SRDP: Secure route discovery for dynamic source routing in MANETs

Routing is a critical function in multi-hop mobile ad hoc networks (MANETs). A number of MANET-oriented routing protocols have been proposed, of which DSR is widely considered both the simplest and the most effective. At the same time, security in MANETs – especially, routing security – presents a number of new and interesting challenges. Many security techniques geared for MANETs have been developed, among which Ariadne is the flagship protocol for securing DSR.The focus of this work is on securing the route discovery process in DSR. Our goal is to explore a range of suitable cryptographic techniques with varying flavors of security, efficiency and robustness. The Ariadne approach (with TESLA), while very efficient, assumes loose time synchronization among MANET nodes and does not offer non-repudiation. If the former is not possible or the latter is desired, an alternative approach is necessary. To this end, we construct a secure route discovery protocol (SRDP) which allows the source to securely discover an authenticated route to the destination using either aggregated message authentication codes (MACs) or multi-signatures. Several concrete techniques are presented and their efficiency and security are compared and evaluated.     

微波中继通信中的路由选择和衰落现象

本文对微波中继通信中衰落现象的形成作了定性的论证,对克服衰落现象提供了理论依据,并对微波天线架设的有关问题进行一般性指导     

Improving route discovery in on-demand routing protocols using two-hop connected dominating sets

Many signaling or data forwarding operations involve the broadcasting of packets, which incurs considerable collisions in ad hoc networks based on a contention-based channel access protocol. We propose the Three-hop Horizon Pruning (THP) algorithm to compute two-hop connected dominating set (TCDS) using only local topology information (i.e., two-hop neighborhood). Because every node has the two-hop neighborhood information, it is possible to maintain fresh routes to all nodes within two hops. In this situation, a TCDS is ideal for the propagation of route request (RREQ) messages in the route discovery process of on-demand routing protocols. THP is shown to be more efficient than all prior distributed broadcasting mechanisms, when a TCDS is preferred over a connected dominating sets (CDS). Like all other algorithms that depend on local topology information, THP is not reliable when the topology changes frequently, and there is a clear trade-off between reliability and efficiency. We describe and analyze two enhancements to THP that address the lack of reliability of neighbor information. First we adopt a virtual radio range (VR), shorter than the physical radio range (RR), and consider as one-hop neighbors only those nodes within VR (we do not use two different radio ranges, as in prior work, because it can incur additional interference). The gap between VR and RR works as a buffer zone, in which nodes can move without loss of connectivity. Second, upon receiving a broadcast packet, the forwarder list in the packet header is analyzed together with the current information about the local neighborhood. Based on that, a node may decide to broadcast the packet even though it has not been selected as a forwarder. We conduct extensive simulations and show that AODV-THP with these two enhancements attains better performance than AODV in terms of delivery ratio, control overhead, packet collisions, and end-to-end delay.     

面向AODV的有效路由选择的研究

按需矢量路由(AODV)是移动自组织网络(MANET)的典型路由,然而AODV路由总是选择最短路径进行通信,这会引起网内流量的不平衡,可能也会引起拥塞问题,最终影响服务质量(QoS)。为此,提出基于AODV的权值路由方案,记为AODV-W。AODV-W路由考虑了路径传输时延、链路稳定性和节点能量,并利用这些信息计算路径权值。再选择权值最低的路径作为数据传输通道。实验数据表明,提出的AODV-W路由提高了数据包传递率和吞吐量。     

多接入中继信道中的单中继选择

研究表明,协作中继选择能提高无线中继网络的鲁棒性和能效。文中研究一个多接入中继信道,包含2个信源,N个中继和1个信宿。中继节点为半双工,对两个信源的信号采用非再生的网络编码。考虑直接链路,基于最佳最差信道、最佳信噪比和最佳调和平均选择,提出新的选择策略。仿真结果表明其在性能上优于原有策略。     

On relay selection for decode-and-forward relaying

In this letter, we consider a multi-relay network operating in decode-and-forward mode. We propose a novel relay selection method with a low implementation complexity. Unlike the competing schemes, it requires neither error detection methods at relay nodes nor feedback information at the source. We derive a closed-form symbol error rate (SER) expression for multi-relay network under consideration and demonstrate that the proposed selection method is able to extract the full diversity. Extensive Monte Carlo simulations are also presented to confirm the derived SER expressions and to compare the performance of the proposed scheme with its competitors.     

Collision resolving relay selection in large-scale blind relay networks

Optimal relay selection in large-scale networks is a difficult task since the network is usually considered as blind due to the high volume and collection difficulty of the relays’ information. In this paper, we develop a collision resolving relay selection (CReS) scheme that achieves the optimal relay from a random set of candidates without the previous knowledge of any individual relay. By introducing stochastic geometry based quality-of-service region, the relation between the distribution of the available relay number and the transmission request is established. Furthermore, the selection phase of the CReS scheme is divided into two sub-phases according to different distributions of the relay number in boundless and bounded regions. A switch rule is proposed when several relays collide in the first sub-phase, followed by the second sub-phase to resolve the collision with the splitting algorithm. The optimal solution that requires minimum selection slots for all sub-phases is derived. In addition, a sub-optimal solution is also explored to reduce the computational complexity. The scheme shows a better applicability than conventional information-based schemes in view of its little information requirement when dealing with large-scale relay allocation problems.     

Multi relay node selection strategy for energy capture collaborative relay network

An energy capture cooperative relay network was studied.Unlike traditional cooperative relay networks,the relay nodes generally did not have a fixed energy supply but could carry out energy capture.For this network,a natural question was how to determine whether the relay nodes perform energy capture or data forwarding,and how to select the relay node to assist the information transmission between the source node and the destination node.Based on this problem,a multi-relay node selection scheme was proposed,which select the operation according to the energy of the current time slot of the relay node.In each time slot,the relay node that meet the battery threshold requirements was selected to assist in transmission.The Markov chain was used to model the charging and discharging process of the relay node battery,and the probability of interruption and throughput of the wireless network was obtained.And the value of the battery threshold when the throughput was maximized,that is,when the probability of network breakage was minimum was solved.Finally,the advantages of this scheme were verified by numerical experiments.     

Joint power allocation and relay selection for decode-and-forward cooperative relay in secure communication

In this paper, we investigate the cooperative strategy with total power constraint in decode-and-forward (DF) relaying scenario, in the presence of an eavesdropper. Due to the difference of channel for each source-relay link, not all relay nodes have constructive impacts on the achievable secrecy rate. Besides, the final achieved secrecy rate depends on both source-relay and relay-destination links in DF relaying scenario. Therefore, the principal question here is how to select cooperative strategy among relays with proper power allocation to maximize the secrecy rate. Three strategies are considered in this paper. First, we investigate the cooperative jamming (CJ) strategy, where one relay with achieved target transmission rate is selected as a conventional relay forwarding signal, and remaining relays generate artificial noise via CJ strategy to disrupt the eavesdropper. Two CJ schemes with closed-form solutions, optimal cooperative jamming (OCJ) and null space cooperative jamming (NSCJ), are proposed. With these solutions, the corresponding power allocation is formulated as a geometric programming (GP) problem and solved efficiently by convex programming technique. Then, to exploit the cooperative diversity, we investigate the cooperative relaying (CR) strategy. An iterative algorithm using semi-definite programming (SDP) and GP together with bisection search method is proposed to optimize the cooperative relaying weight and power allocated to the source and relays. Furthermore, to exploit the advantages of both CR and CJ, we propose an adaptive strategy to enhance the security. Simulation results demonstrate that the efficiency of the proposed cooperative strategies in terms of secrecy rate.     

Efficient route discovery in hybrid networks

Hybrid networks are formed by a combination of access points and mobile nodes such that the mobile nodes can communicate both through the access points and using ad-hoc networking among themselves. This work deals with providing efficient routing between mobile devices in hybrid networks. Specifically, we assume the existence of a spanning tree from each access point to all mobile devices within the transitive transmission range of the access point. We utilize this spanning tree to design a family of efficient point-to-point routing protocols for communication between the mobile devices themselves. The protocols utilize the tree structure in order to avoid expensive flooding of the entire network. The paper includes a detailed simulation study of several representative communication patterns, which compares our approaches to DSR.     

Location-quality-aware policy optimisation for relay selection in mobile networks

Relaying can improve the coverage and performance of wireless access networks. In presence of a localisation system at the mobile nodes, the use of such location estimates for relay node selection can be advantageous as such information can be collected by access points in linear effort with respect to number of mobile nodes (while the number of links grows quadratically). However, the localisation error and the chosen update rate of location information in conjunction with the mobility model affect the performance of such location-based relay schemes; these parameters also need to be taken into account in the design of optimal policies. This paper develops a Markov model that can capture the joint impact of localisation errors and inaccuracies of location information due to forwarding delays and mobility; the Markov model is used to develop algorithms to determine optimal location-based relay policies that take the aforementioned factors into account. The model is subsequently used to analyse the impact of deployment parameter choices on the performance of location-based relaying in WLAN scenarios with free-space propagation conditions and in an measurement-based indoor office scenario.     

Network parameters awareness for routing discovery in autonomic optical Internet

The article proposes a network parameter-awareness (NPA) method and applies it to routing discovery algorithms in autonomic optical Internet. This NPA method can perceive the main parameters of the network, such as delay, jitter and traffic, which can represent the current situation of the network. And these parameters enable network to determine the appropriate nodes for routing discovery. The simulation results of evaluating performance of a network with NPA method and its routing applications show that the method and its applications in routing improve the performance of the network significantly with quality of service (QoS) guaranteed.     

Joint relay selection and opportunistic physical layer network coding for two-way relay channels

Wireless Networks - Physical layer network coding can significantly increase the throughput of two-way relay networks. However, fading phenomenon usually causes great asymmetry between two multiple...     

Outage analysis of opportunistic multi-antenna relay selection in decode-and-forward relay networks

This article studies the closed-form expressions of outage performance for opportunistic relay under aggregate power constraint in decode-and-forward(DF)relay networks over Rayleigh fading channels,assuming that multiple antennas are available at the relay node.According to whether instantaneous signal-to-noise ratio(SNR)or average SNR can be utilized for relay selection,two opportunistic relay schemes,opportunistic multi-antenna relay selection(OMRS)and average best relay selection(ABRS)are proposed.The performances of both two schemes are evaluated by means of theoretical analysis and simulation.It is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and closely approaches the beamforming(BF)scheme known as theoretical outage-optimal.Compared with previous single-antenna opportunistic relaying(OR)scheme,OMRS brings remarkable performance improvement,which is obtained from maximum ratio combining(MRC)and beamforming techniques.It is also shown that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.     

Linear beamformer schemes with simple relay selection in MIMO relay networks

This article considers a wireless multi-hop/mesh network where single multi-antenna source-destination pair communicates through a selected relay subset using simple relay selection under the constraint of fixed relay＇s number. Compared with random selection, the simple relay selection can yield certain capacity advantages while linear zero-forcing （ZF） receiver and linear beamformer are considered at the relay. For match-filter （MF） beamformer and amplified-and-forward （AF） beamformer with a fixed number of relays, the capacities are given. Furthermore, we extend the simple selection methods to the relaying scheme with orthogonal-triangular （QR） beamformer and investigate these linear beamformer schemes over spatially correlated multi-input multi-output （MIMO） links for both the backward and forward channel over the two-bop MIMO relay networks.     

Dynamic joint resource allocation and relay selection for 5G multi-hop relay systems

LTE/LTE-A networks have become widely exploited to address the increasing demands of mobile traffic. Relay technologies have recently been introduced to fulfill such requirements. Currently, the LTE-A relay standard is restricted to two-hop relaying. This architecture minimizes system complexity, but multi-hop relay architecture could potentially provide greater capacity and coverage in the future. However, many complexities of the multi-hop relaying paradigm must be resolved. In this work, we focus on downlink resource allocation and relay selection, by which a user may be connected to a base station through a multi-hop relay and have several relay stations from which to choose within his range. To overcome the additional challenges introduced by multi-hop relay nodes, we propose a dynamic joint resource allocation and relay selection scheme. Numerical results are presented to demonstrate the validity of the proposed algorithm.     

Criterions of designing codebooks and a relay selection scheme for a relay network

For a relay network system with amplify and forward protocol, in this paper, analysis of performance is conducted, and an upper bound of pairwise error probability is obtained. Moreover, a scheme of relay selection is analyzed under assumptions that (i) the relays amplify and forward received signals without any signal processing; (ii) the receiver only knows channel state information from the relays to the receiver; and (iii) the transmitter and the relays do not have any channel state information. Based on the upper bound, a criterion of designing codebook is proposed. Surprisingly, this bound shows that increasing the number of relays can hardly improve performance. Furthermore, the error probability is decreasing with a speed of P^?1, no matter how large the relay number is, where P is the total energy. Also, for the relay selection, the optimal selecting way is to select only one relay with the largest channel gain, which is very different from existing schemes. These results are all confirmed by simulations. Copyright © 2015 John Wiley & Sons, Ltd.     

Amplify-and-forward with partial relay selection

This letter offers a statistical analysis of the basic two-hop Amplify-and-Forward link, where the relay node is selected based on instantaneous and partial knowledge of the channel. In contrast with previously reported work, where relay selection requires global knowledge (2 hops) of the relaying link, the problem considered is interesting in practical ad-hoc systems, where only neighboring (1 hop) channel information is available to the nodes. The probability density function of the received signal-to-noise ratio for the considered relaying link is approximated in closed form, and an asymptotic exponential expression is proposed to simplify performance estimation.     

一种交互式中继选择策略

提出了一种协作中继网络的交互式中继节点选择(IRS)策略。用户首先分布式构造基于信道状况及中继节点负载情况的中继选择函数,选择最优的中继节点;中继节点再根据资源分配情况、业务优先级以及加权信道调度算法进行反向用户选择。仿真结果表明,相比于已研究的算法,所提出的IRS算法结合了信道状况、MAC层资源与用户业务状况等因素,利用用户和中继之间的两步式交互中继选择来调节小区内的用户负载分布,获得了小区吞吐量与用户公平性之间的折衷。