Method and arrangement in a wireless communication system
The present invention relates to a method and arrangement in base station for scheduling user equipments. The base station is adapted to schedule communication from user equipments by sending contention based grants comprising information indicating if the contention based grant should be used for initial transmission or for retransmission. If it is detected that data is not correctly received due to a collision, the information in a following contention based grant is set to indicate that said contention based grant is to be used for initial transmission, while if data is not correctly received, but no collision is detected, the information is set to indicate that the contention based grant is to be used for retransmission. Corresponding method and arrangement in a user equipment is described.
1. A method in a base station for scheduling user equipments in a cell, the base station and the user equipments are comprised in a wireless communication system adapted for contention based transmissions, the method comprising:
sending a contention based grant of a retransmission process to a plurality of user equipments within the cell,
receiving data from at least one of said plurality of user equipments using said contention based grant,
verifying if the data is correctly received from the at least one user equipment, if it is verified that the data is not correctly received:
sending a non-acknowledgement feedback to the plurality of user equipments,
detecting if the data is not correctly received due to a collision, and
sending a following contention based grant belonging to the same retransmission process as the first contention based grant to the plurality of user equipments, wherein the following contention based grant comprises information indicating if the following contention based grant should be used for initial transmission or for retransmission such that:
if it is detected that the data is not correctly received due to a collision, setting the information in the following contention based grant to indicate that said following contention based grant is to be used for initial transmission,
if the data is not correctly received but no collision is detected, setting the information in the following contention based grant to indicate that said following contention based grant is to be used for retransmission.
2. The method according to claim 1 , wherein the information indicating if the following contention based grant should be used for initial transmission or for retransmission is provided as a state bit indicator where a first value indicates that the following contention based grant should be used for initial transmission and a second value indicates that the following contention based grant should be used for retransmission.
3. The method according to claim 2 , wherein the state bit indicator is a New Data Indicator.
4. The method according to claim 1 , wherein the information indicating if the following contention based grant should be used for initial transmission or for retransmission is provided as an identifier used to address the user equipments.
5. The method according to claim 4 , wherein the identifier used to address the user equipments is a Contention Based-Radio Network Temporary Identifier “CB-RNTI”, and wherein different CB-RNTIs are used for indicating if the following contention based grant should be used for initial transmission or for retransmission.
6. An arrangement in a base station for scheduling user equipments in a cell, the base station and the user equipments are comprised in a wireless communication system adapted for contention based transmissions, the base station is adapted to schedule the communication from the user equipments by sending contention based grants, the arrangement comprising:
a transmitter that sends contention based grants and feedback to a plurality of user equipments within the cell,
a receiver that receives data from at least one of the plurality of user equipments,
a verification unit that verifies if the data is correctly received from at least one of the plurality of user equipments,
a detecting unit that detects if the data is not correctly received due to a collision,
a determination unit that generates feedback and set information comprised in a following contention based grant, wherein:
if the data is not correctly received and a collision is detected, the information in the following contention based grant is set to indicate that said second contention based grant is to be used for initial transmission,
if the data is not correctly received but no collision is detected, the information in the following contention based grant is set to indicate that said following contention based grant is to be used for retransmission.
7. A method in a user equipment for assisting a base station in scheduling user equipments in a cell, the base station and the user equipments are comprised in a wireless communication system, the method comprising:
receiving a contention based grant from the base station, comprising information indicating if the contention based grant should be used for initial transmission or retransmission, wherein the information is one of a first contention based-radio network temporary identifier or a second contention based-radio network temporary identifier that is different than the first,
detecting the information comprised in said contention based grant, and
sending data to the base station using said contention based grant, according to either the first or the second contention based-radio network temporary identifier.
8. The method according to claim 7 , wherein the information indicating if the contention based grant should be used for initial transmission or for retransmission is provided as a state bit indicator where a first value indicates that the contention based grant should be used for initial transmission and a second value indicates that the contention based grant should be used for retransmission.
9. The method according to claim 8 , wherein the state bit indicator is a New Data Indicator.
10. The method according to claim 7 , wherein the information indicating if the contention based grant should be used for initial transmission or for retransmission is provided as an identifier used to address the user equipment.
11. The method according to claim 10 , wherein the identifier used to address the user equipment is a Contention Based-Radio Network Temporary Identifier “CB-RNTI”, and wherein different CB-RNTIs are used for indicating if the contention based grant should be used for initial transmission or for retransmission.
12. The method according to claim 7 , further comprising:
if a non-acknowledgement feedback is received and the information comprised in the following grant of the same retransmission process as the first grant indicates that the grant should be used for initial transmission, triggering a radio link control retransmission.
13. The method according to claim 7 , further comprising:
if a non-acknowledgement feedback is received and the information comprised in the following grant of the same retransmission process as the first grant indicates that the grant should be used for retransmission, performing a retransmission of the data with a Hybrid Automatic Repeat Request retransmission.
14. The method according to claim 12 , further comprising:
adding a random delay before the radio link control retransmission of data is performed.
15. The method according to claim 12 , further comprising:
activating a sending prohibit timer, which sending prohibit timer prevents the user equipment from using any contention based grants received from the base station before the sending prohibit timer has timed out.
16. The method according to claim 15 , wherein the sending prohibit timer is arranged to be deactivated when a dynamic grant, dedicated to the user equipment, is received.
17. An arrangement in a user equipment for assisting a base station in scheduling user equipments in a cell, the base station and the user equipments are comprised in a wireless communication system, comprising:
a receiver, adapted to receive a contention based grant comprising information indicating if the contention based grant should be used for initial transmission or for retransmission, wherein the information is one of a first contention based-radio network temporary identifier or a second contention based-radio network temporary identifier that is different than the first,
a detecting unit, adapted to detect said information, and
a transmitter, adapted to transmit data to the base station using said contention based grant, according to either the first or the second contention based-radio network temporary identifier.