WO2000051364A2

WO2000051364A2 - Method for antenna gain acquisition in a cellular system

Info

Publication number: WO2000051364A2
Application number: PCT/SE2000/000176
Authority: WO
Inventors: Michel Desgagne; Sylvain Labonte
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 1999-02-26
Filing date: 2000-01-28
Publication date: 2000-08-31
Also published as: BR0008542A; CA2362899A1; WO2000051364A3; AU3685000A

Abstract

A cell base station includes a first directive antenna array (104) (to form one beam (106) per cell sector) and a second directive antenna array (110) (to form a plurality of narrow (112) beams per cell sector). Location verification modules (132, 134) are further included for operation in connection with each of the first and second directive antenna arrays. To identify and characterize any difference in gain between the first and second directive antenna arrays, mobile station azimuth orientation with respect to the base station is determined and various signal strength and power related measurements and settings are collected from the mobile station and base station. The collected data is then mathematically processed (206, 228, 246) to determine a value indicative of the difference in gain between the first and second directive antenna arrays as a function of the azimuth orientation.

Description

METHOD FOR ANTENNA GAIN ACQUISITION IN A CELLULAR SYSTEM

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application for patent is related to and incorporates by reference previously filed, commonly assigned, co-pending United States Application for Patent Serial No. 08/994,586, filed December 19, 1997, entitled "Method and System for Improving Handoffs in Cellular Mobile Radio Systems".

BACKGROUND OF THE INVENTION

Technical Field of the Invention

The present invention relates to a cellular communications system and, in particular, to a system utilizing smart antenna technology in cellular base stations. Description of Related Art

It is well known in the art to utilize directive antennas in cellular communications networks. The most commonly recognized example of directive antenna use in cellular communications networks is based on the principle of sectorization, as is illustrated in FIGURE 1. A cell site 10 may comprise either one omnidirectional cell or a plurality, for example, three (or more), sector cells 12.

Directive antennas 14, each with an appropriately selected beamwidth for the sector cell 12, are then utilized at each base station 16 to form a plurality of wide beams 18, one per sector cell, with the totality of the beams formed thereby providing substantially omni-directional radio frequency coverage throughout the cell site area. In operation, each of the formed wide beams 18 is in continuous use to provide service within each corresponding sector cell 12.

Another example of directive antenna use in cellular communications networks is based on the use of smart antenna technology, as is illustrated in FIGURE 2A. Directive antennas 20 are utilized at each base station 16 of a cell site 10 to form a plurality of separate, perhaps slightly overlapping, narrow beams 22 within each sector cell 12, with the totality of the beams formed thereby providing substantially omnidirectional radio frequency coverage throughout the cell site area. In operation, and in contrast to the operation of the sectorized beams 18 of FIGURE 1, the narrow beams 22 are intermittently used only when necessary to provide service to one or more mobile stations 24, as is illustrated in FIGURE 2B. Put another way, in smart antenna technology, the base station 16 controls its directive antenna 20 to activate at any given time only those individual ones of the plurality of separate, perhaps slightly overlapping, narrow beams 22 as are needed to serve active mobile stations 24 within the cell site 10.

SUMMARY OF THE INVENTION A first set of transceivers for a base station in a given cell is connected to a first directive (sector) antenna that forms one beam per sector cell. Both traffic and control channel communications with mobile stations located within the given cell may be effectuated through the first directive antenna utilizing the continuously activated sector beams. A second set of transceivers for that same base station in that same given cell is connected to a second directive (smart) antenna that forms a plurality of separate, perhaps slightly overlapping, narrow beams per sector cell. Preferably traffic channel communications may be effectuated through the second directive antenna by activating a certain one of the plurality of narrow beams which points generally in the direction of each mobile station within the given cell. The present invention still further concerns a method and apparatus for identifying and characterizing any difference in gain between the first directive (sector) antenna array and the second directive (smart) antenna array. In accordance with one embodiment for making a gain difference determination, a mobile station located at a known azimuth orientation with respect to the base station makes downlink signal strength measurements with respect to both control channel communications from the base station broadcast using the first directive antenna and traffic channel communications from the base station broadcast using the second directive antenna. The signal strength measurements are reported and then subtracted from each other (taking into account certain power offsets such as backoff and power control) to determine a value indicative of the difference in gain between the first and second directive antennas as a function of the azimuth orientation.

In a second embodiment for making a gain difference determination, a mobile station during pre-handoff verification makes a downlnk received power measurement on control channel communications that are broadcast from the target base station using the first directive antenna. The target base station determines the azimuth orientation with respect to the mobile station and makes an uplink received power measurement using its second directive antenna on the traffic channel communications of the mobile station. These received power measurements are reported, along with information relating to the power level settings for mobile station traffic channel broadcast and base station control channel broadcast, and mathematically manipulated to determine a value indicative of the difference in gain between the first and second directive antennas as a function of the azimuth orientation.

Finally, in a third embodiment for making a gain difference determination, a base station during pre-handoff verification determines the azimuth orientation with respect to the mobile station and makes an uplink signal strength measurement using its first and second directive antennas on the traffic channel communications of the mobile station. The signal strength measurements are reported and then subtracted from each other to determine a value indicative of the difference in gain between the first and second directive antennas as a function of the azimuth orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the method and apparatus of the present invention may be acquired by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein:

FIGURE 1 , previously described, is a diagram of directive antenna beam coverage within a sectorized cell of a cellular communications system;

FIGURES 2A and 2B, previously described, are diagrams of directive antenna beam coverage within a smart antenna equipped cell of a cellular communications system;

FIGURES 3 A and 3B are diagrams of directive antenna beam coverage within a combined sectorized/smart antenna cell of the present invention;

FIGURE 4 is a block diagram of a cellular system including base stations implementing the combined sectorized/smart antenna cell illustrated in FIGURES 3A and 3B;

FIGURE 5 is a flow diagram for a first method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in

FIGURES 3A and 3B;

FIGURE 6 is a schematic diagram illustrating an operating scenario for a second method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in FIGURES 3A and 3B; FIGURE 7 is a flow diagram for a second method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in FIGURES 3 A and 3B and the scenario of FIGURE 6;

FIGURE 8 is a schematic diagram illustrating an operating scenario for a third method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in FIGURES 3 A and 3B; and FIGURE 9 is a flow diagram for a third method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in FIGURES 3 A and 3B and the scenario of FIGURE 8.

DETAILED DESCRIPTION OF THE DRAWINGS Reference is now made to FIGURE 3 A wherein there is shown a diagram of directive antenna beam coverage within a combined sectorized/smart antenna cell 100 of the present invention. A base station 102 for the cell 100 includes a first directive (sector) antenna 104 operable to form a plurality of wide beams 106, one per sector 108, with the totality of the sector coverage formed thereby providing substantially omni-directional radio frequency coverage throughout the cell site area. The base station 102 for the cell 100 further includes a second directive (smart) antenna 110 operable to form a plurality of separate, perhaps slightly overlapping, narrow beams 112 (either switched or steerable) within each sector 108, with the totality of the smart beams formed thereby providing substantially omni-directional radio frequency coverage throughout the cell site area. For ease of illustration only one sector 108 is shown. It is further understood that only one physical directive antenna (comprising, for example, an antenna array) may be needed to implement the logical first and second directive antennas 104 and 110. In operation, each of the wide beams 106 formed by the first directive antenna 104 is in continuous use to provide service within each corresponding sector 108 to mobile stations 114 present therein. With respect to the second directive antenna 110, however, only those narrow beams 112 which are needed to serve active mobile stations 114 therein are in use at a given time, as is illustrated in FIGURE 3B.

It is important for a number of reasons for the system to acquire knowledge of antenna gain with respect to the included directive antenna arrays 104 and 110. For example, knowledge of antenna array gain is needed in making transmitter power adjustment determinations. Additionally, knowledge of antenna gain is needed in evaluating signal strength measurements made by mobile stations in connection with the performance of mobile assisted handoff (MAHO). More specifically, as mobile station may access and use communications channels (Control or traffic) broadcast using either the first directive antenna array 104 or the second directive antenna array 110, it turns out that difference in gain between sector antenna (104) and the smart antenna (110) is a value of great interest to system operators in connection with characterizing their systems, defining/preserving cell boundaries, and troubleshooting system performance. Reference is now once again made to FIGURES 3 A and 3B wherein there is further illustrated the differences in measured antenna gain between the beams 106 and 112 as a function of azimuth orientation. It may be seen in FIGURE 3B that at a certain azimuth orientation angle (θ,) the gain of the first directive (sector) antenna 104 is equal to the gain of the second directive (smart) antenna 110. Conversely, at another angle (θ₂) shown in FIGURE 3 A the gain of the first directive antenna 104 differs quite significantly from the gain of the second directive antenna 110. It would be useful, for at least the applications discussed above as well as other applications, if the difference in gain between the first directive antenna 104 (sector coverage 106) and the second directive antenna 110 (smart antenna beam 112) could be determined and characterized as a function of the azimuth orientation angle θ.

Reference is now made to FIGURE 4 wherein there is shown a block diagram of a cellular system 120 including base stations 122 implementing the combined sectorized/smart antenna cell illustrated in FIGURES 3A and 3B. Each base station 122 includes a plurality of transceivers (Tx/Rx) 124 which operate in either as digital or analog mode on a certain frequency assigned to the cell 100 where the base station is located. A first set 124(1) of one or more of these transceivers 124 (providing at least control and perhaps also traffic channels) are connected to the first directive (sector) antenna 104 supporting the sector beams 106 (see, FIGURES 3 A and 3B). A second set 124(2) of a plurality of these transceivers 124 (most likely providing only traffic channels) are connected to the second directive (smart) antenna 110 supporting the smart antenna beams 112 (see, FIGURES 3 A and 3B). Each base station 122 is connected to a mobile switching center (MSC) 126. This connection may be made either directly (as generally indicated at 128(1)) or through a base station controller (BSC) 130 (as generally indicated at 128(2)). The manner of operation of the mobile switching center 126, base station controller 130 and base stations 122 in a coordinated fashion to provide cellular telephone service to mobile stations is well known to those skilled in the art.

The base station 122 further includes a first location verification module (LVM1) 132 operable in connection with the first directive (sector) antenna 104 to make measurements on mobile station uplink communications. The location verification module 132 is provided with an order to make these measurements. This order specifies a frequency on which the measurements are to made, a time slot within which the measurements are to be made, and a digital voice color code (DVCC) necessary to unambiguously identify the mobile station whose uplink communications are to be measured. Responsive to the received order, the location verification module 132 tunes to the proper frequency within the proper time slot, decodes the DVCC, and then makes the uplink measurements on certain metrics such as signal strength and signal quality. The measurements are then reported for subsequent evaluation in connection with system operation, such as, for example, handoff determinations.

The base station 122 still further includes a second location verification module (LVM2) 134 operable in connection with the second directive (smart) antenna 110 to make measurements on mobile station uplink communications. The location verification module 134 is similarly provided with an order to make these measurements. This order specifies a frequency on which the measurements are to made, a time slot within which the measurements are to be made, and a digital voice color code (DVCC) necessary to unambiguously identify the mobile station whose uplink communications are to be measured. Responsive to the received order, the location verification module 134 tunes to the proper frequency within the proper time slot, decodes the DVCC, and then makes the uplink measurements on certain metrics such as signal strength and signal quality. The measurements are then reported for subsequent evaluation in connection with system operation, such as, for example, handoff determinations. The measurements may also be processed by the second location verification module 134 to determine a direction of arrival (DO A) azimuth orientation angle θ (see, FIGURE 3A) with respect to the mobile station.

Although illustrated as having a location verification module for each of the first directive (sector) antenna 104 and the second directive (smart) antenna 110, it will of course be understood that only one location verification module is typically needed for most applications and it is preferably used in conjunction with, and connected to, the second directive (smart) antenna. It is also possible to utilize a single location verification module in connection with both the first directive (sector) antenna 104 and the second directive (smart) antenna 110.

The base station 122 still further includes a smart antenna controller 136. The smart antenna controller 136 operates responsive to a determined direction of arrival (DOA) azimuth orientation angle θ (see, FIGURE 3 A) identification with respect to a certain mobile station, and then identifies a certain one of the plurality of separate, perhaps slightly overlapping, narrow beams 112 corresponding to that angle for serving the mobile station. The smart antenna controller 136 then configures the second directive antenna 110 for operation to activate the identified beam 112 for handling communications with the mobile station (see, FIGURE 3B).

Reference is now additionally made to FIGURE 5 wherein there is shown a flow diagram for a first method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in FIGURES 3 A and 3B. For purposes of this method, it is assumed that a mobile station 114 within a cell 100 is currently in an on-call mode and is thus engaged in a cellular call on a traffic channel associated with a transceiver 124 in the second set 124(2) of transceivers. Thus, the mobile station 114 is in voice channel communication with the base station 122 through use of a selected one of the smart antenna beams 112. It is further assumed that since an appropriate one of the smart antenna beams 112 has been selected, that the base station 122 is aware of the direction of arrival (i.e., the azimuth orientation angle θ) with respect to the mobile station 114. It is still further assumed that a control channel for the cell 100 is supported by a transceiver 124 in the first set 124(1) of transceivers. Thus, the mobile station 114 is in control channel communication with the base station 122 through use of a sector antenna beam 106.

In step 200, the mobile station makes a signal strength measurement on its serving control channel (SS_{MS cc}). Thus, the mobile station makes its signal strength measurement with respect to cellular communications operation use of the sector antenna beam 106. The signal strength measurement is accordingly indicative of sector antenna beam gain. The mobile station may be told to make this measurement by the mobile switching center or base station by modifying the conventionally downloaded measurement list (which identifies measurement channels of neighboring cells) to additionally include an identification of the control channel utilized by the mobile station in the currently serving cell. Next, in step 202, the mobile station makes a signal strength measurement on its serving traffic channel (SS_{MS τc}). Thus, the mobile station makes its signal strength measurement with respect to cellular communications operation use of the selected one of the smart antenna beams 112. The signal strength measurement is accordingly indicative of smart antenna beam gain. This traffic channel measurement is a conventional measurement made periodically by mobile stations in connection with normal operation. The values of the signal strength measurements made in steps 200 and 202 are then reported to the base station and/or mobile switching center in step 204 along with an identification of the base station made azimuth orientation angle θ to which these measurements relate. The signal strength measurements may then be subtracted from each other (taking into account certain power offsets such as backoff and power control) in step 206 to determine a value indicative of the difference in gain between the sector beam 106 of the first directive antenna array 104 and the selected smart antenna beam 112 of the second directive antenna array 110 at the angle θ. More specifically, the mobile station received signal strengths (SS_{MS CC} and SS_{MS TC}) are related to the base station broadcast signals strength (SS_{BS CC} and SS_{BS TC}) in accordance with the following equations: S _MS,_CC ⁼ kS_{BS CC} " PL + G_{SECT0R ANT}, and (1)

S _{MS τc} = SS_{BS τc} - PL + G_{SMART ANT}(Θ') - ATT, (2)

wherein: PL is the path loss between the mobile station and base station;

C_SECTOR,_ANT ^{is tne} gain of the first directive antenna 104 in the base station;

G_SMART._AN_TCΘ) is ^tne g^am of the second directive antenna 110 in the base station at the determined direction of arrival angle θ; and ATT is the attenuation at the output of the transceiver (i.e., by an attenuator), wherein SS_{BS TC} is measured before the output signal is attentuated. The value of ATT is dynamically controlled by a power control algorithm. The value of interest is the difference in gain between the sector beam 106 of the first directive antenna 104 and the selected smart antenna beam 112 of the second directive antenna 110 at the angle θ. This may be obtained by subtracting Equation (1) from Equation (2) and rewriting as follows:

ΔGATN(Θ) = G_{SMART ιANT}(θ) - G_SECT0R>ANT

⁼ k^_Ms._Tc - _{MS CC} + S_{BS TC} - S_{BS cc} + ATT (3)

wherein: SS_{MS τc} and SS_{MS CC} are known and reported by the mobile station in step 204; θ and (SS_{BS τc} - SS_{BS cc}) = base station backoff value are known by the base station; and the ΔGATN(Θ) value may be normalized as needed for use in any subsequent evaluation, processing or review operation. The process of steps 200-206 may then be repeated (step 208) many times at different angles θ to collect a statistically significant sampling of data and thus create in step

210 a table (or corresponding function) specifying the difference in gain between the first directive antenna array 104 sector beams 106 and the second directive antenna array 110 smart antenna beams 112 as a function of the azimuth orientation angle θ.

Reference is now made to FIGURE 6 wherein there is shown a schematic diagram illustrating an operating scenario for a second method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in FIGURES 3 A and 3B and 4. In this scenario, a mobile station 114 is engaged in a cellular call on a traffic channel and is currently being served by base station 122(s) in the currently serving cell 100(s). While engaged in this call, the mobile station 114 makes conventional MAHO measurements on the control channels broadcast by its neighboring cells 100. Downlink measurements made by the mobile station 114 (and perhaps also uplink measurements made by the currently serving base station 122(s)) indicate that a need for handing off the on going call may arise. A request is accordingly made to the neighboring cells 100, including the cell 100(t), for uplink verification measurements to be made by their base stations 122, such as base station 122(t), on the current traffic channel. The neighboring cell 100 reported verification measurements are then evaluated to select a target cell 100(t) for hand off. The cellular call is then handed over to a traffic channel provided by the target base station 122(t) in the target cell 100(f).

Reference is now additionally made to FIGURE 7 wherein there is shown a flow diagram for a second method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in FIGURES 3 A and 3B and the scenario of FIGURE 6. For purposes of this method, it is assumed that the verification process prior to mobile station 114 handoff is being performed. It is further assumed that the mobile station 114 is engaged in a cellular call on a traffic channel associated with a transceiver 124 in the second set 124(2) of transceivers for the serving base station 122(s). It is further assumed that in the potential target cell 100(t) for handoff, the base station 122(f) second location verification module 134 operable in connection with the second directive antenna array 110 has made uplink measurements on that traffic channel and is aware of the direction of arrival (i.e., the angle θ) with respect to the mobile station 114. It is still further assumed that a control channel for the target cell 100(t) is supported by a transceiver 124 in the first set 124(1) of transceivers for the base station 122(f). Finally, it is assumed that the gain on the second directive (smart) antenna is substantially the same on both the uplink and downlink.

In step 220, the mobile station 114 makes downlink received power measurements on the control channel for the target cell 100(t). Thus, the mobile station 114 makes its received power measurement with respect to cellular communications operation use of the first directive antenna array 104 sector antenna beam 106 of the target cell 100(t). Next, in step 222, the mobile station 114 reports its target cell 100(t) downlink control channel received power measurement value (P_R,MS) ^{to m}e serving base station 122(s) and mobile switching center along with an identification of its own power level setting (P_{T MS}) for uplink traffic channel communications. With respect to the target base station 122(f), in step 224, it makes uplink received power measurements on the traffic channel currently being utilized by the mobile station 114 for its communications with the serving base station 122(s). Thus, the base station 122(t) makes its received power measurement with respect to cellular communications operation use of the second directive antenna array 110 smart antenna beam 112 of the target cell 100(t). Next, in step 226, the target base station 122(t) reports its uplink traffic channel received power measurement value (P_R^_S) to the mobile switching center along with an identification of its own power level setting

(P_{T BS}) for downlink control channel communications as well as the determined direction of arrival (i.e., the angle θ) with respect to the mobile station 114.

The uplink traffic channel received power measurement value (P_R^_S) is related to the mobile station 114 power level setting (P_{T MS}) for uplink traffic channel communications in accordance with the following equation:

P_R,BS ⁼ _T,MS " PL + G_MS?ANT + G_{SMART >ANT}(Θ), (4)

wherein: PL is the path loss between the mobile station and base station;

G_{MS ANT} is the gain of the mobile station 114 antenna; and G_{SMART ANT}(Θ) is the gain of the second directive antenna array 110 in the target base station 122(f) at the determined direction of arrival angle θ. Similarly, the mobile station 114 downlink control channel received power measurement value (P_RιMs) i^s related to the target base station 122(f) power level setting (P_T>BS) for downlink control channel communications in accordance with the following equation:

P_R,MS ⁼ P_T._BS " PL + G_{MS jANT} + G_{SECTOR ANT}, (5)

wherein: G_{SECT0R ANT} is the gain of the first directive antenna array 104 in the target base station 122(f). The value of interest is the difference in gain between the sector beam 106 of the first directive antenna array 104 and the selected smart antenna beam 112 of the second directive antenna array 110 at the angle θ. This may be obtained by subtracting Equation (5) from Equation (4) and rewriting as follows:

ΔGALN(Θ) = G_{SMART >A}Nτ( ) " _SE TOR,ANT

⁼ PR,BS " PR,MS " PT,MS ⁺ °T,BS (°)

wherein: θ, P_{R BS} and P_{τ BS} are known and reported by the target base station in step 226; P_{R MS} and P_{T MS} are known and reported by the mobile station 114 in step 222; and the ΔGATN(Θ) value may be normalized as needed for use in any subsequent evaluation, processing or review operation. In step 228, the mobile switching center processes the collected power information supplied by the mobile station 114 and target base station 122(t) using

Equation (6) to determine the difference in gain between the sector beam 106 of the first directive antenna array 104 and the selected smart antenna beam 112 of the second directive antenna array 110 at the angle θ. The process of steps 220-228 may then be repeated (step 230) many times at different angles θ' to collect a statistically significant sampling of data and thus create in step 232 a table (or corresponding function) specifying the difference in gain between the first directive antenna array 104 sector beams 106 and the second directive antenna array 110 smart antenna beams 112 as a function of the azimuth orientation angle θ. Reference is now made to FIGURE 8 wherein there is shown a schematic diagram illustrating an operating scenario for a third method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in FIGURES 3 A and 3B. In this scenario, a mobile station 114 is engaged in a cellular call on a traffic channel and is currently being served by base station 122(s) in the currently serving cell 100(s). While engaged in this call, a determination is made in the manner described above with respect to FIGURE 6 that there exists a need to handoff the on going call. Each neighboring cell 100 then proceeds to make uplink verification measurements on the current traffic channel. A target cell 100(t) is then selected for hand off. Reference is now additionally made to FIGURE 9 wherein there is shown a flow diagram for a third method of determining antenna gain difference with respect to the combined sectorized/smart antenna cell illustrated in FIGURES 3 A and 3B and the scenario of FIGURE 8. For purposes of this method, it is assumed that the verification process prior to mobile station 114 handoff is being performed. It is further assumed that the mobile station 114 is engaged in a cellular call on a traffic channel associated with a transceiver 124 in the second set 124(2) of transceivers for the serving base station 122(s). It is further assumed that in the potential target cell 100(t) for handoff, the base station 122(f) second location verification module 134 operable in connection with the second directive antenna array 110 has made uplink measurements on that traffic channel and is aware of the direction of arrival (i.e., the angle θ') with respect to the mobile station 114. Finally, it is assumed that the gain on the second directive (smart) antenna is substantially the same on both the uplink and downlink.

In step 240, the target base station 122(t) utilizes its first location verification module 132 operable in connection with the first directive antenna array 104 to make uplink signal strength measurements on the traffic channel currently being utilized by the mobile station 114 for its communications with the serving base station 122(s). Thus, the target base station 122(s) makes its signal strength measurement with respect to cellular communications operation use of the sector antenna beam 106. The signal strength measurement is accordingly indicative of sector antenna beam gain. Similarly, in step 242, the target base station 122(t) further utilizes its second location verification module 134 operable in connection with the second directive antenna array 110 to make uplink signal strength measurements on the traffic channel currently being utilized by the mobile station 114 for its communications with the serving base station 122(s). Thus, the target base station 122(s) makes its signal strength measurement with respect to cellular communications operation use of the selected one of the smart antenna beams 112. The signal strength measurement is accordingly indicative of smart antenna beam gain. Next, in step 244, the target base station 122(s) reports its uplink sector beam traffic channel signal strength measurement value (SS_{TC SECTOR}) and uplink smart antenna beam traffic channel signal strength measurement value (SS_TC ._SMART) o the mobile switching center along with an identification of the determined direction of arrival (i.e., the angle θ') with respect to the mobile station 114.

The signal strength measurements may then be subtracted from each other in step 246 to determine a value indicative of the difference in gain between the sector beam 106 of the first directive antenna array 104 and the selected smart antenna beam

112 of the second directive antenna array 110 at the azimuth orientation angle θ'. The calculation of step 246 maybe mathematically represented by the following equation:

ΔGALN(Θ ) = SS_{TC SMART} - SS_TC R_ECTOR ( ' )

wherein: the ΔGALN(Θ') value may be normalized as needed for use in any subsequent evaluation, processing or review operation.

The process of steps 240-246 may then be repeated (step 248) many times at different angles θ' to collect a statistically significant sampling of data and thus create in step 250 a table (or corresponding function) specifying the difference in gain between the first directive antenna array 104 sector beams 106 and the second directive antenna array 110 smart antenna beams 112 as a function of the azimuth orientation angle θ. Although preferred embodiments of the method and apparatus of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims.

Claims

WHAT IS CLAIMED IS:

1. In a cellular system wherein a certain cell includes both a sector antenna and smart antenna, a method for determining a difference in gain within that certain cell between the sector antenna and the smart antenna, comprising the steps of: having a mobile station positioned within the certain cell make downlink signal strength measurements:

(a) on a control channel broadcast from the sector antenna for the certain cell; and

(b) on a traffic channel broadcast from the smart antenna for the certain cell and utilized by the mobile station for an ongoing call; and determining the difference between the control channel related and traffic channel related mobile station signal strength measurements to provide a value indicative of the difference in gain between the sector antenna and the smart antenna.

2. The method as in claim 1 further including the step of: reporting the mobile station made control channel related and traffic channel related downlink signal strength measurements to a centralized cellular system node; and wherein the step of determining is performed at that centralized cellular system node.

3. The method as in claim 1 further including the step of determining an azimuth orientation angle θ indicative of mobile station position within the certain cell.

4. The method as in claim 3 further including the steps of: repeating the steps of claim 1 at aplurality of azimuth orientation angles θ; and processing a resulting plurality of determined differences in gain to characterize the difference in gain between the sector antenna and the smart antenna throughout the certain cell as a function of azimuth orientation angle θ.

5. The method as in claim 1 wherein the step of determining further includes the step of accounting for certain power offset values in calculating the value indicative of the difference in gain between the sector antenna and the smart antenna.

6. In a cellular system wherein cells include both a sector antenna and smart antenna, a method for determining a difference in gain between the sector antenna and the smart antenna, comprising the steps of: having a mobile station make downlink received power measurements on a control channel broadcast from the sector antenna; having a base station make uplink received power measurements using its smart antenna, the measurements being made on a traffic channel utilized by the mobile station for an ongoing call; and determining the difference between the control channel related downlink mobile station made received power measurements and the traffic channel related uplink base station made received power measurements to provide a value indicative of the difference in gain between the sector antenna and the smart antenna.

7. The method as in claim 6 further including the steps of: reporting the control channel related downlink mobile station made received power measurements to a centralized cellular system node; and reporting the traffic channel related uplink base station made received power measurements to a centralized cellular system node; and wherein the step of determining is performed at that centralized cellular system node.

8. The method as in claim 6 further including the step of determining an azimuth orientation angle θ indicative of mobile station position within a certain cell.

9. The method as in claim 8 further including the steps of: repeating the steps of claim 6 at a plurality of azimuth orientation angles θ ; and processing a resulting plurality of determined differences in gain to characterize the difference in gain between the sector antenna and the smart antenna throughout the certain cell as a function of azimuth orientation angle θ.

10. The method as in claim 6 wherein the step of determining further includes the step of accounting for mobile station transmit power and base station transmit power values in calculating the value indicative of the difference in gain between the sector antenna and the smart antenna.

11. The method as in claim 6 wherein the uplink received power measurements are made by either a currently serving base station or a target base station.

12. In a cellular system wherein cells include both a sector antenna and smart antenna, a method for determining a difference in gain between the sector antenna and the smart antenna, comprising the steps of: having a base station make uplink signal strength measurements: (a) using its sector antenna on a traffic channel utilized by the mobile station for an ongoing call; and

(b) using its smart antenna on the same traffic channel utilized by the mobile station for the ongoing call; and determining the difference between the base station uplink signal strength measurements made on the traffic channel to provide a value indicative of the difference in gain between the sector antenna and the smart antenna.

13. The method as in claim 12 further including the step of: reporting the base station made uplink signal strength measurements to a centralized cellular system node; and wherein the step of determining is performed at that centralized cellular system node.

14. The method as in claim 12 further including the step of determining an azimuth orientation angle θ indicative of mobile station position within a certain cell.

15. The method as in claim 14 further including the steps of: repeating the steps of claim 12 at a plurality of azimuth orientation angles θ; and processing a resulting plurality of determined differences in gain to characterize the difference in gain between the sector antenna and the smart antenna throughout the certain cell as a function of azimuth orientation angle θ.

16. The method as in claim 12 wherein the uplink received signal strength measurements are made by either a currently serving base station or a target base station.

17. A cellular system, comprising: a base station for a certain cell including both a sector antenna and a smart antenna; a mobile station positioned within the certain cell and operable to make and report downlink signal strength measurements: (a) on a control channel broadcast from the sector antenna for the certain cell; and

(b) on a traffic channel broadcast from the smart antenna for the certain cell and utilized by the mobile station for an ongoing call; and processing means responsive to the reported downlink signal strength measurements for determining a difference between the control channel related and traffic channel related mobile station signal strength measurements to provide a value indicative of the difference in gain between the sector antenna and the smart antenna.

18. The cellular system as in claim 17 further including means for determining an azimuth orientation angle θ indicative of mobile station position within the certain cell.

19. The cellular system as in claim 17: wherein the mobile station downlink signal strength measurements are reported for a plurality of azimuth orientation angles θ; and wherein the processing means is responsive to the plurality of reported downlink signal strength measurements for processing a resulting plurality of determined differences in gain to characterize the difference in gain between the sector antenna and the smart antenna throughout the certain cell as a function of azimuth orientation angle θ.

20. The cellular system as in claim 16 wherein processing means operation to determine further accounts for certain power offset values in calculating the value indicative of the difference in gain between the sector antenna and the smart antenna.

21. A cellular system, comprising: a plurality of base stations each including both a sector antenna and a smart antenna; a mobile station operable to make and report received power measurements on a control channel broadcast from the sector antenna; wherein the base station is further operable to make and report uplink received power measurements using its smart antenna, the measurements being made on a traffic channel utilized by the mobile station for an ongoing call; and centralized processing means responsive to the reported power measurements for determining a difference between the control channel related downlink mobile station made received power measurements and the traffic channel related uplink base station made received power measurements to provide a value indicative of the difference in gain between the sector antenna and the smart antenna.

22. The cellular system as in claim 21 further including means for determining an azimuth orientation angle θ indicative of mobile station position within a certain cell.

23. The cellular system as in claim 22: wherein the received power measurements are reported for a plurality of azimuth orientation angles θ; and wherein the centralized processing means is responsive to the plurality of reported received power measurements for processing a resulting plurality of determined differences in gain to characterize the difference in gain between the sector antenna and the smart antenna throughout the certain cell as a function of azimuth orientation angle θ.

24. The cellular system as in claim 21 wherein centralized processing means operation to determine further accounts for mobile station transmit power and base station transmit power values in calculating the value indicative of the difference in gain between the sector antenna and the smart antenna.

25. The cellular system as in claim 21 wherein the uplink received power measurements are made by either a currently serving base station or a target base station.

26. A cellular system, comprising: a plurality of base stations each including both a sector antenna and a smart antenna, the base stations operable to make and report uplink signal strength measurements: (a) using its sector antenna on a traffic channel utilized by the mobile station for an ongoing call; and

(b) using its smart antenna on the same traffic channel utilized by the mobile station for the ongoing call; and centralized processing means responsive to the reported uplink signal strength measurements for determining a difference between the base station uplink signal strength measurements made on the traffic channel to provide a value indicative of the difference in gain between the sector antenna and the smart antenna.

27. The cellular system as in claim 26 further including means for determining an azimuth orientation angle θ indicative of mobile station position within a certain cell.

28. The cellular system as in claim 27: wherein the base station uplink signal strength measurements are reported for a plurality of azimuth orientation angles θ; and wherein the centralized processing means is responsive to the plurality of reported uplink signal strength measurements for processing a resulting plurality of determined differences in gain to characterize the difference in gain between the sector antenna and the smart antenna throughout the certain cell as a function of azimuth orientation angle θ.

29. The cellular system as in claim 26 wherein the uplink received signal strength measurements are made by either a currently serving base station or a target base station.

30. A base station for a cell within a cellular communications system, comprising: a plurality of transceivers operable to provide both traffic and control channels for use by mobile station within the cell, the plurality of transceivers including a first set of transceivers and a second set of transceivers; a sector antenna; means for connecting the first set of transceivers to the sector antenna; a smart antenna; and means for connecting the second set of transceivers to the smart antenna.

31. The base station as in claim 30 further comprising: a location verification module connected with the first set of transceivers to the sector antenna, the location verification module operable to make uplink measurements through the sector antenna on both control and traffic channels.

32. The base station as in claim 31 wherein the location verification module is further operable to process the made uplink measurements to generate data useful in making handoff determinations.

33. The base station as in claim 31 further comprising: a location verification module connected with the second set of transceivers to the smart antenna, the location verification module operable to make uplink measurements through the smart antenna on traffic channels.

34. The base station as in claim 33 wherein the location verification module is further operable to process the made uplink measurements to generate data useful for handoff determinations and further to generate data indicative of a direction of arrival azimuth orientation angle with respect to served mobile stations.

35. The base station as in claim 30 wherein the sector antenna forms one wide beam per sector of the cell, and the smart antenna forms a plurality of narrow beams per sector of the cell.

36. The base station as in claim 30 further including means for determining a difference in gain between the sector antenna and the smart antenna.