Bandwidth on Demand OFDM Signal PAPR Reduction
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Solution Overview
Problem
The challenge in wireless communications is to increase the effective bandwidth of systems by bonding two wireless channels with legacy protocols while maintaining efficiency and backwards compatibility, particularly when combining OFDM signals, which leads to increased peak-to-average power ratio (PAPR) issues due to nonlinearities in power amplifiers, causing inefficiencies and potential interference.
Innovation Solution
The method involves reducing the PAPR of combined OFDM signals by cyclically shifting the time-domain signals to avoid constructive interference of power peaks, using a digital processor to coordinate the modulation of signals and ensure compatibility with legacy equipment, and employing a Shift-and-Add algorithm to optimize the combination of OFDM channels, thereby reducing the PAPR without degrading system performance or requiring side information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple modulated data streams are combined through a common amplifier, then bandwidth is increased, but peak-to-average power ratio increases causing amplifier inefficiency
Solution Approach 1:
The patent applies preliminary action by cyclically shifting the time-domain signals of multiple OFDM channels before they are combined and amplified. This shifting is performed in advance to prevent peak power alignment, ensuring that when signals are summed, their peaks do not constructively interfere. By preparing the signals beforehand with appropriate time shifts, the system achieves bandwidth aggregation while maintaining amplifier efficiency and avoiding excessive PAPR.
2Productivity
If multiple OFDM channels are bonded to increase bandwidth, then data rate is improved, but nonlinear distortion increases due to power amplifier limitations
Solution Approach 1:
The patent employs preliminary action by performing cyclic shifts on the time-domain signals of multiple OFDM channels before combination. This pre-processing ensures that peak powers of individual channels do not align in time, preventing the power amplifier from operating in its nonlinear region. By anticipating and preventing peak alignment through advance signal manipulation, the system achieves high data rates through channel bonding while minimizing nonlinear distortion and maintaining signal quality.
Data Source
AI summary
A system and method for dynamically changing the quality of service (QoS) for a subscriber of a cellular radio system. Bandwidth-on-Demand (BoD) enables the subscriber to dynamically switch to higher bandwidth and to enable a higher throughput. This may be for a limited time or amount of data, for example. The initiation may be by the subscriber, carrier, sponsor, or automatically by an application. The QoS increase may be dynamically priced in a kind of auction. The wireless device may contact the policy servers of a multiple network operator (MNO), which in turn contacts the Authentication, Authorization and Accounting (AAA) server in the MNO's core network. The policy server contacts the scheduler on the serving basestation which then determines whether to allocate more resources (i.e. bandwidth in the form of subcarriers, resource blocks, resource elements, timeslots) to the subscriber. The initiation may start a timer or data counter.