Connection timing with Connection Event Length Extension

Central and peripheral links can extend the event if there is radio time available.

The connection event is the time within a timing-event reserved for sending or receiving packets. This is determined by the bandwidth configuration of the link and the size of the packets. The SoftDevice can be enabled to dynamically extend the connection event length to fit the maximum number of packets inside the connection event before the timing-event must be ended. The time extended will be in one packet pair at a time until the maximum extend time is reached. The connection event cannot be longer than the connection interval; the connection event will then end and the next connection event will begin. A connection event cannot be extended if it will collide with another timing-event. The extend request will ignore the priorities of the timing-events.

To get the maximum bandwidth on a single link, it is recommended to enable Connection Event Length Extension and increase the connection interval. This will allow the SoftDevice to send more packets within the event and limit the overhead of processing between connection events. To get the maximum bandwidth with multiple links, it is recommended to enable Connection Event Length Extension and use the bandwidth levels to set the individual bandwidth requirements of the link. The SoftDevice can then dynamically increase the bandwidth beyond the bandwidth level if there is idle time between the connections. To get idle time between central links, it is possible to give a central link bandwidth priority by giving it the lowest common factor interval. For more information, see Suggested intervals and windows.

Figure 1 shows a scheduling example where idle time in the radio scheduling can be used by the links to achieve higher bandwidth. Here C1 can utilize the free time left by a previously disconnected link C2, C3 has idle time as the last central link, and C0 is benefitting from having a connection interval set to half of that of C1 and C3.