HK1032494A - Apparatus and method for optimized power control - Google Patents

Description

Apparatus and method for optimizing power control

Technical Field

The present invention relates to wireless communication systems. More particularly, the present invention relates to a new and improved apparatus and method for power control of a wireless communication device.

Background

Wireless communication networks have penetrated widely into business, industry, and personal life. Portable handheld wireless communication devices have therefore experienced extensive development in recent years. Such as cellular and Personal Communications Services (PCS) telephones, have become commonplace for business and personal users. In addition, advanced systems such as satellite communication systems utilizing portable hand-held and mobile phones are currently being designed.

One design goal of handheld communication devices is low power consumption. The low power consumption reduces the amount of heat generated and extends battery life, thereby improving the use of the device. Low power consumption also generally allows or results in a reduction in device size.

In a CDMA communication system, the transmit power of signals within the system is controlled so that the power required for any given communication link is maintained at a minimum level. This maximizes the overall capacity of the communication system and maintains mutual interference and signal quality at acceptable levels. By controlling the transmit signal power near the minimum level, its interference with other communication devices or units is reduced. Examples of techniques for power control in such communication systems are given in: united states patent No.5,383,219 entitled "fast forward link power control in cdma systems" granted on 17.1.1995; united states patent No.5,3396,516 entitled "method and system for dynamic modification of control parameters in a transmitter power control system" granted 3/7/1995; and U.S. patent No.5,267,262 entitled "transmitter power control system" entitled 11/30 1993. They are included herein by reference.

One technique to reduce the power consumption of a device is to minimize the power of the transmitted signal. The transmit power is typically reduced as much as possible without compromising communication. One approach is to reduce the transmitted signal power as much as possible while ensuring that the signal-to-noise ratio (SNR) is not below an acceptable level. When the SNR is below an acceptable level, increasing the power restores the SNR to an acceptable level.

This approach has certain advantages because the minimum power consumed by the communication is optimized. When the operating conditions are less than optimal or ideal (e.g., inside a building, in bad weather, etc.), the transmit power is increased to maintain an acceptable SNR and communication quality.

Wireless communication devices (i.e., cellular telephones) may be remotely controlled by some system (e.g., cellular or other wireless communication system). That is, a portion of the communication bandwidth between the device and the base station transceiver is dedicated to transmitting commands and status information. The command and status portions of the bandwidth are used to adjust the power at which the device transmits signals. When the SNR of the communication signal received by the base station is below an acceptable level, the base station sends a command to the wireless device to increase the transmit power. Likewise, if the SNR of the received communication signal is within acceptable limits, the base station commands the device to reduce the transmit power.

However, most conventional systems are limited in the way that they control the transmitter power of the wireless communication device. There is a need for an apparatus and method for optimizing power control in a wireless communication system.

Disclosure of Invention

The present invention is a new and improved apparatus and method for optimizing the setting of thresholds for controlling transmitter power in a communication system. According to the present invention, two parameters are used to determine whether the threshold needs to be adjusted. These two parameters are the operation of the system relative to established thresholds and system performance.

According to the present invention, if the performance of the system is degraded and the system is operating at a threshold, this is an indication that an increase in the threshold is required. Thus, the present invention increases the threshold. Accordingly, the power control portion of the communication system detects that the system is operating below a threshold (i.e., a newly increased threshold) and increases system power according to a power control mode. As a result, the performance of the system is improved. The threshold is further increased if the performance is still decreasing and the system is operating again with the new threshold. This process continues until the system performance returns again to an acceptable level.

Note that if the system performance decreases and the system is operating below the threshold, this is an indication that the threshold need not be adjusted and that the power of the transmitter needs to be increased to raise the system to the threshold. In one embodiment, this is achieved by increasing the power of the transmitter depending on the power control mode of the communication system.

If the system performance is better than desired, this is an indication that the transmitter power may be greater than desired. When system performance is better than desired, the present invention determines whether the system is operating above a threshold. If so, the power of the transmitter is reduced in accordance with the power control mode of the communication system. However, if performance is better than desired and the system is operating at or below the threshold, this is an indication that the threshold may be lowered. Thus, the present invention lowers the threshold. Accordingly, the power control portion of the communication system detects that the system is operating above a threshold and reduces system power according to a power control mode. As a result, the power consumption of the transmitter is reduced. The threshold is further reduced if the performance is still better than required and the system is still operating at or below the new threshold. This process continues until the system performance returns to normal levels again.

Note that if the performance of the system is more than needed and the system is operating above a threshold, this is an indication that the transmitter power should be reduced and that it may not be necessary to adjust the threshold.

In one embodiment, the threshold determination is based on a signal-to-noise ratio (SNR) of the signal received at the receiver. The required SNR level is established as the threshold level. The actual SNR of the received signal is compared to a threshold SNR to determine the operation of the system relative to the threshold.

In one embodiment, system performance is determined based on the error rate of the system. In another embodiment, other metrics are used to determine system performance, such as frame errors, bit error rates, or some other indication of system performance.

An advantage of the invention is that power consumption is reduced as a result of dynamic adjustment of the threshold. Lowering the threshold when the signal quality is high allows the system to reduce transmitter power, thereby reducing power consumption. Increasing the threshold as the signal quality decreases allows the system to maintain an acceptable level of performance.

The features, objects, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings.

Brief description of the drawings

The invention is described below with reference to the accompanying drawings. In the drawings, like reference numerals indicate functionally identical or similar elements. Further, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears.

Fig. 1 is a block diagram illustrating an example communication system.

Fig. 2A and 2B are diagrams illustrating an example process of switching between power control modes.

Fig. 3 is an operational flow diagram generally illustrating an example process of determining and selecting an appropriate power control mode.

FIG. 4 is an operational flow diagram illustrating a process of determining whether to increase a threshold level according to one embodiment of the present invention.

FIG. 5 is an operational flow diagram illustrating a process of determining whether to increase a threshold level according to another embodiment of the present invention.

Preferred embodiments of the invention

I. Summary and discussion of the invention

The present invention is directed to an apparatus and method for providing one or more modes of power control to a communication device. The present invention is further directed to determining and selecting an optimization mode for power control of a communication device based on system performance. Specific embodiments are described below.

Example Environment

Before describing the present invention in detail, it is useful to describe an example environment in which the present invention can be implemented. In a broad sense, the present invention may be implemented in any wired or wireless communication system, particularly one in which it is desirable to control the amount of power provided by a transmitter. Such environments include, but are not limited to, cellular communication systems, personal communication systems, satellite communication systems, and many other well-known systems.

Fig. 1 is a diagram illustrating an example communication system 100. Referring to fig. 1, an exemplary communication system has two transceivers 104a and 104 b. Each transceiver 104a and 104b has a transmitter 108a and 108b and a receiver 112a and 112b, respectively.

Data or other information is transmitted from the transmitter 108(108a, 108b) to the receiver 112(112b, 112a) in another transceiver 104(104b, 104a) that is intended to receive the signal via a transmit path 122. In satellite, cellular, and other wireless communication systems, the transmit path 122 is over the air. However, the invention is not limited to this application and the transmission path 122 may be a wired or other signal transmission medium known in the art.

In some circumstances, transmit path 122 is a packetized data path that transmits data in data packets. This is often the case where the information is in the form of digital data. In other circumstances, analog data is modulated onto a carrier wave and transmitted over transmit path 122.

In the example of a cellular communication system, one transceiver 104(104a, 104b) may be or be located in a hand-held or mobile cellular telephone, while the other transceiver 104(104b, 104a) is located in a base station at a local cell site (cell cite) or physical location that provides service in the current area of the wireless device or telephone. In the example of a satellite communication system, one transceiver 104(104a, 104b) may be a handheld mobile or fixed transceiver (i.e., a satellite phone), while the other transceiver 104(104b, 104a) is located in a gateway (or ground station gateway). As is well known in the art, in the example of a satellite communication system, a satellite (not shown) is used to relay signals between the transceivers 104(104b, 104 a). Alternatively, in the example of a satellite communication system, a transceiver 104 may be located on the satellite.

The invention is described in terms of this example environment. This is described here merely for convenience. The present invention is not limited to application in this example environment. Indeed, it will become apparent to one of ordinary skill in the relevant art(s) after reading the following description how to implement the invention in other environments where the power of a wireless device is or may be controlled remotely.

Power control

In a communication system, power may be controlled using a power control scheme called "power control mode". For purposes of discussion, there are at least two power control modes: "tracking mode" and "burst (burst) mode". The tracking mode and burst mode of power control allow power to be increased when system performance drops below acceptable levels. However, in burst mode, the amount of power increase is greater than the amount of power increase provided in tracking mode.

The selection between tracking mode and burst mode is implemented according to the system performance of the communication link. Specifically, if the system performance is within a preselected, prescribed range, then the tracking mode is utilized. However, if system performance drops below this specified range, burst mode of power control is utilized. The use of burst mode allows the system performance to reach the specified range faster than in the case of tracking mode.

Thus, the tracking mode is well suited for controlling power in a defined operating state where the SNR changes by a small amount above or below a threshold level. In contrast, burst mode is well suited for controlling power in situations where a large power drop is experienced. This may be the case, for example, because the communication link is blocked by a large building or other interfering structure or condition.

In one embodiment, system performance is based on the signal-to-noise ratio (SNR) of a signal transmitted by a transmitter, such as transmitter 108a or 108 b. In this embodiment, the tracking mode causes a small increase in power when the signal-to-noise ratio (SNR) drops below an acceptable level. Burst mode also increases power when the signal-to-noise ratio (SNR) drops below an acceptable level. However, in burst mode, the amount of power increase is greater than that provided by tracking mode. Selection between the two modes is achieved according to how much the SNR drops below an acceptable level. I.e. according to whether the performance of the communication link is considered to be specified. In another embodiment, system performance is not dependent on SNR, but is based on received signal strength.

In another embodiment, system performance is based on the number of frames received with errors. In this embodiment, if the receiver receives a large number of erroneous frames or data (or a specified number of consecutive frames with errors) within a given time period, the burst mode is selected to control the power. On the other hand, if the receiver receives frame errors only occasionally, the tracking mode is selected.

In one embodiment, the power of each mode is incremented between. That is, for a given command or determination to increase power, the power is increased by a preselected incremental amount. The power is not increased again until a subsequent command or determination is made to increase the power again. In another embodiment, for a given command or determination to increase power, the power is stepped up until a subsequent command is received to terminate the power increase. In either embodiment, burst mode provides a greater power increase than tracking mode. That is, the burst mode provides a larger incremental power increase in the first embodiment, and a faster rate of increase in the second embodiment.

Fig. 2A is a diagram illustrating an example operating scheme for controlling power in tracking mode only. In fig. 2A, the horizontal axis represents time and the vertical axis represents SNR. Horizontal line 204 shows the threshold SNR. Line 208 over time shows an example of the actual SNR of the transmitted signal. In the example shown in fig. 2A, the device performs a prescribed operation until time T₁. In this region, the SNR 208 of the transmitter 108 changes by a small amount around the SNR threshold 204. The transmitted power is adjusted in small increments. When the SNR 208 falls below the threshold 204, the work is doneThe rate is incremented. Conversely, when the SNR 208 rises above the threshold 204, the power is decremented. Power regulation is performed using command or control and operation techniques known in the art.

At time T₁At this point, the SNR of the signal traversing (diverting) the transmit path 122 is significantly reduced. This may occur, for example, when a path is blocked. In the tracking mode, power is incremented to improve SNR. However, since the power increases only slightly with each increment in tracking mode, a long time passes before the SNR again reaches an acceptable level. This is defined by the duration t_aAs shown.

Fig. 2B is a diagram illustrating an example operating scheme for selectively controlling power in a tracking mode and a burst mode. As shown in fig. 2A, in fig. 2B, the horizontal axis represents time, and the vertical axis represents SNR. Horizontal line 204 shows the threshold SNR. Line 208 over time shows an example of the actual SNR of the transmitted signal. In the example shown in fig. 2B, the device performs a prescribed operation until time T₁. In this region, the SNR 208 of the transmitter 108 changes by a small amount around the SNR threshold 204. During this time period, the transmitter operates in a tracking mode, adjusting the transmitted power in small increments. When the SNR 208 falls below the threshold 204, the power is incremented.

At time T₁When the transmit path 122 is blocked and the SNR drops significantly, the transmitter power control mode is switched to burst mode. As described above, in the burst mode, the power is increased more than in the tracking mode. Thus, the amount of time t required for the SNR to return to an acceptable level_bThan the time t required in tracking mode_aMuch shorter. At time T₂At this point, when the SNR 208 reaches the threshold 204, the transmitter 108 switches to the tracking mode.

Note that burst mode is generally not desired to be maintained during a defined operating state. This is because a small reduction in SNR results in a large increase in transmitted power in burst mode. This may cause the SNR 208 to rise above the threshold 204 due to excessive transmitter power and consume excessive power. This wastes power and is highly undesirable in systems where power is limiting or where power impacts capacity. Oscillation (oscillatory) conditions that overshoot (overshooting) in each direction may also occur in some cases when the system attempts to compensate and return to the threshold level.

In one embodiment, the selection of the power control mode is made by the receiver 112. In this embodiment, the receiver 112(112a, 112b) instructs the transmitter 108(108b, 108a) (relative to the transceiver 104) to switch the power control mode as necessary. This may be done, for example, in the command portion of the transmitted signal. In another embodiment, the receiver 112 returns information to the transmitter 104 to enable the transmitter 104 to determine whether to switch the power control mode. For example, in this alternative embodiment, receiver 112 may send one or more indications, such as a frame error indication, a bit error rate (biterror rate) value, an SNR value, or some other indication of whether the performance of the system is at an acceptable level.

Fig. 3 is an operational flow diagram generally illustrating a process of determining and selecting an appropriate power control mode in accordance with one embodiment of the invention. At step 304, the receiver 112(112a, 112b) receives the signal transmitted by the transmitter 108(108b, 108 a). In the example environment described above, signals are transmitted over transmission path 122.

The receiver 112(112a, 112b) determines whether the SNR 208 of the received signal exceeds, is at, or is below the preselected threshold 204. This may be done independently of the power control mode in which the communication system is operating. Decision step 308 illustrates this determination. If the SNR 208 of the received signal is above the threshold 204, the power is adjusted downward and the operation returns to step 304 where the receiver 108 continues to receive the transmitted signal. This is shown as step 310 and flow line 362.

If SNR 208 is at threshold 204 and no adjustment is needed, then operation returns to step 304 as indicated by flow line 364. In one embodiment, threshold 204 is not implemented as a single value, but may comprise a receivable range of SNR values.

On the other hand, if the SNR 208 is below the threshold, then operation of the present invention proceeds to step 312. At step 312, the receiver 112 determines whether the drop in SNR 208 is greater than a specification. In other words, the receiver 112 determines whether the SNR 208 is lower than an acceptable amount below the threshold 204 and therefore does not want the tracking mode because it takes longer than necessary to return the SNR 208 to the threshold 204.

If the drop in SNR 208 is within the specified limits, the power control mode is selected as the tracking mode as indicated by block 316. If the power control mode is already the tracking mode, the transmitter 108 maintains the tracking mode. However, if the current power control mode is burst mode, block 316 represents changing from burst mode to tracking mode. At step 320, the power of the transmitter is adjusted in a tracking mode. The receiver 112 continues to receive transmissions as indicated by flow lines 366, 364.

If the drop in SNR 208 exceeds the prescribed limit, the power control mode is selected as burst mode, as shown in step or block 326. The transmitter 108 maintains the burst mode if the power control mode is already the burst mode. However, if the current power control mode is tracking mode, step 326 represents changing from tracking mode to burst mode. At step 330, power is adjusted in a burst mode. The receiver 112 continues to receive transmissions as indicated by flow line 368.

The threshold and values below the threshold may be selected to meet a particular application. In one embodiment, the threshold is not a single value but a range of values, such that a received signal is said to be at the threshold as long as the signal is within the range.

In one embodiment, the determinations of steps 308 and 312 are not made based on SNR per se, but rather are made based on the number of frames received with errors. For example, in one mode of the present embodiment, the receiver 112 determines how many frames out of the X frames received in the past have errors. In this example, if more than Y frames out of the most recently received X frames have errors, indicating that the error rate is outside of an acceptable range, then the preferred power control mode is burst mode.

In another mode of the present embodiment, the receiver 112 determines how many consecutive frames with errors are received. If the number of consecutive frames received with errors meets or exceeds a predetermined limit, indicating that the error rate is outside an acceptable range, then the preferred power control mode is burst mode. The determination of the number of received frames with errors may be accomplished using well-known techniques, for example, using a Cyclic Redundancy Check (CRC) code.

In another embodiment, the present invention focuses on the Bit Error Rate (BER) of the received signal. A BER rise above the threshold is similar to a SNR 208 drop below the threshold 204. If the BER rises above the threshold by a predetermined amount, the system is no longer operating as specified and the preferred power control mode is burst mode.

It will become apparent to one skilled in the relevant art how to utilize other parameters in conjunction with the present invention to determine whether a system is operating as specified.

In the above embodiments, it was described that the receiver 112 determines whether the system is at, above, or below the threshold and whether the system is operating as specified. In this embodiment, receiver 112(112a, 112b) sends a command to transmitter 108(108b, 108a) instructing transmitter 108 to change modes at the appropriate time. In another embodiment, receiver 112 simply provides telemetry to transmitter 108. This telemetry provides transmitter 108 with sufficient information to determine whether the preferred power control mode is a tracking mode or a burst mode.

In one configuration, the receiver provides two feedback indicators in the form of bits (bits) in a message or command. One bit is used to indicate "tracking mode up/down command" and the other bit indicates "burst mode transmit level adjustment". Which is acted upon or implemented by the transmitter. The transmitter makes the determination based on factors such as the number of consecutive frame errors, but is not so limited. In this scheme, the system is provided with a faster reaction time because important events such as errors are reported to the transmitter immediately for power control purposes at the expense of increased bandwidth consumption.

In embodiments where receiver 112 commands transmitter 108 to switch power control modes, the commands may be lost during transmission. Any of several different techniques may be used to control the present scheme. One technique is to use an acknowledgement message to acknowledge receipt of the command.

The second technique is simply to send commands continuously. For example, if the system is operating outside of a specified range, the receiver 112 sends a command during each command frame to track in burst mode until the system returns to specified operation. This technique consumes more bandwidth than is necessary because the command is repeated, and this repetition is in many cases unnecessary. For this reason, this technique may be undesirable.

According to another technique, whether to effect a power control change or command is simply ignored. That is, no check is made to determine whether the transmitter 108 is actually switching power control modes as commanded. While this embodiment may appear counterintuitive, it is actually a preferred embodiment. To understand the reason for this, consider two cases where the switch mode command can be sent by the receiver 112 and where the transmitter 108 does not receive the switch mode command. In the first case, where the SNR 208 is substantially reduced, the receiver 112 commands the transmitter 108 to switch the power control mode to the burst mode. If the transmitter 108 does not receive the command, the only negative result is that the transmitter 108 continues to control power in tracking mode. That is, it takes more time to return to the prescribed operation than in the case where the transmitter 108 receives the command.

In the second case, the transmitter 108 operates in a burst mode and the signal has returned to the specified range. If the transmitter 108 does not receive a command from the receiver 112 to change to tracking mode, the power may be increased more than necessary. However, this is not a fatal error because the system continues to operate. Its only disadvantage is that more power is consumed than is necessary.

After reading the above description, it will become apparent to one skilled in the relevant art how to implement power control mode selection instead of or in addition to tracking mode and burst mode.

Optimization of threshold values

As described above, most power control schemes rely on comparing a communication system parameter (i.e., such as SNR, power level, etc.) to a threshold for that parameter. However, there are also situations where the communication system may operate at or near a threshold and still experience an unwanted level or drop in error. In these cases, the established threshold is too low to achieve acceptable communication.

One criterion used to determine the acceptability of a communication channel is called the "quality" of the signal. When the quality of the signal is high, the system may operate at or near a given threshold without experiencing significant degradation in system performance. However, when signal quality deteriorates, operating at or near the same threshold may result in an unacceptable level of system performance. In other words, a communication system with a higher signal quality may operate at a lower threshold while still maintaining a given level of system performance.

One condition that affects signal quality occurs, for example, when a portable or mobile communication device is operating in an area where signals are blocked. For example, consider a user moving with a portable communication device from a rural area to a metropolitan area. When the user is in a rural area, there are few obstacles. At this setting, the quality of the signal is high and it is acceptable to operate at a given threshold.

When a user enters a large city, several tall buildings block the communication path. As a result of these blockages, the quality of the signal arriving at the receiver from the portable communication device will deteriorate. As a result, even when the device operates at the threshold, the number of errors that occur may increase and system performance deteriorates. To compensate for the degradation in quality, it is desirable to increase the power of the portable communication device to operate above a threshold. However, if the portable communication device is operating in a conventional power control scheme, the power does not increase above the threshold. Therefore, the present invention increases the threshold value, so that the power control mode increases the power of the transmitter.

The present invention increases the threshold of the system such that the power control mode increases the power of the transmitter. In accordance with the present invention, a power control mode is used to maintain the signal level (here, SNR) at a threshold. In addition, the present invention checks system performance (such as error rate) to maintain and update thresholds to maintain acceptable performance levels.

In operation, the present invention determines whether the threshold needs to be modified. According to one embodiment, this determination is made based on two factors: the number of differences between the signal level and the threshold, and a predetermined measure of system performance such as the error rate of the system. If the signal level is at or near the threshold, the system performance is unacceptable (e.g., an excessive number of errors are received), which may be an indication that the threshold needs to be increased. Similarly, if the signal is at or near a threshold and system performance is much better than desired (e.g., error rate is much lower than an established tolerable level), the threshold can be lowered, thereby conserving transmitter power.

Preferably, in one embodiment, the signal level measurement is a comparison of SNR 208 to SNR threshold 204; the metric used to determine system performance is based on the number of errors in the received signal or the number of frames received with errors in the past N frames. After reading this description, it will become apparent to one skilled in the relevant art that the present invention may effect determination of system performance with different parameters and/or different measures of signal strength. For example, the signal level may be the signal strength without regard to the noise level or some other operating parameter. Further, the determination of errors for use as a system metric may be made based on the number of errors in the received signal, the frame error rate, the number of consecutive frame errors, the error rate, or other factors.

Fig. 4 is a diagram illustrating a process of determining whether to increase a threshold according to one embodiment of the present invention. Referring now to fig. 4, the receiver 112 receives a signal from the transmitter 108 and evaluates signal parameters at step 404. As described above, in the preferred embodiment, these parameters are the SNR 208 and the number of frame errors received in the past N frames. For ease of description, this process is described in terms of these parameters, but other parameters may also be utilized as described above.

In step 408, the system checks the number of frame errors made in the past N frames to determine if this number of frame errors is acceptable. If the number of frame errors generated in the past N frames exceeds the established number, this indicates that the system performance is below an acceptable established level. In one embodiment, N is 300, but N may be selected as how many.

If the number of frame errors generated in the past N frames is at a desired level (or within an acceptable range), the system continues to control power using this power control mode for normal operation. This is shown as step 412.

If the number of frame errors generated in the past N frames exceeds the established number (or range), operation continues to step 416 where the present invention determines if the SNR 208 is specified. I.e., whether the SNR is sufficiently close to the threshold 204. In one embodiment, this determination is made by measuring the integrated difference between the measured SNR 208 of the received signal and the threshold 204.

If the SNR 208 is at or near the threshold 204 and the error rate is not acceptable (as determined in step 408), this indicates that the threshold 204 needs to be increased. This occurs at step 420.

However, if the SNR 208 is below the threshold 204 and the error rate is not acceptable (as determined in step 408), this indicates that the power control mode is operating properly. Threshold 204 is not increased because SNR 208 below threshold 204 may result in an unacceptably high error rate (as determined in step 408). Thus, the system continues to control power using this power control mode normal operation at step 412.

Returning now to step 408, if it is determined in step 408 that the number of frame errors made in the past N frames is below the desired number (or range), this is an indication that the threshold 204 may be too high. Thus, at step 424, the system determines whether the SNR 208 is at or near the threshold 204. In one embodiment, this determination is made by measuring the integrated difference between the measured SNR 208 of the received signal and the threshold 204.

If the SNR 208 is above the threshold, the power control mode will reduce the power to keep the system properly. However, if the SNR 208 is at or near the threshold and the error rate is better than expected, this indicates that the threshold 204 may be lowered. This occurs at step 428.

Fig. 5 is a diagram illustrating a process of increasing a threshold value according to another embodiment of the present invention. Referring now to fig. 5, the receiver 112 receives a signal from the transmitter 108 and evaluates the signal parameters at step 504. As described above, in the preferred embodiment, these parameters are the SNR 208 and the number of frame errors received in the past N frames. For ease of description, this process is described in terms of these parameters, but may be replaced with other parameters as described above.

In step 508, the present invention determines whether the system is operating at or sufficiently close to threshold 204. The invention then determines whether the number of errors is acceptable, above normal or below normal.

If the error rate is above normal and the system is operating at or near threshold 204, the threshold is increased as shown in steps 508, 524 and 516.

If the error rate is below normal and the system is operating at or near the threshold, the threshold 204 is lowered as shown in steps 508, 524 and 520.

If the error rate is normal and the system is operating as specified with respect to the threshold, then threshold 204 need not be adjusted and the system continues to adjust power in the desired power control mode. This is shown as steps 508, 524 and 532.

If the error rate is above normal and the system is operating above threshold 204, threshold 204 is increased. This is shown as steps 508, 528 and 520.

If the error rate is below normal and the system is operating above the threshold, the threshold 204 is not adjusted and power is reduced according to the power control mode. This is shown as steps 508, 528 and 532.

If the error rate is below normal and the system is operating below threshold 204, then threshold 204 is lowered as shown in steps 508, 512, and 516.

If the error rate is above normal and the system is operating below threshold 204, then threshold 204 is not adjusted and power is increased according to the power control mode. This is shown as steps 508, 512 and 532.

Conclusion V

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (20)

1. A method for adjusting a threshold in a communication system having at least one mode for controlling power of a transmitter in the communication system during system operation, the method comprising the steps of:

determining performance of the communication system based on a predetermined metric;

determining a power of a transmitter in the communication system relative to a threshold for communication; and

adjusting a value of a threshold and adjusting a power of a transmitter relative to the threshold in accordance with the performance of the communication system.

2. The method of claim 1, wherein said adjusting step comprises the step of increasing said threshold of the communication system when the system is operating at or near the threshold and the performance of the system is below an acceptable level.

3. The method of claim 1, wherein said adjusting step comprises the step of reducing the threshold of the communication system when the system is operating at or near the threshold and the performance of the system is above an acceptable level.

4. The method of claim 1, wherein the predetermined metric is one of a group of error rate, frame error rate, number of consecutive frame errors, and bit error rate for the system.

5. The method of claim 1 wherein said step of determining the performance of the communication system further comprises the step of determining whether a parameter of the communication system is within a defined range.

6. The system of claim 5, wherein said parameter is selected from the group consisting of signal-to-noise ratio, received signal strength, frame error rate frequency, number of consecutive frame errors, and bit error rate.

7. The method of claim 5, further comprising the step of selecting a power control mode based on said determination of whether said parameter is within a range.

8. The method of claim 7, further comprising the step of adjusting the power of the transmitter in accordance with the selected power control mode of the communication system.

9. The method of claim 8 wherein said adjustment of power is an incremental increase in power.

10. The method of claim 7, wherein said step of selecting a power control mode is performed at a transmitter.

11. The method of claim 7, wherein said step of selecting a power control mode is performed at a receiver location, and further comprising the step of sending a command from the receiver location to the transmitter to select the desired power control mode.

12. An apparatus for adjusting a threshold in a communication system having at least one mode for controlling power of a transmitter in the communication system during system operation, the apparatus comprising:

means for determining performance of the communication system based on a predetermined metric;

means for determining a power of a transmitter in the communication system relative to a threshold for communication; and

means for adjusting the value of the threshold in dependence on said performance of the communication system and for adjusting the power of the transmitter relative to said threshold.

13. The apparatus of claim 12, wherein said performance of the communication system is measured in terms of a signal-to-noise ratio comprising a set of one or more of a signal-to-noise ratio, a received signal strength, a frame error rate frequency, a number of consecutive frame errors, and a bit error rate.

14. The apparatus of claim 12, wherein said means for determining performance of a communication system comprises means for determining whether a transmitted signal is at, above, or below a threshold.

15. The apparatus of claim 12 wherein said means for determining the performance of the communication system comprises means for determining whether a parameter of the communication system is within a defined range.

16. The apparatus of claim 15, wherein said parameter is selected from the group consisting of signal-to-noise ratio, received signal strength, frame error rate frequency, number of consecutive frame errors, and bit error rate.

17. The apparatus of claim 15, further comprising means for selecting a power control mode based on said determination of whether said parameter is within a range.

18. The apparatus of claim 17, further comprising means for adjusting the power of the transmitter in accordance with a selected power control mode of the communication system.

19. The apparatus of claim 17, wherein the means for selecting a power control mode is located at a transmitter.

20. The method of claim 17, wherein said means for selecting a power control mode is located at a receiver location, and wherein said apparatus further comprises means for sending a command from the receiver location to the transmitter to select the desired power control mode.