Cell Search Table Segmentation for Memory Reduction
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Solution Overview
Problem
Existing telecommunication systems, particularly those based on the 3GPP TDD standard, require significant memory and power consumption for cell search procedures due to large tables used in frame synchronization and codegroup identification, which is a challenge for future multimode mobile terminals.
Innovation Solution
A method that reduces memory and power consumption by simplifying the tables through exploiting symmetries and redundancies, using sub-tables and combination operations to reproduce the entire correspondence table, and modifying the search procedure to operate on these sub-tables, thereby reducing the size of the tables stored.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large correspondence tables are used for frame synchronization and codegroup identification, then the cell search procedure can be completed accurately, but memory usage and power consumption increase significantly
Solution Approach 1:
The patent divides the large correspondence table into multiple smaller sub-tables, each storing only a portion of the codegroup-scrambling code mappings. This segmentation reduces the memory footprint of individual table structures while maintaining complete coverage through coordinated access to multiple sub-tables using different offset calculations.
Solution Approach 2:
The patent introduces a new dimension to the table access mechanism by adding offset parameters (first offset and second offset) that enable indirect addressing of sub-tables. This dimensional extension allows the system to access distributed sub-tables through calculated offsets from a base address, effectively spreading the large table across multiple smaller memory structures without increasing total memory usage.
2Adaptability or versatility
If large correspondence tables are stored in memory, then all codegroup and scrambling code mappings are available, but the area occupied on the chip increases
Solution Approach 1:
The correspondence table is segmented into multiple sub-tables that can be stored in distributed memory locations on the chip. This segmentation reduces the continuous memory block size required, thereby reducing the chip area occupied by any single memory structure while maintaining total coverage through coordinated access to all sub-tables.
Solution Approach 2:
By introducing offset-based indirect addressing, the patent enables the same logical correspondence data to be accessed through multiple dimensional paths (different base addresses plus offsets). This allows the physical memory layout to be more compact and distributed, reducing the continuous area required on the chip while preserving complete code mapping coverage.
3Loss of information
If complete correspondence tables are accessed during cell search, then all parameters can be identified, but memory access time and latency increase
Solution Approach 1:
The correspondence table is divided into sub-tables that can be accessed in a more efficient manner. By organizing data into smaller, manageable segments with specific access patterns, the system reduces the time required to search and retrieve required parameters compared to accessing a single large monolithic table.
Solution Approach 2:
The patent pre-calculates and stores offset values that enable direct access to the appropriate sub-tables based on the codegroup identification. This preliminary organization of access paths allows the system to quickly locate required data without performing extensive searches through the entire correspondence set, thereby reducing memory access latency.
4Reliability
If large tables are used for synchronization, then frame synchronization can be achieved, but power consumption increases
Solution Approach 1:
The large correspondence table is segmented into smaller sub-tables, which reduces the overall power consumption associated with memory access operations. Smaller memory structures require less energy to access, and the segmented approach allows for more efficient memory access patterns that consume less power during frame synchronization operations.
Solution Approach 2:
By introducing offset-based indirect addressing, the patent enables more efficient memory access patterns that reduce the total number of memory access operations required. This dimensional approach allows the system to calculate and jump directly to relevant sub-tables, reducing unnecessary memory accesses and thereby lowering power consumption during synchronization.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces memory usage and power consumption, achieving a substantial reduction in the area occupied on the chip and improving the efficiency of the cell search process, with a notable reduction in memory accesses and latency.
Implementation Method 1
execution of the second step of the cell search envisages that the secondary synchronization codes Cm, contained in the secondary synchronization channel (SSCH), will be extracted by a correlation process. The samples of the signal received are correlated with the possible secondary synchronization codes Cm transmitted on the SSCH.
Data Source
AI summary
To execute the cell-search procedure in a cellular communication system (such as a system based upon the 3GPP TDD standard), there are available identification codes for the second step (slot synchronization) and for the third step (identification of the scrambling codes). The identification codes are identified by a process of correlation with the received signal and are used for obtaining from a correspondence table the parameters for the execution of the second step (CD) or of the third step (SCR). The correspondence table is stored in a reduced form by the identification, according to rules of symmetry and redundancy, of subtables designed to generate the entire table by appropriate combination operations. The search procedure in the correspondence table thus reduced is conveniently modified by the introduction of the combination operations. A preferential application is in mobile communication systems based upon standards such as UMTS, CDMA2000, IS95 or WBCDMA.