Medium access control in wireless local area network

• US 20050025176A1
• Filed: 07/15/2004
• Published: 02/03/2005
• Est. Priority Date: 07/29/2003
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Youn, Myeon-Kee, Ko, Seong-Yun, Jeon, Seong-Joon, Park, Joo-Yong, Kim, Soung-Kwan
• Application Number:
  US10/891,329
• Publication Number:
  US 20050025176A1
• Time in Patent Office: Days
• US Class Current: 370/448
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 74/085 collision avoidance
• CPC Class Codes: H04W 74/0875 with assigned priorities based access
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

A medium access control method and apparatus and program storage device in a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) based wireless LAN (Local Area Network) classifies stations in a CSMA/CA based wireless LAN system into a number of groups according to a transmission priority to assign a different DIFS (Distributed Coordination Function InterFrame Space) to each group. Different and fixed back-off times are assigned to stations that belong to the same priority group according to the transmission priority, and the back-off time is reset to the back-off time that each station has been assigned for every re-transmission contention, to guarantee a transmission opportunity to the station with the higher transmission priority in the same priority group, and to guarantee a transmission opportunity to the station with the higher transmission priority irrespective of the number of stations that wish to make a transmission, and to reduce a chance of collision so as not to degrade a throughput since the waiting time of each station is different.

Claims

1. A method comprising:

defining a plurality of groups to which a priority has been given, and assigning different DIFSs (Distributed Coordination Function InterFrame Spaces) and maximum back-off times to each group according to the given priority such that a sum of the DIFS and the maximum back-off time of a group to which an arbitrary priority has been given is smaller than a sum of the DIFS and the maximum back-off time of a group having a next lower priority;

organizing stations connected to the wireless LAN (Local Area Network) into defined groups according to a transmission priority;

assigning different fixed back-off times to each station organized into an arbitrary group below a range of the maximum back-off time assigned to a relevant group according to the transmission priority among the stations organized into the relevant group such that the sum of the DIFS and the maximum back-off time of the group to which the arbitrary priority has been given is smaller than the sum of the DIFS and the maximum back-off time of the group having the next lower priority; and

transmitting the assigned DIFS and back-off time to each station in order for each station to reset its back-off timer to the fixed back-off time in every transmission contention by the DIFS assigned to the group into which each station is organized and the back-off time assigned to the stations in the group, and to perform a medium access based on a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance).

2. The method of claim 1, wherein the different DIFSs and maximum back-off times are assigned such that the sum of the DIFS and the maximum back-off time of the group to which the arbitrary priority has been given is smaller than the DIFS of the group having the next lower priority.

3. The method of claim 1, wherein the assigned DIFS and back-off time are transmitted to each wireless LAN station via a management frame.

4. The method of claim 1, wherein, during the assigning of different DIFSs and maximum back-off times to each group, assignments of the back-off times of stations that belong to the group having the lowest priority are in accordance with a ‘

Random Exponential Back-off Algorithm’

defined by IEEE (Institute of Electrical and Electronic Engineers) Standard 802.11.

5. The method of claim 1, wherein the DIFS of a station having the highest priority is larger than a PIFS (Point Coordination Function InterFace Space).

6. The method of claim 1, wherein the back-off time of an arbitrary station is an integer multiple of a slot time.

7. A method comprising:

requesting a register of an AP (Access Point) in a wireless LAN (Local Area Network), the AP classifying each station of a plurality of stations into a plurality of priority groups according to a transmission priority to assign different DIFSs (Distributed Coordination Function InterFrame Spaces) to each priority group, and the AP assigning different fixed back-off times according to the transmission priority in the same group and setting the DIFS and the back-off time of each station such that a sum of the DIFS and the back-off time has a fixed difference according to the transmission priority of each station;

receiving and storing the DIFS and the back-off time set into each station from the AP;

attempting to make a contention for medium access by priority with the DIFS and the back-off time set into each station when access to the medium is required for a data transmission; and

resetting a station'"'"'s back-off time to the fixed back-off time to attempt to make a re-contention for medium access when the station fails in the contention for medium access.

8. The method of claim 7, wherein the different DIFSs and maximum back-off times are assigned to each group according to priority such that the sum of the DIFS and the maximum back-off time of a group to which an arbitrary priority has been given is smaller than the DIFS of the group having the next lower priority.

9. A method comprising:

defining a plurality of groups to which a priority is given at an AP(Access Point), and assigning different DIFSs (Distributed Coordination Function InterFrame Spaces) and maximum back-off times to each group according to priority such that a sum of the DIFS and the maximum back-off time of a group to which an arbitrary priority has been given is smaller than the DIFS of the group having the next lower priority;

organizing stations connected to a wireless LAN (Local Area Network) into defined groups according to a transmission priority at the AP;

assigning at the AP different and fixed back-off times to each station organized into an arbitrary group below a range of the maximum back-off time assigned to the relevant group 1I according to the transmission priority among stations organized into the relevant group;

attempting to make a contention for medium access by priority with the DIFS and the back-off time set into the station when access to the medium is required for a data transmission; and

resetting a station'"'"'s back-off time to the fixed back-off time and attempting to make a re-contention for medium access when the station fails in the contention for medium access.

10. The method of claim 9, wherein, during the assigning of different DIFSs and maximum back-off times to each group, assignments of the back-off times of stations that belong to the group having the lowest priority are in accordance with a ‘

Random Exponential Back-off Algorithm’

defined by IEEE (Institute of Electrical and Electronic Engineers) Standard 802.11.

11. An AP (Access Point) in a (Carrier Sense Multiple Access with Collision Avoidance) based wireless LAN (Local Area Network), comprising:

a memory for storing a program; and

a processor connected to the memory and adapted to execute the program, wherein, in accordance with the program, the processor;

defines a plurality of groups to which a priority is given, and assigns different DIFSs (Distributed Coordination Function InterFrame Spaces) and maximum back-off times to each group according to priority such that a sum of the DIFS and the maximum back-off time of a group to which an arbitrary priority has been given is smaller than the DIFS of the group having the next lower priority;

organizes stations connected to the wireless LAN (Local Area Network) into defined groups according to a transmission priority;

assigns different and fixed back-offtimes to each station organized into an arbitrary group below a range of the maximum back-offtime assigned to the group according to the transmission priority; and

transmits the assigned DIFS and back-off time to each station in order for each station to perform the CSMA/CA based medium access by the DIFS assigned to the group into which the station is organized and the back-off time assigned to the station in the group.

12. A wireless LAN (Local Area Network) station in a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) based wireless LAN, comprising:

a memory for storing a program; and

a processor connected to the memory and adapted to execute the program, wherein, in accordance with the program, the processor;

requests a register of an AP (Access Point) in the wireless LAN, the AP classifying each station into a plurality of priority groups according to a transmission priority to assign different DIFSs (Distributed Coordination Function InterFrame Spaces) to each priority group, and the AP assigning a different fixed back-off time according to the transmission priority in the same group and setting the DIFS and the back-off time of each station such that a sum of the DIFS and the back-off time has a fixed difference according to the transmission priority of each station;

receives and stores the DIFS and the back-off time set into the station from the AP;

attempts to make a contention for medium access by priority with the DIFS and the back-off time set into the station when the station requires access to the medium for a data transmission; and

resets the station'"'"'s back-off time to the fixed back-off time to attempt to make a re-contention for medium access when the station fails in the contention for the medium access.

13. A program storage device, readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method comprising:

defining a plurality of groups to which a priority has been given, and assigning different DIFSs (Distributed Coordination Function InterFrame Spaces) and maximum back-off times to each group according to the given priority such that a sum of the DIFS and the maximum back-off time of a group to which an arbitrary priority has been given is smaller than a sum of the DIFS and the maximum back-off time of a group having a next lower priority;

organizing stations connected to the wireless LAN (Local Area Network) into defined groups according to a transmission priority;

assigning different fixed back-off times to each station organized into an arbitrary group below a range of the maximum back-off time assigned to a relevant group according to the transmission priority among the stations organized into the relevant group such that the sum of the DIFS and the maximum back-off time of the group to which the arbitrary priority has been given is smaller than the sum of the DIFS and the maximum back-off time of the group having the next lower priority; and

transmitting the assigned DIFS and back-off time to each station in order for each station to reset its back-off timer to the fixed back-off time in every transmission contention by the DIFS assigned to the group into which each station is organized and the back-off time assigned to the stations in the group, and to perform a medium access based on a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance).

14. A program storage device, readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method comprising:

requesting a register of an AP (Access Point) in a wireless LAN (Local Area Network), the AP classifying each station of a plurality of stations into a plurality of priority groups according to a transmission priority to assign different DIFSs (Distributed Coordination Function InterFrame Spaces) to each priority group, and the AP assigning different fixed back-off times according to the transmission priority in the same group and setting the DIFS and the back-off time of each station such that a sum of the DIFS and the back-off time has a fixed difference according to the transmission priority of each station;

receiving and storing the DIFS and the back-off time set into each station from the AP;

attempting to make a contention for medium access by priority with the DIFS and the back-off time set into each station when access to the medium is required for a data transmission; and

resetting a station'"'"'s back-off time to the fixed back-off time to attempt to make a re-contention for medium access when the station fails in the contention for medium access.

15. A program storage device, readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method comprising:

defining a plurality of groups to which a priority is given at an AP(Access Point), and assigning different DIFSs (Distributed Coordination Function InterFrame Spaces) and maximum back-off times to each group according to priority such that a sum of the DIFS and the maximum back-off time of a group to which an arbitrary priority has been given is smaller than the DIFS of the group having the next lower priority;

organizing stations connected to a wireless LAN (Local Area Network) into defined groups according to a transmission priority at the AP;

assigning at the AP different and fixed back-off times to each station organized into an arbitrary group below a range of the maximum back-off time assigned to the relevant group according to the transmission priority among stations organized into the relevant group;

attempting to make a contention for medium access by priority with the DIFS and the back-off time set into the station when access to the medium is required for a data transmission; and

resetting a station'"'"'s back-off time to the fixed back-off time and attempting to make a re-contention for medium access when the station fails in the contention for medium access.