Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/06—Reselecting a communication resource in the serving access point
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W36/00—Hand-off or reselection arrangements
  • H04W36/08—Reselecting an access point
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W72/00—Local resource management
  • H04W72/04—Wireless resource allocation

Definitions

• This invention relates generally to cellular communications and applications, and more particularly to a method of providing Time Of Arrival (TOA) positioning data that minimizes the use of traffic channels within the wireless network.
• TOA Time Of Arrival
• the increased demand for wireless (or cellular) communications has resulted in advanced communications systems capable of providing a high quality of service to an increasing number of users.
• the systems that have emerged include analog systems such as the Advanced Mobile Phone System (AMPS), and digital systems such as the Global System for Mobile Communications (GSM) and Digital AMPS (D-AMPS).
• AMPS Advanced Mobile Phone System
• GSM Global System for Mobile Communications
• D-AMPS Digital AMPS
• FDMA Frequency Division Multiple Access
• TDMA Time Division Multiple Access
• TDMA FDMA TDMA FDMA
• a 25 MHZ bandwidth can be divided into 124 carrier frequencies spaced 200 kHz apart, with one or more carrier frequencies assigned to each Base Station in the network.
• Each of the carrier frequencies can be divided in time using a TDMA scheme to define logical channels.
• Channels in turn, may be divided into dedicated subchannels which are allocated to a mobile station.
• a traffic channel also commonly called a communication or transmission channel, is used to carry speech and data (typically non- command) signals over the network.
• Traffic channels are defined in GSM using a multi-frame, or a group of 26 separate TDMA frames. With 26 frames, typically 24 will be used for speech or data, one as a control channel, and one will be unused.
• Control channels also commonly called signaling or common channels
• the common channels are used by idle mode mobile to exchange the signaling information required to change to dedicated mode.
• Mobile systems in the dedicated mode monitor the radio transmissions from the serving base transceiver station for handover and other information.
• the common channels are defined within a 51 -frame multi-frame, so that dedicated mobile stations using the 26-frame multi-frame Traffic Channel (TCH) structure can still monitor control channels.
• TCH Traffic Channel
• CDMA Code Division Multiple Access
• FDMA Frequency Division Multiple Access
• FCC Federal Communications Commission
• the Time of Arrival (TOA) positioning mechanism is based on collecting time of arrival (TOA) measurements computed from access bursts generated by the mobile station. Access bursts are generated during either inter-cell or intra-cell handover and are received and measured by both serving and neighboring base transceiver stations (BTSs). Utilizing access bursts to position the mobile requires additional hardware at the listening BTSs to accurately measure the TOA of the bursts.
• BTSs serving and neighboring base transceiver stations
• a Mobile Station also referred to as a mobile radio, mobile, or mobile handset, which is in idle mode is first assigned a signaling channel before paging, authentication and ciphering is completed.
• the Serving Mobile Location Center (SMLC) then instructs the Base Station Controller (BSC) through the Mobile Switching Center (MSC) to assign a first traffic channel.
• BSC Base Station Controller
• MSC Mobile Switching Center
• This process if often referred to as positioning call set-up.
• the SMLC then directs the BSC to perform a positioning handover (i.e., fake handover) to another traffic channel in order to send a handover access burst from the MS to an array of Location Management Units (LMUs) which obtain the TOA positioning of the MS.
• LMUs Location Management Units
• the present invention provides a method in a wireless communications network of providing Time of Arrival (TOA) positioning data that minimizes the use of traffic channels within the network.
• TOA Time of Arrival
• the present invention is providing a new solution for TOA positioning where the idle MS is first assigned a signaling channel and then directly handed over to a traffic channel.
• the Serving Mobile Location Center (SMLC) instructs the Base Station Controller (BSC) via the Mobile Serving Center (MSC) to perform positioning handover (i.e., fake handover) directly from the signaling channel to a traffic channel reserved for that purpose.
• BSC Base Station Controller
• MSC Mobile Serving Center
• Decreased load on the network without tying up unnecessary network resources is one advantage provided by the present invention.
• Disclosed in one embodiment is a method of providing Time of Arrival (TOA) positioning data that minimizes the use of traffic channels within a wireless communications network.
• the method comprises the steps of assigning a signaling channel to an idle MS within the network and causing a handover of the mobile station directly from the signaling channel to a traffic channel.
• a SMLC in communication with the BSC instructs the BSC to perform a handover. That is, the SMLC transmits a positioning handover instruction to the BSC via the MSC.
• the BSC serving the MS then performs a handover from the signaling channel to the traffic channel.
• the method can further comprise the steps of causing the MS to generate an access burst during handover.
• the step is performed by sending a handover access burst from the MS to a set of Location Management Units (LMUs) used in one embodiment, the access burst is utilized to provide TOA positioning data for the MS.
• LMUs Location Management Units
• the method comprises the step of causing a Location Services (LCS) Information Request (TOA) to be transmitted from the SMLC to the MSC.
• LCS Location Services
• TOA Location Information Request
• TOA Location Information Command
• This step can be performed by reporting Location Information (TOA) to the MSC.
• the reporting step is then followed by the step of sending a LCS Information Report (TOA) from the MSC to the SMLC.
• the method can further comprise the step of causing a LCS Information Request to be transmitted from the MSC to a plurality of Location Management Units (LMUs) adapted to measure TOA access bursts generated by the MS.
• LMUs Location Management Units
• the LMUs are then adapted to relay a LCS Information Response to the MSC.
• the SMLC then performs a location acknowledgment which is then sent to the MSC.
• the method can also comprise the steps of assigning a Stand Alone
• Dedicated Control Channel to the MS, transmitting a handover command to the MS, and performing a handover of the MS from the SDCCH to a traffic channel and causing the MS to generate an access burst during the handover step so that the plurality of LMUs can measure the TOA of the access burst for positioning of the MS.
• Such steps are accompanied by the step of assigning a timer for generation of the access burst during handover. If during the time allocated to the timer expires prior to a successful handover, a handover failure signal is transmitted from the MS to the BTS which then communicates with the BSC for further instruction.
• a technical advantage of the present invention includes less use of traffic channels during positioning handover. Thus, the load on the network is reduced.
• Another technical advantage is that intra-cell handover is performed with less complexity and less time for each TOA positioning request from an MS in idle mode.
• Figure 2 shows the logical architecture for TOA positioning method according to one embodiment
• Figure 3a portrays channeling while mobile in idle mode
• Figure 3b shows channeling while mobile in dedicated mode
• Figure 4 illustrates signaling during TOA positioning call set-up
• Figure 5 shows the present invention according to one embodiment
• Figure 6 is a signaling diagram illustrating the step for positioning the mobile station using a Time of Arrival (TOA) based positioning method.
• TOA Time of Arrival
• FIG. 1 illustrates a GSM network 10 in which the present invention may be used.
• the mobile station 12 comp ⁇ ses mobile equipment 22, comprising a terminal such as a cellular telephone, and a Subscriber Identity Module (SIM) 24.
• SIM 24 contains an International Mobile Subscriber Identity (IMSI) that identifies the subscriber to the GSM network 10, a secret key for authentication, and other information.
• Mobile equipment 22 is uniquely identified by the International Mobile Equipment Identity (IMEI).
• IMEI International Mobile Equipment Identity
• the IMEI and the IMSI are independent, thereby allowing the user personal mobility.
• the BSS 14 comprises two parts, the Base Transceiver Station (BTS) 26 and the Base Station Controller (BSC) 28.
• BTS Base Transceiver Station
• BSC Base Station Controller
• BTS 26 communicates across the standardized Abis interface 30 with BSC 28, allowing operation between components.
• BTS 26 houses radio transceivers that define a cell and handles the radio-link protocols with the mobile station 12. In a large urban area, there may be a large number of BTSs 26 deployed.
• BSC 28 manages the radio resources for one or more BTSs 26, and there may be several BSCs 28 within a BSS 14.
• BSC 28 handles radio-channel setup, frequency hopping, and handovers.
• BSC 28 provides a connection between the mobile station 12 and the MSC 30 of network Subsystem 16.
• the central component of the network subsystem 16 is the Mobile Switching Center (MSC) 30, which acts like a normal switching node of the Public Switched Telephone Network (PSTN), and provides all the functionality needed to handle a mobile subscriber, such as registration, authentication, location updating, handovers, and call routing to a roaming subscriber. These services are provided in conjunction with several functional entities, which together form the network subsystem 16.
• MSC Mobile Switching Center
• the MSC 30 provides the connection to the fixed networks 32 which may include the PSTN or an Integrated Service Digital Network (ISDN), for example.
• the Home Location Register (HLR) 34 and Visitor Location Register (VLR) 36, together with the MSC 30 provide call routing and roaming capabilities for the GSM network 10.
• HLR 34 contains administrative information of the subscriber registered in the corresponding GSM network 10, along with the current location of the mobile station 12.
• the VLR 36 contains selected administrative information from HLR 34 necessary for call control and provisioning of the subscriber services for each mobile currently located in the geographical area controlled by the VLR 36.
• Other registers are used for authentication and security purposes and the network subsystem 16.
• the present invention provides a method for positioning of the mobile station 12 within the coverage area of the GSM network 10 or other Public Land Mobile Network (PLMN) that is more efficient than prior art positioning methods.
• the system for TOA positioning is shown and denoted generally as 40 in Figure 2.
• the system 40 is capable of delivering Time Of Arrival (TOA) positioning data for at least one externally operated and maintained requesting agent 54.
• the requesting agent 54 sends a request for positioning via a Gateway Mobile Location Center (GMLC) 52 which provides an interface for requesting agent 54 to the system 40.
• GMLC Gateway Mobile Location Center
• the GMLC 52 also contains functionality required to support a Location Services (LCS) function that interacts with other entities within the system 40 to determine the location of the MS 12.
• LCS Location Services
• the GMLC 52 provides the entry node for an external LCS client to use to access the PLMN 46.
• the GMLC 52 may request routing information from the Home location Register (HLR) 36. After registration authorization, the GMLC 52 sends a positioning request to and receives location data from the VMSC 30. Once the positioning request has been processed by the VMSC 30, the VMSC 30 communicates with the BSC 28 and the Serving Mobile Location Center (SMLC) 50.
• the SMLC 50 contains the algorithms, methods and systems required to support LCS.
• the SMLC 50 manages the overall coordination and scheduling of resources required to perform positioning of a the MS 12. It also calculates the final location estimate within a specified level of accuracy.
• the SMLC 50 controls a number of LMUs 48 for the purpose of obtaining radio interface measurements to locate or help locate the MS 12 in the area served by the system 40.
• the SMLC 50 is administered with the capabilities and types of measurement produced by each of its LMUs 48.
• LMU 48 is representative of a plurality of LMUs which would normally be used for TOA measurements.
• Signaling between an SMLC 50 and LMU 48 is transferred via the MSC 30 serving the LMU 48.
• the measurements returned by an LMU 48 to an SMLC 50 have a generic status in being usable for more than one positioning method.
• the functionality of the SMLC 50 and GMLC 52 may be combined in the same physical node, combined in existing physical nodes, or reside in different nodes of the system 40.
• the SMLC 50 and GLMC 52 are not interconnected, but communications are provided through the VMSC 30. When the VMSC 30 and GMLC 52 are in different PLMNs 46, they are interconnected through an air interface.
• a positioning handover depicted generally as 60, according to the prior art, is shown as involving a change from a signaling channel (e.g., Stand Alone Dedicated Channel (SDCCH)) 62 to a first traffic channel (TCH) 64, and then to a second traffic channel 66.
• a signaling channel e.g., Stand Alone Dedicated Channel (SDCCH)
• TCH traffic channel
• a mobile station 12 is assigned a SDCCH 62 within the network 10.
• a handover of the mobile station 12 is then preformed from the signaling channel to a reserved traffic channel 64.
• Positioning handover can also occur when the mobile station is placed in dedicated mode, as shown in Figure 3b.
• the traffic channel 64 is already assigned so that assignment to a second traffic channel 66 occurs directly during the handover. Therefore, a second traffic channel 66 is reserved and assigned for positioning handover by the system 40.
• the access burst 68 generated by the MS 12 during the handover is utilized to provide TOA positioning data for
• the existing TOA positioning method allows an MS 12 in idle mode to first be assigned a signaling channel (SDCCH) before paging, authentication and ciphering is complete.
• the SMLC 50 instructs the BSC 28 serving the MS 12 via the MSC 30 to set up a traffic channel 64 (or positioning call set-up).
• the SMLC 50 then instructs the BSC 28 to perform positioning handover (or fake handover) to another traffic channel 66 for sending handover access burst 68 from the MS 12 to the LMUs 48 utilized for measuring the TOA of the access burst.
• This method of performing positioning handover is inefficient since it utilizes the resources of two traffic channels, 64 and 66.
• the current TOA positioning provides for setting up a positioning call before sending a LCS Information Command message for TOA positioning for a MS 12 in idle mode.
• Call set-up 70 is initiated (step 72) where the SMLC 50 is adapted to assign a traffic channel 64 which is then communicated to the MSC 30. The assignment of the traffic channel 64 is then verified (step 74) during a message sent from said MSC 30 to the BSC 28.
• channel activation is performed by the BSC 28 serving the MS 12 and transmitted to the BTS 26.
• the BTS 26 is then adapted to send a channel activation acknowledgment to the BSC 28 (step 78).
• An assignment command is then transmitted from the BSC 28 to the MS 12 (step 80).
• An establishment indication is then performed and sent from the BTS 26 to the BSC 28.
• completion of the assignment is performed (step 84) by the MS 12.
• An assignment traffic channel acknowledgment is then sent from the MSC 30 to the SMLC 50.
• a method of providing Time of Arrival (TOA) positioning data that minimizes the use of traffic channels within the network is illustrated.
• a signaling channel 62 is assigned to an idle mobile station 12 within the network.
• a handover 68 of the MS 12 is then performed directly from the signaling channel 62 to a traffic channel 66.
• the MS 12 is then adapted to generate an access burst during the handover 68, whereas the access burst is utilized to provide TOA positioning data for the MS 12.
• the method of the present invention results in saving the assignment of a second traffic channel during positioning handover (68) and therefore reducing the use of the traffic channels within a network. Furthermore, an intra-cell handover to the same channel, or from a signaling channel to a traffic channel without the need for an additional assignment of a second traffic channel is achieved. This results in less complexity of TOA positioning method, less time for each TOA positioning request from an MS in idle mode, and less signals for TOA positioning method.
• FIG. 6 is a signaling diagram illustrating the step for positioning the MS 12 using a Time of Arrival (TOA) based positioning method, according to one embodiment of the invention.
• the Serving Mobile Location Center (SMLC) 50 Upon reception of a positioning request from a Location Services (LCS), the Serving Mobile Location Center (SMLC) 50 then transmits (step 105) the LCS information request (TOA) to the Mobile Station Controller (MSC) 30.
• the SMLC 50 is responsible for carrying out the positioning request.
• more than one SMLC 50 may be located within each PLMN 46 of the network.
• the MSC 30 (step 110) sends a location information command for TOA positioning to the Base Station Controller (BSC) 28 serving said mobile station.
• BSC 28 then sends a location information report for TOA positioning to the MS 12 controller 30 (step 115).
• the location information report for TOA positioning is then transmitted from the mobile station controller 30 to the SMLC 50 (step 120),
• an LCS information request is then sent from the SMLC 50 to the MSC 30 (step 125).
• the LCS information request (step 130) is then transmitted from the MSC 30 to a plurality of Location Management Units 48.
• the LMUS 48 are responsible for obtaining positioning measurements and providing these measurements to the SMLC 50 for use in calculating location of the MS 12. All communication to and from the LMUS 48 are sent over the air interface. Therefore, each LMU 48 is in wireless communication with an associated Base Station Controller (BTS)
• BTS Base Station Controller
• the SMLC 50 is responsible for selecting which LMUS 48 should obtain the positioning measurements. As such, it is the SMLC 50 which sends LCS information request messages to each of these selected LMUS 48 (step 130).
• a positioning handover occurs when the BSC 28 sends a handover (HO) command message to the MS 12 (step 135), instructing the MS 12 to perform a handover to the serving BTS 26 or a target BTS (not shown) on a specified channel.
• the handover command message also indicates the TDMA frame number that the MS 12 should begin sending access bursts.
• the LMUs 48 make their a Time of Arrival (TOA) measurements of the access burst.
• TOA Time of Arrival
• the BTS 26 will not respond to the handover access message, and the MS 12 will stop sending the access burst upon the expiration of a timer (step 150) within the MS 12. Thereafter, the MS 12 returns to the old channel that it was assigned to, and sends a handover failure message to the BSC 28 (step 155).
• the TOA measurements are forwarded via a LCS information response (step 165) from the LMUS 48 to the SMLC 50 for use in assisting the calculation of the geographical location of the MS 12.
• a LCS information response step 165
• the SMLC 50 calculates the location of the MS 12
• this location is transmitted to the LCS client that requested the positioning.
• the requesting client could be located within the MS 12, within the MSC 30 or could be in external node 54 such as an Intelligent Location (IN) node.
• an acknowledgment of location performance is transmitted (step 170) from the SMLC 50 to the MSC 30.

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• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)

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• 2000
  • 2000-08-31 WO PCT/US2000/024202 patent/WO2001019122A1/en not_active Application Discontinuation
  • 2000-08-31 KR KR1020027002878A patent/KR20020057954A/ko not_active Application Discontinuation
  • 2000-08-31 CN CN 00814850 patent/CN1382361A/zh active Pending
  • 2000-08-31 AU AU73459/00A patent/AU7345900A/en not_active Abandoned
  • 2000-08-31 EP EP00961517A patent/EP1212917A1/de not_active Withdrawn
  • 2000-08-31 BR BR0013736-7A patent/BR0013736A/pt not_active Withdrawn

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