AU702991C - High efficiency sub-orbital high altitude telecommunications system - Google Patents

Description

HIGH EFFICIENCY SUB-ORBITAL HIGH ALTITUDE TELECOMMUNICATIONS SYSTEM ^"

Related Patent Applications:

This patent application is a continuation-in-part of patent application serial no. 08/100,037, filed July 30, 1993, entitled: SUB-ORBITAL, HIGH ALTITUDE TELECOMMUNICATIONS SYSTEM.

Field Of The Invention:

This invention relates to a telecommunications system, and more particularly to a telecommunications system that is operative at the sub-orbital level and provides for increased efficiency and increased utilization of available telecommunica¬ tions channels.

Background of The Invention:

The growth of cellular telecommunications has placed enormous strains on the ability of the industry to satisfactorily handle the telecommunications traffic that has been generated. Consequently, users of present analog cellular telecommuni¬ cations systems find that they may have to wait for a telecommu¬ nications channel to become available before they can place or receive a call. Also, a call in progress may encounter interfer¬ ence in the form of noise or actually over-hearing another conversation. Sometimes, a call may be cut off while in progress if one of the parties moves to a cell that does not have an available telecommunications channel.

The problem is further aggravated by the fact that there are only a limited number of frequencies allocated for cellular telecommunications. Thus, the problem is expected to grow as the demand for cellular telecommunications expands .

The industry has developed several improved analog and digital technologies that have been successfully used to increase the number of communications channels within the limited number of available frequencies.

The most important of these technologies are time division multiple access (TDMA) and code division multiple access (CDMA) .

TDMA is the technology that has the widest use. It enables a single telecommunications channel to be used for several calls. Each call is allocated a particular discrete time interval in the cycle of the telecommunications signals, thus, improving efficiency.

CDMA uses a wide band of spectrum for telecommunications signals to achieve efficiency. It differentiates between calls by imprinting a distinctive "noise" spreading signal over each telecommunications signal to differentiate it from other telecommunications signals in the cell. The receiver with computer assistance decodes the assigned "noise" signal to identify the call and then despreads the telecommunications signal. "Frequency hopping" is a form of CDMA that spreads a call over a series of frequencies. It uses a code to identify the sequence of frequencies that are being used.

Additionally, work has been done with respect to developing systems which can identify weak signals emanating from a cell and segregating those signals from other signals emanating from the same cell so that when combined with a digital multiple access technique such as CDMA, the number of available telecommunica¬ tions channels is dramatically increased.

Attempts to increase the availability of telecommunications channels have also included attempts to make the cells smaller and to reduce the power requirements necessary for communicating with a base station. This follows from the fact that a weak signal has a reduced ability to propagate. Thus, since its strength rapidly dissipates, the same frequency can be used in a nearby non-contiguous cell.

However, to provide the requisite number of cells that would be necessary to support a high volume of telecommunications, there would have to be an enormous number of base stations. Some experts estimate that at least 100,000 cells would be necessary simply to cover major metropolitan areas in the United States. Each cell would require its own stationary antenna tower.

In addition, an enormously complex computer system would be required in order to deal with the hand-offs which would be necessary as the cellular telephones moved from cell to cell and to manage the reuse of the frequencies assigned to particular calls . It is not certain that the problem can be solved with a ground based system at a reasonable cost and in a reasonable period. Thus, while the typical limitations associated with such systems such as line of sight, shadowing due to signal reflec¬ tion, attenuation and horizon limitations, are eliminated by reducing the size and increasing the number of cells, geograph¬ ic, political, environmental and social factors may prohibit the placing of antenna towers in certain locations thereby making it not possible for cells of a suitable size to be achieved in those locations.

A satellite system where each of the satellites functions as a base station node and contributes to the creation of a cellular network avoids these problems. However, in such a system relatively powerful transmitters are required because the satellites typically orbit at about 22,500 miles above the earth. Further, unless they are geosynchronous, a means must be provided for handing off signals from one satellite to another as they pass a given point over the earth. Further, as with terrestrial nodes, a hand off means is needed as a caller moves between cells.

Additionally, satellite systems suffer from the enormous cost in connection with launching, and the virtual impossibility of repair.

Accordingly, with the foregoing in mind, the present invention relates to a wireless telecommunications network system comprising a plurality of telecommunications nodes that are located in a sub-orbital plane. Each of the nodes comprises means for sending and receiving broadband, digital radio telecommunications signals over a wireless telecommunications channel. The telecommunications signals are modulated by code division multiple access spread spectrum technology.

The means for sending and receiving wireless, digital telecommunications signals include a plurality of antennae that are operative to receive relatively weak telecommunications signals from a source. Means are provided for decoding the telecommunications signals received by each of said antennae so that the node can identify the source, and the antenna and decoding means are operative to increase the sensitivity of the node so that it can detect and receive relatively weak telecommu¬ nications signals, so that maximum utilization of the spectrum is made available for use by the telecommunications signals without interference.

Description of the Drawing:

The invention can be further understood by referring to the accompanying drawing of a presently preferred form thereof, and wherein.

Figure 1 is a schematic drawing showing a telecommunications system constructed in accordance with a presently preferred form of the invention.

Figure 2 is a schematic drawing showing an aspect of the detecting and decoding means. Description of a Preferred Embodiment :

Referring now to Figure 1, a system 10 such as that described in patent application serial no. 08/100,037 comprises a ground based portion 12 and an air based portion 14. The air based portion 14 may be located at an altitude of between about

12 to 35 miles above the earth.

The ground based portion 12 may comprise conventional telephone network 16 with branches that are connected to ground stations 18, 120 and 140 having suitable long distance transmit¬ ting and receiving means such as antenna 20, 118 and 138. The ground based portion 12 may also comprise mobile telephones of well known types such as cellular telephones that may be carried by individuals 22 or in vehicles 24. The antennae 20, 188 and

138 are operative to transmit and receive telecommunications signals to and from a sub-orbital, high altitude relay station 28 which is located at an altitude of about 12 to 35 miles above the earth. This altitude is selected because it is well above weather activity so that the relay station will not be subjected to the strains that the weather might cause.

Preferably, there are a plurality of relay stations 28; each comprising a balloon 32 that is retained aloft and on station over a particular place over the earth by using a guidance module 56 which is connected by a guidance antenna 58 to ground link antennae 36 as described in parent patent application serial no. 08/100,037, filed July 30, 1993.

As is well known, each relay station 28 contains means for receiving a telephone telecommunications signal from one of the ground stations 20, 120 and 140 individuals 22 and 122 or vehicles 24 and 124 and then transmitting it to another ground station 120 and 140, individual 122 or vehicle 124 either directly or by way of another relay station. The communications channel so established could be simplex, duplex or half duplex. Once the signal returns to the ground based portion 12 of the system 10, the telecommunications call is completed in a conven¬ tional manner as by being connected to the ground-based, wired telephone system through suitable switches 34, 134 and 144. The switches may be of any type suitable for telecommunications signals including digital and analog.

As is well known, each of the relay stations 28 defines a node in the telecommunications system with each node defining a "cell." Preferably, each of the nodes comprises means for sending and receiving broadband, digital radio telecommunications signals over a wireless telecommunications channel. Preferably, the telecommunications channel has a frequency band width that is greater than about 8 MHz. The telecommunications signals are preferably modulated by code division multiple access spread spectrum technology.

To maximize the utilization of the available frequencies beyond that which is currently available with CDMA, the cells should be relatively small and the signal power required for telecommunications signals very low. This will enhance the reusability of frequencies and reduce interference. However, reduced signal strength makes it more difficult for the base stations to track the movement of particular cellular phones.

A detection system comprising a suitable array of antennae 48 and decoders 44 on each of the relay stations is provided. The detection system is of a type similar to the spatial processing system that is described in FORBES ASAP; June 5, 1995, at pages 125 - 141. The system processes the signal received by each of the antennas in the array. The decoded signals identify the transmitter and its location in the cell. Thus, even though a very weak signal, which ordinarily might be lost, is received by the detection system it can still be recognized and processed to complete a telecommunications channel.

The advantages of the combination of spread spectrum CDMA and the detection system comprising the antenna array described above are enhanced when combined and placed in the sub-orbital plane since all of the disadvantages of both terrestrial and satellite systems are avoided while their advantages, such as vertical signal propagation are maintained thereby increasing the utilization of the telecommunications spectrum. Further, power requirements can be lowered and the weight of the transmitters at the nodes can be reduced correspondingly. In addition because of the modulation technique the number of transmitters can be reduced.

Thus, a large number of telecommunications channels can be established in a cell defined by a particular node without the attendant problems of interference arising from crosstalk, reflection, frequency reuse and the like.

Additionally, the relatively high power requirements that such a system would require if it were associated with a satellite based telecommunications system are avoided.

It is contemplated that the system which has been described will be using code division multiple access spread spectrum technology; encompassing direct sequence and/or frequency hopping techniques .

Still further, while the frequency allocations for the telecommunications system have not been identified with particu¬ larity, it should be understood that they could be the same as those allocated for terrestrial telecommunications, or those allocated for satellite telecommunications. Similarly, it is within the scope of the invention for the frequencies to be those which are exclusively for use by the telecommunications system.

While the invention has been described with respect to certain forms and embodiments, it is apparent that other forms will be obvious to those skilled in the art in light of the foregoing description. Thus, the scope of the invention should not be limited by the description, but rather, only by the scope of the claims appended.

Claims (38)

Claims :

1. A wireless, telecommunications network system comprising a plurality of telecommunications nodes, said nodes being located in a sub-orbital plane at about 12 to 35 miles above the earth, each of said nodes comprising means for sending and receiving broadband, digital radio telecommunications signals over a wireless telecommunications channel, said radio telecommunications signals being modulated by code division multiple access spread spectrum technology, and said means for sending and receiving said radio telecommunications signals further including a plurality of antennae that are operative to receive relatively weak telecommu¬ nications signals from a source, means for decoding the telecommunications signals received by each of said antennae so that said node can identify said source, and said antennae and said decoding means being operative to increase the sensitivity of said node so that it can detect and receive relatively weak telecommunications signals, so that maximum utilization of said spectrum is made available for use by said telecommunications signals without interference.

2. A system as defined in claim 1 wherein said code division multiple access spread spectrum technology is direct sequence.

3. A system as defined in claim 1 wherein said code division multiple access spread spectrum technology is frequency hopping.

4. A system as defined in claim 1 wherein said wireless telecommunications channel has a fre¬ quency band width that is greater than about eight MHz.

5. A system as defined in claim 1 wherein each of said nodes is stationary over its own point on the earth.

6. A system as defined in claim 1 wherein said means for sending and receiving broadband, digital radio telecommunications signals over a wireless telecommunica¬ tions channel comprises at least one transmitter and receiver, and said transmitter and receiver carry a plurality of duplex telecommunications channels.

7. A system as defined in claim 6 wherein said transmitter is low powered and light weight.

8. A system as defined in claim 1 including a terrestrial based telecommunications network, and means for connecting said wireless, telecommunications network system to said terrestrial based telecommunications network.

9. A system as defined in claim 8 wherein said means for connecting said wireless, telecommu¬ nications network system to said terrestrial based telecommu¬ nications network includes switches.

10. A system as defined in claim 9 wherein said switches are digital .

11. A system as defined in claim 9 wherein said switches are analog.

12. A system as defined in claim 1 wherein said nodes are supported by balloons.

13. A system as defined in claim 1 wherein said wireless telecommunication frequencies are the same as those allocated for terrestrial telecommunications.

14. A system as defined in claim 1 wherein said means for sending and receiving broadband, digital radio telecommunications signals over a wireless telecommunica¬ tions channel comprises at least one transmitter and receiver and said transmitter and receiver carry a plurality of simplex telecommunications channels.

15. A system as defined in claim 14 wherein said transmitter is low powered and light weight.

16. A system as defined in claim 1 wherein said means for sending and receiving broadband, digital radio telecommunications signals over a wireless telecommunica¬ tions channel comprises at least one transmitter and receiver, and said transmitter and receiver carry a plurality of half duplex telecommunications channels.

17. A system as defined in claim 16 wherein said transmitter is low powered and light weight .

18. A system as defined in claim 1 wherein said wireless telecommunication frequencies are the same as those allocated for orbital telecommunications.

19. A system as defined in claim 1 wherein said wireless telecommunication frequencies are exclusively used by said telecommunications system.

20. A method for making wireless telecommunications comprising the steps of providing a plurality of telecommunications nodes, said nodes defining a network, locating said nodes in a sub-orbital plane at about 12 to 35 miles above the earth, providing each of said nodes with means for sending and receiving broadband, digital radio telecommunications signals over a wireless telecommunications channel, providing each of said nodes with a plurality of antennae that are operative to receive relatively weak digital, radio telecommunications signals from a source, modulating said telecommunications signals by code division multiple access spread spectrum technology, decoding said telecommunications signals received by each of said antennae so that said node can identify said source, and said antennae and said decoding means being operative to increase the sensitivity of said nodes so that they can detect and receive said relatively weak telecommunications signals, so that maximum utilization of said spectrum is made available for use by said telecommunications signals without interference.

21. A method as defined in claim 20 wherein said code division multiple access spread spectrum technology is modified by direct sequence.

22. A method as defined in claim 20 wherein said code division multiple access spread spectrum technology is modified by frequency hopping.

23. A method as defined in claim 20 wherein said wireless telecommunications channel has a frequency band width that is greater than about eight MHz .

24. A method as defined in claim 20 wherein each of said nodes is stationary over its own point on the earth.

25. A method as defined in claim 20 wherein said step of sending and receiving broadband, digital radio telecommunications signals over a wireless telecommunica¬ tions channel comprises the step of providing a plurality of transmitters and receivers, and each of said transmitters carrying a plurality of duplex telecommunications channels.

26. A method as defined in claim 25 wherein said transmitters are low powered and light weight.

27. A method as defined in claim 20 including the steps of providing a terrestrial based telecommunications network, and connecting said wireless, telecommunications network system to said terrestrial based telecommunications network.

28. A method as defined in claim 27 including the step of providing switches for connecting said wireless, telecommunications network system to said terrestrial based telecommunications network.

29. A method as defined in claim 28 wherein said switches are digital.

30. A method as defined in claim 28 wherein said switches are analog.

31. A method as defined in claim 20 including the step of supporting said nodes by balloons.

32. A method as defined in claim 20 wherein said wireless telecommunication frequencies are the same as those allocated for terrestrial telecommunications.

33. A method as defined in claim 20 wherein said step of sending and receiving broadband, digital radio telecommunications signals over a wireless telecommunica¬ tions channel comprises the step of providing at least .one transmitter and one receiver, and said transmitter and receiver carry a plurality of simplex telecommunications channels.

34. A method as defined in claim 33 wherein said transmitters are low powered and light weight .

35. A method as defined in claim 20 wherein said step of sending and receiving broadband, digital telecommunications signals over a wireless telecommunications channel comprises the step of providing at least one transmitter and one receiver, and said transmitter and receiver carry a plurality of half duplex telecommunications channels.

36. A method as defined in claim 35 wherein said transmitters are low powered and light weight.

37. A method as defined in claim 20 wherein said wireless telecommunication frequencies are the same as those allocated for orbital telecommunications.

38. A method as defined in claim 20 wherein said wireless telecommunication frequencies are exclusively used by said telecommunications system.