OFDM Cell Search Using TDM Sync Channels
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Solution Overview
Problem
The existing WCDMA system's sync channel and common pilot channel structure, along with the cell search process, are not applicable to OFDM-based systems like 3G-LTE, necessitating a new method for initial cell and adjacent cell search in OFDM cellular systems to facilitate efficient handover and reduce cell search time and battery power consumption.
Innovation Solution
The proposed method involves a forward link frame structure in OFDM systems with a sync channel symbol repetition period, using primary and secondary sync channel sequences mapped to subcarriers, allowing for sync acquisition, frame boundary detection, and scrambling code group identification with low complexity, enabling efficient cell search and handover using a single sync channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the existing WCDMA sync channel structure is used, then the cell search process is facilitated with established procedures, but the system cannot be applied to OFDM-based systems like 3G-LTE
Solution Approach 1:
The patent segments the cell search process into three distinct steps: slot synchronization acquisition using primary sync channel, frame boundary and code group ID acquisition using secondary sync channel, and long PN scrambling code ID acquisition using common pilot channel. This segmentation allows the OFDM system to adapt the proven WCDMA cell search methodology to its specific structure while maintaining systematic organization and reducing implementation complexity.
Solution Approach 2:
The patent creates a universal cell search method that works for both WCDMA and OFDM-based systems like 3G-LTE. By defining a standardized three-step process with specific channel functions that can be implemented in different system architectures, the solution achieves broad adaptability across multiple wireless communication standards while maintaining consistent operational procedures.
2Loss of information
If a traditional cell search method is used in OFDM systems, then comprehensive cell information can be acquired, but the cell search time is extended and battery power consumption increases
Solution Approach 1:
The patent performs preliminary synchronization and information acquisition by utilizing the hierarchical structure of sync channels. The primary sync channel first establishes slot synchronization, enabling the mobile station to subsequently efficiently process the secondary sync channel for frame boundary detection. This preliminary action sequence reduces overall cell search time by preparing the system in advance for more complex information acquisition.
Solution Approach 2:
The patent implements a dynamic cell search process where the mobile station adaptively progresses through three steps based on detected synchronization conditions. The process dynamically adjusts the amount of information acquired at each step, allowing the system to complete cell search faster when conditions permit while ensuring comprehensive information acquisition when needed, thereby optimizing both speed and completeness.
3Measurement precision
If multiple channels are used for synchronization, then accurate frame boundary and code group detection can be achieved, but the system complexity increases
Solution Approach 1:
The patent segments the synchronization function across three specialized channels: primary sync channel for slot synchronization, secondary sync channel for frame boundary and code group ID, and common pilot channel for long PN scrambling code ID. This functional segmentation achieves high measurement precision for each synchronization parameter while keeping each channel's structure simple and dedicated to a specific task.
Solution Approach 2:
The patent combines multiple synchronization functions into a coordinated three-step process that uses three channels working together. By merging the synchronization, frame detection, and code identification functions into a unified cell search methodology, the system achieves accurate frame boundary detection while managing overall complexity through integrated processing rather than separate independent systems.
Data Source
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AI summary
Provided are a sync channel of a forward link, a common pilot channel structure, and an initial cell search method and an adjacent cell search method for handover in a cellular system using orthogonal frequency division multiplexing (OFDM). A cell search method in an OFDM cellular system in which a primary sync channel and a secondary sync channel are configured based on time division multiplexing (TDM) includes acquiring sync block synchronization and a primary sync channel sequence number using a primary sync channel symbol included in a frame received by a terminal, detecting a boundary of the frame and a scrambling code group using the sync block and a secondary sync channel symbol included in the frame received by the terminal, and acquiring a scrambling code using the primary sync channel sequence number and the scrambling code group, thereby reducing cell search time with low complexity.