BER Modified Decode-and-Forward Protocol for OFDM-Based Linear Multihop Networks

In orthogonal frequency division multiplexing （OFDM） based multihop communications, the conventional decodeand-forward （DF） relay scheme severely suffers from the error propagation problem. This drawback is serious in multihop networks as errors made by any relay node may fail the decoder at the destination in great chance. In this paper, we propose a bit error rate （BER） modified DF protocol （BMDF） which can be applied to systems where error correction channel coding and M-ary modulation are used. By modeling all links except the last one as a binary symmetric channel （BSC）, we derive a log likelihood ratio （LLR） modification function relying only on the accumulated BER of all previous links to be applied to the output of the soft demapper. Furthermore, to reduce the computational complexity and signaling overhead, the modification function is simplified from its original exponential expression and less BERs are delivered between nodes by making successive subcarriers share the same BER. In addition, for situations where the channel state information （CSI） of forward link is available, the proposed BMDF can be further enhanced by combining with subcarrier pairing （SP） and power allocation （PA）, where a sorted-channel gain SP scheme and a greedy PA algorithm are proposed. The simulation results verify thesignificant performance improvement to the conventional DF.

Using Heuristics to the Controller Placement Problem in Software-Defined Multihop Wireless Networking

Solving the controller placement problem (CPP) in an SDN architecture with multiple controllers has a significant impact on control overhead in the network, especially in multihop wireless networks (MWNs). The generated control overhead consists of controller-device and inter-controller communications to discover the network topology, exchange configurations, and set up and modify flow tables in the control plane. However, due to the high complexity of the proposed optimization model to the CPP, heuristic algorithms have been reported to find near-optimal solutions faster for large-scale wired networks. In this paper, the objective is to extend those existing heuristic algorithms to solve a proposed optimization model to the CPP in software-defined multihop wireless networking (SDMWN).Our results demonstrate that using ranking degrees assigned to the possible controller placements, including the average distance to other devices as a degree or the connectivity degree of each placement, the extended heuristic algorithms are able to achieve the optimal solution in small-scale networks in terms of the generated control overhead and the number of controllers selected in the network. As a result, using extended heuristic algorithms, the average number of hops among devices and their assigned controllers as well as among controllers will be reduced. Moreover, these algorithms are able tolower the control overhead in large-scale networks and select fewer controllers compared to an extended algorithm that solves the CPP in SDMWN based on a randomly selected controller placement approach.

Full Duplex Media Access Control Protocol for Multihop Network Computing

Intelligent communication technologies beyond the network are pro-posed by using a new full-duplex protocol.The Media Access Control(MAC)is a data interaction network protocol,which outperforms the IEEE 802.15.4e.This research discusses the planning and execution of full-duplex(FD)pipeline MAC protocol for multihop wireless networks(MWN).The design uses a com-bination of Radio frequency and baseband methods to realize full-duplexing with smallest impact on cross layer functions.The execution and trial results specify that Pipeline Media Access Control(PiMAC)protocol considerably develops net-work implementation in terms of transmission protocol(TP)and transmission delay.The advantage of using FD-MAC will increase the range of nodes.Also takes benefit of the FD mode of the antenna,which outperforms additionally 80%for all assessed cases.In this analysis,it was considered of that Psz=8184 bits and Rc=1Mbps;that’s,T_(DATA) represents an excellent portion of total UTC.Tests on real nodes displays that the FD theme achieves a median gain of 90%in mix-ture throughput as equated to half-duplex(HD)theme for MWN.The energy con-sumption of proposed system method is 29.8%reduced when compared with existing system method.

Enhanced performance based on cross-layer design from physical to transport layers for multihop wireless networks

This paper puts forward a novel cognitive cross-layer design algorithms for multihop wireless networks optimization across physical,mediam access control （MAC）,network and transport layers.As is well known,the conventional layered-protocol architecture can not provide optimal performance for wireless networks,and cross-layer design is becoming increasingly important for improving the performance of wireless networks.In this study,we formulate a specific network utility maximization （NUM） problem that we believe is appropriate for multihop wireless networks.By using the dual algorithm,the NUM problem has been optimal decomposed and solved with a novel distributed cross-layer design algorithm from physical to transport layers.Our solution enjoys the benefits of cross-layer optimization while maintaining the simplicity and modularity of the traditional layered architecture.The proposed cross-layer design can guarantee the end-to-end goals of data flows while fully utilizing network resources.Computer simulations have evaluated an enhanced performance of the proposed algorithm at both average source rate and network throughput.Meanwhile,the proposed algorithm has low implementation complexity for practical reality.

Jointly optimized congestion control, forwarding strategy,and link scheduling in a named-data multihop wireless network

As a promising future network architecture, named data networking(NDN) has been widely considered as a very appropriate network protocol for the multihop wireless network(MWN). In named-data MWNs, congestion control is a critical issue. Independent optimization for congestion control may cause severe performance degradation if it can not cooperate well with protocols in other layers. Cross-layer congestion control is a potential method to enhance performance. There have been many cross-layer congestion control mechanisms for MWN with Internet Protocol(IP). However, these cross-layer mechanisms for MWNs with IP are not applicable to named-data MWNs because the communication characteristics of NDN are different from those of IP. In this paper, we study the joint congestion control, forwarding strategy, and link scheduling problem for named-data MWNs. The problem is modeled as a network utility maximization(NUM) problem. Based on the approximate subgradient algorithm, we propose an algorithm called ‘jointly optimized congestion control, forwarding strategy, and link scheduling(JOCFS)'to solve the NUM problem distributively and iteratively. To the best of our knowledge, our proposal is the first cross-layer congestion control mechanism for named-data MWNs. By comparison with the existing congestion control mechanism, JOCFS can achieve a better performance in terms of network throughput, fairness, and the pending interest table(PIT) size.

Hierarchical micro-mobility management in high-speed multihop access networks

This article integrates the hierarchical micro-mobility management and the high-speed multihop access networks （HMAN）, to accomplish the smooth handover between different access reuters. The proposed soft handover scheme in the high-speed HMAN can solve the micro-mobility management problem in the access network. This article also proposes the hybrid access muter （AR） advertisement scheme and AR selection algorithm, which uses the time delay and stable route to the AR as the gateway selection parameters. By simulation, the proposed micro-mobility,management scheme can achieve high packet delivery fraction and improve the lifetime of network.

A Hybrid Cache Placement Scheme for Multi-Hop Wireless Service Network

In this paper,a hybrid cache placement scheme for multihop wireless service networks is proposed. In this scheme,hot nodes in data transferring path are mined up by means of rout-ing navigation graph,and whole network is covered with network clustering scheme. A hot node has been chosen for cache place-ment in each cluster,and the nodes within a cluster access cache data with no more than two hops. The cache placement scheme reduces data access latency and workload of the server node. It also reduces the average length of data transferring,which means that fewer nodes are involved. The network system energy con-sumption decreased as involved relay nodes reduced. The per-formance analysis shows that the scheme achieves significant system performance improvement in network environment,with a large number of nodes.