Protecting against link failures in communication networks is essential to increase robustness, accessibility, and reliability of data transmission. Recently, network coding has been proposed as a solution to provide agile and cost efficient network protection against link failures, which does not require data rerouting, or packet retransmission. To achieve this, separate paths have to be provisioned to carry encoded packets, hence requiring either the addition of extra links, or reserving some of the resources for this purpose. In this paper, we propose network protection codes against a single link failure using network coding, where a separate path using reserved links is not needed. In this case portions of the link capacities are used to carry the encoded packets. The scheme is extended to protect against multiple link failures and can be implemented at an overlay layer. Although this leads to reducing the network capacity, the network capacity reduction is asymptotically small in most cases of practical interest. We demonstrate that such network protection codes are equivalent to error correcting codes for erasure channels. Finally, we study the encoding and decoding operations of such codes over the binary field.
@cite_18 , the author extended the protection model in @cite_11 and provided a GMPLS-based implementation of a link protection strategy that is a hybrid of 1+N and 1:N. It is claimed that the hybrid 1+N link protection provides protection at higher layers and with a speed that is comparable to the speed achieved by the physical layer implementations. In addition, it has less cost and much flexibility.
@cite_18 @cite_11
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In [1], the author introduced a strategy to use network coding on p-Cycles in order to provide 1+N protection for straddling connections and links against single link failures in mesh optical networks. In this paper we extend the work in [1] and introduce a GMPLS-based implementation of this strategy for link protection, that is also used to protect on-cycle links. We refer to this scheme as hybrid 1+N protection, since some data units are transmitted without being combined with other data units. The strategy uses a combination of GMPLS standard label switched paths (LSP) for protecting on-cycle links, and modified LSPs, which we refer to as label switched cycles (LSC), for protecting straddling links. The strategy does not have to explicitly detect failures, but rather detects the absence of data units. Destinations receive backup copies of packets within no more than the p-Cycle propagation delay for on-cycle link failures, and no more than the sum of the propagation delays of the p-Cycle and the longest straddling link for straddling link failures. The implementation details of this strategy are presented, and the cost of implementation, in terms of link usage is evaluated and is shown to be modest. This scheme can therefore provide protection at higher layers, at a speed that is comparable to that achieved at the physical layer, but at a much reduced cost, while being flexible, and requiring less involvement from the management and control planes. p-Cycles have been proposed for pre-provisioned 1:N protection in optical mesh networks. Although the protection circuits are preconfigured, the detection of failures and the rerouting of traffic can be a time consuming operation. Another survivable mode of operation is the 1+1 protection mode, in which a signal is transmitted on two link disjoint circuits, and the destination chooses the strongest of the two signals, hence recovery from failures is instantaneous. The disadvantage is the large number of protection circuits. In this paper we introduce a new concept in protection: 1+N protection, in which a p-Cycle can be used to protect a number of bidirectional connections. Data from different circuits are combined using network coding, which can be implemented in a number of technologies. The maximum outage time under this protection scheme is limited to no more than twice the p-Cycle propagation delay. In this paper, a comprehensive study of the downlink performance in a heterogeneous cellular network (or HetNet) is conducted via stochastic geometry. A general HetNet model is considered consisting of an arbitrary number of open-access and closed-access tiers of base stations (BSs) arranged according to independent homogeneous Poisson point processes. The BSs within each tier have a constant transmission power, random fading factors with an arbitrary distribution and arbitrary path-loss exponent of the power-law path-loss model. For such a system, analytical characterizations for the coverage probability are derived for the max-SINR connectivity and nearest-BS connectivity models. Using stochastic ordering, interesting properties and simplifications for the HetNet downlink performance are derived by relating these two connectivity models to the maximum instantaneous received power (MIRP) connectivity model and the maximum biased received power (MBRP) connectivity models, providing good insights about HetNets and their downlink performance in these complex networks. Furthermore, the results also demonstrate the effectiveness and analytical tractability of the stochastic geometric approach to study the HetNet performance. In this paper, we characterize the performance of an important class of scheduling schemes, called greedy maximal scheduling (GMS), for multi-hop wireless networks. While a lower bound on the throughput performance of GMS is relatively well-known in the simple node-exclusive interference model, it has not been thoroughly explored in the more general K-hop interference model. Moreover, empirical observations suggest that the known bounds are quite loose, and that the performance of GMS is often close to optimal. In this paper, we provide a number of new analytic results characterizing the performance limits of GMS. We first provide an equivalent characterization of the efficiency ratio of GMS through a topological property called the local-pooling factor of the network graph. We then develop an iterative procedure to estimate the local-pooling factor under a large class of network topologies and interference models. We use these results to study the worst-case efficiency ratio of GMS on two classes of network topologies. First, we show how these results can be applied to tree networks to prove that GMS achieves the full capacity region in tree networks under the K-hop interference model. Second, we show that the worst-case efficiency ratio of GMS in geometric network graphs is between 1 6 and 1 3.