Cable Modem Heartbeat Timer Extension for 5G CBRS Bandwidth Stability
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Solution Overview
Problem
In 5G CBRS networks, Spectrum Access Systems (SAS) may prematurely de-allocate bandwidth from CBSDs due to temporary inability to send heartbeat messages, caused by overload, software/hardware issues, or critical alarms, leading to loss of necessary bandwidth allocations.
Innovation Solution
A cable modem (CM) maintains both short and long timers for each bandwidth allocation, re-initiates timers upon receipt of heartbeat messages, and transmits stored messages to extend the time before SAS de-allocates bandwidth, allowing CBSDs to maintain allocations even when temporarily unable to send messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SAS uses a timer to monitor heartbeat messages from CBSDs, then the SAS can detect when a CBSD stops needing bandwidth allocation, but the SAS may prematurely de-allocate bandwidth when the CBSD is temporarily unable to send heartbeats due to overload or issues
Solution Approach 1:
The cable modem performs preliminary actions by storing copies of heartbeat messages and proactively transmitting them to the SAS before the timer expires. This preliminary transmission of stored heartbeat messages prevents the timer from expiring due to temporary CBSD unavailability, thereby maintaining reliable bandwidth allocation without premature de-allocation.
2Reliability
If the CBSD sends frequent heartbeat messages to prevent timer expiration, then the bandwidth allocation reliability improves, but the CBSD may become overloaded and unable to send messages in time
Solution Approach 1:
The cable modem acts as an intermediary between the CBSD and the SAS. It receives and stores heartbeat messages from the CBSD, then proactively transmits them to the SAS independently of the CBSD's real-time message generation capability. This intermediary function ensures reliable heartbeat delivery without burdening the CBSD's processing capacity.
3Productivity
If the SAS de-allocates bandwidth immediately upon timer expiration, then the SAS can quickly release unused bandwidth, but the CBSD loses necessary bandwidth during temporary communication disruptions
Solution Approach 1:
The cable modem performs preliminary transmission of stored heartbeat messages to the SAS before the timer expires. This preliminary action extends the effective timer duration, allowing the SAS to maintain bandwidth allocation stability during temporary disruptions while still enabling quick release when the long timer expires, thus balancing both bandwidth release speed and allocation stability.
Data Source
AI summary
In a (5G CBRS) network having a (CBSD) base station communicating with a (SAS) bandwidth manager via a cable modem (CM), the CM maintains a long timer and a short timer for each bandwidth allocation to the CBSD. When the CM receives a heartbeat message from the CBSD, the CM re-starts the long and short timers and transmits the heartbeat message to the SAS. When the short timer expires, the CM re-starts the short timer and transmits a copy of the stored heartbeat message to the SAS. When the long timer expires, the CM stops transmitting a copy of the stored heartbeat message to the SAS. In this way, the CM effectively extends the time limit before the SAS will de-allocate bandwidth from the CBSD to handle situations where the CBSD is temporarily unable to send heartbeat messages to the SAS even though the CBSD still needs the allocated bandwidth.