Packet scheduling in a wireless local area network

• US 20050152373A1
• Filed: 11/17/2004
• Published: 07/14/2005
• Est. Priority Date: 01/08/2004
• Status: Abandoned Application

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Ali, Ahmed
• Application Number:
  US10/991,266
• Publication Number:
  US 20050152373A1
• Time in Patent Office: Days
• US Class Current: 370/395.400
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/2416 Real-time traffic
• CPC Class Codes: H04L 47/2433 Allocation of priorities to traffic types
• CPC Class Codes: H04L 47/2441 relying on flow classification, e.g. using integrated services [IntServ]
• CPC Class Codes: H04L 47/50 Queue scheduling
• CPC Class Codes: H04L 47/522 Dynamic queue service slot or variable bandwidth allocation
• CPC Class Codes: H04L 47/566 Deadline varies as a function of time spent in the queue
• CPC Class Codes: H04L 47/6215 Individual queue per QOS, rate or priority
• CPC Class Codes: H04L 47/6255 queue load conditions, e.g. longest queue first
• CPC Class Codes: H04L 47/788 Autonomous allocation of resources
• CPC Class Codes: H04L 47/805 QOS or priority aware
• CPC Class Codes: H04L 47/808 User-type aware
• CPC Class Codes: H04L 47/824 Applicable to portable or mobile terminals
• CPC Class Codes: H04W 28/02 Traffic management, e.g. flow control or congestion control
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A method for scheduling packets in a wireless local area network begins by mapping a packet to an access category (AC) based on a user priority of the packet. The packet is assigned to a traffic flow (TF) in a station based on the AC of the packet. A packet from the TF is placed into a transmission queue for the AC. A packet from the transmission queue is selected based on a quality of service-based contention resolution function, and the selected packet is transmitted.

Claims

1. A method for scheduling packets in a wireless local area network, comprising the steps of:

mapping a packet to an access category (AC) based on a user priority of the packet;

assigning the packet to a traffic flow (TF) in a station based on the AC of the packet;

placing a packet from the TF into a transmission queue for the AC;

selecting a packet from the transmission queue based on a quality of service-based contention resolution function; and

transmitting the selected packet.

2. The method according to claim 1, wherein the selecting step includes the steps of:

calculating a priority value for each TF; and

selecting a first packet in the TF having the highest priority value.

3. The method according to claim 2, wherein the priority value is calculated according to the equation:

Priority Index=(Alpha×

Data Rate Index)+(Beta×

Delay Index)

where Alpha and Beta are weighting factors, the Data Rate Index is based on an instantaneous data transmission rate, and the Delay index is based on the delay of the first packet in the transmission queue and the queue size.

4. The method according to claim 3, wherein the Data Rate Index is calculated according to the equation:

5. The method according to claim 3, wherein the Delay Index is calculated according to the equation:

Delay Index_n=(A[AC_n]×

First_Pkt_Delay_n(normalized))+(B[AC_n]×

Queue_Size_n)+(C[AC_n]×

Avg_Pkt_Delay_n(normalized))

where A is a weight factor for the packet delay, First_Pkt_Delay_n is the delay experienced by the first packet in AC_n, B is a weight factor for the queue size, Queue_Size_n is the size of AC_n, C is a weight factor for the average packet delay, and Avg_Pkt_Delay_n is a moving average of the packet delay of AC_n over a predetermined number of packets.

6. The method according to claim 3, wherein Alpha and Beta are dynamically adjusted.

7. The method according to claim 6, wherein Alpha and Beta are adjusted based on a number of packets that experience a predetermined delay.

8. The method according to claim 1, wherein the transmitting step includes detecting whether a transmission collision occurs with another packet.

9. The method according to claim 8, wherein if there is no collision, then transmitting the selected packet.

10. The method according to claim 8, wherein if there is a collision, then performing the steps of:

determining which packet has a higher priority;

transmitting the higher priority packet;

executing a back-off procedure for the lower priority packet; and

transmitting the lower priority packet.

11. The method according to claim 10, wherein the executing step includes:

determining a contention window value for the lower priority packet;

updating the contention window value if it is below a maximum value; and

waiting for a time equal to the contention window value.

12. The method according to claim 10, wherein the lower priority packet is transmitted if the channel is idle.

13. The method according to claim 12, wherein if the channel is not idle, then executing another back-off procedure for the lower priority packet.