Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2001-12-26
2003-07-22
Kincaid, Lester G. (Department: 2685)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S404200, C455S445000, C455S067150
Reexamination Certificate
active
06597916
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the determination of the location of a wireless device. More particularly, the present invention relates to the determination of the location of a wireless device with a hybrid system and method that utilizes BSS and NSS subsystems of a wireless communications network.
2. Description of Related Art
Determination of the precise geographic location of a wireless device, such as a cellular phone or personal communications services (PCS) device for example, is a capability that is now being developed and standardized for today's PCS, cellular and satellite based wireless networks. Deployment of this capability is required, for example, in the US to fulfill the FCC's phase
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requirements for E911 calls. Known strategies to obtain a geographic location typically employ either (a) an overlay solution in which the entities that perform location measurement and location computation are external to the wireless communications network and communicate using external or externally available transmission and switching capabilities or (b) an integrated solution in which these entities form part of the wireless network and make use of communication capabilities provided within the network.
A typical terrestrial wireless communications network (for example cellular or PCS) consists of three major subsystems: the Base Station Subsystem (BSS), Network SubSystem (NSS) and Operations and Maintenance Subsystem (OMS). Wireless communication networks are typically categorized into “generations” according to the technology being implemented. For example, the generation of a particular wireless technology is now commonly accepted in the art with first generation corresponding to systems supporting an analog radio interface (e.g. AMPS), second generation supporting a digital radio interface with a peak bit rate for any application of around 64 kbps (e.g. GSM, PCS1900, CDMA IS-95, TDMA) and third generation supporting a peak bit rate for applications of at least 384 kbps (e.g. CDMA2000, WCDMA).
In many existing first and second generation wireless technologies (e.g. GSM, CDMA IS-95, TDMA, AMPS), the BSS includes logically or physically distinct entities to serve as a Base Station Controller (BSC), Base Station Transceiver Station (BTS) and a Transcoding and Rate Adaptation Unit (TRAU). Logically distinct units may be physically supported on a common hardware platform while retaining their distinct functions. The NSS contains logically or physically distinct entities to serve as a Mobile Switching Center (MSC), Visitor Location Register (VLR), Home Location Register (HLR), Authentication Center (AC), Equipment Identification Register (EIR). The functions of these different entities are known to those of ordinary skill in the art of wireless networks. In simple terms, the BSS manages the radio aspects of the network whereas the NSS manages mobility, call control and supplementary services (e.g. call forwarding, short message service). For second generation systems supporting packet data communication—e.g. General Packet Radio Service (GPRS)—other entities are included in the NSS such a Serving GPRS Support Node (SGSN) and Gateway GPRS Support Node (GGSN). For third generation systems, entities are further modified and/or new ones are introduced in the NSS and BSS. The constituents of the BSS and NSS for third generation systems are subject to future developments in technology and standards.
Typical models of a geographic location service in a wireless network (e.g. as being deployed for FCC E911 phase
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) assume that some external user, sometimes termed a “client”, interacts with the wireless network to obtain the geographic location of a Wireless Mobile Subscriber (MS, or “wireless device”) either on demand or when some predetermined event occurs (e.g. the origination of an E911 call). The wireless network then instigates the procedures that will lead to a geographic location estimate for the particular MS.
In order to obtain an accurate geographic location for an MS, radio related measurements must generally be taken involving either (or in some cases both of) the uplink radio transmission from the MS or (and) downlink radio transmission to the MS. The resulting measurements, normally made over a short time period (e.g. a few milliseconds to a few seconds), then form the input to a computational algorithm from which a geographic position (e.g. latitude and longitude coordinates) is produced.
Examples of existing positioning methods include Time Of Arrival (TOA), Time Difference Of Arrival (TDOA), Angle of Arrival (AOA), Timing Advance (TA), Observed Time Difference (OTD), Enhanced Observed Time Difference (EOTD), Observed Time Difference Of Arrival (OTDOA), Global Positioning System (GPS). These methods can be allocated among the following categories (in some cases with different variants of the same method appearing in more than one category):
(a) Network Based (e.g. TOA, TDOA, TA, AOA)—measurements of uplink MS radio transmissions are made by the network with position computation in the network.
(b) Mobile Assisted (e.g. OTD, E-OTD, OTDOA, GPS)—measurements of downlink radio transmission (emanating from the wireless network or from other sources like GPS satellites) are made by the MS. These measurements are then provided to the network where position computation occurs.
(c) Mobile Based (e.g. OTD, E-OTD, OTDOA, GPS)—measurements of downlink radio transmission (emanating from the wireless network or from other sources like GPS satellites) are made by the MS. Position computation using these measurements is then also performed by the MS.
In order to support the above categories, two special functional entities are required in addition to those already existing in the wireless network and MS: a location measurement entity (LME) to perform radio related measurements and a location computation entity (LCE) to compute a geographic location estimate from the measurements provided by the LMEs. These terms are generic and correspond to certain more specific entities in particular wireless technologies. Thus, for example, the LCE can correspond to both the Positioning Determining Entity (PDE) used in ANSI-41 based networks (e.g. TDMA, CDMA IS-95) and the Serving Mobile Location Center (SMLC) defined for GSM and PCS1900 networks. Similarly, the LME can correspond to the radio elements of a Positioning Determining Entity (PDE) in ANSI-41 networks and to the Location Measurement Unit (LMU) defined for PCS1900 and GSM networks. Further, the LME typically may be accessed using only wireline facilities or may be accessed by wireline and wireless means (e.g. RF, microwave) including wireless access similar to or the same as that supported for normal MSs within the wireless network.
One known architectural solution for communicating geographic location information between the LCE and the LME and/or MS is known as an “NSS solution”. The LCE is typically attached and directly accessible only to the NSS. Disadvantageously, this architecture relies on the NSS to support signaling between the LCE and both the LME and MS. Thus, any hardware and/or software limitations and failures in the NSS can negatively impact the timely and accurate flow of information. There may also be signaling limitations in the NSS that restrict the volume of data that can be transferred between an LCE and an LME and between an LCE and an MS per unit of time, resulting in a limitation on the number of location attempts that can be performed per unit of time. This limitation may also produce increased delay for location attempts that do succeed due to the extra signaling delays in the NSS plus any queuing delay when signaling throughput limits are reached. An example of a location application for which these limitations may be significant is “home zone billing”—a service in which an MS subscriber is billed at a special (e.g. flat or reduced) rate when making or receiving calls within a predefined home zone area. To verify whether the MS actually is wi
Kincaid Lester G.
Siemens Information and Communication Networks Inc.
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