Guillaume Villemaud

Opportunistic relaying protocols for human monitoring in BAN

Body Area Networks (BAN) offer amazing perspectives to instrument and support humans in many aspects of their life. Among all possible applications, this paper focuses on body monitoring applications having a body equipped with a set of sensors transmitting in real-time their measures to a common sink. The underlying network topology is a star topology which is quite usual in the broad scope of wireless sensor networks. Therefore, a classical superframe structure as proposed in 802.15.3 or 802.15.4 seems to comply with the needs of such an application. Basically however, the specificities of the BAN channel can reduce the performance of such protocol. Indeed, channel time variations make the star structure unstable and temporary subject to a high packet error rate. A multi-hop mesh topology cannot counteract this problem efficiently, since the pathloss attenuation in a BAN environment is almost independent with the emitter-receiver distance. In this paper, we address this issue by considering the topology of a BAN network as a time-varying fully connected network instead of a star structure. We then show how an opportunistic cooperative mechanism based on a decode-and-forward protocol can address this issue. We derive a performance criterion based on a packet error rate outage and we discuss the implementation of this scheme in the classical superframe structure.

BPSK Bit Error Outage over Nakagami-m Fading Channels in Lognormal Shadowing Environments

In this letter, we address the problem of finding a tractable expression for the bit-error outage (BEO) defined as the probability to observe a given average bit error rate (BER) over a fading channel in a shadowing environment. Our contribution is two-fold: (1) a simple yet tight approximation of the bit error probability (BEP) for binary phase shift keying (BPSK) over a frequency-flat Nakagami-m fading channel is derived, which (2) facilitates the derivation of a tight lower bound of the BEO in presence of lognormal shadowing in closed form. Theoretical results are corroborated by means of simulation results, confirming the tightness of the bounds.

M-ary symbol error outage over Nakagami-m fading channels in shadowing environments

This letter addresses the problem of finding a tractable expression for the symbol error outage (SEO) in flat Nakagami-m fading and shadowing channels. We deal with M-ary phase shift keying (M-PSK) and quadrature amplitude modulation (M-QAM) which extends our previous results on BPSK signaling. We propose a new tight approximation of the symbol error probability (SEP) holding for M-PSK and M-QAM signals which is accurate over all signal to noise ratios (SNRs) of interest. We derive a new generic expression for the inverse SEP which facilitates the derivation of a tight approximation of the SEO in a lognormal shadowing environment.

Design and evaluation of a wideband Full-Duplex OFDM system based on AASIC

Existing methods of self-interference cancellation have greatly reduced the strong self-interference signal for the practical design of Full-Duplex (FuDu) wireless systems. However, current FuDu wireless is hard to be put into practice due to the reason that residual self-interference after interference cancellation is still much stronger than the thermal noise. In this paper, a wideband FuDu OFDM system with a single path self-interference channel is developed based on active analog self-interference cancellation (AASIC) at the RF component. Furthermore, a mathematical model of the wideband FuDu OFDM wireless system and the AASIC at the RF component are presented and elaborated. The performance of this FuDu system is evaluated by ADS-Matlab co-simulation based on the IEEE 802.11g system parameters. The comparison of the spectrum power of signals before and after the AASIC and the bite error rate (BER) performance of the FuDu OFDM wireless system show that the strong self-interference can be significantly reduced to almost noise level.

On predicting fast fading strength from Indoor 802.11 simulations

In this article fast fading in indoor environments is predicted, using the MR-FDPF algorithm. MR-FDPF (frequency domain par flow) is a FDTD like method that can compute indoor radio coverage at a very precise resolution (a few centimeters). Using the simulated points in particular regions, it is possible to plot the distribution of the power signal, and to fit this distribution with Rice laws. In order to confirm our results, real radio measurements have also been done. In the considered environment, MR-FDPF has been proved to be efficient for the prediction of statistics of fading channels in indoor environment.

Full duplex prototype of OFDM on GNURadio and USRPs

Full-duplex is a technology in telecommunication domain that can perform transmitting and receiving at the same time and in the same frequency band. The major obstacle of full-duplex is the self-interference (SI). Some previous works have focused on the SI cancellation in radio frequency (RF), and generally on a narrowband signal model. We have implemented a full-duplex prototype with orthogonal frequency-division multiplexing (OFDM) technology on GNURadio and Universal Software Radio Peripherals (USRP). We focus on the baseband, namely the digital part of the SI cancellation. Our testbed can achieve a digital cancellation of 27dB. After the cancellation, the signal of interest can achieve a bit error rate (BER) in the scale of 10-5 at 4 meters, which is very close to the performance of half-duplex. This is, to our knowledge, the first full duplex implementation for OFDM technology.

Coupled simulation-measurements platform for the evaluation of frequency reuse in the 2.45 ghz ISM band for multimode nodes with multiple antennas

We address the problem of efficiently evaluating performance of concurrent radio links on overlapped channels. In complex network topologies with various standards and frequency channels, simulating a realistic PHY layer communication is a key point. The presented coupled simulation-measurement platform offers a very promising way of rapidly modelling and validating effective performance of multimode, multichannel and multiantenna radio nodes. An accurate analysis of radio channel is performed and then realistic performance with or without antenna processing is shown, verifying theoretical performance. Finally, available performance of concurrent communications on overlapped channels is exposed, showing that this approach is viable to enhance network capacity.

Implementation and validation of a new combined model for outdoor to indoor radio coverage predictions

A new model used to compute the outdoor to indoor signal strength emitted from an outdoor base station is presented. This model is based on the combination of 2 existing models: IRLA (Intelligent Ray Launching), a 3D Ray Optical model especially optimized for outdoor predictions, and MR-FDPF (Multiresolution Frequency Domain ParFlow), a 2D Finite Difference model initially implemented for indoor propagation. The combination of these models implies the conversion of the ray launching paths on the border of the buildings, into virtual source flows that will be used as input for the indoor model. The performance of the new combined model is evaluated via measurements at 2 frequencies (WiMAX and WiFi). This solution appears to be efficient for radio network planning, in term of both accuracy and computational cost.

Analysis and reduction of the impact of thermal noise on the Full-Duplex OFDM radio

Self-Interference has been significantly reduced by current cancelation methods for the practical design of Full-Duplex wireless. However, the residual self-interference is still much stronger than the thermal noise due to many factors, e.g. phase noise in local oscillator, I/Q imbalance, thermal noise and so on, limiting the self-interference cancelation. In this paper, the influence of the thermal noise on the active self-interference cancelation (ASIC) for wideband Full-Duplex OFDM wireless system is analytically studied and demonstrated. We propose a little modification to the structure of data packet of IEEE 802.11g to reduce the impact of the thermal noise on the ASIC for Full-Duplex OFDM radio. The ADS-Matlab co-simulation results show that we can reduce the residual self-interference to only 1.5dB higher than the receiver thermal noise.

Realistic Prediction of BER and AMC for Indoor Wireless Transmissions

Bit error rate (BER) is an important parameter for evaluating the performance of wireless networks. In this letter, a realistic BER for indoor wireless transmissions is predicted. The prediction is based on a deterministic radio propagation model, the Multi-Resolution Frequency Domain ParFlow (MR-FDPF) model, which is capable of providing accurate fading statistics. The obtained BER map can be used in many cases, e.g., adaptive modulation and coding (AMC) scheme or power allocation.