OFDM Subpacket Scheduling for Peak-to-Average Power Ratio Control
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Solution Overview
Problem
CDMA systems face limitations due to Inter-Symbol Interference (ISI) and Multiple Access Interference (MAI) in both downlink and uplink transmissions, while OFDM signals suffer from high peak-to-average power ratio (PAPR) issues, leading to degraded performance and increased costs for power amplifiers.
Innovation Solution
The method involves forming subpackets and determining their peak-to-average power ratio (PAPR) for transmission, allowing for controlled ordering and selection to reduce PAPR in OFDM systems using Hybrid ARQ techniques, thereby optimizing subpacket transmission to minimize interference and power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM modulation is used to reduce ISI and MAI, then data rate and system capacity are improved, but peak-to-average power ratio (PAPR) increases requiring more expensive power amplifiers
Solution Approach 1:
The patent segments the OFDM signal into multiple subpackets, each with lower individual PAPR. By dividing the total data into smaller subpackets that are transmitted sequentially, the system maintains the benefits of OFDM (low ISI, low MAI) while reducing the peak power requirements to levels compatible with standard power amplifiers.
2Ease of operation
If subpackets are transmitted in conventional order, then transmission simplicity is maintained, but PAPR remains high causing clipping and intermodulation products
Solution Approach 1:
The patent dynamically reorders subpackets based on their calculated PAPR values before transmission. Subpackets with lower PAPR are transmitted first, and those with higher PAPR are transmitted later or with adjusted parameters. This dynamic adaptation maintains transmission simplicity while eliminating signal clipping and intermodulation products.
Data Source
AI summary
A method for reducing the peak-to-average power ratio (PAPR) in an OFDM based wireless system is disclosed herein. The reduced PAPR may be achieved by appropriately selecting subpackets for transmission. For example, a scheduler may elect to sequentially transmit the subpackets in an order related to the PAPR of each of the subpackets until at least one of the subpackets is properly received. In one embodiment of the instant invention the order of transmission is selected to be from lowest to highest PAPR.