Linear time adaptive arithmetic coding

The issue of how arithmetic coding should be implemented is addressed. A data structure is described and shown to support adaptive arithmetic coding on an arbitrary-sized alphabet in time linear in the size of the inputs and outputs. Experimental results that show the method to be useful even on relatively small alphabets are given     

Research on adaptive compression coding for network coding in wireless sensor network

Based on the sequence entropy of Shannon information theory, we work on the network coding technology in Wireless Sensor Network (WSN). In this paper, we take into account the similarity of the transmission sequences at the network coding node in the multi-sources and multi-receivers network in order to compress the data redundancy. Theoretical analysis and computer simulation results show that this proposed scheme not only further improves the efficiency of network transmission and enhances the throughput of the network, but also reduces the energy consumption of sensor nodes and extends the network life cycle.     

Variable-rate convolutional network coding

Four types of variable-rate convolutional network codes are investigated over a single-source finite cyclic network.It is found that variable-rate generic,dispersion and broadcast can be implemented on the same network without changing the local encoding kernels of the non-source nodes.The efficient implementation has the advantage that each non-source node only needs to store one copy of the local encoding kernel within a session.However,it is also shown by an example that variable-rate multicast may not always be implemented under the above condition.     

联合网络编码和叠加编码的协作发射策略

提出一种联合网络编码和叠加编码的协作发射策略。对传统的解码转发中继采用网络编码可以提高频谱效率,这是因为放宽了不同数据流之间的正交约束并且可通过预编码/波束形成技术减轻由此带来的干扰。与基于信道状态信息获得近似最优性能但计算繁重的波束形成策略相比,提出利用叠加编码思想确定网络预编码处理向量,该方法无需发射端预知CSI因而大大减小了计算复杂度。理论分析和仿真结果同时表明,所提策略可获得与基于CSI近似最优的线性网络预编码和脏纸网络预编码策略极为相近的性能。     

Topology matters in network coding

Seeking to understand the potential of network coding in future internet endeavors, we consider the vital role of network topology with respect to the potential benefits of Random Linear Network Coding (RLNC). First, we propose a set of metrics that capture the essential trade-offs between throughput, confidentiality and decoding delay. Using large network simulation, we are able to evaluate the behavior of RLNC for various topological classes based on random graphs. Our results show significant differences between local dissemination of information (typical of wireless networks) and long range connectivity (typical of peer-to-peer environments). We believe that our results can help pave the way for the creation of better overlay topologies for RLNC protocols in future internet applications.     

Unachievability of network coding capacity

The coding capacity of a network is the supremum of ratios k/n, for which there exists a fractional (k,n) coding solution, where k is the source message dimension and n is the maximum edge dimension. The coding capacity is referred to as routing capacity in the case when only routing is allowed. A network is said to achieve its capacity if there is some fractional (k,n) solution for which k/n equals the capacity. The routing capacity is known to be achievable for arbitrary networks. We give an example of a network whose coding capacity (which is 1) cannot be achieved by a network code. We do this by constructing two networks, one of which is solvable if and only if the alphabet size is odd, and the other of which is solvable if and only if the alphabet size is a power of 2. No linearity assumptions are made.     

Efficient software-defined passive optical network with network coding

The huge increase in broadband service requires much more bandwidth than ever before; however, due to the cost sensitivity, it is not possible to pursue high transmission rate blindly in the access network, which requires us to consider how to improve network efficiency. In this paper, a software-defined passive optical network architecture with network coding (NC) is proposed to reduce downstream bandwidth consumption and thus increases the throughput and network efficiency. To flexibly implement the coding operation on local peer traffic, the NC pair management scheme is provided and keeps the compatibility with the current multi-point control protocol (MPCP) in a single optical line terminal (OLT). Considering the trends in OLT pooling and the requirement of smooth network upgrade, software-defined networking (SDN) techniques are applied in the NC-based passive optical networks. Through re-arranging the affiliations between the OLTs and optical network units (ONUs), the local traffic between peer ONUs will be led from non-NC-supported OLTs to NC-supported OLTs, and then the downstream efficiency will be still quite high even in a hybrid OLT pool. The experiments and evaluation results show that, the software-defined passive optical networks with NC reduce nearly 50 % occupied downstream bandwidth, when there is local traffic between peer ONUs, even in a hybrid OLT pool.     

基于网络编码与空时编码的协作MAC协议

针对无线ad hoc网络中协作造成的中继效率低以及不同QoS需求难以满足等问题,提出了一种联合网络编码和空时编码的协作MAC协议(NSTCMAC)。NSTCMAC将网络编码与空时编码技术相结合,设计出区分业务类型的协作MAC协议传输机制,以满足不同业务类型的QoS需求;进一步通过马尔科夫链模型分析了区分业务类型的协作机制及性能。仿真结果表明,相比传统的DCF、COOPMAC以及CD-MAC协议,NSTCMAC协议能更好地保证不同的QoS需求,并能有效地解决协作造成的中继效率低的问题。     

An algebraic approach to network coding

We take a new look at the issue of network capacity. It is shown that network coding is an essential ingredient in achieving the capacity of a network. Building on recent work by Li et al.(see Proc. 2001 IEEE Int. Symp. Information Theory, p.102), who examined the network capacity of multicast networks, we extend the network coding framework to arbitrary networks and robust networking. For networks which are restricted to using linear network codes, we find necessary and sufficient conditions for the feasibility of any given set of connections over a given network. We also consider the problem of network recovery for nonergodic link failures. For the multicast setup we prove that there exist coding strategies that provide maximally robust networks and that do not require adaptation of the network interior to the failure pattern in question. The results are derived for both delay-free networks and networks with delays.     

Random network coding in MIMO system

Wireless Networks - Random network coding (RNC) has emerged as a promising technology. In this paper, we seek to answer the question that how RNC benefits cellular systems. A novel RNC-based...