OFDM Pilot Channel Multiplexing for TTI Efficiency
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Solution Overview
Problem
In OFDM-based mobile communications systems, reducing the number of symbols in a transmission time interval (TTI) leads to reduced transmission efficiency of data channels due to the allocation of a significant portion of symbols for common pilot channels, which negatively impacts overall channel efficiency.
Innovation Solution
A transmission apparatus and method that multiplexes a common pilot channel, shared control channel, and shared data channel, allowing for flexible allocation of the common pilot channel in both time and frequency directions, thereby maintaining or improving data channel transmission efficiency even when the number of symbols in the TTI is reduced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the number of symbols in the TTI is reduced, then the transmission time interval is shortened, but the transmission efficiency of the data channel is reduced due to the common pilot channel occupying a larger proportion
Solution Approach 1:
The patent applies dynamics by making the common pilot channel allocation flexible rather than fixed. The system dynamically adjusts the number of common pilot channel symbols and their distribution within the TTI based on the actual number of symbols in the current TTI configuration. This allows the data channel transmission efficiency to be maintained even when the TTI length changes, as the pilot channel overhead adapts proportionally rather than occupying a fixed large portion.
Solution Approach 2:
The patent changes the parameter of pilot channel insertion interval adaptively. Instead of using a fixed insertion interval for common pilot channels, the system adjusts this interval parameter according to the TTI symbol count. When the TTI contains fewer symbols, the insertion interval is reduced accordingly, ensuring that the pilot channel overhead remains appropriate and does not excessively reduce the data channel efficiency.
2Measurement precision
If the common pilot channel is allocated to more symbols, then channel estimation accuracy is improved, but the transmission efficiency of other channels is reduced
Solution Approach 1:
The patent applies partial action by allocating common pilot channels to only the necessary minimum number of symbols required for adequate channel estimation, rather than uniformly allocating them to all symbols. The system determines the optimal insertion interval that provides sufficient channel estimation accuracy while minimizing the overhead on data channel transmission efficiency.
Solution Approach 2:
The patent makes the pilot channel allocation dynamic by adjusting the insertion interval based on channel conditions and TTI configuration. When channel conditions require higher estimation accuracy, the system increases pilot channel density; when conditions are favorable or TTI is short, it reduces density to preserve data transmission efficiency.
Data Source
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AI summary
A disclosed transmission apparatus includes a multiplexing portion that multiplexes a common pilot channel, a shared control channel, and a shared data channel; a symbol generation portion that performs an inverse Fourier transformation on the multiplexed signal so as to generate a symbol; and a transmission portion that transmits the generated symbol. The multiplexing portion multiplexes the shared control channel including control information necessary for demodulation of the shared data channel including a payload and the common pilot channel to be used by plural users in a frequency direction, and the shared data channel in a time direction with respect to the common pilot channel and the shared control channel. Even when the number of symbols composing a transmission time interval (TTI) is reduced, transmission efficiency of channels excluding the common pilot channel can be maintained by reducing insertion intervals of the common pilot channel accordingly.