Solo Communications

RMAPS® Mesh Network

The RMAPS® communication network is a flexible and reliable framework for the data transmission necessary for navigation and mapping purposes. Signal coverage in an RMAPS® network can be extended on-demand with the use of BreadCrumb® devices. Astronauts can communicate directly with these devices or can use them for signal propagation to establish non-line-of-sight communications with the lander at ranges in excess of 2 km.

ZigBee® Protocol (READ MORE...)

The RMAPS® communication network is built upon the ZigBee® and IEEE 802.15.4 standards-based protocols. ZigBee® was chosen due to the need for a flexible yet reliable mesh network capable of connecting large numbers of cheap, low power transceivers. ZigBee® networks have many other advantages including self-healing networks, message routing, and multi-user/multi-frequency capabilities enabling RMAPS® to simultaneously support multiple astronauts. Visit the Zigbee Alliance web site for more information on the ZigBee® protocol and ZigBee® certified products.
Lander Hardware (READ MORE...)

The lander utilizes a Texas Instruments CC2531 which provides a true system-on-chip solution for controlling the RMAPS® communication network. A 0 dBi omnidirectional antenna is connected to the chip circuitry which contains an efficient transceiver capable of 250 kbps peak data rates in the 2.4 GHz band. It is accompanied by an enhanced microcontroller, a 256 Kb programmable flash memory, and 8Kb RAM. The microcontroller is loaded with Solo Communications software that manages the data for mapping and navigational purposes.
Astronaut Hardware (READ MORE...)

The astronaut is equipped with the same Texas Instruments CC2531 chip as the lander. However, the microcontroller is programmed to perform a different subset of functions including distance calculation, optimal signal determination, disambiguation calculations, and a communication link switching mechanism. The astronaut can communicate with the lander by utilizing BreadCrumb® devices to propagate signals back at peak data rates of 250 kbps with the same 0 dBi antenna design that is present on the lander.
BreadCrumb® Devices (READ MORE...)

BreadCrumb® devices are cheap, low power transceivers based on the ZigBee® certified Texas Instruments CC2520. The CC2520 is connected to an ideal, passive RF integrated circuit that requires -20 dBm of RF power to turn-on. These BreadCrumb® devices can be added to any RMAPS® network as a router capable of 250 kbps peak data rates. The BreadCrumb® has an extended temperature operating range of -40°C to +125°C but according to NASA, the temperature on the moon will range from -153°C to +107°C. This could obviously be an issue, but hopefully insulating the chip will provide enough protection without degrading the signal quality since there is unfortunately not a transceiver capable of withstanding such a wide temperature range.

RMAPS® Communication Links

RMAPS® collects and transfers information across two communication link designs. These links have been optimized for reliability and accuracy as the data they transmit is the lifeline of the RMAPS® system.

Astronaut-BreadCrumb® Communication Link (READ MORE...)

The astronaut communicates with BreadCrumb® devices to calculate the distance between them as well as the astronaut's coordinates relative to the lander. The astronaut continuously transmits 2.4 GHz pulses that are searching for BreadCrumb® devices in the vicinity. When a BreadCrumb® receives a strong enough pulse, it will power up and transmit the signal back to the astronaut.
Astronaut-Lander Communication Link (READ MORE...)

The astronaut will also need to communicate with the lander in order to provide coordinates and sensor data such as temperature as measured by the astronaut's ZigBee® chip. The Texas Instruments CC2531 chip is capable of transmitting peak data rates of 250 kbps. This signal will be propagated back to the lander through the RMAPS mesh network using the 0 dBi BreadCrumb® devices deployed by the astronaut. The digital spectrum usage and channels for 2.4 GHz ZigBee® devices is listed below.
Signal Modulation (READ MORE...)

ZigBee® devices are configured to modulate signals using direct sequence spread spectrum. Therefore the spectrum of the signals will be spread across the entire width. Each BreadCrumb® has its own unique pseudorandom chipping sequence consisting of 1023 bits. The astronaut and lander's ZigBee® certified chips are loaded with the complete chipping sequence code book. The received signal will be passed through a matched filter in order to recover the original signal.
Signal Frame (READ MORE...)

The signal frame for the communication link with the BreadCrumb® devices only contains data about the coordinates of the specific BreadCrumb® and the accuracy data pertaining to these coordinates. The BreadCrumb® ID is determined by the astronaut's equipment which uses a matched filter with access to the chipping sequence code book. The signal frame for the communication link to the lander is similar, but carries coordinates and accuracy data for the astronaut instead of a BreadCrumb® However, there are several subframes at the end of the signal frame (shown below) that are used for transmitting various sensor data back to the lander. Data is transmitted at a peak data rate of 250 kbps.

RMAPS

Radiolocation Mapping and Positioning System

RMAPS® Mesh Network

ZigBee® Protocol (READ MORE...)

Lander Hardware (READ MORE...)

Astronaut Hardware (READ MORE...)

BreadCrumb® Devices (READ MORE...)

RMAPS® Communication Links

Astronaut-BreadCrumb® Communication Link (READ MORE...)

Astronaut-Lander Communication Link (READ MORE...)

Signal Modulation (READ MORE...)

Signal Frame (READ MORE...)

What is RMAPS?

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