WO2007120326A2

WO2007120326A2 - Methods and systems for providing enhanced position location in wireless communications

Info

Publication number: WO2007120326A2
Application number: PCT/US2006/061901
Authority: WO
Inventors: Peter J. Black; Matthew S. Grob
Original assignee: Qualcomm Incorporated
Priority date: 2005-12-20
Filing date: 2006-12-12
Publication date: 2007-10-25
Also published as: RU2008129671A; JP2009521192A; US20110149863A1; BRPI0620109A2; EP1972173A2; WO2007120326A3; RU2427982C2; EP1972173B1; SI3514565T1; HUE056338T2; DK3514565T3; US20090160709A1; EP3306338B1; US20140269638A1; EP3514565B1; JP2012114949A; CN101366309A; KR100997625B1; FI3514565T3; CN101366309B

Abstract

Embodiments disclosed herein relate to methods and systems for providing improved position-location (e.g., time-of-arrival) measurement and enhanced position location in wireless communication systems. In an embodiment, an access point may replace information (e.g., data) transmission by a 'known' transmission (or 'reference transmission') at a predetermined time known to access terminals in the corresponding sectors. The access terminals may use the received reference transmission to perform a position-location measurement, and report back the measured information. The access point may also send a reference transmission on demand, e.g., in response to a request from an access terminal in need for a location-based service.

Description

METHODS AND SYSTEMS FOR PROVIDING ENHANCED POSITION LOCATION LN WIRELKSS COMMUNICATIONS

BACKGROI^ND Field

{0001 ) This disclosure relates generalϊs Io w ireless communications. More specifically, embodiments disclosed herein relate to prov iding lmpiw ed time-of-arm al measurement and enhanced position location in wireless communication ss stems.

Background

}⁽KX⁾2] Wireless communication systems are wideh deplo^y ed to prox ide \ arious types of Communications (such as voice and data} to multiple users. Such systems may be based on code dh ision multiple access (COMA), lime dn ision muilipie access ( TDMA). frequency division multiple access (FDMA). or other multiple access techniques A wireless communication system may be designed to implement one or more standards, such as TS-95. cdma2t>00. IS-856. W-CDMA. TD-SCDMA. and other standards

[U003J Presence detection and location-based services have long been sought after in wireless communications. Jn addition to supporting emergency seruces (e.g , EOj 1 calls), wireless operators are striv ing to provide a wide range of new applications targeted for the e\ erydas consumer and enterprise user, such as child locators, turn-by - lum naxigalion, directory sen ices, voice concierge, roadside assistance, and many others. A challenge hence lies in prov iding accurate and reliable position location to enable such applications.

BRIEF DESCRIPTION OF IHE DRAWINGS

}09tt4j FIG. I illustrates an embodiment of a wireless communication s> stem:

JOOUS] FfG, 2 illustrates an embodiment of forward link slot structure in an lS-85(^"< is pe system. {0ΘU6] FΪGs. 3A-3B illustrate embodiments of forward link slot structure for reference transmission; JIKKΪ7] FJ<j 4A illustrates an embodiment of forw ard link structure in an IS-95 t> pe s> stem. [WKIS] FΪC5 4B sliustiates an embodiment of fomaid link stmctuie for reference transmission. [0ΘU9) HG 5 illustrates a flow diagram of a process, which max be issed to implement some disclosed embodiments. ItM)IlJj FlG 6 illustrates a flow diagram of a piocess. which ma\ be used to implement some disclosed embodiments, }rø! 1| FJG 7 illustrates a flow diagram of a process, which ma\ be used to implement some disclosed embodiments, JIKΪ12J FfG 8 illustrates a Slow diagram of a process, which ma\ be used to implement some disclosed embodiments. (WM Jj HG v illustrates a block diagram of an apparatus, in w hich some disclosed embodiments ma\ be implemented, and {0014] FiG 10 illustrates a block diagram of an apparatus, m which some disclosed embodiments ma\ be i mplemented

DETAlLEO DESCRIP TION

(0Θ15J Frnbodirnents disclosed heiein relate to methods and s> stems for pan idtng enhanced position location in w ireless communication s> sterns

{0016] An access point (AP) disclosed herein max include and or implement functions of a base-station transcen ei sy stem (BTS), an access network transceiv er (AND, a modem pool traπsceix ei (MPTK or a Node B (e j. . m a W -CDMA t> pe s^ stem), etc A cell ma> refer to a cov erage area sen iced by an AP A celt max further include one or more sectors For vimphαtx and cSants . the term "vector^"' max be used herein to refer a cell, or a section of a cell, sen teed b\ an AP Further, an access network controller (ANC ) max refei to the portion of a communication s\ s>tem configured to interface xvnh a core netw ork (e g , a packet data network) and route data packets betw een access terminals (AI s) and the core network, perform \ anous radio access and link maintenance functions (such as soft handoff)- control radio transmitters and receiv ers, and so on An ANC max include and/or implement the functions of a base station controller (BSC), such as found in a 2^mi. 3"'. or 4^ύt generation wireless network. An ANC and one or more APs may constitute part of an access network (AN). An access terminal (AT) described herein may refer to various types of devices, including (but not limited to) a wireless phone, a cellular phone, a laptop computer, a multimedia wireless device, a wireless communication personal computer (PC) card, a personal digital assistant (PDA), an external or internal modem, etc. An AT may be any data device thai communicates through a wireless channel and/or through a wired channel (e g.. by way of fiber optic or coaxial cables). An AT may have various names, such as access unit, access node, subscriber unit, mobile station, mobile device, mobile unit, mobile phone, mobile, remote station, remote terminal, remote unit, user device, user equipment, handheld device, etc. Different ATs may be incorporated into a system. ATs may be mobile or stationary, and may he dispersed throughout a communication system. An AT may communicate with one or more APs on a forward link and/or a reverse link at a given moment. The forward link (or downlink) refers to transmission from an AP to an AT, The reverse link (or uplink) refers to transmission from the AT to the AP. Locating a person or an object wireiessly may be achieved in a number of ways.

Time-of- arrival (TOA) measurement, which uses time il takes for a signal to travel as an indirect method of calculating distance, is commonly involved in a number of network- based methods. For example, in some wireless networks, position location services require TOA measurement of the pilot signal (e.g., the earliest path of the pilot). FIG, 1 illustrates a wireless communication system 100 configured to support a number of users, in which various disclosed embodiments and aspects may be implemented, as further described below By way of example, system 100 provides communication for a number of ceils 102, including ceils i02a-102g, with each cell being serviced by a corresponding AP 104 (such as APs 104a- 104g). Bach cell may be further divided into one or more sectors. Various ATs 106, including ATs 106a- 106k. are dispersed throughout the system Each AT 106 may communicate with one or more APs 104 on a forward link and/or a reverse link at a given moment, depending upon whether the AT is active and whether il is m soft handolT, for example. In FIO. i, a solid line with an arrow may indicate information (e.g., data) transmission from an AP to an AT. A broken line with an arrow mav indicate that the AT is receiving the pilot and other signaling/reference signals, but no data transmission, from the AP, as further described below. For clarity and simplicity, the reverse hnk communication is not explicitly shown in FKJ. I . In a high rate packet data (HRPD) system (e.g.. as specified in "cdma2000 High

Rate Packet Data Air Interface Specification,^" 3GFP2 C.S0024-A. Version 2. JuJy 2005. referred to as "IxEV-DO^*' (or ^;1S-85(>^") herein), for example, transmission on forward link is partitioned into a sequence of frames; each frame is further divided into time slots {e.g., 16 slots each with a duration of 1.667 msec); and each slot includes a plurality of time-division-mulupiexed channels. By way of example, FiG. 2 illustrates an embodiment of a forward hnk slot structure 200, such as employed in a IxEV-DO type system. Time slot 200 is divided into two half-slots, with each half-slot having the following channel assignments: pilot channel 2 K), forward medium access control (MAC) channel 220, and forward traffic (or control) channel 230. Pilot channel 210 carries the pilot signal (also commonly termed as the pilot) used by an AT (such as AT 106 in FlG. 1) for .initial acquisition, phase recovers', timing recovery, radio combining, as well as estimating the channel conditions on forward link (e.g., by way of the signal -to-noise-and-interference (SlNR) measurement). MAC channel 220 sets forth the procedures used to receive and transmit oxer the physical layer (which provides the channel structure, frequency, power output. modulation, encoding specifications for forward and reverse links). Traffic channel 230 may earn- information or data (e.g., by way of physical layer packets), e.g., unicast data specific to a particular AT (or user), or broadcast/multicast data to a group of users (e.g.. as specified in "cdma2000 High Rate Broadcast-Multicast Packet Data Air interface Specification;'^* 3GPP2 C S0054-0, Version 2 0, July 2005. referred to as "BCMCS specification^" herein). Traffic channel 230 may also be used to earn,- control messages. Further, pilot channel 210, MAC channel 220, and traffic channel 230 are ame-division- multiplexed withm time slot 200. When there is no traffic on traffic channel 230, an idle slot including pilot channel 210 and MAC channel 220 may be sent Transmission of idle slots serves to decrease interference to other cells on forward Sink. As illustrated in FIG. 2, pilot channel 210 is transmitted in discrete bursts (as opposed to being continuous in time), hence having limited power, In some systems, for example, pilot channel 210 may comprise 96 chips of a particular digital pattern (e.g.. aJl zeros). MAC channel 220 may comprise 64 chips, and each half-slot may comprise 1024 chips. Thus, only a small fraction (e.g., 96/1024) of the available forward link' power is allotted to the pilot channel in such systems, As a result, TOA measurement based on such pilot channel may be susceptible to errors (e.g., particularly when the forward link channel conditions are poor), hence, compromising the accuracy and reliability of associated position location. A need therefore exists for a strong aid clear signal to assist position location. Embodiments disclosed herein relate to methods and systems for providing improved TOA measurement and enhanced position location in wireless communication systems, In an embodiment, an AP may replace normal information (e.g.. data) transmission by a "known'^* transmission (termed "reference transmission'^* herein) at a predetermined time known to ATs in sectors serviced by the AP. The ATs may use the received reference transmission to assist or facilitate position location (e.g.. TOA and/or other position-location measurements). The AP may also send a reference transmission on demand, e g.. in response to a request from an AT (which may be in need for a location-based service). In some embodiments, the reference transmission may include a time slot having a pilot signal and a reference signal in a time-division-muiliplexed format. In other embodiments, the reference transmission may include a time slot having a pilot signal and a reference in a code-division-multiplexed format The reference signal may be similar or substantially identical to the pilot, such that the entire time slot is nearly filled with the pilot, thereby providing a strong signal for TOA arid other position-location measurements. The reference signal may also be different from the pilot, e g , configured to assist the pilot in position location. The ensuing description provides further embodiments and examples. The term "reference signal^" disclosed herein may include any signal that is unmodulated (ε g.. earning no information or data) and known to a receiving AT. For example, the reference signal may comprise a digital pattern (e.g., a sequence of symbols) that is "known^*" in advance to the receiving AT. whereby the AT does not need to decode the reference signal. The reference may carry a unique sector ID (e.g., spread with a pseudorandom (PN) code with a unique offset specific to the sector). The reference signal may be transmitted at substantially the maximum power available to the sector (or '"full sector power^''}, ϊn some embodiments, the reference signal may be a spread-spectrum or other wideband signal (e.g., to occupy the entire traffic channel). A "reference transmission'^* disclosed herein may refer to a forward link transmission including a reference signal. Further, the term "position-location measurement^"' may broadly refer to a measurement associated with position location, including (but not limited to) TOA, time difference of arrival (TDOA), angle of arrival (AOA), advanced forward link trilateration (AFLT). enhanced observed time difference (EOl D). and others, Various aspects, features, and embodiments are described in further detail be! ovv. FIG. 3A illustrates an embodiment of a reference transmission including a time slot 300. which may be used to implement some disclosed embodiments. Time slot 300 is shown in two half-slots, each having pilot channel 310. MAC channel 320. and traffic channel 330 in a time-divisiori-muHiplexed format. Pilot channel 310 carries the pilot. Pilot channel 310 and MAC channel 320 may for example be substantially as described above with respect to the embodiment of FiG. 2. Traffic channel 330 carries a reference signal, in lieu of data In some embodiments, the reference signal may be similar or substantially identical to the pilot, as time slot 350 of FIG. 3B illustrates. As a result; the entire slol 350 is nearly filled with the pilot, as graphically illustrated by the hatched area in the figure, and the full power of lhe entire sector may be substantially devoted to the pilot transmission during this time period. This strong pilot allows the receiving ATs to carry out more accurate and reliable TOA and other position -location measurements. The timing and signaling for such "pilot slot^*' may for example be according to the broadcast/multicast channel structure in a IxEV-DO type system (e.g., as specified m the BCMCS specification). Further, implementation of such "pilot slot^" imposes .minimal changes to the existing network infrastructures and devices In other embodiments, the reference signal may be different from {he pilot The timing and signaling for the reference transmission may for example be according to the broadcast/multicast channel structure in a IxEV-DO type system (e.g., as specified in the FJCMCS specification). In one embodiment, for example, the pilot may comprise a sequence of symbols having all zeros (O^'s), whereas the reference signal may comprise a sequence of symbols having all ones (Ts). In another embodiment, the pilot may comprise the pilot symbols used in a IxEV-DO type system, whereas the reference signal may comprise the pilot symbols used in an i.S-95 type system. In yet another embodiment, the pilot may comprise a particular sequence of symbols, while the reference signal may comprise the sequence configured in reverse, in an alternative embodiment, a known data packet mas be transmitted as the reference signal, e.g., using the broadcast/multicast channel structure and signaling m a JxEV-DO type system (e.g , as specified in the BCMCS specification), A receiving AT may use this reference signal to search for the (weaker) pilot, estimate ^'FOA (and/or perform other position- location measurements), and report back the measured information. In an embodiment, the reference transmission may be carried out by an AP according to a predetermined schedule {e.g., on a regular or periodic basis), so that at known times, ATs in the corresponding sectors may be prepared to perform TOA and/or other position-location measurements, and report back the measured information. In an embodiment, an AP may cam out the reference transmission on demand, e.g.. upon receiving a request from an AT (which may be in need for a location- based service), In an embodiment, an AP may make use of idle slots for reference transmission

(e.g , filing an idle slot substantially with the pilot, such as described above with respect to the embodiment of FlO. 3B), so as to make efficient use of the network resources. For example, the signaling associated with such time slot may indicate to a receiving AT the reference signal carried by the traffic channel, so that the AT may according!} perform TOA and/or other position-location measurements. FlGs. 3A-3B provide some examples of transmitting a reference signal along the pilot in a time-division-multiplexed format. Jn other systems (e.g., as specified m "Physical Layer Standard for cdma2000 Spectrum Systems," 3GPP2 C.SU002-D. Version 2.0, September 2005, referred to as "CDMA2UU0 Ix^'' herein, or as specified in '"Mobile Station-Base Station Compatibility Standard for Wideband Spread Spectrum Cellular Systems;^* ANSlTl A_'ΕJ A -93-B-99, referred to as '1S-95^*' herein), a reference signal may be transmitted along with the pilot in a code-division-mυliiplexed formal, such as described below. |M036] Fl<j 4Λ illustrates an embodiment of forw ard link staiciure in the form of sector power usage \ s time, such as in an JS-05 or CDMA2000 j \ tj pe s> stem Forward link channels including pilot channel 4I d, s\ nc channel 42* K paging channel 43* >, and traffic channels 440. are transmitted in a code-dn isωii-multipiexed foi mat, each \uth a certain fraction of the total sector power For example, pilot channel 410 ma\ be allotted approvimateh 15-20% of the maximum sector power, denoted as Pi_\{raa\) To augment the pilot (e g . for position location purposes ), some or all of the power allotted Io traffic channels 440 ma> be used to transmit a reference signal (in lieu of information transmission) m a specific period of time, such as illustrated in FlG 4B below

(flO37j Foi il lustration and claπlv FiG 4B depicts an embodiment HI winch the power allotted to traffic channels 440 ma\ be substantial dem oted to transmit a reference signal 460 m a time slot 450 Foi example, such ma\ occur in situations wheie an AP sends a reference transmission to the corresponding A Fs according to a predetermined schedule (e g , on a regular or periodical basis), so that at known times, the ATs ma> be piepaied to perform position-location me&surements and report back the measured information In sonic embodiments, the ieference signal ma> be ssmilas or siibstantialh identical to the pilot, as a result, the entire time slot 4^0 ma\ be nearh filled with the pilot, thereby prov iding a strong signal for pυsition-location measurements In other embodiments, the iefeience rna\ also be different from the pilot, such as described aboλ e

]0038] In aUernatn e embodiments, a fraction of the power allotted to traffic channels

440 ma> be used tυ transmit reference signal 460 m time slot 450 Fur example, such ma> occut tn situations where an ΛP carries out a reference tiansmission on demand. e g . in response to reque.st(s) from one oi more A Is m the corresponding sectors (w hich max be m need for position-location sen ices)

}⁽K⁾39] In addition to replacing iofotmation tratisnus^ion b> a reference transmission accotdmg to a piedcternimed schedule or on demand (such as descubed abox e). a pottion of the control channel (e g . the pteamble) or other existing (or know n) signals. ma\ be used to assist the pilot in position location tor example, m some s> stems, the conttol channel ma\ be transmitted on a regulat or periodic basis The preamble of the cυntioi channel vna\ be knowii to a teceπ ing AT (e g . aftei the initial set-up), and therefoie used to assist the pilot m position location (such as in a marmei described abo\ e Λ\ ith iespect to the reference Signal) jiKϊ-Wj FfG 5 illustrates a flow diagram of a piocess 500 %\ hich mas be used Io implement some disclosed embodiments (such as descubed ahm e) Step ^ K⁾ generate a pilot signal and a reference signal the refeience signal compπsing a sequence of sunbols known to an access terminal Stop *>20 tiansmUs the pilot signal and the iefeience su>nai in a time slot

IWM I j In process ^ 00 the pilot signal and the refesence signal ma\ be transmitted m a time-dn ision-niιιltφle\ed foπϊiaf or eode-diusi on-multiplexed foi mat such as described abo\ e In some embodiments the refeienee signal nia\ be simiiai or sub^tamialh identical to the pilot signal In other embodiments the reference signal max be diffei ent H orn the pilot sigrtai e g , coiiiigured to asM^t the pilot Mgnal m position location {e g . t OA and othes position -location measiπ ements). such as descubed alxn e hurther, in a raulti-caiiei wneless cunimunication sy stem tlie tune slot ma\ be tian^milted on a subset (e g . some all υr am combinaiion) of caiiwis

JCW42J FlG 6 illustrates a How diagiam of a psoces^ 600, which max be u^ed to implement some disclosed embodiments (such as described abox e) Piocest» 600 starts at step 610 Step 62o determines it g based mi a pi edetei mined schedule) whether π is tune for earn ing out a refcience tiansmis>sιυn io ΛTs in secto scn icod bx an AP If the outcome of step f>20 ib, ΥF S step 6^0 follows and genesatcs a pilot signal and a refi'ience signal Step 640 transmits the pilot signal and the icieience signal m a time slot (e g . in a {ime-dn ision-multiplexed or cυde-dn ϊsion-mυlfiple\ed foπnat, such as descubed abm e) Subscquenth process 600 tetuins to step 620

}(W43j In ptoccss W)O if the outcome of step <>20 is NO step 6^ς{) follow s and detej mines if theie is a l equest for a location-based s>eix ice from an AF i f the outcome ol step C^O is YLS process 600 jetυrns to step 630 Jf the outcome of step 6⁴H⁾ is " NO step 660 follows and pioceeds w ixh infoimation (e g data) ti^nsnu&mυn ProcetiS 600 subsequent^ teturns to step 620

{0044] MG 7 illu&ti ates <s flow diapam of a process 700 w hich ma\ be used to implement some disclosed embodiments Step 710 lecerv es a pilot signal and a refeience signal in a time slot (e a m a tιme-ιin ision-multψ!c\eιi or codc-dn isiυn- multiplexed format, such as descri bed above). Step 730 performs a position-location measurement based on the pilot signal and the reference signal. Process 700 may further include searching for the pilot signal. In some instances, the reference signal may be similar or substantially identical to the pilot signal, effectively providing a strong pilot for position-location measurements. In other instances, a receiving AT may use the reference signal to search for the (weaker) pilot, estimate TOA (and/or perform other position-location measurements), and report back the measured information. FJG. 8 illustrates a flow diagram of a process SOO, which may be used to implement some disclosed embodiments (such as descri bed above). Process 800 starts ai step 810. Step 820 receives a trine slot hav ing a pilot channel and a reference channel (e.g , in a time-divisiorwnuUipiexed format, such as described above), lhe pilol channel earn ing a pilot signal. Step 830 determines if the traffic channel carries a reference signal. If the outcome of step 830 is "YES,^" step 840 follows and performs a position- location (e.g.. TOA) measurement based on the pilot signal and the reference signal. Process 800 subsequently returns to slep 820. If the outcome of step 830 is "NO," slep 850 follows and proceeds with lhe traffic channel (e.g., decode the data packets carried by the traffic channel). Process 800 subsequently returns to step 820. FlG. 9 shows a block diagram of an apparatus 900, which may be used Io implement some disclosed embodiments (such as described above). By way of example, apparatus 900 may include a reference-generating unit (or module) 910 configured to generate a pilot signal aid a reference signal, wherein the reference signal comprising a sequence of known symbols (e.g.. Io one or more receiving ATs); and a transmitting unit 930 configured to transmit the pilot signal and the reference signal in a time slot, in a multi-carrier system, transmitting unit 930 may be further configured to transmit the time slot on a subset of carriers. Apparatus 900 may also include a multiplexing unit 920 configured to multiplex the pilot signal and the reference signal into the time slot (e.g , in a time-division- multiplexed, or code-division-multiplexed format, such as described above). Apparatus 900 may further include a processing unit (or controller) 940 configured to control and/or coordinate the operations of various units. Apparatus 900 may be implemented in an AF (e.g.. AP 106 in FlG. J ). or other network infrastructure elements. FΪC5, 10 illustrates a block diagram of an apparatus 1000, which mas¹ also be used to implements some disclosed embodiments (such as described above). By way of example, apparatus 1000 may include a receiving unit 1010 configured to receive a pilot signal and a reference signal in a time siot (e.g., in a time-division-multiplexed or code- division-multiplexed format, such as described above); and a measurement unit 1030 configured to perform a position-location (e.g., TOA) measurement based on the pilot- signal and the reference signal. Apparatus 1000 may further include a searching unit 1020, configured to search for the pilot Signal. Apparatus H)OO may also include a processing unit (or controller) 1040, configured to control and/or coordinate the operations of various units Apparatus H)OO may be implemented in an AT, or other communication devices. Embodiments disclosed herein (such as described above) provide some embodiments for enhancing position iocation in wireless communications. There are other embodiments and implementations. Embodiments disclosed herein may be applied to a multi-carrier wireless communication system. For example, a reference transmission may be sent on some, ail. or any combination of carriers. Various units/modules in FlGs. 9-10 and other embodiments may be implemented in hardware, software, firmware, or a combination thereof. In a hardware implementation, various units may be implemented within one or more application specific integrated circuits (ASIC), digital signal processors (DSP), digital signal processing devices (DSFDs), field programmable gate arrays (FPGA), processors, microprocessors, controllers, microcontrollers, programmable logic devices (PLD), other electronic units, or any combination thereof In a software implementation,, various units may be implemented with modules (e.g.. procedures, functions, and so on) that perform the functions described herein The software codes may be stored in a memory unit and executed by a processor (or a processing unit). The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled Io the processor via various means known in the art. Those of skill in the art would understand thai information and signals may be represented using airs- of a variety of different technologies and techniques. For example, data,, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic Ileitis or particles, optical fields or particles, or any combination thereof. Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application aid design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g.. a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. The steps of a method or algorithm described m connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in random access memory (RAM), flash memory, read only memory (ROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, hard disk, a removable disk., a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium mas¹ reside in an ASIC. The ASfC may reside in an AT. In the alternative, the processor and the storage medium may reside as discrete components in an AT. The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art. and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to {he embodiments shown herein but is to be accorded {he widest scope consistent with the principles and novel features disclosed herein. WHAT IS CLAIMED IS:

Claims

C LAIMS

1 Λ method for wueless communications, comprising generating a pilot Signal and a refoionce Signal, the refoionce sjgnal comprising a sequence of s> mbols known to an access terminal, nnd tiansmutϊflg the pilot signal and the reference signal in a time slot

2 The method of claim 1. fusther eompming time-dι\ JSion-mulap1e\ing the pilot signal and the reference signal in the time slot

3 The method of claim 2. \\ herein the urns slot includes a pilot channel Ume- dn ssion-tmiluplexcd with a traffic channel, the pilot channel earn ing the pilot signal and the traffic channel cam ing the reference Signal

4 The method of claim 3. therein the iefeience signal substantial!} occupies the traffic channel

5 The method of claim 2. further comprising transmitting the reference signal at a maximum power

6 Hie method of claim 1. further comprising codc-dj\ ision-mu!uple\mg the pilot signal and the reference signal m the time slot

7 Die method of claim L whet em the reference signal is substanttalh identical to the pilot signal

8 The method of claim 1. whciein the reference signal includes a sector ID

*⁾ The method of claim 1 , wherein the reference signal is transmitted m accordance Λ\ ith a pi edetei mmed schedule

10. The method of claim 1. wherein the reference signal is transmitted in response to a request from the access terminal.

1 1. The method of claim L further comprising transmitting the time slot on a subset of multipl e earn ers ,

12. A communication structure transmitted on a carrier wave, comprising: a pilot channel carrying a pilot signal; and a traffic channel carrying a reference signal, the reference signal comprising a sequence of symbols known to an access terminal.

13. The communication structure of claim 12, wherein the pilot channel is tirne- division-miϊltiplexed with the traffic channel.

14. The communication structure of claim 12. wherein the reference signal is substantially identical to the pilot signal.

15. The communication structure of claim 12, wherein the reference signal includes a sector identifier.

16. An apparatus adapted for wireless communications, comprising: means for generating a pilot signal and a reference signal, the reference signal comprising a sequence of symbols known to an access terminal; and means for transmitting the pilot signal and the reference signal in a time slot.

17. The apparatus of claim 16, further comprising means for multiplexing the pilot signal and the reference signal in the time slot in one of a time-division -multiplexed format and a cod e-di vision-multiplexed format.

I S. The apparatus of claim 16, wherein the time slot includes a pilot channel and a traffic channel, wherein the pilot channel carries the pilot signal and the traffic channel carries the reference signal. 19 The apparatus of ctaun Ib. wherein the reference signal ^ transmitted m accoi dance with a piedeteπmned schedule

20 Fh e apparatus of claim 16, wherein the reference signal is transmitted m response to a request fmm the access terminal

21 The appaiatiis of claim ! <^■>, whcrem the means for transmitting ss further configured to transmit the tπne sϊot on a subset of multiple earners

22 A method for wuele^s communications, comprising recen irtg a pilot signal and a reference signal m a time slot, the iefcrertce signal comprising a sequence of SΛ mbols known to a recen er. and performing a position-location measurement based on the pilot signal and the iefcience signal

23 The method of claim 22. wherein the* time slot includes a pilot channel lime- diusiυn-muitiplexed with a traffic channel the pilot channel earning the pilot signal and the traffic channel earn ing the reference signal

24 Hie method of chum 23. further comprising identify ing the reference signal carried b\ the traffic channel

2^ The method of claim 22 wherein the pilot signal and the reference signal arc code-dn ision-niuHipiexed m the time slot

26 The method of claim 22, further cυmpπses searching (oi the pilot signal

27 Hie method of claim 2<\ wherein the searching for the pilot signal is bz&Qil on the recen ed reference signal

28. The method of claim 22. wherein the reference signal is substantially identical to the pilot signal.

29. An apparatus for wireless communications, comprising; means for receiving a time slot having a pilot channel and a traffic channel; and means for performing a position-location measurement based on the pilot signal and the reference signal.

30. The apparatus of claim 29, further comprising means for searching for the pilot signal.

31. A method for wireless communications, composing: receiving a pilot signal and a portion of a control channel; and performing a position-location measurement based on the pilot signal and the portion of the control channel.

32. The method of claim 3 ! . wherein the portion of the control channel includes a preamble.