Random Access Response Process in a Wireless Communications

1 . A method comprising:

a) receiving, by a wireless device to communicate employing a plurality of cells, at least one control message from a base station, said at least one control message:

i) causing in said wireless device:

(1) configuration of a primary cell and at least one secondary cell in said plurality of cells; and

(2) assignment of each of said at least one secondary cell to a cell group in a plurality of cell groups, said plurality of cell groups comprising:

(a) a primary cell group comprising a first subset of said plurality of cells, said first subset comprising said primary cell; and

(b) a secondary cell group comprising a second subset of said at least one secondary cell; and

ii) comprising:

(1) a primary random access response window parameter for said primary cell; and

(2) a power ramping step value for each cell in a first plurality of cells having configured random access resources;

b) transmitting, by said wireless device, a random access preamble with an initial transmission power on random access resources of a cell in said first plurality of cells in response to receiving a control command;

c) monitoring, by said wireless device, a downlink control channel on said primary cell for corresponding random access response, said monitoring performed within a time frame starting at a subframe that contains the end of transmission of said random access preamble plus k subframes and having a duration smaller than or equal to said primary random access response window regardless of which cell in said first plurality of cells is employed for transmission of said random access preamble, k being an integer greater than one; and

d) retransmitting, with an increased transmission power, said random access preamble on said random access resources if no corresponding random access response is received within said time frame, said increased transmission power depending, at least in part, on said power ramping step value corresponding to said cell in said first plurality of cells.

2 . The method of claim 1 , wherein:

a) uplink transmissions by said wireless device in said primary cell group employ a first synchronization signal transmitted on said primary cell as a primary timing reference; and

b) uplink transmissions in said secondary cell group employs a second synchronization signal on an activated secondary cell in said secondary cell group as a secondary timing reference.

3 . The method of claim 1 , wherein said corresponding random access response comprises:

a) a timing advance command;

b) an uplink grant; and

c) a preamble identifier identifying said random access preamble.

4 . The method of claim 3 , further comprising

a) applying, by said wireless device, said timing advance command to uplink transmission timing of a cell group comprising said cell; and

b) transmitting, by said wireless device, uplink data on said cell in radio resources identified in said uplink grant.

5 . The method of claim 1 , wherein said random access response:

a) does not comprise an index identifying a cell group comprising said cell; and

b) does not comprise an index identifying said cell.

6 . The method of claim 1 , wherein an identifier of said random access response depends, at least in part, on:

a) a subframe index associated with a subframe in which said random access preamble is transmitted; and

b) a frequency index associated with a frequency offset in said random access resources employed for transmission of said random access preamble.

7 . The method of claim 1 , further comprising:

a) repeatedly transmitting, by said wireless device, said random access preamble until:

i) said corresponding random access response is received; or

ii) a first predetermined number of transmissions is reached; and

b) if said first predetermined number of transmissions is reached without receiving said corresponding random access response and if said cell is in said secondary cell group, said wireless device:

i) stopping transmission of said random access preamble; and

ii) keeping a connection with said base station active.

8 . The method of claim 1 , further comprising:

a) repeatedly transmitting, by said wireless device, said random access preamble until:

i) said corresponding random access response is received; or

ii) a second predetermined number of transmissions is reached; and

b) if said second predetermined number of transmissions is reached without receiving said corresponding random access response and if said cell is in said primary cell group, said wireless device:

i) indicating a random access problem to a radio resource control layer in said wireless device; and

ii) said radio resource control layer determining a radio link failure.

9 . The method of claim 1 , wherein said random access preamble is transmitted only one time if said corresponding random access response is received after the first transmission of said random access preamble.

10 . The method of claim 1 , wherein said at least one control message comprises a plurality of media access control dedicated parameters comprising a plurality of time alignment timer values, each time alignment timer value being associated with a unique cell group in said wireless device.

11 . The method of claim 1 , wherein said at least one control message further causes in said wireless device configuration of a time alignment timer for each of said plurality of cell groups, said time alignment timer starting or restarting in response to said wireless device receiving a timing advance command to adjust uplink transmission timing of a commanded cell group in said plurality of cell groups.

12 . The method of claim 1 , wherein said at least one control message comprises a plurality of common parameters for said cell, said plurality of common parameters comprising a plurality of random access resource parameters identifying said random access resources.

13 . A wireless device comprising:

a) one or more communication interfaces;

b) one or more processors; and

c) memory storing instructions that, when executed, cause said wireless device to:

i) receive at least one control message from a base station, said at least one control message:

(1) causing in said wireless device:

(a) configuration of a plurality of cells comprising a primary cell and at least one secondary cell; and

(b) assignment of each of said at least one secondary cell to a cell group in a plurality of cell groups, said plurality of cell groups comprising:

 (i) a primary cell group comprising a first subset of said plurality of cells, said first subset comprising said primary cell; and

 (ii) a secondary cell group comprising a second subset of said at least one secondary cell; and

(2) comprising:

(a) a primary random access response window parameter for said primary cell; and

(b) a power ramping step value for each cell in a first plurality of cells having configured random access resources;

ii) transmit a random access preamble with an initial transmission power on random access resources of a cell in said first plurality of cells in response to receiving a control command;

iii) monitor a downlink control channel on said primary cell for a corresponding random access response, said monitoring performed within a time frame having a duration smaller than or equal to said primary random access response window regardless of which cell in said first plurality of cells is employed for transmission of said random access preamble, k being an integer greater than one; and

iv) retransmit, with an increased transmission power, said random access preamble on said random access resources if no corresponding random access response is received within said time frame, said increased transmission power depending, at least in part, on said power ramping step value corresponding to said cell in said first plurality of cells.

14 . The wireless device of claim 13 , wherein said at least one control message is configured to further cause in said wireless device configuration of a time alignment timer for each of said plurality of cell groups, said time alignment timer starting or restarting in response to said wireless device receiving a timing advance command to adjust uplink transmission timing of a commanded cell group in said plurality of cell groups.

15 . The wireless device of claim 13 , wherein said at least one control message comprises a plurality of common parameters for said cell, said plurality of common parameters comprising a plurality of random access resource parameters identifying said random access resources.

16 . The wireless device of claim 13 , wherein:

a) uplink transmissions by said wireless device in said primary cell group employ a first synchronization signal transmitted on said primary cell as a primary timing reference; and

b) uplink transmissions in said secondary cell group employs a second synchronization signal on an activated secondary cell in said secondary cell group as a secondary timing reference.

17 . A wireless device comprising:

a) one or more communication interfaces;

b) one or more processors; and

c) memory storing instructions that, when executed, cause said wireless device to:

i) receive at least one control message from a base station, said at least one control message:

(1) causing in said wireless device assignment of each of said at least one secondary cell to a cell group in a plurality of cell groups, said plurality of cell groups comprising:

(a) a primary cell group comprising a primary cell; and

(b) a secondary cell group comprising a subset of at least one secondary cell; and

(2) comprising:

(a) a primary random access response window parameter for said primary cell; and

(b) a power ramping step value for each cell in a first plurality of cells having configured random access resources;

ii) transmit a random access preamble with an initial transmission power on a cell in said first plurality of cells in response to receiving a control command;

iii) monitor a downlink control channel on said primary cell for a corresponding random access response, said monitoring performed within a time frame having a duration smaller than or equal to said primary random access response window regardless of which cell in said first plurality of cells is employed for transmission of said random access preamble, k being an integer greater than one; and

iv) retransmit, with an increased transmission power, said random access preamble on said cell if no corresponding random access response is received within said time frame, said increased transmission power depending, at least in part, on said power ramping step value corresponding to said cell.

18 . The wireless device of claim 17 , wherein said corresponding random access response comprises:

a) a timing advance command;

b) an uplink grant; and

c) a preamble identifier identifying said random access preamble.

19 . The wireless device of claim 17 , wherein said random access response:

c) does not comprise an index identifying a cell group comprising said cell; and

d) does not comprise an index identifying said cell.

20 . The wireless device of claim 17 , wherein an identifier of said random access response depends, at least in part, on:

a) a subframe index associated with a subframe in which said random access preamble is transmitted; and

b) a frequency index associated with a frequency offset in said random access resources employed for transmission of said random access preamble.