The present invention discloses a point-to-point telecommunications system with a first transmitter which transmits information to a first receiver via electromagnetic waves. The transmitter transmits on a number of antenna beams, using a first frequency on at least a first and a second of said beams, with said first and second beams containing different information.
In wireless telecommunications systems such as, for example, cellular telephony systems, there is often a need to transmit information from, for example, a base station, to a higher level in the system. With increases in the information transmission capacity within a cell, there will also be demands for significant increases in the capacity to transmit information from a base station to higher levels in the system.
A traditional method of relaying information from the base station to higher levels in the system has been to use radio links, usually in the microwave frequency range, for point-to-point transmission. Conventional methods of increasing the capacity in a radio link have been to use higher order modulation methods, and/or the use of dual orthogonal polarizations for transmitting independent signals.
Higher order modulation and dual polarization systems are expensive, sensitive to interference and will normally not allow more than a fourfold increase in capacity compared to the standard solutions used today over a fixed bandwidth, such as, for example, a channel with 28 MHz bandwidth.
A desired capacity might be in the region of 1 GBps or more, which, using contemporary solutions, would involve several 28 MHz bandwidth channels.
This would in turn lead to a need for more frequency spectrum, which in many cases is not possible, since frequency spectrum is a limited resource, and in many situations the operator can not get more spectrum from the frequency authority.
There is thus a need for a solution or a system which would allow higher capacity transmissions than with contemporary solutions in a point-to-point telecommunications system.
This need is addressed by the present invention in that it discloses a point-to-point telecommunications system which comprises a first transmitter which transmits information to a first receiver via electromagnetic waves. Said first transmitter transmits on a number of antenna beams using a first frequency on at least a first and a second of said beams. Said first and second beams contain different information, and the point-to-point connection between the transmitter and the receiver is achieved by means of at least a first repeater located between the transmitter and the receiver, with the first repeater being used for the first beam.
In another embodiment of the invention, the system can in addition comprise a second repeater, which is used for connecting the first transmitter to the first receiver in the second beam.
Thus, by means of the invention, the transmission capacity can be increased by using a plurality of different antenna beams, all on one and the same frequency, but containing different information, while not requiring more frequency spectrum than one beam.
In addition, so called MIMO equipment can be applied to the proposed system. MIMO, Multiple Input Multiple Output, is usually only used in other types of systems and applications, mainly so called NLOS-systems, Non Line Of Sight systems.
The frequencies of the electromagnetic waves used are in a preferred embodiment on the microwave band, but other wavelengths are also possible, including, for example, optical wavelengths.
The invention will be described in more detail in the following description with reference to the appended drawings, in which
Naturally, there is nothing to stop a point-to point system such as the one in
As is also shown in
A major application for the system shown in
In order to achieve an increase in transmission rates while still using essentially the same modulation methods, the system of the invention makes use of a transmission antenna which can transmit in a plurality of beams, i.e. at least a first and a second beam. The same transmission frequency can be used in both or all of the beams, due to the fact that the beams will be given an angular separation which will accomplish a sufficiently low level of correlation/interference between the beams. The angular separation can be in either azimuth or elevation, or a combination which gives the desired effect
Although the beams are separated in azimuth, they will still be able to reach one and the same receiver in a point-to point system since the system comprises at least one repeater. An example of such a system 200 is shown in
The transmitter 210 transmits on a number of antenna beams, with the example in
Usually, there will be one radio transmitter with an amplifier for each of the transmit frequencies.
The point-to-point connection between the transmitter and the receiver is achieved by means of at least a first repeater 240 located between the transmitter and the receiver, said first repeater being used for one of said beams, 231.
Thus, as shown in
The two transmit beams 230,231, are separated in azimuth and/or elevation by an angle α which is sufficient to avoid interference between the two beams. The transmit beam which is reflected from the repeater 240 to the receiver 220, in
Although the system 200 is described as comprising one transmitter 210 and one receiver 220, a system according to the invention may in fact be a “full duplex” system, i.e. each end of the connection 210-220 comprises both a transmitter and a receiver, so that the system comprises first and second transmitters and first and second receivers.
A version 300 of the invention is shown in
This is merely done in order to achieve the desired angular separation, for which other solutions can also be found, such as directing all four beams in one main direction with an angular separation between them. In
As indicated previously, the repeaters 340-343 can be active or passive repeaters, or a combination of passive and active repeaters can be used within the group of repeaters 340-343.
In similarity with the system described in
Since four beams are used, the transmission capacity of the system 300 in one transmit direction will be 4*(155 Mb/second) on a 28 MHz bandwidth, i.e. 620 Mb/second, without an increased need for bandwidth.
It can be mentioned here that in a system of the invention, e.g. that of
The input to the butler matrix 450 comes from four separate radio chains, one chain comprising one transmitter and one amplifier, 410, 420, 430, 440, each of which generates one modulated data stream. The Butler matrix 450 uses these inputs to generate the four beams 460, 470, 480, 490, each of which contains one of the modulated data streams from the radio transmitters 410-440. The four beams must, as indicated previously, be sufficiently decorrelated i.e. have a sufficiently low degree of interference between them. Said degree is decided by the application in question.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/SE2005/001082 | 7/4/2005 | WO | 00 | 1/3/2008 |