Abstract:
Briefly, an apparatus and a method of determining a quality indicator of a second received signal based on a characteristic of a first received signal. The apparatus is able to receive over a down channel of a wireless communication system a first signal having a predetermined bit sequence and second signals having an unknown bit sequence and to determine the quality indicator of the second received signal based on a characteristic of the first received signal

Description:
BACKGROUND OF THE INVENTION  
       [0001]     In some wireless communication systems such as, for example, cellular -communication systems, a base station may transmit a power control (TPC) command to a mobile station. The mobile station may receive the TPC command and may increase or decrease a transmit power level based on the TPC command. The received TPC command may include noise, distortion, errors in bit sequence, and other types of interference which may reduce the quality of the received TPC.  
         [0002]     Furthermore, poor quality of the received TPC command may cause the mobile station to transmit at a high power level. The high transmit power level may interfere with neighboring mobile stations and/or base stations.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]     The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanied drawings in which:  
         [0004]      FIG. 1  is a schematic block diagram of a wireless communication system according to an exemplary embodiment of the present invention;  
         [0005]      FIG. 2  is a schematic block diagram of a mobile station according to some exemplary embodiments of the invention; and  
         [0006]      FIG. 3  is a schematic flowchart of a method of estimating a quality parameter of a received power control command according to some exemplary embodiments of the invention. 
     
    
       [0007]     It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0008]     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to obscure the present invention.  
         [0009]     It should be understood that the present invention may be used in a variety of applications. Although the present invention is not limited in this respect, the circuits and techniques disclosed herein may be used in many apparatuses such as, for examples base stations and mobile stations of a cellular communication system, wireless local area network (WLAN), metropolitan area network (MAN) or the like. Communication devices intended to be included within the scope of the present invention may include, by a way of example only, cellular radiotelephone portable communication devices, digital communication system portable devices, and the like.  
         [0010]     Types of cellular radiotelephone systems intended to be within the scope of the present invention include, although are not limited to, Code Division Multiple Access (CDMA) and WCDMA cellular radiotelephone portable devices for transmitting and receiving spread spectrum signals, Global System for Mobile communication (GSM) cellular radiotelephone, General Packet Radio Service (GPRS), Extended GPRS, and the like.  
         [0011]     For simplicity, although the scope of the invention is in no way limited in this respect, embodiments of the present that will be described below may be related to a CDMA family of cellular radiotelephone systems that may include CDMA, WCDMA, CDMA 2000, and the like. The term “plurality” may be used throughout the specification to describe two or more components, devices, elements, parameters and the like. For example, “plurality of mobile stations” describes two or more mobile stations. In addition, it should be known to one skilled in the art that the term “a portable communication device” may refer to, but is not limited to, a mobile station, a portable radiotelephone device, a cell-phone, a cellular device, personal computer, Personal Digital Assistant (PDA), user equipment, and the like.  
         [0012]     Some embodiments of the invention may be implemented, for example, using a machine-readable medium or article which may store an instruction or a set of instructions that, if executed by a machine (for example, by a wireless station, and/or by other suitable machines), cause the machine to perform a method and/or operations in accordance with embodiments of the invention. Such machine may include, for example, any suitable processing platform, computing platform, computing device, processing device, computing system, processing system, computer, processor, or the like, and may be implemented using any suitable combination of hardware and/or software. The machine-readable medium or article may include, for example, any suitable type of memory unit, memory device, memory article, memory medium, storage device, storage article, storage medium and/or storage unit, for example, memory, removable or non-removable media, erasable or non-erasable media, writeable or re-writeable media, digital or analog media, hard disk, floppy disk, Compact Disk Read Only Memory (CD-ROM), Compact Disk Recordable (CD-R), Compact Disk Rewriteable (CD-RW), optical disk, magnetic media, various types of Digital Versatile Disks (DVDs), or the like. The instructions may include any suitable type of code, for example, source code, compiled code, interpreted code, executable code, static code, dynamic code, or the like, and may be implemented using any suitable high-level, low-level, object-oriented, visual, compiled and/or interpreted programming language, e.g., C, C++, Java, high level design programming language, assembly language, machine code, or the like.  
         [0013]     Referring firstly to  FIG. 1 , a block diagram of a wireless communication system  100  according to some embodiments of the present invention is shown. Wireless communication system  100  may include a base station  110  and mobile stations  120  and  130 .  
         [0014]     According to this exemplary embodiment, base station  110  may transmit over a downlink channel  111  modulated radio frequency (RF) signals, if desired. Mobile station  120  may transmit over an uplink channel  112  modulated RF signals to base station  110 . According to exemplary embodiments of the invention the modulated RF signals may include, among other signals, pilot signals and transmit power control command signals.  
         [0015]     According to an exemplary embodiment of the present invention, communication system  100  may include a WCDMA channel access scheme which may include one or more pilot signals and one or more TPC command signals. The pilot signal may include a predetermined bit sequence, if desired. The TPC command signal may include unknown and/or uncoded bits sequences, although the scope of the present invention is not limited to this exemplary embodiment. Mobile stations  120  and  130  may control, e.g., vary, their transmit power according to the TPC command received from base station  110 .  
         [0016]     Furthermore, mobile stations  120  and/or  130  may switch their transmitters on and/or off according to a quality indicator of the TPC command. For example, the quality indicator may include an error ratio level, bit error rate (BER) or the like. For example, a first quality threshold level Q out  may be used to switch off the transmitter of the mobile station and a second quality threshold level Q in  may be used to switch on the transmitter. As a non-limiting example, Q out  may have a TPC command error level of 30% and Qin may have a TPC command error level of 20%.  
         [0017]     According to embodiments of the present invention, the TPC command error level may be estimated from a received pilot signal. For example, a noise level and an amplitude of one or more samples of the received pilot signal may be estimated to set the quality indicator of the TPC command signal, for example, BER.  
         [0018]     Turning to  FIG. 2 , a schematic block diagram of a mobile station  200  according to exemplary embodiments of the invention is shown. Mobile station  200  may include, a receiver  210 , a transmitter  250  and at least one antenna  295 .  
         [0019]     Although the scope of the present invention is not limited in this respect, types of antennas that may be used with embodiments of the invention (e.g., antenna  295 ), may include an internal antenna, a dipole antenna, an omni-directional antenna, a monopole antenna, an end fed antenna, a circularly polarized antenna, a micro-strip antenna, a diversity antenna and the like.  
         [0020]     According to embodiments of the present invention, receiver  210  may include a demodulator  215 , a digital receiver (RX)  220 , an estimator  230 , and a memory device  240 . Transmitter  250  may include a power control unit  260  and a power amplifier  270 .  
         [0021]     According to embodiments of the invention, antenna  295  may receive from a base station (e.g., base station  110 ) a modulated RF signal which may include a pilot signal and a TPC command signal. Demodulator  215  may demodulate the RF signal to provide, at least, the pilot signal and the TPC command signal to digital receiver  220 . It should be understood that the pilot signal and the TPC signal may include noise and/or other interferer signals, although the scope of the present invention is not limited in this respect.  
         [0022]     According to embodiments of the present invention, digital receiver  220  may include a rake receiver and/or any other type of digital receiver known in the art of wireless communication systems. Digital receiver  220  may sample the pilot signal and the TPC signal. Samples of the pilot signal and TPC signal may be stored in memory  240 , if desired. In addition, digital receiver  220  and/or estimator  230  may store in memory  240  values of noise level  245  and amplitude  247  of the pilot signal, if desired.  
         [0023]     According to exemplary embodiment of the invention, memory  240  may be a nonvolatile memory device, a volatile memory device, a Flash memory, or the like. More specifically, memory  240  may include, for example, a dynamic read access memory (DRAM), a read only memory (ROM), a Flash memory, a Static RAM (SRAM), or the like.  
         [0024]     Although the scope of the present invention is not limited in this respect, estimator  230  may include a samples counter  234  to count the number of samples and an error counter  236  to count the numbers of samples that includes errors. Estimator  230  may receive from memory  240  values of noise level  245  and amplitude  247  of the pilot signal for estimating a quality indicator of TPC, if desired. For example estimator  230  may determine the quality indicator based on a ratio of the number of errors provided by error counter  236  and the number of samples provided by samples counters  234 .  
         [0025]     In other embodiments of the present invention, estimator  230  may estimate the noise level and the amplitude of the pilot signal from bit sequences of the pilot signal stored in memory  240 , if desired. Estimator  230  may control power control unit  260 , e g., to switch power amplifier  270  and and/or off according to desirable threshold values.  
         [0026]     Turning to  FIG. 3 , an illustration of a flowchart of a method of estimating a quality parameter of a received power control command according to some exemplary embodiments of the invention is shown. Although the scope of the present invention is not limited in this respect, the method may start (text block  300 ) by sampling a desired number of samples, i, of a pilot signal, P i , and for a TPC signal, T i , wherein i may be in a range of 1 to N samples, for example N=240. Furthermore, with embodiments of the present invention, P i  and T i  may refer to a bit sequence and/or a symbol sequence of the pilot signal and the TPC signal, respectively (text block  315 ).  
         [0027]     The samples of the pilot sequence P i  and TPC sequence T i  may be stored in nonvolatile and/or volatile memory device (e.g., memory  240 ). An estimator (e.g., estimator  230 ) may estimate a quality value of the TPC signal, for example BER, based on an estimated noise level and an estimated amplitude of the pilot signal.  
         [0028]     For example, estimator  230  may estimate an amplitudes ratio C according to C=P i /A Ti  based on Piˆ2 and Tiˆ2 (text block  315 ), wherein A Pi  may be an estimated amplitude of the pilot sequence P i  and A Ti  may be an estimated amplitude of the TPC sequence Ti. Furthermore, estimator  230  may perform the above described method on samples i=0 to i=N and may count errors using an errors counter. An initiation of samples counter, e.g., Nsamples, and errors counter, e.g., ErrorsCounter (text block  320 ), may be desired before starting to estimate the quality indicator (e.g., BER) of the TPC sequence. In this exemplary embodiment, the quality indicator may be BER. The BER may be calculated for samples from 0 to N (text block  360 ) and according to BER =ErrorsCounter/(2*Nsamples) (text block  365 ).  
         [0029]     Although the scope of the present invention is not limited in this respect, estimating A Pi  may be done by measuring and averaging the amplitudes of Pi samples (text block  325 ). Estimating A Ti  may be done by multiplying the estimated value of C with the estimated value of A Pi  (text block  325 ). Estimating the noise level of the pilot sequence N Pi  may be done by subtracting a sample and/or the sum of samples of the pilot sequence from the estimated amplitude A Pi  and/or the sum of estimated amplitudes of samples of the pilot sequence, for example N P i=Pi−A Pi  (text block  355 ). Estimating the noise level of TPC sequence N Ti  may be done by normalizing the estimated noise of the pilot sequence N p i (text block  340 ). For example, normalizing the estimated noise level of the pilot sequence N P i may be done with the following equations:
 
 N   Ti   =N   Pi *(NtpcBitsInTpcSample/NpilotBitsInPilotSample)ˆ0.5.
        If (NtpcBitsInTpcSample=NpilotBitsInPilotSample), then it may be assumed that N Ti =N Pi , although the scope of the present invention is not limited in this respect.        
 
         [0031]     According to embodiments of the present invention, an absolute value of the estimated noise level of TPC sequence may be compared to the estimated amplitude of the TPC sequence e.g., A Ti &lt;Abs(N Ti ) (text block  360 ). The errors counter (e.g., ErrorsCounter) may be incremented if the noise level is greater than the amplitude level of the TPC sequence (text block  350 ). For example, the errors counter may be incremented by ½ (one half) error, if desired  
         [0032]     While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.