Wireless Microphone OFDM TDMA Bidirectional Control
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Solution Overview
Problem
Professional microphone and in-ear monitoring systems have been limited by unidirectional radio links with narrow channel transmission, preventing bidirectional control information exchange and requiring parallel frequency multiplexing, which restricts data transmission capabilities.
Innovation Solution
A wireless microphone and in-ear monitoring system utilizing Orthogonal Frequency Division Multiplexing (OFDM) Time Division Multiple Access (TDMA) transmission, allowing for bidirectional data exchange within a wide channel bandwidth, with each TDMA frame containing multiple slots for efficient data transmission and low latency, and incorporating cyclic extensions to counteract channel delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If unidirectional radio links with narrow channel transmission are used, then device complexity is reduced, but bidirectional control information exchange becomes impossible and data transmission capability is restricted
Solution Approach 1:
The patent implements periodic time-division multiplexing where transmission directions alternate in regular intervals (uplink slots and downlink slots within TDMA frames). This periodic switching enables bidirectional communication while keeping each individual transmission simple and unidirectional, thus achieving versatility without excessive complexity.
Solution Approach 2:
The patent transitions from frequency-division multiplexing (parallel frequency channels) to time-division multiplexing (sequential time slots), adding a time dimension to the communication structure. This allows bidirectional control exchange by allocating specific time slots for uplink and downlink communications within the same frequency channel.
2Productivity
If parallel frequency multiplexing is used for microphone and in-ear lines, then simultaneous transmission is achieved, but channel bandwidth is restricted and data transmission capability is limited
Solution Approach 1:
The patent changes the multiplexing parameter from frequency domain to time domain. Instead of allocating separate frequency channels for microphone and in-ear lines, the system uses time-division multiplexing with TDMA frames containing alternating uplink and downlink slots, thereby increasing data transmission capability without requiring additional frequency resources.
Solution Approach 2:
The patent merges microphone transmission and in-ear monitoring reception into a single integrated system sharing the same radio frequency channel. By combining both functions in one system with time-division multiplexing, the patent eliminates the need for separate parallel frequency channels, thus improving productivity while reducing spectral resource requirements.
3Loss of time
If TDMA frames with multiple slots are used, then efficient data transmission and low latency are achieved, but transmission protocol complexity increases
Solution Approach 1:
The patent segments the transmission channel into discrete TDMA frames, each containing multiple time slots allocated for specific purposes (uplink, downlink, guard periods). This segmentation enables efficient time utilization and low latency by ensuring dedicated transmission opportunities for each device, while the structured frame format keeps protocol management systematic rather than chaotic.
Solution Approach 2:
The patent incorporates preliminary synchronization mechanisms where devices align their transmission timing based on predefined frame structures and synchronization signals. This preliminary timing alignment reduces latency by eliminating random access delays and collision resolution time, while the predetermined frame structure simplifies protocol execution compared to dynamic scheduling.
4Reliability
If cyclic extensions are added to OFDM symbols, then robust multipath propagation handling is achieved, but transmission overhead increases
Solution Approach 1:
The patent adds cyclic prefixes (cyclic extensions) to each OFDM symbol as a protective measure against multipath propagation delays. This beforehand cushioning preserves orthogonality of subcarriers by ensuring that delayed multipath components arrive within the guard period rather than causing inter-symbol interference, thereby maintaining reliability while accepting the overhead as a necessary protective measure.
Data Source
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AI summary
The invention relates to a wireless microphone and/or wireless in-ear monitoring system, having at least a first mobile device (MT), in particular having a wireless microphone for wirelessly transmitting first audio signals (UL). The system also has at least one base station for wirelessly receiving first audio signals (UL) transmitted by the at least one mobile device (MT). The wireless transmission is based on an orthogonal frequency-division multiplexing (OFDM) transmission during a TDMA time slot. Each wireless microphone occupies at least one time slot within 2 ms. Each of the TDMA frames has a plurality of slots, each of which has exactly one OFDM symbol. Therefore, exactly one OFDM symbol is transmitted in each TDMA slot. During a time slot provided in accordance with the TDMA, a transmission on the basis of an OFDM method occurs. The TDMA frame length is so short because a latency of < 4 ms is required for professional audio transmission, for example in the case of wireless microphone systems.