In this paper, a wearable three-antenna system aiming for cellular Internet of Things (IoT) applications is proposed. The presented antenna system consists of two cellular antennas (LTE low-and mid-band antennas) and one GPS antenna designed by using the Theory of Characteristic Mode (TCM). Both the simulated and measured results with good agreements are provided in this work. As a result of successful excitation of chassis modes, the proposed cellular antennas can cover the desired cellular bands between 699-862 MHz and 1710-2155 MHz with corresponding wideband matching circuits. Meanwhile, the proposed GPS antenna operates with a good right hand circular polarization (RHCP) performance (at least 5 dB higher gain than left hand circular polarization (LHCP)). Reasonable isolation performances among three antennas are also gained due to utilization of orthogonal modes. The results also show that with the proximity of human body (wrist phantom), over the wideband operation bands all antennas can achieve good efficiency. The averaged levels of-10 dB,-6 dB, and-4 dB, respectively for LTE low band, mid band and GPS band are achieved, indicating its potential in future wearable cellular IoT applications. Index Terms-wearable antenna, Theory of Characteristic Mode (TCM), small mobile terminal antenna, wristband antenna I.

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In 2011, we proposed a new receiver structure called Frequency domain linear MMSE filter with sphere detection for single-carrier frequency-division multiple access (SC-FDMA) uplink transmission. Frame error rate simulations and complexity estimations were used to define the most practical sphere detector algorithm for this receiver. High-level Synthesis (HLS) tools were used for comparing different architectures for the sphere detector. After 2011, the HLS design approach has gained more popularity and the tools have evolved. In this paper, HLS tools from different generations were used for implementing the same K-best list sphere detector. The results were compared and the overall experience of the optimization process and the evolution of the HLS tools was discussed. Additionally, the evolution of FPGA technology was discussed. In conclusion, the HLS tools have evolved into practical implementation tools even for high complex wireless communication algorithms. Moreover, 25% increase in throughput and 58% lower resource usage was achieved with the latest generation FPGA.

In this paper, a simulation study of the effect of antenna locations on antenna matching, bandwidth potential and radiation efficiency performance operating in 3GPP Long Term Evolution (LTE) Band 3 (1710-1880 MHz), Band 20 UL (832-862 MHz) and 2.4 GHz WLAN band (2.4-2.5 GHz), in free space and with phantom, is presented. An inverted F antenna (IFA) is utilized in this study and mounted on a small cellular wrist device. The results indicate that for each band, with efficient excitation of its fundamental mode, an antenna whose electrical field maxima located at short edge of the chassis always has higher bandwidth potential and its radiation efficiency will have less reduction when introducing phantom. Moreover, changes in matching characteristic of different antenna positions vary from each band, indicating the optimal antenna placement to obtain robust matching feature. Therefore, by comparing the variations on antenna behaviors, it provides useful insights into how to select the optimal antenna locations on the device with reduced a user effect for a specific operation band.

In this paper we present the measurement results for time-to-fix, position accuracy, and carrier-to-noise ratio of commercial Global Positioning System (GPS) receivers under the in-device interference from an LTE-M transmitter. The laboratory measurement set-up is built using software-defined radio (SDR) platforms to conductively feed emulated GPS L1 signals and LTE-M interference signals to the antenna input of the GPS receivers. The LTE-M interference from second harmonics is accurately modelled taking into account the transmitter activity patterns in different coverage enhancement modes. According to measurements, there are large variations in interference tolerance between different GPS receivers. REC01 was able to tolerate high level of interference during tracking and also in acquisition as long as the interference pulse duration is not too long (tens of milliseconds). REC02 performed clearly worse and tolerated only low levels of LTE-M interference during both acquisition and tracking. The same measurement set-up can be used with any GPS receiver for designing proper isolation and filtering levels for co-existing LTE-M transmitters.