Macro			Macro			Macro
PN	Tau	Ampl	PN	Tau	Ampl	PN	Tau	Ampl

A	τ_A	P_A1	A	τ_A	P_A2	A	τ_A	P_A3
B	τ_B	P_B1	B	τ_B	P_B2	B	τ_B	P_B3
C	τ_C	P_C1	C	τ_C	P_C2	C	τ_C	P_C3
D	τ_D	P_D1	D	τ_D	P_D2	D	τ_D	P_D3

In another embodiment of the present invention, the handset may be interrogated to determine the time delay of the pilot signal, and the PDE may be used together with a handset to determine the position of the building, using AFLT, or other delay measuring algorithms. The levels of the PNs reported by the handset may be used to determine the floor that the handset is located on. In other words, if Tau measurements establish that the handset is in the building, P_Aand P_Bmeasurements may be compared to determine the floor that the handset is on.

In one embodiment of the present invention, the existing PDE in the system that uses AFLT for position determination may be augmented by an additional 3D, or z-axis PDE. In one embodiment, the device or handset contains an application to allow measurements of the relative levels of the pilot beacons. The application is used in conjunction with an aPDE to determine the z-axis. This may be done 1) with a handset application, 2) without a need for a resident handset application, or 3) the aPDE may be used to establish only the z-axis. In this mode, the aPDE does not need to establish the x-y location since that step is supplied by the existing PDF. The system and method of the present invention provides a relatively straight forward augmentation of 3D position onto existing PDE, with high-integrity. High intensity means that changes to the network, e.g. the removal of a beacon, are known, as opposed to systems that do not control beacons, e.g. Wi-Fi.

Another advantage of the aPDE of the present invention is that all the files that are used for fixes in the existing PDE do not need to be made available to the new PDE. The fix files are not needed it the new PDE. The Tau values are set during installation, and/or when changes are made to the network. The aPDE uses an output file from the existing PDE. The new PDE, on the other hand, uses device measurements themselves and creates new PDE files. Advantages of the use of one system over the other depend on the availability of output files and measurements.

The integrity of the overall system is further ensured by using devices labeled “R” inFIG. 3. These off-air receivers, or handsets, (“R”) are used to monitor the integrity of the transmitted signals from the macro, and/or pilot beacons. If a macro PN change occurs, the “R” device may be used to establish new Tau values for the pilot beacons. Alternatively, or together with “R,” a handset may he used to make test calls to determine location, followed by any Tau value changes if and when they are needed.

For example, an application running on a device, e.g. a smartphone may use device measurements, together with an existing PDE, to determine the position of the device. If the macro network has changed, the position will be reported correctly using measurements of the macro signals. However, the measurements will have errors when reporting measurements made on pilot beacons which have not been corrected to account for the change in the macro. This difference can be used to correct the pilot beacon settings, by using a device application that reports the changed PN offset, for example. One example of such an application is a known PN scanner.

A BTS, or base transceiver station, is a unit that facilitates wireless communication between a handset and the carrier station. In the non-repeater deployment, the Distributed Antenna System (DAS) is coupled to a base station directly using coax or fiber optic cable, for example, a wireless provider may install a base station in the basement of a building to feed the DAS in the building.

In one embodiment, the power levels P_Aa, P_Ba, P_Ca, P_Da, may be chosen to provide coding gain and sensitivity improvement for floor detection. For example, orthogonal codes may he placed on each pilot beacon (e.g. Welsh codes). See Table 2, below, where L is the nominal required level of all PNs. The ±1 dB level may be changed to accommodate the level detection resolution of the handsets. For example, ±2 dB may be required to ensure detection for a larger number of floors, pilot beacons may be placed one per floor with PN levels using a binary code. In one embodiment of the present invention, 15 floors may be encoded using four PNs, 0000 and 1111 cannot be discerned, generally, because absolute PN measurements are not as accurate as relative levels.

TABLE 2

PN_ALevel	PN_BLevel	PN_CLevel	PN_DLevel

Floor 4	L − 1 dB	L − 1 dB	L − 1 dB	L − 1 dB
Floor 3	L − 1 dB	L + 1 dB	L − 1 dB	L + 1 dB
Floor 2	L − 1 dB	L − 1 dB	L + 1 dB	L + 1 dB
Floor 1	L − 1 dB	L + 1 dB	L + 1 dB	L − 1 dB

In certain embodiments of the present invention, the PN signals are generated digitally in a field-programmable gate array (“FPGA”) and transmitted over an antenna. Therefore, the relative PN levels will be retained and used in detecting handset location. Additional floors may be encoded using more PNs, or using multi-level codes or both (e.g. −2 dB, −1 dB, 0 dB, +1 dB, +2 dB per PN).

In another embodiment of the present invention, the level of individual PNs may also be time-modulated. Floors, buildings or other information may be encoded by varying the amplitude of a PN code, and measuring several samples of the PN level. In one embodiment, a PN may have a +2 dB amplitude for T=0 to 2 sec, and have a −2 dB amplitude for T=2 to 4 sec, a +2 dB amplitude for T=4 to 6 sec, and so on. This represents a

coded message

1, 0, 1. A second PN may have a sequence opposite to this, i.e., 0, 1, 0. Other codes are also possible, e.g. 1, 1, 0 and 0, 0, 1 and the like. Thus, using two PN s and three time slots, eight distinct messages may be encoded. In other embodiments, time varying PNs may be mixed with statistically chose PNs to further increase the number of codes.

The method and system of the present invention provides for pilot selection in co-pilot beacon systems. As described previously, pilot beacons have their PNs set based on expected macro pilots in a building or other indoor location. These PNs may be distant PNs, or may be close PNs. If a close PN not applied to a beacon, the accuracy of a fix from a macro PN may be adequate and not require the use of a beacon PN on that particular macro PN. For example, if PNs E, F, and G, as shown inFIG. 1, propagate adequately into the building, then an AFLT fix may be obtained by the PDE without requiring the use of an aPDE. In general, the more PNs that must be transmitted in the building, the higher the cost and the higher the interference. It is important then to determine carefully winch PNs to transmit. In the system as seen inFIG. 1, if PNs E, F, and G do not have adequate power to provide a good fix, then PNs E, F, and G should be added to the transmitted beacon signals in the building.

Pilot beacons of the present invention may be used in several ways. PNs of close-in macro sites can be used to improve AFLT, using the existing PDE. PNs of distant sites, with correct Tau and levels can be used to identify position within a building, using an aPDE, or a modified PDE. PNs with a signal coded to provide additional identification that the signal originated from a pilot beacon, and not the macro network can also be used. In another embodiment of the present invention, any of the PNs transmitted by pilot beacons may also be modulated to identify them as pilot beacons.

In certain embodiments of the present invention, PNs from distant sites are set with Tau values that do not correspond to the macro's expected Tau values. When doing this, the aPDE may be used, since the existing PDE will not generally report these PNs as AFLT fixes due to large errors arid low weighting. The aPDE then has the capability to use the signal strength of these outlying PNs, re-used on beacons, to determine 3D position of a handset or device within a building.

It is somewhat more difficult to use AFLT with the existing PDF to determine position within a building because AFLT resolution is approximately 10 meters, and AFLT resolution is based on the distance to macro sites which may contain multipath components. In one embodiment of the present invention, an augmented PDE may be used with measurements of the signal strength of the distant PNS to determine the fine-positioning within a building. It is not a requirement that the Tau values of the distant PNs be exactly equal to the expected values from line of sight propagation. In practice, the existing PDE corrects for errors due to system deployment, for example, base station Tau setting errors. Pilot beacon offsets need to account for these macro offsets to provide accurate position fixes. In certain embodiments, the Taus may be set to provide a better AFLT fix as compared to that of the existing PN. In other embodiments, an aPDE or an existing PDE may be used with a handset resident application that interrogates registers to perform direct measurements.

Referring toFIG. 4, the system and method of the. present invention uses a combination of PNs that are close and far. The handset application interrogates PHY registers in the handset chipset providing measurements of each PN, level, and delay. These measurements are used together with the PDE output file, optionally, to establish a position estimate. For example, PN signal strength may be determined by the handset application and used by the aPDE for signal-strength-based ranging and positioning. In general, PNs must be on the neighbor list of the serving PN to be scanned by the handset PHY layer. This provision depends on the handsets' algorithm for increasing code search speed.

The method and system of the present invention also provide for embedded pilot beacons. In certain embodiments, positioning pilot beacons may be embedded in the remote units of digital DAS. In a DAS that uses digital processing, it is advantageous to combine the signal processing that generates multiple pilot signals with the processing in the remote traffic signals. This allows separate PNs and modulations, if present, to be placed on each remote, thus enhancing positioning resolution. Normally, an embedded field-programmable gate array (“FPGA”) or application-specific integrated circuit (“ASIC”) in the remote will incorporate the processing necessary to perform the functions required by the pilot beacon transmitters.

In certain embodiments of the present invention with a distributed antenna system (“DAS”), pilot beacons may be injected into the antenna. The level of the pilot beacon power may be set by a measurement of the traffic pilot, or pilots, carried by the DAS. If the traffic pilot reduces in power, there is a possibility that the pilot beacon will be an interference source. Therefore, pilot beacon power may be reduced, to prevent interference.

In certain embodiments of the present invention, the timing of pilot beacons is carried by a signal distributed to the pilot beacons over coax, Ethernet, optical fiber, and the like. The 0.5 pulse-per-second signal is modulated onto a carrier and transmitted to the remote units and/or pilot beacons to be demodulated. Dispersion in the media then can have less impact on time accuracy, as compared to timing transmitted at baseband.

Referring toFIG. 5, connection from A to B may be over a dedicated CAT 5/6 cable carrying a modulated RF signal. In one embodiment, management of the pilot beacon may be done over a dedicated CAT 5/6, or shared with a timing signal. In some embodiments, pilot beacons may be embedded in a repeater. Digital repeaters process signals and provide filtering, usually in a field-programmable gate array (“FPGA”).

A pilot beacon with multiple PNs may be implemented in the repeater digital processing. In another embodiment, the monitor capability shown inFIG. 3 may be implemented within the repeater's digital processing. In some embodiments of the present invention, an RF off-air signal is received, PNs and their levels and/or delays are determined, and the measurements are used to se the PNs, levels, and Taus of the associated mimicking pilot beacons may be automatically updated in a similar way. A PN scanner may be used to determine that a change has occurred and corrections are applied to the pilot beacon settings. In one embodiment, the mimicking pilot beacons described herein may be used together with conventional pilot beacons, together with those that use new unassigned PN offsets, and together with those that are included in the macro database.

While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention.