Power control of remote communication devices

A first communication device is in communication with a second communication device. The communication may be characterized by a first and a second characteristic that are affected by a transmit power of the first communication device, each characteristic having an upper and a lower bound. The transmit power of the first communication device is delayed from being adjusted to bring the communication within the upper and lower bounds of the first criteria and outside the upper and lower bounds of the second criteria when a contrary adjustment of the transmit power of the first communication device was performed until a predetermined amount of time has expired since the contrary adjustment. Thus, unnecessarily repetitive power adjustments are avoided.

BACKGROUND OF THE INVENTION 
 The present invention relates to apparatus and methods for improving 
 cellular communication networks. More particularly, the present invention 
 relates to improved base transceiver station (BTS) architectures in a 
 cellular communication network. 
 Cellular communication systems are well known in the art. In a typical 
 cellular communication system, the mobile stations (MS's) may transmit and
 receive voice and/or data with the cellular network and one another 
 utilizing radio waves. To facilitate discussion, FIG. 1 depicts the 
 architecture of a cellular communication network 100 that implements the 
 well known Global System for Mobile Communication (GSM) standard. Although
 the GSM cellular network is chosen herein for illustration purposes, it 
 should be borne in mind that the invention disclosed herein is not limited
 to any particular standard. 
 In FIG. 1, there is shown a plurality of mobile stations (MS's) 102, 104, 
 and 106, representing the mobile interface with the cellular users. In a 
 typical network, MS's 102, 104 and 106 may be, for example, mobile 
 handsets or fixed mobile stations mounted in vehicles. MSs 102, 104, and 
 106 typically include radio and processing functions for exchanging voice 
 and data via radio waves with transceivers (TRX's) in base transceiver 
 stations (BTS's) 114 and 116. The transceivers (TRX's) are shown in FIG. 1
 as transceivers 114a, 114b, 114c, 116a, and 116b. The BTS's may be thought
 of, in one sense, as the counterpart to the MS's within the cellular 
 network, and its main role is to connect the mobile stations with the rest
 of cellular communication network 100. 
 There is also shown in FIG. 1 a base station controller (BSC) 118, whose 
 function is to monitor and control the BTS's. There may be any number of 
 BSC I 18 in a network, whose responsibility includes, among other 
 responsibilities, radio interface management, e.g., the allocation and 
 release of radio channels and handover management. Mobile Services 
 Switching Center (MSC) 120 controls one or more BSC's 118 and provides the
 basic switching function within the cellular network, including setting-up
 of calls to and from the MS's. MSC 120 also provides the interface between
 the cellular network users (via the BSC and BTS) and external networks 
 (e.g., PSTN or public switched telephone network). The components of GSM 
 cellular network 100 are well known to those skilled in the art and are 
 not discussed in great detail here for brevity's sake. Additional 
 information pertaining to GSM and the cellular networks implementing the 
 GSM standard may be found in many existing references including, for 
 example, Redl, Weber & Oliphant, An Introduction to GSM (Artech House 
 Publishers, 1995). 
 In the prior art, the radio circuitries of the TRX's are typically 
 implemented such that they co-locate with other circuits of the BTS. By 
 way of example, FIG. 2 illustrates in greater detail exemplary prior art 
 BTS 114 of FIG. 1, including TRX's 114a, 114b, and 114c. As is typical, 
 the antennas of the prior art TRX's co-locate with the BTS such that the 
 BTS defines the cell. Although one antenna is shown to facilitate 
 simplicity of illustration, separate transmit and receive antennas may be 
 provided for each TRX, as is well known. Other major functional blocks of 
 BTS 114 includes ABIS interface 202, which implements the circuitry 
 necessary for interfacing between BTS 114 and its BSC. CPU circuit 204 
 implements the call processing functions, including for example LAPDm 
 processing, speech framing, channel coding, interleaving, burst 
 formatting, ciphering, modulation, MS power control and the like. The 
 architecture of the prior art BTS is well known and is not discussed here 
 in great detail for simplicity's sake. 
 It has been found, however, that the conventional BTS architecture has many
 disadvantages. By way of example, the integration of the radio circuitries
 of the TRX's and the processing circuitries of the BTS in one unit results
 in a complex and maintenance-intensive electronic subsystem. Yet prior art
 BTS's are often installed in locations selected primarily for optimum 
 radio transmission quality such as on top of buildings and other outdoor 
 structures instead of ease of access. These locations, being exposed to 
 the elements, are typically hostile to the delicate and complex electronic
 circuits of the prior art BTS. Accordingly, these factors tend to render 
 the installation, maintenance, and upgrade of prior art BTS's difficult 
 and expensive. 
 The integration of the radio circuitries of the TRX's in the prior art BTS 
 also limits the flexibility with which the cell can be modified to 
 accommodate changes in capacity. In the prior art, the BTS, which contains
 the co-resident TRX antennas, essentially defines the cell. Although some 
 cell shaping may be accomplished by, for example, employing directional 
 antennas, the cell is more or less limited by the transmit power of the 
 antennas in the BTS. Scaling the transmit power upward increases the cell 
 size at the expense of capacity since the use of larger cells reduces the 
 ability to reuse frequencies among neighboring cells. Increasing the 
 transmit power also increases the amount of heat generated, thereby 
 reducing the reliability of the circuitries in the prior art BTS unless 
 fans and/or additional heat dissipation techniques are employed. 
 In addition to problems associated with defining a cell, appropriate 
 control of the transmit power of MSs also present a myriad of problems. 
 Ideally, all MSs would transmit at a high enough power providing 
 acceptable signal quality, but low enough where the MSs do not interfere 
 with each other. Thus, upper and lower bounds may be established for the 
 transmit power of the MSs. However, conditions may occur where the 
 transmit power of the MSs fall outside these bounds. Prior art systems 
 have not fully accounted for solving all the situations in which the 
 transmit power of the MSs fall outside the established bounds for 
 transmission. 
 In view of the foregoing, there are desired improved methods and apparatus 
 for overcoming the disadvantages associated with prior art cellular 
 communication systems. 
 SUMMARY OF THE INVENTION 
 To achieve the foregoing and other objects and in accordance with the 
 purpose of the present invention, an improved method and apparatus for 
 controlling the transmit power of a communication device is disclosed. 
 In one embodiment of the present invention, a first communication device is
 in communication with a second communication device. The communication may
 be characterized by a first and a second characteristic that are affected 
 by a transmit power of the first communication device, each characteristic
 having an upper and a lower bound. If the first characteristic falls below
 its lower threshold the transmit power of the first communication device 
 is not increased until a predetermined amount of time has expired if the 
 transmit power was previously decreased. 
 In another embodiment, if the second characteristic falls below its lower 
 threshold the transmit power of the first communication device is not 
 increased until a predetermined amount of time has expired if the transmit
 power was previously decreased. 
 In yet another embodiment, if the first characteristic rises above its 
 upper threshold the transmit power of the first communication device is 
 not decreased until a predetermined amount of time has expired if the 
 transmit power was previously increased. In yet another embodiment, if the
 second characteristic rises above its upper threshold the transmit power 
 of the first communication device is not decreased until a predetermined 
 amount of time has expired if the transmit power was previously increased.
 In a further embodiment, the transmit power of the first communication 
 device is delayed from being adjusted to bring the communication within 
 the upper and lower bounds of the first criteria and outside the upper and
 lower bounds of the second criteria when a contrary adjustment of the 
 transmit power of the first communication device was performed until a 
 predetermined amount of time has expired since the contrary adjustment. 
 An advantage of the present invention is a significant savings in power 
 consumption. By decreasing the number of times that a communication device
 is required to increase and/or decrease its transmit power, more power is 
 conserved. This is especially useful in cellular communication systems 
 where mobile communication devices are often times limited by power 
 capacity. Further, the amount of cycling on the communication device is 
 also decreased. These and other features and advantages of the present 
 invention will be presented in more detail in the following specification 
 of the invention and the Figures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION 
 In accordance with the present invention, methods and apparatus for 
 reducing repetitive power control situations are described. Generally, by 
 limiting the times at which a base transceiver station may instruct a 
 mobile station to increase or decrease the power at which it is 
 transmitting when a previous power adjust command had instructed the 
 opposite, the ping-ponging effect may be reduced. 
 A particular problem associated with prior art cellular communication 
 systems is the method by which BTSs 114 and 116 regulate the transmit 
 power of MSs 102, 104 and 106. Typically, the signal received from an MS 
 102, 104 and 106 received by BTS 114 or 116 is measured by various 
 factors. Signal strength, measured as signal-to-noise ratio, and signal 
 quality, measured as a bit error rate in digital systems, are typically 
 used to define the quality of the signal received from MS 102, 104 or 106.
 The cellular communication system will have an upper level threshold and a
 lower level threshold for both signal-tonoise ratio and bit error rate. 
 When a signal received from MS 102, 104 or 106 received by BTS 114 or 116 
 falls outside the boundaries of the upper or lower threshold, then BTS 114
 or 116 must send a signal to MS 102, 104 or 106 in order to adjust the 
 MS's power output. By adjusting the power output of the MS 102, 104 or 
 106, the signal quality, in terms of signal-to-noise ratio or bit error 
 rate, can be corrected to fall within the appropriate boundaries of the 
 upper and lower thresholds. 
 FIGS. 3 and 4 illustrate certain situations in which prior art systems may 
 have difficulty adjusting the power output of MS 102, 104 or 106 to 
 provide a signal that falls within the boundaries of the upper and lower 
 thresholds. FIG. 3 is a diagrammatic plot of a typical signal-to-noise 
 ratio threshold boundary. Upper threshold 140 delineates the maximum power
 at which MS 102, 104 or 106 should be transmitting. Lower threshold 150 
 delineates the minimum power at which MS 102, 104 or 106 should be 
 transmitting. 
 If a signal falls within the boundaries of upper threshold 140 and lower 
 threshold 150, then typically no power adjustment 104 is required to be 
 sent to MS 102, 104 or 106. Should a received signal from MS 102, 104 or 
 106 be received by TRX 114 or 116 that falls outside the boundaries of 
 upper threshold 104 and lower threshold 150, a power adjustment signal is 
 typically then sent to the MS. For example, signal sample point 201a lies 
 above upper threshold 104. Therefore, the corresponding MS (e.g., 102) 
 sending signal 201a, must then be sent a power adjustment signal in order 
 to reduce its power. Generally, the power adjustment signal will have been
 received by MS 102, and the power output of the MS will be reduced as 
 depicted in the new sample point 202a. In most cases, that will solve the 
 power transmission problem, however, in certain situations, the 
 corresponding BTS (e.g., 114) may be prompted to immediately send another 
 power adjustment signal, increasing the power output of MS 102. 
 Typically, the reason for BTS 114 to send a new power adjustment signal 
 that may raise the power output of MS 102 beyond upper threshold 140 
 again, as depicted in sample point 203a, is related to other signal 
 quality criteria, such as the bit error rate. FIG. 4 illustrates a bit 
 error rate diagram having a bit error rate upper threshold 160 and a bit 
 error rate lower threshold 170. 
 In FIG. 4, bit error rate upper and lower threshold 160 and 170 are 
 indicated by quality levels 2 and 4. These quality levels are outlined in 
 GSM specification 05.08, Version 4.9.0, dated Apr. 15, 1994, which is 
 incorporated herein by reference. Basically, bit error rate quality levels
 indicate the quality of the digital signal received from MS 102, by BTS 
 114. The bit error rate quality levels range from 0 to 7, the lower the 
 bit error rate level, the lower the number of bit errors per symbol 
 received by BTS 114 or 116. Thus, referring back to FIG. 4, if a signal 
 falls within the bit, error rate thresholds 160 and 170, then the signal 
 received from MS 102 by BTS 114 has an acceptable number of bit errors per
 symbol, such that BTS 114 or 116 may properly process the incoming signal.
 When a signal received by BTS 114 or 116 falls above bit error rate upper 
 threshold 160, it typically indicates that the signal quality is too good.
 That is, due to the fact that most cellular communication systems 
 incorporate error encoding, a number of bit errors are acceptable in any 
 transmission. If a signal received by BTS 114 or 116 has an inordinately 
 low number of bit errors, falling above bit error rate upper threshold 
 level 160, then BTS 114 may be able to reduce the power at which MS 102 is
 transmitting. Thus, MS 102 may afford to transmit with more errors, 
 corresponding to a lower transmit power level. 
 For example, signal sample point 241 b falls above bit error rate upper 
 threshold 160. Thus, BTS 114 may be prompted to send a power adjustment 
 signal to MS 102 to reduce the signal power since it may be likely that MS
 102 may be able to transmit at a lower power and incur a few more bit 
 errors per sample, and fall within the appropriate bit error rate 
 threshold. Similarly, if a signal received by BTS 114 should happen to 
 fall below bit error rate lower threshold 170, then BTS 114 may send a 
 power adjustment signal to MS 102 to increase its power such that a better
 bit error rate ratio may be obtained and fall within the bit error rate 
 threshold. 
 In certain situations, the combination of the signal strength, 
 signal-to-noise ratio, and signal quality, bit error rate, may induce BTS 
 114 to repeatedly send power adjustment signals to increase and decrease 
 the power output of MS 102, as illustrated in FIGS. 3 and 4. 
 FIGS. 3 and 4 include four series of signal sample points. Signal sample 
 points with the same reference numeral, i.e., 201a and 201b, represent the
 signal-to-noise ratio and the bit error rate for a single signal sample 
 point, respectively. That is, a single signal sample point 201 a is the 
 signal-to-noise ratio of measurement, and 201 b is the bit error rate 
 measurement. 
 Signal sample points having sequential numbers indicate the successive 
 signal sample points in relation to a particular MS 102, 104 or 106. For 
 example, 201a is a first signal sample point for a particular MS (e.g., 
 102), and the following signal sample points in the sequence 202a, 203a, 
 204a, 205a, 206a, 207a, 208a, and 209a are the successive signal sample 
 points after power adjustment signals have been sent by BTS 114 or 116 to 
 the particular MS, in this case 102. Analogously, signal sample points 
 201b through 209b indicate the successive bit error rate signal sample 
 points during another exemplary communication between a particular MS and 
 a BTS, e.g., 102 and 114. 
 Referring to signal sample point series 201a through 209a and 201b through 
 209b, a ping-pong situation, as discussed earlier, will be described. 
 Signal sample points 201a and 201b indicate a situation where MS 102 may 
 be transmitting at a power greater than signalto-noise ratio upper 
 threshold 140, but at a signal quality that falls within the bit error 
 rate upper and lower threshold 160 and 170g respectively. 
 Typically, prior art systems may send a power adjustment signal to MS 102 
 to decrease its power output since it is transmitting beyond the maximum 
 power threshold 140. After MS 102 has reduced the power at which it is 
 transmitting, a new signal sample point set 202a and 202b may be measured 
 by BTS 114. The new signal sample points 202a and 202b indicate that, 
 although the transmit power of MS 102 now falls within the boundary of the
 signal-to-noise ratio threshold 140 and 150, the signal quality has now 
 fallen below the bit error rate lower threshold 170. 
 Normally, BTS 114 may then send a power adjustment signal to MS 102 to 
 increase the power at which MS 102 is transmitting in order to correct the
 bit error rate problem. Once MS 102 has increased its power, a new set of 
 signal sample points 203a and 203b may be measured by BTS 114. Signal 
 sample points 203a and 203b present a similar problem as indicated by 
 signal points 201a and 201b. That is, although the signal quality falls 
 within the appropriate threshold 160 and 170, the signal strength is once 
 again too high and falls above signal-to-noise ratio threshold 140. 
 Generally, in prior art cellular communication systems, BTS 114 may repeat 
 a power adjustment signal to decrease the power at which MS 102 is 
 transmitting. Again, we are met with the situation where the 
 signal-to-noise ratio of the signal from MS 102 is adequate, but the 
 signal quality falls below bit error rate lower threshold. Prior art 
 cellular communication systems may continue to repeat this process of 
 increasing and decreasing the power at which MS 102 is transmitting in 
 order to attempt to correct this paradoxical situation where one criteria 
 can only be met by violating another signal criteria. 
 Signal sample points 221a through 229a, 221b through 229b, 241a through 
 249a, 241b through 249b, 261a through 269a, and 261b through 269b 
 illustrate other situations in which this ping-pong effect may occur in 
 prior art cellular communication systems. 
 Ping-ponging the power at which MS 102 is transmitting, may have several 
 disadvantages. A primary concern is that additional power consumption 
 caused by the repeated increase and decrease of the power at which MS 102 
 is transmitting. Additionally, ping-ponging may affect the overall 
 communication between MS 102 and BTS 114. Further, the cycling of the 
 power at which MS 102 is transmitting may affect the lifespan of MS 102. 
 While one embodiment of the present invention is described in terms of a 
 cellular communication system, the present invention encompasses any type 
 of communication systems where the transmit power of the communicating 
 devices may be changed. Wireless communication systems utilizing 
 electromagnetic radiation as the communication medium particularly fall 
 within the scope of the present invention. However, the present invention 
 may be suitable for application to wired communication systems as well. 
 In one embodiment of the present invention, the types of power adjustment 
 signals a BTS may send to a mobile station may be limited by timing the 
 interval between the last time that the BTS has sent a contrary power 
 adjustment signal. That is, if a BTS sends a power adjustment signal to a 
 MS to increase the power at which it is transmitting, the base transceiver
 station may then be prevented from sending a power adjustment signal to 
 decrease the MS's transmit power until a predetermined time interval has 
 passed. Similarly, when the base transceiver station has sent a power 
 adjustment signal or command to decrease the power at which a mobile 
 station is transmitting, the BTS may then be limited from sending an 
 increase power command until a predetermined interval of time has passed. 
 FIG. 5 is a diagrammatic block diagram of an improved cellular 
 communication system 500 in accordance with one embodiment of the present 
 invention. Improved cellular communication system 500 includes an MSC 520,
 BSC 518, and a number of BTS's 514 and 516. Improved cellular 
 communication system 500 further includes MSs 502, 504, and 506. 
 As discussed, MSs 502, 504 and 506 are in communication with BTS's 514 and 
 516 via transceivers 514a, 514b, 514c, 516a and 516b. Typically, MSs 502, 
 504 and 506 communicate with BTS's 514 and 516 through the electromagnetic
 spectrum, as known in the art. Unlike prior art systems, improved cellular
 communication system 500 facilitates communication between MSs 502, 504 
 and 506, with BTS's 514 and 516 with minimized repetitive ping-ponging of 
 the MS's transmit power. 
 FIGS. 6 and 7 depict signal power and quality factor diagrams, 
 respectively, in accordance with one embodiment of the present invention. 
 Signal sample point set representing a series of cellular communications, 
 are depicted by the different shapes as seen in FIGS. 6 and 7. One series 
 of signal sample points (e.g., 301a through 308a), represents one series 
 of signal sample points between a BTS and a MS 502, 504 or 506. 
 Improved cellular communication system 500 typically sets thresholds 240, 
 250, 260 and 270 for signal power and quality factors of a signal being 
 received from a MS 502. Referring to FIG. 6, upper signal power threshold 
 240 is set at a predetermined level. Further, lower signal power threshold
 250 is typically also set at another predetermined level. The 
 predetermined levels are dependent on the power outputs of MS 502 and the 
 arrangement of the cell in which improved cellular communication system 
 500 is operating, and various other factors. In one embodiment, upper 
 signal power threshold is set at minus 85 dB and lower signal power 
 threshold is set at minus 95 dB. 
 Referring to FIG. 7, improved cellular communication system 500 also 
 typically sets predetermined quality factor levels, such as upper signal 
 quality factor threshold 260 and lower quality factor threshold 270. As 
 discussed, the GSM specification includes a range of quality factor levels
 ranging from 0 to 7. In one embodiment of the present invention, upper 
 quality factor threshold level is set at 2 and lower quality factor level 
 is set at 4. However, any quality factor level may be chosen for upper 
 quality factor level or theshold 260 and lower quality factor level or 
 threshold 270, as long as upper quality factor level 260 is greater than 
 lower quality factor level 270. 
 For purposes of brevity, further discussion of a communication will be in 
 reference to communications between BTS 514 and MS 502. Signal sample 
 points 301b through 328b of FIG. 7 correspond to sample points 301 a 
 through 308a, but represent the quality factor of the same signal as 
 opposed to the signal power as depicted in FIG. 6. The other signal sample
 point sets depicted by the other shapes in FIGS. 6 and 7 represent 
 different situations in which MS 502 and BTS 514 are communicating. 
 Referring back to FIGS. 3 and 4, it can be appreciated that the starting 
 signal sample points 301a and 301b, 321a and 321b, 341a and 341b, and 361a
 and 361b, represent situations in which ping-ponging may have occurred in 
 prior art systems. However, in improved cellular communication system 500,
 ping-ponging is avoided by limiting BTS 514 from sending successive 
 contrary power adjustment signals. For example, signal sample points 301a 
 and 301b represent the situation where the signal power of a signal from 
 MS 502 to BTS 514, is too strong. 
 In prior art systems, the BTS would have sent a signal to the mobile 
 station to reduce the power of its transmission. In that case, the signal 
 of the mobile station would be represented by signal sample points 302a 
 and 302b where, although the signal power falls within the appropriate 
 threshold as depicted by signal sample point 302a, the signal quality 
 factor level falls below the signal quality lower threshold threshold 270 
 as depicted by signal sample point 302b. In prior art systems, the BTS may
 then have sent a signal to increase the transmit power of MS 502 in order 
 to bring back the signal quality factor above lower quality factor 
 threshold 270. In one embodiment of the present invention, BTS 514 is 
 typically not allowed to send a power adjustment signal to MS 502 to 
 increase its transmitting power to avoid further ping-ponging. 
 Rather than having BTS 514 send a power adjustment signal to a MS 502 to 
 increase its power from the situation depicted in signal sample points 
 302a and 302b, BTS 514 may determine the optimal time to allow MS 502 to 
 increase its transmitting power in order to correct the low signal quality
 level. At the same time, BTS 514 typically avoids power fluctuations which
 would occur had ping-ponging been initiated. 
 The signal from MS 502 to BTS 514 remains at the same level as depicted in 
 302a and 302b for a certain interval of time, as depicted by signal sample
 points 303a, 303b, 304a and 304b of FIGS. 6 and 7. Typically, the 
 intervals between signal sample points, for example, the time interval 
 between 303a and 304a, are predetermined increments of time in which BTS 
 typically sends a power adjustment signal to MS 502. Thus, in a situation 
 depicted by signal sample point 302a through 304a and 302b through 304b, 
 BTS 514 may wait two sample intervals before sending a power adjustment 
 signal to MS 502 to increase its transmit power. 
 MS 502 typically increases its transmit power as soon as it receives the 
 signal received from MS 502 by BTS 514 as represented by signal sample 
 point 305a and 305b. Again, the situation occurs where the signal power is
 greater than the upper signal power threshold 240. However, the quality 
 factor of the signal falls within the appropriate thresholds 260 and 270. 
 Rather than BTS 514 sending an immediate signal to MS 502 to decrease the 
 transmit power, BTS 514 may again wait in order to avoid the deleterious 
 effects of ping-ponging. 
 In the example illustrated in FIGS. 6 and 7, BTS 514 waits two time 
 intervals before sending a power adjustment signal to MS 502 to decrease 
 its transmit power, as depicted by signal sample points 306a and 306b, 
 307a and 307b, and 308a and 308b. Similarly, improved cellular 
 communication system 500 handles the other situations where ping-ponging 
 typically occurs as depicted by signal sample points 321a and b through 
 328a and b, 341a and b through 348a and b, and 361a and b through 318a and
 b. However, the present invention is not limited to the exemplary 
 situations of ping-ponging disclosed in FIGS. 6 and 7, but is suitable to 
 remedy any situation in which the transmit power of MS 502 is required to 
 be repeatedly increased and decreased due to certain signal criteria. 
 FIG. 8 is a diagrammatic flowchart 350 of the operation of an improved 
 cellular communication system, in accordance with one embodiment of the 
 present invention. The illustrated operations may be performed by any 
 suitable element of improved cellular communication system 500. For 
 example, an MSC , BSC or BTS may perform the exemplary operations. In one 
 embodiment, a CPU (not shown) of BTS 514 performs the operations depicted 
 in flowchart 350. 
 Flowchart 350 typically begins at block 352, in which BTS measures the 
 signal received from MS 502 for the relevant signal criteria. The signal 
 criteria may be any suitable criteria relevant to cellular communication 
 systems. By way of example, the criteria may include the signal power as 
 measured by signal-to-noise ratio, bit error rate, intersymbol 
 interference, crosstalk or any other suitable signal characteristic. In 
 one embodiment, the signal power, as measured by signal-to-noise ratio and
 the bit error rate, are used as the signal criteria. 
 In one embodiment, after the signal power and the bit error rate have been 
 measured in block 352, BTS 514 determines whether an overshoot timer is 
 equal to zero in block 354. The overshoot timer typically indicates the 
 amount of time that has passed from the last power adjustment signal that 
 caused one of the criteria, in this case signal power or bit error rate, 
 to overshoot one of the thresholds (e.g., 240, 250, 260 and 270 of FIGS. 6
 and 7). If a previous power adjustment signal had caused the signal from 
 MS 502 to overshoot one of the thresholds 240, 250, 260 and 270, then BTS 
 514 must determine whether a sufficient amount of time has expired before 
 sending a contrary power adjustment signal. If the overshoot timer is 
 equal to zero, then BTS 514 proceeds to block 355 where PC flag is set to 
 zero. 
 PC flag determines what type of overshoot occurred because of the previous 
 power adjustment signal. If PC flag is equal to positive one (+1) then it 
 means that the previous power adjustment signal went below lower signal 
 power threshold 250. If PC flag is equal to negative one (-1), then the 
 previous power adjustment signal caused the signal power of MS 502 to go 
 over upper signal power threshold 240. As may be appreciated, the PC flag 
 need only inform BTS 514 of whether the signal power went over or under 
 the threshold 240 and 250 since ping-ponging only occurs when the signal 
 power, or the quality factors for bit error rates, alternately goes above 
 and below the respective threshold. After setting the PC flag to zero in 
 block 355, BTS 514 proceeds to block 357 to determine whether PC timer is 
 equal to zero. 
 PC timer may be a timer to measure the time intervals between consecutive 
 signal sample points (for example, between 302a and 303a, referring back 
 to FIG. 6). The PC timer time interval may be set to any suitable time 
 increment. By way of example, in one embodiment, power measurements as 
 discussed in reference to block 352, are taken every half second. 
 However, the time interval represented by PC timer may represent several 
 measurement intervals. For example, although power signal measurements are
 taken every half second, BTS 514 may only want to send power adjustment 
 signals to MS 502 every three seconds. In that case, BTS 514 would count 
 down to every sixth measurement intervals before sending any type of power
 adjustment signal. If the PC timer is not equal to zero, then the 
 flowchart 350 returns to block 352 to take further signal measurements. If
 the PC timer is equal to zero, then BTS 514 may proceed. 
 Referring back to block 354, if the overshoot timer is not equal to zero, 
 then flowchart 350 proceeds to block 359 where BTS 514 decrements the 
 overshoot timer. After the overshoot timer has been decremented in block 
 359, BTS 514 proceeds to block 357 as described earlier. 
 Should PC timer be equal to zero, indicating that it is an appropriate time
 to send a new power adjustment signal, BTS 514 proceeds to block 361. In 
 block 361, BTS 514 determines if there are any problems related to the 
 selected criteria. In one embodiment, BTS 514 checks to determine whether 
 the signal power falls outside threshold 240 and 250, or if the signal 
 quality falls outside threshold 260 and 270, in block 361. If there are no
 problems with the signal being transmitted by MS 502, then BTS 514 returns
 to block 352 to take further measurements. If there are problems with the 
 signal related to one of the selected criteria, then BTS 514 proceeds to 
 block 362. 
 In block 362, BTS 514 determines if the signal from MS 502 falls below any 
 of the lower thresholds 250 or 270 in terms of signal power or bit error 
 rate, respectively. Typically, it is preferred to handle any problems 
 related to lower thresholds 250 or 270 before handling any problems 
 related to the upper threshold 240 and 260. Generally, this is because 
 when the signal from MS 502 falls below a lower threshold 250 or 270, the 
 signal is either too low in power or contains too many bit errors per 
 signal. In those cases, the communication between MS 502 and BTS 514 can 
 be seriously affected. However, if the signal power or the quality of the 
 signal surpasses an upper threshold 240 or 260, respectively, then the 
 only problem is that MS 502 is either transmitting at too high a power or 
 the signal quality is high enough such that lower power may be used and 
 still maintain adequate communication between MS 502 and BTS 514. 
 If it is determined that the signal power or the quality factor of the 
 signal from MS 502 falls below one of the lower thresholds 250 or 270, 
 then the operation of BTS 514 proceeds to block 364. In block 364, BTS 514
 determines if PC flag equals negative one. As discussed, if PC flag equals
 negative one, it means that the previous power adjustment signal caused 
 the signal power to fall below lower signal power threshold 250. If the PC
 flag is still negative one, then the overshoot timer for the previous 
 power adjustment signal has not expired. If PC flag is not equal to 
 negative one, then either the PC flag was reset indicating that the 
 overshoot timer has expired, or the previous power adjustment signal 
 caused the signal power to go over upper signal power threshold 240. 
 If PC flag is equal to negative one, then BTS 514 proceeds back to block 
 352 for further signal measurement. If PC flag is not equal to negative 
 one, then BTS 514 proceeds to block 370 where BTS 514 determines the 
 appropriate power command to send to MS 502, as discussed in further 
 detail in reference to FIG. 9. After the appropriate power command has 
 been determined, it is then sent to MS 502 in block 420. After the power 
 command is sent to MS 502, BTS 514 returns to block 352 for further signal
 measurement. 
 Referring back to block 362, if there were no problems with the signal 
 power falling below lower signal power threshold 250 or the signal quality
 falling below lower quality factor level 270, then BTS 514 proceeds to 
 block 366. In block 366, BTS 514 determines whether the PC flag is equal 
 to positive one. Analogous to block 364, if PC flag is equal to positive 
 one, it indicates that the previous power adjustment signal sent by BTS 
 514 to MS 502 caused the signal power to exceed upper signal power 
 threshold 240. In which case, BTS 514 returns to block 352 for further 
 signal measurements. 
 If PC flag is not equal to positive one, then it indicates that the PC flag
 was either reset to zero or the previous power adjustment signal was a 
 signal to MS 502 to decrease its transmit power, which would not affect 
 the current determination. BTS 514 then proceeds to block 390 and 
 determines the appropriate power adjustment command to send to MS 502, as 
 discussed in further detail in reference to FIG. 10. Once the appropriate 
 power adjustment signal has been determined by BTS 514, it is sent to MS 
 502 in block 420. After the power adjustment signal is sent to MS 502, BTS
 514 returns to block 352 for further signal measurements. 
 FIG. 9 is a diagrammatic flowchart of block 370 of FIG. 8. In block 370 BTS
 514 determines the appropriate power command to be sent to MS 502 when a 
 lower threshold problem is present. Flowchart 370 proceeds from block 364 
 of FIG. 8 to block 371. In block 371, BTS 514 determines whether the 
 current signal power level is less than the lower signal power level 
 threshold 250. If the current signal power level is less than the lower 
 signal power level threshold 250, then BTS 514 proceeds to block 380 to 
 determine an appropriate power increment delta. 
 The power increment delta, in block 380, is set as the minimum of a 
 predetermined signal power increment step, power_increment, or the value 
 of the lower signal power level threshold 250 minus the current level, 
 plus one-half the difference of the upper threshold level 240 minus the 
 lower threshold level 250, as represented by the following formula. 
EQU .DELTA.=min [(power_increment), lower threshold 250-current level+((upper 
 threshold 240-lower threshold 250).div.2)] 
 Referring back to block 371, if the current level was not less than the 
 lower signal power level threshold 250, then the current lower threshold 
 problem is not due to signal power, but to the quality factor. That is, 
 the bit error rate of the signal from MS 502 to BTS 514 is too high, and 
 the quality factor of the signal falls below lower quality factor 
 threshold 270. In that case, BTS 514 proceeds to block 374 where the power
 increment is set at a predetermined power increment related to poor signal
 quality, quality_increment. 
 In one embodiment, a predetermined step may be set for the increment or 
 decrement related to the quality factor and the increment or decrement 
 related to the signal power. By way of example, a power related increment,
 power increment, and a power related decrement, power_decrement may be set
 at 2 dB. By way of further example, a quality related increment, 
 quality_increment, and a quality related decrement, quality_decrements may
 be set at 2 dB. However, any suitable increment or decrement may be 
 utilized in accordance with the present invention. 
 After the delta increment has been set to quality_increment in block 374, 
 BTS 514 proceeds to block 376. In block 376 BTS 514 determines whether an 
 overshoot or upper shoot time constant has been set to zero, and whether 
 the current power level is less than the upper signal power threshold 240.
 The upper shoot time constant determines whether overshoots are allowed at
 all by BTS 514, as indicated by its value. If the upper shoot time 
 constant is equal to zero, then BTS 514 is not permitted to send a power 
 adjustment signal to MS 502 that would increase the signal power beyond 
 upper signal power threshold 240. 
 If upper shoot time constant is a value greater than zero, then that value 
 will allow BTS 514 to send a power adjustment signal that would send the 
 signal power beyond upper signal power threshold 240. The upper shoot time
 constant also informs BTS 514 for how long it may remain above upper 
 signal power threshold 240 before being allowed to correct the overshoot. 
 In block 376, in addition to determining if the overshoot time constant is 
 equal to zero or not, BTS 514 also determines whether the current power 
 level is less than the upper signal power level threshold 240. If either 
 of the two criteria are false, then BTS 514 proceeds to block 381 with the
 delta increment being equal to the predetermined quality increment. 
 If both of the two criteria are true, then BTS 514 proceeds to block 378 to
 determine the delta increment. The delta increment is set at the minimum 
 of either the current value of delta, which would be equal to 
 quality_increment, or the value returned by the equation: upper signal 
 power threshold level 240 minus the current power level. 
 After the delta increment has been set by either the blocks 374, 378 or 
 380, BTS 514 proceeds to block 381. In block 381, BTS 514 determines 
 whether the current power plus the incremental delta power adjustment will
 be lower than the maximum power output capable by MS 502. If the delta 
 increment plus the current power is less than the maximum power, then the 
 power adjustment command is set to that sum in block 385. However, if 
 current power plus the delta increment is equal to or exceeds the maximum 
 power capable by MS 502, then the power adjustment command is set to the 
 maximum power level in block 383. After the power adjustment commands have
 been determined in blocks 383 or 385, BTS proceeds to block 387. 
 In block 387, BTS 514 once again determines if the upper shoot time 
 constant is not equal to zero, allowing overshoot. If the upper shoot time
 constant is equal to zero, then the power adjustment command is sent in 
 block 420 of FIG. 8 without setting either the PC flag or the overshoot 
 timer, since the power adjustment command will not have caused an 
 overshoot. 
 However, if upper shoot time constant is not equal to zero, then the power 
 adjustment command may have set the signal power beyond the upper signal 
 power threshold 240. In which case, BTS 514 proceeds to block 389 to set 
 the PC flag equal to positive one indicating that a power adjustment 
 signal has been sent to MS 502 that might have sent the signal power 
 beyond upper signal power threshold 240. At the same time, the overshoot 
 timer is set at the upper shoot time constant minus one in order to set 
 the time interval in which the signal power of the mobile station should 
 not be decremented if the signal power exceeds upper signal power 
 threshold 240. After the appropriate values have been set in block 389, 
 BTS proceeds to block 420 of FIG. 8 where the power adjustment signal 
 command is sent to MS 502. 
 In the preceding, BTS 514 has determined the appropriate power adjustment 
 command to send to MS 502 in order to rectify one of two problems. The two
 problems either being that the signal power of the signal from MS 502 is 
 lower than lower signal power threshold 250, or that the quality of the 
 signal is less than the lower quality factor threshold 270. In either 
 case, if it is determined that in order to resolve one of the two 
 problems, that the signal power should be incremented beyond upper signal 
 power threshold 240, then BTS 514 will have sent the appropriate power 
 increment command but at the same time, set the overshoot timer such that 
 an immediate successive command to decrease power is not sent immediately 
 after the command to increase power. Also, the situation where BTS 514 is 
 not allowed to go beyond upper signal power threshold 240, will typically 
 also have been complied with. 
 FIG. 10 is a diagrammatic flowchart of block 390 of FIG. 8. Flowchart 390 
 determines a power adjustment command when the signal power or the signal 
 quality exceeds upper threshold 240 or 260. Flowchart 390 proceeds from 
 block 366 of FIG. 8 to block 391. 
 In block 391, BTS 514 determines whether the current power level is greater
 than the upper signal power level threshold 240. If the current signal 
 power level is greater than the upper signal power level threshold 240, 
 BTS 514 proceeds to block 400, in which BTS 514 determines the delta 
 decrement. The delta decrement is equal to the minimum of either the 
 power.sub.13 decrement, or the current power level minus upper power level
 240 plus one half the difference between upper power level 240 and lower 
 power level 250, as represented in the following equation. 
EQU .DELTA.=min [(power decrement), current level_upper threshold 240+((upper 
 threshold 240-lower threshold 250).div.2)] 
 If the current signal power level is equal to or less than the upper signal
 power level threshold 240, then BTS 514 proceeds to block 394. In block 
 394, the delta decrement is set to the predetermined step decrement 
 related to quality factor, quality_decrement. Once the delta decrement has
 been set in block 394, BTS 514 proceeds to block 396 to determine if the 
 lower shoot time constant is set to zero. 
 The lower shoot time constant indicates whether BTS 514 is permitted to go 
 below lower signal power level threshold 250. If the lower shoot time 
 constant is equal to zero, then BTS 514 is not permitted to go below lower
 signal power threshold 250. If the lower shoot time constant is greater 
 than zero, then the value indicates that BTS 514 is allowed to go below 
 lower signal power threshold 250 and for how long. 
 If the lower shoot time constant is not equal to zero, then the delta 
 increment remains the value set in 394, the predetermined step quality 
 decrement, and the BTS 514 proceeds to block 401. On the other hand, if 
 the lower shoot time constant is equal to zero, then BTS 514 proceeds to 
 block 398 where the delta decrement is determined. In block 398, the delta
 decrement is set at either the minimum of the current value for the delta 
 decrement, which would be equal to quality_decrement, or the current level
 minus lower power level threshold 250, as represented by the following 
 equation. 
EQU .DELTA.=min[quality decrement, current level-lower power level threshold] 
 After the delta decrement has been set in either blocks 394, 398 or 400 BTS
 514 proceeds to block 401. In block 401, BTS 514 determines whether the 
 current power minus the delta decrement is greater than the minimum power 
 at which MS 502 may transmit. If the current power minus the delta 
 decrement is greater than the minimum power, then the power adjustment 
 command is set at that value set in block 405. Otherwise, if the current 
 power minus the delta decrement is equal to or falls below the minimum 
 power, then the power adjustment command is set to that minimum power 
 level in block 403. 
 Block 405 sets the power adjustment command to the current power minus the 
 delta decrement. Block 403 sets the power adjustment command to the 
 minimum power at which MS 502 may transmit. After the power adjustment 
 command has been determined in either blocks 403 or 405, BTS 514 proceeds 
 to block 407. 
 In block 407, BTS 514 determines again whether the lower shoot time 
 constant is equal to zero or not. If the lower shoot time constant is 
 equal to zero no lower shoot is permitted. The power adjustment command 
 should not have gone beyond the lower signal power level threshold 250 due
 to blocks 396 and 398. The power adjustment command is then sent in block 
 420 of FIG. 8. 
 In the other case, where lower shoot time constant is not equal to zero, 
 then BTS 514 proceeds to block 409. In block 409, BTS 514 sets the PC flag
 equal to minus one, indicating that the power adjustment command 
 decreasing the signal power may have sent the signal power below lower 
 signal power threshold 250. At the same time, the overshoot timer is also 
 set to the lower shoot time constant minus one, such that BTS 514 will be 
 able to determine when to allow an increase in the transmit power of MS 
 502 to occur. After the appropriate values have been set in block 409, BTS
 514 proceeds to block 420 of FIG. 8. 
 In block 420, BTS 514 sends the appropriate power adjustment command to MS 
 502. As may be appreciated, once a power adjustment command has been sent 
 by BTS 514 instructing MS 502 to increase or decrease its signal power 
 such that it will exceed one of the signal power thresholds, BTS 514 will 
 not immediately send a following command contrary to the one just sent. 
 That is, BTS 514 will not cause a ping-ponging effect to occur as 
 described in prior art systems. Rather, BTS 514 in accordance with the 
 present invention, will delay any contrary signals to the previous power 
 adjustment signal in order to avoid ping-ponging. 
 One embodiment of the present invention, as discussed above, deals in 
 particularity with cellular communication systems utilizing GSM 
 specifications. However, the present invention may be utilized in any 
 suitable type of communication systems. 
 A novel aspect of the present invention is the concept of timed transmit 
 power adjustments of conflicting commands. Repeatedly increasing and then 
 immediately decreasing the transmit power of a mobile unit, or any 
 communication device, in order to comply with conflicting criteria may 
 have detrimental effects on the mobile unit without satisfying all the 
 criteria. Thus, a method and apparatus of minimizing repetitive contrary 
 commands reduces the amount of harm caused by more frequent ping-ponging 
 when all criteria cannot be met. At the same time, the timed intervals do 
 not interfere with power adjustments commands that do not cause a 
 ping-pong effect. 
 While the present invention has been described in terms of several 
 preferred embodiments, there are alterations, permutations, and 
 equivalents which fall within the scope of the present invention. It 
 should also be noted that there are many alternative ways of implementing 
 the methods and apparatuses of the present invention. It is therefore 
 intended that the following appended claims be interpreted as including 
 all such alterations, permutations, and equivalents as fall within the 
 true spirit and scope of the present invention.