HK1063892B - Search system to search for a received signal in a spread spectrum system during each search sweep - Google Patents

Description

Search system for searching received signal in spread spectrum system during each search sweep

Technical Field

The present invention is directed generally to wireless spreading devices and, more particularly, to a system and method for acquiring a signal received in a wireless spreading device.

Background

Spread spectrum modulation, including Code Division Multiple Access (CDMA) modulation, is one of several techniques for allowing a large number of system users to share a communication system. Other multiple access techniques include Time Division Multiple Access (TDMA) systems and Frequency Division Multiple Access (FDMA) systems. There are also wireless communication systems based on analog Frequency Modulation (FM), such as the "advanced mobile phone system" (AMPS). In addition, many wireless communication devices employ Global Positioning System (GPS) technology. Some wireless communication systems are capable of operating using multiple technologies (e.g., CDMA and GPS) or on different frequency bands (e.g., cellular frequency bands or "personal communication services" (PCS) frequency bands).

To simplify the discussion, the background of the invention will focus on various CDMA modulation techniques in a wireless communication system. However, the principles discussed are generally applicable to any spread spectrum system. Various CDMA modulation techniques are disclosed in U.S. patent No. 4,901,307, entitled spread spectrum multiple access communication system using satellite or terrestrial repeaters, published 2/13 1990, the disclosure of which is assigned to the assignee of the present invention and is incorporated herein by reference. The above-referenced patents disclose the use of phase coherent and chip synchronous chip sequences defined as "pilot chip sequences" or "pilot signals". The pilot signal may be used to provide phase and time acquisition and tracking and multipath correction.

Various methods for acquiring signals are disclosed in the above referenced patents and in the following patents. The following patents are: (1) united states patent No. 5,781,543 entitled "power efficient acquisition of CDMA pilot signals" issued 7, 14, 1998; and (2) united states patent No. 5,805,648 entitled "method and apparatus for performing search acquisition in a CDMA communication system", issued 9/8/1998. Both of these U.S. patents are assigned to the assignee of the present invention, the disclosures of which are incorporated herein by reference.

When a wireless device is first powered on, the device must acquire signals from a remote location, such as a Base Transceiver System (BTS). A wireless CDMA communication device will typically receive pilot signals from multiple BTSs. The wireless device will search for signals from these BTSs and will establish a communication link with the selected BTS to allow data (e.g., audio signals) to be received and transmitted over the established communication link. The selection of a particular BTS and the actual communication between the wireless communication device and the selected BTS are well known in the art and need not be discussed in detail herein.

As described in the above-referenced patent, in a CDMA communication system, each BTS broadcasts the same pseudo-noise (PN) code pilot signal, but with a different phase offset. The pilot signal can be thought of as a rotating phasor of the form:

s(t)＝Ae^(-ωi+φ)

to acquire the signal, the wireless CDMA device must follow the phase of the signal transmitted by the BTSSynchronized with the frequency omega. The purpose of the "searcher" process in a wireless device is to find the phase of the received signal. The searcher uses the estimated frequency ω. If this estimated frequency is not close enough to the frequency of the pilot, the received signal will not be acquired.

The conventional search pattern searches sequentially for all possible PN phase offsets using a set of hypothetical search parameters. These search parameters may be changed before the next search sequence or search sweep. The search parameters may include the size or window of the search segment, coherent integration length, non-coherent integration length, inferred frequency error, Walsh and quasi-orthogonal function (QQF) parameters, and other search parameters. The search parameters are discussed in more detail in the above-referenced U.S. patent No. 5,805,648. Conventional search methods are able to search only a single pilot channel during each search sweep. Furthermore, conventional search methods can use only a single inferred frequency error during each search sweep.

Conventional search methods can broadcast each pilot signal or 1x signal over a bandwidth of approximately 1.25MHz reasonably well with a single channel. The conventional search method can also perform quite well when the frequency error range is small. Recently, several CDMA techniques (e.g., 3x direct spread spectrum (3xDS) signals, 3x multi-carrier (3xMC) signals, and Orthogonal Transmit Diversity (OTD) signals) have been developed that broadcast a pilot signal over a wider frequency range or in multiple channels. Furthermore, the frequency error range in newer CDMA techniques may be larger than in 1x signals. Conventional search methods cannot take advantage of newer CDMA broadcast techniques. Conventional search methods also have a limited frequency range over which the pilot signal phase will be detected.

It can therefore be appreciated that there is a significant need for an improved system and method for acquiring signals in a wireless spread spectrum device. This and other advantages are provided by the present invention as will be apparent from the following detailed description and the accompanying drawings.

Disclosure of Invention

The present invention is embodied in a system and method for acquiring signals in a wireless spread spectrum device that provides greater flexibility than prior art acquisition architectures. In one embodiment, the invention may be configured to: during each search sweep, signals are searched for in multiple channels. In another embodiment, the invention may be configured to: during each search sweep, multiple presumed frequency errors are used. In an exemplary embodiment, the present invention may be configured to: during each search sweep, multiple channels are searched using multiple hypothesized frequency errors.

The present invention provides a searcher system for searching for a received signal in a spread spectrum system during each search sweep, comprising: a) reconfigurable signal routing circuitry for selecting a route for the received signal; b) a plurality of rotators for adjusting the phase of the received signal to compensate for the presumed frequency error based on the signal received from the search controller, thereby creating one or more frequency bins; c) a plurality of searcher data buffers for storing the phase adjusted signals; d) a generator for generating a pseudo-noise PN signal; e) a PN buffer for storing the generated PN signal; f) pairing logic circuitry to pair the stored phase adjusted signal with the generated PN signal according to the created one or more frequency bins; and g) a search controller for generating control signals to control the operation of the signal routing circuit, the rotator, and the pairing logic circuit.

The present invention also provides a searcher system for searching for a single channel received signal in a spread spectrum system during each search sweep, the searcher comprising: signal routing circuitry for selecting a route for the received signal; a plurality of rotators for adjusting the phase of the received signal to compensate for the presumed frequency error based on the signal received from the searcher to create one or more frequency bins; a plurality of searcher data buffers for storing the plurality of phase adjusted signals; a plurality of generators for generating a plurality of pseudo-noise PN signals; and a plurality of PN buffers for storing the plurality of generated PN signals; wherein the system is dynamically configured to: independently employing each of the plurality of rotators for phase adjustment to independently generate the plurality of generated PN signals and independently pairing the phase adjusted signals stored in the plurality of searcher data buffers with the PN signals stored in the plurality of PN buffers based on the created one or more frequency bins.

The present invention yet further provides a searcher system for searching for a multi-channel received signal in a spread spectrum system during each sweep, the searcher comprising: signal routing circuitry for selecting a route for a channel of the received signal; a plurality of rotators for adjusting a phase of a channel of the received signal to compensate for the presumed frequency error based on the signal received from the searcher, thereby creating one or more frequency bins; a plurality of searcher data buffers for storing the plurality of phase adjusted signals; a plurality of generators for generating a plurality of pseudo-noise PN signals; a plurality of PN buffers for storing the plurality of generated PN signals; wherein the system is dynamically configured to: independently routing a channel of the received signal to any of the plurality of rotators, independently phase adjusting with each of the plurality of rotators, independently generating the plurality of generated PN signals, and independently pairing the phase adjusted signals stored in the plurality of searcher data buffers with the PN signals stored in the plurality of PN buffers based on the created one or more frequency bins.

Drawings

Fig. 1 is a functional block diagram of a CDMA communication device that implements the present invention.

Fig. 2 illustrates operation of the system of fig. 1 to establish a communication link with a remote BTS.

Fig. 3 is a graphical representation of the phase of a pilot signal.

Fig. 4 is a functional block diagram of a prior art searcher for a wireless device.

FIG. 5 is a functional block diagram of a searcher and search controller implementing the present invention.

Fig. 6 illustrates the concept of frequency bin formation using four frequency bins.

Fig. 7 illustrates the concept of frequency bin formation using one frequency bin.

FIG. 8 is a functional block diagram of a searcher and search controller that implements the present invention.

Detailed Description

The present invention increases flexibility in performing a search sweep of a signal in a spread spectrum wireless device. As such, the user is allowed to manually or automatically configure the wireless device to: the signal is searched for according to the operating conditions of the device.

Although the examples presented herein refer to CDMA radiotelephone systems, and more particularly to a system and method for acquiring pilot signals in a CDMA radiotelephone system, the principles of the present invention are applicable to any spread spectrum system.

The present invention is embodied in a system 100 shown in the functional block diagram of fig. 1. The system 100 includes a Central Processing Unit (CPU)102, the CPU102 controlling the operation of the system. Memory 104, which may include Read Only Memory (ROM) and Random Access Memory (RAM), provides instructions and data to CPU 102. A portion of the memory 104 may also include non-volatile random access memory.

System 100, which is typically embodied in a wireless communication device such as a CDMA telephone, also includes a housing 106, with a transmitter 108 and a receiver 110 contained in housing 106 to allow data (e.g., audio communications) to be transmitted and received between system 100 and a remote location (e.g., BTS200) (see fig. 2). The transmitter 108 and receiver 110 may be combined into a transceiver 112. An antenna 114 is connected to the housing 106 and is electrically coupled to the transceiver 112. The operation of the transmitter 108, receiver 110 and antenna 114 is well known in the art and need not be described herein. Although fig. 1 shows antenna 114 as extending from housing 106, some designs may include an internal antenna completely contained within the housing. However, the transmitter 108, receiver 110, and antenna 114 operate in a conventional manner regardless of the location of the antenna.

A data input/output system 116 is communicatively connected to the system 100 for the user to operate in a conventional manner. Data input/output system 116 provides a convenient method by which destination telephone numbers, commands, numeric data, voice data, and other data may be entered. Although fig. 1 shows data input/output system 116 as including a microphone 118, a keypad 120, a data input/output connector 122, a speaker 124, and a display 126 contained within housing 106, data may be received and reproduced for a user by other input devices (e.g., receiver 110), alone and in various combinations.

The system 100 also includes a searcher 128 and a search controller 130. The searcher 128 searches for the phase of the pilot signal received from the BTS; the search controller 130 controls the operation of the searcher 128. In response to a control signal from the search controller 130, the searcher 128 may be configured to: multiple channels are searched using multiple inferred frequency errors. Those skilled in the art will recognize that: the searcher 128 may be implemented in a variety of ways, including as a separate component (e.g., a Digital Signal Processor (DSP), Application Specific Integrated Circuit (ASIC), or the like).

The search controller 130 is shown as a separate block in the functional block diagram of fig. 1 because it performs specific functions, which will be described in detail below. However, one skilled in the art will appreciate that: search controller 130 may be readily implemented as a series of software instructions disposed in memory 104 and executed by CPU 102. Thus, the search controller 130 would be implemented with fewer software modifications to existing hardware. Alternatively, the search controller 130 may be implemented with a separate processor (e.g., a DSP, ASIC, or similar processor). As will be discussed in more detail below: the search controller 130 may selectively generate control signals to control the operation of the searcher 128.

The system may also include other types of wireless systems (e.g., GPS system 132) that may also employ the searcher 128 and search controller 130 of the present invention.

The electrical components of system 100 receive power from battery 134, and battery 134 is connected to housing 106 and supported by housing 106. In the exemplary embodiment, battery 134 is a rechargeable battery. In other embodiments, the system 100 may include a connector (not shown) for connecting to an external power source (e.g., a car power adapter, an AC power adapter, or the like).

The various components of system 100 are coupled together by a bus system 136. bus system 136 may include a power bus, a control bus, and a status signal bus in addition to a data bus. However, for clarity, the various buses are illustrated in FIG. 1 as the bus system 136.

Fig. 2 illustrates system 100 and a plurality of BTSs 200 and 206. The system 100 will search for signals from BTS200 and 206 over communication lines 208 and 214, respectively, and will establish a communication line with the selected BTS (e.g., BTS200) to allow transmission and reception of data (e.g., audio signals) over the established communication line. Once the signal from BTS200 and 206 is found, the selection of the BTS and the actual communication between system 100 and the selected BTS are well known in the art and need not be discussed here.

As described above, the pilot signal can be thought of as a rotating phasor of the form:

s(t)＝Ae^(-ωi+φ)

fig. 3 shows the start time of the pilot signal as a conceptual pointer 300 on the clock 302. Each BTS broadcasts the same pilot signal but with a different phase, which can be viewed as a different start time or position of the pointer 300 and 302 on the clock. Each pointer 300-302 represents a pilot signal broadcast by a different BTS. When viewed in this manner, a 1x signal typically starts at any one of 32,768 chips, which can be considered as a unit of time on a clock. The target of the searcher can be considered as: a start time or chip is found for the pilot signal broadcast by each of several BTSs and the particular BTS used to establish the communication line is selected. The searcher collects a search segment of the data from the signal or window 304 and compares it to the hypothesized PN data set. As will be understood by those skilled in the art, the term "window" refers to the sample size of the selected chip. For example, the window 304 may gather a small set (for example) of 64 chips of data or a larger set (for example) of 256 chips of data. The phase of the pilot signal may be obtained if there is sufficient correlation between the window 304 signal data and the hypothesized PN data set.

Fig. 4 is a functional block diagram of a conventional searcher 400. The conventional searcher 400 searches for pilot signals broadcast by multiple BTSs in a single channel (see fig. 2). Rotator 462 compensates for the estimated frequency error by adjusting the phase of the received signal. Those skilled in the art will recognize that: rotator 462 may be implemented using various electronic components. Rotator 462 may be implemented, for example, using a DSP, complex multiplier, cordic rotator, or similar electronic component. Alternatively, a look-up table in read-only memory may be used, since the result of a given phase shift for a given received signal is known.

The output data from rotator 462 is stored in search data buffer 470 at the chip rate until a window of data is collected. The data is then paired with a data set generated based on a hypothesized PN pilot signal generated by PN generator 479 and stored in PN buffer 480. As described above, this hypothesized PN pilot signal is based on a set of hypothesized search parameters. Then, it is known in the prior art: the paired data signals are despread 482 and processed by summer 484, coherent accumulator 486, energy combiner 488, non-coherent accumulator 490, and peak classifier/detector 492. When there is sufficient correlation between the paired sampled signal data and the hypothesized PN pilot signal data, there will be a peak at a certain chip in the result, indicating acquisition of the phase of the pilot signal. The searcher 400 then determines at which chips the peaks exist and the relative strength of any peak. The detected peaks and their relative strengths are stored on a peak list (not shown) that represents the BTSs for which the pilot signal phases may have been acquired. The process described above is repeated until the pilot signals from several BTSs have been located and stored in the leakage list. The wireless communication device then selects a BTS for establishing a communication link based at least in part on the peak list.

Those skilled in the art will recognize that: the conventional searcher 400 may use multiple PN generators and buffers when the searcher is operating at a speed such that multiple search windows may be collected during each period of the pilot signal. For example, some conventional searchers may operate at a rate that is four times the periodic rate of the pilot signal. Thus, searcher 400 can take advantage of this speed difference by pairing additional sets of window data with additional sets of hypothesis data stored in additional PN buffers. When viewed as a clock (see fig. 3), the searcher may be capable of sampling data, for example, from 1:00 to 2:00, from 4:00 to 5:00, from 7:00 to 8:00, and from 10:00 to 11: 00. Each sample is then compared to a different set of hypothesized PN data stored in a different PN buffer. In this way, more than one search sweep may be performed at a time. Alternatively, a single search sweep may be performed at a higher speed. However, each search sweep is limited to one channel and one extrapolated frequency error.

The present invention improves data acquisition by increasing the flexibility of the searcher 128. Fig. 5 is a functional block diagram of one embodiment of the system 100. the system 100 uses the searcher 128 of the present invention to search for pilots of a 3xMC input signal. The receiver 110 (see fig. 1) receives the signal in which the pilot signal is present. The pilot signal may be either a single channel pilot signal or a multi-channel pilot signal. Fig. 5 illustrates the reception of a 3xMC input signal. In the exemplary embodiment, the signal strength is normalized through the use of an Automatic Gain Control (AGC) circuit 150. AGC circuit 150 (typically including one or more variable gain amplifiers and signal strength detection circuits) is well known in the art and need not be described in greater detail herein.

The received signal is then processed by a filter 152 to separate the signal into its three component channels. The filter 152 may include two rotators and three band pass filters. The received signal is run through a band pass filter to cancel the side channel. This provides a center channel output from filter 152. The frequency of the signal from one of the side channels is concentrated by a rotator that applies a phase shift to bring the frequency of that side channel to the center channel frequency. The signal is then passed through a band pass filter. This provides one of the side channel outputs from filter 152. This process is repeated for the other side channels, thereby producing other side channel outputs. As mentioned above, the rotator in filter 152 may be implemented in any number of ways, as is known in the art.

The output from filter 152 is provided to signal routing circuitry 160. Search controller 130 generates control signals to control the operation of signal routing circuitry 160. Based on these control signals, signal routing circuit 160 sends the signal to be searched to one or more of the plurality of rotators 162 and 168. Those skilled in the art will recognize that: signal routing circuitry 160 may be implemented in a number of ways. For example, as shown in FIG. 5, signal routing circuitry 160 may include a plurality of multiplexer circuits. When the received pilot signal is a multi-channel signal, the signal routing circuit 160 may be configured, in accordance with the control signal received from the search controller 130, to: any one of these channels (e.g., any of the three outputs from the filter 152) is sent to any one or more of the plurality of rotators 162 and 168.

The search controller 130 also generates control signals to control the phase shifts introduced by the rotator 162 168 of those signals to be searched for pilot signals. Based on the control signal received from the search controller 130, the rotator 162 and 168 translate the phase of the received signal to compensate for the estimated frequency error, which is an estimate of the frequency difference between the frequency of the remote device and the signal received from one of the BTSs (e.g., BTS 200). The presumed frequency error may be zero. When multiple rotators 162-168 are used, each rotator may be independently configured to: different phase shifts are introduced to compensate for different presumed frequency errors. As mentioned above, the rotator 162 and 168 may be implemented in any number of ways known in the art.

A "frequency bin" is created when a rotator (e.g., rotator 162) shifts the phase of the signal according to the inferred frequency error. A frequency bin is a range of frequencies around the presumed frequency error where detection of the pilot signal (if present) is likely to occur. Fig. 6 illustrates the use of four frequency bins to search for the pilot signal. Fig. 7 illustrates the use of a single frequency bin to search for a pilot signal with an inferred frequency error of 0. The maximum frequency error range (for which acquisition of pilot signals is likely to occur) is defined by Δ F_maxAnd (4) showing. Assuming that the frequency error range in which it is likely that the acquisition pilot signal occurs is the same for each frequency bin used, the maximum frequency error range af when four frequency bins are used as shown in fig. 6, as compared to when one frequency bin is used as shown in fig. 7, is_maxWill be approximately four times larger. Thus, when multiple frequency bins are used, the probability of acquiring a pilot signal when the frequency error may be high is greatly increased. This multiple frequency bin configuration is particularly advantageous when the range of estimated frequency errors is large.

The outputs from the rotator 162 and 168 are stored in a plurality of searcher data buffers 170 and 176, which may be conveniently implemented as input data shift registers. The data buffer 170-176 stores data contained in the received signal. In one embodiment, data buffer 170 and 176 are implemented using a single input data shift register that is logically divided into a number of fractional segments corresponding to the number of buffers required. In this embodiment, search controller 130 may generate control signals to configure a single data shift register into an appropriate number of fractional segments. In another embodiment, the data buffers 170 and 176 are implemented using separate data shift registers. Implementation of the data buffer 170 and 176 is a matter of design choice and may include, as a design factor, the ability to reuse existing hardware of the system 100 and power consumption considerations.

The pairing logic 178 pairs the data in the data buffers 170-176 with the data in the plurality of PN buffers 180-186. As will be discussed in more detail below: such pairing is based on the desired search sweep configuration. As described above, the data in PN buffer 180-186 corresponds to data from the hypothesized PN pilot signal according to a set of search parameters. The search controller 130 may generate control signals to control the pairing logic 178. Those skilled in the art will recognize that: the pairing logic 178 may be implemented in a number of ways. For example, the pairing logic circuit 178 may include a plurality of multiplexer circuits.

These paired data sets are then processed to determine whether the phase of the pilot signal has been acquired and, if so, to establish synchronization with the signal from a particular BTS (e.g., BTS 200). As mentioned above, methods for the processing of these signals are well known in the prior art and need not be discussed in detail here. Shown in the prior art block diagram of fig. 4: the process can be briefly described as: the energy of each signal pair is combined to detect the presence or absence of a peak at a particular chip. If a peak exists, then indicate: the phase of the pilot signal broadcast by the BTS (e.g., BTS200) has been acquired. Searcher 128 maintains a peak list from which it selects the BTS with which system 100 establishes a communication link.

The use of both the signal routing circuit 160 and the plurality of rotators 162 and 168 allows for greater flexibility than in the prior art in configuring the searcher 128 to perform a search sweep. When receiving a multi-channel signal, the improved searcher 128 may search the signal for more than one channel at a time. Furthermore, by using multiple frequency bins, the improved searcher 128 can acquire signals over a wider frequency range than in the prior art when the frequency error range may be higher.

The number of rotators 162- '168,' data buffers 170- '178, and PN buffers 180-' 186 in a given embodiment is a matter of design choice. Increasing the number of specific components provides greater flexibility but also results in greater cost and power usage. As shown in the examples discussed below, system 100 does not require a one-to-one correspondence of particular components, but the number of each component is related to the mode of operation of searcher 128 that can be configured. Each component may also be selected to take advantage of the speed of the system 100. For example, if the speed of the system 100 is such that four windows can be sampled during each period of the pilot signal, it may be desirable to have four rotators 162 and 168 to take advantage of the system speed. Each PN window sample may be independently processed by a corresponding one of rotators 162-168, thereby greatly increasing acquisition speed.

In the exemplary embodiment, rotator 162 and data buffer 168 and 178 may be shared with other components of system 100 (e.g., GPS system 132) and may be powered down when they are not in use. Although the GPS system 132 operates independently of the system 100, the GPS system 132 utilizes a large number of rotators. These rotators in the GPS system 132 may be assigned to be used as the rotator 162 and 168 in fig. 5 during the initial acquisition of the signal, or whenever the GPS system is not using all of its rotators.

Search controller 130 may be configured to: control signals are generated to control the operation of searcher 128 based on various factors, such as received user input, received signal type, instructions received from a remote location, success rates of previous searches, user and default settings, quality of connection with the remote location, geographic location of system 100, inferred frequency errors, available power, and the like, as well as various combinations thereof. Those skilled in the art will recognize that: the user may configure system 100 to generate control signals; alternatively, at the factory, the system 100 may be preset to generate control signals; or some combination thereof.

In an exemplary embodiment, the search controller 130 may enable each of the various components (e.g., the rotator 162-. Any components not enabled by search controller 130 may be disabled and may be further powered down to reduce current drain on battery 134 (see fig. 1).

For example, in the embodiment shown in fig. 5, system 100 may be configured for operation of a single pilot channel in what may be referred to as a "mode 1 search". Search controller 130 generates control signals to operate system 100 in a particular mode designed to take advantage of these conditions. In this way, the search controller 130 may generate control signals to: (1) routing the single pilot channel signal to a single rotator 162; (2) enabling a single rotator 162; (3) enable a single data buffer 170; and (4) pair the data in the data buffer 170 with the hypothesized PN pilot data in each of the PN buffers 180-186 (by utilizing the faster speed of the searcher 128).

An advantage of system 100 is its versatile, dynamically configurable architecture that allows wireless devices to be operated in many different modes of operation. Table 1 below summarizes various example modes by which the search controller 130 of the embodiment shown in fig. 5 may generate control signals to operate the searcher 128. Those skilled in the art will recognize that: additional search modes may be used.

TABLE 1

Modes 1-3 utilize a single channel but have different numbers of frequency bins based on the estimated frequency error range. Mode 1, discussed in the example above, may be implemented when a single channel is to be searched and the frequency error range is assumed to be small. In mode 1, a single frequency bin is utilized to search for a single channel at high speed. The frequency bins shown in fig. 7 cover the entire frequency range af_maxOver which frequency range an attempt will be made to acquire the phase of the signal。

In mode 2, a single channel is to be searched, but the frequency error is assumed to be high. Thus, four frequency bins may be used, each covering the frequency range Δ F to be searched_maxA part of (a). The search speed in mode 2 is lower than in mode 1 because each frequency bin is searched using the same set of remaining search parameters (except for the inferred frequency error). Thus, when the embodiment shown in fig. 5 is configured to operate in mode 2, the search controller 130 generates control signals to: (1) transmitting a single pilot channel signal to each of the rotators 162 and 168; (2) each rotator 162 is enabled 168 to apply different phase adjustments; (3) each data buffer 170 is enabled 176; (4) storing data according to the same set of hypothetical parameters in each of the PN buffers 180-186; and (5) pairing the data in each data buffer 170-176 with the hypothesized PN pilot data in the PN buffers 180-186.

In mode 3, a single channel will be searched using the presumed medium frequency error. In this way, a moderate search speed with 2 frequency bins can be used. When the embodiment shown in fig. 5 is configured to operate in mode 3, the search controller 130 generates control signals to: (1) routing the single pilot channel signal to two of the rotators 162 and 164; (2) enabling two rotators 162 and 164; (3) enabling two data buffers 170 and 172; and (4) pairing the data in each data buffer 170-172 with the hypothesized PN pilot data in each PN buffer 180-182, resulting in the following four data pairs: 170/180, 170/182, 172/180 and 172/182. In table 1, the channel to be searched in the patterns 1, 2, and 3 is referred to as "channel 0".

As shown in fig. 5, searcher 128 may receive and process multiple channels (e.g., 3xMC signals processed by filter 152) using its dynamically configurable structure. Mode 4 may be used when only a single channel of a multi-channel signal is to be searched. System 100 selects a channel from the various channels used for searching. The selection may be based on which of these channels is "best" according to some criteria. In table 1, this channel is referred to as "channel B". For example, the channel with the highest received power may be selected for searching. Thus, mode 4 can be viewed as a search using mode 1, 2, or 3, with the best channel (i.e., channel B) being viewed as "channel 0". In this mode, the search controller 130 generates control signals to cause the signal routing circuit 160 to route the selected channel (e.g., channel B) to the appropriate rotator 162 168.

In mode 5, two channels of a multi-channel signal (e.g., a 3xMC signal processed by filter 152 as shown in fig. 5) are to be searched. These selected channels are designated "channel B1" and "channel B2" in table 1. As in mode 4, the system 100 may use some criteria to determine which two channels of the multi-channel signal are to be searched. A mode 5 search may be performed in the embodiment shown in fig. 5, by using two sets of search parameters for each channel or a single frequency bin (e.g., mode 5.2), in which case, or two frequency bins for each channel (e.g., mode 5.1), in which case, one set of search parameters may be used. In mode 5.1, the search controller 130 generates control signals to: (1) routing a first selected pilot channel signal (e.g., channel B1) to rotator 162 and 164; (2) routing a second selected pilot channel signal (e.g., channel B2) to rotator 166-168; (3) enabling each rotator 162-168; (4) each data buffer 170 is enabled 176; and (5) the data in the data buffers 170-176 is paired with the hypothesized PN pilot data in the PN buffers 180-186 as follows: 170/180, 172/182, 174/184, 176/186, wherein each PN buffer 180-186 contains the same hypothetical PN pilot data.

In mode 5.2, the search controller 130 generates control signals to: (1) routing a first selected pilot channel signal (e.g., channel B1) to rotator 162 and 164; (2) routing a second selected pilot channel signal (e.g., channel B2) to rotator 166-168; (3) enabling each rotator 162-168; (4) each data buffer 170 is enabled 176; and (5) the data in the data buffers 170-176 is paired with the hypothesized PN pilot data in the PN buffers 180-186 as follows: 170/180, 172/182, 174/184, 176/186, wherein PN buffers 180 and 184 contain one set of hypothesized PN pilot data and PN buffers 182 and 186 contain another set of hypothesized PN pilot data.

In mode 6, three channels of a multi-channel signal (e.g., a 3xMC signal) are to be searched. In the embodiment shown in fig. 5, a single frequency bin is used, and a single set of search parameters is used. This is because each channel requires one rotator (e.g., one of rotators 162 and 168) for each frequency bin to be searched, and there are only four rotators in the embodiment shown in fig. 5. Those skilled in the art will recognize that: alternative embodiments of system 100 may include more rotators and/or other components (e.g., data buffers). As previously mentioned, practical design implementations are a compromise between search speed and the cost of adding additional circuit components that require power in particular. The system 100 may also use a posteriori energy combinations of the three signals. Those skilled in the art will also recognize that: in the embodiment illustrated in FIG. 5, searcher 128 may be configured to perform both mode 6 searches (e.g., using rotator 162 and 166) and mode 1 searches (e.g., using rotator 168).

In mode 7, an OTD signal is to be searched. The OTD signal broadcasts two pilot signals. The search parameters may need to be adjusted to correspond to the parameters of the OTD signal. Otherwise, the mode 7 search may be considered a mode 4 or mode 5 search. In mode 7.1, pilots will be searched in only one of the OTD pilot signals, so mode 7.1 is similar to mode 4, and system 100 may be configured as in modes 1-3, with hypothetical PN signal data modified to correspond to data appropriate for the hypothetical OTD pilot signal.

In mode 7.2 the phases of the pilot signals will be searched in the two OTD pilot signal paths, so that mode 7.2 is similar to mode 5 and the system can be configured as in modes 5.1 and 5.2, the hypothesized PN signal data being modified to correspond to data that fits the hypothesized OTD pilot signals. In mode 7.3, a posteriori energy combinations of OTD pilot signals may be used, as may be done for a 3xMC pilot channel in mode 6.

It should be noted that for clarity, various modes of operation are discussed with respect to particular processing components. For example, mode 3 is described using rotator 162 and 164 and data buffer 170 and 172. However, the flexible system architecture allows for the use of other components in the searcher (e.g., rotator 166 and 168 in mode 3). The present invention is not limited to the particular embodiment shown in fig. 5 nor to the choice of components described for the various modes of operation.

Fig. 8 is a functional block diagram of an alternative embodiment of the searcher 128 of the present invention that may be advantageously implemented in any wireless spread spectrum system. The embodiment of fig. 8 is designed to take advantage of existing hardware in the wireless device, and is particularly designed to avoid having to add additional hardware data shift registers. The embodiment shown in fig. 8 is also designed to utilize a searcher 128 that operates at four times the signal period. This embodiment implements the four data buffers 172-176 as a fractional portion of a single input data shift register. Likewise, despreader 482, adder 484, coherent accumulator 486, non-coherent accumulator 490, and peak classifier/detector 492 are logically divided into four fractional components. The pairing logic 178 includes four multiplexers M1-M4. The PN buffers 182 and 186 are implemented as four-tap (four-tap) buffers. Each PN generator 479 may be independently configured to: hypothesized PN signal data is generated based on a set of different search parameters.

The embodiment shown in fig. 8 also has three additional energy combiners 488 and one combined peak detector/classifier 194. The four fractional parts from peak detector/classifier 492 and the individual outputs of combined peak detector/classifier 194 allow system 100 to track the frequency bins and signal channels in which the peaks are located. For example, if a single frequency bin is used to search for a single channel signal, the combined peak detector/classifier 194 may produce a single combined peak list a. Alternatively, as shown in fig. 8, the combined peak/detector/classifier 194 may generate multiple peak lists if desired, e.g., peak list a corresponding to the peak of a first single signal channel and frequency bin combination and peak list B corresponding to the peak of a second signal channel and frequency bin combination.

The embodiment in fig. 8 also has an a posteriori energy combiner 196 that can combine the energy of each channel from multiple channel signals (e.g., 3xMC or OTD signals) in some manner, if desired.

Table 2 below summarizes various example modes in which the search controller 130 of the embodiment shown in fig. 8 may generate control signals to operate the searcher 128. Those skilled in the art will recognize that: additional search modes may be used.

TABLE 2

In mode 1, the embodiment shown in fig. 8 is configured to: a single frequency bin and four sets of hypothesized PN signal data are used to search a single channel. This mode takes advantage of the fact that: the searcher 128 may complete four cycles during each cycle of the signal. The search controller 130 generates control signals to: (1) an activation energy combiner 488; (2) disabling the posterior energy combiner 196; (3) routing the single channel signal to be searched to each of the four rotators 162 and 168; (4) introducing the same phase offset for each rotator 162-168; (5) generating four independent sets of hypothesized PN signal data; (6) during the first period of the searcher 128, the data in the data buffers 170 and 176 is paired with the data in the first tap of each corresponding PN buffer 180 and 186; (7) during the second period of the searcher 128, the data in the data buffers 170 and 176 is paired with the data in the second tap of each corresponding PN buffer 180 and 186; (8) during the third period of the searcher 128, the data in the data buffers 170 and 176 are paired with the data in the third tap of each corresponding PN buffer 180 and 186; and (9) during the fourth cycle of the searcher 128, the data in the data buffers 170 and 176 is paired with the data in the fourth tap of each corresponding PN buffer 180 and 186. The paired data is processed by searcher 128 to produce peak lists 1-4 and peak list a.

In mode 2, the embodiment shown in fig. 8 is configured to: a single channel is searched using four frequency bins and a set of hypothesized PN signal data. The search controller 130 generates control signals to: (1) an activation energy combiner 488; (2) disabling the posterior energy combiner 196; (3) routing the single channel signal to be searched to each of the four rotators 162 and 168; (4) introducing a different phase offset for each rotator 162-168, thereby creating four different frequency bins; (5) generating the same four sets of hypothetical PN signal data; (6) the data in the data buffers 170-176 are sequentially paired with the data in each tap of each corresponding PN buffer 180-186. The paired data is processed by searcher 128 to produce peak lists 1-4 and peak lists a and B.

In mode 3, the embodiment shown in fig. 8 is configured to: a single channel is searched using two frequency bins and two sets of hypothesized PN signal data. The search controller 130 generates control signals to: (1) an activation energy combiner 488; (2) disabling the posterior energy combiner 196; (3) routing the single channel signal to be searched to each of the four rotators 162 and 168; (4) introducing a certain phase offset to rotators 162 and 164 and a different phase offset to rotators 166 and 168, thereby creating two different frequency bins; (5) generating two separate sets of hypothesized PN signal data and storing a first set of hypothesized PN signal data in PN buffers 180 and 184 and a second set of hypothesized PN signal data in PN buffers 182 and 186; (6) the data in the data buffers 170-176 are sequentially paired with the data in each tap of each corresponding PN buffer 180-186. The paired data is processed by searcher 128 to produce peak lists 1-4 and peak lists a and B.

Those skilled in the art will recognize that: the embodiment shown in fig. 8 may also be configured to operate in other modes (e.g., modes 4-7 discussed above in connection with fig. 5). When it is desired to employ a posteriori energy combining in mode 6 and mode 7.3, the search controller 130 generates control signals to disable the energy combiner 488 and enable the posteriori energy combiner 196.

It should be noted that for clarity, various modes of operation are discussed in terms of particular processing components. For example, mode 3 is described using a particular phase shift for rotators 162 and 164 and a different phase shift for rotators 166 and 168. However, the flexible system architecture allows for the use of other components in the searcher (e.g., using a particular phase shift for rotators 162 and 166 and a different phase shift for rotators 164 and 168). The present invention is not limited to the particular embodiment shown in fig. 8 nor to the choice of components described for the various modes of operation.

It is to be understood that even though numerous embodiments and advantages of the present invention have been set forth in the foregoing description, the foregoing disclosure is illustrative only, and changes may be made in detail, yet remain within the broad principles of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims.

Claims (25)

1. A searcher system for searching for a received signal in a spread spectrum communication system during each search sweep, comprising:

a) reconfigurable signal routing circuitry for selecting a route for the received signal;

b) a plurality of rotators for adjusting the phase of the received signal to compensate for the presumed frequency error based on the signal received from the search controller, thereby creating one or more frequency bins;

c) a plurality of searcher data buffers for storing the phase adjusted signals;

d) a generator for generating a pseudo-noise PN signal;

e) a PN buffer for storing the generated PN signal;

f) pairing logic circuitry to pair the stored phase adjusted signal with the generated PN signal according to the created one or more frequency bins; and

g) a search controller to generate control signals to control operation of the signal routing circuit, the rotator, and the pairing logic circuit.

2. The searcher system of claim 1 wherein the search controller further generates control signals to control operation of the generator.

3. The searcher system of claim 1 wherein the search controller further generates control signals to control operation of the plurality of searcher data buffers.

4. The searcher system of claim 3 wherein the rotator and searcher data buffers are selectively enabled and the received signal is a single channel signal and the search controller generates control signals to:

enabling one of the plurality of rotators;

routing the received signal to an enabled rotator;

adjusting the phase of the received signal;

enabling one of the searcher data buffers;

storing the phase adjustment signal in an enabled searcher data buffer; and

the phase adjustment signal stored in the enabled searcher data buffer is paired with the PN signal stored in the PN buffer.

5. The searcher system of claim 1 wherein the phase adjustment by one of the plurality of rotators is zero.

6. The searcher system of claim 1 wherein each rotator of the plurality of rotators makes a different phase adjustment to the received signal.

7. The searcher system of claim 1 wherein the plurality of searcher data buffers are comprised of an input data shift register.

8. The searcher system of claim 1 wherein the plurality of searcher data buffers are comprised of a plurality of input data shift registers.

9. The searcher system of claim 1 further comprising a plurality of generators for generating a plurality of PN signals and a plurality of PN buffers for storing the plurality of generated PN signals.

10. The searcher of claim 9, wherein each PN buffer of the plurality of PN buffers stores a same generated PN signal.

11. The searcher system of claim 1 wherein the received signal is a multi-channel signal and the search controller generates a control signal to route a channel of the multi-channel signal to one of the plurality of rotators.

12. The searcher system of claim 11 wherein the search controller generates a control signal to route another channel of the multi-channel signal to another rotator of the plurality of rotators.

13. The searcher system of claim 1, further comprising a filter for processing the received signal into a multi-channel signal, wherein the search controller generates a control signal to route one channel of the multi-channel signal to one of the plurality of rotators.

14. The searcher system of claim 13 wherein the search controller generates a control signal to route another channel of the plurality of channel signals to another rotator of the plurality of rotators.

15. The searcher system of claim 1 wherein the spread spectrum communication system is a code division multiple access system.

16. The searcher system of claim 1 wherein the signal routing circuitry comprises a plurality of multiplexer circuits.

17. The searcher system of claim 1 wherein the pairing logic circuit comprises a plurality of multiplexer circuits.

18. The searcher system of claim 1 wherein at least one rotator of the plurality of rotators is shared with another component in the system.

19. The searcher system of claim 1 wherein at least one of the plurality of searcher data buffers is shared with another component of the system.

20. The searcher system of claim 1 wherein the received signal is a multichannel signal, each channel of the multichannel signal containing signal energy, and further comprising an a posteriori energy combiner for selectively combining the energy of the channels of the multichannel signal.

21. The searcher system of claim 1 wherein the received signal is a pilot signal.

22. The searcher system of claim 1 wherein the received signal is a multi-channel pilot signal.

23. The searcher system of claim 1 wherein the received signal is a global positioning system signal.

24. A searcher system for searching for a signal received over a single channel in a spread spectrum system during each search sweep, the searcher comprising:

signal routing circuitry for selecting a route for the received signal;

a plurality of rotators for adjusting the phase of the received signal to compensate for the presumed frequency error based on the signal received from the searcher to create one or more frequency bins;

a plurality of searcher data buffers for storing the plurality of phase adjusted signals;

a plurality of generators for generating a plurality of pseudo-noise PN signals; and

a plurality of PN buffers for storing the plurality of generated PN signals;

wherein the system is dynamically configured to: independently employing each of the plurality of rotators for phase adjustment to independently generate the plurality of generated PN signals and independently pairing the phase adjusted signals stored in the plurality of searcher data buffers with the PN signals stored in the plurality of PN buffers based on the created one or more frequency bins.

25. A searcher system for searching for multi-channel received signals in a spread spectrum system during each sweep, the searcher comprising:

signal routing circuitry for selecting a channel route for the received signal;

a plurality of rotators for adjusting a channel phase of the received signal to compensate for the estimated frequency error based on the signal received from the searcher to create one or more frequency bins;

a plurality of searcher data buffers for storing the plurality of phase adjusted signals;

a plurality of generators for generating a plurality of pseudo-noise PN signals;

a plurality of PN buffers for storing the plurality of generated PN signals;

wherein the system is dynamically configured to: independently routing a channel of the received signal to any of the plurality of rotators, independently phase adjusting with each of the plurality of rotators, independently generating the plurality of generated PN signals, and independently pairing the phase adjusted signals stored in the plurality of searcher data buffers with the PN signals stored in the plurality of PN buffers based on the created one or more frequency bins.