WO2015176996A1

WO2015176996A1 - Adaptation of scell configuration

Info

Publication number: WO2015176996A1
Application number: PCT/EP2015/060441
Authority: WO
Inventors: Joakim Axmon; Muhammad Kazmi; Walter Müller; Dandan HAO
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2014-05-19
Filing date: 2015-05-12
Publication date: 2015-11-26

Abstract

The disclosure concerns a method for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device. The method comprises: acquiring (510, 610) a mobility indication of the wireless communication device; acquiring (520, 620) a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device; and determining (530, 630) whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication.

Description

ADAPTATION OF SCELL CONFIGURATION

Technical Field

The present invention relates generally to the field of carrier aggregation. Background

Intra-Node carrier aggregation

Carrier aggregation was introduced in Release 10 of the E-UTRAN standard as a means for qualifying E-UTRAN to meet the requirements for 4G (1000 Mbit/s) as well as for allowing operators with small (less than 20 MHz) scattered spectrum allocations to provide a good user experience by aggregating the scattered allocations into e.g. 10, 20 MHz or more.

Typically, the UE is connected to a serving cell termed Primary Cell (PCell) on what is referred to as the Primary Component Carrier (PCC). Mobility is catered for on this carrier. In case the UE is using services that require high throughput, the network may activate one or more additional serving cells, each termed Secondary Cell (SCell), on what is referred to as Secondary Component Carrier(s). The activation may happen before or after the SCell has been detected by the UE.

Two types of aggregation scenarios are considered for Release 10:

Intra-band contiguous aggregation,

Inter-band aggregation

and in Release 11, one more is considered:

Intra-band non-contiguous aggregation.

For intra-band contiguous aggregation the PCell and SCell(s) are contiguous in frequency. It is required from the standard that for contiguous intra-band aggregation, the time difference between PCell and SCell is allowed to be at most ±130 ns (3GPP TS 36.104 rev 11.4.0, subclause 6.5.3). It is further assumed in the standard that for this particular scenario, one can use a single FFT to demodulate the signal from both PCell and SCell simultaneously. Thus in practice it is required that the PCell and SCell are co- located, i.e., transmitted from the same site, since otherwise propagation delay would typically make it impossible to use a single FFT. For intra-band non-contiguous aggregation the timing difference is allowed (according to the standard) to be at most ±260 ns, but no assumption is made on that the cells are co-located or that a single FFT can be used.

For inter-band carrier aggregation the timing difference between the PCell and SCell is allowed to be at most ±260 ns (according to the standard). However for this scenario it is further assumed that the cells may be non-co-located and that the UE will have to cope with a propagation delay difference between PCell and SCell of up to ±30 us, resulting in a maximum delay spread of ±30.26 us (3GPP TS 36.300 rev 11.5.0 Annex J).

Fig. 1 illustrates various Carrier aggregation deployment scenarios: (a) Co- located overlaid intra-band (similar path loss for different carriers), (b) Co-located overlaid inter-band (different path loss for different carriers), (c) Co-located inter-band partially overlaid, (d) non-co-located (remote radio heads) inter-band to provide improved throughput at hotspots, and (e) overlaid inter-band scenario with repeaters. (3 GPP TS 36.300 rev 11.5.0 Annex J).

Examples of foreseen deployment scenarios up to 3GPP Rel. 11 are shown in Fig. 1. For co-located intra-band scenario with fully overlapping coverage of PCell and SCell the eNB can configure and activate the SCell when needed, based on reported measurements for PCell alone. The concept of using co-location information and carrier frequency information for taking handover decisions may be implemented according to any suitable approach.

The timing of the SCell is prior known in case the UE has measured (and reported) the cell recently, either as inter- frequency neighbor cell or as a cell on a configured secondary component carrier F2. Additionally, regardless of having been reported before, the timing of the SCell is also considered prior known in case of intra- band contiguous carrier aggregation, i.e., where the spectrums for PCell and SCell are back-to-back. When the UE gets an activation command for the SCell under those conditions, the UE may be able to start reception from the cell without prior fine-tuning of the timing.

In case the cell has not been measured (and reported) previously and is on another band (inter-band scenario) or non-adjacent, the timing of the SCell is not known to the UE. However it shall fall within ±30.26 us (almost half an OFDM symbol) relative to the PCell. In this case the timing of the SCell will typically have to be tuned before the UE can start data reception from the SCell. Future deployment scenarios and inter-node aggregation

Fig. 1 illustrates: (a) Future deployment scenario. Due to the layout of partially overlaid cells in some locations a UE may have to aggregate one carrier (e.g. Fl) from base station A and another (e.g. F2) from base station B. Moreover in particular spots the UE may also aggregate additional carriers, e.g. F3 cell from base station C. (b) UE in coverage of multiple cells at different carriers.

From 3GPP Rel. 12 and onwards so called inter-node radio resource aggregation is under discussion (3GPP TR 36.842). For one of the foreseen scenarios the UE may be connected to a primary cell (master cell) handled by one base station, and simultaneously to between one and four secondary cells (assisting cells) handled by other base station(s). In case the primary cell and secondary cell(s) are on different carriers, the UE can aggregate it similarly to how it is done for the Rel. 11 deployment scenarios in Fig. 1 above; with one difference. Up to 3GPP Rel. 11 the aggregated cells were handled by the same base station with either co-located cells on different carriers but sent from the same site, or non-co-located cells on different carriers, where those one of the carriers used for secondary cells may use RRH (remote radio heads)

(deployment scenarios (d) and (e) in Fig. 1).

One example of inter-node radio resource aggregation/inter-node carrier aggregation is shown in Fig. 2(a). Here a UE that is in coverage of base station A on one carrier (Fl), base station B on the other carrier (F2), and base station C on a third carrier (F3) may aggregate all three carriers even if the cells are handled by different base stations. Up to Rel.11 aggregation would only be done within each respective base station (A or B or C, not in combination). The cells on some carriers may have macro coverage (large cell radius) whereas other may have hotspot coverage (small cell radius).

At a given location there may be multiple such layers as illustrated in Fig. 2(b), overlapping each other at least partially. Although the current assumption in the standard is that the UE shall be capable of aggregating up to 5 carriers, and ongoing standardization work aims at aggregating up to 32 carriers, there is no such limitation on the number of carriers within which the UE may be in coverage. It can be assumed that in future deployment scenarios virtually every suitable spectrum will be used in order to meet the targets for fifth generation of mobile communication systems (5G). It can also be foreseen that there will be a mix of large and small cells i.e. any combination of macro, micro, pico and femto cells, and a mix of intra-node and inter-node aggregation. Moreover mobile base stations are considered for 5G.

The macro cell is served by a wide area (WA) base station aka high power node (HPN). The maximum output power of a HPN can for example typically be between 43-49 dBm. Examples of low power nodes (LPNs) are micro node (aka medium range (MR) base station), pico node (aka local area (LA) base station), femto node (home base station (HBS)), relay node etc. The maximum output power of an LPN for example typically is between 20-38 dBm depending upon the power class. For example a pico node typically has a maximum output power of 24 dBm whereas HBS has a maximum output power of 20 dBm. The HBS, LA BS and MR BS serve femto cell, pico cell and micro cell respectively. The WA BS, HBS, LA BS and MR BS are therefore also called as different base station power classes.

Fig. 3 illustrates an example of future deployment scenario with aggregation using 5 DL carriers; (a) layers with cells on different carriers, (b) cell coverage experienced by UE.

A hypothetical deployment with 5 carriers is illustrated in Fig. 3 where there are two layers with macro cells (Fl and F2), one layer with micro cells and pico cells mixed (F3), one layer with pico cells (F4), and one layer with femto cells (F5) - e.g. hotspots at cafes, restaurants, etc. Examples of typical cell radii for the different kinds of cells are provided in Table 1. The UE will go in and out of coverage of individual cells on one or more of the 5 carriers while mobile. Table 1 : Cell types and typical cell radii

Dual Connectivity

In dual connectivity (DC) the UE can be served by two nodes called master eNB (MeNB) and secondary eNB (SeNB). The UE is configured with PCC from both MeNB and SeNB. The PCell from MeNB and SeNB are called PCell and PSCell (a.k.a. Special SCell) respectively. The PCell and PSCell operate the UE typically

independently. The UE may also be configured with one or more SCCs from each of MeNB and SeNB. The corresponding secondary serving cells served by MeNB and SeNB are called SCell. The UE in DC typically has separate TX/RX for each of the connections with MeNB and SeNB. This allows the MeNB and SeNB to independently configure the UE with one or more procedures e.g. radio link monitoring (RLM), DRX cycle etc on their PCell and PSCell respectively.

Self-organizing networks (SON)

The objective of the SON entity used in E-UTRAN is to allow operators to automatically plan and tune the network parameters and configure the network nodes. The conventional method is based on manual tuning, which consumes enormous amount of time, resources and requires considerable involvement of work force. In particular due to the network complexity and large number of system parameters, it is very attractive to have reliable schemes and mechanism which could automatically configure the network whenever necessary. This can be realized by SON, which can be visualized as a set of algorithms and protocols performing the task of automatic network tuning and configuration. In order to accomplish this, the SON node requires measurement reports, results and feedback from other nodes e.g. UE, base station etc.

Network architecture

Fig. 4 illustrates an example network architecture of a cellular communication network. The base stations (eNodeB, eNB) are communication with neighbor base stations over the X2 interface, e.g. exchanging information on UEs to be handed over, forwarding user plane data from source to target cell during handover, and exchanging information on load and interference. The base stations are further connected to a mobility management entity (MME) which keeps information about the UE (UE context) regarding e.g. UE capabilities. In case an X2 connection is missing between base station neighbors, the handover including packet forwarding is managed by the MME over the SI interface. The base stations are further connected to a serving gateway (SGW) which is handling transport of the user plane data between the base station and one or more packet gateways (PGW) which connect the UE to the internet. The MME in whose pool of base stations the UE resides configures which base station the SGW shall connect to for transport of the UE user plane data.

Fifth generation of mobile communication systems - 5G

The work on 5th generation mobile communication system is still in infancy.

The 4G LTE system is expected to gradually evolve into 5G mobile communication system. Nevertheless it is envisaged that the 5th generation of mobile communication systems will comprise of very dense deployment of MTC devices, very low latency, very high system capacity and peak user data rate, very dense deployment of network with large number of closely placed radio nodes aka ultra-dense network (UDN), massive MIMO, operation at very high frequency in the range between 10-100 GHz (aka millimeter wave) etc.

UE positioning mechanisms

Several positioning methods for determining the location of the target device, which can be a UE, mobile relay, PDA etc exist. Some well-known methods include: Satellite based methods; it uses A-GNSS (e.g. A-GPS) measurements for determining UE position

OTDOA; it uses UE RSTD measurement for determining UE position in LTE

- UTDOA; it uses measurements done at LMU for determining UE position

Enhanced cell ID; it uses one or more of UE Rx-Tx time difference, BS Rx-Tx time difference, LTE RSRP and RSRQ, HSPA CPICH RSCP and Ec/No measurements, GSM carrier RSSI, angle of arrival (AoA) etc for determining the UE position. Fingerprinting is also a special kind of ECID based positioning method.

Hybrid methods; it uses measurements from more than one method for determining UE position

In LTE the positioning node (aka E-SMLC or location server) configures the UE, eNode B or LMU to perform one or more positioning measurements. The positioning measurements are used by the UE or positioning node to determine the UE location. The positioning node communicates with UE and eNode B in LTE using LPP and LPPa protocols.

Reference is made herein to various aspects disclosed in 3GPP TS 36.331 V12.1.0, section 6.2; 3 GPP TS 36.331 V12.1.0, section 6.3.2; 3 GPP TS 36.331 V12.1.0, section 6.3.1; and 3GPP TS 36.213 section 5.2 (e.g. referenceSignalPower - a parameter which provides the downlink reference-signal EPRE, actual value in dBm).

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.

A problem with at least some of the existing solutions is that the number of intra- frequency and inter-frequency carriers to be monitored or used by the UE for data transmission and/or reception is ever increasing, for example, when all available parts of the spectrum are to be utilized to reach the throughput targets for LTE advanced and 5G. Without suitable (smart) strategies when configuring SCells to the UE this will lead to drastic increase in the efforts spent by the UE on measurements (waste of battery), and may also need to unnecessary R C signaling between the network node and the UE, as well as between network nodes in case of inter-node carrier aggregation (waste of capacity).

According to a first aspect, there is provided a method for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device. The method comprises acquiring a mobility indication of the wireless communication device. The method further comprises acquiring a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device. Furthermore, the method comprises determining whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication.

According to a second aspect, there is provided 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 the method according to the first aspect when the computer program is run by the data-processing unit.

According to a third aspect, there is provided a processor configured to perform the method according to the first aspect.

According to a fourth aspect, there is provided an arrangement for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device. The arrangement comprises a mobility unit, a cell size unit, and a determiner. The mobility unit is adapted to acquire a mobility indication of the wireless

communication device. The cell size unit is adapted to acquire a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device. The determiner is adapted to determine whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication.

According to a fifth aspect, there is provided a wireless communication device comprising at least one of the processor of the third aspect and the arrangement fourth aspect.

According to a sixth aspect, there is provided a network node comprising at least one of the processor of the third aspect and the arrangement fourth aspect.

According to a seventh aspect, there is provided a network node for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising the network node and at least one wireless communication device. The network node comprises a receiver adapted to receive at least one of a first list and a second list from a wireless communication device, wherein the first list is indicative of cells that are suitable as secondary cells of the wireless communication device in the carrier aggregation application and the second list is indicative of cells that are unsuitable as secondary cells of the wireless communication device in the carrier aggregation application. The network node also comprises a carrier aggregation configuration unit adapted to configure one or more secondary cells of the wireless communication device based on the first list and/or the second list.

According to an eighth aspect, there is provided a server for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device. The server is associated with the cellular communication system and comprises a database storing, for each of a plurality of cells, one or more of:

statistical cell size information; and

statistical information regarding a length of one or more consecutive time spans during which the cell has been used as secondary cell of one or more wireless communication devices having respective mobility indications.

According to a ninth aspect, there is provided a method for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device. The method comprises acquiring a mobility indication of the wireless communication device. Furthermore, the method comprises acquiring a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device. Moreover, the method comprises determining whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication. The method also comprises configuring, by the network node, one or more secondary cells of the wireless communication device based on the determination of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application.

According to a tenth aspect, there is provided a cellular communication system comprising at least one network node and at least one wireless communication device, and adapted for secondary cell configuration in a carrier aggregation application. The cellular communication system comprises a mobility unit of at least one of the wireless communication device and the network node, adapted to acquire a mobility indication of the wireless communication device. The cellular communication system further comprises a cell size unit of at least one of the wireless communication device and the network node, adapted to acquire a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device. Furthermore, the cellular communication system comprises a determiner of at least one of the wireless communication device and the network node, adapted to determine whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication. Moreover, the cellular communication system comprises a carrier aggregation configuration unit of the network node, adapted to configure one or more secondary cells of the wireless communication device based on the first list and/or the second list.

Brief description of the drawings

Figs. 1-3 illustrate deployment scenarios.

Fig. 4 illustrates an example network architecture.

Figs. 5-7 illustrate methods. Fig. 8 illustrates an example of a source network node forwarding UE speed class to target network node during handover.

Figs. 9-11 show block diagrams.

Figs. 12-16 show flowcharts.

Detailed description

The embodiments described herein 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) comprising circuitry/logic or performing methods according to any of the embodiments. The electronic apparatus may, for example, be a portable or handheld mobile radio communication equipment, a mobile radio terminal, a mobile telephone, a base station, a base station controller, a pager, a communicator, an electronic organizer, a smartphone, a computer, a notebook, a USB-stick, a plug-in card, an embedded drive, or a mobile gaming device.

According to some embodiments, a computer program product comprises a computer readable medium such as, for example, a diskette or a CD-ROM. 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, which may, for example, be comprised in a mobile terminal. When loaded into the data-processing unit, the computer program may be stored in a memory 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, any of the methods shown in the appended Figures. Reference is made herein to various embodiments. However, a person skilled in the art would recognize numerous variations to the described embodiments. 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. 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.

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

According to some embodiments, the network node may take UE speed and SCell size into account when configuring the UE with SCells to prevent unnecessary signaling and drainage of UE battery.

Embodiments include methods and arrangements implemented in a network node and/or a UE:

In case of the method implemented in the network node, the network node takes UE mobility state or attributes (e.g. UE speed, UE direction of motion, UE trajectory etc) into account before configuring SCells with small cell radius since the UE will anyway not be able to utilize those cells since it will enter and leave coverage in a short time. The network node after obtaining UE mobility state determines if a particular cell is suitable as SCell for a particular CA capable UE, and based on that determination decide whether to configure that cell as SCell or not for that UE. The network node may additionally refine its assessment based on historical data on how long time the cell has been usable for aggregation for UEs with particular attributes or in a particular state. In case of the method implemented in the UE, the UE obtains its mobility state or attributes (e.g. UE speed, UE direction of motion, UE trajectory etc), determines one or more cell which are suitable for use as SCell based on one or more suitability criteria and signals to the network node at least one of a first list of cells which are suitable for operating as SCell for this UE and a second list of cells which are not suitable for operating as SCell for this UE. The network node, based on the first and/or second list of cells received from the UE and/or suitable list of cells determined by the network node itself, the network node decides which cells are to be configured as SCell(s) for that UE. The reporting may be periodic or event-triggered (extension of the existing reporting events) .

Terminologies:

In some embodiments, the non-limiting term UE is used. The UE herein can be any type of wireless communication device capable of communicating with network node or another UE over radio signals. The UE may also be radio communication device, target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine communication (M2M), a sensor equipped with UE, PAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE) etc.

In some embodiments, the generic terminology, "radio network node" or simply "network node (NW node)", is used. These terms include any kind of network node which may comprise a base station, a radio base station, a base transceiver station, a centralized controller, a core network node, MME, base station controller, network controller, evolved Node B (eNB), Node B, MeNode B, SeNode B, relay node, access point, radio access point, Remote Radio Unit (RRU), Remote Radio Head (RRH) etc.

Calculation of UE mobility attributes or state

The UE mobility attributes (aka UE mobility state) may be characterized by at least the UE speed. But it may also be characterized by one or more additional characteristics such as UE location, UE direction of motion, UE acceleration, UE trajectory etc. One or more of these attributes can be estimated by the UE and/or by the network node.

The above stated UE mobility attributes can be obtained by measuring signals transmitted by the UE in which case the corresponding measurements are performed in the network node e.g. serving network node such as by the PCell. The UE mobility attributes can also be obtained by using the measurements done by the UE and reported to the network node. More specifically these different attributes may be determined as explained in a few examples below:

- UE speed. May also be interchangeably called UE velocity. For example it can be obtained by measuring Doppler speed of the UE. It can also be obtained by a

GNSS or A-GNSS receiver in the UE;

- UE location. It comprises UE geographical coordinates or UE position with respect to a known or pre-determined location. It can be obtained by using a suitable positioning method such as Enhanced cell ID (ECID), OTDOA, GNSS, A-GNSS, any combination of ECID, OTDOA, GNSS and A-GNSS systems etc;

- UE direction of motion. It can be obtained by measuring direction of arrival of signal such as an angle of arrival measurement performed by the network node. This can be performed if the network node has multiple received antennas or antenna arrays;

- UE acceleration. It can be measured by observing the change in the UE speed over certain time period;

- UE trajectory. This is an overall path of motion over certain time or between any locations of the UE etc. This can be represented by two or more sets of

geographical coordinates along the trajectory traversed by the UE.

The UE may transmit one or more of these attributes to the network node if they are determined by the UE and required by the network node for configuration of SCells. Similarly the network node may transmit one or more of these determined attributes to the UE if they are determined by the network node and are required by the UE for recommending the configuration of SCells. In some embodiments one of more attributes may also be determined by both UE and the network node, and the UE or network node can obtain the final value based on the values determined by both UE and network node. This could be done based on a function of values determined by the UE and the network node; examples of functions are average, maximum, minimum, percentile etc.

Acquisition of UE speed may be made using any suitable method, including but not limited to:

- Calculating speed from GPS information

- Calculating speed based on Doppler frequency

- Calculating speed based on cell drift (where care is taken to compensate clock drift)

- Classifying speed based on e.g. macro cell and/or micro cell handover rate The speed can also be classified from analyzing the timing advance change rate

(Rx-Tx time difference).

To further enhance the classification or calculation of UE speed, any of the methods above can be combined, e.g. going for the majority decision or the maximum indicated speed.

Calculation of hypothetical cell radius

With information on the carrier frequency and Tx transmission power used by the cell an approximate cell radius can be calculated and be used for classification of the cell into macro, micro, pico or femto. Assuming line-of-sight the attenuation of electromagnetic waves can be modeled by Friis' transmission formula,

¾ = ^G X ° X (^) »

p

which states that the fraction of received power at the UE side, ^RX/p_TX' *^s proportional to the square of the ratio between wavelength λ and distance r from the base station antenna. The base station transmission antenna gain factor G_TX is already taken into account in the broadcasted system information on TX power level P_TX, and hence can be assumed to be 1 in the expression above. The UE receiver antenna gain factor G_RX is known by the UE and taken into account when assessing received power P_RX, hence this factor too can be assumed to be 1 in the expression above. The wavelength is depending on the carrier frequency which is known to the UE. Thus the distance between the UE and the base station can be estimated

from which it can be seen that if doubling the frequency, the cell radius is reduced by 50%. The UE uses the derived distance as an indication on the kind of cell. In multipath propagation scenarios without a dominating line-of-sight component Friis' formula is too optimistic and empirical results yield that

more accurately models the attenuation, leading to

More accurate models can be used, such as the Okumura-Hata model which models attenuation in urban areas, but using such models requires information or assumptions on e.g. height at which the antennas are placed. Although educated guesses on antenna heights can be made based on information such as medium or high power and that low frequency most likely means a cell in a tower, it is not needed for the purpose of determining the kind of cell.

A fixed power level P_RX can be used as reference, e.g. -90dBm/15kHz, when calculating the hypothetical cell radius. The calculation does not take the interference situation into account, i.e., does not take into account that the cell radius practically may be smaller due to interference from densely packed neighbor cells, lowering the signal quality (e.g. SINR) below a critical level for channel decoding. However, unless some kind of inter-cell interference coordination scheme is used (e.g. ICIC, elCIC, felCIC) such settings would not make sense. Hence there is typically little harm in disregarding the interference when deriving the hypothetical cell radius.

Further examples of cell radius calculation are disclosed in EP 2665307 Al .

Based on the cell radius, the UE or network node may then classify the cell into either of the categories: macro, micro, pico, or femto.

Description of various embodiments According to some embodiments, there is provided a method for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device. A carrier aggregation application may be defined in accordance with the 3 GPP specification. For example, a carrier aggregation application may be seen as providing service to a wireless communication device using signals transmitted using respective two or more carrier frequencies, wherein one carrier frequency is a primary carrier frequency and the other carrier frequencies are secondary carrier frequencies. The signal transmitted using the primary carrier frequency is typically sufficient for maintaining a connection of the wireless communication device. The signal transmitted using the secondary carrier frequency is typically for enhancing the capacity of the connection. A cell transmitting using the secondary carrier frequency is generally termed a secondary cell.

Embodiments of the method are described below with reference to Figs. 5 and 6. In Fig. 5, the method is mainly performed by the wireless communication device (UE in the Figs). In Fig. 6, the method is mainly performed by the network node (NW in the Figs). It should be note that other alternatives are possible too, with some step or steps being performed in the wireless communication device, and some step or steps being performed by the network node. According to embodiments of the method, a mobility indication of the wireless communication device is acquired. This can e.g. be done by the wireless communication device (step 510 in Fig. 5), or by the network node (step 610 in Fig. 6). The mobility indication may e.g. comprise at least one of a mobility state, a speed, a velocity, an acceleration, a direction of movement, a trajectory of movement, and a geographical location. Furthermore, a cell size indication of a cell is acquired, wherein the cell is a prospect secondary cell of the wireless communication device. This can e.g. be done by the wireless communication device (step 520 in Fig. 5), or by the network node (step 620 in Fig. 6). The cell size indication may e.g. comprise at least one of an estimated cell radius, an actual cell radius, an estimated cell diameter, an actual cell diameter, an estimated cell type, an actual cell type, an average cell size among a plurality of cells using a carrier frequency of the cell, and a smallest cell size among the plurality of cells using the carrier frequency of the cell. The cell type may, for example, refer to a cell power class (e.g. macro, micro, pico, femto). Moreover, it is determined whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication. This can e.g. be done by the wireless communication device (step 530 in Fig. 5), or by the network node (step 630 in Fig. 6).

In some embodiments of the method, (550, 650) secondary cell measurements by the wireless communication device are adapted based on the mobility indication and the cell size indication. This adaptation can e.g. be done, or decided, by the wireless communication device (step 550 in Fig. 5), or by the network node (step 650 in Fig. 6).

In some embodiments of the method, the determination of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application (step 530 or 630) includes the following determinations:

- if a speed indicated by the mobility indication exceeds a first speed threshold, it is determined that the cell is suitable as secondary cell only if a cell size indicated by the cell size indication exceeds a cell size threshold; and

- if the speed indicated by the mobility indication does not exceed a second speed threshold, it is determined that the cell is suitable as secondary cell regardless of the cell size indicated by the cell size indication.

The first and second speed thresholds may or may not coincide. Thus, the second speed threshold may be equal to the first speed threshold. Alternatively, in some embodiments, the second speed threshold is lower than the first speed threshold.

Qualitatively, when the speed does not exceed the second speed threshold, it indicates that the wireless communication device is "closer to being stationary" than when the speed exceeds the first threshold. In some embodiments three or more speed threshold may be applied.

In some embodiments of the method, statistical information regarding a length of one or more consecutive time spans during which the cell has been used as secondary cell of one or more wireless communication devices, that have mobility indications corresponding to the mobility indication of the wireless communication device (i.e. the particular wireless communication device being subject to secondary cell

configuration), is considered in the determination of whether the cell is suitable as secondary cell of the wireless communication device. The one or more wireless communication devices may or may not include the wireless communication device (i.e. the particular wireless communication device being subject to secondary cell configuration). That a mobility indication corresponds to another mobility indication may in some embodiments be interpreted as that the mobility indications are the same, and/or that they are similar (e.g. in a same range).

We now consider the embodiments of the method illustrated in Fig. 5 in some more detail. The wireless communication device may update at least one of a first list and a second list based on the determination, in step 530, of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application. The first list is indicative of cells that are suitable as secondary cells of the wireless communication device. The second list is indicative of cells that are unsuitable as secondary cells of the wireless communication device in the carrier aggregation application. As illustrated with step 540, at least one of the first list and the second list may be transmitted to the network node. As illustrated with step 580, the transmitted list or lists may be received by the network node. As illustrated with step 590, the network node may use the list or lists in configuration of one or more secondary cells of the wireless communication device.

Step 510 of acquiring the mobility indication may comprise performing measurements related to mobility. Alternatively or additionally, Step 510 of acquiring the mobility indication may comprise receiving the mobility indication from network node or other part of the cellular communication system, as illustrated with step 560.

Step 520 of acquiring the cell size indication may comprise performing measurements related to cell size. Alternatively or additionally, step 520 of acquiring the cell size indication may comprise receiving the cell size indication from the network node or other part of the cellular communication system, as illustrated with step 570. Further alternatively or additionally, step 520 of acquiring the cell size indication may comprise acquiring a stored cell-size indication, such as extracting a previously acquired cell size indication from a data storage of the wireless communication device, and/or querying a database reachable via the cellular communication system and storing statistical cell size information. We now consider the embodiments of the method illustrated in Fig. 6 in some more detail. As illustrated with step 690, the network node can configure one or more secondary cells of the wireless communication device based on the determination in step 630 of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application.

Step 610 of acquiring the mobility indication may comprise performing measurements related to mobility. Alternatively or additionally, step 610 of acquiring the mobility indication may comprise receiving the mobility indication from the wireless communication device, as illustrated with step 660, and/or receiving the mobility indication from other nodes of the cellular communication system.

Step 620 of acquiring the cell size indication may comprise performing measurements related to cell size. Alternatively or additionally, step 620 of acquiring the cell size indication may comprise receiving the cell size indication from the wireless communication device, as illustrated with step 670. Further alternatively or additionally, step 520 of acquiring the cell size indication may comprise acquiring a stored cell-size indication, such as extracting a previously acquired cell size indication from a data storage of the cellular communication system, and/or querying a database reachable from the cellular communication system and storing statistical cell size information.

The methods described herein may be implemented in programmable circuitry in the wireless communication device and/or the network node. Thus, according to some embodiments, there is provided a computer program product comprising a computer readable medium (such as a non-transitory 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 a method, which may be any of the methods described herein, when the computer program is run by the data-processing unit. This is schematically illustrated in Fig. 11 with a computer readable medium 1100 and a data-processing unit 1110. The data- processing unit 1110 may e.g. comprise a processing unit 1120 and a memory 1130, which may be used for storage of said computer program when loaded into the data- processing unit 1110. Furthermore, according to some embodiments, there is provided a processor specifically adapted, or configured, to perform a method, which may be any of the methods described herein. Said processor may e.g. be the data-processing unit 1100 in Fig. 11. In some embodiments, the processor is a control unit of the wireless

communication device, such as the control unit 930 of Fig. 9 (to be further described below). In some embodiments, the processor is a control unit of the network node, such as the control unit 1030 of Fig. 10 (to be further described below).

According to some embodiments, there is provided an arrangement for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device. Embodiments of the arrangement are described in the following with reference to Figs. 9 and 10. The arrangement may e.g. be comprised in the wireless communication device 900, as illustrated in Fig. 9, or in the network node 1000 as illustrated in Fig. 10. It should be noted that other alternatives are possible too, where some parts are comprised in the wireless communication device, and some parts are comprised in the network node. According to embodiments, the arrangement comprises a mobility unit (940 in Fig. 9, 1040 in Fig. 10) adapted to acquire a mobility indication of the wireless communication device. Furthermore, the arrangement comprises a cell size unit (950 in Fig. 9, 1050 in Fig. 10) adapted to acquire a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device. Moreover, the arrangement comprises a determiner (960 in Fig. 9, 1060 in Fig. 10) adapted to determine whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication. The mobility unit, cell size unit, and determiner may be part of a control unit (930 in Fig. 9, 1030 in Fig. 10). As indicated above, the control unit may be a programmable control unit, such as a processor. Thus, in some embodiments, one or more of the mobility unit, cell-size unit, and determiner may be implemented with computer program instructions on the control unit.

The arrangement may comprise at least one of a mobility measurement unit (920 in Fig. 9, 1020 in Fig. 10) adapted to perform measurements related to mobility and a receiver (transceiver 910 in Fig. 9, transceiver 1010 in Fig. 10) adapted to receive the mobility indication, e.g. from the network node (in the case of Fig. 9) or the wireless communication device (in the case of Fig. 10).

The arrangement may comprise a cell size measurement unit (920 in Fig. 9, 1020 in Fig. 10) adapted to perform measurements related to cell size. For simplicity in the Fig. s, the same reference numbers have been used as for the mobility measurement unit. The reference numbers 920 and 1020 thus generically indicate a "measurement unit", which may be configured to perform the function of any or both of the mobility measurements and cell size measurements.

The arrangement may comprise a receiver (such as the transceiver 910 in Fig. 9 or 1010 in Fig. 10) adapted to receive the cell size indication, e.g. from the network node (in the case of Fig. 9) or the wireless communication device (in the case of Fig. 10).

The arrangement may comprise a data storage (illustrated in Fig. 9 with reference number 980) comprising previously acquired cell sizes. The arrangement may comprise a querying unit (not explicitly shown) adapted to query a database storing statistical cell size information, e.g. the database 1080 on the server 1090 in Fig. 9.

Referring to Fig. 9, where the arrangement is comprised (or adapted to be comprised) in the wireless communication device, the determiner 960 may be further adapted to update at least one of the above-mentioned first list and a second list based on the determination of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application. The first and/or second list may e.g. be maintained in a temporary storage 970. Furthermore, the arrangement may further comprise a transmitter (such as the transceiver 910) adapted to transmit at least one of the first list and the second list to the network node for use in configuration of one or more secondary cells of the wireless communication device.

Referring to Fig. 10, where the arrangement is comprised (or adapted to be comprised) in the network node, the arrangement may further comprise a carrier aggregation configuration unit 1070 adapted to configure one or more secondary cells of the wireless communication device based on the determination of the determiner 1060 of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application. In the case that the arrangement is comprised in the wireless communication device (as in Fig. 9), the network node may comprise a receiver (such as the transceiver 1010, Fig. 10) adapted to receive at least one of said first list and said second list from the wireless communication device. Furthermore, the network node may comprise a carrier aggregation configuration unit (such as the unit 1070 in Fig. 10) adapted to configure one or more secondary cells of the wireless communication device based on the first list and/or the second list.

According to some embodiments, there is provided a server (e.g. 1090 in Fig. 10) for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device. The server is associated with the cellular

communication system and comprises a database (e.g. 1080 in Fig. 10) storing, for each of a plurality of cells, one or more of statistical cell size information and statistical information regarding a length of one or more consecutive time spans during which the cell has been used as secondary cell of one or more wireless communication devices having respective mobility indications. The server may e.g. be a cloud-based server.

For further illustration of various steps and aspects, a number of numbered example embodiments are described below.

Embodiment 1 :

Network node deciding which cell types to consider for aggregation depending on the UE mobility state (e.g. UE speed).

Fig. 7 illustrates an example with a network node monitoring UE speed and determining which kind of SCells to configure.

A purpose of this embodiment is to only configure the UE with SCCs that carry SCells that will be usable for communication by the UE long time enough, given the velocity of the UE. The cell radius and the UE speed are the major factors for the time a cell can be used. This is essential for avoiding unnecessary signaling between the network node and the UE (e.g. SCell addition, SCell release, SCell activation, SCell deactivation) and potentially also between network nodes in case of inter-node aggregation.

The UE is in connected mode and connected to the PCell. The UE is supporting CA operation on at least one secondary component carrier (700).

The network node estimates regularly the UE mobility state (e.g. velocity)

(710) and classifies the UE into say one out of four categories: UE stationary, UE moving at low speed, UE moving at medium speed, or UE moving at high speed (715). The mapping may for instance be as shown in the table below.

It shall be understood that other speed classes and/or speed ranges can be used.

In case the classification of the UE has changed (716;YES), e.g. from previously low to currently medium speed, the network node does no longer consider femtocells to be suitable for the UE since the cell radius is very limited (up to 10 meters) and the UE will go in and out of coverage of such cells without really having much time to use the cell. If trying to use it for carrier aggregation, it will mean unnecessary signaling (e.g. MAC and/or RRC signaling) between the network node and the UE, unnecessary measurement and radio activities from UE side, and in case of inter-node aggregation, unnecessary signaling over e.g. X2 or SI between the PCell and the concerned SCell or PSCell. Hence the network node may apply mapping of suitable cell types to consider for aggregation for the different UE speed classes, as shown in the table below. Speed class Cell types considered for CA

Stationary Femto, Pico, Micro, Macro

Low Femto, Pico, Micro, Macro

Medium Pico, Micro, Macro

High Micro, Macro

It shall be understood that other speed classes and/or cell type combinations can be used.

Given the current UE speed class the network node checks whether the configured SCells are of the appropriate type (731). In case there are configured SCells that no longer are suitable or SCells that have become suitable, depending on the change in UE speed class, (732;YES), the network node modifies the UE configuration by sending a R CConnectionReconfiguration message to the UE (3GPP TS 36.331 V12.1.0, section 6.2), where the concerned SCells are released, and/or more suitable SCells are added (790).

When determining UE speed class (715) the network node may further apply a hysteresis to prevent frequent jumping between e.g. stationary and medium speed. The hysteresis may for instance be that immediately when it is detected that the UE speed (hence class) has increased, the network node changes the classification of the UE, but should the UE speed decrease, the network node may lower the UE speed class accordingly first after some time (e.g. 60 seconds) and after having several consecutive estimates confirming that the UE speed has decreased. This may prevent e.g. UEs moving in cars and stopping at a red light from being considered stationary, and hence reduces the RRC signaling between the network node and the UE further. Such hysteresis may also be configured differently depending on initial UE speed class and currently determined UE speed class, and may e.g. be longer for a change from low to stationary than for high speed to medium speed.

Fig. 13 illustrates an example classification of UE speed. The UE has been configured to operate in CA mode (1300) and repeatedly estimates its speed according to e.g. some prior art method (1305). It then classifies its speed into: high speed, medium speed, low speed, or stationary (1310). The mapping of estimated speed to speed class may for instance follow the table above. It shall be understood that other speed classes and/or speed ranges can be used.

In case the UE speed class has changed (1315;YES), information about it is shared with the entity that is responsible for scheduling cell search and measurements (1320); here called Measurement Manager.

Embodiment 2:

Network node adapting the SCell measurement cycle to cell types and UE mobility state (e.g. UE speed)

This embodiment is an extension of Embodiment 1, in that the network node further may modify the SCell measurement cycle depending on UE speed class, by sending an updated MeasConfig information element with the

R CConnectionReconfiguration message (3GPP TS 36.331 V12.1.0, section 6.2).

The change of measurement cycle may for instance reflect that when going from UE speed class medium to low, femtocells may be configured, and since the cell radius is small, the SCell measurement rate for the concerned carrier(s) may have to be fairly high, say MeasCycleSCell of 160ms, for the UE quickly to respond to

deteriorated radio conditions in the small cell. However when going from UE speed class low to stationary, the MeasCycleSCell may be relaxed e.g. to 320ms to reflect that the UE more or less is stationary and is not likely to quickly leave the coverage of the femtocell. As an example, measurement cycles as outlined in the table below may be considered.

Speed class Cell types considered for CA

Macro Micro Pico Femto

Stationary 640 ms 640 ms 320 ms 320 ms

Low 640 ms 640 ms 320 ms 160 ms

Medium 320 ms 320 ms 160 ms N/A

High 320 ms 160 ms N/A N/A

It shall be understood that the SCell measurement cycle lengths are just exemplary to illustrate the idea.

By not always configuring the measurement cycle for the worst case expected

UE speed, the UE can save power since it has to turn on receivers for SCCs with inactive SCell(s) less frequently. Radio activity constitutes a significant part of the power consumption for the modem.

The necessary modifications of measurement rates can be done as part of step (790) above.

Variations of this embodiment in include the UE taking into account the characteristics of cells on different carriers, along with the current mobility scenario. Ultra-dense layers with very small cells are monitored up to a particular UE speed, and above that speed the UE refocuses its effort to track small size, medium size and macro cell. At further higher speed the UE refocuses on medium sized and macro cells. This allows the UE to spend the resources more wisely than just blindly applying the legacy measurement and cell search rates (e.g. always every 40ms for active carriers).

Such an approach may allow the UE to optimize the measurement effort where it makes most sense given the radio environment and the network deployment.

Control of UE measurements

When the UE is stationary, it makes sense to put effort on measuring all kinds of cells, but for cells larger than femtocells the cell search rate can be reduced since the UE will not rapidly leave the coverage of the cell and enter coverage of the next. When the UE is at low speed, measurements and cell search may be carried out at higher than nominal rate (the rate at which a legacy UE would carry out

measurements and cell search) for femtocells since the UE may leave and/or enter cell coverage quickly. For picocells the nominal measurement and cell search rate can be used, and for larger cells at least the cell search rate can be below nominal rate. Whether measurements can be so too depends on the quality of the cell and hence how likely it is that the UE will have to find a new candidate.

At medium UE speed it does no longer make sense to measure femtocells since the UE anyway would not have time to utilize the cell before leaving its coverage (cell diameter is about 20m). For picocells measurements and cell search may be carried out at higher than nominal rate, to reflect that the UE is likely to leave and/or enter cell coverage quickly given the speed. Micro- and macrocells are using nominal rate for cell search and measurements.

At high UE speed it no longer makes sense to measure picocells since the UE is likely to leave and/or enter cell coverage quickly. Instead one may increase the measurement rate for macro- and/or microcells.

Storing information about cell characteristics on different carriers

The UE may store history information on cell sizes on different carriers for future use, e.g., to beforehand determine that a complete layer is a femtocell layer and/or picocell layer. It can use such acquired information to proactively modify the measurement rate, e.g. by taking into account whether a layer comprises say both pico- and femtocell, by which at medium UE speed one shall continue to monitor the layer even if the configured SCell right now is a femtocell.

The UE may attach a time stamp to the stored information, to allow it to obsoleted and refreshed after some period of time (e.g. hours or days).

The UE may also share information on cell radius or characteristics of a layer with a proprietary server in the cloud, for other UEs to acquire such information.

The UE may further, e.g. when entering the tracking area, acquire information from the proprietary server on the characteristics of different layers. The information in the database may further be based on finger-printing, allowing the information to be tailored to different geographical areas.

The server may further process and refine the information provided by UEs.

The server may configure the UE to provide such information.

The UE may be configured not to act on its own findings, but only on verified information provided by the server.

Fig. 12 illustrates an example of UE classifying SCell upon receiving a new SCell configuration from the network node.

The UE has been configured to operate in CA mode (1200), and when it receives a new SCell configuration via SCellToAddMod in

RRCConnectionReconfiguration message (1205; YES) it checks whether it already has stored information on how the SCell and/or Secondary Component Carrier has been classfied (1210). If no record of the SCell or the Secondary Component Carrier is found (1215;NO), the UE calculates the physical carrier frequency from dl-CarrierFreq and the extracts the transmit power used for common reference signals from

reference SignalPower (1220). Thereafter it calculates a hypothetical cell radius using a transmission formula and a reference level for the received power (P_RX) (1225), and classifies the cell into: macro, micro, pico or femto (1230). It shall be understood that those are only exemplary; other classes can be used e.g. large, medium, and small. After having classified the cell the UE stores information about it in a database, where the information for instance comprises:

- EARFCN and PCI (identity of the cell)

Neighbor cell EARFCNs and PCIs (identity of neighbor cells for finger printing)

Time stamp (to know when the information was collected)

It shall be understood that additional information may be stored, such as: RSRP values for neighbor cells, GPS coordinate for this location, etc, to further specify the location of the SCell.

Next the UE checks whether the acquired information on the SCell shall change the classification of the carrier, for the concerned location. For instance, in case of mixed cell deployment the UE may first have found a microcell, but later finds out that there also are picocells on the concerned carrier, it may change the classification of the carrier from microcell layer to picocell layer (1240). In case the carrier classification is changed (1245;YES), information about it is shared with the entity that is responsible for scheduling cell search and measurements (1250); here called Measurement

Manager.

For UE classifying PCell, frequency and reference signal transmission power for the PCell can be acquired from system information (SIB2) and/or from the handover command (R CConnectionReconfiguration message including mobilityControlInfo). This classification follows essentially the same flow as for classification of SCell above.

Fig. 14 illustrates an example Measurement Manager adapting measurement approach to cell size and changed conditions regarding UE speed, carrier classification, and activation status on each secondary component carrier.

The UE has been configured to operate in CA mode (1400). In case an SCell is added or removed (1405; YES), the Measurement Manager updates the set of measured carriers if needed (1425). It then decides on measurement approach based on the monitored carriers, the cell sizes on the monitored carriers, the activation status of the SCells, and the UE speed (1430). The measurement approach comprises for instance Total resources to be used (hardware accelerator utilization, digital signal processor utilization, receiver utilizations, memory and memory transfer utilization, power consumption)

Distribution of total resources to be used over the carriers to be measured (measurement rate, cell search rate).

Considering a nominal cell search and measurement rate of one measurement occasion every 40-60ms (typical assumption for legacy UEs in 3 GPP RAN4

standardization work), it may mean that when the UE is in low speed, it measures a carrier with an active SCell where the carrier comprises femtocells more often, e.g. every 20-30ms, since radio conditions are expected to change rapidly due to the small cell radius, and potentially at the expense of measuring a carrier with an active SCell where the carrier comprises macrocells more sparsely, e.g. every 60-80ms. On the other hand, when the UE is at medium or high speed, it may decide to completely skip measurements on carriers with configured SCells where the carrier comprises femtocells since the UE anyway will leave coverage of the cell so fast that it cannot be used for communication. It shall be understood that the selected rates are only exemplary. The essence is that the entity responsible for scheduling measurements is adapting to the conditions.

Besides monitoring whether the measurement configuration has to be updated (1405), Measurement Manager also monitors whether UE speed (1410), Carrier classification (1415) and/or SCell activation status (1420) changes. If so (1410;YES, 1415;YES, and/or 1420;YES), Measurement Manager decides on an appropriate measurement approach (1430) as described above.

As an extension, the Measurement Manager may further account for distance from cell center.

In this embodiment the Measurement Manager uses the measured RSRP and the signaled reference signal transmission power for each configured SCell and calculates an approximate distance from the SCell center using the aforementioned transmission formula. In case the UE is close to the derived cell border, the

Measurement Manager may restore to nominal or increase the measurement rate for that carrier, particularly if good neighbor cells have not yet been identified.

Alternatively, a strict threshold on RSRP may be used to decide when the cell is risking being too weak to be used.

As an additional or alternative extension, Measurement Mgr may further accounting for interference in SCell.

In this embodiment the Measurement Manager uses estimated SINR (or RSRQ) to decide if the SCell signal quality is deteriorating to a level where the cell is risking being too interfered to be used. If the SINR (or RSRQ) falls below a threshold, Measurement Manager may restore to nominal or increase the measurement rate for that carrier, particularly if good neighbor cells have not yet been identified. Fig. 15 illustrates UE downloading SCell and/or carrier classifications from a server. The UE has been configured to operate in CA mode (1500), and is handed over from one PCell to another (1505;YES). If the UE enters a new area (e.g. a tracking area) (1510;YES), it contacts a server to download information on cell sizes on carriers in that area (1515). The information may be partial or complete. The information may for instance comprise:

EARFCN and classification valid for whole area, or

EARFCN and sets of location information and classification, to determine in what area the carrier e.g. comprises picocells and where it comprises macrocells, in case mixed but geographically separated deployment of e.g. pico- and microcells on the carrier, and/or

EARFCNs and list of PCIs including cell classification, or

EARFCNs and list sets of PCIs, location information, and classifications The location information may for instance contain PCIs of cells on other carriers in whose coverage the UE will be when close to the concerned cell (so called finger-print).

The UE may use this as a priori information e.g. in step (1210).

Fig. 16 illustrates UE reporting SCell information to a server.

The UE has been configured to operate in CA mode and further to report SCell classification or derived cell radius to a server (1600). When the UE encounters an SCell (1605; YES), it classifies the cell and then stores the information in a repository for later reporting (1610). When the reporting criterion is fulfilled (e.g. time-based, number of acquired cells-based, etc) (1615;YES), the UE sends the report to the server and then flushes the reporting repository (1620).

Alternatively, the UE may be requested to only classify and later report SCells that are previously unknown, e.g. has not been part of the downloaded information, and/or SCells for which the derived classification differ from the one in the downloaded information.

The information about each cell may for instance comprise:

- EARFCN and PCI (identity of the cell) Neighbor cell EARFCNs and PCIs (identity of neighbor cells for finger printing)

Time stamp (to know when the information was collected)

The server may further sanity check and post-process the reports from multiple UEs before providing it for downloading as outlined above.

Thus, in various embodiments, the UE derives the cell radius for cells on different carriers, and estimates its speed, and then takes the information into account when deciding on how to do measurements. For instance, the UE may decide to skip measurements completely on carriers with configured femtocells (cell radius <10ms) if moving with speed above 10 m/s since it anyway will leave coverage before the cell really can be used. It can then instead save power or focus the resources on carriers with larger cells.

Embodiment 3 :

Network node handling carriers with mixed deployment of e.g. pico- and femtocells.

This embodiment is an extension to Embodiments 1 and 2 in that the network node, when deciding whether to configure SCells and associated measurement cycle to use for the SCC, also considers whether there is a mixed deployment of cells of different sizes, either clustered or scattered.

In case the UE is close to a geographical border between e.g. pico- and femtocells deployments, when the UE is configured with a suitable SCell measurement cycle it is taken into account that a neighboring cell may be a femtocell. Hence instead of configuring the UE with the suggested measurement cycles for picocells, the network node may decide to configure a suitable measurement cycle for femtocells, provided that the UE is in speed class low. In speed class stationary it may still configure the UE according to picocell since the UE is not likely to move into coverage of the femtocell due to being stationary. The similar idea can be extended to other combinations as well, e.g. micro- and picocells, etc. This would be done as part of step (790) above. The network node may use e.g. fingerprinting or other prior art means for determining the location of the UE, and may potentially also take direction into account to see whether the UE is approaching or leaving the area with smaller cells.

Embodiment 4:

Network node tuning basing its decision on historical data

This embodiment is an extension to Embodiments 1-3. The network node may refine its thresholds for UE speed, and/or the assumed cell radius of SCells, and/or used measurement cycles by collecting historical data from interactions with UEs and subjecting the collected data to analysis. The collected data may for instance comprise CQI and measurement reports (RSRP, RSRQ), UE attributes or state, and/or

information on when the UE drops the connection on the concerned carrier. The refined thresholds (e.g. for classification of cell radius or classification of UE speed) may apply for the whole carrier in a wider geographical area, for parts of the coverage of the PCell, or for individual SCells. The purpose is to tune the system to prevent unnecessary signaling and loss of system throughput. Where particular thresholds apply may for instance be determined by the network node based on fingerprinting of measurement reports provided by the UE.

Embodiment 5 :

Forwarding of information on UE speed class at handover.

Fig. 8 illustrates an example of a source network node forwarding UE speed class to target network node during handover.

The source network node may forward information to the target network node on the UE speed class during handover of the UE between PCells. This information may be passed for instance over the X2 interface. This is particularly useful if the UE is in speed class high or medium since the target network node then at least initially does not have to consider aggregation with smaller cells.

New or modified signaling over the X2 interface might be needed for this embodiment. Embodiment 6:

Acquisition from network nodes of cell types

The network node may acquire information on cell types (SCells as well as neighbor cells to the PCell) either by requesting information directly from the concerned network nodes (in case of inter-node aggregation) over the X2 or S 1 interfaces, or other to-be-defined interfaces in case of femtocells (interfaces towards femtocells are still under discussion in the standard); by getting preconfigured with such information; or by requesting such information from another network node e.g. a SON.

The acquired information may for instance comprise:

- EARFCN, PCI, CGI and location information,

Explicit indication of cell type, and/or

Explicit indication of cell radius, and/or

Explicit indication on reference signal transmission power used by the concerned cell.

In case of the latter the network node can itself calculate a hypothetical cell radius based on a transmission formula (e.g. a modified Friis formula) and: downlink carrier frequency, reference signal transmission power, and a reference level for received power (e.g. -90dBm), and use it for the classification of cell types (macro, micro, femto, pico).

The network node may store this information in a local database, or in a database contained in the core network for other network nodes to use.

Embodiment 7:

UE assisted SCell configuration mechanism

In this embodiment the UE obtains and use at least a first set of information and a second set of information to determine at least one of:

a first list of cells, which are suitable for configuration as SCells for this UE and

- a second list of cells, which are not suitable for configuration as SCells for this UE. The suitability of cell as a SCell for this UE is determined by the UE based on one or more criteria. The cell is considered suitable for operating as SCell provided that;

the UE is allowed to access that cell e.g. it is not barred for that UE or does not belong to closed subscriber group (CSG). A cell in a CSG group is allowed to be accessed only to limited UEs;

the UE can received and/or transmit signals in that cell with a quality above a threshold e.g. SINR is above 0 dB.

the UE estimates that it can stay in that cell for certain minimum amount of time e.g. 10 seconds.

The two sets of information comprise of:

the first set of information related to the UE mobility state (as described in section 5); and

the second set of information related to the type of cell or the power class of the base station serving the cell

The UE obtains the first set of information by autonomously determining one or more attributes of its mobility state and/or by receiving such information from the network node e.g. via its PCell.

The UE obtains the second set of information based on one or more of the following mechanisms:

- By reading the system information (SI) of the cell e.g. master information block (MIB) and system information blocks (SIBs). The SI contains implicit or explicit information about the cell type of power class of that cell. Such information may comprise of CSG indicator, explicit information about power class of the BS serving the cell, transmit power of one or more DL control signals (e.g. CRS) etc. The transmit power of certain DL control signals such as of CRS is proportionally reduced with the reduction of BS transmit power. For example 30 dBm and 10 dBm may be used in WA BS and LA BS respectively. BY acquiring such information which is sent in SI, the UE can implicitly determine the power class of the BS that serves that cell; Historical information which maps the cell ID (say PCI) and cell type. The PCI of a cell is determined by the UE during cell search. The UE identifies a cell and checks if it has the stored information about its cell type;

The overall procedure in the UE for determining the cells to be included in the first and the second lists is described with few examples below:

1. If the UE mobility state changes slowly (e.g. low UE speed etc), the cell size is small (e.g. pico cell) and is suitable for use by the UE, then the UE includes that cell in the first list of cells i.e. suitable cell. The cell information may comprise of at least PCI and EARFCN; but it may also include additional information such as CGI, determined power class of BS serving that cell, cell type such as femto or pico etc. The UE may also include those cells which the UE can use as SCell depending upon the UE CA capabilities.

2. If the UE mobility state changes fast (e.g. moderate or higher UE speed etc), the cell size is large (e.g. macro cell) and is suitable for use by the UE, then the UE includes that cell in the first list of cells i.e. suitable cell. The cell information may be the same as in 1).

3. If the UE mobility state changes fast (e.g. moderate or higher UE speed etc), the cell size is small (e.g. femto or pico cell) and is suitable for use by the UE, then the UE includes that cell in the second list of cells i.e. NOT suitable cell. The cell information may be the same as in 1).

The UE transmits the information contained in the first list and/or in the second list to the network node e.g. using RRC signaling. The UE may also transmit its current location if that is available at the UE.

The network node may use the acquired information for configuring the UE with one or more SCells. The network node may also avoid using the cells in the second list as SCells for that UE. In one example the network node may configure the UE with one of the cells belonging to the first list of cells received from the UE. In another example the network node may further take into account one of the cells belonging to the first list of cells received from the UE and also one or more procedure executed by the network node itself according to one or more methods in the preceding sections (i.e. one or more embodiment 1-6). For example the network node may select a cell as SCell which is recommended by the UE in the first cell as well as which is determined by the network node itself using one or more methods in one or more embodiments 1-6.

Some advantages of the disclosed embodiments include:

Some embodiments reduce signaling between the network node and the

UE.

Some embodiments reduce inter-node signaling in case of inter-node aggregation or dual connectivity.

Moreover, some embodiments reduce the measurement effort for the UE and thus reduce battery drainage.

The system throughput may be enhanced since resources are more efficiently used by configuring the most suitable cells as SCells. The rate of configuration and reconfiguration of SCells may be reduced since SCells do not have to be reconfigured very often.

Below follows a list of abbreviations and their respective explanations.

Abbreviation Explanation

BS Base Station

BSC Base station Controller

CA Carrier aggregation

CDMA2000 Code division multiple access 2000

CGI Global cell identity

CSG Closed subscriber group

CPICH Common pilot channel

CRS Cell-specific reference signal

D2D Device-to-Device

DC Dual connectivity

DL Downlink

ECID Enhanced cell identity

Ec/No Ratio of energy per modulating bit to the noise spectral density EDGE Enhanced Data rates for GSM Evolution

EARFCN EUTRA absolute radio frequency channel number eNB Evolved Node B, base station

E-UTRAN Evolved universal terrestrial radio access network

E-UTRA Evolved universal terrestrial radio access

E-UTRA FDD E-UTRA frequency division duplex

E-UTRA TDD E-UTRA time division duplex

GERAN GSM EDGE Radio Access Network

GNSS Global navigation satellite system

GPS Global positioning system

GSM Global system for mobile communication

HD Half Duplex

HRPD High rate packet data

HSPA High Speed Packet Access

LMU Location measurement unit

LPP LTE positioning protocol

LTE Long term evolution

M2M Machine-To-Machine

MDT Minimization of drive test

MeNodeB Master eNodeB

MME Mobility management entity

MTC Machine-Type Communication

OTDOA Observed time-difference of arrival

PBCH Physical broadcast channel

PCC Primary component carrier

PCell Primary Cell

PCI Physical cell identity

PDA Personal digital assistant

PRS Positioning reference signal

PSS Primary synchronization signal

RAT Radio Access Technology RNC Radio Network Controller

RRC Radio resource control

RRH Remote radio head

RRU Remote radio unit

RS Reference signal

RSCP Reveiced signal code power

RSRP Reference signal received power

RSRQ Reference signal received quality

RSSI Received Signal Strength Indicator

RSTD Reference signal time difference

SCC Secondary component carrier

SCell Secondary Cell

SeNodeB Secondary eNodeB

SIB2 System information block 2

SINR Signal-to-Interference Ratio

TDD Time division duplex

UE User equipment

UL Uplink

UTDOA Uplink time difference of arrival

UTRA universal terrestrial radio access

UTRA FDD UTRA frequency division duplex

UTRA TDD UTRA time division duplex

WLAN Wireless Local Area Network

Claims

1. A method for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device, the method comprising:

acquiring (510, 610) a mobility indication of the wireless communication device;

acquiring (520, 620) a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device; and

determining (530, 630) whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication.

2. The method of claim 1 wherein the mobility indication comprises at least one of a mobility state, a speed, a velocity, an acceleration, a direction of movement, a trajectory of movement, and a geographical location.

3. The method of any of claims 1 through 2 wherein the cell size indication comprises at least one of an estimated cell radius, an actual cell radius, an estimated cell diameter, an actual cell diameter, an estimated cell type, an actual cell type, an average cell size among a plurality of cells using a carrier frequency of the cell, and a smallest cell size among the plurality of cells using the carrier frequency of the cell.

4. The method of any of claims 1 through 3 further comprising adapting (550, 650) secondary cell measurements by the wireless communication device based on the mobility indication and the cell size indication.

5. The method of any of claims 1 through 4 wherein the determination of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application comprises: if a speed indicated by the mobility indication exceeds a first speed threshold, determining that the cell is suitable as secondary cell only if a cell size indicated by the cell size indication exceeds a cell size threshold; and

if the speed indicated by the mobility indication does not exceed a second speed threshold, determining that the cell is suitable as secondary cell regardless of the cell size indicated by the cell size indication.

6. The method of any of claims 1 through 5 wherein determining whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application comprises considering statistical information regarding a length of one or more consecutive time spans during which the cell has been used as secondary cell of one or more wireless communication devices having respective mobility indications corresponding to the mobility indication of the wireless communication device.

7. The method of any of claims 1 through 6 wherein the method is performed by the wireless communication device, the method further comprising:

updating at least one of a first list and a second list based on the determination of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application, wherein

the first list is indicative of cells that are suitable as secondary cells of the wireless communication device in the carrier aggregation application; and

the second list is indicative of cells that are unsuitable as secondary cells of the wireless communication device in the carrier aggregation application; and

transmitting (540) at least one of the first list and the second list to the network node for use in configuration of one or more secondary cells of the wireless

communication device.

8. The method of claim 7 wherein acquiring the mobility indication comprises one or more of performing measurements related to mobility, and receiving the mobility indication from the cellular communication system.

9. The method of any of claim 7 through 8 wherein acquiring the cell size indication comprises one or more of performing measurements related to cell size, receiving the cell size indication from the cellular communication system, extracting a previously acquired cell size indication from a data storage of the wireless

communication device, and querying a database reachable via the cellular

communication system and storing statistical cell size information.

10. The method of any of claims 1 through 6 wherein the method is performed by the network node, the method further comprising:

configuring (690) one or more secondary cells of the wireless communication device based on the determination of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application.

11. The method of claim 10 wherein acquiring the mobility indication comprises one or more of performing measurements related to mobility, receiving the mobility indication from the wireless communication device, and receiving the mobility indication from other nodes of the cellular communication system.

12. The method of any of claims 10 through 11 wherein acquiring the cell size indication comprises one or more of performing measurements related to cell size, receiving the cell size indication from the wireless communication device, extracting a previously acquired cell size indication from a data storage of the cellular

communication system, and querying a database reachable from the cellular

communication system and storing statistical cell size information.

13. A computer program product comprising a computer readable medium (1100), 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 according to any of claims 1 through 12 when the computer program is run by the data-processing unit.

14. A processor (930, 1030) specifically adapted to perform the method according to any of claims 1 through 12.

15. An arrangement for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device, the arrangement comprising:

a mobility unit (940, 1040) adapted to acquire a mobility indication of the wireless communication device;

a cell size unit (950, 1050) adapted to acquire a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device; and a determiner (960, 1060) adapted to determine whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication.

16. The arrangement of claim 15 further comprising at least one of:

a mobility measurement unit (920, 1020) adapted to perform measurements related to mobility; and

a receiver (910, 1010) adapted to receive the mobility indication.

17. The arrangement of any of claims 15 through 16 further comprising at least one of:

a cell size measurement unit (920, 1020) adapted to perform measurements related to cell size;

a receiver (910, 1010) adapted to receive the cell size indication;

a data storage (980) comprising previously acquired cell sizes; and

a querying unit adapted to query a database (1080) storing statistical cell size information.

18. The arrangement of any of claims 15 through 17 adapted to be comprised in the wireless communication device, wherein the determiner (960) is further adapted to update at least one of a first list and a second list based on the determination of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application, and wherein the first list is indicative of cells that are suitable as secondary cells of the wireless communication device in the carrier aggregation application and the second list is indicative of cells that are unsuitable as secondary cells of the wireless communication device in the carrier aggregation application; and

further comprising a transmitter (910) adapted to transmit at least one of the first list and the second list to the network node for use in configuration of one or more secondary cells of the wireless communication device.

19. The arrangement of any of claims 15 through 17 adapted to be comprised in the network node and further comprising a carrier aggregation configuration unit (1070) adapted to configure one or more secondary cells of the wireless communication device based on the determination of the determiner of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application.

20. A wireless communication device comprising at least one of the processor of claim 14 and the arrangement of any of claims 15 through 18.

21. A network node comprising at least one of the processor of claim 14 and the arrangement of any of claims 15 through 17 and 19.

22. A network node for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising the network node and at least one wireless communication device, the network node comprising:

a receiver (1010) adapted to receive at least one of a first list and a second list from a wireless communication device, wherein the first list is indicative of cells that are suitable as secondary cells of the wireless communication device in the carrier aggregation application and the second list is indicative of cells that are unsuitable as secondary cells of the wireless communication device in the carrier aggregation application; and

a carrier aggregation configuration unit (1070) adapted to configure one or more secondary cells of the wireless communication device based on the first list and/or the second list.

23. A server (1090) for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device, the server associated with the cellular communication system and comprising a database (1080) storing, for each of a plurality of cells, one or more of:

statistical cell size information; and

24. A method for secondary cell configuration in a carrier aggregation application of a cellular communication system comprising at least one network node and at least one wireless communication device, the method comprising:

acquiring (520, 620) a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device;

determining (530, 630) whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication; and

configuring (590, 690), by the network node, one or more secondary cells of the wireless communication device based on the determination of whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application.

25. A cellular communication system comprising at least one network node and at least one wireless communication device, and adapted for secondary cell

configuration in a carrier aggregation application, the cellular communication system comprising:

a mobility unit (940, 1040) of at least one of the wireless communication device and the network node, adapted to acquire a mobility indication of the wireless communication device;

a cell size unit (950, 1050) of at least one of the wireless communication device and the network node, adapted to acquire a cell size indication of a cell, wherein the cell is a prospect secondary cell of the wireless communication device;

a determiner (960, 1060) of at least one of the wireless communication device and the network node, adapted to determine whether the cell is suitable as secondary cell of the wireless communication device in the carrier aggregation application based on the mobility indication and the cell size indication; and

a carrier aggregation configuration unit (1070) of the network node, adapted to configure one or more secondary cells of the wireless communication device based on the first list and/or the second list.