Cellular Optical Communication Using ACO-OFDM at Cell Edges
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Solution Overview
Problem
Existing optical communication systems struggle to implement an effective OFDM scheme in cellular optical communication systems, particularly in poor communication environments such as cell edges, where signal-to-noise ratios are low and interference from adjacent cells is significant.
Innovation Solution
Adopting an asymmetrically clipped optical (ACO)-OFDM scheme for optical communication between base station apparatuses and terminal apparatuses, especially in cell edge regions, to enhance noise resistance and adapt to varying communication conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ACO-OFDM scheme is used, then noise resistance is improved, but throughput is reduced
Solution Approach 1:
The patent applies different OFDM schemes (DCO-OFDM and ACO-OFDM) to different spatial locations within the cell. ACO-OFDM is used specifically in cell edge regions where noise resistance is critical, while DCO-OFDM is used in cell center regions where throughput is prioritized. This local differentiation resolves the contradiction by optimizing for noise resistance where needed without sacrificing overall system throughput.
Solution Approach 2:
The system dynamically selects between ACO-OFDM and DCO-OFDM schemes based on terminal apparatus location and communication conditions. The base station determines whether to apply ACO-OFDM or DCO-OFDM signaling according to the terminal's position in the cell, allowing the system to adaptively balance noise resistance and throughput requirements.
2Productivity
If DCO-OFDM scheme is used, then throughput is improved, but power efficiency is reduced
Solution Approach 1:
DCO-OFDM is applied specifically in cell center regions where terminal apparatuses are located closer to the base station and experience better signal conditions. In these regions, throughput is the primary concern and power efficiency is less critical. This localized application resolves the contradiction by using DCO-OFDM only where its throughput advantage can be fully utilized without wasting energy in regions where it provides no benefit.
Solution Approach 2:
The system dynamically switches between ACO-OFDM and DCO-OFDM based on terminal location and channel conditions. When terminals are in cell center regions with good signal quality, DCO-OFDM is selected to maximize throughput. When terminals move to cell edge regions, the system transitions to ACO-OFDM for better power efficiency and noise resistance.
3Area of stationary object
If optical communication is performed in cell edge region, then coverage is extended, but signal quality deteriorates
Solution Approach 1:
The patent applies ACO-OFDM signaling specifically to terminal apparatuses located in cell edge regions where signal quality is poor. This localized application of the more robust ACO-OFDM scheme compensates for the degraded signal conditions at cell edges, allowing the system to extend coverage to these regions while maintaining acceptable signal quality through appropriate scheme selection.
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
The ACO-OFDM scheme improves communication quality and accommodates multiple terminal apparatuses within a cell, including those at the edge, by enhancing noise resistance and throughput in challenging optical environments.
Implementation Method 1
data transmission is performed by utilizing the intensity of light emitted by a light emitting element such as a light emitting diode (LED). The transmitting side transmits an optical signal whose intensity is modulated in accordance with the transmission data.
Implementation Method 2
The receiving side acquires the transmission data by directly detecting the intensity of the received optical signal using a light receiving element such as a photodiode (PD).
Data Source
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AI summary
A cellular optical communication system that performs optical communication being wireless communication using light, includes a base station apparatus that manages a cell, and a terminal apparatus that performs the optical communication with the base station apparatus in the cell by using an OFDM scheme. The base station apparatus and the terminal apparatus perform the optical communication using an ACO-OFDM scheme at least when the terminal apparatus is located in a cell edge region.