing
3Object-generated harmful factors
If subcarrier spacing is increased to reduce intercarrier interference, then interference is reduced, but sensitivity to user equipment velocity increases
Solution Approach 1:
The patent changes the subcarrier spacing parameter to larger values, which has the effect of reducing the duration of each OFDM symbol. This shorter symbol duration reduces the accumulation of phase rotation due to Doppler effects, thereby reducing sensitivity to user equipment velocity while also reducing intercarrier interference through the increased frequency separation between subcarriers
Data Source
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AI summary
There is provided a method comprising providing, in dependence on a first subcarrier spacing of a first subframe structure, a second subcarrier spacing of a second subframe structure, wherein the first subframe structure has a first subframe length and at least one first cyclic prefix length and providing a second subframe length of the second subframe structure, the second subframe length comprising m symbols, wherein each symbol contains a second cyclic prefix, the second cyclic prefix length modified by a length variant.