Soft handoff method for a mobile radio communication system

The Invention relates to a cellular mobile radio communication system, in which a base station and a mobile station connected to one another are, and in particular a mobile radio communication system in which a soft Handover control with respect to a forward link (forward link) -Übertragungssignals accomplished is when a mobile station moves between cells. (Handover = Hand-off = Transfer).

In a cellular CDMA (Code Division Multiple Access) system with direct spread is to maximize the communication capacity for reverse link (reverse link) -Übertragungssignale usually a transmission power control of mobile stations is performed to a far-near problem to be avoided. For this purpose, a base station transmits in a downstream channel Transmission power control signals to the mobile station. On the other Side have a base station and a mobile station in a CDMA cellular system with direct spreading each multiple demodulators, So that the a separation of multipath components and a soft hand-over processing can make.

The soft hand-over processing is performed because, as shown in <figref idrefs="S23">5</figref> the accompanying drawings, in which movement of a mobile station <figref>303</figref> from a cell <figref>101</figref> to another cell <figref>102</figref> and arrival at a position in an overlapping region <figref>104</figref> in between the two cells <figref>101</figref> and <figref>102</figref> quality deterioration of the signal occurs, the mobile station <figref>103</figref> of a base station <figref>105a</figref> the cell <figref>101</figref> receives. On this manner, from the base station <figref>105a</figref> and a further base station <figref>105b</figref> the cell <figref>102</figref> essentially the same signals to the mobile station <figref>103</figref> sent, so that the mobile station <figref>103</figref> as soft hand-over processing, the signals from the two base stations <figref>105a</figref> and <figref>105b</figref> modulate and may be composed to obtain a signal with better signal quality. In the reverse link from the mobile station is a <figref>103</figref> transmitted Signal from the base stations <figref>105a</figref> and <figref>105b</figref> demodulates and assembled to improve the signal quality.

In this case, the transmission power control signals from the base stations <figref>105a</figref> and <figref>105b</figref> of the base stations <figref>105a</figref> or. <figref>105b</figref> each independently generated. namely, a transmission power control signal only from the base station <figref>105a</figref> to the mobile station <figref>103</figref> is sent and the mobile station <figref>103</figref> a Transmission power control is carried out, as described above, so that the base station <figref>105a</figref> the can receive signal at an optimum level and then to the controlled transmission power sends, there is a Ge-propelled that of the mobile station <figref>103</figref> Transmitted signal an unexpected may signal and a considerable disruption for the other base station <figref>105b</figref> represents. The mobile station <figref>103</figref> then demodulates the transmission power control signals from two base stations <figref>105a</figref> and <figref>105b</figref> independently and sets the demodulated transmission power control signals together. The mobile station <figref>103</figref> increases its transmit power only if for example, the transmission power control signals from both base stations <figref>105a</figref> and <figref>105b</figref> "UP" mean, however, lowers the mobile station <figref>103</figref> the transmit power if the transmission power control signal from at least one of the base stations <figref>105a</figref> or <figref>105b</figref> "DOWN" means. The mobile station<figref>103</figref> sends to the base stations <figref>105a</figref> and <figref>105b</figref> a reverse link signal with the appropriate transmission power by the transmission power control signals from the base stations <figref>105a</figref> and <figref>105b</figref> to this way independent receives from each other and demodulated.

how was described above, for a CDMA cellular system with direct spreading, the transmission power control a mobile station is an essential and necessary process. Furthermore must Interference in the cellular system as far as possible suppressed, the communication capacity of the The overall system to be maximized. To this end, in the cellular System a soft handover process performed. at this soft handover has the mobile station <figref>103</figref> a transmission power control by the Demodulating and assembling of different transmission power control signals from the two base stations <figref>105a</figref> and <figref>105b</figref> carry out.

If Now the threshold value of the communication quality with which soft hand-over to be started is set to a low level, the growing Number of mobile stations, the need to perform a soft handover, in uses the communication resource for multiple channels is. this leads to to the problem that the communications capacity the entire system decreases.

If however, the threshold value of the communication quality, the the handover is to be started is set to a higher level, can reduce the incidence Soft handoffs are apparently reduced because the probability becomes smaller, that the mobile station <figref>103</figref> is located in a region where carried out the hand-over must become. Thus, the communication capacity of the Gesamtsys&lt;?page 3?&gt;system be increased. It grows however, the risk that a Communication signal to the adjacent base station <figref>105b</figref> be disturbed can, and this leads to the problem that not only the capacity of the overall system is reduced due to the interference, but the stability affected the entire system is.

If the communication capacity the base station <figref>105b</figref> the handover target its limit has reached, when the mobile station <figref>103</figref> in the region is, in the handover accomplished is to be, will be no soft hand-Ovens, but a hard hand-over, by which the frequency channel is changed. If this In case of a reverse link a communication signal from the mobile station <figref>103</figref> in a Sending frequency channel used before the hard handover was leading This, to a significant unexpected interference of communication signals straight from the base station <figref>105b</figref> to be edited. Thus, the problem occurs that the Communication of other mobile stations is disturbed.

The Reference Ling, F. et al: "Behaviour and Performance of Power Controlled IS-95 reverse link under Soft Handover ", IEEE Vehicular Technology Conference, US, New York, IEEE, Conf. 47, 1997, Pages 924-928, describes a mobile communication system in which soft hand-over for transfers of the mobile is provided to the base stations.

<patcit><text>EP 0671819 A</text></patcit> describes a cellular mobile radio system having at least two base stations and at least one mobile unit, which is adapted to cooperate with the base stations a radio medium communicates with each base station means for Detecting the power of the received signals and means for Generating a power control signaling bits for the Controlling the amplitude of a power signal, means for transmitting having the power signal to the mobile unit; the mobile containing unit Means for receiving the power control bits, and means for monitoring the power control for the identification of the base station that a greater number control bits over a transmission frame sent, indicating that the base station, the higher average Power signal over has received the transmission frame; the mobile unit may then Upcoming addressed information frames to that base station that the higher average received power signal.

it is an object of the present invention to provide a mobile radio communication system to disposal provide to the maximum capacity ensuring the overall system, while carried out a soft handover is, and the transmission power of the mobile station in a suitable way controlled to ensure the security of the overall system.

Around To achieve this goal, according to the present invention, a The mobile radio communication system is provided, comprising: at least two adjacent base stations, a mobile station between formed by the base stations and connected with them, cells is movable with means for carrying out a transmission power control in such a way that at least with regard to a control signal a soft hand-off control accomplished is, wherein the mobile station and the base station simultaneously with each other are connected, and is characterized in that, in view on transmitted from the base stations information signals a hard carried out hand-off control is.

There each of the base stations for at least a forward link control signal a soft hand-over control carrying out to the base stations simultaneously to the mobile station to connect while for the to the mobile station transmitted information signals a hard hand-over control accomplished , when in the mobile radio communication system, a handover processing accomplished to be, the communication capacity of the entire system will be compared increased to the alternate system, wherein which the base station for both the forward link control signal and the information signal etc. represents the language and not the forward link control signal, a soft hand-over control performs. Because in the mobile radio communication system further comprises at least a forward link control signal is sent to the mobile station, the stability the entire system can be maintained. Since in the mobile radio communication system the base station of the handover destination even if the communication capacity of the entire system is accessed, for performing the soft handover processing only a forward link control signal sends to the mobile station, to a possible interference in the other to minimize compounds prevents the handover destination a downlink signal with unexpectedly Transmission power receives, So that the increased security of the system can be.

&lt;?page 4?&gt;

in the following the invention with reference to the accompanying Drawings, in which like parts or elements throughout with same reference numerals, exemplified.

<figref idrefs="S19">1A</figref> shows a schematic view illustrating a forward link signal, the sent from a first base station to a mobile station is, when the mobile station is located in a first region,

<figref idrefs="S19">1B</figref> shows a similar View but illustrating forward link signals to that of first base station and from a second base station to the mobile station be sent when the mobile station is in an overlap region is,

<figref idrefs="S19">1C</figref> shows a similar View but illustrating a forward link signal transmitted from the second base station is sent to the mobile station when the mobile station is in a second region,

<figref idrefs="S20">2</figref> shows a diagram illustrating the reception powers of the first and second Base station illustrated, when the mobile station from the first region in the overlap region and then moved to the second region,

<figref idrefs="S21">3A</figref> shows a schematic view illustrating a forward link signal, transmitted from the first base station to the mobile station, when the mobile station is located in the first region,

<figref idrefs="S21">3B</figref> shows a similar View but illustrating forward link signals to that of first and sent to the second base station to the mobile station , when the mobile station is located in the overlap region and the number associated with the second base station mobile stations is equal to or greater than a threshold value Nth,

<figref idrefs="S21">3C</figref> shows a similar View but illustrating forward link signals to that of Sending the first and second base stations to the mobile station , when the mobile station is located in the overlap region and the number associated with the second base station mobile stations equal to or smaller than the threshold value Nth,

<figref idrefs="S21">3D</figref> shows a similar View but illustrating a forward link signal transmitted from the second base station is sent to the mobile station when the mobile station is located in the second region,

<figref idrefs="S22">4A</figref> shows a diagram illustrating a forward link signal transmitted from the second base station is sent to the mobile station when only for a control signal soft handover is carried out,

<figref idrefs="S22">4B</figref> shows a similar View but illustrating a forward link signal in accordance with the IS-95 system according to the prior art of the second base station is sent to the mobile station,

<figref idrefs="S22">4C</figref> shows a similar View but illustrating a forward link signal transmitted from the second base station is sent to the mobile station and its Transmission power is increased, if soft handover only carried out a control signal becomes,

<figref idrefs="S23">5</figref> shows a schematic view in the handover processing a cellular system according to the prior art is illustrated.

in the following are based on the drawings Embodiments of the present Invention explained.

first let on <figref idrefs="S19">1A</figref> to <figref idrefs="S19">1C</figref> reference which illustrate a mobile radio communication system to which The present invention is applied. The mobile radio communication system<figref>1</figref> is a cellular system, the plurality of base stations <figref>2</figref> (<figref>2a</figref> and <figref>2 B</figref>) and multiple mobile stations <figref>3</figref> interconnected by a CDMA (Code Division Multiple Access) system with direct -Sy spread together are connected. In the present embodiment, for simplification of description, only the relationship between the first base station <figref>2a</figref>. a mobile station <figref>3</figref> and the second base station <figref>2 B</figref> explained.

If the mobile station <figref>3</figref> in a first region <figref>4</figref> is, as in <figref idrefs="S19">1A</figref> is shown, communicates the first base station <figref>2a</figref> by a reverse link signal and a forward link signal with the mobile&lt;?page 5?&gt;station <figref>3</figref>, The first base station <figref>2a</figref> sends to the mobile station <figref>3</figref> on Forward link signal including a control signal, such as a transmission power control signal for the mobile station <figref>3</figref> etc. includes, as well as an information signal, eg voice data.

Similar to the first base station <figref>2a</figref> also communicates the second base station <figref>2 B</figref> by a reverse link signal and a forward link signal with the mobile station <figref>3</figref>When the mobile station <figref>3</figref> themselves in a second region <figref>5</figref> is.

On Transmit power controlling signal is a signal for adaptively change the transmit power level of a reverse link signal, so that the mobile station <figref>3</figref> the Reverse link signal with the appropriate power level to the first base station <figref>2a</figref> or to the second base station <figref>2 B</figref> send can.

If the mobile station <figref>3</figref> in the first region <figref>4</figref> is, as in <figref idrefs="S19">1A</figref> is shown, it receives from the first base station <figref>2a</figref> a forward link signal and transmits to the first base station <figref>2a</figref> a reverse link signal. The transmission power of the mobile station <figref>3</figref> in this case, as from section A of <figref idrefs="S20">2</figref> appreciated selected, that the Reception power of the forward link signal from the first base station<figref>2a</figref> equal or higher is defined as a threshold value a and the reception power of forward link signal from the second base station <figref>2 B</figref> is equal to or less than another threshold value b. Therefore receives and demodulates the mobile station<figref>3</figref> just the forward link signal from the first base station <figref>2a</figref>,

If the mobile station <figref>3</figref> by contrast from the first region <figref>4</figref> to the second region <figref>5</figref> and moved to a position in an overlapping region <figref>6</figref> in between the first region <figref>4</figref> and the second region <figref>5</figref> passes, as in <figref idrefs="S19">1B</figref> is shown, a Handover is required, and there is a soft hand-over state set up in which both the first base station <figref>2a</figref> as and the second base station <figref>2 B</figref> send forward link signals. In this case, the reception power of the mobile station reaches <figref>3</figref> from the second base station <figref>2 B</figref> in time t1 the threshold b, as shown in region B of <figref idrefs="S20">2</figref> illustrated is. The mobile station<figref>3</figref> then receives the forward link signals both the first base station <figref>2a</figref> as well as from the second base station <figref>2 B</figref>, When the mobile station<figref>3</figref> themselves further from the first base station <figref>2a</figref> to the second base station <figref>2 B</figref> emotional, is the reception power of the forward link signal from the second base station <figref>2 B</figref> soon greater than the Emp catching performance of the forward link signal from the first base station <figref>2a</figref>. and at the time t2, the reception power from the first base station <figref>2a</figref> the other threshold a. Then receives the mobile station <figref>3</figref> the forward link signal from the first base station <figref>2a</figref> not more, it receives rather, the forward link signal from the second base station <figref>2 B</figref>, In other words, in the region B, in which the time from T1 to t2 moves, the mobile station proceeds <figref>3</figref> in a soft handover state over, in the the forward link signal to both the first base station <figref>2a</figref> as and the second base station <figref>2 B</figref> receives and demodulates.

If the mobile station <figref>3</figref> then from the overlap region <figref>6</figref> continue in the second region <figref>5</figref> moved and in the second region <figref>5</figref> is, as in <figref idrefs="S19">1C</figref> is shown, receives the mobile station <figref>3</figref> the forward link signal from the second base station <figref>2 B</figref> and sends its reverse link signal to the second base station <figref>2 B</figref>, Since the mobile station<figref>3</figref> themselves in this case, as described above, from the first base station <figref>2a</figref> to the second base station <figref>2 B</figref> moves, the received power changes the mobile station <figref>3</figref> in such a way that the reception power of the Forward link signal from the second base station <figref>2 B</figref> equal or greater than the threshold value b while the reception power of the forward link signal from the first base station <figref>2a</figref> equal or is less than the threshold a. Therefore, receives and demodulates the mobile station <figref>3</figref> only the forward link signal from the second base station <figref>2 B</figref>,

it Note that the The mobile radio communication system <figref>1</figref> Alternatively, another System (Mobile Assisted Hand Off: MAHO) could use in the when the mobile station <figref>3</figref> from the first region <figref>4</figref> in the overlap region <figref>6</figref> emotional, the part of the mobile station <figref>3</figref> an instruction for entering the hand-over processing is output, or still another System in which from the side of base station <figref>2</figref> an instruction for the Entering is output in a hand-over state. For the process of transition from a normal state in which the mobile station <figref>3</figref> With the first base station <figref>2a</figref> and with the second base station <figref>2 B</figref> connected is, in a hand-over state, therefore, any system to be used. The mobile radio communication system<figref>1</figref> can also for the process of transition from a hand-over state in a normal state of any use system.

in the Hereinafter, an example for different handover processes describes the response to various types of signals accomplished be, when a mobile station located sequentially from the first region <figref>4</figref> in the overlap region <figref>6</figref> and in the second region <figref>5</figref> moved, as described above with reference &lt;?page 6?&gt;from <figref idrefs="S19">1A</figref>. <figref idrefs="S19">1B</figref> and <figref idrefs="S19">1C</figref> described has been. It is to be noted that in the following description handover processes for informa tion signal and a control signal, particularly a transmission power control signal, to be discribed.

If the mobile station <figref>3</figref> in the first region <figref>4</figref> is, as in <figref idrefs="S19">1A</figref> is shown, it receives from the first base station <figref>2a</figref> a transmission power control signal as a forward link control signal and an information signal. The mobile station <figref>3</figref> demodulates the received transmission power control signal and the information signal. On the basis of the demodulation derived transmission power control signal controls the mobile station <figref>3</figref> your Transmit power at which a reverse link signal to the first base station <figref>2a</figref> Posted shall be.

If the mobile station <figref>3</figref> in the overlap region <figref>6</figref> is, as in <figref idrefs="S19">1B</figref> is shown, it enters in a hand-over mode, in which both the first base station <figref>2a</figref> as and the second base station <figref>2 B</figref> Forward link signals substantially the same content to the mobile station <figref>3</figref> send. In this case, sends the first base station <figref>2a</figref> both a transmission power control signal and an information signal to the mobile station <figref>3</figref>, While the second base station <figref>2 B</figref> just a transmission power control signal sends. In other words, in the overlapping region<figref>6</figref> is the mobile station <figref>3</figref> in a soft hand-over state, in which it regards a transmission power control signal with the first base station <figref>2a</figref> and with the second base station <figref>2 B</figref> connected is. Thus receives and demodulates the mobile station <figref>3</figref> the transmission power control signal and the information signal from the first base station <figref>2a</figref> Posted be, as well as the second of the base station <figref>2 B</figref> sent Transmission power control signal separately. When the mobile station<figref>3</figref> the from the first base station <figref>2a</figref> transmitted transmission power control signal and that of the second base station <figref>2 B</figref> transmitted transmission power control signal receives, it compares the contents of the first of the base station <figref>2a</figref> and the second base station <figref>2 B</figref> received transmission power control signals with each other and laying on the basis of the comparison result executed Operation firmly. shall regard the transmission power control signal the mobile station <figref>3</figref> an operation fixed, on the basis the result of a combination of the control signal from the first base station <figref>2a</figref> and the transmission power control signal from the second base station <figref>2 B</figref> conduct is.

Usually controls the base station <figref>3</figref> the transmit power of reverse link signal to the first base station <figref>2a</figref> or to the second base station <figref>2 B</figref> Posted is to be, in such a manner that they the transmit power of reverse link signal only increased when both the first of the base station <figref>2a</figref> transmitted transmission power control signal and the second of the base station <figref>2 B</figref> sent Transmission power control signal "UP" mean, otherwise, reserves the mobile station <figref>3</figref> the transmission power of the first to the base station <figref>2a</figref> or the second base station <figref>2 B</figref> to transmitting reverse link signal at or reduced. It's closed Note that the Transmission power in accordance with a system can be controlled with the IS-95 of Qualcomm is compliant if the transmission power control signals in other combinations or in a different combination where a plurality of base stations and mobile stations <figref>3</figref> are available to the mobile station <figref>3</figref> Posted be.

it Note that the mobile station <figref>3</figref> with respect to another control signal as a transmission power control signal, the first from the base station <figref>2a</figref> and the second base station <figref>2 B</figref> demodulates the transmitted control signals and that of the modulated signals applied, which has a higher reception power. If the transmitted forward link signal error correction code included, should this simply the amplitude values ​​of the forward link signals are added together and supplied to a soft decision decoder. By these operations, the mobile station <figref>3</figref> the error rate of the control signals decrease, and the response performance to a first of the base station <figref>2a</figref> or the second base station <figref>2 B</figref> increase given instruction.

The mobile station <figref>3</figref> is in the overlap region <figref>6</figref> from a handover state in a normal state when they result from the overlap region <figref>6</figref> in the second region <figref>5</figref> moved as shown in <figref idrefs="S19">1C</figref> illustrated is. Then sends the second base station<figref>2 B</figref> a forward link signal to the mobile station <figref>3</figref>Which is a transmission power control signal and contains an information signal. Similar to in the case described above, in which the mobile station <figref>3</figref> themselves in the first region <figref>4</figref> located, receives and demodulates the mobile station <figref>3</figref> then the forward link signal and controls on the basis of the transmission power control signal the transmit power at which a reverse link signal to the second base station <figref>2 B</figref> should be sent.

how has been described above, in the present mobile radio communication system <figref>1</figref> both from the first base station <figref>2a</figref> as well as from the second base station <figref>2 B</figref> Transmission power control signals to mobile station <figref>3</figref> Posted, when the mobile station <figref>3</figref> in the overlap region <figref>6</figref> is and to be placed in a hand-over state. Consequently takes the mobile station <figref>3</figref> in a soft handover Sta&lt;?page 7?&gt;tus a to the transmission power on the basis of a combination of the control signals from the two base stations <figref>2</figref> control. On the other Page takes the mobile station <figref>3</figref> with respect to an information signal with voice information, etc. in a hard handover status, in which they are an information signal from only one of the base stations receives.

If the mobile station <figref>3</figref> in the mobile radio communication system <figref>1</figref> themselves is in a hand-over state, it is guided in a soft handover state in which only one of the base stations <figref>2</figref> on Information signal to the mobile station <figref>3</figref> sends and both base stations <figref>2</figref> Send transmission power control signals. in the Comparison with an alternative system wherein a soft hand-over state is established by information signals and transmission power control signals separated from both base stations <figref>2</figref> Posted are, therefore, a possible Interference with the other mobile stations <figref>3</figref> in the system be reduced because of a plurality of base stations <figref>2</figref> information signals to the mobile station <figref>3</figref> be sent. Since in the mobile radio communication system<figref>1</figref> control signals from multiple base stations to the mobile station <figref>3</figref> Posted , when the mobile station <figref>3</figref> in a hand-over state is, the reliability of the control signals in comparison with a system in which in the overlap region carried out a hard handover will be improved. Specifically, with regard to a transmission power control signal It is also possible, the transmission power of the mobile station <figref>3</figref> of the second base station <figref>2 B</figref> from to control, since the mobile station <figref>3</figref> located in a soft Hand-over state is located, and it can be prevented that a reverse link signal from the mobile station <figref>3</figref> is sent with a transmission power, of the second base station <figref>2 B</figref> are not anticipated can.

If the mobile station <figref>3</figref> in the overlap region <figref>6</figref> of Mobile radio communication system <figref>1</figref> is, the communication capacity of the entire system be enlarged Since the mobile station <figref>3</figref> for the Control signal in a soft hand-over state for the information signal, however, is placed in a hard handover status. Even if, for example, the communication capacity the second base station <figref>2 B</figref> the mobile radio communication system is accessed, can in the transmission an information signal or a control signal, the influence on the other mobile stations <figref>3</figref> be reduced because of the second base station <figref>2 B</figref> just a transmission power control signal to the mobile station <figref>3</figref> Posted must become. Therefore, in the present mobile radio communication system <figref>1</figref> a With interference from the second base station <figref>2 B</figref> transmitted suppresses signals are, and when the mobile station <figref>3</figref> be first of region <figref>4</figref> in the second region <figref>5</figref> moves, a performed hard handover are such that between the second base station <figref>2 B</figref> and the mobile station <figref>3</figref> on transmitted information signal is where, ultimately, a frequency channel is used, the by itself that in the first region <figref>4</figref> used frequency channel differs.

in the An example is described in which the first base station <figref>2a</figref> and the second base station <figref>2 B</figref> have a threshold, as it is shown in Table 1.

table 1 <img img-content="tb" img-format="tif" he="72" wi="134" file="00110001.tif" />

These Table 1 is for example stored in memories in the first base station <figref>2a</figref> and the second base station <figref>2 B</figref> are incorporated, and is, for example, is read by a CPU so that the CPU processing to perform on the basis of the threshold. Table 1 shows an example of the &lt;?page 8?&gt;Handover processing the base station <figref>2a</figref> or base station <figref>2 B</figref> for the mobile station <figref>3</figref>. located in the overlap region <figref>6</figref> is, when the number of connected mobile stations <figref>3</figref> as a threshold Nth is stored.

If the number of the second with the base station <figref>2 B</figref> associated mobile stations <figref>3</figref> reaches a peak Nfull, is the mobile station <figref>3</figref>That in the overlap region <figref>6</figref> in between the first base station <figref>2a</figref> and the second base station <figref>2 B</figref> is, accordance with Table 1 with regard to a transmission power control signal in a soft Hand-over state added. With regard to an information signal on the other hand a hard handover is performed, wherein a frequency channel is used, which is different from that of the first base station <figref>2a</figref> differs.

If the number of the second with the base station <figref>2 B</figref> associated Mobile stations within the range between the peak Nfull and the threshold value Nth is, the mobile station is <figref>3</figref>. resulting in the overlap region <figref>6</figref> in between the first base station <figref>2a</figref> and the second base station <figref>2 B</figref> is, only with regard to a transmission power control signal in a soft Hand-over state added. On the other hand sends the second base station <figref>2 B</figref> no information signal to the mobile station <figref>3</figref>,

If the number of the second with the base station <figref>2 B</figref> associated Mobile stations smaller than the threshold value Nth and the communication capacity of the second base station <figref>2 B</figref> consequently substantial free Share, is in the overlap region <figref>6</figref> lie lowing mobile station <figref>3</figref> both in terms of the transmit power controlling signal and in terms of the information signal in a soft handover state added.

it If now the operation of the first base station <figref>2a</figref> and the second base station <figref>2 B</figref> described for the case that both in the first base station <figref>2a</figref> and in the second base station <figref>2 B</figref> the Threshold Nth is stored and a particular mobile station <figref>3</figref> themselves of the first region <figref>4</figref> in the second region <figref>5</figref> emotional.

If the mobile station <figref>3</figref> initially in the first region <figref>4</figref> is, sends only the first base station <figref>2a</figref> a control signal and an information signal to the mobile station <figref>3</figref>, like this in <figref idrefs="S21">3A</figref> is shown.

If the mobile station <figref>3</figref> then in the direction of the second base station <figref>2 B</figref> emotional is and in the overlap region <figref>6</figref> is, leads the second base station <figref>2 B</figref> a handover processing according to the in Table 1 above held threshold Nth through. especially when in the second region <figref>5</figref> the number of the second with the base station <figref>2 B</figref> connected mobile stations <figref>3</figref> is greater than the threshold value Nth, the second base station offset <figref>2 B</figref> the mobile station <figref>3</figref> with respect to a control signal in a soft hand-over state, while it mobile station <figref>3</figref> with respect to an information signal placed in a hard handover state by only one of the base stations <figref>2</figref> a signal is sent, as shown in <figref idrefs="S21">3B</figref> illustrated is. The mobile station<figref>3</figref> in particular as regards a transmission power control signal preferably in a soft Hand-over state added.

If in the second region <figref>5</figref> the number of the second with the base station <figref>2 B</figref> associated mobile stations <figref>3</figref> equal to or smaller than the threshold value Nth, the second base station transmits <figref>2 B</figref> a control signal and an information signal to the mobile station <figref>3</figref>, to the mobile station <figref>3</figref> both in terms of the control signal as well as in terms of the information signal in a soft handover state bring to. If the number of the second with the base station<figref>2 B</figref> associated mobile stations <figref>3</figref> is greater as the Nth threshold, the operation returns to that for the above described accompanying Case back, that the exceeded threshold Nth is.

If the mobile station <figref>3</figref> then from the overlap region <figref>6</figref> in the second region <figref>5</figref> moved, sends the second base station <figref>2 B</figref> on Control signal and an information signal to the base station <figref>3</figref>. as in <figref idrefs="S21">3D</figref> is shown.

On this manner, in the mobile radio communication system <figref>1</figref> a soft handover processing both in terms of a control signal and with respect to a carried infor onssignals when the communication capacities of both Base stations have free areas, so that a high communication quality guaranteed can be.

If for the Threshold Nth is prepared only one value, the The mobile radio communication system <figref>1</figref> the soft handover processing and the hard handover processing terms In a&lt;?page 9?&gt;formation signal repeat if necessary. However, it may for example, be provided a hysteresis so that it is prevented that a soft Handover processing repeated and a hard handover processing in changing quickly be.

in the An example is described in which the first base station <figref>2a</figref> and the second base station <figref>2 B</figref> have a threshold, as illustrated in Table 2 below.

table 2 <img img-content="tb" img-format="tif" he="67" wi="133" file="00130001.tif" />

These Table 2 is similar to example as Table 1 described above in the first in the base station <figref>2a</figref> and in the second base station <figref>2 B</figref> stored built-storing and is for example read by a CPU so that the CPU may perform processing based on the threshold.

The Table 2 shows an example of a handover processing in a base station for the mobile station <figref>3</figref>. resulting in the overlap region <figref>6</figref> is, if the value Qth stored as a threshold value for the communication quality is. communication quality here means the communication quality of all communications, of those base stations <figref>2</figref> is carried out, the for a particular mobile station <figref>3</figref> perform a handover processing.

If a particular base station <figref>2 B</figref> Notes that the communication quality of the poorest Qworst has, it enables the mobile station <figref>3</figref>Which in itself the overlap region <figref>6</figref> With another base station is located, according to the Table 2 only with respect to the transmission power control signal in a soft Handover status. With respect to the information signal leads second base station <figref>2 B</figref> a hard handover processing by where they used a channel having a frequency different differs from the frequency of the first base station <figref>2a</figref> used was to which the mobile station <figref>3</figref> previously belonged.

If the second base station <figref>2 B</figref> Notes that the communication quality within a range between the poorest and the threshold Qworst Qth is, it enables the mobile station <figref>3</figref>Which in itself the overlap region <figref>6</figref> With the first base station <figref>2a</figref> is, in respect of the Transmission power control signal in a soft handover state. however sends the second base station <figref>2 B</figref> no information signal to the mobile station <figref>3</figref>,

If the second base station <figref>2 B</figref> Notes that the communication quality lower than the threshold value Qth, they are added in the overlap region <figref>6</figref> lying mobile station <figref>3</figref> both in terms of the transmit power controlling signal and with regard to the information signal in a soft hand-over state.

There the mobile radio communication system <figref>1</figref> in this way the Threshold Qth for the communication quality holds, can the Characteristics of the entire system, ie, both the stability and the communication quality of the system can be improved. It should be noted that the mobile radio communication system<figref>1</figref> a Threshold Qth for the communication quality all base stations <figref>2</figref> may have that the handover processing carry out, and upward beyond thresholds the communication quality, such as the S / N ratios of the of the individual base stations <figref>2</figref> transmitted and received Signals.

&lt;?page 10?&gt;

There in the present mobile radio communication system <figref>1</figref> in the base stations <figref>2</figref> a threshold for the number of connected Mobile stations or for the communication quality is stored, and, even if the communication capacity of the system is accessed, to each mobile station <figref>3</figref> at least one Transmission power control signal can be sent, the second base station <figref>2 B</figref> of the handover destination, a transmission power control signal Send, and the second base station <figref>2 B</figref> receives from the mobile station <figref>3</figref> no signal with unexpected transmission power. In other words, if in the present mobile radio communication system <figref>1</figref> a mobile station <figref>3</figref> for example, from the first region <figref>4</figref> in the second region <figref>5</figref> moves, the second base station <figref>2 B</figref> on Transmission power control signal to the mobile station <figref>3</figref> send, when the mobile station <figref>3</figref> in the overlap region <figref>6</figref> is, even if the communication capacity of the second base station <figref>2 B</figref> full is used. As a result, it can be prevented that the level of the transmission power from the mobile station <figref>3</figref> is so high that it with one of the second base station <figref>2 B</figref> transmitted communication signal interferes and accordingly, the communication of the mobile station <figref>3</figref> optimized be. In addition, the second base station <figref>2 B</figref> then also an information signal with the appropriate transmission power of the mobile station <figref>3</figref> receive, when the mobile station <figref>3</figref> from the overlap region <figref>6</figref> in the second region <figref>5</figref> emotional.

While in the above-described mobile radio communication system <figref>1</figref> a Handover processing accomplished is by adding to the in the overlapping region <figref>6</figref> arranged mobile station <figref>3</figref> only one control signal is sent, such as this in <figref idrefs="S22">4A</figref> is shown, the Transmission power of a control signal to the mobile station <figref>3</figref> Posted is to be compared with the in <figref idrefs="S22">4B</figref> illustrated Case in which both a control signal and an information signal to the mobile station <figref>3</figref> is sent, be as high as this in <figref idrefs="S22">4C</figref> is shown. In which present mobile radio communication system <figref>1</figref> is particularly the transmission power of a transmission power control signal in a control signal increased.

On Thus, the reception error rate of a transmission power control signal the mobile station <figref>3</figref> by increasing the transmission power of a Control signal such as a transmission power control signal can be reduced, when a mobile station <figref>3</figref> only with regard to the control signal is set in a soft handover state. Therefore, in the mobile radio communication system <figref>1</figref> the stability of the overall system elevated , although the communication capacity of the transmission power by increasing the Transmission power control signal is reduced slightly. Even when the transmission power of the transmission power control signal is increased, may in the present mobile radio communication system <figref>1</figref> a Interference can be suppressed with another signal in the entire system, since a soft hand-over processing only with respect to the control signal accomplished , while with respect to the information signal a hard handover processing accomplished , even if the transmission power is increased.

foregoing was a preferred embodiment of the invention using specific terms described. This description is illustrative only, and it is understood that variations and variations can be made without thereby the following by the claims defined scope of the invention.