WO2011097414A1

WO2011097414A1 - Location finding in cellular network with repeater

Info

Publication number: WO2011097414A1
Application number: PCT/US2011/023649
Authority: WO
Inventors: Michiel Petrus Lotter
Original assignee: Nextivity Inc
Current assignee: Nextivity Inc
Priority date: 2010-02-03
Filing date: 2011-02-03
Publication date: 2011-08-11
Anticipated expiration: 2012-08-03

Abstract

A method for locating position of a communication device in a cellular network comprises finding location of a transmitter in the cellular network using a time-domain comparison of signals transmitted from the transmitter and received by at least three receivers; and compensating for delay imposed by presence of a repeater between the transmitter and a receiver of the at least three receivers.

Description

LOCATION FINDING IN CELLULAR NETWORK WITH REPEATER

Michiel Lotter

BACKGROUND [0001] Many advantages are gained, or requirements fulfilled, by a capability to find the location of a handset within a cellular network. For example, under current rules of the United States Government, cellular operators must locate emergency callers anywhere between 50 meters and 300 meters of their actual position, depending on the type of technology used. Code Division Multiple Access (CDMA) carriers utilize handset-based technology, while Global System for Mobile Communications (GSM) operators use what is considered less accurate network-based solutions.

SUMMARY

[0002] Embodiments of a method for locating position of a communication device in a cellular network comprise finding location of a transmitter in the cellular network using a time-domain comparison of signals transmitted from the transmitter and received by at least three receivers; and compensating for delay imposed by presence of a repeater between the transmitter and a receiver of the at least three receivers. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Embodiments of the invention relating to both structure and method of operation may best be understood by referring to the following description and accompanying drawings:

FIGURES 1A and 1 B are schematic block diagrams illustrating time- domain techniques for locating a transmitter, respectively excluding and including a repeater;

FIGURE 2A through 2D are schematic flow diagrams depicting embodiments of a method 200 for locating position of a communication device in a cellular network;

FIGURE 3 is a graph illustrating an example relationship of signal transmission delay to transmit signal power for purposes of exemplifying a technique for location-finding;

FIGURE 4 is a schematic flow chart showing a particular example embodiment of a technique for compensating for the presence of a repeater in a wireless system a time-domain approach to location- finding;

FIGURE 5 is an embodiment of a communication apparatus is shown comprising a communication controller configured to locate position of a communication device in a cellular network; and

FIGURE 6 is a schematic block diagram showing an example embodiment of a Universal Mobile Telecommunications System (UMTS) network capable of supporting the illustrative technique for locating position of a communication device in a cellular network. DETAILED DESCRIPTION

[0004] To find handset location, techniques such as Time- Difference of Arrival (TDOA) or Assisted-GPS (A-GPS) are commonly used. Whenever time-domain based methods are used, the presence of a repeater between the base station and the mobile phone handset can cause the location to be reported incorrectly. Embodiments of the methods and systems are described which address the problem of incorrect reporting and to accurately determine the location of a handset in a cellular network.

[0005] Various time-domain based approaches exist to find the location of a transmitter in a cellular network including, for example Time-of-flight (TOF) measurements and Time-Difference-of-Arrival (TDOA) determinations, both using data acquired at three or more receivers or sites.

[0006] In Time-of-flight (TOF) measurements, three or more receivers calculate the time lapsed from the transmission of the signal at the transmitter to the time the signal is received at each receiver. Knowing the time lapse information, the location of the transmitter can be calculated.

[0007] Time-difference-of-ar val (TDOA) determinations are made by measuring the difference in the arrival times of a signal transmitted by the transmitter at three or more sites. These difference measurements are used to compute the location of the transmitter.

[0008] Other time domain mechanisms exist and are known and variants of the above mentioned methods can also or otherwise be used.

[0009] Referring to FIGURES 1A and 1 B, schematic block diagrams illustrate time-domain techniques for locating a transmitter, respectively excluding and including a repeater. [0010] Whenever repeaters are deployed in a cellular network, the time domain techniques (including the TOF and TDOA techniques) generate inaccurate results. The reason for the errors and inaccuracies is that the entities determining either the absolute arrival times of signals or the time difference between signals arriving from the transmitter do not know whether they are receiving the signals directly from the transmitter or via a repeater that has a specific delay T_r. For example, as shown in FIGURE 1A, receivers 1 , 2 and 3 (Rx1 , Rx2 and Rx3) all receive signals from transmitter 1 (Tx1 ). In each case, the delays are T_dn , T_di2, T_di3, which uniquely define the position of Tx1 .

[0011] FIGURE 1 B considers the same scenario but assumes a repeater is positioned in the path between Rx3 and Tx1 . The delay between Rx3 and Tx1 becomes Td13 (as the signal still needs to travel the same distance) + T_r. For the location finding algorithm, the signal appears to take T_r seconds longer to travel from Tx1 to Rx3 which indicates that Tx1 is further away from Rx3 than is actually the case, leading to a mistake in determining the location of Tx1 .

[0012] Referring to FIGURE 2A through 2D, schematic flow diagrams depict embodiments of a method 200 for locating position of a communication device in a cellular network. The location of a transmitter in the cellular network is found 202 using a time-domain comparison of signals transmitted from the transmitter and received by at least three receivers. An accurate position is located by compensating 202 for the delay imposed by presence of a repeater between the transmitter and a receiver of the at least three receivers.

[0013] Referring to FIGURE 2B, positioning of the transmitter can be compensated 210 by defining 211 a relationship of round-trip delay to transmit power level for a voice call and, upon receipt of a voice call 212, measuring 213 round-trip delay from a handset to a base station and transmit power level of the handset. The method 210 further comprises determining 214 a point in the defined relationship for the measured round-trip delay and the measured transmit level, and determining 215 whether the point in the defined relationship is outside an expected relationship between delay and power level. For a point outside the defined relationship 216, the method 210 further comprises assuming 217 a repeater with fixed delay in a signal transmission path, and subtracting 218 repeater delay from the measured round-trip delay to compensate for the delay.

[0014] In some embodiments, the relationship of round-trip delay to transmit power level for a voice call can be defined and manifest in graphically in a graph or plot. In this manner, the measured round-trip delay and the transmit level can be plotted on the defined graph.

[0015] In some embodiments, the relationship of round-trip delay to transmit power level can be defined based on actual measurements.

[0016] The round-trip delay from a handset to a base station and transmit power level of the handset can be measured in standard measurements performed at the base station.

[0017] For example power control of code division multiple access (CDMA) and/or wideband code division multiple access (WCDMA) networks can be used to adjust transmit power levels of handsets to receive signals at a suitable level.

[0018] Referring to FIGURE 2C, the location of a transmitter in the cellular network can be found 220 using time-of-flight measurements at three or more receivers by calculating 222 the time lapsed from transmission of a signal at the transmitter to time received at the three or more receivers; and

determining 224 the location of the transmitter from the time lapsed calculations. [0019] Referring to FIGURE 2D, the location of a transmitter in the cellular network can be found 230 using time-difference-of-ar val measurements at three or more receivers by measuring 232 a differential in arrival times of a signal transmitted by the transmitter and received at the three or more receivers; and determining 234 the location of the transmitter from differences in the arrival times.

[0020] Code Division Multiple Access (CDMA) and Wideband Code Division Multiple Access (WCDMA) networks deploy power control to adjust the transmit power levels of handsets to enable receiving the signals at the correct level. Generally, the further away the transmitter (handset) is from a base station, the stronger the transmit power level needs to be to ensure that the signal reaches the base station with adequate fidelity. Furthermore, the further away the transmitter (handset) is from the base station, the longer the delay in a signal reaching the base station after the signal has been transmitted. For transmissions in an outdoor environment, a typical graph 300 of signal transmission delay vs. Tx signal power is shown in FIGURE 3. The delay for transmission with no repeater is shown in line 302. If a repeater is introduced into the link, the delay is shown by a line 304 that is essentially shifted up by the repeater delay. In the example of a 5us delay, the delay shift is depicted by the line 304.

[0021] Assuming that the transmit (Tx) power level is known, the graph 400 can be used to determine whether a repeater is or is not used in the link. If the Tx power level is small but the delay is large (such as a 6us delay with only -3dBm or Tx power), the signal is most probably being received via a repeater and the delay introduced by the repeater T_r, can be subtracted from the arrival time of the signal to give an accurate estimation of the location of the transmitter.

[0022] Referring to FIGURE 4, a schematic flow chart shows a particular example embodiment of a technique for compensating the arrival time of a signal for the presence of a repeater in a wireless system a time-domain approach to location-finding.

[0023] The method 400 comprises defining 402 a graph (typically based on actual measurements) that relates Round-Trip-Delay to Tx power level for voice calls.

[0024] When a voice call is made 404 from a handset to the base station, the round-trip-delay and Tx power level of the handset is measured 406. In WCDMA networks, for example, the delay and power level are standard measurements that can be performed at a base station. [0025] The measured delay vs. power level number is plotted 408 on the defined graph. If the point falls above the expected delay vs. power level 410, then the method 400 assumes 412 the signal transmission path includes a repeater with fixed delay T_r.

[0026] The repeater delay is subtracted 414 from the measured round-trip- delay and used this compensated for number in any time domain location calculation.

[0027] The cellular industry continuously attempts to improve the indoor coverage of 3G and 4G systems to meet the rising customer expectation for better voice services and high data-rate service requirements. Thus, many solutions such as Femtocells, 3G-router, and smart repeaters have been developed to address indoor coverage improvements. One such device is a three-hop cellular booster (referred to hereinafter as "Cel-Fi") which is described in detail in patent applications no. WO2005025078 by Mohebbi, filed on 3^rd of September 2003 and WO2005069249 by Mohebbi filed on 12 of January 2004. The Cel-Fi is an example of "smart repeater" for usage in a WCDMA system. However, the ideas and embodiments described herein are not limited to the described 3-hop repeater (Cel-Fi), and thus can be used for any indoor device including a booster, repeater, a router, a Femtocell, and the like. Neither is the disclosure limited to WCDMA system, and with appropriate modifications, can be applied to any type of cellular or wireless system.

[0028] Referring to FIGURE 5, an embodiment of a communication apparatus is shown comprising a communication controller configured to locate position of a communication device in a cellular network. The illustrative communication apparatus can be configured as a smart repeater 500 can be a Cel-Fi, a 3-hop repeater with a middle hop (hop 2) operating in wireless mode in UNII band. In other examples, the middle hop (hop 2) can be over a wire-line such as CAT5, electricity or telephone lines. The middle hop (hop 2) is an "autonomous" hop in that the waveform, bandwidth, and the signaling content is somewhat different from hop 1 that exists between Network unit 502 and Base Transceiver Station (BTS) 506, and hop 3 that exists between User unit 504 and the Mobile Station (MS) 508. The difference in signal characteristics can be due to modulation and/or the control channels that exist between the Network unit 502 and the User unit 504. The waveform and bandwidth are changed to modulate the original signal such that the fading in the middle hop (hop 2) can be mitigated by the use of broadband modulation techniques such as Orthogonal Frequency-Division Multiplexing (OFDM), so that the repeated signal is only subject to two fading hops (hops 1 and 3), or to enable transmission of the captured cellular waveform in a digital mode over wire-line and exchanging control messages. An additional hop that imposes yet another fading pattern (Rayleigh or Rician) on the original signal can degrade the end signal considerably and push the required fading margins on all three hops sufficiently high, to render the repeater ineffective. The middle hop contains a bi-directional link including at least two channels, the "Control" (CCH) and "Traffic" (TCH) channels.

[0029] The smart repeater 500 can be used as a signal booster device operative to reduce network capacity for delivery of high-speed service. The signal booster device can function in combination with a communication controller that is implemented, for example, by a service provider via the communication network, or in the network unit 502 or the user unit 504. The communication controller can be configured to determine whether a subscriber is at a predetermined home location and whether the subscriber is using the signal booster device that conserves network resources. The communication controller can further be configured to assign a maximum data rate according to the determined home location and use of the signal booster device.

[0030] The communication controller can be any control device such as a processor, central processing unit (CPU), computer, controller, control circuitry, and the like. The communication controller can be configured to the locate position of a communication device 508 in a cellular network comprising logic operative to finding location of a transmitter in the cellular network using a time-domain comparison of signals transmitted from the transmitter and received by at least three receivers; and logic operative to compensate for delay imposed by presence of a repeater between the transmitter 508 and a receiver 506 of the at least three receivers.

[0031] The logic can be any entity with logic capability including a processor, a central processing unit (CPU), computer, controller, control circuitry, hardware, software, or other entity capable of performing the described operations.

[0032] In an illustrative embodiment, the communication controller can further comprise logic operative to codify a relationship of round-trip delay to transmit power level for voice calls, logic operative in response to receipt of a voice call for measuring round-trip delay from a handset to a base station and for measuring transmit power level of the handset, and logic operative to apply the measured round trip delay and the measured transmit level to the codified relationship to determine a condition for the received voice call. The communication control can further comprise logic operative to determine whether the received voice call condition is outside an expected relationship between delay and power level, and, for a condition that the received call condition is outside the defined relationship, logic operative to assume presence of a repeater with fixed delay in a signal transmission path and logic operative to subtract repeater delay from the measured round-trip delay to compensate for the delay. [0033] In a particular embodiment, the relationship of round-trip delay to transmit power level can be codified in a graph and the communication controller can comprise logic operative to define the relationship of round-trip delay to transmit power level for a voice call in a graph, and logic operative to plot the measured round-trip delay and the transmit level on the defined graph.

[0034] Some embodiments of the communication controller can further comprise logic operative to define the relationship of round-trip delay to transmit power level based on actual measurements, and logic operative to measure round-trip delay from a handset to a base station and transmit power level of the handset in standard measurements performed at the base station.

[0035] In a particular example embodiment, the logic operative to find location of a transmitter in the cellular network using time-of-flight

measurements at three or more receivers can comprise logic operative to calculate time lapsed from transmission of a signal at the transmitter to time received at the three or more receivers, and logic operative to determine location of the transmitter from the time lapsed calculations.

[0036] In another particular example embodiment, the logic operative to find location of a transmitter in the cellular network using time-difference-of- arrival measurements at three or more receivers can comprise logic operative to measure a differential in arrival times of a signal transmitted by the transmitter and received at the three or more receivers, and logic operative to determine location of the transmitter from differences in the arrival times. [0037] An example network 600 capable of location-finding functionality is shown in FIGURE 6 and includes Radio Network Controllers (RNC) 606 that connect to a Base Transceiver Station (BTS) 608 through a node 610. In the example configuration, the RNC 606 can communicate via networks such as Public Switched Telephone Network (PSTN) 612, Internet Protocol (IP) 624, and other networks through functional blocks including Global System for Mobile Communications (GMSC), Media Gateway (MGW), Gateway GPRS Support Node (GGSN), Mobile Switching Center (MSC), Service GPRS support node (SGSN), and other blocks. The illustrative network 600 may or may not be Home Zone enabled and include functional blocks, "Home-Zone Location Server" (HZLS) 602 and "Home-Zone Service Client" (HZSC) 604. A task of HZLS 602 is establishment of the presence of a subscriber in the "Home-zone" which may be enabled using a new application element, based on an available services such as Short Message Service (SMS) supported by packet or circuit switched bearer services. The new application element also verifies and monitors calls/sessions durations of a subscriber within in the subscriber's "Home-Zone". The monitored information is then passed to HZSC 604, where a database exists for collecting the information supplied by HZLS 602 and uses the information for adjusting service level and generating appropriate billing information.

[0038] Terms "substantially", "essentially", or "approximately", may be used herein, and relate to an industry-accepted tolerance to the corresponding term. Such an industry-accepted tolerance ranges from less than one percent to twenty percent and corresponds to, but is not limited to, functionality, values, process variations, sizes, operating speeds, and the like. The term "coupled", as may be used herein, includes direct coupling and indirect coupling via another component, element, circuit, or module where, for indirect coupling, the intervening component, element, circuit, or module does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. Inferred coupling, for example where one element is coupled to another element by inference, includes direct and indirect coupling between two elements in the same manner as "coupled".

[0039] The illustrative block diagrams and flow charts depict process steps or blocks in a manufacturing process. Although the particular examples illustrate specific process steps or acts, many alternative implementations are possible and commonly made by simple design choice. Acts and steps may be executed in different order from the specific description herein, based on considerations of function, purpose, conformance to standard, legacy structure, and the like. [0040] While the present disclosure describes various embodiments, these embodiments are to be understood as illustrative and do not limit the claim scope. Many variations, modifications, additions and improvements of the described embodiments are possible. For example, those having ordinary skill in the art will readily implement the steps necessary to provide the structures and methods disclosed herein, and will understand that the process parameters, materials, and dimensions are given by way of example only. The parameters, materials, and dimensions can be varied to achieve the desired structure as well as modifications, which are within the scope of the claims. Variations and modifications of the embodiments disclosed herein may also be made while remaining within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1 . A method for locating position of a communication device in a cellular network comprising:

finding location of a transmitter in the cellular network using a time- domain comparison of signals transmitted from the transmitter and received by at least three receivers; and

compensating for delay imposed by presence of a repeater between the transmitter and a receiver of the at least three receivers.

2. The method according to claim 1 further comprising:

defining a relationship of round-trip delay to transmit power level for a voice call;

for a voice call, measuring round-trip delay from a handset to a base station and transmit power level of the handset;

determining a point in the defined relationship for the measured round- trip delay and the transmit level;

determining whether the point in the defined relationship is outside an expected relationship between delay and power level; and for a point outside the defined relationship:

assuming a repeater with fixed delay in a signal transmission path; and

subtracting repeater delay from the measured round-trip delay to compensate for the delay.

3. The method according to claim 2 further comprising:

defining the relationship of round-trip delay to transmit power level for a voice call in a graph.

4. The method according to claim 3 further comprising:

plotting the measured round-trip delay and the transmit level on the defined graph.

5. The method according to claim 2 further comprising:

defining the relationship of round-trip delay to transmit power level based on actual measurements.

6. The method according to claim 2 further comprising:

measuring round-trip delay from a handset to a base station and

transmit power level of the handset in standard measurements performed at the base station.

7. The method according to claim 1 further comprising:

using power control of code division multiple access (CDMA) and/or wideband code division multiple access (WCDMA) networks to adjust transmit power levels of handsets to receive signals at a suitable level.

8. The method according to claim 1 further comprising:

finding location of a transmitter in the cellular network using time-of- flight measurements at three or more receivers comprising: calculating time lapsed from transmission of a signal at the

transmitter to time received at the three or more receivers; and

determining location of the transmitter from the time lapsed calculations.

9. The method according to claim 1 further comprising:

finding location of a transmitter in the cellular network using time- difference-of-ar val measurements at three or more receivers comprising:

measuring a differential in arrival times of a signal transmitted by the transmitter and received at the three or more receivers; and

determining location of the transmitter from differences in the arrival times.

10. A communication apparatus comprising:

a communication controller configured to locate position of a

communication device in a cellular network comprising:

logic operative to finding location of a transmitter in the cellular network using a time-domain comparison of signals transmitted from the transmitter and received by at least three receivers; and

logic operative to compensate for delay imposed by presence of a repeater between the transmitter and a receiver of the at least three receivers.

1 1 . The apparatus according to claim 10 further comprising:

logic operative to codify a relationship of round-trip delay to transmit power level for voice calls;

logic operative in response to receipt of a voice call for measuring

round-trip delay from a handset to a base station and for measuring transmit power level of the handset;

logic operative to apply the measured round trip delay and the

measured transmit level to the codified relationship to determine a condition for the received voice call;

logic operative to determine whether the received voice call condition is outside an expected relationship between delay and power level; and

logic operative for the received voice call condition outside the defined relationship:

logic operative to assume presence of a repeater with fixed delay in a signal transmission path; and

logic operative to subtract repeater delay from the measured round-trip delay to compensate for the delay.

12. The apparatus according to claim 1 1 further comprising:

logic operative to define the relationship of round-trip delay to transmit power level for a voice call in a graph; and

logic operative to plot the measured round-trip delay and the transmit level on the defined graph.

13. The apparatus according to claim 1 1 further comprising:

logic operative to define the relationship of round-trip delay to transmit power level based on actual measurements; and

logic operative to measure round-trip delay from a handset to a base station and transmit power level of the handset in standard measurements performed at the base station.

14. The apparatus according to claim 1 1 further comprising:

logic operative to find location of a transmitter in the cellular network using time-of-flight measurements at three or more receivers comprising:

logic operative to calculate time lapsed from transmission of a signal at the transmitter to time received at the three or more receivers; and

logic operative to determine location of the transmitter from the time lapsed calculations.

15. The apparatus according to claim 1 1 further comprising:

logic operative to find location of a transmitter in the cellular network using time-difference-of-arrival measurements at three or more receivers comprising:

logic operative to measure a differential in arrival times of a signal transmitted by the transmitter and received at the three or more receivers; and

logic operative to determine location of the transmitter from differences in the arrival times.