Anish Prasad Shrestha

On maximal ratio diversity with weighting errors for physical layer security

In this letter, we introduce the performance of maximal ratio combining (MRC) with weighting errors for physical layer security. We assume both legitimate user and eavesdropper each equipped with multiple antennas employ non ideal MRC. The non ideal MRC is designed in terms of power correlation between the estimated and actual fadings. We derive new closed-form and generalized expressions for connection and secrecy outage probability. Next, we investigate asymptotic behavior of the outage probability for high signal-to-noise ratio in main channel between the legitimate user and the transmitter. The asymptotic analysis provides new insights about actual diversity provided by MRC with weighting errors. We substantiate our claims with the analytic results and numerical evaluations.

Secure opportunistic scheduling with transmit antenna selection

We investigate the physical layer security for opportunistic scheduling scheme using transmit antenna selection (TAS) with maximal ratio combining (MRC) at receiver and eavesdropper under a quasi-static Rayleigh fading channel. We assume a scenario composed of a single transmitter, multiple users and a single eavesdropper each equipped with multiple antennas. The transmitter selects best transmit antenna and best user to enhance the secure communication. A theoretical analysis is performed to derive new closed form expressions for probability of positive secrecy and outage probability at a normalized secrecy rate. Furthermore, asymptotic analysis on the outage probability reveals the outage diversity gain and array gain. It is confirmed that number of antennas at eavesdropper impacts on secrecy array gain while the outage diversity gain is determined by the product of number of users and antennas at the transmitter and the user. From numerical results, TAS is verified as a suitable option for secure opportunistic scheduling.

Performance of opportunistic scheduling for physical layer security with transmit antenna selection

We introduce an opportunistic scheduling to enhance the physical layer security with transmit antenna selection (TAS) in multiuser environment. We consider a wireless communication system composed of a single transmitter and multiple legitimate users in the presence of several eavesdroppers with each node having multiple antennas under quasi-static Rayleigh fading channel. The transmitter selects the best transmitting antenna and the best user to maximize signal-to-noise ratio (SNR) at the selected user. The user and eavesdropper can employ either selection combining (SC) or maximal ratio combining (MRC) to combine the received signals. New closed-form expressions for probability of positive secrecy and outage are derived. Moreover, asymptotic analysis reveals the outage diversity gain and array gain for the proposed scheme. The impact of number of users, eavesdroppers, and antennas on secrecy performance are clearly demonstrated with mathematical analysis and numerical results.

Robust and Reliable Predictive Routing Strategy for Flying Ad-Hoc Networks

Ever-increasing demands for portable and flexible communications have led to rapid growth in networking between unmanned aerial vehicles often referred to as flying ad-hoc networks (FANETs). Existing mobile ad hoc routing protocols are not suitable for FANETs due to high-speed mobility, environmental conditions, and terrain structures. In order to overcome such obstacles, we propose a combined omnidirectional and directional transmission scheme, together with dynamic angle adjustment. Our proposed scheme features hybrid use of unicasting and geocasting routing using location and trajectory information. The prediction of intermediate node location using 3-D estimation and directional transmission toward the predicted location, enabling a longer transmission range, allows keeping track of a changing topology, which ensures the robustness of our protocol. In addition, the reduction in path re-establishment and service disruption time to increase the path lifetime and successful packet transmissions ensures the reliability of our proposed strategy. Simulation results verify that our proposed scheme could significantly increase the performance of flying ad hoc networks.

Performance of transmit antenna selection in non-orthogonal multiple access for 5G systems

Transmit antenna selection is very common technique to reduce system complexity and power consumption at transmitter side while maintaining nearly the same performance of multiple antennas. In this paper, we introduce a transmit antenna selection (TAS) scheme for non orthogonal multiple access (NOMA) to improve the performance in terms of total sum rate. We consider a downlink multiuser multi-input single-output communication system where a single base station equipped with multiple antennas with a single radio frequency (RF) chain communicate with several users equipped with single antenna using NOMA. We verify that TAS at the base station considerably provides higher sum rate compared to single antenna system by exploiting spatial diversity.

Enhanced Rate Division Multiple Access for Electromagnetic Nanonetworks

An electromagnetic (EM) nanonetowork is considered to be a key technology in realizing Internet of Nano-Things. However, the traditional communication schemes cannot be directly applied at nanoscale level due to extreme limitation in energy, memory, computational resources, and hardware designs. Due to unique properties of pulse-based communication in nanonetoworks, rate division time-spread ON-OFF keying is considered to be appropriate modulation and channel access mechanism. As such, a symbol in EM nanonetwork would be is represented by either a single pulse or absence of pulse. In rate division, the symbol streams transmitted by multiple users are interleaved by assigning different time periods between two symbols of each user referred as symbol interval. The symbol interval is required to be derived from prime or coprime numbers to minimize the number of collisions. In this paper, we propose a scheme to derive the symbol interval by generating unique prime number at each user node using Prime Mod algorithm. Our scheme do not require coordination between transmitter and receiver and it can be easily implemented in both infrastructure based and ad hoc nanonetworks. Moreover, we show the statistical properties of the computed prime numbers, bounds on prime numbers that can be used, collision probability, and comparison of computational complexity with conventional schemes.

Secure wireless multicasting in presence of multiple eavesdroppers

Physical layer security schemes for wireless communication can prevent eavesdropping even without use of upper layer cryptographic algorithms. As such, physical layer security based on information theoretic constraint is gaining both theoretical and practical importance in research community. In this paper, we investigate the physical layer security for wireless multicasting scheme consisting of a single antenna transmitter with multiple receivers and eavesdroppers both equipped with multiple antennas under quasi-static Rayleigh fading channel. We develop new closed-form expressions for the analysis of probability of positive secrecy as well as outage probability. We show that the physical layer security can be maintained even in presence of multiple eavesdroppers consisting multiple antennas. Furthermore, we also analyze the effect of number of antennas, users and eavesdroppers in the numerical results.

Uncoordinated rate division multiple access with Prime Mod 60 algorithm

Pulse-based communication systems have emerged as a promising candidate in the deployment of short-range wireless networks compare to carrier-based system. The unique properties of pulse communication allow to design interesting medium access schemes where pulse streams transmitted by multiple nodes can be interleaved. Rate division multiple access (RDMA) is one of such schemes where each node is assigned different pulse period. The pulse period for each node in RDMA is required to be derived from relative prime numbers to minimize collision probability. In this paper, we propose a scheme to generate unique prime number using Prime Mod 60 algorithm from which pulse period for each node can be derived. Our scheme enables the implementation of RDMA in a truly uncoordinated fashion. We further investigate the statistical results of computed prime numbers to confirm its feasibility in RDMA.

An energy efficient fair node selection for cooperative in-band and out-of-band spectrum sensing

Abstract In a cooperative cognitive network, multiple secondary user (SU) nodes are selected for spectrum sensing to detect the presence of primary user (PU) nodes in the currently used channel as well as identify other available unused licensed channels. Periodic sensing of such in-band (IB) and out-of-band (OB) channel consumes a considerable amount of energy which is a huge liability to an energy constrained networks. Additionally, SU nodes are selected to meet the requirements such as detection and false alarm probabilities. This results the consecutive selection of same nodes, which depletes the energy of those nodes rapidly shortening the lifetime of nodes and network itself. In this paper, we propose a fair and energy efficient node selection scheme for joint IB and OB spectrum sensing. The SU nodes are grouped based on the energy stored in it referred as residual energy. A joint optimization problem is formulated to minimize energy consumption while ensuring the selected nodes belong to specific group depending on whether sensing is IB or OB. Considering the nature of formulated problem, we use particle swarm optimization to solve it. The results show that proposed scheme not only consumes relatively less energy and reduces the number of dead nodes, but also allows to maintain fair distribution residual energy within the network. Consequently, the network can prolong its spectrum sensing activities for longer duration.

Genetic algorithm based sensing and channel allocation in cognitive ad-hoc networks

We present a novel out-of-band spectrum sensing and channel allocation scheme for frequency hopping based cognitive radio networks using genetic algorithm. Based on the optimized solution derived from GA, a set of nodes for sensing the next hopping channel and a set of nodes for transmitting data on current channel are derived. The channel allocation is performed according to individual traffic demand of each node. Simulation results show that the proposed scheme can achieve reliable spectrum sensing and efficient channel allocation.