Two-hop Wireless Research Articles

Cooperative Transmission against Impersonation Attack and Authentication Error in Two-Hop Wireless Networks

The wireless information-theoretic security from inter-session interference has attracted considerable attention recently. A prerequisite for available works is the precise distinction between legitimate nodes and eavesdroppers. However, the authentication error always exists in the node authentication process in Two-Hop wireless networks. This paper presents an eavesdropper model with authentication error and two eavesdropping ways. Then, the number of eavesdroppers can be tolerated is analyzed while the desired secrecy is achieved with high probability in the limit of a large number of relay nodes. Final, we draw two conclusions for authentication error: 1) the impersonate nodes are chosen as relay is the dominant factor of the transmitted message leakage, and the impersonation attack does seriously decrease the number of eavesdroppers can be tolerated. 2) The error authentication to legitimate nodes is almost no effect on the number of eavesdroppers can be tolerated.

Selection of the Best Two-Hop AF Wireless Link under Multiple Antenna Schemes over a Fading Channel

In evaluating the performance of a dual-hop wireless link, the effects of large and small scale fading has to be considered. To overcome this fading effect, several schemes, such as multiple-input multiple-output (MIMO) with orthogonal space time block codes (OSTBC), different combining schemes at the relay and receiving end, and orthogonal frequency division multiplexing (OFDM) are used in both the transmitting and the relay links. In this paper, we first make compare the performance of a two-hop wireless link under a different combination of space diversity in the first and second hop of the amplify-and-forward (AF) case. Our second task in this paper is to incorporate the weak signal of a direct link and then by applying the channel model of two random variables (one for a direct link and another for a relayed link) we get very impressive result at a low signal-to-noise ratio (SNR) that is comparable with other models at a higher SNR. Our third task is to bring other three schemes under a two-hop wireless link: use of transmit antenna selection (TAS) on both link with weak direct link, distributed Alamouti scheme in two-hop link and single relay antenna with OFDM subcarrier. Finally, all of the schemes mentioned above are compared to select the best possible model. The main finding of the paper is as follows: the use of MIMO on both hops but application TAS on both links with weak direct link and the full rate OFDM with the sub-carrier for an individual link provide a better result as compared to other models.

Performance Evaluation of Two-Hop Wireless Network under Asymmetric Fading Environment

To enhance the reliability of long wireless link, a relay is placed between transmitter and receiver which break the link into two parts: transmitter to relay called 1st hop and relay to receiver called 2nd hop; such arrangement is called two hop wireless links. In two-hop wireless communication sometimes 1st and 2nd hops are affected by different types of fading called asymmetric fading environment. In this paper we consider four different combinations of Rayleigh and Nakagami-m fading on 1st and 2nd hop to observe the profile of combined pdf (probability density function) and cdf (cumulative distribution function). With the help of cdf we determine the variation of outage probability of mixed fading. Finally we plot the SER (symbol error rate) against the SNR (signal to noise ratio) of the 2nd hop for all possible combinations of the two fading taking the SNR of 1st hop as a parameter. Although recent literature deals with asymmetric fading environment but in this paper instead of details statistical model of such fading we provide the relative scenario of mixed fading on 2-hop wireless link.

Markovian Process and Novel Secure Algorithm for Big Data in Two-Hop Wireless Networks

This paper checks the correctness of our novel algorithm for secure, reliable and flexible transmission of big data in two-hop wireless networks using cooperative jamming scheme of attacker location unknown through Markovian process. Big data has to transmit in two-hop from source-to-relay and relay-to-destination node by deploying security in physical layer. Based on our novel algorithm, the nodes of the network can be identifiable, the probability value of the data absorbing nodes namely capture node C, non-capture node NC, eavesdropper node E, in each level depends upon the present level to the next level, the probability of transition between two nodes is same at all times in a given time slot to ensure more secure transmission of big data. In this paper, maximum probability for capture nodes is considered to justify the efficient transmission of big data through Markovian process.

Tabu-Search-Based Metaheuristic Resource-Allocation Algorithm for SVC Multicast Over Wireless Relay Networks

Scalable video coding (SVC) is a promising technology for video multicast to users with different available transmission capacities. On the other hand, adaptive modulation and coding (AMC) schemes provide an efficient way to better utilize wireless network resources. However, the resource-allocation problem to support SVC multicast over wireless relay networks is a challenging one due to the existence of relay stations (RSs). We simplify the resource-allocation problem in this paper by assuming that the modulation and coding schemes (MCSs) assigned to lower video layers have equal or better coverage area than that assigned to higher video layers at each base station (BS)/RS. We discuss the optimal solution to the simplified problem and its relation with the orienteering problem (OP). Then, we propose a tabu search (TS)-based metaheuristic algorithm for dealing with the problem, which has been proven to be an effective and efficient algorithm for OP. The simulation results reveal that the proposed algorithm outperforms other algorithms under the assumptions of two-hop wireless relay networks or separated transmissions for the relay and access links, and it maintains a good approximation to the optimal results.

Joint adaptive power allocation and interference suppression algorithms based on theMSER criterion for wireless sensor networks

In this study, a two-hop wireless sensor network with multiple relay nodes is considered where the amplify-and-forward (AF) scheme is employed. Two algorithms are presented to jointly consider interference suppression and power allocation (PA) based on the minimization of the symbol error rate (SER) criterion. A stochastic gradient (SG) algorithm is developed on the basis of the minimum-SER (MSER) criterion to jointly update the parameter vectors that allocate the power levels among the relay sensors subject to a total power constraint and the linear receiver. In addition, a conjugate gradient (CG) algorithm is developed on the basis of the SER criterion. A centralized algorithm is designed at the fusion center. Destination nodes transmit the quantized information of the PA vector to the relay nodes through a limited-feedback channel. The complexity and convergence analysis of the proposed algorithms are carried out. Simulation results show that the proposed two adaptive algorithms significantly outperform the other previously reported algorithms.

Energy/bandwidth-Saving Cooperative Spectrum Sensing for Two-hopWRAN

A two-hop wireless regional area network (WRAN) providing monitoring services operating in Television White Space (TVWS), i.e., IEEE P802.22b, may employ a great number of subscriber customer-premises equipments (S-CPEs) possibly without mains power supply, leading to requirement of cost-effective a

MPSK Symbol-based Soft-Information-Forwarding Scheme in Rayleigh Fading Channels

In this paper, we proposed a symbol-based multiple phase shift keying (MPSK) soft-information-forwarding (SIF) scheme for a two-hop parallel relay wireless network in Rayleigh fading channel. First the binary information streams at the source are mapped into MPSK symbols, and the relays construct the relay processing function by passing the intermediate soft decisions. Then the relays broadcast the processed symbols to the destination. After the maximum ratio combination, the received symbols at the destination can be decided by maximum-likelihood (ML) decision. Four MPSK symbol-based forwarding schemes are investigated and the simulation results show that the bit error rate (BER) performance of soft information forwarding scheme has better BER performance than the existing memoryless forwarding scheme based on MPSK modulation, and it is more practical than the SIF scheme based on BPSK modulation

Transmission protocol for secure big data in two-hop wireless networks with cooperative jamming

Wireless communications nowadays are increasingly becoming irreplaceable networking technologies for military, governmental and financial communications where the data is exploding in volume, variety and velocity, called big data. This poses great challenges to ensuring security through cryptography. Recently, cooperative jamming has been proved as a promising physical layer technique to provide the everlasting security for wireless networks. Based on this scheme, this paper proposes a two-hop transmission protocol with parameters l, k,r and τ (2HR-(l,k,r,τ)) to ensure secure and reliable big data transmissions in wireless networks with multiple eavesdroppers. We first determine the relay selection region (RSR) as the square of side-length l centered at the middle point between the source and the destination. Then one of the k best relays located in the RSR is randomly selected as the message relay. During the forwarding in both hops, the remaining relays at least distance r away from the intended receivers and with channel gain to the intended receivers less than τ are selected to generate jamming signals to confuse the eavesdroppers. The results in this paper indicate that our protocol can provide flexible control of security, reliability and the energy balance performance, which characterizes how energy consumption for forwarding message is balanced among all the relays.

Degrees of Freedom of Two-Hop Wireless Networks: Everyone Gets the Entire Cake

We show that fully connected two-hop wireless networks with K sources, K relays, and K destinations have K degrees of freedom both in the case of time-varying channel coefficients and constant channel coefficients (in which case the result holds for almost all values of constant channel coefficients). Our main contribution is a new achievability scheme which we call Aligned Network Diagonalization. This scheme allows the data streams transmitted by the sources to undergo a diagonal linear transformation from the sources to the destinations, thus being received free of interference by their intended destination. In addition, we extend our scheme to multihop networks with fully connected hops, and multihop networks with MIMO nodes, for which the degrees of freedom are also fully characterized.

Measuring and modelling the thermal performance of the Tamar Suspension Bridge using a wireless sensor network

A study on the thermal performance of the Tamar Suspension Bridge deck in Plymouth, UK, is presented in this paper. Ambient air, suspension cable, deck and truss temperatures were acquired using a wired sensor system. Deck extension data were acquired using a two-hop wireless sensor network. Empirical models relating the deck extension to various combinations of temperatures were derived and compared. The most accurate model, which used all the four temperature variables, predicted the deck extension with an accuracy of 99.4%. Time delays ranging from 10 to 66 min were identified between the daily cycles of the air temperature and of the structural temperatures and deck extension. However, accounting for these delays in the temperature–extension models did not improve the models' prediction accuracy. The results of this study suggest that bridge design recommendations are based on overly simplistic assumptions which could result in significant errors in the estimated deck movement, especially for temperature extremes. These findings aim to help engineers better understand the important aspect of thermal performance of steel bridges. This paper also presents a concise study on the effective use of off-the-shelf wireless technology to support structural health monitoring of bridges.

Practical throughput analysis for two-hop wireless network coding

Network coding (NC) has been regarded as a promising technology for throughput improvement in wireless networks, so a thorough understanding on the possible throughput gain from using NC is essential for the application of such technology. Available studies of throughput gain from NC, which mainly focus on only coding sub-layer or both MAC layer and coding sub-layer but largely neglect the primary impact of physical-layer, may lead to an inaccurate (or even qualitatively incorrect) estimation of possible coding gain. To have a more thorough understanding on the practical throughput gain of NC, this paper explores the possible coding gain in the typical two-hop wireless relay network with a careful consideration of interactions among physical layer, MAC layer and coding sub-layer. We first develop an embedded Markov chain theoretical framework to capture the complicated interactions among physical layer, MAC layer and coding sub-layer, based on which the close-form expression of throughput is then derived. We further explore the optimal bandwidth allocation problem in relay nodes for throughput maximization, and also provide a coding condition to clarify the scenarios where network coding does improve the throughput. Our analysis indicates that network coding may actually degrade throughput under some scenarios that were misjudged as being beneficial by previous studies without a careful consideration of primary impact of physical-layer.

On Secure Wireless Communications for Service Oriented Computing

Two-hop wireless network serves as the basic net-work model for the study of general wireless networks, while cooperative jamming is a promising scheme to achieve the physi-cal layer security. This paper establishes a theoretical framework for the study of eavesdropper-tolerance capability (i.e., the exact maximum number of eavesdroppers that can be tolerated) in a two-hop wireless network, where the cooperative jamming is adopted to ensure security defined by secrecy outage probability (SOP) and opportunistic relaying is adopted to guarantee relia-bility defined by transmission outage probability (TOP). For the concerned network, closed form modeling for both SOP and TOP is first conducted based on the Central Limit Theorem. With the help of SOP and TOP models and also the Stochastic Ordering Theory, the model for eavesdropper-tolerance capability analysis is then developed. Finally, extensive simulation and numerical results are provided to illustrate the efficiency of our theoretical framework as well as the eavesdropper-tolerance capability of the concerned network from adopting cooperative jamming and opportunistic relaying.

On the Jamming Power Allocation for Secure Amplify-and-Forward Relaying via Cooperative Jamming

In this paper, we investigate secure communications in two-hop wireless relaying networks with one eavesdropper. To prevent the eavesdropper from intercepting the source message, the destination sends an intended jamming noise to the relay, which is referred to as cooperative jamming. This jamming noise helps protecting the source message from being captured reliably at the eavesdropper, while the destination cancels its self-intended noise. According to the channel information available at the destination, we derive three jamming power allocation strategies to minimize the outage probability of the secrecy rate. In addition, we derive analytic results quantifying the jamming power consumption of the proposed allocation methods.

Throughput analysis of two-hop wireless networks with network coding

A Two-hop Wireless Network (TWN) is the basic topology structure that provides network coding opportunity for improving throughput. Network coding on a homogeneous TWN, in which all the data flows have the same packet size and all the links have the same transmission rate, has been extensively investigated. In this paper, network coding on more practical heterogeneous TWNs, featured by various packet sizes and transmission rates, is studied. Based on the Markov model, the throughput of the proposed network coding scheme, together with the throughput gain, is derived, which matches the simulation results very well. Numerical analyses indicate that, encoding the packets with close size and close transmission rate and enlarging buffer size at the relay node help in improving the throughput gain.

Effective Capacity of Two-Hop Wireless Communication Systems

A two-hop wireless communication link in which a source sends data to a destination with the aid of an intermediate relay node is studied. It is assumed that there is no direct link between the source and the destination, and the relay forwards the information to the destination by employing the decode-and-forward scheme. Both the source and intermediate relay nodes are assumed to operate under statistical quality of service (QoS) constraints imposed as limitations on the buffer overflow probabilities. The maximum constant arrival rates that can be supported by this two-hop link in the presence of QoS constraints are characterized by determining the effective capacity of such links as a function of the QoS parameters and signal-to-noise ratios at the source and relay, and the fading distributions of the links. The analysis is performed for both full-duplex and half-duplex relaying. Through this study, the impact upon the throughput of having buffer constraints at the source and intermediate relay nodes is identified. The interactions between the buffer constraints in different nodes and how they affect the performance are studied. The optimal time-sharing parameter in half-duplex relaying is determined, and performance with half-duplex relaying is investigated.

Performance Evaluation of Two-Hop Wireless Link under Nakagami-m Fading

Now-a-days, intense research is going on two-hop wireless link under different fading conditions with its remedial measures. In this paper work, a two-hop link under three different conditions is considered: (i) MIMO on both hops, (ii) MISO in first hop and SIMO in second hop and finally (iii) SIMO in first hop and MISO in second hop. The three models used here give the flexibility of using STBC (Space Time Block Coding) and combining scheme on any of the source to relay (S- R) and relay to destination (R-D) link. Even incorporation of Transmitting Antenna Selection (TAS) is possible on any link. Here, the variation of SER (Symbol Error Rate) is determined against mean SNR (Signal-to-Noise Ratio) of R-D link for three different modulation schemes: BPSK, 8-PSK and 16-PSK, taking the number of antennas and SNR of S-R link as parameters under Nakagami -m fading condition. Keywords—MIMO; MISO; SIMO; TAS; MRC; SER; SNR. I. INTRODUCTION

Joint Linear Receiver Design and Power Allocation Using Alternating Optimization Algorithms for Wireless Sensor Networks

In this paper, we consider a two-hop wireless sensor network (WSN) with multiple relay nodes where the amplify-and-forward (AF) scheme is employed. We present strategies to design jointly linear receivers and the power-allocation parameters via an alternating optimization approach subject to global, individual, and neighbor-based power constraints. Two design criteria are considered: The first criterion minimizes the mean-square error (MSE), and the second criterion maximizes the sum-rate (SR) of the WSN. We derive constrained minimum mean-square error (MMSE) and constrained maximum sum-rate (MSR) expressions for the linear receivers and the power-allocation parameters that contain the optimal complex amplification coefficients for each relay node. Computer simulations show good performance of our proposed methods in terms of bit error rate (BER) or SR compared with the method with equal power allocation and to a two-stage power-allocation technique. Furthermore, the methods with neighbor-based constraints bring flexibility to balance the performance against the computational complexity and the need for feedback information, which is desirable for WSNs to extend their lifetime.

A Two-Hop Wireless Power Transfer System With an Efficiency-Enhanced Power Receiver for Motion-Free Capsule Endoscopy Inspection

This paper presents a wireless power transfer system for a motion-free capsule endoscopy inspection. Conventionally, a wireless power transmitter in a specifically designed jacket has to be connected to a strong power source with a long cable. To avoid the power cable and allow patients to walk freely in a room, this paper proposes a two-hop wireless power transfer system. First, power is transferred from a floor to a power relay in the patient's jacket via strong coupling. Next, power is delivered from the power relay to the capsule via loose coupling. Besides making patients much more conformable, the proposed techniques eliminate the sources of reliability issues arisen from the moving cable and connectors. In the capsule, it is critical to enhance the power conversion efficiency. This paper develops a switch-mode rectifier (rectifying efficiency of 93.6%) and a power combination circuit (enhances combining efficiency by 18%). Thanks to the two-hop transfer mechanism and the novel circuit techniques, this system is able to transfer an average power of 24 mW and a peak power of 90 mW from the floor to a 13 mm × 27 mm capsule over a distance of 1 m with the maximum dc-to-dc power efficiency of 3.04%.

Unique word-based distributed space–time block codes for two-hop wireless relay networks

Distributed space-time block codes (DSTBCs) have been developed to exploit diversity gains in cooperative communications systems. In this paper, we propose a new DSTBC based on unique word (UW) extension, referred to as the D-UW-STBC. The D-UW-STBC is devised for wireless relay networks with the amplify-and-forwarcl protocol and frequency selective fading channels. The data is transmitted from the source to the destination by a block-wise manner, resembling the block level of the Alamouti scheme. At the source, a UW is padded to the tail of each data block, which plays as a cyclic prefix, and thus allows for low-complexity implementation in the frequency domain. The additional purpose of using UW in this paper is to estimate the channels. However, the introduction of UWs makes it difficult to decouple the detection of data blocks. To achieve the orthogonality of the equivalent space-time channel, we carefully cancel the interference induced by the UWs. Also, a least square (LS) channel estimation approach is proposed, in which, the relay is transparent to the source and destination. The optimal UWs arc designed to minimise the effect of additive noise. Bit-crror-ratc (BER) performance comparison of various receiver schemes is carried out by computer simulations.