MXPA98001560A - Method and apparatus necessary to acquire a pilot signal on a receiver c - Google Patents

Abstract

A searcher receiver (114) includes a sampling buffer (202) that stores samples of charged signals using a real-time clock. A real-time linear sequence generator (RT LSG) (206) saves an initial state, a real-time clock is used to time this generator. The RT LSG contents are loaded into a non-real time linear sequence generator (NRT LSG) (208) when sample processing begins. A correlation of the samples is carried out using the unreal time clock to allow the signal processing to be disconnected from the chip speed. It is possible to cancel the power to the analogue end (108) or tune it to another frequency during the processing of time not

Description

METHOD AND EQUIPMENT REQUIRED TO ACQUIRE A PILOT SIGNAL ON A CDMA RECEIVER Field of the invention The present invention relates generally to digital communication, more specifically to a method and equipment necessary for the acquisition of a pilot channel in a broad spectrum communication system such as the code division multiple access cellular telephone system (CDMA). ).

BACKGROUND OF THE INVENTION It was proposed to use direct sequence code division multiple access (DS-CDMA) communication systems in cellular telephone systems with traffic channels located at 800 MHz and in the frequency band of a personal communication system (PCS). ) at 1800 MHz. In a DS-CDMA system, all base stations of all cells can use the same radio frequency communication. A known DS-CDMA system is defined in the provisional standard IS-95 of the Telecommunications Industry Association / Electronic Industry Association (Association of the Telecommunications Industry / Electronic Industry Association) (TIA / EIA) "Mobile Station-Base Station Copatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System "(" Compatibility Standard Mobile Station - Base Station for Dual-Bandwidth Broadband Cellular System "). In addition to the traffic channels, each base station transmits a pilot channel, a synchronization channel and a paging channel. The pilot channel or pilot signal is a pseudorandom noise or a PN code. All mobile stations located within the range commonly receive the pilot channel and use it for the identification of the presence of a CDMA system, the acquisition of an initial system, the transmission in idle mode, the identification of the initial rays and the delay of the base stations that communicate and those that interfere, and for the coherent demodulation of the synchronization, paging and traffic channels.

The pilot signal transmitted by each base station of the system uses the same PN code but with a different phase balance. The base stations are identified exclusively through a phase or a start time for the PN sequences. For example, in IS-95, the sequences have a length of 215 chips and are produced at a chip rate of 1.2288 mega-chips per second, and then they repeat every 26-2 / 3 milliseconds. The minimum time separations have a length of 64 chips, which allows a total of 512 phase assignments of different PN codes for the base stations. At the base station, RF received signals include pilot channels, synchronization, paging and traffic channels from all stations. of base nearby. The mobile station must identify all pilot signals that are received, including the pilot signal from the base station that has the strongest pilot channel. In previous mobile stations, a correlator was used as a search element for receiving pilots. The received PN phase is correlated with system PN codes that are generated in the mobile station. Knowing the correct PN phases of the base site / s with which the mobile station communicates allows a coherent detection of all the other channels transmitted by the base station. The incorrect 'PN' phases will produce a minimum output of the correlator. Because the space of the sequence phase is large, the prior real-time serial correlation technique, which existed in this field, took too much time to correctly locate the energy of the pilot signal. At a minimum and with strong signals, the acquisition of the system can take up to 2.5 seconds or more to power the mobile station. With no reception pilots present, the mobile station will continue to search for the total space of the PN sequence phase until a system time occurs, which can be 15 seconds. Then the mobile station moves to another RF and re-attempts to acquire the CDMA system. The search process is repeated at subsequent frequencies until a pilot signal is found. The prolonged delay in the acquisition of the system is inconvenient and undesirable for most users. A person who uses a radiotelephone expects to be able to use it immediately, with a minimum delay. A delay of up to 2.5 seconds is too much for many users, and in the case of longer delays could have serious consequences, for example, for emergency calls "911". The search method of the pilot channel that existed in the technical field creates greater limitations for all other uses of the pilot channel after the acquisition of the initial system. Typical DS-CDMA mobile station receivers use a ladder handset having three fingers or more, independently controlled, temporarily aligned to the correct PN sequence phases, as determined by the receiver pilot phase search element. Stair fingers are usually assigned to the strongest rays received from all base stations in communication, as determined by the element,; search of pilot phase receiver. Ray assignments are updated in a maintenance process, using the information from the pilot phase search element. If the mentioned search element is slow, which causes a slow maintenance of the allocation of the strongest rays to the fingers, the reception level of the mobile station is reduced in fading conditions. In certain conditions called "fast PN", there is a large percentage of missed calls. The problem of fast NP occurs because the available PN pilot signals change so quickly that the search elements that existed fail to maintain the same level. Inactive transmission is the process of connecting to the paging channel of the base station and listening to it with the strongest pilot that identifies the pilot's search element. When the mobile station receives a page or accesses the system to place a call, it is important that said station is listening to the page from the base station related to the strongest received pilot or trying to access it. This requires a fast pilot phase search element, especially when the mobile station is in motion. The poor performance of the previous search mechanism also affects the smooth transmission performance of the mobile station. When in a call on a traffic channel, the pilot search element is used to maintain the appropriate ladder finger assignments to obtain optimal demodulation of the traffic channel and to identify base sites that interfere. In case of detecting a base site that interferes, the mobile station informs it to the base site as a candidate for smooth transmission. This is a condition of the DS-CDMA system, in which a mobile station communicates with more than one base site simultaneously. It is not necessary to accurately locate, in the pilot phase space, the pilot signals from the adjacent base stations. Consequently, in addition to being fast, the search element must be agile, that is, it must be able to review the total phase space as well as specific PN offset. The new requirements for mobile stations will require MAHHO faculties (strong mobile assisted transmission). In MAHHO, the mobile station changes the frequency of the radiotelephone circuit as it is transmitted from one base station to another. Due to the totally dual nature of the CDMA air interface, it is required to destroy the radiotelephone circuit, go to another frequency, look for pilot signals, return to the original frequency and reacquire the pilot to re-establish the circuit. The previous search item that requires 2.5 seconds to acquire a pilot does not fit the MAHHO purposes. Another limitation of the prior art comprises operation in spaced mode. For portable mobile battery stations, it is also important to conserve battery power when waiting for pages. The IS-95 standard provides a spaced mode that allows portable stations to reduce power except during periods when the base stations transmit the paged information that these portable stations are assigned. The paging space interval can be as short as 1.28 seconds and periods of 1.28 seconds multiplied by powers of two can be used to save more batteries. During these intervals, the mobile station should only control the paging channel up to 160 ms and "sleep" in a low power mode for the remaining time. When operating in spacing mode, a portable station may have to search for the phase space of twenty base stations each time it wakes up. In order to be able to receive the paging space reliably after waking up, the portable station must be listening to the base station that provides adequate signal strength. When the mobile station is in motion, the correct base station to be decoded can easily pass from one paging interval to the next. For this reason, it is very important to have a quick pilot search mechanism to identify the correct base station pilot before starting the assigned paging space. The use of the previous search mechanism requires that the portable station wake up well before the paging space to have sufficient time to search sequentially for the PN sequence phase space. This denies a significant part of the potential battery savings that the spacing mode supports. For all the above, there is a need to have an accurate pilot search mechanism that improves the performance of the mobile station in the identification zones of the DS-CDMA system (service detection), initial system acquisition, mode transmission inactive, smooth transmission, operation in spaced mode and identification of the initial and delay rays of the communicating and interfering base stations, in order to achieve a coherent demodulation of the synchronization, paging and traffic channels.

Succinct description of the schemes The features of the present invention, which are considered novel, are set forth in great detail in the appended claims. It is possible to better understand the invention, together with other objects and advantages that are obtained therefrom, referring to the following description, taken in conjunction with the schemes, in whose figures the identical number corresponds to the same element and where: Fig. 1 is a block diagram of a communication system; Fig. 2 is a block diagram of a searcher receiver for use in the radiotelephone of Fig. 1; Fig. 3 is a flow diagram illustrating a method of operating the radiotelephone of Fig. 1. Fig. 4 is a flow chart illustrating a method of operation of the radiotelephone of Fig. 1. Fig. 5 is a flow diagram illustrating a method of operation of the radiotelephone of Fig. 1.

Detailed description of a preferred arrangement With respect to Fig. 1, a communication system 100 includes a plurality of base stations such as the base station 102 configured for radio communication with a mobile station or more like a radiotelephone 104. The radiotelephone 104 is configured to receive and transmit direct sequence code multiple access signals (DS-CDMA) to communicate with the numerous base stations, including the base station 102. In the illustrated arrangement, the communication system 100 operates according to the provisional standard IS-95 of the TIA / EIA, "Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System", which operates at 800 MHz. Alternatively, the communication system 100 could operate in accordance with other DS-CDMA systems including the 1800 MHz PCS systems or with any other appropriate DS-CDMA system. The base station 102 transmits wide-spectrum signals to the radiotelephone 104. The symbols of the traffic channel are dispersed using a Walsh code in a process known as Walsh coverage. To each mobile station, such as the telephone radio 104, the base station 102 allocates a unique Walsh code, so that the transmission of the traffic channel to each mobile station is orthogonal to the traffic channel transmissions for each mobile station.

In addition to traffic channels, the base station 102 transmits a pilot channel, a synchronization channel and a paging channel. The pilot channel is formed using a zero data stream covered by the Walsh code 0, which consists of all 0. Commonly, all mobile stations located within the range receive the pilot channel, which uses the radiotelephone 104 to identify the presence of a CDMA system, acquisition of an initial system, transmission in idle mode, identification of the initial and delay beams of the communicating and interfering base stations, and for the coherent demodulation of the synchronization, paging and traffic channels. The synchronization channel is used for synchronization of the mobile station with the base station. The paging channel is used to send page information from the base station 102 to the mobile stations, including the radiotelephone 104. In addition to the Walsh coverage, all channels transmitted by the base stations are propagated by a pseudorandom noise sequence. (PN), also called pilot sequence. The base station 102 and all base stations of the communication system 100 are uniquely identified by a single initial phase, also called initial time or phase change, for the pilot channel sequence. The length of the sequences is 215 chips and they are produced at a chip rate of 1.2288 megachips per second and then they are repeated every 26-2 / 3 milliseconds. The minimum allowable time separation is 64 chips, which allows a total of 512 different PN code phase assignments. The propagation pilot channel modulates an RF radio frequency carrier and is transmitted to all mobile stations, including the radiotelephone 104, in a geographical area corresponding to the service of the base station 102. The PN sequence is complex in nature: it comprises both the phase (I) and quadrature (Q) components. Those versed in the technical art will recognize that all the processing of the pilot signal described herein includes both the I components and the Q. The radiotelephone 104 comprises an antenna 106, an analogous end 108, a reception path including an analog-to-digital converter (ADC) 110, a branched receiver 112 and a search receiver 114, a controller 116 and a transmission path. which includes a transmission path circuit 118 and a digital to analog converter 120. The antenna 106 receives RF signals from the base station 102 and from other base stations in the vicinity. Some of the received RF signals are transmitted directly, the base station transmits a line of visual rays. Other received RF signals are reflected in multiplex paths and delayed. The antenna 106 converts the RF signals into electrical signals and provides them to the analogue end 108. Analog end 108 filters the signals and provides conversion to the baseband signals. These signals are supplied to the ADC 110, which converts them into digital data streams for further processing. Receiver 112 includes numerous receiver fingers, including 122, 124, and 126. In the illustrated arrangement, receiver 112 includes three receiving fingers. However, it is possible to use any number of suitable receiving fingers. These fingers respond to a conventional design. Each has a linear finger sequence generator (LSG) 128 used to detect pilot signals on the receiving finger.

The controller 116 includes a clock 134. It controls the synchronization of the radiotelephone 104. The said controller 116 is connected to other elements of the radiotelephone 104. These interconnections are not indicated in Fig. 1 so as not to unduly complicate the scheme. The searcher receiver 114 detects the pilot signals received by the radiotelephone 104 from the plurality of base stations including the 102. The searcher receiver 114 propagates the pilot signals using a correlator with PN codes generated on the radiotelephone 104 using a local reference synchronization. . After this propagation, the signal values for each chip period accumulate in a preselected time interval. This provides a consistent sum of chip values. This sum is compared to a threshold level. Sums exceeding this threshold in general indicate that the appropriate synchronization of the pilot signal has been determined. Next, and together with Fig. 2, the structure and operation of the searcher receiver 114 will be explained. With respect to Fig. 2, the finder receiver 114 includes a sample buffer 202, a correlator 204, and a PN 205 generator. The PN 205 generator includes a real-time linear sequence generator (RT LSG) 206, a non-real time linear sequence generator (NRT LSG) 208, a mask circuit 210, a mask register 214, a deflection controller 216, a deviation counter 217, a clock controller 218 and a clock divider 220. The searcher receiver 114 detects pilot signals to acquire system synchronization for the radiotelephone 104. In accordance with the present invention, the searcher receiver 114 makes a Sampling the received signal at a first speed and storing many signal samples. The searcher 114 then processes the various signal samples at a second rate, which is greater than the first, and identifies one or more signals based on the plurality of pilot signal samples. The sampling buffer 202 collects a predetermined amount of signal samples. The sampling buffer 202 has an input 226 connected to the ADC 110 and an output 224 connected to the correlator 204. The ADC receives an analogous signal (t) from the front end 108 and converts the analog signal into digital samples. The ADC has a clock input 228 connected to the clock controller 218 and produces a digital sample in response to each received clock signal.

The clock controller 218 has an input 232 connected to a clock input a first output 233 connected to the ADC 110, a second output 234 connected to the clock divider 220, and a third output 236 connected to the NRT LSG 208. The clock controller 218 produces clock signals on the first output to provide a real-time sample clock to the ADC 110. clock controller 218 produces clock signals on the second output 234 to provide a real-time clock chip to the RT LSG 206. The real-time clock chip increments the RT LSG 206 as the samples are stored in the sample buffer 202. The clock controller 218 produces clock signals on the third output 236 to provide a non-real time chip clock. The clock input 230 receives clock signals from any suitable source, such as the clock 134 of the controller 116. In the illustrated arrangement, the clock controller 218 provides the real-time sample clock to the ADC 110 at a rate twice as high as the 1,2288 megachips per second. It is possible to select other suitable sampling rates. As a result, during each chip time, two samples are stored in the sample buffer 202.

Said samples are stored sequentially, so the first to enter, the first to exit. A read / write flag 222 indicates the location in the sample buffer to read and write data. A total of 2N samples are saved, where N is the span of the sample buffer in chip intervals. In other words, N is the correlation length and 2N is the size of the buffer. An example for the dimension of the sample buffer is 512. Samples stored in the sample buffer 202 represent the signal received in the radiotelephone 104 from any nearby base station, such as a base station 102 (Fig. 1) . The signal may contain a directly received pilot signal or a multipath beam. The sample buffer 202 has a buffer for storing numerous samples of a received signal. The RT LSG 206 is a conventional linear sequence generator that produces a pseudorandom sequence from a given starting point in response to a clock signal received at an input 240. The RT LSG 206 receives clock signals from the clock controller 218. These signals are real-time clock signals and the RT LSG generates a sequence of values in response to the real-time clock signal. The NRT LSG 208 is a conventional LSG that produces a sequence identical to that produced by the RT LSG 206 when it is loaded with the same state and synchronized with the input 242. According to the present invention, the searcher 114 loads the state of the RT LSG 206 in the NRT LSG 208 at a relative time point. storage of the predetermined amount of samples in sample buffer 202. Substantially at the same time, the contents of RT LSG 206 are transferred to register 214 for subsequent use. The loading operation of the NRT LSG state from the RT LSG state to a specific time point relative to the filling of the buffer memory provides a temporary reference. From this time reference the outputs of non-real time circuits can be matched to the real-time settings using the deviation counter 217. Then, the register saves the initial state of the NRT LSG 208 to allow the NRT LSG to be reset at its initial reference value.

The clock input 242 of the NRT LSG 208 is connected to the second output 236 of the clock controller 218. According to the present, the NRT LSG 208 is synchronized at a different speed from the one of the RT LSG 206, which is at the same time considerably higher Thus, the NRT LSG 208 increases in response to a non-real time clock signal. The mask circuit 210 employs a predetermined mask which, the Exclusive-Ored with the contents of the NRT LSG 208, produces the correct state of the PN 205 generator at a certain point in the future. The mask circuit 210 is loaded with any mask that is stored in the mask register 212, such as mask- '1, mask 2, ... mask M. The masks correspond to the individual phases of the phase space of the pilot signals of the communication system. The correlator 204 establishes a correlation between the various samples of the buffer memory 202 and the sequence of values of the NRT LSG and produces a correlation result. In the illustrated arrangement, the correlator 204 includes a first correlator, including multiplier 250 and summation element 252 and a second correlator, including a summation element 256 and a multiplier 258. The correlator also includes a logic device 254. The multiplier and the addition element produces a first correlation result based on even samples of the sample buffer 202 and provides a first correlation result to the logical device 254. The multiplier and the sum element produce a second correlation result based on odd samples of the sample buffer 202 and provide the second correlation result to the logic device 254. In the second illustrated arrangement, the second correlator, including the multiplier 258, receives samples from the sample buffer 202 that are a sample later (half chip) than the samples received by the first correlator including the multiplier 250. It can be seen that it is possible to process any number of phases shows in correlator 204 if the number of correlators and related logical devices is varied. If it is reduced from two phases to one by sampling once per chip, the necessary equipment is reduced by eliminating a correlator. On the other hand, if the number of phases is increased, a better temporal resolution is obtained for the correlation. The logic device 254 compares the correlation result with a predetermined threshold and discards the correlation results that do not exceed the threshold. The results that at least exceed the threshold are saved as corresponding to possible pilot phases. Thus, the logic device 254 contains some memory for storing data. The recorded correlation results are ordered to obtain an indication of the relative pilot phase correlation. The deviation controller 216 controls the deviation of the NRT LSG 208 to allow a correct alignment of the NRT LSG with the RT LSG. Each time the NRT LSG 208 increases in relation to the RT LSG, the deviation counter 217 increases. At the time when the state of the RT LSG 206 is loaded in the NRT LSG 208, the two sequence generators are synchronized and the deviation counter 217 is initialized. As will be described below, they will not be synchronized during the search operations. However, all that is required to return to the real time reference is to count the number of samples that the NRT LSG has varied with respect to the synchronization point. Deviation counter 217 performs this count. The RT LSG 206 serves as a synchronization reference to maintain a real-time reference and is continuously timed at chip speed. Fig. 3 is a flow diagram illustrating a method for operating the radiotelephone 104 of Fig. 1 to acquire a pilot signal in a CDMA receiver. The method starts at step 302. At 304, the real time clock (RT) is activated. The clock controller 218 provides a clock signal on the second output 234 (Fig. 2) at a speed twice that of the chip rate of 1.2288 megachips per second. This is the real-time clock signal for the ADC 110. The clock divider 220 divides this clock signal to achieve a real-time clock signal for the RT LSG 206. In step 306, the RT LSG is loaded with an initial value, and the synchronization reference is initialized. In step 308, an acquisition mask of the mask register 212 is loaded. The acquisition mask is that which conforms to the initial acquisition of a pilot signal and is, for example, a zero change mask that does not change the contents of the NRT LSG 208. In stage 31T-1 an integration length and a window size are loaded. The size of the window, W, is the number of delays, in chip intervals, that must be processed. In IS-95, the value of the size of the window is received by the radiotelephone 104 from the base station 102. A typical value for the size of the window is 60 chip intervals. The integration length is the number of samples summed by the summation element 252. The integration length in the illustrated arrangement is equal to N, half of the samples in the buffer 202, but which can be any suitable value. In some cases, it is preferable to integrate in less than N. samples. For example, if the analogous end 108 is not properly tuned to the transmit frequency of the base station 102, there is a lack of correlation effect when integrating or making a correlation in a large number of samples. In such a case, the effects of the lack of correlation are reduced by integrating in smaller sample quantities, such as N / 2, N / 4, etc. a first integration is carried out, in which, for example, the first N / 2 samples are integrated, followed by a second integration over the second N / 2 samples. These correlations can be carried out without having to drive the RF components or have to re-take samples, since all the samples are taken, initially, in the sample buffer 202. In Fig. 3, the steps are illustrated 312 and 324 with a dashed line to indicate specifically that they are optional steps. In step 312, the radiotelephone 104 feeds a predetermined portion of the CDMA receiver. In the illustrated arrangement, power is supplied to the radio frequency (RF) components of the radiotelephone 104 (Fig. 1). The RF components include the analogue end 108 and the ADC 110. In step 324, after the sampling steps (step 314-step 322) the supply of the RF components is reduced. This feature allows RF components, which consume relatively large amounts of power from the battery that powers the radiotelephone 104, to receive power only when they need it, during the collection of samples, and thus the battery charge is conserved. Steps 312 and 324 are optional in the sense that they can not be used during all sequences through the flow chart of Fig. 3. Additionally, while in the middle of a call, the radiotelephone can briefly tune to another frequency, collect a sample buffer, re-tune the original frequency and look for pilot energy in the collected samples. In step 314, a first sample is collected in the sample buffer 202. Clock signals are supplied at twice the chip rate to the ADC 110 and two samples (corresponding to a chip) are loaded sequentially into the buffer memory of the processor. shows 202. At the time the first sample is stored in the buffer 202, in step 316, the contents of the RT LSG 206 are loaded into the NRT LSG 208. In step 318, additional samples are collected in the memory intermediate 202 saving a sample of pilot signal in the buffer 202 and the RT LSG 206 is synchronized in step 320. In step 322, the total condition of the buffer memory 202 is controlled. The control remains in the link formed by the stage 318, 320 and 322 until the condition is obtained. Alternatively, another condition is controlled, such as picking up a predetermined number of samples or any other favorable condition. In step 324, the power is optionally reduced to the RF components or the RF is tuned again. In step 326, a non-real time clock is activated. The clock controller 218 supplies the non-real time clock to the NRT LSG 208. The non-real time clock speed can be any available or multiple clock speed but it should be much faster than the real time clock used. to time the samples towards the sample buffer 202. For example, in an IS-95 system where the real-time clock is related to the chip speed of 1.2288 megachips per second, the speed of the non-real time clock it can be 80 MHz. In step 328, the acquisition mask is loaded in the mask circuit 210. In step 330, the samples of the buffer memory 202 are processed, which method is illustrated in more detail in FIG. The method of Fig. 3 ends in step 332. With respect to Fig. 4, a method for operating the radiotelephone 104 of Fig. 1 to process saved pilot signals is illustrated. The method begins in step 402. In step 404, the correlator 204 correlates between the samples stored in the buffer 202 and the contents of the non-real time linear sequence generator (NRT LSG) 208. The result is supplied of the correlation made by the summing device 252 to the logic device 254 which determines whether said result exceeds a threshold, step 406. If not, the control continues in step 412. If the result does indeed exceed the threshold, it is saved. In addition, the value of the deviation counter is stored, which contains the deviation counter 217, step 410. This value corresponds to the number of times the NRT LSG 208 has increased. In step 412, the NRT LSG 208 is increased, and an alignment value of NRT LSG is established for each correlation. Also, the deviation counter 217 is incremented and the size of a window is decreased. In step 414, the size of the window is controlled and if the exit condition is not met, the method remains in the circle that includes step 404-414. In repetitive fashion, the circle correlates the stored samples with the contents of the linear sequence generator, NRT LSG 208. In one arrangement, the invention provides a "soon discard" ability. In the present arrangement, the correlator 204 correlates with a less than complete buffer of samples, for example, N / 2 samples. The result of this correlation is compared with a threshold. If the correlation exceeds the threshold, the remaining samples from the buffer are correlated and the operation as described above proceeds. In a two-phase correlator, as indicated in Fig. 2, if either of the two correlation values exceeds the threshold, the procedure continues as explained. However, if both correlation results are less than the threshold, the correlation is aborted, the NRT LSG 208 and the deviation counter 217 are incremented and processing continues. The ability to soon discard improves the performance of the receiver receiver by allowing PN phases that contain little energy or nothing to be discarded quickly without executing a complete correlation. In step 416, the logic device 254 selects the set of the best correlations to assign at least one receiver finger of the ladder receiver to the detected pilot signals. The set of the best correlations may have one or several correlations, depending on the correlation results and the number of receiving fingers that must be assigned. Based on the results of the correlation, the logic device 254 selects a number of optimal pilot signals corresponding to the receiving fingers of the receiver, 112 to be assigned. If a single beam has been located, either a beam directly received from a base station or a multiple path beam, a single receiving finger will be assigned (Fig. 1), step 418. If several rays from different sources have been located base stations (with different phases of pilot signals), said rays will be assigned to multiple fingers of the receiver 112. Likewise, if all the fingers of the receiver have already been assigned, as part of a maintenance process, the logic device 254 will determine whether a finger must be re-assigned to a different beam according to the results of the correlation. The process of assigning fingers includes the deviation of the LSGs from the fingers to align them with the pilots and the multipath components that are of interest. The value of the deviation counter which was stored in step 410 for a pilot or a route exceeding the threshold in step 405 provides the temporary difference in 1/2 chips between the synchronization of the mobile station and that of the pilot or route of interest. In step 420, the value of the deviation counter stored by the logic device 254 is supplied to the linear sequence generator 128 of the receiving finger which is assigned to the detected pilot signals. In this way, the searcher receiver 114 provides an NRT LSG alignment value that corresponds to one of the best correlations of the finger linear sequence generator that relates to at least one receiving finger. The receiving finger uses the value of the deviation counter to align its finger LSG with the synchronization of the detected pilot signal and begins the detection of the pilot signal. The method relating to the processing of samples ends in step 422. With respect to Fig. 5, a method for operating the radiotelephone 104 of FIG. 1 is illustrated to preserve the finger assignments. The method starts at step 502. At step 504, the mask for a pilot of interest is loaded from mask register 212 to mask circuit 210. On the other hand, the integration length and the window size are loaded. . In step 506, the RF components are fed if necessary. If a search or other frequency is required, it is possible to tune the radio to the new frequency. In step 508, a number of sample pairs equal to half the size of the window (W / 2) are taken in the buffer 202. Sampling is carried out using the real time clock. Sample pairs are taken because, as explained above, the pilot signal is sampled at twice the chip speed.

Each sample corresponds to a chip. Other quantities of chips or samples are taken into the buffer 202 according to the specific instrumentation. In step 510, the contents of the RT LSG are loaded into the NRT LSG 208. By storing W / 2 sample pairs before loading the state of the RT LSG, the NRT LSG effectively advances half the size of the window in chips with regarding the first sample. Then, if the correlations W are made sequentially, starting with the initial state and increasing a chip by correlation, the search will move from -W / 2 to + W / 2. Once the NRT LSG is loaded in step 510, the remaining samples N- (W / 2), step 511 must be collected. Then, as an option, the RF components are shut off in step 512 or turned over. to tune to the original frequency. In step 514, the clock speed NRT is selected and applied to the NRT LSG 208 for processing the samples. The mask of interest is applied to the contents of the NRT LSG 208 in step 516 and in 518, the samples are processed. During step 518, the steps corresponding to step 402 to 422 of FIG. 4 are performed. When the buffer filled with samples is processed, in step 520 it is determined whether there are more pilot signals that are of interest. For example, upon awakening from a spaced sleep period, the searcher receiver 114 has a list of active pilots, a list of candidate pilots and a list of neighboring pilots to search for the energy of the pilot signal and be able to locate appropriate pilot signals for the finger assignment. If there are more drivers of interest, in step 522, the initial state of the NRT LSG 208 that was saved in the register 214 is loaded in the NRT LSG 208, the NRT LSG 208 is reset to an initial state and a new mask is loaded in the mask circuit 210, which causes the NRT LSG to move to the next state. The next state of the NRT LSG corresponds to a new pilot of interest. Other suitable ways to change the state of the NRT LSG include calculating the next state of the NRT LSG and increasing or decreasing the NRT LSG to produce the next state of the NRT LSG. Also, in step 522, the read / write flag 222 of the sample buffer 202 is placed in Ó and the deviation counter 217 is reset. This corresponds to resetting the NRT LSG to an initial state using the reference values of synchronization. The mask is loaded for the next pilot of interest in step 516. Steps 516-522 are repeated until all the pilots of interest have been processed. The method ends in step 524. As can be seen from all the foregoing, the present invention provides a method and equipment for rapidly acquiring pilot signals in a CDMA receiver. Since multiple samples are taken in a buffer, the signal processing of the chip rate can be switched off and decisions can be taken on the acquisition of pilot signals on a much faster basis, using a non-real time clock. Because the receiver's operation is faster, the delays in the acquisition of the pilot channel are substantially eliminated and problems such as the fast PN are also eliminated. In the operation of spaced mode, it is only necessary that the radiotelephone wake up sufficiently in advance to the allocation of its space for the rapid acquisition of the pilot. The maintenance of the pilot channel is also faster, which improves; the reliability of idle transmission and smooth transmission. Since the samples are stored in the buffer, once said samples are collected, the analogue end is free to tune another frequency during the strong mobile assisted transmission (MAHHO). While a particular arrangement of the present invention has been set forth and described, modifications are possible. For example, you can reorder, replace and eliminate the stages, as appropriate. Accordingly, the appended claims attempt to cover all those changes and modifications that are encompassed by the scope and the actual nature of the invention. The following is claimed:

Claims (1)

1. Claims A method for acquiring a signal in a code division multiple access (100) communication system (CDMA). Said method is characterized by: Sampling (318) a received pilot signal at a first speed; Save numerous samples of pilot signals; Process (330) the numerous samples of pilot signals at a second speed, greater than the first, and identify (416) one or more pilpto signals based on the plurality of samples of pilot signals. A method for acquiring a pilot signal in a code division multiple access (112) receiver (CDMA); the CDMA receiver includes, at least, one receiver finger (122, 124, 126). The method is characterized by: Saving (314, 318) a predetermined number of samples of a received pilot signal; Increase (320) a real time linear sequence generator (RT LSG) (206); Charge (316) a state of the RT LSG in a non-real time LSG (NRT LSG) (208) at a specific time point relative to the storage of the predetermined number of samples; Repeatly perform a correlation (4'04) between the stored samples and the contents of the NRT LSG, producing correlations; Increase (412) the NRT LSG after the correlation to establish an alignment value of the NRT LSG; Select a game of the best correlations (416); Providing (418) an alignment value of the NRT LSG corresponding to one of the sets of the best correlations to a linear finger sequence generator (128) related to at least one receiving finger, and detecting the pilot signal in one finger at a minimum using the linear finger sequence generator. A method as set forth in claim 2, further characterized in that the step of increasing the NRT LSG after the correlation includes increasing (412) a deviation counter (216), this counter saves a new corresponding counter value to the number of times the NRT LSG has increased. A method as set forth in claim 2, wherein the storage step, further, is characterized by: feeding (312) a predetermined portion of the CDMA receptor; detect the predetermined number of samples of the pilot signal and cancel the power (324) of the predetermined portion of the CDMA receiver. A method as set forth in claim 2, further characterized by selecting (304), prior to storing the predetermined number of samples, a real-time clock rate, and then selecting a clock rate of not real time; the latter is greater than the multiple of the real-time clock speed. A method as described in claim 3, further characterized by the steps of establishing (304) a real time rate for saving the samples of the pilot signal and establishing (326) a non real time rate for the subsequent processing; the speed of the non-real time clock is greater than the speed of the real-time clock. A radiotelephone (104) allowing operation in a communication system (100) and characterized by comprising: a ladder receiver (112) including numerous receiver fingers (122, 124, 126); a searcher receiver (114), including: a buffer (202) for storing various samples of a received pilot signal; a non-real time linear sequence generator (NRT LSG) (208) for generating a sequence of values; the NRT LSG increases in response to a clock signal; a correlator (204) for effecting a correlation between the plurality of samples and the sequence of values and producing a correlation result, and a synchronization reference (206) for maintaining a real time reference. Said synchronization reference provides the real-time reference to the NRT LSG when a first sample is stored in the buffer; The search receiver detects the received pilot signal to acquire the synchronization of the system for the radiotelephone. A radiotelephone as set forth in claim 7, wherein the synchronization reference is characterized by comprising a real-time linear sequence generator (RT LSG) (206) that generates a sequence of values in response to a time clock signal. real; he NRT LSG increases in response to a non-real time clock signal. A radiotelephone, as set forth in claim 8, further, is characterized by comprising a register (214) for storing an initial state of the NRT LSG; the real time reference is saved in the record when the first sample is saved and transferred from the record to the NRT LSG to set said NRT LSG in the real time reference. A method for updating the assignments of the receiver finger in ladder in a code division multiple access (112) receiver (CDMA). This method is characterized by: a) initializing (510) a synchronization reference (206), saving a synchronization reference value; b) collecting (508) a predetermined amount (511) of pilot signal samples; c) increasing (412) a non-real time linear sequence generator (NRT LSG) (208) to produce a sequence of values; d) performing a correlation (404) between the predetermined number of pilot signal samples and the sequence of values, and producing correlation results; e) repeating steps (c) and (d) a predetermined number of times; f) assigning (418) the receiving fingers according to the results of the correlation; g) passing the NRT LSG to a next state, and h) repeating steps (b) to (g) until all the pilot signals of interest have been processed (520).