HK1073021B - Wireless communications with an adaptive antenna array - Google Patents

Description

Wireless communication with adaptive antenna arrays

Background

FIELD

The present invention relates generally to communication systems, and more particularly to techniques for antenna beam steering in a wireless communication environment.

Background

Mobile radio systems allow users to move freely within a given service area and to communicate via a wireless telephone device or a personal communication system. One such mobile radio system is a Code Division Multiple Access (CDMA) cellular system. CDMA cellular systems are based on modulation and multiple access schemes for spread spectrum communications. In CDMA cellular systems, many signals share the same frequency spectrum, resulting in increased user capacity. This is done by transmitting each signal with a different pseudo-random binary sequence that modulates the carrier, thus spreading the spectrum of the signal waveform. The transmitted signals are separated at the receiver with a correlator using a corresponding pseudo-random binary sequence to despread the spectrum of the desired signal. The undesired signal, whose pseudo-random binary sequence does not match, is not despread in band, but adds noise.

One of the important parameters in determining the capacity of a CDMA cellular system is the ratio of energy per bit to the intensity of the noise power spectrum (E)_b/N_o). Thus, the capacity of a CDMA cellular system can be increased with reduced noise. Since the undesired signals received by the correlator of the receiver are noise, the capacity of the CDMA cellular system can be effectively improved by optimizing the beam pattern of the antenna while blocking the undesired signals. In addition to improving the capacity of a CDMA cellular system, the optimized beam pattern may also reduce the transmit power needed to overcome noise and interference. Reduced power requirements may reduce costs such that lower power cells may be used to a greater extentAnd (4) internal operation. Preferably, the beam pattern is optimized without affecting the CDMA system's ability to process multipath components or search for new communication channels. Accordingly, there is a need in the art for a system and technique for controlling the beam pattern of an antenna to effectively block undesired signals while maintaining the processing of multipath components and searching for new communication channels.

SUMMARY

In one aspect of the invention, a reception method includes forming a first beam to cover an area, detecting a signal within the area with the first beam, and forming a second beam to receive the detected signal.

In another aspect of the invention, a receiver system includes an antenna for forming first and second beams, and a processor for controlling the antenna to search for a first signal with the first beam and receive a second signal with the second beam.

In yet another aspect of the present invention, a method of communication includes transmitting a signal from a base station, forming a first beam at a remote station to search for a transmitted signal within a region, detecting the transmitted signal with the first beam within the region, and forming a second beam at the remote station to receive the signal.

In yet another aspect of the present invention, a remote station includes a processor for controlling an antenna to search for a first signal with a first beam and receive a second signal with a second beam.

In a further aspect of the invention, a computer readable medium containing a receiving method forms a first beam to cover an area, detects a signal within the area with the first beam, and forms a second beam to receive the detected signal.

In another aspect of the invention, a receiver system includes means for forming a first beam through an antenna to search for a first signal, and means for forming a second beam through the antenna to receive a second signal.

It is understood that other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described only embodiments of the invention by way of illustration. As will be realized, the invention is capable of other and different embodiments and its various details are capable of modification in various other respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

Brief description of the drawings

Fig. 1 is a diagram of a CDMA cellular system having a beam steering technique employed by a subscriber station in accordance with an exemplary embodiment;

fig. 2 is a diagram of a CDMA cellular system during soft handoff with a beam steering technique employed by a subscriber station in accordance with an exemplary embodiment;

fig. 3 is a diagram of a CDMA cellular system with beam steering techniques employed by a base station in accordance with an exemplary embodiment;

fig. 4 is a diagram of a CDMA cellular system with beam steering techniques employed by both a base station and a subscriber station in accordance with an exemplary embodiment;

fig. 5 is a functional block diagram of a CDMA cellular device employing beam steering techniques in accordance with an exemplary embodiment.

Detailed Description

In an exemplary embodiment of a wireless communication system, improved user capacity may be obtained by using beam steering techniques to reduce mutual interference among multiple users. For example, in a CDMA cellular system, directional antennas may be used to generate a beam pattern that links a base station to a remote station or subscriber station while minimizing interference from other remote stations of the same or neighboring cells. A directional antenna may comprise an antenna array as consisting of spatially separated individual radiating elements. The individual radiating elements can include dipoles, open-ended waveguides, slots within a waveguide, or any other type of radiating element. The shape and direction of the beam pattern is determined by the relative phase and amplitude of the signals applied to the individual radiating elements. By appropriately varying the relative phases, the shape of the beam pattern can be formed with a plurality of beams. In this way, one or more beams may be used to maintain a communication channel between the base station and the subscriber station, while the remaining beams may be used to search for multipath components and other signals. Beam steering techniques can be employed at subscriber stations and/or base stations. In other terrestrial and satellite radio communication systems, the beam steering techniques described herein may be implemented in a variety of ways depending on overall design constraints and other factors. Thus, any reference to a CDMA cellular system is intended only to illustrate the inventive aspects of the present invention, it being understood that these inventive aspects have a wide range of applications.

Fig. 1 is a diagram of an exemplary CDMA cellular system with beam steering techniques used by subscriber stations. A CDMA cellular system provides a mechanism for a subscriber station 102 to communicate with a network 104. The network 104 is coupled to a Base Station Controller (BSC) 106. BSC 106 communicates with base station 108 over backhaul 110. For ease of explanation, only base station 108 is shown, however, in certain applications, multiple base stations (not shown) may be coupled to BSC 106 via separate backhauls (not shown).

The subscriber station 102 includes an antenna array 112 that forms multiple beam patterns. The subscriber station 102 exchanges signals with a base station 108, which is located within a tracking beam 114 generated by the subscriber station 102. The tracking beam 114 is used to maintain a communication channel between the subscriber station 102 and the base station 108. The search beam 116 can also be formed by the antenna array 112 at the subscriber station, which is scanned in azimuth over a geographic area to search for multipath components of the signal, along with signals from other base stations (not shown). The method provides increased gain for the subscriber station to receive a signal over a communication channel without losing multipath components. Also, the subscriber station retains the ability to obtain new signals from other base stations.

Alternatively, the search function may be performed with an omni-directional beam pattern (not shown). The search function is implemented using a search beam, an omni-directional beam pattern, a wide beam, or any other type of beam, determined by a combination of factors such as search area, overall design constraints, specific application, and propagation environment in which the exemplary CDMA cellular system operates. In at least one embodiment, the antenna array can be adaptively switched between a search beam, an omni-directional beam, and a wide beam to best adapt to changing environmental conditions.

Fig. 2 is a diagram of an exemplary CDMA cellular system using beam steering techniques during soft handoff. Soft handoff is the process of establishing a communication channel with a new base station before disconnecting the existing communication channel with the originating base station. This approach not only reduces the probability of dropped calls, but also makes the user virtually undetectable. Soft handoff may be performed based on the strength of signals received by a subscriber station from multiple base stations. This may be accomplished by measuring the strength of the pilot signal transmitted from each base station at the subscriber station. When the energy level (i.e., power level) received at the subscriber station from the base station exceeds a certain threshold, the base station is added to the subscriber station's active set. When the strength of a pilot signal received at a subscriber station from a base station is below a certain threshold, the base station is removed from the subscriber station's active set. In existing CDMA systems, the base station is not removed from the active set of the subscriber station immediately after the pilot signal strength falls below a threshold. Conversely, the pilot signal strength should be below the threshold for some time before the base station is removed from the active set. This approach reduces the potential for removing base stations from within the active set of the subscriber station due to spurious signal level fluctuations.

As shown in fig. 2, each base station 202a, 202b transmits and receives signals within its respective cell sector 204a, 204 b. Sectorization of CDMA cells is a technique for increasing user capacity. Cells are generally divided in three ways that allow one or more base stations to use one or more 120 ° beamwidths. Due to the wide antenna pattern and propagation irregularities, there is considerable overlap of the coverage areas of the sectors. This overlap is used to implement the handoff function of the pre-disconnection CDMA based soft handoff between two base stations.

The subscriber station 206 is first shown passing through sector 204 a. When turned on, the subscriber station 206 controls the relative phases of signals applied to radiating elements (not shown) to form a beam pattern that can be rapidly swept through a coverage area to acquire or omni-directionally or wide-area. Once the subscriber station 206 detects the pilot signal from the base station 202a, the relative phases of the signals applied to the radiating elements of the antenna array 208 can be adjusted to form a tracking beam 210 that is fixed to the base station 202 a.

In addition to the tracking beams, the beam pattern formed by the antenna array 208 will include a search beam 212 that is scanned in azimuth across the geographic area to search for multipath components from the base station 202a, as well as signals from other base stations. Alternatively, the search function may be performed with an omni-directional beam pattern. The direction of the tracking beam 210 may also be changed to optimize performance on the communication channel between the subscriber station 206 and the base station 202a based on signals received through the search beam or omni-directional beam.

When the subscriber station 206 detects multipath components from the base station 202a with a pilot signal of sufficient strength, the relative phases of the signals applied to the radiating elements of the antenna array 208 can be adjusted to create one or more additional tracking beams (not shown) to increase the gain in the direction of the multipath components. Alternatively, the existing tracking beam 210 may be widened to expand the coverage area to include the communication channel between the subscriber station 206 and the base station 202a as well as the multipath components.

As the subscriber station 206 moves into a soft handoff region where the sector coverage areas overlap, the search beam 212 is continuously scanned in azimuth to detect the pilot signal from the base station 202 b. Upon detecting the pilot signal from the base station 202b, the base station 202b is added to the active set of the subscriber station 206. Accordingly, it is possible to adjust the relative phases of the signals applied to the radiating elements of the antenna array 208 to establish a beam pattern (not shown) with a new tracking beam in the direction of the base station 202b while keeping the original tracking beam 210 pointed at the base station 202a and sweeping the search beam 212 in azimuth. The tracking beams provide increased gain in the direction of the base stations 202a, 202b so that both base stations 202a, 202b can temporarily service the call during soft handoff transfers.

As the subscriber station 206 moves out of the soft handoff region and into the new sector 204b, the strength of the pilot signal from the originating base station 202a decreases until it falls below the threshold that causes the subscriber station 206 to remove the base station 202a from its active set. Thus, the relative phases of the signals applied to the radiating elements of the antenna array 208 may again be adjusted to form a beam pattern that removes the original tracking beam 210 in the direction of the original base station 202a while maintaining the new tracking beam (not shown) pointed at the new base station 202b and sweeping the search beam 212 in azimuth.

Those skilled in the art will appreciate that a variety of different beam patterns may be formed to accommodate receiving signals from the active base station and its multipath components, as well as signals from other base stations. For example, one or more tracking beam forming beam patterns may be used to exchange signals with the active base station. Likewise, one or more tracking beams may be used to form a beam pattern to receive multipath components from an active base station or signals from other base stations. The search function can also be implemented with any number of search beams or omni-directional beams. Furthermore, the antenna array may be controlled to sweep the search beam in azimuth or to rapidly switch the search beam from one location in space to another location in space within the sector. The shapes of the tracking beam and the search beam may also be changed. For example, the beam pattern may be adjusted to have a wider or narrower tracking beam to accommodate changes in the propagation environment that affect the multipath component. In some examples, side lobes of the beam pattern may be used to receive signals from an active base station, receive multipath components thereof, or receive signals from other base stations.

Fig. 3 is a diagram of an exemplary CDMA cellular system with beam steering techniques used by the base station. The base station 302 is shown communicating with the network 304 over a backhaul 306 to a BSC 308. The base station 302 includes a directional antenna, such as an antenna array 310 consisting of spatially separated individual radiating elements. A tracking beam 312 may be formed by the antenna array 310 for maintaining a communication channel with the subscriber station 314 a. A search beam 316 may also be formed by the antenna array 310 which is scanned in the azimuth of its cellular sector, or any other geographical area, for searching for multipath components of the signal as well as signals from other subscriber stations. Alternatively, search beam 316 may be formed with a separate antenna, such as a mechanically scanned parabolic antenna (not shown) or any other directional antenna known in the art.

The search function may alternatively be implemented by controlling the antenna array 310 to form a 120 wide beam pattern (not shown) superimposed on the tracking beam 312. Whether the search function is implemented with searching for sidelobes, a wide beam pattern, or any other type of beam is a function of a combination of factors that dictate the overall design constraints, the particular application, and the propagation environment in which the exemplary CDMA cellular system operates. In at least one embodiment, the antenna array is adaptively switchable between the search beam and the wide beam pattern to best accommodate changing environmental conditions.

In the exemplary embodiment, tracking beam 312 is focused on subscriber station 314a and the search beam is swept across its cellular sector to search for subscriber station signals. When the base station 302 detects a multipath component from the subscriber station 314a with a signal of sufficient strength, the relative phases of the signals applied to the radiating elements of the antenna array 310 may be adjusted to create one or more additional tracking beams (not shown) to increase the gain in the direction of the multipath component. Alternatively, the shape of the existing tracking beam 312 may be widened to expand the coverage area to include the communication channel between the base station 302 and the subscriber station 314a as well as the multipath components.

As the search beam 316 is swept further across the cellular sector, the base station 302 should detect subscriber station signals of sufficient strength as the search beam 316 is swept across the new subscriber station 314 b. The base station 302 is then added to the active set of the new subscriber station 314 b. Thus, it is possible to adjust the relative phases of the signals applied to the radiating elements of the antenna array 310 to establish a beam pattern (not shown) with a new tracking beam in the direction of the base station 314b while the originating tracking beam 312 is directed toward the subscriber station 314a and the search beam 316 is scanned in azimuth.

In fact, considering that a single base station typically serves many calls, separate tracking beams for each active subscriber are rare. Instead, a number of tracking beams are typically employed, each serving all communication channels within the angular region of the cellular sector. For example, the width of each tracking beam may be formed to serve all active subscriber stations within a 10 ° angular region. The width of each tracking beam can be adaptively changed to accommodate many active subscriber stations and changes in the propagation environment. In addition, the width of each tracking beam may be adaptively changed to minimize mutual interference between subscriber stations within the cellular sector. For example, a subscriber station requiring a communication channel with a higher data rate may need to transmit at a higher power level to maintain the same E_b/N_oAnd (4) performance. The gain in the direction of that subscriber station can be increased with a narrow tracking beam to reduce the transmit power required to support higher data rates, thereby reducing interference to other subscriber stations in the same sector. The same result can be obtained if the narrow tracking beam is focused on a subscriber station far away from the base station. Otherwise, each of these subscriber stations may be reduced to maintain the same E by increasing the directional gain of the antenna array at the base station with the narrower tracking beam_b/N_oTransmit power required for performance. For those communication channels requiring reduced data rates or subscriber stations that are physically closer to the subscriber station, a wider tracking beam may be used, or the calls may be served with a 120 ° wide beam.

In a CDMA cellular system using beam steering techniques at both a base station and a subscriber station, a search function at the subscriber station may be performed with an antenna array that adaptively switches between a search beam and an omni-directional beam. This concept is illustrated in fig. 4, which shows an exemplary CDMA cellular system during soft handoff. In the exemplary CDMA cellular system, the base station 402 includes a directional antenna, such as an antenna array 404 comprised of spatially separated individual radiating elements. The base station 402 is shown without a communication channel with a subscriber station and therefore without a tracking beam formed by the antenna array 404. Instead, a search beam 406 is formed by the antenna array 404 and is scanned in azimuth across its cellular sector 408 to search for signals from the subscriber station.

Subscriber station 410 is shown approaching cellular sector 408 of base station 402. The subscriber station also includes a directional antenna, such as an antenna array 412 comprised of spatially separated individual radiating elements. A tracking beam 414 is formed by the antenna array 412 to maintain a communication channel with base stations (not shown) in adjacent cellular sectors during soft handoff. The search beam 416 is also formed by the antenna array 412 at the subscriber station 410 and scanned in azimuth to search for multipath components from neighboring base stations (not shown).

As the subscriber station 410 moves into the cellular sector 408 of the base station 402, signal acquisition may be difficult due to asynchronous steering of the search beam between the subscriber station 410 and the base station 402. An exemplary method of facilitating signal acquisition is to allow the subscriber station 410 and the base station 402 to negotiate the timing of the forward search beam (i.e., the transmission from the base station 402 to the subscriber station 410). This may be accomplished by periodically switching the search beam 416 at the subscriber station 410 to an omni-directional beam (not shown). When forming an omni-directional beam, the subscriber station 410 may monitor the pilot signal strength from the base station from all directions. As the search beam from the base station 402 sweeps through its cell sector 408, the subscriber station 410 should be able to detect the maximum signal strength when the search beam from the base station 402 is focused on the subscriber station 410. If the beam scan pattern of the base station 402 is periodic, the subscriber station 410 should be able to accurately predict when the search beam 406 of the base station 402 will pass. Once the timing of the search beam 406 from the base station 402 is established, the omni-directional beam formed by the subscriber station 410 can be used to receive and store the pilot signal from the base station 402 at the appropriate time. The search beam 416 at the subscriber station 410 may then be effectively swept in the digital domain with the stored pilot signal strength to determine the angular coordinate that produces the maximum pilot signal strength. These angular coordinates may then be used to form a second tracking beam that is focused on the base station 402 within the soft handover area.

Fig. 5 is a functional block diagram of an exemplary CDMA cellular device using beam steering techniques. Although the beam steering techniques described and illustrated in the exemplary CDMA cellular device are performed in the time domain, those skilled in the art will appreciate that many other methods may be used to steer the tracking beams and the search beams. For example, the tracking and search beams may be formed using phased array antennas.

The exemplary beam steering techniques can be used in any CDMA cellular device, such as a base station or a subscriber station. An exemplary CDMA cellular device includes a tracking channel 502 and a search channel 504. Tracking channel 502 includes a transmit path and a receive path. And search channel 504 is a receive-only channel. For ease of illustration, the receive paths of the tracking channel and the search channel are shown separately, however, those skilled in the art will appreciate that the functions may be combined into a single channel and time shared.

An exemplary CDMA cellular device includes an array antenna 506 divided into two groups of spatially separated radiating elements. The first set of radiating elements 506a performs a tracking function and the second set of radiating elements 506b performs a search function. The exact number of radiating elements varies depending on the particular application and design parameters. In the exemplary CDMA cellular device, the tracking function is performed with four dedicated radiating elements and the search function is performed with four different dedicated radiating elements. Alternatively, the radiating elements may be time shared between the tracking and searching functions. In addition, the number of radiating elements may be adaptively varied to facilitate shaping of the waveform pattern. For example, using fewer radiating elements results in a wider beam, while using more radiating elements results in a narrower beam.

The search channel includes a search receiver 508 coupled to a search element 506 b. Searcher receiver 508 amplifies, filters, and downconverts the signal from each searcher element 506b to baseband. An analog-to-digital converter (not shown) within searcher receiver 508 digitally samples the baseband signal from each of the searcher elements and provides the digital baseband samples to a searcher memory 510.

Search memory 510 enhances an omni-directional map of discrete time samples for each search element 506 b. The omni-directional time-aligned discrete samples from search memory 510 are coupled to search filter 512, where an algorithm is invoked for adding a series of weights to each set of time-aligned samplesAs such, the search beam is effectively shaped and controlled in the digital domain. Such algorithms are well known in the art. For example, search memory 510 may be implemented with a first-in-first-out (FIFO) method for storing discrete time samples from each search element 506 b. The FIFO method is a storage method that first retrieves the signal that is stored in the memory for the longest time. Thus, at t₀At time, the signal u received from each search element separately₀，x₀，y₀，z₀Is stored in a FIFO. At t₁At time, the signal u received from each search element is then separately₁，x₁，y₁，z₁Is stored in FIFO₀After the signal received at time. Likewise, at t₂At time, the signal u received from each search element is then separately₂，x₂，y₂，z₂Is stored in FIFO₁After the signal received at time. The search filter 512 will first read the oldest stored signal from the FIFO. In this case, u is first read out from the FIFO₀，x₀，y₀，z₀And couples them to the search filter 512. Here, the signal represents t₀The omni-directional signal of (c). By making a pair t₀The signals at (a) apply different weights and combine them, effectively forming a directional search beam in the digital domain. In particular, a directional search beam can be formed in one angular direction by applying the following algorithm:

(a₀)(u₀)+(b₀)(x₀)+(c₀)(y₀)+(d₀)(z₀)

wherein, a₀，b₀，c₀，d₀Is the weight. By changing the weights, the angular direction of the search beam can be changed. Thus, a directional search beam may be formed in the second angular direction by applying the following algorithm:

(a₁)(u₀)+(b₁)(x₀)+(c₁)(y₀)+(d₁)(z₀)

wherein a is₁，b₁，c₁，d₁Is the weight. The process may be for t₀In any number of desired angular directions. Or, by at t₀In an angular direction of (a) at t₁In a second angular direction of (d), at t₂In a third angular direction, and so on to form a search beam to reduce memory complexity. The search memory 510 provides flexibility to use beam steering techniques or to adaptively switch between the two, depending on system requirements, changing propagation environments, or other factors.

The combined weighted signal from the searcher filter 512 is coupled to a baseband searcher 514 that can estimate the signal strength. In a system using a pilot signal, a baseband searcher may separate the pilot signal from the received signal and compare the pilot signal to a threshold. If the pilot signal strength exceeds the threshold, the weights used by the search filter 512 are coupled to the tracking channel 502 for forming a tracking beam. Alternatively, angular coordinates, or any other signal representation that is weighted, may be coupled to the tracking channel 502 to form a tracking beam.

The tracking channel 502 may operate in either a transmit or receive mode. In transmit mode, the transmit path is coupled to tracking element 506a through duplexer 516. The duplexer 516 provides sufficient isolation to prevent transmitter leakage to desensitize or damage components within the receive path. In receive mode, duplexer 516 directs signals from tracking element 506a to the receive path. The position of the duplexer 516 may be controlled by an external device (not shown), such as a computer, microprocessor, digital signal processor, or any other device known in the art.

A tracking receiver 518 on the receive path is coupled to the duplexer 516. Similar to its searcher receiver 508 counterpart, tracking receiver 518 amplifies, filters, and downconverts the signal from each tracking element 506a to baseband. An analog-to-digital converter (not shown) within tracking receiver 518 digitally samples the baseband signal of each search element 506a and provides the digital baseband samples to tracking memory 520. As will be explained below, the tracking memory 520 provides a mechanism for adjusting the tracking beam to maintain a communication channel with the subscriber station.

The digital baseband samples are read out of the tracking memory 520 and coupled to the tracking filter 522. In the exemplary CDMA cellular device, the weights are fed from the baseband searcher 514 to a tracking filter 522 where they are applied to the digital baseband samples read from the tracking memory 520. For example, if the baseband search 514 determines that the pilot signal strength is sufficient from the combined weighted signals, the combined weighted signals are:

(a₁)(u₀)+(b₁)(x₀)+(c₁)(y₀)+(d₁)(z₀)

constant a₁，b₁，c₁，d₁Can be coupled from the baseband searcher 514 to a tracking filter 522. Tracking filter 522 then adjusts the weights to compensate for the spatial difference between tracking element 506a and search element 506b, and then applies the compensated weights to the digital baseband samples read from tracking memory 520 as follows:

(a₁′)(u₀)+(b₁′)(x₀)+(c₁′)(y₀)+(d₁′)(z₀)

wherein a is₁′，b₁′，c₁′，d₁' is the compensated weighting, and u₀，x₀，y₀，z₀Is at t₀Digital baseband samples from the tracking memory 520. The combined weighted signal from the tracking filter 522 may then be coupled to the demodulator 72 for despreading the spectrum of the desired signal.

The weights applied to the digital baseband samples by tracking filter 522 may be adaptively adjusted to optimize the direction of the tracking beam. This can be accomplished by implementing an algorithm within tracking filter 522It is implemented that the algorithm changes the weights applied to the discrete-time samples so that the maximum pilot signal strength is effectively tracked. For example, the trace memory 520 may be implemented in a first-in-first-out (FIFO) method for storing discrete time samples from each trace element 506 a. Thus, at t₀Respectively received signal u from each search element₀，x₀，y₀，z₀Is stored in a FIFO. Algorithm t for tracking filter sequence invocation₀Effectively steering the tracking beams to adjacent angular directions with a series of weights to the signals. The pilot signals from adjacent angular directions are separated from the received signal within demodulator 524 and compared to each other. The weights that result in the pilot signal with the greatest strength are sent back to the tracking filter 522 for adjusting the tracking beam.

The compensated weights from the tracking filter 522 can also be fed into a tracking filter 526 that follows a modulator 528 on the transmission path. The compensated weights may then be applied to the modulated signal. The tracking filter 526 may further compensate for the weighting applied to the modulated signal due to any factors, including different carrier frequencies as used by the forward and reverse links. The forward link refers to transmission from a base station to a subscriber station, and the reverse link refers to transmission from a subscriber station to a base station. The weighted modulated signals effectively form a transmission beam that coincides with the tracking beam used by the receive path.

The transmitter 530 is coupled to the tracking filter 526. The transmitter 530 upconverts, filters, and amplifies the weighted modulated signal. The output of transmitter 530 is coupled through duplexer 516 to tracking antenna 506a where the signal is transmitted into free space with increased gain in the direction defined by the weighting applied to the signal by tracking filter 526.

Those of skill in the art would appreciate that the various illustrative logical blocks, modules, circuits, and algorithms described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and algorithms have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, or any other combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but, in the alternative, the processor may be a conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The methods or algorithms described in connection with the disclosed embodiments may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

The previous description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without the use of the inventive faculty. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (102)

1. A receiving method, characterized by comprising:

forming one or more search beams to cover an area to detect signals within the area;

detecting signals within the region using one or more search beams; forming one or more tracking beams to receive the detected signals; and

maintaining a communication channel between a first station and a second station using the one or more tracking beams, including receiving a first signal from the second station while searching for one or more additional signals using the one or more search beams.

2. The method of claim 1, wherein the coverage of the area comprises sweeping the search beam over the area.

3. The method of claim 1, wherein the coverage of the area comprises moving the search beam to a plurality of different locations within the area.

4. The method of claim 1, wherein the forming of the search beam comprises forming a plurality of beams to cover the area.

5. The method of claim 1, wherein the forming of the search beam comprises forming an omni-directional beam.

6. The method of claim 1, further comprising detecting a second signal within the area with the search beam, and wherein the forming of the tracking beam comprises forming the tracking beam to receive the signal and the second signal.

7. The method of claim 6 wherein the forming of the tracking beam further comprises forming a plurality of beams, one of the plurality of beams receiving the signal and a second of the plurality of beams receiving the second signal.

8. The method of claim 6, wherein the forming of the tracking beam further comprises forming a tracking beam shape to receive the signal and the second signal.

9. The method of claim 1, further comprising adjusting the tracking beam to track the detected signal.

10. The method of claim 9, wherein the adjustment of the tracking beam comprises moving the tracking beam.

11. The method of claim 9, wherein the adjusting of the tracking beam comprises changing a shape of the tracking beam.

12. The method of claim 1, wherein the forming of the search beam comprises receiving energy through a plurality of spatially separated elements, applying a weight to the received energy from each element, and combining the weighted energy.

13. The method of claim 12, wherein the weight applied to the received energy from each element is different.

14. The method of claim 12, wherein the forming of the tracking beam comprises receiving energy through a second set of spatially separated elements, applying a second weight to the received energy from each of the second set of elements, and combining the second weighted energy, the second weight being based on the weight applied to form the search beam.

15. The method of claim 14, wherein the second weight applied to the received energy from each of the second set of elements is different.

16. The method of claim 14, further comprising tracking the signal by adjusting a second weight applied to the received energy from each of the second set of elements.

17. The method of claim 16, wherein the tracking of the signal comprises moving the second beam to a plurality of locations by adjusting a second weight applied to the received energy from each of the second set of elements and fixing the tracking beam at the location having the highest energy level.

18. A receiver system, comprising:

an antenna for forming one or more search beams and one or more tracking beams; and

a processor for controlling the antenna to maintain a communication channel between the first station and the second station using the one or more tracking beams, including receiving a first signal from the second station while searching for one or more additional signals using the one or more search beams.

19. The receiver system of claim 18 wherein the antenna is further configured to form the search beam as an omni-directional beam.

20. The receiver system of claim 18 wherein the antenna is further configured to form a plurality of search beams.

21. The receiver system of claim 18, wherein the processor is further configured to control the antenna to search for the first signal by sweeping a search beam over an area.

22. The receiver system of claim 18 wherein the processor is further configured to control the antenna to search for the first signal by moving the search beam to a plurality of different locations within the area.

23. The receiver system of claim 18, wherein the processor is further configured to control the antenna to track the second signal.

24. The receiver system of claim 23, wherein the processor is further configured to control the antenna to track the second signal by moving a tracking beam.

25. The receiver system of claim 23 wherein the processor is further configured to control the antenna to track the second signal by changing a shape of the second track.

26. The receiver system of claim 18, wherein the antenna comprises a plurality of spatially separated elements.

27. The receiver system of claim 26 wherein the elements comprise first and second groups, the first group for forming a search beam and the second group for forming a tracking beam.

28. The receiver system of claim 27 wherein the processor further comprises a filter for applying a weight to the received energy from each of the first plurality of elements and combining the weighted energy to form the search beam.

29. The receiver system of claim 28, wherein the filter is further configured to apply different weights to the received energy from each of the first plurality of elements.

30. The receiver system of claim 28, wherein the processor further comprises a searcher for searching the first signal based on the combined weighted energy.

31. The receiver system of claim 30 wherein the processor further comprises a second filter for applying a second weight to the received energy from each of the second plurality of elements and combining the weighted second energies to form the tracking beam, the second weight applied to the received energy from each of the second plurality of elements being responsive to the searcher.

32. The receiver system of claim 31 wherein the second filter is further configured to apply a different second weight to the received energy from each of the second plurality of elements.

33. The receiver system of claim 31 wherein the processor further comprises a demodulator for demodulating the combined second weighted energy.

34. The receiver system of claim 33, wherein the second filter is further configured to adjust the second weight applied to the received energy from each of the second plurality of elements based on the demodulated combined second weighted energy.

35. A method of communication, comprising:

transmitting a signal from a base station;

forming one or more search beams at the remote station to search for a transmitted signal within the region;

detecting a transmit signal with one or more search beams within a region;

forming one or more tracking beams at the remote station to receive the signals; and

maintaining a communication channel between a first station and a second station using the one or more tracking beams, including receiving a first signal from the second station while searching for one or more additional signals using the one or more search beams.

36. The method of claim 35, wherein searching for a signal comprises sweeping a search beam over an area.

37. The method of claim 35, wherein the searching for the signal comprises moving a search beam to a plurality of different locations within the region.

38. The method of claim 35, wherein the formation of the search beam comprises a plurality of beams to cover the area.

39. The method of claim 35, wherein the forming of the search beam comprises forming an omni-directional beam.

40. The method of claim 35, further comprising transmitting a second signal from a second base station and detecting the second transmitted signal with the search beam within the area, wherein the forming of the tracking beam comprises forming the tracking beam to receive the signal and the second signal.

41. The method of claim 40, wherein the forming of the tracking beam further comprises forming a plurality of beams, one of the plurality of beams for receiving the signal and a second of the plurality of beams for receiving a second signal.

42. The method of claim 41, wherein the forming of the tracking beam further comprises forming a shape of the tracking beam to receive the signal and the second signal.

43. The method of claim 35, further comprising adjusting the tracking beam to track the detected signal.

44. The method of claim 43, wherein the adjustment of the tracking beam comprises moving the tracking beam.

45. The method of claim 43, wherein the adjusting of the tracking beam comprises changing a shape of the tracking beam.

46. The method of claim 35, wherein the forming of the search beam comprises receiving energy through a plurality of spatially separated elements, applying a weight to the received energy from each element, and combining the weighted energy.

47. The method of claim 46, wherein the weight applied to the received energy from each element is different.

48. The method of claim 46 wherein the forming of the tracking beam comprises receiving energy through a second set of spatially separated elements, applying a second weight to the received energy from each of the second set of elements, and combining the second weighted energy, the second weight being based on the weight applied to form the search beam.

49. The method of claim 48, wherein the second weight applied to the received energy from each of the second set of elements is different.

50. The method of claim 48, further comprising tracking the signal by adjusting a second weight applied to the received energy from each of the second set of elements.

51. The method of claim 50 wherein the signal tracking comprises moving the tracking beam to a plurality of locations by adjusting a second weight applied to the received energy from each of the second plurality of elements and fixing the tracking beam at the location having the highest energy level.

52. A remote station, comprising:

an antenna for forming one or more search beams and one or more tracking beams; and

a processor for controlling the antenna to maintain a communication channel between the first station and the second station using the one or more tracking beams, including receiving a first signal from the second station while searching for one or more additional signals using the one or more search beams.

53. A remote station as defined in claim 52, wherein the processor is further configured to control the antenna to form the search beam as an omni-directional beam.

54. A remote station as defined in claim 52, wherein the processor is further configured to control the antenna to form a plurality of search beams.

55. The remote station of claim 52, wherein the processor is further configured to control the antenna to search for the first signal by sweeping a search beam over an area.

56. The remote station of claim 52, wherein the processor is further configured to control the antenna to search for the first signal by moving the search beam to a plurality of different locations within the area.

57. The remote station of claim 52, wherein the processor is further configured to control the antenna to track the second signal with the tracking beam.

58. A remote station as defined in claim 57, wherein the processor is further operative to control the antenna to track the second signal by moving a tracking beam.

59. A remote station as defined in claim 57, wherein the processor is further operative to control the antenna to track the second signal by changing a shape of a tracking beam.

60. A remote station as defined in claim 52, wherein the processor further includes a filter to receive energy from multiple elements of the antenna, apply weights to the energy received from each element, and combine the weighted energy to form the search beam.

61. A remote station as defined in claim 60, wherein the filter is further to apply different weights to the energy received from each element.

62. A remote station as defined in claim 60, wherein the processor further includes a searcher to search for the first signal based on the combined weighted energy.

63. A remote station as defined in claim 62, wherein the searcher comprises a correlator for despreading the pilot signal, the search for the first signal being performed based on the pilot signal.

64. The remote station of claim 62, wherein the processor further comprises a second filter for applying a second weight to the energy received from each of the second set of elements of the antenna and combining the weighted second energy to form the tracking beam, the second weight being based on the weight applied to form the search beam.

65. A remote station as defined in claim 64, wherein the second filter is further operative to apply a different second weight to the received energy from each of the second plurality of elements.

66. A remote station as defined in claim 64, wherein the processor further includes a demodulator to demodulate the combined second weighted energy.

67. A remote station as defined in claim 66, wherein the demodulator includes a second correlator to despread the second signal.

68. A remote station as defined in claim 67, wherein the second filter is further to adjust a second weight applied to the received energy from each of the second plurality of elements based on the despread second signal.

69. An apparatus, comprising:

means for forming one or more search beams to cover an area;

means for detecting signals within the region using one or more search beams;

means for forming a tracking beam to receive the detected signal; and

means for maintaining a communication channel between a first station and a second station using the one or more tracking beams comprises receiving a first signal from the second station while searching for one or more additional signals using the one or more search beams.

70. The apparatus of claim 69, wherein the coverage of the area comprises sweeping the search beam over the area.

71. The apparatus of claim 69, wherein the coverage of the area comprises moving the search beam to a plurality of different locations within the area.

72. The apparatus of claim 69, wherein the means for searching for beams comprises means for forming a plurality of beams to cover an area.

73. The apparatus of claim 69, wherein the means for forming a search beam comprises means for forming an omni-directional beam.

74. The apparatus of claim 69, further comprising means for detecting a second signal within the region with the search beam, and wherein the means for forming the tracking beam comprises means for forming the tracking beam to receive the signal and the second signal.

75. The apparatus according to claim 74, wherein the means for forming a tracking beam further comprises means for forming a plurality of beams, one of the plurality of beams receiving the signal and a second of the plurality of beams receiving the second signal.

76. The apparatus of claim 74 wherein the means for forming the tracking beam further comprises means for forming a shape of the tracking beam to receive the signal and the second signal.

77. The apparatus of claim 69, further comprising means for adjusting a tracking beam to track the detected signal.

78. The apparatus of claim 77, wherein the means for adjusting the tracking beam comprises means for moving the tracking beam.

79. The apparatus of claim 77, wherein the means for adjusting the tracking beam comprises means for changing a shape of the tracking beam.

80. The apparatus of claim 69, wherein the means for forming the search beam comprises means for receiving energy through a plurality of spatially separated elements, means for applying a weight to the received energy from each element, and means for combining the weighted energy.

81. The apparatus of claim 80, wherein the weight applied to the received energy from each element is different.

82. The apparatus of claim 80 wherein the means for forming the tracking beam comprises means for receiving energy through a second set of spatially separated elements, means for applying a second weight to the received energy from each of the second set of elements, and means for combining the second weighted energy, the second weight being based on the weight applied to form the search beam.

83. The apparatus of claim 82, wherein the second weight applied to the received energy from each of the second plurality of elements is different.

84. The apparatus of claim 82, further comprising means for tracking the signal by adjusting a second weight applied to the received energy from each of the second set of elements.

85. The apparatus of claim 84 wherein the means for tracking the signal comprises means for moving the tracking beam to a plurality of positions by adjusting the second weight applied to the received energy from each of the second plurality of elements and means for fixing the tracking beam at the position with the highest energy level.

86. A receiver system, comprising:

means for forming one or more search beams and one or more tracking beams by the antenna to receive the second signal;

means for controlling the antenna to maintain a communication channel between the first station and the second station using the one or more tracking beams comprises receiving a first signal from the second station while searching for one or more additional signals using the one or more search beams.

87. The receiver system of claim 86 wherein the means for forming the search beam comprises means for forming the search beam as an omni-directional beam.

88. The receiver system of claim 86, wherein the means for forming a search beam comprises means for forming a plurality of search beams.

89. The receiver system of claim 86 further comprising means for sweeping the search beam over an area.

90. The receiver system of claim 86 further comprising means for searching the first signal by moving the search beam to a plurality of different locations within the region.

91. The receiver system of claim 86 further comprising tracking means for tracking the second signal with a tracking beam.

92. The receiver system of claim 91 wherein the tracking means tracks the second signal by moving a tracking beam.

93. The receiver system of claim 91 wherein the tracking means tracks the second signal by changing a shape of the tracking beam.

94. The receiver system of claim 86 wherein the means for forming the search beam comprises means for receiving energy from a plurality of elements, means for applying a weight to the energy received from each element, and means for combining the weighted energy to form the search beam.

95. The receiver system of claim 94, wherein the weights applied to the received energy from each of the plurality of elements are different.

96. The receiver system of claim 94, further comprising searching means for searching the first signal based on the combined weighted energy.

97. The receiver system of claim 96 wherein the searching means comprises means for despreading the pilot signal, the searching means searching for the first signal being based on the pilot signal.

98. The receiver system of claim 96 wherein the means for forming the tracking beam further comprises means for receiving energy from a second group of elements, means for applying a second weight to the energy received from each of the second group of elements, and means for combining the weighted second energies to form the tracking beam, the second weight being based on the weight applied to form the search beam.

99. The receiver system of claim 98 wherein the second weight applied to the received energy from each of the second plurality of elements is different.

100. The receiver system of claim 98 further comprising demodulation means for demodulating the combined second weighted energy.

101. The receiver system of claim 100 wherein the means for demodulating comprises means for despreading the second signal.

102. The receiver system of claim 101 wherein the means for forming the tracking beam comprises adjusting a second weight applied to the received energy from each of the second plurality of elements based on the despread second signal.