1、ATIS-0700039 ATIS Standard on Guidelines for Emergency Call Location Selection and Reporting by Originating Networks Alliance for Telecommunications Industry Solutions Approved May 16, 2018 Abstract A voluntary agreement for improving location accuracy for emergency calls was developed and signed on
2、 November 14, 2014, by APCO, NENA, AT see Table 5.1). It is likely that in use case 4 (see Table 5.3) a building or place type of RSS or RMS will correspond to a Class of Service value of WDL2, whereas a building or place type of OBM will correspond to a Class of Service value of WDL1 (see Clause 5.
3、1.8). Dispatchable Location Test Bed testing will further clarify these relationships. NOTE: The use of serviceFlag is an inherent part of the LS filtering process. It is likely that in use case 4 with building or place type RSS or RMS will correspond to WDL2. In use case 4 with a building or place
4、type of OBM will correspond to WDL1. Dispatchable Location Test Bed testing will further clarify these relationships. NOTE: Any Use Case could be found within any Place Type. e. Geodetic location obtained from the location determination equipment. f. Serving cell geo coordinates from the cellular ne
5、twork. g. Wi-Fi Access Point. a. MAC Address. i. servingFlag. ii. RSSI. iii. Round trip delay. iv. Channel number. h. Bluetooth beacon (BT-PDA). a. RSSI. ATIS-0700039 9 5.1.6 LS Messaging toward the GMLC (Step 6) Once the LS has obtained the geodetic location and potentially determined a Dispatchabl
6、e Location, it forwards that information to the GMLC through the MME. Attributes forwarded to the GMLC: a. Dispatchable Location (in PIDF-LO from NEAD). b. Method of NEAD-CVC, NEAD-DL1 or NEAD-DL2 (generated by the LS). c. Place Type (in PIDF-LO from NEAD). d. Geodetic location obtained from the loc
7、ation determination equipment. e. Positioning Method of obtaining geodetic location e.g., Assisted Global Positioning System (AGPS). 5.1.7 E2 Response to the Legacy ALI (Step 7) Once the GMLC receives the location information from the LS, it must map the geodetic location and Dispatchable Location i
8、nto the E2 format. It then must determine a Position Source depending upon the information it obtained. The following shows an example of the Location Description parameter populated in the E2 response using example 4 in Table 5.2. 896 N Main ANYTOWN FLOOR 5 ROOM 501 If the XML elements associated w
9、ith the Dispatchable Location exceed the associated E2 element length, the GMLC truncates the string from right to left (left justified). The GMLC populates the Position Source based on a mapping from the location method token value provided in the PIDF-LO from the LS. The GMLC maps a method token v
10、alue of NEAD-CVC to Position Source 55, a location method token value of NEAD-DL1 to Position Source 56, and a location method token value of NEAD-DL2 to Position Source 57. 5.1.8 ALI to PSAP Location Conveyance (Step 8) Once the ALI receives the geodetic location and Dispatchable Location in the E2
11、 response, it returns those along with Class of Service to the PSAP in response to an ALI query. It will convert the Position Source it received in the E2 response into the corresponding Class of Service. If elements received in the E2 response are longer than can be utilized by the PSAP CPE, the AL
12、I truncates the string from right to left (left justified). 6 Location Selection It is expected that wherever possible, the callers estimated geodetic (latitude and longitude), with confidence and uncertainty, will be provided to the ALI servers. Any other location capabilities (i.e., device-based h
13、ybrid) should also be considered in the determination of best latitude and longitude, including z-axis when available. In addition, where available from NEAD data, a chosen AP or BT associated civic address and sub-address location data set will be provided through the E2 and ALI server process to t
14、he PSAP8. Where the NEAD does not provide sufficient coverage, such data may not be available for a given 9-1-1 call, or verification actions may indicate that populated data is not appropriate for use. 8Note that truncation of the location data may be necessary due to limitations in legacy location
15、 delivery protocols and PSAP CPE. ATIS-0700039 10 Additional evaluation in specific carrier location services processing will determine which NEAD AP or BT address and location data that is available should be utilized. Present considerations of concern to Public Safety are listed below and are not
16、meant to be all inclusive. It is expected that additional considerations will be derived over the course of the NEAD multi-year development and deployment life cycle and may result in future revisions. 1. All geodetic locations, including handset derived locations, should be evaluated based on avail
17、able information for quality, timing, and dependability in relation to other location choices for a given 9-1-1 call. Factors to enter into such evaluation include calculated uncertainty and technology type. For example, a small uncertainty device-based hybrid geodetic fix can be used as a distingui
18、shing factor between two candidate Dispatchable Locations returned by the NEAD to the LS. High quality geodetic fixes should be used in aiding the correct selection of DL. 2. When available, the presence of a servingFlag that ties a given user device to a related AP should be utilized to differentia
19、te between surrounding multiple AP instances. This will tend to make the chosen address more relevant to determining the likely user location than if the servingFlag is not utilized. When servingFlag is present it may be more definitive than RSSI based on the assumption that the Wi-Fi access point t
20、hat the device is attached to is the most representative of the users device location. Therefore, higher weighting should be given to the serving access point, especially in consideration of certain building types. For example, in residential environments (e.g., RMS), it may be assumed the caller is
21、 connected to the access point in their own home even if a neighbors Wi-Fi beacon signal is stronger. 3. PlaceType is an important parameter and should be provisioned in the NEAD whenever possible. If PlaceType is available, it is expected to influence the selection of the NEAD-based location and ma
22、y be used in the determination of CVC, DL1, or DL2 labels. The PlaceType should be sent toward the PSAP (e.g., MPC-E2-ALI interfaces). 4. In conjunction with all other parameters, AP signal strength should be considered in the selection of Dispatchable Location. Received Wi-Fi AP signal strength, pa
23、rticularly for APs whose civic addresses are provisioned in the NEAD, is very useful information, which can be used to augment decision making regarding DL or the class of DL. Even in the presence of a serving flag for an AP, signal strength can help differentiate between DL2 and DL1 in a multi-floo
24、r, multi-unit building. Furthermore, in the absence of a serving flag, AP signal strength can help distinguish between CVC and a likely DL1. This is because the received Wi-Fi signal level at the handset correlates well with the number of walls or floors that the signal penetrates to arrive at the h
25、andset. Empirical testing can provide guidance for signal level thresholds that can be used, either in the presence or absence of other factors, to aid in making decisions, including DL2 versus DL1, DL1 versus CVC, and CVC versus a situation where the Wi-Fi signal is likely to be from a neighboring
26、building. 5. Loading of NEAD data must involve an address validation action i.e., Master Street Address Guide (MSAG) or Location Validation Function (LVF), in order to verify the content and format of the data for each AP or BT Reference Point. 6. When the APs or BT Reference Points recognized by th
27、e user device are passed to the NEAD database, the returned result is cross-checked at the Location Server with other available location information to determine whether the AP/BT data may be appropriate to use. This check indicates appropriate proximity with the cell tower and sector data. For exam
28、ple, the geocoded information associated with the civic address of the AP/BT should be in the vicinity of the cell site serving the caller. The exact relationship should be defined and tested during NEAD location accuracy testing in the national Test Bed process. 7. A goal of the location services p
29、rocess is to have consistent Dispatchable Location results delivered from different carriers to the PSAP under similar call circumstances. 8. There should be testing of the location determination system as a whole, which arises from the interactive and interdependent elements of the location determi
30、nation process, including location services logic, NEAD, MPC/GMLC actions, and the ALI server. 9. The NEAD test bed and any other efforts to define how the NEAD related results should be evaluated to help refine the location services processes among carriers to improve the quality and consistency of
31、 the results delivered to the PSAPs. 6.1 Specific Position Methods For further study. ATIS-0700039 11 6.2 Multiple Position Methods For further study. 7 Position Reporting for PSAPs Clauses 5.1.7 and 5.1.8 discuss the interactions between a GMLC and the ALI, and between the ALI and the PSAP, respect
32、ively. Specifically, Clause 5.1.7 discusses how the GMLC will receive the geodetic location and civic location and convert them into an E2 response. The geodetic location will be populated in a Wireless Phase II format. The civic address will be formatted into XML elements and sub address elements a
33、nd will be populated in the LOC field of the E2 response. The LOC field is limited to 60 characters and if the total number of characters exceeds 60 characters, the lower-priority sub-elements will be truncated. The priority of converting XML elements into the LOC field in the E2 Location Descriptio
34、n parameter is as follows (highest on left to lowest on right): BLD|FLR|UNIT|ROOM|SEAT|MP|LOC|LMK (or LMKP) |PLC|UBP The method token value in the PIDF-LO received from the Location Server is converted by the GMLC into Position Source values. The GMLC converts the method token value of NEAD-CVC to P
35、osition Source 55 (CVC), a method token value of NEAD-DL1 to Position Source 56 (DL1), and a method token value of NEAD-DL2 to Position Source 57 (DL2). As discussed in Clause 5.1.8, the ALI server will convert the information it receives in the E2 response into a format that can be transmitted to t
36、he PSAP. The geodetic location will be presented in the same manner as for a Wireless Phase II call. The civic address will be presented in the manner that has been agreed upon by the ALI provider and the PSAP administrator, unless the PSAP CPE provides a modification of the format. In order to disp
37、lay the sub address elements, the PSAP must have the capability to display them on the Telecommunicator screen. If the display has restrictions on the size of the location field, then some information may be truncated and therefore not displayed. For example, some PSAPs have a limit of 20 characters
38、 that can be displayed on the screen. If the GMLC returns 60 characters and the PSAP has a limitation of 20 characters, some important information regarding location may not be displayed. PSAP administrators should evaluate their display formats to assess the impact of receiving sub addressing infor
39、mation. The ALI will convert the Position Source values it received into Class of Service enumerations. It is recommended that PSAPs use these new Class of Service designations and display them on the Telecommunicator display screen. The ALI server will convert Position Source 55 (CVC) to Class of S
40、ervice WCVC, Position Source 56 (DL1) into Class of Service WDL1, and Position Source 57 (DL2) into Class of Service WDL2. 8 Conclusions The guidelines and recommendations presented in this document are based on a combination of conceptual definitions and very limited functional testing of the inter
41、actions between locations servers in wireless networks and the NEAD. As such, the guidelines are initial and broad in nature. As stated under Clause 6, various details pertaining to these guidelines may be refined or expanded as more comprehensive Dispatchable Location testing takes place according
42、to the guidelines in ATIS-0500035. With every test program and analysis of the resulting data, it will be possible to gain a deeper understanding of the interactions between different location servers and the NEAD, the decision-making processes leading to Dispatchable Location determination, and the desired versus achievable Dispatchable Location outcomes under a wide range of conditions. This will lead to more refined guidelines to achieve enhanced Dispatchable Location performance and to promote consistent Dispatchable Location outcomes across networks under similar conditions.
