BACKGROUND

Field of the Disclosure

The present disclosure, for example, relates to wireless communication systems, and more particularly to techniques for accessing a cell using an unlicensed radio frequency spectrum band.

Description of Related Art

Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.

By way of example, a wireless multiple-access communication system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, otherwise known as user equipments (UEs). A base station may communicate with UEs on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station).

Some modes of communication may enable communications with a UE over an unlicensed radio frequency spectrum band, or over different radio frequency spectrum bands (e.g., a licensed radio frequency spectrum band or an unlicensed radio frequency spectrum band) of a cellular network. With increasing data traffic in cellular networks that use a licensed radio frequency spectrum band, offloading of at least some data traffic to an unlicensed radio frequency spectrum band may provide a cellular operator with opportunities for enhanced data transmission capacity. An unlicensed radio frequency spectrum band can also provide wireless access for a venue, such as a stadium or hotel, that may not have access to a licensed radio frequency spectrum band.

Prior to gaining access to, and communicating over, an unlicensed radio frequency spectrum band, a base station or UE may perform a listen before talk (LBT) procedure to contend for access to the unlicensed radio frequency spectrum band. An LBT procedure may include performing a clear channel assessment (CCA) procedure to determine whether a channel of the unlicensed radio frequency spectrum band is available. When it is determined that the channel of the unlicensed radio frequency spectrum band is unavailable, a CCA procedure may be performed for the channel again at a later time.

SUMMARY

The present disclosure, for example, relates to one or more techniques for accessing a cell using an unlicensed radio frequency spectrum band. Under some conditions (e.g., when a cell operating in a licensed radio frequency spectrum band is not available), a UE may access a cell operating in an unlicensed radio frequency spectrum band as the UE's primary cell. One way to access a cell operating in an unlicensed radio frequency spectrum band is to use the random access procedure and radio resource control (RRC) connection setup procedure used for Long Term Evolution (LTE) communications or LTE-Advanced (LTE-A) communications. However, the LTE/LTE-A random access procedure and RRC connection setup procedure involves the transmission of four messages: 1) a random access channel (RACH) preamble transmitted from a UE to a base station; 2) a response transmitted from the base station to the UE; 3) an RRC connection request message transmitted from the UE to the base station; and 4) a channel contention resolution indication and connection configuration message transmitted from the base station to the UE. When transmitted over a licensed radio frequency spectrum band, the four messages are transmitted in a scheduled manner and with guaranteed availability of the licensed radio frequency spectrum band. However, when transmitted over an unlicensed radio frequency spectrum band, each of the four messages may require the performance of one or more CCA procedures to win contention for access to the unlicensed radio frequency spectrum band. Due to the uncertainty of contention for access to the unlicensed radio frequency spectrum band, transmission of the four messages over the unlicensed radio frequency spectrum band may be unreliable or sporadic. Transmission of the four messages over an unlicensed radio frequency spectrum band can also be slow or overhead intensive when compared to transmission of the four messages over a licensed radio frequency spectrum band. The present disclosure describes techniques for reducing the number of messages transmitted to access a cell operating in an unlicensed radio frequency spectrum band.

In an example, a method for wireless communication is described. In one example, the method may include winning a contention for access to an unlicensed radio frequency spectrum band, transmitting a request message upon winning the contention for access to the unlicensed radio frequency spectrum band, and receiving a response message over the unlicensed radio frequency spectrum band. The request message may be transmitted by a UE on an enhanced physical random access channel (ePRACH), to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be received in response to transmitting the request message.

In some examples of the method, the request message may include at least one of a connection setup request; a handover completion indication; a connection reestablishment request; a buffer status report; a device identifier; or a cause value. In some examples of the method, the response message may include at least one of a connection configuration message; a channel contention resolution indication; a scheduled uplink grant; a device identifier; or an indication of a timing adjustment. In some examples of the method, the ePRACH may be transmitted over the unlicensed radio frequency spectrum band. In some examples of the method, the request message may be an unscheduled request message.

In some examples, the method may include receiving, in a system information block, an indication of at least one time window for reception of the response message. In some examples, the method may include monitoring the unlicensed radio frequency spectrum band for the response message during at least one of the at least one time window. In some examples of the method, the indication of the at least one time window may include a first indication of at least one connection establishment time window and a second indication of at least one handover time window.

In some examples, the method may include receiving, in a system information block, a mapping of resource sets of the ePRACH to frequency-interlaced resource blocks. In some examples, the method may include selecting, from among the resource sets of the ePRACH, a resource set for transmitting the request message. In some examples, the method may include receiving, in the system information block, at least one indication of a transport block size for the ePRACH. In some examples, the method may include receiving, in the system information block, at least one power control parameter for the ePRACH.

In some examples, the method may include receiving, in a system information block, an indication of at least one subframe available to perform the transmitting. In some examples, the method may include transmitting a scheduled confirmation message in response to receiving the response message. In some examples, the method may include repeating the transmitting before receiving the response message.

In some examples of the method, the ePRACH may include at least one contention-based resource set. In some examples, the ePRACH may further include at least one dedicated resource set. In some examples, the request message may include a handover completion indication transmitted using one of the at least one dedicated resource set. In some examples, the request message may be transmitted in synchronization with a subframe boundary.

In an example, an apparatus for wireless communication is described. In one example, the apparatus may include means for winning a contention for access to an unlicensed radio frequency spectrum band, transmitting a request message upon winning the contention for access to the unlicensed radio frequency spectrum band, and receiving a response message. The request message may be transmitted by a UE on an ePRACH, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be received over the unlicensed radio frequency spectrum band in response to transmitting the request message. In some examples, the apparatus may further include means for implementing one or more aspects of the method for wireless communication described above.

In an example, another apparatus for wireless communication is described. In one example, the apparatus may include a processor, and memory in electronic communication with the processor. The processor and memory may be configured to win a contention for access to an unlicensed radio frequency spectrum band, to transmit a request message upon winning the contention for access to the unlicensed radio frequency spectrum band, and to receive a response message. The request message may be transmitted by a UE on an ePRACH, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be received over the unlicensed radio frequency spectrum band in response to transmitting the request message. In some examples, the instructions may also be executable by the processor to implement one or more aspects of the method for wireless communication described above.

In an example, a non-transitory computer-readable medium storing computer-executable code for wireless communication is described. In one example, the code may be executable by a processor to win a contention for access to an unlicensed radio frequency spectrum band, to transmit a request message upon winning the contention for access to the unlicensed radio frequency spectrum band, and to receive a response message. The request message may be transmitted by a UE on an ePRACH, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be received over the unlicensed radio frequency spectrum band in response to transmitting the request message. In some examples, the code may also be used to implement one or more aspects of the method for wireless communication described above.

In an example, another method for wireless communication is described. In one example, the method may include transmitting a request message and receiving a response message. The request message may be transmitted by a UE on an ePRACH, without winning a contention for access to an unlicensed radio frequency spectrum band, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be received over the unlicensed radio frequency spectrum band in response to transmitting the request message. In some examples of the method, the request message may be transmitted during a preconfigured uplink CET occasion.

In an example, another apparatus for wireless communication is described. In one example, the apparatus may include means for transmitting a request message and means for receiving a response message. The request message may be transmitted by a UE on an ePRACH, without winning a contention for access to an unlicensed radio frequency spectrum band, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be received over the unlicensed radio frequency spectrum band in response to transmitting the request message. In some examples, the apparatus may further include means for implementing one or more aspects of the method for wireless communication described above.

In an example, another apparatus for wireless communication is described. In one example, the apparatus may include a processor, and memory in electronic communication with the processor. The processor and memory may be configured to transmit a request message and receive a response message. The request message may be transmitted by a UE on an ePRACH, without winning a contention for access to an unlicensed radio frequency spectrum band, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be received over the unlicensed radio frequency spectrum band in response to transmitting the request message. In some examples, the instructions may also be executable by the processor to implement one or more aspects of the method for wireless communication described above.

In an example, a non-transitory computer-readable medium storing computer-executable code for wireless communication is described. In one example, the code may be executable by a processor to transmit a request message and receive a response message. The request message may be transmitted by a UE on an ePRACH, without winning a contention for access to an unlicensed radio frequency spectrum band, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be received over the unlicensed radio frequency spectrum band in response to transmitting the request message. In some examples, the code may also be used to implement one or more aspects of the method for wireless communication described above.

In an example, another method for wireless communication is described. In one example, the method may include winning a contention for access to an unlicensed radio frequency spectrum band, receiving a first request message, and transmitting a response message. The first request message may be received by a base station on an ePRACH, from a first UE, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be transmitted over the unlicensed radio frequency spectrum band, in response to winning the contention for access to the unlicensed radio frequency spectrum band and in response to receiving the first request message from the first UE.

In some examples of the method, the first request message may include at least one of a connection setup request; a handover completion indication; a connection establishment request; a buffer status report; a device identifier; or a cause value. In some examples of the method, the response message may include at least one of a connection configuration message; a channel contention resolution indication; a scheduled uplink grant; a device identifier; or an indication of a timing adjustment. In some cases, the ePRACH may be received over the unlicensed radio frequency spectrum band. In some examples, the method may include requesting from a source base station, between receiving the first request message and transmitting the response message, a context of the first UE.

In some examples, the method may include receiving a respective request message from at least one of a plurality of UEs, with each respective request message including a respective device identifier, and with the first request message including a first device identifier. In these examples, the method may further include resolving channel contention between the plurality of UEs in favor of the first UE, and including the first device identifier in the response message.

In an example, another apparatus for wireless communication is described. In one example, the apparatus may include means for winning a contention for access to an unlicensed radio frequency spectrum band, means for receiving a first request message, and means for transmitting a response message. The first request message may be received by a base station on an ePRACH, from a first UE, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be transmitted over the unlicensed radio frequency spectrum band, in response to winning the contention for access to the unlicensed radio frequency spectrum band and in response to receiving the first request message from the first UE. In some examples, the apparatus may further include means for implementing one or more aspects of the method for wireless communication described above.

In an example, another apparatus for wireless communication is described. In one example, the apparatus may include a processor, and memory in electronic communication with the processor. The processor and memory may be configured to win a contention for access to an unlicensed radio frequency spectrum band, to receive a first request message, and to transmit a response message. The first request message may be received by a base station on an ePRACH, from a first UE, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be transmitted over the unlicensed radio frequency spectrum band, in response to winning the contention for access to the unlicensed radio frequency spectrum band and in response to receiving the first request message from the first UE. In some examples, the instructions may also be executable by the processor to implement one or more aspects of the method for wireless communication described above.

In an example, a non-transitory computer-readable medium storing computer-executable code for wireless communication is described. In one example, the code may be executable by a processor to win a contention for access to an unlicensed radio frequency spectrum band, to receive a first request message, and to transmit a response message. The first request message may be received by a base station on an ePRACH, from a first UE, to access a cell that operates in the unlicensed radio frequency spectrum band. The response message may be transmitted over the unlicensed radio frequency spectrum band, in response to winning the contention for access to the unlicensed radio frequency spectrum band and in response to receiving the first request message from the first UE. In some examples, the code may also be used to implement one or more aspects of the method for wireless communication described above.

In an example, another method for wireless communication is described. In one example, the method may include receiving a first request message and transmitting a response message. The first request message may be received by a base station on an ePRACH, from a first UE, to access a cell that operates in an unlicensed radio frequency spectrum band. The response message may be transmitted over the unlicensed radio frequency spectrum band, in response to receiving the first request message from the first UE and without winning a contention for access to the unlicensed radio frequency spectrum band. In some examples of the method, the request message may be transmitted during a preconfigured downlink CET occasion.

In an example, another apparatus for wireless communication is described. In one example, the apparatus may include means for receiving a first request message and means for transmitting a response message. The first request message may be received by a base station on an ePRACH, from a first UE, to access a cell that operates in an unlicensed radio frequency spectrum band. The response message may be transmitted over the unlicensed radio frequency spectrum band, in response to receiving the first request message from the first UE and without winning a contention for access to the unlicensed radio frequency spectrum band. In some examples, the apparatus may further include means for implementing one or more aspects of the method for wireless communication described above.

In an example, another apparatus for wireless communication is described. In one example, the apparatus may include a processor, and memory in electronic communication with the processor. The processor and memory may be configured to receive a first request message and transmit a response message. The first request message may be received by a base station on an ePRACH, from a first UE, to access a cell that operates in an unlicensed radio frequency spectrum band. The response message may be transmitted over the unlicensed radio frequency spectrum band, in response to receiving the first request message from the first UE and without winning a contention for access to the unlicensed radio frequency spectrum band. In some examples, the instructions may also be executable by the processor to implement one or more aspects of the method for wireless communication described above.

In an example, another non-transitory computer-readable medium storing computer-executable code for wireless communication is described. In one example, the code may be executable by a processor to receive a first request message and transmit a response message. The first request message may be received by a base station on an ePRACH, from a first UE, to access a cell that operates in an unlicensed radio frequency spectrum band. The response message may be transmitted over the unlicensed radio frequency spectrum band, in response to receiving the first request message from the first UE and without winning a contention for access to the unlicensed radio frequency spectrum band. In some examples, the code may also be used to implement one or more aspects of the method for wireless communication described above.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purpose of illustration and description only, and not as a definition of the limits of the claims.

