Selecting a USRP Device - Ettus Knowledge Base

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Application Note Number

AN-881

Revision History

Date Author Details -05-01 Neel Pandeya
Nate Temple Initial creation

-03-26 Nate Temple Update

Abstract

This AN explores the USRP family at a high level, compares devices across several primary features, and walks the reader through the process of selecting a particular device for the their application.

USRP Product Selector

The USRP Product Selector will help you choose the Ettus Research USRP Software Defined Radio products that are the best fit for your application. Based on your answers to a series of questions, the USRP Product Selector will generate a PDF price quote and it to you. The Ettus Research sales team may follow up with you to answer any additional questions that you might have. If you would like a person to talk you through the USRP product selection process, please send an to .

Overview

This guide is provided by Ettus Research to help users select the most appropriate Universal Software Radio Peripheral (USRP&#;) for their specific application. In order to make the selection process as straightforward as possible, a table showing various features is provided as a basis for the selection process.

Understanding DSP Fundamentals

If you are new to the USRP family of products, software defined radio, or digital signal processing in general, it may be useful to perform some simulation of the signals you wish to manipulate before selecting USRP hardware. Simulating signals and algorithms in software frameworks such as GNU Radio or LabVIEW will ensure a proper understanding of various concepts, such as Nyquist theorem, ADC/DAC and limitations, for example. Understanding the basics of signal theory and digital signal processing is the first step towards understanding how to make the best use of an appropriate USRP model. The Suggested Reading page provides access to several resources that may be helpful in understanding the basics.

Common Applications

Table 1 shows USRP/daughterboard combinations commonly used in various application areas. While Table 1 can serve as a starting point for selecting a USRP device, Ettus Research recommends new users evaluate their application requirements against the specifications of the USRP devices. sections of this document will assist in the selection process.

Application Area Common USRP Model Common Daughterboard PHY/MAC Research N200/N210 X300/X310 N300/N WBX/SBX/UBX/CBX Radar Research X300/X310 SBX/UBX OpenBTS B200/B X300/X310 E310/E N200/N210 N300/N E WBX/SBX/UBX/CBX Amarisoft LTE N200/N210 X300/X310 B E N300/N WBX/SBX/UBX/CBX Education B200/B X300/X310 E310/E N200/N210 N300/N E WBX/SBX/CBX/UBX HF Communications N200/N210 X300/X310 LFRX/LFTX Signals Intelligence X300/X310 N300/N E SBX/UBX Distributed RF Sensors E310/E312 N300/N310 E320 N/A Mobile Radios E310/E312 E320 N/A MIMO X300/X310 N SBX/UBX Phased Array X300/X310 SBX/UBX FPGA Computing X310 N E WBX/SBX/UBX/CBX Embedded Computing E310/E312 E320 N/A Small Form Factor (SWaP) B200mini/B205mini E310/E312 E320 N/A Table 1 - Recommended USRP Selection for Various Application Areas
1 - The B2xx, E3xx and N3xx do not support swappable daughterboards

USRP Device Characteristics

Table 2 shows the key characteristics of all USRP models available from Ettus Research. The table is useful for determining the interface type, bandwidth capabilities, and synchronization mechanisms specified for each USRP model. You can use this information, and the requirements for the application in question, to select a USRP radio.

USRP Model Interface Total Host BW (MSPS 16b/8b) Daughterboard Slots ADC Resolution (bits) ADC Rate (MSPS) DAC Resolution (bits) DAC Rate (MSPS) MIMO Capable Internal GPS Disciplined Oscillator (Optional) 1 PPS/Ref Inputs N210 GigE 25/50 1 14 100 16 400 Yes Yes Yes N200 GigE 25/50 1 14 100 16 400 Yes Yes Yes N300 1 GigE

10 GigE

153.6, 125, 122.88 2 16 153.6, 125, 122.88 14 153.6, 125, 122.88 Yes Yes Yes N310 1 GigE

10 GigE

153.6, 125, 122.88 2 16 153.6, 125, 122.88 14 153.6, 125, 122.88 Yes Yes Yes B200mini USB 3.0 61.44 N/A 12 61.44 12 61.44 No No Yes B205mini USB 3.0 61.44 N/A 12 61.44 12 61.44 No No Yes B200 USB 3.0 61.44 N/A 12 61.44 12 61.44 No Yes Yes B210 USB 3.0 61.44 N/A 12 61.44 12 61.44 Yes Yes Yes X300 USB 3.0

1 GigE

10 GigE

PCIe

200 2 14 200 16 800 Yes Yes Yes X310 USB 3.0

1 GigE

10 GigE

PCIe

200 2 14 200 16 800 Yes Yes Yes E310 Embedded 61.44 N/A 12 61.44 12 61.44 Yes No Yes E312 Embedded 61.44 N/A 12 61.44 12 61.44 Yes No Yes E320 Embedded

1 GigE

10 GigE

61.44 N/A 12 61.44 12 61.44 Yes Yes Yes Table 2 - USRP Characteristics by Model

The following sections cover frequently asked questions in choosing a USRP device that&#;s right for your application.

Do I want to perform processing on a host PC, or operate the USRP device in a standalone fashion?

This is an obvious differentiator of the USRP Embedded Series. If you need the USRP to operate a USRP radio without a host PC, the USRP E310/E312/E320 is the most appropriate. The USRP E310/E312/E320 is ideal for applications that might require mobile transceivers or distributed RF sensors. Unless the user has a clear requirement for embedded operation, Ettus Research recommends the USRP N200, N210, B200, B210, X300, X310, N300 or N310. Developing with a host-based platform typically involves less risk and will require less effort to optimize various pieces of the software radio.

In many cases it may be easier to develop with a USRP B200/B210 or USRP N200/N210, then port the code to the USRP E310/E312/E320. The UHD (USRP Hardware Driver) enables this portability. You must also consider the different processing capabilities of the host machine and ARM processor used on the USRP E310/E312/E320.

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Do I Need Synchronization and/or MIMO Capability?

Table 3 summarizes the synchronization features of each USRP device. Table 4 shows recommended solutions for MIMO systems of various sizes.

If you need MIMO capability for your application, Ettus Research recommends the USRP N200/N210, X300/X310, N300/N310 or E320. These units can be synchronized by providing a common time and frequency reference. Two USRP N200/N210s can be synchronized for MIMO operation with an Ettus Research MIMO cable. Alternatively, external 10 MHz reference and 1 PPS signals can be distributed to multiple USRP radios. With proper consideration for interface issues, it is possible to create MIMO system of arbitrary size with the USRP N200/N210, X300/X310, N300/N310 and E320.

The USRP B210, N300, E310/E312/E320 can serve a 2x2 MIMO capability because it has two integrated RF channels. When using the USRP B210 the available bandwidth is limited dependent upon the USB controller, and selected MIMO configuration. The USRP E310/E312's streaming bandwidth is limited to the 1 GigE interface to the ARM CPU. The USRP E320 supports streaming at full rate of 61.44 MS/s (SISO) or 30.72 MS/s (MIMO) via the 10 Gb interface. The USRP N300 supports streaming at 153.6 MS/s (SISO) and 125 MS/s (MIMO) via the 10Gb interface.

USRP Model BW Capability (MSPS w/ 16-bit) MIMO Capable Ext Ref. Input 1 PPS Input Internal GPS Disciplined Oscillator (Optional) Plug and Play MIMO N200 25 X X X X X N210 25 X X X X X N300 153.6, 125, 122.88 X X X X X N310 153.6, 125, 122.88 X X X X X B200mini 61.44 X X B205mini 61.44 X X B200 61.44 X X X B210 61.44 X X X X X X300 200 X X X X X X310 200 X X X X X E310 61.44 X X X X E312 61.44 X X X X E320 61.44 X X X X X Table 3 - Synchronization Capability of USRP Devices

USRP Model 2 x 2 MIMO 4 x 4 MIMO M x N MIMO N200/N210 MIMO Cable OctoClock OctoClock N300 Integrated Octoclock, White Rabbit Octoclock, White Rabbit N310 Integrated Integrated Octoclock, White Rabbit B200mini Not Recommended (SISO Only) Not Recommended Not Recommended B205mini Not Recommended (SISO Only) Not Recommended Not Recommended B200 Not Recommended (SISO Only) Not Recommended Not Recommended B210 Integrated Not Recommended Not Recommended X300 Integrated with Dual Daughterboards OctoClock OctoClock X310 Integrated with Dual Daughterboards OctoClock OctoClock E310 Integrated Not Recommended Not Recommended E312 Integrated Not Recommended Not Recommended E320 Integrated Octoclock Octoclock Table 4 - Recommended Models for MIMO Systems

What Are My Bandwidth Requirements?

Many Bandwidth requirements can also be used to narrow down the USRP selection. As seen in the table, the USRP N200/N210 is capable of streaming up to 50 MS/s in each direction in 8-bit mode, and 25 MS/s in 16-bit mode. The USRP B200 is capable of streaming up to 61.44MS/s total in 16-bit, 12-bit or 8-bit modes. The USRP E320 is capable of streaming up to 61.44 MS/s in 16-bit mode. The X300/X310 is capable of streaming up to 200 MS/s per channel (400 MS/s total) with 160 MHz of usable bandwidth per channel. The N300/N310 is capable of streaming up 122.88, 125 or 153.6 MS/s per channel. The N300/N310 is limited to 2x2 operation when using a 153.6 MS/s sample rate.

However, if there is interest in transmit and/or receiving larger bandwidth signals such as 802.11, the USRP N200/N210, X300/X310, N300/N310 or E320 would be appropriate. Note these limitations are based on the data throughput provided by the corresponding interfaces. It is important to consider the performance of the processing platform, and the computational intensity of the application. The constraints of the processing platform are independent of the full capability of the Ettus Research USRP radio and UHD.

What interface do I prefer to work with?

Assuming you have narrowed the viable devices down based on bandwidth, MIMO and channel count requirements, it is possible to select a USRP device based on the interface.

In general, USB 3.0 ports are more plentiful on computers. This makes the USRP B200/B210/B200mini/B205mini slightly more usable at short ranges. The USRP N200/N210 requires a Gigabit Ethernet port and a PC typically only provides one such port. If internet access is required, the user will also need to plan for an additional network adapter. The USRP X300/X310, N300/N310 and USRP E320 all support streaming via either a 1 GigE or 10 GigE interface.

The Gigabit Ethernet interface of the USRP N200/N210 can operate over significantly longer ranges (typically up to 100ft) compared to the USB interface of the USRP B2xx. This makes it possible to operate the USRP radio it more remote locations further from the host computer. The GigE interface can be accessed via a Gigabit Ethernet switch, allowing access to multiple devices. However, Ettus Research recommends a homogeneous network without other devices, such as network routers attached.

The 10 Gigabit Ethernet interfaces of the USRP N300/N310, X300/X310 and E320 can be operated using multimode fiber optic cables with appropriate adapters which increases the distance from the host computer.

Will I develop custom IP for the USRP device&#;s FPGA?

While most users deploy their USRP devices in a stock configuration, many others customize the FPGA with their own functionality. For example, you may want to offload modulation, demodulation, or other PHY/ MAC operations to the FPGA. This reduces host processing requirements, and may allow data reduction before passing data over the host interface. A summary of the FPGAs used on each USRP model are shown in Table 5.

Model FPGA Vendor FPGA Series FPGA Part Number System Gates Logic Elements Logic Cells Slices DSP48's BRAM DCM's Free Tools? N200 Xilinx Spartan 3A DSP XC3SDA k - 37,440 16,640 84 260k 8 Yes N210 Xilinx Spartan 3A DSP XC3SDA k - 53,714 23,872 126 373k 8 No B200mini Xilinx Spartan-6 XC6SLX75 - - 74,637 93,296 132 3,096k 12 Yes B205mini Xilinx Spartan-6 XC6SLX150 - - 147,443 184,304 180 4,824k 12 No B200 Xilinx Spartan 6 XC6SLX75 - - 74,637 93,296 132 3,096k 12 Yes B210 Xilinx Spartan 6 XC6SLX150 - - 147,443 184,304 180 4,824k 12 No X300 Xilinx Kintex-7 XC7K325T - - 321k 407,600 840 16,020k - No X310 Xilinx Kintex-7 XC7K410T - - 406k 508,400 28,620k - No E310 Xilinx Zynq- XC7Z020 - - 85k 106,400 220 560k - Yes E312 Xilinx Zynq- XC7Z020 - - 85k 106,400 220 560k - Yes E320 Xilinx Zynq- XC7Z045 - - 350k 437,200 900 19.2 Mb - No N300 Xilinx Zynq- XC7Z035 - - 275k 343,800 900 17.6 Mb - No N310 Xilinx Zynq- XC7Z100 - - 444K 554,800 26.5 Mb - No Table 5 - FPGA Resources

The USRP N200 and USRP N210 are great, generic platforms to experiment with FPGA development. However, the important difference between these two is the FPGA size, and requirements for Xilinx development tools. The USRP N200 includes a Xilinx Spartan XC3SDA FPGA. This FPGA is optimized for DSP capability, and the logic can be modified with free Xilinx ISE tools. The USRP N210 includes a Xilinx Spartan XC3DA FPGA. This FPGA provides nearly twice the resources, but requires a licensed seat of the Xilinx development tools for development.

Do I need flexible sample clock frequencies?

Some applications may benefit from a flexible sample clock frequency. The USRP E310/E312/E320 and USRP B200/B210/B200mini/B205mini include a flexible frequency clocking solution. This flexibility allows ideal sample clock frequencies to be used for various communications standards. For example, the GSM implementations commonly use a 52 MHz sample clock.

Do I want or need a rack-mountable solution?

Generally speaking, the selection of the USRP is based on performance requirements of the electrical components. However, the convenience of a rack-mounted solution may be an attractive feature that drives your decision. The USRP N200/N210, X300/X310 and N300/N310 can all be mounted in Ettus Research rack chassis. Up to four N200/N210 USRP devices can be mounted in the 3U chassis. Up to two X300/X310 or N300/N310 USRP devices can be mounted in the 1U chassis.

Will my requirements become more demanding as I learn more about the USRP and RF systems?

One final thing to consider is how your requirements will change over time. While a lower-cost USRP device, such as the USRP B200/B200mini, may meet your immediate requirements, it is possible that the USRP N200/N210, N300/N310 or E320 would be a more appropriate platform as you continue to develop more advanced RF systems. Key improvements to note in the higher-end USRP N200/N210/X300/X310/N300/N310/E320 is the increased bandwidth, increased dynamic range, and MIMO capability.

Fortunately, UHD allows the user to develop a single application compatible with all USRP models. Within certain limitations, the code you develop to work on a USRP B2xx will generally work on any other USRP. You must still consider variables such as sample rate, host interface bandwidth, and synchronization features to ensure compatibility.

Conclusion

This application note presents the functional specifications of each USRP device sold by Ettus Research. The data from this document can be used to make an educated selection of the most appropriate USRP device for a particular user or application. If you have any additional questions, do not hesitate to contact us at .

The electromagnetic spectrum is simultaneously vast and crowded. With billions of connected devices operating globally, these devices&#;whether commercial or military&#;are vying for the use of the spectrum. This competition necessitates the expansion of communications devices into higher frequency portions of the spectrum to provide appropriate bandwidth for devices to operate. While this is beneficial to the devices using the spectrum, it broadens the search area for the signals intelligence receivers that are aiming to maximize the probability of intercepting signals of interest. Tracking the full usable frequency range is challenging, requiring either multiple radios or wideband receivers to cover the plethora of frequency options available to connected devices.

Whether for introducing wider bandwidth systems, cognitive techniques, fully digital beamforming, or any novel capability, functions must be appropriately assessed and validated, likely in software simulation and with real hardware, prior to transferring to fielded deployment. Software defined radios (SDRs) help to bridge the gap from lab-based experimentation to tactical use. 

The Ettus USRP X440 software defined radio has an architecture unlike other USRP devices. The Ettus USRP X440 has a balun-coupled, direct-sampling architecture that provides access to the DACs and ADCs on the onboard Xilinx Zynq RFSoC. It may be used to directly sample frequencies up to 4 GHz, or it may be connected to external front ends for extending to higher frequency coverage. These front ends could be optimized for applications like satellite communications (SATCOM) prototyping, SATCOM ground station deployment, or mmWave and sub-THz 6G research.

Figure 1: Block Diagram of the Ettus USRP X440 Software Defined Radio Device

Without RF circuitry in the device, space is saved, allowing more channels to be incorporated without increasing footprint. The Ettus USRP X440 SDR features 8 TX and 8 RX channels per device. These channels can be made phase coherent by sharing the sample clocks, making the X440 ideal for applications like direction finding and radar research and prototyping.

For more USRP X Seriesinformation, please contact us. We will provide professional answers.