Dynamic Bandwidth Allocation for PON Modulation Switching
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Solution Overview
Problem
In optical communication systems with multiple modulation schemes, the frequent switching of modulation schemes during dynamic bandwidth allocation leads to inefficient signal reception and increased power consumption due to the need for longer guard times, which degrades the overall efficiency of bandwidth usage.
Innovation Solution
Implement a dynamic bandwidth allocation method where bandwidths for uplink signals from ONUs using the same modulation scheme are allocated successively, reducing the number of modulation scheme switches and enabling the shutdown of unused modulation circuit operations, thereby improving signal reception efficiency and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the OLT switches modulation schemes frequently to accommodate different ONUs, then the system can support multiple modulation schemes, but the guard time increases and bandwidth usage efficiency deteriorates
Solution Approach 1:
The patent segments the uplink bandwidth allocation into distinct time slots for different modulation schemes (QPSK and 16QAM). By dividing the transmission schedule into separate segments for each modulation type, the system avoids frequent switching while still supporting multiple schemes. This segmentation is achieved through the DBA process that allocates specific time intervals to each ONU based on their modulation scheme requirements.
Solution Approach 2:
The patent implements preliminary action by having ONUs report their modulation scheme requirements in advance during the registration phase. The OLT then uses this advance information to pre-allocate appropriate time slots in the DBA process, ensuring that ONUs with the same modulation scheme are grouped together. This preliminary planning eliminates the need for frequent switching during actual data transmission.
2Device complexity
If the OLT groups ONUs with different transmission rates together in time slots, then the allocation process is simplified, but the laser switching time increases and signal reception efficiency deteriorates
Solution Approach 1:
The patent applies local quality by treating different modulation schemes differently in the bandwidth allocation process. Instead of uniform treatment, the system identifies and groups ONUs by their specific modulation scheme requirements (QPSK vs. 16QAM) and allocates time slots accordingly. This localized differentiation ensures that each group receives appropriate attention and timing, improving signal reception efficiency while maintaining manageable allocation complexity.
3Reliability
If the OLT ensures long guard times to accommodate laser switching, then the system can reliably switch modulation schemes, but the available bandwidth for data transmission decreases
Solution Approach 1:
The patent uses preliminary action during the registration phase to collect modulation scheme information from all ONUs before the actual data transmission begins. The OLT then uses this advance knowledge to create an optimized DBA allocation that groups compatible ONUs together, minimizing the need for long guard times during data transmission. This preliminary planning allows for more efficient use of available bandwidth while maintaining reliable switching where necessary.
Data Source
AI summary
In a PON system in which plural kinds of modulation schemes coexist, when uplink burst signals from respective ONUs are received, the receiving efficiency degrades as the number of the times of switching of the modulation scheme increases. In an optical access (PON) system supporting plural kinds of modulation schemes, an OLT allocates bandwidths for uplink signals, i.e., transmission timings each including a transmission start time and a transmission duration, to ONUs, respectively, such that the bandwidths allocated to plural ONUs for the same modulation scheme are as successive as possible. Based on the transmission timings allocated to the respective ONUs, the OLT switches the modulation scheme of a modulation-scheme variable burst-mode optical transmitter/receiver by control of a modulation scheme controller.