Yulong Shi

A unified protocol stack solution for LTE and WLAN in future mobile converged networks

The interworking of the LTE system and WLAN technologies has drawn much attention lately, due to the growing demands for various multimedia services and large data traffic in hotspot areas. Existing research studies have mostly investigated the coupling architectures for these two wireless communication standards at the network layer. However, in the current architectures, many important coordination functions and joint optimizations cannot be accomplished efficiently. To tackle this problem, a new CBS solution is proposed, which integrates different RATs at layer 2 in the true sense of convergence. We design a unified protocol stack that includes all the original functions of both LTE and WLAN systems. Then we propose a convergence architecture, the RMC sublayer, for joint management of these two RATs. The proposed CBS solution can support seamless offloading through soft handover, guaranteed QoS, forwarding management by a single IP address, and customized bandwidth aggregation service. Finally, our simulation and initial experiment results demonstrate the feasibility and efficiency of the CBS solution in future mobile converged networks.

Toward software defined AS-level fast rerouting

Abstract Network failures are common on the Internet, and with mission-critical services widely applied, there grows demand for the Internet to maintain the performance in possibilities of failures. However, the border gateway protocol (BGP) can not react quickly to be recovered from them, which leads to unreliable packet delivery degrading the end-to-end performance. Although much solutions were proposed to address the problem, there exist limitations. The authors designed a software defined autonomous system (AS)-level fast rerouting (SD-FRR) to efficiently recover from interdomain link failures in the administrative domain. The approach leverages the principle of software defined networking (SDN) to achieve the centralized control of the entire network. By considering routing policies and BGP decision rules, an algorithm that can automatically find a policy-compliant protection path in case of link failure was proposed. The OpenFlow forwarding rules are installed on routers to ensure data forwarding. Furthermore, to deactivate the protection path, how to remove flow entries based on prefixes was proposed. Experiments show that the proposal provides effective failure recovery and does not introduce significant control overhead to the network.

Distributed location model and algorithm with position uncertainty

Abstract The localization of multiple mobile terminals (MTs) is an encouraging paradigm of applications in wireless networks. Peer-to-peer communication between MTs facilitates the cooperative localization of multiple MTs. For sake of low complexity and high robustness, investigations often focus on the distributed algorithm in cooperative localization. However, the impact from position uncertainty of cooperative MT lacks of analysis in related works. A new distributed location model, as well as corresponding algorithm, is devised when considering both the distance measurement error and the position uncertainty of MTs, which is more judicious than the traditional model for distributed cooperative localization scenario. In addition, the performance of proposed algorithm is analyzed through Cramer-Rao lower bound (CRLB). Simulations indicate that the algorithm outperforms traditional methods in terms of accuracy and robustness.

Relationship-Oriented Software Defined AS-Level Fast Rerouting for Multiple Link Failures

Large-scale deployments of mission-critical services have led to stringent demands on Internet routing, but frequently occurring network failures can dramatically degrade the network performance. However, Border Gateway Protocol (BGP) can not react quickly to recover from them. Although extensive research has been conducted to deal with the problem, the multiple failure scenarios have never been properly addressed due to the limit of distributed control plane. In this paper, we propose a local fast reroute approach to effectively recover from multiple link failures in one administrative domain. The principle of Software Defined Networking (SDN) is used to achieve the software defined AS-level fast rerouting. Considering AS relationships, efficient algorithms are proposed to automatically and dynamically find protection paths for multiple link failures; then OpenFlow forwarding rules are installed on routers to provide data forwarding continuity. Our approach is able to ensure applicability to ASes with flexibility and adaptability to multiple link failures, contributing toward improving the network performance. Through experimental results, we show that our proposal provides effective failure recovery and does not introduce significant control overhead to the network.

Performance analyses and enhancement of distributed cooperative localisation on position ambiguity

Distributed cooperative localisation, owing to its low computational burden, is more attractive in wireless networks than the centralised paradigm. However, the distributed algorithms tend to have worse location accuracy among existing works. In this study, the authors focus on the performance dissimilarity between distributed and centralised localisation algorithms, and analyse the Cramer–Rao lower bound. Then, their performance relationship is investigated, and verified by theoretical proof and extensive simulations. Furthermore, it is observed that the position ambiguity of cooperative mobile terminal is the primary cause of performance loss in the distributed algorithm, in contrast with the centralised one. To suppress the impact of position ambiguity, the authors establish an element-wise-weighted total least-squares model and devise the corresponding distributed localisation algorithm. Numerical simulations indicate that the proposed algorithm outperforms traditional methods.

Cooperative wireless localization based on weighting for vector‐addition error

SUMMARY Localization error occurrence due to a position ambiguity is a very critical problem in wireless distributed cooperative localization, which may, in turn, affect the reliability of the localization of the whole or a major portion of the network. In this paper, we formulate a two-dimensional cooperative localization model via graph partition in arbitrary topologies while considering the cooperative nodes (or neighbors) position ambiguity. Based on this model, we establish a robust algorithm, named weighted factor graph (FG)-based cooperative localization algorithm, by mapping local topologies into the FG and by incorporating the vector-addition error as the weight. The vector-addition error includes the measurement error and the neighbors position ambiguity, simultaneously. The optimal weight is derived theoretically according to the statistic properties of the vector errors and the joint probability density function. Theoretical analysis and numerical results indicate that the proposed algorithm can acquire higher level of accuracy for localization in various topology scenarios in comparison with some typical algorithms. Copyright

Cooperative Group Localization Based on Factor Graph for Next-Generation Networks

In ill-conditioned communication environment, multiple target localization is of important practical significance. The cooperative group localization (CGL) model was firstly put forward, which has verified the effectiveness of localization performance gain and simultaneous multiple target localization in ill conditions. However, there exist two inherent difficulties: the strict demand for CGL topology and the high complexity. By the rational use of information to relax restrictions on topology and by dividing the complex problem into some simple local ones, the factor graph (FG) together with the sum-product algorithm is a perfect candidate for the problems above. In order to solve the two problems, we propose the weighted FG-based CGL (WFG-CGL) algorithm which incorporates the optimal weights based on the information reliability. In order to further reduce the complexity, we propose the low-complexity FG-based CGL (LCFG-CGL) algorithm. The Cramer-Rao lower bound (CRLB) of the localization error in CGL is first derived. Theoretical analysis and numerical results indicate that the proposed algorithms not only perform better in relaxing CGL topology requirement, but also enjoy high localization accuracy under low complexity in comparison with the existing CGL algorithm.