Marco Hernandez

UWB systems for body area networks in IEEE 802.15.6

The paper describes a survey of the physical layer (PHY) of UWB systems for body area networks (BANs) currently in development by the international standard IEEE 802.15.6 Task Group (TG6). The UWB PHY includes IR-UWB and FM-UWB technologies. IR-UWB transceivers for BANs are based on the transmission of a single and relative long pulse per symbol (new paradigm in UWB) or a concatenation or burst of short pulses per symbol (legacy). FM-UWB transceivers are based on the concatenation of a CP-2FSK signal and a wideband FM signal (FM with high modulation index). Such systems are optimized for low power consumption and reliable operation, especially in medical applications.

Uplink performance enhancement for WCDMA systems through adaptive antenna and multiuser detection

Multipath fading and multiple access interference (MAI) are the major constraints on the performance of DS/CDMA systems. Antenna arrays and multiuser detectors have been considered to increase the system capacity through mitigation of such impairments. Multiuser detectors have the capability of eliminating MAI, the near-far problem and providing a significant capacity increase. In order to gain from the enhancements of both: multi-user detection and adaptive antenna, we propose in this paper to combine both schemes for an asynchronous WCDMA system. The performance of the combined scheme is evaluated for the uplink over the Gaussian channel and the UMTS frequency selective Rayleigh fading channel. We make a comparison of the most promising multiuser structures and the recursive least square algorithm to control the beamformer.

Subspace based estimation of parameters and linear space-time multiuser detection for WCDMA systems

The previously developed subspace techniques for estimation of parameters and recovery of WCDMA signals embedded in frequency selective channels have been probed as a very promising techniques with great theoretical and practical importance. Particularly, this paper extends a blind channel estimation algorithm based on intersection of subspaces. Such a scheme is used together with a JADE ESPRIT algorithm, which calculates jointly the relative delays and AOAs of multipath signals based on the shift invariance properties of WCDMA signals. Afterwards, a less complex linear space-time decorrelator with a sliding window of 3 bits over a frequency selective Rayleigh fading channel is studied. We investigate the BER performance of the system by Monte Carlo simulations.

UWB systems for body area networks

The paper describes the physical layer of UWB systems for body area networks currently in development by the IEEE standardization 802.15.6 Task Group. Impulse radio-based UWB systems with non-coherent and differential coherent modulations are envisioned as well as FM-UWB systems. Such systems are optimized for low power and reliability operation especially in medical applications.

Coexistence of UWB systems for body area networks in AWGN

The paper describes a coexistence study of IEEE 802.15.6 UWB devices with other UWB systems, in particular IEEE 802.15.4a (pico-nets) and IEEE 802.15.4f (RFID). At the time of writing this paper, IEEE 802.15.6 and IEEE 802.15.4f are in the last phase before publication. Hence, a brief summary of both PHYs is introduced. On the other hand, IEEE 802.15.6 UWB PHY includes IR-UWB and FM-UWB technologies. The IR-UWB transceivers for BANs are based on the transmission of a single and relative long pulse per symbol (new paradigm in UWB) or a concatenation or burst of short pulses per symbol (legacy), while FM-UWB transceivers are based on the concatenation of a CP-2FSK modulation and a wideband FM. Thus, coexistence between UWB devices becomes very important for reliable operation in medical applications.

Coexistence of IEEE Std 802.15.6 TM -2012 UWB-PHY with other UWB systems

The paper describes a coexistence study of IEEE Std 802.15.6-2012 UWB devices with other UWB systems, in particular IEEE Std 802.15.4a-2007 (pico-nets) devices and IEEE 802.15.4f-2012 (RFID) devices. The recently published IEEE Std 802.15.6™-2012 includes IR-UWB and FM-UWB technologies. The IR-UWB transceivers for BANs are based on the transmission of a single and relative long pulse per symbol (new paradigm in UWB) or a concatenation or burst of short pulses per symbol (legacy), while FM-UWB transceivers are based on the concatenation of a CP-2FSK signal and a wideband FM signal. Thus, coexistence between UWB devices becomes very important for reliable operation in medical applications.

UWB on-off waveform coded modulation for body area networks

The paper considers bit-interleaved coded modulation with on-off signaling constellations based on the IEEE 802.15.6 Standard for future body area networks (BANs) with a wideband PHY. The transmitter of BANs is constrained by the IEEE 802.15.6 Standard to have a conventional BCH(63,51) encoder and finite interleaving. The paper presents a proposal of a simple receiver architecture targeting low power consumption, although sub-optimal respect to the BICM decoder.

Space-time coded soft-iterative multiuser receivers for WCDMA

This paper proposes a soft-iterative multiuser receiver of low complexity, based on the principle of turbo decoding. A serially concatenated system is used, where every user employs a convolutional code, interleaver, space-time block code (STBC) and the spreading operation. The proposed receiver uses a soft-input soft-output (SISO) multiuser detector-decoder, which is basically a soft interference canceller for the space-time coded wideband code division multiple access (WCDMA) signal. In each iteration, extrinsic information is interchanged between the different SISO blocks giving asymptotically unbiased estimates. The introduction of STBC adds decorrelation between the different user signals, relaxing the interleaver design and less iterations are needed for the system to converge. The receiver allows the use of a less complex soft matched filter instead of a minimum mean square error (MMSE) filter. It achieves nearly single-user performance, and gives an excellent trade-off between implementation complexity and performance for advanced WCDMA multiuser receivers.

Array processing and multishot separator for WCDMA uplink transmission

In order to increase the capacity of WCDMA systems in the uplink while avoiding complexity, we investigate a space-time configuration by employing jointly beamforming and multishot multiuser separation. Such a joint structure provides a better bit error rate performance than either techniques used separately. Specifically, we propose a less complex space-time configuration, which is robust to multiple access interference (MAI) over a frequency selective Rayleigh fading channel. We investigate the BER performance of the system by Monte Carlo simulations. The results obtained show that applying space-time processing using a simple beamforming and multishot separator can improve the performance of WCDMA systems considerably.

Non-Orthogonal Multicarrier Modulation for UWB Systems

In this paper, we propose a non-orthogonal multi- carrier system for UWB systems to overcome the problem of intercarrier interference (ICI). The proposed scheme applies a window filtering operation around a group of consecutive subcarriers spanning 500 MHz. The filters samples are used instead of cyclic prefix of conventional OFDM systems. Thus, the proposed scheme is more efficient spectrum-wise. Furthermore, the filtering operation reduces out-of-band sidelobe levels, resulting in better robustness and relaxing the required frequency synchronization accuracy. Compared to other multicarrier approaches like OFDM or filter bank multicarrier, the proposal does not suffer from high overhead. Thus, the proposal is suitable for V2X UWB-applications requiring short burst transmissions and fast TDD switching with relax synchronization block and consequently reduced cost.