MX2007009322A - Base transceiver station (bts) synchronization. - Google Patents

Abstract

In a network overlay wireless location solution for a GSM or UMTS communications network, spectrum utilization can be made far more efficient by synchronizing the BTSs, which can require distributing a timing signal to all BTSs, or installing a satellite-based timing unit in each site. The present invention provides an architecture in which Location Measurement Units (LMUs) are installed at some or all of the BTS sites for the purpose of locating wireless devices. The LMUs are used to measure the timing of various uplink and/or downlink signals in the cellular network in support of various location techniques. These LMUs may include a GPS-based timing reference module, which may be used to synchronize the time bases of all LMUs. To reduce the overall cost of BTS synchronization, the LMU distributes timing signals, including a periodic electrical pulse as well as time description information, on a serial or other interface, which is available for other nodes to use for synchronization. The format of the electrical pulse and time description information is modified through hardware and software to adapt to the various formats required by various BTS types. For example, the BTSs with co-located LMUs can receive a synchronization signal with little or no hardware cost. The External Interface Unit (EIU) described herein may be used to adapt to various BTS hardware formats. For BTS sites not equipped with an LMU, a Timing Measurement Unit (TMU) can be used. The TMU has the single function of providing BTS time signals in the same formats as provided by the LMUs. The time signals provided by the TMUs are synchronous to the signals provided by the LMUs. This timing-only TMU has a lower cost than the LMU because it does not support the uplink or downlink signal measurement functions. This approach allows a cellular operator to synchronize BTSs at a relatively low cost.

Description

SYNCHRONIZATION OF A BASE TRANSCEIVER STATION (BTS) RECIPROCAL RETERANCE The present application claims priority over United States Provisional Application No. 60 / 652,265, filed on February 11, 2005, entitled "Synchronization of a Base Transceiver Station (BTS)", which is incorporated in its entirety to this document by reference to it. FIELD OF THE INVENTION The present invention relates in general to the field of wireless localization and the associated wireless communication systems, and more particularly, but not exclusively, to a system for the synchronization of the Base Transceiver Stations (BTS) of a GSM or UMTS network together with a superimposed wireless location system (LS). BACKGROUND OF THE INVENTION The present invention is specially adapted, but not especially limited, for use with GSM and UMTS systems and the like. GSM represents the Global System for Mobile communications and is a mobile telephone system, widely used in Europe and other parts of the world, while UMTS represents the Universal Mobile Telecommunications System and is the third generation broadband system ( 3G) based on the GSM standard. This specification describes systems and methods for providing timing information derived from the Global Positioning System (GPS) to the base stations of a wireless communication system, for the purpose of network synchronization. For example, synchronization of the GSM network can benefit the wireless carrier in various ways. In non-synchronized GSM networks, inter-channel interference created by frequency re-use can be reduced by synchronization. A reduced level of noise or inter-channel interference allows for tighter frequency re-use patterns, thus allowing the system to increase capacity (eg capacity in Erlang) or improve the quality of voice / data. SUMMARY OF THE INVENTION The following statements summarize several important aspects of the present invention, which are described in more detail in this document: 1. In a wireless location solution superimposed on the network for a wireless communication system comprising a network of Base Transceiver Stations (BTS), for example a GSM or UMTS communication network, a method and system for improving the spectrum by synchronization of the BTS. 2. A method and system as mentioned above, wherein the timing signal is provided to each BTS by a Location Measurement Unit (LMU) or a Timing Measurement Unit (TMU). 3. A method and system as mentioned above, wherein each LMU and each TMU comprises a GPS-based timing reference module and means for generating a periodic timing signal that is synchronized within a predetermined degree. specified accuracy with different timing signals generated for each LMU and each TMU. . A method and system as mentioned above, wherein the LMUs are used to measure the timing of various uplink and / or downlink signals in the cellular network in support of various localization techniques. 5. A method and system as mentioned above, in which the LMU and TMU distribute timing signals, including a periodic electrical pulse as well as temporal description information. 6. A method and system as mentioned above, wherein the electrical pulse format and the timing description information are modified by hardware and software to adapt to the various formats required by the various types of BTS. 7. A method and system as mentioned above, in the BTS with the LMU located together receive a synchronization signal without hardware cost or a small cost, and in which the BTS sites not equipped with an LMU are equipped with a TMU that has the unique function of providing BTS timing signals in the same formats that are provided by the LMUs, in which the timing signals provided by the TMUs are synchronized to the signals provided by the LMUs and the time-only TMUs have a lower cost than the LMU because they do not support the signal measurement functions of the uplink or the downlink . It will be noted that the concept that timing signals are "synchronized" is not limited to signals that are substantially identical or that occur simultaneously. For example, for the purpose of the present invention, two signals can be considered to be sufficiently synchronized, when they are displaced in time but have a known relationship. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 represents an illustrative embodiment of a location solution superimposed only emergency.

Figure 2 depicts various ways of using the synchronization products of the base stations (LMU and TMU) according to the present invention. Figure 3 represents an illustrative embodiment of the internal architecture of a TMU and the external interface. Figure 4 depicts an illustrative relationship between a 1 PPS timing signal and the synchronization data. Figure 5 represents a GSM / UMTS example network that includes a mixture of BTS with possibility of synchronization / location and BTS with possibility of synchronization / without possibility of location. Figure 6 represents the architecture of an External Interface Unit (EIU).

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 1. Overview The present invention is particularly adapted for use in conjunction with a solution superimposed on the network for a GSM communications network. The GSM communications network is specified in the European Telecommunications Standardization Institute (ETSI) and is extended by the Third Generation Partnership Project (3GPP). In a fully integrated solution of Location Services conforming to the GSM specification, the SMLC (Mobile Service Location Center) depends on the existing BSC (Base Station Controller) or the PCU (Packet Control Unit) for provide RF assignment information for the MS (Mobile Station, that is, the mobile unit to be located). By modifying the LMU to monitor the uplink or downlink control channels, it is possible to implement an emergency-only overlay location solution that satisfies the FCC E911 command and does not require any modification to existing handsets or GSM network . In Figure 1, an exemplary architecture for such a solution is illustrated. (For additional information about this architecture, see U.S. Patent Application No. 20040203429, filed September 3, 2002 and published October 14, 2004"E911 Overlay Solution for GSM, for Use ireless Location System "). As shown in Figure 1, the superimposed solution E911 comprises the following elements; 1. A GSM communication network 100, which includes a transmit / receive antenna 102A coupled to the Base Transceiver Station (BST) 104; a Base Station Controller (BSC) 106; a Mobile Switching Center (MSC) 108, and a Mobile Entry Location Center (GMLC) 110. All of these components and subsystems are well known in the art. See for example, 3GPP TS 03.71 V8.6.0 (06 - 2002). 2. A Localization Measurement Unit (LMU) 200A, which as indicated by the dashed line may be located in conjunction with the BTS 104, so that it shares the antenna 102A to receive the RF signals from the Mobile Stations. The LMU 202A can include an internal GPS receiver and thus a GPS antenna 202A can also be provided. The LMU may also provide the capability to monitor and demodulate the direct channel signals transmitted by the BTS to the MS. This monitor port of the direct link can be connected to a separate antenna, or directly to a direct link path of the BTS. In addition, the system can be configured so that, for a given call, there will be a Principal LMU, in this case the LMU 200A, and one or more LMU Cooperators, for example, the LMU indicated 200B. The Cooperating LMUs are generally configured in the same way as the Main LMU, and thus are coupled to the GPS antenna 202B and are typically located in conjunction with a BTS. 3. The LMUs are coupled to a Mobile Service Location Center (SMLC) 300, which in turn is coupled to a Mobile Entry Location Center (GMLC) or a Mobile Positioning Center (MPC) 400. The concept of the LMU, SMLC, GMLC, and MPC are well known, as can be seen in the documents of the GSM specification, which have been cited above. 4. Figure 1 also shows a Mobile Station 500. Indeed, there will typically be many such units in operation within a geographical region, and more than one may be engaged in an emergency call at a particular time. In a cellular / wireless system, such as the GSM system or the UMTS, the use of the spectrum can be made much more efficient by synchronizing the BTS. For example, 10-20% more voice calls can be achieved per unit of bandwidth by synchronizing the BTS. The synchronization of a large number of BTS in a network with an adequate level of accuracy is difficult and requires distributing a timing signal to all BTSs, or installing a satellite-based temporarily unit in each site. Satellite-based tempopting units are expensive and consume pous power and space in BTS sites. The present invention provides an architecture in which Location Measurement Units (LMU) are installed in some or all of the BTS sites for the purpose of locating the wireless devices. The LMUs are used to measure the timing of the various uplink and / or downlink signals in the cellular network in support of various localization techniques. These LMUs can include a GPS-based time-based reference module, which is used to synchronize the time bases of all LMUs. This allows measurements of the relative temporalization differences to be made in support of the location. To reduce the overall cost of BTS synchronization, the LMU distributes timing signals, including a periodic electrical pulse as well as timing description information, over a serial or other interface, which is available to other nodes for use. in synchronization. The electric pulse format and the timing description information are modified using hardware and software to adapt to the different formats required by the different types of BTS. For example, BTSs with LMUs located together can ive a synchronization signal at little or no cost. The EIU described below is used to adapt to the different types of hardware formats of the BTS. Not all BTS sites will be equipped with LMU. For those sites without an LMU, a Timing Measurement Unit (TMU) can be used. The TMU has the sole function of providing BTS timing signals in the same formats as those provided by the LMUs. The timing signals provided by the TMUs are synchronized with the signals provided by the LMUs. These time-only TMUs have a lower cost than the LMUs since they do not support the measurement functions of the uplink or downlink signals. This set of products allows a cellular operator (wireless carrier) to synchronize the BTS at a relatively low cost. 2. Synchronization of the BTS. In accordance with the present invention, the LMU may contain a high performance GPS iver to provide a common high psion timing reference for all LMUs within the location system. The GPS iver may provide a timing reference to a jointly located base station for the purposes of synchronization of the base station network, i.e. to synchronize the BTS within a specified degree of accuracy. In one implementation As an example of the invention, the LMU contains a network synchronization interface that can be adapted to be compatible with the corresponding interface over the associated BTS. In this way, by adding software modifications, the existing LMUs can be updated to a configuration compatible with the BTS interface. This software update is called the BSS Timing Option (BTO), and can be installed in existing LMU / BTS installations and equipped with the new LMUs. For BTS sites without an installed LMU, a Timing Measurement Unit (TMU) may be employed. The TMU contains a GPS iver and software necessary to conform the timing interface of the BTS. A site may contain a mixture of LMU with BTO and TMU timing modules or the carrier may choose to use only the TMU to synchronize sites where LMU has not yet been installed. The Timing Measurement Unit is an independent product that can be used independently of the Wireless Location Systems. The TMU contains a built-in GPS iver, which includes a GPS antenna, for the purpose of establishing precise timing stamps. The timing output includes a signal of 1 pulse per second (PPS) and the timing information. The TMU provides data in a pre-specified ASCII format developed for use with the particular BTS equipment used. The synchronization products of the True Position base station can be used in several ways, as previously mentioned and is represented in Figure 2: 1) In uses without infrastructure that have neither location capability nor synchronization capacity. 2) When an already synchronized BTS is updated to include the location capability. 3) When updating a BTS that allows the location to incorporate the synchronization. 3. Timing Measurement Unit (illustrative embodiment) To enable the operation of the GSM synchronized by the wireless carrier, a TMU can be used to provide a periodic signal and the timing data information related to the BTS. The TMU preferably includes a GPS receiver designed to provide this periodic signal and the timing data information related to the BTS, on, for example, an RS-422 communication interface. In an exemplary embodiment, the TMU is a stand-alone device containing a GPS / device (GPS) receiver, an 80C51 microcontroller (C51), a serial interface for supplying timing information to the BTS, and a console interface. The purpose of the TMU is to obtain accurate timing information from the GPS and supply it to the BTS. The timing is provided to the BTS in the form of a signal of one pulse per second (PPS) which is preceded by a serial message announcing the precise instant of the pulse rise slope. The LMU attempts to maximize the amount of time that the timing information can provide to the BTS. With To this end, the TMU takes steps to bring GPS online as quickly as possible after a loss of power and keeps it online whenever possible. For maintenance and testing support, the TMU has three operating modes, start mode, test mode and functional mode. The start mode allows the TMU control program to be updated after production. The test mode allows testing and diagnosing the hardware platform of the TMU. The functional mode provides the main functionality of the TMU to provide timing to the BTS. The TMU provides synchronization information as described above for two fundamental reasons: 1) When an LMU is not present in the BTS. When an LMU is present, the synchronization information is provided by the LMU through an External Interface Unit (EIU). The External Interface Unit takes the signal of 1 PPS and the information signal related to the timing and converts both signals to an RS-422 communication format for interfacing with the BTS. 2) When an LMU is used with the team using its signal output capability already, so that it is unable to provide the timing signals. Figure 3 shows an illustrative embodiment of the internal architecture of the TMU and the external interfaces. The received GPS satellite signal is entered into the internal GPS receiver of the TMU. An internal microcontroller provides the following capabilities: 1) Format the GPS timing data in a format series as may be required. 2) Update of the TMU control program through the external RS-232 Console port. 3) Control of the tricolor LED indicator indicating the health of the TMU, and the synchronization status. 4) Reset capability through the front panel reset switch. The 1PPS signal output from the GPS receiver, and the serial timing data signal output formatted from the microcontroller are both converted to the RS-422 signal levels, and output to the BTS. The signals of 1 PPS and serial data are branched to the 4 ports comprising a quad output connector. Each output port provides both 1 PPS and the serial data output in RS-422 signal levels. The control program of the TMU microcontroller can be updated through the RS-232 console port.

The TMU will transmit the synchronization timing data messages, and the signal from 1 PPS to the BTS at RS-422 signal levels as shown in Figure 3. The timing synchronization data interface with the BTS can be a serial communications link. The signals of 1 PPS distributed by the TMU to each of the four output ports can have a frequency of 1 Hz and an accuracy of 100 ns RMS with respect to the UTC time. The physical layer of the serial communications link is based on an RS-422 UART. The specific characteristics are the following: • RS-422 interface with 100 ohms termination in the BTS.

• No parity • One start bit • 8 bit data length • One stop bit. An RS-422 transmitter in the TMU provides the signal of a PPS. The rise time from 10 to 90% may be less than 10 nsec at each output port of the TMU. The BTS can include a built-in 100-ohm termination. The timing data is preceded by the pulse of a PPS. See Figure 4 for timing details. The arrows in Figure 4 show the slope of the pulse rise of 1 PPS. The data signal containing the timing information is preceding the corresponding PPS pulse. Figure 5 is a schematic diagram showing a GSM or UMTS network in which the BTS are synchronized using the timing information obtained from an LMU or a TMU. The LMU may or may not require an EIU, depending on the requirements of the BTS interface as discussed in this document.

Functional Description of the TMU (illustrative embodiment) As discussed, the TMU provides timing for a BTS that will enable the BTS to synchronize its operation with other BTSs in its network. The TMU obtains timing information from its integral GPS receiver and provides it to the BTS with a PPS signal and messages from PPS Periodic Report and Position Dates. The TMU is used in locations where an LMU is not present or in which the timing signals are not available from the LMU used. Where the LMU is used, the LMU can provide the same timing functionality as the TMU using an EIU. The synchronized BTS can increase the capacity of the network through the precise management of radio resources. The TMU software, in a preferred embodiment, supports three modes of operation: start mode, test mode and functional mode. Although each mode provides a mechanism for switching the others, each mode is independent and mutually exclusive. That is, the start mode does not support the test mode functionality, the test mode does not support the start mode functionality, neither the start mode nor the test mode supports any operational functionality, and the functional mode does not support no functionality of the other two modes. To use the functionality in any way, the TMU must first be switched to that mode by the appropriate mechanism (usually a console command). Once switched to a particular mode, it is understood that the functionality of the other modes is not available. For example, when the test mode has been switched, the timing synchronization to the BTS is inhibited since this functionality is only supported by the functional mode. The timing of the BTS can not be resumed until the TMU is returned to functional mode. Certain conditions may prevent switching from one mode to another. For example, it is not possible to switch from the mode of start if the valid program image is not present. In addition, certain conditions can cause an automatic switch to a mode. For example, the TMU will automatically switch to the start mode with a reset if the valid program image is not present. The current mode of the TMU can be identified by the console indicator. The console indicator lists the current mode as follows. • "TMU >" for the functional mode • "Boot >" for the start mode • "Test >" for the test mode Start mode The start mode allows updating the TMU software on the site. In start mode, a software image can be downloaded through the console port. The downloaded image will replace the image stored in the flash memory. Only portions of the image of the functional and test modes can be replaced using this method. The portion of the start mode of the image can only be replaced during production or through the JTAG port. The start mode can be entered by a console command or can be invoked automatically after a reset if the valid program image is not found. Certain failure conditions, such as exceeding the time of the watchdog, may produce a reset that may result in the start mode being invoked. Start mode is output by a reset when a valid program image is present. The reset can be implemented by pressing the reset button, power off and on of power or by a console command. You can not exit start-up mode if a valid program image is not present. When the start mode is successfully exited, the TMU returns to the functional mode. Test Mode The test mode supports the console commands directly exerted by the TMU hardware. The commands are usually low level commands or high level commands. The low level commands directly manipulate the TMU hardware and do not provide or provide a small translation for the operator. Low level commands are useful for card-level tests and troubleshooting. The high-level commands provide a signal interpretation and manipulate the combinations of signals to support the interaction with the hardware by the operator. These commands are useful when a functional topic is diagnosed. The test mode is intended for use during the manufacturing test, installation, field fault diagnosis and repair. The test mode is intended for use by a trained technician. The test mode can be entered from the functional mode by a console command. The test mode is exited by any reset and the TMU returns to the functional mode (provided that the image of a valid program is present). Functional Mode The functional mode is the main mode of the TMU. When in the functional mode, the TMU operates autonomously towards its main objective, supplying precise timing information to the BTS. While it is In the functional mode, the TMU can send alarms and status information to the console port. In addition, the functional mode supports the commands of the console that allow to investigate the functional conditions and the manipulation of functional parameters. Functional mode is automatically entered after any reset, if a valid program image is present. The functional mode can be exited by invoking the test mode or the start mode through a console command. From the functional mode it can exit automatically if certain fault conditions are detected. Functional States The status LED on the front panel of the TMU reflects the current status of the TMU. The status of the TMU is determined by its mode of operation and the conditions of departure. Of the ten (10) possible states of the LED, only the following are defined as valid. The LED statuses always indicate the existing conditions. CONTINUOUS RED (failure) - This indicates a fault, so that the TMU is unable to function normally and must be replaced or repaired by a qualified technician. GREEN FLASHING (initializing) - This indicates that the TMU is functional and no unexpected conditions have been detected. This state can only exist immediately following a reset and indicates that the necessary conditions have not yet been established to provide timing to the BTS. If the required conditions can not be established within a period of two minutes following a reset, the state will proceed to INTERMITTENT AMBER. Once you have left this state, the TMU does not return to this state until it is reset again. • CONTINUOUS GREEN (fully functional) - This indicates that the TMU is operating normally, there are no pending alarm conditions, and the BTS is being supplied with accurate timing. • INTERMITTENT AMBER (damaged) - This indicates that the TMU is fully functional but that there are conditions or alarms that prevent the TMU from providing timing to the BTS. This state is always the result of external influences, so that the replacement of the TMU itself does not circumvent the issue. When all pending conditions disappear, the TMU will return to the CONTINUOUS GREEN state. Alarms and Status Messages In the functional mode, the TMU monitors conditions that may affect its ability to provide accurate timing information to the BTS. further, also observes exceptions or conditions found in the execution of its programming. Messages concerning these conditions will be sent to the console. These messages are alarms or status. A message from this is purely informative and can indicate anything of interest. The sending of a status message has no effect on the TMU. The alarms indicate conditions that can impact the operation of the TMU. The existence of alarms may result in a change in the status of the TMU. When multiple alarms are indicated, the most rigorous state is assumed. Table 1 - TMU alarms Functional Processes This section describes the procedures followed by the illustrative software of the TMU. With the exception of some of the initial boot processing, all procedures refer to the functional mode.

Start The start procedure is carried out following any reset of the C51. The purpose of this boot process is to raise the platform and establish a functional status. The boot procedure also performs a self-test of the TMU platform and the integrity check of the software. If the software integrity test fails, the TMU enters the startup mode. Control C51 of the establishment The first part of the start procedures establishes the operation of the C51 and configures the I / O for the control of the TMU platform. 1. Check the presence of a software image. 2. Check the integrity of the software image. 3. Configure the I / O mapping of the C51. 4. Inhibit the PPS and the Serial output to the BTS. 5. Configure the LED driver. 6. Check and switch to the external oscillator. 7. Configure the serial communications ports. GPS Establishment Control The second part of the startup procedure establishes GPS control. When GPS control is established, the MTU can perform a warm restart or a cold restart. The cold restart assumes that the GPS device must be fully re-initialized and that all previous information is lost. Under these conditions, several minutes may be required before the timing can be re-established. A warm reboot tries to reset the timing sooner by keeping the information stored in the GPS. This is possible because GPS is a subsystem independent of the TMU. Under some conditions, such as a button reset, the C51 resets but the GPS does not. Also, since no power interruption has been experienced, the GPS is still operating normally. In these cases, the hot re-start resets the GPS control without interrupting its operation. A cold restart of the GPS will be carried out if any of the following conditions exist, otherwise a hot restart will be attempted. • The C51 has experienced a power-on reset. • A hardware auto-reset is commanded. • GPS does not respond to communications. • The GPS self-test indicates an error. • The reset button was pressed when the status of the LED was different from the CONTINUOUS GREEN. Re-start Cold A cold re-start of the GPS involves the following stages. 1. Give the GPS a hardware reset by asserting its reset signal line. 2. Send the command $ PFEC, GPclr, 1. 3. Stop all periodic information messages. 4. Carry out a self-check. 5. Set the timing for periodic messages. 6. Set the PPS delay due to the cable length. 7. PPS Control Mode is set to always exit Proceed to set the position Hot Restart A hot restart of the GPS involves the following stages. 1. Give the GPS a hardware reset by asserting its reset signal line. 2. Send the command $ PFEC, GPclr, 2. 3. Stop all periodic information messages. 4. If the GPS fails to return response messages, perform a Cold Restart. 5. Carry out a self-check. 6. If the Self-Test indicates that the data returned is bad, perform a Cold Restart. 7. Set the timing for periodic messages. 8. Set the PPS delay due to the length of the cable. 9. Set the PPS Control Mode to always exit. 10. Proceed to establish the position.

Establishing the Position Once the TMU has established GPS control, its next objective is to establish its position. The GPS must determine its position before it is able to produce accurate temporal information. Following a hot restart, the TMU checks the GPS to determine if the position is already known and fixed (fixed observation mode) by the GPS. If the position is both known and fixed, the TMU reads the location from the GPS and proceeds normally. If the position is known but not fixed, the TMU read the location and proceed with the self-inspection as described in the next section. If the position is unknown (or in the case of a cold restart), the TMU proceeds with the establishment of its position. The TMU can obtain its position information (latitude, longitude and altitude) from one of the three sources, console input, non-volatile memory or self-inspection. The TMU stores its last known position in its non-volatile memory. To determine its current position, the TMU fixes the GPS to the estimated observation mode and fixes the initial position to its last known position. The TMU then proceeds with the self-inspection. The position can be entered manually through a console command. If this is done, the location replaces the location stored in the non-volatile memory, the GPS is set to the estimated observation mode and the data of the specified location is written to the GPS as the starting position. The TMU then proceeds with the self-inspection. When the position is unknown, there is no last location stored, and there is no console entry, the TMU completely depends on the self-inspection process. In this case, the GPS is set to the estimated observation mode, and the last known location is used as the starting position. Then the self-inspection process is allowed to correct the location information. If the last known location is too distant from the current location, it may take an additional amount of time for the TMU to establish its timing synchronization.

Self-inspection The TMU uses the self-inspection process to determine its exact position and, therefore, produce the most accurate timing. To determine the location, the TMU places the GPS within the observation mode is mistaken. In this mode, the GPS will determine its location from the satellites you can observe. While performing the self-inspection, the TMU will periodically read the location data from the GPS and compute an average location. Note that self-inspection does not prevent the TMU from taking out the time synchronization information once an initial location has been established by the GPS. The self-inspection process will continue up to 12 hours. At the end of the self-inspection period, the GPS will be set in the fixed observation mode and the computed average location will be fixed. The location determined by the self-inspection will replace the last known location stored in the non-volatile memory of the TMU. Averaging the Position While the self-inspection is performed, the TMU obtains the estimated location information once every minute in the $ GPGGA message. The TMU implements independent means for the parameters of longitude, latitude and altitude. The TMU implements a majority vote algorithm on the entire portion of each parameter and an average fractional portion. The entire portion of latitude and longitude includes the whole numbers of degrees and minutes. The entire portion of the latitude is the totality of hundreds of meters. The fractional portion is the fraction of minutes of latitude or longitude and altitude in module 100.

For whole portions, the majority vote algorithm observes the current reported value; the two values previously reported and the value of the last known location (LKL). If the entire portion of the reported values are in agreement with each other but at variance with the LKL, the LKL is rejected and replaced with the entire portion that agrees. For example, if the entire portion of the three most recent latitude values agree but disagree with the LKL, the entire portion of the LKL is replaced with the value on which they agree. The fractional portion of the LKL is replaced with the average of the fractional portions of the values that allow it. If the entire portion of the four values match, the fractional portion of the newest value is averaged within the LKL. If all the values coincide, except for the newest value, the fractional portion of the new value is not averaged in the LKL. The fractional portion is computed by a direct average of all contributions since the LKL was replaced the last time. The majority vote algorithm helps protect the average from the influence of anomalous locations. Additional algorithms or rules can be used to determine the stability of the location average and allow a faster change to the fixed position mode. Last Known Location The TMU stores its last known location in its non-volatile memory. This location is used to speed the establishment of the GPS timing output. To minimize non-volatile memory wear, the value will be updated only in one of the following conditions. • When a manual location is entered through a console command. • Upon completion of self-inspection processing. • Each time, the mean of the self-inspection differs from the location stored in more than one hundredth of a minute of latitude or longitude, or more than 10 meters of altitude. Antenna Cable Length The length of the cable to the GPS antenna can affect the accuracy of the PPS. The MTU requires that this value be entered manually during installation. The POSITION console command is provided for this purpose. The cable length will be stored in the non-volatile memory and will be used each time the GPS is configured.

Initiation Output to the BTS The TMU configures the GPS to start taking timing data immediately. The TMU configures the GPS to start taking out the PPS signal immediately. If the GPS is in the fixed observation mode, the PPS will be accurate as long as at least one satellite is available. If the GPS is in the estimated observation mode, the PPS will be accurate if 4 satellites are available to fix the position, the UTC parameter is available, the ephemeris data for the satellite is available, and the UTC computation is completed . The TMU will begin by sending the Periodic Pulse Report (GPppr) and the Position Dates Report (GPGGA) to the BTS immediately after initialization. As soon as the GPS PPS signal is available, the TMU will also begin supplying the PPS signal to the BTS. However, the GPS field of this GPppr will indicate "PPS Not synchronized" until all the alarm conditions marked with Green In termi tente in the above table are eliminated.

Supporting Greater Accuracy of Timing The TMU tries to support the highest possible timing precision by allowing the GPS to use its DGPS and TRAIM features. These features are enabled by default. Loss of Synchronization. Once the timing output has started satisfactorily, the occurrence of any critical alarm will cause the GPSS field to indicate, "PPS Not synchronized" until the condition is removed. Supported BTS Messages The TMU supports only messages that are mandatory. In addition, only the mandatory fields within these messages are supported. These messages are: 1. Periodic PPS Report 2. Periodic Data Report Periodic PPS Report (SPTP, GPppr) The TOW Normal Deviation field of the GPS of the Periodic PPS Report will be filled in as follows. • If 5 or more satellites are used for positioning, the field will be set to 50 nsec. • If 4 or less satellites are used for positioning, the field will be set to 100 nsec. • If there are no satellites available, the field of This is your GPS will be set to (3) PPS not synchronized Position Data (&GPGGA) Optional fields will not be provided; DGPS Dates Time, DGPS Station ID and check sum. Fields; DOP, Geoid of Al ti tude, and Geoid Unit are fixed in white. Operation of the Console Port The console port allows human interaction and monitoring of the TMU through an ASCII terminal or terminal simulation software. After the reset or by entering an escape at the command prompt, the console interface enters the display mode in the status bar. In this mode, alarms and other events that produce character strings of status are sent to the console. The console can collect these character strings to monitor the functioning and health of the TMU. When the enter key is pressed while in the status display mode, the console interface changes to the command entry mode and issues the command prompt. The command prompt reflects the current mode of operation of the TMU; initialization, test or functional. The commands can then be entered and the results sent to the console. All spontaneous alarms and the output of status strings will be inhibited while in command input mode. The available commands are limited to the mode of operation of the TMU. The operator can change the modes to obtain access to the desired commands. The operator You will be aware of the consequences of invoking any mode of operation of the TMU. 4. External Interface Unit (EIU) (illustrative embodiment) As discussed, to enable the synchronized operation of the GSM, a signal of 1 PPS can be provided to the BTS. For sites that already use an LMU with them, the 1 PPS signal may already be available in the existing LMUs (since the LMUs include built-in GPS receivers). However, for certain types of BTS equipment, the following may be true: • The 1 PPS signal needs to be converted to RS-422 signal levels for this application. • In addition to the conversion of 1 PPS, the timing information related to the 1 PPS signal on the RS-422 interface also needs to be sent using the proprietary protocol called by the manufacturer of the BTS equipment (eg Ericsson). The protocol conversion hardware unit that performs these two operations is called EIU and is applicable to sites that already have an LMU used there. Impact on the GBE and the connectivity of the piE card • The EIU will connect to the RS-232 serial port of 9 terminals in the LMU. This is the same port that is also used to connect GBE (ground-based electronics) to AOA uses. Therefore, in its present form the GBE and the EIU can not be used together. Therefore, the installation of EIU preludes the use of AOA. The solution to this problem is to use a TMU instead of an EIU in the cases where an AOA is needed. Similar to the previous problem is the case of using the environment card (which is sometimes called the mini-environment card, or mE card). It also uses the same port and can not be used where the EIU is used.

Architecture Figure 6 represents an example architecture for an EIU, which shows the internal architecture and external interfaces of the EIU. It connects the 9 terminals of the serial port and the 1 PPS on the LMU side, and converts both of these interfaces to RS-422 signal levels for connection to the BTS. The signals of 1 PPS and serial data are broadcast to the 4 ports that comprise a quad output connector. Each output port provides both a serial data output and 1 PPS at RS-422 signal levels. LMU-N interface The illustrative EIU receives the timing messages from its LMU interface in the RS-232 signal levels / format. The outputs of the RS-232 signal connection terminals will be as shown in Table 1. The EIU receives the 1 PPS signal from the LMU through its 1 PPS port. The 1 PPS EIU port appears as a 50 ohm load from the outside.

End Description name 1 Signal 1,7,8,9 NC 2 RX Port 1 receiver, from the PC to the processor Table: Outputs from the RS-232 Connector Terminals BTS Interface The EIU transmits the synchronization data messages from the LMU and the 1PPS signal to the BTS at RS-422 signal levels as shown in Figure 4. The interface of the synchronization data with the BTS is a serial communications link. The 1PPS signal will have a frequency of 1 Hz and an accuracy of 100 ns RMS in the EIU output port of 1 PPS with respect to the UTC timing. The outputs of the signal connection terminals for each port will be as shown in the following table.

Table: RS-422 Single Port Terminal Outputs Series Communications Link The physical layer of the serial communications link is based on an RS-422 UART. The specific features are as follows: • RS-422 interface with 100-ohm termination on the BTS • 9600 bits / sec • No parity • One start bit • A length of 8 bits of data • One stop bit One PPS One transmitter RS-422 drains the signal from a PPS in the EIU. The rise time from 10 to 90% will be less than 10 ns at the exit of the EIU. The BTS has a built-in 100 Ohm termination. 5. Conclusion The true scope of the present invention is not limited to the illustrative and preferred embodiments currently described herein. For example, the above description of the Wireless Location System uses explanatory terms, such as LMU, TMU, BTS, BSC, SMLC, and the like, which should not be construed so as to limit the scope of protection of the following claims, or by the otherwise implies that the inventive aspects of the Wireless Location System are limit to the particular methods and apparatus described. In addition, as will be understood by those skilled in the art, many of the inventive aspects described in this document can be applied in location systems that are not based on TDOA techniques. In such non-TDOA systems, the SMLC described above would not be required to perform the TDOA calculations. Similarly, the invention is not limited to systems that employ LMUs built in a particular way, or systems that employ specific types of receivers, computers, signal processors, etc. The LMU, SMLC, etc., are essentially data collection and processing devices that can take a variety of forms without departing from the inventive concepts described in this document. Given the rapid decline in the costs of digital signal processing and other processing functions, it is easily possible, for example, to transfer processing for a particular function from one of the functional elements (such as the SMLC) described in this document to another functional element (such as the LMU) without changing the inventive operation of the system. In many cases, the implementation site (ie, the functional element) described in this document is merely a designer's preference and not a hardware requirement. Accordingly, no attempt is made to limit the scope of protection of the following claims to the specific embodiments described above, except as they may be expressly limited as such. In addition, any reference in this document to control channels or voice channels will refer to all types of control or voice channels, whatever the preferred terminology for a particular air interface. In addition, there are many types of air interfaces (eg, IS-95 CDMA, CDMA 2000, and WCDMA UMTS) used worldwide, and unless otherwise indicated, there is no attempt to exclude any air interface from the inventive concepts described in this specification. Moreover, those skilled in the art will recognize other interfaces used in other parts that are derived or similar in kind to those described above.

Claims (23)

1. In a wireless location solution superimposed on the network for a wireless communication system comprising a network of Base Transceiver Stations (BTS), a method of improving the spectrum, comprising synchronizing a plurality of BTS with a timing signal, wherein at least one BTS is provided with said timing signal by a Timing Measurement Unit (TMU).

2. A method as recited in claim 1, wherein said wireless communication system comprises a GSM communications network.

3. A method as recited in claim 1, wherein said wireless communication system comprises a UMTS communications network.

4. A method as recited in any of claims 1-3, wherein the timing signal is provided to each BTS by a Location Measurement Unit (LMU) or by a Timing Measurement Unit (TMU).

5. A method as recited in claim 4, wherein each LMU and TMU comprises a GPS-based timing reference module and means for generating a periodic timing signal that is synchronized to a pre-specified degree of accuracy. with signs of timing generated by each of the other LMU and TMU.

6. A method as recited in claim 5, wherein the LMUs are used to measure the timing of the uplink and / or downlink signals in the cellular network in support of location techniques.

7. A method as recited in claim 6, wherein the LMU and TMU distribute the timing signals, including a periodic electrical pulse as well as a timing description information.

8. A method as recited in claim 7, wherein the electrical pulse format and the timing description information are modified by hardware and software to suit the formats required for the various types of BTS.

9. A method as recited in claim 8, wherein BTSs with LMUs located together receive a synchronization signal at little or no hardware cost, and in which BTS sites not equipped with an LMU are equipped with a TMU having the sole function of providing BTS timing signals in the same formats that are provided by the LMUs, in which the timing signals provided by the TMUs are synchronous with the signals provided by the LMUs and the TMU of only The timing has a lower cost than the LMU since it does not support the measurement functions of the uplink or downlink signals.

10. A wireless location system superimposed on the network for use in association with a wireless communication system comprising a network of Base Transceiver Stations (BTS), comprising a plurality of Location Measurement Units (LMU) and at least a Timing Measuring Unit (TMU), and a mechanism for synchronizing a plurality of BTS with a timing signal, wherein at least one BTS is provided with said timing signal by said, at least one, TMU.

11. A wireless location system as mentioned in claim 10, wherein said wireless communication system comprises a GSM communications network.

12. A wireless location system as mentioned in claim 10, wherein said wireless communication system comprises a UMTS communications network.

13. A wireless location system as recited in any of claims 10-12, wherein the timing signal is provided to each BTS by a Location Measurement Unit (LMU) or a Timing Measurement Unit (TMU). ).

14. A wireless location system as recited in claim 13, wherein each LMU and each TMU comprises a timing based reference module. in GPS and a means for generating a periodic timing signal that is synchronized within a pre-specified degree of precision with the timing signals generated by each of the other LMUs and TMUs.

15. A wireless location system as recited in claim 14, wherein the LMUs are used to measure the timing of the uplink and / or downlink signals in the cellular network in support of location techniques.

16. A wireless location system as mentioned in claim 15, wherein the LMUs and TMUs distribute timing signals, including a periodic electrical pulse as well as timing description information.

17. A wireless location system as mentioned in claim 16, wherein the electrical pulse format and the timing description information are modified by hardware and software to suit the formats required by the various types of BTS.

18. A wireless location system as recited in claim 17, wherein BTSs with LMUs located together receive a synchronization signal at a small cost or without hardware cost, and in which the BTS sites not equipped with an LMU are equipped with a TMU that has the sole function of providing signals BTS timing in the same formats that are provided by the LMUs, in which the timing signals provided by the TMUs are synchronized with the signals provided with the LMUs and the time-only TMUs have a lower cost than the LMUs because they do not they support the measurement functions of uplink or downlink signals.

19. A wireless location system for use in association with a wireless communication system comprising a network of Base Transceiver Stations (BTS), comprising a plurality of Location Measurement Units (LMU) and at least one Measurement Unit Timing (TMU), wherein said LMUs and at least one TMU are operative to synchronize a plurality of BTS with a timing signal, wherein at least one of said BTS is provided with said timing signal by said, minus one, TMU; and wherein each LMU and each TMU comprises a GPS-based timing reference module and means for generating timing description information and a periodic timing signal that is synchronized with the timing signals generated by each of the other LMUs and TMU.

20. A wireless location system as mentioned in claim 19, wherein BTS with LMUs located together receive a synchronization signal at little or no hardware cost, and in which the BTS sites not equipped with an LMU are equipped with a TMU that has the unique function of providing BTS timing signals in the same formats that are provided by the LMUs, in which the timing signals provided by the TMUs are synchronized with the signals provided by the LMUs and the TMU have a lower cost than the LMU because it does not support the functions of measuring the signals of the uplink or the downlink.

21. A wireless location system as mentioned in claim 20, wherein said wireless communication system comprises a GSM communications network.

22. A wireless location system as mentioned in claim 20, wherein said wireless communication system comprises a UMTS communications network.

23. A wireless location system as mentioned in claim 20, wherein the format of the timing signal and the timing description information are modified by hardware and software to suit the formats required by the various types of BTS. . Summary of the Invention In a wireless network leased solution for a GSM or UMTS communications network, the use of spectrum can be made much more efficient by synchronizing the BTSs, which may require distributing a time signal for all BTSs or installing a BTS. unit of time based on satellite, in each site. The present invention provides an architecture in which Location Measurement Units (LMUs) are installed in some or all of the BTS sites for the purpose of locating wireless devices. The LMUs are used to measure the timing of the different up and / or down signals in the cellular network in support of several lease techniques. These LMUs can include a GPS-based timing reference module, which can be used to synchronize the time bases of all LMUs. To reduce the total cost of synchronizing BTSs, the LMU distributes timing signals, including a periodic electrical pulse as well as information on the time description, on a serial or other interface, which is available for other nodes to be used for synchronization. . The format of the electrical pulse and information on the time description is modified through hardware and software to adapt the various formats required by various types of BTS. For example, BTSs with co-located LMUs can receive a synchronization signal at little or no hardware cost. The External Interface Unit (EIU) described here can be used to adapt to various BTS hardware formats. For BTS sites not equipped with an LMU, a Timing Measurement Unit (TMU) can be used. The TMU has the only function to provide BTS timing signals in the same formats as those provided by the LMUs. The timing signals provided by the TMUs are synchronized with the signals provided by the LMUs. This TMU that is only for timing has a lower cost than the LMU because it does not support the measurement functions of the ascending or descending signal. This proposal allows the cellular operator to synchronize the BTSs at a relatively low cost.