JPH0591004A - Mobile body satellite communication equipment - Google Patents

Abstract

PURPOSE:To make voice communication and packet communication compatible and to make the packet communication efficient. CONSTITUTION:A reception radio wave intensity from a communication satellite 10 is detected by a reception level detector 40 and reception level data for a prescribed time are stored in a storage section 44 by implementing the detection for a prescribed time. When a perspective rate is discriminated to be 90% or over based on a reception level for 10min just before, for example, a changeover device 26 is thrown to the position of a voice communication system 30 to allow the voice communication system to be offered. Even when the perspective rate is 90% or below, if it is discriminated that the mobile equipment is stopped at a perspective location based on data from a running state detector 46, the voice communication service is offered. Furthermore, when the situation differs from those above, the packet communication service is selected, and the packet length and the packet re-transmission interval in this case are decided by the accumulation probability distribution of the perspective consecutive time and the shield consecutive time decided by the reception level for 10min just before.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile satellite communication device mounted on a mobile body such as an automobile and performing radio communication with a satellite.

[0002]

2. Description of the Related Art Conventionally, a mobile communication system in which a transceiver is mounted on a mobile body such as an automobile to perform radio wave communication has been widespread. In particular, the spread of car phones and mobile phones is remarkable, the number of subscribers to them is increasing rapidly, and the service area is expanding. However, a car phone is a system based on communication between a wireless base station on the ground and a transceiver of a mobile body, and the service area of one base station is a radius of 2 to 3 km in the urban area and in the suburbs. It is about 5 to 10 km. For this reason, it is necessary to construct a huge number of base stations in order to extend the service area to mountainous areas, etc., and it is virtually impossible to extend the service nationwide with such a system. ..

On the other hand, if satellite communication, which has been attracting attention in recent years, is used, the satellite has a wide area (the satellite can be seen all over the country and its service area is wide), and broadcast (simultaneous communication is carried out). It is possible that telecommunications services will be possible nationwide due to the merit of being able to provide many services at the same time).

[0004] Here, satellite communication is used for telephone communication, which has conventionally required real-time communication, and data communication capable of batch processing by collecting data to some extent, and FAX communication is also used in mobile communication. And batch processing such as data processing using computers and
There is a telephone communication by voice.

In the normal case, packet-type digital communication is used in batch data processing, and voice communication such as telephone communication is real-time transmission in which a communication line is continuously occupied and data is transmitted. is doing.

On the other hand, what is the packet format digital communication?
The data is divided into data having a predetermined length (a packet obtained by adding a header part accommodating the destination and other information to the divided data) is transmitted. The packet communication is intended to improve the efficiency of data transmission in a large number of communication lines, and the packet length (data length of one packet) is set to a length suitable for these processes. ..

If the transmission is not successful, it is retransmitted after a predetermined time (this is called a retransmission interval). This retransmission interval also takes into consideration the time required for processing for one packet transmission. Was decided.

[0008]

However, in the case of mobile communication, a mobile body such as a car equipped with a transceiver moves to various places. For this reason, there are cases where the moving body is in an urban area with many radio wave shields such as buildings (where the visibility of the satellite is poor), and in the suburbs where there are few obstacles for radio transmission and reception (where the visibility of the satellite is good). In mobile communication, the propagation characteristics of radio waves vary greatly depending on the position of the mobile body.

In urban areas, it is considered that the satellite can see through the satellite for a very short time, and in suburban areas, the satellite can see in the satellite for a long time. Therefore, if the packet length is fixed, the probability of retransmission is very high due to the fact that communication for that packet is not completely performed in urban areas, and the packet length is increased in suburban areas. There is a problem in that the efficiency of transmission deteriorates due to the short setting.

Further, in a telephone communication or the like which requires real-time transmission, if the satellite cannot be seen through the communication, the transmission becomes impossible. Therefore, in urban areas, it is considered preferable not to provide such a service, since it is impossible to perform telephone communication using satellites. However, there is a demand to use real-time communication using satellites in the case of a suburban area where satellites have a high probability of seeing, or when a moving body stops in a place where satellites can see.

The present invention has been made in view of the above problems, and an object thereof is to provide an efficient mobile satellite communication system.

[0012]

A mobile satellite communication device according to the present invention is a device that is mounted on a mobile body and performs radio wave communication of data delimited by a predetermined data length with a satellite. Level detection means for detecting the received power level of the transmitted electric wave, reception state determination means for determining whether the line-of-sight state or shielded state is based on the level detected by the level detection means, and the determination result by this reception state determination means. A duration determination unit that determines the duration of the line-of-sight state, a distribution calculation unit that calculates the cumulative probability distribution of the duration of the line-of-sight state based on the determination result of the predetermined time by the duration determination unit, and the distribution calculation unit And a data length setting means for setting a data length in communication according to the calculation result.

Further, the mobile satellite communication device is mounted on a mobile body and performs radio wave communication of both real-time transmission for sequentially transmitting data with a satellite and packet transmission for transmitting data in batches. Level detection means for detecting the received power level of the transmitted radio wave, line-of-sight state determination means for determining the degree of line-of-sight state from the detection result of this level detection means for a predetermined time, and the determination result of this line-of-sight state determination means. Accordingly, it has a switching means for switching between real-time transmission and packet transmission.

[0014]

In this way, the line-of-sight continuation time is obtained based on the received power level obtained by the level detecting means, and the data length in communication is determined according to the cumulative probability distribution of the line-of-sight continuation time. Here, if the data length is shorter than the line-of-sight duration, the data can be transmitted. By setting the data length at a time when the cumulative probability of the line-of-sight duration is about 90%, the success of data transmission can be confirmed. The probability can be set to about 90%, and data can be transmitted with a sufficient probability. Then, by changing the data length at any time according to the reception state at that time, it is possible to always perform data transmission in an optimum state.

Further, the line-of-sight state is detected, real-time communication such as telephone communication is performed only when the line-of-sight state is very good, and packet communication is performed when the line-of-sight state is not so good. As a result, efficient transmission can be performed by combining the features of both.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

Analysis of Radio Propagation Situation First, the present inventor investigated radio wave propagation characteristics in urban areas and suburbs. Figure 4 shows the measurement results of the satellite line-of-sight ratio on roads in Tokyo and around Nagoya. In the figure, (A) shows the line-of-sight ratio of the communication satellite ETS-V on the major roads in Tokyo, and the line-of-sight ratio is 77.7 to 94 for roads running parallel to the line-of-sight of the communication satellite. 1.9%, and on a road running perpendicular to the line-of-sight of communication satellites, the line-of-sight ratio is 3
It was 5.0 to 72.3%. Further, (B) shows the prospective place ratios in the major regions of Tokyo and Nagoya, which are 63.9 to 82.3% in Tokyo and 75.4 to 7 in Nagoya.
It was 97.4%. Here, the line-of-sight place ratio is a ratio of places where satellite radio waves can be received.

Thus, it was found that the line-of-sight ratio is approximately 30 to 80% in the urban area and 90% or more in the suburbs, which means that there is a large difference in the line-of-sight ratio depending on the road. Then, this line-of-sight place ratio can be regarded as the ratio of the area where the communication service by the satellite radio waves is available.

Next, FIGS. 5 and 6 show the cumulative probability distributions of the line-of-sight continuation length and the occlusion continuation length of the satellite. The line-of-sight continuation length indicates the distance over which satellite radio waves can be continuously received, and the shield continuation length indicates the distance over which satellite radio waves cannot be continuously received. The receivable and unreceivable are determined by whether or not the received radio wave intensity is equal to or higher than a predetermined value (a value that can be sufficiently received by an ordinary receiver).

According to this result, the line-of-sight continuation is about 40% in Owariasahi City over 10 meters, about 20% in Naka Ward, Nagoya City, and about 20% in Tokyo Ward (Chiyoda Ward, Minato Ward, Shinjuku Ward, Shibuya Ward). , About 10%. From this, it was found that the probability that the outlook continuation length is long increases in the suburbs. In addition, the probability that the shielding continuation length is 10 m or more is high in the Tokyo area and Naka-ku, Nagoya city, and the shielding of 100 m or more is occurring. Therefore, it can be seen that the probability of a long duration of shielding is higher in urban areas.

From these survey results, the satellite line-of-sight rate is about 30 to 80% in urban areas, and the probability of long shielding duration is high, while in the suburbs, the satellite line-of-sight rate is 90% or more. There is a high probability that the long outlook will continue. Therefore, it was found that packet communication is suitable for urban areas and real-time transmission such as telephone communication is also possible for suburban areas.

Further, in packet communication, it has been found that the longer the packet length and the shorter the retransmitting interval are, the better the transmission efficiency is. However, like the mobile satellite communication, the radio wave propagation characteristics influence the surrounding environment. When receiving, it is considered that the optimum packet length exists depending on the surrounding environment. For this reason,
It is considered that the transmission efficiency can be maintained high by changing them according to the surrounding environment.

That is, if the packet length and the packet retransmission interval are simply determined by the line-of-sight continuation length and the shielding continuation length, it is considered that the probability of error becomes too large and sufficient transmission / reception cannot be achieved. If the packet length and the packet retransmission interval are determined from the cumulative probability distribution of the line-of-sight / shielding duration, it is considered that the values can be set to suitable values according to the propagation situation. Therefore, when 90% of the line-of-sight duration is 1 second or longer and 10% or more of the shielding duration is 50 seconds or longer, the packet length is set to 1 second and the packet retransmission interval is set to 50 seconds, so that the communication It is thought that the efficiency can be set high enough.

The line-of-sight / shielding duration can be known by the in-vehicle receiver constantly monitoring the radio waves of the satellite. Therefore, if the level of the radio wave of the satellite is monitored for a predetermined time (for example, about 10 minutes), it is possible to detect the line-of-sight / shielding time that is correct to some extent. Therefore, the cumulative probability distribution of the line-of-sight / shielding time is calculated from the line-of-sight / shielding duration of a predetermined time, and the packet length and the packet retransmission time are determined from this, and this is updated at any time to keep track of the surrounding environment in which the automobile runs. It is considered that the packet length and the packet retransmission interval can be optimized according to the change of

Next, from FIGS. 4 to 6 described above, it is considered that there is no problem even if a voice communication service (for example, telephone communication) that requires real-time transmission is used because satellites are often visible in the suburbs. However, in urban areas it is unlikely that satellites can be seen through, so it is considered that the call duration is short and reliability is low. Therefore, real-time transmission is not suitable in urban areas, and it is considered preferable to provide real-time transmission services only in suburbs. It is considered that if the above-mentioned line-of-sight place rate is high, the call duration time becomes long, and if the line-of-sight place rate is low, the call duration time becomes short. Therefore, if these voice communication services are provided only when the line-of-sight duration is considered to be 90% or more and when the line-of-sight is considered to be long, voice that requires real-time transmission will be provided in the suburbs and urban areas. It is considered that the communication service can be provided with sufficient accuracy, and in such a case, the probability of interruption in the middle of communication is low, and complaints from customers can be reduced.

Configuration of the Embodiment FIG. 1 is an overall block diagram showing the configuration of the embodiment, and performs wireless communication with a communication satellite 10. For this wireless communication, it has an antenna 22 and a transceiver 24, and transmits and receives radio waves of 1.5 and 1.6 GHz from the antenna 22. A packet communication system 28 and a voice communication system 30 are connected to the transceiver 24 via a switch 26. The packet communication system 28 is a system that divides data that does not require real-time processing, such as a facsimile and a data processing terminal, into packets of a predetermined size and transmits / receives the packets. Then, the packet length and the retransmission interval in the packet communication system 28 are set by the condition setting unit 32.

On the other hand, the voice communication system 30 requires real-time processing like ordinary telephone communication, and when this voice communication system is operating, it occupies a predetermined channel of satellite communication. , Send and receive data.

On the other hand, a reception level detector 40 is connected to the transceiver 24. This reception level detector 40 is
The intensity of the received signal output from the transceiver 24 is detected, and the detection result is supplied to the control unit 42. The control unit 42 processes the received data and controls the switching unit 26 and the condition setting unit 32.
4 is connected. Then, the control unit 42 stores a predetermined amount of data regarding the reception level from the reception level detector 40 in the storage unit 44, and based on this, determines the reception state. Further, the control unit 42 includes a traveling state detector 46.
Is connected and recognizes the state such as whether the moving body is stopped or running. A speedometer or the like can be used as the traveling state detector 46.

Providing Voice Communication Service Next, an algorithm for providing voice communication service in urban areas will be described with reference to FIG. When the power of the mobile satellite communication device mounted on the mobile body is turned on, the control channel transmitted from the satellite (which is always transmitted) is received, and it is determined whether communication with the satellite 10 is possible. To do. That is, the antenna 22, the transceiver 24, and the switch 2
From the received radio waves sent via 6, it is judged whether or not the radio waves of the satellite control channel can be received (S101). When the control channel can be received, the control unit 4
2 measures the received power level in line-of-sight from the detection value from the reception level detector 40 (S102). This is because even if the satellite 10 can be seen,
This is because the received power levels are different, so that the received power level in line-of-sight can be accurately grasped.

After setting the variable k = 2 (S10
3) The received radio wave level of the control channel from the satellite is measured, and this is substituted into the variable Lev (k) and stored in the storage unit 44 (S104). Then, k = k + 1 is set (S10
5), it is determined whether k = 600 (S106). If k is 600 or less, the process returns to S104 and is repeated. As a result, the array variable Lev (k) becomes 5
99 pieces of data will be stored. Here, this interval is every 0.1 seconds. Then, k = 1 (S10
7), the control channel level at that time is measured (S108), and the obtained 600 Lev (1) to Lev are obtained.
The line-of-sight ratio is analyzed from the v (600) data.
That is, as described above, when the mobile body is traveling in the suburbs with few obstacles, the probability that the received power level is sufficiently high (line-of-sight rate) is 90% or more. In this case, there are very few problems even if the voice communication service is provided. Therefore, it is determined whether or not the line-of-sight place ratio is 90% or more (S110), and if it is 90% or more, the voice communication service is enabled, and the control unit 42 controls the switch 26 to control the voice communication system 30. To the transceiver 24. As a result, the passenger of the mobile body can receive voice communication services such as telephone communication. Then k =
It is set to k + 1 (S112), and it is determined whether k = 600 (S113). Then, when k is not 600, it is determined whether or not to end (S114) and S108.
Return to. Therefore, in S108, one of the values of 600 is replaced with the next received data, and in this state, the line-of-sight place ratio is analyzed again in S109.
At 10, it is judged whether 90% or not. Therefore, it is always determined whether or not the voice communication service is possible, taking into consideration the line-of-sight place rate for the immediately preceding one minute. Note that S1
If k = 600 in 13, the process returns to S107, clears k = 1, and continues the operation.

On the other hand, the line-of-sight ratio is 9 in S110.
If it is not 0% or more, it is then determined whether or not the current satellite is in sight (S115). Then, if it is the current prospect, it is next determined whether or not the vehicle is stopped (S11).
6). This means that even if the line-of-sight ratio is poor, the line-of-sight state should continue after the vehicle is stopped. Therefore, there is no problem even if you provide voice communication service,
This is because the voice communication service should be provided. For this reason,
If the vehicle is stopped, k = k-1 is set (S11).
7) and returns to S111.

Further, in S115, when the satellite is not currently in sight, the voice communication service is impossible, so it is judged that the packet communication service can be added (S118), and the process returns to S112.

Here, the determination in S116 as to whether or not the vehicle is stopped is made based on the detection result from the traveling state detector 46.

As described above, in this embodiment,
Since the voice communication service is provided when the line-of-sight ratio is 90% or more, the optimal service can be provided according to the situation. Further, since the voice communication service is provided while the vehicle is stopped, if the situation becomes worse, the voice communication service can be received by stopping the mobile body at the line-of-sight place. In this way, a suitable combination of real-time service and packet communication service can be achieved.

Condition setting in packet communication Next, when packet communication is carried out, the packet length in the packet communication system 28,
Determine the packet retransmission interval. Therefore, this will be described with reference to FIG. First, when packet communication is to be started, the received power level at the time of line-of-sight is stored (S201, S202). Then, after setting a variable k = 1 for determining the repetition frequency (S203),
The output value from the reception level detector 40 is an array variable Lev
The value of (k) is stored in the storage unit 44 (S204).
Next, k = k + 1 is set (S205), and it is determined whether k has reached 600 (S206). In this way
Control channel level measurement up to k up to 600,
Repeat the memory of the level at that time. Here, this loop is controlled so that it is performed every 0.1 seconds, and therefore, by processing for 60 seconds, 600 reception level values are stored in the storage unit 4.
4 will be stored.

Next, the obtained 600 level values Lev
By comparing each value of (1) to Lev (600) with the received power level at the time of line-of-sight, it is determined whether the line-of-sight or the line-of-sight and the line-of-sight / blocking duration are calculated. Then, the cumulative probability distribution of this line-of-sight / occlusion duration is obtained, and the line-of-sight duration 90% value and the blockage duration 1
Find the 0% value. When the 90% value of the line-of-sight duration is 1 second and the 10% value of the shielding duration is 50 seconds, the packet length is 1 second and the packet retransmission interval is 50 seconds. As a result, the packet length and the packet retransmission interval can be set to optimum values.

Therefore, the control unit 42 sends this data to the condition setting unit 32, and changes the packet length and the retransmitting interval by the packet communication system 28 to be performed thereafter. Next, in S108, k = 1 is returned to, the level of the control channel is measured, and the value at that time is set as Lev (k) to 1
Replace only one (S209). Next, based on Lev (1) to Lev (600) in which this value is replaced by one, the line-of-sight / shielding duration is analyzed, the packet length and the packet retransmission interval are determined, and the condition setting unit 32 is set. It is controlled (S210). Further, it is determined whether k = 600 by setting k = k + 1 (S211) (S212), and this is 6
If it does not reach 00, the process returns to S209. On the other hand, k = 6
When it becomes 00, it is determined whether or not to end (S2
13) The process returns to S208 and is reset to k = 1. In this way, according to this embodiment, after the packet length and the packet retransmission interval are determined according to the measurement for the first minute,
The old data and the new data are sequentially replaced every 0.1 seconds, and the packet length and the packet retransmission interval are newly determined. In this way, it is possible to always determine the optimum packet length and retransmission interval for the reception situation of the last minute. In this example, the packet length and the packet retransmission interval are determined by the data of the immediately preceding 1 minute, but it may be about 10 minutes.

[0038]

As described above, according to the present invention,
Real-time services and packet communication services can be switched according to the situation, and more advanced services can be provided. Further, in the packet communication service, the packet length can be automatically set according to the environmental conditions, so that very efficient communication can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an embodiment.

FIG. 2 is a flowchart showing an algorithm for determining voice communication service provision.

FIG. 3 is a flowchart showing an algorithm for determining a packet length and a packet retransmission interval.

FIG. 4 is an explanatory diagram showing a measurement result of a line-of-sight place ratio.

FIG. 5 is a characteristic diagram showing a cumulative probability distribution of a line-of-sight continuation length.

FIG. 6 is a characteristic diagram showing a cumulative probability distribution of occlusion duration.

FIG. 7 is a characteristic diagram showing a cumulative time distribution of shielding / line-of-sight duration.

[Explanation of symbols]

 10 communication satellite 22 antenna 24 transceiver 26 switcher 28 packet communication system 30 voice communication system 32 condition setting unit 40 reception level detector 42 control unit 44 storage unit 46 running state detector

Claims (2)

[Claims] 1. A mobile satellite communication device mounted on a mobile body for performing radio wave communication between a satellite and data delimited by a predetermined data length, the received power level of radio waves transmitted from the satellite. Level detection means for detecting the line-of-sight condition, a reception state determination means for determining whether the line-of-sight state or the shielding state is detected from the level detected by the level detection means, and a determination of the duration of the line-of-sight state based on the determination result of the reception state determination means Time determination means, distribution calculation means for calculating a cumulative probability distribution of the duration of the line-of-sight state based on the determination result of the predetermined time by the duration determination means, and data length in communication according to the calculation result of the distribution calculation means. A mobile satellite communication device, comprising: a data length setting means for setting. 2. A mobile satellite communication device mounted on a mobile body for performing radio wave communication of both real-time transmission for sequentially transmitting data with a satellite and packet transmission for transmitting data batchwise, the satellite comprising: Level detection means for detecting the received power level of the radio wave transmitted from the device, line-of-sight state determination means for determining the degree of line-of-sight state from the detection result of the level detection means for a predetermined time, and the determination result of the line-of-sight state determination means A mobile satellite communication device comprising: switching means for switching between real-time transmission and packet transmission according to the above.