SE505915C2 - Cellular mobile communication system - Google Patents

Abstract

The present invention relates to a cellular mobile communication system comprising a number of radio base stations (BS) and a number of mobile stations (MS) wherein the system comprises a number of cells which are arranged in at least two different layers of preference. Connections carried on the communications system can be handed over from one cell to another and at least one signal parameter is measured or monitored. At least one threshold is given at least for each cell in the lower layers or at least one signal parameter. The system furthermore comprises means for deciding on and controlling handover decisions comprising a priority ranking arrangement based on a number of criteria of which one is based on a comparison between a monitored value (Io) of a signal parameter with the threshold value (Io) of the serving cell and a second one is based on a comparison of the monitored value of a signal parameter (Ii) with the corresponding threshold value (Ii) for a neighbour cell wherein handovers are governed by the priority ranking arrangement so that a systematic passing also up as well as down between layers is obtained.

Description

15 20 25 30 505 915 2 organized in the most appropriate way.

PRIOR ART A number of attempts have been made to give a cellular mobile communication system a suitable cell structure.

A famous systene applies' so. called "umbrella" cell therapy.

Different bell bearings, are in cases ie preference bearings or priority bearings, this is arranged according to selection and location of the radio base stations. Powerful base stations with high antennas then constitute so-called umbrella cells, while low-power base stations which, for example, are mounted at street level form so-called "microcells" because "so-called" picocells "can be arranged which can then, for example, be mounted indoors. There are thus either two or three different cell layers. In this case, the normal cell selection mechanism, locating, is the mechanism responsible for obtaining the desired behavior. However, no logic is dedicated to the purpose. The purpose of using so-called "umbrella cells" is to provide a safety net for the normal cellular network by bridging coverage holes, providing extra capacity in call set-up procedures and to act as a rescue in the event of radio interference, etc. The purpose of microcells (in relation to umbrella cells or normal cells) is to provide the main capacity, especially in areas with high traffic density. The umbrella cell system therefore directs the traffic to the appropriate cells in the appropriate warehouse to ensure call continuity and to ensure that call set-up procedures are successful. However, the cell structure with umbrella cells without dedicated logic does not work satisfactorily when base stations belonging to different layers are located close to each other. The cell rolling mechanism, locating, will then result in a number of unnecessary handovers such as from a microcell to a umbrella cell even if the microcell provides radio conditions that are adequate. This is illustrated in Figure 1 which shows two microcells under one umbrella cell. For the mobile station MS 1, the microcell C; to provide the highest signal strength. Consequently, that cell will carry the compound. The mobile station MS 2 will be in radio shadow from both the microcell base stations BS 1 and BS 2. In this case, the umbrella cell CU fulfills its task and provides coverage where the microcells Ck, C, fail to do so. However, for the mobile station MS 3, the microcell base station BS 2 is within sight and would therefore be able to handle the connection without problems. Nevertheless, the umbrella cell base station BSU, which is also in sight and has a higher signal strength, will therefore take over the connection. Also in the case of, for example, radio interference and call set-up blocking, connections will unnecessarily be taken over or maintained by the umbrella cell or will generally be maintained or taken over by cells that are less suitable.

This will lead to a waste of capacity which in turn can lead to lost connections and so on. In other words, the utilization of less suitable resources will increase. In addition, efficient frequency planning and efficient sizing of the hardware is difficult. Furthermore, the number of handovers becomes unnecessarily high, which results in a high load on selectors and thus a non-negligible risk that connections will be lost.

In another known systenx, different cell layers have been assigned different priorities and a priority has been given for handover to the umbrella cell layer which is higher than the priority for handover due to a number of other radio network functions.

Interactions radio network functions have been given different priorities. A higher layer has been given a higher priority in cases of radio interference and call connection overload, etc. Thus, the transition between the layers is triggered by a number of different special events such as at and near (high BER, congestion call connection poor quality bit error rate). Also in this case, connections are not always directed towards the most adequate cell layer.

In addition, cover holes are not covered properly.

GB-A-2 242 806 describes a cellular system which replenishes macro- and microcells. Handover is always done via the macro cell layer to avoid unnecessary handovers from macro cell to micro cell and back again. A handover to a lower layer is made only if the link from the equipment to the base station associated with the underlying microcell has a quality that exceeds given criteria for a time interval that exceeds a given time interval.

Thus, also in this case, the "wrong" resource will be greatly exploited.

WO-Al-92/02105 discloses a cellular radio system. A handover initiation system comprises means for determining the distance of a mobile station from a base station of a cell and means for measuring the signal strength to determine the path of the mobile station. Using the location determination system, it is possible, using the information stored therein and the signal character of the estimated distance, to determine the existence of a mobile station within a microcell. The system further comprises means for storing information pairs regarding the existence and signal character of said location and means for forming a current pair comprising these parameters for a mobile station moving and means for comparing stored parameters with current parameters. However, also in this case, the wrong resources will be used, which leads to an inefficient use of the resources and an increased risk of lost connections, etc. DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a cellular mobile communication system as initially referred to where cells are organized in preferential storage in such a way that the system resources are optimally utilized.

A further object of the invention is to provide a system through which it is at the same time possible to ensure that the traffic is directed to the cells for which the network is dimensioned, that there is free capacity in the cells to provide extra capacity during call connection and to ensure that there is free capacity in the cells so that they can act as rescue cells at the same time as call continuity and successful call connection can be guaranteed. It is also an object of the invention to direct the connections to cells which can reliably take care of the connection and to bridge cover holes. A further object of the invention is to enable an efficient frequency planning and, an efficient dimensioning of the hardware in the system. A further object of the invention is to keep the number of handovers at a low level and to minimize the load on gears as well as to minimize the risk of losing connections.

These as well as other objectives are achieved by a system of the above-mentioned type comprising control means comprising a ranking device based on a number of criteria.

One criterion is based on a comparison of the current monitored value of a signal parameter of the serving cell with the given threshold value of the serving cell and a second criterion is based on a comparison of the current monitored value of a signal parameter of a neighboring cell with the given cell. the threshold value for that neighboring cell. Handover between cells 10 15 20 25 30 505 915 6 is controlled by the priority ranking device in such a way that a systematic transition between cells or cell layers or levels is obtained, also for transition up and down between the layers.

It is also an object of the invention to provide a method for controlling the handover method in a cellular mobile communication system where the cells are arranged hierarchically in at least two different layers or levels so that the system resources are optimally utilized and so that the traffic or connections are directed to the adequate cells. in accordance with the dimensioning of the system, etc.

These and other objectives are achieved through a procedure in which a priority ranking is performed based on a number of criteria.

The method comprises the following steps: - introducing a threshold value for the serving cell; - introducing a threshold value for at least each cell that is not in the top layer; monitoring at least signal connection parameters for the serving cell; monitoring of at least one signal connection parameter for a number of neighboring cells; - comparing the current monitored value of the signal parameter of the serving cell with the threshold value of the serving cell; - comparing the monitored value of the signal parameter for the neighboring cells with the respective threshold value for these cells; performing handovers in accordance with the priority device in such a way that a systematic transition up as well as down among the cell layers is obtained. may be modified to include any method particular embodiment or any combination as further developed with respect to the system itself.

A number of advantageous embodiments are given, for example, by the features of the appended subclaims.

With the cellular system in accordance with the invention, connections will be systematically routed to a lower layer and in the event of radio interference and, inter alia, in the event of a call set-off block, connections will be systematically redirected to cells which can take care of them in a reliable manner. By introducing a threshold value for each cell, a systematic transition between layers is obtained. The threshold can, for example, refer to signal strength, tensile attenuation or both parts. Other signal parameters are also possible. Which signal parameter (I) is used depends on the general handover strategy that the system applies. In a special exemplary embodiment, the so-called mobile-assisted handover strategy (MAHO) is used. Then the mobile station performs signal strength, (and / or other) measurements on the radio energy emitted from a number of surrounding base stations. The mobile station sends these measured values to the base station, which transmits them to the unit responsible for the decision logic. However, other handover strategies can also be used, such as NCHO (network-controlled handover) where the mobile is passive, MCHO (mobile-controlled handover) where the mobile both measures received signal strengths, etc. and makes decisions regarding handover.

In a special execution example, time division multiple access (TDMA) is used. With the system according to the invention, the threshold is used for transition upwards as well as downwards, ie to go to cells with a higher preference level as well as to cells with a lower preference level or which have a lower priority. According to a special embodiment, the threshold is modified with the hysteresis which is added or subtracted depending on the direction of movement. In the normal case, i.e. when no special events or concurrent functions are requested, a condition for going to a higher layer is that, if the signal strength (in this particular case) monitored from the cell currently in use for the connection, i.e. the serving cell, decreases below the threshold of the particular cell (in an advantageous embodiment with subtracted hysteresis), the system expands the group of neighboring cells which are selectable for handover with cells in a higher hierarchical layer. However, the cells in the higher layer have a lower priority than the cells in the current layer and the lower layer. A condition for going to a lower layer is that if the signal strength monitored or measured for a neighboring cell in a lower hierarchical layer rises above the threshold for an advantageous embodiment with added to that cell (in hysteresis) and the cell will be added the group of neighboring cells are selectable for handover. This cell will have a higher priority than cells in the current layer or in higher layers.

In advantageous embodiments, the interaction with other radio network functions is treated. Examples of other radio network functions are intra-cell handover, overlying-underlying subcell handover, assignment to another cell, extended area, "directed retry", alarm handover, etc. In particular, one or more of these or other radio network functions are given different priorities in relation to each other and to normal handover functions. This is particularly relevant when different radio network functions suggest different types of actions. In particular, the invention allows mobile phones at the same time. stations are systematically routed to the lowest possible warehouse.

This saves capacity in the higher layers for extraordinary events such as, for example, coverage gaps or call set-up blocking, etc.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in the following in a more detailed manner in a non-limiting manner with reference to the accompanying figures, in which: Figure 2 very schematically illustrates a mobile communication system, Figure 3 illustrates a flow chart of the main flow in the localization process, Figure 4 illustrates how categories of handover candidates are arranged in a particular case.

DETAILED DESCRIPTION OF THE INVENTION The cellular communication system comprises a cellular structure in which the cells are arranged in at least two layers in a hierarchical manner.

Figure 2 very schematically illustrates a cellular mobile communication system, in this case the GSM system. Figure 2 is shown only for brief explanatory reasons and very schematically indicates a part of a mobile cellular system and it of course has in no way any limiting effect on the invention.

The base station system BSS comprises a number of base transceiver stations BTS, a group of BTSs being controlled by a base station controller BSC and a number of base station switching centers BSCs being controlled by a mobile switching center MSC for the switching system SS which controls calls to and from the network such as the public switched telephone network PSTN , the public mobile land network PLMN, the packet-switched public data network PSPDN, the circuit-switched public data network, the integrated digital service network ISDN or any other network. 10 15 20 25 505 915 10 The connection point further comprises a visitor register VLR which comprises a data location area, a home register CPR with data on subscribers, etc. which, however, is not relevant to the present invention. OMC indicates an operation and maintenance center OMC in a manner known per se. Dashed lines in the figures refer to information transmission and solid lines refer to and dashed call connections and information transmission lines; also refers, in the case of boxes, alternative networks, alternative or optional functions (for SS, etc.).

In accordance with the invention, a threshold is introduced at least for each cell that is not in the top layer. This is a feature of the provision of a systematic transition between the layers. The threshold can refer to the signal strength or tensile attenuation or both or any other parameter depending on the handover strategy applied in the system (among other things). In the embodiments which will be described in the following, only the cases relating to a signal strength threshold will be described. However, this is in no way limiting and the method when applying, for example, a tensile cushioning threshold or any other threshold or both is substantially identical.

The threshold is used to go up as well as down in cell hierarchy.

According to advantageous embodiments, the threshold for going up and down is generally referred to as a threshold. However, it may be modified with a hysteresis that is added or subtracted depending on the direction of movement. In a generalized case, the condition for going up, i.e. from a lower layer to a higher layer, is that if the signal strength measured from the cell currently providing the »connection, i.e. the serving cell, is below the threshold of that cell (Especially with subtracted hysteresis ), the system expands the group of neighboring cells selectable for handover to cells in a higher hierarchical base ranking list is formed. 505 915 'll stock. The cells in the higher layer will have a lower priority than cells in the current layer and in each lower layer.

The corresponding condition for going down, i.e. from a higher layer to a lower layer, is that if the signal strength measured from a neighboring cell in a lower hierarchical layer rises above the threshold of that cell (especially with hysteresis added), that cell will be added to the group of neighboring cells that are selectable for handover.

That cell will have a higher priority than cells in the current layer or in a higher layer.

The cell structure can thus be said to be a hierarchical cell structure.

This affects and modifies the location function.

The basic ranking is made over different cell levels and a This list includes a number of candidates and the list is organized depending on different conditions.

The organization can be controlled by a table and, for example, provided as permanent station data. The candidates in the list are also divided into categories which will be discussed further below.

In the following, some concepts will be explained. Base ranking refers to the ranking of cells that is based on signal strength and / or tensile attenuation criteria (or any other appropriate parameter). "Locating" refers to the procedure which, using measured values and parameter data, suggests the most suitable connection. The result of the localization process is a list of possible candidates, the candidate list, for handover or award. Alarm refers to a condition that requires an urgent handover. This is the case if the transmission quality is too low, if the time alignment (TA) is too large, if the time dispersion is too large or if some other criterion for extraordinary radio events is met depending on the physical measurements available for the radio link. In the umbrella cell concept, a cell can be defined as an umbrella cell.

An umbrella cell is a cell in a network of large cells that covers the However, normal network. this invention is based on a concept of hierarchical cells.

In general, a large number of different requirements will be placed on the base station switching center BSC for the location algorithm.

The localization algorithm is defined here specifically as a collective term for cell and subcell selection, including all types of intra-cell exchange of channel. The localization function generally describes a functionality that comprises one of several functional components in the localization algorithm. In the following, a handover generally describes a channel change between cells. In the following, reference will be made to the measured parameters or quantities. These are quantities that are monitored in (in a special exemplary embodiment) the mobile station MS, and in the BTS, for example as specified in the GSM of a measuring device recommendations. If the mobile-assisted handover strategy MAHO, the quantities networked or monitored in will be applied, the mobile station MS will be transmitted to the BSC by air.

Quantities measured or monitored in the base transceiver station BTS are transmitted to the BSC. However, the ways in which the measurements are performed are informed about, and so on. depends on the special handover strategy used. In a particular embodiment, as will be discussed further below, the measurements considered include uplink and downlink signal strength and uplink and downlink signal quality measurements. As already mentioned, there are of course a number of other options. In the same embodiment, reported quantities refer to quantities used in the mobile station MS. The reported values are transmitted from the MS to the BSC, the base station switching center, by air.

Reports considered in the described example include time alignment TA coming from the BTS. As in any known system, filtration may be necessary. It may be necessary to even out stochastic variations, etc. However, this will not be discussed further.

In a particular embodiment, such as in a number of known systems, cell and subcell evaluations may be performed together in a cycle completed at least within a SACCH (slow associated control channel) period, and repeated every SACCH period unless special mechanisms prevent selection over a time interval. However, this is an example among many others.

As will be discussed in more detail below, the cell selection is based on the ranking in the established ranking list.

The ranking list is advantageously established at the beginning of the cycle in accordance with given basic principles. The final cell selection is obtained by reorganizing the list in accordance with different principles that depend on different criteria which will be discussed further below. The location function continuously monitors and evaluates the radio environment and suggests the most suitable cell (and / or subcell).

Based on a number of comparisons of 'measured' values. for 'measured and reported quantities a candidate list is produced. This list of candidates includes cells in order of preference. In an advantageous embodiment, the signal quality and ID alignment are continuously monitored and evaluated together with an estimate of the signal strength_ (which includes possible filter functions). The candidate list that is produced will, for example, be sent in a manner known per se to the call process manager to be used for channel allocation. In general, the location comparison and the preparation of the candidate list in accordance with the given conditions will begin immediately after the initiation of the location algorithm. 10 15 20 25 505 915 14 Once the candidate list has been received by the function that handles the candidate list, the candidates are used in attempts to allocate the channel in accordance with the information in each candidate facility. In the experiments, the candidates are used in the order in which they are placed on the list, for example with one experiment for each candidate. If the channel allocation to a particular candidate fails (for example in case of block), the next candidate on the list 'shall be used for the next attempt, and so on. until the channel has been successfully allocated or all candidates have been tried without success. This is a process which is generally known per se, which can of course be more or less modified or completely replaced by another process without therefore departing from what is encompassed by the present invention.

The interactions with other network functions such as intra-cell handover, overlying-underlying subcell handover, extended area, "directed retry", assignment to another cell, alarm handover, etc. will be discussed later. This is relevant in the particular case when different radio network functions proposes different types of actions at the same time.The cell candidates are in accordance with the invention sorted into categories depending on a number of factors, in an exemplary embodiment of three factors namely the layer, the ranking as compared to the serving cell and a measured parameter such as signal strength (or road loss or Each combination of results from the evaluations of the radio network control functions is connected to a defined list of categories describing the candidates' preference in a so-called "handover candidate list". Figure 3 illustrates in a general way the main flow of the localization procedure in a particular embodiment.

Timing reports TA and the measurement results are filtered in Q where 10 15 20 25 30 505 915 15 among other things the bit error rate is checked and so on. In Q, the base arrangement is performed, which will be discussed in more detail later. In Q, the hierarchical cell evaluations are performed, ie. the evaluations regarding whether a cell is above / below a threshold value, etc. This is followed by the (Q) evaluations in relation to other radio network functions, such as, for example, alarm conditions, overlying / underlying evaluations, intra-cell evaluations, etc. These so-called flags are introduced in the tables and are examples of conditions that can be controlled or modified.

This is followed by the organization procedure which depends on Q-Q and in which a candidate list is organized. Then proceed in the same way as in any known system or localization flow.

In the specifically described embodiment, in the initialization procedure, the base station switching center block BSC is initialized, the channel allocation process is initialized, and the table (s) are read. The initiations are performed upon activation of a locating individual or cell, for example upon handover upon receipt of a complete handover signal in the BSC from the MS (mobile station) in the handover process. Among other things, the parameters read, better / worse, above / below the threshold are read. The initiation block further comprises the so-called CPH process (call process manager) which handles the BSC (base station switching center) signaling, data structure, updating and processing of parameters, for example signal strength, etc. reports the active location authority. The procedures are referred to here. in a simplified manner because most of the steps in the procedure correspond to the procedures performed in known cellular mobile communication systems, for example with conventional umbrella cells. For example, filtering functions are performed in a manner known per se, and so on. The basic ranking procedure will be further discussed below with respect to two examples for establishing a priority table based on a hierarchical structure comprising two and three levels, respectively.

In the localization procedure, for example, the measured value reports can be taken care of directly in the localization procedure itself or they can be placed in a buffer. However, it is advantageous if they are handled directly. Alarm conditions as well as overlying / underlying evaluation and intracellular evaluation are handled in a similar way as in known cellular systems that include umbrella cells. After the intracell evaluation, the * follows. organization procedure. This differs from known systems and will be discussed and illustrated further below. The organization procedure may comprise an assessment procedure after which the list is sent in a manner known per se and the administration of the allocation response is processed in some appropriate manner.

According to an exemplary embodiment, the organizing procedure may, for example, comprise four procedures in which cross-reference tables are formed for cells in the parameter list, for example the signal strength and so on. against cells cells in in the ranking list, the parameter list. against cells in the measured value list, cells in the ranking list against cells in the parameter list and cells' in the ranking list. against cells in the measured value list. This procedure is accompanied by a second procedure in which each cell in the ranking list is fragmented with respect to three parameters, namely (as referred to above) 1 - layer 2 - better or worse than serving cell, and 3 - if it is above or below its own threshold . The cells are then sorted into a three-dimensional data structure. The ranking list is reviewed in the order specified by the ranking.

Table data exists in some suitable way that is generally known per se. Especially with respect to one embodiment, the known umbrella cell concept can be said to be extended to a hierarchical cell structure. Thereby, it can be used, for example, to cover cover holes from normal cells. According to an UPP embodiment (which either includes a hysteresis threshold or not, or a second threshold), the transitions between normal cells and "umbrella" cells can be controlled by the threshold (signal strength threshold I ") and the modified threshold, i.e. the signal strength threshold modified by hysteresis HRS". In a special embodiment, these parameters (the first and the second threshold) can be defined for normal cells, ie not for cells that form so-called "umbrellas". In this particular case, this leads to a base ranking list (referred to in (Figure 3), among others, which includes 7 categories. This is illustrated in Tables I, II and III. Table I illustrates a table for the ranking in a two-layer structure where the serving cell is in the bottom layer and the signal strength of the serving cell is below the threshold Table 2 illustrates a table for the structure of Table I but where the serving cell is in the bottom layer and the signal strength of the serving cell is above the threshold Table III illustrates a table for the structure in Table I but where the serving cell is in a higher layer (forming an "umbrella" cell), Table I .flLllaïiLlku 123456 1 O-OOOO lbo, 2b, lbu; 2 O-0001 lbo, 2b, lbu, S ; 3 O-0010 lbo, 2b, lbu, s; 4 O-0011 lbo, Eb, lbu, s; 5 O-0100 lbo, 2b, lbu, lwo, 2w, lwu, 10 15 20 25 kßm flfl ï 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Table II Falla \ OCO \ ï0 \ U'lrbbJl \) | f- '505 915 0-0101 0-0110 O-0111 0-1000 0-1001 0-1010 0-1011 0-1100 0-1101 0-1110 0-1111 1000-- 1001-- 1010-- 1011-- 1100-- 1101-- 1110-- 1111-- yillhgz 123456 o-oooo o-oool o-0010 o-0011 o-o1oo o-0101 0-0110 0-0111 0-1000 lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo, lbo , lbø, lbo; 1bO; lbo, lbo, lbo, lbó, lbo, lbo, lbo, 18 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b, 2b , 2b, lwo, S, S, S, lwo, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu , 2b, lwo, lwo, lWO, 2b, s, lwo, 2w, lwu; s, lwo, 2w, lwu; s, lwo, 2w, lwu; lwo, 2w, lwu; lwo, 2w, lwu, s; lwo, 2w, lwu, s; lwo, 2w, lwu, s; lwo, 2w, lwu; lwo, 2w, lwu, s; lwo, 2w, lwu, s; lwo, 2w, lwu, s; S; S; S; S; s, lwo, 2w, lwu; s, lwo, 2w, lwu; lwo, 2w, lwu, s; lwo, 2w, lwu, s; 2w, lbu, lwu; 2b, 2w, lbu, lwu; 2b, 2w, lbu, lwu; 2b, 2w, lbu, lwu; 2w, lbu, lwu; 10 15 20 25 30 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Table III Ealla mw fl ml fl nßwNi-J | - * OP |> - 'lJ k) H b) F * »ß O-1001 0-1010 0-1011 0-1100 0-1101 0-1110 0-1111 1000-- 1001-- 1010-- 1011-- 1100-- 1101-- 1110-- 1111-- yillkgz 123456 o-oooo o-ooo1 o-0010 o-oo11 o-o1oo o-0101 o-o11o o-ø111 o-1ooo o-1001 0-1010 O-1011 o-11oo o-1101 505 19 lbo, lwo, 2b, 2w, lbo, lwo, 2b, 2w , lbo, lwo, 2b, 2w, lbo, lwo, 2b, 2w, lbo, lwo, 2b, 2w, lbo, lwo, 2b, 2w, lbo, lwo, 2b, 2w, lbo, s, lbu; lbo, s, 2b, lbu; lbo, s, 2b, lbu; lbo, s, 2b, lbu; lbo, s, lwo, 2b, lbo, s, lwo, 2b, lbo, lwo, 2b, 2w, lbo, lwo, 2b, 2w, Kansseri fi z lbo, lwo, 2b; 1bo, 1wo, 2b, s; lbo, lwo, 2b, s; lbo, lwo, 2b, s; lbo, lwo, 2b, 2w, lbo, lwo, 2b, s, lbo, lwo, 2b, s, lbo, lwo, 2b, s, lbo, lwo, 2b, 2w, lbo, lwo, 2b, 2w, lbó, lwo, 2b, 2w, lbo, lwo, 2b, 2w, lbo, lwo, 2b, 2w, lbo, lwo, 2b, 2w, 2w, 915 "lbu, lwu, s; lbu, lwu, s; lbu, lwu, s; lbu, lwu; lbu, lwu, s; lbu, lwu, s; lbu, lwu, s; 2w, lbu, lwu; 2w, lbu, lwu; lbu, lwu, s; lbu, lwu, s; lbu, lwu; 2w, lbu, lwu; lbu, lwu; 2w, lbu, lwu; lbu, lwu; lbu, lwu, s; lbu, lwu, s; lbu, lwu, s; lbu, lwu; lbu, lwu, s; 10 15 20 25 505 915 20 15 0-1110 lbo, lwo, 2b, 2w, lbu, lwu, s; 16 0-1111 lbo, lwo, 2b, 2w, lbu, 1wu, s; 17 1000-- lbo, lwo , 2b, s, lbu, 1wu; 18 1001-- lbo, lwo, 2b, s, lbu, lwu; 19 1010-- lbo, lwo, 2b, s, lbu, lwu; 20 1011-- lbo, lwo, 2b , s, lbu, lwu; 21 1100-- lbo, lwo, 2b, s, 2w, lbu, lwu; 22 5 1101-- lbo, lwo, 2b, s, 2w, lbu, lwu; 23 1110-- lbo, lwo, 2b, 2w, lbu, lwu, s; 24 1111-- lbo, lwo, 2b, 2w, lbu, lwu, s; For cells at level 1 (the lowest layer), in this embodiment so-called normal cells, compare signal strength with the threshold value . In the case of the embodiment described here, "above" for serving cells means that the signal strength I0 2 If '-HJ' and "below" for serving cells means that the signal strength ID <If'-4% "while for neighboring cells" above "means that the signal strength Ii z If * + HQ ”while" below "means that the signal strength Ii <Ii" + Hi ".

The candidate list is organized depending on different conditions. This means that one or more categories which may normally be on the list may be removed from the list, and categories may be added etc and categories 'are arranged in an appropriate' order depending on the Organization as such table forms special needs and requirements. is controlled by a table as mentioned above. This permanent station data but it can also be changeable and possible to correct etc. The table includes a part that is referred to as a condition. The conditions may, for example, be in accordance with the following table, hereinafter referred to as Table A: 1 - allocation request received, 2 - AW state (which means allocation to inferior cell), 3 - alarm about excessive time alignment (TA), 4 - poor quality alarm, 10 15 20 25 30 505 91-5 '21 5 - overlying-underlying subcellsbyte, 6 - intra-cell handover.

(Table A) Of course, other conditions are also possible as well as there may be fewer or more conditions, depending on the special needs and special requirements. The terms can be true, indicated by "1", false denote e "O" and finally they can be irrelevant,. Denoted "-".

Furthermore, the table refers to different categories. In the tables illustrated in Tables I-III means: s - serving cell, 1 bo - better cell in layer 1, SS (signal strength) above threshold, 1 bu - better cell in layer 1, SS below threshold, 1 wo - inferior cell in layer 1, SS above threshold, 1 wu - inferior cell in layer 1, SS below threshold, 2 b - better cell in layer 2, 2 w - inferior cell in layer 2.

Table I illustrates the serving cell in layer 1 (normal) with the signal strength being below the threshold. 24 different cases are illustrated.

In Tables I-III, reference is made to whether the serving cell has a signal strength that is above or below the threshold of the serving cell (see also Tables IV-VII).

Tables I-III have been prepared in accordance with guidelines that have given a certain order of priority between the various radio network functionalities. This order of priority is given by the following table, hereinafter referred to as Table B: - normal handover - time alignment TA alarm - transition to a higher layer subcell change - intracell handover - BQ alarm \ l ON U'l rä UJ h.) HI - transition to higher layer (Table B) Table II illustrates the serving cell in layer 1 (normal) and where the signal strength is above the threshold for 24 cases and finally Table III illustrates the serving cell in layer 2 (which in this case refers to an "umbrella "cell) for 24 different cases. In particular, it is also possible to divide a number of cases into different cases for subcell exchange conditions, which, however, will not be discussed further here.

The design discussed above refers to a case with two cell layers or levels. Of course, there can be several layers. In the following, another embodiment will be described. In this case, there are three different cell layers.

The hierarchical cell structure according to the invention can be applied to the umbrella cell functionality. An umbrella cell functionality provides a second level in a network comprising large cells which are logically (and physically) organized above the original cell network and which act as a backup network for this. In the present the embodiment introduces a third level which is logically (and physically) arranged below the original cell network and which comprises small cells.In a special embodiment this level forms a microcell network.

Here the first level or the lowest level (level 1) or the bottom level is called the micro level and the second level or the middle level is called a normal or an original level and the third level or top level can be called a third or an upper level . In general, the intention of allocating mobile stations in the hierarchical cell structure is to fill the lowest level first, ie. the mobile station should be served by a cell in the lowest possible level or layer because this level in particular has the highest jcapacity. This has the consequence that the mobile station will not always be served by the best cell, for example from a signal strength point of view or road loss point of view of a cell which is good enough and which is in the lowest possible layer.

The invention relates in particular to handling with a threshold and with a system of tables as illustrated, for example, in Tables I-III, and further allows any other strategy by changing the priorities as given, for example, by Table B as referred to above.

In addition, the system includes tables such as, for example, in Table I, which allow different strategies to be applied in different layers. In this way, for example, traffic can be routed to any warehouse and not just to the lowest, and so on.

Of course, the invention also relates to networks having more than two or three layers, but since the principle is the same regardless of the number of layers, only networks comprising two or three layers of structures are described in more detail here. 10 15 20 25 bUb via 24 A hierarchical cell structure in accordance with the invention can relate both to the umbrella cell concept and to cells that are generally in different layers or at different levels. By introducing the signal strength threshold If * or an upward transition threshold below which a transition may be made, transitions to a logically higher level or layer are facilitated. A flag shall be set, in a manner known per se, indicating that a handover to a cell in a higher layer is allowed when the signal strength of the serving normal cell falls below If * -Hf '. The flag can, for example, be referred to as a higher level transition flag allowed. A candidate list containing only better cells with respect to the base ranking should be sent if the flag is set (and if no other flags are set). However, if the list is empty, ie there are no better cells; then the mobile station remains in the current cell, ie in the serving cell. However, if, after handover to a cell at a higher level, the signal strength from a cell in a lower layer again rises above the threshold, this cell should not be immediately (according to the particular embodiment) included in the candidate list. The signal strength should preferably reach a level slightly above I "or the threshold I" '+ H "or a threshold for transition downwards to obtain a hysteresis effect which will prevent repeated handovers or so-called" ping-pong handovers ". a cell at a lower level exceeds I "+" H, a flag is set (in this particular embodiment). This flag can be seen as an indication that transition to a lower level is allowed. The candidate list containing the lower level cell exceeding I "+ H" will then be sent.

I '' and Hf refer to cell parameters here and the serving cell uses its own threshold values in the evaluation of I "-H" (I0 "- Hff) (for a possible transition to a higher level). When the serving cell evaluates neighbors, it uses the threshold values corresponding to the neighboring cells (lff + Hfl). 10 15 20 25 30 yflaggan 505 915 ”25 If a third level is introduced during the other two levels, the cells at that level shall generally be ensured traffic with priority over all the other levels. In the following, the bottom level is called level 1. In order to get a candidate list, a basic ranking is performed among all cells that meet a minimum criterion. After that, a level-oriented redistribution is made. Each cell in the lower layer that has a signal strength that exceeding If '+ Hf * (referring to a preferred embodiment) will set a flag indicating that transition to a lower layer is allowed, which will make the cell to the highest candidate on the candidate list. If there are several such cells, the result of the base ranking device will be used in the ranking. If higher layer transfer is allowed, the compilation of the candidate list generally proceeds as follows: cells that are better than the serving cell, in the same or in a higher layer can be candidates, cells in the same layer have priority over cells in higher layers. Cells' among the "better" overlying cells with a signal strength below the threshold for higher layer transition allowed, have a lower priority, (if there are any at all). In the last category, cells at a higher level have priority over cells at a lower level. This is due to the fact that transition to a cell in a lower layer with a signal strength below the threshold for higher layer transition allowed, would immediately result in a transition to a higher layer in any case. This saves two unnecessary handovers. However, if an alarm flag is set at the same time as the flag indicating that change to a higher layer is allowed, then worse cells can also be entered on the candidate list. The compilation of the candidate list is given by the table that implements the priority principle considered in the previous. The table can be provided as permanent station data that allows adjustment of the algorithm without changing the current code. However, in an alternative embodiment, the table is not permanent but can be changed, for example by command. Of course, it is possible to provide means which, for example, are to prevent handover to lower level cells under certain circumstances, such as in the case of a mobile station moving rapidly, and so on. In addition, it is possible to add additional cell types, such as indoor cells or pico cells, and so on. Thereby, it may be introducing more levels in: necessary to the cell ranking list.

The thresholds and hysteresis parameters can be set per BSC or per cell level or per MSC level or per system level.

In the case of three layers or levels, the base ranking is made over the three cell levels. The candidates. in the candidate list, as already discussed above, are divided into categories and the reported signal strength, signal strength threshold and hysteresis and cell level are used to provide the categories for the neighboring cells. Likewise, as already referred to, it does not have to be the signal strength but it can also be the tensile attenuation, the signal strength as well as the tensile attenuation or some other suitable parameter.

Tables IV-VIII show from which the candidate lists are formed as already mentioned above with reference to the exemplary embodiment which comprises two cell layers. First, a base ranking is performed, preferably among those cells that meet a minimum criterion of exceeding the threshold value for at least a given signal parameter. Table IV shows the ranking arrangement in a three-layer structure where the serving cell is in the lowest layer and the signal strength of it, the serving cell is below the threshold, Table V is a table for the same structure as in Table IV but where the signal strength of the serving cell is above threshold, Table VI is a table for the same structure as in Table IV but where the serving cell is in the second layer and where the signal strength of the serving cell is below the threshold, Table VII is a table for the same structure as in Table VI but the signal strength of the serving cell is above the threshold, and Table VIII is a table for the structure of Table IV but where the serving cell is in the third or top layer.

Tabelrïv all .. links: 1 0000000010, 1b0, 2bo, 3bo, 3bu, 2bu, lbu; 2 1000000010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, s, lwo, 2w0, 3wO, 3wu, 2wu, lwu; .3 0100000010, lbo, 2bo, 3bo, 3bu, 2bu .lbu, s; 4 0010000010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, lwo, 2wo, 3wo, 3wu, 2wu, lwu; s 1o1ooooo1o, 1bo, 2bo, 3bo, 3bu, 2bu, 1buj lwo, zwo, 3wo, 3wu, 2wu, lwu, s; 6 0110000010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, s; 7 0000100010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, s; 8 1000100010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, s, lwo, 2wo, 3wo, 3wu, 2wu, lwu; 9 0100100010, lbo, 2bo, 3bo, 3bu, 2bu, lbu s; 10 0010100010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, lwo, 2wo, 3wo, 3wu, 2wu, lwu, s; 11 1010100010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, lwo, 2wo, 3wo, 3wu, 2wu, lwu, s; 12 0110100010, lbo, 2bO, 3bo, 3bu, 2bu, lbu, s; 13 0000010010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, s; 14 0010010010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, lwo, 2wo, 3wo, 3wu, 2wu, lwu, s; 15 0000110010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, s; 16 0010110010, lbo, 2bo, 3bo, 3bu, 2bu, lbu, lwo, 2wo, 10 15 20 25 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 505 915 0001000010, 1001000010, 0101000010, 0011000010, 1011000010 , 0111000010, 0001100010, 1001100010, 0101100010, 0011100010, 1011100010, 0111100010, 0001010010, 0011010010, 0001110010, 0011110010, 3wo, lbo, 3wo, lbo, 2wo, lbo, lbo, 3wo, lbo, 3wo, lbo, lbo, lbo , 2wo, lbo, lbo, 3wo, lbo, 3wo, lbo, lbo, 2wo, lbo, 3wo, lbo, 2wo, lbo, BWO, 28 3wu, 2bo, 3wu, 2bo, 3wo, 2bo, 2bo, 3wu, 2bo, 3wu, 2bo, 2bo, 3wo, 2bo, 3wo, 2bo, 2bo, 3wu, 2bo, 3wu, 2bo, 2bo, 3wo, 2bo, 3wu, 2bo, 3wo, 2bo, 3wu, 2wu, 3bo, 2wu, 3bo, 3wu, 3bo, 3bo, 2wu, 3bo, 2wu, 3bo, 3bo, 3wu, 3bo, 3wu, 3bo, 3bo, 2wu, 3bo, 2wu, 3bo, 3bo, 3wu, 3bo, 2wu, 3bo, 3wu, 3bo, 2wu, lwu, 3bu, lwu; 3bu, 2wu, 3bu, 3bu, lwu; 3bu, lwu, 3bu, 3bu, 2wu, 3bu, 2wu, 3bu, 3bu, lwu, 3bu, lwu, 3bu, 3bu, 2wu, 3bu, lwu, 3bu, 2wu, 3bu, lWLl, S7 2bu, 2bu, lwu; 2bu, 2bu, 2bu, 2bu, 2bu, 2bu, lwu; 2bu, lbu, lbu, lbu; lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lbu, lwo, 2wo, s, lwo, lwo, 2wo, lwo, 2wo, S. s, lwo, s, lwo, SI lwo, 2wo, lwo, 2wo, S, s, lwo, lwo, 2wo, s, lwo, lwo, 2wo, 10 20 25 505 915 29 Table V 331.1 i 1 0000000000, lbo, 2 1 billion, lbo, s, 1wo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; 3 0100000000, lbo, s, lbu; 4 "0010000000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; 5 1010000000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu , lbu, lwu, s; 6 0110000000, 1bo, 2bo, 3bo, 3bu, 2bu, lbu, s; 07 oooolooooo, lbo, s, - »8 1000100000, lbo, s, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; 9 0100100000, lbo, s, lbu; 10 0010100000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; 11 1010100000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; 12 0110100000, lbo, 2bo, 3bo, 3bu, 2bu, lbu, s; 13 0000010000, lbo , s; 14 0010010000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; 15 0000110000, lbo, s; 16 0010110000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; 17 0001000000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, 1bu, lwu; 18 1001000000, lbo, s, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; 19 0101000000, lbo, s, 2bo, 3bo, 3bu, 2bu, lbu; 20 0011000000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 10 15 20 25 21 22 23 24 25 26 27 28 29 30 31 32 Table VI "11 Û) | - '| -' NP '505 915 1011000000, 0111000000, 0001100000, 1001100000, 0101100000, 0011100000, 1011100000, 0111100000, 0001010000, 0011010000 , 0001110000, 0011110000, Villkgr 0000000110, 1000000110, 0100000110, 0010000110, 1010000110, 30 2bu, 2wu, lbu, lwu; lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; lbo, 2bo, 3bo, 3bu, 2bu, lbu, s; lbo, s, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; lbo, s, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; lbo, s, 2bo, 3bo, 3bu, 2bu, lbu; lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; lbo, lwo, 2bo, 2wo, 3bø, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; lbo, 2bo, 3bo, 3bu, 2bu, lbu, s; lbo, s0, lwø, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; lbo, s, lwo, 2bo, 2wo, 3bo 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; Kggggoriçr lbo, lwo, 2bo, 3bo, 3bu, 2bu, lbo, lwo, 2bo, 3bo, 3bu, 2bu, s, 2wo, 3wo, 3wu, 2wu, lbu, lwu; lbo, 1wo, 2bo, 3bo, 3bu, 2bu, s, lbu, lwu; lbo, lwo, 2bo, 3bo, 3bu, 2bu, 2wo, 3wo, Bwu, 2wu, lbu, lwu; lbo, lwo, 2bo, 3bo, 3bu, 2bu, 2wo, 3wo, 10 15 20 25 30 10 11 12 013 .14 15 16 17 18 19 20 21 22 23 24 0110000110, 0000100110, 1000100110, 0100100110, 0010100110, 1010100110, 0110100110 , 0000010110, 0010010110, 0000110110, 0010110110, 0001000110, 1001000110, 0101000110, 0011000110, 1011000110, 0111000110, 0001100110, 1001100110, 31 3wu, 2wu, lbo, lwo, lbo, lbo, lwo, lwo, lwo 1bu, 1wu; lbo, lwo, 3wu, 2wu, lbo, lwo, 3wu, 2wu, lbo, lwo, lbo, lwo, lbo, lwo, 3wu, 2wu, lbo, lwo, lbo, lwo, 3wu, 2wu, lbo, lwo, 3wu, 2wu, lbo, lwo, 3wo, 3wu, lbo, lwo, 1bu, 1wu; lbo, lwo, 3wu, 2wu, lbo, lwo, 3wu, Zwu, lbo, lwo, lbo, lwo, 3wo, 3wu, lbo, lwo, 3wo, 3wu, 505 915 'lbu, 2bo, 2bo, 2bo, 2wu, 2bo , 2bo, lbu, 2bo, 2bo, 2bo, 2bo, lbu, 2bo, 2bo, lbu, 2bo, lbu, 2bo, 2wu, 2bo, 2bo, lbu, 2bo, 2bo, 2bo, 2wu, 2bo, Zwu, lbu, lbu , lwu, S; 3bo, 3bu, 2bu, 3bo, 3bu, 2bu, 3bo, 3bu, 2bu, lbu, lwu; 3bo, 3bu, 2bu, 3bo, 3bu, 2bu, lwu, S; 3bo, 3bu, 2bu, lwu, S; 3bo, 3bu, 2bu, 3bo, 3bu, 2bu, 3bo, 3bu, 2bu, lwu, S; 3bo, 3bu, 2bu, 3bo, 3bu, 2bu, lwu, S; 3bo, 3bu, 2bu, lwu; 3bo, 3bu, 2bu, lbu, lwu; 3bo, 3bu, 2bu, 3bo, 3bu, 2bu, lwu; 3bo, 3bu, 2bu, lwu, S; 3bo, 3bu, 2bu, 3bo, 3bu, 2bu, lbu, lwu; 3bo, 3bu, 2bu, lbu, lwu; lbu, lbu, lbu, lwu, s; S I S, 2wo, S f 2wo, 3wo, 2wo, 3wo, lwu, S; S I 2wo, 3wo, S, 2wo, 3wo, 2wo, 3wo, s, 2wo, S. 2wo, 3wo, 2wo, 3wo, 1wu, S; S, 2wo, S, 2WO, 10 15 20 25 b) S 505 915 25 0101100110, 26 0011100110, 27 1011100110, 28 0111100110 29 0001010110, 30 0011010110, 31 0001110110, 32 0011110110, Table VII Fgl; Vi11gg; 1 0000000100, 2 1000000100, 3 0100000100, 4 0010000100, 5 1010000100, 6 0110000100, 7 0000100100, 8 1000100100, 9 0100100100, 10 0010100100, 32 lbo, lwo, 2bo, lbo, lwo, 2bo, 3wu, 2wu, lbu, lbo , lwo, 2bo, 3wu, 2wu, lbu, lbo, lwo, 2bo, lbo, lwo, 2bo, 3wo, 3wu, 2wu, lbo, lwo, 2bo, 3wu, 2wu, lbu, lbo, lwo, 2bo, 3wo, 3wu , 2wu, lbo, lwo, 2bo, 3wu, 2wu, lbu, Kgteggrier lbo, lwo, 2bo; lbo, lwo, 2bo, 3wu, 2bu, 2wu, 1bo, lwo, 2bo, lbo, lwo, 2bo, 2bu, 2wu, lbu, lbo, lwo, 2bo, 2bu, 2wu, lbu, lbo, lwo, 2bo, lbo, lwo, 2bo, lbo, lwø, 2bo, 3wu, 2bu, 2wu, lbo, lwo, 2bo, lbo, lwo, 2bo, 2bu, 2wu, lbu, 3bo, 3bu, s, lbu, lwu; 3bo, 3bu, 2bu, 2wo, 3wo, lwu, S; 3bo, 3bu, 2bu, 2wo, 3wo, lwu, S; 3bo, 3bu, 2bu, lbu, 1wu, s; 3bo, 3bu, 2bu, s, 2wo, lbu, lwu; 3bo, 3bu, 2bu, 2wo, 3wo, lwu, S; 3bo, 3bu, 2bu, s, 2wo, lbu, lwu; 3bo, 3bu, 2bu, 2wo, 3wo, lwu, s; s, 2wo, 3bo, 3bu, 3wo, lbu, lwu; s, 2bu, lbu, lwu; 2wo, 3bo, 3bu, 3wo, 3wu, lwu; 2wo, 3bo, 3bu, 3wo, 3wu, lwu, S; 3bo, 3bu, 2bu, lbu, 1wu, s; S, s, 2wo, 3bo, 3bu, 3wo, lbu, lwu; S, 2bu, lbu, lwu, 2wo, 3bo, 3bu, 3wo, 3wu, 1vu, S, 10 15 20 25 30 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 1010100100, 0110100100, 0000010100, 0010010100, 0000110100, 0010110100, 0001000100, 1001000100, 0101000100, 0011000100, 1011000100, 0111000100, 0001100100, 1001100100, 0101100100, 0011100100, 1011100100, 0111100100, 0001010100, 33 lbo, lw, lwo, lwo, 2 , lbo, lwo, 2bu, 2wu, lbo, lwo, lbo, lwo, 2bu, 2wu, lbo, lwo, 2bu, 2wu, lbo, lwo, 3wu, 2bu, lbo, lwo, 1bu, 1wu; lbo, lwo, 2bu, 2wu, lbo, lwo, 2bu, 2wu, lbo, lwo, lbo, lwo, 3wu, 2bu, lbo, lwo, 3wu, 2bu, lbo, lwo, 1bu, lwu; lbo, lwo, 2bu, 2wu, lbo, lwo, Zb fi, 2wu, lbo, lwo, lbo, lwo, 3wu, 2bu, 505 915 '2bo, lbu, 2bo, 2bo, 2bo, lbu, 2bo, 2bo, lbu, 2bo , lbu, 2bo, 2wu, 2bo, 2bo, lbu, 2bo, lbu, 2bo, 2bo, 2wu, 2bo, 2wu, 2bo, 2bo, lbu, 2bo, lbu, 2bo, 2bo, 2wu, 2wo, 3bo, 3bu, 3wo , 3wu, lwu, s; 3bo, 3bu, 2bu, lbu, 1wu, s; S; 2wo, 3bo, 3bu, 3wo, 3wu, lwu, S; S I 2wo, 3bo, 3bu, 3wo, 3wu, lwu, S; 2wo, 3bo, 3bu, 3wo, 3wu, lwu; s, 2wo, 3bo, 3bu, 3wo, lbu, lwu; s, 3bo, 3bu, 2bu, 2wo, 3bo, 3bu, 3wo, 3wu, lwu; 2wo, 3bø, 3bu, 3wo, 3wu, lwu, S; 3bo, 3bu, 2bu, lbu, 1wu, s; s, 2wo, 3bo, 3bu, 3wo, lbu, lwu; s, 2wo, 3bo, 3bu, 3wo, lbu, lwu; s, 3bo, 3bu, 2bu, 2wo, 3bo, 3bu, 3wo, 3wu, lwu, s; 2wo, 3bo, 3bu, 3wo, 3wu, lwu, S; 3bo, 3bu, 2bu, lbu, lwu, s; s, 2wo, 3bo, 3bu, 3wo, lbu, lwu; 505 915 34 30 0011010100, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, 1wu, s; 31 0001110100, lbo, lwo, 2bo, s, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; 32 0011110100, lbo, 1wo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; Table “VIII Fa1l Villkg; Kat r 'r 1 0000001000, lbo, lwo, 2bo, 2wo, 3bo, 3bu; 2 1000001000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, s, 3wo, 3wu, 2bu, 2wu, lbu, lwu; 3 0100001000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, s, 2bu, 2wu, lbu, lwu; 4 0010001000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu; 5 1010001000, lbo, 1wo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; 6 0110001000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 2bu, 2wu, lbu, 1wu, s; 7 0000101000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, s; 8 1000101000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, s, 3wo, 3wu, 2bu, 2wu, lbu, lwu; 9 0100101000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, s, 2bu, 2wu, lbu, lwu; 10 0010101000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, 1wu, s; 11 1010101000, lbo, lwø, 2bø, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, lbu, lwu, s; 12 0110101000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 2bu, 2wu, lbu, lwu, s; 13 0000011000, lbo, lwo, 2bo, Zwo, 3bo, 3bu, s; 10 15 20 25 30 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 0010011000, 0000111000, 0010111000, 0001001000, 1001001000, 0101001000, 001001000, 1011001000, 0111001000, 0001101000, 1001101000, 0101101000, 0011101000, 10 0111101000, 0001011000, 0011011000, lbo, 2bu, lbo, lbo, 2bu, lbo, 2bu, lbo, 3wu, lbo, 2wu, lbo, 2bu, lbo, 2bu, lbo, lbu, lbo, 3wu, lbo, 3wu, lbo, 2wu, lbo, 2bu, lbo, 2bu, lbo, lbu, lbo, 3wu, lbo, 2bu, 35 lwo, 2wu, lwo, lwo, 2wu, lwo, 2wu, lwo, 2bu, lwo, lbu, lwo, 2wu, lwo , 2wu, lwo, lwu, lwo, 2bu, lwo, 2bu, lwo, lbu, lwo, 2wu, lwo, 2wu, lwo, lwu, lwo, 2bu, lwo, 2wu, 2bo, lbu, 2bo, 2bo, lbu, 2bo , lbu, 2bo, 2wu, 2bo, lwu; 2bo, lbu, 2bo, lbu, 2bo, 2bo, 2wu, 2bo, 2wu, 2bo, lwu; 2bo, lbu, 2bo, lbu, 2bo, 2bo, 2wu, 2bo, lbu, 505 2wo, lwu, 2wo, 2wo, lwu, 2wo, lwu; 2wo, lbu, 2wo, 2wo, lwu; 2wo, lwu, 2wo, 2wo, lbu, 2wo, lbu, 2wo, 2wo, lwu, 2wo, lwu, 2wo, 2wo, lbu, 2wo, lWLl, 915 3bo, 3bu, 3wo, S; 3bo, 3bu, s; 3bo, 3bu, 3wo, S7 3bo, 3bu, 3wo, 3bo, 3bu, s, lwu; 3bo, 3bu, s, 3bo, 3bu, 3wo, 3bo, 3bu, 3wo, S7 3bo, 3bu, 2bu, 3bo, 3bu, s, lwu; 3bo, 3bu, s, lwu; 3bo, 3bu, s, 3bo, 3bu, 3wo, Si 3bo, 3bu, 3wo, S7 3bo, 3bu, 2bu, 3bo, 3bu, s, lwu; 3bo, Bbu, 3wo, S; 3wu, 3wu, 3wu, 3wo, 2bu, 3wu, 3wu, 2wu, 3wo, 3wo, 2bu, 3wu, 3wu, 2wu, 3wo, 3wu, 10 15 20 25 505 915 36 31 0001111000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, s, 3wo, 3wu, 2bu, 2wu, 1bu, lwu; 32 0011111000, lbo, lwo, 2bo, 2wo, 3bo, 3bu, 3wo, 3wu, 2bu, 2wu, 1bu, lwu, s; Then a hierarchical cell evaluation is performed, ie. a level-oriented redistribution is made. This means that a candidate list is compiled controlled by one or more tables.

Examples of such tables are IV-VIII. These tables will be explained in the following. As above, TA refers to time alignment and AW refers to allocation to inferior cell. In the tables, the number defines the layer, ie in this case three layers, layer 1, layer 2 and layer 3 where layer 1 is the lowest layer, and so on.

Better and worse are illustrated by b and w while o and u mean above and below the respective threshold, plus or minus hysteresis depending on which case, for example whether a hysteresis is applied or not. If hysteresis is used, this can be handled with the localization function.

Similar to the exemplary embodiment of a hierarchical 2-layer structure, the table (IV-VIII) includes a number of conditions, namely: 1 - allocation request arrived and, AW (allocation to inferior cell) condition, 2 - allocation request arrived and not AW condition, 3 - high time alignment (TA) alarm, 4 - poor quality alarm, 5 - overlying-underlying subcell change request, 6 - Intracell handover request, 7.8 - layer, where 00 indicates the lowest layer, 01 indicates the second layer, 10 indicates the third layer and finally indicates the top layer, the signal strength of the own cell below the threshold is not used (but in this case denoted 0).

This table will hereinafter be referred to as Table C.

Table IV refers to layer 1 below, ie the own cell (the serving cell) is in the lower layer (conditions 7 and 8) and the signal strength is below the threshold for the special cell (condition 9). 32 different cases are indicated in the table.

Table V a shows layer 1 above, ie the own cell is in the lower layer and the signal strength is above the threshold.

Table VI refers to layer 2 below, ie the second layer where the own cell is in the second (intermediate) layer and where the signal strength is below the threshold for the particular cell; i.e. I, <Iztr.

Table VII refers to layer '2 above, ie the second layer and a signal strength exceeding the threshold (I, <I;').

Finally, Table VIII refers to layer 3 above, which denotes layer 3, the own cell in the upper layer in this case and a signal strength exceeding the threshold. Alternatively, the threshold is not checked.

In the following, two special examples will be given regarding the interaction of the hierarchical cell structure with other network functions. In particular, the interaction with other network functions is given a priority which gives the sorting order in the priority table for the system is based both on whether the tables (such as I-VIII) 10 15 20 25 30 505 915 38 on the priority between the radio network functions or not.

In a first example, the interaction with the intra-cell handover function will be described for a particular embodiment. Two or more radio network functions can express their request simultaneously.

In this case, the intra-cell handover function suggests a channel change within a cell while the hierarchical cell structure function suggests a handover to another cell either in a higher layer or in a lower one. In this particular example, handover to a higher layer takes precedence over an intra-cell handover (see Table B).

However, an intra-cell handover has priority over, for example, a quality alarm handover, but of course a quality alarm handover can as an alternative have priority over an intra-cell handover and so on. This is due to the special needs and requirements of the system.

Once measurements on neighboring cells have been received from the mobile, the corresponding cells will be categorized according to the combination of three parameters, namely 1 - the hierarchical layer to which they belong, 2 - their ranking as to whether they are better or worse than the serving cell according to with normal location criteria, and finally 3 - if the measured signal strength is above or below the threshold for that cell. In this case, if three hierarchical layers are implemented, twelve categories are obtained.

In general, all possible situations and combinations of situations that are relevant to the various radio network-controlled function evaluations are analyzed. Based on that, a unique sequence of cell categories is assigned to the particular combination of evaluation results. The sequencing of categories can, for example, be done to fulfill a given priority list, such as the one given in Table B. This sequence or candidate list, as already explained above, thus represents the list of handover candidates in the particular preference scheme. Figure 4 explains can be arranged in 8 in Table I. I further how the different cell categories priority in a list, eg cases 6, 7, Table I form the two categories 2bo and 2bu a single category 2b. For 2w, a corresponding merger has been made for 2wo and 2wu.

Furthermore, in Figure 4, o / u (above / below) refers to the signal strength of neighboring cell Ii which is above / below the threshold value of the neighboring (or candidate) cell Iff. The reason for this division is to avoid unnecessary ping-pong handover effects (to first go down one layer and immediately afterwards have to go up to a higher layer again).

In the following, an example will be considered where the structure comprises two cell layers and where the serving cell is in the lower layer. It is assumed that in addition to normal location, the radio network evaluations have proposed three actions at the same time.

Namely, a handover due to poor quality alarms, to a higher hierarchical layer and an overlying-underlying subcell change. In this case, a handover to a higher hierarchical layer has the highest priority while a handover due to an alarm The highest if poor quality has the lowest priority. the priority of all is to remain in the lower layer, ie a normal better cell handover initiated by normal localization. With this combination of evaluation results, the candidate list of handover candidates is obtained as illustrated in Figure 4. First, a ranking of the locating function is performed where the cells are designated better and worse than the serving cell and then the handover candidate list is established As above, above / below the threshold refers to the threshold for the particular cell. According to this list, the highest priority is to stay in the lower layer but only if there is a better cell as illustrated on the first line. The next highest priority will be to go up to the upper layer, which is illustrated on lines 2 and 3 in Figure 4. If the transition to a better cell will result in an immediate move up to a higher layer or an "umbrella" cell, which is the case if the signal strength of the cell is below the threshold, the first handover will not take place and instead there will be a handover directly to which is illustrated on the upper cell or to the "umbrella" lines 1 and 4. In third place will be the execution of a subcellular switch as illustrated by row 5. Finally, the lowest priority is to switch to a cell that is ranked as inferior to the cell currently serving the connection. Also in this case, a cell in the lower layer has precedence over a cell in the upper layer, but not if a handover to the upper layer would follow, which can be seen in lines 6-8 in Figure 4.

The advantageous embodiments of the invention are applicable or FHMA (frequency on TDMA (time division multiple access) skip multiple access) or CDMA (code division multiple access). In addition, the invention is not limited to any particular handover strategy, but a number of different strategies can be mobile-assisted-handover strategy, used such as MAHO, network-controlled handover NCHO or mobile-controlled handover MCHO.

Through the invention, it is possible to apply a systematic approach in the creation of hierarchical cell structures.

Of course, any number of layers can be formed and the detailed conditions for transition between the layers. can be controlled in terms of criteria for change between layers as well as a detailed interplay with other radio network controlled functions.

Depending, among other things, on the fact that transitions between layers in general can be predicted, a systematic cell planning and dimensioning becomes possible. Furthermore, it is possible to direct mobile stations to the lowest layer in a systematic manner which, as already mentioned above, saves on the capacity of the upper layers for, for example, a coverage gap or call set-up latch and so on.

Alternatively, it is possible to route mobile stations to any preference warehouse.

The invention is thus intended, inter alia, to make it possible to direct the traffic to the cells for which the network or hierarchical cellular system HCS is actually dimensioned and to ensure that there is free capacity in the cells which are to provide extra capacity for call connection and which act as rescue cells.

Cells in a higher layer have priority in case of coverage holes and in case of radio interference to ensure call continuity. In case of call set-up blocking, cells in a higher layer also have priority to ensure that connection procedures are successful.

The invention is of course not limited to the embodiments shown, but it can be varied in a number of ways within the scope of the claims.

In particular, the invention can be applied to generally any known standard such as GSM, PDC, all PCS standards, IS54, IS90, ADC, (D-) AMPS, DECT and so on.

Claims (30)

505 915 42 PATENT REQUIREMENTS A cellular mobile communication system having a number of radio base stations (BS) and a number of mobile stations (MS), said system comprising a number of cells which are arranged in at least two different locations or levels whereby handover can be made for mobile stations (MS) from a cell to another and further comprising means for monitoring or measuring at least one signal connection parameter for at least those cells which are not in the uppermost layer and where at least one threshold value (I ° ", If ') for said at least one signal parameter is given for at least each cell (Co, CÜ¿q_u_m) which is not in the top layer, the system further comprising control means for deciding and controlling handovers, characterized in that the cells are arranged in a hierarchical structure and that the control means comprise a device for priority ranking by which at least one base ranking and hierarchical cell evaluations are performed which are based on a number of criteria of which a first a criterion is based on a comparison of the current monitored value (IQ) of a signal parameter (I, & IN H_) for the serving cell with the given threshold value (I§ ') for the serving cell (CO) or the cell currently serves a given connection, and a second criterion based on a comparison of the current, monitored value (Ii) for a signal parameter for a neighboring cell with the given threshold value (If ') for the same neighboring cell (Ci) whereby via an organizing procedure using the results from at least the base ranking and the hierarchical cell evaluations, eg using tables, a candidate list is obtained which is used for channel allocation and / or cell selection in such a way that systematic control to or transition between cells or cell layers is obtained, also for transition up and down between cell layers, whereby control can take place to any layer. 505 '915 45' A system according to claim 1, characterized in that the first criterion used for deciding whether a handover from a cell in a lower hierarchical layer to a cell in a higher hierarchical layer shall be taken into account. 3. A system according to claim 2, characterized in that according to the first criterion a cell in a higher layer is selectable for handover if the current value of the monitored signal parameter value (Ia) for a serving cell (Co) is smaller than the threshold value (I ° ") and / or the threshold value (I °") modified with a hysteresis (HJ ') for that cell. A system according to claim 3, characterized in that a cell in a higher hierarchical layer is selectable for handover if the current value of the monitored signal parameter (IQ) is less than the threshold value minus a hysteresis (HJ '). A system according to any one of the preceding claims, characterized in that the second criterion used for deciding whether a handover from a higher hierarchical layer to a cell in a lower hierarchical layer is to be considered. System according to claim 5, characterized in that according to the second criterion a cell (Ci) in a lower hierarchical layer is selectable for handover if the current monitored value of the monitored signal parameter (I,) exceeds the threshold value (If ' ) for that cell and / or the threshold value (If ') modified by a hysteresis (Hf'). ' System according to claim 6, characterized in that the threshold value (ïff) is modified in such a way that a hysteresis (Hf ') is added thereto. System according to one of the preceding claims, characterized in that the cells (C °, Cä) are sorted into categories based on a number of sorting criteria. System according to claim 8, characterized in that a sorting criterion comprises normal location, ie the neighboring cells (Ci): are ranked in comparison with the serving cell (Co) such as if they are better or worse than this for at least one monitored signal parameter (In: IF1). A system according to any one of the preceding claims, characterized in that the cells (Ck) are sorted into categories based on criteria with respect to both the monitored signal parameter as compared with the monitored corresponding value of the serving cell (Co) and the monitored the value of a cell (Ci) as compared to the threshold value of the same cell (Ci). 11. ll. Systems according to any one of the preceding claims, characterized in that the cells are sorted into categories based on which layer they are in. 12. A system according to any one of claims 8-11, characterized in that the priority ranking device comprises a number of criteria relating to a number of conditions and that the cells are arranged in accordance with the sorting criteria depending on whether the conditions are met or not. 13. A system according to claim 12, .505 915 4É, characterized in that at least some of the conditions are s 1: alarm criteria such as, for example, alarms of poor quality, etc. A system according to any one of the preceding claims, characterized in that the priority ranking device comprises an organization table for cell categories which are sorted according to a number of criteria. A system according to claim 14, characterized in that the cells are sorted in the organization table into different categories which depend at least on the first and the second criterion and a number of conditions. 16. A system according to any one of the preceding claims, characterized in that the signal parameter is the signal strength. 17. A system according to any one of the preceding claims, characterized in that the signal parameter (s) is the tensile attenuation or both the road loss and the signal strength. A system according to any one of the preceding claims, characterized in that the cells are divided into two different layers. 19. A system according to any one of claims 1-17, characterized in that the cells are divided into three different layers, for example pico-cells, micro-cells and macro-cells. A system according to any one of claims 1-17, characterized in that the cells are divided into more than three layers. A system according to any one of the preceding claims, characterized in that the handover strategy used is the mobile-assisted handover strategy (MAHO). A system according to any one of the preceding claims, characterized in that a threshold value (I§ ', If') is given for cells also in the uppermost layer. 23. A system according to any one of the preceding claims, characterized in that interaction with other network functions is given a priority which gives the sorting order in the priority table for the system. System according to any one of the preceding claims, characterized in that for a special network-controlled function evaluation, a unique sequence of cell categories is assigned to said combination of evaluation results. A system according to any one of the preceding claims, characterized in that time division multiple access (TDMA) or frequency division multiple access (FDMA) or code division multiple access (CDMA) is applied. System according to any one of the preceding claims, characterized in that it is a telephone communication system. 27. A system according to any one of the preceding claims, characterized in that the GSM standard is used. 505 915 4? System according to any one of claims 1-26, characterized in that the ADC, PDC or DECT standard is used. 29. A system according to any one of claims 1-26, characterized in that it is an ISDN communication system. A method of performing handover between a mobile station and different cells in a cellular mobile communication system comprising a number of radio base stations and a number of mobile stations, the system comprising a number of cells which are arranged in at least two different layers or levels, the method comprising the following: step: - “introducing a threshold value for at least one signal parameter for the cell serving a given connection; introducing a threshold value for at least one signal parameter for at least each cell that is not in the top layer; monitoring said at least one signal parameter for the serving cell; monitoring said at least one signal parameter for a number of neighboring cells; - comparing the current monitored value of the signal parameter of the served cell with the threshold value of the serving cell; - comparison of the monitored value of the signal parameter of the neighboring cell with the threshold value of each cell; - use of the comparisons to provide a base ranking list, - performing hierarchical cell level evaluations comprising a level-oriented redistribution m.a.p. if cells are above / below the respective threshold, - performing an organizational procedure using a number of conditions, where said organizational procedure is for example 505 915 4% table controlled, to establish a cell candidate list, sending the cell candidate list to a call handling process s.a. channel allocation and / or cell selection takes place in accordance with the given ranking in such a way that systematic transitions between cell layers are also obtained for transition up and down or that control can take place to any layer.