WO2015115960A1

WO2015115960A1 - Random access channel performance control

Info

Publication number: WO2015115960A1
Application number: PCT/SE2014/051516
Authority: WO
Inventors: Per Skillermark
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2014-01-30
Filing date: 2014-12-17
Publication date: 2015-08-06
Anticipated expiration: 2016-07-30

Abstract

Arandom access channel performance controlmethod of a wireless communication device is disclosed, wherein the wireless communication device is adapted to communicate with a network node of a wireless communication network. The method comprises sending a random access congestion message to the network node over a random access emergency channel if a congestion condition is met. Also disclosed is a corresponding random access channel performance control method of a network node of a wireless communication network, wherein the network node isadapted to communicate with a wireless communication device. The method comprises detecting a random access congestion message on a random access emergency channel and scheduling an increased amount of communication resources for the random access channel based on the detected random access congestion message. To be published with Figure 2.

Description

RANDOM ACCESS CHANNEL PERFORMANCE CONTROL

Technical Field

The present disclosure relates to the field of random access of wireless communication systems. More particularly, it relates to control of the random access channel performance of wireless communication systems.

Introduction

Uplink random access is typically an important functional component of many typical wireless (radio) communication systems (see e.g. Figure 1 for a schematic example of part of a wireless communication system, where a wireless communication device (WCD) 100 communicates with a network node (NWN) 101 as illustrated by the arrow 102). When operating in a typical wireless communication network (hereinafter also referred to as a network, e.g. a cellular network), wireless communication devices (hereinafter also referred to as devices, e.g. user equipments - UE) may use an uplink random access channel to request resources for uplink data transmission (a scheduling request) and/or to transmit small amounts of data. If the random access procedure is not working properly for some reason, the performance of the entire network may be severely degraded.

A random access scheduling request message from a device may typically be transmitted over a contention-based channel and a typical signaling scheme may follow the below procedure (steps/items 1-3):

1. RACH (scheduling request). Compare with 231 of Figure 2. The device randomly selects a random access resource and transmits the scheduling request message in the uplink to a node (e.g. an access node - AN - or access point AP) of the network.

2. RACH response (scheduling grant). Compare with 232 of Figure 2. If the scheduling request message is received by the network node, a response message including a scheduling grant is transmitted in the downlink to the device. The scheduling grant indicates which resources have been assigned to the device for uplink data transmission. 3. Data transmission. Compare with 233 of Figure 2. The device transmits data in the uplink using the assigned resources.

For the situation where the random access channel is used for transmission of small amounts of data, the data is transmitted as part of a random access message corresponding to that of item 1 and the network responds with a positive or negative acknowledgement in a message corresponding to that of item 2. In this situation, item 3 is typically not present.

If the random access attempt in item 1 fails (i.e. if the transmitted random access message is not received by the network, e.g., due to contention), the device will not receive any corresponding response from the network in item 2. In a typical random access approach, the device will then try to retransmit the random access message after a back-off period having a random (or pseudo-random) duration. Typically, if no response to the retransmission is received from the network, the device tries to retransmit the random access message a certain number of times before it concludes that the random access attempt has failed and that the message could not be delivered.

In many typical modern wireless communication systems, the amount of resources assigned to random access is not predefined but can be dynamically adapted (e.g. based on the demand). The term resource is used herein to denote any suitable communication resource (e.g. in terms of time, frequency, code, sub-carrier, resource block, resource element, etc.) as applicable to a wireless communication system under consideration.

For example, in standardization according to the Third Generation Partnership Project, Universal Mobile Telecommunication Standard - Long Term Evolution (3 GPP UMTS LTE) the basic random access resource unit is a time-frequency block comprising six resource blocks during a sub-frame of one millisecond. It is possible to assign multiple such blocks for random access and it is also possible to vary in which sub-frames the random access resource assignments appear. In UMTS LTE, devices are informed about the random access resource allocation via downlink broadcasting. On one hand, one would like to assign a large amount of resources to the random access in order to limit the number of collisions (contentions) and achieve a high random access performance. On the other hand, resources assigned to random access are (typically) not used for data transmission. Hence, one would like to limit the resources assigned to random access in order to maximize the resources that can be used for data

transmission. Accordingly, to achieve a high overall network performance it may be beneficial to find a proper balance between resources assigned to random access and data transmission. Similar situations and considerations may arise in other systems with dynamic random access resource allocation.

In addition to dynamic random access resource allocation, it is often possible to influence the performance of the random access channel in other ways also, e.g. by adjusting the (average) back-off time for retransmission, by giving devices different priorities, and/or by adjusting the power used for a random access message transmission (and/or retransmission).

However, it is typically difficult, or even impossible, to efficiently monitor and/or adequately control the performance of a random access channel (RACH).

For example, a failed random access attempt cannot (by definition) be recorded by the network. One possible solution comprises the network using indirect measures and/or requesting information from the devices to be able to track and control the random access performance.

In UMTS LTE, the Medium Access Control (MAC) specification states that a failed random access attempt (characterized by the fact that the UE has tried to

(re)transmit the corresponding message a certain number of times) should be reported to higher layers (see e.g. 3GPP TS36.321 "Medium Access Control (MAC) protocol specification", v.11.3.0 (2013-06)) where it may be made available to the network. The network also has the possibility in UMTS LTE to request (via Radio Resource Control - RRC) that a device sends a UEInformationRequest message, which may contain a random access report request (rach-ReportReq) (see e.g. 3GPP TS 36.331 "Radio Resource Control (RRC); Protocol Specification", vl 1.5.0 (2013-09)). The rach- ReportReq includes the number of transmission attempts (numberOfPreamblesSent) that was required to deliver the random access message of the latest successfully completed random access procedure. It also includes a flag (contentionDetected) that indicates whether contention resolution was not successful for at least one of the transmitted preambles for the latest successfully completed random access procedure. This procedure exemplified by UMTS LTE is associated with a delay before the relevant information can be used in random access control. Furthermore, it only provides information regarding the latest successfully completed random access procedure. Moreover, using this solution to get continuous information about the random access channel performance (for all devices) is typically costly in terms of signaling overhead.

Thus, there is a need for alternative (and preferably improved) solutions for monitoring and/or controlling the performance of a random access channel (RACH). Preferably, such solutions are efficient, in particular in terms of one or more of delay and signaling overhead.

Summary

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.

It is an object of some embodiments to overcome at least some of the above disadvantages and to provide solutions for monitoring and/or controlling the performance of a random access channel.

A first aspect is a method of a wireless communication device for random access channel performance control, wherein the wireless communication device is adapted to communicate with a network node of a wireless communication network.

The method comprises sending a random access message to the network node over the random access channel as a first attempt, wherein the random access message is indicative of a sequential number defining the first attempt, and monitoring receipt from the network node of a random access response message corresponding to the first attempt random access message.

The random access channel performance may, for example, be measured in terms of a random access success rate. The random access success rate may, for example, be computed as a ratio between a number of random access messages successfully received at the network node and a sum of a number of attempts used by the wireless communication device to send the random access messages.

Alternatively or additionally, the random access channel performance may, for example, be measured in terms of a random access failure rate. The random access failure rate may, for example, be computed as one minus the random access success rate.

Yet alternatively or additionally, the random access channel performance may, for example, be measured in terms of a random access channel utilization. The random access channel utilization may, for example, be computed as a ratio between a number of random access messages successfully received at the network node and an amount of communication resources scheduled for the random access channel.

The control of the random access channel performance may, for example, comprise determining an amount of communication resources for the random access channel based on the sequential number, and scheduling the determined amount of communication resources for the random access channel.

Generally, scheduling of communication resources should, in the context of communication resources for the random access channel, be interpreted as allocation of communication resources for the random access channel.

The determination of the amount of communication resources for the random access channel may comprise increasing, decreasing or leaving unchanged a currently scheduled amount of communication resources for the random access channel.

For example, the amount of communication resources for the random access channel may be decreased if the random access success rate is above a first random access success rate threshold, increased if the random access success rate is below a second random access success rate threshold, and left unchanged if the random access success rate is between the first and second random access success rate thresholds, wherein the second random access success rate threshold is smaller or equal to the first random access success rate threshold.

A similar example may be applied for the random access failure rate.

One or both of these examples may additionally be combined with application of the random access channel utilization. For example, the amount of communication resources for the random access channel may be decreased if the random access success rate is above the first random access success rate threshold and the random access channel utilization is below a first random access channel utilization threshold, increased if the random access success rate is below the second random access success rate threshold and the random access channel utilization is above a second random access channel utilization threshold.

In some embodiments, the method may further comprise (if the random access response message corresponding to the first attempt random access message is not received) sending the random access message to the network node over the random access channel as a second attempt, wherein the random access message is indicative of a sequential number defining the second attempt, and monitoring receipt from the network node of a random access response message corresponding to the second attempt random access message.

In some embodiments, the method may further comprise (if the random access response message corresponding to the second attempt random access message is not received) iterating sending of the random access message to the network node over the random access channel as a further attempt, wherein the random access message is indicative of a sequential number defining the further attempt, and monitoring of receipt from the network node of a random access response message corresponding to the further occasion (i.e. the further attempt) random access message. The iteration may, for example, proceed until a random access response message is received or the random access message has been sent as a maximum number of attempts.

Sending the random access message as a first/second/further attempt should be understood as performing a first/second/further transmission of the random access message.

Sending the random access message as a first/second/further attempt may be seen as an attempt to convey the random access message to the network node. If the random access message is received by the network node, the network node transmits a corresponding random access response message to the wireless communication device. Hence, reception by the wireless communication device of a random access response message may be interpreted as the attempt to convey the random access message to the network node was successful.

Thus, according to some embodiments, the random access message is first transmitted and if no corresponding random access response message is received, the random access message is retransmitted until a corresponding random access response message or until the random access message has been (re)transmitted as a maximum number of times.

That the random access message is indicative of a sequential number defining the first/second/further attempt may, for example, imply that the first transmission of the random access message includes an indication that it is the first transmission, that the second transmission (first retransmission) of the random access message includes an indication that it is the second transmission, etc. The sequential numbers may, for example, be 0, 1, 2, etc. or 1, 2, 3, etc. The applicable sequential number may, in various embodiments, be comprised in (or prepended or appended to) the random access message.

In some embodiments, the method may further comprise sending a random access congestion message to the network node over a random access emergency channel if a congestion condition is met.

The random access congestion message may comprise a flag according to some embodiments (e.g. a single bit set to a first value if the congestion condition is not met and to a second value if the congestion condition is met).

The congestion condition may, for example, be based on one or more of the following congestion metrics:

a ratio between a number of random access response messages successfully received from the network node and a sum of a number of attempts used by the wireless communication device to send the corresponding random access messages,

a ratio between a number of times random access messages have been sent by the wireless communication device using the maximum number of attempts without successful receipt of a corresponding random access response message from the network node and a total number of random access messages sent by the wireless communication device, and one minus any of the two ratios above.

For example, the congestion condition may comprise one of the congestion metrics being on a first side of a congestion condition threshold.

Some or all of the ratios mentioned above in connection with the first aspect may, for example, be determined over a specific time duration. Alternatively or additionally, some or all of the ratios may be subject to filtering over time.

A second aspect is a method of a network node of a wireless communication network for random access channel performance control, wherein the network node is adapted to communicate with a wireless communication device. The method comprises receiving a random access message from the wireless communication device over the random access channel (wherein the random access message is indicative of a sequential number defining a number of attempts used by the wireless communication device to send the random access message), and transmitting a random access response message corresponding to the random access message to the wireless communication device. The method also comprises determining an amount of communication resources for the random access channel based on the sequential number, and scheduling the determined amount of communication resources for the random access channel.

In some embodiments, the method may further comprise detecting a random access congestion message on a random access emergency channel, and scheduling an increased amount of communication resources for the random access channel based on the detected random access congestion message.

In some embodiments, the second aspect may additionally have features identical with or corresponding to any of the various features as explained above for the first aspect.

A third aspect is a method of a wireless communication system for random access channel performance control, wherein the wireless communication network comprises a network node and a wireless communication device adapted to

communicate with each other. The method comprises steps corresponding to one or more of the steps described above for the first and/or second aspect. A fourth aspect is a computer program product comprising a computer readable medium, having thereon a computer program comprising program instructions. The computer program is loadable into a data-processing unit and adapted to cause execution of one or more of the steps described above for the first and/or second aspect when the computer program is run by the data-processing unit.

A fifth aspect is an arrangement for a wireless communication device for random access channel performance control, wherein the wireless communication device is adapted to communicate with a network node of a wireless communication network. The arrangement comprises a transceiver and a controller. The controller is adapted to cause the transceiver to send a random access message to the network node over the random access channel as a first attempt, wherein the random access message is indicative of a sequential number defining the first attempt, and to monitor receipt from the network node of a random access response message corresponding to the first attempt random access message.

In some embodiments, the fifth aspect may additionally have features identical with or corresponding to any of the various features as explained above for the first aspect.

A sixth aspect is a wireless communication device comprising the arrangement of the fifth aspect.

A seventh aspect is an arrangement for a network node of a wireless communication network for random access channel performance control, wherein the network node is adapted to communicate with a wireless communication device. The arrangement comprises a transceiver, a scheduler and a controller. The controller is adapted to cause the transceiver to receive a random access message from the wireless communication device over the random access channel (wherein the random access message is indicative of a sequential number defining a number of attempts used by the wireless communication device to send the random access message), and to transmit a random access response message corresponding to the random access message to the wireless communication device. The controller is also adapted to determine an amount of communication resources for the random access channel based on the sequential number, and cause the scheduler to schedule the determined amount of communication resources for the random access channel.

In some embodiments, the seventh aspect may additionally have features identical with or corresponding to any of the various features as explained above for the second aspect.

An eighth aspect is a network node comprising the arrangement of the seventh aspect.

A ninth aspect is a wireless communication system comprising the network node of the eighth aspect and the wireless communication device of the sixth aspect.

A tenth aspect is a random access message for random access channel performance control. The random access message comprises an indication indicative of a sequential number defining a number of attempts used by a wireless communication device to send the random access message.

An eleventh aspect is a random access emergency channel adapted to convey a random access congestion message to a network node if a congestion condition is met.

In some embodiments, the tenth and eleventh aspects may additionally have features identical with or corresponding to any of the various features as explained above for the first and second aspects.

A twelfth aspect is a method of a wireless communication device for random access channel performance control, wherein the wireless communication device is adapted to communicate with a network node of a wireless communication network. The method comprises sending a random access congestion message to the network node over a random access emergency channel if a congestion condition is met.

In some embodiments, the twelfth aspect may additionally have features identical with or corresponding to any of the various features as explained above for the first aspect.

Further aspects are a method of a network node, a computer program product, an arrangement of a wireless communication device, a wireless communication device, an arrangement of a network node and a network node with features corresponding to those of the twelfth aspect.

A thirteenth aspect is a method of a network node of a wireless communication network for random access channel performance control, wherein the network node is adapted to communicate with a wireless communication device. The method comprises detecting a random access congestion message on a random access emergency channel and scheduling an increased amount of communication resources for the random access channel based on the detected random access congestion message.

A fourteenth aspect is an arrangement for a wireless communication device for random access channel performance control, wherein the wireless communication device is adapted to communicate with a network node of a wireless communication network. The arrangement comprises a transceiver and a controller. The controller is adapted to cause the transceiver to send a random access congestion message to the network node over a random access emergency channel if a congestion condition is met.

A fifteenth aspect is an arrangement for a network node of a wireless communication network for random access channel performance control, wherein the network node is adapted to communicate with a wireless communication device. The arrangement comprises a transceiver, a scheduler and a controller. The controller is adapted to detect a random access congestion message on a random access emergency channel and cause the scheduler to schedule an increased amount of communication resources for the random access channel based on the detected random access congestion message.

An advantage of some embodiments is that a wireless communication device noticing a congestion of the random access channel may reliably convey this information to the network node.

Another advantage of some embodiments is that a wireless communication device may make the network node aware of how many times it had to transmit a random access massage before it was received by the network node.

Yet another advantage of some embodiments is that dynamic adaptation of the amount of random access resources by the network node may be more adequate.

An advantage of some embodiments is that improved monitoring

(observability), control and efficiency of the random access channel are provided.

Another advantage of some embodiments is that enhanced random access performance leads to improved overall network performance. Brief Description of the Drawings

Further objects, features and advantages will appear from the following detailed description of embodiments, with reference being made to the accompanying drawings, in which:

Fig. 1 is a schematic drawing illustrating part of an example wireless communication system according to some embodiments;

Fig. 2 is a combined flowchart and signaling diagram illustrating example method steps and signaling according to some embodiments;

Fig. 3 is a schematic drawing illustrating an example random access message structure according to some embodiments;

Fig. 4 is a plot illustrating example application of some embodiments; Fig. 5A is a block diagram illustrating an example arrangement according to some embodiments;

Fig. 5B is a block diagram illustrating an example arrangement according to some embodiments;

Fig. 6A is a block diagram illustrating an example arrangement according to some embodiments;

Fig. 6B is a block diagram illustrating an example arrangement according to some embodiments;

Fig. 7 is a signaling diagram illustrating example signaling according to some embodiments; and

Fig. 8 is a schematic drawing illustrating a computer readable medium according to some embodiments.

Detailed Description

In the following, embodiments for RACH performance observability and control will be described.

Two approaches that may be used to achieve improved observability and control of the random access channel are presented. The two approaches can be implemented separately or jointly and may be exemplified as follows.

According to one example of the first approach, the (re)transmission number of the random access attempt is included in the random access message. Thus, a sequential number defining the attempt is indicated in a sent random access message. For example, the sequential number may be equal to one (1) for the first transmission, to two (2) for the first retransmission, to three (3) for the second retransmission, and so on. In this way, the network can monitor over time how large fraction of the random access attempts that are delivered at the first, second, third (and so on) attempt and estimate the random access failure rate (or success rate). The random access resources may then be adapted accordingly. For example, when the random access failure rate increases, the network may increase the amount of resources assigned to random access and when the random access failure rate decreases, the network may decide to lower the amount of resources assigned to random access. In this way, it may be possible to adapt earlier and more smoothly to changes in the random access channel demand.

According to one example of the second approach, a random access emergency channel is provided that the devices can use to indicate (signal) to the network that random access has stalled. This is typically a common uplink channel (e.g. simply defined by a set of predefined (physical) resources (defined by, e.g., time, frequency, or code usage)) that any device can access when the random access channel has stalled completely. As soon as the network detects activity (e.g. a random access congestion message) in the random access emergency channel it may conclude that random access is working very poorly and act to solve the problem.

Figure 1 illustrates a typical network scenario where a wireless communication device 100 communicates with a network node 101 as illustrated by 102. The communication may be directed in both ways (i.e. from the wireless communication device 100 to the network node 101 and vice versa), as indicated by 102 in Figure 1.

Figure 2 illustrates an example implementation of methods according to some embodiments and will be referred to in the following.

Figure 2 illustrates an example method 201 performed by a wireless communication device (WCD) 210 (e.g. the wireless communication device 100 of Figure 1), an example method 202 performed by a network node (NWN) 220 (e.g. the network node 101 of Figure 1) and example signaling between the wireless

communication device 210 and the network node 220 in connection with performing the methods 201, 202. The example methods 201 and 202 are for random access channel performance control.

The method 201 may start in step 211, where the wireless communication device 210 sends (i.e. transmits - TX) a random access (RA) message 231 to the network node 220. The random access message is sent over a random access channel, the resources of which have been allocated by the network node.

The random access message 231 may comprise a scheduling request (i.e. a request for uplink scheduling for transmission of data) and/or small amounts of data.

The first time a random access message is sent in step 21 1 is considered to be a first attempt to convey the random access message to the network node, and the random access message is indicative of a sequential number defining that the transmission is such a first attempt. For example, the sequential number may be included in the random access message (as illustrated in step 211 of Figure 2), or appended/prepended to the random access message.

When the random access message has been sent in step 211, the method 201 proceeds to step 212, where the wireless communication device monitors receipt of a random access response message from the network node.

Typically, the wireless communication device is aware of when receipt of a random access response message corresponding to the random access message 231 may be expected (e.g. a time interval, or particular moment, defined in relation to the transmission of step 211), and the monitoring of step 212 may be adapted based of this knowledge. For example, the monitoring may be limited in time accordingly.

If the attempt to convey the random access message to the network node is successful, the random access message and the sequential number is received (RX) by the network node in step 221 of method 202. The sequential number received in step

221 may be used by the network node to adjust the amount of random access resources in step 228 which will be described later.

When the random access message is received by the network node in step 221 , the method 202 proceeds to step 222 where a random access response message 232 is transmitted to the wireless communication device. The random access response message

232 corresponds to the random access message 231 received in step 221.

If the random access message 231 comprises a scheduling request the random access response message typically comprises a scheduling grant (i.e. uplink scheduling for transmission of data). If the random access message 231 comprises small amounts of data the random access response message typically comprises an acknowledgement of reception.

If a random access response message 232 (corresponding to the random access message 231) is received by the wireless communication device (Yes-path out from step 212), the attempt to convey the random access message to the network node was successful. If the random access response message comprises a scheduling grant, the wireless communication device may transmit data 233 accordingly in step 213 and the data may be received by the network node in step 223.

If no random access response message is received by the wireless

communication device during the monitoring (No-path out from step 212), it may be concluded that the attempt to convey the random access message to the network node was not successful.

Typically, the wireless communication device then repeats the transmission of the random access message (i.e. performs a new attempt to convey the random access message to the network node) until it receives a random access response message.

This is illustrated in Figure 2 by the method 201 looping back to step 211, where the wireless communication device 210 sends the random access message again.

The second time a random access message is sent in step 21 1 is considered to be a second attempt to convey the random access message to the network node, the third time a random access message is sent in step 21 1 is considered to be a third attempt to convey the random access message to the network node, and so on for each further time a random access message is sent in step 21 1. The sequential number is incremented accordingly to define that the current transmission is such a second/third/further attempt.

A back-off time is often applied (as illustrated in step 215 in the loop back from step 212 (No-path) to step 21 1), whereby the wireless communication device does not perform retransmission of the random access message immediately following the determination that no random access response message was received, but waits during the back-off time before proceeding to step 211. The back-off time may, for example, be a random or pseudo-random duration of time. The length of the back-off time may be determined by the wireless communication device. In some embodiments, an expected value of the length of the back-off time may be determined by the network node.

In some implementations, the wireless communication device transmits the random access message at most a maximum number of times (i.e. a maximum number of attempts are applied). This is illustrated by step 214, reached from step 212 (No-path), in Figure 2. Step 214 comprised determining whether or not the random access message has been transmitted the maximum number of times.

If it is determined in step 214 that the random access message has not yet been transmitted the maximum number of times (No-path out of step 214) the method 201 loops back to step 211 (possibly via step 215) where a new attempt to convey the random access message is performed.

If it is determined in step 214 that the random access message has been transmitted the maximum number of times (Yes-path out of step 214) the method 201 is either ended or proceeds to step 216 depending on the particular implementation.

The determination of step 214 may typically be implemented as a comparison between a counter for random access message transmissions and a threshold relating to the maximum number of times.

For example, if the sequential number indicated by the random access message is 1 for the first attempt, 2 for the second attempt, etc., step 214 may comprise determining if the sequential number is lower than the maximum number of attempts (threshold value). If the sequential number is lower than the maximum number of attempts, further transmissions of the random access message may be performed and if the sequential number is equal to the maximum number of attempts, further transmissions of the random access message should not be performed.

Steps 211, 212, 213, 214, 215 and steps 21 1, 222 together with steps 228 , 229 (described later) illustrate one example of the first approach, wherein the

(re)transmission number of the random access attempt is included in the random access message.

The first approach is typically beneficial to appropriately and efficiently control the amount of resources allocated to random access in a system with dynamic random access allocation.

The amount of resources allocated to random access may be increased, decreased or kept unchanged depending on the sequential number received in step 220.

For example, if the sequential number (typically a filtered or averaged value, based on a plurality of random access messages received by the network node, possibly from several different wireless communication devices) is low (e.g. lower than a first threshold) the amount of random access resources may be decreased, if the sequential number is high (e.g. higher than a second threshold) the amount of random access resources may be increased, and if the sequential number has a medium value (e.g. higher than the first threshold and lower than the second threshold) the amount of random access resources may be left unchanged.

If the random access channel is very bad (e.g. if collisions occur almost all the time and (almost) no random access messages are successfully conveyed to the network node), the first approach may be less beneficial and the second approach may be more beneficial.

Steps 216, 217, 218 and step 227 together with steps 228, 229 (described later) illustrate one example of the second approach, wherein a random access emergency channel is provided.

In the second approach, the emergency channel may be used to force an increase of the amount of resources allocated to random access.

The first and second approaches may be used separately or in combination (as illustrated by the Yes-path out from step 214).

In step 216, the wireless communication device determines whether or not a congestion condition is met.

The congestion condition is meant to indicate when the random access channel works very poorly (e.g. if collisions occur almost all the time and (almost) no random access messages are successfully conveyed to the network node).

For example, if the wireless communication device detects that the maximum number of transmissions is reached without receipt of a corresponding random access response message (Yes-path out from step 214) for a number of (successive) random access messages it may be determined that the congestion condition is met.

Other congestion conditions may, of course, be equally applicable in various embodiments.

The congestion condition may, for example, be based on (e.g. an average or filtered value of) one or more of the following congestion metrics: a ratio between a number of random access response messages received from the network node and a sum of a number of attempts used to send the corresponding random access messages (similar to λ described below), a ratio between a number of times random access messages have been sent using the maximum number of attempts without receipt of a corresponding random access response message and a total number of random access messages sent, and

one minus any of the two ratios above.

The congestion condition may, for example, comprise one of the congestion metrics being on a first side of a congestion condition threshold.

If it is determined that the congestion condition is not met (No-path out from step 216), the method 201 is ended in step 218.

If it is determined that the congestion condition is met (Yes-path out from step 216), the method 201 proceeds to step 217 where a random access congestion message 237 is sent (transmitted - TX) to the network node. Thereafter, the method 201 is ended in step 218.

The random access congestion message 237 is sent over a random access emergency channel. This channel may typically comprise a communication resource specifically dedicated for the purpose of conveying random access congestion messages.

The random access congestion message 237 is received (i.e. detected) by the network node in step 227.

In step 228, the network node uses the sequential number(s) received in step 221 and/or the random access congestion message detected in step 227 to determine the amount (increased/decreased/unchanged) of random access resources.

For example, the received sequential number(s) (typically from a plurality of wireless communication devices performing random access to the network node) may be averaged or filtered over time and used to determine if the amount of random access resources should be increased, decreased or unchanged.

In some embodiments, the sequential number is only used to determine if the amount of random access resources should be increased or unchanged. In some embodiments, the sequential number is only used to determine if the amount of random access resources should be increased or decreased.

The determination may be based on one or more thresholds. One or more hysteresis may also be applied according to some embodiments (e.g. a hysteresis in time and/or a hysteresis in threshold values).

The metric for determining the amount of random access resource may, for example, be (e.g. an average or filtered value of) one or more of the following:

a ratio between a number of random access messages received from wireless communication devices and a sum of a number of attempts (indicated by the sequential number) used to send the corresponding random access messages (compare with λ described below), and one minus the ratio above.

Furthermore, if a random access congestion message is detected the network node may determine to increase the amount of random access resources immediately (regardless of other parameters such as the sequential number(s)).

The determined amount of random access resources are scheduled accordingly in step 229 and information regarding which communication resources are available for random access is transmitted (e.g. broadcast) to the wireless communication device(s) as illustrated by 239 . In the background section above, a typical RACH procedure was described (steps/items 1-3, compare with 231, 232, 233 of Figure 2) for the case when a contention-based RACH is used to request resources for data transmission.

In step 1, the random access message 231 (e.g. a RACH scheduling request) is transmitted over a contention-based channel. If any other user decides to transmit a RACH at the same time using the same resources, a contention occurs and it is likely that the RACH message cannot be correctly delivered. If no contention happens, the network responds with a random access response message 232 (e.g. a scheduling grant) in step 2 that indicates which resources may be used for uplink data transmission, and the device transmits data in the uplink in step 3. According to some embodiments (as illustrated by the example of Figure 3 that shows a RACH message (packet) with the information about the RACH transmission attempt appended), the RACH transmission attempt number (Seq. nbr) 310 is included in (or otherwise attached to) the RACH message 300 of step 1. If the RACH message is transmitted for the first time, the RACH transmission attempt number may equal one (1). If the message is transmitted for the second time, i.e., is retransmitted for the first time because the initial transmission failed, the RACH transmission attempt number may equal two (2) and so on. Including this information in the message makes it possible for the network to determine an appropriate amount of communication resources for the random access channel based on the sequential number and scheduling the determined amount of communication resources accordingly. For example, the network may more accurately monitor the performance of the RACH channel and (based on the RACH performance) increase or decrease the amount of resources assigned to the RACH.

Based on the successfully received RACH messages the network may estimate the RACH success rate (random access success rate), e.g., according to equation (1) below:

where X is the estimated RACH success rate, N is the number of successfully recorded RACH messages in the considered time window, and _; is the transmission attempt (indicated by the sequential number) at which RACH message /^' was successfully delivered. The RACH success rate, as defined here, may take on values between zero (0) and one (1); a low value - close to zero - indicates that the RACH channel works poorly whereas a high value - close to one - indicates that the RACH channel performs well. Alternatively, one may use the RACH failure rate (random access failure rate) j, defined as:

ή = 1 - λ

(Eq. 2). A failure rate close to zero indicates a well-functioning RACH whereas a failure rate close to one indicates a poorly functioning RACH. The estimates of the RACH success rate and failure rate provided here are typically representative of the true RACH performance as long as the RACH performance is relatively high, i.e., as most of the RACH messages can be delivered (within the maximum number of transmission attempts).

The network may use one (or more) of these estimates of the RACH success rate or failure rate when adapting the RACH resource allocation (compare with step 228 or Figure 2). An example is provided in Figure 4, in which the RACH failure rate (fj) 410 is used in combination with the random access channel utilization (RACH resource utilization - RACH RU) (0) 420 to adapt the resource assignment. The RACH resource utilization is defined as the ratio between the number of successfully received RACH messages (N) and the number of available RACH resources (M). That is: υ-—

^~M (Eq. 3). In the example in Figure 4 (an example of how the RACH success rate and the

RACH RU may be used to adapt the RACH resource assignment), the RACH failure rate is initially close to zero, i.e., the RACH seems to work well, while the RACH resource utilization is relatively high but falling. At point ti the RACH resource utilization has fallen below some threshold while at the same time the RACH failure rate still is low. This triggers the network to reduce the RACH resource allocation (i.e. decrease RACH resources). After this point, the RACH resource utilization increases and the RACH failure rate increases (perhaps caused by the prior reduction in resources, possibly combined with an increased load on the RACH) and at point t₂, when the RACH failure rate has increased to a relatively high value and the RACH resource utilization is again on a high value, the network decides to increase the amount of resources used for RACH.

Yet another decision variable could be the utilization and demand on the uplink data channel. If uplink data channel utilization and demand is low, there is less incentive to reduce the resource assigned to the RACH as more resources to the uplink data channel is not associated with any substantial benefits in terms of improved uplink data channel performance, and vice versa.

Alternatively or additionally (i.e. as a complement) to the continuous resource allocation mechanisms described above, the RACH emergency channel can be used. Devices may follow a predefined protocol and only make use of the RACH emergency channel under certain conditions (e.g. if, during a recent time duration, a large fraction of the RACH messages could not be delivered). As soon as the network detects activity (237) in the random access emergency channel it may try to take appropriate measures to improve the random access performance (e.g. by quickly increasing the RACH resource allocation).

Figures 5A, 5B, 6A and 6B illustrate example implementations of

arrangements for a device and a network node, respectively, according to some embodiments. The example arrangements may, for example, be adapted to perform method steps as described above in connection to Figure 2.

Figure 5A illustrates an example arrangement 500 for a wireless

communication device for random access channel (RACH) performance control according to some embodiments.

The example arrangement 500 may for example be comprised in the wireless communication device 100 of Figure 1 and/or the wireless communication device 201 of Figure 2. Furthermore, the example arrangement 500 may be adapted to perform the method 201 of Figure 2.

The arrangement 500 comprises a transceiver (TX/RX) 510 and a controller (CNTR) 520.

The controller 520 is adapted to cause the transceiver 510 to transmit a RA message to a network node over the RACH, wherein the RA message is indicative of a sequential number defining which attempt - in a sequence of attempts - the transmission of the RA message corresponds to (compare with step 211 of Figure 2).

The controller 520 is also adapted to monitor receipt from the network node of a RA response message corresponding to the transmission of the RA message (compare with step 212 of Figure 2) . The controller 520 is also adapted to cause the transceiver to iteratively retransmit the RA message as long as no random access response message is received (compare with the iteration of steps 21 1 and 212 in Figure 2). As described in connection to Figure 2, the iteration may be performed with a back-off time between re- transmissions (compare with step 215 of Figure 2). Furthermore, the iteration may be terminated - even if no RA response message is received - when the RA message has been transmitted a maximum number of times (compare with step 214 of Figure 2).

The controller 520 is also adapted determine if a congestion condition has been met (compare with step 216 of Figure 2) and transmit a RA congestion message (compare with step 217 of Figure 2) to the network node if the congestion condition is met.

Other features disclosed above in connection with Figure 2 may be equally applicable to the example embodiment 500 of Figure 5A.

Figure 5B illustrates an example arrangement 550 for a wireless

The example arrangement 550 may for example be comprised in the wireless communication device 100 of Figure 1 and/or the wireless communication device 201 of Figure 2. Furthermore, the example arrangement 550 may be adapted to perform the method 201 of Figure 2.

The arrangement 500 comprises a transceiver (TX RX) 570, a sequential number counter (NBR) 581, a monitor (MON) 582 and a congestion detector (CONG) 583.

The sequential number counter 581, the monitor 582 and the congestion detector 583 may, for example, be comprised in a controller (CNTR) 580.

The transceiver 570 is adapted to transmit a RA message to a network node over the RACH, wherein the RA message is indicative of a sequential number defining which attempt - in a sequence of attempts - the transmission of the RA message corresponds to (compare with step 21 1 of Figure 2). The sequential number counter 581 is adapted to provide the sequential number and update (e.g. increment) it appropriately for each transmission of the RA message. The monitor 582 is adapted to monitor receipt from the network node of a RA response message corresponding to the transmission of the RA message (compare with step 212 of Figure 2).

The transceiver is adapted to iteratively retransmit the RA message as long as no random access response message is received (compare with the iteration of steps 21 1 and 212 in Figure 2). For example, the monitor 582 may iteratively cause an update of the sequential number of the sequential number counter 581 and a retransmission if no RA response message is received.

As described in connection to Figure 2, the iteration may be performed with a back-off time between re-transmissions (compare with step 215 of Figure 2).

Furthermore, the iteration may be terminated - even if no RA response message is received - when the RA message has been transmitted a maximum number of times (compare with step 214 of Figure 2).

The transmission of the RA message by the transceiver 570 may be controlled by the controller 580. For example, the sequential number counter 581 may implement a function that terminates the iteration when the maximum number of transmissions have been performed.

The congestion detector 583 is adapted determine if a congestion condition has been met (compare with step 216 of Figure 2) and cause the transceiver 570 to transmit a RA congestion message (compare with step 217 of Figure 2) to the network node if the congestion condition is met. The congestion detector 583 may, for example, base its determination on information from the monitor 582 and/or the sequence number counter 581.

Other features disclosed above in connection with Figure 2 may be equally applicable to the example embodiment 550 of Figure 5B.

Figure 6A illustrates an example arrangement 600 for a network node for random access channel (RACH) performance control according to some embodiments.

The example arrangement 600 may for example be comprised in the network node 101 of Figure 1 and/or the network node 220 of Figure 2. Furthermore, the example arrangement 600 may be adapted to perform the method 202 of Figure 2. The arrangement 600 comprises a transceiver (TX RX) 610, a scheduler (SCH) 630 and a controller (CNTR) 620.

The controller 620 is adapted to cause the transceiver 610 to receive a RA message from a wireless communication device over the RACH, wherein the RA message is indicative of a sequential number defining how many attempts have been used by the wireless communication device to transmit the RA message (compare with step 221 of Figure 2).

The controller 620 is further adapted to cause the transceiver 610 to transmit a RA response message to the wireless communication device corresponding to the received RA message (compare with step 222 in Figure 2).

The controller 620 is also adapted to cause the transceiver 610 to receive a RA congestion message from the wireless communication device over a RA emergency channel (compare with step 227 of Figure 2).

The controller 620 is further adapted to determine an amount of RA resources for the RACH based on the sequential number and/or the RA congestion message (compare with step 228 or Figure 2).

The controller 620 is further adapted to cause the scheduler 630 to schedule the determined amount of RA resources for the random access channel (compare with step 229 of Figure 2), and the transceiver 610 is adapted to provide information regarding the RA resources to the wireless communication device(s).

Other features disclosed above in connection with Figure 2 may be equally applicable to the example embodiment 600 of Figure 6A.

Figure 6B illustrates an example arrangement 650 for a network node for random access channel (RACH) performance control according to some embodiments.

The example arrangement 650 may for example be comprised in the network node 101 of Figure 1 and/or the network node 220 of Figure 2. Furthermore, the example arrangement 650 may be adapted to perform the method 202 of Figure 2.

The arrangement 650 comprises a transceiver (TX/RX) 670, a scheduler (SCH) 690, a sequential number tracker (NBR) 681, a random access congestion message detector (DETECT) 683 and a random access resource amount determiner (AMOUNT) 684. The sequential number tracker ( BR) 681, the random access congestion message detector (DETECT) 683 and the random access resource amount determiner (AMOUNT) 684 may, for example, be comprised in a controller (CNTR) 680.

The transceiver 670 is adapted to receive a RA message from a wireless communication device over the RACH, wherein the RA message is indicative of a sequential number defining how many attempts have been used by the wireless communication device to transmit the RA message (compare with step 221 of Figure 2).

The transceiver 670 is also adapted to transmit a RA response message to the wireless communication device corresponding to the received RA message (compare with step 222 in Figure 2).

The transceiver 670 is further adapted to receive a RA congestion message from the wireless communication device over a RA emergency channel (compare with step 227 of Figure 2).

The random access resource amount determiner 684 is adapted to determine an amount of RA resources for the RACH based on the sequential number and/or the RA congestion message (compare with step 228 or Figure 2).

In analogy with the description above, if the random access congestion message detector 683 detects that the transceiver 670 has received a RA congestion message, the random access resource amount determiner 684 may determine to increase the amount.

Also in analogy with the description above, the random access resource amount determiner 684 may determine whether the amount should be

increased/decreased/unchanged based on the sequential number received by the transceiver 670. The sequential number tracker 681 may be adapted to calculate a filtered or averaged sequential number (possibly based on RA messages from several wireless communication devices) and provide it to the random access resource amount determiner 684 for use in the amount determination.

The random access resource amount determiner 684 is further adapted to cause the scheduler 690 to schedule the determined amount of RA resources for the random access channel (compare with step 229 of Figure 2), and the transceiver 670 is adapted to provide information regarding the RA resources to the wireless communication device(s).

Other features disclosed above in connection with Figure 2 may be equally applicable to the example embodiment 650 of Figure 6B.The UMTS LTE random access procedure between a wireless communication device (WCD) 710 and a network node (NWN) 720, illustrated in Figure 7, comprises four steps (731 1, 732_1, 731 2, 732_2) prior to data transmission (733) (compare with items 1-3 described in the background section). In the first step (731_1) the UE randomly selects and transmits a random access preamble and the network responds with a random access response (second step, 732_1). In UMTS LTE it is typically not possible to detect contention during these steps since if more than one UE uses the same preamble at the same time the eNodeB will just detect that a single random access preamble is used and act as if it was transmitted by a single UE. Instead, any possible contention is detected and resolved in steps three (731_2) - RRC signaling (over PUSCH) - and four (732_2) - RRC signaling (over PDSCH).

Including the random access attempt number in the first step (731 1) would require a redesign of the physical channel used in the initial step of the random access procedure. This is possible, but a possibly more attractive solution may be to include the random access attempt in the RRC signaling in the third step (731_2). Thus, either (or both) of the messages 731_1 and 731_2 may be considered as a random access message (compare with 231 of Figure 2).

Possible solutions to include a random access emergency channel in UMTS LTE include reserving a special random access preamble for the random access emergency channel and/or dedicating some time-frequency resources for this purpose (and then avoid scheduling any data in these specific resources). If the former solution is employed, and if backwards compatibility is desired, the random access emergency channel preamble should typically be selected considering the allocation of preambles to cells such that no preamble is simultaneously assigned to both normal RACH usage and the RACH emergency channel.

The described embodiments and their equivalents may be realized in software or hardware or a combination thereof. They may be performed by general-purpose circuits associated with or integral to a communication device, such as digital signal processors (DSP), central processing units (CPU), co-processor units, field- programmable gate arrays (FPGA) or other programmable hardware, or by specialized circuits such as for example application-specific integrated circuits (ASIC). All such forms are contemplated to be within the scope of this disclosure.

Embodiments may appear within an electronic apparatus (such as a wireless communication device or a network node) comprising circuitry /logic or performing methods according to any of the embodiments.

According to some embodiments, a computer program product comprises a computer readable medium such as, for example, a diskette or a CD-ROM 800 as illustrated in Figure 8. The computer readable medium may have stored thereon a computer program comprising program instructions. The computer program may be loadable into a data-processing unit 830, which may, for example, be comprised in a mobile terminal or network node 810. When loaded into the data-processing unit, the computer program may be stored in a memory 820 associated with or integral to the data-processing unit. According to some embodiments, the computer program may, when loaded into and run by the data-processing unit, cause the data-processing unit to execute method steps according to, for example, the methods shown in any of the Figures 2 and 7.

Reference has been made herein to various embodiments. However, a person skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the claims. For example, the method embodiments described herein describes example methods through method steps being performed in a certain order. However, it is recognized that these sequences of events may take place in another order without departing from the scope of the claims.

Furthermore, some method steps may be performed in parallel even though they have been described as being performed in sequence.

In the same manner, it should be noted that in the description of embodiments, the partition of functional blocks into particular units is by no means limiting.

Contrarily, these partitions are merely examples. Functional blocks described herein as one unit may be split into two or more units. In the same manner, functional blocks that are described herein as being implemented as two or more units may be implemented as a single unit on other embodiments.

Hence, it should be understood that the details of the described embodiments are merely for illustrative purpose and by no means limiting.

Claims

1. A random access channel performance control method of a wireless communication device (100, 210, 500, 550, 710), wherein the wireless communication device (100, 210, 500, 550, 710) is adapted to communicate (102) with a network node (101, 220, 600, 650, 720) of a wireless communication network, the method comprising:

sending (217) a random access congestion message (237) to the network node over a random access emergency channel if a congestion condition is met.

2. The method of claim 1 further comprising:

sending (21 1) a random access message (231, 300, 731 1, 731_2) to the network node (101, 220, 600, 650, 720) over the random access channel as a first attempt, wherein the random access message is indicative of a sequential number (310) defining the first attempt; and

monitoring (212) receipt from the network node (101, 220, 600, 650, 720) of a random access response message (232) corresponding to the first attempt random access message.

3. The method of claim 2 further comprising, if the random access response message corresponding to the first attempt random access message is not received: sending (21 1) the random access message to the network node (101, 220, 600, 650, 720) over the random access channel as a second attempt, wherein the random access message is indicative of a sequential number (310) defining the second attempt; and

monitoring (212) receipt from the network node (101, 220, 600, 650, 720) of a random access response message (232) corresponding to the second attempt random access message.

4. The method of claim 3 further comprising, if the random access response message corresponding to the second attempt random access message is not received, iterating:

sending (21 1) of the random access message to the network node (101, 220, 600, 650, 720) over the random access channel as a further attempt, wherein the random access message is indicative of a sequential number (310) defining the further attempt; and

monitoring (212) of receipt from the network node (101, 220, 600, 650, 720) of a random access response message (232) corresponding to the further attempt random access message.

5. The method of claim 4 wherein the iteration proceeds until (214, 215): a random access response message is received; or

the random access message has been sent as a maximum number of attempts.

6. A random access channel performance control method of a wireless communication device (100, 210, 500, 550, 710), wherein the wireless communication device (100, 210, 500, 550, 710) is adapted to communicate (102) with a network node (101, 220, 600, 650, 720) of a wireless communication network, the method comprising:

7. A random access channel performance control method of a network node (101, 220, 600, 650, 720) of a wireless communication network, wherein the network node (101 , 220, 600, 650, 720) is adapted to communicate (102) with a wireless communication device (100, 210, 500, 550, 710), the method comprising:

detecting (227) a random access congestion message (237) on a random access emergency channel; and

scheduling (228, 229) an increased amount of communication resources for the random access channel based on the detected random access congestion message.

8. The method of claim 7 further comprising:

receiving (221) a random access message (231, 300, 731 1 , 73 1_2) from the wireless communication device (100, 210, 500, 550, 710) over the random access channel, wherein the random access message is indicative of a sequential number (310) defining a number of attempts used by the wireless communication device (100, 210, 500, 550, 710) to send the random access message; and

transmitting (222) a random access response message (232) corresponding to the random access message to the wireless communication device (100, 210, 500, 550, 710).

9. The method of claim 8 further comprising:

determining (228) an amount of communication resources for the random access channel based on the sequential number; and

scheduling (229) the determined amount of communication resources for the random access channel.

10. A random access channel performance control method of a network node (101 , 220, 600, 650, 720) of a wireless communication network, wherein the network node (101 , 220, 600, 650, 720) is adapted to communicate (102) with a wireless communication device (100, 210, 500, 550, 710), the method comprising:

11. A computer program product (800) comprising a computer readable medium, having thereon a computer program comprising program instructions, the computer program being loadable into a data-processing unit and adapted to cause execution of the method of any of claims 1 through 10 when the computer program is run by the data-processing unit.

12. A random access channel performance control arrangement for a wireless communication device (100, 210, 500, 550, 710), wherein the wireless communication device (100, 210, 500, 550, 710) is adapted to communicate (102) with a network node (101, 220, 600, 650, 720) of a wireless communication network, the arrangement comprising: a transceiver (510, 570) and a controller (520, 580), the controller adapted to:

cause the transceiver to send a random access congestion message (237) to the network node (101, 220, 600, 650, 720) over a random access emergency channel if (216) a congestion condition is met.

13. The arrangement of claim 12, wherein the controller is further adapted to: cause the transceiver to send a random access message (231, 300, 731 1,

731_2) to the network node (101, 220, 600, 650, 720) over the random access channel as a first attempt, wherein the random access message is indicative of a sequential number (310) defining the first attempt; and to

monitor receipt from the network node (101, 220, 600, 650, 720) of a random access response message corresponding to the first attempt random access message.

14. The arrangement of claim 13 wherein the controller is further adapted to, if the random access response message corresponding to the first attempt random access message is not received:

cause the transceiver to send the random access message to the network node (101, 220, 600, 650, 720) over the random access channel as a second attempt, wherein the random access message is indicative of a sequential number (310) defining the second attempt; and to

monitor receipt from the network node (101, 220, 600, 650, 720) of a random access response message (232) corresponding to the second attempt random access message.

15. The arrangement of claim 14 wherein the controller is further adapted to, if the random access response message corresponding to the second attempt random access message is not received, iterate:

causing the transceiver to send the random access message to the network node

(101, 220, 600, 650, 720) over the random access channel as a further attempt, wherein the random access message is indicative of a sequential number (310) defining the further attempt; and

monitoring receipt from the network node (101, 220, 600, 650, 720) of a random access response message (232) corresponding to the further attempt random access message.

16. The arrangement of claim 15 wherein the controller is further adapted to perform the iteration until (214, 215):

a random access response message is received; or

the random access message has been sent as a maximum number of attempts.

17. A random access channel performance control arrangement for a wireless communication device (100, 210, 500, 550, 710), wherein the wireless communication device (100, 210, 500, 550, 710) is adapted to communicate (102) with a network node (101, 220, 600, 650, 720) of a wireless communication network, the arrangement comprising: a transceiver (510, 570) and a controller (520, 580), the controller adapted to:

cause the transceiver to send a random access message (231, 300, 731 1, 731_2) to the network node (101, 220, 600, 650, 720) over the random access channel as a first attempt, wherein the random access message is indicative of a sequential number (310) defining the first attempt; and to

18. A wireless communication device (100, 210, 500, 550, 710) comprising the arrangement of any of claims 12 through 17.

19. A random access channel performance control arrangement for a network node (101, 220, 600, 650, 720) of a wireless communication network, wherein the network node (101, 220, 600, 650, 720) is adapted to communicate (102) with a wireless communication device (100, 210, 500, 550, 710), the arrangement comprising a transceiver (610, 670), a scheduler (630, 690) and a controller (620, 680), the controller adapted to:

detect a random access congestion message (237) on a random access emergency channel; and

cause the scheduler to schedule an increased amount of communication resources for the random access channel based on the detected random access congestion message.

20. The arrangement of claim 19, wherein the controller is further adapted to cause the transceiver to:

receive a random access message (231, 300, 731 1, 731 2) from the wireless communication device (100, 210, 500, 550, 710) over the random access channel, wherein the random access message is indicative of a sequential number (310) defining a number of attempts used by the wireless communication device (100, 210, 500, 550,

710) to send the random access message; and transmit a random access response message corresponding to the random access message to the wireless communication device (100, 210, 500, 550, 710).

21. The arrangement of claim 20 wherein the controller is further adapted to: determine an amount of communication resources for the random access channel based on the sequential number; and

cause the scheduler to schedule the determined amount of communication resources for the random access channel.

22. A random access channel performance control arrangement for a network node (101, 220, 600, 650, 720) of a wireless communication network, wherein the network node (101, 220, 600, 650, 720) is adapted to communicate (102) with a wireless communication device (100, 210, 500, 550, 710), the arrangement comprising a transceiver (610, 670), a scheduler (630, 690) and a controller (620, 680), the controller adapted to cause the transceiver to:

receive a random access message (231, 300, 731_1, 731_2) from the wireless communication device (100, 210, 500, 550, 710) over the random access channel, wherein the random access message is indicative of a sequential number (310) defining a number of attempts used by the wireless communication device (100, 210, 500, 550, 710) to send the random access message; and

transmit a random access response message corresponding to the random access message to the wireless communication device (100, 210, 500, 550, 710).

23. A network node (101, 220, 600, 650, 720) comprising the arrangement of any of claims 20 through 22.