Selecting a USRP Device - Ettus Knowledge Base

From 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 - Updates

Abstract

This application note provides an overview of the USRP device family, compares various models based on key features, and guides users through selecting the right device for their specific application needs.

USRP Product Selector

The USRP Product Selector is a tool designed to aid in selecting the most suitable Ettus Research USRP Software Defined Radio (SDR) products based on your application requirements. By answering a series of questions, the USRP Product Selector will generate a PDF price quote which will be sent to you. The sales team at Ettus Research may reach out to assist with any additional inquiries you may have. For personalized support in navigating the USRP product selection, please send an inquiry.

Overview

Ettus Research provides this guide to assist users in determining the most appropriate Universal Software Radio Peripheral (USRP) for their particular application. To simplify the selection process, we have included a feature comparison table.

Understanding DSP Fundamentals

For individuals new to the USRP product line, software defined radio, or digital signal processing (DSP), it is beneficial to simulate the signals you intend to work with before choosing USRP hardware. Utilizing simulation tools like GNU Radio or LabVIEW can ensure clarity on concepts such as the Nyquist theorem and ADC/DAC limitations. A basic understanding of signal theory and DSP is essential for optimizing the chosen USRP model. Resources for further reading are available on our Suggested Reading page.

Common Applications

Table 1 outlines typical USRP and daughterboard combinations commonly utilized in various fields. It serves as a general starting point for selecting a USRP device, yet new users should closely match their application requirements to the detailed specifications of USRP devices provided in subsequent sections.

Table 1 - Recommended USRP Selection for Various Application Areas
Note: The B2xx, E3xx, and N3xx models do not support interchangeable daughterboards.

USRP Device Characteristics

Table 2 provides key attributes for all USRP models available from Ettus Research. This data aids in determining interface types, bandwidth capacities, and synchronization options suitable for each model. Use this information alongside your application's requirements to select the most appropriate USRP radio.

Table 2 - USRP Characteristics by Model

This section addresses common queries related to choosing the right USRP device for your needs.

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

This is a key distinction, particularly among the USRP Embedded Series. If your application requires the USRP to function without a host PC, the E310/E312/E320 versions are most suitable. These devices are great for mobile transceivers or distributed RF sensors. Absent a specific requirement for embedded operation, it is recommended to use models such as N200, N210, B200, B210, X300, X310, N300, or N310. Developing on a host platform generally involves reduced risk and less effort to optimize software radio components.

In many cases, developers begin with a USRP B200/B210 or N200/N210 and later transition their code to the E310/E312/E320. The UHD (USRP Hardware Driver) facilitates this relocation, though considerations about processing capabilities of the host machine and the ARM processor on the embedded models must be made.

Additional reading:
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Do I Need Synchronization and/or MIMO Capability?

Table 3 outlines the synchronization capabilities of each USRP device. Table 4 details recommended solutions for varying sizes of MIMO systems.

For applications necessitating MIMO capability, Ettus Research suggests models including the N200/N210, X300/X310, N300/N310, and E320. These models enable synchronization through shared time and frequency references. Multiple USRP N200/N210 units can synchronize MIMO operations with an Ettus Research MIMO cable. Alternatively, external 10 MHz and 1 PPS signals can synchronize multiple radios. With suitable interface management, MIMO systems of arbitrary sizes can be created using the specified models.

The B210, N300, E310/E312/E320 support 2x2 MIMO operations, while bandwidth can be limited by the selected USB controller and MIMO setup. The E310/E312's streaming bandwidth caps at the 1 GigE interface to the ARM CPU. The E320 allows full streaming rates of 61.44 MS/s for SISO or 30.72 MS/s for MIMO operations over the 10Gb interface. The N300 provides streaming capabilities of 153.6 MS/s for SISO and 125 MS/s for MIMO over the 10Gb interface.

Table 3 - Synchronization Capability of USRP Devices

What Are My Bandwidth Requirements?

Your bandwidth requirements can further narrow down your selection of USRP devices. As demonstrated in the earlier table, the N200/N210 models can stream up to 50 MS/s in 8-bit mode and 25 MS/s in 16-bit mode. The B200 supports 61.44 MS/s in total, while the E320 also streams at 61.44 MS/s using 16-bit mode. The X300/X310 models can stream both channels at 200 MS/s (total of 400 MS/s) using 160 MHz of usable bandwidth each. The N300/N310 can reach 122.88, 125, or 153.6 MS/s per channel, albeit limited to 2x2 operation at the 153.6 MS/s sample rate.

If your interest lies in transmitting or receiving wider bandwidth signals, such as those for 802.11, then the N200/N210, X300/X310, N300/N310, or E320 are more suitable. Keep in mind that these limits derive from data throughput of corresponding interfaces, necessitating acknowledgment of performance from the processing platform and the application’s computational demands.

What interface do I prefer to work with?

Once you've narrowed down your choices based on bandwidth, MIMO, and channel counts, consider the interface of the USRP device. Generally, USB 3.0 ports are more readily available on computer systems, enhancing the usability of B200, B210, B200mini, and B205mini for short distances. The N200/N210 models rely on Gigabit Ethernet ports, frequently limited to one per PC, requiring supplemental network adapters if internet access is needed. Models like X300/X310, N300/N310, and E320 provide streaming through either 1 GigE or 10 GigE interfaces.

The GigE interface of N200/N210 permits longer operational ranges (up to 100 ft) compared to USB interfaces of B2xx models, thus enabling deployment of radios farther from host computers. These devices can interconnect via a Gigabit Ethernet switch, allowing multiple devices to access the network; however, a homogeneous network setup is preferred to avoid possible connectivity issues with attached routers or other devices.

In high-bandwidth applications, the 10 Gigabit Ethernet interfaces on the N300/N310, X300/X310, and E320 can utilize multimode fiber optic cables with appropriate adapters, further extending the operational range from the host system.

Will I develop custom IP for the USRP device's FPGA?

While many users deploy their USRP devices in standard configurations, others choose to customize the FPGA for tailored functionality. This is often done to commit modulation, demodulation, or other PHY/MAC operations to the FPGA, subsequently lightening the processing load on the host and potentially reducing data volume transmitted over the interface. The summary of FPGA resources for each USRP model is included in Table 5.

Table 5 - FPGA Resources

The N200 and N210 models are excellent platforms to explore FPGA development. However, they differ in FPGA size and tools needed for development. The N200 uses the Xilinx Spartan XC3SDA FPGA, optimized for DSP with modifications possible through free Xilinx ISE tools. The N210 features the bigger Spartan XC3DA FPGA, offering nearly double the resources, but necessitating a licensed version of Xilinx tools for modifications.

Do I need flexible sample clock frequencies?

Applications demanding flexible sample clock frequencies will find the E310/E312/E320 and B200/B210/B200mini/B205mini devices accommodating. Their adjustable clock solutions allow for ideal sample clock frequencies suitable for various communication standards, such as the GSM that typically utilizes a 52 MHz sample clock.

Do I want or need a rack-mountable solution?

Generally, the choice of USRP should match the performance needs of the electrical components. However, the benefits of a rack-mounted solution could be a strong factor influencing your purchase. The N200/N210, X300/X310, and N300/N310 can all be housed in dedicated Ettus Research rack chassis, with the capability of accommodating up to four N200/N210 USRP devices in a 3U chassis or two X300/X310 or N300/N310 devices in a 1U chassis.

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

Lastly, consider how your requirements may evolve over time. While a lower-cost USRP, like B200/B200mini, may fulfill your current needs, higher-end models such as N200/N210, N300/N310, or E320 may become more fitting as your expertise expands in developing more complex RF systems. Major enhancements in these higher-end models include improved bandwidth capacity, dynamic range, and MIMO capabilities.

Fortunately, the UHD allows users to create a single application that is compatible with all USRP models. With certain limitations, the code that functions on a B2xx typically translates effectively across the USRP range. It's essential to keep in mind variables like sample rate, host interface bandwidth, and synchronization features to ensure compatibility.

Conclusion

This application note outlines the functional specifications of each USRP device available from Ettus Research. Use the information provided here to make an informed decision in selecting the optimal USRP device for your needs. Should you have any further questions, please reach out to us.

Ettus Research - Software Defined Radio

Digilent proudly presents a curated collection of Ettus Software Defined Radios and related accessories. Ettus Research's USRP is recognized globally as the leading provider of software-defined radio platforms. But what exactly is USRP? Ettus Research Universal Software Radio Peripheral (USRP) devices offer a flexible and adaptable platform for radio frequency (RF) applications, enabling users to transmit and receive signals over a broad spectrum of frequencies and bandwidths.

USRP by Ettus is a robust SDR platform, delivering unmatched flexibility and adaptability. It enables users to configure and customize both hardware and software in alignment with their specific application needs. Be it wireless communication, signal processing, radar, or scientific inquiry, the USRP Ettus is equipped to fulfill those requirements.

We provide a diverse range of USRP Ettus products tailored to diverse needs, including the B200/B200mini/B210, B205mini-i, and N310 models. The B200/B210 stands out as a compact, budget-friendly USRP board that allows for up to 56 MHz of instantaneous bandwidth. Meanwhile, the B205mini-i is an economical, USB-powered module capable of providing up to 30 MHz of bandwidth, and the N310 offers a high-performance platform supporting up to 1.2 GHz of instantaneous bandwidth.

By endorsing a wide range of development environments on a broad portfolio of high-performance RF hardware, the USRP platform is the preferred SDR solution for countless engineers, hobbyists, and students worldwide, dedicated to exploring, prototyping, and innovating cutting-edge wireless technologies across various applications. This software-defined radio collection strikes a balance between user-friendliness and a thriving open-source software ecosystem. Leveraging the capabilities of the USRP Hardware Driver (UHD), engineers are equipped with a multitude of software options, from open-source solutions to graphical system designs.

If you seek cognitive radio solutions, or are looking for competitive USRP pricing, or specific Ettus daughterboards, Digilent has what you need to achieve your wireless communication goals. Our commitment to quality ensures enhancements in both our product offerings and customer service.

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