Patent Description:
Random Access in long term evolution (LTE) is specified in <NUM>rd Generation Partnership Project (3GPP) documents <NUM> and <NUM>. A number of signaling steps are required for a wireless device (WD) to perform initial access, and also for every time the WD transitions from "idle" mode to "connected" mode.

To handle small data transfers more efficiently, the 3GPP has studied methods to reduce the signaling overhead when transitioning from radio resource control (RRC) idle to RRC connected. One of the chosen solutions is introduction of an 'RRC resume' procedure, which is based on re-using the WD context from the previous RRC connection for the subsequent RRC connection setup. By storing the WD context in the base station, e.g., evolved node B (eNB), the signaling required for security activation and bearer establishment at the next RRC idle to RRC connected transition can be avoided.

RRC resume is realized by introducing two new procedures `RRC Suspend' and 'RRC Resume'. The eNB suspends a connection by sending a `RRC Connection Suspend' message to the WD. This is shown in <FIG>. This may happen for example after the WD has been inactive for a certain period. Both the WD and eNB stores the WD context and the associated identifier (referred to as Resume ID). The WD context contains, for example, bearer configuration and security related parameters.

At the next transition from RRC idle to RRC connected, the WD resumes the connection by sending a 'RRC Connection Resume Request' to the eNB. This is shown in <FIG>. The message contains the previously received Resume ID which the eNB uses to retrieve the WD context. An authorization token is also provided to allow the eNB to securely identify the WD. Assuming the WD context is found and the authorization token is valid, the eNB responds with a "RRC Connection Resume" to confirm that the connection is being resumed. The WD acknowledges the reception by sending "RRC Connection Resume Complete".

RRC resume procedure is not necessarily limited to a single cell or single eNB, but can also be supported across eNBs. Inter eNB connection resumption is handled using context fetching, whereby the resuming eNB retrieves the WD context from the suspending eNB over the X2 interface. The resuming eNB provides the Resume ID which is used by the suspending eNB to identify the WD context.

Note that the RRC Connection Suspend, RRC Connection Resume Request, RRC Connection Resume, and RRC Connection Resume Complete messages may differ in name in the final specification of RRC resume by the 3GPP. Further details regarding RRC connection establishment may be found in the 3GPP technical specification <NUM> V14. Shortened processing time is known in the neighbouring fields of Random Access, for example from document <NPL>).

In current LTE, the WD is expected to respond to a RRC Connection Resume message from the network with a RRC Connection Resume Complete. Before the WD responds, it applies the new configuration as indicated by the network.

In LTE, processing time for RRC procedures is specified in the RRC protocol specification. For example, processing time is specified for RRC connection establishment (RRC connection setup/RRC connection resume) and RRC connection reconfiguration procedures.

In legacy LTE, a WD sends RRC Connection Resume Complete with timing n+k subframes after receiving RRC Connection Resume (where n is the time at which the DL RRC message is received, and k is the processing delay requirement). The timing n+k is referred to herein as a legacy processing time. However, in some cases the processing time requirement is smaller than permitted by the legacy processing time.

Some embodiments advantageously provide methods and devices for setting a processing time for a wireless device, WD, to respond to a radio resource control, RRC, connection resume message. The invention is defined by the independent claims <NUM>, <NUM>, <NUM> and <NUM>.

Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to control plane latency reduction by indication of processing requirements. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

The claimed invention corresponds to the <FIG> , <FIG> , <FIG> , <FIG> and to the related text of the description. The rest of the description and the figures disclose non-claimed features and are presented for illustration purposes only.

In legacy LTE, a WD sends RRC Connection Resume Complete with timing n+k subframes after receiving RRC Connection Resume. However, in some cases the processing requirement is smaller and the processing can be done faster. As a means to reduce the transition time from IDLE to CONNECTED, the WD context from RRC CONNECTED can be stored by the network, and later fetched when the WD should resume to CONNECTED mode. This enables a shorter transition time.

Although reference is made to LTE and 3GPP compliant systems, the embodiments described herein are not so limited and may be implemented in other wireless communication systems. The term wireless device or mobile terminal used herein may refer to any type of wireless device communicating with a network node and/or with another wireless device in a cellular or mobile communication system. Examples of a wireless device are user equipment (UE), target device, device to device (D2D) wireless device, machine type wireless device or wireless device capable of machine to machine (M2M) communication, PDA, tablet, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongle, etc..

The term base station, e.g. a Radio Base Station (RBS), sometimes may be referred to herein as, e.g., evolved NodeB "eNB", "eNodeB", "NodeB", "B node", or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as, e.g., macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the wireless devices within range of the base stations. In the context of this disclosure, downlink (DL) refers to the transmission path from the base station to the wireless device. Uplink (UL) refers to the transmission path in the opposite direction, i.e., from the wireless device to the base station.

In 3GPP LTE, base stations may be directly connected to one or more core networks. Further, although embodiments are described with reference to base stations, it is understood that the embodiments described herein can be implemented in or across any suitable network node, of which base stations are a type.

Embodiments provide a way to signal the processing requirement to a new WD in the RRC Connection Resume. If short processing is indicated, the WD replies with RRC Connection Resume Complete along with new timing n+knew subframes. It will be understood by those skilled in the art that the timings referred to herein can be defined in terms of subframes or any other suitable timing metric (e.g., milliseconds, seconds, frames, transmission time intervals, slots, symbols, etc).

<FIG> is a diagram of a wireless communication network <NUM> configured for setting a processing time between an idle state and a connected state of a WD. The system typically includes multiple base stations referred to collectively herein as base stations <NUM>. For ease of reference only two base stations 20A and 20B (collectively referred to herein as base stations <NUM>) are shown in <FIG>. The base stations <NUM> typically may be in communication with a plurality of wireless devices referred to collectively herein as WDs <NUM>. For ease of reference only two WDs 40A and 40B are shown in <FIG>. The base stations <NUM> may also be in communication with each other by an X2 interface. Further, the base stations <NUM> may typically be in communication with a network cloud <NUM> that may include a backhaul network, the Internet and the public switched telephone network (PSTN). Although embodiments are described herein with reference to certain functions being performed by base stations <NUM>, it is understood that the functions can be performed in other network nodes and elements. It is also understood that the functions of the base stations <NUM> or other network nodes can be distributed across network cloud <NUM> so that other nodes can perform one or more functions or even parts of functions described herein.

In some embodiments described herein, the base stations <NUM> may include a short processing time conditions determiner <NUM> to determine whether conditions exists to indicate to the WD <NUM> that a short processing time is to be implemented. In some embodiments, the WDs <NUM> may include a transmission time determiner <NUM> for determining whether the time for transmitting the RRC connection resume complete message is to be sent after a short processing time or after a legacy processing time.

During RRC Resume, the base station <NUM> fetches the stored context for a WD <NUM>. In the context, the base station <NUM> may identify a WD <NUM> as being a new WD. For a new WD, the base station <NUM> identifies the processing steps required in the WD <NUM> before it can transmit the RRC Connection Resume Complete message.

The condition for which processing time to apply may be based on complexity. If no complex reconfiguration is needed in the WD <NUM>, the base station <NUM> may conclude that a shorter processing time can be applied. Otherwise, a legacy processing time may be applied.

In an embodiment, if a predefined set of reconfigurations and/or steps of reconfiguration (or a subset thereof) is required in the WD <NUM>, the base station <NUM> may conclude that a shorter processing time can be applied. In some embodiments, when a reconfiguration comprises only parameters which must be signalled (i.e., cannot be omitted from signaling) and other parameters remain the same and may be restored from a stored/cached WD context, the base station <NUM> may conclude that a shorter processing time can be applied.

As another example, in some embodiments, when a reconfiguration updates only aspects of the WD configuration/state which must be changed (e.g., security keys for ciphering) and other configuration/state remains the same and may be restored from a stored/cached WD context, the base station <NUM> may conclude that a shorter processing time can be applied.

The set of reconfiguration actions that require a longer processing time in the WD <NUM> can be known to the network and the WD <NUM>. If any of these actions is required during the reconfiguration, the longer time is explicitly or implicitly indicated and assumed by both network and WD <NUM>, otherwise the shorter time is assumed. As a baseline, the actions for RRC connection resume when the WD <NUM> has remained in the cell as specified in the context may be assumed to be associated with the shorter time.

In one embodiment, the network, e.g., base station <NUM>, indicates to the WD <NUM> in a sysinfo (SI) message that a reduced processing time is expected. In other embodiments, the network may indicate the expectation of reduced processing time in layer <NUM>/layer <NUM> (L1/L2) control signaling; e.g., with downlink control information (DCI) on L1/L2 control channel (e.g., physical downlink control channel (PDCCH)), with L2 control (e.g., media access control (MAC) control element) or with layer <NUM> (L3) control (e.g., in RRC message). Based on the received indication, the WD <NUM> then applies the rules related to explicit or implicit indication of timing as formulated in the subsections below.

The base station <NUM> may indicate the timing of the RRC Connection Resume Complete message in the RRC Connection Resume message. This indication can be one bit (flag) indicating either long (legacy) timing n+k subframes or short (new) timing n+knew subframes. In one embodiment, knew is explicitly indicated with <NUM> bits. In another embodiment, knew is indicated as knew = k-kstep, where k is the legacy timing and kstep is indicated with <NUM> bits. The times knew and/or kstep can be hardcoded in a specification, be signaled as an absolute value or signaled as an index into a table in a specification providing implicit determination of timing.

In one embodiment, the processing timing is not explicitly indicated to the WD <NUM> by the network, e.g., base station <NUM>. Instead the WD determines the required processing time from the set of tasks required in the reconfiguration. The mapping between reconfiguration tasks and processing time is known in both the WD <NUM> and the network, e.g., base station <NUM>.

In one example, the short processing time is applied when the reconfiguration requires reconfigurations/processing steps/tasks/actions from a predefined/specified set of reconfigurations/processing steps/tasks/actions; and long (legacy) timing otherwise.

In another example, the short processing time can apply when a reconfiguration comprises only parameters which are mandatory to signal (i.e., cannot be omitted from signaling) and other parameters remain the same and may be restored from a stored/cached WD context; and long (legacy) timing otherwise.

In another example, the short processing time can apply when a reconfiguration updates only aspects of the WD configuration/state which must be changed (e.g., security keys for ciphering) and other configuration/state remains the same and may be restored from a stored/cached WD context; and long (legacy) timing otherwise.

The WD <NUM> applies the indicated timing n+k subframes or n+knew subframes for the transmission of RRC Connection Resume Complete.

The base station <NUM> schedules and expects to receive the RRC Connection Resume Complete n+k or n+knew subframes after RRC Connection Resume has been sent.

The base station <NUM> identifies a new WD <NUM> from the stored context during RRC Resume, and assesses the processing need in the WD <NUM>. If a reduced timing can be used, it is signaled in the RRC Connection Resume message. The WD <NUM> applies the indicated timing for the RRC Connection Resume Complete message.

<FIG> is a block diagram of an embodiment of a base station <NUM> that includes processing circuitry <NUM>. In some embodiments, the processing circuitry may include a memory <NUM> and processor <NUM>, the memory <NUM> containing instructions which, when executed by the processor <NUM>, configure processor <NUM> to perform the one or more functions described herein. In addition to a traditional processor and memory, processing circuitry <NUM> may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry).

Processing circuitry <NUM> may include and/or be connected to and/or be configured for accessing (e.g., writing to and/or reading from) memory <NUM>, which may include any kind of volatile and/or non-volatile memory, e.g., cache and/or buffer memory and/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/or optical memory and/or EPROM (Erasable Programmable Read-Only Memory). Such memory <NUM> may be configured to store code executable by control circuitry and/or other data, e.g., data pertaining to communication, e.g., configuration and/or address data of nodes, etc. Processing circuitry <NUM> may be configured to control any of the methods described herein and/or to cause such methods to be performed, e.g., by processor <NUM>. Corresponding instructions may be stored in the memory <NUM>, which may be readable and/or readably connected to the processing circuitry <NUM>. In other words, processing circuitry <NUM> may include a controller, which may comprise a microprocessor and/or microcontroller and/or FPGA (Field-Programmable Gate Array) device and/or ASIC (Application Specific Integrated Circuit) device. It may be considered that processing circuitry <NUM> includes or may be connected or connectable to memory, which may be configured to be accessible for reading and/or writing by the controller and/or processing circuitry <NUM>.

The memory <NUM> is configured to store the WD context <NUM>. The processor <NUM> includes a short processing time condition determiner <NUM> which is configured to determine whether conditions exists to indicate to the WD <NUM> that a short processing time is to be implemented. A receiver <NUM> is configured to receive from the WD <NUM> a radio resource control, RRC, connection resume request from the WD <NUM>. A transmitter <NUM> is configured to send to the WD <NUM> an RRC connection resume message indicating an expectation of a short processing time, when short processing time conditions exist, and to send to the WD <NUM> an RRC connection resume message indicating an expectation of a legacy processing time when short processing time conditions do not exist.

<FIG> is block diagram of an alternative embodiment of the base station <NUM> that may be implemented at least in part with software modules executable by a processor. A short processing time conditions determiner module <NUM> is configured to cause a processor to determine when short processing time conditions exist. The receiver module <NUM> is configured to receive from the WD <NUM>, an RRC connection resume request. The transmitter module <NUM> is configured send to the WD <NUM> an RRC connection resume message.

<FIG> is a block diagram of a wireless device <NUM> having processing circuitry <NUM>. In some embodiments, the processing circuitry may include a memory <NUM> and processor <NUM>, the memory <NUM> containing instructions which, when executed by the processor <NUM>, configure processor <NUM> to perform the one or more functions described herein. In addition to a traditional processor and memory, processing circuitry <NUM> may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry).

The memory <NUM> is configured to store an RRC connection resume message <NUM>. The processor <NUM> implements a transmission time determiner <NUM> configured to determine from the RRC connection resume message when to send an RRC connection resume complete message. The receiver <NUM> is configured to receiving from the base station <NUM> the RRC connection resume message. The transmitter <NUM> is configured to send to the base station <NUM> the RRC connection resume complete message at a first time when the RRC connection resume message indicates an expectation of a short processing time, and send to the base station <NUM> the RRC connection resume complete message at a second time when the RRC connection resume message indicates an expectation of a legacy processing time.

<FIG> is a block diagram of an alternative embodiment of the WD <NUM> that includes a transmission time determiner module <NUM> configured to determine from the RRC connection resume message when to send an RRC connection resume complete message. The receiver module <NUM> is configured to receive from the base station <NUM> the RRC connection resume message. The transmitter module <NUM> is configured to send to the base station the RRC connection resume complete message at a first time when a message received from the base station (e.g. the RRC connection resume message) indicates an expectation of a short processing time, and send to the base station the RRC connection resume complete message at a second time when the RRC connection resume message indicates an expectation of a legacy processing time. The first time is based on the short processing time and the second time is based on the legacy processing time.

<FIG> is a flowchart of an exemplary process for setting a processing time for responding to a radio resource control, RRC, connection resume message by a wireless device, WD <NUM>. The process optionally includes storing a WD context at the base station <NUM> when communication between the WD <NUM> and the base station <NUM> enters an idle state (block S100). The process also optionally includes receiving from the WD <NUM> via the receiver <NUM> a radio resource control, RRC, connection resume request (block S102). The process also includes determining when short processing time conditions exist (block S104). For example, short processing time conditions may be determined to exist if the reconfiguration of the RRC connection for the WD uses steps from a predefined set of steps. Alternatively or additionally, short processing time conditions may be determined to exist if the reconfiguration of the RRC connection for the WD uses only parameters which are mandatory to signal. Alternatively or additionally, short processing time conditions may be determined to exist if the reconfiguration of the RRC connection for the WD updates only security keys. When short processing time conditions exist, the process includes sending to the WD <NUM> via the transmitter <NUM> a message (e.g. an RRC connection resume message) indicating an expectation of a short processing time (block S106). When short processing time conditions do not exist, the process includes sending to the WD <NUM> via the transmitter <NUM> an RRC connection resume message indicating an expectation of a legacy processing time (block S108).

<FIG> is a flowchart of an exemplary process in a wireless device, WD, <NUM> for responding to a radio resource control, RRC, connection resume message from a base station <NUM>. The process includes receiving from the base station <NUM> via the receiver <NUM> the RRC connection resume message (block S110). The process also includes determining from a message received from the base station (e.g. the RRC connection resume message) when to send an RRC connection resume complete message <NUM> (block S112). The process also includes determining whether a short processing time is indicated (block S <NUM>). The process also includes sending to the base station <NUM> via the transmitter <NUM> the RRC connection resume complete message at a first time when the message indicates an expectation of a short processing time (block <NUM>). The process also includes sending to the base station <NUM> via the transmitter <NUM> the RRC connection resume complete message at a second time when the message indicates an expectation of a legacy processing time (block S118).

Claim 1:
A method in a network node (<NUM>) for setting a processing time for a user equipment (<NUM>), UE, to respond to a radio resource control, RRC, connection resume message, the RRC connection resume message relating to establishment or reconfiguration of an RRC connection for the UE (<NUM>), the method comprising:
determining (S104) when short processing time conditions exist in relation to the establishment or reconfiguration of the RRC connection for the UE;
when short processing time conditions exist, sending (S106) to the UE an RRC connection resume message, the RRC connection resume message indicating a short processing time; and
when short processing time conditions do not exist, sending (S108) to the UE an RRC connection resume message, the RRC connection resume message indicating a legacy processing time, wherein the legacy processing time is longer than the short processing time.