Transmitter Device Variable Subframe Offset for LAA Spectrum Efficiency
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Solution Overview
Problem
Conventional Licensed Assisted Access (LAA) E-UTRAN NodeB systems face mismatches between Modulation and Coding Scheme (MCS) selection and Transport Block Size (TBS) selection, leading to poor support for UE-specific reference signals, especially in fractional subframes with odd numbers of OFDM symbols, causing errors in signal decoding and reduced spectrum efficiency.
Innovation Solution
A transmitter device with a processor configured to map signals into a first subframe and a second subframe with a variable time offset, allowing for flexible transmission timing that supports UE-specific reference signals and maximizes spectrum efficiency by separating fixed and flexible timing channels, thereby reducing complexity and improving RRM measurement performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a transport block is transmitted over a fractional subframe immediately after preamble transmission, then the downlink transmission can start as soon as possible, but mismatch between MCS selection and TBS selection occurs
Solution Approach 1:
The transmission is divided into two independent parts: a first subframe carrying signals suitable for fixed timing (discovery signals, synchronization signals, broadcast channels) and a second subframe with variable timing carrying data channels. This segmentation allows each part to operate under its own timing constraints without interfering with the other, resolving the contradiction between immediate transmission start and MCS-TBS matching accuracy.
Solution Approach 2:
The patent introduces dynamic timing adjustment by allowing the second subframe to have a variable time offset relative to the first subframe. This dynamic structure enables the system to adapt transmission timing based on channel conditions and requirements, starting transmission immediately when channel is clear while maintaining proper MCS-TBS matching through flexible timing configuration.
2Reliability
If TBS scaling is applied to match TBS and MCS when number of OFDM symbols differs from baseline, then MCS-TBS matching is improved, but additional complexity is introduced
Solution Approach 1:
The patent extracts the timing-sensitive data channel transmission from the fixed-timing first subframe and places it in the variable-timing second subframe. By separating these functions, the system eliminates the need for complex TBS scaling calculations, as the second subframe's timing is explicitly configured to match the actual number of OFDM symbols available, making TBS determination straightforward without additional scaling complexity.
3Productivity
If fractional subframe contains odd number of OFDM symbols carrying UE-specific reference signals, then transmission efficiency is improved, but code-multiplexed reference signals cannot be distinguished
Solution Approach 1:
The patent resolves the reference signal ambiguity by introducing a new dimension - the subframe timing structure. By placing UE-specific reference signals and data channels in a separate second subframe with explicit timing configuration, the system provides sufficient time resources for proper code multiplexing operation, allowing receivers to correctly distinguish and decode reference signals even when the total symbol count is odd.
4Ease of operation
If fixed subframe timing is used for all channels, then synchronization is simplified, but flexible timing for data channels is restricted
Solution Approach 1:
The patent segments channels into two categories with different timing requirements: signals suitable for fixed timing (discovery signals, synchronization signals, broadcast channels) placed in the first subframe, and data channels requiring flexible timing placed in the second subframe. This segmentation allows the system to maintain simple synchronization for critical signals while providing timing flexibility for data transmission.
Solution Approach 2:
The first subframe serves as a universal container for all signals that require fixed timing, establishing a common reference frame for synchronization. The second subframe then builds upon this universal timing base to provide flexible data transmission, allowing the system to maintain both synchronization simplicity and timing adaptability through this multi-functional structure.
Data Source
AI summary
Embodiments relate to a transmitter device and a receiver device. The transmitter device comprises a processer configured to: map at least one first signal to a first subframe, map at least one second signal to a second subframe having a variable time offset in relation to the first subframe; and a transceiver configured to transmit the first signal in the first subframe, transmit the second signal in the second subframe. The receiver device comprises a receiving device configured to receive a first signal transmitted in a first subframe, and receive a second signal transmitted in a second subframe having a variable time offset in relation to the first subframe; and a processor configured to process the received first signal, and process the received second signal. Furthermore, the embodiments also relate to corresponding methods, a computer program, and a computer program product.