Cooperative network implementation using open-source platforms

In the previous chapter, we have examined medium access control (MAC) layer issues in cooperative networks and have introduced several cooperative MAC protocols to help exploit cooperative advantages from the MAC layer. In this chapter, we take a further look at other higher-layer issues in cooperative networks, including quality-of-service (QoS), routing, and security. First, we examine the advantages of cooperation in terms of enhancing the QoS for networks that support, e.g., multimedia applications. The concept of effective capacity is utilized to characterize the QoS and conditions are provided on when a certain QoS requirement can be met. Secondly, we introduce the role of cooperative transmissions in network routing problems.

In order to cope with the degradation of communication quality due to fading of wireless signals when transmitted over long distances, cooperative communication techniques are often applied to long-distance wireless communications due to their relay cooperative forwarding characteristics. A reasonable relay assignment scheme can significantly improve the network throughput. In order to solve the problem of irrational relay resource assignment in the existing relay assignment under the multi-node cooperative communication network, this paper proposes a relay assignment method that balances the communication quality (BQRA). Firstly, a multi-node cooperative communication system model is established, and a node pre-assignment set is established based on node distance. Then, with the goal of maximizing the overall network capacity, the proposed relay assignment method is used to allocate relay nodes for each source node. The effective performance of the proposed method is evaluated through simulation experiments. Simulation results show that the system channel capacity index is slightly better than several other methods. 15% increase in system channel capacity compared to the classical relay assignment method, LIRA.

Cooperative communication is shown to be an efficient method of combating fading in wireless networks. By ”sharing” their antennas cooperating single-antenna nodes create a virtual multi-antenna system and therefore, benefit from spatial diversity. Network coding being a particular cooperative communication technique provides substantial gains in data rate, especially in networks with many sink nodes. By allowing intermediate nodes of a network to mix the incoming data streams, one can achieve the multicast capacity. Recently, Xiao and Skoglund showed that binary network coding (BNC) is not optimal for multi-user multi-relay networks in terms of diversity and proposed diversity network coding (DNC) scheme that outperforms BNC approach. Following this approach we examine potential diversity gains of using the DNC scheme for multi-source line networks. We show that the DNC technique outperforms both conventional time-orthogonal transmission and the BNC scheme. Further, the problem of optimal scheduling of the transmission is explored. We formulate the optimization problem and propose efficient solutions. Numerical results are presented to support theoretical findings.

Wireless sensor network is the network of tiny size of sensor nodes. These sensor nodes have sensing capability and transmit the sensed information to sink node. If the energy of sensor nodes is not utilised properly, it results in performance degradation of the network. Sleep scheduling approach and cooperative communication techniques can be employed to enhance the network performance. Cooperative communication follows the relay-based transmission. The nodes turn its radio sleep and awake in sleep scheduling approaches. This paper considers the merits of both techniques and proposes the sleep scheduling-based cooperative data transmission approach for WSN. In this approach, optimal number of virtual cluster heads are calculated by the sink node according to the number of nodes and area of interest. The real cluster head is decided based on the distance and energy of the sensor nodes from the virtual cluster head. The node is paired with each other and follows the sleep scheduling approach. Further, the energy-efficient relay selection and data transmission according to cooperative technique improves the network performance. The simulation analysis shows that the proposed routing protocol outperforms the related existing routing protocols.

In wireless communications, the cooperative communication (CC) technology\npromises performance gains compared to traditional Single-Input Single Output\n(SISO) techniques. Therefore, the CC technique is one of the nominees for 5G\nnetworks. In the Decode-and-Forward (DF) relaying scheme which is one of the CC\ntechniques, determination of the threshold value at the relay has a key role\nfor the system performance and power usage. In this paper, we propose\nprediction of the optimal threshold values for the best relay selection scheme\nin cooperative communications, based on Artificial Neural Networks (ANNs) for\nthe first time in literature. The average link qualities and number of relays\nhave been used as inputs in the prediction of optimal threshold values using\nArtificial Neural Networks (ANNs): Multi-Layer Perceptron (MLP) and Radial\nBasis Function (RBF) networks. The MLP network has better performance from the\nRBF network on the prediction of optimal threshold value when the same number\nof neurons is used at the hidden layer for both networks. Besides, the optimal\nthreshold values obtained using ANNs are verified by the optimal threshold\nvalues obtained numerically using the closed form expression derived for the\nsystem. The results show that the optimal threshold values obtained by ANNs on\nthe best relay selection scheme provide a minimum Bit-Error-Rate (BER) because\nof the reduction of the probability that error propagation may occur. Also, for\nthe same BER performance goal, prediction of optimal threshold values provides\n2dB less power usage, which is great gain in terms of green communicationBER\nperformance goal, prediction of optimal threshold values provides 2dB less\npower usage, which is great gain in terms of green communication.\n

The performance of traditional TCP congestion control protocol degrades when congestion and contention increase in ad hoc networks that use the IEEE 802.11 DCF. Many of the problems result from medium contention at the media access control (MAC) layer. In this paper, we present a new contention-based congestion control (CBCC) method according to a novel congestion information from MAC layer. This proposal aims to avoid the congestion nodes and guarantee better performance in terms of delay, packet delivery ratio, and throughput. By monitoring the number of one node entry the backoff algorithm, our CBCC scheme can calculate the congestion metric called backoff state ratio, a more accurate metric to characterize the network congestion status. Node uses this indication to determine whether to drop a packet or not. Simulation results show that the algorithm can greatly increase the network throughput and effectively control the network congestion at the MAC layer.

In a wireless communication system, a cooperative communication technique is a communication method for improving performance. In the conventional scheme, when a destination user is located in the cell boundary, one base station communicates with a destination user. At a same time, a destination user communicates with other base stations which cooperate with base station. If a distance between a base station and a destination user is far, the quality of communication is degraded by the effect of channel attenuation. Therefore, this paper proposes an enhanced cooperative transmission scheme using the orthogonal frequency multiplexing in the wireless communication system. The proposed scheme uses extra relays between a base station and a destination user. When the channel state of a destination user is bad, other base stations are used. In order to obtain better performance than the conventional scheme, the cooperative decode and forward (DF), and space time cyclic delay diversity (STCDD) and cyclic delay diversity (CDD) are applied in the extra relays. In simulation results, the proposed scheme has higher error and throughput performances than the conventional scheme for obtaining diversity gain when the used modulation scheme is increased. Also, the proposed scheme which uses cooperative DF has slightly better error and throughput performances than the proposed scheme which uses cooperative STCDD and CDD due to less error propagations and resultant higher diversity gain.

Energy efficiency and Quality of Service (QoS) have become major requirements in the research and commercial community to develop green communication technologies for cost-effective and seamless convergence of all services (e.g., data, 3D media, Haptics, etc.) over the Internet. In particular, efforts in wireless networks demonstrate that energy saving can be achieved through cooperative communication techniques such as multihop communications or cooperative relaying. Game-theoretic techniques are known to analyze interactions between collaborating entities in which each player can dynamically adopt a strategy that maximizes the number of bits successfully transmitted per unit of energy consumed, contributing to the overall optimization of the network in a distributed fashion. As for the core networks, recent findings claimed that resource over-provisioning is promising since it allows for dynamically booking more resources in advance, and multiple service requests can be admitted in a network without incurring the traditional per-flow signaling, while guaranteeing differentiated QoS. Indeed, heavy control signaling load has recently raised unprecedented concerns due to the related undue processing overhead in terms of energy, CPU and memory consumption. While cooperative communication and resource over-provisioning have been researched for many years, the former focuses on wireless access and the latter on the wired core networks only. Therefore, this chapter investigates existing solutions in these fields and proposes new design approach and guidelines to integrate both access and core technologies in such a way as to provide a scalable and energy-efficient support for end-to-end QoS-enabled communication control. This is of paramount importance to ensure rapid development of attractive 3D media streaming in the current and future Internet.

Energy-efficient relay selection and power allocation for multi-source multicast network-coded D2D communications

This paper proposes two metrics for evaluating the low probability of detection (LPD) performance in cooperative wireless communication networks. One metric is the distance ration between the minimum range of all the interceptor-relay/transmitter pairs and the intended transmitter-destination distance. Another is the ratio between the average range of all interceptor-relay/transmitter pairs and the intended transmitter-destination distance. The two metrics are compared with the distance ratio defined for the point-to-point communication systems with a simple relay network topology. The results show that the cooperative networks exhibit worse LPD performance than the point-to-point systems when the same receivers are used in both cooperative network and point-to-point system.

Cooperative communication combats the effects offadingwithoutthe need for multiple antennas.The cooperative networks use multiple distributed nodes that virtually behave like multiple antennas each having their own local oscillators. But the oscillators cause multiple Carrier Frequency Offsets (CFO), unknown channel gains and Multiple Timing Offsets (MTO). For a good performance of the system perfect synchronization is needed which is achieved by estimation and compensation of multiple offsets. Also, the coverage and capacity can be improved by employing intermediate nodes called relays within cooperative networks. These cooperative relay networks can perform in a better manner even when considering MCFOs, MTOs and unknown channel gains by having more computationally efficient decoders that can use Maximum Likelihood (ML) estimation subject to the Cramer-Rao Lower Bound (CRLB) on the variance of any impartial estimate. The simulation results show that frequency offset still exist after Amplify and Forward (AF) relaying. The performance of a conventional cooperative network seems to have improved with respect to Bit Error Rate of the system when an AF relay is hosted. The estimate of the frequency offset is chosen such that it gives the signal, a high probability of occurrence using ML estimator. In ML estimate, since the bias and variance is difficult to compute, a lower bound called the CRLB on the variance of any unbiased estimate is derived which is satisfied by the ML estimator.Keywords: AF, Cooperative Communication, CFO, ML Estimation and Compensation, OFDM

With the evolution of wireless systems, cooperative communications are promoted as promising candidate for future radio access technologies. However, due to the different processing and propagation delays among distributed relays, cooperative networks can be asynchronous. A possible solution is to apply a distributed synchronization which unfortunately increases the amount of needed power and time for the communication. Therefore, space time codes that can tolerate the delays are used here in cooperative networks in order to reduce this additional signaling for several multiple access technologies. The performance enhancement of the proposed scheme compared to another existing code is shown by numerical simulations.

The Scalable Video Coding (SVC) compression technique is extension of H.264/AVC which is developed by Joint Video Team of the ITU-T VCEG and the ISO/IEC MPEG. SVC enables scalability support and capable to adapt bitrate with lower temporal or spatial resolutions for wireless channel bandwidth those varying with time. In this paper, we proposed a cross-layer mechanism, which includes video packet prioritization and Quality of Services (QoS) mapping, for the transmitting SVC video over the IEEE 802.11n wireless networks without aggregation. The proposed mechanism delivery enables interaction with Medium Access Control (MAC) layer, providing controlling of different Access Classifications (ACs) for video packets. Our purposed Traffic Queue Controlling Cross-layer Mechanism (TQCCLM) performs with the SVC packet prioritization at the MAC layer according to Temporal Identification (TId) Quality Identification (QId) values of incoming video SliceData and access queue length. Simulation results shows that the proposed mechanism improves SVC video quality when compared to IEEE 802.11n EDCA default mapping method.

A new cooperative communication algorithm for improving connectivity in the event of network failure in VANETs

Multiple-input multiple-output techniques enhance wireless communications performance by taking advantage of spatial diversity. However, most traditional MIMO systems hardly achieve large spatial diversity because of limited terminal size. In this article, we present recent advances of the distributed MIMO technologies in cooperative wireless networks. We also compare and discuss various relay protocols and cooperative strategies. Our simulation results indicate that distributed MIMO systems can provide larger spatial diversity, and the data rate in cooperative networks can be significantly increased.