MBMS Acknowledgements on RACH Channel Collision Prevention
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Solution Overview
Problem
The existing uplink channel structure in mobile 3G communication systems, specifically the random access channel (RACH), is not designed to handle large numbers of simultaneous feedback transmissions from user equipments receiving Multimedia Broadcast Multicast Service (MBMS) data, leading to collisions and interference with non-MBMS related uplink activities, which hinders efficient feedback collection and service management.
Innovation Solution
Divide MBMS sessions into data transmission and feedback periods, and spread uplink feedback transmissions over time or using different RACH sub-channels and signatures to minimize collisions, with user equipments or the network calculating unique delay times or random waiting periods to prevent simultaneous transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the random access channel is used for transmitting MBMS feedback information from multiple user equipments, then feedback collection is enabled, but transmission collisions occur due to simultaneous channel accesses
Solution Approach 1:
The patent segments the feedback transmission process by dividing user equipments into different groups based on their MBMS service subscriptions. Each group is assigned specific RACH resources (preambles, time slots, or frequency channels), thereby segmenting the previously collision-prone single channel into multiple organized transmission paths that reduce collisions while enabling comprehensive feedback collection.
2Productivity
If all user equipments transmit feedback simultaneously on the RACH, then feedback collection is efficient, but collisions with non-MBMS transmissions and among MBMS users increase
Solution Approach 1:
The patent implements periodic action by organizing feedback transmissions in structured time slots or frames. Different user equipment groups are assigned specific periodic transmission opportunities within the RACH framework, ensuring that feedback is collected systematically over time rather than all at once, thereby maintaining efficiency while minimizing collisions with non-MBMS traffic and among MBMS users.
3Adaptability or versatility
If the RACH is used for MBMS feedback without dedicated resources, then channel utilization is maximized, but feedback transmission reliability deteriorates due to lack of resource allocation
Solution Approach 1:
The patent applies local quality by assigning specific RACH resource characteristics (particular preambles, time slots, or frequency channels) to different user equipment groups based on their MBMS service requirements. This localized resource allocation within the broader RACH framework ensures that each group has dedicated transmission quality while maintaining overall channel flexibility and high utilization.
Data Source
AI summary
The present invention relates to multicast communication systems and in particular to the implementation of a random access uplink channel, which can be used, e.g., for transmission of acknowledgement messages for received data. In order to prevent frequent collisions on said channel, the transmission of acknowledgement messages is spread at least over time or, additionally, with regard to another distinguishing channel property, e.g. a RACH sub-channel or RACH-signature.