FI108762B - Method for achieving diversity, and base station device - Google Patents

Description

108762

A method for providing repetition and base station equipment

Engineering

The present invention relates to a method of providing repetition in a radio system in which transceivers are connected to other transceivers by radiation patterns formed by one or more antennas.

State of the art! 10 In radio systems, the quality of the signal between connections between different transceivers is constantly changing. This applies to all radio systems, but especially to those in which either of the transceivers is mobile. A typical system with varying signal quality is a cellular radio system. In a cellular radio environment, the signals between a base station and a subscriber terminal experience various fades and distortions, which seek to develop means to mitigate the effects of interference on the connection.

20 Radio systems generally employ a variety of repetition or diversity techniques, in particular to eliminate Rayleigh distributed interference. Repeat Method *, which refers to methods in which the signal is transmitted. more than one signal component is utilized.

From each of these signal components, a higher quality component may be selected at each instant, or alternatively, the components may be combined advantageously, thereby:, i .: maximizing the signal quality.

• S · Various playback methods are available.

In cellular radio systems, a repeater in which the signal is transmitted and received using more than one antenna is commonly used. Other known methods are, for example, polarization repeater, 'jitter', * ··· '' switched pattern 'and beam repeater. These repeat methods 35 are described in more detail in references [1] to [5]. References are listed at the end of the Explanatory Memorandum.

Many of these repetition methods ('jitter', 'switched pattern' and beacon repetition) are based on modifying the radiation pattern or beam direction of the antenna. Thus, their performance-5 kI depends on the antenna beam width. In addition, especially in microcells, the average power of the signal received by the antenna is substantially dependent on the beam direction. For example, if a signal is received by two beams and the average power level of the signal received by the second beam is significantly higher than the average power level of the signal received by the other beam, then the diversity advantage is lost. Repeat methods based on antenna beam modification are thus environmentally dependent, particularly in microcells.

15 The polarization repeat, which is based on the use of two different polarizations, horizontal and vertical polarization, is also very sensitive to the environment, as shown in [5]. The received average power levels of the different polarizations differ, in particular due to the lack of reflections. Also, the direction of the mobile station antenna relative to the vertical direction is of great importance for the functionality of the Polarization Repeater.

The major disadvantage of position repeater is that it requires more than one antenna to operate, which increases costs and can be difficult to position, especially in a microcell environment.

Characteristics of the Invention

It is, therefore, an object of the present invention to provide a repetition method that achieves good repetition improvement and is not environmentally dependent, as is known in the art. The object of the invention is. further implement an apparatus whereby repetition improvement can be achieved inexpensively and is easy to position.

This is achieved by a method of the type 35 described in the introduction, which is characterized in that two or more radiation patterns of differing phase radiation patterns are generated by the transceiver antennas of the 108762 receiver antennas.

The invention further relates to a base station apparatus 5 comprising one or more antennas by means of which the base station is in communication with the subscriber terminals within its coverage area. The base station apparatus according to the invention is characterized in that the base station comprises means for generating two or more radiation patterns identical in power radiation pattern with different phase radiation patterns with antennas.

The solution according to the invention has several advantages. In the solution according to the invention, the average power of different antenna beams is avoided. Thus, the solution according to the invention is not environmentally dependent like previous methods. In a preferred embodiment of the invention, antenna beams are provided using a single compact antenna. Also, diversity implementation is not dependent on antenna parameters such as beam widths or directions, so these considerations can be optimized for coverage aspects.

Explanation of patterns · ·. In the following, the invention will be explained in more detail with reference to the examples of the accompanying drawings, in which Fig. 1 illustrates an example of a radio system in which the invention may be applied, Fig. 2 illustrates an example of phase radiation; Figure 3 illustrates a first example of a transceiver implementing the invention, and. Figure 4 illustrates another example of a transceiver implementing the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS The solution according to the invention for repetition »» * * 4 108762 can be applied in any radio system in which transceivers communicate with one another over a radio path. One such radio system is a cellular radio system typically consisting of a plurality of cells each having a base station communicating with a subscriber terminal in its area. The invention will now be described, by way of example, but not limited to, a cellular radio system and, in particular, base station equipment of the system.

Figure 1 illustrates an example of a cellular radio system in which the invention can be applied. The figure shows a base station 100, and a plurality of subscriber terminal devices 102-106, to which the base station communicates by means of the radiation emitters 15 to 110 formed by one or more antennas 108.

One known way of implementing antenna 108 is to form an antenna from a plurality of antenna elements to which the signal to be transmitted is applied, with a weighting of each element as desired to provide the desired radiation pattern. Correspondingly, 20 also operates in the receiving direction. The different weighting of the elements thus produces different radiation patterns. In this way, different antenna beams can be formed or implemented with the same antenna. omnidirectional antenna pattern. An antenna consisting of elements can also be called an antenna array, although '·' is not a set of separate antennas, but a single antenna consisting of elements.

: .j .: The basic idea of the solution according to the invention is that::: that the transceiver antennas produce two or more radiation patterns of the same power radiation pattern, the phase radiation patterns of which differ. . ··. The resulting radiation patterns may be in the form of either a radial 116 or a beam 110-114, depending on the application. The radiation patterns may be consistent in either horizontal or vertical directions, or both. 1 »t · 5 108762

In a preferred embodiment of the invention, the antenna used is an antenna array, i.e., it consists of a plurality of antenna elements that can be controlled using weight factors, as described above. The antenna array weighting coefficients are selected so as to produce two or more radiation patterns of the same power beam having different phase beam patterns.

Referring to Fig. 2, the phase radiation patterns of two antenna patterns of 10 omnidirectional power radiation patterns are illustrated. The figure shows the horizontal angle on the horizontal axis and the phase on the vertical axis, and the two phase radiation patterns 150, 152. The phase patterns in the picture can be obtained, for example, with an eight-element antenna array. As will be appreciated, the steps are congruent with only a few individual angles.

Let us now consider the utilization of the second embodiment of the invention in the receiving direction. There are different options for exploiting the repetition. The first option uses a single receiver. Here, for the sake of simplicity, suppose that two radiation patterns are formed which have a uniform power pattern but differ in phase patterns. Upon receiving, the transceiver receives ·, momentarily, a signal with one phase radiation pattern and measures the signal quality, and momentarily, with a second, ·,. * 25 radiation pattern, measures the signal quality, and selects a radiation pattern providing better quality. The control of antenna elements can be implemented, for example, by means of digital signal processing.

In another alternative, when received, the transceiver receives a plurality of different phase radiation patterns and preferably combines the received signals.

. * · *. In this case, the receiver apparatus must comprise two separate receivers, the received signals of which are combined.

Next, the structure of the base station apparatus implementing solution 108762 of the invention will be considered. Figure 3 illustrates a first example of an apparatus for implementing the present invention with regard to the receiver side. The apparatus comprises an antenna array 200 consisting of a plurality of antenna-5 elements 202-206. The weighting means may be implemented by methods known to those skilled in the art. From the weighting means, the signal is applied to the radio frequency parts 210 of the ra-10, where the signal is converted to baseband or intermediate frequency. From the radio frequency sections, the signal is further transmitted to baseband sections 212, where other signal processing, such as channel decoding, deinterleaving and speech coding, is performed. These steps are not essential to the present invention. It should be noted here that the location of the weighting means 208 and the radio frequency parts 210 may also be different, i.e. that the weighting is performed after the radio frequency parts. Thus, weighting can be performed both digitally and analogously, as will be apparent to one skilled in the art. The stage at which the weighting is performed is not relevant to the present invention.

The apparatus further comprises control means 214 which control the operation of other parts of the apparatus. Control · ,; The means may be implemented by means of a general or signal processor • · '·' *, to which processor steps »» ♦ required by the invention are programmed. Alternatively, the control means may also be implemented as discrete components or as an ASIC.

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The control means 214 also control the weighting means 208 and 30 of the radio frequency means 210 so that the signal is momentarily received with a single phase radiation pattern and min. ···. measuring the signal quality, and temporarily measuring the signal quality with the second phase beam pattern. Based on the measurements, the control '···' means 214 select • '35 a better quality radiation pattern. Measurement • «t · II» »7 108762 can be performed in rapid succession without any change in propagation conditions in the radio channel.

Next, the structure of the base station apparatus 5 implementing the second embodiment of the solution according to the invention will be considered. Figure 4 illustrates another example of the apparatus for implementing the invention, the receiver side of the case. The apparatus comprises an antenna array 200 consisting of a plurality of antenna elements 202 to 206. The antenna elements are coupled to the weighting means 208, where the desired weighting of the signals received by the antenna-10 elements is performed. From the weighting means, the signal is applied to radio frequency sections 300, 302, where the signal is converted to baseband or intermediate frequency. From the radio frequency section 300, 302, the signal is further transmitted to baseband sections 304, where other signal processing such as channel decoding, deinterleaving and speech coding is performed. These steps are not essential to the present invention. As noted above, it should be noted that the positioning of the weighting means and the RF components may also be different, i.e., the weighting is performed after the RF components. Thus, weighting can be performed both digitally and analogously, as will be apparent to one skilled in the art.

The apparatus further comprises control means 214 which control the operation of other parts of the apparatus. In this embodiment of the invention 25, the control means 214 control the radio frequency means 300, 302 such that the signal can be continuously received with two different phase radiation patterns.

In the baseband sections 304, both sig V signals can be processed, and the means 306 30 comprising baseband sections 304 advantageously combine the received signals using known combining methods. Signal combining can also be performed on radio frequency sections, as will be apparent to one skilled in the art. Although in this example only two signals and a phase pattern are combined, the * 35 invention is naturally not limited thereto, but there may be more than one phase pattern.

Although the invention has been described above with reference to the example of the accompanying drawings, it is to be understood that the invention is not limited thereto, but can be modified in many ways within the scope of the inventive idea set forth in the appended claims.

Reference publications: [1] O. Norklit, J. Andersen: Mobile Radio Environments 10 and Adaptive Arrays, Proc. IEEE PIMRC, Sept 1994, p. 725-728.

[2] O. Norklit, C. Eggers, J. Andersen: Jitter Diversity in Multipath Environments, Proc 45th IEEE Veh. Tech. Conf., Chicago, 1993, p. 853-857.

15 [3] T. Aubrey, P. White: A Comparison of Switched Pat tern Diversity Antennas, Proc. 43rd IEEE Veh. Tech. Conf., Secausus, p. 89-92.

[4] K. Nikoskinen, J. Lempiäinen, K. Heiska: Beam Diversity Simulations in Microcellular Environments, 20 Proc. AP-S / URSI International Symposium, Baltimore, 1996, vol. 449-452.

I [5] A. Turkmani, A. Arowojolu, P. Jefford, C.

An Experimental Evaluation of Performance • • Two-Branch Space and Polarization Diversity Schemes 25 at 1800 Mhz, IEEE Trans. Veh. Tech. , vol 44, no.2, • ·

May 1995, p. 318-326.

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Claims (10)

A method for providing repetition in a radio system, wherein the transceivers (100-106) communicate with other transceivers by radiation patterns 110-116 formed by one or more antennas, characterized in that two or more power radiation patterns are formed by the transceiver antennas. with diffuse radiation patterns. A method according to claim 1, characterized in that the radio system comprises a plurality of base stations (100) and subscriber terminals (102-106), which base stations are in communication with the subscriber terminals in their area, and that the radiated patterns of phase radiation pattern are during. Method according to claim 1 or 2, characterized in that the radiation patterns formed 20 are in the form of an omnidirectional shape (116). Method according to claim 1 or 2, characterized in that the radiation patterns are formed. are substantially conical in shape (110-114). A method according to claim 1 or 2, characterized in that the antennas (200) used in the transceiver * consist of a plurality of antenna elements (202-206), and that one antenna generates: : two or more radiation patterns of the same power radiation pattern, the phase radiation patterns of which differ from each other. A method according to claim 1 or 2, characterized in that, when receiving, the transceiver receives a signal momentarily with one phase radiation pattern and measures the quality of the signal, and momentarily with another phase radiation pattern measures the signal. II »I» 10 108762 dun, and selects a radiation pattern for better reception. 7. A method according to claim 1 or 2, characterized in that, when received, the transceiver receives at all times a plurality of phase radiation patterns and preferably combines the received signals. A method according to claim 1 or 2, characterized in that the radiation patterns can be coincident in the horizontal or vertical directions, or both. A base station apparatus comprising one or more antennas (200) by which the base station (100) communicates with the subscriber terminals 15 (102-106) within its coverage area by means of radiation patterns (110-116), characterized in that the base station comprises means (208, 214) generate two or more radiation patterns of identical power radiation pattern with antennas having different phase radiation patterns. 9 108762 Claims: Base station apparatus according to claim 9, characterized in that the antennas (200) used in the base station comprise a plurality of antenna elements (202-206), and that the base station comprises means (208, ·, 214) for generating two or more power . an radiation pattern having an identical radiation pattern, the phase radiation patterns of which are different from each other. «* Ti · {IM • • ·« · »*», k * It * »t» t * * * * * t »i *» «· t · • I t I t» I · · it »ik 11 * 1 »» »• i * I« t> I k ltk * kk * k * k * * 108762 11 i