CN111165059B

CN111165059B - Handover procedure for wireless networks using beamforming

Info

Publication number: CN111165059B
Application number: CN201780095270.7A
Authority: CN
Inventors: 贺敬; 李海涛; 张力; 姚春海
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy
Priority date: 2017-09-27
Filing date: 2017-09-27
Publication date: 2023-05-26
Anticipated expiration: 2037-09-27
Also published as: EP3689083A1; WO2019061082A1; CN111165059A; EP3689083A4

Abstract

Various communication systems may benefit from improved methods for handoff when beamforming is used. For example, in the case of intra-network or inter-network handover, it may be advantageous to use a method comprising: the method includes receiving a dedicated random access channel configuration associated with at least one first downlink beam, determining that the apparatus is not in a coverage area of the at least one first downlink beam, and transmitting a random access message for at least one second downlink beam using the dedicated random access channel configuration associated with the at least one first downlink beam based on the determination.

Description

Handover procedure for wireless networks using beamforming

Technical Field

The present invention relates generally to an apparatus, method and computer program for a handover procedure for a wireless network using beamforming.

Background

Embodiments of the present invention relate to wireless or mobile communication networks such as, but not limited to, global system for mobile communications, GSM, wideband code division multiple access, WCDMA, long term evolution, LTE, and/or 5G radio access technologies, which may also be referred to as new radio access technologies NR. Since establishment, LTE has been widely deployed in various environments involving data communication, and the third generation partnership project 3GPP is still developing LTE. Likewise, 3GPP also developed a 5G/NR standard. In general, the goal of 3GPP is to further develop and improve wireless cellular systems.

One of the topics related to LTE and 5G/NR in the 3GPP discussion is mobility. As the mobile terminal moves, it may be necessary to hand over the mobile terminal from one base station to another to maintain connectivity. Such a handover may be required within the network (intra-network handover) or between networks (inter-network handover). In general, improved switching procedures are needed to achieve efficient operation.

Beamforming may be used in wireless networks to steer transmissions and/or receptions to a certain direction for better performance than omni-directional transmissions and/or receptions. However, if the user equipment moves, a continuous connection should be maintained even if beamforming is used.

Similar enhancements may also be employed in other wireless cellular systems such as GSM and WCDMA, for example. In addition to different wireless cellular systems, these enhancements may also be utilized in connection with or in combination with a number of other wireless systems, such as wireless local area networks, WLANs, and worldwide interoperability for microwave access WiMAX systems.

Disclosure of Invention

According to some embodiments, an apparatus may comprise at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: the method includes receiving a dedicated random access channel configuration associated with at least one first downlink beam, determining that the apparatus is not in a coverage area of the at least one first downlink beam, and transmitting a random access message for at least one second downlink beam using the dedicated random access channel configuration associated with the at least one first downlink beam based on the determination.

According to some embodiments, the first method may comprise: the method includes receiving a dedicated random access channel configuration associated with at least one first downlink beam, determining that the apparatus is not in a coverage area of the at least one first downlink beam, and transmitting a random access message for at least one second downlink beam using the dedicated random access channel configuration associated with the at least one first downlink beam based on the determination.

According to some embodiments, an apparatus may comprise at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to: transmitting a dedicated random access channel configuration associated with the at least one first downlink beam to the user equipment, and receiving a random access message for the at least one second downlink beam from the user equipment on the dedicated random access channel associated with the at least one first downlink beam.

According to some embodiments, the second method may comprise: transmitting a dedicated random access channel configuration associated with the at least one first downlink beam to the user equipment, and receiving a random access message for the at least one second downlink beam from the user equipment on the dedicated random access channel associated with the at least one first downlink beam.

According to some embodiments, a computer program product may be configured to control an apparatus to perform a process according to the first or second method.

According to some embodiments, an apparatus may include means for performing the first or second method.

Drawings

For a more complete understanding of example embodiments of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a conventional procedure for handoff;

fig. 2 illustrates an example of a handover procedure according to an embodiment of the present invention;

FIG. 3 illustrates a process according to some embodiments of the invention;

FIG. 4 illustrates a flow chart of a method according to an embodiment of the invention;

FIG. 5 illustrates a flow chart of a method according to an embodiment of the invention;

fig. 6 illustrates an apparatus according to an embodiment of the invention.

Detailed Description

Embodiments of the present invention relate to a handover procedure for a wireless network using beamforming and provide an improved solution for handover when using beamforming.

In the case of wireless communication, radio resources can be allocated in two ways. Dedicated resources may be used by only one device and thus collisions may be avoided. On the other hand, shared resources may be shared among multiple devices, which may lead to situations in which conflicts occur.

For example, the random access channel RACH may be utilized to access a wireless communication system or when a mobile station is handed over from one base station to another within or between networks. Both dedicated resources and shared resources may be used for random access, depending on the situation. Contention-free random access, CFRA, refers to the use of dedicated resources, while contention-based random access, CBRA, refers to the use of shared resources. RACH resources may be, for example, preambles, sequences, frequency resources or time resources. For example, the preamble may include a cyclic prefix CP, a sequence, and a guard time. The sequence may be a Zadoff-Chu sequence or another suitable sequence. Furthermore, RACH resources may also refer to a set of resources, such as two or more preambles, two or more sequences, two or more frequency resources, or two or more time resources. In some embodiments, the RACH resource may be a physical random access channel, a PRACH resource, or a set of PRACH resources.

Dedicated resources and shared resources may also be utilized with beamforming. By using beamforming, transmission and/or reception may be directed to optimize communications by adjusting the radiation pattern of the antenna array on the transmitter and/or receiver side. Thus, beamforming may be bi-directional. For example, beamforming may be seen as directing a power lobe in a certain direction. In the case of beamforming, RACH resources or resource sets may be associated with a downlink beam or set of downlink beams.

The user equipment UE may report measurement information per beam or per beam set to the base station if beamforming or any other similar technique is used. The reported information may indicate a reference signal CSI-RS based on the synchronization signal SS and/or the channel state. In some embodiments, this information may be transmitted to the base station BS in a measurement report. For example, the received information may be used at the BS to adjust the resource allocation accordingly.

Fig. 1 illustrates a procedure for an inter-BS handover (i.e., an intra-network handover). The present invention is described in the context of this architecture, but may be employed in any suitable alternative network architecture, such as for inter-network handover. As a starting point, the UE may be in a CONNECTED state, for example, in an RRC-CONNECTED state. In case of an upcoming handover of a UE, the source base station and the target base station may also utilize reporting information related to the beam or the set of beams. The source BS may receive reporting information from the UE regarding the beam or set of beams, for example, in a measurement information message (110).

Also, the source BS may transmit or forward information about the beam or set of beams to the target BS, e.g., in a handoff request message (120). After receiving this information, the target BS may perform admission control and select the most appropriate beam for the UE. The target BS may also allocate dedicated random access channel resources associated with the most appropriate beam for the UE accordingly. If a set of RACH resources is allocated, those resources may be associated with a set of downlink beams.

The target BS may then transmit a message to the source BS, e.g., an acknowledgement message regarding the upcoming handoff (130). The target BS may also generate RRCConnect ionReconfiguration messages for the UE, which may be part of the message. The RRCConnect ionReconfiguration message may also include an information element related to mobilityControlInfo.

The source BS may transmit information included in the received message to the UE, possibly in the form of a handover command (140). That is, the message may be transmitted from the target BS to the UE via the source BS. In some embodiments, the handover command (140) may include at least the cell identity of the target BS. Alternatively or additionally, the handover command (140) may include information required to access the target BS. Such information may be sufficient for the UE to access the target BS. For example, in some cases, the handover command (140) may include information required for CBRA and/or CFRA. In the case of beamforming, the handover command (140) may also include information about the beam or set of beams.

For example, the target BS may provide the UE with a common RACH configuration as a shared resource and/or a dedicated RACH configuration as a dedicated resource. In some embodiments, the common RACH configuration may be common RACH resources associated with SS blocks that all UEs may use. In addition, in some embodiments, the dedicated RACH configuration may be a dedicated RACH resource associated with a dedicated SS block and/or associated with a dedicated CSI-RS that only one UE may use.

The common RACH configuration may be identical to the configuration information broadcast in the system information block. Thus, the UE may use the common RACH configuration for performing CBRA. On the other hand, the dedicated RACH configuration may be allocated to only one specific UE for performing CFRA.

If the target BS uses beamforming, the dedicated RACH resource configuration may be associated with one beam or set of beams. The configuration may be associated with SS block(s) and/or CSI-RS(s). In some embodiments, one RACH resource may be allocated to a UE for performing CFRA, and in some embodiments, a RACH resource set may be allocated. The dedicated RACH resource configuration may include one RACH resource per beam if a RACH resource set is allocated. For example, if three dedicated RACH resources are configured to be associated with three beams, the dedicated RACH configuration may include one resource per beam.

After receiving the handover command, the UE may handover to or access the target BS. To this end, the UE may utilize information received in the handover command (140), such as, for example, information required for CBRA and/or CFRA. Once the UE has decided to hand over to the target BS, it may send a message, e.g., a hand over complete message (150), to the target BS to access the target BS. The transmission of the message may be accomplished by utilizing the CBRA and/or information required by the CFRA.

However, one problem may be that if beamforming is used at the target BS, the UE may move after it has reported beam measurement information, at least in some cases. In this case, it may occur that one or more beams indicated in the handover command (140) are no longer suitable for accessing the target BS, i.e., the indicated one or more beams may be invalid. For example, the target BS may allocate dedicated RACH resources related to the first downlink beam or the first set of downlink beams to the UE. However, if the UE has moved, the quality of the first downlink beam or the first set of downlink beams may be reduced due to the movement of the UE. On the other hand, it may happen that the quality of the second downlink beam or the second set of downlink beams has improved and that the second downlink beam or the second set of downlink beams will now be better for the UE.

Thus, if in this case the UE would send a message to the target BS using the configured dedicated RACH resources associated with the first downlink beam(s), the target BS would respond by sending a message using the first downlink beam(s). Thus, the UE will not correctly receive the message from the target BS. Thus, the random access procedure will continue and after several attempts the UE will fall back to CBRA. This will cause a significant delay to the switching procedure. One possible solution might be to configure the UE such that it immediately falls back to CBRA as soon as it notices that the first downlink beam(s) are not suitable for communication. However, CBRA should generally be avoided because CBRA is a shared resource and thus collisions may occur, which again increases latency. That is, the dedicated RACH resource (i.e., CFRA) should be used first to provide a better success rate and lower latency than CBRA.

In view of the above drawbacks, certain embodiments of the present invention may improve handover procedures, particularly when beamforming is used at the target BS. Embodiments of the present invention support faster random access for mobile UEs. Furthermore, embodiments of the present invention provide a robust solution in which the UE may not have to fall back to the CBRA even if the UE has moved from the coverage area of the first downlink beam(s) to the coverage area of the second downlink beam(s).

For example, if the UE has moved away from the coverage area of the first downlink beam(s) associated with the indicated dedicated RACH resource, the UE may continue to use the dedicated RACH resource, e.g., if the target BS may receive omnidirectionally. To this end, the target BS may indicate to the UE that it may use the dedicated RACH resources even if it is not moved out of the coverage area of the first downlink beam(s). In this case, the UE may indicate the index of the second downlink beam(s) to the target BS so that the target BS may transmit a response message to the UE using the second downlink beam(s).

Alternatively, if the UE knows that the target BS is able to receive dedicated RACH resources in only a certain direction, the UE may quickly fall back to use CBRA for the second downlink beam(s). This may be beneficial, for example, if the uplink is beamformed in the target BS, i.e., the target BS uses beamforming in reception. For this option, the target BS may indicate to the UE that it cannot use the dedicated RACH resources even if it moves out of the coverage area of the first downlink beam(s). That is, even if the target BS moves out of the coverage area of the first downlink beam(s), it can indicate to the UE whether it can use the dedicated RACH resources.

Even though the allocated dedicated RACH resources may be a set of resources, one issue to consider is how many resources should be included in the set. This results in a trade-off between RACH resource consumption and the likelihood of the UE using CFRA. Once the dedicated RACH resource is configured for a UE, it will be temporarily unavailable to any other UE. Thus, one network implementation may be to configure a small number of dedicated RACH resources, e.g., only one. However, in that case, the possibility that the UE moves out of coverage of the dedicated RACH resource increases as compared to the case in which a large number of RACH resources are to be allocated. In practice, RACH resources are limited and, therefore, it may not be desirable to reserve many dedicated RACH resources for handover of a single UE. Some embodiments of the present invention support saving resources of dedicated RACH resources, since one UE can be allocated fewer resources while also minimizing latency.

Examples of how this can be achieved are provided below. Fig. 2 shows an example of a network scenario according to an embodiment of the invention. The network may comprise a core network, two or more base stations BS (210, 220) and at least one user equipment UE (230). The BS (210) may be a source BS for handover and the BS (220) may be a target BS for handover.

In the context of 5G/NR and intra-network handover, the BSs (210, 220) may be referred to as gNBs. On the other hand, in the context of LTE and intra-network handover, the BSs (210, 220) may be referred to as enbs. In the case of an inter-network handover, BS (210) may be a gNB and BS (220) may be an eNB, or vice versa. However, the present invention is not limited to any particular definition of BS, i.e., one skilled in the art will understand how to apply the present invention to different wireless systems, possibly with various names of BSs (210, 220). Likewise, even though the invention is described using UE (230) as an example, other names may be used, such as mobile station or wireless terminal.

As a starting point, the UE (230) may be associated with the BS (210). In some embodiments, the UE may be in an rrc_connected state. The UE (230) may perform measurements related to one or more beams and report information related to the measurements to the BS (210). If the received power of the first downlink beam (240) is above a threshold (A4 event) or better than the offset of the received power of the serving beam (A3 event), the UE (230) may report, for example, a measurement related to the first downlink beam (240), wherein the serving beam is associated with the BS (210).

After detecting the need for a handoff, the BS (210) may transmit a message to the BS (220) via a fixed backhaul connection. The message may include information related to beam measurements reported by the UE (230). Based on this information, the BS (220) may determine that the UE (230) may use dedicated RACH resources for accessing the BS (220). The dedicated RACH resources may be used for a beam or a set of beams. Referring to fig. 2, a dedicated RACH resource may be associated with a first downlink beam (240).

The BS (220) may then transmit a message including information on the dedicated RACH to the BS (210). In some embodiments, the message may be in the form of an RRCConnectionReconfiguration message, possibly including a mobilityControlInfo information element. The message may also include an indication or instruction as to whether the UE (230) should continue to use the dedicated RACH resource even though it finds that it has moved away from the coverage area of the first downlink beam (240) associated with the dedicated RACH resource. The BS (210) may transmit or forward the message to the UE (230). That is, the message is transmitted from the BS (220) to the UE (230) via the BS (210).

Referring again to fig. 2, the ue may have moved along the trajectory (260) during the handover procedure. Thus, the UE (230) may determine whether the first downlink beam (240) associated with the dedicated RACH is still suitable for communication. In other words, the UE (230) determines whether it has moved away from the coverage area of the first downlink beam (240). The determination may be based on the most recent measurement.

For example, the UE (230) may compare the received power of the first downlink beam (240) to a threshold or offset between the received power of the first downlink beam (240) and the serving beam. For example, if the received power (e.g., reference signal received power, RSRP) is above a threshold, the first downlink beam (240) may be determined to be suitable for communication. However, if the received power is below the threshold, the first downlink beam (240) may be determined to be unsuitable for communication.

In some embodiments, the received power of the first downlink beam (240) may be compared to the received power of the second downlink beam (250). For example, if the received power of the first downlink beam (240) is much lower than the received power of the second downlink beam (250), it may be determined that the first downlink beam (240) is not suitable for communication and the second downlink beam (250) is suitable for communication.

If it is determined that the first downlink beam (240) is not suitable for communication, but the second downlink beam (250) is suitable, the UE (230) may indicate this by transmitting a first message to the BS (220) to access the BS (220). The first message may include information related to the second downlink beam (250). Such information may include, for example, measurement information related to the second downlink beam (250), an index related to the second downlink beam (250), or a measurement report related to the second downlink beam (250). The measurement report may also include information related to one or more other beams. After transmitting the first message to the BS (220), the UE (230) may begin monitoring or receiving a random access response message from the BS (220) on the second downlink beam (250).

Based on the received information about the second downlink beam (250), the BS (220) may then select the second downlink beam (250) as the appropriate beam instead of the first downlink beam (240) and inform the UE (230) accordingly. The BS (220) may also transmit a subsequent downlink message to the UE (230) by using the selected beam. That is, after receiving the random access response message, the UE (230) may use it to configure for accessing the BS (220) and to receive the transmission accordingly.

The new information measured in the first message may relate to one or more downlink beams measured by the UE, or to other auxiliary information that the target BS may use to identify the current location of the UE (230) and the best beam, and/or to an offset between the allocated beam index and the best beam index. In the scenario of fig. 2, the best beam may be the second downlink beam (250), while the allocated beam index is related to the first downlink beam (240).

The transmission of the first message from the UE (230) to the BS (220) may depend on an indication as to whether the UE (230) should continue to use dedicated RACH resources even if it is found to have moved away from the coverage area of the first downlink beam (240). For example, the BS (220) may instruct the UE (230) not to use the dedicated RACH resource. In this case, the UE (230) may immediately start the random access procedure using CBRA, i.e. if the BS (220) finds that it has moved away from the coverage area of the first downlink beam (240), the UE (230) may be instructed to use CBRA. Thus, the UE may use the CBRA with the common RACH resources associated with the beam it is measured to be suitable (e.g., the second downlink beam (250) in fig. 2). In this case, if the dedicated RACH resource associated with the first downlink beam (240) is to be used, the BS (220) is anyway unable to correctly receive the first message, since the BS will receive with beamforming.

Moreover, the BS (220) may instruct the UE (230) to continue using dedicated RACH resources even if it finds that it has moved away from the coverage area of the first downlink beam (240). In this case, the UE (230) may transmit a random access message for a suitable beam (e.g., the second downlink beam (250) in fig. 2) using the dedicated RACH resource. The UE may indicate in the first message, for example, an index of the appropriate beam or some other information related to the appropriate beam. In some embodiments, if the UE (220) is using transmit beamforming, it may form a beam from what it measured as the appropriate downlink beam.

Fig. 3 illustrates a process according to some embodiments of the invention. During or prior to the handover procedure, the UE may receive a dedicated RACH configuration associated with the first downlink beam(s) in step 310. In addition, if the UE finds in step 320 that it has moved away from the coverage area of the first downlink beam(s), the UE may receive instructions related to using the dedicated RACH configuration. In some embodiments, dedicated signaling may be used to receive instructions. However, although such instructions may be optional. In some embodiments, for example, based on the UE's own capabilities, the UE may be configured to use a dedicated RACH configuration if the UE finds that it has moved away from the coverage area of the first downlink beam(s) by default. In this case, the UE may receive the information in a broadcast message such as, for example, in a system information block SIB.

Thereafter, in step 330, the ue may determine whether it is in the coverage area of the first downlink beam(s). If so, the UE may transmit a random access RA message for the first downlink beam(s) using a dedicated RACH configuration associated with the first downlink beam in step 340. Thereafter, the UE may begin monitoring for, and receiving, random access response messages on the first downlink beam(s).

However, if the UE determines that it is not in the coverage area of the first downlink beam(s), the process may proceed to step 350, where the UE may determine whether the dedicated RACH configuration may be used for the second downlink beam(s) based on the received instructions regarding the use of the dedicated RACH configuration, for example, if the UE finds that it has moved away from the coverage area of the first downlink beam(s). If so, the UE may transmit a random access message for the second downlink beam(s) using the dedicated RACH configuration in step 360. On the other hand, if it is determined that the dedicated RACH configuration may not be used for the second downlink beam(s), the UE may directly transmit an RA message for the second downlink beam using CBRA in step 360. Thereafter, the UE may begin monitoring for, receiving random access response messages on the second downlink beam(s). Once the UE has received the random access response message, it may use the information therein to receive subsequent downlink transmissions.

Then, fig. 4 illustrates a method according to some embodiments. In some embodiments, the UE may perform the method. As shown in fig. 4, the method may include receiving a dedicated random access channel configuration associated with at least one first downlink beam at 410. In some embodiments, the UE may receive a dedicated random access channel configuration from the BS. In case of handover, the BS may be a source BS for handover. The at least one first downlink beam and/or the at least one second downlink beam may comprise one downlink beam or a set of downlink beams of the target BS, but not all.

The method may further include determining that the UE is not in a coverage area of at least one first downlink beam at 420. Moreover, the method may include determining that the UE is not in the coverage area of the at least one first downlink beam, for example, by examining measurements related to the at least one first downlink beam. Alternatively or additionally, the method may include determining that the UE is not in the coverage area of the at least one first downlink beam by comparing the received power of the at least one first downlink beam to a threshold. Likewise, the method may further comprise determining that the UE is in the coverage area of the at least one second downlink beam, which may be done by using the same procedure as determining that the UE is not in the coverage area of the at least one first downlink beam.

In some embodiments, the method may further comprise: if or when it is determined that the apparatus is not in the coverage area of the at least one first downlink beam, i.e. the at least one first downlink beam is unsuitable for communication, an instruction to use a dedicated random access channel configuration for transmitting random access messages for the at least one second downlink beam is received.

Additionally or alternatively, the method may further comprise: if or when it is determined that the UE is not in the coverage area of the at least one first downlink beam, instructions are received to not use a dedicated random access channel configuration associated with the at least one second downlink beam. In other words, the method may further comprise: if or in the event that it is determined that the UE is not in the coverage area of the at least one first downlink beam, an instruction to use contention-based random access in relation to the at least one second downlink beam is received.

The method may further comprise: at step 430, a random access message for the at least one second downlink beam is transmitted based on the determination to use a dedicated random access channel configuration associated with the at least one first downlink beam. In the case of a handover, the method may include: a dedicated random access channel configuration for at least one first downlink beam is received from a source base station and a random access message is transmitted to a target base station for handover.

The method may further comprise: the random access message is transmitted using a dedicated random access channel based on the received instruction. In some embodiments, the method may further comprise: after transmission of the random access message, monitoring or receiving a random access response message from the base station is started on the at least one second downlink beam. Moreover, the method may include receiving a subsequent downlink transmission based on information contained in the random access response message.

Alternatively or additionally, the method may include transmitting the random access message using contention-based random access. The decision to transmit the random access message using contention-based random access may be based on the received random access channel configuration instruction without dedicated random access channel configuration for transmitting the random access message for the at least one second downlink beam.

The random access message may include a preamble associated with a dedicated random access channel configuration and information related to at least one second downlink beam. The information may include, for example, an index associated with the at least one second downlink beam, any other information that may be used to calculate an index associated with the at least one second beam, measurement information related to the at least one second downlink, or a new measurement report.

Fig. 5 illustrates another method according to some embodiments. In some embodiments, the method may be performed by a base station. For example, in the case of a handover, the method may be performed by the target base station. The method may include: in 510, a dedicated random access channel configuration associated with the at least one first downlink beam is transmitted to the user equipment. Alternatively or additionally, the method may comprise: an instruction to not use a dedicated random access channel configuration for transmitting random access messages for at least one second downlink beam is transmitted. Such instructions may be given, for example, for a scenario in which the user equipment may determine that the UE is not in the coverage area of the at least one first downlink beam.

In step 520, the method may include: for example, if an instruction to use the dedicated random access channel configuration has been transmitted to transmit a random access message for at least one second downlink beam and the user equipment determines that it is not in the coverage area of at least one first downlink beam, then the random access message for the at least one second downlink beam is received from the user equipment on the dedicated random access channel associated with the at least one first downlink beam. Likewise, the method may further comprise: for example, if an instruction to not use the dedicated random access channel configuration has been transmitted to transmit a random access message for at least one second downlink beam and the user equipment has determined that it is not in the coverage area of at least one first downlink beam, then the random access message is received using contention-based random access.

Fig. 6 illustrates an apparatus (10) according to an embodiment of the invention. For example, the apparatus (10) may be a wireless device such as a user equipment. In other embodiments, such (10) may be, for example, a base station, an access point, a software defined network, an SDN controller, a cloud base station controller or a centralized base station controller.

The wireless device or user device may be a mobile station, an MS provided with wireless communication capabilities (such as a mobile phone or a smart phone or a multimedia device), a computer provided with wireless communication capabilities (such as a tablet computer), a personal data or digital assistant PDA provided with wireless communication capabilities, a portable media player, a digital camera, a camcorder, a navigation unit provided with wireless communication capabilities, or any combination thereof. The wireless device or user device may be a sensor or smart meter or other device that may generally be configured for a single location. In addition, the wireless device or user device may be a device-to-device user device or a device for machine-type communications.

The apparatus (10) may include a processor (22) to process information and perform instructions or operations. The processor (22) may be any type of general purpose or special purpose processor. Although a single processor (22) is shown in fig. 6, multiple processors may be used according to other embodiments. By way of example, the processor (22) may also include one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor DSP, a field programmable gate array FPGA, an application specific integrated circuit (SIC, and processors based on a multi-core processor architecture.

The apparatus (10) may further include a memory (14) coupled to the processor (22) to store information and instructions executable by the processor (22). The memory (14) may be one or more memories and may be of any type suitable to the local application environment and may be implemented using any suitable volatile or non-volatile data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. For example, the memory (14) may include any combination of random access memory RAM, read only memory ROM, a static storage device such as a magnetic or optical disk, or any other type of non-transitory machine or computer readable medium. The instructions stored in the memory (14) may include program instructions or computer program code which, when executed by the processor (22), enable the apparatus (10) to perform the tasks described herein.

The apparatus (10) may also include one or more antennas (not shown) to transmit signals and/or data to the apparatus (10) and/or to receive signals and/or data from the apparatus (10). The apparatus (10) may further include a transceiver (28), the transceiver (28) modulating information onto a carrier waveform for transmission by the antenna(s) and demodulating information received via the antenna(s) for further processing by other elements of the apparatus (10). In other embodiments, the transceiver (28) may be capable of directly transmitting and receiving signals or data.

The processor (22) may perform functions associated with the operation of the apparatus (10) including, but not limited to, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus (10), including processes related to communication resource management.

In certain embodiments, the memory (14) stores software modules that provide functionality when executed by the processor (22). The module may include an operating system (15) that provides operating system functionality for the device (10). The memory may also store one or more functional modules (18), such as applications or programs, to provide additional functionality to the apparatus (10). The components of the apparatus (10) may be implemented in hardware or as any suitable combination of hardware and software.

The described features, advantages, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention.

Moreover, those of ordinary skill in the art will readily appreciate that the invention discussed above may be practiced with steps in a different order and/or with hardware elements in a different configuration than that disclosed. Thus, while the invention has been described based upon these preferred embodiments, it would be apparent to those skilled in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention.

In an exemplary embodiment, an apparatus, such as a user equipment or a base station, may include means for performing the above embodiments, and any combination thereof.

In another exemplary embodiment, an apparatus, such as a user equipment or a base station, may include at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform the above-described embodiments and any combination thereof.

In another exemplary embodiment, a computer program product may be configured to control an apparatus to perform a process according to the above-described embodiments and any combination thereof. The computer program product may be embodied on a non-transitory computer readable medium.

Claims

1. An apparatus for communication, comprising:

means for receiving a dedicated random access channel configuration associated with at least one first downlink beam;

means for determining that the apparatus is not in a coverage area of the at least one first downlink beam; and

means for transmitting a random access message for at least one second downlink beam using the dedicated random access channel configuration associated with the at least one first downlink beam based on the determination.

2. The apparatus of claim 1, further comprising:

means for determining that the apparatus is in a coverage area of the at least one second downlink beam.

3. The apparatus of claim 1, further comprising:

when it is determined that the apparatus is not in the coverage area of the at least one first downlink beam, receiving instructions to transmit the random access message for the at least one second downlink beam using the dedicated random access channel configuration.

4. The apparatus of claim 3, further comprising,

means for transmitting the random access message using the dedicated random access channel based on the received instruction.

5. The apparatus according to any of claims 1-4, wherein the random access message comprises: a preamble associated with the dedicated random access channel configuration and information related to the at least one second downlink beam.

6. The apparatus of any one of claims 1-4, further comprising:

means for starting monitoring or receiving a random access response message from a base station on the at least one second downlink beam after the transmission of the random access message.

7. The apparatus of any one of claims 1-4, further comprising:

means for receiving instructions to use contention-based random access when it is determined that the apparatus is not in the coverage area of the at least one first downlink beam.

8. The apparatus of any one of claims 1-4, further comprising:

means for transmitting the random access message using contention-based random access.

9. The apparatus of any one of claims 1-4, further comprising:

means for receiving the dedicated random access channel configuration for the at least one first downlink beam from a source base station; and

means for transmitting the random access message to a target base station for handover.

10. The apparatus of any of claims 1-4, wherein the random access message comprises measurement information related to the at least one second downlink beam.

11. The apparatus of any one of claims 1-4, further comprising:

means for determining that the apparatus is not in the coverage area of the at least one first downlink beam by comparing the received power of the at least one first downlink beam to a threshold.

12. An apparatus for communication, comprising:

transmitting to the user equipment a dedicated random access channel configuration associated with the at least one first downlink beam; and

means for receiving a random access message for at least one second downlink beam from the user equipment on the dedicated random access channel associated with the at least one first downlink beam, the random access message being transmitted by the user equipment based on a determination that the user equipment is not in a coverage area of the at least one first downlink beam.

13. The apparatus of claim 12, further comprising:

transmitting instructions to use the dedicated random access channel configuration for transmitting the random access message for the at least one second downlink beam when it is determined that the user equipment is not in the coverage area of at least one first downlink beam; and/or

Means for transmitting instructions to not use the dedicated random access channel configuration for transmitting the random access message for the at least one second downlink beam when it is determined that the user equipment is not in the coverage area of the at least one first downlink beam.

14. A method of communication, comprising:

receiving a dedicated random access channel configuration associated with at least one first downlink beam;

determining that the apparatus is not located in a coverage area of the at least one first downlink beam; and

based on the determination, a random access message for at least one second downlink beam is transmitted using the dedicated random access channel configuration associated with the at least one first downlink beam.

15. A method of communication, comprising:

a random access message for at least one second downlink beam is received from the user equipment on the dedicated random access channel associated with the at least one first downlink beam, the random access message being transmitted by the user equipment based on a determination that the user equipment is not in a coverage area of the at least one first downlink beam.