MXPA98006862A - Allocation of frequency adapted in a telecommunication system - Google Patents

Abstract

The present invention relates to a telecommunications network, a method and apparatus for assigning channels that make signal quality measurements for channels that are in use or available for use, and for channels that may become available for use. . The channels already selected (ie the channels in use or available for use) that exhibit poor signal quality characteristics are exchanged with the candidate channels (ie, the channels that may become available for use), which They exhibit better signal quality characteristics, so as to improve the overall quality of the signals of the

Description

ALLOCATION OF ADAPTED FREQUENCY IN A TELECOMMUNICATION SYSTEM BACKGROUND The present invention relates to cellular telecommunications systems and, more particularly, to the automatic assignment of frequency channels to cells in a cellular telephone system. In cell phone networks, the maintenance or improvement of voice quality in each communication channel is of great importance. One factor that affects voice quality is the level of channel interference as a whole. The interference of channels together results when two cells, geographically placed one next to another, use the same frequency. One way to avoid this problem is to assign a dedicated group of frequency channels to each cell in the network, so that two cells do not use the same frequency channel. While this will clearly avoid the interference problem of joint channels, the network will quickly deplete the frequency channels, since there is only a fixed number of frequency channels available. To avoid exhausting the available frequency channels, cell phone networks employ reuse designs. These reuse designs allow a network to assign a frequency channel to more than one cell. While some interference from joint channels is expected, excessive interference from joint channels can be avoided by ensuring that two or more frequency channels are sufficiently separated. In general, reuse designs are well known to ordinary experts in the art. A fixed reuse design, as one term suggests, involves assigning a fixed dedicated group of frequency channels to each cell in the network. Frequency channels can be signaled to more than one cell, as long as the cells are sufficiently separated to avoid excessive interference of joint channels. As previously mentioned, each cell in a network, which employs a fixed frequency channel reuse design, will be limited to the specific frequency channels assigned; therefore, traffic handling capacity for each cell will be limited despite avoiding excessive interference from joint channels. In other words, fixed reuse designs are inherently inflexible; there is no provision to adjust the assignments of the frequency channel in each cell, as the demand fluctuates from one cell to another over the course of a given period of time. The result is a degradation in both voice quality and traffic handling capacity. Therefore, adapted reuse designs, also known as adapted channel allocation designs, were conceived. The reused frequency channel reuse designs attempt to avoid degradation in voice quality and traffic handling capacity by providing more flexibility. Rather than assigning a fixed group of frequency channels to each cell in the network, assignments will vary over time to meet the changing needs of each cell. The way in which this is achieved is by periodically measuring the quality of the signal for each frequency channel in each cell. As required, the cells will have assigned frequency channels as long as the signal quality measurements for the channels meet or exceed certain signal quality criteria. For example, if cell A requires an additional frequency channel to handle an increase in telephone traffic, the frequency X channel will probably not be assigned if it is already being used by a nearby cell. The interference of joint channels, due to the use of frequency channel X, in the nearby cell, will be measured in cell A as interference. Thus, the frequency X channel will not meet the required signal quality criteria. There are different types of adapted channel assignment designs. The main difference between each design is the application of the criteria used to determine if a frequency channel should or should not be assigned in a given cell at a given time. For example, H. Eriksson, in "Improvement of the Capacity for the Allocation of the Adapted Channel", IEEE Global Telecomm. Conf., Pages 1355-1359, November 28 to December 1, 1988, suggests using mobile systems to measure the downlink signal quality for each channel, then the channels are assigned based on those that have the highest carrier for the channels. interference ratios (C / I). A somewhat different approach is expressed by G. Riva in "Performance Analysis of an Enhanced Dynamic Channel Allocation Scheme for Mobile Radio Cell Systems," 42nd IEEE Veh. Tech. Conf., Pages 794-797, Denver 1992, where frequency channels can be assigned if their signal quality measurements meet or exceed a pre-set C / I threshold. In Y. Furuya et al., "Channel Segregation, An Allocated Adapted Channel Allocation Scheme for Mobile Communication Signals", Second Nordic Seminar on Digital Land Mobile Radio Communication. pages 311-315, Stockholm, October 14-16, 1986, an adapted channel allocation design is described by which the recent history of signal quality for each channel is measured and used in making channel allocation decisions.

When a conventional adaptive channel allocation design is employed, it is more effective to measure both the uplink (i.e., the radio path from the mobile system to the base station) and the downlink (i.e. radio from the base station to the mobile system), the signal quality for each frequency channel. In digital systems, such as the D-AMPS (Digital Advanced Mobile Phone System), uplink measurements can be made by the equipment located in the base station. The downlink measurements can be made by a control delivery unit assisted by a mobile system, in each mobile unit; this mobile unit then transmits the measurements back to the base station. While the adapted channel allocation strategies provide a more flexible design that ultimately reaches the best signal quality and traffic handling capacity, the design and frequency assignment is still, for the most part, a manual process. Network operators use offline tools, terrain maps, and signal quality measurements, as described above, to manually assign the most effective frequency channels for each cell. However, this process quickly becomes non-controllable as more base stations and cells are added per unit area to improve traffic handling capacity and meet the demand of a growing number of cell phone users. The inability to maintain the manual assignment of frequency channels eventually causes a degradation in signal quality and traffic handling capacity; therefore, this manual process is not acceptable. It is thus of great interest to develop algorithms and tools to avoid difficult work and that it consumes the necessary time for the planning and assignment of the manual frequency. Ideally, base stations should be able to select their own frequencies without manual intervention of the operator and to adapt a changing radio environment, due to the addition of new base stations, cells, geographical obstructions or simply periodic fluctuations in the traffic. Accordingly, the invention features an automatic frequency assignment system adapted to improve both voice quality and traffic handling capacity.

COMPENDIUM It is an object of the invention to provide a channel allocation strategy that automatically responds to changes in the radio frequency (RF) medium, based exclusively on the information that is available in the base station of a cell, by automatically selecting those channels of frequency that, on average, exhibit the lowest interference levels. It is a further object of the invention to provide a channel assignment strategy that responds to changes in the RF environment by automatically exchanging the frequency channels that, on average, exhibit a relatively low signal quality with frequency channels that, on average, exhibit a relatively high signal quality. It is still another object of the invention to provide a channel allocation strategy that responds to changes in the RF environment by automatically adding and removing frequency channels for use in a cell, when necessary, so that the frequency channels that remain in use are those that exhibit, on average, the highest signal qualities. According to one aspect of the invention, the above objects and others are achieved in a method and apparatus for assigning frequency channels, by measuring the signal quality of both uplink and downlink, for a plurality of selected frequency channels; comparing the quality of the measured signal of the uplink with that of the downlink for each selected frequency channel; identifying a frequency channel selected from among the plurality of selected frequency channels, if the measurement of the quality of the downstream signal for that frequency channel is worse than the measurement of the quality of the upstream signal by at least one amount previously defined and the quality of the downlink signal is less than a previously defined threshold; identify the qualified candidate frequency channel and exchange it with the selected frequency channel, previously identified. In another aspect of the invention, the frequency channels are assigned by measuring the signal quality of the uplink and downlink for a plurality of candidate frequency channels; identifying a qualified candidate frequency channel from among the plurality of candidate frequency channels; and assign the qualified candidate frequency channel to a base station in the telecommunications network. The identification of the qualified candidate frequency channel further involves determining whether the quality of the downlink signal measured for a candidate frequency channel is not significantly less than the quality of the uplink measured signal, for the candidate frequency channel; determining whether the channel separation between the candidate frequency channel and the near selected frequency channel is greater than a minimum, previously defined, separation requirement of channels; and finally, determining whether the candidate frequency channel, in combination with one or more selected frequency channels, causes third order intermodulation products in addition to the selected frequency channel to be exchanged.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of the invention will be understood from reading the following detailed description in conjunction with the drawings, in which: Figure 1 is a block diagram illustrating ten cells in a cellular radiotelephone system mobile, to which the invention is applied; Figure -2 is a diagram showing the organization of the frequency channels in each cell of a cellular network, according to an aspect of the invention; Figure 3 is a diagram illustrating the base station within a cell, which includes the equipment in the base station used to transmit, receive, measure and filter each frequency channel in the cell, in accordance with an aspect of the invention; Figure 4 is a flow chart illustrating the process of comparing and exchanging selected frequency channels and qualified candidate frequency channels; Figure 5 is a diagram illustrating the adaptation filter; Figure 6 is a diagram showing how the downlink for a frequency channel can be adversely affected by the interference of joint channels, even if the base station in the cell is not aware of the problem; Figure 7 is a flow chart illustrating the process of measuring and comparing BER and forced exchange; and Figures 8a and 8b are diagrams illustrating both a continuous band of frequencies and two non-continuous frequency bands.

DETAILED DESCRIPTION The various features of the invention will now be described with respect to the figures, wherein similar parts are identified with the same reference characters. Figure 1 is a schematic diagram illustrating the relationship between 10 cells (C1-C10) in a typical cellular phone network 100 (here referred to as the "cellular network"), such as D-AMPS. Generally, a cellular network will have many more than ten cells; however, 10 are sufficient for illustrative purposes. In each cell, Cl to CÍO, there is a base station Bl to B10. Although Figure 1 shows the base stations placed towards the center of each cell, these base stations can be located anywhere in the cell. Base stations located toward the center typically employ omni-directional antennas, while base stations placed towards a cell boundary will typically employ directional antennas. The mobile units M1-M10 represent the mobile telephone units. Of course, these mobile units can be moved around a cell or they can be moved from one cell to another. Typically, there will be many more mobile units of ten. Again, it is sufficient to show ten mobile units for illustrative purposes. The cellular network 100 illustrated in Figure 1 also has a switching center (MSC). This MSC is connected to each of the base stations by cable, radio links or both (not shown in Figure 1). The MSC is also connected to a fixed telephone switching unit (also not shown in Figure 1). The cellular network 100, illustrated in Figure 1, uses a fixed number of radio frequencies (channels) for communication. In the invention, the frequency channels correspond to the frequencies in the 800 MHz band or the 1900 MHz band. Although the invention is intended for use in a system, such as the CM588 digital system of Eriksson Radio, in order to To facilitate frequency planning for digital traffic channels, the invention will work in a dual mode system, where the analog and digital frequencies share the spectrum of each cell. This may be important in the unfolding phase, first of all that manually tuned combiners have been replaced. In a cellular network employing a conventional, fixed or adapted allocation strategy, each cell is assigned a number of frequency channels that correspond to a subset of all the frequency channels available to the cellular network as a whole. Figure 2 illustrates that with this invention, each cell in the network can select, for use in the cell, frequency channels of the same general set of frequencies. For example, if there is a number n of frequency channels in a cellular network comprising N numbers of cells, each cell can be defined by the whole set of frequency channels f ^ a fn. While cell 1 to cell N can have the same set of frequency channels from which to select, each cell will select (ie assign) only those frequency channels that have the best average signal quality. The invention accomplishes this by carrying out several measurements of the signal quality (explained more fully below) in the set of frequencies in the cell.

Therefore, signal quality measurements are made not only on those frequency channels in use or available for use, but also on those frequency channels that are not currently used or available for use, although they can become available a time later. These various measurements of signal quality are processed, filtered and evaluated, as described in more detail below, and used as a basis for the exchange of frequency channels that are used or available for use, with frequency channels that They are not used and they exhibit a better average signal quality. According to one aspect of the invention, there are two types of frequency channel exchange: a basic exchange and a forced exchange, both of which are written in more detail below. To facilitate the automatic exchange of the frequency channels within a given cell, the invention classifies each frequency channel assigned to a cell in one of the following groups. First, selected frequency channels (here named as the selected frequency channels), are those whose frequency channels are currently used or are available for use in a cell. In a preferred embodiment of the invention, the selected frequency channels are always digital channels. In order for a frequency channel to be a selected frequency channel, the base station must have a transmitter-receiver and, where it is expandable, a combiner tuned to the corresponding frequency. Second, the candidate frequency channels are all other frequency channels not currently available for use in the cell. However, the candidate frequency channels may become available for use if they are exchanged with one of the selected frequency channels. An exchange can only take place if the signal quality of the candidate frequency channel is significantly better (as defined below) than the signal quality of one of the selected frequency channels. In addition, the candidate frequency channel must comply with certain other signal quality criteria. Candidate frequency channels that meet these other signal quality criteria will be named as qualified candidate frequency channels. In one embodiment of the invention, a candidate frequency channel becomes a qualifying candidate frequency channel if the quality measurement of the downlink signal for the candidate frequency channel is not significantly less than the quality measurement of the candidate. the uplink signal for the candidate frequency channel. In another embodiment of the invention, a candidate frequency channel becomes a qualified candidate frequency channel if, in addition to the measurement of the quality of the downlink signal, which is not significantly less than the measurement of the quality of the Uplink signal, as described above, there is a sufficient frequency separation (as defined below) between the candidate frequency channel and the near selected frequency channel. In a preferred embodiment of the invention, a candidate frequency channel becomes a qualified candidate frequency channel if, in addition to a measurement of the downlink signal quality, which is not significantly less than the quality measurement of the the uplink signal and a suitable frequency separation, as described above, the frequency of the candidate channel, when combined with any of the selected frequencies (in addition to the selected frequency with which it can be exchanged), does not result in products of third order intermodulation, which are equal to the frequencies of the selected channels. Likewise, in a preferred embodiment of the invention, signal quality is measured in terms of the level of interference, where a low signal quality equals the high interference level. These criteria are: 1) the quality of the downlink signal, 2) the sufficient separation of the channel, 3) the absence of certain third order intermodulation products, which will be described in more detail below. In addition to the selected frequency channels and the candidate frequency channels, there are also permanently selected frequency channels. These permanently selected frequency channels, unlike the selected frequency channels, can be analogue or digital channels and, in a preferred embodiment, the permanently selected frequency channels can only be exchanged manually. In a preferred embodiment, the frequency channels may also be classified as supplementary selected frequency channels or supplementary non-selected frequency channels. These supplementary selected frequency channels are really a subset of permanently selected frequency channels and are used for measurement purposes. Supplementary non-selected frequency channels are not available in the cell but, in a preferred embodiment, they can be made available by manual resources. The unselected supplementary frequency channels are used for measurement purposes. The specific manner in which the invention performs the various measurements of signal quality and channel exchanges will now be described in more detail. As noted before, there are two different channel exchange strategies, a basic exchange and a forced exchange. The basic channel exchange strategy will be described first. With the basic exchange strategy, the quality of the uplink signal of each frequency channel was measured for all selected frequency channels and all candidate frequency channels. In a preferred embodiment, the uplink signal quality was measured in terms of the uplink interference level. For selected frequency channels, the uplink interference levels were measured by the corresponding transceivers, located in the base station of each cell. For example, Figure 3 shows a base station 310, in a cell 302, where this base station contains transmitter-receivers, TXCVR 1, 2, 3, 4, ..., m. These transmitters-receivers 1, 2, 3, 4, ..., m, are each tuned to one of the respective frequencies corresponding to selected frequency channels 1, 2, 3, 4, ..., m. Each of these transceivers 1, 2, 3, 4, ..., m measures the strength of the signal during inactive time periods (here named as time slots) in the corresponding selected frequency channel. Each selected frequency channel contains three time slots. During each time slot, a transmitter-receiver can transmit and receive a separate call. The division of frequency channels selected in this manner is known in the art as multiple time division access (TDMA). When any of the three time slots becomes inactive (ie, there is no phone call in the time slit), the corresponding transmitter-receiver measures the strength of the signal for the corresponding selected frequency channel, during these inactive time slots. Because there is no voice signal in the empty time slot, the measurement of the signal strength represents the interference level of the selected frequency channel due to the interference of joint channels from other cells in the network, interference from adjacent channels , and noise. Although the supplementary selected frequency channels are not automatically exchanged with the qualified candidate frequency channels, the measurements of the uplink signal strength are made. If a supplementary selected frequency channel is a digital channel, the strength of the signal is measured during the inactive time slots. If a supplementary selected frequency channel is an analog channel, the measurements of the signal strength are made continuously at inactive time intervals, previously designated, since there are no time slots associated with the analog channels. For the candidate frequency channels, the uplink interference levels are measured by much in the same way as the uplink interference levels are measured for the selected frequency channels. The interference levels are measured by a scanner receiver 304, also located in the base station of the cell. This scanner receiver 304 can be tuned to one of the respective frequencies corresponding to the candidate frequency channels or the supplementary unscreened frequency channels. Unlike the selected frequency channels, there are no time slots associated with the candidate frequency channels, because the base station does not transmit voice traffic over these channels. Again, the signal strength directly measures the level of interference in the corresponding candidate frequency channel due to the interference of joint channels and the interference of adjacent channels from other cells in the network, and the noise. The scanner receiver 304, shown in the Figure 3, is similar to transceivers, TXCR 1, 2, 3, 4, ..., m. The difference between them is essentially functional. Since there is no voice traffic within this cell over the candidate frequency channels, the scanning receiver needs only to receive and measure the signal strength. However, when a separate transmitter-receiver is necessary for each selected frequency channel, only one scanner receiver is necessary to make measurements for all candidate frequency channels. The scan receiver goes through each of the frequencies associated with the candidate frequency channels and measures the strength of the corresponding signal for each of them. As mentioned previously, all measurements of the signal strength, which include the uplink measurements described above, are preferably filtered continuously using the adaptation filters located in the base station (not illustrated in Figure 3). By filtering the measurements of the strength of the uplink signal, the decisions regarding the exchange of the frequency channels are not based on measurements of the instantaneous signal strength. The base station then transmits the measurements of the strength of the filtered signal to the MSC 303, which performs a comparison between the filtered selected frequency channel, the measurement of the strength of the uplink signal (i.e. the level of interference) with the filtered candidate frequency channel, the measurement of the strength of the uplink signal (ie, the level of interference). The MSC 303, based on this comparison, decides whether an exchange is guaranteed. The method for comparing the uplink interference levels of the selected frequency channel with the uplink levels of the qualified candidate frequency channel and performing a frequency selection and exchange, will now be described in more detail. As noted above, the primary purpose of the invention is to automatically replace the frequency channels that have the highest interference levels. If there is a qualified candidate frequency channel with a better interference level (ie, less interference), the system will initiate an exchange. Figure 4 illustrates the method used to compare and exchange a qualified candidate frequency channel with a selected frequency channel. First, the MSC 303 determines if any of the candidate frequency channels are qualified. The method to qualify a candidate frequency channel was previously mentioned, but will be described in more detail below. If none of the candidate frequency channels are qualified, no exchange takes place. This step is illustrated in Figure 4 as step 401. If there is at least one candidate frequency channel, the MSC 303 compares the level of uplink interference, filtered, of the selected frequency channel, which has the interference level of Higher top link with the qualified candidate frequency channel, which has the lowest uplink interference level. This step is illustrated as step 402. If the uplink interference level, filtering of the selected frequency channel, IUsc, exceeds the level of uplink interference, filtered, of the qualified candidate frequency channel, ItjgC, by at least a predetermined amount, PA, the MSC 303 initiates an exchange of the qualified candidate frequency channel in place of the selected frequency channel. This step is illustrated as the "yes" path of the decision block 403. Even if the automatic channel assignment is deactivated, and the MSC 303 does not initiate exchanges between the qualified candidate frequency channels and selected frequency channels, the invention will continue to send measurements of the uplink interference level to the filters that, in turn, will continue to update and store filtered leakage interference levels. In accordance with one aspect of the invention, the MSC 303 does not execute the exchange instantaneously. The actual exchange may be delayed for a period of time equal to the time it takes to transmit the filtered interference data to the MSC 303 from the base station 301 plus the time it takes the MSC 303 to evaluate the filtered interference data. This delay period is not illustrated in Figure 4. In addition, the MSC 303 may further delay the execution of the exchange due to the voice signals that may be present in any of the three time slots of the selected frequency channel. Because it would be preferable to do the exchange while there is voice traffic in the selected frequency channel, the method initiates a wait cycle to allow all three time slots to clear. This step is illustrated in Figure 4 as steps 404 and 405. During this wait cycle, the MSC 303 prevents assigning new calls to the selected frequency channel. Once the time slots are cleared, the MSC 303 will execute the exchange (step 406). As noted above, with respect to step 403, the difference between the filtered uplink interference level of the qualified candidate frequency channel and the filtered uplink interference level of the selected frequency channel must be greater than or equal to the predetermined amount. This predetermined amount, also referred to as the "hysteresis", is a system parameter and the value is mutually adjusted. The parameter for employing hysteresis is to ensure that the MSC 303 does not attempt to initiate an exchange when the quality of the uplink signal of the candidate frequency channel marginally exceeds the quality of the uplink signal of the selected frequency channel. If the method does not employ hysteresis, cyclical, extremely small fluctuations, at the level of uplink interference, filtering, of one or both frequency channels may be sufficient to initiate a back-and-forth exchange, between the two channels of frequency, where both channels have levels of uplink interference, filtered, that are virtually equal. In addition to the exchange of frequency channels, described above, another aspect of the invention provides a second type of exchange, named as a forced exchange. This second type of channel exchange takes into account the signal quality of the downlink as well as the quality of the uplink signal, comparing the two for each selected frequency channel. In a preferred embodiment, the downlink signal quality and the uplink signal quality are measured in terms of the Bit Error Rate (BER). The purpose of forced exchange is to ensure that the selected frequency channels, which otherwise have good link signal quality, do not remain in use if the quality of the downlink signal has deteriorated substantially. For example, assuming that in a cellular system, there is a mixture of cells with a Fixed Channel Assignment, and cells where the frequency selection is made automatically, according to the invention. This can frequently occur in practice, especially where a cellular system is in transition from a fixed channel allocation system to an automatic channel allocation system of the invention. In this situation, there may be a period of time where some base stations are still operating in a fixed group of frequency channels, while others are operating in accordance with the invention. Considering Figure 6, assuming that the base stations, A and B, which correspond to cells A and B (not illustrated in the Figure), have directional antennas, as indicated in the figure. Likewise, a cell A is an automatic channel assignment cell, where cell B is an automatic channel assignment cell. Assume that the two cells share a common frequency channel, where transmissions on the channel are illustrated as 601, 602 and 603. Although a mobile unit 604 in cell B can be greatly affected by the base station in cell A, as is shown by the downlink transmission 602, the base station B may never be aware of the problem because the directional antenna in the base station B prevents this base station B from interference emanating from the mobile unit 605 and the station base in cell A. This base station A, on the other hand, will receive the interference of joint channels on the selected frequency, but will be unable to interchange the frequencies because it is a fixed channel assignment cell. In most cases, a candidate frequency channel will never be qualified if its level of downlink interference is substantially affected by the interference of joint channels and the interference of adjacent channels. Therefore, the candidate frequency channel will not be exchanged with a selected frequency channel, thus helping to ensure that the selected frequency channels have a good downlink signal quality. However, in the event that such exchange takes place, or in the situation where the quality of the downlink signal deteriorates substantially after an exchange takes place,, this second type of exchange or forced exchange, based on the BER measurements of uplink and downlink will correct the problem. Referring now to Figure 7, the strategy of forced exchange will now be explained in more detail. Once a frequency channel is selected for use in a cell (i.e., it is designated as a selected frequency channel) as illustrated in block 701., the invention begins to measure the BER for the uplink and downlink. For the uplink, the base station measures the BER for each call (ie, each time the slot is used for voice traffic) on the selected frequency channel, as illustrated in block 702. For the downlink , the mobile unit measures the BER, then transmits the measurement back to the base station, as illustrated in blocks 703 and 704. This base station calculates the average BER values of the uplink and the average BER values of the downlink for each call segment, using filters 705 and 706 that average them. At the end of each call segment, the base station transmits average, updated BER values for both the uplink and downlink of each selected frequency channel to the MSC 303. The MSC 303 filters the BER value of the average uplink and the BER value of the average downlink for the call segment, using adaptation filters 707 and 708 (described in more detail below). The MSC then calculates a difference value, as illustrated by block 709. This MSC 303 then compares the difference value to a predefined threshold value, as shown in block 710. MSC 303 also compares the BER value of the downlink (i.e., the output of block 708) to a previously defined quality level. , as shown in block 711. If the BER value of the filtered downlink, average, is greater than the BER value of the filtered uplink, average by at least the threshold value previously defined and the downlink value filtered, average, is greater than the previously defined quality level, the MSC 303 will initiate a forced exchange between the selected frequency channel and the best qualified candidate frequency channel, as illustrated in block 712, assuming that at least one candidate frequency channel It is qualified. The best-qualified candidate frequency channel is the qualified candidate frequency channel that exhibits the highest quality of the uplink signal (ie, the lowest level of interference). Forced exchange is attempted to supplement the basic exchange. Although both types of exchanges occur independent of each other, forced exchange helps to ensure that selected frequency channels that otherwise exhibit good uplink signal quality are replaced if the downlink signal has deteriorated after being placed. in use in the cell (that is, assigned). The purpose of the invention is not only to provide an automatic channel assignment, but also to ensure that the selected frequency channels are those that exhibit the best average signal quality. In order to achieve this, the invention, as mentioned above, filters each measure of interference level and each BER measurement over prolonged periods of time. Using these filters, the invention can provide automatic channel allocation that is less affected by fluctuations in the system (i.e., fluctuations in signal strength and BER). In a preferred embodiment of the invention, there are many filters that are used. For each selected frequency channel, the base station maintains an adaptation filter,. for uplink signal strength measurements (i.e., the interference level), and an averaging filter for both uplink and downlink BER measurements. The MSC maintains an adaptation filter for both uplink and downlink BER average measurements. For each candidate frequency channel and for each additional unselected frequency channel, the base station maintains an adaptation filter for the uplink signal strength measurements (ie, the interference level) and an averaging filter for the measurements of the downlink signal strength. The MSC maintains an adaptation filter for average downlink signal strength measurements. For each supplementary selected frequency channel, the base station maintains an adaptation filter for measurements of the uplink signal strength. When a measurement is made, if it involves a BER or interference level, the input values and the output values associated with the corresponding adaptation filters are updated, as illustrated in Figure 5. For example, if the value of Uplink interference at this time point is Iin (n) 505, the filtered uplink interference value, I0ut (n) 506 is derived as follows: Iout (n) = (1 ~ k) Iout (n-1) + k Iin (n) where Iout (n) 504 is an ex-filtered uplink interference value, after the adaptation filter was updated to the last one. The interference value I0ut (n) 506? E stored in the transmitter-receiver or the scan receiver (depending on whether the measured uplink corresponds to a selected frequency channel or a candidate frequency channel), and it becomes the value for I0ut (n-1) 504 during the next filter update. The parameter k 501 is a weight factor representing the importance of the new or updated measurement I'm (rí) 505. It is preferably calculated from a filter time constant, T (not illustrated in Figure 5) and the period update, dt (that is, the time that has elapsed since the previous update) is as follows: k = min (0.2, dt / T).

As dt increases, the adaptation filter places greater emphasis (ie, importance) on the updated Iin (n) 505 measurement. However, in no case will k exceed the value of 0.2. The filter time constant, T, is a parameter that is adjusted manually and determined empirically • (for example, by means of simulators), in order to provide the best filter response. The actual value of T will vary from one cell to another and may vary depending on how the frequency channel is currently defined (i.e., as a selected frequency channel, candidate frequency channel, supplementary frequency channel and the like). In general, T is a very large number compared to dt, so the output I (out (n) 506 of the filter is not influenced by short or instantaneous fluctuations in signal quality.) In addition, there are many periods of time where it is beneficial preserve the filtered output measurement.This can be achieved by adjusting the value of T to infinity.At the end of the time period, the value of T can be readjusted to its previous value and the filter will resume where it was left and separated, without having to restore an average measurement of operation As explained above, the invention does not exchange a candidate frequency channel with a selected frequency channel, unless the candidate frequency channel is a qualified candidate frequency channel. preferred embodiment of the invention, a candidate frequency channel becomes a qualified candidate frequency channel if all three following criteria are met: 1) the interference level of downlink, filtering, of the candidate frequency channel is not significantly greater than the level of uplink interference, filtering; 2) there is sufficient frequency separation between the frequency of the candidate channel and the nearest selected channel frequency, excluding the frequency of the selected channel to be exchanged with the candidate frequency channel; and 3) the frequency of the candidate-frequency channel, when combined with any of the frequencies of the selected channel, in addition to the frequency of the selected channel with which it will be exchanged, will not result in third-order intermodulation products, which they are equal to the selected channel frequencies, again, in addition to that with which the candidate frequency channel is to be exchanged. These three criteria will now be described in greater detail. First, the invention takes into consideration the level of downlink, filtered interference, to prevent the exchange of a selected frequency channel with the candidate frequency channel having a downlink with significantly more interference than that of the uplink. As mentioned previously, the strength of the uplink signal (i.e., the interference level) for each candidate frequency channel (and the supplementary unselected frequency channel) was measured at the base station by a corresponding scan receiver. (reference is made to Figure 3). The strength of the downlink signal for one or more candidate frequency channels was measured by the control unit assisted by the mobile unit in each mobile unit. This mobile unit then transmits these measurements back to the base station. More specifically, the base station, at the start of each call segment, allocates, for the purpose of measurement, one or more candidate frequency channels (and supplementary unscreened frequency channels) to the mobile unit associated with the call segment. . A call segment is defined as the period of time during which a call is active on a given frequency channel. Since the mobile unit is just a voice traffic of reception and transmission over one of the three time slots associated with the call segment, the mobile unit can measure during the two remaining time slots, the strength of the downlink signal for many candidate frequency channels (or supplementary non-selected frequency channels). In a preferred embodiment of the invention, the mobile unit is capable of measuring up to twelve non-selected, candidate or supplementary frequency channels during the two remaining time slots. The mobile unit then transmits the measurements of the downlink signal strength back to the base station. The base station allocates the frequency channels at the start of each call segment in a cyclical fashion within each group (ie, qualified candidate frequency channels, candidate frequency channels, supplementary unscreened frequency channels, etc.). .). If there is any qualified candidate frequency channel already designated, 25% of the measurement resources (ie, every fourth call segment in the cell) r. it should preferably be used to measure the ten best qualified candidate frequency channels, or all qualified candidate frequency channels, whichever is the smallest. The remaining 75% of the measurement resources (ie, three out of four call segments in the cell) are preferably used to measure the remaining candidate frequency channels and the supplementary non-selected frequency channels. If the number of non-selected, candidate and supplementary frequency channels remaining is less than forty, the measurements should preferably be distributed uniformly for all additional unscreened frequency channels. One way to achieve this is to cycle through a list of channels within each of the two groups defined above, that is, 25% of the group and 75% of the group. The strength of the downlink signal for each measured frequency presented by the mobile unit is filtered in the base station 301 using the averaging filters. At the end of each call segment, the measurements of the average strength of the downlink signal are transmitted by the base station 301 to the adaptation filters located in the MSC 303. The measurements of the strength of the uplink signal are filter at the base station using adaptation filters. The base station then transmits the signal strength measurements to MSC 303 periodically. The MSC 303 also maintains the adaptation filters for measurements of the downlink signal strength for each candidate frequency channel and each additional unselected frequency channel in the cell. The MSC 303 then determines whether the downlink signal strength, Ido n For each candidate frequency channel is significantly greater than the strength of the filtered uplink signal, IUp for the candidate frequency channel. If so, the candidate frequency channel is not qualified. More specifically, the candidate frequency channel is not qualified if: -ip < . down + -lif ~ ^ marg) where Ifjf is an adjustment (in dB) that is adjusted for the systematic differences between the uplink and the downlink. Typically, 1-jjf is determined by averaging the filtered uplink interference level for all candidate frequency channels in the cell and subtracting the filtered downlink average interference level for all candidate frequency channels. Imarg is a margin (in dB) that defines how much of the downlink interference level must be greater than the level of uplink interference (ie signal strength) before the candidate is assumed qualified. The value of Imarg is a parameter that is determined empirically and adjusted manually. The second criterion for rating a candidate frequency channel is that this candidate frequency channel can not cause third order intermodulation products, when combined with any of the selected frequency channels used in the cell. The third order intermodulation products are defined by the following formula: f¡m = 2 * f! -f2 where the frequency of the candidate channel and the frequency of the selected channel are applied to the variables f ^ and f2 in both combinations. If fj_m corresponds to a transmitter-receiver frequency of the base station in the cell, the candidate frequency channel is not qualified. When a new selected frequency channel is added to the base station, this candidate frequency channel to be chosen must first pair with all the channel frequencies selected in use in the cela. When an existing selected frequency channel is exchanged with the best candidate frequency channel, the frequency of the candidate channel should pair with all the frequencies of the selected channel in use in the cell, except the frequency of the selected channel to be exchanged.

The third criterion for rating a candidate frequency channel establishes how close two transmitter frequencies can be to each other. When a candidate frequency channel does not meet the channel separation requirements when paired with the selected frequency channels in the cell, it does not include the selected frequency channel to be exchanged, the candidate frequency channel should preferably not be qualified . Channel separation is preferably measured at 30 kHz intervals from the center frequency of one channel to the center frequency of the other channel. The actual channel separation value is manually adjusted, and is usually a function of the antenna combining ability. In addition to the automatic allocation of the channel through the forced channel exchange strategies, described above, the invention provides an automatic channel selection in the seizure of the voice channel. In other words; during the seizure of a new traffic channel in the call setting, the invention automatically selects any idle time slot in the selected frequency channel that exhibits the lowest filtered, filtered interference measurement (best) . Also, in another aspect of the invention, the best selected frequency channel continues to be seized in the voice channel, when or not the automatic channel assignment is enabled or disabled. The automatic channel selection in the seizure of the voice channel, in conjunction with the automatic channel assignment, provides the best possible radio link quality. As noted above, one purpose of the invention is to provide automatic channel allocation to allocate more efficiently channels in a cell in response to a constant change in the RF environment. To fulfill this objective, the invention is not only capable of exchanging channels through the basic and forced exchange strategies described above, but also through adding and suppressing channel frequency channels adjusted in a cell. In order to meet larger demands within a cell, the invention can increase the number of selected frequency channels used in a cell. This is related to unlocking and involves the addition or activation of a new transmitter-receiver in the base station. By adding one or more selected frequency channels, the invention uses the best qualified candidate frequency channels (i.e., qualified candidate frequency channels having the lowest level of filtered uplink interference). In addition, the channel separation requirements should preferably be met with respect to all selected frequency channels. In another aspect of the invention, if there is not a qualified candidate frequency channel due to failure to comply with channel separation requirements or due to the presence of certain intermodulation products, the minimum channel separation requirement is temporarily decreased. by one interval at a time (ie, a range of 30 kHz as described above) until at least one candidate frequency channel passes (ie, qualifies). If more than one candidate frequency channel passes, then the one with the lowest level of uplink interference, filtered, is chosen. Once the candidate frequency channel is selected, the minimum normal channel separation requirement is reset. Although the channel selection requirement is violated for a short period of time, the channel separation requirements are finally met after a few channel exchanges. According to yet another aspect of the invention, the addition of new selected frequency channels may be prevented under certain circumstances. First, assuming a continuous band of frequencies, as illustrated in Figure 8a, the addition of new selected frequency channels will be impeded if the number of transceivers, including the one to be added, is greater than a limit Nt_j_m , where Nj_im is defined by the following equation: lim Nfreq / (Fsep + 2) Nfreq is the number of frequencies in the frequency band that is used and Fsep is the channel separation requirement. If the frequency band is not continuous, as illustrated in Figure 8b, the number of transceivers does not compare to the limit, N | ¡m. Second, the addition of a new selected frequency channel may be impeded if, in temporarily reducing channel separation to qualify a candidate frequency channel (as described above), the channel separation is decreased to 1/2, the minimum normal separation requirement, without identifying a qualified candidate frequency channel. Even if unlocking is allowed, a transceiver is never taken into service until the transmitter-receiver tuning time has elapsed. In still another aspect of the invention, the selected frequency channels can be removed from a cell (ie not selected), it is also capable of removing them. The frequency associated with the selected frequency channel that is removed will become a supplementary channel or a candidate frequency channel. Also, if the frequency is not associated with the selected frequency channel, which has the highest filtered uplink interference level, the frequency will become the best qualified candidate. The invention will then automatically change the frequency with the selected frequency channel having the highest filtered uplink interference level during the next evaluation occurrence. Another feature of the invention is the provision of a switch to enable and disable automatic channel assignment. When disabled, the cellular network must assign channels manually. However, even if the automatic channel assignment is disabled, the invention preferably continues to measure, filter and store uplink and downlink interference levels (i.e., the signal strength) and BER values of uplink and downlink, such as It was defined before. Therefore, when the automatic channel assignment is once again enabled or restored, the filtered interference and the filtered BER data are not lost. Also, the invention provides the ability to enable or disable automatic channel assignment for individual cells, for a list of cells and for all cells in a cellular network.

The invention has been described with reference to a particular embodiment. However, it will be readily apparent to those skilled in the art that it is possible to incorporate the invention into specific forms in addition to those of the preferred embodiments, described above. This can be done without departing from the spirit of invention. The preferred embodiments are merely illustrative and should not be considered restrictive in any way. The scope of the invention is provided by the appended claims, rather than by the foregoing description, and all variations and equivalents within the range of the claims are intended to be encompassed therein.

Claims (32)

R E I V I N D I C A C I O N S

1. In a telecommunications network, a method for allocating frequency channels, which comprises the steps of: measuring the quality of the uplink signal for each plurality of selected frequency channels; measuring the quality of the downlink signal for each plurality of selected frequency channels; comparing the quality of the uplink signal measured with the quality of the measured downlink signal for each plurality of selected frequency channels; identifying a frequency channel selected from the plurality thereof, if the quality of the measured downlink signal for this selected frequency channel is less than a first amount, previously defined, and the quality of the downlink signal measured , for the selected frequency channel, is less than the quality of the uplink signal measured, by at least a second previously defined amount; identify a qualified candidate frequency channel; and exchange this qualified candidate frequency channel with the selected frequency channel.

2. The method of claim 1, wherein the steps of measuring the quality of the uplink signal for each of the plurality of selected frequency channels and measuring the quality of the downlink signal for each of the plurality of channels of selected frequencies, each comprising the steps of: measuring the bit error rate of the uplink and measuring the downlink bit error rate for each selected frequency channel.

3. The method of claim 1, wherein the step of identifying a qualified candidate frequency channel comprises the steps of: measuring the strength of the uplink signal for each of the plurality of candidate frequency channels; using the measurement of the strength of the uplink signal for each of the plurality of candidate frequency channels, to identify a set of qualified candidate frequency channels; and identifying a qualified candidate frequency channel from the qualified candidate frequency channel set.

4. The method of claim 3, wherein the step of identifying a qualifying candidate frequency channel from the qualified candidate frequency channel set comprises the steps of: comparing the measurement of the uplink signal strength for each candidate frequency channel qualified in the set of qualified candidate frequency channels; and selecting the qualified candidate frequency channel with the strength of the lowest signal.

5. The method of claim 1, further comprising the steps of: measuring the strength of the uplink signal for each plurality of selected frequency channels; measuring the strength of the uplink signal for each plurality of qualified candidate frequency channels; using the measurements of the strength of the uplink signal for each plurality of selected frequency channels to choose a selected frequency channel; using the measurements of the strength of the uplink signal to face a plurality of qualified candidate frequency channels, to choose a qualified candidate frequency channel; comparing the measurement of the uplink signal strength of the selected selected frequency channel with the measurement of the uplink signal strength of the selected qualified candidate frequency channel; and exchanging the selected selected channel with the chosen qualified candidate frequency channel, if the measurement of the strength of the uplink signal of the chosen selected frequency channel is greater than the measurement of the uplink signal strength of the frequency channel Qualified candidate chosen by at least a third previously defined amount.

6. The method of claim 5, wherein the steps of measuring the strength of the uplink signal for each plurality of selected frequency channels and measuring the strength of the uplink signal for each plurality of qualified candidate frequency channels, each which comprises the step of measuring the levels of the interference signal.

7. The method of claim 5, wherein the step of using the uplink signal strength measurements for each plurality of candidate frequency channels qualified to choose a qualifying candidate frequency channel comprises the steps of: measuring the force of the uplink signal for each plurality of candidate frequency channels; using the measurement of the strength of the uplink signal for each plurality of candidate frequency channels to identify a set of qualified candidate frequency channels; and choosing a qualified candidate frequency channel from the pool of qualified candidate frequency channels.

8. The method of claim 7, wherein the step of choosing a qualifying candidate frequency channel from the set of qualified candidate frequency channels comprises the steps of: comparing the measurement of the strength of the uplink signal for each candidate frequency channel qualified in the set of qualified candidate frequency channels with the measurement of the uplink signal strength of another qualified candidate frequency channel in the set of qualified candidate frequency channels; and choosing the qualified candidate frequency channel with a measurement of the lower signal strength.

9. The method of claim 5, wherein the step of using the measurement of the quality of the uplink signal for each plurality of frequency channels for choosing a selected frequency channel comprises the steps of: comparing the strength measurements of the uplink signal for each plurality of selected frequency channels; and choose the frequency channel selected with the highest signal strength measurement.

10. The method of claim 3, wherein the step of using the measurement of the uplink signal strength for each plurality of candidate frequency channels to identify a set of qualified candidate frequency channels comprises the steps of: measuring the force of the downlink signal for each plurality of candidate frequency channels; and using the measurement of the uplink signal strength for each plurality of candidate frequency channels and the measurement of the downlink signal strength for each plurality of candidate frequency channels to identify a set of qualified candidate frequency channels; and comparing the measurement of the strength of the uplink signal with the measurement of the strength of the downlink signal for each plurality of candidate frequency channels and designating a candidate frequency channel as a qualified candidate frequency channel only if the measurement of the downlink signal strength of the candidate frequency channel is not greater than the measurement of the uplink signal strength by more than a third predetermined amount.

11. The method of claim 10, wherein a candidate frequency channel becomes identified as a candidate frequency channel only if the channel separation between the candidate frequency channel and the nearest selected frequency channel is greater than a requirement. minimum channel separation previously defined.

12. The method of claim 11, wherein the candidate frequency channel becomes identified as the qualifying candidate frequency channel only if the candidate frequency channel, in combination with any of the plurality of selected frequency channels, except the frequency channel. selected frequency identified, does not produce third order intermodulation products, equivalent to the plurality of selected frequency channels in addition to the identified selected frequency channel.

13. In a telecommunications network, a method for allocating frequency channels, comprising the steps of: measuring the strength of the uplink signal for each plurality of candidate frequency channels; measuring the strength of the downlink signal for each plurality of candidate frequency channels; choosing a qualified candidate frequency channel from the plurality of candidate frequency channels; and assigning the selected qualified candidate frequency channel to a base station in the telecommunications network, wherein the step of choosing a qualified candidate frequency channel comprises the step of: comparing the measurement of the strength of the uplink signal with the measuring the downlink signal strength for each plurality of candidate frequency channels and designating a candidate frequency channel as the qualified candidate frequency channel only if the measurement of the downlink signal strength of the candidate frequency channel is not greater than the measurement of the uplink signal strength by more than a third predetermined amount.

14. The method of claim 13, wherein the candidate frequency channel is identified as a qualified candidate frequency channel only if a channel separation between the candidate frequency channel and a nearest selected frequency channel is greater than a separation requirement. of previously defined minimum channel.

15. The method of claim 14, wherein the previously defined minimum channel separation requirement is defined by a number of 30 KHz intervals, which separate the center frequency for each of two adjacent frequency channels.

16. The method of claim 14, wherein the step of assigning the qualified candidate frequency channel chosen to a base station in the telecommunications network comprises exchanging the selected qualified candidate frequency channel with a selected frequency channel, and wherein the candidate frequency channel is identified as a qualifying candidate frequency channel only if the candidate frequency channel, in combination with any of a plurality of selected frequency channels, except the selected frequency channel with which the frequency channel The qualified candidate will be exchanged, does not produce third-order intermodulation products, equivalent to any of the plurality of selected frequency channels, in addition to the selected frequency channel with which the qualified candidate frequency channel is to be exchanged.

17. In a telecommunications network, an apparatus for assigning frequency channels, comprising: an element for measuring the quality of the uplink signal for each of a plurality of selected frequency channels; an element for measuring the quality of the downlink signal for each of the plurality of selected frequency channels; an element for comparing the quality of the uplink signal measured with the quality of the measured downlink signal for each of the plurality of selected frequency channels; an element for identifying a frequency channel selected from the plurality of selected frequency channels, if the quality of the downlink signal measured for the selected frequency channel is less than a previously defined first quantity and the quality of the link signal Descending measure for the selected frequency channel is less than the quality of the uplink signal measured by at least a second previously defined amount; an element to identify a qualified candidate frequency channel; and an element for exchanging the qualified candidate frequency channel with the selected frequency channel.

18. The apparatus of claim 17, wherein the element for measuring the quality of the uplink signal for each of the plurality of frequency channels. selected and the element for measuring the quality of the downlink signal for each of the plurality of selected frequency channels, each of which comprises: an element for measuring the bit error rate of the uplink and measuring the rate of downlink bit error for each of the selected frequency channels.

19. The apparatus of claim 17, wherein the element for identifying a qualified candidate frequency channel comprises: an element for measuring the strength of the uplink signal for each of a plurality of candidate frequency channels; an element for using the measurement of the uplink signal strength for each of the plurality of candidate frequency channels to identify a set of qualified candidate frequency channels; and an element for identifying a frequency channel - qualified candidate of the set of qualified candidate frequency channels.

20. The apparatus of claim 19, wherein the element for identifying a qualified candidate frequency channel from the set of qualified candidate frequency channels comprises: an element for comparing the measurement of the uplink signal strength for each qualified candidate frequency channel in all of them; and an element for selecting the qualified candidate frequency channel with a lower signal strength.

21. The apparatus of claim 17, further comprising: an element for measuring the strength of the uplink signal for each of the plurality of selected frequency channels; an element for measuring the strength of the uplink signal for each of a plurality of qualified candidate frequency channels; an element for using the measurements of the uplink signal strength for each of the plurality of selected frequency channels to choose a selected frequency channel; an element for using the uplink signal strength measurements for each of the plurality of qualified candidate frequency channels for choosing a qualified candidate frequency channel; an element for comparing the measurement of the uplink signal strength of the chosen selected frequency channel with the measurement of the uplink signal strength of the qualified candidate frequency channel; and an element for exchanging the selected selected channel with the chosen qualified candidate frequency channel, if the measurement of the uplink signal strength of the chosen selected frequency channel is greater than the measurement of the strength of the uplink signal of the selected frequency channel. qualified candidate frequency channel chosen by at least a third previously defined amount.

22. The apparatus of claim 21, wherein the element for measuring the strength of the uplink signal for each of the plurality of selected frequency channels and the element for measuring the strength of the uplink signal for each of the plurality of qualified candidate frequency channels, each comprising an element for measuring the levels of the interference signal.

23. The apparatus of claim 21, wherein the element g > to use the uplink signal strength measurements for each of the plurality of candidate frequency channels qualified to choose a qualified candidate frequency channel, comprising: an element for measuring the strength of the uplink signal for each of the plurality of candidate frequency channels; an element for using the measurement of the strength of the uplink signal for each of the plurality of candidate frequency channels to identify a set of qualified candidate frequency channels; and an element for choosing a qualified candidate frequency channel from the set of qualified candidate frequency channels.

24. The apparatus of claim 23, wherein the element for choosing a qualifying candidate frequency channel from the set of qualified candidate frequency channels comprises: an element for comparing the measurement of the strength of the uplink signal for each channel of candidate frequency qualified in the set thereof, with the measurement of the strength of the uplink signal of another qualified candidate frequency channel in the set thereof; and an element for choosing the qualified candidate frequency channel with the measurement of the lowest signal strength.

25. The apparatus of claim 21, wherein the element for using the measurement of the quality of the uplink signal for each of the plurality of frequency channels selected to choose a selected frequency channel comprises: an element for comparing the measurements of the strength of the uplink signal for each of the plurality of selected frequency channels; and an element for choosing the frequency channel selected with a measurement of the highest signal strength.

26. The apparatus of claim 19. wherein the element for using the measurement of the strength of the uplink signal for each of the plurality of candidate frequency channels for identifying a set of qualified candidate frequency channels, comprises: an element for measuring the strength of the downlink signal, for each of the plurality of candidate frequency channels; an element for using the measurement of the uplink signal strength for each of the plurality of candidate frequency channels and the measurement of the downlink signal strength for each of the plurality of candidate frequency channels to identify a set of qualified candidate frequency channels; and an element for comparing the measurement of the strength of the uplink signal with the measurement of the strength of the downlink signal for each of the plurality of candidate frequency channels and designating a candidate frequency channel as the channel of frequency. Qualifying candidate frequency only if the measurement of the strength of the downlink signal of the candidate frequency channel is not greater than the measurement of the strength of the uplink signal by more than a third predetermined amount.

27. The apparatus of claim 26, further comprising an element for identifying a candidate frequency channel as a qualifying candidate frequency channel only if the channel separation between the candidate frequency channel and a nearest selected frequency channel is greater than a minimum channel separation requirement previously defined.

28. The apparatus of claim 27, further comprising an element for identifying a candidate frequency channel as a qualified candidate frequency channel only if the candidate frequency channel, in combination with any of the plurality of selected frequency channels, except the channel of selected frequency identified, does not produce third-order intermodulation products, equivalent to any of the plurality of selected frequency channels, in addition to the identified selected frequency channel.

29. In a telecommunications network, an apparatus for assigning frequency channels, which comprises: an element for measuring the strength of the uplink signal for each of a plurality of candidate frequency channels; an element for measuring the strength of the downlink signal for each of the plurality of candidate frequency channels; an element for choosing a qualified candidate frequency channel from the plurality of candidate frequency channels and an element for assigning the qualified candidate frequency channel chosen to a base station in the telecommunications network, in which the element for choosing the frequency channel Qualified candidate comprises: an element for comparing the measurement of the uplink signal strength with the measurement of the downlink signal strength for each of the plurality of candidate frequency channels and designating a candidate frequency channel as a channel of qualified candidate frequency only if the measurement of the downlink signal strength of the candidate frequency channel is not greater than the measurement of the uplink signal strength by more than a third predetermined amount.

30. The apparatus of claim 29, further comprising an element for identifying a candidate frequency channel as a qualified candidate frequency channel, only if a channel separation, between the candidate frequency channel and a frequency channel closer, is greater that a minimum channel separation requirement previously defined.

31. The apparatus of claim 30, wherein the predetermined minimum channel separation requirement is defined by a number of 30 kHz intervals separating a frequency from the center for each of the two adjacent frequency channels.

32. The apparatus of claim 30, wherein the element for assigning the qualified candidate frequency channel chosen to a base station, in the telecommunications network, comprises: an element for exchanging the selected qualified frequency channel chosen with a selected frequency channel; and an element for identifying a candidate frequency channel as the qualified candidate frequency channel, only if this candidate frequency channel, in combination with any of a plurality of selected frequency channels, except the selected frequency channel, with which the Qualified candidate frequency channel is to be exchanged, it does not produce third-order intermodulation products, equivalent to any of the plurality of selected frequency channels, in addition to the selected frequency channel with which the qualified candidate frequency channel is to be exchanged .