Methods And Arrangements For Handover

• US 20110310852A1
• Filed: 06/26/2009
• Published: 12/22/2011
• Est. Priority Date: 02/09/2009
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonakliebolaget Lm Ericsson (Publp
• Inventors: Dimou, Konstantinos, Dahiman, Erik
• Granted Patent: US 9,155,010 B2
• Time in Patent Office: Days
• US Class Current: 370/332
• CPC Class Codes: H04W 36/08 Reselecting an access point

Abstract

Methods and arrangements for autonomous handover are provided. In a step, a mobile terminal sends a measurement report to a first network node. In another step, the mobile terminal starts a timer for measuring a wait period. In a further step, the mobile terminal waits until the wait period has expired. In still another step, the mobile terminal measures a signal used for mobility evaluations from the first radio network node. In yet another step, the mobile terminal performs random access to the second radio network node, if appropriate. Furthermore, the first radio network node sends information about random access channel (RACH) characteristics. Moreover, the first radio network node may send the wait period to the mobile terminal. In another step, the first radio network node sends the terminal context to neighbouring radio network nodes.

Claims

1. A Method in a mobile terminal for performing handover from a first radio network node to a second radio network node in a radio communication system, wherein the radio communication system comprises the mobile terminal, the first radio network node and the second radio network node, the method comprising the steps of:

measuring a first signal evaluation value on a first signal received from the first radio network node,

sending a measurement report comprising the first signal evaluation value to the first network node,

in association with the moment of sending the measurement report, starting a timer for measuring a wait period,

when the wait period has expired, measuring a second signal evaluation value on a second signal received from the first radio network node,

obtaining a signal evaluation value difference by subtracting the first signal evaluation value from the second signal evaluation value,

comparing the obtained signal evaluation value difference with a threshold value and

if the signal evaluation value absolute difference is higher than the threshold value, performing random access to the second radio network node.

2. The method according to claim 1, wherein the first and second signal evaluation values comprises any of Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ).

3. The method according to claim 1, wherein the method comprises the further step of:

sending a scheduling request to the first radio network node, if a random access to the second radio network node is to be performed.

4. The method according to claim 1, wherein the value of the wait period is received from the first radio network node.

5. The method according to claim 1, wherein the value of the wait period is set to a multiple of the measurement period used by the mobile terminal.

6. The method according to claim 1, wherein the value of the wait period is set to 1 or 2 times a measurement period comprised in the group:

40 ms, 50 ms and/or 66.66 ms.

7. The method according to claim 1, wherein the threshold value is determined based on at least one value of a handover hysteresis value and the speed of the mobile terminal.

8. An arrangement in a mobile terminal for performing handover from a first radio network node to a second radio network node in a radio communication system, wherein the radio communication system comprises the mobile terminal, the first radio network node and the second radio network node, the arrangement comprising:

a first measurement unit, adapted to measure a first signal evaluation value on a first signal received from the first radio network node,

a sending unit, adapted to send a measurement report comprising the first signal evaluation value to the first network node,

a timer, adapted to measure a wait period,

a second measurement unit, adapted to measure a second signal evaluation value on a second signal received from the first radio network node,

an obtaining unit, adapted to obtain a signal evaluation value difference by subtracting the first signal evaluation value from the second signal evaluation value,

a comparison unit, adapted to compare the obtained signal evaluation value difference with a predetermined threshold value, and

a random access performing unit, adapted to perform random access to the second radio network node.

9. A method in a first radio network node for assisting a mobile terminal in performing handover from a first radio network node to a second radio network node in a radio communication system wherein the radio communication system comprises the mobile terminal, the first radio network node and the second radio network node, the method comprising the steps of:

sending radio signal related information to the mobile terminal, which radio signal related information comprise any of;

random access channel characteristics, synchronization information, and/or cell information.

10. The method according to claim 9, wherein the method comprises the further step of:

sending a wait period to the mobile terminal.

11. The method according to claim 10, wherein the value of the wait period is set to a multiple of the measurement period used by the mobile terminal.

12. The method according to claim 10, wherein the value of the wait period is set to 1 or 2 times a measurement period comprised in the group:

40 ms, 50 ms and/or 66.66 ms.

13. The method according to claim 9, wherein the method comprises the further step of:

receiving a scheduling request from the mobile terminal, if the mobile terminal is going to perform a random access to the second radio network node.

14. The method according to claim 9, wherein the method comprises the further step of:

forwarding a terminal context associated with the mobile terminal, to the second radio network node.

15. An arrangement in a first radio network node for assisting a mobile terminal for performing handover from a first radio network node to a second radio network node in a radio communication system, wherein the radio communication system comprises the mobile terminal, the first radio network node and the second radio network node, the arrangement comprising:

a sender, adapted to send radio signal related information to the mobile terminal, which radio signal related information comprise any of;

random access channel characteristics, synchronization information, and/or cell information.