"Developers, makers and enthusiasts working on a MIMO system may be interested in a new piece of hardware, launched by the Crowd Supply website last month, called the XYNC."
"Con diversos modelos que van de menos a más potencia, esta radio definida por software con capacidad MIMO puede ser utilizada en conexión con otra placa idéntica para otorgar todavía mayor funcionalidad."
If you’re working on a massive MIMO system or have a large swath of spectrum you need to monitor, XYNC (pronounced iks-sync) is right for you. XYNC builds on the success of the Octopack SDR we offered during the XTRX campaign and takes into account feedback from the original Octopack users.
A single XYNC comes equipped with four or eight removable XTRX boards, metal installation brackets, cables for all of the TX/RX ports and the GPS port, and a special board for synchronizing the XTRX units. Each onboard XTRX provides two transmit channels and two receive channels. Thus, XYNC Octo (with eight XTRX units) has 16 transmit and 16 receive channels. Two XYNC Octos can be synchronized and will give you 32 transmit and 32 receive channels.
On the digital side, each XTRX unit is connected to a PCIe switch that multiplexes the XTRX PCIe lanes into a single PCIe 2.0 x4 connector. This makes it very compact and easy to install into a standard PC. Just don’t forget to provide enough air flow for cooling, as setups like this can get quite hot.
A single XTRX is shown above. XYNC includes up to eight XTRX boards.
XYNC is based on multiple synchronized XTRX SDRs, so the maximum achievable RF bandwidth is a function of the individual XTRX RF bandwidths.
If you want to tune XYNC channels to receive or transmit at different parts of the spectrum, please keep two things in mind:
XYNC uses a PCIe switch to connect all of its XTRXs to a single PCIe bus. The XTRXs are connected to the PCIe switch with PCIe 2.0 x1 buses, and the switch is connected to the host with a PCIe 2.0 x4 bus, which introduces additional limits to the XYNC sampling rate and throughput compared to a single XTRX.
Expanding on the (theoretical) maximum XTRX throughput limits, we get the following throughput per channel for XYNC Octo in various configurations. Green cells indicate combinations of sample rate and PCIe bus configuration where the sampling rate is not limited by the PCIe bus but by the XTRX itself.
|Mode||IQ x Ch x bits||Bits total||PCIe 1.0 x1 (max 1,750 Mbps)||PCIe 2.0 x1 or PCIe 1.0 x2 (max 3,500 Mbps)||PCIe 2.0 x2 (max 7,000 Mbps)||PCIe 2.0 x4 XYNC Total throughput (max 14,000 Mbps)||PCIe 2.0 x4 per XYNC Octo channel (max 14,000 Mbps)|
|8-bit SISO||2 x 1 x 8||16 bits||109 Msps||219 Msps||438 Msps||875 Msps||109 Msps|
|12-bit SISO||2 x 1 x 12||24 bits||73 Msps||146 Msps||292 Msps||583 Msps||73 Msps|
|16-bit SISO||2 x 1 x 16||32 bits||55 Msps||109 Msps||219 Msps||438 Msps||55 Msps|
|8-bit MIMO||2 x 2 x 8||32 bits||55 Msps||109 Msps||219 Msps||438 Msps||55 Msps|
|12-bit MIMO||2 x 2 x 12||48 bits||36 Msps||73 Msps||146 Msps||292 Msps||36 Msps|
|16-bit MIMO||2 x 2 x 16||64 bits||27 Msps||55 Msps||109 Msps||219 Msps||27 Msps|
In the table above, SISO configurations mean that only one receive and one transmit channel is used on each XTRX, i.e., XYNC Octo would have 8x8 RX/TX channels. MIMO configurations mean that both receive and both transmit channels are used on each XTRX, i.e., XYNC Octo would have 16x16 RX/TX channels. This is why SISO configurations enjoy twice the bandwidth per channel of MIMO configurations – they have half as many channels between which to share that bandwidth.
What exactly does XYNC synchronize? The answer is a bit complex. Below are some important facts you should keep in mind:
Note that the XYNC software package does not currently include the phase calibration algorithm. Please contact us directly if you need support with phase calibration.
XYNC consists of three main units:
The power consumption of the PCIe switch and frontend units is relatively constant at about 10 W.
XTRX power consumption varies significantly depending on whether you’re doing RX, TX, or both; on whether you’re doing continuous or burst TX/RX; and on output power, internal gains, bandwidth, digital pre-processing, and a few other parameters. Maximum XTRX power consumption at maximum sample rate and gains is approximately 3 W, for a total of 34 W maximum power consumption for the entire XYNC Octo system.
XYNC is powered from two different sources, a PCIe edge connector and a 6-pin 12 V GPU ATX Molex connector:
|PCIe Switch Unit:||PCIe edge connector|
|Synchronization & Frontend Unit:||6-pin 12 V GPU ATX Molex connector|
|XTRX Units:||PCIe edge connector|
6-pin 12 V GPU ATX Molex connectors, which are typically used to provide power to video cards, look like the following:
In terms of voltages, XYNC uses 3.3 V and 12 V from the PCIe connector and 12 V from the 6-pin ATX connector for the synchronization logic on the synchronization & frontend unit.
With tens of watts of power consumption, cooling is important. Output power and other parameters of the LMS7002M chips we’re using begin to degrade at about 80°C. It’s important to keep the ambient temperature significantly below that to provide enough of a temperature gradient for the chips to cool. If you’re interested in phase stability, it’s also important to keep the temperature as stable as possible – temperature changes can noticeably affect phase stability, causing phase differences between the XYNC channels to drift.
For general applications, we recommend at least providing a stable flow of air through the PCIe compartment. For industrial applications, an external box with a passive heatsink might be a good choice. You can connect such a box to the PCIe bus with a PCIe bus extender.
Fairwaves is happy to work with backers on heat dissipation designs that will keep your XYNC operating safely under its target conditions.
During the original XYNC campaign, we offered a few XYNC variants in addition to the currently available XYNC Octo:
For more information on these variants, see the archived campaign page.
Crowd Supply is handling all shipping. Take a look at their Frequently Asked Questions (FAQ) page for answers to the most common fulfillment questions.