In this dissertation, we investigate the problem of designing an ultra-low power $M$-ary frequency shift keying (MFSK) system. In Chapter 2, We design a communication system that operates under stringent power constraints, but is flexible with bandwidth constraints. Our approach is to consider some of the key elements in a transceiver and optimize them for low power consumption, as opposed to optimizing them to minimize, say, average probability of error. An obvious consequence of this is that high complexity components of the system, such as matched filters, forward error correction that employs iterative decoders, coherent demodulators, and bandwidth-efficient modulation formats, are not feasible for this research. Rather, our system is designed using MFSK with non-coherent detection, optimized two-pole bandpass filters (BPF), and Reed-Solomon (RS) codes with hard-decision decoding. Among other things, we show that by properly optimizing the key parameters of the BPFs and RS codes, we can design the system to be significantly less complex than an optimal one, and only lose about 1.2 dB in terms of performance.

In Chapter 3, We extend the results from Chapter 2 to incorporate fast frequency hopping (FFH) and intelligent jamming. The system still operates under stringent power constraints, but is flexible with bandwidth constraints. Our system is designed using MFSK with non-coherent detection and fast frequency hopping (FFH), optimized two-pole BPF, and RS codes with hard-decision decoding. Among other things, we show that by properly optimizing the key parameters of the BPFs and RS codes, we can design the system to be significantly less complex than the MF system with a performance loss of less than 1.4 dB in terms of performance in most scenarios that we considered. Further, the 2-pole BPF system can actually outperform the corresponding MF system by up to 2.4 dB with multi-tone jamming.

In Chapter 4, we extend the results from Chapter 2 to incorporate Gaussian filtering. We improve our previous design by considering the power-bandwidth tradeoff, and we show that we can save a large percentage of system bandwidth by sacrificing a small amount of power, when the demodulator and coding parameters are optimized. For example, we can save 50\% of system bandwidth at the cost of 1 dB loss in performance compared to our previous system design. We quantify the performance loss as a function of both the system bandwidth saved and the time-bandwidth product of the Gaussian filter. We keep $M = 16$ as our baseline design, and compare the performance of the $M$-ary GFSK system with the corresponding MFSK system.

Most modern communication networks suffer from both intentional and unintentional interference. In this dissertation, we investigate three separate issues in modern wireless communication networks: sensing disruption attacks on cognitive radio networks (CRNs), sharing disruption attacks on cognitive radio non-orthogonal multiple access (CR-NOMA), and error analysis in millimeter-wave (mmWave) communication under unintentional interference environments.In the first problem, we propose a different approach for sensing disruption attacks in CRNs. We examine the optimal strategy for an intelligent adversary who aims to manipulate busy bands so that they appear to be free. This approach involves contaminating noise power measurements, as demonstrated through a two-step sensing scheme that combines energy detection with noise power estimation by secondary users. We demonstrate that the optimal strategies for sensing link disruptions include equal-power and partial-band flipping, from deriving the maximum average number of missed detections under specific power constraints of the adversary. Secondly, we examine the vulnerabilities of spectrum sharing in a CR-NOMA network, proposing a new type of attack termed sharing disruption. This attack disrupts the channel estimation phase, leading to a denial-of-service (DoS) for secondary users. We derive the optimal power allocation to maximize disruption, calculating the maximum average number of DoS bands under specific adversary power constraints. Additionally, we compare optimal power allocation with uniform power allocation. Lastly, we investigate the error performance of mmWave bands in the presence of unintentional interference. This analysis is motivated by the anticipated increase in number of users in near future. We examine M-ary quadrature amplitude modulation (M-QAM) across Nakagami-m channels, taking into account the impacts of directional antennas and blockage. We derive the average probability of error with employing a stochastic geometry framework that provide different insights for mmWave networks, particularly in device-to-device (D2D) communications.

Device-to-device (D2D) communication allows direct transmission between multiple transmitter-receiver pairs in cellular systems by reusing the spectrum, and offloads local traffic from the base station.

In resource allocation for a D2D video transmission system in a block fading environment, the performance improvement by applying the exact symbol error rate (SER) is compared with the conventional signal-to-interference-plus-noise-ratio (SINR) based SER evaluation method that uses a Gaussian approximation (GA) for the aggregated interference. An analytical SER expression for a D2D system using multicarrier bandlimited QAM is derived and then used in the resource allocation algorithm. Centralized resource allocation for the D2D system is considered, given knowledge of the channel state information and the rate distortion information of the video streams, and an iterative algorithm for subcarrier assignment and power allocation is proposed. Bit-level simulations for different numbers of D2D pairs demonstrate a considerable improvement on user capacity and video peak signal-to-noise ratio by incorporating the proposed SER expression compared to the GA. By invoking the conditions under which the central limit theorem holds, and comparing these conditions with the number of interferers and the power ratio of the dominant interferer in the simulated D2D system, the reason why the GA for the interference results in a pessimistic performance is also studied.

Resource allocation algorithms for D2D video transmission with a filter bank multicarrier waveform in a Rayleigh fading environment are investigated. The co-channel interference between D2D pairs is analyzed, and a cross-layer algorithm with a subcarrier assignment outer loop and a power control inner loop, which aims to optimize the overall video quality, is proposed. Unlike the non-convexity in physical layer power control for maximizing the total throughput, the cross-layer power control problem is convex under certain conditions, so a high quality solution for power control can be efficiently found. Simulation results demonstrate a higher overall video quality by the proposed cross-layer algorithm compared to baseline algorithms.

In this paper, we study the weight enumerator and the numerical performance of a class of binary linear block codes formed from a family of rate-compatible punctured convolutional (RCPC) codes. Also, we present useful numerical results for a well-known family of RCPC codes.