MXPA01003812A - Offline page monitoring - Google Patents

Abstract

A novel and improved method for performing paging is described. In one embodiment of the invention a searcher (206) is used to detect spread spectrum signals. Samples received RF signals are stored in a sample buffer. During standby mode, the samples are gathered during paging slots assigned to the mobile. A set of searches are performed on the samples, and if pilot signals are detected additional demodulation is performed to detect paging messages. The resulting set of demodulation data may be combined to increase detection. After a page message has been detected, additional demodulation resources may be activated to process more complete page messages, or other information channels. In one embodiment of the invention, the searcher (206) includes a demodulator to perform quick page detection without the use of finger elements to reduce idle mode power consumption.

Description

CHECK OUT OF LINE PAGE BACKGROUND OF THE INVENTION I. Field of the Invention The present invention relates to wireless communications. More particularly, the present invention relates to a novel and improved browser for detecting page messages in extended spectrum communications.

II. Description of the Related Art In the North American Patent Application Serial No. 08 / 316,177 entitled "Multipath Search Processor For A Spread Spectrum Multiple Access Communication System" (Application U77) is described a scanning system for detecting the spread spectrum signals . The scanner is particularly suitable for use in a CDMA-based digital cell phone system to identify the pilot channels transmitted within the CDMA system. Once the pilot channel is identified, the telephone, or "the subscriber unit", uses the associated time measurement information to perform functions such as verification of page messages and directed communications.

The scanner? 177 usually works in combination with a group of digital elements and a decoder placed in a single integrated circuit.

• Together, the components perform the necessary processing for CDMA communications and page verification. For example, in order to receive a CDMA signal, the browser performs the search of the pilot channel in several time shifts. Once a pilot channel is detected, the digital elements are activated to process an associated data channel, such as a paging channel or a traffic channel. To perform the search and signal processing, the scanner and the digital elements receive the generated samples in response to the RF signals received by the unit of the subscriber. Samples are normally generated by an RF / IP unit inside the mobile phone or the subscriber unit. ^ In general, it is desirable to reduce the energy consumption of a subscriber unit to reduce the size and weight of the battery. Additionally, it is desirable to increase the reliability with which the page and other messages are received and processed by the subscriber unit. For this purpose, as well as other objectives, the present invention is directed. BRIEF DESCRIPTION OF THE INVENTION The present invention is an improved and novel method for carrying out paging. In a • embodiment of the invention an explorer is used to detect extended spectrum signals. Samples of received RF signals are stored in a sample buffer. During the reserve mode, the samples are collected during the matching of the openings assigned to the mobile. A group of searches is performed on the samples, and if the pilot signals are detected, the additional demodulation is performed to detect the paging messages. The resulting group of demodulation data can be combined to increase detection. After a page message has been detected, additional demodulation resources can be activated to more complete processes of the page messages, or other information channels. In one embodiment of the invention, the explorer includes a demodulator to perform the rapid detection of a page without the use of digital elements to reduce the power consumption of the inactive mode.

BRIEF DESCRIPTION OF THE DRAWINGS The features, objectives, and advantages of the present invention will become clearer from the detailed description indicated below when taken in conjunction with the drawings in which similar reference characters are identified correspondingly to • throughout the description and wherein: Figure 1 is a cell phone system configured in accordance with one embodiment of the invention; Figure 2 is a block diagram of a subscriber unit configured in accordance with an embodiment of the invention; flB Figure 3 is a flow chart illustrating the process performed within a subscriber unit when performed in accordance with one embodiment of the invention; Figure 4 is a block diagram of a search when configured in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES An improved and 20 novel method and apparatus for detecting paging messages is described. The exemplary embodiment described herein is indicated in the context of the digital cellular telephone system. Although the use of this context is advantageous, the different embodiments of the invention can be incorporated into different environments or configurations. In general, the different systems described herein can be formed using processors controlled by the set of programs (software), integrated circuits, or • discrete logic, however, implementation in an integrated circuit is preferred. The data, instructions, commands, information, signals, symbols and microcircuits (chips) that can be referred to throughout the application are advantageously represented by voltages, currents, electromagnetic waves, fields or magnetic particles, fields or optical particles, or a combination of them. In addition, the blocks shown in each block diagram can represent the physical components of computation (hardware) or stages of the method. Figure 1 is a highly simplified block diagram of a cellular telephone system configured in accordance with the use of the present invention. The ^^ mobile phones and other communication systems 10 (subscription units) are located between the base stations 12, which are coupled to the base station controller (BSC) 14. The mobile interconnection center MSC 16 connects the BSC 14 to the public interconnection telephone network (PSTN) 18. During the operation, some mobile telephones direct telephone calls interconnecting with base stations 12 while others are in an idle mode, or in standby, where they are verified for page messages. According to the use of some CDMA communication protocols, a subscriber unit 10 can be interconnected simultaneously with two base stations 12 in a soft or flexible manner. A system and method for operating a cell phone using CDMA techniques is described in US Pat. No. 5,103,459 entitled "System and Methodo for Generating Signal Waveforms in a CDMA Cellular Telephone System" assigned to the assignee of the present invention and incorporated herein by reference. reference (patent 59). The system of the patent 59 is configured substantially in accordance with the use of the IS-95 over the standard air interface. Additionally, in one embodiment of the invention, the paging of a subscriber unit 10 is performed substantially in accordance with the paging method described in U.S. Patent Applications serial numbers 08 / 865,650, and 08 / 890,355 both entitled "Dual Chanel". Slotted Paging "assigned to the assignee of the present invention and incorporated herein by reference (dual-channel paging applications). In these patent applications, the use of a fast paging message (quick page) transmitted over a reduced coding channel is described. One or more fast pages are transmitted before the full page message (full page) allows a subscriber unit to reduce the verification time of the page, and therefore reduces the reserve power consumption. If the subscriber unit does not receive a positive fast page, then the entire page that reduces the power consumption of the inactive mode is not verified. Figure 2 is a block diagram of a demodulator used to process the CDMA signals according to one embodiment of the invention. The received samples (Rx) are generated by the RF / IF system 190 and the antenna system 192, which receive the RF signals, filter, down-convert and digitize the RF signals in the baseband. The samples are supplied to a multiplexer 202 and to the sample RAM 204. The output of the multiplexer 202 is provided in the scanning unit 206 and the digital elements 208, which are coupled to the control unit 210. The combiner 212 couples the decoder 214 to the digital elements 208. Normally, the control unit 210 is a microprocessor controlled by the set of programs, and can be located in the same integrated circuit or in a separate integrated circuit.

During the operation, the samples received (samples) are stored in the sample RAM 200 and are applied to a multiplexer 202. The sample multiplexer • 202 supplies either the real-time samples or the stored sample to the scanning unit 206 and the digital elements 208. The control unit 210 configures the digital elements 208 to perform the demodulation at different time shifts based on the results Search for the unit of m? scan 208. The demodulation results are combined and passed to a decoder 214, which generates the data. In general, the search performed by the browser 208 uses non-coherent demodulation of the pilot channel to test the time hypothesis that corresponds to several sectors, base stations and multiple trajectories, while the demodulation ^^ carried out by the digital elements 208 is carried out by means of the coherent demodulation of the data channel.

Non-coherent demodulation does not require carrying the information phase, but detects the energy of the signal instead of the data contained in the signal (for certain types of waveform). The coherent demodulation requires the information phase, and therefore more information about the signal, but the data transmitted in the signal can be determined. Throughout this application, the term demodulation only refers to coherent demodulation, while the search refers to non-coherent demodulation. In one embodiment of the invention, the non-propagation was performed by multiplying the samples received with the complex conjugate of the PN sequence and assigning the Walsh function to a single time hypothesis and digitally filtering the resulting samples, often with an accumulator circuit integrated fl and data download. In one embodiment of the invention, a reinforced scanner is provided to perform the search of the pilot channel and the demodulation of a paging channel in the samples stored in the sample RAM. The demodulation and search can be performed at various time shifts, and the demodulation results are combined to determine if it was received • a page message. Preferably, the page channel demodulated by the browser is similar to the channel of the fast paging described above in the dual channel paging applications referred to above. When the message duration is shorter for fast paging (microcircuits of 128 or 256 PN at 1.2288 Mcps is 104 or 208 microseconds) and the If necessary misalignment is less, (approximately 100-400 microseconds) the required received samples can be entered into memory and processed "off-line" for energy savings. • Figure 3 is a flow chart illustrating the operation of the demodulator of Figure 2 during the idle mode according to one embodiment of the invention. The inactive mode is the state where the subscriber unit is energized but a call is not made. During idle mode the unit of the ^ P subscriber verifies the paging messages addressed to it. The paging message can indicate an incoming communication or telephone call. As mentioned above, the invention is described in the context of a dual channel paging system as is described in dual-channel paging applications. In a step 300, the subscriber unit collects and stores the samples received in step 302 during the quick paging space assigned to it.

In one embodiment, the collection has been performed by activating the RF / IF unit 190, storing the samples in the sample RAM, and then deactivating the RF / IF system 190. Normally the subscriber unit collects the samples for a longer duration that of a single fast paging space so that the multiple time shift signals are stored within the group of samples received. In step 304 of the scanning unit 206 • (from Figure 2) a pilot search is performed on the samples stored in several time displacements. Additionally, the pilot search for the different signals can be performed. For example, the search can be performed by the signals of different base stations that use different, or different displacements, of pilot codes. When a local maximum is detected over a certain threshold, and the combined function is allowed for the particular search window, the resulting hypothesis is demodulated and combined. The stage is carried out once all the hypotheses have been completed in a list of search. In one embodiment of the invention, it is preferable to have the sample RAM 302 considerably larger to cover the displacement time of a group of multipath signals. Therefore, looking simply the same group of samples in different displacements, the different pilots are detected. Similarly, the same group of samples can be demodulated in different shifts to process the fast pages. Since a fast page channel designed to coherent signaling provides a good execution, therefore it is preferred in several cases. A rapid paging system can also be designed for non-coherent signaling. • In step 306, the browser 206 is interconnected to the demodulation mode, and the paging channel associated with each signal detected during the search mode is demodulated to determine whether a fast page has been received. The fast pages are processed by performing the coherent demodulation in the fl group of page channels corresponding to the group of pilot channels detected during the search. Thus, in one embodiment of the invention the fast page channel is demodulated within the browser after the search is performed. Each demodulation is done in a Particular displacement within the samples, and the resulting group of the soft demodulation decision data is variously combined using an accumulator within the browser 206. In step 308 the combined demodulation data is examined for determine whether a positive fast page has been received (ie an indication of the next full paging message can be directed to this subscriber unit 10). If not, the subscriber unit returns to step 300. In that case, the digital elements 208, The decoder 214 and the RF / IF unit 190 are activated in step 310, and the entire page is processed in step 312. In an alternative embodiment of the invention, the subscriber unit continues to search for the files. • i for other pilots to find new signals for I to process when the next paging space i occurs. Additionally, if the quick paging channel i is not received with sufficient quality, then the step i i 310 is performed to ensure in any way that a message of the entire page is not lost.

• To perform fast page search and processing within the scan unit 206, the quick paging channel may be verified without having to activate the digital elements until a rapid posilive page is received.

Generally, most of the quick page messages will be negative, indicating that no call or message is pending. Therefore, the time that the digital elements 208 and other circuits are activated is significantly reduced. Therefore, the The reduction of the circuitry used to carry out the verification of the fast page channel increases the reservation time of the subscriber unit. This reduction in the circuitry is achieved by taking advantage of the reduced coding level of the subscriber. fast paging channel and fast page message and storage of samples received for processing. This reduced coding allows the demodulation of the fast paging channel with a limited amount of demodulation functionality, and therefore with additional complexity limited in the browser. Also, the use of the sample RAM 204 allows to perform the demodulation of the multiple time shift using a single demodulation machine within the browser 206, which further reduces the circuitry necessary for the verification of the paging messages. The additional energy saving is carried out by carrying out the search and verification of the page channel using stored samples. In one embodiment, the fast paging channel is an uncoded bit OOK BPSK sent once or twice. In particular, the time that the RF / IF unit 190 operates during each page cycle is reduced by storing the samples when they are generated. Once the samples are stored, the subscriber unit deactivates the RF / IF unit to save energy, and searches the samples repeatedly at different displacements or different pilot signals, or both, using only the digital circuitry. As mentioned above, performing the different searches on the same samples allows the RF unit to be turned off once the initial group of samples is collected. Turning off the RF unit reduces the power consumption of the mobile during idle mode. In contrast, if the samples were not stored, additionally the samples would have to be collected again if necessary to search for the different pilot signals and time shifts. This continuous collection of pilot data will require that the RF unit remain on, and therefore consume energy, for a longer period of time, which will reduce the reservation time of the subscriber unit 10. The described modality of the invention provides the execution improvements as well as the consumption of power of inactive mode improved. In particular, by performing demodulation and searching in the same group of samples, the execution of the demodulation is improved.

^^ This is because the best signals as measured by the pilot channel scanner will be the best signals for the demodulation of the paging channel because the group of samples is the same. In alternative systems, the search is performed in a first group of samples and the results of the explorer are used to determine how to demodulate the channels of paging in a second group of samples. While the correspondence is normally reasonable between the search results and the paging channel quality if the time span between the two events • is smaller, any difference in the channel between the search and the demodulation is virtually eliminated when compared to the fading of the channel de-correlation time through conducting the search and demodulation in the same samples. Figure 4 is a block diagram of the browser 206 when configured according to one embodiment of the invention. The synchronized and quadrature phase samples are read from the sample RAM 302 (Figure 2) and not scattered by the QPSK 402 decoder using a PN code from the PN code generator 404, wherein the PN code is comprised of a synchronized portion (PNl) and a phase quadrature portion (PNQ). The resulting synchronization and phase quadrature components of the QPSK 402 despacker are applied to the multipliers 406a-d. After the processing of the sample RAM, arbitrary clock frequencies, such as 19 MHz, may occur without regard to the proportion of the original microcircuit. During the search mode, the generators of the Walsh code 408 and 410 generate the pilot channel Walsh code that is applied to multipliers 406a-406d. Multipliers 406a - 406d and accumulators 408a - 408d operate to discover the test without spreading with the • Pilot Walsh code from the 5 Walsh pilot code generator 408. Multiplication of the QPSK and WALSH defroster can occur for, or be integrated as a single operation for the equivalent results. The uncovered pilot samples of the accumulators 408a and 408b are applied twice to the multipliers 420 and 422: once directly and once by the multiplexers 422. The result is that the uncovered pilot samples are squared, and the yields are added by the adder 412. Therefore, in the search mode, the point product of the pilot data discovered, and also the correlation energy of the pilot channel in the current displacement. ^^ Similarly, the uncovered pilot samples of accumulators 408c and 408d a are applied to the yields of the square circuits 410 which are summed by the adder 412. Therefore, the square circuits 410 and the adder 412 act to calculate the point product of the pilot data discovered with it, and therefore the energy channel correlation pilot in current displacement.

The dotted products of the adders 412 and 422, received by the local maximum calculator 414, are received. The local maximum calculator 414 determines the • maximum possibility of displacement, or the 5 displacements, of a group of displacements (or hypotheses) attempted by the explorer based on the correlation energy. For example, the local maximum calculator 414 can save the greatest local energy in a group of over-correlated correlation energies to isolate the sample closest to the true displacement. The multipliers 406a and 406b and the accumulators 408a and 408b operate to discover the non-scattered samples with the Walsh code of fast paging from the fast page Walsh code generator. 15 The displacement group is generated according to the time of the PN and Walsh codes and is adjusted in relation to the samples. In an example search, you • adjust the PN and Walsh codes in small increments around the particular search regions.

Typically, code generators are configured by a control system that also defines the search regions with an initial offset and a final offset. The control system can be a microprocessor or a digital signal processor controlled by the set of programs stored in memory.

The maximum tracker N16 collects the group of N major correlation energies for the different search regions. N is an integer, preferably in the range 4 to 16. The use of another criteria for the collected search results, such as the diversity of signal sources, is consistent with the use of the invention. The resulting group of correlation energies and the associated displacements (search results) are reported to the control system. ß Once the search operation has been performed in the exemplary embodiment of the invention, the control system configures the browser to perform demodulation in the paging channel for a group of signals and offsets based on the results of search. To perform the demodulation of the page channel (preferably the fast page channel), the Walsh 410 generator is configured to generate the code ^^ of Walsh of the paging channel, and 423 multiplexers are configured to apply the output of the accumulators 408c and 408d to multipliers 420. Additionally, accumulators 408a and 408b are configured to integrate exactly over the duration of the bit. For each signal to be demodulated, the control system configures the PN generator and the generators of Walsh to the particular offset, and the samples are demodulated again. The uncovered samples of the fast paging channel of the accumulators 408a and 408b are applied to the multipliers 420. Additionally, the uncovered samples of the pilot channel are applied to the multipliers 420 by means of the multiplexers 423. To realize the knitted product of the pilot and paging data, the outputs of the multipliers 420 are added by the adder 422, and the resulting soft decision data of the resulting fast paging channel are received by the insurers 424. Several other methods for adjusting the phase of the carrier will be clear including the use of a cross product operation or other rotary phase methods. The knitted product retrieves the data that is synchronized with the pilots & weights to combine. The output of the insurers 424 is then received by the combiner accumulator 426. For each demodulated signal, the accumulator 426 is added to the demodulation results. Once the signal group is demodulated, the combined fast page data is generated in the control system, which estimates the transmitted data by taking a firm decision based on the accumulated soft decision data. Based on the firm decision, it is determined if a quick page has been sent.

Additionally, in one embodiment of the invention, the energy of the discovered pilot channel data is recalculated by performing a dot product operation, and the resulting pilot energy is accumulated for each signal by the accumulator 426. The accumulated pilot energy is send to the control system. In one embodiment of the invention, the control system determines whether the fast paging data is relied upon based on the accumulated pilot energy. If the accumulated pilot energy is earlier than a certain threshold, then the fast paging channel turns out to be reliable. On the other hand, the next fast page space is then processed, or the entire paging channel is processed. As noted above, using the same samples to process the pilot and paging channels ensures that the channel is the same for both processes, that improve the execution of the demodulation. Therefore, a system and method for performing the verification of a page has been described. The above description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. The various modifications to these modalities will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other modalities without the use of the inventive faculty. Therefore, the present invention is not intended to be limited to the embodiments shown herein but will be granted to the broadest scope consistent with the principles and novel features described herein.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects or products to which it refers.

Claims (11)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A system for receiving pages characterized in that it comprises: a storage unit for storing the first received samples; a reinforced scanner to detect the correlation energy of a pilot channel and to demodulate a first paging channel within the first received samples; and a demodulation element for demodulating a second paging channel within other received samples. The system according to claim 1, characterized in that it additionally comprises: the decoder for deciphering the soft decision data of the demodulation element. 3. The system according to claim 1, characterized in that it additionally comprises: the RF unit for generating the received samples. 4. The system according to claim 1, characterized in that it additionally comprises: the control unit for activating the scanner 5 during the quick page openings, and to activate the demodulation unit during the full paging openings when a quick page message is received. 5. The system according to claim 1, characterized in that the combined scanner is comprised of: a first processing element for not spreading a pilot channel; a second processing element for not spreading the pilot channel and for not spreading the first paging channel; a phase adjustment demodulation circuit ^^ to rotate the first paging channel data using the pilot channel of the first processing element; a correlation energy circuit to calculate the correlation energy for the second processing element. 6. The system according to claim 5, characterized in that the phase of the adjustment circuit is a two-dimensional vector point product or cross product between the data and the pilot complex baseband signals. • The system according to claim 5, characterized in that it additionally comprises: a combiner circuit for combining the diversity of demodulated data, wherein the scanner performs multiple demodulations within the data? J? Stored for the first paging channel, and the combiner that combines the soft decision data of the multiple demodulations. 8. The system according to claim 7, characterized in that the combiner is 15 comprises of an accumulator. The method according to claim 7, characterized in that the search step is comprised of the steps of: searching for a pilot channel; 20 do not scatter the pilot channel; do not spread the first paging channel; demodulating the first paging channel by projecting the first data of the paging channel not scattered over the data of the non-scattered pilot channel. 10. The method according to claim 7, characterized in that the search step is comprised of the steps of: demodulating a pilot channel; demodulate such a pilot channel; demodulate the first paging channel; calculate the correlation energy from the pilot channel data; project the first data of the paging channel using the data from the pilot channel; calculate a correlation energy for the pilot information channel data. 11. The method according to claim 7, characterized in that it additionally comprises the steps of; accumulating the demodulated data, wherein the multiple demodulations are performed within the stored data for the first paging channel, and the accumulation step accumulates the soft decision data from the multiple demodulations.