JP3003320B2 - Mobile satellite communication equipment - Google Patents

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 wave 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 object such as an automobile and performs radio wave communication has been widely used. In particular, the spread of car phones and mobile phones is remarkable, the number of subscribers is rapidly increasing, and the service area is expanding. However, a car phone or the like is a system based on communication between a radio base station on the ground and a transceiver of a mobile body. The service area of one base station is a radius of 2 to 3 km in an urban area, and a radius of 2 to 3 km in a suburb. 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, and it is considered that it is practically impossible to extend the service nationwide with such a system. .

[0003] On the other hand, the use of satellite communication, which has been attracting attention in recent years, allows the satellite to have a wide area (satellite can be seen all over the country and its service area is wide) and broadcast (a large number of simultaneous communications are performed). Communication services can be provided at the same time, and a large number of services can be provided at the same time).

Here, the satellite communication is conventionally used for telephone communication which requires real-time communication and data communication which can collectively process data to some extent and perform batch processing. In mobile communication, FAX communication is also used. And those that can perform batch processing such as data processing using computers,
There is telephone communication by voice.

[0005] Normally, data communication that can be processed in a batch manner uses packet-type digital communication, and telephone communication using voice uses real-time transmission that continuously occupies a communication line and transmits data. are doing.

On the other hand, packet format digital communication
The data is divided into data of a predetermined length (a packet obtained by adding a header section containing destination and other information to the divided data is called a packet) and transmitted. This packet communication is intended to improve the efficiency of data transmission over a large number of communication lines, and the packet length (the data length of one packet) is set to a suitable length for these processes. .

[0007] When transmission fails, the packet is retransmitted after a predetermined time (this is called a retransmission interval). The retransmission interval also takes into account the time required for processing for transmitting one packet. Was decided.

[0008]

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

[0009] In urban areas, the duration of the situation where the satellite can be seen is considered to be very short, and in the suburbs, the duration of the situation where the satellite can be seen is considered to be sufficiently long. Therefore, if the packet length is fixed, the probability of retransmission due to incomplete communication of the packet in an urban area becomes extremely high, and the packet length in a suburb is reduced. There is a problem that the transmission efficiency is deteriorated due to the short setting.

[0010] In telephone communication or the like that requires real-time transmission, if the satellite cannot be seen during the communication, the transmission becomes impossible. Therefore, it is considered that it is preferable not to provide such a service in urban areas since telephone communication using a satellite is impossible. However, in suburban areas where there is a high probability of seeing satellites, or when a mobile object stops in a place where satellites can be seen, there is a demand to use real-time communication using satellites.

[0011] The present invention has been made in view of the above problems, and has as its object to provide an efficient mobile satellite communication system.

[0012]

The mobile satellite communication apparatus according to the present invention SUMMARY OF THE INVENTION were mounted on a mobile, mobile satellite communication for performing radio communication data divided into a predetermined data length between a satellite <br /> Device, a level detecting means for detecting a received power level of a radio wave transmitted from a satellite, a receiving state determining means for determining whether the state of visibility or shielding from the level detected by the level detecting means, A duration determining means for determining the duration of the line-of-sight state from the determination result of the reception state determining means, and a distribution for calculating 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 determining means. a calculation unit, and a data length setting means for setting the data length in the communication according to the calculated result of the distribution calculating means, have a, the data length setting means, outlook like
If the duration of the outlook is short, the
Data length is set shorter than
You. In addition, the distribution calculation means may include a
The judgment result is accepted at every first predetermined time, and the judgment result is
Of the cumulative probability distribution based on the value at the second predetermined time
Calculation and the cumulative probability distribution is updated every first predetermined time.
Preferably .

The present invention is also directed to a mobile satellite communication device mounted on a mobile body and performing both radio communication of real-time transmission for sequentially transmitting data to and from a satellite and packet transmission for batch transmission of data. A level detecting means for detecting a reception power level of a radio wave transmitted from a satellite;
Received from the detection result of the predetermined time in this level detection means
Is the probability of a line-of-sight location where the
Line-of-sight location ratio detection means for detecting a line-of- sight location ratio, and switching means for switching between real-time transmission and packet transmission in accordance with the detection result of the line-of-sight location ratio ,
If the line- of-sight location rate is higher than
Employed real-time transmission when it is determined that, viewed
When it is determined that the pass-through location ratio is less than a predetermined value , packet transmission is employed.However, even when the line-of-sight location ratio is determined to be less than a predetermined value, the reception power level is at or above a predetermined value and the satellite can be seen through at that time. Wherein the real-time transmission is adopted when the moving body is stopped.

[0014]

As described above, the line-of-sight duration 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 duration. Here, if the data length is shorter than the line-of-sight continuation time, the data can be transmitted. By setting the data length at a time when the cumulative probability of the line-of-sight continuation time is about 90%, the data transmission is successfully completed. The probability can be set to about 90%, and data transmission can be performed with a sufficient probability. By changing the data length at any time according to the reception state at that time, data transmission can always be performed in an optimal state. Calculation of cumulative probability distribution
Timing can be optimized.

Further, the line-of-sight location ratio is detected, and the line-of-sight
Real-time communication such as telephone communication is performed only when the probability is good, and packet communication is performed when the line-of-sight location is not good. Thereby, efficient transmission combining both features can be performed. In particular, since real-time communication can be performed when the moving object stops, there is no problem when stopping the vehicle and calling.

[0016]

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

Analysis of Radio Wave Propagation Conditions First, the present inventor investigated radio wave propagation characteristics in urban and suburban areas. Figure 4 shows the measurement results of the line-of-sight location ratio of satellites on roads in Tokyo and around Nagoya. In the figure, (A) shows the line-of-sight location ratio of the communication satellite ETS-V on major roads in Tokyo. For a road running parallel to the line-of-sight direction of the communication satellite, the line-of-sight location ratio is 77.7 to 94. 0.9%, and on roads running perpendicular to the line-of-sight
It was 5.0-72.3%. (B) shows the prospective location ratio in major areas of Tokyo and Nagoya, 63.9 to 82.3% in Tokyo and 75.4 to 75.4% in Nagoya.
97.4%. Here, the line-of-sight location ratio is a ratio of locations where satellite radio waves can be received.

As described above, the line-of-sight ratio is about 30 to 80% in an urban area and 90% or more in a suburb, and the line-of-sight ratio greatly differs depending on the road. The line-of-sight location ratio can be regarded as a ratio of an area where a communication service using satellite radio waves is available.

Next, FIGS. 5 and 6 show the cumulative probability distribution of the line-of-sight continuation length and the occlusion continuation length of the satellite. The line-of-sight continuation length indicates a distance at which the satellite radio wave can be continuously received, and the shielding continuation length indicates a distance at which the satellite radio wave cannot be continuously received. The receivable state and the non-receivable state were determined based on whether or not the received radio wave intensity was equal to or more than a predetermined value (a value that can be sufficiently received by a normal receiver).

According to these results, the prospective continuation length is about 40% for Owariasahi city in 10m or more, about 20% in Naka ward in Nagoya city, and about 20% in Tokyo area (Chiyoda ward, Minato ward, Shinjuku ward, Shibuya ward). , About 10%. This shows that the longer the outskirts, the higher the probability that the outlook continuation length will be longer. In addition, the continuation length of the shield is more likely to be 10 m or more in the Tokyo area and the Naka ward in Nagoya city, and a shield of 100 m or more has occurred. Therefore, it is understood that the probability of a longer shielding continuation length increases in an urban area.

According to the results of these surveys, in urban areas, the line-of-sight location ratio of satellites is about 30 to 80%, and the probability of long occlusion continuity is high. In the suburbs, the line-of-sight location ratio of satellites is 90% or more. Yes, it turns out that the probability of a long outlook continuation length is high. Therefore, it has been found that packet communication is suitable in urban areas and real-time transmission such as telephone communication is also possible in suburban areas.

In packet communication, it is known that the longer the packet length and the shorter the retransmission interval, the better the transmission efficiency. However, as in mobile satellite communication, the radio wave propagation characteristics are affected by the surrounding environment. If received, it is considered that there is an optimal packet length depending on the surrounding environment. For this reason,
If these are changed according to the surrounding environment, it is considered that transmission efficiency can be maintained high.

That is, if the packet length and the packet retransmission interval are simply determined based on the line-of-sight continuation length and the shielding continuation length, it is considered that an error probability becomes too large and sufficient transmission and 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 / blocking duration, it is considered that a suitable value according to the propagation situation can be obtained. Therefore, when 90% or more of the line-of-sight continuation time is 1 second or longer and 10% or more of the occlusion continuation time is 50 seconds or longer, the packet length is set to 1 second, and the packet retransmission interval is set to 50 seconds. It is considered that the efficiency can be set sufficiently high.

The line-of-sight / shielding duration can be known by the on-board receiver constantly monitoring the satellite radio waves. Therefore, by monitoring the level of the radio wave of the satellite for a predetermined time (for example, about 10 minutes), it is possible to detect the line-of-sight / shielding continuation time to some extent. Therefore, the cumulative probability distribution of the line-of-sight / shielding time is determined 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 are updated as needed, so that the surrounding environment of the vehicle in which the vehicle is running is constantly updated. It is considered that the packet length and the packet retransmission interval can be optimized in response to the change of the packet length.

Next, from FIGS. 4 to 6 described above, it is considered that no problem will occur even if a voice communication service (for example, telephone communication) that requires real-time transmission is used because the satellite can often be seen in the suburbs. However, in urban areas, since there are few cases where the satellite can be seen, it is considered that the call duration is short and the reliability is low. For this reason, real-time transmission is unsuitable in urban areas, and it is considered preferable to provide real-time transmission services only in suburbs. Then, it is considered that if the above-mentioned line-of-sight location ratio is high, the call duration is longer, and if the line-of-sight location ratio is low, the call duration is shorter. Therefore, if these voice communication services are provided only when the line-of-sight continuation time is considered to be long, such as a line-of-sight location ratio of 90% or more, or when the vehicle stops, voices that require real-time transmission in suburban areas and urban areas can be provided. The communication service can be provided with sufficient accuracy. In such a case, the probability of interruption during the communication is low, and it is considered that complaints from customers can be reduced.

[0026] Configuration of the Embodiment FIG. 1 is an overall block diagram showing the configuration of an embodiment performs wireless communication with the communication satellite 10. For this wireless communication, it has an antenna 22 and a transceiver 24, and transmits and receives 1.5 and 1.6 GHz radio waves 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 transmits and receives data that does not require real-time processing, such as a facsimile and a data processing terminal, into packets of a predetermined size. The packet length and 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 occupies a predetermined channel of satellite communication when the voice communication system is operating. Send and receive data.

On the other hand, a reception level detector 40 is connected to the transceiver 24. This reception level detector 40
It detects the intensity of the received signal output from the transceiver 24, and supplies the detection result 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 are connected. Then, the control section 42 stores a predetermined amount of data on the reception level from the reception level detector 40 in the storage section 44, and determines the reception state based on the data. The control unit 42 includes a traveling state detector 46.
Is connected, and recognizes a state such as whether the moving body is stopped or how the moving body is traveling. Note that a speedometer or the like can be used as the traveling state detector 46.

Provision of Voice Communication Service Next, an algorithm for providing a voice communication service in an urban area will be described with reference to FIG. When the power of the mobile satellite communication device mounted on the mobile body is turned on, a control channel transmitted from the satellite (which is constantly transmitted) is received, and it is determined whether or not communication with the satellite 10 is possible. I do. That is, the antenna 22, the transceiver 24, the switch 2
It is determined whether or not a radio wave of the satellite control channel can be received based on the received radio wave transmitted through No. 6 (S101). When the control channel is successfully received, the control unit 4
2 measures the reception power level at the time of 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 through, due to environmental conditions such as weather,
The reason is that the received power level at the time of line of sight is accurately grasped because the received power level is different.

After setting the variable k = 2 (S10
3) The level of the received radio wave of the control channel from the satellite is measured, and the measured level is substituted for the variable Lev (k) and stored in the storage unit 44 (S104). Then, k = k + 1 is set (S10
5) It is determined whether or not k = 600 (S106). If k is equal to or less than 600, the process returns to S104 and repeats. Thus, 5 is added to the array variable Lev (k).
99 data will be stored. Here, this interval is set every 0.1 second. Then, k = 1 (S10
After 7), the control channel level at that time is measured (S108), and the obtained 600 Lev (1) to Lev (1) to Le are obtained.
The line-of-sight location ratio is analyzed from the data of v (600).
That is, as described above, the probability that the received power level is sufficiently high (line-of-sight location ratio) is 90% or more, for example, when the moving object is traveling in a suburb with few obstacles. In this case, there are very few cases where a problem occurs even when the voice communication service is provided. Then, it is determined whether or not the line-of-sight location ratio is 90% or more (S110). If the line-of-sight location ratio 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. Is connected to the transceiver 24. Thereby, the passenger of the mobile body can receive the voice communication service such as the telephone communication. Then, k =
It is set to k + 1 (S112), and it is determined whether or not k = 600 (S113). If k is not 600, it is determined whether or not the processing is to be terminated (S114), and S108 is performed.
Return to Accordingly, one of the values of 600 is replaced in the next reception data in S108, and in this state, the line-of-sight location ratio is analyzed again in S109 and S1
At 10, it is determined whether or not 90% has been reached. Thus, it is always determined whether or not the voice communication service is possible in consideration of the line-of-sight location ratio for the immediately preceding one minute. Note that S1
If k = 600 in 13, the process returns to S107, clears to k = 1, and continues the operation.

On the other hand, the line-of-sight location ratio is 9 in S110.
If it is not 0% or more, it is next determined whether or not the current satellite is in line of sight (S115). Then, if it is the current outlook, it is determined whether or not the vehicle is stopped next (S11).
6). This means that, even in a situation where the line-of-sight location ratio is poor, if the vehicle is stopped, the line-of-sight state should continue thereafter. Therefore, there is no problem with providing voice communication services.
This is because a voice communication service should be provided. For this reason,
If the vehicle is stopped, k = k-1 (S11).
7) Return to S111.

If it is determined in step S115 that the satellite is not currently in line of sight, it is determined that the packet communication service can be added because the voice communication service is not available (S118), and the process returns to S112.

Here, the determination as to whether or not the vehicle is stopped in S116 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 location ratio is 90% or more, it is possible to provide an optimum service according to the situation. In addition, since the voice communication service is provided while the vehicle is stopped, if the situation worsens, the user can stop the vehicle at the line of sight and receive the voice communication service. In this way, a suitable combination of the real-time service and the packet communication service can be achieved.

Setting of Conditions in Packet Communication Next, when performing packet communication, 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 reception power level at the time of line of sight is stored (S201, S202). Then, after setting the variable k = 1 for determining the repetition frequency (S203),
The output value from the reception level detector 40 is stored in the array variable Lev.
The value of (k) is stored in the storage unit 44 (S204).
Next, assuming that k = k + 1 (S205), it is determined whether or not k has reached 600 (S206). In this way,
level measurement of the control channel until k reaches 600,
The memory of the level at that time is repeated. Here, this loop is controlled so as to be performed every 0.1 second. 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 reception power level at the time of line of sight, it is determined whether the line of sight or the line of sight is blocked and the line of sight / blocking time is calculated. Then, the cumulative probability distribution of the line-of-sight / blocking duration is obtained, and the line-of-sight duration 90% value and the blocking duration 1
Find the 0% value. When the 90% value of the line-of-sight continuation time is 1 second and the 10% value of the occlusion continuation time 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 retransmission interval of the packet communication system 28 performed thereafter. Next, in S108, k is returned to 1, the level of the control channel is measured, and the value at that time is set as Lev (k) by 1
Only one is replaced (S209). Next, based on Lev (1) to Lev (600) in which only one of these values has been replaced, the line-of-sight / blocking duration is analyzed, the packet length and the packet retransmission interval are determined, and the condition setting unit 32 Control is performed (S210). Further, it is determined whether or not k = 600 by setting k = k + 1 (S211) (S212).
If it does not reach 00, the process returns to S209. On the other hand, k = 6
If it is 00, it is determined whether or not to end (S2
13) Return to S208 and reset k = 1. Thus, according to the present embodiment, after the packet length and the packet retransmission interval are determined according to the measurement for the first minute,
Every 0.1 second, old data and new data are sequentially replaced, and the packet length and packet retransmission interval are newly determined. In this way, it is possible to always determine the optimal packet length and retransmission interval for the immediately preceding reception situation of one minute. In this example, the packet length and the packet retransmission interval are determined based on the immediately preceding data of one minute, but may be set to about 10 minutes.

[0038]

As described above, according to the present invention,
Mobile switching between the real-time service and the packet communication service can be performed according to the situation, and a more advanced service can be provided. Further, in the packet communication service, the packet length can be automatically set according to the environmental conditions, so that extremely efficient communication can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a flowchart illustrating an algorithm of a voice communication service provision determination.

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

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

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

FIG. 6 is a characteristic diagram showing a cumulative probability distribution of a shielding continuation length.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Communication satellite 22 Antenna 24 Transceiver 26 Switch 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 (3)

(57) [Claims] 1. A mobile satellite communication device mounted on a mobile body and performing radio wave communication of data divided into a predetermined data length with a satellite, the reception power level of a radio wave transmitted from a satellite Level detecting means for detecting a state of the vehicle, receiving state determining means for determining whether the state of visibility is a blocking state from the level detected by the level detecting means, and continuation of determining the duration of the line of sight state from the result of determination by the receiving state determining 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 a data length in communication according to the calculation result of the distribution calculation means. a data length setting means for setting, to possess, the data length setting means, the duration of the expected state is short
Data is longer than when the duration of the line-of-sight state is long.
A mobile satellite communication device characterized by setting a short data length . 2. The apparatus according to claim 1 , wherein said distribution calculating means outputs a determination result from said duration determining means.
Accepted at every first predetermined time,
Calculate the cumulative probability distribution based on the value at a fixed time, and
The cumulative probability distribution is updated at every first predetermined time.
Mobile satellite communication equipment. 3. A mobile satellite communication device mounted on a mobile body and performing both radio wave communication of real-time transmission for sequentially transmitting data to and from a satellite and packet transmission for batch transmission of data, comprising: level detecting means for detecting a received power level of the sent come waves from received from the detection result of the predetermined time in this level detection means
Is the probability of a line-of-sight location where the
Line-of-sight location ratio detection means for detecting a line-of- sight location ratio, and switching means for switching between real-time transmission and packet transmission according to the detection result of the line-of-sight location ratio. Above a certain
Employed real-time transmission when it is determined that, viewed
When it is determined that the pass-through location ratio is less than a predetermined value , packet transmission is employed.However, even when the line-of-sight location ratio is determined to be less than a predetermined value, the reception power level is at or above a predetermined value and the satellite can be seen through at that time. A mobile satellite communication device, which employs real-time transmission when the mobile is stopped.