This paper proposes an improved method for reconstructing wideband sparse spectrum. We utilize a multicoset setup based on time delay. The simple multicoset setup is more suitable for practical implementation in comparison to more sophisticated sub-Nyquist systems. We first introduce the general reconstruction model that solves for a fixed number of variables. We employ a simple machine learning technique to classify the aliased sub-Nyquist bins into two categories. The classification method reduces the reconstruction time by decreasing the number of combinations and variables needed for resolving the signals. The saving in solution time is significant at low occupancy levels. Furthermore, the approach is robust against higher noise levels, because although the classification accuracy decreases as SNR decreases, the reduction in the accuracy of the classifier does not adversely affect the overall detection. We define detection performance metrics and provide simulation results to demonstrate the effectiveness of our approach.

Direct device-to-device (D2D) communications between mobile terminals in cellular networks allows operators to offload proximity traffic from the Radio Access Network (RAN) and permits out-of-coverage terminals to maintain peer-to-peer communications. In this study, we consider D2D communications in the context of the Long Term Evolution (LTE) RAN and, in particular, the scenario in which D2D communications share LTE uplink resources. Specifically, we evaluate the performance degradation of the cellular LTE uplink in the presence of interference from in-band (underlay) D2D communications. Through physical layer simulations, we quantify the increase in signal-to-noise ratio (SNR) needed to maintain a certain data rate or coverage criterion as a function of the induced noise rise and under various multipath channel conditions. The results can be used to develop physical layer models for network-layer analyses of D2D and cellular network performance.

Due to very low power communication, wireless body area networks are potentially susceptible to interference from other coexisting wireless systems including other BANs that might exist in their vicinity. Using power control to combat this interference might not be efficient. It could also lead to situations with higher levels of interference in the system. On the other hand, interference mitigation can help to not only preserve link quality but also allow more nodes to simultaneously operate. This paper proposes several interference mitigation schemes such as adaptive modulation as well as adaptive data rate and duty cycle for body area networks. Interference Mitigation Factor (IMF) is introduced as a measure to quantify the effectiveness of the proposed schemes.

A low complexity Parallel Interference Cancellation (PIC) technique is proposed to suppress Multi-Access Interference (MAI) and minimize near-far effect for multi-user communication using Direct-Sequence Code Division Multiple Access (DS-CDMA). Interference signal is estimated using a relationship between cyclic correlation of the received signal and user's code of the interferer without requiring any knowledge of the channel condition. The user's codes for the multi-user DS-CDMA communication are constructed by using a set of m-sequences. The cyclic correlation is performed using Fast Walsh-Hadamard Transform (FWHT) which exhibits low computational complexity, i.e., it does not require any multiplication/division operations. In addition to low complexity, the proposed technique does not require complicated channel condition estimation and has no convergence issues. The uncoded Bit Error Rate (BER) performance of the proposed interference cancellation is calculated and compared with the conventional one over three different types of channels: AWGN, slow Rayleigh fading, and multipath channels.

A low complexity Parallel Interference Cancellation (PIC) technique that is applicable to body area networks (BANs) is presented. Using Direct-Sequence Code Division Multiple Access (DS-CDMA), the technique aims at suppressing interference caused by rapid changes in relative sensors position due to body parts motion as well as interference from adjacent BANs. Interference signal is estimated using a relationship between cyclic correlation of the received signal and interferer code without requiring any knowledge of the channel condition. The codes for the multi-sensor DS-CDMA communication are constructed by using a set of m-sequences. The cyclic correlation is performed using Fast Walsh-Hadamard Transform (FWHT) which exhibits low computational complexity. In addition to low complexity, the proposed technique does not require complicated channel condition estimation and has no convergence issues. The uncoded Bit Error Rate (BER) performance of the proposed interference cancellation over a body-surface channel is calculated and compared with the conventional scheme.

Knowledge of the propagation media is a key step toward a successful transceiver design. Such information is typically gathered by conducting physical experiments, measuring and processing the corresponding data to obtain channel characteristics. In case of medical implants, this could be extremely difficult, if not impossible. In this paper, an immersive visualization environment is presented, which is used as a scientific instrument that gives us the ability to observe RF propagation from medical implants inside a human body. This virtual environment allows for more natural interaction between experts with different backgrounds, such as engineering and medical sciences. Here, we show how this platform has been used to determine a statistical path loss model for medical implant communication systems.

The paper examines protocols for voice/data integration in hybrid packet radio networks consisting of satellite and terrestrial components. The same protocols can be useful in the context of mixed-media packet radio networks employing HF ground radio links and EHF SATCOM radio links. As part of the integration protocol the ground subnetwork employs code-division multiple-access with movable boundary in the code domain to serve both the voice traffic and the retransmitted data traffic; on the satellite subnetwork framed ALOHA with movable boundary is used for both data and voice. A complete analysis of the channel-access protocols for both traffic types is provided based on a multi-dimensional Markovian model of the integrated voice/data system. The performance of the hybrid network is evaluated in terms of voice and data throughput, voice blocking probability, and data delay. It is observed that appropriate splitting of the retransmission traffic between the satellite and ground subnets may increase the overall data throughput when the voice load is high.>

The authors derive optimal admission policies for integrated voice and data traffic in packet radio networks employing code division multiple access (CDMA) with direct-sequence spread spectrum (DS/SS) signaling. The network performance is measured in terms of the average blocking probability of voice calls and the average delay and packet loss probability of data messages. The admission scheme determines the number of newly arrived voice users that are accepted in the network so that the long-term blocking probability of voice calls is minimized. In addition, new data arrivals are rejected if the mean delay or the packet loss probability of data exceeds a desirable prespecified level. A semi-Markov decision process (SMDP) is used to model the system operation. Then, a value iteration algorithm is used to derive the optimal admission control. Two models for the other-user interference of the CDMA system are considered: one based on thresholds and another based on the graceful degradation of the CDMA system performance, and their performance is compared. These admission policies find application in emerging commercial CDMA packet radio networks including cellular networks, personal communication networks, and networks of LEO satellites for global communications.>