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wiki:wiki3:faq_multicast_3.x [2019/02/18 14:20] tda created |
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- | ===== What is Unicast and Multicast ? ===== | + | ===== What are Unicast and Multicast? ===== |
Unicast messages are sent to a single end-device and multicast messages are sent to multiple end-devices. All devices of a multicast group must share the same multicast address and associated encryption keys. | Unicast messages are sent to a single end-device and multicast messages are sent to multiple end-devices. All devices of a multicast group must share the same multicast address and associated encryption keys. | ||
- | All end-devices must listen to the multicast channel in order to get multicast messages (end-devices must be C-class). The best use-cases for Multicast is Lighting domain and Firmware update. | + | All end-devices must listen to the multicast channel in order to receive multicast messages (end-devices must be C-class). The best use-cases for Multicast are Lighting domain and Firmware update. |
- | ===== How can I know that multicast messages are correctly received by my end-devices ? ===== | + | ===== How can I know that multicast messages are correctly received by my end-devices? ===== |
- | There is no ACK for Multicast messages. So we don't know if the multicast message has been received by all end-devices. | + | There is no ACK for Multicast messages. So from the WMC side, we cannot know if the multicast message has been received by all end-devices. |
- | ===== What is the mantadory information to create a Multicast group ? ===== | + | ===== What are the requirements to create a Multicast group? ===== |
- | The mandatory information is : \\ | + | The mandatory requirements are : \\ |
- | * a Cluster name | + | * a cluster name |
- | * a Multicast address: DevAddr, a 32 bit network address (must be unique and not belong to an existing end-device)\\ | + | * a multicast address: DevAddr, a 32 bit network address (must be unique and not belong to an existing end-device)\\ |
- | * the Application session key (AppSKey) and Network session key (NWkSKey) used for frames encryption, 32 digits hexadecimal string. | + | * the application session key (AppSKey) and network session key (NWkSKey) used for frames encryption, 32 digits hexadecimal string. |
- | * radio settings: a fixed frequency in MHz (float32)and a DataRate (a string formatted as "SFxxBWyyy" with xx from 7 to 12 and yyy = 125/250/500 for LoRa modulation or yyy=5000 for FSK modulation) | + | * radio settings: a fixed frequency in MHz (float32) and a DataRate (a string formatted as "SFxxBWyyy" with xx from 7 to 12 and yyy = 125/250/500 for LoRa modulation or yyy=5000 for FSK modulation) |
* a frame counter: FCntDown | * a frame counter: FCntDown | ||
* the LoRaWAN MAC version: for Europe 868 MHz, select 1.0.2 MAC version and Regional parameters B revision to be compatible with WMC 2.x | * the LoRaWAN MAC version: for Europe 868 MHz, select 1.0.2 MAC version and Regional parameters B revision to be compatible with WMC 2.x | ||
The multicast address and associated network session key and application session key must come from the application layer. \\ | The multicast address and associated network session key and application session key must come from the application layer. \\ | ||
- | Class-C Multicast downlinks SHALL NOT carry MAC commands. | + | Class-C multicast downlinks SHALL NOT carry MAC commands. |
- | ===== Can several Muticast groups have the same multicast adress ? ===== | + | ===== Can several Multicast groups have the same multicast adress? ===== |
Yes. The same multicast adrress can be used by several Multicast groups. | Yes. The same multicast adrress can be used by several Multicast groups. | ||
- | ===== Can a end-device belong to several Multicast groups ? ===== | + | ===== Can an end-device belong to several Multicast groups? ===== |
- | Yes. A end-device can belong to several multicast groups. | + | Yes. An end-device can belong to several Multicast groups. |
- | ===== Which gateways are chosen for a C-Multicast DataDown ? ===== | + | ===== Which gateways are chosen for a C-Multicast DataDown? ===== |
- | LNS selects gateways according to the following : | + | |
- | * Retrieve all end-devices owned by the group. | + | The LNS selects gateways according to the dutycycle and the coverage of each gateway. |
- | * Retrieve gateways used by these end-devices to send DataUp messages. | + | |
- | * Check duty cycle. | + | |
- | * Check DLAllowed. | + | |
- | * Compute coverage of each gateway. | + | |
- | * If one gateway covers all end-devices, select it. | + | |
- | * If several gateways cover all-devices, select the one with with the lower duty cycle. | + | |
- | * If no gateways cover all end-devices: | + | |
- | * Remove end-devices not covered by any gateways. | + | |
- | * Select gateways covering end-devices covered by only one gateway. | + | |
- | * For remaining end-devices (covered by several gateways), select the gateway with the best coverage. | + | |
- | In all cases, a gateway cannot be selected if its duty cycle is over the maximum limit or if downlink is not allowed by its owner. | + | In any case, a gateway cannot be selected if its duty cycle is over the maximum limit or if downlink is not allowed by its owner. |
- | If a end-device has never transmitted data, it won't be taken into account for the choice of gateways used for multicast DataDown. | + | If an end-device has never transmitted data, it won't be considered when doing the selection of gateways used for Multicast DataDown. |
- | Here are some specific main cases: | ||
- | * **Case 1** : | + | ===== Which gateways are choosen for a Unicast DataDown? ===== |
- | * Gateway 1 covers all-devices | + | The LNS selects gateways according to their SNR (Signal/Noise ratio). The gateway with the higher SNR (lowest noise) is choosen in priority. |
- | * Duty cycle is under its maximum limit | + | |
- | * => **Gateway 1 is selected to send the multicast DataDown message** | + | |
- | {{:wiki3:mcc001_1_gw_full_coverage.png|}} | + | |
- | * **Case 2** : | + | |
- | * Gateway 1 and Gateway 2 cover all end-devices | + | |
- | * Duty cycle is under its maximum limit for both gateways | + | |
- | * Gateway 2 duty cycle is lower | + | |
- | * => **Gateway 2 is selected to send the multicast DataDown message** | + | |
- | {{:wiki3:mcc002_2_gw_full_coverage.png|}} | + | |
- | * **Case 3** : | + | |
- | * Gateway 1 covers all end-devices | + | |
- | * Gateway 2 covers 80% of the end-devices | + | |
- | * Duty cycle is under its maximum for both gateways | + | |
- | * => **Gateway 1 is selected to send the multicast DataDown message** | + | |
- | {{:wiki3:mcc003_2_gw_full_and_partial_coverage.png|}} | + | |
- | * **Case 4** : | + | |
- | * Gateway 1 covers 70% of the end-devices (4, 5, 6, 7, 8, 9, 10) | + | |
- | * Gateway 2 covers 80% of the end-devices (1, 2 ,3 ,4, 5, 6, 7, 8) | + | |
- | * Duty cycle is under its maximum limit for both gateways | + | |
- | * => **Gateway 1 and 2 are selected to send the multicast DataDown message** | + | |
- | {{:wiki3:mcc004_2_gw_partial_coverage.png|}} | + | |
- | * **Case 5** : | + | |
- | * Gateway 1 covers 90% of the end-devices (1, 2 ,3 ,4, 5, 6, 7, 8, 9) | + | |
- | * Gateway 2 covers 70% of the end-devices (1, 2 ,3 ,4, 5, 6, 7, 8) | + | |
- | * Gateway 3 covers 10% of the end-devices (10) | + | |
- | * Duty cycle is under its maximum limit for all gateways | + | |
- | * => **Gateway 1 and 3 are selected to send the multicast DataDown message** | + | |
- | {{:wiki3:mcc005_3_gw_partial_coverage.png|}} | + | |
- | * **Case 6** : | + | |
- | * Gateway 1 covers 90% of the end-devices (1, 2 ,3 ,4, 5, 6, 7, 8, 9) | + | |
- | * Gateway 2 covers 70% of the end-devices (1, 2 ,3 ,4, 5, 6, 7, 8) | + | |
- | * Gateway 3 covers 10% of the end-devices (10) | + | |
- | * Duty cycle is over for Gateway 1 | + | |
- | * Duty cycle is under its maximum limit for Gateway 2 and 3 | + | |
- | * => **Due to its duty cycle, Gateway 1 cannot be used to send the multicast DataDown message. So Gateways 2 and 3 are selected. End-devices 8 and 9 may not be covered.** | + | |
- | {{:wiki3:mcc006_3_gw_partial_coverage_dc_over.png|}} | + | |
- | ===== Which gateways are choosen for a Unicast DataDown ? ===== | + | ===== Is it possible that a end-device receive a C-Multicast DataDown from multiple gateways at the same time? ===== |
- | LNS selects gateways according to their SNR (Signal/Noise ratio). The gateway with the higher SNR (lowest noise) is choosen in priority. | + | This case is not managed by the LNS yet. |
- | + | ||
- | ===== Is it possible that a end-device receive a C-Multicast DataDown from 2 different gateways at the same time ? ===== | + | |
- | For the moment, this case is not managed. | + | |