User's Manual

V3d Product Specification, Version 2.06
3.2.2 ORBCOMM Satellite System
The ORBCOMM system is a two-way system that supports communication to and from mobile
or fixed Subscriber Communicators (SCs). In most applications, a message or other data is first
generated by an SC. From that source, the data is transmitted to the nearest ORBCOMM
satellite. The satellite downlinks the data to the selected Gateway Earth Station (GES), which
then transmits the data to the desired Gateway Control Center (GCC). Within the GCC, the
data is processed and forwarded to its ultimate destination by the Gateway Message Switching
System (GMSS). The destination may be another SC, a pager, a corporate resource
management system or any personal or business e-mail or Internet address.
The ORBCOMM system is available to transfer information for an end user whenever a satellite
is in view of the SC. If the satellite is connected to a GES, the satellite is considered in real-time
messaging mode and the message is passed immediately through to the GCC for routing to its
final destination. If the satellite is not connected to a GES, the satellite switches to a store-and-
forward mode to accept GlobalGrams. GlobalGrams are short messages (up to approximately
200 bytes) stored on-board the satellite until it connects to the SC’s host GCC through an
affiliated GES.
3.2.3 ZigBee Wireless
The Zigbee wireless link is a designed to be a very low-cost, very low-power, two-way wireless
communications standard. The IEEE 802.15.4 standard defines the lower two layers: the
physical layer and the medium access control (MAC) sub-layer. The ZigBee Alliance builds on
this foundation by providing the network layer and the framework for the application layer.
The IEEE 802.15.4 standard has two physical layers that operate in two separate frequency
ranges: 868/915 MHz and 2.4 GHz. The lower physical layer covers both the 868 MHz
European band and the 915 MHz band that is used in countries such as the United States and
Australia. The higher frequency layer, 2.4 GHz, is used virtually world-wide, and is the band to
be used for V3d functions.
3.2.3.1 Mesh Communications
A planned future capability of the V3d includes wireless communications with enabled devices
and other V3d’s using ZigBee protocols
1
. The ZigBee wireless link is to be used for future
sensor integration, whereby discrete sensors located in the container are linked and bound to
the V3d without wires. Also, in a mesh network configuration, buried V3d devices may be able
to communicate and gain access to a satellite or cellular link through a neighboring V3d device.
3.2.3.2 Transmit Power Level
Allowable ZigBee transmit power, in the 2.45GHz band, varies by country. In the U.S., the FCC
maximum is 1000 mW, ETSI (Europe) is 100 mW, and Japan is 10 mW. The upper transmit
power used in the V3d is to be determined, based on field tests and regulatory constraints. The
lower transmit power is to be a minimum of 1 mW.
1
The described functionality is not delivered by MobiApps but is expected to be realized by
software developed by SPC and hosted partly on the Blackfin, partly on the EM250 ZigBee IC.
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