OFDM Tone Assignment for Synchronized Push-to-Talk Group Calls
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Solution Overview
Problem
Existing communication systems, particularly public wireless networks like GSM and TDMA, face challenges in synchronizing mobile units for simultaneous message reception, leading to unpredictable push-to-talk experiences due to variations in data packet timing, which is not accurately replicated in traditional public wireless networks.
Innovation Solution
An orthogonal frequency-division multiplexed (OFDM) wireless communication system synchronizes mobile units by assigning the same OFDM tones to group members, ensuring simultaneous communication through a base station and controller network, allowing for efficient group calls even across different base stations and sectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If data packet technologies are used for group calls, then network coverage and flexibility are improved, but simultaneous message reception synchronization deteriorates due to variations in data packet timing
Solution Approach 1:
The system performs preliminary synchronization by assigning specific OFDM tones to group members before communication occurs. The base station pre-configures the tone assignment information and distributes it to all mobile units, ensuring that when group communication occurs, all units are already synchronized to receive messages simultaneously without latency.
Solution Approach 2:
The invention changes the communication parameter from general data packet transmission to specific OFDM tone assignment. By allocating particular frequency tones to group members and using these dedicated tones for group calls, the system achieves precise synchronization while maintaining the flexibility of packet-based networks.
2Manufacturing precision
If phone call establishment is used to synchronize transmissions, then simultaneous communication is achieved, but call setup time increases causing lag between push-to-talk button press and communication establishment
Solution Approach 1:
The system performs preliminary action by pre-assigning OFDM tones to group members and pre-distributing tone assignment information before any communication occurs. This eliminates the need for time-consuming call establishment procedures, allowing immediate push-to-talk functionality with no lag between button press and communication establishment.
3Manufacturing precision
If iDEN time division technique is used to place all receiving units in receive mode simultaneously, then message reception synchronization is improved, but network compatibility and flexibility deteriorate
Solution Approach 1:
The invention changes the synchronization approach from time division (iDEN) to frequency division (OFDM). By using specific frequency tones assigned to group members within the OFDM framework, the system achieves precise message reception synchronization while maintaining compatibility with standard OFDM networks and avoiding the need for proprietary time division techniques.
Data Source
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AI summary
A system to permit push-to-talk communications in an orthogonal frequency division multiplexed (OFDM) communication network. Individual wireless communication devices that are part of a Group Call are assigned the same set or sets of OFDM tones for a downlink timeslot. Because each wireless communication device receives the same set of tones, each device will receive a communication simultaneously. The assigned OFDM tones need not be contiguous within a block of available tones. Because a large number of OFDM tones are available, the concept may be extended to a large number of groups that each separately support a Group Call function.