What is the Advantage and Disadvantage of USRP X Series

When choosing the right USRP device for your application, a good place to start is by asking yourself a few questions related to signal parameters, size, weight, power, cost (SWaP-C), performance, and environmental application requirements. Question one: What center frequency and bandwidth do I require?

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This question is easy enough to answer, but the next one is more involved: How do I plan to move signal data on or off the device?

This brings into focus the importance of data interfaces. For example, the USRP-290x&#;models are connected to the host through USB and are limited by the maximum sustained bandwidth of that interface, whereas the&#;Ettus USRP X440 is equipped with two 100 GbE interfaces capable of moving much more data.

To learn more about USRP interface bandwidth considerations, read about USRP Bandwidths and Sampling Rates on the Ettus Research knowledge base.

Most USRP devices have a maximum frequency up to 6 GHz and some higher; however, the NI Ettus USRP X410 can operate in the 7 GHz band. On the lower frequency end, some radios go down to 75 MHz and some as low as DC depending on the analog chipset used. See Figure 16 for a breakdown of each model.

Figure 3: The Ettus USRP X410, built on an RFSoC, is a high-frequency wideband SDR with a center frequency up to 7.2 GHz

Cost and Performance Trade-offs

There are trade-offs to consider when choosing a USRP device, specifically cost versus performance. If you require a radio at a great value and you do not have advanced FPGA or wide bandwidth requirements, the NI USRP 290x or Ettus Research B200mini are great options. If you need the widest bandwidth and frequencies up to 7.2 GHz, the NI Ettus USRP X410 may be the best fit. There are many options available in between these two examples. Figure 15 below gives a full break down across all models.

Figure 4: USRP B200 and USRP B200mini Low SWaP-C SDRs

If you need frequencies up to 7.2 GHz, the NI Ettus USRP X410 may be the best fit. If you require the widest possible instantaneous bandwidth, the NI Ettus USRP X440 may meet the need. There are many options available beyond these examples; Figure 16 provides a full breakdown across all models.

Figure 5: The Ettus USRP X440 offers up to 1.6 GHz bandwidth per channel, with a direct sampling transceiver architecture

Stand-Alone or Host-Connected SDR Options

The USRP was conceived as a computer peripheral to connect software to the electromagnetic spectrum. Applications have evolved since the first USRPs, and many require an embedded processor onboard. You may require this stand-alone configuration if your application has the SDR physically distributed from a centralized control system or deployed on its own. If stand-alone is a key requirement, you will need to decide if a Xilinx Zynq&#; Multiprocessor System on Chip (MPSoC) or RF System On Chip (RFSoC) is sufficient or if you require a powerful Intel X86 processor onboard. Table 1 provides a breakdown of various models and their onboard processors; consult USRP specification documents for more details.

Radio ModelOnboard ProcessorUSRP N320, USRP N321, USRP N310Xilinx Zynq MPSOCUSRP E31XXilinx Zynq MPSOCUSRP E320Xilinx Zynq MPSOCNI Ettus USRP X410, USRP X440Xilinx Zynq Ultrascale+ RFSOC ZU28DRUSRP Intel Core i7 EQ (2 GHz Quad Core) 

 

Table 1: Stand-Alone Capable USRP Models with Onboard Processors

Figure 6: USRP Stand-Alone SDR with Built-in Intel Core i7

Ruggedization and Harsh Environments

Although many USRPs are used in the lab, some applications require operation in outdoors or in harsher environments. If your application requires extended operating temperatures or can&#;t rely on air-cooling, you may want to consider the Ettus Research branded Embedded Series for your application. Additionally, under the Ettus Research brand, there are options to configure the USRP B205mini for extended temperature range with the use of the industrial grade aluminum enclosure assembly for low SWaP operation. Alternatively, if you have extreme environmental requirements, we would love to connect you with our experienced ruggedization partners; contact us to explore these options.

Figure 7: Embedded Series, USRP E320

Multichannel Synchronization

Many applications require multiple input and multiple output (MIMO) configurations with varying levels of synchronization. Some MIMO systems simply require a shared clock for ADCs and DACs, while others require every channel to be locked to a common clock and local oscillator for a full phase coherent operation.

A common MIMO application is for communications with spatial multiplexing. As this only requires clock synchronization, most USRPs with an external 10 MHz reference clock will be sufficient. An example of such a system was built by The University of Bristol and Lund University when they broke the wireless spectral efficiency world record using an SDR-based massive MIMO system. The Massive MIMO Prototyping System used in this application is composed of NI USRP Software Defined Radio Devices with onboard FPGAs.

Figure 8: USRP N320 and N321 with Built-In LO Distribution Interfaces

When a full phase coherent operation is required, you have a few options to consider. If you require up to four channels of receive only operation, the Ettus Research USRP X310 with two TwinRx daughterboards can be set up to share the LO and operate in a phase coherent manner. If more than four channels are required, then consider the Ettus Research USRP N320 and N321 (shown in Figure 8) or the NI Ettus USRP X440. Since the USRP X440 is built with a direct-sampling intermediate frequency (IF) architecture, synchronization can be achieved by sharing sample clocks across up to eight transmit and eight receive channels. It is prepared for multidevice synchronization to an externally provided reference clock signal.

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The USRP N321 comes equipped with built-in LO distribution hardware allowing for up to&#;128 x 128 phase coherent operation: a 32 x 32 configuration example is shown in Figure 9.

 

Figure 9: USRP N320 and N321 Multichannel Phase Coherent System

Distributed Multi-Radio Synchronization

In some applications, radios require synchronization but are not co-located. In these instances, a full phase coherent operation is a challenge; however, one can use GPS-based synchronization to get frequency and phase stability with a GPS disciplined oscillator (GPSDO). Many USRP models are equipped with a GPSDO from the factory. To learn more, read &#;Global Synchronization and Clock Disciplining with NI USRP-293x Software Defined Radio.&#;

Figure 10: USRP X310 with Onboard GPS Disciplined Oscillator

Inline Signal Processing and FPGA Considerations

Some applications have processing requirements that are best suited for an onboard FPGA. These applications often have wide signal bandwidths or low/deterministic latency requirements. In these cases, picking a radio with the ability to program the FPGA is important. Many of the USB and lower-cost USRP models, such as the USRP B200mini or the N210, are built with smaller FPGA devices and as such do not have the space to add user code. Many of the higher end radios come equipped with Kintex 7 class devices all the way up to the state-of-the-art Ettus USRP X410 and X440 with the Xilinx Zynq UltraScale+ RFSoC. Devices built on Xilinx Zynq include additional cores such as onboard soft-decision forward error correction (SD-FEC), multi-Arm processors, and built-in ADCs and DACs.

USRP ModelOnboard FPGAUSRP N320, USRP N321, USRP N310Xilinx Zynq MPSOCUSRP E31XXilinx Zynq MPSOCUSRP E320Xilinx Zynq MPSOCEttus USRP X410, USRP X440Xilinx Zynq Ultrascale+ RFSOC ZU28DRUSRP , USRP X310Xilinx Kintex 7 410T

 

Table 2: Comparison of FPGA Enabled USRPs

Figure 11: Comparison of FPGA Resources across NI FPGA Products

 

Earlier this month, Ettus Research announced its newest addition to the USRP software defined radio family &#; the release of the USRP &#; X300 and X310. So far, the community has expressed excitement about the product and its high-performance nature.  We thought we would take opportunity to highlight features, discuss the new applications this series enables, and paint a picture of how it fits into the overall Ettus Research product portfolio. 

New Features Extend the USRP to a New Level

A quick look into the history of products like the N-Series shows a lot of happy customers and cool applications like ionospheric RADAR, WiFi-based gesture recognition, and test beds for cognitive radio.   We&#;re excited to announce that the USRP X Series builds on the success of the USRP N200/N210.  It extends the capability of the USRP product line with important new features: 

• Dual 10 Gigabit Ethernet Interfaces&#;10 times faster than the 1 GigE interfaces of the USRP N200 and N210.  This allows users to stream more bandwidth (up to 120 MHz per RF channel) for processing on a host PC or other architectures.  Users can also drop back to 1 GigE for older PCs.
• PCI Express Interface &#; Increased bandwidth, like the 10 GigE interface, but with the added benefit of very low interface latency. Advancements in areas like PHY/MAC research are now capable with the X300 and X310
• Two daughterboard Slots &#; Now, users looking to build MIMO setups, or use multiple daughter boards tuned to different bands can do so very easily.  Combining multiple units provides scalable systems with high channel-density.
• Kintex-7 &#; A large FPGA with a significant amount of free resource that can be used to implement custom DSP functions.  Porting these functions to the FPGA will allow developers to achieve greater processing throughput in their system.

There are also other notable features like sleek 1U form factor, internal GPSDO, 1 GB of DDR3 for high-speed buffering, and more.  

 

How Ettus and National Instruments are helping to solve a massive wireless challenge

Today, wireless engineers face a number of fascinating challenges &#; crowded spectrum, a wide array of new wireless standards (802.11ac, LTE-A, etc.), and pressure to prove out concepts on tighter budgets.  Also, with the exponentially increasing demand for data, there is an expectation that wireless technology will evolve at a faster pace.

We have created the USRP X300 and USRP X310 to support advanced research, and allow engineers to pave the way for faster data services for a global civilization.  The USRP X300/X310 was designed to meet the demands of research areas like next generation 5G wireless standard prototyping, multi-channel spectrum scanning and analysis, and even active radar prototyping and development.

Our Commitment to Low Cost, Accessible Platforms

While the USRP X300 and USRP X310 is a compelling platform for all forms of research and prototyping, we are still dedicated to serving our audience with lower cost options.  Ettus Research continues to invest in the affordable Bus Series with devices like the USRP B200 ($675) and we have ambitious plans ahead for our Embedded Series.  It&#;s also worth noting, that the FPGA architectures and driver (UHD) implementations are common across all of our devices.  This combination of consistent software architecture and a full spectrum of products make it very easy for our customers to move up and down the price/performance curve for our products.

 The Future Ahead

We are very excited about the endless possibilities that our new products will enable our customers to accomplish.  We hope that you check in regularly to see how we&#;re making this happen.