Sensor collision (interference) is studied in a large network of low bit-rate sensors that communicate via backscatter, i.e. modulate the reflection of a common carrier transmitted by a central reader. Closed-form analysis is provided, quantifying sensor collision (interference) in high-density, backscatter sensor networks (BSN), as a function of number of tags and aggregate bandwidth. Analysis is applicable to a broad class of sensor subcarrier modulations, propagation environments and reader antenna directivity patterns. It is discovered that anti-collision performance in high-density backscatter sensor networks is feasible provided that appropriate modulation is used at each sensor. That is due to the round-trip nature of backscatter communication as well as the extended target range, which both impose stringent requirements on spectrum efficiency, not easily met by all modulations. Furthermore, aggregate bandwidth savings for given anti-collision performance are quantified, when simple division techniques on subcarrier (modulating) frequency and space (via moderately directive hub antenna) are combined.

The network planning problem of placing replicated servers with QoS constraints is considered. Each server site may consist of multiple server types with varying capacities and each site can be placed in any location among those belonging to a given set. Each client can be served by more than one location as long as the round-trip delay of data requests satisfies predetermined upper bounds. Our main focus is to minimize the cost of using the servers and utilizing the link bandwidth, while serving requests according to their delay constraint. This is an NP-hard problem. A pseudopolynomial and a polynomial algorithm that provide guaranteed approximation factors with respect to the optimal for the problem at hand are presented

We consider the problem of precomputing constrained widest paths and multicast trees in a communication network. Precomputing and storing of the relevant information minimizes the computational overhead required to determine an optimal path when a new connection request arrives. We evaluate algorithms that precompute paths with maximal bandwidth (widest paths), which in addition satisfy given end-to-end delay constraints. We analyze and compare both the worst case and average case performance of the algorithms. We also show how the precomputed paths can be used to provide computationally efficient solutions to the constrained widest multicast tree problem. In this problem, a multicast tree with maximal bandwidth (widest multicast tree) is sought, which in addition satisfies given end-to-end delay constraints for each path on the tree from the source to a multicast destination.

The problem of routing in a network where QoS constraints are placed on network traffic is considered. We provide two optimal algorithms that are based on determining the discontinuities of functions related to the optimization at hand. The proposed algorithms have pseudopolynomial worst case running time and for a wide variety of tested networks they have fairly satisfactory running times. They perform significantly better than the algorithm based on the direct application of the dynamic programming equations and can also be used in conjunction with known polynomial-time approximation algorithms to provide good average case behavior, in addition to guaranteeing polynomial worst-case running time.