MXPA98004213A - Means to increase capacity in radiocellular systems (moviles and fij - Google Patents

Abstract

A method for installing a plurality of directional beams (61-64) in a radiocell system having a plurality of antennas that each communicate over a respective corresponding sector area. Interference between geographically close sectors is reduced by the method that results in an improvement in the performance of the carrier-to-interference ratio. The carrier frequencies of two internal beams transmitted through the antenna an exchange for two internal beams that are transmitted in substantially the same direction by another antenna. This results in improved carrier-to-interference performance for the four beams transmitted by the antennas. The exposed techniques are applicable to systems (tri-cellular) excited by corner or excited from the cent

Description

MEANS FOR INCREASING CAPACITY IN RADIOCELULAR SYSTEMS (MOBILE AND FIXED) Field of the Invention The present invention relates to a method for operating an antenna installation in a cellular communication system and more particularly to a method for assigning frequencies to directional antennas of multiple beams BACKGROUND OF THE INVENTION In conventional radio-cellular systems, the geographic areas are divided into a plurality of adjacent cells, in which mobile stations within a cell communicate with a base transceiver station. In general, each mobile (or set of mobiles that share a multiplexed channel) that communicates with a base station in a cell uses a carrier frequency different from other mobiles in the cell, in order to avoid interference with other mobiles. In this way, the number of mobiles that can be serviced in a cell is limited by the number of available carrier frequencies. There is a growing demand for capacity to use radio-cellular systems, however, the frequency band within which radio-cellular systems operate is limited in amplitude and therefore, to provide an increasing capacity in the system, the available carrier frequencies are re-use from cell to cell. The re-use of frequencies in a locality is restricted by the co-frequency interference between the different cells that reuse the same frequency, or nearby and that are geographically close to each other. To obtain the maximum capacity in a system comprising a plurality of cell areas, the designers of radiocell systems try to reuse as much as possible the many different carrier frequencies of the set of carrier frequencies available in each cell. However, there are limits on the reuse of carrier frequencies in a cell due to other potentially interfering signals, particularly from: (1) the interference between a carrier frequency in a first cell and an identical frequency re-used in the surrounding cells and (2) the interference between a hand frequency used in a first cell and the adjacent carrier frequencies used in the surrounding cells. The minimum physical distance between the geographic cells that re-use the same carrier frequency or an adjacent carrier frequency is limited by the required quality of the signals received at the carrier frequency. A metric used to describe the quality of the signal is referred to in the material as the carrier-to-interference ratio (C / I ratio). The C / I ratio is a ratio of signal strength of a desired carrier frequency received with a signal strength of received interference carrier frequencies and noise. Several physical factors can affect the performance of C / I in cellular systems, including building reflections, geography, antenna radiation patterns, the mobile station's transmission power, and the locations of mobile stations within a cell. . In general, the calculation of the distances between the cells that re-use an interfering carrier frequency is a complex problem, however, a general approach can be found for calculations in William Chien-Yeh Lee's Cellular Mobile Telecommunications Systems published by McGraw Hill Book Company, New York 1989 (which are incorporated herein by reference). Taking as an example a TDMA system of Amps. Digital (multiple access and time division) that has 12.5 MHz of frequency spectrum available, for example in a 850 MHz band, the individual carrier frequencies are separated by spaces of each 30 KHz, giving a total of 416 carrier frequencies available through the entire network. The 416 carrier frequencies are divided so that the individual carrier frequencies are re-used from cell to cell. Taking as an example a n-reuse factor of base station of 7 (n = 7), for cells excited from the center, 416 - ^ - 7 = 59 carrier frequencies are assigned to each cell. However, with a base station re-use factor of n = 4, this gives 416 ^ 4 = 104 carrier frequencies per cell, resulting in a greater capacity than for a reuse factor of n = 7. At a base station re-use factor of n = 4, the cells re-using the same carrier frequency (the frequency re-use cells) are closer to each other than to a reuse factor of base station of n = 7, resulting in greater interference and a lower C / I ratio in the case of the base station re-use factor of n = 4 than in the case of the base station re-use factor of n = 7 To implement the frequency of the lower base station reuse factor (n = 4), the reuse cells must be closer to each other than with the base station re-use greater than n = 7. However, the distance between the re-use cells must be large enough so that the carrier-to-interference ratio is high enough to allow the radio-cellular telecommunications apparatus to distinguish the signals on each re-used carrier frequency in a cell of the interference frequencies present in other cells through the network. The performance of C / I is a limiting factor in the implementation of a lower base station reuse factor. SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved proportion of interference-to-interference for a plurality of beams that re-use beam-beam frequencies and to provide an acceptably low level of total interference, thereby enabling a greater amount of interference. -use of the frequencies and providing a gain of capacity for a cellular radiocommunication system. According to one aspect of the present invention, there is provided a radiocell system having a plurality of base stations, each capable of communicating over a plurality of sector areas using a plurality of directional beams, a method for installing the plurality of beams directional, the method comprising the steps of: in a first base station, forming a first set of beams in a first sectorial area; in a second base station, forming a second set of beams in a second sectorial area; wherein at least one beam of the first set is directed in a substantially equal direction and re-uses the same first frequency as at least one beam of the second set; and at least one remaining beam of the first set re-uses the same second frequency as at least one remaining beam of the second set, the remaining beam of the first set being directed in a direction pointing away from the remaining beam of the second set. The first set of beams uses a set of carrier frequencies, each beam of the first set being assigned a respective corresponding carrier frequency of the set of carrier frequencies, the carrier frequencies differing from each other and the second set of beams re-uses the set of carrier frequencies. Preferably, each set of beams comprises at least one internal beam and at least one external beam; wherein an external beam of the second set re-uses a frequency of an external beam of the first set, the external beam of the second set directed in a direction substantially equal to the external beam of the first set; and an internal beam of the second set re-uses a frequency of an internal beam of the first set, directed the internal beam of the second set away from the internal beam of the first set. According to a second aspect of the present invention, there is provided a radiocell system having a plurality of base stations communicating with each other over a plurality of sector areas, by means of a plurality of directional beams, a method for installing the plurality of directional beams, comprising the steps of: assigning a first set of beams to a first base station over a first of said sector areas; assigning a second set of beams to a second base station over a second of said sector areas; wherein each beam of the first set corresponds to a respective beam of the second set; wherein a beam of the first set has a common carrier frequency and a common address with a corresponding beam of the second set; and a beam of the first set has a common carrier frequency but with a different address to a corresponding beam of the second set. Preferably, each set of beams comprises an external beam and an internal beam; and an external beam of the first set has a common carrier frequency and a common address with an external beam of the second set; and an internal beam of the first set has a common carrier frequency but a different address to an internal beam of the second set. In one embodiment, the base stations each serve to communicate over three sectors excited by respective adjacent hexagonal flanges, each of substantially equal area in a tri-cellular facility. The use of a plurality of directional beams in a single cell of a tri-cellular installation can allow an improved ratio of carrier to interference and allow a more frequent frequency re-use in a radiocell system. Preferably, each of the bundle comprises four directional beams. Preferably, each of the set of directional beams comprises two internal beams and two external beams. The invention includes a radiocell system having a plurality of base stations and a total network control frequency setting table which defines which carrier frequencies are assigned to which beams transmitted by the antennas to operate a method according to the second aspect in the I presented . According to a third aspect of the present invention, there is provided a radiocell apparatus comprising a plurality of base stations each capable of communicating with a respective plurality of corresponding sector areas, each of the base stations capable of forming a plurality of beams directionals that cover their plurality of corresponding respective sector areas, wherein a first base station and a second base station are separated from each other; a first set of beams extends from the first base station in a first pattern over a first sectorial area; a second set of beams extends from the second base station in a second pattern over a second sector area, substantially replicating the second pattern to the first pattern; a plurality of carrier frequencies is assigned to the first set of beams in a first order; the plurality of carrier frequencies is re-used by said second set of beams, the set of carrier frequencies being assigned to the second set of beams in a second order, different from the first order. Preferably, the beams of the first set extend along directions that diverge within an angle of 60 ° from a principal direction of the first cell; the beams of the second set extend along diverging directions within a 60 ° angle from a main direction of the second cell; and substantially coinciding the principal directions of the first and second cells with each other. According to a fourth aspect of the present invention, there is provided a radiocell system having a plurality of base stations, each capable of communicating over a plurality of directional beams, each of the plurality of base stations operating a common set of frequencies. carriers re-used between the base stations, a method of assigning carrier frequencies comprising the steps of: forming in a first base station a first set of directional beams over a first said sector area, each of the beams directed in a respective one of a plurality of directions; in a second base station, forming a second set of directional beams on a second said sectorial area, each beam of the second set also directed in a respective one of the plurality of directions; assigning the set of carrier frequencies to the first set of beams in a first order; and assigning the same set of carrier frequencies to the second set of beams in a second order, the second order of the first order being different. According to a fifth aspect of the present invention, there is provided a radiocell system having a plurality of base stations each operating a common set of carrier frequencies on a respective said corresponding sector area, the plurality of base stations each operating a set of directional beams in a common pattern, a frequency assignment method comprising the steps of: assigning for each of the first set of base stations the common set of carrier frequencies to the set of beams in a first order; and for each of a second set of base stations, assign the common set of frequencies to the set of beams in a second order, wherein the second order is different from the first order. Preferably, the first set of base stations is installed substantially along a first line and the second set of base stations is installed substantially along a second line. Preferably, the first line is substantially parallel to the second line. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention and to demonstrate how it can be carried out, specific embodiments, methods and processes according to the present invention will now be described only by way of example with reference to the drawings FIG. 1 illustrates an installation of three-sector hexagonal cells excited from the center, in which each sector is attended by a plurality of directional beams, * Figure 2 illustrates a tri-sector installation of the prior art wherein each of the three sectors of a tri-cellular area is served by a separate beam; Figure 3 illustrates the beam coverage of a tri-cellular area sector of the prior art installation of Figure 2, showing an outline of -3dB and an outline of -lOdB, illustrating the coverage of the cell from a beam that originates in a corner of the sector; Figure 4 illustrates a directional beam approach having frequency re-use between cells for sectors excited by edges with four beams per sector in a tri-cellular facility; Figure 5 illustrates a graph of the carrier-to-noise ratio and interference corresponding to the approach in Figure 4; Figure 6 illustrates a directional beam approach for the edge-driven sectors that have a frequency re-use between the sectors with four beams per sector in a tri-cellular installation according to a specific method of the invention herein; and Figure 7 illustrates a graph of noise to interference ratio corresponding to the arrangement of Figure 6.

DETAILED DESCRIPTION OF THE BEST MODE FOR CARRYING OUT THE INVENTION The best mode contemplated by the inventors to carry out the invention will now be described by way of example. In the following description numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention can be practiced without the use of these specific details. In other cases, well-known methods and structures have not been described so as not to obscure the present invention unnecessarily. In this specification, the term sector is used to denote an azimuth angular view range of a base station nominally 120 ° or less over which the radio base station produces the beam coverage.

Typically, a sector can subtend an angle of view (Azimuth angle) of nominally 120 ° in a three-sector installation per base station as illustrated in Figures 1 and 6 herein. In a six-sector installation per base station (a hex-sectored facility), each sector can subtend a nominal angle of 60 ° from a base station. In a hexagonal cellular installation, excited from the center, tri-sectorized, conventional, a sector may comprise a nominal quadrilateral area, which is excited by edge or by corner. Three such sectors form a nominally hexagonal cell. In a conventional tri-cellular installation, a sector comprises a nominally hexagonal area excited from an edge or corner. Three such sectors surround a base station in order to provide a tri-cellular area. In each case, the sector is excited by edge and extends radially outward from the base station. A growing capacity can be achieved on a tri-sectorized cell installation, excited from the center, of the prior art, having three sectors of 120 ° each served by a separate azimuth beam of 120 °, by the use of a plurality of directional beams in each sector, as shown in Figure 1 here. Referring to Figure 1, there is shown an example of a geographic area served by a radio-cellular network that covers a plurality of cells excited from the center, nominally hexagonal, divided each cell into three sectors of 120 °, attended each sector by four directional beams. The first, second and third hexagonal cells 100, 101, 102, respectively, re-use a common set of frequencies and are separated from each other by other intermediate cells 103-105 that use different frequencies in the first to third cells and which do not interfere with the common frequencies used in the first to third cells. Each of the first, second and third cells is tri-sectorized into three sectors of 120 °, where four directional beams per sector are provided. It is possible to use a plurality of directional beams to increase the capacity of a radiocell system by reducing the interference from surrounding beams that reuse the common frequencies. Using the example of a base station re-use factor n = 7, where 416 - ^ - 7 = 59 carrier frequencies per cell are assigned to each cell, where the cell is divided into three sectors, each sector having four directional beams , 19 carrier frequencies can be assigned to each set of four beams 106-109 in a sector as shown in Figure 1. Most of these frequencies can be assigned traffic, but some are reserved for control purposes. A base station re-use factor of n = 4 gives carrier frequencies per cell. In a hexagonal cell divided into three sectors, each sector having an installation of multiple beams of four beams per sector, 34 carrier frequencies can be assigned per sector, that is through four directional beams, in a sector of 120 °. The improvement in the C / I ratio obtained by the use of directional beams within a sector allows the implementation of a lower base station re-use factor n which would otherwise be available with a cell installation energized from the center, divided into three sectors. Considering now a conventional tri-cellular installation (otherwise known as corner-excited or edge-excited cells) as shown in Figure 2 herein, a base station serves three nominally hexagonal sectors comprising a three-dimensional region. cellular, from a position in a center of the tri-cellular region where the three sectors meet each other. Conventionally, network programmers use nominally hexagonal areas that are called "cells" to plan for terrestrial cellular network coverage. However, the installation of the three edge-driven, nominally hexagonal sectors surrounding a base station has become known as a tri-cellular installation. In this specification, the terminology used for each edge-excited area surrounding a base station is maintained as a sector, according to the above description without taking into account whether the area excited by edge is nominally hexagonal or quadrilateral or any other shape. The tri-cellular installation has an inherent advantage in terms of C / I performance compared to a hexagonal cell, divided into three sectors, excited from the center, conventional, equivalent, of comparable area, because a beam can be used narrower in each sector of the tri-cellular installation compared to each sector of the installation excited from the center, divided into three sectors, known. Referring to Figure 3 herein, an installation of a sector of a tri-cellular installation of three sectors is illustrated, in which a hexagonal sector 300 is covered by a beam having a coverage pattern having a beam amplitude. Angular 60 ° 301 to -3 dB gain. Such beam amplitude can give the adequate performance for the coverage of an angle azimuth of 120 ° 302 in the corner of the sector where the base station is located, as the beam coverage pattern moves away from the power, as such so that a contour of -10 dB 303 of the beam, the nearest corners 304, 305 of the nominally hexagonal sector that is adjacent to the corner occupied by the base station is relatively close to the base station compared to the corners they look at. opposite direction 306, 307 and are within the contour of -10 dB of the beam with the result of acceptable power levels that are available for communication with mobile stations in the nearest corners 304, 305. In this way, the installation The known tri-cell has an inherent advantage over the hexagonal cell installation, divided into three sectors, excited from the center, known, in terms of which a Narrow down to cover an equivalent area. The reduced power received in the downlink by the mobile stations located in the corners closest to the corner of the base station is compensated by the fact that these corners are closer to the corner of the base station than other parts of the sector three-cell Typically, an azimuth beam amplitude of -3 dB from 60 ° to 70 ° is acceptable for tri-cellular sector coverage. Referring to Figure 4 of the accompanying drawings, there is illustrated a radiocell system serving a geographic area divided into a plurality of edge-driven, hexagonal, adjacent sectors 40 of substantially equal area with each other in a cellular configuration, in which a plurality of base stations B are each surrounded by a respective set of three corresponding hexagonal sectors, to which they give service. Each base station has one or more directional beam antennas 45. Each base station supports the coverage of its three surrounding sectors comprising a tri-cellular region. The tri-cellular regions are shown enclosed by a thick line in Figure 4. A plurality of B frequency re-use base stations using a common set of frequencies are installed in a plurality of substantially straight lines that are approximately parallel to each other. yes, the base stations of a line separating in an approximately equidistant manner from each other along the line. The base stations of a line are placed outside the base stations of a surrounding line. Each tri-cellular area comprises three nominally hexagonal sectorial areas. Each sectorial area is served by a plurality of beams extending substantially radially outward from the base station and covering the area of the sector. The plurality of beams extends either side of a main length of the sector, the main length extending between a corner of the hexagonal sector in which the base station is located and an additional corner of the sector opposite the corner in which the base station is located. Each beam is of relatively narrow beam amplitude, typically of the order of 45 ° to 60 ° of azimuth in the gain contour of -3 dB. For ease of description, a method corresponding to a sector of a tri-cellular region will be described hereinafter, the tri-cellular regions being supported by two base stations that are separated from each other and re-use a common set of carrier frequencies. It will be understood that the coverage of all sectors in the radiocellular system requires the duplication of the method described so far. In figure 4, a first set of directional beams 41A, 42A, 43A and 44A has been labeled for one of the sectors covered by the first frequency re-use base station 45A and a second set of directional beams has been labeled. labeled 41B, 42B, 43B and 44B for one of the sectors covered by the second frequency re-use base station 45B. When reference is made to Figure 4 herein, a beam referenced by a number 41 must represent the beam 41A, 41B or any other beam of equivalent re-used carrier frequency and a substantially similar address, transmitted by any other base station of frequency re-use 45 in Figure 4. Likewise, beams referenced by a number 42, 43 or 44 must represent beams of identical re-used carrier frequency and substantially similar address of any base station of frequency re-use 45 in Figure 4. All other sectors in Figure 4 have a corresponding pattern of four beams 41 to 44 that use other frequencies, but these are not illustrated for clarity. In the beam installation shown in Figure 4, the external beam 41A supported by the first base station 45A re-uses the same carrier frequency as the external beam 41B supported by the second base station 45B. Likewise, all internal beams 42, have the same carrier frequency with each other and similarly the internal beams 43 re-use another same carrier frequency and the external beams 44 re-use an additional equal carrier frequency as between the first and the second base stations 45A, 45B in Figure 4. The sector served by the first base station 45A containing the first set of directional beams 41A-44A uses the same set of frequencies as the second set of beams 41B-44B of the second base station 45B serves the second three-cell area. Similarly, other surrounding frequency re-use base stations 45C, 45D, 45E, 45F, 45G, serving a respective corresponding tri-cellular area, re-use the same frequencies as the first base station 45A, assigning those reuse frequencies to corresponding third, seventh, bundle bundles 41C-41G, 42C-42G, 43C-43G, 44C-44G, as shown in Figure 4. Each re-use sector of frequency contains a set of directional beams 41-44. In each case, the directional beams extend radially around the corresponding respective base station and either side of a main length of the respective corresponding sector served by the bundle set. Each sector that contains a set of beams that re-uses the same set of frequencies has a main length that extends in the same direction towards each other sector that reuses the same set of frequencies. Each beam of the first set of beams 41A-44A extends in a respective general direction, which is equal to a respective corresponding beam 41B-44B of a corresponding sector comprising a second tri-cellular area supported by a second base station of re-use 45B. The plurality of frequency re-use base stations 45 is installed in such a way that for each sector of the tri-cellular area supported by the respective corresponding re-use base station 45, beams 41, 44 at an outer edge of each individual sector of the tricellular area extend along a line pointing the view to an intermediate area between the respective, more external corresponding beams, 41B, 41C, re-using a same frequency as 41A. Because the beams 41A-C are directional, the probability of interference between these re-use frequency beams is reduced. Referring to Figure 5 herein, graphs of carrier-to-interference ratio are illustrated corresponding to four beams of a sector of the arrangement shown in Figure 4. Graph line 51 shows a graph of the carrier-to-interference level in decibels on a vertical axis, against the beam amplitude on a horizontal axis for the external beam 41 in Figure 4 on the beam amplitudes in the range of 20 ° to 50 °. Similarly, the graph lines 52, 53 and 54 in Figure 5 correspond to internal beams 42, 43 and external beam 44 in Figure 4, respectively. As can be seen from the graph lines 51 and 54 in FIG. 5, the two external beams 41 and 44 of a sector in FIG. 4 have a relatively higher carrier-to-interference performance compared to internal beams 42, 43. The innermost beams 42A, 43A of the first base station 45A extend in a direction pointing to respective corresponding internal beams 42B, 43B of the first adjacent row re-use sector of the first row re-use base station , second base station 45B. The areas covered by the internal beams 42B, 43B receive the interference from the corresponding internal beams of the first adjacent row frequency re-use base station 42A, 43B, respectively. Beams 42B and 43B in FIG. 4 experience reduced performance of interference-to-interference due to interference resulting from beams 42A and 43A transmitted by antenna 45A having the same carrier frequencies and traveling in substantially the same direction. Figure 6 illustrates a directional beam arrangement in a sector of a tri-radiocell system with apparatus components identical to those shown in Figure 4 but employing a specific method for the installation of frequency re-use beams , which is the object of the present invention. For ease of description hereinafter, a method corresponding to a sector of a tri-cellular region supported by a base station will be described. It will be understood that the coverage of the three sectors supported by a base station requires the duplication of the method described later. For this section of the description, a beam referred by a number 61 will represent the first external beam 61A, 61B, or any other substantially similar address beam supported by any base station in Figure 6 that reuses a common set of carrier frequencies. Likewise, the beams referred to by a number 62, 63 must represent internal beams of substantially similar address supported by any base frequency re-use station 65 in Figure 6 and beams referred by the number 64 must represent second external beams of any base frequency re-use station 65. The first external beam 61 has a same carrier frequency for all base stations 65 in FIG. 6. The second external beam 64 also has a same carrier frequency for all base stations 65 in Figure 6. However, the carrier frequencies of the two internal beams 62 and 63 have been interchanged with each other, between the first and second base stations 65A and 65B so that the internal beam 62A of the first sector of reuse of frequency served by the first base station sector 65A has the same carrier frequency as opposed to the internal beam 63B of the second frequency re-use sector of the second station first row frequency re-use base 65B and an internal beam 63A of the first frequency re-use sector has the same carrier frequency as the opposite internal beam 62B of the second frequency re-use sector. The alternating pattern of the carrier frequencies of the two internal beams transmitted by the base stations 65A and 65B is repeated throughout the array of frequency re-use base stations so that the two internal beams of all stations adjacent bases have alternating carrier frequencies in order to minimize the total interference. In the installation of Figure 6 here, the first base station 65A communicates with the first sectorial area served by the first beam set 61A-64A and the second frequency re-use base station 65B communicates with the second one. sector area served by the second set of frequency re-use beams 61B-64B. The external beams 61A, 64A of the first set of beams are directed in the same direction as the respective corresponding external beams 61, 64 of the plurality of other sets of beams (second to seventh sets of beams 61-64 corresponding to the second to seventh base stations of frequency re-use 65B-65G). Due to the arrangement of the base stations, installed substantially along straight lines parallel to each other where the frequency re-use base stations are substantially equidistant from each other along each line, the external beams 61, 64 of a sector of a tri-cellular area extend along a line of sight that points toward an area between the respective beams of re-use of corresponding, adjacent, closest frequencies, 61, 64 of the base stations of Re-use of adjacent frequencies and interference between external frequency re-use beams 61, 64 of the adjacent frequency re-use sectors is relatively low. The first internal beams of frequency re-use 62, of each frequency re-use sector along a line of base stations, for example a first line comprising the fourth base station 65D, the first base station 65A and the seventh base station 65G, all are directed in the same direction and use the same frequency. However, the first corresponding internal frequency re-use beams of an adjacent parallel line of frequency re-use base stations, comprising for example the second base station 65B and the third base station 65C use a different frequency, is say, the frequency used by the second internal beams 63 of the frequency re-use base stations along the first line comprising the fourth base station 65D, the first base station 65A and the seventh base station 65G. In the tri-cell areas corresponding to the base stations along the second line, the frequencies of the two internal beams 62, 63 are inverted in comparison to the respective corresponding beams of tri-cellular areas served by base stations along the first adjacent parallel line of base stations comprising the fourth, first and seventh stations base 65D, 65A, 65G. In other words, by examining the relationship between frequency re-use in the first base station 65A and the second base station 65B, the first base station 65A communicates with a first sectorial area of a three-cell area using a first set of beams , the second frequency re-use base station 65B communicates with the second sector of a second tri-cellular area using a second set of beams, at least one beam of the first set addressing in a direction substantially equal to that of a corresponding beam of the second set and remaining at least one beam of the first set that reuses a second same frequency as a beam of the second set, going away from that beam. The external beams 61A, 64A of the first set of beams have the same address as the respective corresponding external beams 61B, 64B of the second set of beams, indicating the respective corresponding beams of each set in the same direction with each other and using the same frequency between yes. The internal beams 62A, 63A of the first set of beams and the internal beams 62B, 63B of the second set of beams re-use the same two frequencies with each other, however, the first internal beam 62A of the first set has a carrier frequency re- commonly used by directing the second, internal, opposite beam 63B of the second set in different directions from each other and the second, opposite internal beam 63A of the first set with the same common carrier frequency as the first internal beam 62B of the second set also directed in different directions between yes. The first beam set 61A-64A extending from the first base station 65A is installed in a first radially extending pattern from the first base station, while the second beam set 61B-64B extends in a second pattern substantially radially outward from the second base station 64B, re-using the first and second sets of beams, a common set of carrier frequencies, the carrier frequencies being assigned to the first beam set 61A, 64A in a different order compared to its assignment to the second set of beams 61B-64B. Figure 7 illustrates here the interference-to-carrier ratio graphs corresponding to four beams transmitted by a base station 65 in the beam arrangement shown in Figure 6. Graph line 71 shows a carrier-to-interference level in decibels on a vertical axis, plotted against the amplitude of the beam for the beam 61 in Figure 6 on beam amplitudes in the range of 20 ° to 50 °. Similarly, the graph lines 72, 73 and 74 correspond to beams 62, 63 and 64 in Figure 6, respectively. As can be seen from the graph lines 71 and 72 of FIG. 7, the two external beams 61 and 64 in FIG. 6 achieve relatively greater interference carrier performance for the beam amplitudes in the 20 ° range. fifty. An improvement in the carrier-to-interference frequency performance resulting from alternating the re-used carrier frequencies between the internal beams 62 and 63 in Figure 4, is observed for both internal beams represented by lines of graphs 72 and 73, as compared to the installation of figure 4 in the present. For the line of graph 72 (which represents beam 62 in Figure 6) the performance of carrier to interference is significantly improved. For the line of graph 73 (which represents beam 63 in Figure 6) the performance of carrier to interference is also improved.

Claims (14)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. 1. In a radiocell system having a plurality of base stations, each capable of communicating over a plurality of sector areas using a plurality of directional beams, a method of installing said plurality of directional beams, said method comprising the steps of: in a first base station, forming a first set of beams in a first sectorial area; in a second base station, forming a second set of beams in a second sectorial area; wherein at least one beam of said first set is directed in a substantially equal direction and re-uses the same first frequency as at least one beam of said first set; and at least one remaining beam of said first set re-uses a second frequency equal to at least one remaining beam of said second set, said beam of said first set remaining directed in a direction pointing away from said remaining beam of said second set . The method according to claim 1, characterized in that said first set of beams uses a set of carrier frequencies, each beam of said first set being assigned to a corresponding respective carrier frequency of said set of carrier frequencies, said carrier frequencies being different from each other. and said second set of beams re-uses said set of carrier frequencies. The method according to claim 1, characterized in that each said set of beams comprises at least one internal beam and at least one external beam; wherein said external beam of said second set re-uses a frequency of an external beam of said first set, said external beam of said second set directed in a direction substantially equal to said external beam of said first set; and an internal beam of said second set re-uses a frequency of an internal beam of said first set, said internal beam of said second set being directed away from said internal beam of said first set. 4. In a radiocell system having a plurality of base stations each communicating over a plurality of sector areas, by means of a plurality of directional beams, a method for installing said plurality of directional beams, comprising the steps of: assigning a first set of said beams to a first said base station over a first said sector area; assigning a second set of beams to a second said base station over a second said sector area; wherein each beam of said first set corresponds to a respective beam of said second set; wherein a beam of said first set has a common carrier frequency and a common direction with a corresponding beam of said second set; and a beam of said first set has a common carrier frequency but with a different direction for a corresponding beam of said second set. 5. A method according to claim 4, characterized in that each set of beams comprises an external beam and an internal beam; and an external beam of said first set has a common carrier frequency and a common direction with an external beam of said second set; and an internal beam of said first set has a common carrier frequency but a different direction for an internal beam of said second set. The method according to claim 4, characterized in that said base stations each serve to communicate on three edge-driven, hexagonal, adjacent, respective, corresponding sectors, each of substantially equal area in a tri-cellular installation. The method according to claim 4, characterized in that each said set of beams comprises four directional beams. 8. The method according to claim 4, characterized in that each said set of directional beams comprises two internal beams and two external beams. 9. A radiocell apparatus comprising a plurality of base stations, each capable of communicating with a corresponding respective plurality of sector areas, each said base station capable of forming a plurality of directional beams that cover their respective plurality of corresponding sector areas, in where: a first said base station and a second said base station are separated from each other; a first set of said beams extends from said first base station in a first pattern over a first sectorial area; a second set of said beams extends from said second base station in a second pattern over a second sectorial area, said second pattern substantially doubling said first pattern; a plurality of carrier frequencies is assigned to said first set of beams in a first order; said plurality of carrier frequencies is re-used by said second set of beams, said set of carrier frequencies being assigned to said second set of beams in a second order, different to said first order. 10. The radiocell apparatus according to claim 9, characterized in that said beams of said first set extend along diverging directions within an angle of 60 ° from a main direction of said first cell; said beams of said second set extend along diverging directions within an angle of 60 ° from a main direction of said second cell; and said principal directions of said first and second cells are substantially coincident with each other. 11. In a radiocell system having a plurality of base stations, each capable of communicating over a plurality of sector areas by forming a plurality of directional beams, each of said plurality of base stations operating a common set of carrier frequencies re-used between said base stations, a method for assigning said carrier frequencies comprising the steps of: forming in a first said base station a first set of directional beams over a first said sectorial area, each said beam directed in a respective one of a plurality of addresses; forming in a second said base station, a second set of directional beams over a second said sectorial area, each beam of said second set also directed towards a respective one of said plurality of directions; assigning said set of carrier frequencies to said first set of beams in a first order; and assigning said same set of carrier frequencies to said second set of beams in a second order, said second order of said first order being different. 12. In a radiocell system having a plurality of base stations each covering a plurality of sector areas and each operating a common set of carrier frequencies on said respective corresponding sector area, each of said plurality of base stations operating a set of directional beams in a common pattern, a frequency assignment method comprising the steps of: for each of a first set of said base stations, assigning said common set of carrier frequencies to said set of beams in a first order; and for each of a second set of said base stations, assigning said common set of frequencies to said set of beams in a second order, wherein said second order is different from said first order. The method according to claim 12, characterized in that said first set of base stations is installed substantially along a first line; and said second set of base stations is installed substantially along a second line. The method according to claim 13, characterized in that said first line is substantially parallel to said second line.