JPH0847036A - Radio communication system - Google Patents

Abstract

PURPOSE:To reduce the system installation and operation cost and to decrease the probability of interference by using a channel whose priority is higher decided by history and providing a lower limit or an upper limit to the priority. CONSTITUTION:Subscriber radio stations 112, 122 make communication with radio base stations 111, 121, 131, 141 so long as the stations 112, 122 are resident in any of service zones 110, 120, 130, 140 corresponding to the radio base stations 111, 121, 131, 141. Priority is placed onto each radio channel and the priority is decided by the history of the use of channel and a channel with higher priority is being used sequentially. The priority of using a channel, is decided by, e.g. placing the higher priority to the channel used in each communication. As the expression method of priority, a counter is provided and the priority is expressed by the content of the counter. In this case, an upper limit and a lower limit are set to a figure for expressing the priority.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless communication system, and more particularly to a wireless communication system capable of easily reducing the risk of interference when interference in a wireless channel exists in principle. .

[0002]

2. Description of the Related Art In radio communication, the same frequency is generally used repeatedly in order to increase the efficiency of frequency use. In this case, since the same frequency is used at the same time, the risk that two or more signals collide and damage communication in one wireless channel, that is, so-called interference may not be avoided in principle. Therefore, particularly in a mobile radio communication system in which the location of a radio device moves, as in a cellular car telephone system,
A plurality of communication zones are set, and a radio channel used for each zone is determined so that interference does not occur as much as possible. Detailed literature on the design of such systems (Ito,
Matsuzaka, "Outline of Car Telephone System", Research Practical Report, Vol. 26, No. 7, 1977, pp. 1821-1836) It is intended to guarantee the probability of interference to be a certain value or less by separating the distance over a certain distance.

[0003]

In such a conventional system, however, it is necessary to design a planar zone and a channel in advance, so that it is necessary to accurately determine basic parameters such as radio wave propagation characteristics. At the same time, in order to manage the spread system,
There is a drawback that the system operation becomes large-scale.

By the way, it is well known that a demand for a mobile phone, a wireless local area phone, a data system or the like is increasing as a recent trend of mobile radio communication.
In these systems, the available power is limited, so that the communication zone becomes a small area (hereinafter referred to as a micro zone) and the cost of building or operating the system must be reduced. At this time, first, the narrowing of the zone makes it extremely difficult to accurately determine the radio wave propagation characteristics, and thus it becomes difficult to predict the probability of interference in advance. This is due to installation conditions such as partitioning of rooms and metal equipment such as lockers in the building.
Considering that the radio wave propagation characteristics change significantly, it can be easily understood. The problem is further complicated in high-rise buildings because the zones are three-dimensional. As a next problem, it is conceivable that the construction and operation of the system become difficult due to an increase in the number of wireless telephones or data terminal devices accommodated in the system. Because of these problems, it is not possible to introduce the basic idea of a conventionally known car telephone system into a micro zone system as it is.

The multi-channel cordless telephone (Kawasaki, Kato, Yoshizawa, "New Cordless Telephone" facility, Shi-36-3, pp. 134-141) currently under development is considered as a kind of micro zone system. be able to. The method of eliminating the management of the wireless zone and the wireless channel, which is one of the basic ideas of the system, is effective for reducing the construction and operation costs of the system. However, since this cordless telephone considers only indoor movement and movement is registered one-to-one with the base station,
There is a restriction that you cannot move in a wide area like a car phone. In addition, instead of designing a zone, this system prepares a large number of channels, observes empty channels prior to communication, and simultaneously escapes to another channel each time there is interference during communication. Has adopted. However, this method cannot sufficiently prevent interference. That is, first, the problem is that the interference detection is not perfect. Next, even if interference can be detected,
It must be guaranteed that another channel is free. This will be a problem when cordless phones are prevalent.

The present invention eliminates the drawbacks of the conventional system as described above, and provides a radio communication system capable of reducing the cost of system construction and operation and reducing the probability of interference. It is in.

[0007]

SUMMARY OF THE INVENTION The present invention provides a wireless communication system in which one or more of a plurality of wireless channels can be used arbitrarily. This is realized by adding a function that is determined based on the past history of use and that is used sequentially from the channel with the highest priority.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, a different priority is added to each channel used in each zone, so that the probability of interference can be reduced even if channels are not fixedly assigned to each zone in advance. The basic principle is that it can be reduced. Between two or more zones that may cause interference, the use priority of the channel is different for the same channel, which reduces the probability of interference.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a conceptual diagram of a wireless communication system for explaining an embodiment of the present invention. Radio base stations 111 and 12
The range in which the level of the transmission carrier signal emitted from the base station 1, 131, 141 is equal to or higher than the minimum input reference level is the service zone 110, 120, 13 for each wireless base station.
It becomes 0,140. Since the shape of the service zone is a minute zone, the service zone has a complicated shape due to the irregularity of the radio wave propagation characteristic described above. Subscriber radio station 112,1
22 actually exists in large numbers, but here,
For simplicity, only two are shown. A subscriber wireless station can communicate with a base station as long as it is located in any zone. In a place where two or more zones overlap, the subscriber radio station can, of course, communicate with any of the base stations forming the respective zones, but when the same channel is used simultaneously in the two zones. Will cause interference. It is desirable to consider the arrangement of the wireless base stations so as to minimize the overlap of the zones in consideration of the radio wave propagation characteristics. However, the feature of the present invention is that the reference for this arrangement is loose. That is, as described below, the probability of interference is reduced even if the zone overlap is large.

The radio base station and the subscriber radio station have a plurality of channels. However, the number of channels actually used simultaneously may be one or two or more. In the present invention, when starting communication in a certain zone, it is premised that it is confirmed that a channel to be used in another zone is not already used in advance. Find another free channel. This function is the same as a conventional multi-channel cordless telephone.

Here, the problem is that detection of an empty channel is incomplete, and in fact, it is determined that an already used channel is empty, resulting in interference. The cause of such erroneous detection is that the level of the received signal temporarily falls below the sensitivity due to irregular propagation characteristics due to the movement of the subscriber wireless station. It is conceivable that another system may start communication between the time immediately after the detection of an empty channel and the actual communication. In the present invention, in order to avoid such a problem, priority is given to each channel, the priority is determined by the past history of channel use, and the channels with higher priorities are used sequentially.

FIG. 2 shows an example of priorities set by the past history of channel use for the zone structure shown in FIG. Here, it is assumed that the total number of channels is 10. The height of the bar in each channel corresponds to the priority, and here, the higher the height, the higher the priority. In zone number 1, channel numbers 1, 2,
3, the channel numbers 6 and 7 are given higher priority in the zone number 2, the channel numbers 8, 9, and 10 are given the higher priority in the zone number 3, and the channel numbers 1 and 2 are given the higher priority in the zone number 4. Channel numbers 4 and 5 have the same priority for all zones.

In a conventional multi-channel cordless telephone, this is equivalent to giving equal priority to all channels. This is a different concept from the priority of the present invention, since the use of a common channel is not allowed between zones that may cause at least interference in the conventional cellular car telephone. That is, in the present invention, it is observed that even if the priority of a certain channel is the lowest, all the channels with higher priorities are used and the channel to be used is vacant. If so, communication on that channel is allowed.

The probability of interference is reduced with the system of the present invention as compared to conventional multi-channel cordless telephones, where all channels are given equal priority. The reason is that the channel priority is assigned differently to zones that may cause interference, so the probability of using the same channel between zones that may cause interference decreases. This is because the probability of interference is originally reduced without depending on the detection of an empty channel or the detection of interference.

In the examples shown in FIGS. 1 and 2, in the zone numbers 1 and 4, the priority of the channel numbers 1 and 2 is high because the overlap of the zones is small and the possibility of interference is low. It is. As described above, the present invention has effects similar to those of the conventional cellular car telephone system in terms of interference and effective use of frequency.

First, the advantage of the present invention is that the zone design (channel assignment) in consideration of interference is much easier than that of the conventional cellular car telephone system. The reason is the same as for a multi-channel cordless phone without any zone design,
This is because even if channels with high possibility of causing interference are assigned to two or more zones in order to detect a vacant channel, the interference can be almost avoided in actual communication. For interference during a call, it is possible to escape to a vacant channel as in the conventional example. As a second feature, according to the present invention, basically, all channels can be selected in each zone. Therefore, if the traffic volume to be generated increases, even if the channel has a low priority, the other zones can be selected. If the channel is not used, the channel can be used, thereby increasing the channel use efficiency.

The priority of the channel use is determined based on the past history of the channel use of each zone. The method will be described below. First, the first possible method is
Every time communication is performed, the priority of the channel used there is raised. By performing such an operation, even if each channel initially has the same priority, it is assumed that a channel (here, the number i is assumed) of a certain zone (here, the number i is assumed). j) will be used once, then
Since the channel has a higher priority, the channel is then used in priority and the priority will be higher and higher thereafter.

By the way, in the zone of the number h, which is likely to cause interference with the zone of the number i, the channel of the number j is given priority in the zone of the number i in the observation of the empty channel prior to the communication. Since the channel is used, the probability of observing that the channel with the number j is empty is low, and the priority of the channel does not increase, and the priority of the other channels increases. Also, in the zone of number 1 which is close to the zone of number i currently being considered, but has no possibility of causing interference, the j-th channel having a high priority in the zone of number i is similarly prioritized. The degree increases.

For example, in the case of FIG. 1 and FIG. 2, if the priority of the channels of Nos. 1 and 2 becomes high in the zone of No. 1 and the zone of No. 2 or 3 adjacent thereto becomes , 2 are given higher priority. In the zone of No. 4 which has no possibility of causing interference with the number 1 and has the possibility of causing interference with the zones of Nos. 2 and 3, the channels of high priority (numbers 4-10 ) Can be avoided, so that the priority of the remaining channels of numbers 1, 2, and 3 will eventually increase. By such operation, the priority of the channel is determined, so that the probability of interference becomes the minimum, and at the same time, the repeated use of the frequency is automatically performed.
Optimal channel assignment can be achieved.

As described above, the method of variably determining the priority of the channel based on the actual use of the channel is that even if there is a difference in the traffic volume generated in each zone, the traffic volume is not changed between the zones causing interference. The number of channels with high priority is distributed according to the size of. In addition, if traffic changes occur between zones, channel redistribution will occur accordingly.

The method of determining the priority of a channel based on the track record of channel use may be any method as long as the priority of a specific channel selectively grows in a certain zone. For example, when observing whether or not a channel is empty before using the channel, it is conceivable to raise the priority if the channel is free and to lower the priority if the channel is already used. In addition, if communication is terminated without receiving interference from other zones while communicating using a certain channel, the priority may be increased, and if interference is received, the priority may be reduced conversely. Conceivable. At this time, any method of interference detection may be used. For example, papers (Kozono, Sakamoto, “Measurement of co-channel interference in mobile communication”), IEICE Transactions, vol.J68-B, 10
The method described on page 9-116, January 1985) is considered. As a method of expressing the priority, for example, a counter can be provided and expressed by the contents of the counter.
At this time, since the priority is infinitely high or low, it is naturally necessary to set an upper limit and a lower limit for the number indicating the priority.

FIG. 3 shows an embodiment of the radio transceiver according to the present invention. When a transmission request signal is input from the input / output terminal 301, the control circuit 302 sets a use channel and performs transmission and reception at a frequency determined by the frequency synthesizer 303 according to a flowchart shown in FIG. If there is no usable channel, a busy signal is output to the input / output terminal 301. Here, 309 is a transmission signal input terminal, 310 is a modulator, 31
Reference numeral 1 denotes a transmission circuit, and 305 denotes a duplexer for sharing the antenna 304 for transmission and reception. The modulator 310 performs the modulation and, at the same time, transmits the transmission wave only when receiving the transmission enable signal output from the control circuit 302. The transmission circuit 311 has a transmission frequency determined by an output signal of the frequency synthesizer 303, and includes other operations such as normal amplification and frequency modulation. A reception signal input from the antenna 304 is input to the reception circuit 306 from the duplexer 305. Here, the receiving circuit has a receiving frequency determined by an output signal of the frequency synthesizer 303, and includes other operations such as normal amplification, frequency conversion, and band limitation. The intermediate frequency signal which is the output signal of the receiving circuit 306 is branched into two, one of which is input to the demodulating circuit 307, and the demodulated receiving signal is obtained at the output terminal 308. The other output signal of the receiving circuit 306 is input to the control circuit. As described above, except for the operation of the control circuit, the configuration of the wireless transceiver according to the present invention is no different from the normal configuration.

The control circuit 302 can be realized by the circuit shown in FIG. 4, for example. The output signal of the receiving circuit 306 is input to an input terminal 401, is converted into a signal representing the receiving level by a receiving level detecting circuit 402, and is passed through an analog / digital converting circuit 403 to a microprocessor 404.
Is taken into.

The operation of the microprocessor 404 will be described with reference to the flowchart of FIG. Upon receiving the transmission request signal during standby, the base transceiver station tests the channel having the highest priority. After that, the frequency synthesizer 30 adjusts the reception frequency to the frequency of the corresponding channel.
3 and controls the output signal of the reception level detection circuit 402. It is determined whether or not the channel is empty based on whether or not the reception level signal is equal to or less than a predetermined reference value.
If it is determined that the channel is empty, the priority of the channel is increased by a predetermined value and then transmission and reception are performed on the channel. When the communication is completed, the state returns to the standby state. In the determination as to whether or not the channel is empty, if it is determined that the channel is not empty, the priority of the channel is reduced by a predetermined value.

Subsequently, it is determined whether or not the channel is the last one among the channels usable by the radio transceiver. If it is determined that this channel is not the last channel, that is, that there are still available channels, the channels that have been tested so far are excluded from the next empty channel test. , The channel with the highest priority is tested. Hereinafter, the same operation is repeated until an empty channel is found. If no empty channel is found until the last channel,
After outputting a busy signal, it returns to the standby state.

In this example, the case where the priority is variably set prior to the use of the channel depending on whether or not the channel is empty has been described, but other methods can be easily realized by the combination of the microprocessor and the frequency synthesizer. . However, it is natural that the same operation can be realized by a digital circuit without using a microprocessor. In the embodiment of the present invention, the channel setting is performed by the wireless transceiver of the base station, but it may be performed by the subscriber wireless station. Further, in the embodiment of the present invention, a distinction is made between a base station and a subscriber radio station. However, no distinction is necessary from the operating principle of the present invention.

[0027]

As described above, according to the present invention, the optimum channel division is automatically generated by determining the priority of the channel from the history of channel use, so that the design and operation of zones and channels are simplified. At the same time, there is an effect that the probability of occurrence of interference decreases. The wireless channel of the present invention may be a channel divided on a frequency axis, a channel divided on a time axis, or the like, and is not limited to a specific type in realization. The modulation method used in each zone may be any method as long as it can observe the use of the wireless channel or the interference.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a wireless communication system according to the present invention.

FIG. 2 is a diagram for explaining channel priorities in the present invention.

FIG. 3 is a block diagram showing an embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration example of a control circuit.

FIG. 5 is a flowchart showing an operation of the control circuit.

[Explanation of symbols]

 110, 120, 130, 140 Service zone 111, 121, 131, 141 Radio base station 112, 122 Subscriber radio station 302 Control circuit 303 Synthesizer 304 Antenna 306 Receiving circuit 307 Demodulating circuit 310 Modulator 311 Transmitting circuit 402 Receiving level detecting circuit 403 analog-to-digital converter 404 microprocessor

Claims (1)

[Claims] 1. A base station and a subscriber radio station communicating with the base station, wherein one or a plurality of arbitrary channels among a plurality of radio channels can be used, and a channel to be used is A wireless communication system having a function of starting communication after confirming that it is an empty channel, assigning priority to each channel, setting priority according to past history of channel use, A wireless communication system characterized by being used sequentially and having an upper limit or a lower limit in priority.