WO2011099906A1

WO2011099906A1 - Method and arrangement for adapting semi-persistently configured, periodic resources in a wireless communications network

Info

Publication number: WO2011099906A1
Application number: PCT/SE2010/050170
Authority: WO
Inventors: Kristina Jersenius; Mehdi Amirijoo; Erik Eriksson; Fredrik Gunnarsson; Yin Liu; Yu QIAN; Xinghua SONG
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2010-02-12
Filing date: 2010-02-12
Publication date: 2011-08-18
Also published as: EP2534913A1; CN102742347A

Abstract

The invention relates to a method and arrangement (500) in a network communication node (13, 14) for adapting an amount of periodic resources. The periodic resources are semi statically configured to a user equipment (11, 12) within a cell (10) of a radio telecommunications network (1). The network communication node (13,14) is comprised in the radio telecommunications network (1) and controls an amount of radio channel resources within the cell (10) of a radio control channel. The amount of periodic resources is defined as a size of a control region, which control region is at least a part of the amount of radio channel resources. The user equipment (11,12) uses a specific control signalling type on the radio control channel. The network communication node determines a traffic load in the cell (10) and obtains a periodicity requirement indication, which indication is based on the control signalling type. The network communication node then determines the size of the control region based on the determined traffic load in the cell (10) and the obtained periodicity requirement indication and thereby adapts the amount of periodic resources for the cell (10).

Description

Method and arrangement for adapting semi-persistently configured, periodic resources in a wireless communications network

TECHNICAL FIELD

The present invention relates to a method and an arrangement in a network communication node. In particular, the invention relates to adapting an amount of periodic resources within a radio communication network.

BACKGROUND

A radio communications network is a cellular system comprising a number of cells. Each cell may serve a number of user terminals, with the generic name User Equipment "UE", communicating through radio base stations connected to a core network. In cellular mobile communication networks of today user equipments are assigned periodic resources for control signaling to the radio base stations. This is the case for 3G Long Term Evolution (LTE) Rel 8 where user equipments may be assigned multiple periodic resources but also in other types of systems such as Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communication (GSM) and/or the like.

A network communications node, such as a radio base station or a network controller node, in the communications network controls an amount of radio channel resources of a radio control channel of one ore more cells in the communications network. A control region of the amount of radio channel resources defines an amount of periodic resources that is semi statically configured to user equipments in the cells and are allocated to be used by user equipments within the cells for a certain type of control signaling, which control signaling is transmitted from the user equipment with a certain periodicity, e.g. the user equipment transmits the control signalling every 10th ms.

Examples of such periodic resources are:

Channel State Information (CSI) reporting resources

CSI reporting resources are periodic resources assigned to user equipments on the physical uplink control channel (PUCCH). In, for example, LTE uplink, a resource unit is a resource block comprising of 7, or 6, Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols in time, a slot of length 0.5 ms, and 12 sub-carriers, 180 KHz, in frequency. Resource allocation is typically done for resource block pairs, 1 resource block pair being 1 subframe, that is, 2 slots, in time and 12 sub-carriers in frequency. PUCCH occupies resource blocks on the edge of the uplink frequency spectrum. Multiple user equipments may be allocated resources on the same PUCCH resource block by utilizing code multiplexing. The CSI reporting resource is used by the user equipments to report measured downlink Channel Quality Indicators (CQI), Rank Indicators (Rl) and Precoding Matrix Indicators (PMI). This information may be utilized for e.g. for downlink channel dependent scheduling, downlink link adaptation and multi antenna transmissions, for example, MIMO. CSI information may also be reported a- periodically on the physical uplink shared channel (PUSCH). The resources for a-periodic reporting on PUSCH are dynamically allocated by the base station, not semi-statically configured, that is, continuously reported and allocated for the present user equipments not also for future user equipments or usage. CSI reports may include frequency selective information or only wideband information. To report frequency selective information periodically on PUCCH requires multiple reports. With a-periodic reporting on PUSCH, the frequency selective information is reported in one report.

Scheduling request (SR) resources

SR resource is a periodic single bit resource used by the user equipment to indicate buffer status, i.e. that the user equipment has data to transmit. The SR resources are located on the PUCCH.

Sounding resources

Sounding resources are used to transmit reference symbols over the entire or parts of the uplink bandwidth. Sounding reference signals may provide the radio base station, such as an eNodeB, with information about channel quality. This information may be utilized e.g. for uplink channel dependent scheduling, uplink link adaptation, and also for downlink beam forming in case of reciprocal channels as in time division duplex (TDD).

The sounding reference signals are transmitted on the last symbol in the subframe.

Several user equipments may transmit sounding in the same subframe. The multiplexing of user equipments may be done by frequency domain multiplexing and by code division multiplexing.

There are also other periodic resources that may be semi statically configured to user equipments. As stated above, the periodic resources are semi statically configured to a user equipment. That means that the periodic resource is valid until further notice and a reconfiguration command is needed to change the configuration. The reconfiguration usually takes time and cost in radio resources. In the examples above configuration and reconfiguration are done using radio resource control (R C) signalling. In previous systems a big area comprising a number of cells has been configured to support a number of user equipments over a period, for example, by estimating a load in the area. When the load changes in the network then network reconfigures the size of the control region.

Since there is a cost related to reassigning resources, the common solution is to decide resources on a number of supported user equipments and is done for the entire network or for subparts of big areas of the network. The problem with the existing solution is that the configuration may count on the worse case scenario allocating unnecessary large amount of radio channel resources to the control region, or that pre-allocation does not cover the worst case, i.e. do not support enough user equipments, and the system has to reconfigure user equipments when more user equipments enter, that is, that continuous reconfiguration is required with increased signaling.

SUMMARY

An object of the present solution is to provide a mechanism for using control channel resources in an efficient manner.

In a first aspect the object is achieved by a method in a network communication node, such as a radio base station or a network controller node, for adapting an amount of periodic resources for a cell in a radio communications network. The periodic resources are semi statically configured to a user equipment within the cell. The network

communication node is comprised in a radio telecommunications network and controls an amount of radio channel resources of a radio control channel within the cell. The amount of periodic resources is defined as a size of a control region, which control region is at least a part of the amount of radio channel resources. Also, the user equipment uses a specific control signalling type on the radio control channel. The network communication node determines a traffic load in the cell and obtains a periodicity requirement indication, which indication is based on the control signalling type. For example, determines maximal amount of user equipments from historic data and traffic type requiring resource update every second.

The network communication node determines the size of the control region based on the determined traffic load in the cell and on the obtained periodicity requirement indication and thereby adapting the amount of periodic resources for the cell.

In order to perform the method an arrangement in the network communication node is provided. The arrangement is for adapting an amount of periodic resources for a cell in a radio communications network. The periodic resources are semi statically configured to a user equipment within the cell. The network communication node is comprised in a radio telecommunications network and controls an amount of radio channel resources of a radio control channel within the cell. The amount of periodic resources is defined as a size of a control region, which control region is at least a part of the amount of radio channel resources. Also, the user equipment uses a specific control signalling type on the radio control channel.

The arrangement comprises a determining circuit configured to determine the traffic load in the cell and an obtaining circuit configured to obtain the periodicity requirement indication. Furthermore, the arrangement comprises a size determining circuit coupled to the determining circuit and the obtaining circuit and the size determining circuit is configured to determine the size of the control region based on the determined traffic load in the cell and on the obtained periodicity requirement indication. By basing the determination of the size of the control region, and thereby the pre- allocation of resources, on measurements done in the cell giving information on expected load and requirements on periodicities an efficient usage of control channel resources is provided. Furthermore, the determining of the size of the control region may also take typical propagation conditions into account as well.

Embodiments herein are enabled to take into account that different cells have different load and different requirement on periodicities. In addition to this, different user equipments within the different cells may have different periodicity requirements due to differences in channel and traffic behaviour. By implementing the solution it is avoided that the periodicities were initially sat to low or the resource region to small. Thus, the control channel resources are used in a more efficient and optimized manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described in more detail in relation to the enclosed drawings, in which:

Figure 1 is a block diagram showing a schematic overview of a radio

communications network,

Figure 2 is a combined flowchart and signalling diagram of an embodiment of a method,

Figure 3 is a block diagram showing a schematic flowchart in a radio communication node,

Figure 4 is a block diagram showing a schematic flowchart of a method in a network communication node, and

Figure 5 is a block diagram showing schematic overview of an arrangement in a network communication node.

DETAILED DESCRIPTION

In Fig. 1 a schematic overview of a radio communications network 1. As shown, the radio communications network 1 is a cellular system and comprises a number of cells, a cell 10 is shown in Fig. 1. Each cell may comprise a number of user terminals, with the generic name "UE", User Equipment, two are shown as a first user equipment 11 and a second user equipment 12 within the cell 10 in Fig 1 . The first user equipment 1 1 is exemplified as a mobile phone and the second user equipment 12 is exemplified as a portable computer used close to the cell border.

For each cell in the radio communications network 1 , there is a controlling node also know as a network communication node, generically referred to as a "radio base station", RBS, which is shown as 13 in Fig 1. One role of the RBS 13 is that all traffic to and from the user equipments 1 1 and 12 in the cells 10 is routed via the RBS 13. The telecommunications network 1 may comprise a Long Term Evolution (LTE) network as well as other networks such as Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications (GSM) or the like. An RBS may be denoted as NodeB or eNodeB in some of the networks.

The user equipments 1 1 , 12 in the cell 10 have some type of periodic control signaling to transmit to the radio base station 13. The transmissions of this control signaling require a certain amount of radio channel resources. An amount of resources is semi statically configured for the cell 10 to be used for periodic resources, which amount forms a control region of the total amount of radio channel resources. By semi statically means that the radio resources of the control region are deposited or pre-allocated over a time period for the periodic resources. The time period is determined by the period of updating the availability of resources needed. The idea of embodiments herein is that the radio base station 13 determines a size, also known as an amount, of the control region based on measurements giving information about cell specific features. Such cell specific features may be estimated number of user equipments that should be able to transmit the control signaling, required periodicity of the control signaling and/or isolation and time dispersion estimates. The user equipment is typically configured with a resource, a time offset and a periodicity, i.e. a resource valid every 5, 10, 20 ... ms. Herein a short periodicity is used for resources reoccurring often and long periodicity is used for resources with a long time in-between occurrences.

During operation, the radio base station 13 assigns the periodic resources of the control region to the user equipments 1 1 , 12, which assigned periodic resources the user equipments 1 1 , 12 then use for the transmission of the control signaling. This may be performed by using some type of control signaling, for example, RRC signaling or the like.

The determination of the size of the control region for the cell 10 may also be performed in a different network communication node, such as a Network control node 14, or the like. As stated above, the basic concept of the proposed solution is to base the selection of the size of a control region on measurements done in the cell giving information on the expected traffic load and requirements on periodicities. The

requirements on the periodicities may depend on factors such as speed and traffic characteristics commonly present in the cell. Periodicity herein means the time interval for| which the assigned resource is valid, or the time period for which the resource reoccur. For example, a high historic traffic load and a short periodicity results in a larger control region of a cell than a cell of lower traffic load and longer periodicity.

Some embodiments may, when deciding the size of the control region, add additional resources to enable reconfiguring specific user equipments for which it is identified that their required periodicities are different than the commonly required periodicity in the cell.

Hence, a mechanism is provided that enables an efficient usage of channel resources in the radio communications network.

In Fig. 2, a schematic combined signaling scheme and flowchart of a method in the radio communications network 1 is shown. In the illustrated example, the semi static resources are Scheduling Request (SR) resources and the first user equipment 1 1 , referred below to as the user equipment 1 1 , uses the SR to indicate to the radio base station 13 that the user equipment 1 1 wants scheduled resources for uplink transmission.

Step 21 : The network communications node 13, in the illustrated example; the radio base station 13, determines a size of a control region of the total of radio channel resources of a control channel. The size defines the amount of SR resources to be pre- allocated for user equipments within the cell 10 and is based on the historical amount of user equipments, and the requirement of periodicity of control signaling for SR. This determination may be active per cell and the determining step may use measurements and/or counters in the cell to form a default configuration for the cell. The determining step comprises three steps

Step 21 a. Estimate the maximum number of user equipments to support Step 21 b. Obtain required periodicity

Step 21 c. Determine required control region

Step 21 a is estimated from an historic traffic load. The traffic load may be monitored in a monitoring node or in the same node. The estimation may be based on traffic load over a preset time, for example, an hour, a day or the like. Step 21 b is dependent on the control signaling type. Periodicity means the time interval for which the assigned resource is valid, or the time period for which the resource reoccurs. Turning to the above exemplified periodic resources, the periodicity depends for CSI resources on

o Traffic type

o Velocity of the user equipments in the cell, that is, user equipments

traveling with high speed through the cell results in a Shorter periodicity than user equipments traveling slow. Short or low periodicity means a periodicity with short time between reoccurring periodic resources. The velocity may be monitored by the radio base station or the network control node, measured or reported,

o Fading, or the like. Fading is related to how fast the channel varies in time and how much it varies in frequency. As an example, a channel varying fast in time may result in a short periodicity, i.e. short time between reoccurring resources, but this could also have some relation to the fading in frequency. The fading may be monitored by the radio base station or the network control node, measured or reported.

For SR resources, as illustrated, the periodicity depends on

o Traffic type (uplink), SR is only used if a buffer status report is triggered by the user equipment.

For Sounding resources, the periodicity depends on

o Traffic type (uplink and downlink)

o Velocity of the user equipments in the cell, The velocity may be monitored by the BS/Control node, measured or reported

o Fading. The fading may be monitored by the BS/Control node, measured or reported. Step 21 c is determining the size of the control region. The size of the control region defines the maximum amount of periodic resources used by user equipment over a period of time within the cell. The size of the control region is dependent on steps 1 , 2 and, when relevant, e.g. when code division is used to multiplex several user equipments on the same frequency resource, which is the case for PUCCH and sounding, also how many user equipments which can be multiplexed on the same control channel resource dependent on the estimated isolation and time dispersion properties of the control channel.

An isolation estimate per cell may be derived from Reference Signal Received Power (RSRP) measurements. For example, the user equipment 1 1 may, for

handover/cell selection purposes, measure received signal power from multiple cells and report this to the base station. This reports may be used to classify how isolated the cell is from other cells.

A time dispersion estimate per user equipment may be derived from uplink sounding and data transmission measurements, for example, by making a correlation on time of a received signal and measure the time between tops as known in the art. The time dispersion estimates per user equipment may be weighed together into one cell estimate e.g. by taking an average over the estimates, considering only the maximum estimate or by taking the xth percentile of the estimate. In some embodiments, estimation in different time slots, giving different configurations in different times of the day. Further extensions include having a fixed control region calculated to be sufficient for the time slot having the highest load, but to give periodicities according to expected load in the current time slot. In some embodiments, additional resources are added to step 21 c to enable user equipment specific (re)configuration within the cell. If it is identified that a user equipment has a larger resource need than the default configured resource it can be assigned more resources without having to reconfigure all the user equipments in the entire cell. The amount of additional resources can be selected dependent on estimated or measured amount of deviation from the cell specific default configuration.

Step 22: The radio base station 13 assigns a SR resource to the user equipment 1 1 from the control region. Step 23:

The radio base station 13 informs the user equipment 1 1 about the assigned SR resource by performing control signaling to the user equipment 1 1 , for example, RRC signaling. Step 24: The user equipment 1 1 transmits a SR on the assigned or allocated SR resource to the radio base station 13 when a certain trigger condition is met. For example, the user equipment 1 1 has a certain buffer size to transmit. This resource may for example be a PUCCH resource.

Fig. 3 shows the 3 different steps 21 a-21 c in a schematic block diagram. Step 31

To estimate the expected number of user equipments, counters can be used.

Different assumptions may be used. A simplified method is to take the maximum experienced number of user equipments, with a scaling factor to take height for load variation. An alternative is to assume that user equipments arrive according to a Poisson process, use the statistical data to estimate the intensity of the process, set a probability, e.g. 99 %, that the number of the user equipments in the cell is smaller than a certain number of user equipments X and then finally given the probability and the estimated intensity calculate X. X is then considered to be the expected number of user equipments in the cell. Step 32

There are different ways to obtain or estimate the periodicity requirement indication for the control signaling types.

For CSI

The required periodicity of the CSI reporting depends mainly on how long a channel state estimate can be considered to be valid. This depends on channel properties and user equipment speed. The channel properties and user equipment speed can be estimated, in terms of channel variation in time and frequency, from CQI reports or uplink sounding and data transmissions. These estimates may be weighed together into cell specific estimates by e.g. taking the maximum of the user equipment estimates, the average user equipment estimate or the xth percentile user equipment estimate. A fast channel variation in time requires a short period time. If the channel variation in time is slow and the channel variation varies a lot in frequency, there may be gains in doing frequency selective scheduling. This requires frequency selective reporting of CQI. It may be argued that it is more efficient to report frequency selective CQI information a- periodically on PUSCH. PUSCH reporting requires explicit downlink signaling and also has a cost in uplink overhead. If PUCCH or PUSCH is more efficient depends on traffic and system. Therefore, one might select a long period time on PUCCH if the channel variation in time is slow and the channel varies a lot in frequency.

The traffic type of the user equipments is also considered, user equipments with low amount of data is in less need of CQI reports.

The required periodicities in different channel conditions and for different traffic types can be estimated through simulations. For SR

The SR periodicity depends mainly on the traffic type and the requirements of the traffic type. Traffic with tight delay requirements need shorter SR periods, that is, short periodicity, than best effort user equipments. Nominal values can be configured for each Quality of Service Class Identifier (QCI).

For Sounding

The required sounding periodicity of a user may depend on the channel conditions, fading and user equipment speed, and the traffic condition, together with the intended use of sounding. Sounding can be used for uplink scheduling and link adaptation, and also for downlink beam forming in case of reciprocal channels as in time division duplex (TDD). As for CSI, common channel time and frequency variation estimates can be obtained from weighing together user equipment specific estimates of channel time variation derived from CSI reports and uplink sounding and data

transmissions. Fast channel variations in time require short sounding periodicities. If the channel variations in time are moderate to high and/or the channel variations in frequency are small, the gains with frequency selective scheduling in uplink are small. Moreover, long-term beamforming shows similar performance as short-term beamforming in this case. A periodicity with longer periods may then be selected, with a long periodicity. If the intended use of sounding is uplink scheduling and/or link adaptation uplink traffic conditions are considered when selecting the sounding periodicity. If the intended use is downlink beamforming, downlink traffic conditions as well as the sounding bandwidth configuration are considered.

Step 33 Step 31 gives an estimate of the total number of user equipments and the number of user equipments with certain pre-defined traffic types, based on QCI or other indication, as an alternative, it may be decided on one common periodicity for all user equipments in the cell by weighing together the required periodicities of the different traffic types considering the most commonly occurring traffic type or the traffic type with the shortest required periodicity. For example, the traffic load may be expressed as a totally load of user equipments or a load of user equipment per QCI. Step 32 combined with step 31 gives a cell resource need estimate. This resource need is then mapped to an amount of physical resources based on, in some embodiments, interference requirement, cell isolation and time dispersion of the control channel. In a well isolated cell and on a control channel with low time dispersion the resource utilization on the control channel can be higher, the cell hence need to configure less physical resources for a specific resource need than if the cell is poorly isolated and the time dispersion of the control channel is high.

The advantage of the present solution is that the control region size will be better calibrated to the expected requirements in each cell. This results in increased throughput and lower delay.

The method steps in the network communication node, referred to as the radio base station 13 or the network controller node 1 in the figures, for adapting an amount of periodic resources in the cell 10 oaccording to some general embodiments will now be described with reference to a flowchart depicted in Fig. 4. The steps do not have to be taken in the order stated below, but may be taken in any suitable order. The network communication node 13, 14 is comprised in the radio telecommunications network 1 and controls an amount of radio channel resources within the cell 10 of a radio control channel. The amount of periodic resources is defined as a size of a control region. The control region is at least a part of the amount of radio channel resources of the control channel. The user equipment 1 1 , 12 uses a control signaling type on the radio control channel.

Step 41

The network communication node 13, 14 determines the traffic load in the cell 10. For example, the network communication node 13, 14 estimates maximum number of user equipments to support. The maximum number of user equipments to support may also be a fixed value, such as a highest number of user recorded in the cell. This may be measured or reported within the cell 10.

Step 42

The network communication node 13, 14 obtains periodicity requirement indication based on the control signalling type in the cell. This may be performed by estimating the periodicity requirement indication or by a fixed preset value. The indication may be a time value indicating the time interval for which the assigned resource is valid, or the time period for which the resource reoccur.

Examples of control signalling types may be SR, CQI reporting, sounding or the like.

For example, the control signaling type may be CQI reporting or sounding and the periodicity requirement indication of a CQI report may be estimated based on a channel variation in time indication and/or a channel variation in frequency indication.

In some embodiments, the estimating of periodicity requirement indication depends on channel properties and speed of the user equipment 1 1. The estimation, in terms of channel variation in time and frequency, is based on CQI reports or uplink sounding and data transmissions, wherein these estimates is weighed together into cell specific estimates.

In some embodiments, the periodicity requirement indication of CQI reports on PUCCH may be estimated depending on channel variation in time and frequency. In some embodiments, the periodicity requirement indication of a CQI report on PUCCH may be estimated to a first value if the channel variation in time is below a channel variation in time threshold, and to a second value being lower than the first value if the channel variation in time is higher than the channel variation in time threshold.

In some embodiments, the periodicity requirement indication of CQI reports on PUCCH may be estimated depending on channel variation in time and frequency. If the channel varies a lot in frequency and the channel variation in time is slow, the periodicity is set to a large value, i.e. the time between reoccurring resources is long. If the channel varies only a little in frequency, the periodicity is set to a value depending on the channel variation in time; small value , i.e. the time between reoccurring resources is short, if the channel varies quickly in time and large value, i.e. the time between reoccurring resources is long, if the channel varies slowly in time. Furthermore, if the channel variation in frequency is high and the channel variation in time is low, one may utilize a-periodic CQI reporting on PUSCH instead of periodic CQI reporting on PUCCH to obtain frequency-selective CQI reports in an efficient way.

Therefore, the periodicity requirement indication on PUCCH may be set to a large periodicity value in case of high channel variation in frequency and low channel variation in time.

In some embodiments a whole table of different threshold values of channel variation in frequency and time may be used for mapping threshold values to different periodicity requirement indication estimates.

The number of supported user equipments may be fixed, and/or the required periodicity may be fixed.

The steps 41 and 42 do not need to be in a certain order or may be performed simultaneously.

Step 43

This is an optional step as indicated by the dashed line. The network

communication node 13,14 determines how many user equipments that can be multiplexed on the same control channel resource dependent on an estimated isolation and time dispersion properties of the control channel. This determination may be taken into account when determining the control region size.

The network communication node 13,14 may derive the isolation estimate per cell from reference received signal power measurements.

The network communication node 13, 14 may also estimate a time dispersion per user derived from uplink sounding and data transmission measurements, which time dispersion estimates per cell is weighed together into one cell estimate, considering only the maximum estimate or by taking the xth percentile estimate.

Step 44

The network communication node 13, 14 determines a size of the control region based on traffic load, and on the obtained periodicity requirement indication of the control signalling type, in the cell 10. The size of the control region is determined per cell level and the control signalling type. As stated above, the size of the control region defines the total amount of periodic resources for the cell 10 that are semi statically configured to the user equipments within the cell 10. In some embodiments, the output from step 43 is also taken into account.

The determining of the control size region may be performed in different time slots, giving different configurations in different times of the day.

The determining of the control region size may be calculated to a fixed control region size to be sufficient for the time slot having the highest load, but to give

periodicities according to expected load in the current time slot.

Step 45

This is an optional step as indicated by the dashed line. The network

communication node 13,14 may then assign at least one periodic resource to a user equipment 1 1 , 12 in the cell 10 to be used for control signaling. As stated above, the semi statically configured periodic resource is part of the control region with the determined size. The assigned at least one periodic resource and sometimes also the total control region resource may be signalled to the user equipment 1 1 , 12.

Step 46

This is an optional step. The network communication node 13, 14 adds additional resources to enable user equipment specific configuration within the cell 10.

In order to perform the method steps above an arrangement 500 in the network communication node 13,14 is provided.

Fig. 5 shows a schematic overview of the arrangement 500 in the network communication node 13, 14. The arrangement 500 is for adapting an amount of periodic resources for a cell in a radio communications network. The periodic resources are semi statically configured to a user equipment 1 1 , 12 within the cell 10. The network

communication node 13,14 is comprised in the radio telecommunications network 1 and controls an amount of radio channel resources within the cell 10 of a radio control channel. The amount of periodic resources is defined as a size of a control region, which control region is at least a part of the amount of radio channel resources. The user equipment 1 1 , 12 uses a specific control signalling type on the radio control channel.

The arrangement 500 comprises a determining circuit 501 configured to determine the traffic load in the cell 10. Furthermore, the arrangement 500 comprises an obtaining circuit 502 configured to obtain the periodicity requirement indication, which indication is based on the control signaling type. The arrangement 500 further comprises a size determining circuit 503 being coupled to the determining circuit 501 and the obtaining circuit 502 and is being configured to determine the size of the control region based on the determined traffic load in the cell 10 and on the obtained periodicity requirement indication. Thereby, the amount of periodic resources for the cell 10 is adapted by the arrangement 500.

In some embodiments , the arrangement 500 comprises an assigning circuit 504 coupled to the size determining circuit 503, which assigning circuit 504 is configured to assign at least one periodic resource to the user equipment 1 1 to be used for control signaling from the user equipment 1 1. The assigning circuit 504 may further be connected to a transceiver (TX/RX) circuit 505, for signaling the at least one periodic resource and sometimes also the total control region resource may be signalled to the user equipment 1 1 .

The arrangement may further comprise a deriving circuit 506 configured to derive the isolation estimate per cell from reference received signal power measurements received over the transceiver circuit 505.

The arrangement 500 may further comprise an estimating circuit 507 coupled to the transceiver circuit 505, which estimating circuit 507 is configured to estimate a time dispersion per user equipment derived from uplink sounding and data transmission measurements. The time dispersion estimates per cell may be weighed together into one cell estimate, considering only the maximum estimate or by taking the xth percentile estimate.

In some embodiments, the arrangement 500 comprises a further determining circuit 508 coupled to the size determining circuit 503, the deriving circuit 506, the estimating circuit 507, which further determining circuit 508 is configured to determine how many user equipments that can be multiplexed on the same control channel resource dependent on an estimated isolation and/or time dispersion properties of the control channel. This determination may be taken into account when determining the control region size in the size determining circuit 503. The arrangement may further comprise an adding circuit 509 coupled to the size determining circuit 503, which adding circuit 509 is configured to add additional resources to the size of the control region to enable user equipment specific configuration within the cell.

The present mechanism for assigning semi statically periodic resources to user equipment may be implemented through one or more processors, such as a processing circuit 510 in the network communication node 13, 14 depicted in Fig. 5, together with computer program code for performing the functions of the present solution. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the present solution when being loaded into the network communication node 13, 14. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the network communication node 3, 14.

The arrangement may further comprise a memory circuit configured to be used in the process to store data, applications and the like thereon.

In the drawings and specification, there have been disclosed exemplary embodiments of the invention. However, many variations and modifications can be made to these embodiments without substantially departing from the principles of the present invention. Accordingly, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined by the following claims.

Claims

A method in a network communication node (13,14) for adapting an amount of periodic resources, which periodic resources are semi statically configured to a user equipment (11 , 12) within a cell (10) of a radio telecommunications network (1 ) and which network communication node (13, 14) is comprised in the radio telecommunications network (1) and controls an amount of radio channel resources within the cell (10) of a radio control channel, wherein the amount of periodic resources is defined as a size of a control region, which control region is at least a part of the amount of radio channel resources, and which user equipment (1 1 , 12) uses a specific control signalling type on the radio control channel, the method comprising

- determining (41 ) a traffic load in the cell (10),

- obtaining (42) a periodicity requirement indication, which indication is based on the control signalling type, and

- determining (44) the size of the control region based on the determined traffic load in the cell (10) and the obtained periodicity requirement indication and thereby adapting the amount of periodic resources for the cell (10).

A method according to claim 1 , further comprising

- assigning (45) at least one periodic resource to the user equipment (1 1 ) to be used for control signaling from the user equipment (1 1 ).

A method according to any of the claims 1 -2, wherein the traffic load is determined by estimating maximum number of user equipments to support or by a fixed value.

A method according to any of the claims 1 -3, wherein the periodicity requirement indication is obtained by estimating the periodicity requirement indication based on the control signalling type of the user equipment (1 1 ,12), or by a fixed preset value/indication.

A method according to claim 4, wherein control signalling type is Channel Quality Index 'CQI' reporting or sounding, and wherein the periodicity requirement indication of a CQI reporting or sounding is estimated based on a channel variation in time indication and/or a channel variation in frequency indication.

6. A method according to claim 5, wherein the channel variation in time and/or frequency is retrieved from CQI reports or uplink sounding and data transmissions, and wherein these estimates is weighed together into cell specific estimates.

A method according to any of the claims 1 -6, further comprising

- determining (43) how many user equipments that can be multiplexed on the same control channel resource dependent on an estimated isolation and/or time dispersion properties of the control channel, and take this determination into account when determining (44) the control region size.

A method according to claim 7, further comprising

- deriving the isolation estimate per cell from reference received signal power measurements.

A method according to any of the claims 7-8, further comprising

- estimating a time dispersion per user equipment derived from uplink sounding and data transmission measurements, which time dispersion estimated per cell is weighed together into one cell estimate, considering only the maximum estimate or by taking the xth percentile estimate.

0. A method according to any of the claims 1-9, wherein the determining (44) of the size of the control region is performed in different time slots, giving different configurations in different times of the day.

1 1 . A method according to claim 10, wherein a determined size is calculated to a fixed control region size value to be sufficient for the time slot having the highest load, but to give periodicities according to expected load in the current time slot.

12. A method according to any of the claims 1 -1 1 , further comprising

- adding (46) additional resources to the size of the control region to enable user equipment specific configuration within the cell (10).

13. A method according to any of the claims 1 -12, wherein the at least one periodic resource and/or the total control region resource is signalled to the user equipment (1 1 , 12).

14. A method according to any of the claims 1-13, wherein the control signalling type comprises Scheduling Request, Channel Quality Index reporting or Sounding.

15. An arrangement (500) in a network communication node (13, 14) for adapting an amount of periodic resources in a cell (10) of a radio telecommunications network (1 ), which periodic resources are semi statically configured to a user equipment (1 1 , 12) within the cell (10) and which network communication node (13, 14) is comprised in the radio telecommunications network (1 ) and controls an amount of radio channel resources within the cell (10) of a radio control channel, wherein the amount of periodic resources is defined as a size of a control region, which control region is at least a part of the amount of radio channel resources and said user equipment (1 1 ,12) uses a specific control signalling type on the radio control channel, the arrangement (500) is characterised in comprising,

a determining circuit (501 ) configured to determine a traffic load in the cell (10), an obtaining circuit (502) configured to obtain a periodicity requirement indication, which indication is based on the control signalling type, and

a size determining circuit (503) coupled to the determining circuit (501 ) and the obtaining circuit (502) and configured to determine the size of the control region based on the determined traffic load in the cell (10) and on the obtained periodicity requirement indication, and thereby the arrangement (500) is configured to adapt the amount of periodic resources for the cell (10).