FFRO Frequency Allocation for OFDM Capacity and Interference
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Solution Overview
Problem
Conventional fractional frequency reuse (FFR) techniques face challenges in balancing cell capacity and co-channel interference (CCI) in orthogonal frequency division multiplexing (OFDM) systems, restricting spectrum efficiency due to constraints on sub-channel sets in each cell.
Innovation Solution
The method of fractional frequency reuse with an ordering scheme (FFRO) allocates a common sub-channel set and dedicated sub-channel sets to cells based on cluster sizes, using modulo operations to partition sub-carriers and specify allocation orders for each cell type, thereby reducing interference and increasing capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional fractional frequency reuse (FFR) is used to reduce co-channel interference (CCI), then CCI is reduced, but cell capacity is reduced due to constraints on sub-channel sets
Solution Approach 1:
The frequency spectrum is segmented into common sub-channel sets and dedicated sub-channel sets. Each cell type within a cluster is assigned specific dedicated sub-channel sets, while common sub-channel sets are shared across all cells. This segmentation allows interference reduction in dedicated sets while maintaining capacity through common sets.
Solution Approach 2:
Different cells within the same cluster are assigned different dedicated sub-channel sets based on their cell type (e.g., center cells vs. edge cells). This local differentiation optimizes interference management for each cell's specific position and traffic characteristics, allowing capacity optimization without compromising overall interference reduction.
2Productivity
If frequency reuse factor is increased to improve cell capacity, then cell capacity increases, but co-channel interference (CCI) from neighboring cells increases
Solution Approach 1:
The system dynamically assigns different dedicated sub-channel sets to different cell types within a cluster. Center cells, edge cells, and corner cells each have optimized sub-channel assignments based on their interference environment. This dynamic allocation allows the system to achieve frequency reuse factor close to 1 while maintaining low CCI through position-aware resource allocation.
3Object-affected harmful factors
If constraints are imposed on sub-channel sets in every cell to reduce interference, then co-channel interference is reduced, but spectrum efficiency is restricted
Solution Approach 1:
Common sub-channel sets are designed to be universally accessible by all cell types within a cluster, serving multiple cells simultaneously. This multi-functional allocation allows the same frequency resources to be reused across different cells, significantly improving spectrum efficiency while the dedicated sub-channel sets provide the necessary interference protection.
Data Source
AI summary
Disclosed herein is a method for fractional frequency reuse with ordering scheme (FFRO) to increase capacity of orthogonal frequency division multiplexing (OFDM) systems while reducing interference due to the use of a common sub-channel set. Each cell includes a common sub-channel set assigned in common to all cells provided in a cluster and a dedicated sub-channel set assigned differently to all of the cells. The method includes classifying the cells into at least one type according to cluster sizes, and allocating the dedicated sub-channel set by frequency partitioning scheme based on the cell type.