MXPA96001063A

MXPA96001063A - Method and apparatus for balancing the direct link communication transfer limit with the reversal communication transfer limit, in a communication system

Info

Publication number: MXPA96001063A
Application number: MXPA/A/1996/001063A
Authority: MX
Inventors: Padovani Roberto; A Weaver Lindsay Jr; E Bender Paul
Original assignee: Qualcomm Incorporated
Priority date: 1994-07-21
Filing date: 1996-03-20
Publication date: 1997-06-01

Abstract

The present invention relates to a system having a plurality of base stations for bidirectional communication with a mobile unit, wherein the information is communicated to the mobile unit from a plurality of base stations on a direct link and the information is communicated to the plurality of base stations from the mobile unit in a reverse link, and wherein each base station defines a direct link coverage area and a reverse link coverage area, a method for controlling the coverage areas of the base stations which is characterized in that it comprises the steps of: measuring a reverse link power level received at a first base station and a second base station, and adjusting a forward link power level at the first base station and the second base station based on the measurement of the reverse link power level in the first and second base stations, to maintain a balance of a location of The equivalent performance of the direct link in relation to an equivalent reverse link performance location, between the first and second base stations

Description

METHOD AND APPARATUS FOR BALANCING THE TRANSFER LIMIT OF DIRECT LINK COMMUNICATION WITH THE LIMIT OF TRANSFER OF INVERSE LINK COMMUNICATION. IN A CELLULAR COMMUNICATION SYSTEM BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates to communication systems, particularly with a method and apparatus for performing the transfer of transmission between two sectors of a common base station.

II Description of Related Art In a multiple-access cellular telephone system by "code division (CDMA) or personal communication system, a common frequency band is used for communication with all base stations in a system. common frequency allows communication, simultaneously, between a mobile unit and more than one base station.The signals occupying the common frequency band are discriminated at the receiving terminal (either within the mobile unit or the base station) through of broad-spectrum CDMA waveform properties, based on the use of high-speed pseudo-noise (PN) codes and orthogonal Walsh codes.

P1051-96MX speed and Walsh orthogonal codes are used to "odd signals transmitted from base stations and mobile units. Transmitting terminals (either within a mobile unit or within a base station) using different PN codes or PN codes that are offset in time, produce signals that can be received separately at the receiving terminal. In an illustrative CDMA system, each base station transmits a pilot signal having a scatter code > JN common, which is shifted in the code phase of the pilot signal from other base stations. During the operation of the system, the mobile station is provided with a list of the code phase shifts corresponding to the neighboring base stations surrounding the base station, through which communication is established. The mobile unit is equipped with a search element that allows the mobile unit to track the signal strength of the pilot signal from a group of base stations that includes the neighboring base stations. A method and system for ÷ providing communication with the mobile unit through more than one base station during the transfer process is presented in U.S. Pat. No. 5,267,261 granted on November 30, 1993, entitled "METHOD AND APPARATUS FOR BALANCING THE DIRECT LINK TRANSFER LIMIT WITH THE P1051-96MX INVERSE LINK TRANSFER LIMIT IN A CELLULAR COMMUNICATION SYSTEM ", assigned to the assignee of the present invention Using this system, the communication between the mobile unit and the end user is not interrupted by the eventual transfer from a base station This communication type can be considered as a "soft" transfer since the communication with the subsequent base station is established before the communication with the riginal base station is terminated When the mobile unit is in communication with two base stations, from the signals coming from each base station a single signal is generated for the end user by means of a cellular or personal communication system controller.The soft transfer assisted by mobile unit operates based on the intensity of the pilot signal of several sets of base stations, as measured by the mobile unit The active set is the set of base stations through which active communication is established. The neighbor set is a set of base stations that surround an active base station comprising base stations that have a high probability of having a pilot signal strength of sufficient level to establish communication. The candidate set is a set of base stations that P1051-96MX has a pilot signal strength of sufficient level to establish communication. When communications are initially established, a mobile unit communicates through a first base station and the Active Set contains only the first base station. The mobile unit monitors the intensity of the pilot signal from the base stations of the Active Set, the Candidate Set, and the Neighbor Set. When a pilot signal from a base station in the Neighbor Set exceeds a predetermined threshold level, the base station is added to the Candidate Set and removed from the Neighbor Set in the mobile unit. The mobile unit communicates a message to the first base station that identifies the new base station. A cellular or personal communication system controller decides whether communication is established between the new base station and the mobile unit. If the cellular or personal communication system controller decides to do so, the cellular or personal communication system controller sends a message to the new base station with the identification information about the mobile unit and a command or command to establish the communications with it. A message is also transmitted to the mobile unit through the first base station. The message identifies a new active set that includes the first base station and the new base station. The P1051-96MX I 5 The mobile unit searches for the information signal transmitted from the new base station and establishes communication with the new base station without terminating the communication through the first base station. This process can continue with 5 additional base stations. When the mobile unit communicates through multiple base stations, it continues to monitor the signal strength of the base stations of the Active Set, the Candidate Set, and the Neighbor Set. If the Signal intensity corresponding to a base station of the active set falls below a predetermined threshold during a determined period of time, the mobile unit generates and transmits a message to report this case. The controller of the cellular communication system or staff receives this message through at least one of the base stations with which the mobile unit is communicating. The cellular or personal communication system controller may decide to terminate communications through the base station which has a weak intensity of pilot signal. The cellular or personal communication system controller when deciding to terminate communications through a base station generates a message identifying a new active set of base stations. The A?? set active does not contain the base station with which P1051-96MX will end the communication. The base stations through which the communication is established, send a message to the mobile unit. The cellular or personal communication system controller also communicates information to the base station to terminate communications with the mobile unit. The communications of the mobile unit are conducted or guided in this way, only through the base stations identified in the new active set. Because the mobile unit is communicating with the end user through at least one base station at all times through smooth transfer processes, there is no interruption in communications between the mobile unit and the end user. A soft transfer provides significant advantages in its inherent "set before interrupting" communication over conventional "break before set" techniques used in other cellular communication systems. In a cellular or personal communication telephone system, maximizing the capacity of the system in terms of the number of simultaneous telephone calls that can be handled is extremely important. The capacity of the system in a wide-spectrum system can be increased to the maximum, if the transmitter power of each mobile unit is controlled in such a way that each signal P1051-96MX transmitted reaches the receiver of the base station at the same -dvel. In a real system, each mobile unit can transmit the minimum signal level that produces a signal-to-noise ratio that allows for an acceptable data recovery. If a signal transmitted by a mobile unit reaches the receiver of the base station with a power level that is very low, the error rate can be too high to allow high-quality communications, due to the interference of the other mobile units . On the other hand, if the signal transmitted by the mobile unit is at a power level that is very high when it is received at the base station, communication with this particular mobile unit is acceptable, but this high power signal acts as a interference from the other mobile units. This interference can adversely affect communications' with other mobile units. Therefore, to maximize the capacity in an illustrative CDMA broad spectrum system, the transmit power of each mobile unit in communication with a base station is controlled by the base station to produce the same nominal signal power received in the base station. In the ideal case, the total power of the signal received at the base station is equal to the nominal power received from each mobile unit multiplied by the number of mobile units that transmit P1051-96 X within the coverage area of the base station, plus the power received at the base station from mobile units in the coverage area of the neighboring base stations. The loss of propagation in the radio channel can be characterized by two separate phenomena: the average loss of propagation and the weakening of propagation. The direct link, from the base station to the mobile unit, operates on a different frequency of the reverse link, from the "mobile unit to the base station." However, because the direct link and reverse link frequencies are within In the same band of frequencies, there is a significant correlation between the average propagation loss of the two links On the other hand, the weakening of propagation is an independent phenomenon for the direct link and the reverse link and varies as a function of time. However, the weakening characteristics in the channel are the same for both the direct link and the inverse link, because the frequencies are within the same band, therefore, the average weakening of the channel with time, for both links, it is usually the same In an illustrative CDMA system, each mobile unit estimates the direct link propagation loss based on the total power in the entrance to the mobile unit. The P1051-96MX total power is the sum of the power of all base stations operating in the same frequency assignment, as perceived by the mobile unit. From the estimate of the average propagation loss of the forward link, the mobile unit adjusts the transmission level of the reverse link signal. The transmission power of the mobile imity is also controlled by one or more base stations. Each base station with which the mobile unit is in "communication" measures the intensity of the signal received from the mobile unit The intensity of the measured signal is compared to a desired intensity level of the signal for that particular mobile unit in the base station A command or power adjustment command is generated by each base station and sent to the mobile unit in the direct link In response to commands or commands for the adjustment of the base station power, the unit The mobile unit increases or decreases the transmit power of the mobile unit by a predetermined amount.When a mobile unit is in communication with more than one base station, commands or commands to adjust the power are provided from each base station. mobile acts on these multiple commands of power adjustment of the base station to avoid transmission power levels that can P1051-96MX adversely interfere with other communications of the mobile unit and still provide sufficient power to support the communication of the mobile unit with at least one of the base stations. This power control mechanism is completed by causing the mobile unit to increase its level of transmission signal, only if each base station with which the mobile unit is in communication requires an increase in the power level. The mobile unit lowers its transmission signal level if any base station, with which the mobile unit is in communication, requires that the power be decreased. A system for controlling the power of the base station and of the mobile unit is presented in U.S. Patent No. 5,056,109, entitled "METHOD AND APPARATUS FOR BALANCING THE DIRECT LINK TRANSFER LIMIT WITH THE TRANSFER LIMIT INVERSE LINK IN A CELLULAR COMMUNICATION SYSTEM ", granted on October 8, 1991 and assigned to the assignee of the present invention. The diversity of the base station in the mobile unit is an important consideration in the smooth transfer process. The power control method described above operates optimally when the mobile unit communicates with each base station through which communication is possible. By doing so, the mobile unit avoids inadvertently interfering with the P1051-96MX signal of the mobile unit at an excessive level, but unable to communicate a power adjustment command to the mobile unit because the communication is not established with it. Each base station coverage area has two transfer limits. A transfer limit is defined as the physical position between two base stations where the link would carry out the same, without considering with which of the base stations the mobile unit was in communication. Each base station has a limit of "direct link transfer and a reverse link transfer limit." The direct link transfer limit is defined as the position where the mobile unit's receiver would perform the same without taking into account which the base station was receiving it, the reverse link transfer limit is defined as the position of the mobile unit where two base station receivers would perform the same with respect to that mobile unit, ideally, these limits must be balanced, meaning that the same physical position, if not, the capacity of the network can be reduced as the power control process is altered or the transfer region expands unreasonably Note that the balance of the transfer limit is a function of the P1051-96MX time since the reverse link power increases as the number of mobile units increases. An increase in reverse power decreases the effective size of the coverage area of the base station, and causes the reverse link transfer boundary to move inward toward the base station. Unless a compensation mechanism for the direct link is incorporated into the base station, even a system that is initially perfectly balanced will periodically unbalance depending on the load. The present invention is an apparatus and method for compensating a base station to achieve a balanced transfer limit condition under varying load conditions. The balance of a base station increases and decreases the coverage area of the base station automatically, as necessary to balance the direct link transfer limit with the reverse link transfer limit. This process is called base station breathing. Therefore, the object of the present invention is to provide the method and apparatus for balancing the forward link transfer limit with the reverse link transfer limit. Another objective of the present invention is to provide a method and apparatus for monitoring P1051-96MX Another objective of the present invention is to provide a method and apparatus for continuous monitoring and continuous reaction to the reverse link load to maximize the capacity of the system.

SUMMARY OF THE INVENTION The present invention defines a method and an apparatus for balancing the forward link transfer limit with the reverse link transfer limit. The method and apparatus are based on the measurement of the reverse link power level in the base station and the adjustment of the forward link power level to compensate for the reverse link load. Each base station in the system is initially calibrated, so that the sum of the noise in the path of the unloaded receiver and the desired pilot power is equal to some constant. The calibration constant is consistent through the base station system. As the system is loaded (ie, the mobile units begin to communicate with the base stations), a compensation network maintains constant the relationship between the reverse link power received at the base station and the pilot power transmitted from the base station. The load of a base station effectively moves the closest reverse link transfer limit to the station P1051-96MX base. Therefore, to limit the same effect in the direct link, the pilot power decreases as the load increases.

BRIEF DESCRIPTION OF THE DRAWINGS The features, objectives, and advantages of the present invention will be more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which the same reference numbers identify, correspondingly , to the same parts in all the drawings, and wherein: Figures 1A-1C show three unbalanced transfer conditions; Figures 2A-2C illustrate the effect of the load on the transfer-limits and the effect of the compensation of the breathing or pulsation mechanism; and Figure 3 is a highly simplified block diagram of the breathing or pulsation mechanism in a base station.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES The diversity of the base station in the mobile unit is an important consideration in the smooth transfer process. The power control method, described above, operates optimally when the P1051-96MX do so, the mobile unit avoids inadvertently interfering with communications through a base station that receives the signal from the mobile unit at an excessive level, but unable to communicate a command or command to adjust the power to the mobile unit because communication with it is not established. A typical cellular, local wireless circuit, or personal communication system contains some base stations that have multiple sectors. A multisector base station comprises multiple independent transmit and receive antennas, as well as independent processing circuitry. The present invention also applies to each sector of a sectorized base station and to the independent base stations of a single sector. The term base station can be assumed to refer to either a sector of a base station or a base station of a single sector. Each base station has a physical coverage area in which communication with the base station is possible. Each coverage area of the base station has two transfer limits. A transfer limit is defined as the physical position between two base stations, where the link would be made in the same way without considering which of the base stations the mobile unit was in communication with. Each base station has a P1051-96MX form without considering with which of the base stations the mobile unit was in communication. Each base station has a transfer limit direct link and a reverse link transfer limit. The direct link transfer limit is defined as: the position where the receiver of the mobile unit will make the transfer without taking into account which base station was receiving it. The reverse link transfer limit is defined as: the position of the mobile unit where two base station receivers would make the transfer with respect to the mobile unit. The present invention is described herein based on a system that has a soft transfer capability. Nevertheless, the invention also applies to the rigid transfer operation. A transfer limit is always defined between at least two base stations. For example, in Figure 1A, the forward link transfer limit 60 is a function of the power transmitted from the base station 10 and from the base station 40, as well as the interference from other surrounding base stations (not shown) and other sources within the band. The reverse link transfer limit 50 is a function of the power level received in the base station 10 and in the base station 40 from a mobile unit in P1051-96MX mobile units and other sources in the band. Note that the power level received in the base station 10 and the power level received in the base station 40 are somewhat independent / Ya < If the base station 10 has a greater number of mobile units located within its coverage area and the base station 40 only has one mobile unit, the interference to the base station 40 will be much smaller. Ideally, the forward link transfer limit and the reverse link transfer limit are co-positioned so that the optional capacity of the system can be achieved. If they are not co-positioned, then three situations can occur which are detrimental to capacity. Figure 1A shows the first of these situations. A smooth transfer region is located in the physical region between two base stations in which the mobile unit located within the region will likely establish communication with both base stations. In Fig. 1A, the shaded portion represents the soft transfer region 20. In the soft transfer assisted by mobile unit, the transfer region is defined by the characteristics of the direct link. For example, in Figure 1A, the soft transfer region 20 represents the region where both the signal quality of the base station 10 and the signal quality of the base station 40, P1C51-96MX region where both the signal quality of the base station 10 and the signal quality of the base station 40, is sufficient to support communications. When the mobile unit 30 enters the soft transfer region 20, it will notify, regardless of which base station is in communication, that the second base station is available for communications. The system controller (not shown) establishes communication between the second base station and the mobile unit 30 as described in the aforementioned U.S. Patent No. 5,267,261. When the mobile unit 30 is in soft transfer between the base station 10 and the base station 40, both stations control the transmit power of the mobile unit 30. The mobile unit 30 decreases its transmit power if any of the base stations requests a decrease that increases its transmit power, only if each base station requests an increment as disclosed in the aforementioned U.S. Patent No. 5,056,109. Figure 1A shows the first situation that is detrimental to the capacity of the system. In Figure 1A, the forward link transfer limit 60 and the reverse link transference limit 50 are significantly unbalanced (i.e., separated). The mobile unit 30 is located in a position where the communication is Direct P1051-96MX is better with the base station 40, but the performance of the reverse link would be better if the mobile unit 30 were communicating with the base station 10a. In this situation, the mobile unit 30 is transmitting more power than it would be transmitting if it were in communication with the base station 10. The increase in the transmission power is added unnecessarily to the total interference of the system, affecting, therefore, adverse way, capacity. The total power consumption of the mobile unit 30 is also increased, thus decreasing the life of its battery. This endangers the communication link if the mobile unit 30 reaches its maximum transmission power and is unable to respond to orders to increase the power. Figure IB shows an alternate result but also detrimental to an unbalanced transfer condition. In Figure IB, the soft transfer region 70 is located around the limit 50 ^ of reverse link transfer. This transfer position could be the result of an alternative transfer scheme where the transfer is based on the performance of the reverse link, instead of the direct link performance. In one of these cases, each base station would try to measure the power received from each mobile unit. When the measured power level exceeds a threshold or exceeds the level P1051-96MX received at the other base stations, communication with a second base station will be established. In Figure IB, the mobile unit 30 is located in a region where communication is established only with the base station 10. As in Figure 1A in the region where the mobile unit 30 is located, the link performance direct is better with the base station 40, but the reverse link performance is better with the base station 10. Unlike the reverse link, the forward link does not have a large dynamic range of transmit power and as the mobile unit 30 moves towards the base station 40, the interference of the base station 40 increases as the power level received from the base station 10 decreases. If the power level of the base station 10 falls below a sufficient signal to the level of interference or below a certain level of absolute, the communication link is in danger of being lost. The power level transmitted from the base station 10 is slowly decreased within a limited dynamic range, as the mobile unit 30 moves away from the base station 10. This increase in power interferes adversely with other users in the base station 10. and at base station 40, unnecessarily decreasing capacity. Another alternative is a combined transfer scheme, based on both the performance of the direct link P1051-96MX Another alternative is a combined transfer scheme, based on both direct link performance and reverse link performance. Figure 1C shows this environment. In Figure 1C, the transfer region 80 is larger and encompasses both the reverse link transfer limit 50 and the direct link transfer limit 60. But the unnecessary soft transfer directly decreases the capacity of the system. The purpose of the soft handoff is to provide the establishment of the transfer before interrupting the transfer between base stations, and to provide an efficient power control mechanism. However, if the soft transfer region is very large, the negative effects become significant. For example, in Figure 1C, both the base station 10 and the base station 40 must transmit to the mobile unit 30 while the mobile unit 30 is in the soft transfer region 80. In this way, the total transfer of the system increases while the mobile unit 30 is in the soft transfer region 80. In addition, the resources in both the base station 10 and the base station 40 must be dedicated to the signal received from the mobile unit 30. Therefore, increasing the size of the soft transfer region is not an efficient use of capacity and the resources of the system.

P1051-96MX The solution to these adverse effects is to balance (ie, physically align) the reverse link transfer limit with the forward link transfer limit, or vice versa. Even if this was done at each base station in a static condition, the balance would be lost as the system is used. For example, the signal at the interference level of the reverse link signal received at the base station is a function of the number, position, and transmission power level of the mobile units within their coverage area. As the load on a base station increases, the interference increases, and the reverse link transfer limit contracts to the base station. The direct link limit is not affected in the same way, so a system that is initially balanced can be unbalanced over time. To maintain the balance, the present invention defines a "pulse or respiration" method of the size of the coverage area of the base station. The pulse or respiration mechanism effectively moves the forward link transfer limit to the same position as the reverse link transfer limit. The two limits depend on the performance of at least two base stations. For the breath or pulse to be effective, the reverse link transfer limit and the forward link transfer limit must be aligned initially. The P1051-96MX Direct link performance can be controlled by the base station. In an illustrative CDMA system, each base station transmits a pilot signal. The mobile units make the transfer based on the intensity of the perceived pilot signal as described above. By changing the power level of the pilot signal transmitted from the base station, the position of the forward link transfer limit can be manipulated. The reverse link performance can also be controlled by the base station. The performance of the noise in the receiver of the base station establishes the minimum level of reception power that can be detected. The noise performance of the receiver is normally defined in terms of a global noise data of the system. By controlling the noise data of the receiver, for example by injecting noise or adding attenuation, the performance of the reverse link, and hence the limit of reverse link transfer, can be adjusted. To balance transfer limits, the performance of each base station must be controlled to be the same as the performance of other base stations in the system. Therefore, we define a broad constant of system performance to be used by each base station in the system. You could also define a dynamic constant that is the same for each base station, but that is allowed to change over time. For the sake of P1051-96MX simplicity of design and implementation, in this mode a fixed constant is preferred. The constant is defined in terms of the sum of the receiver propagation noise in decibels (dB) and the maximum desired power of the pilot signal in dB as demonstrated below. The best selection of the constant takes advantage of the available system performance. Therefore, to define-á l 'constant, Knivei, the following equation is used: Knivel = MAX [NRX: I > Max: \ Equation 1 all / where: NRx: Is the propagation noise of the base station receiver in dB; PMax: Is the maximum desired power of the pilot signal of the base station i in dB; and MAX r -i: find the largest sum of all the entire base stations of the system. Note that once Kn¿vei is selected, artificial means can be used to increase the propagation noise of the non-loaded system of each base station to satisfy the constant. To demonstrate that adjusting the sum of the received power and the power transmitted to a Kn¿vei effectively balances the system, you can do various P1051-96MX assumptions. The first assumption is that in any base station that uses multiple redundant antennas for reception and transmission, antennas have been balanced to have the same performance. Also, the analyzes assume that an identical decoding performance is available in each base station. This assumes a constant proportion between the total direct link power and the power of the pilot signal. And it assumes reciprocity in the loss of direct link propagation and in the loss of reverse link propagation. To find the direct link transfer limit between two arbitrary base stations, the base station A and the base station B, let us begin by noting that the direct transfer limit occurs when the ratio of the power of the pilot signal to the total power, it is the same for the two base stations. Suppose that the mobile unit C is located in the limit, mathematically in units of linear power (like Watts): Pilot Power of A Received in C Pilot Power of B Received in C Total Power Received in C Total Power Received in C Equation 2 Note that the power received in the mobile unit is equal to the transmitted power multiplied by the propagation loss, equation 2 becomes: P1051-96MX Power Pilot Transm. from A X Loss of Propagation from A to C Transm. Pilot Power from A X Loss of Propagation from A to C Total Power Received in C Total Power Received in C Equation 3 Re-adjusting equation -3 and eliminating the common denominator, we obtain: Pilot Power Transmitted from A Loss of Path Propagation from B to C Pilot Power Transmitted from B Loss of Propagation of Trajectory from A to C Equation 4 Following the same procedure for the reverse link and noting that the reverse link transfer limit occurs when each base station perceives the same signal to interference ratio for the mobile unit: C power received in A Power of C Received in B Total Power Received in A Total Power Received in B Equation 5 Note that the power received in the base station is equal to the power transmitted from the mobile unit multiplied by the path loss, equation 5 becomes: "**« nda Transm. From CX Loss of Propagation from C to A Transm. Power from CX Loss of Propagation from C to B Total Power Received at A Total Power Received at B Equation 6 Reconstituting Equation 6 and eliminating the common numerator, we obtain: Total Power Received in A Loss of Propagation of Trajectory from C to A: = Total Power Received in B Loss of Propagation of Trajectory from C to B Equation 7 Due to the supposed reciprocity in the losses P1051-96MX of direct and reverse link propagation in any position, Equations 4 and 7 can be combined to produce: Total Power Received in A Pilot Power Transmitted from B = Total Power Received in B Pilot Power Transmitted from A Equation 8 Changing the units of equation 8 ade linear power to dB, we obtain: Total Power Received in A (dB) - Total Power Received in B (dB) = Pilot Power Transmitted from B (dB) - Pilot Power Transmitted from A (dB) Equation 81 Equation 81 is equivalent to the exposed premise since: if the Total Power Received in A (dB) + Pilot Power Transmitted from A (dB) = n ^ vei and Total Power Received in B (dB) + Pilot Power Transmitted from B (dB) = Knivei then equation 8 will be satisfied. And the direct link transfer limit and the reverse link transfer limit are co-positioned. Three mechanisms are needed to effect pulse or respiration fusion: a means to initial adjust the performance to ???? ß ?, a means to monitor fluctuations in the reverse link, and a means to change the performance of the link direct in response to P1051-96MX reverse link fluctuations. A method for initially adjusting the performance to ^ level 'is to adjust the desired maximum intensity of the pilot signal taking into account the variations with temperature and time, and adding the attenuation in line with the receiver in a condition of no signaling. exit, until the performance of n¿vei is achieved. By adding attenuation, the receiver is desensitized and the noise data of the receiver is effectively increased. This also requires that each mobile unit transmits more power in a proportionate manner. The added attenuation must be kept at the minimum dictated by Knivel. Once the initial balance is reached, the power that enters the base station can be measured to monitor the performance of the reverse link. Various methods can be used. The measurement can be made by monitoring an AGC (Automatic Gain Control) voltage or by directly measuring the input level. This method has the advantage that if an interference element is present (such as an F signal) this energy will be measured and the transfer limits will be attracted closer to the base station. By attracting the transfer limit closer to the base station, the interference element can be removed from the coverage area of the base station and its effect reduced to a minimum. The measurement P1051-96MX can be performed by simply counting the number of users communicating through the base station and estimating the total power based on the fact that each signal of the mobile unit nominally arrives at the base station at the same signal level. As the reverse link power increasesThe direct link power must be "decreased." This can be easily achieved using an existing AGC circuit within the transmission circuitry or by providing a controllable attenuator in the transmission path In the illustrative transfer scheme described above, the transfer limits are based on the measurement of the intensity of the pilot signal in the mobile unit.An alternative the control of the total transmission power would be to control only the level of the pilot signal.For the designer of the coverage area, this scheme can have a Certain attractiveness, but controlling the total power of transmission including jointly traffic signals (eg active calls) and pilot signals, has some advantages: First, the ratio of the intensity of the pilot signal to the intensity of the traffic channel signal remains fixed.The mobile unit may be waiting for a proportion n fixed and you can allocate your resources based on the proportion. If the P1051-96MX mobile unit to receive two equally powerful pilot signals, each corresponding to a traffic channel having a different power level, could result in a sub-optimal decision in the allocation of resources of the mobile unit. Adjusting the total power is also advantageous, because it reduces the interference with other base station coverage areas. If the pilot signal is not strong enough to guarantee a transfer in the coverage area of a neighboring base station, the high power traffic channel signal adds unnecessary and unnecessary interference to that area. Of course, in some applications, it may be advantageous to combine the methods for controlling the power of the pilot signal in some cases and the total power transmission in other cases. In another application, it may be advantageous to change the ratio of the pilot power to the power of the traffic channel. In an ideal configuration, the pulse or respiration mechanism would measure the reception power and change the transmit power in a proportionate manner. However, some systems can not use the proportional method and instead can change the transmission level only a fraction of the perceived change in reception power. For example, if a system was designed in which the »estimated power received was P1C51-96 X difficult and imprecise, system designers may wish to decrease the sensitivity to inaccuracy. A change in the transmission level that is only a fraction of the change in reception power achieves desensitization while avoiding a general imbalance of the transfer limits. Other alternatives change the transmission level only when the level of the receiver exceeds a predetermined threshold. This method could be used to deal mainly with interference elements. Of course, this method can be combined with a system that changes the transmission level in only a fraction of the perceived change in reception power. The pulse or breathing mechanism must have a carefully considered time constant. The pulse or breathing mechanism may cause transfers from the mobile unit. To effect a transfer, the mobile unit must detect the power change and send a message to the base station. The system controller must make a decision and notify the base stations. A return message will be sent to the mobile unit. This process takes time and the pulse or breathing process must be slow enough to allow this process to proceed smoothly. The pulse or breathing process naturally P1051-96 X will limit itself to avoid full convergence of the coverage area of the base station due to excessive users in the system. The CDMA system has a large capacity and a limited soft capacity. The term limited soft capacity refers to the fact that one more user can always be added, but to a certain number of users, each additional user affects the quality of communication of all other users. To a larger number of users, the communication quality of each user becomes unusable and the entire link with each mobile unit is lost. To avoid the loss of the link, each base station limits the number of mobile units with which it will establish communication. Once this limit has been reached, the system will reject attempts to establish additional calls, that is, the generation of new calls is blocked. The limit is a design parameter and normally fits approximately 75% of the theoretical capacity. This gives the system a certain margin and allows the system to accept an emergency call even when it is in the limited condition. This limit on the total number of mobile units that communicate within the coverage area of a single base station naturally limits the maximum power received and therefore limits the interval of the pulse or breathing process of the operation.

P1051-96MX Figures 2A-2C illustrate the pulse or respiration mechanism of the base station. In Figure 2A, the base station 100 has a circular coverage area 130 in an unloaded condition. The coverage area of the base station 100 has been balanced in an unloaded condition and the coverage areas of the forward and reverse links are aligned with the circular coverage area 130. The base station 110 has a circular coverage area 140 in an unloaded condition The aperture area of the base station 110 has also been balanced in an unloaded condition and the coverage areas of the forward and reverse links are aligned with the circular coverage area 140. The operation of the base stations 100 and 110 has been balanced to Kn- [vei in an unloaded condition, and line 120 represents the position in which the operation with each base station is the same and hence both transfer limits. In Figure 2B, the base station 110 has been heavily loaded and the base station 100 is lightly charged. The coverage area of the reverse link has contracted to the position of the circular coverage area 145, while the direct link coverage area remains in the circular coverage area 140. The "light load" of the base station 100 has not affected the coverage area of the base station 100, which is still in the coverage area Circular P1051-96MX 130. Note that the reverse transfer limit between base station 100 and base station 110 has been moved to line 125, while the forward link transfer limit remains on line 120. In this way, the undesirable unbalanced transfer limit condition has been generated. - In Figure 2C, the base station 110 has implemented the pulse or base station breathing mechanism. The effect has been to move the forward link transfer limit to the circular coverage area 145. Line 125 now represents both the forward link transfer limit and the inverse one. In Figures 2B and 2C, the X's represent the users of the system. In particular, user X 150 is located at the transfer limit of Figure 2B. Due to its position, the user X is in soft transfer between the base station 100 and the base station 110. Note that in Figure 2C, the user X 150 is now in the depth of the coverage area of the base station 100 and not in the soft transfer region between the base station 100 and the base station 110. Therefore, the heavily loaded base station 110 has effectively transferred part of its load to the slightly charged base station 100. Fiura 3 is a block diagram that shows P1051-96MX a lustrative base station breathing configuration. The antenna 270 receives signals at the base station 300. The reception signals then pass to the variable attenuator 200 which has been used to initially adjust the operating Kn¿vei. The reception signals pass to the power detector 210. The power detector 210 generates a level that indicates the total power in the received signal. The low pass filter 220 averages the power indication and reduces the response time of the respirator. The scale and the threshold 230 adjust the desired ratio and the displacement of the relationship between the increase 1 in the power of the reverse link and the decrease in. the power of the direct link. The scale and threshold 230 emit a control signal for the variable gain device 240. The variable gain device 240 accepts the transmission signal and supplies a controlled gain output signal to the high power amplifier (HPA) 250. The HPA 250 amplifies the transit signal and passes it to the antenna 260 for transmission over the wireless link There are many variations of the configuration of Figure 3. For example, antennas 260 and 270 can each comprise two antennas. Or, conversely, the antennas 260 and 270 may be the same antenna. The power detection of Figure 3 is based on the full power of P1051-96MX the incoming signal within the band of interest. As noted above, the power detection may be based only on the number of mobile units that have established communication with the base station. Also the low pass filter 220 can be a linear filter or a non-linear filter (such as a slow speed limiting filter). There are many obvious variations of the present invention, as presented by including simple changes in the Architecture. The prior description of the preferred embodiment is provided to enable any person skilled in the art to make or use the present invention. The various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, it is not intended that the present invention be limited to the embodiments shown herein, but rather be in accordance with the broadest scope consistent with the principles and novel features disclosed herein.

P1051-96MX

Claims

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property; 1. In a system having a plurality of base stations capable of bidirectional communication with a mobile unit, wherein the information is communicated to the mobile unit from a plurality of base stations in an * > direct link and the information is communicated to the plurality of base stations from the mobile unit in a reverse link, and wherein each base station defines a direct link coverage area and a reverse link coverage area, a method for controlling the coverage areas of the base stations characterized in that it comprises the steps of: measuring a received reverse link power level in a first base station and in a second base station / and adjusting-a direct link power level in the first base station and in the second base station based on the measurement of the reverse base power level in the first and second base stations, to maintain a balance of an equivalent performance location of the forward link in relation to an equivalent performance location P1051-96MX reverse link, between the first and second base stations. A method according to claim 1, characterized in that the product of the reverse link power level in the first base station and the direct link power level in the first base station is equal to a constant; and the product of the reverse link power level in the second base station and the forward link power level in the second base station is equal to said constant. 3. A method according to claim 1, characterized in that the product of the level of "reverse link power at the first base station and the direct link power level at the first base station is equal to a constant when the power level of reverse link in the first base station is greater than a threshold; and the product of the link power level, inverse in the second base station and the direct link power level in the second base station, is equal to said constant when the reverse link power level in the second base station is greater to said threshold. 4. In a system having a plurality of base stations, each of said plurality of base stations has a corresponding direct link coverage area and a corresponding coverage area of P1051-96MX reverse link, wherein each of the plurality of base stations is able to communicate with a mobile unit located within the corresponding direct link coverage area and each of the plurality of base stations is capable of receiving communication from a mobile unit located within the corresponding reverse link coverage area, üh method for aligning a position of a first direct link coverage area with a position of a first reverse link coverage area corresponding to a first base station that characterized in that it comprises the steps of: measuring a load level of the reverse link coverage area indicative of the position of the first reverse link coverage area; and changing the position of the first direct link coverage area based on the measured load level. The alignment method according to claim 4, characterized in that the measured load level of the reverse link coverage area comprises the energy received from a set of mobile units located within the first reverse link coverage area. 6. The alignment method according to claim 5, characterized in that the load level of the reverse link coverage area further comprises the P1051-96MX energy received from a user that is not from the system and a. a set of mobile units located within a reverse link coverage area corresponding to a second base station. 7. The alignment method according to claim 4, characterized in that the step of changing the position of the first direct link coverage area is limited to a minimum coverage area limit. The alignment method according to claim 4, characterized in that the step of the measurement comprises the step of counting the number of mobile units in communication with the first base station. 9. A method for balancing the boundaries of the base station in a system comprising "a plurality of base stations, characterized in that it comprises the steps of: transmitting a forward link signal to a selected power level from a first base station that defines a first direct link coverage area; receiving a reverse link signal at a first power level in the first base station defining a first reverse link coverage area; transmitting a direct link signal to a selected power level from a second base station defining a second direct link coverage area, wherein the first direct link coverage area and the P1051-96MX second direct link coverage area is intercepted to define a direct link equality position in which a mobile unit receives communication with the same level of performance with the first base station and with the second base station; and receiving a reverse link signal at a power level in the second base station defining a second reverse link coverage area, wherein the first reverse link coverage area and the second coverage area 'reverse link' are intercepted to define a reverse link equality position, wherein the first base station and the second base station receive communication from a mobile unit in the reverse link equality position with the same level of performance; wherein the selected power level of the forward link signal from the first base station and the selected power level of the forward link signal from the second base station are selected in such a way that the link equality position "direct and" The position of equality of the reverse link is the same 10. The method for balancing the limits of the base station according to claim 9, characterized in that it also comprises the steps of: receiving.-, in the first base station the link signal inverse to a second power level higher than P1051-96MX first power level received at the first base station, whereby a second reverse link coverage area smaller than the first base station is defined and defines a new reverse link equality position; and transmitting from the first base station the direct link signal to a lower power level that defines a second direct link coverage area and a new direct link equality position, such that the new direct link equality position be the same as the new reverse link equality position. The method for balancing the limits of the base station according to claim 9, characterized in that each of the plurality of base stations in the system transmits a pilot signal, and because the direct link signal from the first base station is the signal pilot corresponding to the first base station. The method for balancing the limits of the base station according to claim 9, characterized in that each of the plurality of base stations in the system transmits a pilot signal and message signals, and because the forward link signal of the first base station is the pilot signal and the message signals corresponding to the first base station. 13. The method for balancing the limits of the base station according to claim 9, characterized in that P1051-96MX the product of the selected power level of the direct signal of the first base station and the first power level of the reverse link signal of the first base station is equal to a constant. The method for balancing the limits of the base station according to claim 13, characterized in that the product of the selected power level of the forward link signal of the second base station and the power level of the reverse link signal of the second base station is equal to a constant. 15. The method for balancing the limits of the base station according to claim 13, characterized in that the constant is dynamic and varies with time. 16. The method for balancing the limits of the base station according to claim 9, characterized in that the first power level of the reverse link signal in the first base station comprises an amount of artificial power, so that the product of the selected power level of the forward link signal of the first base station and the power level of the reverse link signal of the first base station is equal to a constant. 17. The method for balancing the limits of the base station according to claim 16, further characterized in that the power of the reverse link signal in the P1051-9GMX second base station comprises a quantity of artificial power so that the product of the power level of the forward link signal of the second base station and the power level of the reverse link signal of the second base station is equal to constant said 18. An apparatus for controlling a position of a direct link coverage area and a reverse link coverage area of a base station in a system of base stations capable of bidirectional communication with a Set of mobile units, characterized in that it comprises: a antenna system for receiving a signal that enters a reception power level and for providing a transmission signal at a transmission power level; a power detector having an input coupled to the antenna system and having an output to provide an indication of the output of the power level proportional to the power level of reception; and a variable attenuator coupled to the output of the power detector to receive a power control signal and receive an information signal, and. providing a controlled power information signal wherein the output of the variable attenuator is coupled to the antenna system, thereby adjusting the transmission power level; P1051-96MX where the product of the power level of reception of the input signal and the transmission power level of the transmission signal is controlled to maintain the balance in the position of the direct link coverage area and the coverage area of reverse link. 19. The apparatus for controlling the coverage area of a base station according to claim 18, characterized in that it further comprises an attenuator located between the receiving antenna and the power detector to adjust the product to a constant when the power level of The input signal is minimal. 20. The apparatus for controlling the coverage area of a base station according to claim 18, characterized in that it further comprises means for scaling and selecting the output indication of the power level, being located between the power detector and the variable attenuator. P1051-96MX