Preamble group selection in random access of wireless networks

1. A method for selecting a transport block size (TBS) of a first uplink message (RACH Msg3) transmitted on a Physical Uplink Shared Channel (PUSCH) during a random access procedure in a User Equipment (UE) accessing a radio access network, comprising:

receiving a pathloss threshold parameter;

estimating a downlink pathloss value indicative of radio link conditions between the UE and a base station (eNB) serving the UE;

selecting from a set of TBS values a smaller value of TBS if the determined pathloss value is greater than an operating power level of the UE minus the pathloss threshold parameter; and

sending a random access request containing an indication of the selected TBS.

2. The method of claim 1 , wherein the pathloss threshold parameter is received from the eNB serving the UE.

3. The method of claim 1 , wherein the smaller value of TBS is selected from the set of TBS values if the TBS required to transmit the RACH Msg3 does not exceed the smaller value, regardless of the pathloss value.

4. The method of claim 1 , wherein a larger value of TBS is selected from the set of TBS values if the pathloss value is less than the operating power level of the UE minus the pathloss threshold parameter and the TBS required to transmit the RACH Msg3 exceeds the smaller TBS value.

5. The method of claim 1 , wherein the TBS is selected from a set of two possible values.

6. A base station (eNB) configured to receive a first uplink message (RACH Msg3) transmitted on a Physical Uplink Shared Channel (PUSCH) during a random access procedure by a User Equipment (UE) accessing a radio access network, comprising:

a transmitter for transmitting a pathless threshold parameter to a UE, wherein said UE performs:

estimating a downlink pathless value indicative of radio link conditions between the UE and said eNB serving the UE;

selecting from a set of Transport Block Size (TBS) values a smaller value of TBS if the determined pathless value is greater than an operating power level of the UE minus the pathless threshold parameter; and

sending a random access request containing an indication of the selected TBS.

7. The base station of claim 6 , wherein the pathless threshold parameter is sent from the eNB serving the UE.

8. The base station of claim 6 , wherein a smaller value of TBS is selected from the set of TBS values if the TBS required to transmit the RACH Msg3 does not exceed the smaller value, regardless of the pathless value.

9. The base station of claim 6 , wherein a larger value of TBS is selected from the set of TBS values if the pathless value is less than the operating power level of the UE minus the pathloss threshold parameter and the TBS required to transmit the RACH Msg3 exceeds the smaller TBS value.

10. The base station of claim 6 , wherein the TBS is selected from a set of two possible values.

11. A method of operating a base station (eNB) configured to receive a first uplink message (RACH Msg3) transmitted on a Physical Uplink Shared Channel (PUSCH) during a random access procedure by a User Equipment (UE) accessing a radio access network, comprising:

transmitting a pathloss threshold parameter to a UE, wherein said UE performs:

estimating a downlink pathloss value indicative of radio link conditions between the UE and said eNB serving the UE;

selecting from a set of Transport Block Size (TBS) values a smaller value of TBS if the determined pathloss value is greater than an operating power level of the UE minus the pathloss threshold parameter; and

sending a random access request containing an indication of the selected TBS.

12. The method of claim 11 , wherein the pathloss threshold parameter is sent from the eNB serving the UE.

13. The method of claim 11 , wherein a smaller value of TBS is selected from the set of TBS values if the TBS required to transmit the RACH Msg3 does not exceed the smaller value, regardless of the pathloss value.

14. The method of claim 11 , wherein a larger value of TBS is selected from the set of TBS values if the pathloss value is less than the operating power level of the UE minus the pathloss threshold parameter and the TBS required to transmit the RACH Msg3 exceeds the smaller TBS value.

15. The method of claim 11 , wherein the TBS is selected from a set of two possible values.

16. A User Equipment (EU) configured to transmit a first uplink message (RACH Msg3) on a Physical Uplink Shared Channel (PUSCH) during a random access procedure, comprising:

a receiver for receiving a pathloss threshold parameter from a base station (eNB);

a processor for estimating a downlink pathloss value indicative of radio link conditions between the UE and said eNB serving the UE;

a selector for selecting from a set of Transport Block Size (TBS) values a smaller value of TBS if the determined pathloss value is greater than an operating power level of the UE minus the pathloss threshold parameter; and

a transmitter for sending a random access request containing an indication of the selected TBS.

17. The user equipment of claim 16 , wherein the pathloss threshold parameter is sent from the eNB serving the UE.

18. The user equipment of claim 16 , wherein a smaller value of TBS is selected from the set of TBS values if the TBS required to transmit the RACH Msg3 does not exceed the smaller value, regardless of the pathloss value.

19. The user equipment of claim 16 , wherein a larger value of TBS is selected from the set of TBS values if the pathloss value is less than the operating power level of the UE minus the pathloss threshold parameter and the TBS required to transmit the RACH Msg3 exceeds the smaller TBS value.

20. The user equipment of claim 16 , wherein the TBS is selected from a set of two possible values.