Contract design for relay incentive mechanism under dual asymmetric information in cooperative networks

Cooperative relay network can effectively improve the wireless spectrum efficiency and extend the wireless network coverage. However, due to the selfish characteristics of wireless nodes, spontaneous cooperation among nodes is challenged. Moreover, wireless nodes may acquire the different network information with the various nodes’ location and mobility, channels’ conditions and other factors, which results in information asymmetry between the source and relay nodes. In this paper, the incentive issue between the relay nodes’ cooperative service and the source’s relay selection is investigated under the asymmetric information scenarios. By modeling cooperative communication as a labour market, a contract-theoretic model for relay incentive is proposed to achieve the twin objectives of ability-discrimination and effort-incentive. Considering the feature of asymmetric information, the static and dynamic information of the relay nodes are systematically discussed. To effectively incentivize the potential relay nodes to participate in cooperative communication, the optimization problems are formulated to maximize the source’s utility under the multiple information scenarios. A sequential optimization algorithm is proposed to obtain the optimal wage-bonus strategy with the low computational complexity under the dual asymmetric information scenario. Simulation results show that the optimal contract design scheme is effective in improving the performance of cooperative communication.     

An adaptive routing algorithm considering position and social similarities in an opportunistic network

An opportunistic network (OPPNET) is a wireless networks without an infrastructure. In OPPNET, communication intermittently occurs when one node meets with another node. Thus, a connected path between the source and destination nodes rarely exists. For this reason, nodes need not only to forward messages but are also to store and carry messages as relay nodes. In OPPNET, several routing algorithms that rely on relay nodes with appropriate behavior have been proposed. Some of these are referred to as context-ignorant routing algorithms, which manipulate flooding, and others are referred to as context-aware routing algorithms, which utilize the contextual information. We propose a routing algorithm that employs a novel similarity based on both position and social information. We combine the position similarity with the social similarity using the fuzzy inference method to obtain the enhanced performance. Through this method, the proposed algorithm utilizes more proper relay nodes in forwarding adaptively and achieves significant improvement on the performance especially under memory constrained environment. We analyze the proposed algorithm on the NS-2 network simulator with the home-cell community-based mobility model. Experimental results show that the proposed algorithm outperforms typical routing algorithms in terms of the network traffic and delivery delay.     

A Contract-Based Model for Multiuser Cooperative Relay in Wireless Communication Networks

Cooperative communication utilizes multi-user spatial diversity to improve spectrum efficiency and channel capacity. However, due to the limited wireless network resource, the selfish relay nodes may be unwilling to offer their relay assistance without any extra incentive. In this paper, the incentive issue between multiple wireless nodes’ relay service and multiple sources’ relay selection is investigated. By modelling multi-user cooperative relay as a labour market, a contract model is proposed with the combination of relay power and basic wage. A relay factor is introduced to describe the contract-relay strategy in cooperative communication. To incentivize the relay nodes to participate in multiple sources’ relay efficiently and credibly, an optimization problem of multi-user relay incentive is formulated to obtain the sources’ maximum cooperative utility under the individually rational restraints. By exploiting the hidden convexity of the non-convex problems in both single-source and multi-source scenarios, the efficient iterative algorithms are developed. Numerical results show that the performance of our approach yields a significant enhancement compared with the equal relay-power and equal relay-factor strategies.     

Secure Relay Selection of Cognitive Two-Way Denoise-and-Forward Relaying Networks

In this paper, secrecy performance of a cognitive two-way denoise-and-forward relaying network consisting of two primary user (PT and PD) nodes, two secondary source (SA and SB) nodes, multiple secondary relay (\({\textit{SR}}_i\)) nodes and an eavesdropper (E) node is considered, where SA and SB exchange their messages with the help of one of the relays using a two-way relaying scheme. The eavesdropper tries to wiretap the information transmitted between SA and SB. To improve secrecy performance of the network, two relay selection schemes called maximum sum rate and maximum secrecy capacity based relay selection (MSRRS and MSCRS) are proposed and analyzed in terms of intercept probability. It is proved that the MSRRS and MSCRS schemes have the same secrecy performance. Two parameters called average number gain and average cost gain are proposed to show the performance of the proposed relay selection schemes. Numerical results demonstrated that with 10 relay nodes, the proposed relay selection schemes can achieve, respectively, 3.7 dB and 1.9 dB’s improvements in terms of the reduced intercept probability and the enhanced secrecy capacity compared to the traditional round-robin scheme.     

Resource Allocation for Aggregate Multimedia and Healthcare Services over Heterogeneous Multi-Hop Wireless Networks

Nowadays, the pervasive wireless networks enable ubiquitous high-rate wireless access from everywhere. In this work, we discuss the integration of complementary wireless techniques to construct a personal moving network. The personal wireless devices (  smartphones, camcorders, and netbooks) and even medical monitoring sensors are interconnected with a wide-area backbone through a local multi-mode gateway. The mobile nodes in a personal moving network move in group and are provided seamless connectivity through a backhaul relay channel from the local gateway toward the backbone network. In some specific scenarios, the local gateway can be as simple as a multi-radio smartphone. In this study, we investigate the construction and resource allocation for a personal moving network. Aggregate multi-service traffic of interactive data, conversational video, and electrocardiography (ECG) monitoring are considered in the resource allocation. We develop a stochastic Petri net to model the access selection scheme, which is logically clear and easy to follow. The flow-level performance is evaluated in terms of new connection blocking probability and handoff dropping probability. We further analyze the packet-level performance of the heterogeneous two-hop network. Considering the urgency of medical services, a non-preemptive priority policy is applied to mitigate the impact of background traffic and prioritize the transmission of ECG data.     

Gateway load balancing using multiple QoS parameters in a hybrid MANET

A Mobile ad hoc network (MANET) is a self configurable wireless network in which mobile nodes communicate with each other in a multihop fashion without any pre-installed infrastructure. A MANET can be considered to be a standalone network. To enhance the connectivity of a MANET it can be connected to the fixed network, thus forming a heterogeneous network. The integration of MANET and the Internet is called a hybrid MANET which is facilitated by special nodes called Internet gateway nodes. Load balancing among gateways is a challenging task when a MANET is connected to Internet. Gateway nodes with higher loads will lead to disconnected networks and depletes the node’s resources which include their batteries, memory and bandwidth quickly. Gateway selection based on the shortest path may increase traffic concentration on one particular gateway which leads to congestion and increases delay in the network. In this paper a QoS based load balancing mechanism has been proposed among multiple gateway nodes that provide communication between mobile nodes and fixed nodes in the Internet to select lightly loaded gateways so that more packets will be delivered to the fixed host in the Internet. The proposed QoS based scheme selects four QoS parameters that are (1) connecting degree, (2) interface queue length, (3) routing table entries and (4) hop count. A weight based method is used to select the gateway which combines all four QoS metrics. Simulation results demonstrate that when compared with individual parameter, the average ETE delay, queue size and traffic load of gateway generated by proposed algorithm is decreased by 17, 25 and 15 % respectively and when compared with existing schemes, the average ETE delay, queue size and traffic load of gateway is decreased by 25, 25 and 16 % respectively.     

Incentive Mechanisms for Cooperative Wireless Networks with Adverse Selection and Moral Hazard

Cooperative communication is a promising technique to improve utilization of the wireless spectrum resource. However, due to the limited wireless network resource, the selfish relay nodes may be unwilling to offer their relay help without any extra incentive. In this work, we study a contract-based mechanism for incentivizing cooperative relay in the presence of the dual asymmetric information. By modelling multi-user cooperative relay as a labour market, a principal-agent model is proposed with the combination of relay power, basic wage and relay bonus in the continuous type scenario. And an optimization problem of multi-user relay incentive is formulated to achieve the twin objectives of ability-discrimination and effort-incentive. Numerical results show that the optimal contract design scheme is effective in improving the performance of cooperative communication.     

Performance Analysis of Optimum Combining Technique in OFDM Based Full Duplex Multiantenna DF Relay Network with Narrowband Interference

In this paper, optimum combining technique is applied to minimize the effect of Narrowband Interference (NBI) in Orthogonal Frequency Division Multiplexing based full duplex relay network. The NBI signal is assumed to be quasi-static over the duration of a transmitted signal. Multiple antennas are employed at Decode and Forward relay and destination nodes. The Probability Density Function of Signal to Interference Ratio at relay and destination nodes is derived using Hotelling’s T ² distribution. Analytical expression for the end-to-end outage probability of the proposed network is derived using the hypergeometric functions. As the weight vector of the optimal combiner is determined using the statistics of the interference channels, the performance of the proposed network becomes better than the network with maximal ratio combining.     

3G 蜂窝网络中GLR 故障恢复分析

在3G蜂窝网络中,归属位置寄存器(HLR)、网关位置寄存器(GLR)、访问位置寄存器(VLR)组成三级数据库结构。当漫游移动用户在GLR中的位置信息错误或过时时,对该用户的入呼将失败。由于三层结构设计中,GLR与HLR的通信一般涉及国际长途信令,使得GLR的故障恢复设计非常重要。为尽可能减少对长途资源的占有,对GLR故障恢复提出了一种新的算法并对其性能作了相应的分析。     

Inter-Relay Interference Cancellation Using MIMO Detection

Recent mobile applications have required high data rate. In metropolitan areas where data traffic is higher than other areas, heterogeneous networks (HetNet) are used to meet the traffic demand (Hoadley and Maveddat in IEEE Commun Mag 19(2):4–5, 2012). The HetNet has several low power base stations or remote radio heads in a macro cell coverage and sometimes coordinates the low power transmission points forming virtual multiple-input and multiple-output system. In this paper, inter-relay interference (IRI) cancellation for two-path relay system is considered. In existing schemes, IRI cancellation is performed at a destination node but proposed method performs the cancellation at relay nodes to reduce the complexity of detection algorithm for the destination node. Simulation results also show that the method of this paper achieves better BER performance than the existing schemes.     

Predictability of Aggregated Traffic of Gateways in Wireless Mesh Network with AODV and DSDV Routing Protocols and RWP Mobility Model

When evaluating the performance of routing protocols in wireless mesh network (WMN), we need deeper analysis from the aspect of network traffic complexity to show how traffic characteristics are influenced by routing protocols and node mobility. The predictability of network traffic can be used as one metric of complexity and can be analyzed by multi-scale entropy (MSE) method. With 20 different random waypoint (RWP) mobility scenarios and with destination sequenced distance vector (DSDV), a typical proactive protocol, and Ad hoc on-demand distance vector (AODV), a typical reactive protocol, the predictabilities of aggregated traffic of gateway in WMN are analyzed using MSE method to show how different routing protocols bear different mobility scenarios. The MSE results show that the aggregated traffic of gateway with DSDV is more difficult to be predicted than that with AODV for different mobility scenarios. The maxspeed parameter of RWP dominates the traffic predictability for AODV. Both of the pause time and the maxspeed parameters, have great influence on the traffic predictability for DSDV. The reasons lie in the behaviors of routing protocols, i.e., AODV has up-to-date paths while DSDV does not.     

Traffic load metrics for multihomed mobile IP and global connectivity

Support for host mobility an essential and necessary feature for roaming users who connect to wireless networks via access points. Access points may have different capabilities, be connected to different networks and be installed by different providers. A mobile host will discover multiple access points in this environment. In such an environment, a mobile host should be able to use the best available connection to communicate with a correspondent host and perhaps use multiple connections for different hosts. In areas with wireless local area network access, pockets with limited or no coverage could exist. Such restricted connectivity could be compensated by neighbor hosts who form an ad hoc network and relay packets until they reach an access point. This paper describes and discusses a proposed solution towards enabling and supporting connectivity in wireless networks. In the proposed solution the network layer software will evaluate and decide which wireless network connections to use. A Running Variance Metric (RVM) and a Relative Network Load(RNL) are used to measure the traffic load of access points in wireless access networks. RVM and RNL can be efficiently used for both infrastructure networks and ad hoc networks. Multihomed Mobile IP (M-MIP) is an extension of Mobile IP that enables mobile hosts to use multiple care-of addresses simultaneously. The extension enhances network connectivity by enabling the mobile host, the home agent and correspondent hosts to evaluate and select the best connection. A proposed gateway architecture using M-MIP that integrates wired IP networks with ad hoc networks is described. The M-MIP and gateway architecture using the RVM and RNL metrics have been validated with simulation studies and results are presented.     

Optimal Power Allocation in an Amplify-and-Forward Untrusted Relay Network with Imperfect Channel State Information

The characteristics of the wireless medium create difficulty to shield the data transmission from unauthorized recipients. In this paper, power optimization in an amplify-and-forward untrusted relay network is presented, using cooperative jamming transmission to prevent the untrusted relay from intercepting the confidential signals. Considering imperfect channel estimation error at the destination, an optimal power allocation (OPA) is designed to maximize the achievable secrecy rate for the network. Simplified OPA is derived for high signal-to-noise ratio regime with imperfect CSI and the ergodic secrecy rate is also analyzed to evaluate the achievable average secrecy rate for different scenarios as a common performance metric. The numerical results show that when the error of CSI is considered, the proposed OPA generates limited and acceptable degradation on the secrecy rate.     

Comparative performance analysis of cooperative and multi dual‐hop relay networks using MGF approach

In this paper, we analyzed and compared the performance of cooperative diversity systems such as cooperative and multi dual‐hop networks with non‐regenerative relay nodes. The contributions of this study are twofolds. Firstly, analytical expressions of outage probability P_out and average symbol error rate ASER are derived using moment generating function (MGF) analysis of the received SNR with the assumption that the channel experiences Weibull fading and the best relay selection is used. Then, using the analytical results, comparative performance evaluation of cooperative and multi dual‐hop relay networks is done for varying number of relay nodes and different receive diversity schemes such as maximal ratio combining (MRC) and selection combining (SC). The results show that the cooperative relay network has better performance than a multi dual‐hop relay network in terms of P_out and ASER. The results also show that the multi dual‐hop network can achieve the same performance as the cooperative network with the requirement that it needs the deployment of three times more relay nodes.     

A Novel Technique for Gateway Selection in Hybrid MANET Using Genetic Algorithm

Integration of Mobile Ad hoc NETworks (MANETs) with the Internet has been paid immense attention in the field of heterogeneous networks. In MANET some intermediate nodes called Internet Gateways (IGs) are responsible for sending the data traffic of source nodes towards the fixed nodes in the Internet. The key issue considered while selecting IG nodes is its optimised throughput with the reduced delay in resource constraint mobile nodes. In this paper, a genetic algorithm inspired Delay Sensitive Gateway Selection (DSGS) scheme is proposed considering the issue of network delay by minimising the total distance travelled by the source nodes to the gateway. The performance of the proposed GA-based DSGS scheme is studied using a comparative approach. The simulation results demonstrate that the proposed scheme significantly outperforms the conventional schemes and is capable of achieving higher network throughput while minimising the end-to-end delay.

     

Sparse traffic grooming in WDM networks using coarse granularity OXCs

Providing grooming capability to optical crossconnects (OXCs) in wavelength division multiplexing (WDM) networks can allow an effective use of the network bandwidth, however, it increases the node cost that operators must sustain when compared to a non-grooming network. Therefore, operators might consider using sparse grooming instead of full grooming networks. In this article we consider sparse groomed optical networks. Our contribution is 2-fold. First, we address the grooming placement problem that seeks for a set of grooming nodes in the network that leads to the highest overall throughput. This problem is separated into two sub-problems: (i) selection of nodes having grooming capability; (ii) maximization of network throughput assuming the grooming nodes found by the previous step. These two sub-problems are mathematically formulated for different OXC placing strategies considering a static traffic scenario. In the second part, we design a practical heuristic grooming algorithm suitable for dynamic traffic scenarios. The benefit of using sparse grooming nodes, when compared with a non-grooming scenario, is evaluated in terms of throughput and optical port utilization. Our analysis differs of previous ones since it considers grooming at a granularity coarser than the traffic granularity, which is an important aspect since network cost improvement can be obtained at the expense of irrelevant performance impairments. Results show that the insertion of coarse granularity OXCs can be a viable solution for network throughput increase since this can be done at the expense of relatively few or no extra optical ports.

An Energy-Efficient and Collision-Avoidance MAC Protocol with Pre-scheduling for Wireless Sensor Networks

In this paper, we propose energy efficient MAC protocols for data gathering tree structure. The basic concept of the proposed protocol is that it reduces traffic overloads in low depth nodes by introducing full sleep state for one frame. To maximize network performance, we only control traffic from non-relay nodes which are leaf nodes in the tree. We introduce a new superframe structure for pre-scheduling to alleviate contentions and packet collisions between children nodes. In addition, leaf nodes go into a full sleep mode for one superframe in heavy traffic loads by using control packets, which results in a considerable reduction of energy consumption at low depth nodes. Simulation results show the proposed protocol saves more energy and achieves better packet delivery ratio compared to the DMAC with a moderate increase of a latency performance.     

The Efficiency of Traffic Engineering with Regard to Link Failure Resilience

IP networks have established as a global telecommunication platform with increasing user population and an extending spectrum of services. The traffic is also steadily increasing, recently driven by peer to peer networking in addition to client server based applications. Network planers and operators have to ensure the scalability of IP platforms in a permanent upgrade process for transmission capacities. At present, Deutsche Telekom and other telecommunication network providers are introducing traffic engineering methods to achieve an optimum resource utilization.In a first step, traffic engineering can be applied to a predefined network topology, but a comprehensive approach has to be coordinated with a process for upgrading the link capacities and has to prepare for relevant failure scenarios. We have evaluated the efficiency of traffic engineering together with simple link upgrade strategies in order to get a maximum throughput. Therefore a predefined traffic matrix T is taken into account. The optimization goal is to scale the traffic matrix by a maximum factor _max such that the traffic demand _max T can still be carried on the available network resources. The influence of the network topology on the evaluation results is shown in examples with regard to single link failures.     

Performance evaluation of multicast relay network using LDPC and convolutional channel codes along-with XOR network coding

In this paper,we have compared the performance of joint network channel coding(JNCC) for multicast relay network using low density parity check(LDPC) codes and Convolutional codes as channel codes while exclusive or(XOR) network coding used at the intermediate relay nodes.Multicast relay transmission is a type of transmission scheme in which two fixed relay nodes contribute in the second hop of end-to-end transmission between base transceiver station(BTS) and a pair of mobile stations.We have considered one way and two way multicast scenarios to evaluate the bit error rate(BER) and throughput performance.It has been shown that when using XOR network coding at the intermediate relay nodes,the same transmission becomes possible in less time slots hence throughput performance can be improved.Moreover we have also discussed two possible scenarios in the proposed system model,in which both diversity and multiplexing gain has been considered.It is worth notifying that BER and throughput achieved for LDPC codes is better than Convolutional codes for all the schemes discussed.