WO2020207553A1

WO2020207553A1 - Congestion control in cellular communication

Info

Publication number: WO2020207553A1
Application number: PCT/EP2019/058774
Authority: WO
Inventors: Nuno Manuel KIILERICH PRATAS; Claudio Rosa; Frank Frederiksen; Benny Vejlgaard; Morten Toft
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2019-04-08
Filing date: 2019-04-08
Publication date: 2020-10-15
Anticipated expiration: 2021-10-08

Abstract

A network node, a user node, methods and computer programs are disclosed. The network node may monitor at least one bandwidth portion for activity in cellular communication in an unlicensed spectrum, and identify a channel congestion based on the monitoring. The network node may also transmit a congestion control message when the channel congestion ends. The user node may listen for a congestion control message upon the start of a random access channel procedure in cellular communication in an unlicensed spectrum; and apply a signaled congestion avoidance policy, when identifying the congestion control message.

Description

CONGESTION CONTROL IN CELLULAR COMMUNICATION

TECHNICAL FIELD

The present application generally relates to the field of wireless communications. In particular, the present application relates to a user node and a network node for wireless communication, and related methods and computer programs .

BACKGROUND

Some wireless communication techniques, for example, wireless communication performed in an unli censed spectrum, may require that before any transmis sion can be done over a wireless medium a check needs to be passed, for example, a Listen Before Talk (LBT) check. The check requirement may have a significant per formance impact on radio communication protocols, for example, due to the induced delays that depend on the degree of channel activity. Namely, whenever an LBT check fails, then the user node cannot proceed with the transmission and may have to re-attempt the channel ac cess at a later opportunity (including a new LBT check) .

SUMMARY

An example embodiment of a network node com prises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the network node to at least perform: monitoring at least one bandwidth por tion for activity in cellular communication in an unli censed spectrum; identifying a channel congestion based on the monitoring; and transmitting a congestion control message when the channel congestion ends.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the channel congestion is identified based on listen before talk check fails.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the activity is caused by activity of nodes of another net work .

In an example embodiment, alternatively or in addition to the above-described example embodiments, the congestion control message comprises at least one of a duration of the channel congestion, at least one traffic class that can ignore the congestion control message, and an indication identifying a congestion avoidance behavior to apply when receiving the congestion control message .

In an example embodiment, alternatively or in addition to the above-described example embodiments, the indication identifies a fixed length window back-off, a variable length window back-off based on the duration of the channel congestion, or a back-off selection based on when a user node started to attempt its transmission.

In an example embodiment, alternatively or in addition to the above-described example embodiments, transmitting the congestion control message comprises transmitting the congestion control message by a random access load control radio network temporary identifier.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the at least one memory and the computer program code con figured to, with the at least one processor, cause the network node to at least perform: determining a duration of the channel congestion; and transmitting the conges tion control message when the channel congestion ends and when the duration exceeds a channel congestion threshold .

In an example embodiment, alternatively or in addition to the above-described example embodiments, the at least one memory and the computer program code con figured to, with the at least one processor, cause the network node to at least perform: transmitting a load control information message before causing transmission of the congestion control message, the load control in formation message comprising at least one of a load control function activation element, the random access load control radio network temporary identifier, at least one traffic class allowed to ignore the congestion control message, and a default congestion avoidance be havior to apply when receiving the congestion control message .

In an example embodiment, alternatively or in addition to the above-described example embodiments, the network node comprises a base station.

An example embodiment of a user node comprises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the user node to at least perform: listening for a congestion control message upon the start of a random access channel procedure in cel lular communication in an unlicensed spectrum; and ap plying a signaled congestion avoidance policy, when identifying the congestion control message.

In an example embodiment, alternatively or in addition to the above-described example embodiments, listening for a congestion control message upon the start of a random access channel procedure comprises listening the congestion control message before initi ating a physical random access channel procedure.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the at least one memory and the computer program code con figured to, with the at least one processor, cause the user node to at least perform: identifying a channel congestion in the cellular communication in the unli censed spectrum, and wherein the listening comprises listening for the congestion control message before at tempting a new physical random access channel procedure transmission .

In an example embodiment, alternatively or in addition to the above-described example embodiments, the congestion control message is signaled by a random ac cess load control radio network temporary identifier.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the at least one memory and the computer program code con figured to, with the at least one processor, cause the user node to at least perform: receiving a load control information message before the congestion control mes sage, the load control information message comprising at least one of a load control function activation el ement, the random access load control radio network tem porary identifier, at least one traffic class allowed to ignore the congestion control message, and a default congestion avoidance behavior to apply when receiving the congestion control message. In an example embodiment, alternatively or in addition to the above-described example embodiments, the user node comprises a mobile terminal.

An example embodiment of a method comprises monitoring, by a network node, at least one bandwidth portion for activity in cellular communication in an unlicensed spectrum; identifying, by the network node, a channel congestion based on the monitoring; and trans mitting, by the network node, a congestion control mes sage when the channel congestion ends.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the method comprises transmitting, by the network node, the congestion control message by a random access load con trol radio network temporary identifier. In an example embodiment, alternatively or in addition to the above-described example embodiments, the method comprises determining, by the network node, a duration of the channel congestion; and transmitting, by the network node, the congestion control message when the channel congestion ends and when the duration ex ceeds a channel congestion threshold.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the method comprises transmitting, by the network node, a load control information message before causing trans mission of the congestion control message, the load con trol information message comprising at least one of a load control function activation element, the random access load control radio network temporary identifier, at least one traffic class allowed to ignore the con gestion control message, and a default congestion avoid ance behavior to apply when receiving the congestion control message.

An example embodiment of a method comprises listening, by a user node, for a congestion control message upon the start of a random access channel pro cedure in cellular communication in an unlicensed spec trum; and applying, by the user node, a signaled con gestion avoidance policy, when identifying the conges tion control message.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the method comprises identifying, by the user node, a chan nel congestion in the cellular communication in the un licensed spectrum, and wherein the listening comprises listening for the congestion control message before at tempting a new physical random access channel procedure transmission .

In an example embodiment, alternatively or in addition to the above-described example embodiments, the method comprises receiving, by the user node, a load control information message before the congestion con trol message, the load control information message com prising at least one of a load control function activa tion element, the random access load control radio net work temporary identifier, at least one traffic class allowed to ignore the congestion control message, and a default congestion avoidance behavior to apply when re ceiving the congestion control message. In an example embodiment, alternatively or in addition to the above-described example embodiments, the user node comprises a mobile terminal.

An example embodiment of a network node com prises means for performing: monitoring at least one bandwidth portion for activity in cellular communication in an unlicensed spectrum; identifying a channel con gestion based on the monitoring; and transmitting a con gestion control message when the channel congestion ends .

In an example embodiment, alternatively or in addition to the above-described example embodiments, the method comprises transmitting, by the network node, the congestion control message by a random access load con trol radio network temporary identifier. In an example embodiment, alternatively or in addition to the above-described example embodiments, the network node comprises means for performing: determining a duration of the channel congestion; and transmitting the congestion control message when the channel conges tion ends and when the duration exceeds a channel con gestion threshold.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the network node comprises means for performing: transmit ting a load control information message before causing transmission of the congestion control message, the load control information message comprising at least one of a load control function activation element, the random access load control radio network temporary identifier, at least one traffic class allowed to ignore the con gestion control message, and a default congestion avoid ance behavior to apply when receiving the congestion control message.

An example embodiment of a user node comprises means for performing: listening for a congestion control message upon the start of a random access channel pro cedure in cellular communication in an unlicensed spec trum; and applying a signaled congestion avoidance pol icy, when identifying the congestion control message.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the user node comprises means for performing: identifying a channel congestion in the cellular communication in the unlicensed spectrum, and wherein the listening comprises listening for the congestion control message before at tempting a new physical random access channel procedure transmission .

In an example embodiment, alternatively or in addition to the above-described example embodiments, the user node comprises means for performing: receiving a load control information message before the congestion control message, the load control information message comprising at least one of a load control function ac tivation element, the random access load control radio network temporary identifier, at least one traffic class allowed to ignore the congestion control message, and a default congestion avoidance behavior to apply when re ceiving the congestion control message.

In an example embodiment, alternatively or in addition to the above-described example embodiments, the user node comprises a mobile terminal. An example embodiment of a computer program comprises instructions for causing an apparatus to per form at least the following: monitoring at least one bandwidth portion for activity in cellular communication in an unlicensed spectrum; identifying a channel con gestion based on the monitoring; and transmitting a con gestion control message when the channel congestion ends .

An example embodiment of a computer program comprises instructions for causing an apparatus to per form at least the following: listening for a congestion control message upon the start of a random access chan nel procedure in cellular communication in an unlicensed spectrum; and applying a signaled congestion avoidance policy, when identifying the congestion control message.

An example embodiment of a non-transitory com puter readable medium comprises program instructions for causing an apparatus to perform at least the following: monitoring at least one bandwidth portion for activity in cellular communication in an unlicensed spectrum; identifying a channel congestion based on the monitor ing; and transmitting a congestion control message when the channel congestion ends.

An example embodiment of a non-transitory com puter readable medium comprises program instructions for causing an apparatus to perform at least the following: listening for a congestion control message upon the start of a random access channel procedure in cellular communication in an unlicensed spectrum; and applying a signaled congestion avoidance policy, when identifying the congestion control message.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the example em bodiments and constitute a part of this specification, illustrate example embodiments and together with the description help to explain the principles of the exam ple embodiments. In the drawings:

FIG. 1A illustrates an example embodiment of the subject matter described herein illustrating a net work node;

FIG. IB illustrates an example embodiment of the subject matter described herein illustrating a user node ;

FIG. 2A illustrates an example embodiment of the subject matter described herein illustrating a method;

FIG. 2B illustrates an example embodiment of the subject matter described herein illustrating a method;

FIG. 2C illustrates an example embodiment of the subject matter described herein illustrating a method;

FIG. 2D illustrates an example embodiment of the subject matter described herein illustrating a method;

FIGS. 3A - 3C show an example embodiment of the subject matter described herein illustrating effects of applying a signaled congestion avoidance policy;

FIGS. 4A - 4C show an example embodiment of the subject matter described herein illustrating effects of applying a signaled congestion avoidance policy; and

FIG. 5 shows an example embodiment of the sub ject matter described herein illustrating effects of applying a signaled congestion avoidance policy.

Like reference numerals are used to designate like parts in the accompanying drawings.

DETAILED DESCRIPTION

Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description pro vided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The de scription sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

FIG. 1A illustrates an example embodiment of the subject matter described herein illustrating a net work node 100.

The network node 100 comprises one or more pro cessors 102, and one or more memories 104 that comprise computer program code. The network node 100 may also include a transceiver 106, as well as other elements, such as an input/output module (not shown in FIG. 1A) , and/or a communication interface (not shown in FIG. 1A) .

Although the network node 100 is depicted to include only one processor 102, the network node 100 may include more than one processor. In an example embodi ment, the memory 104 is capable of storing instructions, such as an operating system and/or various applications.

Furthermore, the processor 102 is capable of executing the stored instructions. In an example embod iment, the processor 102 may be embodied as a multi core processor, a single core processor, or a combina tion of one or more multi-core processors and one or more single core processors. For example, the processor 102 may be embodied as one or more of various processing devices, such as a coprocessor, a microprocessor, a con troller, a digital signal processor (DSP) , a processing circuitry with or without an accompanying DSP, or var ious other processing devices including integrated cir cuits such as, for example, an application specific in tegrated circuit (ASIC) , a field programmable gate array (FPGA) , a microcontroller unit (MCU) , a hardware accel erator, a special-purpose computer chip, or the like. In an example embodiment, the processor 102 may be con figured to execute hard-coded functionality. In an ex ample embodiment, the processor 102 is embodied as an executor of software instructions, wherein the instruc tions may specifically configure the processor 102 to perform the algorithms and/or operations described herein when the instructions are executed.

The memory 104 may be embodied as one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination of one or more volatile memory devices and non-volatile memory devices. For ex ample, the memory 104 may be embodied as semiconductor memories (such as mask ROM, PROM (programmable ROM) , EPROM (erasable PROM) , flash ROM, RAM (random access memory) , etc . ) .

The network node 100 may be, for example, a base station. The base station may include, for example, a fifth-generation base station (gNB) providing an air interface for user nodes to connect to a wireless net work via wireless transmissions.

The at least one memory 104 and the computer program code are configured to, with the at least one processor 102, cause the network node 100 to at least perform monitoring at least one bandwidth portion for activity in cellular communication in an unlicensed spectrum; identifying a channel congestion based on the monitoring; and transmitting a congestion control mes sage when the channel congestion ends. The congestion control message may be sent to user nodes that are wait ing to start a random access channel procedure or cur rently executing the random access channel procedure.

FIG. IB illustrates an example embodiment of the subject matter described herein illustrating a user node 110.

The user node 110 comprises one or more pro cessors 112, and one or more memories 114 that comprise computer program code. The user node 110 may also in clude a transceiver 116, as well as other elements, such as an input/output module (not shown in FIG. IB), and/or a communication interface (not shown in FIG. IB) .

Although the user node 110 is depicted to in clude only one processor 112, the user node 110 may include more processors. In an example embodiment, the memory 114 is capable of storing instructions, such as an operating system and/or various applications.

Furthermore, the processor 112 is capable of executing the stored instructions. In an example embod iment, the processor 112 may be embodied as a multi core processor, a single core processor, or a combina tion of one or more multi-core processors and one or more single core processors. For example, the processor 112 may be embodied as one or more of various processing devices, such as a coprocessor, a microprocessor, a con troller, a digital signal processor (DSP) , a processing circuitry with or without an accompanying DSP, or var ious other processing devices including integrated cir cuits such as, for example, an application specific in tegrated circuit (ASIC) , a field programmable gate array (FPGA) , a microcontroller unit (MCU) , a hardware accel erator, a special-purpose computer chip, or the like. In an example embodiment, the processor 112 may be con figured to execute hard-coded functionality. In an ex ample embodiment, the processor 112 is embodied as an executor of software instructions, wherein the instruc tions may specifically configure the processor 112 to perform the algorithms and/or operations described herein when the instructions are executed.

The memory 114 may be embodied as one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination of one or more volatile memory devices and non-volatile memory devices. For ex ample, the memory 114 may be embodied as semiconductor memories (such as mask ROM, PROM (programmable ROM) , EPROM (erasable PROM) , flash ROM, RAM (random access memory) , etc . ) .

The user node 110 may be any of various types of devices used directly by an end user entity and ca pable of communication in a wireless network, such as user equipment (UE) . Such devices include but are not limited to smartphones, tablet computers, smart watches, laptop computers, Internet-of-Things (IoT) devices, any hand-held or portable devices etc.

The at least one memory 114 and the computer program code are configured to, with the at least one processor 112, cause the user node 110 to perform lis tening for a congestion control message upon the start of a random access channel procedure in cellular commu nication in an unlicensed spectrum; and applying a sig naled congestion avoidance policy, when identifying the congestion control message.

FIG. 2A illustrates an example embodiment of the subject matter described herein illustrating a method .

At 200, at least one bandwidth portion is mon itored for activity in cellular communication in an un licensed spectrum.

At 202, a channel congestion is identified based on the monitoring.

At 204, a congestion control message is trans mitted, when the channel congestion ends.

The steps 200-204 may be performed by a network node, for example, a base station. Further, a computer program comprising instructions for causing an apparatus to perform, may perform the steps 200-204.

FIG. 2B illustrates an example embodiment of the subject matter described herein illustrating a method .

At 206, a congestion control message is lis tened for upon the start of a random access channel procedure in cellular communication in an unlicensed spectrum.

At 208, a signaled congestion avoidance policy is applied, when identifying the congestion control mes sage .

The steps 206-208 may be performed by a user node, for example, a mobile terminal. Further, a com puter program comprising instructions for causing an apparatus to perform, may perform the steps 206-208.

FIG. 2C illustrates an example embodiment of the subject matter described herein illustrating a method .

At 200, the network node 100 monitors at least one bandwidth portion for activity in cellular communi cation in an unlicensed spectrum. The unlicensed spec trum may refer, for example, to New-Radio Unlicensed (NR-U) . It is to be understood that the New-Radio Unli censed (NR-U) is only one example of possible environ ments where cellular communication in an unlicensed spectrum may be performed, and the illustrated solution is applicable in any other environment providing cellu lar communication in an unlicensed spectrum. The activ ity may be caused by activity of nodes of another net work. In the unlicensed spectrum, when a node, for ex ample, a user node wants to transmit data, first it has to check with, for example, an LBT check whether it can transmit the data. Whenever an LBT check fails, the user node cannot proceed with the data transmission and will have to re-attempt the channel access at a later oppor tunity. This may include also performing a new LBT check .

A reference 214 indicates that the channel be tween the network node 100 and the user nodes 110 is occupied, for example, due to channel occupation by user nodes from another network. The network node 100 identifies 202 a channel congestion situation based on the monitoring. The net work node 100 may perform LBT checks, for example, pe riodically (for example, in every slot) . When the number of consecutive slots where the LBT check fails is greater than a predetermined threshold value, the net work node 100 may identify the channel situation as a channel congestion. Alternatively or in addition, the network node 100 may determine a duration of the channel congestion. For example, the network node 100 may de termine a time period during which the LBT checks have failed. If the time period is longer than a threshold time period, the network node 100 may identify the chan nel situation as a channel congestion. Alternatively or in addition, the network node 100 may identify the chan nel situation as a channel congestion, when X % of ob served slots had an LBT check fail in an observation window of a duration of Y slots. X and Y may have a variety of positive values.

Further, when the channel congestion situation (determined, for example, based on the LBT check fails) prevails consistently for a time period above a conges tion control threshold, the network node 100 may start estimation of the number of backlogged user nodes. The estimation may be based, for example, on the observed number of arrivals in a previous predetermined period of time.

When the channel congestion ends, the network node 100 transmits a congestion control message 210, for example, a proactive congestion control message. In an example embodiment, the network node 100 may transmit the congestion control message when the channel conges tion ends and when the duration exceeds a channel con gestion threshold. The channel congestion threshold may be set to any desired value. For example, for 30 kHz sub-carrier spacing, the congestion threshold may be either 20 sub-frames or 10 ms (which corresponds to 20 sub-frames, each with duration of 0.5 ms), or a duration of 1 frame, with duration of 10 ms.

The congestion control message may be trans mitted to all user nodes which are currently executing (or are about to execute) a random access procedure. In an example embodiment, the proactive congestion control message 210 may be transmitted by using a predetermined random access load control radio network temporary iden tifier (RALC-RNTI) .

Further, in an example embodiment, the conges tion control message 210 may comprise at least one of the following: a duration of the channel congestion, at least one traffic class that can ignore the congestion control message, and an indication identifying a con gestion avoidance behavior to apply when receiving the congestion control message. The duration of the channel congestion may be expressed, for example, as a number of sub-frames, frames or time period. A traffic class may be identified, for example, with a bit string. The indication may refer, for example, to a label identify ing the specific behavior. By using multiple different labels, multiple different behaviors may be identified by the network node 100 towards the user nodes 110.

Further, the indication may identify one or more of the following congestion avoidance behaviors: a fixed length window back-off, a variable length window back-off based on the duration of the channel conges tion, and a back-off selection based on when a user node started to attempt its transmission. The back-off se lection would ensure that user nodes that have waited the most, are served first. It is to be understood that the above list is non-limiting and other behaviors ad ditionally or alternatively to the listed behaviors may be applied.

At the user node 110 side, each user node 110 listens for the congestion control message 210 upon the start of a random access channel procedure 212A, 212B, 212C in cellular communication in the unlicensed spec trum, and applies a signaled congestion avoidance pol icy, when identifying the congestion control message 210. The congestion control message 210 may provide an indication for the user node 110 that a congestion sit uation in cellular communication in the unlicensed spec trum has ended. In an example embodiment, the congestion control message 210 may be received by using a prede termined random access load control radio network tem porary identifier (RALC-RNTI).

Further, in an example embodiment, the user nodes 110 may only be required to monitor the RALC-RNTI for a congestion control message before initiating the physical random access channel (PRACH) procedure. The network node 100 may transmit the congestion control message 210 at the same time as the remaining minimum system information (RMSI) message. The RMSI may be transmitted in a system information block (SIB) 1. When acquiring the PRACH configuration in the RMSI, the user node 110 may also determine whether to apply congestion avoidance .

Further, in an example embodiment, the user nodes 110 that are currently performing a random access channel procedure may be required to monitor the RALC- RNTI for the congestion control message 210 before at tempting a new PRACH transmission if they have experi enced congestion earlier. The congestion may be identi fied by the user nodes 110, for example, by the fact that LBT checks have failed consistently for a certain time period.

In an example embodiment, the congestion con trol message 210 may comprise at least one of the fol lowing: a duration of the channel congestion, at least one traffic class that can ignore the congestion control message, and an indication identifying a congestion avoidance behavior to apply when receiving the conges- tion control message. Further, the indication may iden tify one or more of the following congestion avoidance behaviors: a fixed length window back-off, a variable length window back-off based on the duration of the channel congestion, and a back-off selection based on when a user node started to attempt its transmission. The back-off selection may ensure that user nodes that have waited the most, are served first. It is to be understood that the above list is non-limiting and other behaviors additionally or alternatively to the listed behaviors may be used.

In an example embodiment, the illustrated so lution may also allow for the network node to provide a signal that allows the user nodes (or selected user nodes) to perform the random access channel procedure without any LBT process. Under certain unlicensed access regulations, it may be possible to have temporary trans missions without LBT process conditioned that such hap pen on rare occasions.

FIG. 2D illustrates an example embodiment of the subject matter described herein illustrating a method. The signaling diagram illustrated in FIG. 2D is similar than the one illustrated in FIG. 2C. Therefore, identical parts are not repeated here.

In FIG. 2D, before transmitting the congestion control message 210, the network node 100 may send a load control information message 216 by a system infor mation block (SIB) . If the SIB is SIB1, then this may correspond to the RMSI, and if it is a SIB other than the SIB1, then it may correspond to non-RMSI. The load control information message 216 may provide some be forehand information associated with a later sent con gestion control message 210 to the user nodes 110. The load control information message 216 may provide at least one of the following:

• a toggle stating that a load control function is activated • the RALC-RNTI to be used (for example, the actual value used)

• one or more traffic classes that can ignore the congestion control message 210 (for example, emer gency traffic and other priority traffic)

• a default congestion avoidance behavior upon re ceiving the congestion control message 210.

Even if the default congestion avoidance be havior may be signaled to the user nodes 110 by the network node 100 via the load control information mes sage 216, the network node 100 may be able to update the congestion control message 210 with a new congestion avoidance behavior. This may provide a faster update than just sharing this information through the earlier sent load control information message through the SIB as the SIB may be broadcast to the user nodes 110 in a longer time period.

FIGS. 3A - 3C show an example embodiment of the subject matter described herein illustrating effects of applying a signaled congestion avoidance policy. On the left side, the y axis shows the number of backlogged user nodes, and on the right side, the y axis shows the probability of collision. The x axis shows PRACH slots.

FIG. 3A illustrates an example showing latency and the number of backlogged user nodes due to large periods of listen before talk (LBT) failures during a random access channel (RACH) procedure. When the access fails (due to collision, i.e. multiple user nodes se lecting the same preamble) , then each user node performs independently of each other a random back-off within a common back-off window length and re-attempts the RACH access procedure. FIG. 3A illustrates an example showing a situation in which no pre-backoff is applied after the LBT interruption is performed, and each UE performs an independent backoff.

FIG. 3B illustrates an example showing a sit uation in which pre-backoff is applied after the LBT interruption, but the backoff is a random backoff of the same length for every user node.

FIG. 3C illustrates an example showing a sit uation in which pre-backoff is applied after the LBT interruption, but the random backoff is proportional to the waiting time of the user node during the LBT inter ruption .

Further, as can be seen from FIG. 3C compared to and 3A, the probability of collision and the number of backlogged user nodes are right after the LBT inter ruption at a much lower level.

FIGS. 4A - 4C show an example embodiment of the subject matter described herein illustrating effects of applying a signaled congestion avoidance policy. The y axis shows the latency as the number of PRACH slots, and the x axis shows an arrival time as the number of PRACH slots .

FIG. 4A illustrates an example showing a sit uation in which no pre-backoff is applied after the LBT interruption is performed.

FIG. 4B illustrates an example showing a sit uation in which pre-backoff is applied after the LBT interruption, but the backoff is a random backoff of the same length for every user node.

FIG. 4C illustrates an example showing a sit uation in which pre-backoff is applied after the LBT interruption, but the random backoff is proportional to the waiting time of the user node during the LBT inter ruption .

FIG. 5 shows an example embodiment of the sub ject matter described herein illustrating effects of applying a signaled congestion avoidance policy. The y axis shows a cumulative distribution function (CDF) , and the x axis shows latency as the number of PRACH slots. The baseline 500 corresponds with the situation in FIGS. 3A and 4A, the proposal 502 corresponds with the situ ation in FIGS. 3B and 4B, and the enhanced proposal 504 corresponds with the situation in FIGS. 3C and 4C.

One or more of the above illustrated examples and example embodiments may provide a channel congestion aware congestion procedure, thus reducing the access delaying following an unexpected congestion situation due to, for example, interference from another network or system. Further, one or more of the above illustrated examples and example embodiments may provide a solution in which user nodes can be served with a more determin istically latency. This may help in time critical use cases where latency matters. Furthermore, one or more of the above illustrated examples and example embodi ments may allow user nodes with the longest wait to be able to access the PRACH resources sooner, such that initial access related timeouts are avoided, preventing even longer access times.

Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equiv alent features and acts are intended to be within the scope of the claims.

It will be understood that the benefits and advantages described above may relate to one example embodiment or may relate to several example embodiments. The example embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter de scribed herein. Aspects of any of the example embodi ments described above may be combined with aspects of any of the other example embodiments described to form further example embodiments without losing the effect sought .

The term 'comprising' is used herein to mean including the method, blocks or elements identified, but that such blocks or elements do not comprise an exclu sive list and a method or apparatus may contain addi tional blocks or elements.

It will be understood that the above descrip tion is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of example embodiments. Although various example embodiments have been described above with a certain degree of particu larity, or with reference to one or more individual example embodiments, those skilled in the art could make numerous alterations to the disclosed example embodi ments without departing from the spirit or scope of this specification .

Claims

CLAIMS :

1. A network node (100), comprising: at least one processor (102); and

at least one memory (104) including computer program code;

the at least one memory (104) and the computer program code configured to, with the at least one pro cessor (102), cause the network node (100) to at least perform:

monitoring at least one bandwidth portion for activity in cellular communication in an unlicensed spectrum;

identifying a channel congestion based on the monitoring; and

transmitting a congestion control message when the channel congestion ends.

2. The network node (100) according to claim 1, wherein the channel congestion is identified based on listen before talk check fails.

3. The network node (100) according to claim 1 or 2, wherein the activity is caused by activity of nodes of another network.

4. The network node (100) according to any of claims 1 to 3, wherein the congestion control message comprises at least one of a duration of the channel congestion, at least one traffic class that can ignore the congestion control message, and an indication iden tifying a congestion avoidance behavior to apply when receiving the congestion control message.

5. The network node (100) according to claim 4, wherein the indication identifies a fixed length win dow back-off, a variable length window back-off based on the duration of the channel congestion, or a back- off selection based on when a user node started to at tempt its transmission.

6. The network node (100) according to any of claims 1 to 5, wherein transmitting the congestion con trol message comprises transmitting the congestion con trol message by a random access load control radio net work temporary identifier.

7. The network node (100) according to any of claims 1 to 6, wherein the at least one memory (104) and the computer program code configured to, with the at least one processor (102), cause the network node (100) to at least perform:

determining a duration of the channel conges tion; and

transmitting the congestion control message when the channel congestion ends and when the duration exceeds a channel congestion threshold.

8. The network node (100) according to any of claims 1 to 7, wherein the at least one memory (104) and the computer program code configured to, with the at least one processor (102), cause the network node (100) to at least perform:

transmitting a load control information mes sage before causing transmission of the congestion con trol message, the load control information message com prising at least one of a load control function activa tion element, the random access load control radio net work temporary identifier, at least one traffic class allowed to ignore the congestion control message, and a default congestion avoidance behavior to apply when re ceiving the congestion control message.

9. The network node (100) according to any of claims 1 to 8, wherein the network node comprises a base station .

10. A user node (110), comprising:

at least one processor (112); and

at least one memory (114) including computer program code;

the at least one memory (114) and the computer program code configured to, with the at least one pro cessor (112), cause the user node (110) to at least perform:

listening for a congestion control message upon the start of a random access channel procedure in cel lular communication in an unlicensed spectrum; and

applying a signaled congestion avoidance pol- icy, when identifying the congestion control message.

11. The user node (110) according to claim 10, wherein listening for a congestion control message upon the start of a random access channel procedure comprises listening the congestion control message before initi ating a physical random access channel procedure.

12. The user node (110) according to claim 10, wherein the at least one memory (114) and the computer program code configured to, with the at least one pro cessor (112), cause the user node (110) to at least perform: identifying a channel congestion in the cellu lar communication in the unlicensed spectrum, and wherein the listening comprises listening for the con- gestion control message before attempting a new physical random access channel procedure transmission.

13. The user node (110) according to any of claims 10 to 12, wherein the congestion control message is signaled by a random access load control radio net work temporary identifier.

14. The user node (110) according to any of claims 10 to 13, wherein the congestion control message comprises at least one of a duration of the channel congestion, at least one traffic class that can ignore the congestion control message, and an indication iden tifying a congestion avoidance behavior to apply when receiving the congestion control message.

15. The user node (110) according to claim 14, wherein the indication identifies a fixed length window back-off, a variable length window back-off based on the duration of the channel congestion, or a back-off se lection based on when a user node started to attempt its transmission .

16. The user node (110) according to any of claims 10 to 15, wherein the at least one memory (114) and the computer program code configured to, with the at least one processor (112), cause the user node (110) to at least perform:

receiving a load control information message before the congestion control message, the load control information message comprising at least one of a load control function activation element, the random access load control radio network temporary identifier, at least one traffic class allowed to ignore the congestion control message, and a default congestion avoidance be havior to apply when receiving the congestion control message .

17. The user node (110) according to any of claims 10 to 16, wherein the user node (110) comprises a mobile terminal.

18. A method comprising:

monitoring, by a network node (100), at least one bandwidth for activity in cellular communication in an unlicensed spectrum; identifying, by the network node (100), a chan nel congestion based on the monitoring; and

transmitting, by the network node (100), a con gestion control message when the channel congestion ends .

19. The method according to claim 18, wherein the channel congestion is identified based on listen before talk check fails.

20. The method according to claim 18 or 19, wherein the activity is caused by activity of nodes of another network.

21. The method according to any of claims 18 to 20, wherein the congestion control message comprises at least one of a duration of the channel congestion, at least one traffic class that can ignore the conges tion control message, and an indication identifying a congestion avoidance behavior to apply when receiving the congestion control message.

22. The method according to claim 21, wherein the indication identifies a fixed length window back off, a variable length window back-off based on the duration of the channel congestion, or a back-off se lection based on when a user node started to attempt its transmission .

23. The method according to any of claims 18 to 22, wherein transmitting the congestion control mes sage comprises transmitting the congestion control mes sage by a random access load control radio network tem porary identifier.

24. The method according to any of claims 18 to 23, further comprising: determining, by the network node (100), a du ration of the channel congestion; and

transmitting, by the network node (100), the congestion control message when the channel congestion ends and when the duration exceeds a channel congestion threshold .

25. The method according to any of claims 18 to 24, further comprising:

transmitting, by the network node (100), a load control information message before causing transmission of the congestion control message, the load control in formation message comprising at least one of a load control function activation element, the random access load control radio network temporary identifier, at least one traffic class allowed to ignore the congestion control message, and a default congestion avoidance be havior to apply when receiving the congestion control message .

26. The method according to any of claims 18 to 25, wherein the network node comprises a base sta tion.

27. A method comprising:

listening, by a user node (110), for a conges tion control message upon the start of a random access channel procedure in cellular communication in an unli censed spectrum; and

applying, by the user node (110), a signaled congestion avoidance policy, when identifying the con gestion control message.

28. The method according to claim 27, wherein listening for a congestion control message upon the start of a random access channel procedure comprises listening the congestion control message before initi ating a physical random access channel procedure.

29. The method according to claim 27, further comprising :

identifying, by the user node (110), a channel congestion in the cellular communication in the unli censed spectrum, and wherein the listening comprises listening for the congestion control message before at tempting a new physical random access channel procedure transmission .

30. The method according to any of claims 27 to 29, wherein the congestion control message is sig naled by a random access load control radio network temporary identifier.

31. The method according to any of claims 27 to 30, wherein the congestion control message comprises at least one of a duration of the channel congestion, at least one traffic class that can ignore the conges tion control message, and an indication identifying a congestion avoidance behavior to apply when receiving the congestion control message.

32. The method according to claim 31, wherein the indication identifies a fixed length window back off, a variable length window back-off based on the duration of the channel congestion, or a back-off se lection based on when a user node started to attempt its transmission .

33. The method according to any of claims 27 to 32, further comprising:

receiving, by the user node (110), a load con trol information message before the congestion control message, the load control information message comprising at least one of a load control function activation el ement, the random access load control radio network tem porary identifier, at least one traffic class allowed to ignore the congestion control message, and a default congestion avoidance behavior to apply when receiving the congestion control message.

34. The method according to any of claims 27 to 33, wherein the user node (110) comprises a mobile terminal .

35. A computer program comprising instructions for causing an apparatus to perform at least the fol lowing :

identifying a channel congestion based on the monitoring; and

transmitting a congestion control message when the channel congestion ends.

36. A computer program comprising instructions for causing an apparatus to perform at least the fol lowing :

applying a signaled congestion avoidance pol icy, when identifying the congestion control message.