Propagation delay difference reporting for multiple component carriers
The invention relates to methods for reporting on downlink timings by a mobile terminal in a mobile communication system. In order to allow for an aggregation access point to obtain information on propagation delay differences of downlink transmissions on aggregated serving cells, the invention suggests the mobile terminal to report timing information based on reception time difference information for a the target/reference cell. The mobile terminal performs measurements relating to transmission and/or reception time differences on the target/reference cell, and reports same to the eNodeB. The eNodeB compares the measurement result to a predefined maximum propagation delay time difference. Alternatively, the mobile terminal performs the measurements, compares same to the predefined maximum propagation delay time difference and then report the comparison result to the eNodeB.
1. A method, comprising:
determining, by a mobile terminal, a reception time difference or propagation delay difference for downlink transmissions from an aggregation access point to the mobile terminal via a downlink component carrier of a first radio cell and via a downlink component carrier of a second radio cell, respectively;
aligning uplink transmissions transmitted from the mobile terminal to the aggregation access point via an uplink component carrier of the first radio cell and an uplink component carrier of the second radio cell to arrive at the aggregation access point simultaneously, the aligning including adjusting a timing advance for uplink transmissions on the uplink component carrier of the second radio cell based on a timing advance for uplink transmissions on the uplink component carrier of the first radio cell and the determined reception time difference; and
transmitting, by the mobile terminal, a notification to the aggregation access point when at least one of the reception time difference and propagation delay difference exceed a threshold in connection with a receiving window buffer size supported by the mobile terminal.
2. The method according to claim 1 , wherein the downlink component carrier and the uplink component carrier of one of the radio cells is established between the aggregation access point and the mobile terminal, while the downlink component carrier and the uplink component carrier of the other radio cell is established between another access point and the mobile terminal.
3. The method according to claim 2 , wherein the another access point maintains a bi-directional interface to the aggregation access point via which transmissions from the mobile terminal are forwarded to the aggregation access point and transmissions from the aggregation access point are forwarded to the mobile terminal.
4. The method according to claim 2 , wherein the another access point is a Frequency Selective Repeater (FSR) or a Remote Radio Head (RRH) controlled by the aggregation access point, and the aggregation access point is an eNode B.
5. The method according to claim 1 , comprising:
transmitting uplink data via the time aligned first component carrier and the time aligned second component carrier from the mobile terminal to the aggregation access point,
combining the uplink transmissions of the mobile terminal received via the time aligned first component carrier and the time aligned second component carrier by the aggregation access point.
6. The method according to claim 5 wherein the combination of the uplink data of the mobile terminal is performed by an RLC entity of the aggregation access point and/or by a physical layer entity of the aggregation access point.
7. The method according to claim 1 , wherein the time aligned uplink component carrier of the first radio cell is time aligned by the mobile terminal and an access point performing a random access procedure configuring the timing advance for the uplink component carrier of the first radio cell.
8. The method according to claim 1 , comprising receiving a command from the aggregation access point to time align the uplink component carrier of the second radio cell based on the reception time difference.
9. The method according to claim 1 , wherein determining by the mobile terminal a reception time difference or propagation delay difference for downlink transmissions comprises calculating the reception time difference or propagation delay difference by subtracting the time of arrival of the beginning of a sub-frame having a given sub-frame number and being received via the downlink component carrier of the second radio cell from the time of arrival of the beginning of the next sub-frame having the same sub-frame number and being received via the downlink component carrier of the first radio cell.
10. The method according to claim 1 , wherein the mobile terminal maintains a respective timing advance value for each uplink component carrier or maintains a respective timing advance value for each group of one or more uplink component carriers, wherein uplink transmissions on the one or more uplink component carriers of a group experience the same propagation delay.
11. A mobile terminal, comprising:
processing circuitry, which, in operation:
determines a reception time difference or propagation delay difference for downlink transmissions from an aggregation access point to the mobile terminal via a downlink component carrier of a first radio cell and via a downlink component carrier of a second radio cell, respectively; and
aligns uplink transmissions from the mobile terminal to the aggregation access point via an uplink component carrier of the first radio cell and an uplink component carrier of the second radio cell to arrive at the aggregation access point simultaneously, the aligning including adjusting a timing advance for uplink transmissions on the uplink component carrier of the second radio cell based on a timing advance for uplink transmissions on the uplink component carrier of the first radio cell and the determined reception time difference; and
a transmitter, which, in operation:
transmits an uplink transmission to the aggregation access point via the time aligned uplink component carrier of the first radio cell and the time aligned uplink component carrier of the second radio cell; and
transmits a notification to the aggregation access point when at least one of the reception time difference and propagation delay difference exceed a threshold in connection with a receiving window buffer size supported by the mobile terminal.
12. The mobile terminal according to claim 11 , wherein the downlink component carrier and the uplink component carrier of one of the radio cells is established between the aggregation access point and the mobile terminal, while the downlink component carrier and the uplink component carrier of the other radio cell is established between another access point and the mobile terminal.
13. The mobile terminal according to claim 12 wherein the another access point maintains a bi-directional interface to the aggregation access point via which transmissions from the mobile terminal are forwarded to the aggregation access point, and transmissions from the aggregation access point are forwarded to the mobile terminal.
14. The mobile terminal according to claim 12 wherein the another access point is a Frequency Selective Repeater (FSR) or a Remote Radio Head (RRH) controlled by the aggregation access point, and the aggregation access point is an eNode B.
15. The mobile terminal according to claim 11 , wherein the time aligned uplink component carrier of the first radio cell is time aligned by the mobile terminal and an access point performing a random access procedure configuring the timing advance for the uplink component carrier of the first radio cell.
16. The mobile terminal according to claim 11 , wherein the processing circuitry, in operation, responds to a command from the aggregation access point to time align the uplink component carrier of the second radio cell based on the reception time difference.
17. The mobile terminal according to claim 11 , wherein the processing circuitry, in operation, determines the reception time difference or propagation delay difference by subtracting the time of arrival the beginning of a sub-frame having a given sub-frame number and being received via the downlink component carrier of the second radio cell from the time of arrival the beginning of the next sub-frame having the same sub-frame number and being received via the downlink component carrier of the first radio cell.
18. The mobile terminal according to claim 11 , wherein the mobile terminal maintains a respective timing advance value for each uplink component carrier or maintains a respective timing advance value for each group of one or more uplink component carriers, wherein uplink transmissions on the one or more uplink component carriers of a group experience the same propagation delay.