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--- wiki:wiki3:faq_multicast_3.x [2019/03/27 18:08]
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+++ wiki:wiki3:faq_multicast_3.x [2019/06/21 15:44]
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@@ Line 2: / Line 2: @@
-===== 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.
-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
   * 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. \\
-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.
-===== 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.
-===== Which gateways are choosen for a Unicast DataDown ? =====
+===== Which gateways are choosen for a Unicast DataDown? =====
-LNS selects gateways according to their SNR (Signal/Noise ratio). The gateway with the higher SNR (lowest noise) is choosen in priority.
+The LNS selects gateways according to their SNR (Signal/Noise ratio). The gateway with the higher SNR (lowest noise) is choosen in priority.
-===== Is it possible that a end-device receive a C-Multicast DataDown from 2 different gateways at the same time ? =====
+===== Is it possible that a end-device receive a C-Multicast DataDown from multiple gateways at the same time? =====
-For the moment, this case is not managed.
+This case is not managed by the LNS yet.

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