JPS5828975B2 - Information transmission system for fixed subscribers and mobile subscribers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a wireless communication network comprising a plurality of radio concentrators spatially arranged with respect to each other in a cell-like manner including overlapping radio areas; have a predetermined frequency distribution plan for each radio area, and that this plan does not result in co-channel interference within the respective radio area, including extended edge coverage, where subscribers and radio concentrators A mobile subscriber in a large radio communication network in which the exchange of information regarding the radio capabilities between the mobile subscriber and the Concerning methods for transmitting information.

Public mobile radio services and non-public mobile radio services include radio communication networks with various network configurations.

However, there are significant differences between public land mobile radios and non-public land mobile radios.

Public land mobile radio has mobile telephone subscribers who are connected to the exchanges of the public telephone network via radio exchanges.

On the other hand, non-public land mobile radio subscribers include public safety agencies such as the police, fire department, accident rescue, and disaster relief, as well as taxi operators,
These include transportation companies, industrial radio subscribers, commercial radio subscribers, and construction companies.

For non-public land mobile radio subscribers who do not require long-distance communications, most information transmission can take place via short-range radio concentrators.

This means that such subscribers hardly need to be connected via long-distance radio telephone exchanges, but only via local connection switch frames.

In addition to these mobile radio services, there are radio services for fixed subscribers.

However, wireless service for fixed subscribers is limited to man-made and sparsely populated areas.

In addition to transmitting calls, it is also necessary to transmit documents and still images.

Radio operations also require calls (e.g. pagers and emergency calls)
Also used for

Since various wireless services coexist, various subscribers use these wireless services, and therefore various wireless communication networks coexist, it is not possible to save frequencies as desired.

Furthermore, since the wireless concentrator stations must be configured and installed taking into account the maximum communication load within each area, the various devices become extremely expensive.

To expand radio services, frequency conservation is an issue in the area of non-public land mobile radio, while high equipment costs are an issue in the area of public land mobile radio.

The basic problem of the present invention is to develop the information transmission method described at the beginning, which is improved in terms of frequency conservation and also enables cost reduction of the entire wireless concentrator equipment even when the maximum communication load is taken into account. It is to provide.

According to the present invention, this problem is solved as follows.

That is, each mobile subscriber receives information about continuously transmitted free channels of the radio concentrator.
Each subscriber belongs to a wireless concentrator that constitutes one wireless area, and is tuned to a functional channel that is receivable during operation, and based on the instantaneous reception status of the functional channel, including information about empty channels, it is possible to determine which wireless area the subscriber is in. A mobile subscriber who has decided to register and who has also registered in the respective radio area always monitors the information regarding free channels available by the radio concentrator in the radio area to which it belongs in the idle state and uses the predetermined If it is detected that the number of free channels has decreased by more than the limit value, it is tested whether it is possible to change the region to another wireless region with the number of free channels greater than this limit value and good radio conditions, and If a change is possible, it is accomplished by deregistering in one radio region and registering in the other radio region.

In a wireless communication network where radio concentrators are arranged in a cellular manner, as is well known, if a sufficient distance is provided between radio concentrators with the same transmitting and receiving frequencies, a relatively small number of transmitting and receiving frequencies can be used. I can make it in time.

This is because if a sufficient distance is provided between radio concentrators having the same transmission frequency and reception frequency, co-channel interference in the individual radio concentrator stations can be prevented.

For example, "Jaarbuch des electrifications fernmerdebesens" 1970 yearbook, 21, Georg Heidezka, Bad Winsheim, pages 305 to 311, the 380th edition of the 1970 yearbook, 21. In Figure 1) a cellular wireless communication network using seven frequency groups is illustrated.

In this wireless communication network, frequencies are assigned to individual wireless concentration stations according to a so-called diamond diagram.

The invention is based on the following recognition: the number of transmitting and receiving frequencies provided at each radio concentrator depends on the maximum communication load.

If a mobile subscriber can decide which wireless concentrator he should apply to based on predetermined criteria, the number of transmitting and receiving frequencies provided to each wireless concentrator can be reduced.

Moreover, it is advantageous to set the minimum number of channels that the mobile subscriber deems appropriate from among the available channels provided by the radio concentrator based on his/her own radio technology situation as the criterion for self-interest.

If the amount of communication load in each wireless concentrator area is used as a standard, it is possible to prevent imminent overload of the wireless concentrator in advance by allowing subscribers to evacuate to an adjacent wireless concentrator area. Therefore, it is possible to prevent the radio concentrator from being blocked and unable to process other channels.

It is extremely useful to use the amount of communication load in each radio concentration area as a reference in this way.

The above-described functions of the mobile subscriber correspond to the function of expanding or contracting the service area of the wireless concentrator depending on the amount of communication load.

If the communication load on the wireless concentrator increases and approaches the maximum communication load, the service area of the wireless concentrator will shrink.

On the other hand, the service area of the adjacent wireless concentrator is accordingly expanded to the area around the expanded boundary.

The communication load on the wireless concentrator drops to a relatively small value,
On the other hand, if it is necessary to reduce the communication load of an adjacent wireless concentrator, the service area of the wireless concentrator whose communication load has decreased is expanded, and the service area of the adjacent wireless concentrator is reduced.

Each mobile subscriber monitors the communication load of the wireless communication network in the area of the wireless concentrator by checking the number of vacant channels of the wireless concentrator that he has applied for or can apply for.

According to an embodiment of the present invention, each mobile subscriber constantly monitors the amount of communication load on the free channels provided by the wireless concentrator to which he/she subscribed under free conditions, and when the number of free channels falls below a predetermined limit value. When checking, it is checked whether it is possible to change the application from the wireless concentrator to another wireless concentrator that provides a number of vacant channels exceeding a predetermined limit, and if the result of the check is positive, The change in the application is carried out only when it is determined that good information transmission with the other radio concentrator is sufficiently possible in view of the state of its own radio technology.

It is also impossible to configure the subscriber to incregate all the channels of the radio concentrator at a predetermined rhythm, and to determine from the result of this incorporation whether there are free channels of the radio concentrator. isn't it.

However, this method takes a considerable amount of time.

Therefore, according to an embodiment of the present invention, information indicating the amount of communication load in a radio concentrator area is continuously transmitted via a functional channel within the radio concentrator area, so that each mobile subscriber can Incrogate the functional channels in the area of the subscribed radio concentrator and monitor the information.

It is advantageous if only information indicating whether the communication load in the radio concentration area exceeds or falls below a predetermined limit threshold is transmitted via the functional channel as information indicating the communication load in the radio concentration area.

According to another embodiment of the invention, digital information transmission (for example binary frequency modulation) is used as the information transmission.

As is well known, binary signals can be reproduced very well, and therefore the signal-to-noise ratio required for perfect reception of binary signals is reduced to 10.
It can be set to a value smaller than dB.

The area around the extended boundary of each radio concentration area can be penetrated quite deeply into the adjacent radio concentration area.

Therefore, the overlap area of adjacent radio concentration areas can be expanded to a considerable extent.

In such an overlapping area, a subscriber can select one wireless concentration area from two or more wireless concentration areas to transmit information.

If digital information transmission is used, communication secrecy can be maintained simply, reliably, and at low cost using a digital confidential communication system.

Furthermore, if a digital transmission system is used, it is possible to unify the wireless communication networks used for various wireless services, which has a great advantage.

That is, various types of information such as telephone calls, documents, still images, pagers, and emergency calls are transmitted at the same bit rate using a common wireless communication device.

It is advantageous to set the bit rate to approximately 5 Kbit/S.

In this case, by reducing the redundancy of broadband information such as telephone calls, and then transmitting broadband information such as telephone calls, 5K b
t Adapt to a bit rate of t/S.

A wireless communication network using the information transmission system of the present invention has sufficient responsiveness to fluctuations in the communication load of the wireless communication network in the wireless concentration area.

Therefore, the transmitter/receiver of the wireless concentrator can be configured based on the average communication load.

Not only can this number of frequencies be saved, but equipment costs can be significantly reduced.

Next, the present invention will be explained in detail with reference to the drawings with reference to embodiments.

FIG. 1 shows a wireless communication network in which wireless concentrators are arranged in a cellular manner.

The wireless communication network of FIG. 1 is a mobile wireless communication network and is expandable.

The average radius R of each radio concentration area is approximately 15 kIn.

The wireless communication network shown in FIG. 1 uses a duplex method in the UHF band of about 450 MHz.

A frequency interval of about 10 MHz is provided between the transmitting band and the receiving band so that the transmitting band and the receiving band are completely electromagnetically compatible.

When allocating frequencies, transmission bands and reception bands are handled together.

As is clear from FIG. 1, the wireless communication network is divided into frequency allocation areas.

Each frequency allocation area has seven radio concentrators 1-7.

In FIG. 1, three different frequency allocation regions are illustrated.

These frequency allocation areas have left-sloping lines, right-sloping lines, and
It has a horizontal line.

The wireless concentrator 1 is indicated by an x mark.

The remaining radio concentrators 2 to 7 are indicated by circles.

The wireless concentrator 1 is different from the remaining wireless concentrators 2 to 7,
This is because it has the function of a wireless switching center so that it can be connected to the switching center of the public telephone communication network.

All of the frequency allocation areas having the seven wireless concentrators 1 to 7 have the same configuration and the same frequency allocation.

The area numbers of the wireless concentrators 1 to 7 are indicated by 1 to 7.

The areas of radio concentrators 1 to 7 are overlapped with each other so that there is no gap in which mobile subscribers cannot be captured.

It is desirable to reduce co-channel interference as much as possible even in the overlap region of the radio concentrators 1 to 7.

Co-channel interference between remote radio concentrators rather than adjacent radio concentrators occurs depending on the minimum level difference between channels at the mobile subscriber's reception point.

This minimum level difference between channels depends on the modulation method.

When determining frequency distribution/location within a frequency allocation area, the above circumstances must be taken into consideration by taking into consideration the upper placement pattern of adjacent frequency allocation areas.

Frequencies are assigned to individual radio concentrators such that there is a distance greater than a predetermined minimum distance between radio concentrators that have the same area number and therefore use the same radio frequency.

This predetermined minimum distance is, for example, about 80 IarL. In this way, co-channel interference will not occur in directly adjacent radio concentration areas.

By dividing the transmission band and the reception band into 120 channel groups, and assigning seven channels to each channel group, it is possible to allocate one channel from each channel group to each radio concentration area.

Moreover, it is advantageous if the channels assigned to the individual radio concentration areas occupy a constant position in the channel group.

For example, the first channel of each channel group is assigned to the radio concentration area 1.

The second channel of each channel group is assigned to the radio concentration area 6.

The third channel of each channel group is assigned to the radio concentration area 4.

Same below. If the frequency arrangement is determined in this way, a frequency interval corresponding to six channels will be created between the channels used by the individual radio concentrators.

Therefore, sufficient frequency spacing is provided between the channels of the individual radio concentrator areas, and adjacent channel interference of the transmitters of the radio concentrators can be reliably prevented.

FIG. 3 is a diagram plotting the relationship between distance and electric field strength in the wireless communication networks of FIGS. 1 and 2. FIG.

In FIG. 3, the transmission level is shown in OdBm.

As shown in Fig. 3, the transmission level is determined by the distance (unit Iar
L).

The horizontal lines in Fig. 3 indicate the radio concentration areas FBI, FB2,
FB5.

FB1' is plotted by distance.

Wireless concentration area FBI, FB2. FB5 belongs to the same frequency allocation area.

The radio concentration area FBI' belongs to a frequency allocation area adjacent to the frequency allocation area.

The attenuation characteristic of the transmission level is actually accompanied by drift, but the third
It is omitted in the figure for simplicity.

The average distance between directly adjacent radio concentrators is denoted by R'.

In the case of FIG. 1, R=151 an, so R' is, for example, about 13.5 ICIn.

The reason why R and R' take different values is because directly adjacent radio concentration areas overlap with each other.

Due to the frequency allocation described above, the wireless concentration area FBI, FBI
' uses the channel of frequency f1.

Frequency f2 in radio concentration areas FB2 and FB5, respectively.
．． Use channel f5.

The boundary between the wireless concentrator area FBI and the wireless concentrator area FB2 is at a distance R' from the wireless concentrator 1.

The level difference between the same channels at the boundary between the wireless concentration area FBI and the wireless concentration area FB2 is approximately 35 dB.

By the way, in the case of digital transmission, the critical level difference between the same channels is 6 dB over a distance of about 32 axes.

This value is based on a case where an antenna with a height of 75 m is used for a radio concentrator in a central European region where there is an average height difference of 50 m.

In the case of digital information transmission, the service area of a wireless concentrator can be considerably extended to the area of adjacent wireless concentrators.

In other words, if an adjacent wireless concentrator needs assistance (so-called adjacent area assistance), and the wireless concentrator to be assisted is able to handle its own communication load and still have some leeway to provide assistance,
The service area of the radio concentrator to be assisted can be substantially expanded to penetrate considerably into the area of neighboring radio concentrators.

If this is possible, even if a particular wireless concentrator is flooded with subscribers and an imminent overload situation occurs, it will be possible to cope with this situation.

Therefore, in addition to taking into account the maximum amount of communication load that occurs over a short period of time, it is possible to configure a wireless concentrator based on the average amount of communication load.

FIG. 2 extracts and shows two frequency allocation regions of the wireless communication network of FIG.

Next, mutual assistance between adjacent radio concentrators will be explained in detail with reference to FIG.

In the left-hand part of FIG. 2, the mobile subscriber T1 is located in the border area of the radio concentration area 1.

It is assumed that the mobile subscriber T1 has already applied to the nearest radio concentrator, radio concentrator 1, and has been vacant ever since.

In this state, the mobile subscriber T1 constantly interrogates the functional channels of the radio concentrator 1.

Information indicating the number of usable free channels of the wireless concentrator 1 is stored in the functional channel.

The functional channel therefore informs the mobile subscriber T1 of the number of available free channels of the radio concentrator 1.

When the amount of communication load on the radio concentrator exceeds the limit threshold, information indicating that there is a risk of overload is sent to the mobile subscriber T1 as a signal.

When the mobile subscriber T1 confirms this signal, the mobile subscriber T1 then checks whether there is anything connectable to the adjacent wireless concentrator areas 3 and 4 and calculates the communication load in the wireless concentrator areas 3 and 4. It is automatically determined based on the situation of own wireless technology.

If the result of this judgment is positive and either of the radio concentrator areas 3 and 4 is connectable, the mobile subscriber T1 withdraws the application to the radio concentrator 1 and , 4, apply for one that is connectable.

That is, when an imminent communication overload condition occurs in the wireless concentrator 1, the service area of the wireless concentrator 1 contracts from area 1 to partial area A, so to speak.

The ring-shaped area A' remaining after excluding the partial area A from the area 1 is covered by the area of the wireless concentrators 2 to T adjacent to the wireless concentrator 1.

Therefore, a mobile subscriber located in the ring-shaped area A' is captured by one of the radio concentrators 2-7.

In Figure 2, the contraction of the service area of wireless concentrator 1 is shown as follows:
It is indicated by an arrow pointing in the direction from the radio concentration areas 2 to 7 to the radio concentration area 1.

The right-hand portion of FIG. 2 illustrates a case that is contrary to the case shown in the left-hand portion.

In the right-hand part of FIG. 2, subscriber T2 is located in radio concentration area 2. In FIG.

Since the wireless concentrator 2 is in an imminent overload condition, the subscriber T2 subscribes to the wireless concentrator 1.

The wireless concentrator 1 provides a sufficient number of free channels, and the subscriber T2 has confirmed that the wireless concentrator 1 is connectable, judging from his own wireless technology situation.

In this case, the wireless concentrator 1 uniformly expands its service area from the area 1, thereby forming a ring-shaped expanded peripheral area B.

The subscriber T2 located within the radio concentration area 2 is captured by the ring-shaped extended peripheral area B.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a wireless communication network in which wireless concentrators are arranged in a cell-like manner, FIG. 2 is a partial schematic diagram of a wireless communication network used to explain the present invention, and FIG. It is a diagram showing the relationship between distance and electric field strength of radio waves in a communication network. 1 to 7...Radio concentrator or radio concentrator area, FBI
, FB2, FB5, FBI'... Radio concentration area, TI, T2... Subscriber, B... Ring-shaped extended peripheral area.

Claims (1)

[Scope of Claims] 1. A wireless communication network is connected to a plurality of wireless concentrators spatially arranged in a cellular manner including overlapping wireless areas, and the wireless communication network is connected to a predetermined wireless concentrator station. have a frequency distribution plan that ensures that this plan does not result in co-channel interference within each radio area, including extended edge coverage, and that there is no co-channel interference between subscribers and radio concentrators. for the transmission of digital information to mobile subscribers within a large-scale radio communications network in which the exchange of information regarding the radio functionality of the In this scheme, each mobile subscriber TI, T2 each uses one radio region 1°2...7 for information regarding continuously transmitted vacant channels of the radio concentrator. Determines which wireless region the subscriber should register in based on the instantaneous reception status of the functional channels that belong to the constituent wireless concentrators and are receivable during operation, and also includes information about vacant channels. , and furthermore, a mobile subscriber who has registered in each radio region constantly monitors the information regarding free channels available by the concerned radio concentrator in the radio region to which it belongs in the free state, and detects free channels below a predetermined limit value. If it is detected that the
Test whether a region change is possible to another radio region with a number of free channels above this limit and good radio conditions, and if this change is possible, deregister and deregister in one radio region. An information transmission scheme for fixed and mobile subscribers, characterized in that this change is carried out by registering in the radio region of the other. 2. The system of claim 1, wherein the radio concentrator for the transmitter-receiver set is configured based on the average traffic load.