Non-cooperative Scheme Research Articles

Distributed Joint Cluster Formation and Resource Allocation Scheme for Cooperative Data Collection in Virtual MIMO-Based M2M Networks

An efficient data collection scheme plays an important role for the real-time intelligent monitoring in many machine-to-machine (M2M) networks. In this paper, a distributed joint cluster formation and resource allocation scheme for data collection in cluster-based M2M networks is proposed. Specifically, in order to utilize the advantages of cooperation, we first propose a hierarchical transmission model which contains two communication phases. In the first phase, the intracluster information sharing is carried out by all the nodes within the same cluster. Then these nodes transmit the total information to the BS cooperatively with virtual-MIMO (VMIMO) protocol in the second phase. To grasp the properties and advantages of this cooperative transmission strategy, the theoretical analysis results are provided. The key issue in this system is to form the clusters and allocate resources efficiently. Since the optimization problem on this issue is an NP-hard problem, a feasible joint scheme for the cluster formation and resource allocation is proposed in this paper, which is carried out via coalition formation game with a distributed algorithm. This scheme can reduce the complexity while keeping an attractive performance. Simulation results show the properties of the proposed scheme and its advantages when comparing with the noncooperative scheme for the data collection in a practical scenario.

A Cooperative Mobile Satellite Communication System with the Dynamic Space-Time Coding

Channels of mobile satellite communications are affected by multipath fading and shadowing attenuation. At the same time, diversity gains are believed to improve the transmission reliability in fading channels. Considering that the traditional Space-Time Coding (STC) is not suitable for the cooperative mobile satellite communication, in this paper, a new cooperative mobile satellite communication system is proposed based on the Dynamic Space-Time Coding (D-STC). The transmitting energy of the proposed scheme is saved by avoiding forwarding erroneous signals in cooperative users. Meanwhile, this system benefits from diversity gains and the transmission is robust. Additionally, a closed-form expression of the outage probability for the proposed scheme is derived, and then it is demonstrated that this scheme is much better than the existing noncooperative scheme and schemes with traditional STCs in the outage performance. Finally, the analytical result is supported and validated by numerical simulations.

Outage Analysis of Cooperative Transmission with Energy Harvesting Relay: Time Switching versus Power Splitting

This paper investigates the multiuser transmission network with an energy harvesting (EH) cooperative relay, where a source transmits independent information to multiple destinations with the help of an energy constrained relay. The relay can harvest energy from the radio frequency (RF) signals transmitted from the source, and it helps the multiuser transmission only by consuming the harvested energy. By adopting the time switching and the power splitting relay receiver architectures, we firstly propose two protocols, the time switching cooperative multiuser transmission (TSCMT) protocol and the power splitting cooperative multiuser transmission (PSCMT) protocol, to enable the simultaneous information processing and EH at the relay for the system. To evaluate the system performance, we theoretically analyze the system outage probability for the two proposed protocols and then derive explicit expressions for each of them, respectively. Numerical results are provided to demonstrate the accuracy of our analytical results and reveal that compared with traditional noncooperative scheme our proposed protocols are green solutions to offer reliable communication and lower system outage probability without consuming additional energy. In particular, for the same transmit power at the source, the PSCMT protocol is superior to the TSCMT protocol to obtain lower system outage probability.

Cooperative waiting‐time reduction for cognitive radio networks using Stackelberg game

Waiting time occupies an important position in user's quality-of-service (QoS) evaluation system. However, in conventional overlay cognitive radio networks (CRN), the secondary users are not permitted to transmit any personal information whenever the spectrum is occupied by primary users. It follows that the waiting time of users depends heavily on the primary spectrum occupancy, which, in turn, cannot guarantee the QoS of the secondary users. To remedy this, a game theoretical cooperative waiting-time reducing method (CWTRM) is proposed in a self-generated CRN to meet users’ waiting-time demands. The proposed scheme divides the users to temporary primary and secondary groups instead of introducing an extraneous secondary network. Specifically, waiting users are served as temporary secondary users. The cooperation between them and the temporary primary users is proceeded in each frame to make reuse of the unused time fractions, thereby reducing the global waiting time of the network. The optimal relay power, pricing and corresponding cooperating strategies are determined with the utilisation of Stackelberg game and Hungarian method. Finally, the superiority of the proposed CWTRM over non-cooperative schemes is validated through simulations.

On relay selection and power allocation in cooperative free-space optical networks

Drawing increasing attention, free-space optics (FSO) is a cost-effective technology to support data intensive communications. Cooperative diversity is considered to be an effective means for combating weather turbulence in FSO networks. In this paper, we consider the challenging problem of joint relay selection and power allocation in FSO networks. The objective was to maximize the FSO network-wide throughput under constraints of a given power budget and a limited number of FSO transceivers. The problem is formulated as a mixed integer nonlinear programming (MINLP) problem, which is NP-hard. We first adopt the reformulation-linearization technique (RLT) to derive an upper bound for the original MINLP problem. Due to the relaxation, the solutions obtained from RLT are infeasible. We then propose both centralized and distributed algorithms using bipartite matching and convex optimization to obtain highly competitive solutions. The proposed algorithms are shown to outperform the noncooperative scheme and an existing relay selection protocol with considerable gains through simulations.

A dynamic clustering algorithm for downlink CoMP systems with multiple antenna UEs

Coordinated multi-point (CoMP) schemes have been widely studied in the recent years to tackle the inter-cell interference. In practice, latency and throughput constraints on the backhaul allow the organization of only small clusters of base stations (BSs) where joint processing (JP) can be implemented. In this work we focus on downlink CoMP-JP with multiple antenna user equipments (UEs) and propose a novel dynamic clustering algorithm. The additional degrees of freedom at the UE can be used to suppress the residual interference by using an interference rejection combiner (IRC) and allow a multistream transmission. In our proposal we first define a set of candidate clusters depending on long-term channel conditions. Then, in each time block, we develop a resource allocation scheme by jointly optimizing transmitter and receiver where: a) within each candidate cluster a weighted sum rate is estimated and then b) a set of clusters is scheduled in order to maximize the system weighted sum rate. Numerical results show that much higher rates are achieved when UEs are equipped with multiple antennas. Moreover, as this performance improvement is mainly due to the IRC, the gain achieved by the proposed approach with respect to the non-cooperative scheme decreases by increasing the number of UE antennas.

Analysis of cooperation gain for adaptive networks in different communication scenarios

Adaptive networks are well suited to perform distributed estimation task where the observations collected by nodes of a network are used to estimate a common network-wide desired parameter. Although the benefits of cooperation are clear for the networks with ideal links, in the presence of noisy links their behavior changes considerably. Thus, it is important to analyze, in this case, when and to what extent the cooperation improves the estimation performance. In this paper, we study the influence of noisy links on the effectiveness of cooperation for two important types of adaptive networks, i.e. incremental LMS adaptive network (ILMS) and diffusion LMS (DLMS). We first define the concept of cooperation gain and compute it for the ILMS and the DLMS algorithms with ideal and noisy links. We show that when the links are ideal, both ILMS and DLMS algorithms provide increased performance in comparison with the non-cooperative solution. On the other hand, in the presence of noisy links, the cooperation gain is not always influential, and based on the channel and data statistics, for some values of step-size, a non-cooperative scheme outperforms the ILMS and DLMS algorithms. We present some simulation results to clarify the discussions.

Secure Communications with Untrusted Secondary Nodes in Cognitive Radio Networks

We consider a cooperation scenario between primary users and untrusted secondary users in cognitive radio networks. The secondary users are willing to help the primary users to relay the primary users' messages in reward for being allowed to share the primary users' spectrum bands. However, the primary users might be reluctant to accept this help, since the secondary users are untrustworthy and may try unauthorized decoding of the primary users' messages. This paper will answer the question: when is this cooperation mutually beneficial for primary and secondary users? Taking an approach of information-theoretic secrecy, such as coding techniques for wiretap channels, the primary users can allow the secondary users to sense and relay the message, while ensuring that the secondary users are ignorant of the primary users' messages. We characterize an achievable secrecy rate of primary users with a rate of the secondary users' communication. From the derived rate pairs, an optimization problem is formulated such that the secondary transmitter distributes its transmit power to maximize its data rate while providing a higher secrecy rate to the primary users. We demonstrate that this cooperation can provide a positive secrecy rate, even when a non-cooperative scheme achieves a zero secrecy rate.

Simultaneous Information and Energy Transfer in Large-Scale Networks with/without Relaying

Energy harvesting (EH) from ambient radio-frequency (RF) electromagnetic waves is an efficient solution for fully autonomous and sustainable communication networks. Most of the related works presented in the literature are based on specific (and small-scale) network structures, which although give useful insights on the potential benefits of the RF-EH technology, cannot characterize the performance of general networks. In this paper, we adopt a large-scale approach of the RF-EH technology and we characterize the performance of a network with random number of transmitter-receiver pairs by using stochastic-geometry tools. Specifically, we analyze the outage probability performance and the average harvested energy, when receivers employ power splitting (PS) technique for "simultaneous" information and energy transfer. A non-cooperative scheme, where information/energy are conveyed only via direct links, is firstly considered and the outage performance of the system as well as the average harvested energy are derived in closed form in function of the power splitting. For this protocol, an interesting optimization problem which minimizes the transmitted power under outage probability and harvesting constraints, is formulated and solved in closed form. In addition, we study a cooperative protocol where sources' transmissions are supported by a random number of potential relays that are randomly distributed into the network. In this case, information/energy can be received at each destination via two independent and orthogonal paths (in case of relaying). We characterize both performance metrics, when a selection combining scheme is applied at the receivers and a single relay is randomly selected for cooperative diversity.

Performance Analysis of Local and Cooperative Spectrum Sensing in Cognitive Radio Networks

Cognitive radio (CR) has recently been identified as a promising technology to solve the spectrum inefficiency problem. CR users or secondary users (SUs) need to sense the presence of primary users (PUs) constantly and rapidly to utilize their unused spectrum. However, detection is compromised when a user experiences shadowing or fading effects. In such cases, the user cannot distinguish between an unused band and a deep fade. So, cooperative spectrum sensing is proposed to improve sensing performance. In this paper, we analyze the different spectrum sensing schemes with different fusion rules and their comparative behavior has also been studied. Moreover, the relationship between the throughput and sensing time in local and cooperative spectrum sensing has been investigated for PU protection and SU spectrum utilization mode. We also observe that average channel utilization depends on the number of cooperative users under PU protection scenario. The analytical results show that cooperative spectrum sensing employing OR rule has better performance than other fusion rules as well as non-cooperative scheme.

Improving Macrocell Downlink Throughput in Rayleigh Fading Channel Environment Through Femtocell User Cooperation

This paper studies cooperative techniques that rely on femtocell user diversity to improve the downlink communication quality of macrocell users. We analytically derive and evaluate the achievable performance of these techniques in the downlink of Rayleigh fading channels. We provide an approximation of both the bit-error rate (BER) and the data throughput that macrocell users receive with femtocell user cooperation. Using simulations, we show that under reasonable SNR values, cooperative schemes enhance the performances of macrocells by improving the BER, outage probability, and data throughput of macrocell users significantly when compared with the traditional, non-cooperative schemes.

Rao test based cooperative spectrum sensing for cognitive radios in non-Gaussian noise

In this paper, we address the problem of spectrum sensing in the presence of non-Gaussian noise for cognitive radio networks. A novel Rao test based detector, which does not require any a priori knowledge about the primary user (PU) signal and channels, is proposed for the detection of a primary user in non-Gaussian noises that are molded by the generalized Gaussian distribution (GGD). The statistic of the proposed Rao detector is derived and its detection performance is analyzed in the low signal-to-noise ratio regime and compared to that of the traditional energy detection. Furthermore, the Rao-based detection is extended to a multi-user cooperative framework by using the “k-out-of-M” decision fusion rule and considering erroneous reporting channels between the secondary users and the fusion center due to Rayleigh fading. The global cooperative detection and false alarm probabilities are derived based on the cooperative sensing scheme. Analytical and computer simulation results show that for a given probability of false alarm, the Rao detector can significantly enhance the spectrum sensing performance over the conventional energy detection and the polarity-coincidence-array (PCA) method in non-Gaussian noises. Furthermore, the proposed cooperative detection scheme has a significantly higher global probability of detection than the non-cooperative scheme.

Incorporating Observation Quality Information into the Incremental LMS Adaptive Networks

In this paper we investigate the effect of observation quality information (OQI) on the performance of a special class of adaptive networks known as distributed incremental least-mean square (DILMS) algorithm. To this aim we consider two different cases: (1) a homogeneous environment where all the nodes have the same observation noise variance (ONV) and (2) an inhomogeneous environment, where different nodes have different ONVs. In the first case we show that, for the same steady-state error, the DILMS algorithm has faster convergence rate in comparison with a non-cooperative scheme. In the second case, we first show that regardless of what ONVs are, the steady-state curves of mean-square deviation, excess mean-square error and mean square error (MSE) in each node are monotonically increasing functions of step-size parameter. Then, to use the OQI, we reformulate the parameter estimation as a constrained optimization problem with MSE criterion as the cost function and ONVs as the constraints. Using the Robbins-Monro method to solve the resultant problem, a new algorithm (which we call noise-constrained incremental LMS algorithm) is obtained which has faster convergence rate than the existing incremental LMS algorithm. Simulation results are also provided to clarify the performance of proposed algorithm.

Asynchronous Cooperative Relaying for Vehicle-to-Vehicle Communications

Cooperative diversity exploits the broadcast nature of wireless channels and uses relays to improve link reliability. Most of the cooperative communication protocols are assumed to be synchronous in nature, which is not always possible in vehicle-to-vehicle (V2V) communication due to fast moving nature of the nodes. Also the relay nodes are assumed to be half duplex which in turn reduces the spectral efficiency. In this paper, we propose an asynchronous cooperative communication protocol exploiting polarization diversity, which does not require synchronization at the relay node. Dual polarized antennas are employed at the relay node to achieve full duplex amplify-and-forward (ANF) communication. Hence the transmission duration is reduced which results into an increased throughput rate. Capacity analysis of the proposed scheme ascertains the high data rate as compared to conventional ANF. Bit error rate (BER) simulation also shows that the proposed scheme significantly outperforms both the non-cooperative single-input single-output and the conventional ANF schemes. Considering channel path loss, the proposed scheme consumes less total transmission energy as compared to the conventional ANF and non-cooperative scheme. Thus the proposed scheme is suitable for high rate and energy efficient relay-enabled communication.

Energy efficiency of some non-cooperative, cooperative and hybrid communication schemes in multi-relay WSNs

In this paper we analyze the energy efficiency of single-hop, multi-hop, cooperative selective decode-and-forward, cooperative incremental decode-and-forward, and even the combination of cooperative and non-cooperative schemes, in wireless sensor networks composed of several nodes. We assume that, as the sensor nodes can experience either non line-of-sight or some line-of-sight conditions, the Nakagami-m fading distribution is used to model the wireless environment. The energy efficiency analysis is constrained by a target outage probability and an end-to-end throughput. Our results show that in most scenarios cooperative incremental schemes are more energy efficient than the other methods.

Protocol design and performance analysis for cognitive cooperative networks with multiple antennas

Abstract In this article, we deal with a novel access protocol design for cognitive cooperative networks with multiple antennas. According to the principles of cognitive radio, the secondary user (SU) can exploit the primary user (PU) burstiness to access the licensed spectrum in the proposed access protocol. To get more access opportunities to the licensed spectrum, the SU simultaneously relays the PU’s packets and transmits its own packets based on the superposition coding. Furthermore, to concurrent transmission of the PU’s packets and SU’s packets based on the superposition coding such that they are received without the interference at the primary receiver and secondary receiver respectively, two weight vectors at the SU equipped with multiple antennas are designed based on zero-forcing algorithm. Specifically, from a networking perspective, we analyze the performance of the proposed access protocol in terms of the maximum stable throughput and the average end-to-end delay for both the PU and SU based on the principles of queueing theory. In addition, to protect the PU’s performance and exhibit the advantage of adopting multiple antenna technology, we jointly optimize the parameter of superposition coding and the number of antennas, and define the maximum stable throughput cooperative gain compared to the non-cooperative access scheme. More importantly, the impact of imperfect channel state information (CSI) at the SU on the maximum stable throughput and the average end-to-end delay performance is evaluated in the simulations from a practical point of view. Analysis and simulation results demonstrate that the proposed access protocol achieves significant performance gains for both the PU and the SU, outperforms the existing cooperative access protocol based on the dirty-paper coding, and keeps robust against to the imperfect CSI.

Distributed LMS estimation over networks with quantised communications

This article investigates the problem of distributed least mean-square (D-LMS) estimation over a network with quantised communication. Each node in the network has a quantiser consisting of a first-order dynamical encoder-decoder and can only communicate with its neighbours. Then a new D-LMS estimator is proposed by employing a weighted sum of the internal state differences between each node's quantiser and those of its neighbours. Performance analysis of the proposed quantised D-LMS algorithm is studied in terms of mean-square transient and steady-state measurements. We show that for Gaussian data and sufficiently small step sizes, the proposed cooperative D-LMS with quantisation is mean-square stable in all quantisation levels including the 1-bit case, and its performance approaches the cooperative D-LMS without quantisation when the quantisation step size is fairly small. Furthermore, although in unquantised case (infinite precision), the cooperative D-LMS always outperforms the non-cooperative D-LMS scheme (without communications among the neighbours); however, we show that due to the existence of quantisation error, the cooperative D-LMS with quantisation does not always outperform the non-cooperative D-LMS scheme, especially when the quantisation step size is quite large. Finally, numerical simulations also demonstrate that our theoretical performance matches well with experimental performance.

Concatenated RS-Convolutional Codes for Cooperative Wireless Communication

In the last few years, several works have investigated the performance of cooperative wireless systems with various types of channel codes such as Low Density Parity Check (LDPC), Turbo, CRC, convolutional and recently Reed Solomon (RS) codes. These cooperative schemes give power to single antenna mobiles to originate virtual multiple antennas transmitter, MIMO system, by sharing their antennas so that diversity gain is achieved. The most common cooperative schemes are decode and forward (DF) and coded cooperation (CC). Concatenated Reed Solomon and convolutional codes have been used by several wireless communication standards like digital video broadcasting (DVB) standards and IEEE 802.16e WiMAX standard. In this paper, we develop two different coded cooperation schemes and apply them to the mandatory structure of physical layer specifications of IEEE 802.16e WiMAX. The results attained for both coded cooperation schemes present magnificent diversity gains over non-cooperative scheme.

Network-MIMO for downlink in-band relay transmissions

With the objective of improving the spectral efficiency and coverage homogeneity of wireless cellular systems in the downlink, we investigate how to take advantage of two promising transmission technologies envisioned in current standards: network-MIMO and relay stations (RSs). It is assumed that half-duplex RSs are deployed in a cellular system, where the duration of the relay-receive and the relay-transmit phases is fixed beforehand for all cells. In order to reduce the spectral efficiency loses associated to half-duplex relaying, we propose the use of base station (BS) cooperation under a network-MIMO precoding strategy based on block-diagonalization zero-forcing, and optimize radio resources under the convex performance criteria constrained by the per-BS power, modulation and coding schemes and the transmission rate in the relay-transmit phase. By applying convex optimization techniques, the optimal precoding strategy is derived and a suboptimal low complexity solution is also proposed. The obtained solutions are evaluated at system level and compared to other cooperative and non-cooperative BS-based schemes.

A new distributed cooperative MIMO scheme for mobile ad hoc networks

In this paper, we introduce a new communication scheme based on cooperative multiple-input multiple-output (MIMO) communication for mobile ad hoc networks (MANETs) in which nodes are endowed with M antennas. According to our new approach, adjacent nodes no longer interfere with each other but rather cooperate attempting to communicate concurrently. In our scheme, during transmissions, the nodes send packets from only one of their antennas, while during reception, they use all of their antennas to receive and decode packets from multiple close nodes simultaneously. Therefore, each distributed MIMO system in this scheme consists of multiple transmitting nodes acting as a single-array of multiple antennas. We derive upper and lower bounds on the receiver node ergodic capacity in the network where the wireless channel is modeled with both large and small-scale fluctuations. These bounds are compared with Monte-Carlo simulation of point-to-point and cooperative MIMO communications in MANETs. We demonstrate that the capacity of MANETs with multiple antennas is improved using cooperation compared to non-cooperative schemes, i.e., point-to-point MIMO communication. In addition, under the above communication model, we demonstrate that the lower and upper bounds of the ergodic capacity grows linearly with the number of receiving antennas M.