JPH0225301B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for collecting the status of a large number of devices (mobile stations) such as an AVM system (automatic vehicle position display device) using a central processing unit (base station).
Regarding a method of allocating time slots to each device and sequentially collecting data using a wireless channel, this method aims to improve data collection efficiency by specifically switching the number of time slots.

Used for wireless taxi dispatch services
In the AVM system, data collection is performed using a polling method. Figure 1 is an example.
The information needed at the dispatch center (base station) includes, for example, data on how many empty cars are in the area where the customer orders. This data is obtained every time the base station 5 transmits a polling signal P. That is, when each mobile station (taxi) ₁ to ₄ receives the polling signal P, it transmits its own data (vehicle number, location,
Condition, etc.) Return D ₁ to _{D 4} in order. For this reason 1
Even when a channel radio line is used, the data D ₁ to D ₄ are identified by the base station 5 without interference, and the status of each mobile station can be automatically grasped without any operation by the driver. However, the contents of orders from customers change significantly depending on the time of day, season, etc., so if data is always collected at a fixed time slot, most of the empty car data will be discarded if the number of empty car requests is small. Moreover, it is a waste of time to collect even such data. For example, if the number of time slots is 20, each time slot
If it takes 0.2 seconds, one polling takes 4 seconds to collect all the data.

The present invention reduces the number of time slots when the amount of data required is small, and also allows two or more pieces of data to be returned simultaneously in the same time slot, thereby shortening the total data collection time. The present invention provides a data collection system in which each mobile station, upon receiving a polling signal from a base station, sends back its own data using a radio link of the same frequency at different time slots predetermined for each mobile station. The station can select and transmit a first polling signal and a second polling signal, and the mobile station can select and transmit a first polling signal and a second polling signal. A common second polling signal is transmitted to multiple mobile stations in response to the second polling signal.
The base station is characterized in that the base station is assigned a time slot, the base station transmits data in the time slot corresponding to the received polling signal, and the base station collects data from the mobile station in accordance with the time slot corresponding to the transmitted polling signal. However, this will be explained in detail below with reference to the illustrated embodiment.

3 and 4 are explanatory diagrams showing one embodiment of the present invention, and FIG. 3 shows the first
a polling signal P ₁ and a second polling signal P ₂
This shows that. The first polling signal P ₁ is similar to P in Figure 2, and is for all mobile stations 1 to 4 in the target area.
From time slot T ₁ to T ₄ , empty car data D ₁ to _{D 4}
Used when sucking up. The polling type "empty car (long)" means that all time slots _T1 to _T4 are used to collect data _D1 to _D4 .
On the other hand, the second polling signal _P2 has a polling type of "empty car (short)" and means the following. In other words, among mobile stations 1 to 4 in the target area, mobile stations 1 and 2 normally have time slots T ₁ ,
Data D ₁ and D ₂ may be returned at time slot T ₂ , but data D ₃ and D _{4 of mobile stations 3 and 4} are sent back at time slot T ₃ and T ₄ .
Instead, it must be sent back using T ₁ and T ₂ . Figure 4 is the time chart at this time, and in the end, the data is at time slot _T1 .
D ₁ and D ₃ are returned at the same time, and the time slot
At T ₂ , data D ₂ and D ₄ are returned simultaneously.

If two types of data exist in the same time slot, they will interfere because they are on the same channel. but,
Due to the nature of the wireless link, base station 5 tends to receive data with higher field strength preferentially, so for example, if mobile stations 1 and 2 are closer to base station 5 than mobile stations 3 and 4, respectively. are data D ₁ , D ₂
only is played. Since the data D ₃ and D ₄ at this time are not reproduced, the amount of information collected will be halved if you follow the general idea of data collection. However, in polling for empty cars, only mobile stations with empty cars send back data, and mobile stations with actual cars do not send back data, so in the above example, data D ₁ to _{D 4} are all empty car information. Therefore, even if data D ₃ and D ₄ are buried in the shadow of data D ₁ and D ₂ , it will be known that mobile stations 1 and 2 are empty, and a small number of empty cars in the target area can be quickly found. I can fully meet your needs. Of course, if the mobile stations 1 and 2 are actual vehicles, the data D ₁ and D ₂ will not be returned, so the data D ₃ and
From _D4 , it can be determined that mobile stations 3 and 4 are empty. In this example, since the number of time slots is halved, the polling time is also halved, but if the number of time slots is reduced to 1/3, 1/4, . . . , the polling time can be further reduced.

As described above, according to the present invention, all data can be collected over a long period of time, but a small number of data can be collected in a short period of time. This is effective in cases where there are various demands.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a data collection system employing a polling method, FIG. 2 is a time chart thereof, and FIGS. 3 and 4 are explanatory diagrams showing an embodiment of the present invention. In the figure, 1 to 4 are mobile stations, 5 is a base station, P ₁ , P ₂
is a polling signal, _T1 to _T4 are time slots,
_D1 to _D4 are returned data.

Claims (1)

[Claims of Claims] 1. A data collection method in which each mobile station, upon receiving a polling signal from a base station, returns its own data at different time slots predetermined for each mobile station using a radio line with the same frequency. In this case, the base station can select and transmit a first polling signal and a second polling signal, and the mobile station can transmit a first time slot that is different for each mobile station in response to the first polling signal. A common second time slot is assigned to a plurality of mobile stations in response to the second polling signal, and the base station transmits data in a time slot corresponding to the received polling signal, and the base station receives the transmitted polling signal. A time slot switching type data collection method characterized by collecting data from a mobile station according to a time slot corresponding to a signal.