Method for calculating transfer parameters for a communication device, method for communication and communication device therefor

Abstract

Method for calculating a rate (T Best , M Best ) of handover parameters, in particular a TTT value (T) and a HOM value (M), for a communication device for use in a communication handover from a source base station to a destination base station, comprising the steps: a) Determining / setting context-specific parameters, which include at least position data (PosData) and movement data (x 0 ,v,φ) of the communication device; b) selecting a target base station from a plurality of base stations; c) Defining a candidate set (S T , S M ) of values for each parameter from the set of parameters; d) Calculating an overall failure probability (F(T,M)) taking into account the context-specific parameters for a plurality of sets of transfer parameters, wherein the values of the transfer parameters each represent a selection from the respective candidate set (S T , S M ) are; e) Selection of the sentence (T Best , M Best ) of transfer parameters as the result for which the overall failure probability (F(T,M)) is the lowest.

Description

[0001] The invention relates to a method for calculating a set of handover parameters for a communication device for use in a communication handover from a source base station to a destination base station. The invention also relates to a method for communication between a communication device and at least one source base station and at least one destination base station, as well as a communication device for this purpose.

[0002] In mobile telecommunications networks, such as GSM (Global System for Mobile Communications), UMTS (Universal Mobile Telecommunications System), or LTE (Long Term Evolution), it is necessary for mobile terminals (UEs) or communication devices to be able to switch from one radio cell to another during a call or data connection without interrupting the connection. This process is referred to as handover.

[0003] The connection handover can be assessed using key performance indicators (KPIs). These can be information regarding the failure of the radio link (also known as radio link failure or RLF) or the frequency of a handover / handover ping-pong (also known as handover ping-pong rate or HPR). The HPR describes the frequency of multiple consecutive connection handovers between two long-distance communication cells. The KPIs depend on several handover parameters that can influence the connection handover process. These include, for example, the TTT value or time-to-trigger value, which specifies the time interval that must be waited for to trigger a connection handover or handover before the handover is actually carried out. Another relevant parameter is the handover offset margin (HOM value or M value).This HOM value is essentially a difference between the signal strength measured at the terminal device between the currently serving radio cell and the future radio cell. A handover is only initiated if the signal strength of the current radio cell is worse by at least the difference value over a specified time interval (e.g., TTT value or T-value).

[0004] The current state of the art with regard to handover procedures is predominantly based on assigning handover parameters globally or on a cell-by-cell basis. Accordingly, only cell-specific handover parameters are assigned to a cell, so the aforementioned handover ping-pong effects or radio link failures, i.e., radio link errors (RLF), can still occur. Furthermore, it is known that radio link errors can occur with existing handover procedures due to premature handovers (E_RLF) and late handovers (L_RLF).

[0005] US 2010 / 0 273 487 A1 discloses a method for adjusting a handover parameter in a cellular radio communication system. Information about actual handovers that have occurred between one or more cell pairs, as well as about handover errors, is collected. The collected handover information is processed to determine a handover oscillation rate or handover cost associated with the cell pair. If the handover performance is deemed acceptable, the determined handover oscillation rate or the determined handover cost is compared with a corresponding predetermined target value. One or more handover parameters associated with at least one of the cells in the cell pair are adjusted based on the comparison.

[0006] US 2001 / 0 046 879 A1 discloses a method for cell selection in a cellular mobile communication system having a plurality of cells, each with at least one base station, and a mobile station for communicating with the mobile communication system, using an air interface scheme supported by the at least one base station and the mobile station through an air interface connection to one of the at least one base station. The method comprises the following steps: measuring the quality of the connections between the mobile station and the base stations; determining the communication capabilities of the base stations and the mobile station; estimating a quality of service value for each possible connection between the mobile station and the base stations; and selecting the cell having the base station having the highest estimated quality of service.

[0007] In the article “Enhanced handover mechanism in long term evolution (LTE) networks” by Hussein, YS, Ali, BM, Varahram, P. and Sali, A., published in Scientific Research and Essays, 2011, Vol. 6, pp. 5138-5152, different algorithms for enhanced handover procedures based on terminal device requirements and quality of service targets are discussed.

[0008] Based on this prior art, the object of the present invention is to improve the handover. In particular, a calculation method is to be provided that enables efficient and uninterrupted communication with at least one source base station and at least one destination base station, in particular for the 3GPP LTE standard. In particular, the object of the present invention is to largely avoid radio link errors due to too early handover (E_RLF) and too late handover (L_RLF). Furthermore, a corresponding communication method and a corresponding communication device are to be specified that improve the communication quality.

[0009] This object is achieved by the method for calculating a set of transfer parameters according to claim 1.

[0010] In particular, the object is achieved by a method for calculating a set of handover parameters, in particular a TTT value and a HOM value, for a communication device for use in a communication handover from a source base station to a destination base station, comprising the steps: a) Determining / setting context-specific parameters, which include at least position data (PosData) and movement data of the communication device; b) selecting a target base station from a plurality of base stations; c) specifying a candidate set of values for each parameter from the set of parameters; d) calculating an overall failure probability taking into account the context-specific parameters for a plurality of sets of transfer parameters, wherein the values of the transfer parameters are each a selection from the respective candidate set; e) Selecting the set of transfer parameters as the result for which the overall failure probability is lowest.

[0011] The handover parameters calculated using the method for calculating a set of handover parameters are the trigger time interval, in particular the TTT value (T value) and / or radio quality information, in particular the HOM value (M value). The HOM value describes a difference between the signal strength of the currently serving radio cell and the future radio cell. A handover is only initiated if the signal strength of the current radio cell is worse by at least the difference value over a specified time interval (e.g. TTT value). The handover data preferably consists of sets of TTT values (T value) and HOM values (M value): (T; M). This means that at a specific position orFor a specific position data set, a specific transfer parameter set is calculated taking into account road data and optionally taking into account the speed of travel data and the direction of travel data and optionally taking into account other context-specific parameters: (T; M).

[0012] In other words, sets of transfer parameters are first provided. This applies to both the TTT value and the HOM value. These sets of transfer parameters can be different or the same for different target base stations. After context-specific parameters, which include at least the position data (PosData) and movement data of the communication device, have been determined or specified, and a target base station has been selected from a multitude of possible target base stations located in the immediate vicinity of the source base station, sets or sets of possible transfer parameters, i.e., candidate sets of transfer parameters, can be specified.

[0013] Using the defined candidate sets, the overall failure probability, i.e., the probability of failure of a voice and / or data connection between the communication device and the selected target base station, is calculated. This calculation is performed taking into account the context-specific parameters for a plurality of sets of transfer parameters, with the values of the transfer parameters each being a selection from the respective candidate set. The overall failure probability is therefore calculated several times for each selection regarding a TTT value and an HOM value. After calculating the overall failure probability for a plurality of sets of transfer parameters, the set of transfer parameters (T; M) with the lowest overall failure probability is selected as the result.

[0014] In a further embodiment of the invention, the overall failure probabilities for several or all possible target base stations are carried out for a plurality of sets of handover parameters, wherein as a result the target base station and a set of handover parameters are selected for which the overall failure probability is the lowest.

[0015] The context-specific parameters may further include a signal transmission strength (P) of the target base station and / or a path loss (I) and / or fading (h). Path loss (I) describes the loss of electromagnetic power between a transmitter and a receiver. A low path loss typically indicates good reception. Fading (h) refers to fluctuations in the received field strength during radio transmissions caused by interference or shadowing.

[0016] The path loss between a specific base station and a specific communication device can be calculated using the following formula l:= (G n G0λ 2 ) / (4πd) 2 be calculated, where G n is the gain of the transmitter antenna, G0 is the gain of the receiver antenna, λ is the wavelength of the transmitted signal and d is the distance between the base station and the communication device.

[0017] The RSRP value (Reference Signal Received Power) can be calculated using the following formula RSRP or R=Plh.

[0018] The described movement data of the communication device, which are part of the context-specific parameters, include movement speed data and / or movement direction data of the communication device.

[0019] Preferably, in a step f), the value of the overall failure probability and / or the selected set of transfer parameters are stored in a memory.

[0020] The total failure probability is preferably the weighted sum of the failure probability of the source base station before / at handover and the failure probability of the target base station after / at handover. It can be expressed using the following formula: F(T,M):=αnOntHO+αmOmtHO

[0021] The calculation of the overall failure probability and the selection of the set of transfer parameters as the result for which the overall failure probability is lowest are repeated continuously at equal time intervals.

[0022] The object mentioned at the outset is further achieved by a method for communication between a communication device and at least one source base station and at least one target base station, wherein a method for calculating a set of transfer parameters, as already described, is carried out for the communication transfer from a source base station to a target base station.

[0023] The communication procedure includes in particular the following steps: g) receiving an initial set of transfer parameters from a / the originating base station; h) Calculating an overall failure probability for the initial set of transfer parameters; i) Selection of a set of transfer parameters, as already described, if a defined threshold value with regard to the overall failure probability is exceeded and / or the overall failure probability for the initial set of transfer parameters does not agree with the overall failure probability of a previous calculation step.

[0024] Accordingly, step e), i.e. the selection of the set of transfer parameters as the result for which the overall failure probability is lowest, is only carried out if: - a defined threshold (µ) is exceeded with regard to the overall probability of failure and / or - the overall failure probability for the initial set of parameters does not match the overall failure probability of a previous calculation step.

[0025] Here, a value of the total failure probability stored in memory can be compared with a currently calculated value.

[0026] After establishing a voice and / or data connection between the communication device and the originating base station, the following steps are preferably carried out in a current time window: j) Determining / receiving position data (PosData) of the communication device; k) determining / receiving context-specific parameters, which include at least movement data of the communication device; l) determining a candidate set of values for each transfer parameter (TTT value and HOM value) from the set of transfer parameters (T; M); m) calculating an overall failure probability taking into account the context-specific parameters for a plurality of sets of transfer parameters, the values of the transfer parameters each being a selection from the respective candidate set; n) selecting the set of transfer parameters as the result for which the overall failure probability is lowest; o) Handover of the voice and / or data connection to the destination base station taking into account the selected set of handover parameters.

[0027] The context-specific parameters include, in particular, a signal transmission strength of the target base station and / or a path loss and / or fading. The movement data of the communication device include movement speed data and / or movement direction data.

[0028] Steps j) to o) are repeated continuously at equal time intervals.

[0029] Preferably, the method further comprises the following step: p) Modification of the TTT value and / or the HOM value of the communication device, wherein the modification comprises an optimization according to minT,MF(T,M):=αnOntHO+αmOmtHO st T∈ST,M∈SM includes.

[0030] The aim of the modification is to optimize the handover parameters with regard to too early handover (E_RLF) and too late handover (L_RLF). A handover that is performed too early is considered in relation to the probability of failure of a possible target base station. (OmtHO) whereas a handover carried out too late is considered in connection with the probability of failure of the initial base station OntHO ). Accordingly, a TTT value and / or a HOM value are optimized in such a way that the weighted sum of the failure probabilities OntHO and OntHO minimized as best as possible and thus the overall probability of failure is minimized as best as possible.

[0031] The communication procedure may further comprise the following step: q) storing a / the modified TTT value and / or a / the modified HOM value together with handover qualities indicating the quality of the handover from a / the source base station to a / the destination base station.

[0032] The object mentioned at the outset is further achieved by a communication device, in particular a (mobile) terminal, for calculating a set of transfer parameters for use in a communication transfer from a source base station to a destination base station and / or for communication with at least one source base station and at least one destination base station.

[0033] The communication device preferably comprises: - at least one position determination unit for determining position data of the communication device; - at least one radio transceiver unit for communicating with at least one source base station and at least one destination base station; - at least one calculation unit for calculating transfer parameters.

[0034] The calculation unit can, for example, be configured to request the required transfer parameters from a base station. The transfer parameters can be determined in or by a base station and transmitted to the communication device.

[0035] Preferably, this communication device is mobile and / or part of a mobile device (e.g., a vehicle). The communication device can therefore be a mobile communication device, e.g., a mobile phone, or an on-board computer of a vehicle with appropriate interfaces.

[0036] The positioning unit can receive data from an external device to determine the position or derive corresponding positioning data independently. A corresponding positioning unit can be a module belonging to a global navigation satellite system, i.e., a GNSS module, such as a GPS module, a GLONASS module, or a Compass module according to the Chinese standard, which is built into the communication device or provides corresponding data to the communication device. The positioning data can be, for example, geographical data or data identifying a specific street, a specific road section, a specific city, and / or a specific country.

[0037] The radio transceiver unit is used for communication with at least two base stations. Communication with at least one source base station and at least one destination base station, which are geographically separated from each other, is preferably carried out without interruption, i.e., in a continuous, temporally continuous manner. Accordingly, a handover from a source base station to a destination base station is necessary. The handover is performed based on handover parameters. At least one calculation unit is provided to calculate the handover parameters.

[0038] In a further embodiment of the invention, the communication device can comprise a detection unit for detecting the speed of travel data and / or the direction of travel data of the communication device. The speed of travel data and / or the direction of travel data of the communication device are taken into account when calculating a set of transfer parameters. Accordingly, the detection unit for detecting the aforementioned data is signal-connected to the calculation unit, so that the data detected by the detection unit can be transmitted to the calculation unit. If the communication device is part of a vehicle, for example, the speed of travel data is the speed of the vehicle. The direction of travel data therefore corresponds to the direction of travel of the vehicle.Thus, speed and direction data can be included in the calculation of the sets of transfer parameters.

[0039] In summary, it is theoretically possible that the sets of parameters can be calculated in a centralized or decentralized manner.

[0040] In a centralized embodiment of the aforementioned method or communication device, at least one base station has a calculation unit for calculating sets of transfer parameters. The communication device transmits the position or GNSS data as well as other context-specific parameters to the base station, so that the base station calculates the overall failure probability and selects sets of transfer parameters (T; M). The transfer parameters or the specific TTT value and / or the specific HOM value are then transmitted from a base station to a / the communication device using a transmission unit.

[0041] In a decentralized embodiment of the invention, a base station or the base station transmits the digital map with candidate sets of transfer parameters stored therein to the (mobile) terminal or communication device. With the aid of an algorithm, the optimal transfer parameters can be calculated based on the position data determined by the position determination unit and the associated road data.

[0042] The object mentioned above is further achieved by a vehicle having a communication device, as already described above, and / or which executes a method for calculating a set of transfer parameters, in particular a TTT value and an HOM value, as already described above, and / or executes a method for communication between a communication device and at least one source base station and at least one destination base station, as already described above. This vehicle can comprise a navigation system that determines or provides the position data.

[0043] Similar advantages arise as already described in connection with the communication device and / or the described calculation and / or communication methods.

[0044] To calculate the total failure probability and / or a set of transfer parameters (T Best , MBest ) as the result where the overall failure probability (F(T,M)) is the lowest, the following algorithm can be applied:

[0045] The following principles are used in formulating the algorithm:

[0046] The interference detected by a communication device / terminal in an LTE system is assumed to be averaged over a resource block. The signal-to-interference-plus-noise ratio (SINR) depends on the allocated bandwidth: γn=Pnlnhnωn∑i=1i≠nNi=1Pilihi+ωnσ2=Rnωn∑i=1i≠nNi=1Ri+ωnσ2 where ω n ∈ [0, 1] is a portion of the allocated bandwidth and σ 2 symbolizes the variance of the noise at the receiver.

[0047] From formula (1) it can be concluded that the SINR value can be estimated depending on the measured RSRP value (R=Plh). A describes the average value of h. The parameters (path loss) and A (average value of h) can be calculated based on the following context information as in Fig. 1 can be calculated: Regarding the moving communication device, the speed v, the position and trajectory (a sequence of positions x 0 , ..., x t and the horizontal angle of movement ψ) are determined using GPS data. It is assumed that the position x 0 of the communication device, the height (a n ) and the antenna tilt angle and azimuth (ϑ n , φ n) are known to both the respective base station (source base station, target base stations). The index n denotes the respective base station. For example, n=1 can be the source base station, n=2 a possible first target base station, and n=3 a possible second base station. The path loss coefficient I at time t can also be specified for each base station: lnt The path loss coefficient lnt can be seen from a distance dnt between the communication device and the respective base station and the amplification of the transmitter antenna (“antenna gain”) G n t of the respective base station, which in turn depends on the difference between the antenna tilt angle and the so-called elevation-of-arrival (ϑn−θnt) and the difference between antenna azimuth and the so-called "azimuth of arrival" (φn−ϕnt) depends.

[0048] With reference to Fig. 1 the parameters ϕnt and θnt and dnt calculated using the following formulas: ϕnt=ϕn0+arccos(bn2+cn2−(υt)22bncn) where θnt=arctan(anbn);dnt=an2+bn2 bn=(υt)2+cn2+2υtcncos(ϕn0−ψ) cn=dn0cosθn0

[0049] Theoretically, some or all of these parameters can be estimated or approximated using appropriate formulas. It is also conceivable to measure some or all of these values or to use previously calculated values to estimate future ones. If the value for lnt was estimated, samples of h n from a number K of previous RSRP measurements Rnk=Pnklnkhnk with k ∈ {t - k0 - K,t - k0 - 1}, k0,K ∈ N. As already mentioned, Pnk in this case known. The unknown parameter A n can be calculated according to maximum probability 1k∑k=t−k0−Kt−k0−1hnk can be estimated. In the current time slot t, Ant based on the specified maximum probability.

[0050] A handover process occurs at time A3. This A3 event is the time when a target base station in a neighboring long-distance communication cell delivers a better signal with a difference strength of HOM than the source base station currently being served.

[0051] The analytical expression for the probability of failure is Pr(X1≤∑i=2NXi)=1−∏i=2N(11+λ1λi)

[0052] By introducing a constant c, formula (4) can be modified as follows: Pr(X1≤∑i=2NXi+c)=1−exp(−λ1c)∏i=2N(11+λ1λi)

[0053] The RSRP value (R=Plh) is exponential with the rate parameter βit distributed: βit=λit / Pitlit=1 / PitlitAit=1 / E[Rit]

[0054] Together with formula (5), the total failure probability F(T,M) between a base station i and a communication device at time t can be easily defined: Oit=Pr(γit≤γth)=Pr(1ωitγthRit≤∑j=1j≠iNRjt+σ2) =1−exp(−ωitγthβitσ2)∏j=1j≠iN(11+βitβjtωitγth)

[0055] The formula (7) is therefore used in the calculation of the total failure probability F(M, T) according to the invention.

[0056] t HO denotes the time slot of the handover, whereas t0 denotes the time slot in which no handover from a source base station (BS n ) to a target base station (BS m) has been performed. The time slot of the handover can be regarded as the first time point of a sequence of events (t = t HO - T + 1, ..., t HO ). The probability that a handover HO occurs at a time t > t0 depends on the following three events: E1t:=∩τ=t−T+1t{RmτRnτ≥M}if t≥t0+T E2t:={Rmt−TRnt−T<M}if t> t0+T E3t:=∩τ=t0+Tt−T−1E1τ¯if t>1>t0+2T E1t occurs when the HO criteria are met for the time period [t-T+1, t]. E2t occurs when the HO criteria are not met for the time (tT), whereas E3t occurs if the handover was not performed over time (tT-1).

[0057] Accordingly, where Hn→mt=Pr(E1t∩E2t∩E3t)if t≥t0+THn→mt:=0 if t <t0+T which means that Hn→mt=(∏ν=t−T+1tCn→mν)⋅(1−Cn→mt−T)⋅Vn→mt and Cn→mt=Pr(RmtRnt≥M)={11+βmtβntMif t>t00o.w. and Vn→mt={1−∑τ=t0+Tt−T−1Hn→mτif t>t0+2T1 ow where Cn→mt describes the probability that the HO criteria RmtRnt in time slot t are fulfilled and Vn→mt describes the probability that the communication device will not be handed over to a target base station over time (tT-1).

[0058] In the following, it is assumed that a handover or transfer to a target base station occurs in a time interval [t0+1, t0+K'] with a probability greater than 1- ε, where ε ≥ 0 is an arbitrarily small constant, where K' must satisfy the following condition: K′=arg minK{K:∑t=t0+1t0+KHn→mt≥1−∈}

[0059] Accordingly, the total failure probability to be determined with respect to base station i can be approximated by the following formula: OitHO≈∑t=t0+1t0+K′OitHn→mt, for i∈N

[0060] The aim of the calculation to be carried out is to identify radio link errors due to early handover (E_RLF), which are related to the failure probability of the target base station (Omt) and due to late handover (L_RLF), which is related to the failure probability of the initial base station (Ont) The two initial problems are formulated at time t0 as follows P1: minM,T maxt∈[t0+1,tHO]OntP2: minM,T maxt∈[t0+1,tHO]Omt where tHO=arg maxt∈[t0+1,tHO]Ont=arg maxt∈[tHO,t0+L]Omt and L is a sufficiently large constant, but must still be within the range of the context-specific parameters.

[0061] The goal is therefore to optimize the sets of transfer parameters according to the following formula: minM,TF(M,T):=αnOntHO+αmOmtHOs.t. M∈SM,T∈ST where S M and S T are finite sets of possible HOM values and TTT values, respectively. The probabilities OntHO and OmtHO can be calculated using formulas (16), (7), (12) and (15).

[0062] The invention is described below by means of several embodiments, which are explained in more detail with reference to figures.

[0063] Here we show: Fig. 1 geometric relationships between a moving vehicle and a base station; Fig. 2 a system with a source base station and a destination base station and a communication device, wherein the communication device is designed such that communication can take place between the communication device and both base stations; Fig. 3 components of a communication device; Fig. 4 a schematic representation of a source base station and two target base stations and three spanned remote communication cells with a communication device located in a remote communication cell; and Fig. 5 an assignment table that assigns transfer parameters in each position in connection with recorded speeds and direction data.

[0064] In the following description, the same reference numbers are used for identical and equivalent parts.

[0065] The Fig. Figure 2 shows a system with a source base station 10 and a destination base station 20. A vehicle 30 is also provided. The vehicle 30 is located on a road in a radio cell 11 spanned by the base station 10. The destination base station 20 also spans a radio cell 21.

[0066] The vehicle 30 is designed in such a way that it can communicate with both the source base station 10 and the destination base station 20, wherein in the embodiment according to Fig. 2, communication—a data and / or voice connection—is currently established between the source base station 10 and the vehicle 30. The vehicle 30 is located on a road leading toward the destination base station 20 and thus toward the second radio cell 21. According to the communication device according to the invention or the method according to the invention, handover parameters are to be calculated so that the vehicle 30 can be handed over from the first radio cell 11 to the second radio cell 21, wherein this connection handover or handover does not necessarily have to take place at the boundary 25 between the two radio cells 11 and 21.

[0067] Rather, when calculating the handover parameters, the invention uses, among other things, knowledge of the course of the road and / or the speed and / or direction of travel of the vehicle 30 and / or a signal transmission strength of the target base station and / or a path loss and / or a fading in order to carry out an optimal handover. The described context-specific parameters are used to calculate an overall failure probability for a plurality of sets of handover parameters, wherein the values of the handover parameters are each a selection from the respective candidate set. During the calculation, a set of handover parameters is subsequently selected as the result for which the overall failure probability is lowest, taking into account the context-specific parameters.

[0068] According to Fig. 3 shows the vehicle 30, which, according to the invention, comprises a communication device 40, which, as shown, comprises a radio transceiver unit 41, a calculation unit 42, and a memory 43. This memory 43 can also be implemented in the base stations 10 or 20 or at a higher level of the system. Likewise, the vehicle 30 comprises a GNSS module 50, which supplies position data PosData to the communication device 40.

[0069] This position data PosData can, for example, be an identification number that indicates a specific section of a specific street in a specific city in a specific country.

[0070] For example, a lookup table with candidate sets of values for each transfer parameter from the set of transfer parameters is stored in the storage device 43. Furthermore, values regarding an overall failure probability can be temporarily stored in the storage device.

[0071] Optionally, the vehicle 30 can have a detection unit 60 for detecting the current speed 61 of the vehicle and the direction of travel of the vehicle 62. The data from the detection unit are transmitted to the communication device 40, in particular to the calculation unit 41, so that the transfer parameters (T; M) can be calculated depending on the position as well as the current speed and direction of travel of the vehicle.

[0072] As in Fig. As shown in Figure 4, the vehicle 30 is on a road 70 leading from a first radio cell 11 to a second radio cell 21. Also shown are the source base station 10 and the destination base stations 15 and 20. Furthermore, road data regarding the road layout and the radio wave propagation or radio wave strength of the base stations are stored in memories 13 and 23 assigned to the base stations 10 and 20.

[0073] In the described embodiment, the position data (PosData) are determined by the GNSS module 50. Theoretically, however, it is also conceivable for the base station to determine the position data of the vehicle 30. For example, the position data can be determined by triangulation using multiple base stations.

[0074] The vehicle 30 according to Fig. 4 includes a detection unit 60 for detecting the current speed 61 and the direction of movement 62 of the vehicle. The direction 62 therefore indicates that the vehicle 30 is moving east on the road 70 toward the radio cell 21.

[0075] According to the described algorithm, a list of all possible target base stations, for example, at a distance of 3 km, can first be created in the sense of a distance threshold D. Preferably, at least seven target base stations are available for selection. First, a target base station is selected from a large number of base stations. In the described case, this is target base station 20. Target base station 20 is therefore preferred over target base station 15. For this target base station 20, a large number of TTT values and a large number of HOM values are specified in a table, for example. These form the candidate sets (S T , S M) of values for each transfer parameter from the set of transfer parameters. With regard to the HOM values (in [dB]), values from 0 - 12 (with a separation of 0.5 from each other) can be specified, so that 24 possible values are stored for one HOM value. With regard to the TTT values (in [s]), values from 0.4 - 5.12 can be specified. Preferably, 14 possible values are specified in connection with the TTT value. With the 24 possible HOM values and the 14 possible TTT values, 24*14 pairs / sets of transfer parameters can be formed.

[0076] The calculation according to the described algorithm, taking into account the context-specific parameters, which include, among other things, the position data and movement data of the communication device 40, can be carried out for all possible pairs of transfer parameters, e.g. (0;0,4), (0,5;0,4), etc.

[0077] In the final step e), for example, the set (0.064; 2.5) is selected because, according to the calculation, the overall failure probability of the voice and / or data connection with the specified transfer parameters is the lowest. For this set (T Best , M Best ) of transfer parameters, the overall failure probability F(T,M) with respect to the target base station 20 is the lowest. It can be provided that the calculated sets (T Best , M Best ) in a memory, which may be memory 13, 23, or 43, so that the values can be stored in the communication device 40 and / or in a base station (10 or 20) and / or in a central server. By repeatedly storing corresponding data, an assignment table can be generated.

[0078] Fig.5 shows a corresponding assignment table for determining the transfer parameters, which is used to determine at what point in time the vehicle 30 is transferred from the first radio cell 11 to the second radio cell 21, whereby this transfer does not necessarily have to take place at the boundary 25 between the two radio cells 11, 21. The transfer parameters were determined with the help of other communication devices that were already on the road 70 at an earlier time and stored the optimized transfer parameters in a memory 13, 23, or 43.

[0079] The assignment table shows, by way of example, that eleven position data items can result from radio cell 11, in which vehicle 30 is located. In this case, position 3 is occupied in the radio cell. This position 3 indicates that the vehicle is on state road 70 in long-distance communication cell 11. Specifically, the vehicle is on road 70 in section 2. The maximum permitted speed in this section is 100 km / h, with the average speed being 82 km / h. With the help of the detection unit 60, the direction of travel 62 "EAST" was determined. The current speed 61 is 95 km / h, so the transfer parameters TTT value = and the HOM value = 3.0 are determined. The transfer parameters (0.064; 2.5) are transmitted to the radio transceiver unit so that an optimized handover or connection transfer can be performed.

[0080] The individual embodiments described can be combined in various ways according to the invention. List of reference symbols 10 Output base station 11 First radio cell 13 storage 15 Target base station 20 Target base station 21 Second radio cell 23 storage 25 limit 30 vehicles 40 Communication device 41 Radio transmitter / receiver unit 42 Calculation unit 43 storage 50 GNSS module 60 recording units 61 Current speed 62 direction 70 Street

Claims

[1] Method for calculating a set (T Best , M Best ) of handover parameters, in particular a TTT value (T) and a HOM value (M), for a communication device for use in a communication handover from a source base station to a destination base station, comprising the steps: a) Determining / setting context-specific parameters, which include at least position data (PosData) and movement data (x 0 ,v,φ) of the communication device; b) selecting a target base station from a plurality of base stations; c) Defining a candidate set (S T , S M ) of values for each parameter from the set of parameters; d) Calculating an overall failure probability (F(T,M)) taking into account the context-specific parameters for a plurality of sets of transfer parameters, wherein the values of the transfer parameters each represent a selection from the respective candidate set (S T , S M ) are; e) Selection of the sentence (T Best , M Best ) of transfer parameters as the result for which the overall failure probability (F(T,M)) is the lowest. [2] Method according to claim 1, characterized in that the context-specific parameters comprise at least one signal transmission strength parameter (P) of the target base station and / or at least one path loss parameter (I) and / or at least one fading parameter (h). [3] Method according to claim 1 or 2, characterized by that the movement data of the communication device contain movement speed data (v) and / or movement direction data, in particular position (x 0) and direction of movement (φ). [4] Method according to one of claims 1 to 3, characterized by , f) Storing the value of the total probability of failure (F(T,M)) and / or the selected rate (T Best , M Best ) of transfer parameters into a memory (13). [5] Method according to one of the preceding claims, characterized by that the total failure probability (F(T,M)) is a weighted sum of the failure probability of the initial base station OmtHO and the probability of failure of the target base station OntHO at a handover and preferably according to the formula F(T,M):=αnOntHO+αmOmtHO is calculated. [6] Method for communication between a communication device and at least one source base station (10) and at least one target base station (15, 20), wherein for the communication transfer from the source base station (10) to the target base station (15, 20) a set (T Best , M Best ) of transfer parameters, in particular a TTT value (T) and a HOM value (M), is calculated according to the method according to one of claims 1 to 5. [7] Method according to one of the preceding claims, in particular according to claim 6, characterized by , g) Receiving an initial sentence (T Aus , M Aus ) of transfer parameters from a / the source base station (10); h) Calculating an overall probability of failure (F(T,M)) for the initial rate (T Aus , M Aus ) of transfer parameters; i) Carrying out a calculation method according to one of claims 1 to 5, only if a defined threshold value (µ) with regard to the overall failure probability (F(T,M)) is exceeded and / or the overall failure probability (F(7,M)) for the initial set (T Aus , M Aus ) of transfer parameters is not related to the overall failure probability (T Aus , M Aus ) of a previous calculation step. [8] Method according to one of the preceding claims, in particular according to claim 6 or 7, wherein after the establishment of a voice and / or data connection between the communication device and the output base station, the following steps are carried out in a current time window: j) Determining / receiving position data (x 0 ) of the communication device; k) determining / receiving context-specific parameters comprising at least movement data of the communication device (v,φ ); I) Defining a candidate set (S T ,S M ) of values for each parameter from the set of parameters; m) Calculating an overall failure probability (F(7,M)) taking into account the context-specific parameters for a plurality of sets of transfer parameters, wherein the values of the transfer parameters each represent a selection from the respective candidate set (S T ,S M ) are; n) Selection of the set of transfer parameters (T Best , M Best ) as the outcome for which the overall probability of failure (F(T,M)) is the lowest; o) Handover of the voice and / or data connection to the destination base station taking into account the selected set of handover parameters (T Best , M Best ). [9] Method according to one of the preceding claims, in particular according to one of claims 6 to 8, characterized by that the context-specific parameters include a signal transmission strength (P) of the target base station and / or a path loss (I) and / or a fading (h). [10] Method according to one of the preceding claims, in particular according to one of claims 6 to 9, characterized by that the movement data of the communication device include movement speed data (v) and / or movement direction (φ). [11] Method according to one of the preceding claims, in particular according to one of claims 6 to 10, characterized by that steps j) to o) are preferably repeated continuously at predetermined time intervals. [12] Method according to one of the preceding claims, in particular according to one of claims 6 to 11, characterized by , p) Modification of the TTT value and / or the HOM value of the communication device, wherein the modification comprises an optimization according to minT,MF(T,M):=αnOntHO+αmOmtHOs.t. T∈ST,M∈SM includes. [13] Method according to one of the preceding claims, in particular according to one of claims 6 to 12, in particular according to claim 12, characterized by , q) storing a / the modified TTT value and / or a / the modified HOM value together with handover qualities indicating the quality of the handover from a / the source base station to a / the destination base station. [14] Communication device (40), in particular (mobile) terminal, for calculating a set of handover parameters (T, M) for use in a communication handover from a source base station (10) to a destination base station (20), according to one of claims 1 to 5 and / or for communication with at least one source base station (10) and at least one destination base station (20), according to one of claims 6 to 13, comprising: - at least one position determination unit (50) for determining position data (PosData) of the communication device (40); - at least one radio transceiver unit (41) for communication with at least one source base station (10) and at least one destination base station (20); - at least one calculation unit (42) for calculating transfer parameters (T Best , M Best ). [15] Vehicle with a communication device according to claim 14 and / or for carrying out a communication according to one of claims 6 to 13, and / or for calculating a set of transfer parameters according to one of claims 1 to 6, wherein the position determination unit is a navigation system.

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