CN101036312A - Method and apparatus for controlling transmit power in a wireless communications device - Google Patents

Abstract

Systems and techniques for wireless communications are disclosed. The systems and techniques include the generation of a signal, the setting of an average transmit power of the signal transmission as a function of a first threshold relating to out-of-band emissions, the clipping of the signal as a function of a second threshold relating to peak transmit power, and the transmission of the signal over a wireless medium.

Description

Method and apparatus for controlling transmission power of a wireless communication device

Priority claims under 35 U.S.C. §119

This patent application claims Provisional Application No. 60/599,390, filed August 6, 2004, entitled "Method for Clipping peak Transmit Power while Limiting Out-of-Band Emissions in Wireless Communications System", assigned to the assignee of the present invention priority, which is hereby expressly incorporated by reference.

technical field

The present invention relates generally to wireless communications, and more particularly to systems and methods for controlling the transmit power of a wireless communications device.

Background technique

Wireless communication systems are designed to allow multiple users to share a common communication medium. There are countless multiple access techniques in the art, such as Code Division Multiple Access (CDMA), Time Division Multiple Access, Frequency Division Multiple Access, and many others like them. The multiple access concept is based on the allocation of channels to separate the communications of multiple users. For example, in a CDMA communication system, channel separation is achieved by modulating a carrier with a different code to transmit each signal, thereby spreading the signal across the frequency spectrum. The transmitted signal can be separated by a demodulator in the receiver by despreading the desired signal with the corresponding code. Unwanted signals with mismatched codes simply become noise.

The receiver's ability to separate the transmitted signal from the noise can be measured by the signal-to-noise ratio (SNR). The average signal transmit power can be controlled at the transmitter to obtain a specified signal-to-noise ratio at the receiver according to quality of service requirements. Typically, higher signal-to-noise ratios are required to achieve the higher data rates required for video or other high-bandwidth transmissions. Higher signal-to-noise ratios are also required when the transmitter is farther away from the receiver. In both cases, the SNR improvement can be achieved by increasing the average signal transmission power at the transmitter. Unfortunately, this increase has the potential to cause signal power spikes to exceed regulatory limits, such as those set by the FCC. This situation can occur in code division multiple access communication systems, in which each user transmits simultaneously in the same frequency spectrum. Multilevel modulation and transmit pulse shape filtering further increase the likelihood of peak transmit power exceeding regulatory limits.

One way to increase the average transmit power while maintaining the peak transmit power within specified limits is to clip the signal when the instantaneous transmit power exceeds a certain threshold. However, clipping the signal can significantly increase out-of-band radiation and cause signal distortion. Out-of-band emissions are also regulated, thus significantly limiting the use of clipping to reduce signal power spikes.

Therefore, there is a need in the art to optimize the average transmit power, maintain the required quality of service, and at the same time make the peak transmit power and out-of-band radiation still meet the regulatory limit requirements.

Contents of the invention

In one aspect, a wireless communication method of the present invention includes generating a signal; setting an average transmit power of the signal according to a first threshold related to out-of-band radiation; and clipping the signal according to a second threshold related to peak transmit power ; and transmitting the signal over a wireless medium.

In another aspect, a wireless communication device of the present invention includes a user interface configured to generate a signal; a power control module configured to set an average transmit power of the transmitter according to a first threshold related to out-of-band radiation; a peak amplitude a limiter configured to limit the signal according to a first threshold related to a peak transmit power; and a transmitter configured to transmit the signal over a wireless medium.

In yet another aspect, a wireless communication device of the present invention includes means for generating a signal; for setting an average emission of said signal emission according to a first threshold related to out-of-band radiation resulting from clipping said signal means for power; means for clipping the signal according to a second threshold related to peak transmit power; and means for transmitting the signal over a wireless medium.

Obviously, other embodiments of the invention will become apparent to those skilled in the art from the following detailed description, in which various embodiments of the invention are described illustratively. The invention is capable of other and different embodiments, and its several details can be modified in various respects, all without departing from the scope and spirit of the invention. Accordingly, the drawings and detailed description are illustrative and not present execution.

Description of drawings

Figure 1 is a functional block diagram illustrating an example of a variable data rate code division multiple access communication system;

Figure 2 is a functional block diagram illustrating an example of a subscriber station used in a variable data rate code division multiple access communication system;

Figure 3 is a functional block diagram illustrating an example of a power control module used by a subscriber station operating in a variable data rate code division multiple access communication system;

Figure 4 is a functional block diagram illustrating one embodiment of a peak amplitude limiter used by a subscriber station operating in a variable data rate code division multiple access communication system; and

Figure 5 is a functional block diagram illustrating another embodiment of a peak amplitude limiter for use by a subscriber station operating in a variable data rate code division multiple access communication system.

Detailed ways

The detailed description given below in conjunction with the accompanying drawings is a description of various embodiments of the present invention, and does not mean that they are the only embodiments for practicing the present invention. The detailed description includes numerous specific details in order to facilitate a comprehensive understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form so as not to overwhelm the main topic.

In the following detailed description, various power control techniques may be described for a code division multiple access wireless communication device. Although these power control techniques are well suited for this application, it will be apparent to those skilled in the art that these aspects of the invention can be equally applied to various other communication and/or electronic devices. Accordingly, any reference to a code division multiple access wireless communication device is merely illustrative of some aspects of the present invention, which have broad applicability.

1 is a functional block diagram illustrating an example of a code division multiple access communication system employing a variable data rate request scheme. This code division multiple access communication system can include a wireless network 102 having a base station controller (BSC) 104 . The wireless network 102 and the communication network 105 may be connected by a base station controller 104 . The communication network 105 may be a packet network, such as the Internet, an enterprise network, and the like. Communications network 105 may also be a circuit switched network, such as the Public Switched Telephone Network (PSTN). Wireless network 102 may be implemented with any number of base stations distributed throughout a geographic area. This geographic area can be further divided into smaller areas called cells, each cell being served by a base station. For simplicity, one base station 106 is shown, which is under the control of the base station controller 104 to serve an entire sector. Three subscriber stations 108a-c are shown communicating with base station 106. Each subscriber station 108a-c may access the communication network 105, or otherwise communicate with other subscriber stations, through one or more base stations.

In this illustrative code division multiple access communication system, the forward link and reverse link data rates can be controlled by techniques known in the art to optimize system capacity. "Forward link" refers to transmissions from base station 106 to subscriber station 108 and "reverse link" refers to transmissions from subscriber station 108 to base station 106 . For purposes of illustration, the concepts of the invention will be described with respect to the reverse link, with the understanding that the concepts of the invention can be applied to the forward link as well.

In the reverse link, base station 106 may determine the data rate for reverse link communications with each subscriber station within its cell. The data rate selected by base station 106 may be based on the type of communication supported, or other criteria. For example, for communications with video applications, the base station may determine that a high data rate is required. Conversely, base station 106 may select a lower data rate for voice communications. Other factors may also be considered by the base station when deciding to assign a particular data rate to the subscriber station 108 . For example, a fairness criterion that takes into account the amount of information to be transmitted by the subscriber station 108 and the delay that the subscriber station 108 has experienced may be considered. In any case, the data rate selected by the base station 106 may be embedded in the forward link transmissions to the subscriber stations 108 .

A power control system can be used to reduce mutual interference between multiple subscriber stations operating in the same cell. The average reverse link transmit power is usually controlled through two power control loops. The first power control loop is an open loop. Open-loop control is designed to control the average reverse link transmit power based on path loss, base station loading effects, and environmentally induced phenomena such as fast fading and shadowing. The second power control loop is a closed loop. The closed-loop control can correct the open-loop control to achieve the desired signal-to-noise ratio and frame error rate (FER) at the base station. This may be accomplished by measuring the average reverse link transmit power at base station 106, providing a feedback signal to subscriber station 108, and adjusting the average reverse link transmit power. Both open loop control and closed loop control are well known in code division multiple access communication systems.

In the illustrative embodiment of the CDMA communication system described thus far, it is possible that the reverse link peak transmit power measured over a certain period of time is significantly higher than that measured over a longer period of time average power. The relationship between the two can be defined in terms of peak-to-average ratio (PAR). If a power control system is used to limit the peak transmit power according to regulatory limits, or other system requirements, then a critical PAR can be determined that gives the maximum average transmit power that meets the out-of-band radiation requirements. For example, if the system requires no more than 20 watts of peak transmit power, and it is determined that the critical PAR of the subscriber station is 10 times the above average transmit power, then the average transmit power needs to be limited to no more than 2 watts to meet the out-of-band radiation requirements. If the average transmit power exceeds 2 watts, the out-of-band emission requirements may not be met.

Critical PAR can be determined based on the system's requirements for peak transmit power and out-of-band emissions, as well as one or more parameters related to signal processing. The one or more parameters described above may include transmit filter characteristics, signal data rate and/or modulation scheme. Critical PAR can be determined by an offline calibration procedure. Calibration procedures can be performed in various ways. For example, a limiter can be used to clip a signal when the signal exceeds peak power while the average power slowly increases from a minimum value to a maximum value. The average transmit power can be controlled with feedback from the base station through an analog power control loop. During the calibration procedure, out-of-band emissions can be monitored with any standard test equipment. The average transmit power that causes out-of-band radiation to reach the limits imposed by system requirements is recorded. The critical PAR is then calculated from the system requirements for peak transmit power and the average transmit power recorded during the calibration procedure. In a manner described in more detail below, the critical PAR can be stored in the subscriber station and used during operation to limit the average transmit power.

In a CDMA communication system with variable transmission formats, the critical PAR may be calculated for each transmission format during a calibration procedure. Each transmission format can include data rate, modulation scheme, coding scheme and payload size. In one embodiment of the CDMA communication system, each data format can be identified by its data rate, each data rate has a fixed coding and modulation scheme, and a fixed payload size. In this embodiment, the results of the calibration procedure may be recorded as shown in Table 1 below.

Table 1 Data rate (kbps) Critical PAR(dB) 0 8.55 19.2 6.88 38.4 6.03 76.8 5.17 115.2 4.81 153.6 4.55 230.4 4.43 307.2 4.34 460.8 5.63 614.4 5.48 921.6 6.53 1228.8 6.36

Table 1 lists the critical PAR for each data rate. This table can be stored in the subscriber station 108 and used during operation to limit the average transmit power of the subscriber station. This enables different average transmit powers to be used for each data rate so that the highest allowed average transmit power is always used.

Figure 2 is a functional block diagram illustrating an example of a subscriber station used in a variable data rate code division multiple access communication system. Subscriber station 108 may include receiver 202 and transmitter 204 coupled to antenna 206 . The peak and average power of the transmitter 204 may be controlled by a power control module 209 .

Receiver 202 may include a receiver analog front end (AFE) 208 and a receiver processor 210 . Receiver analog front end 208 may be used to amplify, filter and downconvert radio frequency (RF) signals received from antenna 206 to digital baseband signals. The receiver analog front end 208 may also provide a receiver signal strength indicator (RSSI) signal to the power control module 209 to calculate the path loss between the base station and the subscriber station for open loop control.

The digital baseband signals generated by receiver analog front end 208 may be provided to receiver processor 210 . Receiver processor 210 may be used to convert the digital baseband signals into the information required to drive various user interfaces 211 (eg, display, ringer, vibrator, speaker, etc.). Converting the digital baseband signal to this information may involve various signal processing functions including demodulation, forward error correction and spread spectrum processing.

The digital baseband signal may also include multiple control signals. One such control signal is feedback from the base station indicating whether to increase or decrease the average transmit power at the reverse link base station. This feedback signal can be extracted by the receiver processor 210 and provided to the power control module 209 for closed-loop control calculation. Another control signal included in the digital baseband signal may be a command for the subscriber station to operate at a specific data rate. Receiver processor 210 may be used to extract this command and provide it to transmitter 204 .

The transmitter 204 may include a transmitter processor 212 . Transmitter processor 212 may use data rate commands from receiver processor 210 to control information received from various user interfaces (e.g., keypad, touchpad, mouse, joystick, microphone, digital camera, etc.) The data rate of the resulting digital baseband signal. Transmitter processor 212 may also provide various signal processing functions, such as coding for forward error correction at the base station, and modulation and spread spectrum processing.

A peak amplitude limiter 214 may be used to limit the peak transmit power where this is required, for example, to comply with regulatory limits. As will be described in more detail below, the peak amplitude limiter 214 may apply a clipping algorithm to the digital baseband signal to limit the peak transmit power based on the input it receives from the power control module 209 . Although the peak amplitude limiter 214 is drawn as a separate entity in the transmitter 204, it is clear to those skilled in the art that the peak amplitude limiter 214 may be a part of the transmitter processor 212 or a part of the subscriber station. any other entity. Additionally, peak amplitude limiter 214 may also be implemented in the analog domain as part of transmitter analog front end 218 .

In the subscriber station embodiment shown in FIG. 2, the power limited signal from peak amplitude limiter 214 may be provided to transmitter analog front end 218. A transmitter analog front end 218 may be used to upconvert the digital baseband signal to a radio frequency signal, while filtering and amplifying. The gain control signal generated by the power control module 209 may be used to control an amplifier in the analog front end 218 of the transmitter. In a manner to be described in detail hereinafter, the gain control signal can be generated from the open loop and closed loop power control loops to limit it to the highest level at which out-of-band emissions and distortion caused by clipping the signal meet system requirements.

Figure 3 is a functional block diagram illustrating an example of a power control module for a subscriber station operating in a variable rate code division multiple access communication system. Although the power control module 209 is drawn as a separate entity in the subscriber station 108, it will be clear to those skilled in the art that the power control module 209 may be implemented in the transmitter 204, receiver 202 or anywhere else in the subscriber station 108. The power control module 209 may be implemented as hardware, software, firmware, or any combination thereof. As an example, the power control module 204 may be implemented as power control software running on a microprocessor. The microprocessor may be dedicated to running power control software independently of the transmitter 204 and receiver 202 . Alternatively, the power control software may be run by an existing microprocessor in the transmitter 204, receiver 202, or anywhere else in the subscriber station 108.

The power control module 209 may include two power control loops. Open loop control 302 may be used to generate an estimate of the required average transmit power based on the average of the RSSI signal from receiver analog front end 208 in a manner known in the art. Closed loop control 304 may be used to generate a closed loop estimate from the feedback it receives from the base station via receiver processor 210, also in a manner known in the art. The closed loop estimate can be used to increase or decrease the current open loop estimate. This can be done by using adder 306 to add the closed loop estimate and the open loop estimate. The sum of the closed loop estimate and the open loop estimate gives a gain control signal which represents the average reverse link power required by the base station.

The gain control signal generated by summer 306 may be provided to limiter 310 prior to application to transmitter analog front end 218 . Limiter 310 may be used to ensure that the average transmit power does not cause out-of-band radiation and distortion beyond system requirements. This is accomplished by an algorithm 312 that determines the maximum average transmit power from the critical PAR for the data rate and the modulation scheme employed by the subscriber station. The critical PAR may be obtained from a look-up table 314 that maps the data rate and modulation scheme to the critical PAR for each data rate for a variable data rate subscriber station with a particular modulation scheme, such as Table 1 given above.

Converter 316 may be used to convert the gain control signal generated by summer 306 into an average transmit power (P_avg) expressed in decibels. The average transmit power P_avg represents the employed transmit power and is related to the transmit power radiated according to the antenna gain. Transformer 316 may be a look-up table generated during subscriber station calibration.

Algorithm 312 can be used to ensure that the average transmit power P_avg resulting from the gain control signal satisfies the following expression:

P_avg＜P_max-Critical PAR (1)

Among them, P_max represents the system requirement on the peak transmit power. For example, the peak transmit power P_max may be set to a prescribed limit. The peak transmit power P_max can be programmed into the limiter 310 or supplied to it from an external memory in the subscriber station.

In the case that the average transmit power does not satisfy the formula (1), the algorithm 312 may reduce the average transmit power P_avg to the limit given by the peak transmit power P_max minus the critical PAR. This is the maximum average transmit power at which the out-of-band radiation and distortion obtained after limiting the signal meet the system requirements. The average transmit power P_avg set by the algorithm 312 may be sent back to the converter 316 for conversion into a gain control signal before being provided to the transmitter analog front end 218 .

The average transmit power P_avg generated by the converter 316 from the gain control signal may also be provided to the peak amplitude limiter 214 in the transmitter. The peak amplitude limiter 214 can be used to measure the average root mean square (RMS) envelope power of the digital baseband signal over a time window and adjust the complex envelope when it exceeds the equivalent value of P_max.

Figure 4 is a functional block diagram illustrating one embodiment of a peak amplitude limiter for use with a transmitter operating in a variable data rate subscriber station. Peak amplitude limiter 214 may be configured to receive a digital baseband signal from transmitter processor 212 . A digital baseband signal may consist of a series of digital samples, each sample having an in-phase component I(n) and a quadrature component Q(n). The in-phase and quadrature components of the digital signal may be scaled by a pair of multipliers 402a and 402b. Scaled digital samples may be output from peak amplitude limiter 214 and provided to transmitter analog front end 218 for digitization, filtering, amplification and upconversion to a radio frequency signal.

The scaled values input to multipliers 402 a and 402 b may be generated by power detector 404 and scaled value generator 406 . The average envelope power of the digital baseband signal over a time window can be measured with the power detector 404 using the following formula:

$\mathrm{<span\; class="notranslate">\; IQ</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}<span\; class="notranslate">\; =</span>{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; I</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 0.5</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

where N is the number of digital samples in the time window.

The average envelope power of the digital baseband signal (IQ_avg) may be provided to scale value generator 406 . The scaling value generator 406 can be used to determine whether the average envelope power of the digital baseband signal exceeds the equivalent value of P_max. In the case that the average envelope power of the digital baseband signal does not exceed the equivalent value of P_max, the scaling value generator 406 provides "1" to the multipliers 402a and 402b. On the other hand, if the average envelope power of the digital baseband signal exceeds the equivalent value of P_max, the scaling value generator 406 can provide a scaling value to the multipliers 402a and 402b to clip the signal. The scaling value generator 406 can be implemented with the following formula:

$\mathrm{<span\; class="notranslate">\; amp</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; scale</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; max</span>}}}\frac{{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; I</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 0.5</span>}}}{\mathrm{<span\; class="notranslate">\; IQ</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The scaled values output from the scaled value generator 406 to the multipliers 402a and 402b can be defined as:

1/amp_scale (4)

Figure 5 is a functional block diagram illustrating another embodiment of a peak amplitude limiter for use with a transmitter operating in a variable data rate subscriber station. Similar to the embodiment described with reference to FIG. 4, the peak amplitude limiter 214 can be configured to receive a digital baseband signal from the transmitter processor 212, comprising a series of digital samples, each sample having an in-phase component I(n) and Quadrature component Q(n). In this case, however, the in-phase and quadrature components of the digital samples can be scaled independently of each other. The in-phase component may be scaled by an in-phase multiplier 502a and the quadrature component may be scaled by a quadrature multiplier 502b. Respectively scaled digital samples may be output from peak amplitude limiter 214 and provided to transmitter analog front end 218 for digitization, filtering, amplification and upconversion to a radio frequency signal.

The scaled value input to in-phase multiplier 502a may be generated by in-phase power detector 504a and in-phase scaled value generator 506a. The scaled value input to quadrature multiplier 502b may be generated by quadrature power detector 504b and quadrature scaled value generator 506b. Power detectors 504a and 504b operate independently of each other, as do scaling value generators 506a and 506b.

The in-phase power detector 504a can be used to measure the average envelope power of the in-phase component of the digital baseband signal according to the following formula:

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; I</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 0.5</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

The average envelope power of the in-phase component of the digital baseband signal (I_avg) may be provided to the in-phase scale value generator 506a. The in-phase scaling value generator 506a can be used to determine whether the average envelope power of the in-phase component of the digital baseband signal exceeds the equivalent value of P_max. In the case that the average envelope power of the in-phase component of the digital baseband signal does not exceed the equivalent value of P_max, the in-phase scaling value generator 506a provides "1" to the in-phase multiplier 502a. On the other hand, if the average envelope power of the in-phase component of the digital baseband signal exceeds the equivalent value of P_max, the in-phase scaling value generator 506a can provide the scaling value to the in-phase multiplier 502a to limit the in-phase component of the signal . The in-phase scaling value generator 506a can be implemented with the following formula:

$\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; amp</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; scale</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; max</span>}}}\frac{\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; I</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

The scaled value provided to the in-phase multiplier 502a output from the in-phase scaled value generator 506a can be defined as:

1/I_amp_scale (7)

The average envelope power of the quadrature component of the digital baseband signal can be measured with the quadrature power detector 504b using the following formula:

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; N</span>}}\underset{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; Q</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; ]</span><span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 0.5</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

The average envelope power of the quadrature component (Q_avg) of the digital baseband signal may be provided to the quadrature scale value generator 506b. Quadrature scaling value generator 506b may be used to determine whether the average envelope power of the quadrature component of the digital baseband signal exceeds the equivalent value of P_max. In the case that the average envelope power of the quadrature component of the digital baseband signal does not exceed the equivalent value of P_max, the quadrature scaling value generator 506b provides "1" to the quadrature multiplier 502b. On the other hand, if the average envelope power of the quadrature component of the digital baseband signal exceeds the equivalent value of P_max, the quadrature scaling value generator 506b can provide the scaling value to the quadrature multiplier 502b for the quadrature component of the signal Clipping is performed. The quadrature scaling value generator 506b can be implemented with the following formula:

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; amp</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; scale</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; max</span>}}}\frac{\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; ]</span>}{\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; \_</span>\mathrm{<span\; class="notranslate">\; avg</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

The scaling value provided to the quadrature multiplier 502b output from the quadrature scaling value generator 506b can be defined as:

1/Q_amp_scale (10)

The various illustrative logical blocks, modules, circuits, units and/or components described herein with reference to the embodiments disclosed herein may be implemented using a general purpose processor, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable Gate arrays (FPGAs) or other programmable logic components, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor can be a microprocessor, however, the processor can also be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing components, eg, a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such combination.

The methods or algorithms described here in conjunction with the embodiments disclosed herein may be directly implemented by hardware, by software modules executed by a processor, or by a combination of both. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. The memory can be coupled to the processor such that the processor can read information from, and write information to, the storage medium. A storage medium may also be integrated in the processor.

The foregoing description of the disclosed embodiments is presented to enable those skilled in the art to utilize the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles presented here may be applied to other embodiments. Accordingly, the invention is not limited to the embodiments disclosed herein, but is consistent with the scope of the claims, wherein reference to an element in the singular does not mean "one and only one" unless expressly stated, but rather "one or more ". All structural and functional equivalents to the elements of the various embodiments described in this disclosure, as well as thereafter known to those skilled in the art, are expressly incorporated by reference and are to be encompassed within the scope of the claims. Furthermore, nothing herein disclosed is dedicated to the public regardless of whether such disclosure is expressly recited in the claims. No claim element should be read under the terms of the sixth paragraph of 35 U.S.C. § 112 unless the element is explicitly referred to by "means for" or in a method claim by "a step of..." to this unit.

Claims (25)

1. A wireless communication method, comprising: generate a signal; setting the average transmit power of the signal according to a first threshold related to out-of-band radiation; clipping the signal according to a second threshold related to peak transmit power; and The signal is transmitted over a wireless medium. 2. The method of claim 1, wherein the average transmit power of the signal transmission is set to a highest level at which the out-of-band radiation does not exceed the first threshold. 3. The method of claim 2, wherein the average transmit power of the signal transmission is based on a parameter setting related to the signal. 4. The method of claim 3, wherein the parameters include at least one of signal data rate, signal modulation scheme, signal coding scheme, and signal payload size. 5. The method of claim 3, further comprising querying a look-up table mapping the parameters to peak-to-average power ratios, and wherein the average transmit power of the signal transmission is based on the peak-to-average power ratio and the described above for the second threshold setting. 6. The method of claim 5, wherein the average transmit power of said signal transmission is obtained by generating a gain control signal independent of said parameter, and limiting said gain control signal, wherein said signal is transmitted by applying said limited gain control signal to a transmitter. 7. The method of claim 6, wherein said gain control signal generated independently of said parameter is a function of feedback indicative of said wireless medium quality from a remote source. 8. The method of claim 6, wherein said gain control signal generated independently of said parameter is a function of the power of a signal received over said wireless medium from a remote source. 9. The method of claim 1, wherein the signal is clipped by determining that an average envelope power of the signal is above the second threshold, and scaling the signal in response to this determination. 10. The method of claim 9, wherein the signal includes an in-phase (I) component and a quadrature (Q) component, wherein the average envelope power of the signal is obtained from the amplitudes of the in-phase and quadrature components of the signal definite. 11. The method of claim 9, wherein the signal includes an in-phase (I) component and a quadrature (Q) component, wherein the average envelope power of the signal is independent for each of the in-phase and quadrature components , where the in-phase and quadrature components are independently scaled. 12. A wireless communication device comprising: a user interface configured to generate a signal; a transmitter configured to transmit said signal over a wireless medium; a power control module configured to set the average transmit power of the transmitter according to a first threshold related to out-of-band radiation; and A peak amplitude limiter configured to limit the signal according to a first threshold related to peak transmit power. 13. The wireless communication device of claim 12, wherein the power control module is further configured to set an average transmit power of the transmitter to a highest level at which the out-of-band radiation does not exceed the first threshold . 14. The wireless communication device of claim 13, wherein the power control module is further configured to set an average transmit power of the transmitter based on a parameter related to the signal. 15. The wireless communication device of claim 14, wherein the parameters include at least one of a signal data rate, a signal modulation scheme, a signal coding scheme, and a signal payload size. 16. The wireless communication device of claim 14 , further comprising a look-up table mapping the parameter to a peak-to-average power ratio, wherein the power control module is further configured to query the look-up table to access the parameter peak-to-average power ratio, and set the average transmit power of the transmitter according to the peak-to-average power ratio and the second threshold. 17. The wireless communication device of claim 16, wherein the power control module is further configured to generate a gain control signal independent of the parameter, limiting the gain control signal, and applying the limited gain control signal to the transmitter to set the average transmit power. 18. The wireless communication device of claim 17 , further comprising a receiver configured to extract feedback from a signal received from a remote source indicative of the quality of the wireless medium, wherein the power control module Also configured to generate the gain control signal based on the feedback. 19. The wireless communication device of claim 17 , further comprising a receiver configured to receive a signal from a remote source and measure the power of the received signal, wherein the power control module is further configured to The gain control signal is generated based on the measured power of the received signal. 20. The wireless communication device of claim 12, wherein the peak amplitude limiter is further configured to limit the signal by calculating an average envelope power of the signal, and if the The signal is scaled when the average envelope power of the signal exceeds the second threshold. 21. The wireless communication device of claim 20, wherein the signal includes an in-phase (I) component and a quadrature (Q) component, wherein the peak amplitude limiter is further configured to extract from the in-phase and quadrature (Q) components of the signal The magnitude of the quadrature component calculates the average envelope power of the signal. 22. The wireless communication device of claim 20 , wherein the signal includes an in-phase (I) component and a quadrature (Q) component, wherein the peak amplitude limiter is further configured for the in-phase and quadrature each of the in-phase and quadrature components to independently calculate the average envelope power of the signal, and if its corresponding average envelope power calculation exceeds said second threshold, independently calculates each of said in-phase and quadrature components zoom. 23. A wireless communication device comprising: Components used to generate signals; means for transmitting said signal over a wireless medium; means for setting an average transmit power of said signal transmission based on a first threshold related to out-of-band radiation; and means for clipping the signal according to a second threshold related to peak transmit power. 24. A processor for wireless communications, the processor configured to control the following operations: generate a signal; setting the average transmit power of the signal according to a first threshold related to out-of-band radiation; and The signal is clipped according to a second threshold related to peak transmit power. 25. A storage medium for wireless communication comprising software configured to control: generate a signal; setting the average transmit power of the signal according to a first threshold related to out-of-band radiation; and The signal is clipped according to a second threshold related to peak transmit power.

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