Radio Handover Optimization via Pre-Scanning
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Solution Overview
Problem
The existing two-way radio communication systems, such as those following the DMR standard, face inefficiencies in handover processes between RF sites, leading to noticeable audio holes during calls due to prolonged switching times and delays in finding alternative channels with sufficient signal strength.
Innovation Solution
The system optimizes handover by scanning signal strength indicators for alternative traffic channels during ongoing calls, determining suitable channels with embedded link control messages, and utilizing delay information to synchronize directly with the selected channel, eliminating the need for control channel registration and announcements, thereby reducing switching times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radio follows the standard roaming process including control channel registration and waiting for traffic channel announcements, then the radio ensures proper protocol compliance and channel coordination, but the handover time becomes excessively long (up to 1.5 seconds) causing noticeable audio holes
Solution Approach 1:
The radio performs preliminary scanning of alternative traffic channels and their signal strengths during the ongoing call on the current channel. By proactively identifying suitable alternative channels before handover is triggered, the radio eliminates the need to wait for control channel announcements during the handover process, thus reducing handover time while maintaining protocol compliance
Solution Approach 2:
The patent extracts the traffic channel selection process from the control channel dependency. Instead of waiting for the control channel to announce traffic channel information, the radio independently selects the alternative traffic channel based on pre-scanned signal strength information, separating these functions to reduce handover delay
2Measurement precision
If the radio waits for control channel announcements to obtain alternative traffic channel information, then the radio ensures accurate channel assignment, but the waiting time (up to 540 ms per channel) significantly delays the handover process
Solution Approach 1:
The radio performs preliminary scanning and evaluation of alternative traffic channels and their signal strengths while the call is ongoing on the current channel. This advance preparation provides the radio with ready-to-use channel information, eliminating the need to wait for control channel announcements during handover and thus reducing waiting time while maintaining accurate channel selection
3Reliability
If the radio performs comprehensive channel scanning and registration procedures, then the radio ensures proper system integration and channel coordination, but the complexity of the handover process increases leading to longer switching times
Solution Approach 1:
The patent extracts the traffic channel selection function from the control channel registration process. The radio independently selects the alternative traffic channel based on pre-scanned signal strength information without requiring control channel registration or waiting for announcements, thereby simplifying the handover process while maintaining system integration
Solution Approach 2:
The radio performs self-service by independently identifying and selecting the alternative traffic channel based on its own measurements of signal strength during preliminary scanning. The radio does not need to wait for or process control channel announcements for channel selection, reducing process complexity while ensuring proper system coordination
Data Source
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AI summary
A radio receives audio information on a first traffic channel in a radio frequency (RF) site. The radio receives, on the first traffic channel, an announcement of alternative traffic channels on which the audio information is also transmitted in adjacent RF sites. The radio determines signal strength indicators for the alternative traffic channels in the adjacent RF sites while continuing to receive the audio information on the first traffic channel. The radio determines that a signal strength associated with the first traffic channel is below a first threshold. Based on the determination and as a function of the scanning, the radio roams to a second traffic channel, selected from the alternative traffic channels, in an adjacent RF site where a signal strength associated with the second traffic channel is above a second threshold. The radio receives the audio information via the second traffic channel.