# V2X use case: Discovery of predicted QoS on potential routes for vehicular UEs
This section describes a use case that the user can accomplish using the V2X Information Service API of MEC Sandbox from a MEC application.
Objective:
* As a MEC Sandbox User, I have a MEC Application that wants to determine the best route among potential routes based on the predicted QoS that a vehicular UE may experience along the route.
* MEC Application provides route information to the MEC Sandbox V2X Information Service API for all potential routes. Route information includes route origin and destination; intermediate waypoints may also be provided. Estimated journey start time and arrival time at each location may also be provided.
* V2X Information service returns predicted QoS in the form of Reference Received Signal Power (RSRP) and Reference Received Signal Quality (RSRQ) for each point along all potential route(s). <br>**NOTE:** These route points must be within the Monaco city map and lie under the coverage area of the V2X network scenario. Otherwise, minimum values (zero) of RSRP and RSRQ will be returned by default.
* Based on the response provided by the V2X Information service, MEC Application can determine the route where the vehicular UE will experience the best QoS in terms of RSRP and RSRQ.
*See [user interface](../Sandbox-User-Interface#mec-sandbox-wireframe) for frontend details*
| Operation | Notes |
| --------- | ------ |
| 1. Log-in on the Sandbox landing page with access credentials & go to the User Sandbox area | _See [frontend](../Sandbox-User-Interface#sbox03)_ |
| 2. Select the V2X network scenario `4g-5g-macro-v2x` to deploy in the user sandbox. <br><br> _See [relevant scenario](./macro-networks.md#macro-network-4g-5g-v2x) for more details_ | _See [frontend](../Sandbox-User-Interface#sbox04)_ |
| 3. Find the V2X Information Service URL endpoints & configure them into the MEC application or environment | _See [frontend](../Sandbox-User-Interface#sbox05a)_ |
| 4. Start the MEC application or environment | MEC Application will have a set of route points in the form of geo coordinates (lat/long) for all potential routes that a vehicular UE may take on its journey. <br><br> The MEC application should be able to provide this information in the form of a standard data model specified in ETSI GS MEC030 v2.2.1 |
| 5. `POST .../<user-specific-mec-sandbox-url>/mep1/vis/v2/provide_predicted_qos` | Request body for the `POST .../provide_predicted_qos` request contains route(s) information and is formulated by populating the relevant attributes in the standard `PredictedQos` data model, specified in "ETSI GS MEC030 v2.2.1" <br><br> See Swagger UI by using the ["Try-it in browser" option](../Sandbox-User-Interface#sbox05a) for more information on the PredictedQos data model and example request & response bodies for the `/provide_predicted_qos` endpoint |
| 6. MEC application parses the received `PredictedQos` data model in the response body to determine the best possible route based on the RSRP and RSRQ values that are returned by the V2X Information service | Depending on the design scenario and implementation logic of user's MEC application, a decision can be made for the best possible route on the basis of available predicted QoS values or the information could be relayed to the vehicular UE as is. <br><br> Accurate and timely predictions of radio environment at locations planned to be visied by the vehicle can enable the UE to decide whether to trigger, modify or postpone the application of certain V2X functionalities and/or download of content delivery / software packages |
