There is the consensus that we need some kind of duty cycling MAC layer within RIOT. Within this issue we can provide a collection of open topics and progression. Feel free to add open points, topics and PRs.

Overview and open PRs:

• nomac [merged -> net: added ng_nomac MAC implementation #2426]
  - [ ] csma_mac (@jremmert-phytec-iot) [pr -> Initial import of csma_mac protocol #2467] - (currently outdated and based on depricated assumptions, will update soon)
• lpm [pr -> saml21: add lpm implementation #3019, cpu/samd21: implement low power modes #2309, drivers/ng_at86rf2xx: initial commit of refactoring #2650,~~ kinetis: Add LPM implementation #2605~~]
• lwmac [pr -> Simple duty cycling 802.15.4 MAC protocol #3730]

Current Issues:

Message dispatching

When a node will be associated to an PAN-coordinator, the transmitting and receiving time is guided on the superframe architecture. That means there will be timespans, where the node can not send messages. Nevertheless, there will be incoming task-messages from upper-layer to the MAC layer task.

1. Messages from upper layer (Low-prio)
2. Messages from driver (isr-events) (High-prio)
3. Messages from timer (High-prio)
   There must be a mechanism that (i) keeps the message queue empty. (ii) Takes care of the current MAC-layer state (just try to send a new packet when the MAC layer handled the previous one).

Storing state variables for the MAC-layer state machine.

1. Static variables: Problem when we have more than one MAC-layer
2. Store them in the device-descriptor: The same device-descriptor may be used in different MAC-layer. How to choose the fitting variable set (at compile time)?
3. ?

Open Topics:

1. Move the packet assemble from IEEE 802.15.4 compatible device-drivers to the MAC-layer.
2. Procedure to configure the MAC-layer and start device discovery and associate with PAN (some Auto-init procedure).
   • Initialize capability information field according to the device capability [IEEE 802.15.4 , section 5.3.1.2].
   • Notify upper layer about established link (associate successfull).
3. Implement MAC commands (MLME management service) [IEEE 802.15.4 standard section 6.2]
   • Scan
   • Associate, Disassociated
   • ...
4. Implement TSCH MAC commands (MLME management service) [IEEE 802.15.4e standard section 6.2.0b]
   • ...