WO2012045337A1

WO2012045337A1 - Handover-related mobility optimization in cellular communication systems

Info

Publication number: WO2012045337A1
Application number: PCT/EP2010/064878
Authority: WO
Inventors: Dirk Rose; Bernhard Wegmann; Andreas Lobinger
Original assignee: Nokia Siemens Networks Oy
Priority date: 2010-10-06
Filing date: 2010-10-06
Publication date: 2012-04-12

Abstract

There are provided measures for handover-related mobility optimization in cellular communication systems, said measures exemplarily comprising acquiring a location of a terminal (S1, S1') with respect to a base station of a cellular communication system, and setting handover-related mobility parameters (S2, S2') in a terminal-specific manner depending on the acquired location of the terminal with respect to the base station. Said mobility parameters are applied (S3, S3') for handover applied mobility optimization in cellular communication systems based on a LTE, a LTE-Advanced, an UMTS, a GERAN a UTRAN radio access system.

Description

DESCRIPTION Title Handover-related mobility optimization in cellular communication systems

Field of the invention The present invention relates to handover-related mobility optimization in cellular communication systems.

Background of the invention In the development of radio communication systems, in par^¬ ticular cellular communication (like for example GSM

(Global System for Mobile Communication) , GPRS (General Packet Radio Service) , HSPA (High Speed Packet Access) , UMTS (Universal Mobile Telecommunication System) or the like) , efforts are made for an evolution of the radio ac^¬ cess part thereof. In this regard, the evolution of radio access networks (like for example the GSM EDGE radio access network (GERAN) and the Universal Terrestrial Radio Access Network (UTRAN) or the like) is currently addressed. Such improved radio access networks are sometimes denoted as evolved or advanced radio access networks (like for example the Evolved Universal Terrestrial Radio Access Network (E- UTRAN) ) or as being part of a long-term evolution (LTE) or LTE-Advanced, also generally referred to as International Mobile Communications - Advanced (IMT-A) . Although such de^¬ nominations primarily stem from 3GPP (Third Generation Partnership Project) terminology, the usage thereof herein^¬ after does not limit the respective description to 3GPP technology, but generally refers to any kind of radio ac^¬ cess evolution irrespective of the underlying system architecture . In the following, for the sake of intelligibility, LTE

(Long-Term Evolution according to 3GPP terminology) or LTE- Advanced is taken as a non-limiting example for a radio ac^¬ cess network of cellular type being applicable in the context of the present invention and its embodiments. However, it is to be noted that any kind of radio access network of cellular type, such as GSM, GPRS, HSPA and/or UMTS, may likewise be applicable, as long as it exhibits comparable features and characteristics as described hereinafter.

In the development of cellular systems in general, and ac^¬ cess networks in particular, the concepts of SON (self op^¬ timizing networks) and, in particular, MRO (mobility ro^¬ bustness optimization) are proposed. These concepts are particularly applicable for intra-RAT (radio access technology) mobility, namely e.g. for intra-base station hand^¬ overs, also referred to as intra-site handovers (i.e. hand^¬ overs within the coverage area of a single base station or site) . Such intra-base station handovers may for example be inter-sector handovers (i.e. handovers between different sectors (also referred to as logical cells) of the coverage area of a single base station or site) .

The target of MRO is to optimize configuration of network parameters, particularly mobility parameters (e.g. handover (HO) trigger parameters, HO thresholds or timers) . In this regard, it is an aim to reduce radio link failures (RLF) and call drop (CDR) probabilities caused by too late hand- over decisions, as well as non-suitable handover decisions in general .

In the case of an LTE/LTE-Advanced-based radio access sys- tern, as exemplarily assumed herein, as well as in any radio access system applying a frequency reuse of one, certain problems arise in handover-related mobility handling, espe^¬ cially in terms of interference. In the intra-LTE case, i.e. the case of intra-RAT handovers in the LTE network environment, the cellular communication system is mainly based on a sectored (cell) layout with a frequency reuse of one. As a consequence, the inter-cell interference plays a dominant role in terms of throughput and connection stability, mainly in the vicinity of cell or sector borders .

Conventionally, an intra-LTE handover is preferably trig^¬ gered by measurement reporting events A3 and A5 according to 3GPP specifications, where the measured quantity is RSRP (reference signal received power) or RSRQ (reference signal received quality) , respectively. The value of the measured quantity being compared with trigger event thresholds may be L3 filtered (by a layer 3 (L3) filter) , and the report- ing condition shall be fulfilled during a time-to-trigger. The thus used measurement parameters are cell-specific and are provided by the serving eNodeB (i.e. a base station) via higher layer signaling. In order to avoid unnecessary and/or un-reliable handovers (i.e. too fast handovers and ping-pong cases) , sufficiently high values for the filter coefficient of the L3 filter and the time-to-trigger have to be utilized. However, such conventional cell-specific setting of mobil^¬ ity parameters is not sufficient and may lead to inferior results, particularly (but not exclusively) in a sectored (cell) layout.

Typically, an inter-sector area in close vicinity to the antenna (i.e. the serving base station) yields a completely different interference behavior compared with an inter- sector area being farther away from the antenna. This is an effect of the limited overlap between the cell sectors which leads to severe issues in terms of RLF or CDR.

Terminals (such as user equipment UE) moving in close vi^¬ cinity to the antenna experience large signal quality changes over a small distance of movement. Transformed into time domain (via terminal speed) , the handover execution may be too slow and, thus, cannot avoid an RLF and/or an increase in CDR probability. This situation has been ob^¬ served in drive tests e.g. in 3G live networks and can be proven in detail by means of calculations/simulations. As a result, it is known that severe problems in terms of RLF and CDR exist near the site (base station) location when the terminal crosses inter-sector borders. This fact is mainly caused by the sectored (cell) layout in connection with certain antenna characteristics. In particular, a near-perpendicular crossing of an intra-eNodeB/NodeB border in close vicinity to the antenna (base station) location with high speed leads to very rapidly changing channel con^¬ ditions and quality.

Figure 1 shows an illustration of a scenario as well as drive test and simulation results for a conventional intra- base station (such as e.g. inter-sector) handover processing .

Figure 1 (a) shows the underlying scenario in which a base station with three beams (i.e. three sectors or logical cells) covering 120° each is disposed in close vicinity to a road on which a terminal denoted as UE is moving in the direction of the arrow. On its movement on the road, the terminal is first served by a first sector denoted by the number 1, and then, in close vicinity to the serving base station, the terminal crosses the border to a second sector denoted by the number 2 and is then - at some point - handed over to the second sector denoted by the number 2. In this example scenario, the terminal will not be handed over to a third sector denoted by the number 3.

Figure 1 (b) shows drive test results in the scenario ac^¬ cording to Figure 1 (a) , where a received signal code power (RSCP) of the individual sectors being served by the serv- ing base station is plotted over the traveled distance. As is evident from Figure 1 (b) , the signal levels of the indi^¬ vidual sectors (which are denoted by the same numbers as the individual sectors in Figure 1 (a) ) dramatically change around the distance 0 indicating the sector border between the first and second sectors. Namely, the signal level of the first sector (thick solid line) decreases by about 20 dB, while the signal level of the second sector (dotted line) increases by about 20 dB, and the signal level of the third sector (thin solid line) , which is not involved in the present intra-base station handover process, remains substantially constant. Figures 1 (c) and 1 (d) show simulation results in the sce^¬ nario according to Figure 1 (a) , wherein the signal levels of the individual sectors are denoted by the same numbers as the individual sectors in Figure 1 (a) . In Figure 1 (c) a signal to interference-pus-noise ratio (SINR) of the serv^¬ ing sector (i.e. the first sector before handover and the second sector after handover) is plotted over the traveled distance, and in Figure 1 (d) a reference signal received power (RSRP) of the individual sectors being served by the serving base station is plotted over the traveled distance. As is evident from Figure 1 (c) , the SINR of the serving sector drops dramatically upon crossing the physical sector border (i.e. the SINR level of the still serving first sec^¬ tor decreases) and recovers after the handover has been executed (i.e. the SINR level of the newly serving second sector increases) . That is, if the handover execution is too slow, the risk of an RLF is extremely high. For example, an RLF may be detected, if the SINR stays below a cer^¬ tain threshold, potentially also considering the time for which the SINR stays below this threshold. For example, an RLF may be detected, if the SINR stays below -8dB for ap^¬ proximately 400 ms . As is evident from Figure 1(d), the simulation results of the signal levels of the individual sector basically correspond to the drive test results ac- cording to Figure 1 (b) .

In view of the above, when the terminal is physically lo^¬ cated in the second sector (i.e. when the terminal has al^¬ ready crossed the physical sector border) , but the first sector is still serving the terminal (i.e. a handover to the second sector has not yet occurred) , then the second sector introduces a huge interference to the serving signal of the terminal (i.e. the signal of the first sector) . Namely, as the old (serving) cell/sector's signal decreases and the new (neighbor) cell/sector's signal increases very fast, a fast (or even fastest possible) handover decision is required especially in the vicinity of the base station so as to avoid problems in terms of RLF and CDR.

Such problems arise both in 3G and 4G (LTE) cellular commu^¬ nication systems. While in 3G networks, the situation may be less critical as soft handover (SHO) is usable, i.e. the HO radio link addition is typically triggered before the "physical" border (where both signals are of equal

strength) is reached, the described problems can also be observed in 3G networks even when SHO is applied. In 4G (LTE) networks, the situation is even more critical as there is no SHO in use, i.e. the HO condition is typically fulfilled after the physical border is reached, when the neighbor cell/sector's signal is already some decibel above the serving cell/sector's signal.

The conventional techniques for (intra-base station) hand^¬ over are not sufficient in view of these problems.

As outlined above, cell-based values are conventionally configured for the described HO parameters. The disadvan^¬ tage is that a fixed cell-based configuration is only a compromise and does not really help in the above situation due to the different requirements and demands applicable within a single cell. Currently, there exists no mechanism to handle such critical situations.

Conventionally, if more reliable and stable but conse^¬ quently slower HO settings (e.g. large time-to-trigger, large filter coefficient) are used, the RLF/CDR risk is very high for the problematic part in the vicinity of the base station. Reducing these values leads to very fast HO decisions, which counteracts the RLF/CDR problem, but leads to an increase in unwanted (i.e. non-suitable) HO decisions for the remaining part of the cell. Therefore, such ap^¬ proach degrades performance of the radio access network as well as the evolved packet system (e.g. increased signal^¬ ing, processing load for radio as well core network) and finally also user perception (e.g. risk of HO failure, throughput lowered due to service interruption periods) .

In order to reduce such problems, it might be conceivable to try avoiding network/cell layouts which are prone to such scenarios. For example, one could avoid placing anten^¬ nas near to roads with fast moving terminals, which natu^¬ rally is in praxis not applicable for a high number of cases. Another countermeasure could be to increase overlaps between sectors/cells or to avoid sectored layouts at all. This would, however, lead to severe capacity degradations.

In view thereof, there are several problems in conventional techniques for (intra-base station) handover, which may not be easily overcome in consideration of other requirements and demands of cellular communication system, in particular radio access networks. Such problems are to be overcome or at least mitigated for providing an efficient handover- related mobility optimization in cellular communication systems .

Accordingly, there is a demand for mechanisms for handover- related mobility optimization in cellular communication systems . Summary of embodiments of the invention

The present invention and its embodiments aim at solving the above problems .

The present invention and its embodiments are made to pro^¬ vide for mechanisms for handover-related mobility optimiza^¬ tion in cellular communication systems.

According to an exemplary first aspect of the present in^¬ vention, there is provided a method comprising acquiring a location of a terminal with respect to a serving base sta^¬ tion of a cellular communication system, and setting hand- over-related mobility parameters in a terminal-specific manner depending on the acquired location of the terminal with respect to the serving base station.

According to further developments or modifications thereof, one or more of the following applies:

- the parameter setting comprises configuring at least two sets of handover-related mobility parameters being ap^¬ plicable for different locations of the terminal with re^¬ spect to the serving base station, and selecting one of the at least two sets of handover-related mobility parameters depending on the acquired location of the terminal with re^¬ spect to the serving base station,

- the parameter setting comprises assigning one out of at least two handover-related criticality zones depending on the acquired location of the terminal with respect to the serving base station, and setting the handover-related mo^¬ bility parameters depending on the assigned handover- related criticality zone, - the location of the terminal with respect to the serv^¬ ing base station comprises a distance between the terminal and the serving base station,

- a most critical handover-related criticality zone is defined as an area closest to the serving base station,

- the parameter setting is such that the handover-related mobility parameters enabling a fast handover decision are set for the most critical handover-related criticality zone,

- the parameter setting comprises applying a hysteresis in re-assigning a handover-related criticality zone due to a movement of the terminal by using spatial margin at the edge of a handover-related criticality zone,

- the handover-related parameters comprise one or more of a time-to-trigger value, a layer 3 filter coefficient, an offset value and a cell-individual offset defining a hand^¬ over border,

- the above-outlined method is operable at the terminal,

- the location acquisition comprises receiving an indica- tion of the location of the terminal with respect to the serving base station from the serving base station,

- the method further comprises receiving at least two sets of handover-related mobility parameters being applica^¬ ble for different locations of the terminal with respect to the serving base station from the serving base station,

- the method further comprises deciding on the need of a handover on the basis of the set terminal-specific hand^¬ over-related mobility parameters,

- the above-outlined method is operable at the serving base station,

- the location acquisition comprises measuring the location of the terminal with respect to the serving base sta- tion using at least one of signal propagation delay, signal strength, global position system, and timing advance,

- the method further comprises signaling the set hand^¬ over-related mobility parameters to the terminal,

- the handover-related mobility parameters relate to a handover of the terminal between two sectors being served by the serving base station,

- the terminal comprises a user equipment,

- the base station comprises one of a NodeB, an eNodeB, a radio network controller and a base station controller, and/or

- the cellular communication system is in accordance with one of a LTE, a LTE-Advanced, an UMTS, a GERAN and a UTRAN radio access system.

According to an exemplary second aspect of the present in^¬ vention, there is provided an apparatus comprising a proc^¬ essor configured to acquire a location of a terminal with respect to a serving base station of a cellular communica- tion system, and set handover-related mobility parameters in a terminal-specific manner depending on the acquired lo^¬ cation of the terminal with respect to the serving base station . According to further developments or modifications thereof, one or more of the following applies:

- the processor is further configured to configure at least two sets of handover-related mobility parameters be^¬ ing applicable for different locations of the terminal with respect to the serving base station, and select one of the at least two sets of handover-related mobility parameters depending on the acquired location of the terminal with re^¬ spect to the serving base station, - the processor is further configured to assign one out of at least two handover-related criticality zones depend^¬ ing on the acquired location of the terminal with respect to the serving base station, and set the handover-related mobility parameters depending on the assigned handover- related criticality zone.

- the location of the terminal with respect to the serv^¬ ing base station comprises a distance between the terminal and the serving base station,

- the processor is further configured to define an area closest to the serving base station as a most critical handover-related criticality zone,

- the processor is further configured to set the handover- related mobility parameters such that handover-related mo- bility parameters enabling a fast handover decision are set for the most critical handover-related criticality zone,

- the processor is further configured to apply a hystere^¬ sis in re-assigning a handover-related criticality zone due to a movement of the terminal by using spatial margin at the edge of a handover-related criticality zone,

- the above-outlined apparatus is operable as or at the terminal ,

- the processor is further configured to receive an indi^¬ cation of the location of the terminal with respect to the serving base station from the serving base station,

- the processor is further configured to receive at least two sets of handover-related mobility parameters being ap^¬ plicable for different locations of the terminal with re- spect to the serving base station from the serving base station,

- the processor is further configured to decide on the need of a handover on the basis of the set terminal- specific handover-related mobility parameters,

- the above-outlined apparatus is operable as or at the serving base station,

- the processor is further configured to measure the lo^¬ cation of the terminal with respect to the serving base station using at least one of signal propagation delay, signal strength, global position system, and timing advance,

- the processor is further configured to signal the set handover-related mobility parameters to the terminal,

- the terminal comprises a user equipment,

According to an exemplary third aspect of the present in^¬ vention, there is provided a computer program product including a program comprising software code portions being arranged, when run on a processor of an apparatus (such as e.g. according to the above second aspect and/or develop^¬ ments or modifications thereof) , to perform the method ac^¬ cording to the above first aspect and/or developments or modifications thereof. According to further developments or modifications thereof, the computer program product according to the third aspect comprises a computer-readable medium on which the software code portions are stored, and/or the program is directly loadable into a memory of the processor.

By way of exemplary embodiments of the present invention, there are provided mechanisms for handover-related mobility optimization in cellular communication systems. Such mechanisms according to exemplary embodiments of the present in^¬ vention may be particularly effective in terms of SON and/or MRO. By way of exemplary embodiments of the present invention, there is provided a technique for a terminal-specific and location-based setting of (handover-related) mobility pa^¬ rameters. In other words, exemplary embodiments of the pre^¬ sent invention provide for measures for effecting different terminal-specific parameterizations for handover evalua^¬ tion/decision depending on a terminal location with respect to a serving base station.

Brief description of the drawings

In the following, the present invention will be described in greater detail by way of non-limiting examples with ref^¬ erence to the accompanying drawings, in which Figure 1 shows an illustration of a scenario as well as drive test and simulation results for a conventional intra- base station handover processing, Figure 2 shows a schematic diagram of a cell division into handover-related criticality zones and the application thereof according to exemplary embodiments of the present invention,

Figure 3 shows a signaling diagram illustrating an exemplary procedure according to exemplary embodiments of the present invention, Figure 4 shows a signaling diagram illustrating another exemplary procedure according to exemplary embodiments of the present invention,

Figure 5 shows a flowchart illustrating an exemplary method according to exemplary embodiments of the present inven^¬ tion, and

Figure 6 shows a block diagram illustrating exemplary devices according to exemplary embodiments of the present in- vention.

Detailed description of embodiments of the present inven^¬ tion The present invention is described herein with reference to particular non-limiting examples and to what are presently considered to be conceivable embodiments of the present in^¬ vention. A person skilled in the art will appreciate that the invention is by no means limited to these examples, and may be more broadly applied. Generally, the present invention and its embodiments relate to (handover-related) mobility in cellular communication systems . In particular, the present invention and its embodiments are mainly described in relation to 3GPP specifications be^¬ ing used as non-limiting examples for certain exemplary network configurations and deployments. In particular, an LTE/LTE-Advanced (E-UTRAN) radio access network and corre- sponding standards (Release-8, Release-9, and Release-10 and beyond) are used as a non-limiting example for the ap^¬ plicability of thus described exemplary embodiments. As such, the description of exemplary embodiments given herein specifically refers to terminology which is directly re- lated thereto. Such terminology is only used in the context of the presented non-limiting examples, and does naturally not limit the invention in any way. Rather, any other network configuration or system deployment, etc. may also be utilized as long as compliant with the features described herein.

While the present invention and its embodiments are de^¬ scribed with respect to LTE/LTE-Advanced systems, the prob^¬ lems addressed may also be identified in other systems (in particular, other radio access systems or technologies) and the present invention and its embodiments are equally ap^¬ plicable in such other systems (in particular, other radio access systems or technologies) . For example, the present invention and its embodiments are equally applicable to all cases of cellular communication systems (such as e.g.

UMTS) , particularly where a frequency reuse of one is ap^¬ plied, such as e.g. in UTRAN and (partly) in GERAN. It is to be noted that the present invention and its em^¬ bodiments are specifically applicable to sector level. That is, according to exemplary embodiments of the present in^¬ vention (upon which the subsequent description is exempla- rily based) , a coverage area of a serving base station

(site) may be sectored (wherein a sector may be considered to correspond to a (logical) cell) , and the base station may be a base station serving the sector (i.e. logical cell) in which the terminal resides.

For the purpose of the present invention and its embodi^¬ ments, the following understanding regarding the underlying network configuration/structure is assumed as a basis. A base station (site) has a certain coverage area, and serves a terminal residing in its coverage area. The cover^¬ age area of a (serving) base station may be unsectored or sectored. In the unsectored case, the base station (site) serves a single sector of 360°. In the sectored case, the base station (site) serves more than one sector, namely n sectors of 360/n°. For example, the base station (site) may serve 2 sectors of 180° each, three sectors of 120° each (which case is exemplarily assumed in the subsequent de^¬ scription) , and so forth.

A sector may be considered to represent a (logical) cell. Such consideration is particularly applicable in cases where a single frequency bearer is used in the sector. In this case, each sector comprises a single (physical) cell.

Also, a sector may be considered to represent plural (logi^¬ cal) cells. Such consideration is particularly applicable in cases where plural frequency bearers are used in the sector. In this case, each sector comprises plural (physi^¬ cal) cells. For example, in a 3/3/3 configuration, a base station (site) has three sectors and three frequency carri^¬ ers (being used in each sector) , and each sector, thus, has three (logical) cells, resulting in a total of nine (logi^¬ cal) cells per base station (site) . Such case is applicable e.g. in UMTS and LTE systems.

A sector/cell may be defined by a PCI (physical cell id) e.g. in LTE, a scrambling code (in WCDMA) , and the like, as well as a Global Cell ID. Accordingly, for a base station (site) with three sectors/cells, one cell ID per sector (i.e. a total of three cell IDs per site) is assigned, and 3 sectors/cells are defined thereby.

The operation of the base station (site) is based on a fre^¬ quency reuse of one. That is, the entire coverage area (i.e. all sectors, if any) is served by the same frequency. A handover under consideration in the present specification particularly relates to a handover of a terminal between two sectors being served by the same serving base station, i.e. an inter-sector handover, wherein the terminal maintains to be served by the same frequency. This is also re- ferred to as an intra-frequency handover.

Hereinafter, various embodiments and implementations of the present invention and its aspects or embodiments are de^¬ scribed using several alternatives. It is generally noted that, according to certain needs and constraints, all of the described alternatives may be provided alone or in any conceivable combination (also including combinations of in^¬ dividual features of the various alternatives) . In the following, exemplary embodiments of the present in^¬ vention are described with reference to methods, procedures and functions.

According to exemplary embodiments of the present inven^¬ tion, there is proposed a terminal-specific and location- based setting of (handover-related) mobility parameters. That is, (handover-related) mobility parameters to be used for making a handover evaluation and/or decision by a terminal are adjusted (or, stated in other words, decided) in a terminal-specific manner depending on a location of the terminal with respect to a serving base station of a cellu^¬ lar communication system. The location of the terminal with respect to the serving base station may correspond to a lo^¬ cation of the terminal with respect to the serving base station and may, for example, be a distance between the terminal and the base station serving the sector in which the terminal resides.

In this regard, for example, the base station may be repre^¬ sented by its antenna. That is to say, the location of the terminal with respect to the serving base station according to exemplary embodiments of the present invention may cor- respond to a location of the terminal with respect to the antenna of the serving base station and may, for example, be a distance between the terminal and the antenna of the base station serving the sector in which the terminal resides. Stated in other terms, a relevant position of a serving base station according to exemplary embodiments of the present invention may be the position of the antenna of the serving base station or, in particular, the serving base station' s antenna serving the sector in which the terminal resides.

Generally, it is to be noted that the term "location" as used herein is deemed to be equivalent to terms such as "position" or the like.

According to exemplary embodiments of the present inven^¬ tion, (handover-related) mobility parameters may comprise one of more of a time-to-trigger, a (layer 3) filter coefficient, offset [dB] values or cell-individual offsets de^¬ fining the handover border.

According to exemplary embodiments of the present inven- tion, the location of the terminal with respect to the base station (for example, its antenna) may be derived via dif^¬ ferent methods. For example, measurements of signal propa^¬ gation delays and/or signal strength, GPS-based measure^¬ ments or a combination of different methods may be used in this regard. As an example, the location detection accord^¬ ing to exemplary embodiments of the present invention may be based on a Timing Advance (TA) , which method is exempla- rily used as a non-limiting example in the further description for the purpose of an intelligible explanation only. Generally, any other method can be equally used, preferably when a sufficient accuracy can be provided (wherein a reso^¬ lution should, for example, be approximately 100 meters or better) . According to exemplary embodiments of the present inven^¬ tion, the terminal-specific and location-based setting of (handover-related) mobility parameters may comprise a se^¬ lection of a specific set of mobility parameters (and/or a specific set of values of relevant mobility parameters) out of a plurality of (pre) -configured sets of mobility parame^¬ ters (and/or their values) . That is, different sets of mo^¬ bility parameters (and/or their values) may be applicable and, thus, may be selected/set/adj usted for different ter^¬ minal locations, e.g. different distances between terminal and base station.

According to exemplary embodiments of the present inven- tion, the terminal-specific and location-based setting of (handover-related) mobility parameters may be based on a division of a sector into different handover-related criti^¬ cality zones, i.e. zones/areas within the serving sector which exhibit a different criticality in terms of handover requirements or demands. That is, criticality zones may be applicable and, thus, may be assigned for different termi^¬ nal locations, e.g. different distances between terminal and base station, and the parameter setting may be effected on the thus assigned criticality zone. Stated in other words, different (sets of) mobility parameters (and/or their values) may be applicable and, thus, may be se^¬ lected/set/adjusted for different criticality zones repre^¬ senting different terminal locations, e.g. different dis^¬ tances between terminal and base station.

For example, according to exemplary embodiments of the pre^¬ sent invention, a critical zone may be defined as an area close (i.e. in (close) vicinity) to the serving base sta^¬ tion. As mentioned above, such critical zone may e.g. be defined as an area close (i.e. in (close) vicinity) to the antenna of the serving base station or, in particular, the serving base station' s antenna serving the sector in which the terminal resides. In case of a sectored site, a division into different hand^¬ over-related criticality zones, i.e. zones/areas within the serving sector, according to exemplary embodiments of the present invention leads to a sub-sectorization, i.e. to a sub-sectored (cell) layout.

Figure 2 shows a schematic diagram of a cell division into handover-related criticality zones and the application thereof according to exemplary embodiments of the present invention .

As shown in Figure 2, a base station denoted as eNodeB has three beams, thus realizing a coverage area or site having three sectors (which are not illustrated as such) . The bor^¬ der of the site is depicted by a solid line circle. In the thus depicted example, the site, i.e. each sector, is di^¬ vided into two handover-related criticality zones, and the border thereof, which may be determined by a terminal- specific threshold, is depicted by two broken line circles. It is to be noted that the representation of the border of the two criticality zones by two circles indicates that a hysteresis is applied (as the border would be represented by a single circle in the absence of hysteresis) .

In the thus depicted example, a critical zone is defined as an area close (in (close) vicinity) to the base station. According to exemplary embodiments of the present inven^¬ tion, terminals (denoted as UE in Figure 2) residing in this critical zone are configured to use mobility parame^¬ ters rendering a faster (or even fastest possible) HO evaluation and/or decision. That is, for terminals residing within this critical zone, (a set of) mobility parameters (is) are set/adj usted/selected which (is) are most appro^¬ priate in view of the terminal location within the critical zone, while for terminals residing outside this critical zone, (a set of) different mobility parameters (is) are set/adj usted/selected which (is) are most appropriate in view of the terminal location outside the critical zone. For example, a faster handover for terminals residing in this critical zone may be accomplished by setting of mobil^¬ ity parameters such that the time-to-trigger, the (layer 3) filter coefficient and/or the offset [dB] values are re^¬ duced and/or the cell-individual offsets are changed so as to shift the handover border.

According to exemplary embodiments of the present inven- tion, the belonging of a terminal to a specific criticality zone, i.e. the assignment of a specific criticality zone for a specific terminal, may be accomplished by comparing the determined terminal location with a threshold. For ex^¬ ample, in case of detecting the distance between terminal and base station as terminal location by using a TA meas^¬ urement, a TA threshold may be used for distinguishing be^¬ tween the respective criticality zones.

It is to be noted that, while Figure 2 exemplarily depicts a case with two criticality zones being separated by a sin^¬ gle border (represented by a single threshold) , more than two criticality zones being separated by more than one bor^¬ der (represented by more than one threshold) may equally be applied. In such case, more than one comparison of a deter- mined terminal location and respective thresholds is to be effected for assigning an applicable criticality zone for a specific terminal. In the thus depicted example applying a hysteresis, enter^¬ ing and leaving of the criticality zone by the terminal is detected by using a spatial margin (i.e. the gap (differ^¬ ence in radius) between the two broken line circles accord- ing to Figure 2) . That is, it may be detected that the ter^¬ minal enters the critical zone (event Y according to Figure 2) if the terminal location falls below a criticality zone threshold (e.g. a specific TA value), and it may be de^¬ tected that the terminal leaves the critical zone (event X according to Figure 2) if the terminal location exceeds the sum of the criticality zone threshold and a margin value (e.g. the specific TA value plus a hysteresis value) . In Figure 2, these cases are indicated by bold arrows repre^¬ senting the terminal movement, respectively.

According to exemplary embodiments of the present inven^¬ tion, when the terminal is detected to enter the critical zone (e.g. event Y in Figure 2), mobility parameters ren^¬ dering a faster (or even fastest possible) handover evalua- tion and/or decision are set for the terminal, while, when the terminal is detected to leave the critical zone (e.g. event X in Figure 2), the terminal is switched back to the normal mobility parameters, i.e. the mobility parameters rendering a normal handover evaluation and/or decision in order to make the handover more reliable outside the criti^¬ cal zone.

Accordingly, in the exemplary case of Figure 2, a detection mechanism of a parameter re-configuration (due to terminal movement) is such that the terminal is set to be starting to evaluate HO based on a critical zone parameter set when entering the critical zone is detected if measured TA < TA_critical holds, and the terminal is configured with the "standard" set of HO parameters when leaving the critical zone is detected if measured TA > TA_critical + margin. A similar approach is taken for initialization of the HO parameters. Namely, when the terminal is getting connected with the base station, a valid TA value is needed, and this value is further evaluated in order to select the desired HO parameters .

That is, the terminal-specific and location-based setting of (handover-related) mobility parameters according to ex^¬ emplary embodiments of the present invention exhibits a dy^¬ namic and/or adaptive nature/characteristic.

According to exemplary embodiments of the present inven- tion, the terminal-specific and location-based setting of (handover-related) mobility parameters, i.e. the switching between different HO parameters, may be realized by differ^¬ ent methods . Figure 3 shows a signaling diagram illustrating an exemplary procedure according to exemplary embodiments of the present invention. In Figure 3, the terminal is exemplarily denoted as UE, and the base station is exemplarily denoted as eNodeB. The thus depicted exemplary procedure represents a first conceivable implementation of exemplary embodiments of the present invention, in which the base station (e.g. eNodeB) executes the setting of (handover-related) mobility parameters . The exemplary procedure of Figure 3 is, as a non-limiting example, essentially based on the layout according to Fig^¬ ure 2 and the usage of a TA-based measurement of a UE- eNodeB distance as terminal location. Basically, according to Figure 3, the eNodeB acquires a terminal location by measuring/estimating a timing advance (TA) value which is used as input for HO parameter deci- sions/settings . The HO parameter decisions/settings are ef^¬ fected on the basis of the thus acquired terminal location, as outlined above. The updated HO parameters are signaled to the individual UEs via L3 signaling messages or the like. That is, triggers for updates are given by location acquisition (e.g. TA estimation) at the eNodeB side.

Particularly, the eNB may configure a measurement identi^¬ fier based on a valid UE-specific TA measurement. As the TA is known and updated by the eNB itself, the eNB may decide when a modification of a certain measurement event is needed (such as events X and Y according to Figure 2) . This modification is then signaled to the UE by, for example, an RRC RECONFIGURATION message providing an optimized parame^¬ ter set, i.e. the (set of) mobility parameters being set/adj usted/selected at the eNodeB depending on the ac^¬ quired terminal location. Such eNodeB-based parameter set^¬ ting and updating is needed every time a certain measure^¬ ment event occurs . The RRC Connection Reconfiguration message includes meas^¬ urement control information. According to exemplary embodiments of the present invention, the measurement control in^¬ formation includes a terminal-specific measurement configu^¬ ration depending on the terminal location (i.e. on the ba- sis of a TA value or any other location information) .

It is an advantage of the first conceivable implementation of exemplary embodiments of the present invention, as il- lustrated by Figure 3, that standardized procedures, such as RRC RECONFIGURATION messages, may be applied.

Figure 4 shows a signaling diagram illustrating another ex- emplary procedure according to exemplary embodiments of the present invention. In Figure 4, the terminal is exemplarily denoted as UE, and the base station is exemplarily denoted as eNodeB. The HO parameter decisions/settings is based on (pre- ) configured (sets of) HO parameters. The thus depicted exemplary procedure represents a second conceivable imple^¬ mentation of exemplary embodiments of the present inven^¬ tion, in which the terminal (e.g. UE) executes the setting of (handover-related) mobility parameters on the basis of the (sets of) HO parameters provided by the eNodeB.

The exemplary procedure of Figure 4 is, as a non-limiting example, essentially based on the layout according to Fig^¬ ure 2 and the usage of a TA-based measurement of a UE- eNodeB distance as terminal location.

Basically, according to Figure 4, the UE acquires a termi^¬ nal location by receiving a respective indication from the eNodeB, which is used as input for HO parameter decisions/settings. The HO parameter decisions/settings are ef- fected on the basis of the thus acquired/received terminal location, as outlined above. The HO parameter deci^¬ sions/settings is based on (pre- ) configured (sets of) HO parameters provided by the eNodeB in advance. The updated HO parameters are used for deciding on the need of a hand- over, i.e. for handover evaluation and/or decision.

Particularly, in active state the UE may be permanently in^¬ formed about the actual TA measurement (signaled in MAC) by the eNodeB. When configuring the measurement event, the eNodeB may provide two or more different (sets of) mobility parameters for a certain measurement event together with a TA value (or range) . The validity for each parameter set, i.e. the applicability for a certain parameter set to be set/adj usted/selected, is then derived from the current TA measurement from the eNodeB and the previously provided pa^¬ rameter sets, and then applied autonomously by the UE . The second conceivable implementation of exemplary embodi^¬ ments of the present invention, as illustrated by Figure 4, needs an extension of standardized procedures such as an existing measurement control, such as RRC RECONFIGURATION messages .

It is an advantage of the second conceivable implementation of exemplary embodiments of the present invention, as il^¬ lustrated by Figure 4, that subsequent event updates (i.e. messages 3 to 6 according to Figure 3) are not required, since the UE is informed about the different parameter sets building the basis for the HO parameter setting in the original message (i.e. message 1 according to Figure 4) .

Figure 5 shows a flowchart illustrating an exemplary method according to exemplary embodiments of the present inven^¬ tion .

As shown in Figure 5, a method according to exemplary embodiments of the present invention comprises operations SI and S2 and, optionally, S3, and may be realized by a termi^¬ nal (or a processor thereof) or a base station (or a processor thereof) . Depending on whether the method is realized by the base station in accordance with the first conceiv- able implementation (as illustrated by Figure 3) or the terminal in accordance with the second conceivable imple^¬ mentation (as illustrated by Figure 4), a certain combina^¬ tion of the variants available by operations SI' through S3' is applicable.

A method according to Figure 5 comprises an operation of acquiring a location of a terminal with respect to a serving base station of a cellular communication system, i.e. a base station (for example, its antenna) serving the sector in which the terminal resides (SI) . Such acquiring may com^¬ prise (SI') measuring the location at the base station, e.g. using at least one of signal propagation delay, signal strength, global position system, and timing advance, in case of the first conceivable implementation, or receiving an indication of the location of the terminal at the terminal from the base station in case of the second conceivable implementation . A method according to Figure 5 comprises an operation of setting handover-related mobility parameters in a terminal- specific manner depending on the acquired location of the terminal with respect to the base station (for example, its antenna) (S2) . Such setting may, irrespective of the first or second conceivable implementation, comprise (S2') con^¬ figuring at least two sets of handover-related mobility pa^¬ rameters and selecting one of the at least two configured sets of handover-related mobility parameters depending on the acquired location of the terminal with respect to the base station (for example, its antenna), and/or assigning one out of at least two handover-related criticality zones depending on the acquired location of the terminal with re^¬ spect to the base station (for example, its antenna) , and setting the handover-related mobility parameters depending on the assigned handover-related criticality zone. In case of the second conceivable implementation, the configuring may comprise receiving at least two sets of handover- related mobility parameters from the base station. All op^¬ erations in this regard may be accomplished with or without applying hysteresis, e.g. in re-assigning a handover- related criticality zone due to a movement of the terminal by using spatial margin at the edge of a handover-related criticality zone, as outlined in connection with Figure 2.

A method according to Figure 5 may comprise an operation of employing the (handover-related) mobility parameters as set in operation S2 or S2'. Such employing may comprise (S3') signaling the set handover-related mobility parameters from the base station to the terminal in case of the first con^¬ ceivable implementation, or deciding on the need of a handover on the basis of the set terminal-specific handover- related mobility parameters in case of the second conceiv- able implementation.

The above-described procedures and functions may be imple^¬ mented by respective functional elements, processors, or the like, as described below.

While in the foregoing exemplary embodiments of the present invention are described mainly with reference to methods, procedures and functions, corresponding exemplary embodi^¬ ments of the present invention also cover respective appa- ratuses, network nodes and systems, including both software and/or hardware thereof. Respective exemplary embodiments of the present invention are described below referring to Figure 6, while for the sake of brevity reference is made to the detailed descrip^¬ tion of respective corresponding methods and operations ac- cording to Figures 2 to 5 above.

In Figure 6 below, the solid line blocks are basically con^¬ figured to perform respective operations as described above. The entirety of solid line blocks are basically con- figured to perform the methods and operations as described above, respectively. With respect to Figure 6, it is to be noted that the individual blocks are meant to illustrate respective functional blocks implementing a respective function, process or procedure, respectively. Such func- tional blocks are implementation-independent, i.e. may be implemented by means of any kind of hardware or software, respectively. The arrows interconnecting individual blocks are meant to illustrate an operational coupling there^¬ between, which may be a physical and/or logical coupling, which on the one hand is implementation-independent (e.g. wired or wireless) and on the other hand may also comprise an arbitrary number of intermediary functional entities not shown. The direction of arrow is meant to illustrate the direction in which certain operations are performed and/or the direction in which certain data is transferred.

Further, in Figure 6, only those functional blocks are il^¬ lustrated, which relate to any one of the above-described methods, procedures and functions. A skilled person will acknowledge the presence of any other conventional func^¬ tional blocks required for an operation of respective structural arrangements, such as e.g. a power supply, a central processing unit, respective memories or the like. Among others, memories are provided for storing programs or program instructions for controlling the individual func^¬ tional entities to operate as described herein. Figure 6 shows a block diagram illustrating exemplary devices according to exemplary embodiments of the present in^¬ vention. In view of the above, the thus described apparatus on the left side may represent a (part of a) apparatus such as a terminal/UE or base station/eNodeB, as described above, and the thus described apparatus on the right side may represent a (part of a) counterpart apparatus such as a base station/eNodeB or terminal/UE, as described above.

According to Figure 6, the left-handed apparatus is an ap- paratus according to exemplary embodiments of the present invention. This apparatus is configured to perform a proce^¬ dure as described in conjunction with Figure 5. In case of the first conceivable implementation (as illustrated by Figure 3) this apparatus may be implemented by/in/as a base station such as e.g. an eNodeB, and in case of the second conceivable implementation (as illustrated by Figure 4), this apparatus may be implemented by/in/as a terminal such as a UE . Therefore, while basic operations are described hereinafter, reference is made to the above description of Figures 2 to 5 for details thereof.

According to Figure 6, the thus depicted apparatus accord^¬ ing to exemplary embodiments of the present invention com^¬ prises a processor and a transceiver as well as, option- ally, a memory.

The processor may be specifically configured to acquire a location of a terminal with respect to a (serving) base station of a cellular communication system, thus representing means for acquiring a terminal location. In other words, the processor may have a corresponding location acquiring functionality.

Depending on the implementation, the processor may be specifically configured to measure/estimate the terminal loca^¬ tion, thus representing means for measuring/estimating the terminal location, or the processor may be specifically configured to receive an indication of the terminal loca^¬ tion, thus representing means for receiving an indication of the terminal location. In other words, depending on the implementation, the location acquiring functionality may comprise a corresponding measuring or receiving functional- ity, as evident from the above. Further, the processor may be specifically configured to set handover-related mobility parameters in a terminal-specific manner depending on the acquired location of the terminal with respect to the base station, thus representing means for setting handover- related mobility parameters. In other words, the processor may have a corresponding mobility parameter setting functionality. The processor may be specifically configured to configure parameter sets and to select a parameter set, thus representing means for configuring and selecting pa- rameter sets, and/or the processor may be specifically con^¬ figured to assign criticality zones and to set the mobility parameters according thereto, thus representing means for assigning criticality zones and setting parameters based thereon. In other words, the mobility parameter setting functionality may comprise a corresponding parameter set configuring and selecting functionality and/or a corresponding criticality zone assigning and mobility parameter setting functionality, as evident from the above. Further, the processor may be specifically configured to apply a hysteresis, e.g. in re-assigning a handover-related criti- cality zone due to a movement of the terminal by using spa^¬ tial margin at the edge of a handover-related criticality zone, thus representing means for applying a hysteresis. In other words, the mobility parameter setting functionality may further comprise a corresponding hysteresis applying functionality, as evident from the above. The processor may be specifically configured to employ the set mobility parameters, thus representing means for em^¬ ploying the set mobility parameters. In other words, de^¬ pending on the implementation, the processor may have a mobility parameter employing functionality. Depending on the implementation, the processor may be specifically configured to signal the set mobility parameters to a terminal, thus representing means for signaling set mobility parame^¬ ters, or to decide on the need of a handover on the basis of the set mobility parameters, thus representing means for making a handover evaluation and/or decision. In other words, depending on the implementation, the mobility parameter employing functionality may comprise a mobility pa^¬ rameter signaling functionality or a handover deciding functionality .

The transceiver may be specifically configured to perform respective functions depending on the implementation. In case of the first conceivable implementation, the trans^¬ ceiver may be specifically configured to transmit at least two configured sets of handover-related mobility parameters to the terminal, thus representing means for transmitting configured mobility parameter sets, and/or to signal the set handover-related mobility parameters to the terminal, thus representing means for signaling the set handover- related mobility parameters to the terminal. In case of the second conceivable implementation, the transceiver may be specifically configured to receive at least two configured sets of handover-related mobility parameters from the base station, thus representing means for receiving configured mobility parameter sets, and/or to receive, from the (serv^¬ ing) base station, an indication of the location of the terminal with respect to the (serving) base station, thus representing means for receiving an indication of a terminal location.

The memory may be specifically configured to store any data required for and/or resulting from the above-described functionalities. For example, the memory may store the set mobility parameters or mobility parameter sets, the config^¬ ured plurality of mobility parameter sets, the plurality of and/or the assigned criticality zone, and the like. According to Figure 6, the right-handed apparatus is an ap^¬ paratus according to exemplary embodiments of the present invention, which is a counterpart apparatus to the above- described apparatus according to exemplary embodiments of the present invention. In case of the first conceivable im- plementation (as illustrated by Figure 3) this apparatus may be implemented by/in/as a terminal such as e.g. a UE, and in case of the second conceivable implementation (as illustrated by Figure 4), this apparatus may be implemented by/in/as a base station such as an eNodeB. Therefore, while basic operations are described hereinafter, reference is made to the above description of Figures 2 to 5 for details thereof . According to Figure 6, the thus depicted apparatus accord^¬ ing to exemplary embodiments of the present invention com^¬ prises a processor and a transceiver as well as, optionally, a memory.

The operations and specific configurations of the proces^¬ sor, transceiver and memory are evident from the above descriptions including that of the left-handed apparatus ac^¬ cording to Fig. 6.

In particular, in case of the first conceivable implementa^¬ tion, the transceiver may be specifically configured to re^¬ ceive (a set of) set handover-related mobility parameters being signaled from the base station, thus representing means for receiving set mobility parameters. The processor may be specifically configured to receive the (set of) re^¬ lated mobility parameters from the transceiver, and to de^¬ cide on the need of a handover on the basis of the set mo^¬ bility parameters, thus representing means for making a handover evaluation and/or decision. In other words, the processor may have a handover deciding functionality operating on the basis of the terminal-specific and location- based setting of mobility parameters according to exemplary embodiments of the present invention.

In particular, in case of the second conceivable implemen^¬ tation, the processor may be specifically configured to configure a plurality of (at least two) (sets of) related mobility parameters which build the basis for a subsequent setting/adj ustment/selection thereof depending on a terminal location, thus representing means for configuring mobility parameters. The transceiver may be specifically con^¬ figured to transmit the plurality of (at least two) config- ured (sets of) handover-related mobility parameters to the terminal, thus representing means for transmitting configured mobility parameters or parameter sets. Further, in case of the second conceivable implementation, the processor may be specifically configured to meas^¬ ure/estimate the terminal location, thus representing means for measuring/estimating the terminal location. In other words, the processor may have a location acquiring func- tionality. The transceiver may be specifically configured to transmit an indication of the terminal location to the terminal, thus representing means for transmitting an indication of the terminal location. The memory may be specifically configured to store any data required for and/or resulting from the above-described functionalities. For example, depending on the implementa^¬ tion, the memory may store the set mobility parameters or mobility parameter sets, the configured plurality of mobil- ity parameter sets, the plurality of and/or the assigned criticality zone, and the like.

According to exemplarily embodiments of the present invention, a system may comprise any conceivable combination of the thus depicted apparatuses (such as one or more termi^¬ nals and associated one or more base stations) .

In general, it is to be noted that respective functional blocks or elements according to above-described aspects can be implemented by any known means, either in hardware and/or software, respectively, if it is only adapted to perform the described functions of the respective parts. The mentioned method steps can be realized in individual functional blocks or by individual devices, or one or more of the method steps can be realized in a single functional block or by a single device. Generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention. Devices and means can be implemented as individual devices, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved. Such and similar principles are to be considered as known to a skilled person.

Software in the sense of the present description comprises software code as such comprising code means or portions or a computer program or a computer program product for performing the respective functions, as well as software (or a computer program or a computer program product) embodied on a tangible medium such as a computer-readable (storage) me- dium having stored thereon a respective data structure or code means/portions or embodied in a signal or in a chip, potentially during processing thereof.

Generally, for the purpose of the present invention as de- scribed herein above, it should be noted that

- method steps and functions likely to be implemented as software code portions and being run using a processor at one of the entities, a network element, or a terminal (as examples of devices, apparatuses and/or modules thereof, or as examples of entities including apparatuses and/or mod^¬ ules therefor) , are software code independent and can be specified using any known or future developed programming language, such as e.g. Java, C++, C, and Assembler, as long as the functionality defined by the method steps is pre^¬ served;

- generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the invention in terms of the functionality implemented;

- method steps, functions, and/or devices, apparatuses, units or means likely to be implemented as hardware compo^¬ nents at a terminal or network element, or any module (s) thereof, are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS (Metal Oxide Semiconduc^¬ tor) , CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL (Transis^¬ tor-Transistor Logic), etc., using for example ASIC (Appli- cation Specific IC (Integrated Circuit)) components, FPGA (Field-programmable Gate Arrays) components, CPLD (Complex Programmable Logic Device) components or DSP (Digital Sig^¬ nal Processor) components; in addition, any method steps and/or devices, units or means likely to be implemented as software components may for example be based on any secu^¬ rity architecture capable e.g. of authentication, authori^¬ zation, keying and/or traffic protection;

- devices, apparatuses, units or means can be implemented as individual devices, apparatuses, units or means, but this does not exclude that they are implemented in a dis^¬ tributed fashion throughout the system, as long as the functionality of the device, apparatus, unit or means is preserved,

- an apparatus may be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of an apparatus or module, instead of being hardware implemented, be implemented as software in a (software) module such as a computer program or a computer program product comprising executable software code por^¬ tions for execution/being run on a processor;

- a device may be regarded as an apparatus or as an assem- bly of more than one apparatus, whether functionally in co^¬ operation with each other or functionally independently of each other but in a same device housing, for example.

The present invention also covers any conceivable combina- tion of method steps and operations described above, and any conceivable combination of nodes, apparatuses, modules or elements described above, as long as the above-described concepts of methodology and structural arrangement are ap^¬ plicable .

In view of the above, there are provided measures for hand^¬ over-related mobility optimization in cellular communica^¬ tion systems, said measures exemplarily comprising acquiring a location of a terminal with respect to a base station of a cellular communication system, and setting handover- related mobility parameters in a terminal-specific manner depending on the determined location of the terminal with respect to the base station. Said measures may exemplarily be applied for handover-related mobility optimization in cellular communication systems based on a LTE, a LTE-

Advanced, an UMTS, a GERAN and a UTRAN radio access system.

As compared with conventional solutions, the present inven^¬ tion and/or exemplary embodiments may advantageously pro- vide for a setting of mobility (HO) parameters on the basis of a terminal (UE) position (e.g. dependent on a distance between terminal (UE) and base station (eNodeB) ) , as well as an adaptive/dynamic change of mobility (HO) parameters depending on the terminal (UE) location which may exempla- rily represented by a TA measurement value. For example, sectors may be (virtually) sub-sectored, thus defining critical and less critical zones in terms of mobility (HO) requirements/demands, which may build the basis for a cor^¬ responding setting of mobility (HO) parameters. In view of whether the terminal is located within or outside the critical zone, different mobility (HO) parameters are set and used for mobility-related (HO) decisions. Thereby, an optimization of mobility (HO) processing may be achieved, in particular but not exclusively for base station (e.g. inter-sector) handovers, and RLF and CDR properties may be improved in that too early or too late handovers may be avoided. According to various conceivable implementations, the currently valid mobility (HO) parameters may be set at the base station and signaled to the terminal upon change (i.e. initialization or reconfiguration upon a reconfiguration event) , or various mobility (HO) parameters building a basis of setting are provided from the base station to the terminal and the terminal makes the decision by itself.

Even though the invention is described above with reference to the examples according to the accompanying drawings, it is to be understood that the invention is not restricted thereto. Rather, it is apparent to those skilled in the art that the present invention can be modified in many ways without departing from the scope of the inventive idea as disclosed herein.

Claims

1. A method comprising

acquiring a location of a terminal with respect to a serving base station of a cellular communication system, and setting handover-related mobility parameters in a termi^¬ nal-specific manner depending on the acquired location of the terminal with respect to the serving base station.

2. The method according to claim 1, wherein the parameter setting comprises

configuring at least two sets of handover-related mobil^¬ ity parameters being applicable for different locations of the terminal with respect to the serving base station, and selecting one of the at least two sets of handover- related mobility parameters depending on the acquired loca^¬ tion of the terminal with respect to the serving base sta^¬ tion .

3. The method according to claim 1 or 2, wherein the parameter setting comprises

assigning one out of at least two handover-related criticality zones depending on the acquired location of the terminal with respect to the serving base station, and

setting the handover-related mobility parameters depend^¬ ing on the assigned handover-related criticality zone.

4. The method according to any one of claims 1 to 3, wherein the location of the terminal with respect to the serving base station comprises a distance between the terminal and the serving base station.

5. The method according to claim 3 or 4, wherein

a most critical handover-related criticality zone is de^¬ fined as an area closest to the serving base station, and/or the parameter setting is such that the handover-related mobility parameters enabling a fast handover decision are set for the most critical handover-related criticality zone.

6. The method according to any one of claims 3 to 5, wherein the parameter setting comprises

applying a hysteresis in re-assigning a handover-related criticality zone due to a movement of the terminal by using spatial margin at the edge of a handover-related criticality zone.

7. The method according to any one of claims 1 to 6, wherein the handover-related parameters comprise one or more of a time-to-trigger value, a layer 3 filter coefficient, an off- set value and a cell-individual offset defining a handover border .

8. The method according to any one of claims 1 to 7, wherein the method is operable at the terminal, and

the location acquisition comprises receiving an indication of the location of the terminal with respect to the serving base station from the serving base station.

9. The method according to claim 8, further comprising

receiving at least two sets of handover-related mobility parameters being applicable for different locations of the terminal with respect to the serving base station from the serving base station, and/or

deciding on the need of a handover on the basis of the set terminal-specific handover-related mobility parameters.

10. The method according to any one of claims 1 to 7, wherein the method is operable at the serving base station, and the location acquisition comprises measuring the loca- tion of the terminal with respect to the serving base station using at least one of signal propagation delay, signal strength, global position system, and timing advance.

11. The method according to claim 10, further comprising

signaling the set handover-related mobility parameters to the terminal .

12. The method according to any one of claims 1 to 11, wherein the handover-related mobility parameters relate to a handover of the terminal between two sectors being served by the serving base station.

13. The method according to any one of claims 1 to 12, wherein

the terminal comprises a user equipment, and/or

the base station comprises one of a NodeB, an eNodeB, a radio network controller and a base station controller, and/or

the cellular communication system is in accordance with one of a LTE, a LTE-Advanced, an UMTS, a GERAN and a UTRAN radio access system.

14. An apparatus comprising

a processor configured to

acquire a location of a terminal with respect to a serv^¬ ing base station of a cellular communication system, and

set handover-related mobility parameters in a terminal- specific manner depending on the acquired location of the terminal with respect to the serving base station.

15. The apparatus according to claim 14, wherein the proces^¬ sor is further configured to

configure at least two sets of handover-related mobility parameters being applicable for different locations of the terminal with respect to the serving base station, and 4 b select one of the at least two sets of handover-related mobility parameters depending on the acquired location of the terminal with respect to the serving base station. b

16. The apparatus according to claim 14 or lb, wherein the processor is further configured to

assign one out of at least two handover-related criti^¬ cality zones depending on the acquired location of the termi^¬ nal with respect to the serving base station, and

10 set the handover-related mobility parameters depending on the assigned handover-related criticality zone.

17. The apparatus according to any one of claims 14 to 16, wherein the location of the terminal with respect to the lb serving base station comprises a distance between the termi^¬ nal and the serving base station.

18. The apparatus according to claim 16 or 17, wherein the processor is further configured to

20 define an area closest to the serving base station as a most critical handover-related criticality zone, and/or

set the handover-related mobility parameters such that handover-related mobility parameters enabling a fast handover decision are set for the most critical handover-related

2b criticality zone.

19. The apparatus according to any one of claims 16 to 18, wherein the processor is further configured to

apply a hysteresis in re-assigning a handover-related 30 criticality zone due to a movement of the terminal by using spatial margin at the edge of a handover-related criticality zone .

20. The apparatus according to any one of claims 14 to 19, 3b wherein the handover-related parameters comprise one or more of a time-to-trigger value, a layer 3 filter coefficient, an offset value and a cell-individual offset defining a handover border .

21. The apparatus according to any one of claims 14 to 20, wherein

the apparatus is operable as or at the terminal, and the processor is further configured to receive an indi^¬ cation of the location of the terminal with respect to the serving base station from the serving base station.

22. The apparatus according to claim 21, wherein the processor is further configured to

receive at least two sets of handover-related mobility parameters being applicable for different locations of the terminal with respect to the serving base station from the serving base station, and/or

decide on the need of a handover on the basis of the set terminal-specific handover-related mobility parameters.

23. The apparatus according to any one of claims 14 to 20, wherein

the apparatus is operable as or at the serving base sta^¬ tion, and

the processor is further configured to measure the loca- tion of the terminal with respect to the serving base station using at least one of signal propagation delay, signal strength, global position system, and timing advance.

24. The apparatus according to claim 23, wherein the proces- sor is further configured to

signal the set handover-related mobility parameters to the terminal .

25. The apparatus according to any one of claims 14 to 24, wherein the handover-related mobility parameters relate to a handover of the terminal between two sectors being served by the serving base station.

26. The apparatus according to any one of claims 14 to 25, wherein

the terminal comprises a user equipment, and/or

27. A computer program product including a program comprising software code portions being arranged, when run on a proces^¬ sor of an apparatus, to perform the method according to any one of claims 1 to 13.

28. The computer program product according to claim 27, wherein the computer program product comprises a computer- readable medium on which the software code portions are stored, and/or wherein the program is directly loadable into a memory of the processor.