CA2281578A1 - Method of assigning and selecting radio channel - Google Patents
Method of assigning and selecting radio channel Download PDFInfo
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- CA2281578A1 CA2281578A1 CA002281578A CA2281578A CA2281578A1 CA 2281578 A1 CA2281578 A1 CA 2281578A1 CA 002281578 A CA002281578 A CA 002281578A CA 2281578 A CA2281578 A CA 2281578A CA 2281578 A1 CA2281578 A1 CA 2281578A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
- H04W16/06—Hybrid resource partitioning, e.g. channel borrowing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
- H04W16/12—Fixed resource partitioning
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/02—Selection of wireless resources by user or terminal
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/04—Wireless resource allocation
- H04W72/044—Wireless resource allocation based on the type of the allocated resource
- H04W72/0453—Resources in frequency domain, e.g. a carrier in FDMA
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W76/00—Connection management
- H04W76/10—Connection setup
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
A method of assigning a plurality of radio channels to realize a radio mobile communication system in which a plurality of radio channels are simultaneously used in each of a plurality of zones (1-7) that form an area (8) where radio channels are repeatedly reused. At least one of the radio channels is assigned for preferential use in each zone, while the other channels are assigned for use in any adjacent zones. A mobile station (10) selects a first radio channel at a frequency (f1) that has been assigned to a visited zone (1). The mobile station then detects unused radio channels at different frequencies (f2-f7) assigned to adjacent zones to select one as a second channel, informs the base station in the visited zone (1) of the selected channels, and uses the radio channels to establish the connection to the base station of the visited zone (1).
Description
DESCRIPTION
TITLE OF THE INVENTION
RADIO CHANNEL ASSIGNMENT AND SELECTION METHOD
TECHNICAL FIELD
The present invention relates to a radio channel 1o assignment method and an assigned radio channel selection method, which are applied to a mobile radio communications system employing simultaneous multiple radio channels.
BACKGROUND ART
In order to improve the frequency utilization efficiency of a mobile radio communications system, some radio channel assignment methods of the mobile radio communications system have been researched up 2o to now: a method of fixedly assigning radio channels to each zone (Fixed Channel Assignment: FCA); and a method of dynamically assigning radio channels to a plurality of zones (Dynamic Channel Assignment: DCA) are known. In addition, a radio channel assignment method of simultaneously using the two methods are proposed.
The FCA has already come into practice in the mobile communications system: an analog NTT system and a digital mobile communications method (personal digital cellular : PDC ) are typical examples . As for the DCA, it has been put to practical use in a digital cordless form until now.
In such an FCA mobile communications system, a radio channel is conventionally established between a base station and a mobile station by selecting an 1o idle radio channel from among radio channels assigned to the base station in the zone visited by the mobile station, thereby setting up a mobile radio channel with that radio channel. Although the radio channels assigned to each base station are decided such that interference with the other base stations does not exceed a predetermined cochannel interference level, it is mainly assumed that only a single channel is used in the mobile radio communications system.
In contrast with this, a mobile radio 2o communications method has emerged recently which assigns multiple radio channels to a mobile station.
In the communications system that employs the multiple radio channels, a mobile station uses two or more channels assigned to the base station in the zone (visited zone) that the mobile station is present so as to implement high-speed or high-quality transmission.
This method, however, is essentially the same as the radio channel assignment method within a cluster of cells in that although it employs multiple channels, it only utilizes radio channels assigned to the visited zone to be used precedently.
Thus , as compared with the method of using a single radio channel, the method of using simultaneous multiple channels has a problem of reducing the total 1o frequency utilization efficiency (a product of the utilization efficiency on the frequency axis and the utilization efficiency on the spatial axis).
Therefore, an object of the present invention is to provide a radio channel assignment and selection method without involving degradation in the total frequency utilization efficiency as compared with the method of using the single radio channel, even if a mobile station employs multiple radio channels simultaneously.
DISCLOSURE OF THE INVENTION
To achieve the object, in a first aspect of the present invention, there is provided a radio channel assignment method which is associated with a plurality of zones constituting a cluster based on frequency reuse of radio channels , in order to implement a mobile radio communications system by employing multiple radio channels in each one of the plurality of zones , the radio channel assignment method comprising the steps of assigning to at least one of the multiple radio channels a radio channel over which the one of the plurality of zones itself has priority; and assigning to a remainder of the multiple radio channels a radio channel available in a zone adjacent 1o to the one of the plurality of zones.
By thus assigning the radio channel in the mobile ratio communications system, a radio channels over which the visited zone has priority can be assigned to at least one of the multiple radio channels the mobile station uses simultaneously, and an idle radio channel selected from radio channels precedently available in zones adjacent to the visited zone can be used as the remainder of the multiple radio channels.
2o This makes it possible to prevent reduction in the frequency utilization efficiency in the cluster in spite of the simultaneous use of the multiple radio channels.
The radio channel assignment method in accordance with the present invention can be applied independently of whether the radio channels are established bythe frequency division multiple access, time division multiple access or code division multiple access, or by any combination of them.
If the transmission quality is degraded because of cochannel interference during the use of the radio channel over which an adjacent zone has priority, the mobile device can utilize an idle radio channel over which another zone has priority by carrying out handover to that idle radio channel. This enables a 1o continuous use of the multiple channels.
In a second aspect of the present invention, there is provided a radio channel selection method which is carried out by a mobile station visiting one of a plurality of zones constituting a cluster for frequency reuse of radio channels, in order to implement a mobile radio communications system by employingsimultaneousmultiple radio channels in each one of the plurality of zones, the radio channel selection method comprising the steps of:
2o selecting at least one of the multiple radio channels from radio channels assigned to the zone visited by the mobile station; and selecting a remainder of the multiple radio channels from radio channels assigned to a plurality of zones adjacent to the zone visited by the mobile station, and using the selected radio channel in the VlSl.ted zone .
Here, the radio channel selection method as claimed in claim 9, wherein selection of the radio channel of one of the adjacent zones by the mobile station may comprise the steps of:
detecting a received level of a radio channel in the adjacent zones;
measuring cochannel interference from the received level detected;
Zo comparing the received level detected with a predetermined level;
setting up the radio channel as a radio channel between the mobile station and a base station in the visited zone when the received level compared is less than the predetermined level; and selecting another radio channel of the adjacent zones by returning to the step ( 1 ) when the received level compared is greater than the predetermined level.
The radio channel selection method as claimed in 2o claim 10 , wherein the selection of the radio channel of one of the adjacent zones by the mobile station may further comprise the step of:
controlling transmission power of the base station and mobile station connected to the radio channel setup between the visited zone base station and the mobile station such that the transmission power approach a predetermined receiving sensitivity.
The radio channel selection method as claimed in any one of claims 9-12, wherein the mobile station that implements the radio channel selection method may be a mobile device.
The radio channel assignment method and selection method in accordance with the present invention have the following advantages of:
(1) Improving the frequency utilization efficiency 1o as compared with the conventional radio channel assignment method in the mobile communications employing multiple radio channels;
(2) Enabling high speed transmission;
(3) Applicable to an existing mobile radio communications method using a single carrier; and (4) Applicable to an existing mobile station by a simple expansion of channel control of the existing mobile station.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagram showing a radio zone configuration for illustrating a radio channel assignment method in accordance with the present invention;
Fig. 2 is a diagram showing a zone configuration simplifying the embodiment in Fig. 1;
Fig. 3 is a~diagram illustrating the relationship between Figs. 3A and 3B;
Figs. 3A and 3B are block diagrams showing a configuration of a mobile station associated with the radio channel assignment in accordance with the present invention;
Fig. 4 is a flowchart illustrating a selection processing by the mobile station for explaining the radio channel selection method in accordance with the 1o present invention;
Fig. 5 is a flowchart illustrating remaining steps of the selection method of Fig. 4;
Figs. 6A and 6B are diagrams illustrating the application of the radio channel assignment to frequency division multiple access;
Figs. 7A and 7B are diagrams illustrating the application of the radio channel assignment to time division multiple access;
Figs. 8A and 8B are diagrams illustrating the 2o application of the radio channel assignment to code division multiple access;
Figs . 9A and 9B are diagrams illustrating a method of carrying out the radio channel assignment by simultaneous use of the frequency division multiple access and time division multiple access;
Figs. 10A and 10B are diagrams illustrating a _8_ method of carrying out the radio channel assignment by simultaneous use of the time division multiple access and code division multiple access;
Figs. 11A and 11B are diagrams illustrating a method of carrying out the radio channel assignment by simultaneous use of the code division multiple access and frequency division multiple access; and Figs. 12A and 12B are diagrams illustrating a method of carrying out the radio channel assignment 1o by simultaneous use of the frequency division multiple access, time division multiple access and code division multiple access.
BEST MODE FOR CARRYING OUT THE INVENTION
The radio channel assignment in accordance with invention will now be described with reference to the accompanying drawings from the following point of view: a method of assigning channels by dividing them into channels over which the current zone has priority, 2o and channels over which the other zones have priority;
and a method for a visitor mobile station to select multiple channels from among a plurality of channels assigned to individual zones in accordance with the present invention.
Fig . 1, relating to the radio channel assignment , shows a switching center 108 , base stations ( 101-107 ) _ g _ connected the switching center, and interconnection between switching centers, in which the switching center 108 functions as a regional center of a cluster 100 consisting of seven zones each including its own base station.
In Fig . 1, the switching center 108 is connected with the base stations (101-107) in the individual zones through dedicated lines 109 consisting of common communications channels. In the radio channel to assignment method in accordance with the present invention, the switching center 108 instructs the base stations ( 101-107 ) of available radio channel numbers through the dedicated lines 109 according to a predetermined radio channel assignment scheme.
Fig. 1 illustrates a case in which the radio channels are assigned by frequency division multiple access (FDMA).
For example, in an 800 MHz band FDMA system with 60 radio channels, the radio channel numbers assigned 2o to respective zones are as shown in table 1, in which the radio channels each have a 25 kHz bandwidth with a frequency interval of 50 kHz. For example, if the radio channel No. 1 is assigned to 800.050 MHz, the radio channel No. 60 becomes 803.000 MHz.
Table 1 Base station Assigned radio channel numbers numbers 1 1, 2, 4, 5 3, 2 10,11, 12, 13,14, 15,16, 17,18, 19, 20 3 30,31, 32, 33,34, 35,36, 37 4 6, 7, 9, 21,22, 23,24, 25,26, 27, 28, 8, 29 38,39, 40, 41,42, 43,44, 45,46 6 50,51, 52, 53,54, 55,56, 57,58, 59, 60 7 47,48, According to Table 1, radio channels 1-5 are 5 assigned to the base station 1. This means that five carries from 800.050 MHz to 800.250 MHz are assigned.
As for the assignment of the radio channels to the individual zones, the switching center of Fig. 1 includes a cross-reference table as Table 1. The to assignment table stored in the switching center 108 can be stored instead in a higher rank switching center that carries out the overall control of a plurality of switching centers. As a method for storing the table, for example, it is implemented in the form of software stored in a base station controller in the switching center.
A method will now be described for establishing a channel between a mobile station and the base station by effectively selecting multiple radio channels from the channels assigned to the zones with maintaining the frequency utilization efficiency. Referring Fig.
2, a method will be described, for the purpose of simplicity, which selects only two simultaneous radio channels from the radio channels assigned to the zones by the frequency division multiple access.
As shown in Fig. 2, as the radio communications to zones, there are seven zones ( zones 1-7 ) constituting a cluster 8 with zone 1 being adjacent to zones 2-7. Frequencies fl-f7 are respectively assigned to the base stations of the respective zones : there are one radio channel which the visitor mobile station can use precedently, and six radio channels over which the other zones have priority. For example, as for zone 1, the radio channel of the frequency f 1 is assigned as a channel over which zone 1 has priority, and the channels of the frequencies f2-f7 are assigned as 2o channels over which the other zones ( zones 2-7 ) have priority, and a base station 10 of zone 1 has equipment enabling the communications using these radio channels .
The mobile station in each individual zone not only can communicate through the radio channel over which the visited zone has priority, but also has a function to communicate through one of the channels over which the other zones have priority.
As a method of identifying the radio channel over which the visited zone has priority, because the base station broadcasts its own identification number through a control channel, the mobile station can identify the radio channel over which it has priority from the identification number by receiving the control channel containing the identification number.
Next , taking an example in which a mobile station to in a certain zone establishes two simultaneous channels , a method a mobile station uses to select the channels from the plurality of radio channels thus assigned will be described in connection with a conf igurat ion .
A mobile station as shown in Figs . 3A and 3B has in its radio stage a couple of transmitting and receiving sections. A first receiving section 110 and a second receiving section 120 comprise RF (radio frequency) amplifiers 112 and 122, receiving mixers 114 and 124, IF amplifiers 116 and 126 and demodulators 118 and 128, respectively, and convert received radio channels with different frequencies to baseband signals . A first transmitting section 130 and a second transmitting section 140 comprise modulators 136 and 146 , transmitting mixers 134 and 144 , and RF amplifiers 132 and 142. The first transmitting section 130 and second transmitting section 140 transmit transmitted signals fed from a baseband signal processor 150 through radio channels with different frequencies . A
frequency synthesizer 103 supplies the receiving mixers 114 and 124 in the first and second receiving sections ( 110 and 120 ) and the transmitting mixers 134 and 144 in the first and second transmitting sections (130 and 140) with corresponding frequencies, thus determining the receiving frequencies and to transmitting frequencies.
The received signals from the radio stage and the transmitted signals to the radio stage are processed by a received signal processor 152 and a transmitted signal processor 154 in the baseband signal processor 150. A signal from the received signal processor 152 is fed to a user of the mobile station through a telephone receiver 170. A signal from a telephone transmitter 180 is processed by the transmitted signal processor 154 and transferred to the radio stage . A
2o controller, which consists of a controller 160 including key pad 190 and a CPU, controls the baseband signal processor 150 and the radio section. The baseband signal processor comprises a transmitting/receiving timing controller that supplies the controller with timing signals.
Next, referring to Fig. 2, first, the steps of making effective use of the radio channels will be described briefly which are taken by the mobile station with the foregoing configuration and by the base station in the visitor location of the mobile station.
The mobile station 10 visiting zone 1 establishes in zone 1 the first radio channel of the frequency fl over which the mobile station has priority. The establishment of the channel is carried out in the same manner as the establishment of a conventional radio to channel between a mobile station and a base station in an ordinary visited zone.
Subsequently, the mobile station 10 observes the cochannel interference of the other radio channels, and sets up a channel with a radio channel whose interference level is less than a predetermined level.
The radio channel setup can utilize the radio channels over which the other zones have priority.
Thus, the mobile station 10 establishes between it and the base station in its visited zone 1 the second 2o radio channel of the frequency f2 over which zone 2 has priority. In this case, the mobile station notifies the base station in the visited zone 1 of using the second radio channel, first . The base station in zone 1 sets up the channel to the mobile station in zone 1 using the second radio channel.
The mobile station 10 uses the first and second radio channels. The mobile station continually observes the cochannel interference of the second radio channel. If the channel quality of the second radio channel degrades during the communication, the mobile station performs handover to a radio channel over which another zone has priority. For example, it performs handover to a radio channel over which the third zone has priority. In this case also, the mobile station notifies the base station in the visited zone of the radio channel to be handed over, so that the base station can set up a channel using the radio channel over which zone 3 has priority.
The reason for observing the degradation of the channel quality will now be described. The radio channels over which other zones have priority can be precedently used by these zones . If two or more zones including the current zone and another zone use a particular radio channel over which the another zone has priority, the quality of that channel is degraded 2o because of the cochannel interference. Detecting the degradation in the channel quality due to the cochannel interference, the mobile station using the radio channel over which the visited zone does not have priority relinquishes the second channel and performs handover to another radio channel.
These operations enable the mobile station to continually use two radio channels.
Although the case of establishing two simultaneous radio channels is described above, three or more simultaneous radio channels can be set up.
Next, the channel selection operation by the mobile station will be described in more detail.
As described above, the mobile station 10 selects the radio channel of the frequency f 1, f first , which is assigned to the base station of zone 1, as the first 1o radio channel. Then, the mobile station communicates with the base station to establish the radio channel, and controls the frequency synthesizer 103 to tune the first transmitting section 130 and first receiving section 110 of Figs. 3A and 3B to that frequency.
Subsequently, the mobile station 10 detects an idle radio channel in one of the adjacent zones with a frequency different from the frequency of the visited zone . This is carried out by the second transmitting section 140 and second receiving section 120 of Figs .
3A and 3B. Assume that the radio channel of the adjacent zone 2 with the frequency f2 as illustrated in Fig. 2 is detected to be idle. The mobile station selects it as the second radio channel, and notifies the visitor location base station of the radio channel selected, thereby establishing the radio channel between the visitor location base station and the mobile station l Thus , the mobile station can use the two radio channels simultaneously as the visited zone radio channels . Because the idle channel is used, the frequency utilization efficiency of the mobile radio communication system is not reduced.
The simultaneous use of the radio channel in the visited zone of the mobile station and the radio channel in the adjacent zone enables the efficient channel selection.
io Thus, in the radio channel selection method, the radio channel that is assigned in advance to the visited zone of the mobile station is selected first .
Then, the radio channel that is assigned in advance to one of the adjacent zones is selected as the radio channel of the visited zone.
The second selection of the radio channel, however, causes the cochannel interference mentioned above, which becomes a major factor of degrading the quality in the radio channel between the visited zone and the 2o adjacent zone. To avoid the cochannel interference in the radio channel selection method in accordance with the present invention when the visited zone base station and the mobile station establish, as the radio channel of the visited zone, the radio channel using the idle channel of one of the adjacent zones, the mobile station and the base station can carry out the - 1s -transmission power control to reduce the cochannel interference to the adjacent zone.
Afterward, if the second radio channel selected undergoes the degradation in the channel quality due to the cochannel interference, the mobile station immediately performs the handover to another radio channel of one of the adjacent zones.
The series of the foregoing processes in accordance with the present invention has an advantage to of being able to achieve the mobile radio communications using simultaneous multiple radio channels without reducing the frequency utilization efficiency, with circumventing the effect of the cochannel interference.
z5 The series of the foregoing operations will now be described with reference to Fig. 4, and particularly the selection of the second radio channel will be described in more detail . Here , as in Fig . 2 , the radio channel selection of two simultaneous radio channels 2o by the mobile station will be described.
Fig. 4 illustrates the processing of the second selection by the mobile station 10 after the first channel selection. Since the first radio channel is the radio channel that is assigned to the visited zone, 25 and is selected in the same manner as a conventional radio channel, description thereof is omitted here.
First , the mobile station 10 detects , as the second radio channel , an idle radio channel of one of the zones adjacent to the visited zone ( S202 ) . Then, the mobile station measures the cochannel interference to the idle channel from the base station ( S204 ) , and makes a decision as to whether the power ratio to the measured value is greater than or less than the predetermined value (S206).
If the decision result indicates that the 1o predetermined value is exceeded, the mobile station notifies the visitor location base station of the idle channel (S208). The mobile station carries out subsequent communication with the visitor location base station. Then, the mobile station and the visited zone base station carries out the transmission power control of the second channel with each other ( S210 ) , thereby adjusting the transmission power to about a required receiving sensitivity (S212). In this case, the controller 160 performs the transmission power 2o control of the RF amplifier 142 of Fig. 3B at the mobile station side . This control can be low-speed control at every several second interval. Although the transmission power control requires a wide dynamic range from the maximum transmission power to around the required receiving sensitivity, the accuracy of a few decibels is enough as the accuracy of the transmission power control because the purpose of the transmission control is to reduce the cochannel interference . Thus , the selection of the second radio channel is completed (S214).
If the decision result at step S206 indicates that the predetermined level is not exceeded, the mobile station detects another radio channel of one of the adjacent zones (S202). Subsequently, the mobile station selects the radio channel to be used through 1o the foregoing radio channel selection processing.
As for the second radio channel, the interference measurement is continued even during the communications, the processing of which will now be described with reference to the flowchart of Fig. 5.
In the flowchart of Fig. 5, the mobile station carries out the cochannel interference measurement ( 5220 ) in conjunction with the transmission power control after the selection. If the measurement result of the interference is less than the predetermined level, it 2o continues to use the radio channel (YES at step S222) .
On the contrary, if the interference exceeds the predetermined level, the handover is performed to an idle channel of another adjacent zone. The processing of selecting the idle channel is the same as the channel selection as illustrated in Fig. 4.
The foregoing processing is described taking an example of carrying out the communications with the base station through the two radio channels as described above in connection with Fig. 4. When the mobile station requires three or more radio channels , it carries out the foregoing idle radio channel selection processing by the number of required radio channels after the second radio channel selection, thereby achieving the radio channel selection in the same manner. This makes it possible to assign multiple io radio channels to the mobile station without impairing the frequency utilization efficiency.
So far, the method of assigning the radio channels and selecting the radio channels from among the channels assigned in accordance with the present invention is described in connection with the example in which the radio channels are mainly configured by the frequency division multiple access. The channel assignment in accordance with the present invention, however, is not limited to this. The radio channel 2o assignment in accordance with the present invention is also applicable to other radio communications systems like various types of multiplexing systems such as a TDMA ( time division multiple access ) system in which channels consist of slots based on the time division multiple access, and a CDMA (code division multiple access) system with its channel configured using orthogonal codes.
Applications of the radio channel assignment method in accordance with the present invention will now be described for each radio channel configuration including the foregoing configuration based on the frequency division multiple access.
[Frequency Division Multiple Access]
Figs . 6A and 6B show an example in which the present invention is applied to frequency division radio 1o channels. Fig. 6A shows an example of forming one cluster from seven zones as in Fig. 2. As shown in Fig. 6B, the radio channels are established by dividing the frequency band . In Fig . 6B , the radio channel of a particular frequency band is precedently assigned to the first zone, and the mobile station roaming in the first zone has priority over that radio channel.
The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular carrier over which 2o zone 1 has priority. As the second radio channel, it selects, for example, a carrier over which zone 3 has priority, that is , the channel with low interference so as to be used by zone 1. If the channel quality of the second radio channel degrades, the mobile station performs handover to a carrier over which zone 6 has priority, for example.
[ Time Divisionf Multiple Access ]
Figs . 7A and 7B show an example in which the present invention is applied to time division radio channels .
Fig. 7A shows an example of forming one cluster from seven zones as in Fig. 6A. As shown in Fig. 7B, the radio channels consist of time slots, and the individual zones have time slots over which they have priority.
The mobile station tries to use two radio channels 1o simultaneously. First, as the first radio channel, the mobile station uses a particular time slot over which zone 1 has priority. As the second radio channel, it uses in zone 1 a time slot over which zone 3 has priority. If the channel quality of the second radio channel degrades , the mobile station performs handover to a time slot over which another zone has priority (for example, to a radio channel of zone 6).
[Code Division Multiple Access]
Figs . 8A and 8B show an example in which the present 2o invention is applied to code division radio channels .
Fig. 8A shows an example of forming one cluster from seven zones as in Fig. 6A. As shown in Fig. 8B, the radio channels are configured using multiple orthogonal codes, and by spreading a signal by multiplying the signal by the orthogonal codes.
The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular orthogonal code over which zone 1 has priority. As the second radio channel, it uses in zone 1 an orthogonal code over which zone 3 has priority. If the channel quality of the second radio channel degrades, the mobile station performs handover to a radio channel over which another zone has priority (for example, to a radio channel of zone 6).
1o [ Frequency Division Multiple Access and Time Division Multiple Access]
Figs . 9A and 9B show an example in which the present invention is applied to radio channels established by using both the frequency division multiple access and time division multiple access at the same time. Fig.
9A shows an example of forming one cluster from seven zones as in Fig. 6A. As shown in Fig. 9B, the radio channels are established by dividing according to frequencies and time slots.
2o The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular carrier and time slot over which zone 1 has priority. As the second radio channel, it uses in zone 1 a radio channel consisting of a carrier and time slot over which zone 3 has priority. If the channel quality of the second radio channel degrades, the mobile station performs handover to another radio channel over which another zone has priority (for example, to a radio channel of zone 6).
[Time Division Multiple Access and Code Division Multiple Access]
Figs. 10A and 10B show an example in which the present invention is applied to radio channels established by using both the time division multiple io access and code division multiple access. Fig. 10A
shows an example of forming one cluster from seven zones as in Fig. 6A. As shown in Fig. lOB, the radio channels are established by dividing according to time slots and orthogonal codes.
The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular time slot and orthogonal code over which zone 1 has priority. As the second radio channel, it uses in zone 1 a time slot 2o and orthogonal code over which zone 3 has priority.
If the channel quality of the second radio channel degrades, the mobile station performs handover to a radio channel over which another zone has priority ( for example, to a radio channel of zone 6).
[ Code Division Multiple Access and Frequency Division Multiple Access]
Figs. 11A and 11B show an example in which the present invention is applied to radio channels established by using both the code division multiple access and frequency division multiple access. Fig.
11A shows an example of forming one cluster from seven zones as in Fig . 6A . As shown in Fig . 11B , the radio channels are established by dividing according to orthogonal codes and frequencies.
The mobile station tries to use two radio channels 1o simultaneously. First, as the first radio channel, the mobile station uses a particular orthogonal code and carrier over which zone 1 has priority. As the second radio channel, it uses in zone 1 an orthogonal code and carrier over which zone 3 has priority. If the channel quality of the second radio channel degrades, the mobile station performs handover to a radio channel over which another zone has priority ( for example, to a radio channel of zone 6).
[Frequency Division Multiple Access, Time Division 2o Multiple Access and Code Division Multiple Access]
Figs. 12A and 12B show an example in which the present invention is applied to radio channels established by using the frequency division multiple access, time division multiple access and code division multiple access simultaneously. Fig. 12A
shows an example of forming one cluster from seven zones as in Fig-. 6A . As shown _ in Fig . 12B , the radio channels are established by dividing according to frequencies, time slots and orthogonal codes.
The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular carrier, time slot and orthogonal code over which zone 1 has priority.
As the second radio channel, it uses in zone 1 a carrier, time slot and orthogonal code over which zone 3 has to priority. If the channel quality of the second radio channel degrades, the mobile station performs handover to a radio channel over which another zone has priority (for example, to a radio channel of zone 6).
As described above, the radio channel assignment method in accordance with the present invention is applicable independently of the way the radio channels are established, that is, independently of whether they are established by any one of the frequency division multiple access, time division multiple 2o access and code division multiple access, or by their combinations.
Furthermore, since the mobile station can establish multiple radio channels using one or more radio channels other than the radio channel precedently assigned to the visited zone, the frequency utilization efficiency can be improved.
TITLE OF THE INVENTION
RADIO CHANNEL ASSIGNMENT AND SELECTION METHOD
TECHNICAL FIELD
The present invention relates to a radio channel 1o assignment method and an assigned radio channel selection method, which are applied to a mobile radio communications system employing simultaneous multiple radio channels.
BACKGROUND ART
In order to improve the frequency utilization efficiency of a mobile radio communications system, some radio channel assignment methods of the mobile radio communications system have been researched up 2o to now: a method of fixedly assigning radio channels to each zone (Fixed Channel Assignment: FCA); and a method of dynamically assigning radio channels to a plurality of zones (Dynamic Channel Assignment: DCA) are known. In addition, a radio channel assignment method of simultaneously using the two methods are proposed.
The FCA has already come into practice in the mobile communications system: an analog NTT system and a digital mobile communications method (personal digital cellular : PDC ) are typical examples . As for the DCA, it has been put to practical use in a digital cordless form until now.
In such an FCA mobile communications system, a radio channel is conventionally established between a base station and a mobile station by selecting an 1o idle radio channel from among radio channels assigned to the base station in the zone visited by the mobile station, thereby setting up a mobile radio channel with that radio channel. Although the radio channels assigned to each base station are decided such that interference with the other base stations does not exceed a predetermined cochannel interference level, it is mainly assumed that only a single channel is used in the mobile radio communications system.
In contrast with this, a mobile radio 2o communications method has emerged recently which assigns multiple radio channels to a mobile station.
In the communications system that employs the multiple radio channels, a mobile station uses two or more channels assigned to the base station in the zone (visited zone) that the mobile station is present so as to implement high-speed or high-quality transmission.
This method, however, is essentially the same as the radio channel assignment method within a cluster of cells in that although it employs multiple channels, it only utilizes radio channels assigned to the visited zone to be used precedently.
Thus , as compared with the method of using a single radio channel, the method of using simultaneous multiple channels has a problem of reducing the total 1o frequency utilization efficiency (a product of the utilization efficiency on the frequency axis and the utilization efficiency on the spatial axis).
Therefore, an object of the present invention is to provide a radio channel assignment and selection method without involving degradation in the total frequency utilization efficiency as compared with the method of using the single radio channel, even if a mobile station employs multiple radio channels simultaneously.
DISCLOSURE OF THE INVENTION
To achieve the object, in a first aspect of the present invention, there is provided a radio channel assignment method which is associated with a plurality of zones constituting a cluster based on frequency reuse of radio channels , in order to implement a mobile radio communications system by employing multiple radio channels in each one of the plurality of zones , the radio channel assignment method comprising the steps of assigning to at least one of the multiple radio channels a radio channel over which the one of the plurality of zones itself has priority; and assigning to a remainder of the multiple radio channels a radio channel available in a zone adjacent 1o to the one of the plurality of zones.
By thus assigning the radio channel in the mobile ratio communications system, a radio channels over which the visited zone has priority can be assigned to at least one of the multiple radio channels the mobile station uses simultaneously, and an idle radio channel selected from radio channels precedently available in zones adjacent to the visited zone can be used as the remainder of the multiple radio channels.
2o This makes it possible to prevent reduction in the frequency utilization efficiency in the cluster in spite of the simultaneous use of the multiple radio channels.
The radio channel assignment method in accordance with the present invention can be applied independently of whether the radio channels are established bythe frequency division multiple access, time division multiple access or code division multiple access, or by any combination of them.
If the transmission quality is degraded because of cochannel interference during the use of the radio channel over which an adjacent zone has priority, the mobile device can utilize an idle radio channel over which another zone has priority by carrying out handover to that idle radio channel. This enables a 1o continuous use of the multiple channels.
In a second aspect of the present invention, there is provided a radio channel selection method which is carried out by a mobile station visiting one of a plurality of zones constituting a cluster for frequency reuse of radio channels, in order to implement a mobile radio communications system by employingsimultaneousmultiple radio channels in each one of the plurality of zones, the radio channel selection method comprising the steps of:
2o selecting at least one of the multiple radio channels from radio channels assigned to the zone visited by the mobile station; and selecting a remainder of the multiple radio channels from radio channels assigned to a plurality of zones adjacent to the zone visited by the mobile station, and using the selected radio channel in the VlSl.ted zone .
Here, the radio channel selection method as claimed in claim 9, wherein selection of the radio channel of one of the adjacent zones by the mobile station may comprise the steps of:
detecting a received level of a radio channel in the adjacent zones;
measuring cochannel interference from the received level detected;
Zo comparing the received level detected with a predetermined level;
setting up the radio channel as a radio channel between the mobile station and a base station in the visited zone when the received level compared is less than the predetermined level; and selecting another radio channel of the adjacent zones by returning to the step ( 1 ) when the received level compared is greater than the predetermined level.
The radio channel selection method as claimed in 2o claim 10 , wherein the selection of the radio channel of one of the adjacent zones by the mobile station may further comprise the step of:
controlling transmission power of the base station and mobile station connected to the radio channel setup between the visited zone base station and the mobile station such that the transmission power approach a predetermined receiving sensitivity.
The radio channel selection method as claimed in any one of claims 9-12, wherein the mobile station that implements the radio channel selection method may be a mobile device.
The radio channel assignment method and selection method in accordance with the present invention have the following advantages of:
(1) Improving the frequency utilization efficiency 1o as compared with the conventional radio channel assignment method in the mobile communications employing multiple radio channels;
(2) Enabling high speed transmission;
(3) Applicable to an existing mobile radio communications method using a single carrier; and (4) Applicable to an existing mobile station by a simple expansion of channel control of the existing mobile station.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagram showing a radio zone configuration for illustrating a radio channel assignment method in accordance with the present invention;
Fig. 2 is a diagram showing a zone configuration simplifying the embodiment in Fig. 1;
Fig. 3 is a~diagram illustrating the relationship between Figs. 3A and 3B;
Figs. 3A and 3B are block diagrams showing a configuration of a mobile station associated with the radio channel assignment in accordance with the present invention;
Fig. 4 is a flowchart illustrating a selection processing by the mobile station for explaining the radio channel selection method in accordance with the 1o present invention;
Fig. 5 is a flowchart illustrating remaining steps of the selection method of Fig. 4;
Figs. 6A and 6B are diagrams illustrating the application of the radio channel assignment to frequency division multiple access;
Figs. 7A and 7B are diagrams illustrating the application of the radio channel assignment to time division multiple access;
Figs. 8A and 8B are diagrams illustrating the 2o application of the radio channel assignment to code division multiple access;
Figs . 9A and 9B are diagrams illustrating a method of carrying out the radio channel assignment by simultaneous use of the frequency division multiple access and time division multiple access;
Figs. 10A and 10B are diagrams illustrating a _8_ method of carrying out the radio channel assignment by simultaneous use of the time division multiple access and code division multiple access;
Figs. 11A and 11B are diagrams illustrating a method of carrying out the radio channel assignment by simultaneous use of the code division multiple access and frequency division multiple access; and Figs. 12A and 12B are diagrams illustrating a method of carrying out the radio channel assignment 1o by simultaneous use of the frequency division multiple access, time division multiple access and code division multiple access.
BEST MODE FOR CARRYING OUT THE INVENTION
The radio channel assignment in accordance with invention will now be described with reference to the accompanying drawings from the following point of view: a method of assigning channels by dividing them into channels over which the current zone has priority, 2o and channels over which the other zones have priority;
and a method for a visitor mobile station to select multiple channels from among a plurality of channels assigned to individual zones in accordance with the present invention.
Fig . 1, relating to the radio channel assignment , shows a switching center 108 , base stations ( 101-107 ) _ g _ connected the switching center, and interconnection between switching centers, in which the switching center 108 functions as a regional center of a cluster 100 consisting of seven zones each including its own base station.
In Fig . 1, the switching center 108 is connected with the base stations (101-107) in the individual zones through dedicated lines 109 consisting of common communications channels. In the radio channel to assignment method in accordance with the present invention, the switching center 108 instructs the base stations ( 101-107 ) of available radio channel numbers through the dedicated lines 109 according to a predetermined radio channel assignment scheme.
Fig. 1 illustrates a case in which the radio channels are assigned by frequency division multiple access (FDMA).
For example, in an 800 MHz band FDMA system with 60 radio channels, the radio channel numbers assigned 2o to respective zones are as shown in table 1, in which the radio channels each have a 25 kHz bandwidth with a frequency interval of 50 kHz. For example, if the radio channel No. 1 is assigned to 800.050 MHz, the radio channel No. 60 becomes 803.000 MHz.
Table 1 Base station Assigned radio channel numbers numbers 1 1, 2, 4, 5 3, 2 10,11, 12, 13,14, 15,16, 17,18, 19, 20 3 30,31, 32, 33,34, 35,36, 37 4 6, 7, 9, 21,22, 23,24, 25,26, 27, 28, 8, 29 38,39, 40, 41,42, 43,44, 45,46 6 50,51, 52, 53,54, 55,56, 57,58, 59, 60 7 47,48, According to Table 1, radio channels 1-5 are 5 assigned to the base station 1. This means that five carries from 800.050 MHz to 800.250 MHz are assigned.
As for the assignment of the radio channels to the individual zones, the switching center of Fig. 1 includes a cross-reference table as Table 1. The to assignment table stored in the switching center 108 can be stored instead in a higher rank switching center that carries out the overall control of a plurality of switching centers. As a method for storing the table, for example, it is implemented in the form of software stored in a base station controller in the switching center.
A method will now be described for establishing a channel between a mobile station and the base station by effectively selecting multiple radio channels from the channels assigned to the zones with maintaining the frequency utilization efficiency. Referring Fig.
2, a method will be described, for the purpose of simplicity, which selects only two simultaneous radio channels from the radio channels assigned to the zones by the frequency division multiple access.
As shown in Fig. 2, as the radio communications to zones, there are seven zones ( zones 1-7 ) constituting a cluster 8 with zone 1 being adjacent to zones 2-7. Frequencies fl-f7 are respectively assigned to the base stations of the respective zones : there are one radio channel which the visitor mobile station can use precedently, and six radio channels over which the other zones have priority. For example, as for zone 1, the radio channel of the frequency f 1 is assigned as a channel over which zone 1 has priority, and the channels of the frequencies f2-f7 are assigned as 2o channels over which the other zones ( zones 2-7 ) have priority, and a base station 10 of zone 1 has equipment enabling the communications using these radio channels .
The mobile station in each individual zone not only can communicate through the radio channel over which the visited zone has priority, but also has a function to communicate through one of the channels over which the other zones have priority.
As a method of identifying the radio channel over which the visited zone has priority, because the base station broadcasts its own identification number through a control channel, the mobile station can identify the radio channel over which it has priority from the identification number by receiving the control channel containing the identification number.
Next , taking an example in which a mobile station to in a certain zone establishes two simultaneous channels , a method a mobile station uses to select the channels from the plurality of radio channels thus assigned will be described in connection with a conf igurat ion .
A mobile station as shown in Figs . 3A and 3B has in its radio stage a couple of transmitting and receiving sections. A first receiving section 110 and a second receiving section 120 comprise RF (radio frequency) amplifiers 112 and 122, receiving mixers 114 and 124, IF amplifiers 116 and 126 and demodulators 118 and 128, respectively, and convert received radio channels with different frequencies to baseband signals . A first transmitting section 130 and a second transmitting section 140 comprise modulators 136 and 146 , transmitting mixers 134 and 144 , and RF amplifiers 132 and 142. The first transmitting section 130 and second transmitting section 140 transmit transmitted signals fed from a baseband signal processor 150 through radio channels with different frequencies . A
frequency synthesizer 103 supplies the receiving mixers 114 and 124 in the first and second receiving sections ( 110 and 120 ) and the transmitting mixers 134 and 144 in the first and second transmitting sections (130 and 140) with corresponding frequencies, thus determining the receiving frequencies and to transmitting frequencies.
The received signals from the radio stage and the transmitted signals to the radio stage are processed by a received signal processor 152 and a transmitted signal processor 154 in the baseband signal processor 150. A signal from the received signal processor 152 is fed to a user of the mobile station through a telephone receiver 170. A signal from a telephone transmitter 180 is processed by the transmitted signal processor 154 and transferred to the radio stage . A
2o controller, which consists of a controller 160 including key pad 190 and a CPU, controls the baseband signal processor 150 and the radio section. The baseband signal processor comprises a transmitting/receiving timing controller that supplies the controller with timing signals.
Next, referring to Fig. 2, first, the steps of making effective use of the radio channels will be described briefly which are taken by the mobile station with the foregoing configuration and by the base station in the visitor location of the mobile station.
The mobile station 10 visiting zone 1 establishes in zone 1 the first radio channel of the frequency fl over which the mobile station has priority. The establishment of the channel is carried out in the same manner as the establishment of a conventional radio to channel between a mobile station and a base station in an ordinary visited zone.
Subsequently, the mobile station 10 observes the cochannel interference of the other radio channels, and sets up a channel with a radio channel whose interference level is less than a predetermined level.
The radio channel setup can utilize the radio channels over which the other zones have priority.
Thus, the mobile station 10 establishes between it and the base station in its visited zone 1 the second 2o radio channel of the frequency f2 over which zone 2 has priority. In this case, the mobile station notifies the base station in the visited zone 1 of using the second radio channel, first . The base station in zone 1 sets up the channel to the mobile station in zone 1 using the second radio channel.
The mobile station 10 uses the first and second radio channels. The mobile station continually observes the cochannel interference of the second radio channel. If the channel quality of the second radio channel degrades during the communication, the mobile station performs handover to a radio channel over which another zone has priority. For example, it performs handover to a radio channel over which the third zone has priority. In this case also, the mobile station notifies the base station in the visited zone of the radio channel to be handed over, so that the base station can set up a channel using the radio channel over which zone 3 has priority.
The reason for observing the degradation of the channel quality will now be described. The radio channels over which other zones have priority can be precedently used by these zones . If two or more zones including the current zone and another zone use a particular radio channel over which the another zone has priority, the quality of that channel is degraded 2o because of the cochannel interference. Detecting the degradation in the channel quality due to the cochannel interference, the mobile station using the radio channel over which the visited zone does not have priority relinquishes the second channel and performs handover to another radio channel.
These operations enable the mobile station to continually use two radio channels.
Although the case of establishing two simultaneous radio channels is described above, three or more simultaneous radio channels can be set up.
Next, the channel selection operation by the mobile station will be described in more detail.
As described above, the mobile station 10 selects the radio channel of the frequency f 1, f first , which is assigned to the base station of zone 1, as the first 1o radio channel. Then, the mobile station communicates with the base station to establish the radio channel, and controls the frequency synthesizer 103 to tune the first transmitting section 130 and first receiving section 110 of Figs. 3A and 3B to that frequency.
Subsequently, the mobile station 10 detects an idle radio channel in one of the adjacent zones with a frequency different from the frequency of the visited zone . This is carried out by the second transmitting section 140 and second receiving section 120 of Figs .
3A and 3B. Assume that the radio channel of the adjacent zone 2 with the frequency f2 as illustrated in Fig. 2 is detected to be idle. The mobile station selects it as the second radio channel, and notifies the visitor location base station of the radio channel selected, thereby establishing the radio channel between the visitor location base station and the mobile station l Thus , the mobile station can use the two radio channels simultaneously as the visited zone radio channels . Because the idle channel is used, the frequency utilization efficiency of the mobile radio communication system is not reduced.
The simultaneous use of the radio channel in the visited zone of the mobile station and the radio channel in the adjacent zone enables the efficient channel selection.
io Thus, in the radio channel selection method, the radio channel that is assigned in advance to the visited zone of the mobile station is selected first .
Then, the radio channel that is assigned in advance to one of the adjacent zones is selected as the radio channel of the visited zone.
The second selection of the radio channel, however, causes the cochannel interference mentioned above, which becomes a major factor of degrading the quality in the radio channel between the visited zone and the 2o adjacent zone. To avoid the cochannel interference in the radio channel selection method in accordance with the present invention when the visited zone base station and the mobile station establish, as the radio channel of the visited zone, the radio channel using the idle channel of one of the adjacent zones, the mobile station and the base station can carry out the - 1s -transmission power control to reduce the cochannel interference to the adjacent zone.
Afterward, if the second radio channel selected undergoes the degradation in the channel quality due to the cochannel interference, the mobile station immediately performs the handover to another radio channel of one of the adjacent zones.
The series of the foregoing processes in accordance with the present invention has an advantage to of being able to achieve the mobile radio communications using simultaneous multiple radio channels without reducing the frequency utilization efficiency, with circumventing the effect of the cochannel interference.
z5 The series of the foregoing operations will now be described with reference to Fig. 4, and particularly the selection of the second radio channel will be described in more detail . Here , as in Fig . 2 , the radio channel selection of two simultaneous radio channels 2o by the mobile station will be described.
Fig. 4 illustrates the processing of the second selection by the mobile station 10 after the first channel selection. Since the first radio channel is the radio channel that is assigned to the visited zone, 25 and is selected in the same manner as a conventional radio channel, description thereof is omitted here.
First , the mobile station 10 detects , as the second radio channel , an idle radio channel of one of the zones adjacent to the visited zone ( S202 ) . Then, the mobile station measures the cochannel interference to the idle channel from the base station ( S204 ) , and makes a decision as to whether the power ratio to the measured value is greater than or less than the predetermined value (S206).
If the decision result indicates that the 1o predetermined value is exceeded, the mobile station notifies the visitor location base station of the idle channel (S208). The mobile station carries out subsequent communication with the visitor location base station. Then, the mobile station and the visited zone base station carries out the transmission power control of the second channel with each other ( S210 ) , thereby adjusting the transmission power to about a required receiving sensitivity (S212). In this case, the controller 160 performs the transmission power 2o control of the RF amplifier 142 of Fig. 3B at the mobile station side . This control can be low-speed control at every several second interval. Although the transmission power control requires a wide dynamic range from the maximum transmission power to around the required receiving sensitivity, the accuracy of a few decibels is enough as the accuracy of the transmission power control because the purpose of the transmission control is to reduce the cochannel interference . Thus , the selection of the second radio channel is completed (S214).
If the decision result at step S206 indicates that the predetermined level is not exceeded, the mobile station detects another radio channel of one of the adjacent zones (S202). Subsequently, the mobile station selects the radio channel to be used through 1o the foregoing radio channel selection processing.
As for the second radio channel, the interference measurement is continued even during the communications, the processing of which will now be described with reference to the flowchart of Fig. 5.
In the flowchart of Fig. 5, the mobile station carries out the cochannel interference measurement ( 5220 ) in conjunction with the transmission power control after the selection. If the measurement result of the interference is less than the predetermined level, it 2o continues to use the radio channel (YES at step S222) .
On the contrary, if the interference exceeds the predetermined level, the handover is performed to an idle channel of another adjacent zone. The processing of selecting the idle channel is the same as the channel selection as illustrated in Fig. 4.
The foregoing processing is described taking an example of carrying out the communications with the base station through the two radio channels as described above in connection with Fig. 4. When the mobile station requires three or more radio channels , it carries out the foregoing idle radio channel selection processing by the number of required radio channels after the second radio channel selection, thereby achieving the radio channel selection in the same manner. This makes it possible to assign multiple io radio channels to the mobile station without impairing the frequency utilization efficiency.
So far, the method of assigning the radio channels and selecting the radio channels from among the channels assigned in accordance with the present invention is described in connection with the example in which the radio channels are mainly configured by the frequency division multiple access. The channel assignment in accordance with the present invention, however, is not limited to this. The radio channel 2o assignment in accordance with the present invention is also applicable to other radio communications systems like various types of multiplexing systems such as a TDMA ( time division multiple access ) system in which channels consist of slots based on the time division multiple access, and a CDMA (code division multiple access) system with its channel configured using orthogonal codes.
Applications of the radio channel assignment method in accordance with the present invention will now be described for each radio channel configuration including the foregoing configuration based on the frequency division multiple access.
[Frequency Division Multiple Access]
Figs . 6A and 6B show an example in which the present invention is applied to frequency division radio 1o channels. Fig. 6A shows an example of forming one cluster from seven zones as in Fig. 2. As shown in Fig. 6B, the radio channels are established by dividing the frequency band . In Fig . 6B , the radio channel of a particular frequency band is precedently assigned to the first zone, and the mobile station roaming in the first zone has priority over that radio channel.
The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular carrier over which 2o zone 1 has priority. As the second radio channel, it selects, for example, a carrier over which zone 3 has priority, that is , the channel with low interference so as to be used by zone 1. If the channel quality of the second radio channel degrades, the mobile station performs handover to a carrier over which zone 6 has priority, for example.
[ Time Divisionf Multiple Access ]
Figs . 7A and 7B show an example in which the present invention is applied to time division radio channels .
Fig. 7A shows an example of forming one cluster from seven zones as in Fig. 6A. As shown in Fig. 7B, the radio channels consist of time slots, and the individual zones have time slots over which they have priority.
The mobile station tries to use two radio channels 1o simultaneously. First, as the first radio channel, the mobile station uses a particular time slot over which zone 1 has priority. As the second radio channel, it uses in zone 1 a time slot over which zone 3 has priority. If the channel quality of the second radio channel degrades , the mobile station performs handover to a time slot over which another zone has priority (for example, to a radio channel of zone 6).
[Code Division Multiple Access]
Figs . 8A and 8B show an example in which the present 2o invention is applied to code division radio channels .
Fig. 8A shows an example of forming one cluster from seven zones as in Fig. 6A. As shown in Fig. 8B, the radio channels are configured using multiple orthogonal codes, and by spreading a signal by multiplying the signal by the orthogonal codes.
The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular orthogonal code over which zone 1 has priority. As the second radio channel, it uses in zone 1 an orthogonal code over which zone 3 has priority. If the channel quality of the second radio channel degrades, the mobile station performs handover to a radio channel over which another zone has priority (for example, to a radio channel of zone 6).
1o [ Frequency Division Multiple Access and Time Division Multiple Access]
Figs . 9A and 9B show an example in which the present invention is applied to radio channels established by using both the frequency division multiple access and time division multiple access at the same time. Fig.
9A shows an example of forming one cluster from seven zones as in Fig. 6A. As shown in Fig. 9B, the radio channels are established by dividing according to frequencies and time slots.
2o The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular carrier and time slot over which zone 1 has priority. As the second radio channel, it uses in zone 1 a radio channel consisting of a carrier and time slot over which zone 3 has priority. If the channel quality of the second radio channel degrades, the mobile station performs handover to another radio channel over which another zone has priority (for example, to a radio channel of zone 6).
[Time Division Multiple Access and Code Division Multiple Access]
Figs. 10A and 10B show an example in which the present invention is applied to radio channels established by using both the time division multiple io access and code division multiple access. Fig. 10A
shows an example of forming one cluster from seven zones as in Fig. 6A. As shown in Fig. lOB, the radio channels are established by dividing according to time slots and orthogonal codes.
The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular time slot and orthogonal code over which zone 1 has priority. As the second radio channel, it uses in zone 1 a time slot 2o and orthogonal code over which zone 3 has priority.
If the channel quality of the second radio channel degrades, the mobile station performs handover to a radio channel over which another zone has priority ( for example, to a radio channel of zone 6).
[ Code Division Multiple Access and Frequency Division Multiple Access]
Figs. 11A and 11B show an example in which the present invention is applied to radio channels established by using both the code division multiple access and frequency division multiple access. Fig.
11A shows an example of forming one cluster from seven zones as in Fig . 6A . As shown in Fig . 11B , the radio channels are established by dividing according to orthogonal codes and frequencies.
The mobile station tries to use two radio channels 1o simultaneously. First, as the first radio channel, the mobile station uses a particular orthogonal code and carrier over which zone 1 has priority. As the second radio channel, it uses in zone 1 an orthogonal code and carrier over which zone 3 has priority. If the channel quality of the second radio channel degrades, the mobile station performs handover to a radio channel over which another zone has priority ( for example, to a radio channel of zone 6).
[Frequency Division Multiple Access, Time Division 2o Multiple Access and Code Division Multiple Access]
Figs. 12A and 12B show an example in which the present invention is applied to radio channels established by using the frequency division multiple access, time division multiple access and code division multiple access simultaneously. Fig. 12A
shows an example of forming one cluster from seven zones as in Fig-. 6A . As shown _ in Fig . 12B , the radio channels are established by dividing according to frequencies, time slots and orthogonal codes.
The mobile station tries to use two radio channels simultaneously. First, as the first radio channel, the mobile station uses a particular carrier, time slot and orthogonal code over which zone 1 has priority.
As the second radio channel, it uses in zone 1 a carrier, time slot and orthogonal code over which zone 3 has to priority. If the channel quality of the second radio channel degrades, the mobile station performs handover to a radio channel over which another zone has priority (for example, to a radio channel of zone 6).
As described above, the radio channel assignment method in accordance with the present invention is applicable independently of the way the radio channels are established, that is, independently of whether they are established by any one of the frequency division multiple access, time division multiple 2o access and code division multiple access, or by their combinations.
Furthermore, since the mobile station can establish multiple radio channels using one or more radio channels other than the radio channel precedently assigned to the visited zone, the frequency utilization efficiency can be improved.
Claims (12)
1. A radio channel assignment method which is associated with a plurality of zones constituting a cluster based on frequency reuse of radio channels, in order to implement a mobile radio communications system by employing multiple radio channels in each one of the plurality of zones, said radio channel assignment method comprising the steps of:
assigning to at least one of the multiple radio channels a radio channel over which the one of the plurality of zones itself has priority; and assigning to a remainder of the multiple radio channels a radio channel available in a zone adjacent to the one of the plurality of zones.
assigning to at least one of the multiple radio channels a radio channel over which the one of the plurality of zones itself has priority; and assigning to a remainder of the multiple radio channels a radio channel available in a zone adjacent to the one of the plurality of zones.
2. The radio channel assignment method as claimed in claim 1, wherein said multiple radio channels are configured by frequency division multiple access.
3. The radio channel assignment method as claimed in claim 1, wherein said multiple radio channels are configured by time division multiple access.
4. The radio channel assignment method as claimed in claim 1, wherein said multiple radio channels are configured by code division multiple access using orthogonal codes.
5. The radio channel assignment method as claimed in claim 1, wherein said multiple radio channels are configured by simultaneously using frequency division multiple access and time division multiple access.
6. The radio channel assignment method as claimed in claim 1, wherein said multiple radio channels are configured by simultaneously using time division multiple access and code division multiple access.
7. The radio channel assignment method as claimed in claim 1, wherein said multiple radio channels are configured by simultaneously using frequency division multiple access and code division multiple access.
8. The radio channel assignment method as claimed in claim 1, wherein said multiple radio channels are configured by simultaneously using frequency division multiple access, time division multiple access and time division multiple access.
9. A radio channel selection method which is carried out by a mobile station visiting one of a plurality of zones constituting a cluster for frequency reuse of radio channels, in order to implement a mobile radio communications system by employing simultaneous multiple radio channels in each one of the plurality of zones, said radio channel selection method comprising the steps of:
selecting at least one of the multiple radio channels from radio channels assigned to the zone visited by said mobile station; and selecting a remainder of the multiple radio channels from radio channels assigned to a plurality of zones adjacent to the zone visited by the mobile station, and using the selected radio channel in the visited zone.
selecting at least one of the multiple radio channels from radio channels assigned to the zone visited by said mobile station; and selecting a remainder of the multiple radio channels from radio channels assigned to a plurality of zones adjacent to the zone visited by the mobile station, and using the selected radio channel in the visited zone.
10. The radio channel selection method as claimed in claim 9, wherein selection of the radio channel of one of the adjacent zones by the mobile station comprises the steps of:
detecting a received level of a radio channel in the adjacent zones;
measuring cochannel interference from the received level detected;
comparing the received level detected with a predetermined level;
setting up the radio channel as a radio channel between the mobile station and a base station in the visited zone when the received level compared is less than the predetermined level; and selecting another radio channel of the adjacent zones by returning to the step (1) when the received level compared is greater than the predetermined level.
detecting a received level of a radio channel in the adjacent zones;
measuring cochannel interference from the received level detected;
comparing the received level detected with a predetermined level;
setting up the radio channel as a radio channel between the mobile station and a base station in the visited zone when the received level compared is less than the predetermined level; and selecting another radio channel of the adjacent zones by returning to the step (1) when the received level compared is greater than the predetermined level.
11. The radio channel selection method as claimed in claim 10, wherein the selection of the radio channel of one of the adjacent zones by the mobile station further comprises the step of:
controlling transmission power of the base station and mobile station connected to the radio channel setup between the visited zone base station and the mobile station such that the transmission power approach a predetermined receiving sensitivity.
controlling transmission power of the base station and mobile station connected to the radio channel setup between the visited zone base station and the mobile station such that the transmission power approach a predetermined receiving sensitivity.
12. The radio channel selection method as claimed in any one of claims 9-11, wherein the mobile station that implements the radio channel selection method is a mobile device.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP358535/1997 | 1997-12-25 | ||
| JP35853497 | 1997-12-25 | ||
| JP35853597 | 1997-12-25 | ||
| JP358534/1997 | 1997-12-25 | ||
| PCT/JP1998/005859 WO1999034630A1 (en) | 1997-12-25 | 1998-12-24 | Method of assigning and selecting radio channel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2281578A1 true CA2281578A1 (en) | 1999-07-08 |
Family
ID=26580799
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002281578A Abandoned CA2281578A1 (en) | 1997-12-25 | 1998-12-24 | Method of assigning and selecting radio channel |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JP3795536B2 (en) |
| CA (1) | CA2281578A1 (en) |
| WO (1) | WO1999034630A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2721886A4 (en) * | 2011-06-16 | 2015-05-20 | Blackberry Ltd | Mobile guided uplink interference management |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7444127B2 (en) * | 2004-04-15 | 2008-10-28 | Qualcomm Incorporated | Methods and apparatus for selecting between multiple carriers using a receiver with multiple receiver chains |
| US6990324B2 (en) | 2004-04-15 | 2006-01-24 | Flarion Technologies, Inc. | Methods and apparatus for selecting between multiple carriers using a single receiver chain tuned to a single carrier |
| JP5780334B2 (en) * | 2009-09-25 | 2015-09-16 | ソニー株式会社 | Relay device, management server, and communication terminal |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63190435A (en) * | 1987-02-02 | 1988-08-08 | Nippon Telegr & Teleph Corp <Ntt> | Radio channel control system |
| JP3404206B2 (en) * | 1996-01-08 | 2003-05-06 | 株式会社日立製作所 | Slot allocation method |
-
1998
- 1998-12-24 WO PCT/JP1998/005859 patent/WO1999034630A1/en active Application Filing
- 1998-12-24 JP JP51601399A patent/JP3795536B2/en not_active Expired - Fee Related
- 1998-12-24 CA CA002281578A patent/CA2281578A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2721886A4 (en) * | 2011-06-16 | 2015-05-20 | Blackberry Ltd | Mobile guided uplink interference management |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3795536B2 (en) | 2006-07-12 |
| WO1999034630A1 (en) | 1999-07-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 20031224 |