Airtime-aware scheduling for wireless local-area network

1. A method for communication, comprising:

accepting, in an Access Point (AP), downlink data items for transmission over a wireless downlink channel to multiple terminals served by the AP;

assessing aggregate airtimes for the respective terminals, by summing, for each terminal, an aggregate downlink airtime that was previously allocated to the terminal on the wireless downlink channel and an aggregate uplink airtime that was previously used by the terminal on a wireless uplink channel from the terminal to the AP; and

scheduling transmission of the downlink data items on the wireless downlink channel, depending one aggregate airtimes assessed for the terminals.

2. The method according to claim 1 , wherein scheduling the transmission comprises scheduling the transmission of the downlink data items regardless of Quality-of-Service (QoS) classes with which the downlink data items are associated.

3. The method according to claim 1 , wherein scheduling the transmission comprises allocating a next transmission slot to a terminal that was previously allocated a smallest aggregate airtime among the terminals served by the AP.

4. The method according to claim 1 , and comprising periodically resetting the aggregate airtimes.

5. The method according to claim 1 , wherein assessing the aggregate airtimes comprises assessing respective differences between the aggregate airtimes and a minimal aggregate airtime, and wherein scheduling the transmission comprises scheduling the transmission depending on the differences.

6. The method according to claim 1 , wherein scheduling the transmission comprises assigning to the terminals respective time slots having lengths that do not exceed a predefined maximum length.

7. The method according to claim 1 , and comprising scheduling the transmission of uplink data items from the terminals to the AP depending on the aggregated uplink airtimes assigned to the respective terminals.

8. The method according to claim 1 , wherein each of the terminals is associated with one of multiple virtual networks, and wherein scheduling the transmission comprises assigning airtime to each of the virtual networks depending on the assessed aggregate airtimes.

9. The method according to claim 8 , wherein the multiple virtual networks are identified with respective different Basic Service Set Identifiers (BSSIDs).

10. The method according to claim 1 , wherein scheduling the transmission comprises assigning airtime to multiple streams that are addressed to a same terminal.

11. The method according to claim 1 , wherein scheduling the transmission comprises assigning airtime to multiple different streams that belong to a same QoS class.

12. A wireless Access Point (AP), comprising:

a transmitter, which is configured to transmit downlink data items over a wireless downlink channel to multiple terminals served by the AP; and

a processor, which is configured to assess aggregate airtimes for the respective terminals, by summing, for each terminal, an aggregate downlink airtime that was previously allocated to the terminal on the wireless downlink channel and an aggregate uplink airtime that was previously used by the terminal on a wireless uplink channel from the terminal to the AP, and to schedule transmission of the downlink data items on the wireless downlink channel depending on aggregate airtimes assessed for the terminals.

13. The AP according to claim 12 , wherein the processor is configured to schedule the transmission of the downlink data items regardless of Quality-of-Service (QoS) classes with which the downlink data items are associated.

14. The AP according to claim 12 , wherein the processor is configured to allocate a next transmission slot to a terminal that was previously allocated a smallest aggregate airtime among the terminals served by the AP.

15. The AP according to claim 12 , wherein the processor is configured to periodically reset the aggregate airtimes.

16. The AP according to claim 12 , wherein the processor is configured to assess respective differences between the aggregate airtimes and a minimal aggregate airtime, and to schedule the transmission depending on the differences.

17. The AP according to claim 12 , wherein the processor is configured to schedule the transmission by assigning to the terminals respective time slots having lengths that do not exceed a predefined maximum length.

18. The AP according to claim 12 , wherein the processor is configured to schedule the transmission of uplink data items from the terminals to the AP depending on the aggregated uplink airtimes assigned to the respective terminals.

19. The AP according to claim 12 , wherein each of the terminals is associated with one of multiple virtual networks, and wherein the processor is configured to assign airtime to each of the virtual networks depending on the assessed aggregate airtimes.

20. The AP according to claim 19 , wherein the multiple virtual networks are identified with respective different Basic Service Set Identifiers (BSSIDs).

21. The AP according to claim 12 , wherein the processor is configured to schedule the transmission by assigning airtime to multiple streams that are addressed to a same terminal.

22. The AP according to claim 12 , wherein the processor is configured to schedule the transmission by assigning airtime to multiple different streams that belong to a same QoS class.

23. A system, comprising:

multiple terminals; and

an Access Point (AP), which is configured to transmit downlink data items over a wireless downlink channel to the terminals, to assess aggregate airtimes for the respective terminals, by summing, for each terminal, an aggregate downlink airtime that was previously allocated to the terminal on the wireless downlink channel and an aggregate uplink airtime that was previously used by the terminal on a wireless uplink channel from the terminal to the AP, and to schedule transmission of the downlink data items on the wireless downlink channel depending on aggregate airtimes assessed for the terminals.