AssistNow
u-blox A-GNSS services
Services
The challenge of stand-alone GNSS
GNSS users expect instant
position information. With
standard positioning this is
often not possible because at
least four satellites must be
identified, and their complete
orbital position data (called
Ephemeris) received. Under
adverse signal conditions,
data downloads from the
satellites to the receiver can
take minutes, hours or even fail altogether.
Assisted GNSS (A-GNSS) accelerates calculation of position by
delivering satellite data such as Ephemeris, Almanac, accurate
time and satellite status to the GNSS receiver via wireless networks
or the Internet. This aiding data enables a GNSS receiver to
compute a position within seconds, even under poor signal
conditions.
AssistNow A-GNSS services
(Support GPS and GLONASS)
AssistNow Online and AssistNow Offline are u-blox’ end-to-end
A-GNSS services for OEM customers and their end users. These
services boost GNSS acquisition performance for devices with or
without network connectivity. AssistNow Online and AssistNow
Offline can either be used alone or in combination.
AssistNow A-GNSS services require no additional hardware
and generate virtually no CPU load. The system is very easy to
implement and can be installed and operational within a day.
u-blox cellular modules feature an embedded AssistNow client
making integration simple.
AssistNow Autonomous
AssistNow Autonomous is an embedded feature available free-of-
charge that accelerates GNSS positioning by capitalizing on the
periodic nature of GNSS satellite orbits. GNSS orbit predictions are
directly calculated by the GNSS receiver and no external aiding
data or connectivity is required. AssistNow Autonomous can be
used alone, or together with AssistNow Online or AssistNow
Offline for increased positioning speed and accuracy.
AssistNow Offline
With AssistNow Offline, users download u-blox’ Differential
Almanac Correction Data from the Internet at their convenience.
The correction data is then transferred to the mobile terminal via
TCP/IP, serial port, memory card, etc, and can either be stored in
the GNSS receiver’s Flash EPROM (if available) or in the memory
of the application processor. Therefore, the service requires no
connectivity at system start-up and enables a position fix within
seconds, even when no network is available.
u-blox provides correction data valid from 1 to 35 days. The size
of these files increases with the length of the prediction period,
from as little as 3 kB to 125 kB. Positioning accuracy decreases
with the length of the correction data duration, with 1–3 day
data providing relatively high accuracy and 10–35 day data
progressively less accuracy. Regular updates help to ensure a high
level of position accuracy.
AssistNow Online
With AssistNow Online, an internet-connected GNSS device
downloads assistance data from u-blox’ AssistNow Online Service
at system start-up. The service works on all standard mobile
communication networks that support Internet access, including
GPRS, UMTS and Wireless LAN. No special arrangements with
mobile network operators are needed to enable AssistNow
Online, making this solution network operator independent and
globally available. u-blox only sends ephemeris data for those
satellites currently visible to the mobile device requesting the data,
thus minimizing the amount of data transferred.
time
Legend
true satellite orbit
broadcast ephemeris orbit
(downloaded from the satellite)
broadcast eph. used beyond validity
period (unusable for navigation)
AssistNow Autonomous orbit
(autonomously generated from
broadcast ephemeris)
Production Information
UBX-13003352 - R01
Legal Notice
u-blox reserves all rights to this document and the information contained herein. Products, names, logos
and designs described herein may in whole or in part be subject to intellectual property rights. Reproduc-
tion, use, modification or disclosure to third parties of this document or any part thereof without the
express permission of u-blox is strictly prohibited.
The information contained herein is provided “as is” and u-blox assumes no liability for the use of the
information. No warranty, either express or implied, is given, including but not limited, with respect to the
accuracy, correctness, reliability and fitness for a particular purpose of the information. This document may
be revised by u-blox at any time. For most recent documents, visit www.u-blox.com.
Copyright © 2013, u-blox AG
Ordering information
Contact u-blox to obtain access to the free AssistNow service.
This service is available to u-blox OEM customers.
AssistNow Online AssistNow Offline AssistNow Autonomous
Data download frequency At every startup Once every X days Never
Data retrieval at start-up Data downloaded from server Pre-downloaded data from local
memory
Retrived from local memory
Aiding data type Ephemeris, almanac, time, health Differential almanac correction
data
Automatically generated
Data validity period 2 - 4 hours 35 days Up to 6 days
Size of downloaded data 1 - 3 kB 10 kB (1 day) ... 125 kB (35 days) N.A.
Acquisition (TTFF) performance As low as 1 second As low as 5 seconds As low as 10 seconds
Free service Best-effort Best effort N.A.
Premium service Guaranteed availability based on
service level agreement
Guaranteed availability based on
service level agreement
N.A.
Benefits of AssistNow
• Fast Time-To-First-Fix, even under poor signal conditions
• Global coverage
• Network operator independent
• No additional hardware required
• Free best-effort service
• Guaranteed QoS option for premium customers
• Low CPU load
• Available for all u-blox GNSS products
• Easy to install and use
• u-blox cellular modules include an embedded AssistNow
client for effortless implementation
Free and premium service options
AssistNow data is collected by u-blox’ global array of satellite
receivers, and maintained in real-time on u-blox AssistNow servers
accessible via the Internet. For best-effort applications, u-blox
provides AssistNow free-of-charge to its customers.
For applications requiring a guaranteed minimum Quality of
Service (QoS), u-blox provides AssistNow Premium which provides
guaranteed availability based on a service level agreement and
24/7 support.
Contact us
For contact information, see www.u-blox.com/contact-us.
Production Information
UBX-13003352 - R01
www.u-blox.com