JPH01181336A - Communication equipment for tdma satellite communication system - Google Patents

Abstract

PURPOSE:To improve the transmission efficiency by setting a prescribed short guard time even to a mobile ground station and attaining the communication. CONSTITUTION:A position location means 1 locates the position of a ground station, a distance calculation means 2 calculates a distance between the ground station and a satellite repeater based on a ground station position information signal and a transmission time control means 4 can locates a TDMA burst signal 103 on a TDMA frame at the reception point of the satellite repeater always within a prescribed time range independently of the location of the ground station by controlling the transmission time of the Time Division Multiple Access (TDMA) burst signal 103 based on the distance information signal 102. Thus, the communication is attained while the guard time between the TDMA signals 103 is set to a prescribed time even to a mobile ground station. Thus, the transmission efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to time division multiple access (time division multiple access).
nMultiple Access:TDMA
) - Regarding communication equipment in ground stations of satellite communication systems, in particular T
The present invention relates to a communication device for a DMA satellite communication system.

(Prior art) Conventionally, in a satellite communication system using a repeater mounted on a geostationary satellite, a TDMA satellite communication method has been used in which multiple ground stations use the same frequency and use the satellite repeater in a time-sharing manner. . In a TDMA satellite communication system, each ground station transmits its own communication signal as an intermittent signal (TDMA burst signal) at an individually determined time every orbit, and the TDMA burst signal transmitted from each main station is the receiving point of the satellite transponder (for example, the input end of the antenna of the transponder)
, the TDMA burst signals are arranged in a row so as not to overlap each other on the time axis, and there is a time period (guard) between each TDMA burst signal arranged in the -column number to avoid signal overlap.
For example, as shown in the TDMA frame configuration diagram in Figure 4, each TDM
The A burst signal is TDM at the reception point of the satellite repeater.
They are located in a predetermined time range on the A frame and are transmitted from each ground station at a predetermined time so that they are arranged in a line with a guard band.

The reference burst shown in FIG. 3 is a TDMA burst signal that is used for each ground station to operate synchronously and is transmitted from the reference station, which is one of the ground stations. This is a TDMA burst signal containing communication information transmitted from a ground station (traffic station) that performs communication.

The radio wave propagation time until the TDMA burst signal transmitted from the ground station reaches the satellite repeater is related to the distance between the ground station and the satellite repeater, and furthermore, the distance between each ground station and the satellite repeater is constant. However, in order to configure a normal TDMA frame at the reception point of the satellite repeater, the transmission time of the TDMA burst signal transmitted from each ground station must be set at the same time between the ground station and the satellite repeater. Considering the distance of
Adjustment settings are made individually for each ground station.

If the ground station is a fixed station, the distance between the fixed ground station and the satellite repeater is a fixed value unique to that fixed ground station, so the transmission time of the TDMA burst signal of that fixed ground station depends on the construction of that station. After that, the transmission time is generally fixed and a predetermined short guard time is set for operation. When the ground station is a mobile station, the position of the mobile ground station is not fixed and always changes, so the distance (=D) between the mobile ground station and the satellite repeater changes from time to time. As a result, T
The radio wave propagation time (=T) required for the DMA burst signal to reach the satellite repeater is not constant but varies, and TDM
The time position of the TDMA burst signal on the A frame varies. In other words, the radio wave propagation time changes according to T=D/C (where C is the speed of light)
.

Here, the distance is given as follows.

-11111・(1) R: Radius of the earth H: Orbital altitude of the satellite EI: Latitude of the ground station EK: Longitude of the ground station SK: Longitude of the satellite Minimum distance within the moving range of the moving ground station D mln and the radio wave propagation time corresponding to the maximum distance 1.8 T w
a I a and T IIIaX, the time position on the TDMA frame of the TDMA burst signal transmitted from the mobile ground station is the radio wave propagation time difference ΔT =
T −−−T−t−= D −−−/ CD −+m/
C varies by an amount corresponding to 2ΔT.

Fluctuations in the time position on the TDMA frame of the TDMA burst signal transmitted from the mobile ground station will be explained with reference to the timing diagram of the TDMA burst signal transmitted from the mobile ground station in the related art in FIG. The time point when the reference burst, which is a TDMA burst signal transmitted from the reference station, reaches the receiving point of the satellite repeater is the time reference time zero, that is, the start of the reference burst on the TDMA frame at the receiving point of the satellite repeater. Think of it as time zero.

If the delay time due to the satellite repeater is T', time t = T'
The reference burst is retransmitted from the satellite transponder. If the mobile earth station is located at a minimum distance D1a, the reference burst reaches the mobile earth station after T wa I n hours after retransmission. The mobile ground station receives and processes the reference burst;
Send a traffic burst after a predetermined time T''.

The predetermined time T'' is a fixed value. The transmitted traffic burst reaches the satellite transponder after T ea I n time has elapsed.

That is, the trapic burst transmitted from the mobile ground station located at the minimum distance Dmla is at time t=T'+T, 1 . +T#+T1゜= (
T′ +T″) + 27@Im.

Then, if the mobile earth station is located at the maximum distance D wax, the reference burst will be retransmitted after T,. The mobile ground station is reached after a certain amount of time has elapsed. The mobile earth station transmits a traffic burst after T″ time and reaches the satellite transponder after TllaX time. That is, the traffic burst transmitted from the mobile earth station located at maximum pressure 1llllD□8 is a TDMA frame. Upper time t=T' +T,,,+
T"+T,,,=(T'+T")+27. Exists in □. Ultimately, the TDMA burst signal (i.e., traffic burst) transmitted from the mobile ground station
The time position on the frame is ((T'+T'')+2
7. ,,]-((T'+T'') +2 T-+nl=
2 (T-, XT-+-)=varies by an amount equivalent to 2ΔT.

Therefore, a guard time that is 2ΔT longer than a guard time set for a fixed ground station is set and operated for a mobile ground station.

As explained above, in conventional TDMA satellite communication systems, a predetermined short guard time is set for fixed ground stations, and a predetermined long guard time is set for mobile ground stations.
In order to prevent the TDMA burst signals transmitted from each ground station from overlapping each other at the receiving point of the satellite repeater, the TDMA burst signals are
They communicate with each other using ground station communication devices that transmit MA burst signals.

(Problem to be solved by the invention) However, in the conventional communication device described above, T.
The transmission time of the DMA burst signal is adjusted and set individually for each orbit, but since it is a fixed value, it cannot be adjusted for mobile ground stations in response to changes in the distance between the mobile ground station and the satellite repeater. It is necessary to set a long guard time. For this reason, there is a problem that the communication capacity of the traffic burst decreases and the transmission efficiency deteriorates.
40°, EK = 81°), the distance between the mobile ground station and the satellite repeater is D = 37833
．． 8081am to D' = 37802.057k
m, and the distance difference ΔD is ΔD = D − D'
= 31.751km. (However, the radius of the earth R
= 6378km, satellite altitude H = 35787km,
The longitude of the satellite is 5K = 100°. ) This distance difference Δ
When D is converted into time difference ΔT, ΔT=ΔD/C=
It becomes 0.106m5. (However, the speed of light C = 2997
93 +++/Sec. ) This radio wave propagation time difference ΔT is, for example, when the signal transmission speed is 56 kbps.
In this case, the signal transmission time for 1 bit is 1/56
Since X 10 = 0.0179 m5, this corresponds to a variation of approximately 6 bits. If the signal transmission rate is higher, the variation corresponds to a larger number of bits. The distance traveled by one degree of longitude on the ground is approximately 11 degrees on the equator.
This change in radio wave propagation time is a major problem when communicating from a mobile ground station that travels over a wide area, such as a car, aircraft, or ship, which is equivalent to 1 km.

An object of the present invention is to provide a means for locating the self-position of a ground station, a means for calculating the distance between the ground station and a satellite repeater based on a position information signal as a result of the locating, in order to solve the above-mentioned problems of the conventional technology. , by having a means for controlling the transmission time of the TDMA burst signal using the calculated distance information signal, the TDMA burst signal is transmitted at the transmission time corrected for changes in radio wave propagation time, and the TD at the reception point of the satellite repeater is
The time position of the TDMA burst signal on the MA frame is
Regardless of the location of the mobile ground station, it is always located within a predetermined time range, and communication can be performed with a predetermined short guard time set even for the mobile ground station, which improves transmission efficiency. An object of the present invention is to provide a communication device that enables high-speed communication.

(Means for Solving the Problems) In order to achieve the above object, the present invention has the following means configuration.

That is, the communication device for a TDMA satellite communication system of the present invention is a time division multiple access (TDMA) satellite in which a plurality of ground stations communicate with each other by using one satellite repeater in a time division manner using the same radio frequency. In a ground station of a communication system, a position locating means for automatically locating the self-position of the ground station on the earth; a distance calculating means for calculating a distance between the ground station and the satellite repeater based on a position information signal output from the position locating means; a communication signal generating means for generating a TDMA burst signal including communication information; a TD transmitted from the ground station to the satellite repeater;
When the MA burst signal arrives at the receiving point of the satellite repeater, within a predetermined time range allocated to each ground station on the TDMA frame at the receiving point, the TDMA burst signal that arrived will be able to determine the position of the ground station. a transmission time control means for controlling the transmission time of the TDMA burst signal based on the distance information signal output from the distance calculation means so that the TDMA burst signal is always located regardless of the location; modulating the carrier signal with the TDMA burst signal whose transmission time is controlled; and transmitting means for high-frequency converting the modulated carrier signal, amplifying the high-frequency signal, and transmitting the high-frequency signal to the satellite repeater.

(Function) Hereinafter, the function of the communication device of the present invention having the above means configuration will be explained.

The positioning means receives and processes radio signals transmitted by existing ground-based positioning systems or satellite-mounted positioning systems currently under construction, determines the self-position of one ground station, and determines the latitude of the ground station. - A zero position information signal that outputs a position information signal including longitude information is input to a distance calculation means. The distance calculation means calculates the distance between the ground station and the satellite repeater based on the radius of the earth, the orbital altitude and longitude of the satellite, and the latitude and longitude of the ground station. The radius of the earth and the altitude and longitude values of the geostationary satellite are fixed values and are fixedly set as predetermined values. The latitude and longitude values of a ground station are variable values in the case of a mobile ground station, but are updated and set in real time by position information signals.

A distance information signal is output as a distance calculation result based on these set values, and is input to the transmission time control means. on the other hand,
The communication signal generation means generates a TDMA burst signal containing communication information, and the TDMA burst signal output from the communication signal generation means is input to the transmission time control means. The transmission time control means controls the transmission time of the TDMA burst signal based on the distance information signal. That is, in the transmission time control means, when the TDMA burst signal transmitted from the ground station to the satellite repeater reaches the receiving point of the satellite repeater, the TDMA burst signal is allocated to each ground station on the TDMA frame at the receiving point. TDM reached within a predetermined time range
The transmission time of the TDMA burst signal is controlled so that the A burst signal is always located regardless of the location of the ground station.

The TDMA burst signal whose transmission time is controlled is input to the transmitting means. The transmitting means modulates the carrier signal with a TDMA burst signal, converts the modulated carrier signal into a high frequency signal, amplifies the high frequency signal, and transmits it to the satellite repeater.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a communication device for a TDMA satellite communication system according to the present invention. 1 is a position locator that automatically locates the self-position of the ground station, 2 is a distance calculator that calculates the distance between the ground station and the satellite repeater based on the ground station's position information, and 3 is a TDMA burst signal that includes communication information. 4 is a transmission time controller that controls the transmission time of the TDMA burst signal based on distance information; 5 is a transmitter that transmits the TDMA burst signal whose transmission time is controlled to the satellite repeater; Position information signal output from position locator 1, 102
103 is a TDMA burst signal output from the communication signal generator 3. 6 The position locator 1 is a ground-based position locating system, such as a four-run system, or a satellite. Onboard positioning systems, e.g. Global Positioning System (Global Pos)
itioning System: Receives and processes radio signals transmitted by GPS (see Telecommunications Times, March 1987 issue, pages 25-31), locates the ground station's own position, and automatically detects the latitude and longitude values of the ground station. . A position information signal 101 containing latitude and longitude information of the ground station is sent to the position locator 1.
and is input to the distance calculator 2. The distance calculator 2 calculates the distance between the ground station and the satellite repeater according to the above-mentioned equation (1). Each parameter necessary to calculate the distance is set as follows.

The radius of the earth, the orbital altitude of the satellite, and the longitude of the satellite are fixed values, and respective predetermined values are fixedly set in advance. (Note that since the satellite is a geostationary satellite, the latitude of the satellite is zero degrees.) Also, the latitude and longitude values of the ground station are obtained from the position information signal 101 input to the distance calculator 2, and are calculated in real time. Update is set. A distance information signal 102 related to the distance calculated based on these set values is output from the distance calculator 2 and input to the transmission time controller 4. On the other hand, a communication signal generator 3 generates a communication signal for communication between ground stations. In a TDMA satellite communication system, each ground station uses the same frequency and uses a satellite repeater in a time slot that is individually assigned to each ground station, so the communication signal transmitted from the ground station is The communication signal generated by the communication signal generator 3 is a temporally intermittent signal (TDMA burst signal).
TD containing 0 communication information that is a DMA burst signal
MA burst signal 103 is output from communication signal generator 3 and input to transmission time controller 4 . Transmission time controller 4
controls the transmission time of the TDMA burst signal 103 based on the distance information signal 102.

That is, the transmission time controller 4 determines the distance between the ground station and the satellite repeater from the distance information signal lO2. For the TDMA burst signal 103, Td= (T, +2T, a,) 2Do/C= (To
+27. -) 2T.

-1--(2) Control the transmission time by giving the following time delay. (However, T
, is the processing time of the circuit of the transmission time controller 4, C is the speed of light, T
o is the radio wave propagation time with respect to the distance DO. ) If the mobile ground station is located at maximum distance, , 8, then Do=D l
1lIN+ T O= T IIIK and T a
A time delay of =T is applied to the TDMA burst signal 103. Furthermore, if the mobile ground station is located at the minimum distance D 5aln, then T d = T p + 2 (T-XT-
+1l) = T, +2ΔT, and the time delay is 2ΔT more than the maximum distance, □.
The transmission time control is applied to the burst signal 103 to correct the time position fluctuation (=2ΔT) of the TDMA burst signal on the TDMA frame according to the prior art shown in FIG.

That is, by applying the time delay T given by the above equation (2) to the TDMA burst signal 103, the second
As shown in the timing diagram of the TDMA burst signal transmitted by the mobile ground station of the present invention, the TDMA burst signal transmitted from the mobile ground station is transmitted at a predetermined position on the TDMA frame regardless of the location of the mobile ground station. (Maximum distance D
am, l). The TDMA burst signal output from the transmission time controller 4 is input to the transmitter 5.

The transmitter 5 modulates the carrier signal with a TDMA burst signal, for example performs phase modulation, converts the modulated carrier signal into a high frequency signal, amplifies the high frequency signal, and transmits it to the satellite repeater.

(Effects of the Invention) As explained above, the present invention locates the self-position of the ground station using the position locating means, and calculates the distance between the ground station and the satellite repeater based on the ground station position information using the distance calculating means. ,
By controlling the transmission time of the TDMA burst signal based on the distance information by the transmission time control means, the time position of the TDMA burst signal on the TDMA frame at the reception point of the satellite repeater is always kept at a predetermined time regardless of the position of the ground station. may be located within a time range of

Therefore, it is possible to perform communication with a mobile ground station by setting the guard time between TDMA burst signals to a predetermined short time range, and there is an effect that communication with high transmission efficiency becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a communication device for a TDMA satellite communication system according to the present invention, and FIG.
FIG. 3 is a timing diagram of a TDMA burst signal transmitted from a conventional mobile ground station, and FIG. 4 is a TDMA frame configuration diagram. 1...Position locator, 2...Distance calculator, 3...Communication signal generator, 4...
Transmission time controller, 5...Transmitter, 101...
...Position information signal, 102...Distance information signal, 103...TDMA burst signal. Hon-Kamei/ITDMA 猜KA L 通见 System ■ 10th course on fireflies Wood grain 1 illustration Garlic Ascending Quim Gubutsu TDAM Fram Bridge Weizu Pavilion Genealogy

Claims (1)

[Claims] In a time division multiple access (TDMA) satellite communication system, where multiple ground stations use the same radio frequency to communicate with each other by using one satellite repeater in a time-division manner, the self-position of the ground station on the earth is a position locating means for automatically locating;
Distance calculating means for calculating the distance between the ground station and the satellite repeater based on the position information signal output from the position locating means; Communication signal generating means for generating a TDMA burst signal including communication information; From the ground station to the satellite repeater. When the transmitted TDMA burst signal reaches the reception point of the satellite repeater, the TDMA burst signal that arrived at the TDMA frame at the reception point is within a predetermined time range allocated to each ground station.
In order to ensure that the burst signal is always located regardless of the position of the ground station, T
a transmission time control means for controlling the transmission time of the DMA burst signal; modulating a carrier signal with the TDMA burst signal whose transmission time has been controlled; converting the modulated carrier signal to a high frequency;
A communication device for a TDMA satellite communication system, comprising: transmitting means for amplifying a high frequency signal and transmitting it to a satellite repeater.