Communication on licensed and unlicensed bands

Abstract

Methods and apparatus are provided for communication on licensed carriers and on unlicensed carriers. The base station can perform a clear channel assignment (CCA) to reserve the unlicensed carrier and enable transmissions from user equipments (UEs) on the unlicensed carrier. The base station can configure random access preamble transmission from a UE on the unlicensed carrier. One or more UEs can perform CCA and reserve the unlicensed carrier using transmissions of reference signals. A UE can indicate to the base station a CCA outcome through a licensed carrier. A UE can also experience large propagation loss and may not be able to correctly perform CCA.

What is claimed is: 
     
         1 . A method for wireless communications, comprising:
 performing, by a user equipment (UE), a sensing on a carrier to determine availability of the carrier for the UE to transmit;   transmitting, by the UE, a reference signal (RS) when the UE determines the carrier to be available based on the sensing, wherein the RS transmission is within a first subframe (SF) and over a period that starts from the time the UE determines the carrier to be available and transmits the RS until the end of the first SF; and   transmitting, by the UE, data information in a SF after the first SF.   
     
     
         2 . The method of  claim 1 , wherein the RS includes a sounding RS (SRS) with transmission parameters configured to the UE and wherein the SRS transmission parameters include a spectral comb that is common among all UEs transmitting SRS in response to determining availability of the carrier based on respective sensing. 
     
     
         3 . The method of  claim 2 , wherein performing sensing on a bandwidth of the carrier comprises sensing on a bandwidth of the carrier that does not include the spectral comb. 
     
     
         4 . The method of  claim 1 , wherein the performing sensing on a bandwidth of the carrier is performed by one or more other UEs and the one or more other UEs transmit a RS when the one or more other UEs determine the carrier to be available based on respective sensing and wherein at least one of the one or more other UEs transmit the RS in a different bandwidth of the carrier than the UE. 
     
     
         5 . The method of  claim 1 , further comprising transmitting, by the UE, a signal in a physical uplink control channel (PUCCH) on one other carrier to indicate unavailability of the carrier based on the sensing and wherein the PUCCH has a structure used to also convey acknowledgement signals from UEs or scheduling request signals from UEs. 
     
     
         6 . The method of  claim 1 , wherein the sensing is a detection of a downlink RS and the UE transmits the RS after the transmission of the downlink RS. 
     
     
         7 . A method for wireless communications, comprising:
 generating by a User Equipment (UE) a first data transport block (TB) for transmission in a first subframe (SF) and a second data TB for transmission in a second SF;   performing, by the UE, sensing on a carrier to determine availability of the carrier for the UE to transmit in the first SF or in the second SF;   determining, by the UE, unavailability of the carrier for the UE to transmit in the first SF and availability of the carrier for the UE to transmit in the second SF; and   transmitting, by the UE, the first data TB in a first bandwidth of the carrier in the second SF and the second data TB in a second bandwidth of the carrier in the second SF wherein the first bandwidth and the second bandwidth are not overlapping.   
     
     
         8 . The method of  claim 7 , wherein the first data TB and the second data TB correspond to different hybrid automatic repeat request processes. 
     
     
         9 . A method for wireless communications, comprising:
 performing, by a base station, sensing on a carrier to determine availability of the carrier for the base station to receive in a subframe (SF);   receiving, by the base station, a repetition of a channel transmission in the SF when the base station determines the carrier to be available based on the sensing; and   suspending, by the base station, a reception of the repetition of the channel transmission in the SF when the base station determines the carrier to not be available based on the sensing.   
     
     
         10 . The method of  claim 9 , wherein the base station transmits in the SF in a bandwidth that is different than a bandwidth of the repetition of the channel transmission in the SF. 
     
     
         11 . A User Equipment (UE) comprising:
 an energy detector configured to perform sensing on a carrier to determine availability of the carrier for the UE to transmit; and   a transmitter configured to transmit a reference signal (RS) when the UE determines the carrier to be available based on the sensing, wherein the RS transmission is within a first subframe (SF) and over a period that starts from the time the first UE determines the carrier to be available and transmits the RS until the end of the first SF, and to transmit data information in a SF after the first SF.   
     
     
         12 . The UE of  claim 11 , wherein the RS includes a sounding RS (SRS) with transmission parameters configured to the UE and wherein the SRS transmission parameters include a spectral comb that is common among all UEs transmitting SRS in response to determining availability of the carrier based on respective sensing. 
     
     
         13 . The UE of  claim 12 , wherein the UE performs sensing on a bandwidth of the carrier that does not include the spectral comb. 
     
     
         14 . The UE of  claim 11 , wherein one or more other UEs perform sensing on the carrier and the one or more other UE transmit a RS when the one or more other UEs determine the carrier to be available based on respective sensing and wherein at least one of the one or more other UEs transmits the RS in a different bandwidth of the carrier than the UE. 
     
     
         15 . The UE of  claim 11 , wherein the UE transmits a signal in a physical uplink control channel (PUCCH) on one other carrier to indicate unavailability of the carrier based on the sensing and wherein the PUCCH has a structure used to also convey acknowledgement signals from UEs or scheduling request signals from UEs. 
     
     
         16 . The UE of  claim 11 , wherein the sensing is a detection of a downlink RS and the UE transmits the RS after the transmission of the downlink RS. 
     
     
         17 . A User Equipment (UE), comprising:
 a processor configured to generate a first data transport block (TB) for transmission in a first subframe (SF) and a second data TB for transmission in a second SF;   an energy detector configured to perform sensing on a carrier in the first SF and in the second SF;   a controller configured to process the result of the energy detector, wherein the controller determines unavailability of the carrier for the UE to transmit in the first SF and availability of the carrier for the UE to transmit in the second SF; and   a transmitter configured to transmit the first data TB in a first bandwidth of the carrier in the second SF and the second data TB in a second bandwidth of the carrier in the second SF wherein the first bandwidth and the second bandwidth are not overlapping.   
     
     
         18 . The UE of  claim 17 , wherein the first data TB and the second data TB correspond to different hybrid automatic repeat request processes. 
     
     
         19 . A enhanced NodeB (eNB) comprising:
 an energy detector configured to perform sensing on a carrier to determine availability of the carrier for the base station to receive in a subframe (SF); and   a receiver configured to receive a repetition of a channel transmission in the SF when the base station determines the carrier to be available based on the sensing and to suspend reception of the repetition of the channel transmission in the SF when the base station determines the carrier to not be available based on the sensing;   
     
     
         20 . The eNB of  claim 19 , wherein the base station further comprises of a transmitter configured to transmit in the SF and in a bandwidth that is different than a bandwidth of the repetition of the channel transmission in the SF.