KR950012831B1 - Satellite signaling system having a signal beam with a variable beam area - Google Patents

Abstract

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Description

Satellite signal display system with signal beam with variable beam area

The state of the art satellite paging system includes a fixed position antenna mounted on a satellite in synchronous orbit. Typically in such a system, the antenna is fixed such that the falling point or "falling anticipation point" of the signal beam covers a portion of the earth "tapped" to the satellite, ie about one third of the earth's surface.

The ground level strength of the signal transmitted by the antenna in these conventional systems is very uniform over the covered area, but the signal strength is very weak. Ground level signal sensitivity is very weak to allow paging coverage in the building because this creates a problem even for the most enhanced synchronous satellite. For example, for a synchronous satellite with 400 watts of radiation, a state-of-the-art select call paging receiver using the POCSAG paging protocol at a bit rate of 512 bits per second has been observed to have a signal margin of only 2 dB. That is, the average signal strength on the ground is only 2 dB above the minimum level required to operate the paging device. Thus, given that most buildings attenuate the RF paging signal by 20 dB, these systems cannot be used for signal paging users in buildings.

The solution to current system problems is to reduce the bandwidth of the paging receiver by lowering the data rate to 60 boards or less. However, this makes the system extremely expensive and impractical in the light of the few users who can be served by the paging system. In other words, a low bit rate can support only a small volume of paging traffic.

The aforementioned pending US patent application describes a satellite paging system using an antenna with a relatively small "expected drop point" or beam-width in order to achieve a significantly higher ground level signal sensitivity, wherein the antenna beam has a large area. Adjusted to cover different geographic areas in a repeating pattern to obtain coverage. Finally, the combination of a relatively high ground level signal strength, a beam scan operation on the earth's surface, and a phaser battery saver that turns the paging receiver on and off in synchronization with the beam scan operation results in a signal display of 512 or 1200 boards. It allows data rates to be used and provides a first practical approach for implementing paging systems based on very large area or earth satellites.

However, the improved system described in pending applications has several limitations. Firstly, the 512 baud or 1200 baud signal display rates achievable by the system are not high enough to support a very large number of users who may eventually require terrestrial paging systems. Secondly, the system can handle regional population differences by varying the length of time that the scanning beam is placed to cover a given area. Finally, the system has no way of exploiting the fact that most of the developed national population lives in cities with high population needs.

It is therefore an object of the present invention to provide an improved satellite signal display system with a relatively large message throughput.

Another object of the present invention is to provide a satellite signal display system that can accommodate local differences in signal display.

Another object of the present invention is to provide a satellite signal display system capable of selectively supporting a relatively high signal display rate.

It is still another object of the present invention to provide a satellite signal display system capable of supporting a sufficient number of users to make the system economically independent.

According to the present invention, there is provided a satellite signal display system comprising an antenna and a satellite connected to a satellite to provide a signal beam having multiple positions and beam regions. The satellite can control the position of the antenna so that the signal beam can be directed to various locations on Earth in a predetermined sequence. The antenna is provided to change the area of the signal beam in accordance with the position to which the signal beam is directed. The signal beam includes a data signal having a data rate that can be changed by the system according to the beam area, for example, when the signal beam is directed at a location with a close population, the antenna has a high data rate. The beam area and data rate are varied to provide a data signal and a small beam area. When the signal beam is directed to a location with a sparse population, the antenna changes the beam area and data rate to provide a large beam area and a data signal with a low data rate.

Thus, by having a movable antenna that carries a variable beam area and a signal beam having a variable data rate, the beam area and data rate can be varied for each particular location, and thus the signal at ground level for each location. It will be appreciated that the strength will be sufficient to allow paging coverage in the building. The data rate is varied to maximize the throughput of the signal display system.

Since the antenna is arranged so that it can be moved in a predetermined sequence, the signal beam can be directed to a specific area sequentially, which in turn actuates the antenna to scan a very large area thereby providing intercontinental earth coverage. do.

The satellite signal display system according to the present invention is described through an embodiment with reference to the accompanying drawings.

The present invention relates to a satellite signal display system having a signal coverage over a very wide area. The present invention relates in particular to satellite signal display systems such as, but not limited to, those that may be used in satellite paging systems.

1 is a diagram of a satellite paging system of the Jongno technique.

2 is a diagram of a satellite paging system in accordance with the present invention.

3 is a block diagram of a system incorporating the present invention.

4 is a flowchart showing the operation of the system shown in FIG. 3 in detail.

5A is a schematic diagram of a batch sequence of down-link signals transmitted in accordance with the present invention.

FIG. 5B is a schematic diagram of signal constellations forming a portion outside the sequence shown in FIG. 5A.

FIG. 5C is a schematic of the signal arrangement forming part of the arrangement shown in FIG. 5B.

6 is a block diagram of a paging receiver of the type that may be used in a satellite satellite signal display system.

FIG. 7 is a timing diagram showing in detail the operation of the battery saver circuit of the pager shown in FIG.

8A and 8B are flowcharts showing in detail the operation of the phaser decoder shown in FIG.

Referring first to FIG. 1, the satellite paging system 2 of the Jongle technique comprises a fixed antenna 4 mounted on a satellite 6 in a synchronous orbit around the earth 8. The operation of the antenna 4 is controlled by the satellite 6.

The antenna 4 is installed such that the signal beam 10 transmitted therefrom (shown in dashed lines in FIG. 1) has a beam area covering the part of the earth's surface visible to the satellite 4.

As mentioned above, the satellite paging system 2 may provide paging coverage in buildings because the signal strength at the earth's surface is very weak if the data beam of the signal beam 10 is not reduced to 60 boards or less. Can't.

Referring to FIG. 2, to avoid these problems, according to a preferred embodiment of the present invention, the satellite paging system 20 is steerable or mobile installed on the satellite 24 in a synchronous orbit around the earth 26. Possible antennas 22 are included. The movement and operation of the movable antenna 22 is controlled by the satellite 24.

The movable antenna 22 causes the transmitted signal beam 27 (indicated by dashed lines 21 and 23 in FIG. 2) to be directed to a particular location on the surface of the earth, whereby the satellite 24 is “visible” to it. It may be moved by satellite 24 to scan the entire portion of the in " earth surface. The movable antenna 22 scans each topographic position for a predetermined time driver in a predetermined sequence.

The movable antenna 22 is arranged to have a transmitted signal beam 27 (indicated by a dashed line in FIG. 2) a variable beam region 28 and a signal data rate which can be varied accordingly. As the movable antenna 22 scans each topographic location, the satellite 24 provides sufficient signal sensitivity at the earth's surface for each location to maximize the throughput of the paging system 20 and allow paging coverage in the building. The optimal beam area and commercial signal data rate are selected to provide. While the beam area and bit rate of the down-link signal for each beam position are selected using a relationship in which the ground level signal changes inversely with the beam area, the ground level signal strength required for reliable communication in the building is determined by the bit rate. Depends directly on Thus, for a densely populated urban area, the beam area 28 is reduced to the area needed to cover the city, while the data rate is increased to a large value that allows reliable signal reception in large urban buildings. . In contrast, in rural areas with low population densities, the beam area 28 is extended and the signal data rate is reduced to allow reliable coverage over very large areas.

For example, for a satellite paging system with an effective radiant force (ERP) of 400 watts, the signal data rate of 600 boards is sufficient to provide good in-building coverage in rural areas with a large beam diameter of 1,287.4752 kilometers but low population density. It provides ground level signal strength that is 20dB above the paging threshold. The ground level signal strength varies with the second power of the beam diameter, and reducing the diameter by a factor of 4 from 1,287.4752 kilometers to 321.8688 kilometers allows the signal display data rate to be increased up to 9600 baud while population density is increased. It maintains the same signal strength margin required to ensure paging services in good buildings in high urban areas.

In accordance with the present invention, the satellite paging system 20 operates in the following manner. Referring to FIG. 3, paging messages from many lands based on paging system terminals are directed to ground base terminal 70 via a public telephone network, or some other communication circuit. The terminal 70 processes the incoming message and together with the control signal from the ground station satellite controller 74 an up-link where the final output paging signal is transmitted to the satellite 24 using known optical or wireless communication techniques. Is applied to transmitter 76.

An up-link signal consisting of a signal and a paging data signal necessary for controlling the operation of the satellites that control the operation of the alternately movable antenna 72 is via the up-link transmitter via the transmitting antenna 80 and the receiving antenna 72. Is sent to the up-link receiver 78. The transmitted up-link signal consists of a signal and a paging data signal necessary to control the operation of the satellite which in turn controls the operation of the movable or adjustable antenna 72. It should be appreciated that the up-link data can be transmitted at much higher data rates than that used for down-link transmission.

The movable antenna 88 is directed by an antenna control system 92 coupled to the satellite paging controller 82 to scan a specific location on the earth's surface for a predetermined time in a given sequence. When the beam of the movable antenna 88 is directed to a specific location, the down-link transmitter 86 is arranged in correspondence with the specific location during the time slot assigned to that location via the paging signal generator 84. Will send the paging signal.

In operation, the satellite 24 scans the surface of the earth 26 by adjusting the movable antenna 88 towards a particular topographic position on the earth's surface for a predetermined time in a given sequence. When the movable antenna 88 is directed at a particular position, the beam area 28 and signal data rate are adjusted to a value corresponding to that particular position. The satellite 24 then transmits a paging signal in an arrangement that matches a particular location during the time slot assigned to that location.

The control logic of the operation of the satellite paging system 20 of FIG. 2 is shown in the flowchart of FIG.

The satellite paging system 20 is enabled (block 102) and the next topographic location is selected (block 104). The antenna 22 is moved so that the signal beam is directed to the next topographical position (block 104). The beam area 28 is adjusted to a value corresponding to the next topographical position at tooth 108 and the signal data rate is adjusted to a value corresponding to the next topographical position at 110. After these values are set, the signal beam 27 is turned on (block 112) and the paging signal is sent to 114. The paging signal is transmitted for a predetermined time slot, and when this time slot expires, the routine branches to turn off the signal beam 27 (block 118). If the satellite paging system is disabled, the routine ends at block 122. If no disable signal is detected at block 120, the routine returns to block 104 to select the next topographic location and the routine is restarted accordingly.

FIG. 5A shows an embodiment showing one of the signals transmitted from the satellite antenna 22. The signal 40 is a time-division multiplexed binary paging signal and includes a sequence of batches 42-50. Each arrangement corresponds to a particular terrain location in which is the scanning area covered by satellite 24. For example, batch 42 may match New York, batch 44 may match Boston, batch 46 Chicago, or the like. Each batch is sent to the appropriate location according to the sequential basis. In an example, the POCSAG signal presentation protocol is used for the signal presentation format in each batch.

5B includes a preamble 62 where each arrangement (eg 42) is followed by an N frame 64.

Finally, FIG. 5C shows a display 61 representing one of the frames of FIG. 5A. The frame 61 includes a synchronization code 63 followed by a unique area identification code 65 that matches the topographical position covered by the batch transmission. The confirmation code 65 is followed by an address signal 66 to address a given pager.

The format of the frame 61 enables the operation of the pager battery saver to be synchronized with the scanning sequence of the movable antenna 24 by using the synchronization code 63. A pager operating within a particular geographic location will be powered up to decode the paging signal once the satellite 24 is sent to its geographic location once it is synchronized. This provides good pager battery life.

In addition, the confirmation code 65 of the frame 61 confirms the current operating position relative to the pager. Thus, if the pager is outside its operating area, confirmation code 65 may be displayed on the display or used to enable different operating modes of the pager, such as, for example, a "roaming" mode. Provide position information to the pager.

The pager in the paging system operates to synchronize their battery savers for the proper placement in signal transmission from the satellites using the synchronization code of the appropriate placement signal. Once the pager is synchronized, it will decode the appropriate paging signal.

The details of the operation of the paging receiver in a new satellite system are best described with respect to FIGS. 6, 7 and 8.

6 is a block diagram of a paging receiver suitable for use in a satellite paging system. With one exception, conventional selective call paging receivers are well known in the art. An exception is that the signal display rate and detection bandwidth of the receiver depend on the position of the receiver. These parameters can be set by making a different pager for each position in the satellite system or by changing these parameters via information stored in the code plug. Details of how to make a pager with variable bit rate and decoding bandwidth have been transferred to the assignee of the present invention, and a US patent entitled "Wireless Communication Receiver with a Device for Changing the Bit Rate of a Receiver" invented by Davis. It is fully described in US Pat. No. 4,816,820.

The receiver shown in FIG. 6 uses a microprocessor base decoder 124 programmed to decode the signal presentation protocols shown in FIGS. 5A, 5B, and 5C. The operation of this type of decoder has been transferred to the assignee of the present invention and described in US Pat. No. 4,518,916, entitled "Power Consumption Cosmic Paging Device," by Davis et al. The wireless receiver 126 receives the signal via the antenna 128. The output of the receiver 126 is applied to the microcomputer decoder 124 via the low pass filter l30 and the data limiter 132. The holding wave pass filter 130 communicates with the receiver control logic 134 which is alternately controlled by the microcomputer 124. As can be seen from the foregoing, the microcomputer decoder 124 also communicates with the code plug address and selection memory 136 and with the output signal indicator 138 and the user via user control.

In particular, the decoder is programmed to install a signal from the satellite and synchronize its decoding operation to the operation timing of the beam. To synchronize to the signal indication waveform, the decoder remains on until it decodes a downlink signal. The decoder then synchronizes the received signal with the decoding operation using well-known synchronization techniques including set bit synchronization and frame synchronization with the received signal. The bit synchronization process includes adjusting the bandwidth of the frequency pass filter to match the bit rate of the received signal. By doing this, the receiver synchronizes the operation of its own battery saving circuitry with the predetermined timing of the other link transmissions of the satellite using information which may be included in the program ROM or code plug of the microcomputer decoder and the selection memory. As a result, the receiver battery saver only activates the pager during the period the satellite transmits to the terrain where the pager is present. For example, FIG. 7A shows the preamble 62 and the synchronization code 63, which in turn are followed by the area identification portion 65. FIG. The area checking unit 65 and the address number 2 130 form a structure referred to as group 1. Each sequential group includes first and second address rolls as shown in FIG. 7A. The sync code 63 is repeated after the eighth group. Thus, when the receiver is programmed to respond to group 4 addresses, the battery saver circuitry within the receiver may be used during the search operation during which the receiver searches for the preamble 62 and the synchronization code 63 and for the time that the group 4 address is delivered. And each sync code interval 136 driver phaser will be active. This is shown in Figure 7b.

8A and 8B are flowcharts describing the operation of the receiver. After initialization, the receiver is turned on (l40) and the receiver is turned off (145) to search for the bit synchronization 142 for a predetermined search period (144). If bit synchronization is achieved prior to the end of this predetermined search period 146, the receiver will again search for synchronization code 148. Again, assuming that a synchronization code is detected 150 prior to expiration of a given search period 152, the location code will be decoded 154 and the battery saver timing circuit will be synchronized 156. The receiver will then begin searching for the address signal 158. If the address signal is detected 160, an alert signal will be generated 162. If no address signal is detected, the receiver will continue to search for the address signal until the battery saver tie and circuitry indicate it is time to sebe 164 the battery. If the end of the batch is not detected 166, the timer will be set to wait for the next frame 168. If the end of the batch is detected, the timer will be reset to wait for the next batch 170. In either case, the receiver will turn on after a suitable time 174.

After initialization, the receiver is turned on trying to establish synchronization for a given search period. Searches for bit synchronization include data searches at various bit rates used in the system. If bit synchronization is achieved prior to the end of a given search period, the receiver will begin searching for the synchronization code. Again, assuming that a synchronization code is detected prior to expiration of a given search period, the location code will be decoded and the battery saver timing circuit will be synchronized. The receiver will then start searching the address signal. If an address signal is detected, an alarm signal will be generated. If no address signal is detected, the receiver will continue to search for the address signal until the battery jammer timing circuit indicates that it is time to save the battery.

If the end of the battery is not detected, the timer will be set to wait for the next frame. If the end of the batch is detected, the timer will be reset to wait for the next branch. In either of these cases, the phase receiver will turn on at a suitable time.

It should be appreciated that the claimed invention provides for paging coverage in practical buildings over a very wide area.

It should be appreciated that the present invention claimed may be used to provide national or continental paging coverage. In addition, it can be used in connection with current land based paging systems to provide nationwide coverage when a paging subscriber leaves his daily location.

Claims (12)

A satellite, an antenna coupled to the satellite to provide a signal beam having a variable beam area, the antenna of which the signal beam provided by the antenna is a meta signal having a variable data rate, and the signal beam having a plurality of predetermined beam areas Control means coupled to the antenna for providing information to the antenna so as to define one of the plurality of predetermined data rates and to specify that the meta signal has one of a plurality of predetermined data rates, the plurality of predetermined beam regions in response to one of the plurality of predetermined beam regions. A satellite signal display system comprising control means for determining one predetermined data rate. 2. The apparatus of claim 1, wherein said control means instructs said antenna to sequentially provide said signal beam to a plurality of predetermined locations on earth, said control means in response to one of said plurality of predetermined locations. A satellite signal display system for defining a beam area and the data signal. 3. The apparatus of claim 2, wherein the control means instructs the antenna to provide the signal beam at one of a plurality of predetermined positions with high population density, the control means having a high data rate and one of a plurality of predetermined beam regions that are small beam regions. A satellite signal display system for defining a signal beam and a data signal at one of a plurality of predetermined data rates. 3. The plurality of predetermined means according to claim 2, wherein the control means instructs the antenna to provide the signal beam at one of the plurality of predetermined positions having a low population density, and the signal beam and data signal are large beam areas. A satellite signal display system defining one of the beam regions and one of said plurality of predetermined data rates, said data rate being low. 3. The apparatus according to claim 2, comprising a plurality of signal arrangements provided in said data signal being a predetermined sequence, wherein one of said plurality of arrangements corresponds to one of said plurality of predetermined positions and represents one of said plurality of predetermined positions. Having a predetermined transmission time corresponding to an acknowledgment code, said satellite signal indicating system also comprising a transmission means rate connected to said antenna for transmitting said data signal, said control means causing said antenna to cause said antenna to be in said plurality of predetermined positions. When instructing the provision of the signal beam to one, the transmitting means is instructed by the control means to transmit one of a plurality of batches corresponding to one of the plurality of predetermined positions during the corresponding predetermined transmission time. Satellite signal display system connected to the control means. 6. The apparatus of claim 5, comprising a portable select signal receiver located at one of the plurality of predetermined locations, the receiver corresponding to receiving only one of the plurality of batches corresponding to one of the plurality of predetermined locations. And a receiving means selectively operated during a transmission time of the satellite signal display system. 6. The apparatus of claim 5, comprising a portable select signal receiver for receiving and decoding the data signal, wherein the portable select signal receiver corresponds to one of the plurality of predetermined locations in response to decoding the positioning code. Satellite signal display system that can be synchronized to one of the batches. An antenna having an adjustable beam, a first receiver for receiving communication information and control information, sequentially directing the adjustable beam to a plurality of predetermined locations in response to the control information and the plurality of predetermined beams in response to the control information Control means coupled to the antenna and the first receiver for controlling the antenna to vary the beam area of the adjustable beam corresponding to a position, a first transmitter coupled to the antenna and the control signal for transmitting a paging signal Thereby, the paging signal includes a data signal having a plurality of signal arrangements containing the communication information and arranged in a predetermined sequence, wherein the plurality of signal arrangements are transmitted at one of a plurality of predetermined data rates, The arrangements each match one of the plurality of predetermined positions and the plurality of arrangements are each multiple A first transmitter having an identification code indicative of a corresponding one of the predetermined positions of the first transmitter, wherein one of the plurality of predetermined data rates is determined by the control means in response to the beam area, and the plurality of receivers for receiving the paging signal; At least one select call receiver installed at one of the predetermined positions of the at least one select call receiver, wherein the at least one select call receiver at one of the plurality of predetermined positions is responsive to the confirmation code and corresponds to one of the plurality of predetermined positions; Satellite signal display system responsive to one of the arrangement of the. 9. The satellite signal display system of claim 8, comprising a second transmitter for transmitting the communication and control information to the first receiver. Transmitting paging information and control information to a satellite receiver; adjusting beams of antennas connected to the satellites to a plurality of predetermined positions in response to the control information; changing the area of the beam according to the plurality of predetermined positions Transmitting a paging signal from the satellite to a paging receiver in at least one of the plurality of predetermined locations at a predetermined time corresponding to one of the plurality of predetermined locations and at a data rate corresponding to an area of the beam. Wherein the paging signal is taken from the paging information. The method of claim 10, wherein the transmitting of the paging information and the control information comprises transmitting the control information and the plurality of signal arrangements arranged in the predetermined sequence, wherein the plurality of signal arrangements are respectively located at one of the plurality of predetermined positions. And corresponding multiple signal arrangements each having a predetermined transmission time in combination therewith. A satellite, first means for transmitting paging information to the satellite, at least one pager receiver, and second means for transmitting a paging signal having a variable data rate from the satellite to a plurality of predetermined locations in a predetermined sequence; A movable antenna for providing a signal beam having a variable beam area, and the second means for installing the antenna so that the signal beam is directed to the plurality of predetermined positions in the predetermined sequence and in accordance with the predetermined sequence. And a satellite paging system for varying the beam area and the data rate.