WO2018027933A1

WO2018027933A1 - Detection-less radio resource management measurement

Info

Publication number: WO2018027933A1
Application number: PCT/CN2016/094950
Authority: WO
Inventors: Li Zhang; Haitao Li; Yanji Zhang; Ren Da
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2016-08-12
Filing date: 2016-08-12
Publication date: 2018-02-15

Abstract

Various communication systems may benefit from appropriate measurements. For example, certain wireless communication systems may benefit from an approach in which detection-less radio resource management measurements may be taken. A method can include determining that handover of a user equipment is possible. The method can also include providing the user equipment with measurement assistance information. The measurement assistance information can be configured to permit the user equipment to hand over from a non-anchor physical resource block of a source cell to a non-anchor physical resource block of a target cell.

Description

DETECTION-LESS RADIO RESOURCE MANAGEMENT MEASUREMENT

BACKGROUND：

Field：

Various communication systems may benefit from appropriate measurements. For example， certain wireless communication systems may benefit from an approach in which detection-less radio resource management measurements may be taken.

Description of the Related Art：

Among other things， the Release 14 (Rel-14) enhanced narrowband (NB) -internet of things (IoT) (eNB-IoT) work item (WI) relates to mobility and service continuity enhancements， including enhancements to connected mode mobility in order to improve service continuity and avoid non-access-stratum recovery for both control plane and user plane solutions without increasing user equipment (UE) power consumption. In Rel-13 NB-IoT， the only mobility mechanism for connected mode is radio link monitoring， which means that when the serving cell is in bad condition， the UE has to trigger radio link failure and close the connection before performing re-establishment (for a user plane solution) to switch to a neighbor cell. Release 13 does not support a handover mobility mechanism that does not close the connection.

The WI also relates to non-anchor physical resource block (PRB) enhancements， such as support of transmission of NB-IoT physical random access channel (NPRACH) on a non-anchor NB-IoT PRB and support of transmission of paging on a non-anchor NB-IoT PRB.

With the current mobility mechanism， when a UE is moving to an intra-frequency neighbor cell， the handover (HO) should be triggered based on the configured radio resource management (RRM) measurement event based on reference signal received power (RSRP) /reference signal received quality (RSRQ) measurements， which can only be performed after the cell detection， after the UE confirms the existence of the cell and has complete downlink synchronization by acquiring primary synchronization signal (PSS) /secondary synchronization signal (SSS) . For LTE intra-frequency HO， there is no need to configure measurement gap to perform intra-frequency cell detection and RRM measurements.

For NB-IoT， NB PSS (NPSS) /NB SSS (NSSS) are transmitted in anchor PRBs only. The UE needs to first switch to anchor PRBs to perform the cell detection before performing NB RSRP (NRSRP) /NB RSRQ (NRSRQ) measurements. It implies that if the UE is working in a non-anchor PRBs， the measurement gap would be required even for NB-IoT intra-frequency HO， where the source and target NB-IoT cells are in the same narrowband.

In addition， upon handover， the UE may need to perform random access (RA) on the anchor PRB of the target cell even if the UE has received a dedicated configuration by radio resource control (RRC) connection reconfiguration message during HO procedure for RA on non-anchor PRB. Also， it may happen that although the non-anchor PRB of a neighbor cell has already satisfied the configured HO threshold， the corresponding anchor PRB may not be good enough to trigger the measurement report. Thus， handover to the non-anchor PRB of an intra-frequency neighbor based on the measurement of anchor PRB of the neighbor cell may not always be feasible.

As NB-PSS and NB-SSS are not transmitted on non-anchor PRBs of a cell， following the Rel-13 idle mode mobility mechanism， the UE in RRC_IDLE camps on the NB-IoT cell on which the UE has received NPSS/NSSS， NB physical broadcast channel (NPBCH) and system information block (SIB) transmissions always， which means anchor PRB only.

If UE can only camp on anchor PRB， the paging and RA load on anchor PRB will be quite big. This will cause a big burden on the paging and RACH， especially considering the huge number of NB-IoT UEs in the network， the large number of repetitions needed for UEs in deep coverage， and the limited number of anchor PRBs considering channel raster.

SUMMARY：

The claims set forth below provide non-limiting examples of certain embodiments， which may be used alone or in combination with one another.

BRIEF DESCRIPTION OF THE DRAWINGS：

For proper understanding of the invention， reference should be made to the accompanying drawings， wherein：

Figure 1 illustrates a method according to certain embodiments.

Figure 2 illustrates another method according to certain embodiments.

Figure 3 illustrates a further method according to certain embodiments.

Figure 4 illustrates a system according to certain embodiments.

DETAILED DESCRIPTION：

When NPRACH and paging can be supported on non-anchor PRB of an NB-IoT cell， it may be useful to enable UE camping on non-anchor PRB in idle mode to， for example， achieve load balancing when setting up a new connection.

Certain embodiments provide detection-less RRM measurement in order to support various functions. For example， certain embodiments may provide efficient intra-frequency HO from a non-anchor PRB of the source cell to the same non-anchor PRB of the target cell. Moreover， certain embodiments may provide fast paging for UE. Additionally， certain embodiments may provide reliable connection establishment by indicating a preferred non-anchor PRB， for example， for Rel-14 eNB-IoT.

Various methods and systems， according to certain embodiments， may enable the eNB-IoT UEs to perform detection-less RRM measurements in both idle and connected modes. These detection-less RRM measurements may permit efficient intra-frequency handover.

To support efficient intra-frequency handover from a non-anchor PRB of the source cell to a non-anchor PRB of the target cell for an NB-IoT UE in connected mode， the source cell can first provide the UE with the measurement assistance information that helps the UE to perform the detection-less RRM measurements of the intra-frequency neighbor cells. The measurement assistance information can contain， for example， the following information elements： physical cell identifiers (PCIs) used in the intra-frequency neighbor cells； narrowband reference signal (NB-RS) subframe locations of the neighbor cells， as NB-RSs may not be transmitted in all subframes； and timing offsets between the neighboring cells and the serving cell on the non-anchor PRB if， for example， those cells are not time-synchronized.

With the above assistance information available， the UE may be able to perform the detection-less RRM measurements without the need of a measurement gap， because the UE may know exactly when and where the NB-RS are transmitted from the non-anchor PRB of neighboring cells， as well as the exact NB-RS patterns. Thus， the UE may be able to measure NRSRP/NRSRQ of the neighboring cells for supporting intra-frequency handover directly from one non-anchor PRB of the source cell to another non-anchor PRB of the target cell. Intra-frequency handover efficiency and reliability can be significantly improved without the need to configure the measurement gap for cell detection and identification on anchor PRBs of the neighboring cells during handover procedure.

Certain embodiments may also incorporate fast paging from non-anchor cartier. The paging transmission over non-anchor PRB for Rel-14 NB-IoT may resemble the enhanced machine type communication (eMTC) scheme， as to assigning the PRB for paging transmission. For example， the PRB may be derived from the UE_ID. However， this kind of selection does not consider the radio link situation of the PRB. Thus the selected PRB might not be able to provide reliable paging transmission.

Normally the eNB can configure the PRB that could provide a more stable radio link connection for the UE in CONNECTED state. The PRB that the UE used in connected mode may be a good candidate for receiving paging in idle mode.

When an eNB-IoT UE goes into idle after working with a non-anchor PRB， the UE may try to monitor paging from this last serving non-anchor PRB unless a cell reselection has been triggered. The last serving eNB may attempt to page the UE from the non-anchor PRB where the UE was working in CONNECTED state firstly. If there is no paging response， the eNB could page the UE from other cells.

The last serving non-anchor PRB information could be provided to the MME when the connection is released and included in the paging message from MME later.

The fast paging could be requested by the UE or enabled by an eNB based on the UE’s capability， such the mobility status information of the UE， or the like. If fast paging is not configured， the UE can then detect the paging message from the derived PRB according to a default approach， such as an previous approach.

NB-IoT UEs may have low mobility. For example， a given UE may be stationary or may rarely move. Thus， the fast paging scheme according to certain embodiments may benefit a UE with low mobility by greatly improving the successful rate of paging， reducing the paging delay， and improving radio resource utilization efficiency.

Detection-less RRM measurements may also be used to support reliable connection establishment. When the UE is in idle state， the eNB may broadcast the measurement assistance information that helps the UE to perform the detection-less RRM measurements of the non-anchor PRBs of the same cell. The broadcast measurement assistance information can contain， for example， the following information elements： PCIs used in the non-anchor PRBs； NB-RS subframe locations of the non-anchor PRBs， as NB-RSs may not be transmitted in all subframes； timing offsets between the neighboring cells and the serving cell if those cells are not time-synchronized； and timing offsets between the non-anchor PRB and the anchor PRB of the serving cell if those PRBs are not time-synchronized.

With the above information， the eNB-IoT UE may be able to perform the detection-less RRM measurements on the non-anchor PRBs and select the most suitable PRB for reliable connection establishment. During connection set up， the UE may indicate the preferred non-anchor PRB to the cell， for example the carrier with the strongest NRSRP/NRSRQ measurements.

The UE may start PRACH from the preferred non-anchor carrier. Thus， the eNB can know implicitly the selected non-anchor carrier from UE. Alternatively， the indication of the preferred cell may be included in message 3 of the NPRACH procedure.

After getting the preferred non-anchor PRB from the UE， the network may assign the UE to the preferred non-anchor PRB. This assignment may， for example， enhance reliability for connection establishment and the data transmission that follows.

Figure 1 illustrates a method according to certain embodiments. As shown in Figure 1， the method can include， at 110， determining that handover of a user equipment is possible. The method can also include， at 120， providing the user equipment with measurement assistance information. The measurement assistance information can be configured to permit the user equipment to hand over from a non-anchor physical resource block of a source cell to a non-anchor physical resource block of a target cell.

The measurement assistance information can include various information such as at least one the following： a physical cell identifier used in an intra-frequency neighbor cell； a narrowband reference signal subframe location of the neighbor cell； a timing offset between the neighboring cell and a serving cell on the non-anchor physical resource block， a timing offset between the non-anchor physical resource block and the anchor physical resource block of the serving cell； a timing offset between the neighboring cell and the serving cell； or any combination thereof.

Providing the measurement assistance information can include broadcasting the measurement assistance information. Other ways of delivering the measurement assistance information are also permitted.

The method can also include， at 130， receiving measurement assistance information. This can be the same information provided at 120. The method can further include， at 140， handing over from a non-anchor physical resource block of a source cell to a non-anchor physical resource block of a target cell， based on the measurement assistance information.

The handing over can be performed without configuring a measurement gap for cell detection and identification an anchor physical resource block. For example， the handing over can include performing one or more detection-less radio resource management measurements.

Figure 2 illustrates another method according to certain embodiments. As shown in Figure 2， the method can include， at 210， releasing a connection to a user equipment. The method can also include， at 220， providing last serving non-anchor physical resource block information to a mobility management entity when the connection is released.

The last serving non-anchor physical resource block information can be provided to the mobility management entity based on a request from the user equipment or based on detection of a capability of the user equipment.

The method can include， at 230， receiving last serving non-anchor physical resource block information at a mobility management entity when a connection to a user equipment is released. This can be the same information provided at 220. The method can further include， at 240， paging the user equipment based on the last serving non-anchor physical resource block information.

Figure 3 illustrates a further method according to certain embodiments. The method can include， at 310， determining that a user equipment is in idle state. The method can also include， at 320， providing the user equipment with measurement assistance information. The measurement assistance information can be configured to permit the user equipment to connect to a non-anchor physical resource block of a cell.

As in the example of Figure 1， the measurement assistance information can include one or more of the following： a physical cell identifier used in an intra-frequency neighbor cell； a narrowband reference signal subframe location of the neighbor cell； a timing offset between the neighboring cell and a serving cell on the non-anchor physical resource block， a timing offset between the non-anchor physical resource block and the anchor physical resource block of the serving cell； a timing offset between the neighboring cell and the serving cell； or any combination thereof.

Providing the measurement assistance information can include broadcasting the measurement assistance information.

The method can further include， at 330， receiving measurement assistance information. This can be the same information provided at 320. The method can additionally include， at 340， connecting to a non-anchor physical resource block of a cell， based on the measurement assistance information.

The connecting can include， at 342， performing detection-less radio resource management measurements on a non-anchor physical resource block. The connecting can also include， at 344， selecting a physical resource block for connection establishment based on the measurements. The connecting can additionally include， at 346， indicating， implicitly or explicitly， the physical resource block to the cell.

In Figures 1 and 3， the determination step may be omitted. For example， the resource measurement assistance information may be provided regardless of any prior determination that the UE is idle or may possibly hand over.

Figure 4 illustrates a system according to certain embodiments of the invention. It should be understood that each block of the flowchart of Figures 1 through 3 may be implemented by various means or their combinations， such as hardware， software， firmware， one or more processors and/or circuitry. In one embodiment， a system may include several devices， such as， for example， network element 410 and user equipment (UE) or user device 420. The system may include more than one UE 420 and more than one network element 410， although only one of each is shown for the purposes of illustration. A network element can be an access point， a base station， an eNode B (eNB) ， or any other network element， such as a mobility management entity (MME) or any other element shown or described herein.

Each of these devices may include at least one processor or control unit or module， respectively indicated as 414 and 424. At least one memory may be provided in each device， and indicated as 415 and 425， respectively. The memory may include computer program instructions or computer code contained therein， for example for carrying out the embodiments described above. One or

more transceiver

416 and 426 may be provided， and each device may also include an antenna， respectively illustrated as 417 and 427. Although only one antenna each is shown， many antennas and multiple antenna elements may be provided to each of the devices. Other configurations of these devices， for example， may be provided. For example， network element 410 and UE 420 may be additionally configured for wired communication， in addition to wireless communication， and in such a

case antennas

417 and 427 may illustrate any form of communication hardware， without being limited to merely an antenna.

Transceivers

416 and 426 may each， independently， be a transmitter， a receiver， or both a transmitter and a receiver， or a unit or device that may be configured both for transmission and reception. The transmitter and/or receiver (as far as radio parts are concerned) may also be implemented as a remote radio head which is not located in the device itself， but in a mast， for example. It should also be appreciated that according to the “liquid” or flexible radio concept， the operations and functionalities may be performed in different entities， such as nodes， hosts or servers， in a flexible manner. In other words， division of labor may vary case by case. One possible use is to make a network element to deliver local content. One or more functionalities may also be implemented as a virtual application that is provided as software that can run on a server.

A user device or user equipment 420 may be a mobile station (MS) such as a mobile phone or smart phone or multimedia device， a computer， such as a tablet， provided with wireless communication capabilities， personal data or digital assistant (PDA) provided with wireless communication capabilities， portable media player， digital camera， pocket video camera， navigation unit provided with wireless communication capabilities or any combinations thereof. The user device or user equipment 420 may be a sensor or smart meter， or other device that may usually be configured for a single location.

In an exemplifying embodiment， an apparatus， such as a node or user device， may include means for carrying out embodiments described above in relation to Figures 1 through 3.

Processors

414 and 424 may be embodied by any computational or data processing device， such as a central processing unit (CPU) ， digital signal processor (DSP) ， application specific integrated circuit (ASIC) ， programmable logic devices (PLDs) ， field programmable gate arrays (FPGAs) ， digitally enhanced circuits， or comparable device or a combination thereof. The processors may be implemented as a single controller， or a plurality of controllers or processors. Additionally， the processors may be implemented as a pool of processors in a local configuration， in a cloud configuration， or in a combination thereof.

For firmware or software， the implementation may include modules or units of at least one chip set (e.g.， procedures， functions， and so on) .

Memories

415 and 425 may independently be any suitable storage device， such as a non-transitory computer-readable medium. A hard disk drive (HDD) ， random access memory (RAM) ， flash memory， or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor， or may be separate therefrom. Furthermore， the computer program instructions may be stored in the memory and which may be processed by the processors can be any suitable form of computer program code， for example， a compiled or interpreted computer program written in any suitable programming language. The memory or data storage entity is typically internal but may also be external or a combination thereof， such as in the case when additional memory capacity is obtained from a service provider. The memory may be fixed or removable.

The memory and the computer program instructions may be configured， with the processor for the particular device， to cause a hardware apparatus such as network element 410 and/or UE 420， to perform any of the processes described above (see， for example， Figures 1 through 3) . Therefore， in certain embodiments， a non-transitory computer-readable medium may be encoded with computer instructions or one or more computer program (such as added or updated software routine， applet or macro) that， when executed in hardware， may perform a process such as one of the processes described herein. Computer programs may be coded by a programming language， which may be a high-level programming language， such as objective-C， C， C++， C#， Java， etc.， or a low-level programming language， such as a machine language， or assembler. Alternatively， certain embodiments of the invention may be performed entirely in hardware.

Furthermore， although Figure 4 illustrates a system including a network element 410 and a UE 420， embodiments of the invention may be applicable to other configurations， and configurations involving additional elements， as illustrated and discussed herein. For example， multiple user equipment devices and multiple network elements may be present， or other nodes providing similar functionality， such as nodes that combine the functionality of a user equipment and an access point， such as a relay node.

Certain embodiments may have various benefits and/or advantages. For example， according to certain embodiments direct HO between non-anchor PRB from source to target cell can be supported for connected mode. This may avoid requiring that HO to a non-anchor PRB must be via the anchor PRB.

Moreover， according to certain embodiments， a UE in idle mode can camp on the “last serving” non-anchor PRB. If mobility and system information change are rare events， a lot of paging and NPRACH overhead can be saved on the anchor PRB. With UE indication of preferred PRB of a selected cell， the network can assign the UE to the preferred PRB for better connection condition.

One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order， and/or with hardware elements in configurations which are different than those which are disclosed. Therefore， although the invention has been described based upon these preferred embodiments， it would be apparent to those of skill in the art that certain modifications， variations， and alternative constructions would be apparent， while remaining within the spirit and scope of the invention.

List of Abbreviations

IoT Internet of Things

NB-IoT Narrowband IoT

eNB-IoT Enhanced NB-IoT

RACH Random Access Channel

NPRACH Narrowband Physical Random Access Channel

PSS Primary Synchronization Signal

NPSS Narrowband Primary Synchronization Signal

SSS Secondary Synchronization Signal

NSSS Narrowband Secondary Synchronization Signal

NB-RS Narrowband Reference Signal

HO Handover

PCI Physical cell identification

PRB Physical resource block

RSRP Reference Signal Received Power

NRSRP Narrowband RSRPRSRQ Reference Signal Received Quality

NRSRQ Narrowband RSRQ

Claims

A method， comprising：

determining that handover of a user equipment is possible；

providing the user equipment with measurement assistance information，

wherein the measurement assistance information is configured to permit the user equipment to hand over from a non-anchor physical resource block of a source cell to a non-anchor physical resource block of a target cell.
The method of claim 1， wherein the measurement assistance information comprises at least one a physical cell identifier used in an intra-frequency neighbor cell； a narrowband reference signal subframe location of the neighbor cell； a timing offset between the neighboring cell and a serving cell on the non-anchor physical resource block， a timing offset between the non-anchor physical resource block and the anchor physical resource block of the serving cell； a timing offset between the neighboring cell and the serving cell； or any combination thereof.
The method of claim 1 or claim 2， wherein providing the measurement assistance information comprises broadcasting the measurement assistance information.
A method， comprising：

receiving measurement assistance information； and

handing over from a non-anchor physical resource block of a source cell to a non-anchor physical resource block of a target cell， based on the measurement assistance information.
The method of claim 4， wherein the measurement assistance information comprises at least one a physical cell identifier used in an intra-frequency neighbor cell； a narrowband reference signal subframe location of the neighbor cell； a timing offset between the neighboring cell and a serving cell on the non-anchor physical resource block， a timing offset between the non-anchor physical resource block and the anchor physical resource block of the serving cell； a timing offset between the neighboring cell and the serving cell； or any combination thereof.
The method of claim 4 or 5， wherein the handing over is performed without configuring a measurement gap for cell detection and identification an anchor physical resource block.
The method of any of claims 4-6， wherein the handing over comprises performing detection-less radio resource management measurements.
A method， comprising：

releasing a connection to a user equipment； and

providing last serving non-anchor physical resource block information to a mobility management entity when the connection is released.
The method of claim 8， wherein the last serving non-anchor physical resource block information is provided to the mobility management entity based on a request from the user equipment or based on detection of a capability of the user equipment.
A method， comprising：

receiving last serving non-anchor physical resource block information at a mobility management entity when a connection to a user equipment is released； and

paging the user equipment based on the last serving non-anchor physical resource block information.
A method， comprising：

determining that a user equipment is in idle state；

providing the user equipment with measurement assistance information，

wherein the measurement assistance information is configured to permit the user equipment to connect to a non-anchor physical resource block of a cell.
The method of claim 11， wherein the measurement assistance information comprises at least one a physical cell identifier used in an intra-frequency neighbor cell； a narrowband reference signal subframe location of the neighbor cell； a timing offset between the neighboring cell and a serving cell on the non-anchor physical resource block， a timing offset between the non-anchor physical resource block and the anchor physical resource block of the serving cell； a timing offset between the neighboring cell and the serving cell； or any combination thereof.
The method of claim 11 or 12， wherein providing the measurement assistance information comprises broadcasting the measurement assistance information.
A method， comprising：

receiving measurement assistance information； and

connecting to a non-anchor physical resource block of a cell， based on the measurement assistance information.
The method of claim 14， wherein the measurement assistance information comprises at least one a physical cell identifier used in an intra-frequency neighbor cell； a narrowband reference signal subframe location of the neighbor cell； a timing offset between the neighboring cell and a serving cell on the non-anchor physical resource block， a timing offset between the non-anchor physical resource block and the anchor physical resource block of the serving cell； a timing offset between the neighboring cell and the serving cell； or any combination thereof.
The method of claim 14 or 15， wherein the connecting comprises performing detection-less radio resource management measurements on a non-anchor physical resource block.
The method of claim 16， wherein the connecting comprises selecting a physical resource block for connection establishment based on the measurements.
The method of claim 17， wherein the connecting comprises indicating， implicitly or explicitly， the physical resource block to the cell.
An apparatus， comprising：

means for performing the method according to any of claims 1-18.
An apparatus， comprising：

at least one processor； and

at least one memory including computer program code，

wherein the at least one memory and the computer program code are configured to， with the at least one processor， cause the apparatus at least to perform the method according to any of claims 1-18.
A computer program product encoding instructions for performing a process， the process comprising the method according to any of claims 1-18.
A non-transitory computer-readable medium encoded with instructions that， when executed in hardware， perform the method according to any of claims 1-18.