Patent Description:
3GPP cellular wireless systems, such as Long-Term Evolution (LTE) and New Radio (NR), use Discontinuous Reception (DRX) feature that allows the UE to stop monitoring the Physical Downlink Control Channel, PDCCH, during certain recurring time periods. This helps the UE to reduce battery consumption and increase the duration between recharging occasions.

A DRX cycle begins with a first phase called On-duration during which the UE is awake and monitors the PDCCH, followed by a second phase called Opportunity for DRX as shown in <FIG>. There are thus two re-occurring states of reception. The UE is either active (awake) or inactive (asleep). The DRX cycle then comprise pre-configured regular periods of DRX activity, when the UE receiver is active and the PDCCH is monitored, that are referred to as On-duration. The total time during which the UE monitors the PDCCH is defined as the active time. This comprises the aggregate of phases On-duration as depicted in <FIG> but also all time when either of timers drx-lnactivityTimer or drx-RetransmissionTimer is running. It also includes the time when UE awaits a contention resolution or an Uplink, UL, grant for either new transmission or adaptive retransmission.

The UE indicates its DRX capability to network (eNodeB/gNodeB) in initial context setup. The DRX capability may be: no, partial, or full support. The network then configures UE with a DRX setting. The network only schedules the UE during periods of active time.

The DRX configuration has a possible impact on the network capacity, such as the UE throughput. The purpose of the DRX configuration is to improve UE battery saving while it also results in some degradation of the system performance. The reduction in battery consumption versus the data throughput to the UE must be balanced in the best way by the DRX configuration.

A Service Specific DRX feature makes it possible to configure different DRX parameter settings for different services to optimize the DRX configuration for the respective service. In this way, UE battery can be saved with much less negative impact on the system performance. The Service Specific DRX feature uses QoS Class Identifier (QCI) dependent DRX settings which are defined by the operator.

Downlink, DL, and uplink, UL, transmissions are scheduled by the network node (eNodeB or gNodeB), while in the future it can be envisioned that the scheduling may be handled by the Cloud in full or partly. Scheduling can be done dynamically, i.e. the eNodeB schedules the UL transmission per transmission occasion defined as transmission time interval, TTI, or multiple TTls (TTI bundling). <FIG> shows along a horizontal time line, an example sequence of events involving an eNodeB, eNB, in the upper line, and a UE that is configured with DRX, in the lower horizontal line. The eNodeB sends a dynamic grant to the UE during the On-duration phase of the DRX cycle that grants the UE resources on the Physical Uplink Shared Channel, PUSCH for transmission of new data. The receipt of the grant triggers the drx-Inactivity Timer to run and will keep the UE receiver active for <NUM> in the example, while the On-duration will run out after <NUM>. The UE will transmit data or a buffer status report, BSR, in the granted resources. A bit later, new data enters the UE transmit buffer, and the UE transmits a scheduling request, SR, on the Physical Uplink Control Channel, PUCCH. The SR transmission triggers the activation of the receiver until a dynamic grant is received. The receipt of the grant of resources for the transmission of the new data, triggers the drx-activity timer to run, in the example for a period of <NUM>. The transmission of data from the UE in the resources granted is not shown to keep the sequence of events simple in <FIG>.

Alternatively, scheduling is made by the semi persistent scheduling, SPS, framework, wherein multiple periodic occasions are granted at the same time, i.e. prior to the arrival of all data at transmission buffers. Configuration of SPS includes the periodicity of the grant being signaled via RRC, and the activation of the configured grant is signaled via PDCCH. The activation grant indicates frequency resources, modulation and coding scheme, MCS, for future SPS occasions.

SPS was enhanced in LTE rel-<NUM> to support latency reduction of UL data transmissions. As compared to UL dynamic scheduling, SPS can do UL transmission more quickly, since it removes the steps of the UE sending a scheduling request and the eNodeB responding by an UL dynamic grant. By the introduction of short SPS in release <NUM>, latency is further reduced, as the SPS periodicity is reduced to less than <NUM>. Release <NUM> also includes the possibility to skip an uplink transmission when there is no data in the UE buffer. This option, referred to as skipUplinkTx, is available for both dynamic and SPS grants.

DRX with UL short-SPS presents special challenges to the scheduler in both UL and DL directions. A pending Scheduling Request, SR, sent by the UE on PUCCH, as is shown in <FIG>, indicates to the network that the UE is awake and eligible for scheduling, as the UE will stay DRX active until it has received a scheduling grant or a SR period runs out.

The receipt of a dynamic scheduling message, either of a scheduling grant or a scheduling assignment on the PDCCH channel, for the transmission of new data, triggers a drx-InactivityTimer to run, and while running keeps the UE DRX active. While being DRX active the UE may receive further scheduling messages.

When the UE is UL SPS activated, it has a configured grant that it can use for UL transmissions on SPS occasions. This reduces the need of sending SR and waiting for dynamic scheduling messages granting uplink transmissions. With UL short-SPS the UE will not send SR under following scenarios:.

Under these conditions, the only occasion for the UE to be scheduled in downlink is during the DRX On-Duration. <FIG> similarly to <FIG> discloses sequence of actions in the eNodeB and UE along time lines but in the example of the UE being configured with SPS in addition to DRX. When new data arrives in the UE transmit buffer, the UE make use of the next SPS transmission opportunity for its transmission. However, upon the receipt of the data in the eNode B transmission buffer, a scheduling assignment can be received only when the UE is DRX active. However, waiting for the On-Duration to start until the scheduling assignment can be sent, increases the round-trip time (RTT) delay and hence the end-to-end latency for DL data. This defeats the purpose of UL short-SPS which targets latency minimization. So, while the short SPS UL configuration decreases UL latency it has a negative impact on the downlink transmission latency.

One way to improve the DL latency would be to disable DRX or use a lowest possible DRX configuration e.g. DRX cycle = <NUM>. However, a delay to the next DRX On-Duration still must be tolerated. This would also increase the UE battery consumption.

There is a need to have a better balance between the UL and DL latency while at the same time avoid increase in battery consumption.

In a draft to <NPL>, the above problems is proposed to be overcome by the UE becoming DRX active after an UL configured grant. The proposal however requires update of the UE capabilities. Accordingly, one object of the technology here presented is to improve the UL latency for a UE that is configured with DRX, and with short SPS in the UL, while at the same time avoid increase in battery consumption, and to do so for UEs having the conventional capabilities a provided by the standard.

Accordingly, one object of the technology presented is to reduce the latency in DL transmission for a UE configured with DRX and with SPS.

The invention is described by the combination of the embodiments related to <FIG>, <FIG>, and <FIG>.

The technology here presented relates to a method in a network for keeping control of a User Equipment, UE, and the function typically resides in a network node co-functioning with a scheduler, such as a radio base station, an eNodeB, gNodeB, a remote radio head, a Radio Equipment, RE and Radio Equipment Controller, REC, or it may alternatively at least partly reside in functions in the Cloud in cooperation with any of the type of nodes mentioned. The node serves a specific UE with communication services and controls or obtains information that the UE is configured with Discontinuous Reception, DRX, and with an UL Semi-Persistent Scheduling SPS. The UL SPS configuration may be a short SPS. The information comprises the DRX cycle length, the occasions and length of the preconfigured active periods, also referred to as On-duration, and the drx-Inactive timer length.

The method is intended for a network node that possesses the described type of information for a specific UE and comprises steps that will here be described with reference to <FIG>:.

The UL grant and the DL assignment thereby function as a Wake-up grant/assignment and that is sent for keeping the UE DRX active. While being DRX active the UE will monitor the Physical Downlink Control Channel, PDCCH, and may then receive a DL assignment from the network that schedules resources on the Physical Downlink Shared Channel, PDSCH, for DL data transmission. The Wake-up grant/assignment serves as an opportunity to open a period when a DL assignment may be sent to the UE for the transmission of the DL data. The Wake-up grant/assignment may be sent when there is data buffered for DL transmission but also when there is no data awaiting transmission in the downlink. The Wake-up grant or assignment may be sent for example when the network estimates that DL data will arrive while the drx-Inactivity timer will be running as a result of the Wake-up grant/assignment. By sending the Wake-up grant or assignment to the UE the network gets further opportunity to schedule the UE in the DL.

The proposed solution is based on <NPL>: "When a DRX cycle is configured, the Active Time includes the time while:.

When the above condition applies the UE will be regarded as eligible for receipt of an UL scheduling grant. This is the situation when the UE has transmitted UL data or a BSR in one of the preconfigured SPS, or short SPS, occasions in the UL, during a window that is utilized in step <NUM> for sending the Wake-up grant/assignment.

The HARQ response is sent on the Hybrid-ARQ Indicator Channel, PHICH, in a process synchronized to the UL data transmission. In accordance with <NPL> the UE will monitor the PDCCH when a HARQ response is due and may then receive an UL grant or a DL assignment. The UL grant and the DL assignment are in the form of a Downlink Control Information, DCI, message. The LTE principle is that the UL timing of any retransmissions of data is synchronized to the time of the first transmission. This is referred to as synchronous retransmission and avoids the need for sending UL grants for the retransmission. At the occasion when the HARQ response is due, the network may in addition to the HARQ response also send an UL grant or a DL assignment. In LTE the transmission timing of a HARQ response is synchronized the to the UL transmission timing and is typically made in the <NUM> transmission time interval, TTI, next to that of the receipt of the HARQ response. This time is typically too short to enable the scheduling of resources on the PDSCH for DL data that may be buffered for transmission to the UE. In the technology here proposed the transmission of a dynamic UL grant or a DL assignment with the HARQ response is utilized to trigger a drx-Inactivity timer to run and keep the UE DRX active while running. The dynamic UL grant/DL assignment thereby functions as a DRX wake up of the UE and that while being DRX active can receive a DL assignment on the PDCCH, and received DL data on the PDSCH.

<FIG> illustrates a sequence of events along a horizontal time line of a UE (lower line) and that of a network node (upper line) and that is here presented by an eNodeB, eNB. The UE is configured with DRX, comprising preconfigured cyclic periods of On-duration when the UE monitors the PDCCH, followed by possible periods of DRX inactivity. In the example the On-duration is <NUM> and the cycle is <NUM>. The UE is also configured with short SPS, in the example granting the UL transmissions at preconfigured TTIs, short TTIs, slots or sub-slots with <NUM> interval, and that are illustrated in <FIG> by the regularly distributed arrows in upwards direction. The eNodeB monitors the periods of the DRX activity and SPS occasions and is aware of when the UE is DRX active. The eNodeB keeps its own receiver active over time. <FIG>, <FIG> and <FIG> illustrates steps performed by a network node according to some embodiments, and that may follow upon each other in sequence from <FIG> and further to <FIG>. The proposed method may comprise following steps by the network node, and that are illustrated in <FIG>, and in <FIG>, <FIG> and <FIG>:.

Before the UL grant or DL assignment is transmitted to wake up the UE from DRX sleep the further optional step may be performed:.

In case it is determined that an UL grant shall be transmitted to wake up the UE from DRX sleep the further optional step may be performed before transmission:.

A PUSCH transport format, TFS, is selected, in step <NUM>. TFS is a function which take SINR, required TBS as input, and output Modulation and Coding Scheme, MCS, Physical Resource Blocks, PRB and TBS. It can be implemented with different algorithms for different vendors. The implementation of this module is not the emphasis of this technology, it is therefore only referred as a black box function. In case it is determined that a DL assignment shall be transmitted to wake up the UE from DRX sleep it may further be observed that:.

The receipt of the dynamic UL grant triggers the drx-Inactivity timer to run and the UE becomes DRX active. In <FIG>, this the period of drx-Inactivity timer when the UE enters the awake mode from the sleep mode is illustrated by a hashed line box. The eNodeB keeps a corresponding timer to monitor the time when the UE stays DRX active, and this period is also illustrated by a hashed line box on the eNodeB time line.

Optional to what has been disclosed, the eNodeB could have skipped the Wake-up grant/assignment transmission if the UE would shortly be entering the DRX On-Duration period. By shortly is here typically meant <NUM> or less, albeit in some situations such as if there is no DL data available, and the traffic load generated by other UEs is high the Wake-up grant may optionally be skipped also if there are <NUM>, <NUM> or even <NUM> until the next DRX On-duration period.

To improve the chances that the Wake-up UL grant/assignment is sent at a time that triggers the drx-Inactivity timer to run while DL data arrives at the eNodeB DL data buffer, the arrival timing of the DL data may be predicted. The prediction may be based on the average time between UL data transmission on PUSCH and a corresponding arrival of data in DL, when both relates to the same Logical Channel, LC. The arrival is typical on the Radio Link Control, RLC, layer and handled per LC. The drx-Inactivity timer may then be set as equal to or greater than the average time between the UL transmission and the DL arrival of data.

In case the DL data has not arrived when the drx-Inactivity timer is about to run out, another Wake-up grant may be sent triggering the drx-Inactivity timer to restart.

<FIG> is a flowchart that illustrates a method for a network node, such as the eNodeB, gNodeB, RE, REC, and that comprises optional steps in addition to those disclosed in <FIG>. Steps that may optionally be included are indicated by hashed boarder lines in the flowchart:.

The NDI, in the DCI serving as Wake-up grant or as a Wake-up assignment is toggled to indicate new data, and thereby triggers the drx-Inactivity timer to run. Some resources on the PUSCH in the case of a Wake-up grant or some resources on the PDSCH, in the case of the of a Wake-Up assignment, need be scheduled. Time is short for the scheduling the Wake-up grant/assignment and if just a small amount of resources in the PUSCH/PDSCH are occupied, the better chance that the Wake-up grant/assignment can be sent. If there is no data buffered for transmission padding may be sent on either of the PUSCH and PDSCH.

The Wake-up grant/assignment is transmitted on the PDCCH in the same opportunity as the HARQ-response is transmitted on the PHICH, and that means that in the case of LTE that are transmitted in the OFDM symbols within a TTI that makes up the control region, or in case of short TIIs being used in LTE or in case of NR the sPDCCH and PHICH are coded over the same OFDM symbols.

The term UE, User Equipment, used in this description may refer not only to the end terminal as defined in the 3GPP specifications for the LTE or NR but may refer to any type of wireless device communicating with a node and/or with another wireless device in a cellular or mobile communication system. It should be noted that the "user" in the term "User Equipment" in no way restricts the terminal to be in the hands of a human user, but the UE may be a machine communicating with other machines. Examples of UEs include a mobile phone, a smart phone, a PDA (Personal Digital Assistant), a portable computer (e.g., laptop, tablet), a sensor, a modem, a machine-type-communication (MTC) device / machine-to-machine (M2M) device, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles, a D2D capable device, or another device that can provide wireless communication. A UE may also be referred to as, a station (STA), a device, or a terminal in some embodiments.

The term "network node" as is used can be any kind of network node that handles some of the scheduling functions, possibly in cooperation with the Cloud in which some of the scheduling functions such as policy settings or prediction of DL data arrival timing may be computed. The "network node" may comprise a Node B, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, eNode B, base station controller (BSC), base transceiver station (BTS), or a part of a base station/eNodeB/ gNodeB that may have a split architecture and then the function mainly resides in a Radio Equiment Controler, REC, a Equiment Controler, RE, relay donor node controlling relay.

In the examples disclosed names of channels in the LTE system have been used, while it should be understood that also channels with functions such as a Shared Downlink Data Channel, a Downlink Control Channel, a Shared Uplink Data Channel, and a Uplink Control Channel may be used despite their names may be other than the LTE PDSCH, PDCCH, PUSCH, and PUCCH.

<FIG> is a block diagram of a structure of a network node <NUM> that is adapted for the technology here proposed. Just the structures relevant for the technology proposed is shown for better overview. It comprises a DL transmitter <NUM>, and an UL receiver <NUM>, and a scheduler <NUM> with separate sections <NUM>, <NUM> for scheduling resources on the PDSCH and the PUSCH in respectively the DL and the UL communication directions. The scheduler <NUM> is connected to the transmitter <NUM> and to the receiver <NUM>. The transmitter <NUM> and receiver <NUM> are both adapted to transmit/receive over a radio interface, or are connected to respectively a radio transmitter and a radio receiver in another entity over for example a front haul network and that are not depicted in <FIG>.

The general function of the scheduler <NUM> is to schedule the resources on the radio interface for communication with a plural UE in contention of the resources on the PDSCH and the PUSCH. When describing the technology of this application the focus is on the UE that is configured with DRX and SPS. The SPS configuration may be for a short SPS.

The scheduler communicates its scheduling decisions via the DL transmitter <NUM> to the UEs over the PDCCH in the form of DCI messages, as scheduling grants providing resources on the PUSCH for the UL transmissions and scheduling assignments providing resources on the PDSCH for the DL transmissions. DL data arrives to the network node <NUM> over, for example an S1 interface to the core network, that is not shown in <FIG>, and a DL buffer <NUM> buffers the data until it is scheduled and transmitted. The DL scheduler <NUM> is informed of the amounts of data in the DL buffer for the specific UE, and the UL scheduler <NUM> receives a BSR from the UE informing of the amount of data awaiting UL transmission. The scheduler <NUM> also assigns priorities to the different UEs, based on factors such as the amounts of data in their respective buffer, how long the data has been buffered, and the type of service that the UE is involved in. Which of the UEs that are scheduled are based on their respective priority. Scheduling in UL and DL are conventionally made in separate processes, and a specific UE may be given different priorities for the UL transmission and the downlink transmission. The DL buffer <NUM>, have sections for the data for the respective UEs.

The network node <NUM> is adapted to perform the functions as described with reference to <FIG>. It may optionally also be adapted to perform the further functions as are described in the flowchart of <FIG>, <FIG>, <FIG> and <FIG>. In one embodiment the UL receiver <NUM> monitors the receipt of any UL transmission from the UE in the TTIs granted by SPS, or in the short TTIs granted by the short SPS, and informs the scheduler <NUM> when UL data or a BSR is received. The scheduler <NUM> may then control its UL scheduler <NUM> to trigger the transmission of the Wake-up UL grant in the same TTI, short TTI or slot as that of the HARQ response. The UL scheduler <NUM> then informs the DL scheduler <NUM> of the drx-Inactivity timer running. As an alternative to triggering the transmission of a Wake-up uplink grant the scheduler <NUM> may control the DL scheduler <NUM> to transmit a Wake-up DL assignment. The scheduler <NUM> in the embodiment of <FIG> possess information on the DRX process, including the periods in which the UE keeps its receiver active, i.e. is DRX active, and possesses information on the UE UL SPS configuration. The scheduler determines whether to send a Wake-up grant/assignment, in steps such as disclosed in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>. The scheduler may also determine whether a Wake-up grant or Wake-up assignment should be sent or not. Which one of the two alternatives to be used to Wake-up the UE receiver may for example be based on the load on the UL and DL, and if the DL has the better capacity a DL assignment is selected to Wake-up the UE.

In one embodiment disclosed in <FIG>, there is a processor circuitry <NUM> that controls the interactions between the transmitter <NUM>, the receiver <NUM> and the scheduler <NUM>. In this embodiment the processor circuitry <NUM> keeps control over the DRX configuration in the UE, possesses information of the periods when the UE receiver is active and triggers the UL scheduler to schedule the transmission of the UL grant or the DL assignment in the same TTI or slot as that of the transmission of the HARQ response, for the purpose of Waking up the UE from DRX sleep. Optionally there may also be a memory <NUM> that stores the instructions that when run on the processor circuitry <NUM>, makes the processor circuitry <NUM> control the network node to perform the functions as discloses with reference to any of <FIG>, <FIG>, <FIG>, <FIG> and <FIG>. In the alternative with no memory, the functions of the processor circuitry <NUM> may be hard coded into the processor circuitry <NUM>.

It the technology presented here there is a first Wake-up grant or assignment that make the UE DRX active, and when the UE has become DRX active the DL assignments for DL data are transmitted. There are several reasons for the two-step approach. The Wake-up grant assignment is transmitted under short time constraints, that may not admit for the data being scheduled. Scheduling is complicated, decision are made under short time constraints, and the UL and DL are typically handled by separate sections <NUM>, <NUM> of the scheduler <NUM> that work independently though information is exchanged. The UL scheduler controls the UL SPS grant to the UE and is configured to provide the HARQ responses and is configured to adapt the retransmission of data from the UE by transmitting an UL grant. The UL scheduler is therefore adapted from early releases of the standard to send a UL grant over the PDCCH at the same time as the HARQ response. The UL grant need just grant a small quantity of the PUSCH resource, for a single resource block, as its purpose is to wake up the UE from DRX sleep, and not to transmit UL data. The chances of succeeding in scheduling the UE in the same TTI as that of the HARQ-response improves by just a minor resource of the PUSCH is granted. The chances of succeeding in awaking the UE in the same TTI as that of the HARQ response improves by using a robust PDCCH.

Should there be limited capacity on the PUSCH, a DL assignment may alternatively be sent to wake up the UE from DRX sleep. The by assigning just some minor resources on the PDSCH or some minor resources on the PUSCH the better chances that the Wake-up assignment or the Wake-up grant will be scheduled at the same occasion as that of the HARQ-response transmission, whether it be the same TTI, the same sTTI, the same slot or the same sub-slot depending on the UE configuration.

The chances of the Wake-up grant/assignment being detected by the UE improves if the PDCCH carrying the Wake-up grant/assignment is made robust.

Moreover, those skilled in the art will appreciate that the functions and means explained herein may be implemented using software functioning in conjunction with a programmed microprocessor or general-purpose computer, and/or using an application specific integrated circuit (ASIC). It will also be appreciated that while the current invention is primarily described in the form of methods and devices, the technology may also be embodied in a computer program product as well as a system comprising a computer processor and a memory coupled to the processor, wherein the memory is encoded with one or more programs that may perform the functions disclosed herein.

Claim 1:
A method in a network node for enabling DL scheduling of an UE configured with Discontinuous reception, DRX, including preconfigured recurring On-duration periods, to enable the DL scheduling in periods outside the On-duration periods, the UE further being configured with an UL semipersistent scheduling, SPS, granting the UE UL transmission in recurring Transmission Time Intervals, TTIs, short TTIs, slots or sub-slots said method comprising the steps of:
- monitoring (<NUM>) a receipt of a transmission from the UE in any of the recurring TTIs, short TTI, slots or sub-slots of the SPS configuration; and responsive to the receipt of an UL transmission,
- transmitting (<NUM>), according to a synchronous HARQ process, a HARQ response to the UL transmission and at the same occasion transmitting a dynamic UL grant or a DL assignment to the UE, wherein the transmitted of the UL grant and the DL assignment triggers the UE to stay in DRX active mode for a period, and,
- sending (<NUM>) a scheduling assignment to the UE during the period of the UE staying in DRX active mode.