Granted Patent B2

US 11,212,818 · App. 16/272,255 · Granted Dec 28, 2021

Abstract

Claims (40)

1. A method comprising:

transmitting, from a lower layer a Baseband Unit (BBU) of a Cloud based Radio Access Network (C-RAN) to a layer of a Remote Radio Unit (RRU) of the C-RAN, via a fronthaul interface, a data transmission at a target subframe agreed on between the BBU and the RRU, wherein the data is sent before the RRU performs a Listen Before Talk (LBT) operation for the data, wherein the BBU has a Control Unit (CU) that is configured to set a timer, based on an end-to-end latency requirement of data traffic, and is configured to attempt transmission on an unlicensed band of a cell operating in an unlicensed spectrum, and

the CU is configured to transmit an RRU buffer depth (BRU) amount of the data at a CU transmission time threshold at which the CU is required to transmit the data to the RRU to be transmitted over the air (OTA) at T start (CUTth).

2. The method of claim 1 , wherein the CU is further configured to:

for the target subframe, transmit an LBT physical downlink shared channel (PDSCH) request to the RRU;

determine if an LBT PDSCH response is received from the RRU at the CU;

determine if the LBT PDSCH response is successful; and

if the LBT PDSCH response is successful, increment a CU transmission start time (T start ) by a buffer depth of the RRU (T start =T start +B RU .), or

reset the LBT operation if the received LBT PDSCH response is not successful.

3. The method of claim 2 , wherein the CU is further configured to:

increment the CU transmission start time (T start ) by the buffer depth of the RRU (T start =T start +B RU .) when the LBT PDSCH response from the RRU is determined to be successful;

determine if the remaining data is less than the buffer depth of the RRU (B RU ); and

if so, transmit the remaining data to the RRU at the CU transmission time threshold CUT th , or

if not, transmit only the B RU amount of data to the RRU.

4. The method of claim 3 , wherein if the CU determines that the LBT PDSCH response is not received from the RRU at the CU, the CU is further configured to:

determine if a current time is a latest time the CU is expected to receive the LBT PDSCH response from the RRU (T NOW =LBT TH );

if so, update the time when the data is supposed to be transmitted OTA (OTA T start =T start +┌B RU ┐); and

continue to determine if the LBT PDSCH response is not received from the RRU at the CU.

5. The method of claim 3 , wherein if the CU determines the current time is not the latest time the CU is expected to receive the LBT PDSCH response from the RRU (T NOW =LBT TH ), the CU is further configured to:

determine if the current time is equal to the CU transmission time threshold CUT th , and:

if so, transmit B RU worth of data; or

if not, return to determining if the LBT PDSCH response has been received.

6. The method of claim 1 , wherein the RRU is configured to:

determine if an LBT physical downlink shared channel (PDSCH) request is transmitted by the CU;

start an LBT spectrum sensing if the LBT PDSCH request is received from the CU;

determine if an LBT timer for the LBT spectrum sensing has expired; and

if the LBT timer has expired, if the send a failure message to the CU and terminate the LBT process; or

if the LBT timer has not expired, determine that a current time is a start time (T start ) and whether a channel is not acquired; and

if no channel is acquired, increment the T start by x(T start =T start +x) and continue the LBT spectrum sensing.

7. The method of claim 6 , wherein the RRU is further configured to:

determine if a channel is acquired at time Tacq; and

if no channel is acquired, discard any expired symbols from a buffer of the RRU and buffer any newly received data; and

continue the LBT spectrum sensing.

8. The method of claim 7 , wherein the RRU is further configured to:

if the channel is acquired, send an LBT PDSCH success message to the CU;

send a reservation signal OTA until T start ;

send the buffered data OTA and update T start as T start =T start +B RU ;

determine if the buffered data is less than the buffer depth of the RRU B RU ; and

if so, continue to send the buffered data OTA; and

if the remaining buffered data is not less than the buffer depth of the RRU B RU , send the remaining buffered data OTA and perform a data reception check.

Assignments (13)