USRP N210 Research Articles

Development of a GFDM waveform with radio defined with software

In this paper the performance of a Generalized Frequency Division Multiplexing waveform is evaluated when compared to an Orthogonal Frequency Division Multiplexing signal. For the development of the previous waveforms, the GNU radio software and the Software Defined Radio (SDR) equipment USRP N210 are used. Through a spectrum analyzer the power of both waveforms are measured and the Out-of-Band Radiation is analyzed. Then, the results obtained are compared and the advantages and disadvantages of the implementation of GFDM as a waveform within the fifth generation systems are exposed.

Regret Minimization for Primary/Secondary Access to Satellite Resources With Cognitive Interference

There are different forms of uncertainty in satellite communications, including cognitive interferers, channel conditions, packet traffic, and spectrum occupancy of users across channels. In addition, delay (such as propagation delay observed over satellite links) increases spectrum uncertainty and makes spectrum sensing and spectrum access two challenging tasks. To address such challenges, this paper presents a regret minimization solution for primary user (PU) and secondary user (SU) spectrum access to satellite resources in the presence of cognitive interferers. This robust game theoretic solution supports hierarchical spectrum sharing and dynamic spectrum access over multiple channels. Users select channels for data transmission and perform power control to optimize individual utility functions that are random due to different forms of uncertainty. The proposed game engine based on regret minimization framework provides a low-complexity and fast solution compared with traditional game solutions based on expected utility maximization. Detailed numerical results evaluate throughput and delay of PUs and SUs in the presence of cognitive interferers and compare the robust game theory-enabled approach with two benchmark schemes (with and without knowledge on channel availability). To support controllable and repeatable test and evaluation with real radios, an emulation testbed is built with software-defined radios connected with a network channel emulator that generates channel, mobility, and interference effects for satellite communications. GNU Radio modules are developed for cognitive network functionalities and run on USRP N210 radios that represent SU, PU, interferer, and satellite nodes. Emulation tests validate the effectiveness of the proposed solution under real radio effects.

Performance characterization of USRPs

This paper presents transmitter and receiver characterization and calibration results for software defined radio systems designed using the combination of RF front end hardware like USRPs (from Ettus Research) and software interfaces like GNU Radio. The main motivation for this study was the lack of useful references pertaining to calibration of such SDR systems, confining them to proof of concept experimentation. Measurements were taken using an SDR system designed using the USRP N210 with WBX daughterboard, GNU Radio utilities, and laboratory instruments. The main aim was to determine the differences between the values obtained on the GNU Radio spectrum analyzer software GUI utility and a laboratory spectrum analyzer. One-dB compression point, third order Input Intercept point and transmitted power variation with gain were measured to determine calibration factors and offsets. Experiments were conducted over sample set of USRP N210 devices to get standardized values. The calibration factors thus obtained were used in indoor path-loss modeling and position location estimation using the CORNET nodes at Virginia Tech to determine their effectiveness. As expected the root mean square deviations from expected values were lower when calibration factors were used to correct the power measurement readings from the GNU Radio utilities.

Come and Be Served: Parallel Decoding for COTS RFID Tags

Current commodity RFID systems incur high communication overhead due to severe tag-to-tag collisions. Although some recent works have been proposed to support parallel decoding for concurrent tag transmissions, they require accurate channel measurements, tight tag synchronization, or modifications to standard RFID tag operations. In this paper, we present BiGroup , a novel RFID communication paradigm that allows the reader to decode the collision from multiple commodity-off-the-shelf (COTS) RFID tags in one communication round. In BiGroup , COTS tags can directly join ongoing communication sessions and get decoded in parallel. The collision resolution intelligence is solely put at the reader side. To this end, BiGroup examines the tag collisions at RFID physical layer from constellation domain as well as time domain, exploits the under-utilized channel capacity due to low tag transmission rate, and leverages tag diversities. We implement BiGroup with USRP N210 software radio that is able to read and decode multiple concurrent transmissions from COTS passive tags. Our experimental study gives encouraging results that BiGroup greatly improves RFID communication efficiency, i.e., 11 times performance improvement compared with the alternative decoding scheme for COTS tags.

An adaptive hybrid ARQ method for coexistence of ZigBee and WiFi

With the rapid development of modern communication technology, all kinds of radio technologies emerge endlessly. As different wireless networks share the same spectrum, coexistence of the heterogeneous networks becomes a challenging problem, especially the coexistence between ZigBee and WiFi. Much research has been done to solve this problem, and some coexistence methods have been proposed, such as the spectrum allocation, power control and so on. However, the proposed methods are either too complex to implement or need additional hardware cost. This paper proposes an easy and feasible method called AHA for ZigBee. The method modifies the current FEC coding method and additionally colligates energy sensing and adaptive retransmission. By implementing the method on ZigBee using USRP N210 devices, it is demonstrated that AHA effectively improves the communication performance of ZigBee under WiFi interference.

A cognitive radio based solution to coexistence of FH and OFDM signals implemented on USRP N210 platform

A cognitive radio based solution to coexistence of FH and OFDM signals implemented on USRP N210 platform

Erratum: A cognitive radio based solution to coexistence of FH and OFDM signals implemented on USRP N210 platform (2017, vol. 9, no. 1, pp. 20-25)

Erratum: A cognitive radio based solution to coexistence of FH and OFDM signals implemented on USRP N210 platform (2017, vol. 9, no. 1, pp. 20-25)

We Can Hear You with Wi-Fi!

Recent literature advances Wi-Fi signals to “see” people's motions and locations. This paper asks the following question: Can Wi-Fi “hear” our talks? We present WiHear, which enables Wi-Fi signals to “hear” our talks without deploying any devices. To achieve this, WiHear needs to detect and analyze fine-grained radio reflections from mouth movements. WiHear solves this micro-movement detection problem by introducing Mouth Motion Profile that leverages partial multipath effects and wavelet packet transformation. Since Wi-Fi signals do not require line-of-sight, WiHear can “hear” people talks within the radio range. Further, WiHear can simultaneously “hear” multiple people's talks leveraging MIMO technology. We implement WiHear on both USRP N210 platform and commercial Wi-Fi infrastructure. Results show that within our pre-defined vocabulary, WiHear can achieve detection accuracy of 91 percent on average for single individual speaking no more than six words and up to 74 percent for no more than three people talking simultaneously. Moreover, the detection accuracy can be further improved by deploying multiple receivers from different angles.

DiFuse: distributed frequency domain user selection for multi-user MIMO networks

Optimal user selection is important in increasing the capacity of Multi-User Multi-Input Multi-Output Wi-Fi networks, yet it faces a significant challenge; the multi-user diversity gain can be overwhelmed by the formidable Channel State Information (CSI) acquisition overhead. To lessen the overhead, existing schemes adopt the greedy user selection which generally takes the projected norm as the user selection metric, since it considers both the channel power gain and the orthogonality. However, the projected norm suffers from occasional poor user selection, since it does not take the optimal sum capacity gain into account. This paper proposes a new distributed user selection protocol called DiFuse. To employ the sum capacity gain as the user selection metric in DiFuse, each user cleverly computes its own estimated capacity gain by overhearing the CSI feedback from others. The users then simultaneously transmit their feedbacks at the frequency domain via the distributed feedback contention, which effectively reduces the feedback overhead. Then the AP collectively utilizes them for user selection that achieves the maximum positive increment to the sum capacity gain. We implemented the prototype of DiFuse on the USRP N210, and evaluated its performance via both testbed experiments and trace-driven emulations. The results showed that DiFuse outperforms the throughput of the existing scheme called OPUS by 1.8 $${\times }$$ on average, while maintaining better fairness.

Performance Improvement Techniques for OFDM system using Software Defined Radio

Improved spectral and energy efficiency are two key requirements for the next generation (5G) wireless communication systems. The inefficiency and non-linearity of traditional power amplifiers (PA) pose significant challenges to meet these requirements, especially for multicarrier modulation signals with high peak to average power ratio (PAPR). Orthogonal frequency division multiplexing (OFDM) is currently the most widely used multi carrier modulation technique; it has been adopted in many wireless communication standards including IEEE 802.11, 802.16, 3GPP Long Term Evolution and WiMAX. When a high PAPR signal process through a nonlinear power amplifier (PA), intermodulation distortion is generated, creating out-of-band emission that can interfere with other transmission in adjacent bands. In addition, in-band distortion, which degrades the bit error rate performance, occurs. Hence, I have addressed these problems by employing four different PAPR reduction techniques such as Phase modulation, Rail clipping, Sample and Hold approach and Threshold methods based on amplitude clipping. For practical proof of the proposed concepts, I have chosen software defined radio as an experimental setup that employs USRP N210 as hardware and GNU Radio as software.

Speech Quality Measurement of GSM Infrastructure Built on USRP N210 and OpenBTS Project

The paper deals with the methodology for speech quality measuring in GSM networks using Per- ceptual Evaluation of Speech Quality (PESQ). The pa- per brings results of practical measurement of own GSM network build on the Universal Software Radio Peripheral (USRP N210) hardware and OpenBTS soft- ware. This OpenBTS station was installed in open ter- rain, and the speech quality was measured from dier- ent distances from the transmitter. The limit param- eters of OpenBTS station with USRP N210 were ob- tained.

BER Analysis with Adaptive Modulation Coding in MIMO-OFDM for WiMAX using GNU Radio

This paper explores how MIMO increases channel capacity and how the fundamental characteristics of a MIMO system can create significant test challenges. Spatial modulation (SM) is the latest developed modulation method in the field of communication. The latest research on this shows that SM is useful to achieve the multiplexing gain for the single antenna system, this avoids the inter-channel interference but the spatial modulation is inherently unable to get transmit-diversity. In other words, SM is a novel modulation technique which combines the high multiplexing gain provided by the spatial modulation and transmit-diversity gain, given by the space time block codes (STBCs) technology. Different space-time block coding (STBC) schemes including Alamouti’s STBC for 2 transmit antennas as well as orthogonal STBC (OSTBC) for 3 and 4 transmit antennas are explored. The result of using these MIMO techniques is higher data rate or longer transmit range without requiring additional bandwidth or transmit power. This paper presents a detailed study of diversity coding for MIMO systems. In addition, adaptive modulation and coding (AMC) technique in conjunction with MIMO techniques constitute a technological breakthrough that greatly helps in satisfying the ever increasing demands of wireless networks. This paper presents a performance study of Mobile WiMAX networks based on MIMO and AMC perspectives. It also describes how to implement WiMAX PHY with MIMO on software defined radio (SDR) experimental setup with the help of USRP N210 as hardware and GNU Radio as software platforms.

Concatenated Coding in OFDM for Wimax Using USRP N210 and GNU Radio

A software Defined Radio (SDR) device employs a reconfigurable hardware (Universal Software Radio Peripheral-USRP) that may be programmed over-the-air or software (GNU Radio) to function under different Wireless standards. This paper analyzes the effect of various parameters such as channel noise, frequency offset, timing offset, timing beta, FLL (Frequency Lock Loop) bandwidth, Costas loop (phase) bandwidth, filter roll off factor and multiply const on OFDM signal in WiMAX physical layer with concatenated coding using SDR test bed. Concatenated coding is performed by suggesting RM coder and Convolutional coders as inner code and outer codes respectively. Moreover, bit error rate and symbol error rates performance are analyzed by varying bits per symbol, window size and modulation scheme. Results proved that BER and SER values are improved as modulation scheme size (M) is increased. OFDM signal transmission and reception is performed using USRP N210 and configured by GNU radio in the laboratory environment.

A Methodology for Measuring Voice Quality Using PESQ and Interactive Voice Response in the GSM Channel Designed by OpenBTS

This article discusses a methodology for rating the quality of mobile calls. Majority telecommunications service from the perspective of the whole world is using mobile telephony networks. One of the problems affecting this service and its quality are landscape barriers, which prevent the spread signal. Price and complex construction of classic BTS does not allow their dense distribution. In such cases, one solution is to use OpenBTS technology. Design of OpenBTS is more available, so it can be applied to much more places and more complex points. Purpose of this measurement is a model for effective stations deployment, due to shape and distribution of local barriers that reduce signal power, and thus the quality of speech. GSM access point for our mobile terminals is OpenBTS USRP N210 station. The PESQ method for evaluating of speech quality is compared with the subjective evaluation, which provides Asterisk PBX with IVR call back. Measurement method was taken into account the call quality depending on terminal position. The measured results and its processing bring knowledge to use this technology for more complicated locations with degraded signal level and increases the quality of voice services in telecommunications.