Method and apparatus for real time scheduling of traffic in wireless networks

• US 20080232285A1
• Filed: 03/24/2008
• Published: 09/25/2008
• Est. Priority Date: 03/23/2007
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Aad, Imad, Loyola, Luis, Hofmann, Philipp, Widmer, Jorg
• Granted Patent: US 8,085,807 B2
• Time in Patent Office: Days
• US Class Current: 370/310
• CPC Class Codes: H04W 74/02 Hybrid access
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02
• CPC Class Codes: H04W 74/085 collision avoidance

Abstract

A method for scheduling of traffic in wireless networks, whereas said network comprises real-time stations intending to send real-time traffic and best-effort stations sending best effort traffic, said method comprising:

transmitting by a primary real-time station periodically a real-time access marker to thereby define rounds;
assigning a sequence number to each station in said network which intends to send real-time traffic;
based on the sequence number assigned to a station, defining a fixed backoff time at which a packet from this station is transmitted after the start of a round to thereby establish a sequence in which the real-time packets are sent by the different realtime stations, said method being characterized by further comprising:
overhearing for a predetermined period of time the traffic by a station which intends to send real-time traffic;
if from said overhearing said station concludes that there is already a primary station transmitting real-time access markers, assuming by said station a sequence number based on the number of real-time stations which already are sending real-time traffic.

Claims

1. A method for scheduling of traffic in wireless networks, whereas said network comprises real-time stations intending to send real-time traffic and best-effort stations sending best effort traffic, said method comprising:

transmitting by a primary real-time station periodically a real-time access marker to thereby define rounds;

assigning a sequence number to each station in said network which intends to send real-time traffic;

based on the sequence number assigned to a station, defining a fixed backoff time at which a packet from this station is transmitted after the start of a round to thereby establish a sequence in which the real-time packets are sent by the different realtime stations, said method being characterized by further comprising;

overhearing for a predetermined period of time the traffic by a station which intends to send real-time traffic;

if from said overhearing said station concludes that there is already a primary station transmitting real-time access markers, assuming by said station a sequence number based on the number of real-time stations which already are sending real-time traffic.

2. The method of claim 1, further comprising:

if from said overhearing said station concludes that there is not yet a primary station sending real-time access markers, assuming by said station the role of said primary station and starting to send real-time access markers.

3. The method of claim 1, further comprising:

assigning a maximum number of RT slots per round to each station;

based on the sequence number assigned to a station and the number of RT slots it is allowed to transmit, defining a sequence of fixed backoff times at which packets from this station are transmitted after the start of a round to thereby establish a sequence in which the real-time packets are sent by the different realtime stations.

4. The method of claim 1, wherein said real-time access marker comprises an indication of the number of stations which currently are sending real-time traffic in said network and the number of RT slots each station has reserved, and

incrementally assigning a new sequence number to a real-time station which newly wants to send real-time traffic based on the number of real-time stations which are already sending real-time traffic.

5. The method of claim 1, further comprising:

dividing said rounds into a part being used for real-time traffic in which real-time packets can be scheduled and a part being reserved for best effort traffic.

6. The method of claim 1, wherein

if a best effort station does not finish its transmission before the end of the round having a duration of T, thereby taking over a fraction Δ

T of the next round, the next real-time access marker is sent with a delay of Δ

T and the next round duration is shortened to T−

Δ

T.

7. The method of claim 1, further comprising:

if a packet from a real-time station does not use the RT slot assigned to it based on the sequence number of said station, taking over said RT slot by the succeeding station.

8. The method of claim 1, wherein

a real-time station uses only a defined number of RT slots per round and further packets are ,,downgraded”

and transmitted in best effort mode.

9. The method of claim 8, whereas if a downgraded packet can not be transmitted within a given round it is upgraded again in the next round.

10. The method of claim 1, further comprising:

before a new real-time station starts to send real-time packets, checking whether the sum of the so far reserved time for real-time transmission and the so far reserved time for best effort traffic plus the transmission time necessary for the traffic of the new station does exceed the round duration, and

if it does exceed said duration, sending said traffic from said new station in best effort mode, and

if it does not exceed said duration, allowing said new station to join the other real-time stations as a further real-time station.

11. The method of claim 1, further comprising:

setting the duration field in the real-time access marker to a duration corresponding to the remaining backoff of the last RT station/packet in the round to avoid that a best effort station takes over a RT slot which has been assigned to a real-time station.

12. The method of claim 1, further comprising:

setting the duration field in a real-time packet to a duration such that it can be avoided that a best effort packet can capture a RT slot which is reserved for this or its succeeding real-time packet.

16. A computer program comprising computer program code means adapted to perform the steps of a method according to claim 1 when said program is run on a computer.

13. An apparatus for scheduling of traffic in wireless networks, whereas said network comprises real-time stations intending to send real-time traffic and best-effort stations sending best effort traffic, said apparatus comprising:

a module for transmitting by a primary real-time station periodically a real-time access marker to thereby define rounds;

a module for assigning a sequence number to each station in said network which intends to send real-time traffic;

a module for based on the sequence number assigned to a station, defining a fixed backoff time at which a packet from this station is transmitted after the start of a round to thereby establish a sequence in which the real-time packets are sent by the different realtime stations, said apparatus further comprising;

a module for overhearing for a predetermined period of time the traffic by a station which intends to send real-time traffic;

a module for assuming by said station a sequence number based on the number of real-time stations which already are sending real-time traffic if from said overhearing said station concludes that there is already a primary station transmitting real-time access markers.

14. A realtime-station for scheduling of traffic in wireless networks, whereas said network comprises real-time stations intending to send real-time traffic and best-effort stations sending best effort traffic, said realtime-station comprising:

a module for receiving a real-time access marker sent periodically by a primary real-time station to thereby define rounds;

a module for assigning a sequence number to said realtime-station in said network which intends to send real-time traffic;

a module for based on the sequence number assigned to said station, defining a fixed backoff time at which a packet from this station is transmitted after the start of a round to thereby establish a sequence in which the real-time packets are sent by the different realtime stations, said realtime-station further comprising;

a module for overhearing for a predetermined period of time the traffic by a station which intends to send real-time traffic;

a module for assuming by said realtime-station a sequence number based on the number of real-time stations which already are sending real-time traffic if from said overhearing said station concludes that there is already a primary station transmitting real-time access markers.

15. The realtime-station of claim 14, further comprising:

a module for, if from said overhearing said realtime-station concludes that there is not yet a primary station sending real-time access markers, assuming by said realtime-station the role of said primary station and starting to send real-time access markers.