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The design of survivable all-optical networks based on self-healing WDM rings (SHR/WDM) to provide 100% protection from any single link failure requires the joint solution of three sub-problems. These are the ring cover of the mesh topology (the RC sub-problem), the routing of working lightpaths between node pairs to support traffic demands (the WL sub-problem) and the selection of the SHR/WDM spare wavelengths for the protection of every link traffic (the SW subproblem). This paper presents an integer linear programming (ILP) formulation of the problem of minimizing the total wavelength mileage (λ-miles) required to support a set of given traffic demands in a given network topology using SHR/WDM employing 1:N line protection mechanism (the WRL problem). This formulation allows to jointly and optimally solve the three subproblems, and yields up to 15% reduction of the total λ-miles required by existing solutions that separately resolve the sub-problems. A simplified sub-optimal solution of the WRL problem is also provided, that yields results few percent worse than the optimal solution and that is tractable for networks whose size is on the order of the pan-European network, i.e., 19 nodes

One class of wireless sensor networks makes use of sensor nodes that recharge their batteries by harvesting energy from the surrounding environment. Being continuously recharged, the battery does not need to be replaced regularly and the sensor node is maintenance-free. A key module in such sensor network solutions is the data link automatic repeat request (ARQ) protocol, which must be designed to reliably deliver sensor nodes data at the minimum energy cost. With this objective in mind, two ARQ protocol classes are compared. In one class, each sensor node operates individually. In the other, the concept of cooperative communications is adopted, whereby neighboring sensor nodes help each other during the retransmission process.It is shown that the use of cooperative ARQ protocols in energy harvesting sensor networks enables sensor nodes to balance their energy consumption to match their own battery recharge rate. In turn, a balanced energy consumption-to-recharge rate ratio has the potential to improve the network throughput. Both classes of ARQ protocols are analyzed and compared. Estimated throughput gains are discussed under various network scenarios.

In this paper we analyze the worst-case behavior of general connection-oriented networks, with first-in-first-out (FIFO) queueing policy, forwarding packets along an arbitrary system of routes. A worst-case bound is proven for the end-toend queueing delay and buffer size needed to guarantee lossfree packet delivery, given that sources satisfy a given source rate condition. The results are based on a novel deterministic approach and help in reconciling the discrepancy between the unstable worst-case behavior of FIFO-based networks and their good practical performance.Index Terms-Deterministic delay bound, FIFO, packet flow.

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Abstract-In cooperative ARQ protocols, data frame retransmissions may be performed by a neighboring node (the relay) that has successfully overheard the source's frame transmission. One advantage is the diversity provided by the relay. The three-way (source, destination, relay) frame exchange sequence required in the cooperative ARQ protocols may however introduce extra latency when compared to non-cooperative ARQ protocols. To take advantage of cooperative ARQ protocols, it is then necessary to resort to selective repeat solutions.The focus of the paper is to derive a delay model for cooperative selective repeat ARQ protocols in slotted radio networks. The derived analytical model quantifies, with closed formulas, the queueing and transmission delay experienced by Poisson arriving data frames, whose retransmissions are performed by a single relay.