Device and method for CDMA-signal power estimation

#The present invention relates generally to wireless telecommunication systems, and more specifically to reliably estimating the power of a signal received in a receiver operating according to a CDMA (or similar) standard, even if the signal includes a significant amount of interference. The present invention is especially useful when the receiver uses the economically advantageous direct-conversion architecture because the direct-conversion open-loop power control circuit filters out less interference when compared to a standard super-heterodyne receiver.

#Wireless telecommunication technology has revolutionized the way people communicate over a distance. From the inception of modern telecommunication systems in the nineteenth century, virtually all such systems, save those relying on line-of-sight, are operated over a wire. Using a pattern of electrical signals transmitted from one end of the wire to the other, devices at each end have been able to establish effective and reliable communications. More accurately, to traverse long distances the electrical signals traveled a number of wires interconnected by switches to form a network. The switches permit almost any desired combination of wires to be connected so that any device may connect and communicate with any other, so long as they are both linked to the network and not otherwise occupied. This type of network, which started as telegraph and became telephone, is now often referred to as the plain-old telephone system (POTS). Similar private or limited-access networks are also in current use. Such networks provide a reliable vehicle for communications traffic, including voice and data, between devices such as telephones and computers. The main disadvantage of the POTS and similar wire line systems is that these devices must be located at a network-access point to which they are physically connected, and cannot be relocated during an ongoing communication session. In addition, whatever network resources are employed to establish the continuous connection between the calling party and the called party must remain so employed for the duration of the session-even at intervals where no actual communication is taking place.

#Wireless communications, which rely chiefly on radio waves, address both of these concerns. Although the first radio transmission took place years ago, it is only in the relatively recent past that the technology has progressed to allow widespread use of wireless communication by the general population. A great many people now subscribe to mobile as well as (or instead of) wireline service. Typically, subscribers will have one or more mobile stations capable of radio communication with network transceivers located through the network coverage area. The mobile station itself includes a transmitter and a receiver, and will usually be a telephone, computer, personal digital assistant (PDA), or similar device. Naturally, there is no requirement that the mobile station actually be movable, and as used herein the term “mobile station” will apply to these devices and any others similarly capable of radio communication with a wireless network.

#FIG. 1 is a block diagram illustrating selected components of a typical wireless telecommunication network as might be used in communicating with mobile stations practicing received-power estimation according to the present invention;

#FIG. 2 is a block diagram illustrating the power estimation components of a typical super-heterodyne receiver of the prior art;

#FIG. 3 is a block diagram illustrating the power-estimation components of a direct-conversion-architecture receiver configured according to an embodiment of the present invention;

#The present invention provides a device and method for estimating the power level of a received CDMA (or similar) RF signal. The estimated power level provides an indication of the transmission power needed to send a communication signal back to the original sending station. This sending station is generally a base station in a wireless network, and the power-level estimation is performed by a mobile station linked to the base station. Regulatory mobile-station transmission power helps to equalize the various mobile-station signals received at the base station, regardless of its distance to the mobile transmitter.

#FIG. 3 is a block diagram illustrating selected components of a direct-conversion receiver 300 configured according to an embodiment of the present invention. In this embodiment, received-signal power estimation is accomplished using two automatic gain control (AGC) loops, delineated with broken lines as analog AGC loop 320 and digital AGC loop 340. The input to analog AGC loop 320 occurs at variable-gain amplifier 322, which receives and amplifies a complex signal from baseband analog filter 315. The amplified complex signal from variable-gain amplifier 322 becomes the input for the analog-to-digital (A/D) converter 324. The complex output from AID converter 324 is, in turn, the input for analog AGC 326. The output from the analog AGC 326 is an analog-gain value, which is used to control variable-gain amplifier 322. Variable gain amplifier 322 in this configuration attempts to keep constant at a pre-determined level the power level of the output to A/D converter 324.

#As mentioned above, the input to analog AGC loop 320 is received from baseband analog filter 315. This filter receives the complex baseband signal from mixer 310, which down-converts the received RF signal after it has been amplified by low-noise amplifier (LNA) 305. LNA 305 is preferably controlled by an LNA gain-value, also output from analog AGC 326.