Although Decentralized Finance (DeFi) applications facilitate tamper-proof transactions among multiple anonymous users, since attackers can access the smart contract bytecode directly, vulnerabilities in the transaction mechanism, contract code, or third-party components can be easily exploited to manipulate token prices, leading to financial losses. Since price manipulation often relies on specific states and complex trading sequences, existing detection tools have limitations in addressing this problem. In addition, to swiftly identify the root cause of an attack and implement targeted defense and remediation measures, auditors typically prioritize understanding the methodology behind the attack, emphasizing 'how' it occurred rather than simply confirming its existence. To address these problems, this paper presents a novel automatic price manipulation detection and analysis framework, named DeFort, which contains a price manipulation behavior model to guide on-chain detection, multiple price monitoring strategies to detect pools with abnormal token prices, and various profit calculation mechanisms to confirm attacks. Based on behavioral models, DeFort can automatically locate transactions and functions that cause abnormal price fluctuations and identify attackers and victims. Experimental results demonstrate that DeFort can outperform state-of-the-art price manipulation detection methods. Furthermore, after monitoring 441 real-world projects for two months, DeFort successfully detected five price manipulation attacks.

Despite achieving superior performance in human-level control problems, unlike humans, deep reinforcement learning (DRL) lacks high-order intelligence (e.g., logic deduction and reuse), thus it behaves ineffectively than humans regarding learning and generalization in complex problems. Previous works attempt to directly synthesize a white-box logic program as the DRL policy, manifesting logic-driven behaviors. However, most synthesis methods are built on imperative or declarative programming, and each has a distinct limitation, respectively. The former ignores the cause-effect logic during synthesis, resulting in low generalizability across tasks. The latter is strictly proof-based, thus failing to synthesize programs with complex hierarchical logic. In this paper, we combine the above two paradigms together and propose a novel Generalizable Logic Synthesis (GALOIS) framework to synthesize hierarchical and strict cause-effect logic programs. GALOIS leverages the program sketch and defines a new sketch-based hybrid program language for guiding the synthesis. Based on that, GALOIS proposes a sketch-based program synthesis method to automatically generate white-box programs with generalizable and interpretable cause-effect logic. Extensive evaluations on various decision-making tasks with complex logic demonstrate the superiority of GALOIS over mainstream baselines regarding the asymptotic performance, generalizability, and great knowledge reusability across different environments.

Conventional interference suppression techniques based on scalar antenna array may not be effective, when the satellite and interference signals have similar directions of arrival. In this paper, a power inversion (PI) algorithm with a novel constraint is proposed which is applied to electromagnetic vector sensor (EMVS) arrays and improve the performance of the standard PI algorithm. Interference with different polarization parameters than the satellite signal can be suppressed even when they have the same incident direction. A fast implement scheme is designed for the proposed algorithm and is effective for the Beidou satellite system public service signal.

Millimetre‐wave (MMW) in 60 GHz extremely high‐frequency band is deemed as a promising technique in indoor localisation based on its high multipath resolution, which can achieve higher measurement precision than ultra‐wideband system. To reduce the positioning errors, this study presents a new threshold determination scheme based on the extreme learning machine by analysing the characteristics of the received MMW pulses from the energy detector receiver. For each given signal‐to‐noise ratio, the thresholds are examined. The impacts on ranging accuracy are analysed due to the integration periods and propagation models. Results show the developed method can extensively improve the ranging precision.

Extreme learning machine (ELM) has attracted considerable attention in recent years due to its numerous applications in classification and regression. In this study, the authors investigate the performance of an ELM‐based threshold selection algorithm for 60 GHz millimetre wave time of arrival estimation using energy detector (ED). A hybrid metric based on the skewness, kurtosis, standard deviation, and slope of the ED values is employed. The optimal normalised threshold for different signal‐to‐noise ratios (SNRs) is investigated, and the effects of the integration period and channel model are examined. Performance results are presented which show that the proposed ELM‐based algorithm provides high precision and better robustness than existing techniques over a wide range of SNRs for the IEEE 802.15.3c CM1.1 and CM2.1 channel models. Further, the performance is largely independent of the integration period and channel model.

A generalised selection transmission (GST) and generalised selection combining (GSC) scheme is proposed for two‐way relay networks where two multi‐antenna sources exchange information via a single‐antenna relay. New exact and asymptotic expressions are derived for the outage probability and symbol error rate (SER) in Rayleigh fading. Moreover, a tight upper bound on the ergodic sum‐rate is presented. These results are used to demonstrate that the proposed GST/GSC scheme preserves the full diversity order, which equals the minimum number of antennas at the two sources. It is also shown that the impact of the number of selected antennas lies in the array gain only. Furthermore, the GST/GSC scheme significantly improves the performance relative to single‐antenna selection, and only incurs a negligible reduction in performance relative to all‐antenna beamforming. Finally, the optimal relay location that minimises the SER is determined analytically. It is observed that the optimal relay location shifts towards one source when the number of selected or available antennas at the other source increases.

In this paper, we investigate the performance of Nth best relay selection networks with secrecy constraints where several eavesdroppers try to overhear the source message. In order to enhance the network security, a single jammer is introduced to jam the eavesdroppers. In addition, sub-optimal selection strategy is introduced to combat the malicious attempt of eavesdroppers. We derive the exact secrecy performance in terms of probability of the non-zero secrecy capacity and the secrecy outage probability of the proposed relay selection approach. Based on these expressions, the effect of several important network parameters, i.e., the number of relays and the number of eavesdroppers, as well as the quality of the relay links, jammer links, and eavesdroppers links, on the proposed network are analytically characterized.

Pulse waveforms for 60 GHz impulse radio (IR) communication systems are investigated. The power spectral densities of the pulses are examined for compliance with Federal Communications Commission (FCC) spectral regulations. The error probability and capacity of M ‐ary pulse position modulation (PPM) 60 GHz IR systems with a correlation receiver using different pulse waveforms are analysed. Both orthogonal and non‐orthogonal PPM is considered with additive white Gaussian noise and IEEE 802.15.3c channel models. Analytical and simulation results are presented, which show that an autocorrelation function that decays quickly provides a lower probability of error and better capacity. Among the pulse waveforms examined in this study, the truncated sinc pulse is the best in terms of compliance with FCC regulations and the PPM error probability and capacity.

Differential pulse position amplitude modulation (DPPAM) is considered in an ultra wideband (UWB) communication system. DPPAM combines differential pulse position modulation (DPPM) and pulse amplitude modulation (PAM) to provide good performance with low computational complexity. The DPPAM UWB signal is derived from that of pulse position amplitude modulation (PPAM). The frame error rate (FER) of MN- ary DPPAM systems over additive white Gaussian noise (AWGN) and indoor fading channels is analyzed. The results show that the FER performance with 2N-ary DPPAM is better than that with 2N-ary DPPM and PPM, and MN-ary (M>;2) DPPAM provides a good compromise between FER and complexity.

In this letter, system capacity and error probability of orthogonal space-time block coding (STBC) is considered for PAM/PSK/QAM modulation in correlated Nakagami fading channels. The approach is based on an equivalent scalar AWGN (additive white Gaussian noise) channel with a channel gain proportional to the Frobenius norm of the matrix channel for the STBC. Closed form capacity and error probability expressions are derived for Nakagami fading channels. Numerical results are given to illustrate the theory.

Recently, pulse position amplitude modulation (PPAM) has been proposed for ultra-wideband (UWB) communication systems. PPAM combines pulse position modulation (PPM) and pulse amplitude modulation (PAM) to provide better performance and higher system capacity with low computational complexity. A RAKE receiver can make use of the rich multipath of UWB systems to improve system performance and capacity. In this paper we present the performance and capacity of a time hopping (TH) UWB system with PPAM modulation and RAKE reception over a practical multipath fading channel. Error probability and a union bound on performance, single user capacity and a capacity/distance bound based on FCC Part 15 rules, are derived. This analysis is extended to the multiple access case. Numerical results are given to illustrate the analysis.

In this paper, the error probability of orthogonal space-time block coding (STBC) is considered in correlated flat fading channels. The approach is based on an equivalent scalar AWGN (additive white Gaussian noise) channel. Closed form error probability expressions are derived for PSK/PAM/QAM on correlated fading channels.

In this paper, the capacity of orthogonal space-time block coding (STBC) is considered for PAM/PSK/QAM modulation in correlated flat fading channels. The approach is based on an equivalent scalar AWGN (additive white Gaussian noise) channel with a channel gain proportional to the Frobenius norm of the matrix channel for STBC.

In this letter, we propose a new modulation scheme called pulse position amplitude modulation (PPAM) for ultra-wideband (UWB) communication systems. PPAM combines pulse position modulation and pulse amplitude modulation to provide good system performance and low computational complexity. The channel capacity of PPAM is determined for a time-hopping multiple-access UWB communication system. The error probability and performance bounds are derived for a multiuser environment.

In this paper, we propose a new modulation scheme called biorthogonal pulse position modulation (BPPM) for ultra-wideband (UWB) communication systems. A set of N=2/sup k+1/ BPPM signals are constructed from 2/sup k/ orthogonal PPM signals by including the antipodal version of the orthogonal PPM signals. The channel capacity of BPPM is determined for a time-hopping multiple access UWB communication system. The error probability and performance bounds are derived for a multiuser environment. It is shown that N-ary BPPM has better performance than N-ary PPM with the same throughput and half the computational complexity.

The Shannon capacity of orthogonal space-time block codes (STBC) is considered for Rayleigh, Ricean and Nakagami-m uncorrelated fading channels and correlated Rayleigh fading channels. In this paper, STBC capacity expressions are derived for several fading channels. The Shannon capacity of a multiple antenna wireless system over a fading channel with continuous-valued inputs and continuous-valued outputs can be obtained.

In this paper, we develop a simple closed-form series expression for the error probability of maximum ratio combining (MRC) multichannel reception of M-ary coherent systems over flat Ricean fading channels. This series expansion provides a simple and numerically efficient mean of calculating the error probability with controlled accuracy. M-ary PAM, PSK and QAM systems are investigated.

In this paper, we propose a new modulation scheme called pulse amplitude position modulation (PPAM) for ultra-wideband (UWB) communication systems. PPAM combines pulse position modulation (PPM) and pulse amplitude modulation (PAM) to provide good system performance and low computational complexity. A set of MN-ary, M=2/sup k/, N=2/sup N/. PPAM signals are constructed from N-ary orthogonal PPM signals by including M-ary PAM signals in each dimension. It is shown that MN-ary PPAM has better performance than MN-ary PAM and less complexity than MN-ary PPM for MN>2. The channel capacity of PPAM is determined for a time-hopping multiple access UWB communication system. The error probability and performance bounds are derived for a multiuser environment. In particular, it is shown that for M=2. 2N-ary PPAM signals have better performance than 2N-ary PPM with the same throughput and half the computational complexity.