AssistNow User guide 

Service license and pricing

AssistNow Predictive Orbits is provided Free of Charge and included with all M9 and F9 u-blox GNSS receivers (and next generations) upon registration in Thingstream service delivery platform. 

AssistNow Live Orbits is available in two pricing variants:

• As a bundle, included in the GNSS receiver price. It provides a lifetime license with a guaranteed service for 5 years after which the standard Service terms applies. This option is now available for the following products (but others will come in the future):

  • MAX-M10N-00B

  • MAX-M10N-10B

  • NEO-M9V-20B

• With a pay-as-you-go pricing model, you pay only for the service requests effectively done by your fleet. The Scale plan automatically scales up and down providing every month the best possible pricing. Details are  available at our pricing page 

Performance

The following table reports the main performance and specification of AssistNow service. Time-To-First-Fix highly dependent by the environment where the asset is located and by which A-GNSS data are fed into the GNSS receiver, and by the device design and shall be tested carefully with a device prototype to evaluate the performance achievable in regards of TTFF and accuracy.

It's worth noting that reducing the TTFF, is critical for two reasons:

• minimize the device energy consumption

• achieve faster the target accuracy. Typically the IoT environments are complex with urban canyon and partial sky view and the first position fix might not be accurate enough for your application. But the most of the times, the accuracy improves over the time because the GNSS receiver can acquire more satellite signals and  improve the estimation. The faster you get an initial position fix the faster you can achieve your target accuracy.

The following chart shows a typical TTFF comparison with and without AssistNow. It's worth noting that the performance greatly depend on the device design and the environment, therefore you might experience different results in different testing conditions. The chart shows:

• the improvement in TTFF using AssistNow

• the tiny TTFF variance when using Live Orbits.

Pre-requisites and Hardware supported

• A u-blox GNSS receiver (chip or module) from M9 and F9  and above and the knowledge about how to configure the receiver

• An account/domain in the Thingstream service delivery platform. Sign-up is free of charge. If you do not have a domain,  get it by signing up at https://portal.thingstream.io/

• the selection of the option that best matches the required performance between:

  • Predictive Orbits 

  • Live Orbits 

• the u-center 2 evaluation tool greatly help the evaluation and design phases 

If you are using an M8 receiver you can still rely on the legacy AssistNow service (Online and Offline), as long as you already have an active AssistNow token. Technical documentation is available  at this page.  Please see the additional information about maintenance and support at the end of this guide.

If you are completely new to A-GNSS technology or you would like to have a deeper understanding, you are suggested to read this Assisted GNSS article

System architecture

The system architecture is reported in the picture below. To use AssistNow :

• The Host processor needs the capability to connect to Internet. Please note that Low Bandwidth connectivity like LoRa and Sigfox and NB-IoT does not have enough bandwidth to download the A-GNSS data. If you are planning to use these connectivity you might consider the u-blox CloudLocate service

• The https protocol stack is required to request the A-GNSS data to AssistNow service using the HTTPS REST API

• A bidirectional direct connection between the Host processor and the GNSS interface using any of the interface available, to inject the aiding data into the GNSS receiver, get the acknowledge message and all the relevant positioning message s for your application

Getting started using u-center 2 evaluation tool

u-center 2 is the u-blox evaluation tool for GNSS receivers and allows you to easily configure the receiver and experiment the performance improvement using the AssistNow service.

• The easiest way proceed is to connect an Evaluation Kit (EVK), select the type of A-GNSS data that you want to use and start doing some test.

• If you are connecting the chip/module  in the device to u-center 2 (instead of the EVK), you need to retrieve the credentials (Chipcode) to access to AssistNow service  using the Zero Touch Provisioning procedure described in the next section. Once retrieved, the Chipcode shall be configured in u-center.

u-center 2 can be downloaded from the u-blox web site: https://www.u-blox.com/en/u-center-2

u-center 2 automatically retrieve and inject the A-GNSS data into the receiver. You can simulate and compare multiple scenarios and evaluate which configuration performs better in your use case, without writing any code. For example you can compare:

• performance with no A-GNSS data, with Predictive Orbits and with Live Orbits

• performance during a cold, warm and hot start

• performance using only some GNSS

u-center 2 is a very useful tool also when you are in the process of writing your firmware because it allows you to analyze the command, the receiver response and output messages and check that your firmware is acting properly.

Note: when usingu-center and an Evaluation kit you get free unlimited access to Predictive Orbits and Live Orbits. To know more about usage policies in any other set-up please read the dedicated section

If you are new to u-center or you need more information on how to use AssistNow in u-center, take a look at this short guide

Using AssistNow service

When designing  the device firmware,  you shall consider the following steps in order to use the AssistNow service:

1. Register the device int the u-blox Thingstream service delivery platform and obtain the device credentials to access to the service through the AssistNow Zero Touch Provisioning procedure. The credentials are uniquefor each device. 

2.  retrieving the A-GNSS data from the service using the REST API and the credentials

3. injecting the A-GNSS data into the GNSS receiver. The data delivered by the service do not need additional manipulation and can be injected into the GNSS receiver immediately like they are provided by the service. AssistNow service exchange information via the HTTPS over SSL protocol. 

4. save the data for further reuses without additional download from the service, according the the validity period of each data type.

Device registration

The AssistNow Zero Touch Provisioning (ZTP) procedure is required to obtain the credentials (Chipcode) used to request the A-GNSS data to AssistNow service. The procedure is needed only once but can be also used to get new fresh  credentials in case of suspicious activity or compromised credentials.

The Chipcode is unique per device

ZTP streamlines device setup, eliminating the need for manual configuration for each device. With ZTP, adding devices to your fleet is simplified, making it ideal for large-scale deployments. And the Chipcode provides secure authentication, protecting your devices and data from unauthorized access.

Refer to the Device registration guide  to know the implementation details. ZTP is required both for Predictive Orbits and Live Orbits but both variants share same Chipcode 

Obtaining A-GNSS data

To retrieve the A-GNSS data, the device firmware shall use the REST API, including:

• the hostname

• the authentication code (Chipcode)

• the data to be requested, according to the selected option (Live or Predictive Orbits)

Upon reception of  the HTTPS GET request, the server responds with the required messages in binary format and a status code in text format. After delivery of all data, the server terminates the connection. All data (with the exception of hostname, which is used to establish the connection) is carried solely within the encrypted connection and is protected from man-in-the-middle attacks in the same way that any HTTPS data is.

Here below an example of service request:

https://AssistNow.services.u-blox.com/GetAssistNowData.ashx?chipcode=XXXXXXXXX&gnss=gps,glo&data=uporb_1,ualm

where:

• chipcode is the device authentication credential obtained  during the device registration (ZTP procedure)

• gnss is the list of GNSS constellation for which the A-GNSS data are needed

• data is the list of A-GNSS data requested to the service

Detailed information are described in the Service integration guide.

A-GNSS data injection in the receiver 

The A-GNSS data returned by AssistNow service are encoded in a sequence of UBX-MGA-*** messages containing the requested assistance in u-blox (UBX) protocol.  The section in the UBX messages in the Service integration guide provides a comprehensive list of all the available data  and which UBX message is delivered for each service option. 

To understand the frame structure and get more details of the data fields of each message you are invited to refer to the GNSS receiver Interface description. Go to the Product selector, select the desired GNSS receiver and find the Interface description document in the Documentation & resources section.

For u-blox receivers that have flash storage, all the data can be directly transferred to the flash until it is needed.

Receivers without flash storage or with insufficient spare flash memory can store A-GNSS data in the host and send them to the receiver when needed. 

The Host software guide explains how to properly design the device firmware to store and inject data into the receiver in all the possible configurations. 

Note: the data provide by the service do not need additional manipulation by the device Firmware and can be injected in the receiver as sent by the service.

A-GNSS data storage 

The Time-To-First-Fix after a receiver power interruption is dependent on the amount of operational data available at startup. Satellite broadcast information and an estimate of accurate time can be fetched form the AssistNow service. In addition, the following techniques can restore the data that was stored prior to powering down.

• Battery-backed RAM (BBR): the receiver operational state stored in this RAM can be maintained during power outages by connecting the V_BCKP pin to an independent supply, e.g. a battery. This is a recommended method as it will maintain all A-GNSS related information, any user configuration, calibration data, and an estimate of time via the real-time clock. 

• Database dump: The receiver can be made to dump the state of its navigation database in the form of a sequence of UBX messages reported to the host; these messages can be stored by the host and then sent back to the receiver when it has been restarted. 

• For Predictive Orbits , whose data validity is longer than Live Orbits, the A-GNSS data can be saved also in the Host  or in the  GNSS receiver Flash (if available)

The Host software guide provide more details about each option

The best data storage strategy greatly depend on the type of data used (Live vs. Predicted), the use case, how often the receiver is switched-on during the day and for how long time. 

Service usage policies

According to the type of A-GNSS data required and the Hardware used, the device is subject to policies that limits  the usage (per day or per month), according to the following table.

Note: in case the the maximum allowed number of request is achieved, the event is shown in the Thingstream platform. The usage counter is reset at 00.00 UTC of the day/month.