TECHNICAL FIELD OF THE INVENTION

This invention relates generally to the field of wireless communications systems and, more specifically, to a smart antenna system and method.

BACKGROUND OF THE INVENTION

The rising use of mobile communications systems has led to an increasing demand for enhancing efficiency and performance characteristics, such as increasing network capacity, data rate, signal quality, network coverage, and power efficiency. When a wireless signal is transmitted to a receiver, such as an antenna, the receiver often receives interference along with the signal, making it difficult for the receiver to determine the original signal. This interference may include interference caused by the multipath phenomenon and/or co-channel interference caused by other signals or random noise in the same frequency as the original signal. Smart antenna (SA) systems are designed to reduce these types of interferences, and thus enhance the performance characteristics discussed above.

A smart antenna system is generally located near a base station transceiver and combines an array of antenna elements with digital signal processing capabilities to receive and transmit signals in a spatially sensitive manner. In other words, a smart antenna can adapt the direction of transmissions in response to the signals it receives. Thus, a smart antenna system may be said to track, or follow, mobile communication devices (such as mobile phones or personal digital assistants) as they change their location or active status (such as idle, ready, or standby). For example, when a mobile user is located in a particular location within a sector, the smart antenna system may select a best beam that provides the best coverage for that location and transmit signals to and receive signals from the mobile through that best beam. As the user moves to new locations, the smart antenna system may adapt by switching to the beam or beams that provide the best coverage for those locations.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method and apparatus for beam selection in a smart antenna apparatus are provided that substantially eliminate or reduce the disadvantages and problems associated with previously developed methods and apparatuses.

In one embodiment of the present invention, a smart antenna apparatus including a receiving system, one or more beam analysis modules, a control channel monitoring module, a processing system, and a receiving beam switch is provided. The receiving system is operable to receive a plurality of uplink beams, each including traffic signals transmitted by a mobile station. The beam analysis modules are operable to analyze the uplink beams to determine one or more characteristics of each uplink beam. The control channel monitoring module is operable to monitor control channel signals being communicated from a base station transceiver. The control channel signals may include synchronization signals. The processing system is operable to synchronize the smart antenna apparatus with the base station transceiver using the synchronization signals received by the control channel monitoring module. The processing system is further operable to determine a selected beam from the plurality of uplink beams based at least in part on the one or more characteristics determined by the beam analysis modules. The receiving beam switch is operable to switch to the selected beam to allow the selected beam to be communicated to the base station transceiver.

In another embodiment, a smart antenna method is provided. The method includes receiving a plurality of uplink beams, each including traffic signals transmitted by a mobile station. The method further includes analyzing each of the uplink beams to determine one or more characteristics of each uplink beam. The method further includes monitoring control channel signals communicated from a base station transceiver. The control channel signals may include synchronization signals. The method further includes synchronizing the smart antenna apparatus with the base station transceiver using the synchronization signals. The method further includes determining a selected beam from the plurality of uplink beams based at least in part on the determined characteristics of each uplink beam. The method further includes allowing the selected beam to be communicated to the base station transceiver.

Various embodiments of the present invention may benefit from numerous technical advantages. It should be noted that one or more embodiments may benefit from all, some, or none of the advantages discussed below.

One technical advantage includes a smart antenna apparatus that may be coupled to a new or existing base station transceiver as an add-on or applique without having to modify, alter, or reconfigure the base station transceiver or any other component of the base station system, such as base station controllers. Thus, the cost and labor of modifying or altering base station system and/or dealing or negotiating with the manufacturer of the components of base station system, such as base station transceivers and base station controllers, is reduced or eliminated. Moreover, the smart antenna apparatus may be compatible with base station transceivers produced by a variety of manufacturers. For example, the smart antenna apparatus may be compatible with all base station transceivers using standard base station transceiver interfaces. Thus, the installation costs of the smart antenna apparatus are reduced as compared with traditional smart antenna systems. Moreover, the operating costs of the smart antenna apparatus are reduced as compared with traditional smart antenna systems.

In addition, the presence and operation of the smart antenna apparatus may be transparent to the base station system, including the base station transceiver. In other words, the smart antenna apparatus causes little or no delay in the reception and transmission of radio signals to and from the base station transceiver. Thus, the smart antenna apparatus may operate without affecting the timing of the cellular network or any mobile stations.

In addition, the beam selection systems and methods provided by smart antenna apparatus provide a number of advantages. For example, smart antenna apparatus may reduce the interference, such as multi-path and co-channel interference, associated with uplink signals received by a new or existing base station transceiver. In addition, the smart antenna apparatus may reduce the interference associated with downlink signals received by mobile stations. Thus, the smart antenna apparatus may increase the effective capacity and improve the overall performance of the base station transceiver without requiring any modifications to the base station transceiver. For example, since using narrow beams generally increases the range (or coverage) of effective reception and transmission as compared with wide beams, the smart antenna apparatus may increase the range of the base station transceiver to which it is added. Moreover, the smart antenna apparatus may improve the signal-to-noise ratio (SNR) of transmitted and/or received signals, and thus increases the data rate which may be transmitted and/or received by the base station transceiver.

Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, and for further features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1

illustrates a wireless communication system including a smart antenna system and a base station in accordance with an embodiment of the present invention;

FIG. 2

illustrates the general architecture and operation of the smart antenna system of

FIG. 1

including a smart antenna apparatus and an antenna unit;

FIG. 3

illustrates a receiving system of the smart antenna apparatus of

FIG. 2

;

FIG. 4

illustrates a processing system of the smart antenna apparatus of

FIG. 2

;

FIG. 5

illustrates a system for monitoring control signals being communicated from a base station transceiver to mobile stations and synchronizing the smart antenna apparatus with the base station transceiver using the control signals in accordance with an embodiment of the present invention;

FIG. 6

illustrates a method for monitoring control signals being communicated from a base station transceiver to mobile stations in accordance with an embodiment of the present invention;

FIG. 7

illustrates a method for synchronizing the smart antenna apparatus with the base station transceiver during start-up in accordance with an embodiment of the present invention;

FIG. 8

illustrates a method for maintaining the smart antenna apparatus in synchronization with the base station transceiver during steady-state operation in accordance with an embodiment of the present invention;

FIG. 9

illustrates a system for monitoring signaling information being communicated via an interface between a base station transceiver and a base station controller in accordance with an embodiment of the present invention;

FIG. 10

illustrates a method for monitoring signaling information being communicated via the interface illustrated in

FIG. 9

;

FIG. 11

illustrates a system for determining beam selections with the smart antenna apparatus of

FIG. 2

;

FIG. 12

illustrates a system for determining fast decision beam selections in accordance with an embodiment of the present invention;

FIG. 13

illustrates a method for determining fast decision beam selections in accordance with an embodiment of the present invention;

FIG. 14

illustrates a system for controlling the gain settings for each beam receiver for determining fast decision beam selections in accordance with an embodiment of the present invention;

FIG. 15

illustrates a method for controlling the gain settings for each beam receiver for determining fast decision beam selections in accordance with an embodiment of the present invention;

FIG. 16

illustrates a system for determining smart decision beam selections including a smart decision beam selection module in accordance with an embodiment of the present invention;

FIG. 17

illustrates the architecture and operation of the smart decision beam selection module of

FIG. 16

in accordance with an embodiment of the present invention;

FIG. 18

illustrates a method for determining smart decision beam selections in accordance with an embodiment of the present invention;

FIG. 19

illustrates a correlation module for determining a correlation quality of each uplink beam for use in determining smart decision beam selections in accordance with an embodiment of the present invention;

FIG. 20

illustrates a method for determining a correlation quality uplink beams by correlating a signal sequence in each uplink beam with one or more known training sequences in accordance with an embodiment of the present invention;

FIG. 21

FIG. 22

illustrates a system for determining whether to use a fast decision beam selection or a smart decision beam selection for a particular time slot in accordance with an embodiment of the present invention; and

FIG. 23

illustrates a method for determining whether to use a fast decision beam selection or a smart decision beam selection for a particular time slot in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Example embodiments of the present invention and their advantages are best understood by referring now to

FIGS. 1 through 23

of the drawings, in which like numerals refer to like parts.

Generally, a smart antenna system is provided as an add-on to an existing base station in a wireless communications system. The smart antenna system combines an antenna unit that may include a smart antenna array and optionally a backup sector antenna with a smart antenna apparatus having signal processing capabilities to receive and transmit signals in a spatially sensitive manner, or in other words, along one or more selected beams. The smart antenna apparatus is operable to execute one or more algorithms, based on a number of inputs, to select an uplink beam for uplink signals and a downlink beam for downlink signals. The uplink beam is used to communicate uplink signals received from a mobile station to a base station transceiver. The downlink beam is used to communicate downlink signals from the base station transceiver to the mobile station.

The smart antenna apparatus may include a fast decision beam selection module to make beam selections in substantially real time and a smart decision beam selection module to make beam selections based on more input and processing. The smart antenna apparatus may be operable to determine whether to use the results from the fast decision beam selection module or the smart decision beam selection module depending on the particular circumstances. In general, the smart antenna apparatus may use the fast decision beam selection module to make beam selections during the initiation of a call from a mobile station and then switch to the smart beam selection module after the call is established.

The smart antenna system may collect and use signaling information for making beam selection determinations generally as follows. The base station transceiver and the base station controller communicate signaling and traffic information with each other via an interface, such as an A-bis interface in a GSM or GPRS environment or an LUB interface in a 3G environment. The smart antenna apparatus includes a monitoring system coupled to the signaling interface and operable to receive signaling information being communicated between the base station transceiver and the base station controller without affecting, or disturbing, the communication of the signaling or traffic information between base station transceiver and the base station controller. The signaling information received by the monitoring system may then be decoded, filtered and/or otherwise processed to determine relevant signaling information for the smart antenna apparatus. The relevant signaling information may be used by a smart antenna processing system in selecting uplink and/or downlink beams.

In addition, the smart antenna apparatus may also be operable to synchronize itself with the base station transceiver in time and frequency using control channel signals being communicated from the base station transceiver to one or more mobile stations. The smart antenna apparatus may include a control channel monitoring module operable to convert control channel signals received from the base station transceiver in a downlink frequency to a frequency that may be received by a smart antenna receiver. A processing module may execute one or more synchronization algorithms using the control channel signals as input in order to synchronize the smart antenna apparatus with the base station system in time and frequency.

The smart antenna apparatus may be coupled to the existing base station as an applique with little or no modification needed to be made to any component of the base station, including the base station transceiver. In particular, the signaling information monitoring system is operable to passively monitor the signaling information being communicated between the base station controller and the base station transceiver without making any modifications to the base station controller or the base station transceiver. In addition, the control channel monitoring module is operable to passively monitor the control channel information being communicated from the base station transceiver to the mobile stations without making any modifications to the base station transceiver. Thus, the smart antenna apparatus may be easily and inexpensively coupled to a variety of existing base stations.

FIG. 1

illustrates an embodiment of a wireless communication system 10 that includes a base station system 12, a smart antenna system 14, and one or more mobile stations 15. In one embodiment, wireless communication system 10 operates in a GSM (Global System for Mobile Communications) environment. However, wireless communication system 10 may operate according to other wireless standards including, for example, CDMA (Code Division Multiple Access) standards such as IS-95A and IS-95B, CDMA 2000, W-CDMA, TD SCDMA, TETRA, and TDMA (Time Division Multiple Access) standards such as IS-136 and IS-54, without departing from the scope of the present invention.

Base station system 12 may include one or more base station transceivers 24, a base station controller 26, and any other suitable components of a wireless communications base station. Smart antenna system 14 may include an antenna unit 18 and a smart antenna apparatus 16. Smart antenna apparatus 16 may be coupled to base station system 12 as an add-on or an applique.

Base station transceiver 24 is generally operable to communicate radio signals to and from antenna unit 18 via one or more radio signal wires 40 and 42. In this manner, base station transceiver 24 is operable to transmit radio signals to and receive radio signals from one or more mobile stations 15 via antenna unit 18. Base station controller 26 is generally operable to control the operation of one or more base station transceivers 24.

Base station controller 26 and base station transceiver 24 may be coupled by an interface 36. Interface 36 may be operable to communicate signals, including traffic and control (or signaling) information, between base station controller 26 and base station transceiver 24, as described in greater detail with reference to

FIG. 9

In a GSM (Global System for Mobile Communications) environment, base station system 12 may be a Base Station System (BSS), base station transceiver 24 may be a Base Transceiver Station (BTS) and base station controller 26 may be a Base Station Controller (BSC). In a third-generation (3G) environment (such as W-CDMA or CDMA 2000, for example), base station system 12 may be a Radio Network Server (RNS), base station transceiver 24 may be a Node B base station, and base station controller 26 may be a Radio Network Controller (RNC). Base station system 12, base station transceiver 24, and base station controller 26 may alternatively be any other suitable base station components in other wireless communication environments or under different communication standards.

Antenna unit 18 may include a smart antenna array 28 including a plurality of antenna elements 30. Antenna unit 18 may also include a sector antenna 31 operable to transmit and/or receive signals throughout a sector. In some embodiments, sector antenna 31 is comprised of one or more antenna elements similar to antenna elements 30 in smart antenna array 28. In the embodiment shown in

FIG. 1

, antenna unit 18 is located on an antenna tower 22. However, antenna unit 18 may be otherwise located, for example on a building. Preferably, signals directed to and from antenna unit 18 are generally unobstructed near antenna unit 18, or in other words, antenna elements 30 can â€œseeâ€ a large area.

Traditional sector antennas used in cellular communication systems transmit radio signals in a wide beam to a relatively wide area, or sector, since the location of mobile stations is unknown to the system. Such systems pollute the electromagnetic environment by transmitting signals in unnecessary directions. In contrast, smart antenna system 14 divides the wide beam into a plurality of narrow beams. For example, in the embodiment shown in

FIG. 1

, smart antenna system 14 divides a wide beam 32 covering an approximate 120 degree range into seven narrow beams 34. This is accomplished by manipulating the phase of the signals received by antenna elements 30 of smart antenna array 28. In some embodiments, narrow beams 34 are formed using a beamforming network, sometimes referred to as a BFN. In contrast, sector antenna 31 transmits and receives signals throughout the sector through wide beam 32, bypassing the beamforming network. Signals may be communicated between antenna unit 18 and a particular mobile station 15 via a narrow beam 34 or via wide beam 32 (using sector antenna 31), depending on various parameters.

Antenna unit 18 may be coupled to smart antenna apparatus 16 by one or more radio signal wires 40 operable to communicate radio signals between antenna unit 18 and smart antenna apparatus 16. For example, antenna unit 18 may be coupled to smart antenna apparatus 16 by a plurality of radio signal wires 40, each corresponding to a narrow beam 34. Similarly, smart antenna apparatus 16 may be coupled to base station transceiver 24 by one or more radio signal wires 42 operable to communicate radio signals between smart antenna apparatus 16 and base station transceiver 24. Radio signal wires 40 and 42 may include any wire media suitable for communicating radio frequency signals. For example, in one embodiment, radio signal wires 40 and 42 are radio frequency (RF) cables.

When a mobile station 15 transmits uplink signals, the uplink signals may be received along any number of narrow beams 34 due to multi-path or other interference phenomena, and/or due to overlapping areas covered by adjacent narrow beams 34. The uplink signals received via each narrow beam 34 are communicated to smart antenna apparatus 16 via radio signal wires 40. In one embodiment, one or more separate radio signal wires 40 are provided to communicate the signals received via each narrow beam 34.

Smart antenna apparatus 16 processes uplink signals received along each narrow beam 34 and/or other input signals or data to select the best narrow beam 34 and to allow uplink signals received via that narrow beam 34 to be communicated to base station transceiver 24 via radio signal wires 42. For example, smart antenna apparatus 16 may select the best narrow beam 34 based on one or more inputs or parameters. One input may include signaling information received by signaling information monitoring system 106 (described below in connection with

FIG. 2

). Other example inputs or parameters include signal strength, signal quality, relevant power, and signal history of signals received from one or more mobile stations 15. After smart antenna apparatus 16 communicates the uplink signals received via the selected narrow beam 34 to base station transceiver 24, the uplink signals may be processed and/or further communicated by base station system 12. It should be noted that the term â€œnarrow beamâ€ as used in this document applies both to the physical beams through which antenna unit 18 transmits and receives signals (as indicated using reference numeral 34 in

FIG. 1

) as well as the signals received via each of the physical beams.

When downlink signals are to be transmitted from base station system 12 to mobile station 15, the downlink signals are communicated from base station transceiver 24 to smart antenna apparatus 16 via radio signal wires 42. Smart antenna apparatus 16 may select a best narrow beam 34 through which to send the downlink signals. Like the beam selection for uplink signals discussed above, the beam selection for the downlink signals may be based on one or more inputs or parameters, including signaling information received by signaling information monitoring system 106. Other example inputs or parameters include signal strength, signal quality, and signal history of signals received from one or more mobile stations 15.

Smart antenna apparatus 16 may switch from one narrow beam 34 to another narrow beam 34 accordingly. For example, when mobile station 15 moves to a new location, smart antenna system 14 may switch from one narrow beam 34 to another narrow beam 34 for receiving uplink signals from and/or transmitting downlink signals to mobile station 15. In this manner, smart antenna system 14 may locate and track mobile stations 15 as they move within wide beam 32, and transmit signals to and receive signals from each mobile stations 15 via one or more appropriate narrow beams 34. At a particular point in time, the narrow beam 34 selected as the best beam for communicating uplink signals received from mobile station 15 to base station transceiver 24 may be the same as, or different from, the narrow beam 34 selected as the best beam for communicating downlink signals to mobile station 15. This may provide an advantage in situations in which the best beam for receiving uplink signals from a mobile station is not the same as the best beam for transmitting signals to that mobile station. This may be likely, for example, in high-interference environments, such as dense or urban environments.

Base station system 12 may communicate with mobile stations 15 within a range of frequencies, which may be divided into a number of frequency bands. According to some wireless communication standards, the available bandwidth is divided into a number of frequency bands, which may each be referred to simply as a frequency. In some standards, each uplink frequency (in other words, a frequency used for uplink communications) may be associated with a corresponding downlink frequency, such that pairs of frequencies are available. For example, in a P/E/R-GSM 900 environment, each frequency (both uplink and downlink) has a bandwidth of 200 kHz, and each uplink frequency band is offset from its corresponding downlink frequency band by 45 MHz. Typically, due to limitations of signal interference and cost, only a portion of the frequencies available in a particular environment are used by any particular base station transceiver. For example, in one embodiment, four pairs of uplink and downlink frequencies are to be used by each base station transceiver. It should be noted that in other standards, such as the TD-SCDMA standard, one frequency is used for both uplink and downlink communications.

In a GSM environment, signals may be communicated in different frequencies over a period of time, which is divided into frames that are each divided into eight time slots, or channels. Each time slot, or channel, is either a control channel or a traffic channel. Control channels are operable to carry control signals and/or signaling or paging signals, while traffic channels are operable to carry voice and/or other data signals. In the GSM standard, one of the eight channels in a particular frequency, which may be referred to hereinafter as the control frequency, is designated as the control channel. The remaining channels in the control frequency may be traffic channels operable to carry conversations. The control frequency thus consists of one control channel and seven traffic channels. Each remaining frequency may be referred to as a traffic frequency consisting of eight traffic channels. Generally, each traffic channel can support one conversation or other communication in full rate, two conversations or other communications in half rate, or an unlimited number of conversations or other communications in GPRS or group mode.

When a particular mobile station 15 is engaged in a call, voice and/or other data signals intended for that mobile station 15 are transmitted from base station system 12 via smart antenna array 28 within a particular traffic channel (or time slot) in a particular frequency. The mobile station 15 will â€œlistenâ€ for the voice and/or data signals only in the particular traffic channel in the particular frequency. Thus, mobile station 15 must know when, and at which frequency, to â€œlistenâ€ for the voice signals, and thus must be synchronized to base station transceiver 24.

Smart antenna apparatus 16 must also be synchronized with base station transceiver 24 in order to operate properly. For example, smart antenna apparatus 16 must be synchronized with base station transceiver 24 in order to perform its beam-switching functions as discussed above. Further, in some embodiments, smart antenna apparatus 16 should be synchronized with base station 12 more accurately than mobile station 15 is synchronized with base station 12. The synchronization of smart antenna apparatus 16 with base station 12 is discussed in greater detail below with reference to

FIGS. 5 through 8

FIG. 2

illustrates the general architecture and operation of smart antenna system 14. As discussed above, smart antenna system 14 includes smart antenna apparatus 16 and antenna unit 18. Smart antenna apparatus 16 includes a receiving system 100, a processing system 102, a storage system 103, a control channel monitoring module 104, and a signaling information monitoring system 106. In some embodiments, smart antenna apparatus 16 also includes one or more diplexers, such as diplexers 120 and 122.

Receiving system 100 is generally operable to receive radio signals communicated from mobile stations 15. In particular, receiving system 100 may receive analog radio signals communicated from mobile stations 15, received at antenna unit 18, and communicated to receiving system 100 via paths 150 and 152. Receiving system 100 may be further operable to convert the analog radio signals to digital signals and communicate the digital signals to processing system 102.

As shown in

FIG. 3

, receiving system 100 may include one or more frequency receiver units 108, each corresponding with a particular frequency (in other words, a frequency band) and thus operable to receive signals communicated by mobile stations 15 via that frequency. Each frequency receiver unit 108 may include one or more beam receivers 112 operable to receive signals communicated in a particular frequency. Each frequency receiver unit 108 may include a beam receiver 112 corresponding with each narrow beam 34. For example, in one embodiment in which smart antenna system 14 divides wide beam 32 into seven narrow beams 34, each frequency receiver unit 108 includes eight beam receivers 112, one for each of the seven narrow beams 34 and one for wide beam 32, which is received by sector antenna 31. Beam receivers 112 may be operable to convert received radio frequency signals into baseband signals. In a particular embodiment, the beam receivers 112 are identical to each other.

Receiving system 100 may also include one or more samplers 116 operable to convert signals from analog to digital. In particular, one or more samplers 116 may convert analog signals received by each beam receiver 112 to digital signals such that the signals may be processed by processing system 102.

Referring again to

FIG. 2

, processing system 102 is generally operable to perform beam-selection functions. In particular, processing system 102 may execute one or more algorithms based on various inputs and/or parameters to determine a transmitting beam selection 124 and a receiving beam selection 126. In other words, processing system 102 is operable to select one of the narrow beams 34 to communicate signals received by antenna unit 18 to base station transceiver 24, and one of the narrow beams 34 (which may be the same or a different narrow beam 34) to transmit downlink signals to mobile stations 15.

As shown in

FIG. 4

, processing system 102 may include one or more processing modules 62 operable to process received signals, such as signaling signals, control signals, and/or traffic signals. In some embodiments, processing system 102 includes one processing module 62 for each frequency used by smart antenna system 14. Thus, each processing module 62 may process signals communicated in one of the frequencies used by base station transceiver 24. Each processing module 62 is generally operable to perform one or more functions, including beam-selection functions. In an environment using time division muliplexing, such as a GSM environment, each processing module 62 may be operable to determine both uplink and downlink beam selections for communicating signals in each time slot. Thus, in some embodiments, each processing module 62 is operable to determine both uplink and downlink beam selections for each time slot in a particular frequency.

Processing modules 62 may make beam selection decisions based on one or more inputs or parameters, including signals received from receiving system 100 and/or signaling information received from signaling information monitoring system 106. For example, each processing module 62 may be operable to execute one or more beam-selection algorithms to make beam selection determinations. In one embodiment, each processing module 62 is operable to execute a fast decision beam-selection algorithm or a smart decision beam-selection algorithm based on one or more parameters, such as whether the processor has knowledge of the number and/or location of mobile stations 15 using the frequency corresponding with that processing module 62.

One or more processing modules 62 may also be operable to synchronize smart antenna apparatus 16 with base station transceiver 24 in time and/or frequency. In particular, one or more processing modules 62 may be operable to execute one or more synchronization algorithms using control signals, including synchronization signals, received from control channel monitoring module 104 to synchronize smart antenna apparatus 16 with base station transceiver 24.

Processing system 102 may also include a central processing unit, such as host processor 118, operable to further process the output of each processing module 62. In one embodiment, host processor 118 is operable to determine errors or whether the outputs of one or more processing module 62 are valid or require modification.

Each processing module 62 may include one or more processors 63, such as microprocessors, digital signal processors, or any other type of processors capable of executing an algorithm. In one embodiment, each processing module 62 includes one or more programmable digital signal processors. Although processing system 102 as described above includes discrete processing modules 62 for processing signals at different frequencies or for performing different functions, it should be understood that the processing functions performed by smart antenna system 14 may be performed by any appropriate number and combination of processing modules 62.

Referring again to

FIG. 2

, storage system 103 is operable to store information or data for use by smart antenna apparatus 16. In particular, storage system 103 may store information received from signaling information monitoring system 106. Storage system 103 may also be operable to provide information to and receive information from processing system 102.

Control channel monitoring module 104 is generally operable to receive control channel signals, including synchronization signals, being communicated from base station transceiver 24 to antenna unit 18, and to prepare such signals to be processed by processing system 102. In some embodiments, control channel monitoring module 104 is operable to filter and convert the control channel signals from a base station transmitting frequency to a smart antenna receiving frequency, receive and sample the signals, and communicate the signals to processing system 102. The control channel signals, including the synchronization signals, may then be processed by processing system 102 in order to synchronize smart antenna apparatus 16 with base station transceiver 24, as discussed in greater detail below with reference to

FIGS. 5 through 8

Signaling information monitoring system 106 is generally operable to monitor, or receive, signaling information (in other words, base station control information) being communicated between base station transceiver 24 and base station controller 26 via interface 36. Signaling information monitoring system 106 may also be operable to extract a subset of relevant information from the received signaling information to communicate to processing system 102 as an input in making beam-selection determinations. The relevant information may include information related to one or more mobile stations 15, such as frequency hopping, for example. The systems and methods for monitoring the signaling information are discussed in greater detail below with reference to

FIGS. 9 and 10

The various systems and modules of smart antenna apparatus 16, including receiving system 100, processing system 102, control channel monitoring module 104, and signaling information monitoring system 106, as well as the components of each system and module, may or may not be co-located, and may be divided and/or combined in any appropriate manner. For example, smart antenna apparatus 16 may include a ground unit located on or near the ground and a tower unit coupled to antenna tower 22. In one embodiment, smart antenna apparatus 16 includes a ground unit located on the ground and a tower unit located near the top of antenna tower 22 proximate antenna unit 18. In another embodiment, smart antenna apparatus 16 includes a ground unit and a tower unit both located on or near the ground. In another embodiment, smart antenna apparatus 16 includes only one unit such that the components of smart antenna apparatus 16 are generally co-located.

As shown in

FIG. 2

, antenna unit 18 may include antenna array 28 comprising antenna elements 30, as well as a beam forming network (BFN) 128. Beam forming network 128 is operable to form a plurality of uplink beams 130, each corresponding with, and communicating signals received via, one of the narrow beams 34 by controlling the amplitude and phase of signals received by antenna elements 30. In one embodiment, beam forming network 128 forms seven uplink beams 130.

In operation, uplink analog signals are communicated by one or more mobile stations 16 via one or more narrow beams 34 and received by antenna array 28. Beam forming network 128 forms a plurality of uplink beams 130 and communicates uplink beams 130 to smart antenna apparatus 16. Uplink beams 130 are received by receiving system 100. In one embodiment in which smart antenna apparatus 16 includes diplexer 122, uplink beams 130 are received by receiver system 100 after passing through diplexer 122. Each uplink beam 130 may be received by a separate frequency receiver unit 108. Each beam may then be converted from analog to digital by a sampler 116.

The digital uplink beams 130 are then communicated to processing system 102. Using the received uplink beams 130, signaling information received from signaling information monitoring system 106, and/or other parameters as input, processing system 102 executes one or more beam-selection algorithms to determine a receiving beam selection 126 corresponding to one of the uplink beams 130. The receiving beam selection 126 is communicated to a receiving beam switch 127 which filters the uplink beams 130 received from beam forming network 128 such that only the uplink beam 130 corresponding to the receiving beam selection 126 may pass through to base station transceiver 24. In one embodiment in which smart antenna apparatus 16 includes diplexer 120, the uplink beam 130 is received by base station transceiver 24 after passing through diplexer 120.

In particular, each processing module 62 may execute one or more beam-selection algorithms to determine a receiving beam selection 126 for each frequency used by smart antenna system 14. In addition, in a time division multiplexing environment, such as a GSM environment, each processing module 62 may determine a receiving beam selection 126 for each time slot in each frequency.

In one embodiment, each processing module 62 determines a receiving beam selection 126 by determining a fast decision beam selection using a fast decision beam selection module and/or a smart decision beam selection using a smart decision beam selection module. The processing module 62 may determine whether to use the fast decision beam selection or the smart decision beam selection as the receiving beam selection 126 based on one or more parameters, such as whether the processor has prior knowledge of a particular mobile stations 15.

In some embodiments, the fast decision beam selection module is operable to determine the receiving beam selection 126 in real time. In other words, the fast decision beam selection module is operable to determine a fast decision beam selection based on signals communicated via each uplink beam 130 in a first portion of a particular time slot, and receiving beam switch 127 is operable to switch to the fast beam selection in real time such that signals communicated via the selected uplink beam 130 in a subsequent portion of the same time slot may pass through receiving beam switch 127 to base station transceiver 24.

In contrast, the smart decision beam selection module may determine the receiving beam selection 126 to be used by receiving beam switch 127 in later time slots or frames. For example, in one embodiment, the smart decision beam selection module determines a smart decision beam selection based on the signals received in the current time slot and one or more previous time slots, but receiving beam switch 127 does not switch to the smart decision beam selection until the following frame. Thus, in this embodiment, receiving beam switch 127 may switch to the uplink beam 130 corresponding with the smart decision beam selection in the frame following the last frame used in determining the smart decision beam selection.

Downlink signals are communicated from base station transceiver 24 to be transmitted to one or more mobile stations 15 via antenna unit 18. The downlink signals are received by smart antenna apparatus 16 and a downlink beam 132 corresponding with one of the narrow beams 34 is selected for communicating the downlink signals to the mobile stations 15. In one embodiment in which smart antenna apparatus 16 includes diplexer 120, the downlink signals pass through diplexer 120 before being assigned to a narrow beam 34.

A transmitting beam switch 125 is operable to assign the downlink signals to a downlink beam 132 based on a transmitting beam selection 124 determined by processing system 102. The same or similar inputs and/or parameters used to determine receiving beam selection 126 may be used by processing system 102 to determine transmitting beam selection 124. The downlink signals are assigned to the downlink beam 132 corresponding to the transmitting beam selection 124 and the downlink beam 132 is communicated to antenna unit 18 and transmitted through the corresponding narrow beam 34. In one embodiment in which smart antenna apparatus 16 includes diplexer 122, the downlink beam 132 is received by antenna unit 18 after passing through diplexer 122.

As with the uplink beam selection, each processing module 62 may execute one or more beam-selection algorithms to output a transmitting beam selection 124 for each frequency used by smart antenna system 14. In addition, in a time division multiplexing environment, such as a GSM environment, each processing module 62 may determine a transmitting beam selection 124 for each time slot in each frequency. At any particular time, the transmitting beam selection 124 for a particular downlink channel may or may not be the same as the receiving beam selection 126 determined for the corresponding uplink channel. In other words, the narrow beam 34 corresponding with the uplink beam 130 selected for communicating uplink signals from a mobile station 15 to base station transceiver 24 may not always be the same narrow beam 34 selected for communicating downlink signals from base station transceiver 24 to that mobile station 15. In addition, as with the receiving beam selection, each processing module 62 may determine a transmitting beam selection 124 by determining a fast decision beam selection using a fast decision beam selection module and/or a smart decision beam selection using a smart decision beam selection module.

As discussed above, the inputs used by processing system 102 in making beam selection determinations may include signaling information received from signaling information monitoring system 106. In operation, signaling information monitoring system 106 monitors, or receives, signaling information being communicated between base station transceiver 24 and base station controller 26 via interface 36. Signaling information monitoring system 106 extracts relevant information from the received signaling information and communicates this information to processing system 102 as an input for making beam selections. The systems and methods for monitoring the signaling information are discussed in greater detail below with reference to

FIGS. 9 and 10

Processing system 102 is synchronized and kept in synchronization with base station transceiver 24 using control signals received from control channel monitoring module 104. In operation, control channel monitoring module 104 receives, or monitors, control channel signals (including synchronization signals) being communicated from base station transceiver 24 to antenna unit 18. Control channel monitoring module 104 filters and converts the control channel signals from a base station transmission frequency to an smart antenna receiving frequency, receives and samples the signals, and communicate the signals to processing system 102. Processing system 102 uses the signals to synchronize itself with base station transceiver 24 in time and frequency. Processing system 102 may execute one or more synchronization algorithms using the control channel signals as input to synchronize itself with base station transceiver 24. The system and method of synchronization is discussed in detail below with reference to

FIGS. 5 through 8

illustrate example systems and methods for accurately synchronizing smart antenna apparatus 16 with base station transceiver 24 in time and frequency. In general, smart antenna apparatus 16 uses the same synchronization signals that are used by mobile station 15 to synchronize mobile station 15 with base station transceiver 24. In one embodiment, the synchronization signals are obtained by smart antenna apparatus 16 from the radio signals being communicated from base station transceiver 24 to antenna unit 18 via radio signal wires 42 and 40. The path of the radio signals transmitted from base station transceiver 24 may be split at smart antenna apparatus 16 such that one path is used to synchronize smart antenna apparatus 16 with base station transceiver 24 and another path continues to, and is transmitted by, antenna unit 18 in order to synchronize mobile stations 15 with base station transceiver 24.

In this manner, smart antenna apparatus 16 may be synchronized accurately with base station transceiver 24 using the radio signals communicated from base station transceiver 24 via radio signal wires 40. Thus, in some embodiments, the components of base station system 12, including base station transceiver 24, do not need to be modified, altered, or reconfigured in order for smart antenna apparatus 16 to be synchronized with, and maintained in synchronization with, base station transceiver 24. In one embodiment, smart antenna apparatus 16 may be synchronized accurately with base station transceiver 24 using only signals received from base station transceiver 24 via radio signal wires 42. Thus, the cost and labor of modifying or altering base station system 12 and/or dealing or negotiating with the manufacturer of the components of base station system 12, such as base station transceiver 24, is reduced or, in some embodiments, eliminated.

In addition, smart antenna apparatus 16 may be synchronized accurately with base station transceiver 24 without interfering with the radio signals being communicated from base station transceiver 24 and intended for mobile stations 15. This is accomplished by splitting the path of the radio signals communicated from base station transceiver 24 into a first path directed toward antenna unit 18 for synchronizing mobile stations 15 and a second path directed toward a smart antenna receiver and processor for synchronizing smart antenna apparatus 16, as discussed below in greater detail.

FIG. 5

illustrates an embodiment of a base station transceiver 24, a smart antenna apparatus 16, and an antenna unit 18 for synchronizing smart antenna apparatus 16 with base station transceiver 24. Smart antenna apparatus 16 includes a radio wire input 64, a splitter 50, control channel monitoring module 104, and processing module 62. Radio wire input 64 is operable to be coupled to one or more radio signal wires 42 to receive radio signals communicated from base station transceiver 24. In particular, radio wire input 64 may be operable to receive signals communicated in a control channel, including control signals communicated within the control channel.

Splitter 50 is operable to split the path of a signal into two or more paths. For example, splitter 50 may be a bi-directional or a tri-directional coupler. In the embodiment shown in

FIG. 5

, splitter 50 is a bi-directional coupler operable to divide an input path 66 of radio signals received from radio wire input 64 into a first output path 68 directed toward antenna unit 18 and a second output path 70 directed toward first filter 52. Like input path 66, output paths 68 and 70 may be operable to communicate signals received by radio wire input 64. In addition, splitter 50 may be operable to divide signal path 66 without interfering with signals communicated from signal path 66 to signal path 68. Thus, control channel monitoring module 104 may be operable to passively monitor, or receive, the control signals being communicated from base station transceiver 24 to antenna unit 40. For example, the control signals may be monitored without using active components. In one embodiment, the control signals being communicated from base station transceiver 24 to antenna unit 40 are monitored without amplifying the control signals.

In the embodiment shown in

FIG. 5

, control channel monitoring module 104 comprises a first filter 52, a signal mixer 54, a second filter 56, a receiver 58, and a sampler 60. First filter 52 may include an attenuator 72 and a bandpass filter 74. Attenuator 72 is operable to reduce the amplitude of radio signals by a predetermined amount without introducing distortion to the signals. Bandpass filter 74 allows a specific band of frequencies to pass through while blocking or absorbing other frequencies outside the specified band. In one embodiment, bandpass filter 74 allows the band of frequencies defined by the downlink control frequency to pass through, while blocking or absorbing other frequencies.

Signal mixer 54 is operable to mix, or combine, the signals received from first filter 52 with a conversion signal 76 in order to convert the signals from one frequency to another frequency (in other words, from one frequency band to another frequency band). Signal mixer 54 may be operable to convert the signals from the downlink frequency at which the signals were transmitted from base station transceiver 24 to the corresponding uplink frequency at which the signal may be received by receiver 58. For example, as discussed above, in the P/E/R-GSM 900 standard, downlink frequencies are offset from their corresponding uplink frequencies by 45 MHz. Thus, as shown in

FIG. 2

, conversion signal 76 may be approximately a 45 MHz signal such that signal mixer 54 is operable to convert the signal from a downlink frequency to an uplink frequency which may be received by receiver 58. It should be understood that in some embodiments, conversion signal 76 is defined according to the offset between downlink frequencies and corresponding uplink frequencies according to the particular communication environment. For example, in a GSM 850 environment, as in the P/E/R-GSM 900 environment, conversion signal 76 may be approximately a 45 MHz signal. In a GSM 1900 environment, conversion signal 76 may be approximately an 80 MHz signal. In a GSM 1800 environment, conversion signal 76 may be approximately a 95 MHz signal. In a GSM 480/450 environment, conversion signal 76 may be approximately a 10 MHz signal.

Second filter 56 may include a receiving frequency bandpass filter 78 and an attenuator 80. Like bandpass filter 74, bandpass filter 78 allows a specific band of frequencies to pass through while blocking or absorbing other frequencies outside the specified band. In one embodiment, bandpass filter 78 allows the band of frequencies defined by the corresponding uplink frequency to pass through, while blocking or absorbing other frequencies. Like attenuator 72, attenuator 80 is operable to reduce the amplitude of radio signals by a predetermined amount without introducing distortion to the signals.

Receiver 58 is operable to receive signals from second filter 56 and is generally operable to receive radio signals within a particular frequency band. In one embodiment, receiver 58 is operable to receive signals within the uplink frequency bandwidth (in other words, the bandwidth of signals transmitted by mobile stations 15). In some embodiments, receiver 58 is similar or identical to other receivers used by smart antenna apparatus 16 to receive radio signals from mobile stations 15, such as beam receivers 112. In a particular embodiment, receiver 58 is one of the beam receivers 112.

Sampler 60 is operable to convert signals from analog to digital. Sampler 60 may convert analog signals received by receiver 58 to digital signals such that the signals may be processed by processing module 62.

Processing module 62 is operable to process radio signals using one or more synchronization algorithms 82. In one embodiment, processing module 62 is operable to execute one or more synchronization algorithms 82 using digital signals received from sampler 60 as input to synchronize smart antenna apparatus 16 with base station transceiver 24 in time and frequency. In the embodiment shown in

FIG. 3

, synchronization algorithms 82 include a coarse timing synchronization algorithm 86, a frame synchronization algorithm 88, a fine timing synchronization algorithm 90, and a fine frequency synchronization algorithm 92. Coarse timing synchronization algorithm 86 and frame synchronization algorithm 88 generally perform rough synchronizations, while fine timing synchronization algorithm 90 and fine frequency synchronization algorithm 92 are generally fine tuning algorithms. These particular synchronization algorithms 82 are discussed in greater detail below with reference to

FIGS. 4 and 5

. In one embodiment, processing module 62 is operable to execute one or more synchronization algorithms 82 in order to locate the control signals within the control frequency and to use certain control signals, such as time and frequency synchronization signals, to synchronize smart antenna apparatus 16 with base station transceiver 24.

Base station transceiver 24 may include one or more radio wire outputs 84 operable to receive one or more radio signal wires 42. Thus, smart antenna apparatus 16 may be coupled to base station transceiver 24 via one or more radio signal wires 42.

FIG. 6

illustrates a method of synchronizing smart antenna apparatus 16 with base station transceiver 24 using radio frequency control signals transmitted by base station transceiver 24. Generally, base station transceiver 24 transmits radio signals via radio signal wires 42 in a control frequen