TDD Physical Broadcast Channel Mapping for Capacity and Complexity
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Solution Overview
Problem
The existing methods for sending the physical broadcast channel in the Frequency Division Duplex (FDD) system are unsuitable for the Time Division Duplex (TDD) system, as they fail to meet the increased capacity requirements, are incompatible with the different synchronization signal positions, and introduce complexity due to varying cyclic prefix configurations.
Innovation Solution
A method for sending the physical broadcast channel in the TDD system, where the channel is transmitted in the middle 1.08 MHz of the frequency band, avoiding pilot positions and using the same method for both normal and extended cyclic prefixes, with specific configurations across 4 OFDM symbols in the first subframe, optimizing the TDD frame structure to meet capacity demands and reduce system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the FDD physical broadcast channel sending method is used in TDD, then the system can maintain simplicity, but the physical broadcast channel capacity requirement in TDD cannot be met
Solution Approach 1:
The physical broadcast channel is segmented into multiple parts and mapped to different resource elements in the time-frequency grid. The channel bits are divided and distributed across multiple SC-FDMA symbols and subcarriers, enabling increased capacity while maintaining structured transmission suitable for TDD
Solution Approach 2:
The patent transitions from the FDD frequency-domain multiplexing approach to a TDD time-domain oriented approach. The physical broadcast channel is mapped across multiple time slots and symbols in the TDD frame structure, utilizing the time dimension more effectively to achieve higher capacity
2Reliability
If the physical broadcast channel is configured to be sent before and after the synchronization signal as in FDD, then channel estimation can be performed, but the sending positions become incompatible with TDD frame structure
Solution Approach 1:
Instead of placing the physical broadcast channel before and after synchronization signals as in FDD, the patent inverts the approach by placing it within the downlink pilot time slot structure specific to TDD. The channel is mapped to resource elements within the DwPTS region, adapting to TDD's unique frame structure while maintaining reliable transmission
Solution Approach 2:
The patent applies different mapping strategies for different regions of the TDD frame structure. Within the DwPTS region, specific resource elements are allocated for the physical broadcast channel, while other regions maintain their dedicated functions. This localized adaptation ensures both frame structure compatibility and reliable channel estimation
3Reliability
If different sending methods are used for normal and extended cyclic prefixes as in FDD, then optimal performance can be achieved for each case, but system complexity increases
Solution Approach 1:
The patent implements a universal mapping method that works for both normal and extended cyclic prefixes. The same resource element allocation pattern and modulation scheme are applied regardless of cyclic prefix type, allowing the system to handle both cases with a single unified approach, thereby reducing complexity while maintaining adequate performance
Data Source
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AI summary
A method for sending a physical broadcast channel in the TDD system is disclosed, which is: a signal of a physical broadcast channel is not sent in a pilot position, and the signal of the physical broadcast channel is sent on 4 OFDM symbols of the first subframe of one radio frame. Through the present invention, the extension requirement of the physical broadcast channel capacity in the TDD can be met, and the system complexity is reduced due to the normal cyclic prefix and extended prefix using the same sending method.