Dynamic Frequency Hopping in Variable Bandwidth OFDM Systems

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Solution Overview

Problem

Frequency hopping techniques have not been effectively implemented in Orthogonal Frequency Division Multiplexing (OFDM) systems that allow variable bandwidth allocations, as the number of available hopping patterns changes with bandwidth allocations, and bandwidth allocations depend on instantaneous channel conditions, making it difficult to avoid collisions and reduce system efficiency.

Innovation Solution

A method that dynamically allocates subcarriers to mobile terminals based on their channel conditions and determines frequency hopping patterns 'on-the-fly' for each scheduling interval, signaling bandwidth allocations and frequency offsets in a scheduling grant, allowing flexible and efficient use of radio resources.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If frequency hopping patterns are predefined in OFDM systems, then system complexity is reduced, but adaptability to variable bandwidth allocations and instantaneous channel conditions deteriorates

Engineering Contradiction:

Improvesystem complexityVSAvoidadaptability to variable bandwidth allocations

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic frequency hopping patterns that adapt to variable bandwidth allocations and instantaneous channel conditions. The frequency hopping sequence is generated dynamically based on current system state rather than being predefined, allowing the system to flexibly respond to changing bandwidth requirements and channel conditions while maintaining manageable complexity through structured generation methods.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If frequency hopping patterns are established without considering bandwidth allocations, then bandwidth allocation flexibility is improved, but collision avoidance capability deteriorates

Engineering Contradiction:

Improvebandwidth allocation flexibilityVSAvoidcollision avoidance capability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent performs preliminary determination of frequency hopping patterns based on anticipated bandwidth allocations and channel conditions before actual transmission occurs. By pre-calculating hopping sequences that account for expected bandwidth requirements and potential collisions, the system maintains allocation flexibility while ensuring reliable collision avoidance through advance planning.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system incorporates feedback mechanisms that monitor actual bandwidth allocations and channel conditions, then adjust frequency hopping patterns accordingly. This closed-loop approach ensures that hopping sequences remain optimized for current system state, maintaining both allocation flexibility and collision avoidance capability through continuous adaptation based on real-time feedback.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9496918B2Multicarrier communication system employing explicit frequency hopping

Publication Date: 2016.11.15 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Variable bandwidth assignment and frequency hopping are employed to make efficient use of radio resources. Variable bandwidth assignment is achieved by dynamically allocating different numbers of subcarriers to different mobile terminals depending on their instantaneous channel conditions. The frequency hopping patterns are determined “on-the-fly” based on the current bandwidth assignments. The bandwidth assignments and frequency hopping patterns are signaled to the mobile terminals in a scheduling grant.