JPH0659039B2 - Wireless communication system - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention makes it easy to reduce the risk of interference in wireless communication systems, especially when interference in the wireless channel is present in principle. Wireless communication system that can be performed.

(Prior Art and Problems Thereof) In wireless communication, it is common practice to use the same frequency repeatedly in order to increase the efficiency of frequency utilization. In this case, since the same frequency is used at the same time, the risk that two or more signals collide with each other in one radio channel to impair communication, so-called interference, cannot be avoided in principle. So in particular,
In a mobile radio communication system in which the location of the radio moves, like the cellular car telephone system, multiple communication zones are set, and the radio channels used for each zone are set so that interference does not occur as much as possible. There is. As a transfer to the detailed literature on the design method of such a system (Ito, Matsuzaka, “Outline of Car Telephone System”, Research Report, Vol. 26, No. 7 (1977), 1821-1836) The general idea is to ensure that the probability of interference is below a certain value by separating zones that use the same frequency over a certain distance. By the way, in such a conventional system, since it is necessary to design a planar zone and channel in advance, it is necessary to accurately determine basic parameters such as radio wave propagation characteristics, and at the same time, spread in a planar manner. There is a drawback that the system operation becomes large in order to manage the system.

By the way, as a recent trend of mobile radio communication, it is well known that demands for mobile phones, radio telephones for wireless channels, data systems and the like are increasing. In these systems, due to the limited power available,
The communication zone becomes a small area (hereinafter referred to as a smile zone), and at the same time, the cost of constructing or operating the system must be reduced. At this time, first, it becomes difficult to accurately determine the radio wave propagation characteristics due to the narrowing of the zone, and thus it becomes difficult to predict the probability of interference in advance.
This can be easily understood by considering that the radio wave propagation characteristics greatly change depending on the installation conditions such as partitioning of rooms and metal equipment such as lockers in a building or the like. In high-rise buildings, the zone becomes three-dimensional, which further complicates the problem. The next problem is that the number of wireless telephones or data end devices accommodated in the system increases, which makes it difficult to construct and operate the system. Since these problems are expected, the basic idea of the conventionally known car telephone system cannot be directly applied to the minute zone system.

The multi-channel cordless telephone (Kawasaki, Kato, Yoshizawa, “New Cordless Telephone” facility, Shi-36-3, 134-141 pages) currently under development can be considered as a kind of micro zone system. . The method of eliminating the management of the wireless zone and the wireless channel, which is one of the basic ideas of this system, is effective in reducing the construction and operation costs of the system. However, this cordless telephone has a restriction that it cannot move in a wide range like a car telephone because it is registered only in the base station and the movement is registered one-to-one. Furthermore, in this system, instead of designing a zone, a large number of channels are prepared, empty channels are observed prior to communication, and at the same time, when interference is received during communication, a method of escaping to another channel is provided. It is adopted. However, this method cannot sufficiently prevent interference.
That is, first, the problem is that interference detection is not perfect. Then, even if interference can be detected, it must be guaranteed that another channel is free. This will be a problem when many cordless phones become popular.

(Object of the Invention) The present invention provides a wireless communication system that eliminates the drawbacks of the conventional system as described above, can reduce the cost of system construction and operation, and can reduce the probability of interference. To do.

(Structure of the Invention) The present invention provides a priority to each channel for a wireless communication system that can arbitrarily use one or a plurality of channels among a plurality of wireless channels, and assigns the priority to the past of channel usage. By defining the history and adding the function to use sequentially from the channel with high priority,
Will be realized.

(Outline of the Present Invention) The present invention adds different priorities to the channels used in each zone so that interference can be prevented even if channels are not fixedly assigned to each zone in advance. The basic principle is that the probability 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.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings. First
FIG. 1 is a conceptual diagram of a wireless communication system for explaining an embodiment of the present invention. The service zone 110, 120, 130, 140 for each wireless base station is a range in which the level of the transmission carrier signal emitted from the wireless base station 111, 121, 131, 141 is equal to or higher than the minimum reception input reference level. Since the shape of the service zone is a minute zone, it has a complicated shape due to the irregularity of the radio wave propagation characteristics described above. Although there are actually many subscriber wireless stations 112 and 122, only two are shown here for the sake of simplicity. A subscriber radio 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 naturally communicate with any of the base stations forming each zone, but when the same channel is used in two zones at the same time. Will cause interference. It is desirable that the arrangement of the radio base stations be made so that the overlapping of zones is minimized in consideration of the characteristics of radio wave propagation.
However, the feature of the present invention is that the reference for this arrangement is loose. That is, as will be described below, the probability of interference decreases even if the zones overlap greatly.

The radio base station and the subscriber radio station have a plurality of channels. However, the number of channels actually used at the same time may be one or two or more. The present invention presupposes that before starting communication in one zone, it is confirmed in advance that the channel to be used in another zone is not already used. Find another free channel. This feature is similar to traditional multi-channel cordless phones. Here, the problem is that the detection of a vacant channel is incomplete, and it is actually judged that a channel that is already in use is vacant, resulting in interference. The cause of such an erroneous detection is that the level of the received signal temporarily falls below the sensitivity because the propagation characteristics are irregular due to the movement of the subscriber wireless station. Or, it is possible that another system starts communication during the time from immediately after the detection of an empty channel to 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 determined 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, and 3 are
In zone number 2, channel numbers 6 and 7 are given high priority, in zone number 3, channel numbers 8, 9 and 10 are given high priority, and in zone number 4, channel numbers 1 and 2 are given high priority. The channel numbers 4 and 5 are given the same priority for all zones. This is equivalent to giving equal priority to all channels in a conventional multi-channel cordless telephone. This is a different concept from the priority in the present invention, because the conventional cellular car telephone does not allow the use of a common channel during at least potentially interfering zones. That is, in the present invention, even if the priority of a certain channel is the lowest, it is observed that all the channels of higher priority are used, and that the channel to be used is vacant. Communication on that channel is allowed.

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

In the example shown in FIGS. 1 and 2, zone numbers 1 and 4
In both cases, the reason why the channel numbers 1 and 2 have high priority is that the overlapping of the zones is small and the possibility of interference is low. Thus, in terms of interference and effective use of frequency, the present invention provides an effect close to that of the conventional cell type mobile telephone system.

If the features of the present invention are shown in comparison with the conventional cell type automobile telephone system, firstly, zone design (channel allocation) in consideration of interference is much easier. The reason is the same as in the case of a multi-channel cordless phone without zone design, even if channels with high possibility of causing interference are assigned to two or more zones in order to detect an empty channel. ,
This is because 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, in the present invention, basically, all channels can be selected in each zone. Therefore, even if a channel with a low priority is used if the call volume generated is increased,
If the channel is not used in another zone, the channel can be used, thereby increasing the channel use efficiency.

The priority of channel use is determined by the past history of channel use of each zone, and the method will be described below. First, the first conceivable method is to raise the priority of the channel used in each communication. By performing such an operation, even if each channel initially has the same priority, it is assumed that a channel (here, the zone with the number i) is a channel (here, the number is temporarily assigned). j) will be used once, the priority of the channel will be higher next time, so that the channel will be used next, and the priority will be further increased. . By the way, in the zone of number h, which may cause interference with the zone of number i, which is being considered, the channel of number j is preferentially used in the zone of number i in the empty channel observation performed prior to communication. Because
The probability of observing that the channel of number j is empty becomes low, the priority of that channel does not become high, and the priority of other channels becomes high. Also,
In the zone of number l, 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 has the same priority. Get higher For example, in the case of FIGS. 1 and 2, if the priority of the channels of the numbers 1 and 2 becomes high in the zone of the number 1, the number 2 adjacent to the zone 1
Alternatively, in the zone of 3, the channel priorities other than the channels of numbers 1 and 2 are high. In the zone of number 4, which has no possibility of causing interference with the number 1 and has the possibility of causing interference with the zones of the numbers 2 and 3, channels of high priority (number 4 to Since 10) can be avoided, the priority of the remaining channels of numbers 1, 2, and 3 will eventually increase. By such an operation, the priority of the channel is determined, so that the probability of interference is minimized, and at the same time, the frequency is changed and used automatically, and almost the optimum channel allocation is achieved. You can do it.

In this way, the method of variably setting the priority of a channel according to the actual use of the channel can reduce the call volume between zones that cause interference even if there is a difference in the call volume generated in each zone. Accordingly, the number of high-priority channels will be distributed. Furthermore, even if a change in call volume occurs between zones, channel redistribution occurs correspondingly.

Any method may be used to determine the priority of a channel based on the track record of channel usage, as long as the priority of a specific channel selectively grows in a certain zone. For example, when observing whether or not the channel is an empty channel before using the channel, it is possible to raise the priority if it is vacant and lower it if it is already used. In addition, if you end communication without receiving interference from other zones while you are using a certain channel, you can increase the priority, and if you are worried about interference, decrease the priority. Can also be considered. At this time, any method may be used for the interference detection, for example, paper, (Kozono, Sakamoto, "Measurement of co-channel interference amount in mobile communication", IEICE Transactions, vol. J68-B, 109-. 116 pages, 1985
The method described in (January 1) can be considered. As a method of expressing the priority, for example, a counter is provided and the content of the counter can be used for expression. At this time, the priority becomes infinitely high or low, and thus it is naturally necessary to set an upper limit and a lower limit to the number indicating the priority in terms of design.

An embodiment of a wireless transceiver according to the present invention is shown in FIG.
When the transmission request signal is input from the input / output terminal 301, the control circuit 302 sets the channel to be used and sets the frequency synthesizer according to the flowchart shown in FIG. 5 described later.
Transmission and reception are performed at a frequency determined by 303.
If there is no available channel, a high signal is output to the input / output terminal 301. Here, 309 is a transmission signal input terminal, 310 is a modulator, 311 is a transmission circuit, and 305 is an antenna 3.
It is a duplexer for sharing 04 for sending and receiving. At the same time that the modulator 310 performs modulation, it transmits a transmission wave only when it receives a transmission enable signal output from the control circuit 302. The transmission circuit 311 has a transmission frequency of frequency synthesizer 303.
It is determined by the output signal of, and other operations such as normal amplification and frequency conversion are included. The reception signal input from the antenna 304 is input to the reception circuit 306 from the duplexer 305. Here, in the receiving circuit, the receiving frequency is determined by the output signal of the frequency synthesizer 303, and other normal amplification,
Includes operations such as frequency conversion and band limitation. Receiver circuit 306
The intermediate frequency signal, which is the output signal of, is split into two, one of which is input to the demodulation circuit 307, and the demodulated reception 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, for example, the circuit shown in FIG. The output signal of the reception circuit 306 is input to the input terminal 401, converted into a signal representing the reception level by the reception level detection circuit 402, and taken into the microprocessor 404 through the analog-digital conversion circuit 403.

The operation of the microprocessor 404 will be described with reference to the flowchart of FIG. The radio transceiver of the base station checks the channel having the highest priority when receiving the transmission request signal while waiting. After that, the frequency synthesizer 303 is controlled so that the reception frequency becomes the frequency of the corresponding channel, and the output signal of the reception level detection circuit 402 is observed. Whether or not the channel is empty is determined depending on whether or not the reception level signal is less than or equal to 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 communication is completed, it returns to the standby state. In the above-mentioned determination of whether or not the channel is empty, if it is determined that the channel is not empty, the priority of the channel is decreased by a predetermined value. Subsequently, it is determined whether or not the channel is the last one of the channels usable by this wireless transceiver. If it is determined that this channel is not the last one, that is, there are still available channels, the channels that have been tested up to this point are excluded from the next empty channel test. , Test the channel with the highest priority. Less than,
The same operation is repeated until an empty channel is found. if,
If no empty channel is found up to the last channel, it outputs a busy signal and then returns to the standby state.

In this example, the priority is variably set prior to the use of the channel depending on whether the channel is empty or not. However, 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 the 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, the base station and the subscriber radio station are distinguished from each other, but the principle of operation of the present invention does not require any distinction.

(Effects of the Invention) As described above, in the present invention, by determining the priority of a channel from the history of channel usage, a nearly optimal channel division is automatically generated, so that the design and operation of the zone and the channel are simple. At the same time, there is an effect that the probability of occurrence of interference is reduced. The wireless channel of the present invention may be a channel divided on the frequency axis, a channel divided on the time axis, or the like, and is not limited to a specific type in terms of implementation. 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 for explaining a wireless communication system of the present invention, FIG. 2 is a diagram for explaining channel priority in the present invention, and FIG. 3 is a block diagram showing an embodiment of the present invention. 4 and 5 are block diagrams showing a configuration example of the control circuit, and FIG. 5 is a flow chart showing the operation of the control circuit. In the figure, 110, 120, 130, 140 ... service zone,
111, 121, 131, 141 ... Radio base station, 112, 122 ... Subscriber radio station, 302 ... Control circuit, 303 ... Synthesizer, 30
4 ... Antenna, 306 ... Receiving circuit, 307 ... Demodulating circuit, 3
10 ... Modulator, 311 ... Transmission circuit, 402 ... Reception level detection circuit, 403 ... Analog-digital converter, 404 ... Microprocessor.

Claims (5)

[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 the channel to be used is A wireless communication system that has 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 usage, A wireless communication method characterized by being used sequentially. 2. The wireless communication system according to claim 1, wherein each time a channel is used, the priority of the channel is relatively increased. 3. When observing whether or not the channel is an empty channel before using the channel, if the channel is an empty channel, the priority of the channel is increased, and if it is not the empty channel, the priority of the channel is increased. The wireless communication system according to claim 1, wherein the wireless communication system is reduced. 4. The priority of a channel is increased if the channel is not interfered with by another signal while the channel is in use, and the priority of the channel is decreased if the channel is interfered with. The wireless communication method described in 1). 5. The wireless communication system according to claim 1, wherein the priority has an upper limit or a lower limit.