Cyclic Delay Diversity Gap Filler for DMB Reception
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Solution Overview
Problem
Terrestrial Digital Multimedia Broadcasting (DMB) systems face challenges in providing cyclic delay diversity due to the structure of conventional gap fillers, which simply amplify signals without demodulation, leading to interference and reduced reception capability in blanket areas, necessitating high transmission power and increased manufacturing costs.
Innovation Solution
A gap filler apparatus and method that includes a receiver for OFDM signals, symbol synchronization for determining a cyclic delay within the guard interval, and an amplifier to transmit the cyclic-delayed signals, enabling cyclic delay diversity and improving reception capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional gap fillers simply amplify signals without demodulation, then device complexity is reduced, but reception capability deteriorates due to lack of cyclic delay diversity
Solution Approach 1:
The patent applies parameter changes by modifying the time delay parameter of the transmitted signal. Specifically, it introduces cyclic delay diversity by delaying the OFDM signal by different amounts (within the guard interval) before transmission from different gap fillers. This changes the temporal parameter of the signal to create diversity paths, improving reception capability without requiring full demodulation and retransmission capabilities at each gap filler.
2Reliability
If more gap fillers are deployed to improve reception in blanket areas, then reception capability is improved, but manufacturing cost increases
Solution Approach 1:
The patent uses parameter changes (cyclic delay) to enable existing gap fillers to provide diversity gain without adding more infrastructure. By adjusting the delay parameter within the guard interval, the system achieves better reception in blanket areas using the same number of gap fillers, thereby avoiding additional manufacturing costs.
3Reliability
If transmission power is increased to improve reception capability, then reliability is improved, but energy consumption increases
Solution Approach 1:
The patent employs periodic action through cyclic delay diversity, where signals are transmitted periodically from multiple gap fillers with different delay values within the guard interval. This creates multiple delayed versions of the signal that combine at the receiver, improving reception capability through diversity gain rather than requiring increased transmission power.
4Reliability
If cyclic delay exceeds guard interval, then diversity gain is increased, but inter-symbol interference occurs
Solution Approach 1:
The patent carefully controls the delay parameter to be within the guard interval duration. This parameter constraint ensures that the delayed signals from different gap fillers arrive at the receiver within the protective guard interval, preventing inter-symbol interference while still providing frequency diversity gain through the delayed paths.
Data Source
AI summary
A gap filler apparatus providing cyclic delay diversity in a digital multimedia broadcasting (DMB) system. In the gap filler apparatus, a receiver receives an orthogonal frequency division multiplexing (OFDM) signal transmitted as a broadcasting signal. A symbol synchronization unit acquires symbol synchronization of the OFDM signal, detects a guard interval of an OFDM symbol using the symbol synchronization, determines a sample length, by which the OFDM symbol is cyclic-delayed within the guard interval, and cyclic-delays the OFDM signal by the determined sample length. An amplifier amplifies the cyclic-delayed OFDM signal. A transmitter transmits the amplified OFDM signal to a wireless network.