Special issue on amateur drone and UAV communications and networks

Jamalipour, Abbas,Kaleem, Zeeshan,Lorenz, Pascal,Choi, Wan Editorial Department of Journal of Communications 2018 Journal of communications and networks Vol.20 No.5

<P>The development of the mini-drones, formally called unmanned air vehicles (UAVs) have captured the attention of hobbyists and the investors due to their enormous applications. Drones have endless commercial applications as well due to the irrelatively small size and ability to fly without an on-board pilot such as in agriculture, photography, surveillance, and numerous public services. The use of drones for achieving high speed wireless communication is one of the most significant applications for next generation communication system (5G). Indeed, drone-based communication network offers encouraging solution to provide wireless connectivity for devices without infrastructure coverage due to e.g., severe shadowing by urban or mountainous terrain, or damage to the communication infrastructure caused by natural disasters.</P>

RA-eV2V: relaying systems for LTE-V2V communications

Park, Seungil,Kim, Byungjun,Yoon, Hoyoung,Choi, Sunghyun Editorial Department of Journal of Communications 2018 Journal of communications and networks Vol.20 No.4

<P>Emerging Long Term Evolution-based vehicle-to-vehicle (LTE-V2V) communication will support exchange of safety-related broadcast messages among vehicles. Such messages are generated periodically to announce one's own current state to other neighboring vehicles. The message reception performance in LTE-V2V drops sharply as communication distance increases if the communication channel is in a non-line-of-sight (NLOS) situation. To alleviate the problem, we propose a relaying system, called relayassisted enhanced V2V (RA-eV2V). In RA-eV2V, Road side unit (RSU) is in charge of relaying messages, received from vehicular user equipments (V-UEs). The operation of RSU is fully independent from other entities, meaning that the deployment of RSU on the road has no constraint at all. Moreover, there is no change from the current 3GPP standard operation on V-UE side either. In our realistic simulation, RA-eV2V hugely outperforms the 3GPP baseline scheme, e.g., by up to 36.5% in terms of message reception ratio in NLOS situations. Moreover, the feasibility of RA-eV2V is proven through real-map based simulation, which realistically reflects the actual situations on the roads.</P>

Positioning of UAVs for throughput maximization in software-defined disaster area UAV communication networks

ur Rahman, Shams,Kim, Geon-Hwan,Cho, You-Ze,Khan, Ajmal Editorial Department of Journal of Communications 2018 Journal of communications and networks Vol.20 No.5

<P>The throughput of a communication system depends on the data traffic load and the available capacity to support that load. In an unmanned aerial vehicle (UAV)-based communication system, the UAV position is one of the major factor affecting the capacity available to the flows (data sessions) being served. This paper proposes a centralized algorithm for positioning UAVs to maximize the throughput of a software-defined disaster area UAV communication network. The software-defined networking controller maintains upto date information about the network topology as well as the data rate demands and paths of the flows. The proposed algorithm utilizes this information to determine the positions for the UAVs such that the total throughput is maximized. The algorithm was simulated using MATLAB. The results showed that an average throughput improvement of 26% can be achieved by optimally positioning the UAVs.</P>

White-box AES implementation revisited

Baek, Chung Hun,Cheon, Jung Hee,Hong, Hyunsook Editorial Department of Journal of Communications 2016 Journal of communications and networks Vol.18 No.3

<P>White-box cryptography presented by Chow et al. is an obfuscation technique for protecting secret keys in software implementations even if an adversary has full access to the implementation of the encryption algorithm and full control over its execution platforms. Despite its practical importance, progress has not been substantial. In fact, it is repeated that as a proposal for a white-box implementation is reported, an attack of lower complexity is soon announced. This is mainly because most cryptanalytic methods target specific implementations, and there is no general attack tool for white-box cryptography. In this paper, we present an analytic toolbox on white-box implementations of the Chow et al.'s style using lookup tables. According to our toolbox, for a substitution-linear transformation cipher on n bits with S-boxes on m bits, the complexity for recovering the key obfuscated in the white-box implementation is O((3n/max(m(Q), m))2(3max(mQ,m)) + 2min {(n/m) L(m+3)2(2m), (n/m) L(3)2(3m) + n log L . 2(L/2)}), where m(Q) is the input size of nonlinear encodings, m(A) is the minimized block size of linear encodings, and L = lcm(m(A), m(Q)). As a result, a white-box implementation in the Chow et al.'s framework has complexity atmost O (min {(2(2m)/m) n(m+4), n log n.2(n/2) }), which is much less than 2(n). To overcome this, we introduce an idea that obfuscates two advanced encryption standard (AES)-128 ciphers at once with input/output encoding on 256 bits. To reduce storage, we use a sparse unsplit input encoding. As a result, our white-box AES implementation has up to 110-bit security against our toolbox, close to that of the original cipher. More generally, we may consider a white-box implementation of the t parallel encryption of AES to increase security.</P>

Channel AoA estimation for massive MIMO systems using one-bit ADCs

Kim, Hwanjin,Choi, Junil Editorial Department of Journal of Communications 2018 Journal of communications and networks Vol.20 No.4

<P>Although massive multiple-input multiple-output (MIMO) can enhance the overall system performance significantly, it could suffer from high cost and power consumption issues due to using a large number of radio frequency (RF) chains. Two different approaches are commonly exploited to overcome these issues. The first approach is using hybrid beamforming, which consists of analog and digital beamforming, to reduce the total number of RF chains. The second approach is adopting low-resolution analog-todigital converters (ADCs) for each RF chain. For both approaches, channel estimation becomes a difficult task. This paper addresses the problem of channel angle of arrival (AoA) estimation in massive MIMO using both hybrid beamforming and one-bit magnitudeaided (OMA) ADCs. An iterative algorithm is developed to estimate the channel AoA, and the appropriate threshold per iteration is analyzed. Numerical results show that the proposed technique can achieve sufficient AoA estimation performance with practical values of the signal-to-noise ratio (SNR).</P>

Opportunistic relaying for low-altitude UAV swarm secure communications with multiple eavesdroppers

Liu, Hongwu,Yoo, Sang-Jo,Kwak, Kyung Sup Editorial Department of Journal of Communications 2018 Journal of communications and networks Vol.20 No.5

<P>In this study, we investigate the secrecy outage performance achieved by opportunistic relaying for a low-altitude unmanned aerial vehicle (UAV) swarm secure communication system in the presence of multiple UAV-eavesdroppers. In the primary channel, multiple UAV-transmitters are connected to a ground station via the ground-to-air (G2A) wireless backhaul and a UAV-transmitter and UAV-relay are selected to transmit the source signal to a far ground destination under air-to-air and air-to-ground Nakagami-m fading links. In the eavesdropping channel, maximum ratio combining is applied across multiple UAV-eavesdroppers for intercepting the legitimate transmissions from both the selected UAV-transmitter and UAV-relay. The backhaul reliability and eavesdropping probability are introduced to reflect the practical constraints on the G2A wireless backhaul and UAV-eavesdropper cooperation, respectively. The closed-form expression for the secrecy outage probability is derived in terms of the UAV cooperation, backhaul reliability, eavesdropping probability, and Nakagami-m fading parameters. In the high signal-to-noise ratio region, the asymptotic secrecy outage probability is also derived. It is shown that the secrecy diversity gain achieved by opportunistic relaying is jointly determined by the UAV cooperation and shape factors of Nakagami-m fading links in the primary channel. The analytical secrecy outage metrics achieved by opportunistic relaying are verified by Monte Carlo simulation results.</P>

Mitigating stealthy jamming attacks in low-power and lossy wireless networks

Heo, Jeongyoon,Kim, Jung-Jun,Paek, Jeongyeup,Bahk, Saewoong Editorial Department of Journal of Communications 2018 Journal of communications and networks Vol.20 No.2

<P>Jamming in wireless networks has advanced to be more stealthy and long-lasting with limited energy. Stealthy attackers transmit short jamming signals to become less detectable with less energy, and yet powerful enough to ruin entire packet transmission procedures. In this article, we deal with three types of stealthy attacks: ‘Reactive jamming’, ‘Jamming ACK’, and ‘Fake ACK’ attacks. These attacks are fatal to low-power and lossy wireless network (LLN) applications because they not only interfere with communication, but also cause LLN devices to quickly drain their batteries. To counter these attacks, we present Dodge-Jam, a lightweight anti-jamming technique suitable for LLN environments to address the stealthy jamming attacks. It protects ACK packet by switching the ACK exchange channel to a channel calculated based on the content of a data packet. Moreover, by partitioning a packet into multiple blocks and performing logical shifts of the blocks when retransmitting the packet, it helps the receiver recover the original packet from received multiple erroneous packets. We implement Dodge-Jam on practical embedded devices, and evaluate its performance through mathematical analysis and experiments on a multi-hop LLN testbed. Our results show that Dodge-Jam successfully avoids many stealthy jamming attacks, recovers jammed packets, and significantly improves packet delivery performance of single-hop and multi-hop networks with small overhead.1</P>

Hidden Markov model based drone sound recognition using MFCC technique in practical noisy environments

Shi, Lin,Ahmad, Ishtiaq,He, YuJing,Chang, KyungHi Editorial Department of Journal of Communications 2018 Journal of communications and networks Vol.20 No.5

<P>The development of drones has captured the attention of hobbyists and investors alike; drones now have greater commercial and military applications owing to their relatively small size and ability to fly without an on-board pilot. However, certain drone applications may pose serious threats to public safety. The most important problem to be addressed is the recognition of drones in security-sensitive areas. This paper presents an approach to recognize drones through sounds emitted by their propellers using Mel frequency cepstral coefficients (MFCCs) technique for feature extraction and the hidden Markov model (HMM) approach for classification. In the feature extraction stage, two schemes for feature vectors (one using twenty-four MFCCs and the other using the proposed thirty-six MFCCs) are applied, where additional dynamic information of the features is added in the latter. The classifier based on HMMs is then trained using the extracted features according to different training datasets in order to validate the effect of the number of sound types in each cluster on the recognition rate performance. We perform experiments for drone sound recognition utilizing various training datasets for the purpose of classifier optimization, as well as for the two MFCC schemes that are applied in each trial, using the same training datasets for a fair comparison. The experimental results finally validate the feasibility and effectiveness of our proposed methods with relatively high recognition rates, even in noisy environments.</P>

Efficient decoding of block turbo codes

Son, Jaeyong,Kong, Jun Jin,Yang, Kyeongcheol Editorial Department of Journal of Communications 2018 Journal of communications and networks Vol.20 No.4

<P>Block turbo codes (BTCs) under iterative decoding are product codes showing excellent performance with reasonable complexity, whose component codes are conventionally decoded in two stages. The Chase algorithm is employed in the first stage to make a list of candidate codewords from the received vector, while the extrinsic information for iterative decoding is generated in the second stage. In this paper, we propose an efficient decoding algorithm for BTCs. The proposed algorithm can avoid a number of unnecessary hard-decision decoding operations by imposing two conditions on the Chase algorithm. Also, it simply computes the extrinsic information for the decision codeword. Numerical results demonstrate that the proposed algorithm has not only much lower computational complexity, but also a little better performance than the conventional decoding scheme based on the Chase algorithm. Furthermore, it can provide a trade-off between the performance and the computational complexity of BTCs by properly selecting a decoding parameter.</P>

Discrete-time Gaussian interfere-relay channel

Moon, Kiryang,Yoo, Do-Sik,Oh, Seong-Jun Editorial Department of Journal of Communications 2016 Journal of communications and networks Vol.18 No.3

<P>In practical wireless relay communication systems, non-destination nodes are assumed to be idle not receiving signals while the relay sends messages to a particular destination node, which results in reduced bandwidth efficiency. To improve the bandwidth efficiency, we relax the idle assumption of non-destination nodes and assume that non-destination nodes may receive signals from sources. We note that the message relayed to a particular node in such a system gives rise to interference to other nodes. To study such a more general relay system, we consider, in this paper, a relay system in which the relay first listens to the source, then routes the source message to the destination, and finally produces interference to the destination in sending messages for other systems. We obtain capacity upper and lower bounds and study the optimal method to deal with the interference as well as the optimal routing schemes. From analytic results obtained, we find the conditions on which the direct transmission provides higher transmission rate. Next, we find the conditions, by numerical evaluation of the theoretical results, on which it is better for the destination to cancel and decode the interference. Also we find the optimal source power allocation scheme that achieves the lower bound depending on various channel conditions. We believe that the results provided in this paper will provide useful insights to system designers in strategically choosing the optimal routing algorithms depending on the channel conditions.</P>