Accurate Signal Recovery in UHF Band Reuse-1 Cellular OFDMA Downlinks

<pre>Accurate signal recovery is challenging for non-co-located transmit antennae deployments due to Inter Tower Interference (ITI) in reuse-1 cellular OFDMA networks. In the sub-1 GHz UHF band where only SISO deployment is possible, interference aware receiver algorithms are essential to mitigate the ITI. In this work, we develop a Joint Modified Least Squares (JmLS) algorithm for channel estimation in the presence of ITI. Firstly, it is shown that the JmLS algorithm achieves the Cramer-Rao lower bound. Next, an approach to managing the possibly distinct carrier frequency offsets of the different co-channel signals of interest is proposed. This improves the quality of the bit-level Joint Log-Likelihood Ratio. Finally, the impact of the choice of pilot sub-carrier information in the block modulated air-interface on the coded block error rate performance is studied. In particular, a comparison is made between (i) frequency orthogonal pilots from the different sectors, vis-a-vis, (ii) a pilot-on-pilot arrangement using pseudo-orthogonal sequences. The study indicates that based on the extent of frequency selectivity and the number of interferers being considered, (ii) is advantageous when the set of ITI pilots incident on a receiver is small when compared to the set of all possible pilots.</pre>

Accurate Signal Recovery in UHF Band Reuse-1 Cellular OFDMA Downlinks

<pre>Accurate signal recovery is challenging for non-co-located transmit antennae deployments due to Inter Tower Interference (ITI) in reuse-1 cellular OFDMA networks. In the sub-1 GHz UHF band where only SISO deployment is possible, interference aware receiver algorithms are essential to mitigate the ITI. In this work, we develop a Joint Modified Least Squares (JmLS) algorithm for channel estimation in the presence of ITI. Firstly, it is shown that the JmLS algorithm achieves the Cramer-Rao lower bound. Next, an approach to managing the possibly distinct carrier frequency offsets of the different co-channel signals of interest is proposed. This improves the quality of the bit-level Joint Log-Likelihood Ratio. Finally, the impact of the choice of pilot sub-carrier information in the block modulated air-interface on the coded block error rate performance is studied. In particular, a comparison is made between (i) frequency orthogonal pilots from the different sectors, vis-a-vis, (ii) a pilot-on-pilot arrangement using pseudo-orthogonal sequences. The study indicates that based on the extent of frequency selectivity and the number of interferers being considered, (ii) is advantageous when the set of ITI pilots incident on a receiver is small when compared to the set of all possible pilots.</pre>

Genetic Algorithms to Maximize the Relevant Mutual Information in Communication Receivers

The preservation of relevant mutual information under compression is the fundamental challenge of the information bottleneck method. It has many applications in machine learning and in communications. The recent literature describes successful applications of this concept in quantized detection and channel decoding schemes. The focal idea is to build receiver algorithms intended to preserve the maximum possible amount of relevant information, despite very coarse quantization. The existent literature shows that the resulting quantized receiver algorithms can achieve performance very close to that of conventional high-precision systems. Moreover, all demanding signal processing operations get replaced with lookup operations in the considered system design. In this paper, we develop the idea of maximizing the preserved relevant information in communication receivers further by considering parametrized systems. Such systems can help overcome the need of lookup tables in cases where their huge sizes make them impractical. We propose to apply genetic algorithms which are inspired from the natural evolution of the species for the problem of parameter optimization. We exemplarily investigate receiver-sided channel output quantization and demodulation to illustrate the notable performance and the flexibility of the proposed concept.

Covert Anti-Jamming Communication Based on Gaussian Coded Modulation

In several wireless communication systems, robustness against jammers and covertness against eavesdroppers are required simultaneously. In this paper, we propose a novel covert anti-jamming communication system. The properties of both anti-jamming and covertness are achieved through the Gaussian-coded time-frequency modulation scheme. We propose two receiver algorithms based on the sparse signal recovery framework. The receiver algorithms estimate and remove the jamming signal from the received signal. In addition, it is difficult to distinguish the proposed signal from the actual Gaussian noise in both the time and frequency domains. We compare the covertness of the proposed communication system with that of a conventional digital modulation system in terms of the probability of detection. We numerically evaluated the bit error rate of the proposed system to demonstrate its anti-jamming performance.