Tone Hopping Allocation for Uplink Interference Reduction
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Solution Overview
Problem
In cellular wireless systems, transmissions from one sector can collide with those from adjacent or neighboring sectors, leading to prolonged interference due to the use of the same tones, especially in periodic or nearly periodic situations, which affects communication quality and base station detection capabilities.
Innovation Solution
The system allocates tones using a combination of cell and sector identifiers to minimize collisions by implementing unique tone hopping sequences for each sector and neighboring cells, using functions like fsT(j,k)=s/((1/j)+T*k+k^2) to determine tone allocations, ensuring that tones are reassigned periodically to different hopping sequences, thereby reducing repeated collisions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same tone hopping sequence is used in adjacent sectors and neighboring cells, then the system complexity is reduced and implementation is simplified, but transmission collisions and correlated interference occur repeatedly over time
Solution Approach 1:
The patent applies local quality by making each sector and neighboring cell use a unique tone hopping sequence tailored to its specific location and identifier. Instead of a uniform hopping sequence across all sectors, each sector s has a distinct sequence determined by its sector ID and cell ID, creating locally optimized quality that prevents correlated interference while maintaining systematic control.
Solution Approach 2:
The patent changes the parameters of the tone hopping sequence by incorporating sector-specific identifiers (sector ID and cell ID) into the hopping function. The hopping sequence is determined by parameters such as sector ID, cell ID, and tone index, which vary across different sectors and cells, thereby transforming the static hopping pattern into a dynamic, location-dependent sequence that avoids repeated collisions.
2Reliability
If tone hopping sequences are made unique for each sector and neighboring cell using cell and sector identifiers, then transmission collisions and correlated interference are minimized, but the system complexity and computational requirements increase
Solution Approach 1:
The patent segments the tone hopping control into two independent identifier components: cell ID and sector ID. This segmentation allows the system to manage complexity by breaking down the unique identification into hierarchical levels (cell level and sector level), where each level contributes to the overall hopping sequence determination without requiring a completely new sequence for every possible combination.
Solution Approach 2:
The patent implements preliminary action by pre-defining the tone hopping sequences based on sector IDs and cell IDs before actual transmission occurs. The hopping sequences are determined in advance using the identifiers, allowing wireless terminals to autonomously select appropriate sequences without real-time computation, thereby reducing operational complexity while maintaining unique sequences for each sector and cell.
3Adaptability or versatility
If large sector identifiers are used to control hopping sequences in multi-sector cells, then the ability to support a large number of sectors is improved, but the identifier length and processing overhead increase
Solution Approach 1:
The patent segments the sector identification into a hierarchical structure where sector ID is separated from cell ID. This segmentation allows the system to support multiple sectors within each cell using compact sector IDs (e.g., 0-7 for up to 8 sectors), while the cell ID provides the broader network context. The combined use of these segmented identifiers achieves high adaptability without requiring excessively long single identifiers.
Data Source
AI summary
Methods and apparatus for allocating and hopping tones for uplink communications purposes in adjacent sectors and neighboring cells of an OFDM system are described. Physical tones used in each sector and cell are allocated to tone hopping sequences according to a tone to tone hopping sequence allocation function which uses both a cell identifier and sector identifier. Different sectors and cells use different tone to tone hopping sequence allocation functions through the use of different cell and/or sector identifiers to minimize the number of collisions between hopping sequences of adjacent sectors and neighboring cells. Uplink tone hopping sequences, corresponding to logical tones are allocated to uplink communications channels. Uplink communications channels are used by wireless terminals, e.g., mobile nodes, to transmit data to base stations. Over time, a wireless terminal uses the tones included in the uplink tone hopping sequences corresponding to uplink communications channels it is authorized to use.