Broadcast Phase Research Articles

Pigeon Inspired Optimization Based Centroid Selection in TGVFCMS for Energy-Efficient Wireless Sensor Network

Wireless Sensor Network (WSN) includes large quantities of sensing node used in various situations to collect data. WSN considers applications to collect data from remote locations, for example in environment surveillance, military, transport protection, etc. An energy efficient routing protocol is essential to handle the discharged electricity of the system and to minimize traffic and upstairs during data broadcast phases to fulfill the sensing, communication and processing tasks of the WSN. The biggest problem in the WSN is that energy resources are small. In this study, an energy-efficient routing protocol improves energy efficiency with the life span of sensor nodes by using optimization algorithm Pigeon Inspired Optimization (PIO). Clustering technique i.e. Total Generalized Variation Fuzzy c-means clustering (TGVFCMS) is used to select the Cluster Head (CH) and CH folds and bandage the information and direct it to the board node. By its fitness feature, PIO helps to initialize the centroid. After MATLAB simulation, the energy consumption rate was reduced to 25.03% while using PIO. Finally, comparisons are made between the work proposed and the existing current work to assess the effectiveness of the work proposed.

Performance analysis of physical-layer network coding with QPSK modulation in wireless IoT networks

In this paper, we mathematically analyze bit-error rate (BER) and diversity order of physical-layer network coding (PNC) scheme in the two-way relay channel (TWRC) under the assumption of multiple antennas at relay node. We assume the quadrature phase shift keying (QPSK) modulation for simple data transmission in IoT applications, and max–min transmit antenna selection (TAS) scheme in the broadcast (BC) phase for achieving full diversity gain. In particular, we obtain the upper bound of BER at the multiple access (MA) phase, while deriving the exact BER performance at the BC phase. To the best our knowledge, the mathematical analysis in this paper is the first analytical results in the literature. Through computer simulations, the analytical results are validated.

Distributed space‐time block coding based cooperative generalized spatial modulation

SummaryIn this study, two novel distributed space‐time block coding based cooperative generalized spatial modulation networks are proposed, and their theoretical analyses are derived. The first network is a three‐node cooperative system, consisting of a source (S), a relay (R), and a destination (D). In this design, S sends a GSM symbol to R and D in the broadcast phase. In the relay phase, if R decodes the received signal correctly, it encodes the orthogonal counterpart of the GSM symbol, and sends it to D. If R has a decoding error, it sends a failure to S, and S realizes the R's transmission. The second network is designed with two relays. Here, S sends the GSM symbol to , , and D in the broadcast phase. In the relay phase, if both relays decode the incoming signal correctly, regenerates the GSM symbol coming from S, and encodes the orthogonal version of it. After encoding, both send them to D in a successive manner. If any or both relays fail, S sends the symbol of in the relay phase. Theoretical and asymptotic analyses as well as simulation results are provided for both networks. It is seen that derived analytical expressions match with the simulation curves. Moreover, since we use the GSM in the proposed methods, their data rates are higher for the same number of transmit antennas. Even for the same spectral efficiency, they provide a significant diversity gain and a better error performance than the existing methods.

Stochastic Geometry Framework for Ultrareliable Cooperative Communications With Random Blockages

We study an industry automation scenario where a central controller broadcasts critical messages to the wireless devices (e.g., sensors/actuators). We devise a stochastic geometry framework where the rate coverage probability of devices is modeled by taking into account the density of roaming blockages over the factory floor. To alleviate the loss in the coverage, we adopt a two-phase transmission policy, where in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">broadcast phase</i> , the central controller broadcasts the messages intended for the devices in the network area. The devices in coverage in the broadcast phase act as decode-and-forward relays in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">relay phase</i> , so as to reinforce the signal strength at the devices in outage. The total downlink transmission time is, therefore, partitioned into two phases by a tunable factor. Finally, we study the optimal value of the partitioning factor with varying device densities, blockage densities, and file sizes, and we highlight that a longer transmission time should be allotted to the broadcast phase in the case of larger file sizes or lower transmit power of the controller.

A simple Encoding Scheme to Achieve the Capacity of Half-Duplex Relay Channel

In this paper, the Half-Duplex Relay Channel (HDRC) is thoroughly investigated. Even though this channel model is widely studied, the capacity is not yet fully understood and particularly has not been tightly expressed. In this work, a new capacity expression of the discrete memoryless HDRC is explicitly established. In particular, a new expression of the achievable rate is derived by taking advantage of the well-known capacity results of both the degraded broadcast channel and the multiple access channel. Specifically, in order to obtain the achievable rate, the transmission from the source to destination is operated over two phases. In the first phase, the broadcast phase, the source broadcasts to both relay and destination. In the second phase, both source and relay transmit to destination to form multiple access channel. Then, we prove that the new achievable rate meets the cut-set outer bound such that the capacity of the discrete memoryless HDRC is attained. Next, the new derived capacity result is extended to the case of additive Gaussian channel. Further, the attained capacity is analytically and then numerically shown to encompass all well-known available findings in the literature. Additional numerical examples are also shown to present the cases in which the relay is beneficial and how the achievable capacity varies with the source-relay and relay-destination channel gains.

Do not forget the past: A buffer-aided framework for relay based key generation

We address relay-assisted key generation wherein two wireless nodes, that have no direct channel between them, seek the assistance of an intermediate relay to generate secret keys. In a celebrated version of the relay-assisted protocol, as applied by Lai et al., Zhou et al., Wang et al., and Waqas et al., the relay node generates pair-wise keys with the two nodes, and then broadcasts an XOR version of the two keys. Although such protocols are simple and effective, we observe that they face reduction in key rates due to two problems. First, for confidentiality, the relay broadcasts an XOR function of the pair-wise keys thereby pruning the length of the shared key to be the minimum of the key lengths of the pair-wise keys. Secondly, the broadcast phase may also experience outages thereby not being able to share the generated key in every round of the protocol. Identifying these issues, we propose a buffer-aided relaying protocol wherein buffer is used at the relay to store unused secret bits generated in the previous rounds of the protocol so as to provide confidentiality in the subsequent rounds of broadcast. On this buffer-aided protocol, we propose a power-allocation strategy between the phases of key generation and broadcast so as to maximize the throughput and key rate. Rigorous analyses show that buffer-aided relay when implemented along with the proposed power-allocation strategy offer remarkable advantages over existing baselines.

Precoded Spatial Modulation-Aided Cooperative NOMA

In this letter, a precoded spatial modulation-aided cooperative nonorthogonal multiple access (NOMA), referred to as PC-NOMA, has been proposed for multiple-input and multiple-output (MIMO) downlink scenario. In PC-NOMA scheme, the base station (BS) broadcasts three users' information over two time slots: in the first slot, the two near users receive data through direct links and in the second slot, the third user (far) receives data indirectly from the near users. The precoded direct links' signal has been superposed with indirect link's signal in broadcast phase at the BS. The indirect link's signal has been decoded and forwarded at the direct link's user using the successive-interference cancellation (SIC) method in cooperative phase. The symbol error rate (SER) and mutual information (MI) under inter-users interference (IUI) have been derived for the proposed PC-NOMA. The impact of various system parameters, such as the number of transmitting and receiving antennas, have been analyzed for the proposed PC-NOMA.

Dynamic optimized cooperation in multi‐source multi‐relay wireless networks with random linear network coding

The authors present a strategy that improves the reliability of data transmission from multiple sources towards a destination D via multiple relays over wireless channels. After the broadcast phase, the destination selects the best cooperative direct link sources with the highest instantaneous signal-to-noise ratio , then generates and sends the random linear network coding coefficient matrix to the relays. After receiving the random linear network coding–coded symbols (packets) from the relays, D completes the reception and decoding of all source nodes packets. Monte Carlo simulations are conducted with Galois field (GF) () symbols ( = 2, 4 and 8) and the results are compared with the scenario of static cooperative direct links. An important decrease of symbol error rate (SER) is achieved. Furthermore, the efficiency of this approach is confirmed for the whole range of possible values of path loss exponent on direct links, that is, all types of environment between source nodes and destination D.

Secure Computation-and-Forward With Linear Codes

We discuss secure transmission via an untrusted relay when we have a multiple access phase from two nodes to the relay and a broadcast phase from the relay to the two nodes. To realize the security, we construct a code that securely transmits the modulo sum of the messages of two nodes via a multiple access channel. In this code, the relay cannot obtain any information with respect to the message of each node, and can decode only the modulo-sum of the messages of the two nodes. Our code is constructed by simple combination of an existing linear code and universal2 hash function.

JavaSim-IBFD-CRNs: Novel java simulator for in-band Full-Duplex cognitive radio networks over Internet of Things environment

Multi-channel non-time-slotted cognitive radio ad hoc networks are attractive to researchers nowadays; because they utilize the spectrum efficiently and represent a useful network design for Internet of Things (IoT) applications. From this point, a simulator that mimics these networks is developed using Java language. Further, researchers have proven that many problems facing these networks can be solved by using Full Duplex (FD) nodes. Thus, the proposed simulator is extended to support FD cognitive radio nodes. Each one of these nodes is allowed to receive in a sweeping pattern from various nodes, while transmitting to another node. In an alternative scenario, the node can transmit in a sweeping pattern to various nodes while receiving from one node in a specific direction. Both scenarios are adopted in the route request packet broadcasting phase. However, in the route reply packet delivery, the nodes are allowed to operate in FD transmit and sense or in FD transmit and receive modes. Interestingly, the simulator is tested using FD protocol, also introduced in this paper, that can be useful for IoT applications. Besides the proposed protocol is compared with very recent and close related routing protocol called Probabilistic and Deterministic Path Selection (PDPS). The results are logical; as they are compatible with the theoretical expectations, and the FD protocol surpassed PDPS by almost doubling the throughput.

Joint relay selection and power allocation for NOMA‐based multicast cognitive radio networks

In this study, the problem of joint relay selection and power allocation (J-RS-PA) for NOMA-based multicast cognitive radio networks is considered. In particular, the aim is to simultaneously maximise the end-to-end SINR/SNR of the primary and secondary transmitter–receiver (TR) pairs, subject to quality-of-service (QoS) constraints. Communication between the primary and secondary TR pairs is performed over two-phases, namely, the broadcasting phase, and the cooperation phase. In the broadcasting phase, the primary and secondary transmitters broadcast their data symbols; while in the cooperation phase, the selected relay forwards the decoded symbols to their intended receivers. However, the formulated J-RS-PA problem happens to be non-convex, resulting in computationally-prohibitive complexity. Consequently, an optimal low-complexity two-stage relay selection and power allocation (TS-RS-PA) algorithm is devised, which is based on the solution of linear programming problem reformulations. Simulation results are presented to validate the proposed TS-RS-PA algorithm, which is shown to yield the optimal SINR/SNR values in comparison to the J-RS-PA scheme, but with lower computational complexity, while satisfying QoS constraints.

Secrecy outage in a two-hop decode and forward relay network with accumulated harvested energy

In this paper, physical layer security is investigated under the accumulation of harvested energy in a particular frame of communication by a selected relay in an eavesdropper attacking network. The energy is accumulated at the multiple decode and forward (DF) relays by the energy harvester over several frames. The communication occurs between the source and the destination in two-phases using half-duplex mode. The first phase is a broadcasting phase in which the source broadcasts the information signal to the relays where a selected relay decodes the message and the second phase is relaying phase in which the selected relay encodes the message and forwards the signal to the destination. In the relaying phase, the selected relay also transmits a jamming signal along with the information signal to jam the eavesdropper. The forwarded signal of the selected relay is also received by the passive eavesdropper who tries to eavesdrop the message. Each relay is helped by two omnidirectional antennas, while the source, destination and the EAV use a single omnidirectional antenna. The relay selection is based on the maximizing secrecy capacity. The selected relay uses the received signal from one antenna to harvest the energy, while it uses the received signal from another antenna to decode the message. The harvested energy by a relay over a single frame may not be sufficient for successful forwarding of information which requires accumulation of harvesting energy over multiple frames. We have analyzed the physical layer secrecy in terms of several metrics such as secrecy outage probability (SOP), ergodic secrecy capacity, probability of strictly positive secrecy capacity and the secrecy throughput under a scenario where accumulated harvested energy is used in a particular frame. The impact of source transmit power, number of relays, number of frames used for harvesting energy and target secrecy rate is investigated on secrecy outage probability, ergodic secrecy rate, probability of strictly positive secrecy capacity and secrecy throughput. The MATLAB based simulation results verify the analytical results. We observe that the performance in terms of the SOP improved by 98.29% for three relays with respect to a single relay at 20dBm source’s transmit power.

Relay Selection Schemes for FSO Communications over Turbulent Channels

Free Space Optics (FSO) Communication has attracted the attention of the researchers in the last decade due to its high data rate, security, and low cost. Relay-assisted techniques are used to divide the distance to shorter hops in order to mitigate the effects of turbulence, weather attenuation, pointing error, and geometric loss. Choosing an active relay per time slot has been proven to enhance the performance of the system and decrease the loading effect on the system when compared to all active relays. This paper investigates the best relay that can be selected according to the source to relay (S-R) channel coefficient, relay to destination (R-D) channel coefficient, and source to destination (S-D) channel coefficient. A comprehensive comparison is applied to the three following cases: (a) Broadcast phase from source to relay to select the best (Proactive-Relay); (b) Broadcast phase from relay to destination after broadcasting to all relays then select (Reactive-relays); and, (c) Direct link from source-to-best relay-to-destination to conclude which method is better for different scenarios, such as turbulence regime, number of relays, different pointing error effect, and severity of S-R as compared to R-D and vice versa. The selection methods regard to four aspects: (1) Number of relays (two or three relays); (2) Distance between Source-Relay and Relay-Destination (D = 400–600 m, 500–500 m, and 600–400 m); (3) The different turbulence of Log-normal channel and Gamma-Gamma channel (with a refractive index coefficient( C n 2 = 0.5 × 10−14, 2 × 10−14 and 5 × 10−14)); and finally, (4) Beam waist ω z (pointing error).

An open modal stabilizing [formula omitted]-wave algorithm for arbitrary networks

A system that operates in multipleinput and corresponding operationalmodes depending on external input is referred to as an open modal (multi-mode) system. An input mode refers to a particular type and pattern of input whereas an operational mode refers to the operational semantics or the specification implemented by an algorithm. An open modal stabilizing system can operate in multiple operational modes and, eventually enters an operational mode depending on its current input mode. Such a system can be viewed as a generalization of the closed single-mode stabilizing systems that do not receive external input and implement a single operational mode upon entering a legitimate configuration.A wave is a distributed execution, often made up of a broadcast phase followed by a feedback phase, requiring the participation of all the system processors before a particular event called decision is taken. Wave algorithms with one initiator such as the 1-wave algorithm (Bui et al., 1999) have been shown to be very efficient for broadcasting messages in networks. However as the network size increases, having a single initiator adversely affects the message delivery times to nodes further away from the initiator. As a remedy, broadcast waves can be initiated by multiple initiator nodes forming a collection of waves covering the entire network to reduce the completion times of broadcasts. Solutions to global-snapshots, distributed broadcast and various synchronization problems can be solved efficiently using waves with multiple concurrent initiators (Prakash and Singhal, 1994).In this paper, we propose the first open modal stabilizing m-wave (multi-initiator wave) algorithm implementing concurrent waves started by multiple initiator processors. An m-wave is an execution in which a (non-empty) set of processors initiate broadcasts such that each processor in the network receives a broadcast that was initiated in the current m-wave. A broadcast is said to be initiated by a processor, if the processor has received an input and started the broadcast by informing others of this event. Since the algorithm is a modal algorithm, it is capable of operating in multiple operational and input modes, where the operational mode is determined by the input mode. Due to being stabilizing, the algorithm eventually behaves according to its specification, that is, after a delay and possible attempts to complete waves, every initiated m-wave is completed as per its specification. In addition, after stabilization, if the input mode changes, the system remains in a legitimate configuration, however, enters a new operational mode after a delay in which the corresponding broadcast semantics is implemented.

Performance Evaluation of Generalized Buffer-State-Based Relay Selection in NOMA-Aided Downlink

In this paper, we propose a novel buffer-state-based (BSB) non-orthogonal multiple access (NOMA)-aided downlink scheme for a two-hop cooperative network supporting multiple relay and destination nodes. More specifically, in the broadcast phase, the source node broadcasts information packets to multiple selected relay nodes. In the relaying phase, a selected relay node transmits packets to multiple destination nodes based on the NOMA principle. Here, the use of buffer at the relay nodes allows us to achieve a flexible relay selection. Furthermore, with the aid of buffer-state-based relay selection, the detrimental effects of empty- and full-buffer states are avoided. The theoretical outage probability and average packet delay are derived for our proposed scheme, based on the Markov-chain model. Our simulation results demonstrate that the proposed scheme outperforms the existing max-link and BSB relay selection benchmarks.

Secret Group-Key Generation at Physical Layer for Multi-Antenna Mesh Topology

In this paper, we propose a secret group-key generation scheme in physical layer, where an arbitrary number of multi-antenna LNs (LN) exist in mesh topology with a multi-antenna passive eavesdropper. In the first phase of the scheme, pilot signals are transmitted from selected antennas of all nodes and each node estimates channels linked to it. In the second phase, each node sequentially broadcasts a weighted combination of the estimated channel information using selected coefficients. The other LNs can obtain the channel information used for group-key generation while the eavesdropper cannot. Each node then can generate a group key by quantizing and encoding the estimated channels into keys. We apply well-known quantization schemes, such as scalar and vector quantizations, and compare their performance. To further enhance the key-generation performance, we also provide how to determine the antennas at each node used for group-key generation and the coefficients used in the broadcast phase. The simulation results verify the performance of the proposed secret group-key generation scheme using various key-related metrics. We also verify the practical robustness of our scheme by implementing a testbed using universal software radio peripheral. After generating secret common key among three nodes, we also test it using the National Institute of Standards and Technology test suit. The generated key passes the test and it is random enough for communication secrecy.

Non-Orthogonal Multiple Access With Cooperative Truncated ARQ and Relay Selection

In this paper, we propose a cooperative truncated automatic repeat-request (T-ARQ)-based non-orthogonal multiple access schemes with relay selection. There are two phases in our proposed scheme. In the broadcast phase, an access point superimposes the signals of near-user U1 and far-user U2 and then broadcasts the composite signal to both users and all the relays. All the terminals will try to decode the signal of U2 by treating the signal of U1 as interference. After that, U1 and relays will further decode the signal of U1 by canceling the signal of U2. The relays that can correctly decode the signals of U2 and U1 are classified into two decoding sets. In the cooperative T-ARQ phase, the relay from the decoding set with the best channel quality toward U2 or U1 is selected to retransmit the signal if necessary. Considering the various decoding statuses of U1, U2, and relays, we analyze the system throughput and reveal the impacts of key parameters, such as power allocation factor, transmit power, and target rate. The numerical results show that our proposed scheme can achieve much higher throughput than the T-ARQ-based time-division multiple access schemes.

Impact of Pre-and Post-Equalization on the Performance of PNC

The work presented considers a Physical Layer Network Coded (PNC) communication which is affected by Intersymbol Interference (ISI) due to Rayleigh fading channel. A pre-equalizer filter configured to combat the ISI is considered at the end nodes. The relay uses the Amplify and Forward (AF) strategy. The signal in the Multiple Access (MAC) phase is amplified at the relay and forwarded to the receiving nodes. The signal received by the end nodes in the broadcast (BC) phase is subjected to post-equalization by a receiver filter configured to overcome ISI. The performance of the PNC with only pre-equalizer applied, only post-equalization applied and the combined effect of pre-equalizer and post-equalizer is simulated .Simulation results indicate that the performance of PNC when only pre-equalizer applied , only post-equalization is applied are not much varying but better than the no equalization case. But the combined effect of pre-and post-equalization is much improved.

Relay performance optimisation based on signal space reconstruction

In this study, the authors study the interference exploitation problem in multi-input multi-output (MIMO) multi-way relay channel, which is MIMO Y channel. In this channel, multiple users complete the exchange of information among users through a common relay in the multiple access channel phase and broadcast phase. Each user sends signals to other users and receives the signals sent by other users. For a three-user transmission model, each user and relay have three antennas, respectively. To achieve better decoding performance at the relay, they design precoding vectors on the basis of traditional signal space alignment (SSA) so that the intersection subspaces hold orthogonal. Corresponding optimisation rules are proposed for zero-forcing and maximum-likelihood decoders. It is seen from the simulation results that the proposed algorithm greatly improves the decoding accuracy compared with the traditional SSA relay decoding, and reduce the computational complexity. Because of the improvement of the performance of relay decoding, the reliability of the whole transmission system will be improved.

Wireless Bidirectional Relaying Using Physical Layer Network Coding With Heterogeneous PSK Modulation

In bidirectional relaying using physical layer network coding (PLNC), it is generally assumed that users employ same modulation schemes in the multiple access phase. It may not be desirable for the users to always use the same modulation schemes, particularly when user-relay channels are not equally strong. Such a scheme is called heterogeneous PLNC where users employ different modulation schemes. In this paper, we provide a general analytical framework to find the network coding maps to be used at the relay during the broadcast phase, when the users employ heterogeneous, but symmetric phase-shift keying modulations. The fade state plane is partitioned into regions, where given network coding maps are employed. This partition has been obtained analytically, which is computationally efficient when compared to the computationally intensive approach taken by Zhang et al. which uses brute force computer-based search. Performance results are provided in terms of relay error rate and bit error rate.