Zone Controller Multicast Unicast Call Information Transmission
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Solution Overview
Problem
Communication systems with trunked call setups experience prolonged call setup times and potential loss or truncation of call information due to long link delays between geographically distributed sites connected via varying transport types.
Innovation Solution
A system and method where the zone controller determines participating sites with long link delays and uses both IP multicast and unicast addresses to ensure all sites receive call information, with unicast transmission continuing until the delayed site joins the multicast group, preventing information loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If IP multicast is used for call information distribution, then call setup time is reduced and information transmission efficiency is improved, but sites with long link delays cannot receive complete call information
Solution Approach 1:
The system performs preliminary identification of sites with long link delays before multicast transmission begins. The zone controller determines which sites require unicast supplementation in advance, allowing the system to prepare alternative delivery paths before the call information transmission starts, ensuring these sites can receive complete information despite the delayed multicast arrival.
Solution Approach 2:
The zone controller acts as an intermediary that manages multiple transmission paths. It receives call information via multicast, identifies sites with long delays, and intermediates by sending supplemental unicast transmissions to those specific sites. This intermediary function ensures that all sites, regardless of their link delay characteristics, receive complete call information.
2Reliability
If unicast transmission is used for all sites, then all sites receive call information reliably, but call setup time increases and transmission efficiency decreases
Solution Approach 1:
The system applies different transmission qualities to different sites based on their link delay characteristics. Sites with normal link delays receive call information efficiently via IP multicast, while only sites identified as having long link delays receive supplemental unicast transmissions. This local differentiation optimizes the overall system performance by applying reliability measures only where necessary.
Solution Approach 2:
The system dynamically changes the transmission parameter (from multicast-only to unicast supplementation) based on the link delay parameter of each site. The zone controller modifies the delivery mechanism for specific sites with long delays, changing their reception mode from pure multicast to a combination of multicast and unicast, thereby adapting the transmission parameters to site-specific conditions.
3Reliability
If the zone controller monitors and manages multiple transmission paths, then call information completeness is ensured for all sites, but system complexity increases
Solution Approach 1:
Sites with long link delays perform self-identification by responding to probe messages from the zone controller. Instead of requiring complex centralized monitoring of all sites, the system allows sites to self-report their delay status, reducing the burden on the zone controller. The zone controller simply manages the unicast supplementation for identified sites, rather than continuously monitoring all transmission paths.
Data Source
AI summary
A system and method for transmitting call information in a communication system having sites with long link delays. Upon a call being initiated within the communication system, a zone controller determines the participating sites that are to be involved in the call and assigns an IP multicast group address for the call. The zone controller also determines whether any of the participating sites have a long link delay. If any of the participating sites do have a long link delay, the zone controller also assigns an IP unicast address for each such site. The call information is then transmitted both on the IP multicast address as well as on each assigned IP unicast address to ensure that the call is received by each participating site without the loss of call information.