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This study adopts the opposing theoretical views of legitimacy - institutional and strategic - in evaluating firm performance and top management commitment as antecedents to green procurement and green supplier development. Additionally, the impact of green procurement and green supplier development on supplier performance is analysed. Using a sample of western European companies, we develop a structural equation model to test our hypotheses. We find that the buying firm's market performance positively relates to the adoption of green procurement. While financial performance has no effect on green procurement, top management commitment is found to be an important driver of both green procurement and green supplier development. Moreover, the relationship between green procurement and supplier performance is fully mediated by green supplier development. The paper addresses a research gap concerning firm-level antecedents for green procurement and green supplier development showing that both practices may impact supplier performance. Furthermore, it is shown that legitimacy concerns drive basic green procurement, whereas top management is decisive for advanced practices, such as green supplier development. © 2013 Taylor & Francis.

The increasing importance of sustainable behaviour in business has enhanced its impact on supply chain management. Firms foster sustainability in their supplier base in reaction to growing sustainability requirements in various ways, including sustainable supplier co-operation. Knowledge about the effects of sustainable supplier co-operation on firm performance is limited; therefore, this study tests antecedents and implications of sustainable supplier co-operation according to the triple bottom line. A survey of Western European firms reveals that sustainable supplier co-operation has generally positive effects on firm performance across social, green and economic dimensions. However, only green practices have positive significant effects on economic performance, not social practices (e.g., child labour rules). In contrast to practitioner perceptions, investments in sustainability, for example through sustainable supplier co-operation does indeed result in sufficient returns.

Frequency Assignment is an important approach to mitigate multi-cell interference in cellular systems. In this paper, we consider frequency hopping as one possible frequency assignment approach. In particular we focus our attention on cognitive radio cellular systems as one of the very promising future access technologies, taking IEEE 802.22 as an example. While the optimal frequency assignment for such a system is conceptually straightforward as well as computationally complex, we demonstrate that usage of distributed methods leads to a significant loss of assignment efficiency. In addition, we suggest means of mitigating this adverse effect.

Wireless operators incorporate multiradio access technologies aiming at expanding their customer base and benefiting from synergies of existing and planned infrastructure. The result is areas with overlapping radio access technologies, enabling users to select from a large pool of available connections, based on several criteria. In these increasingly complex scenar­ios the importance of handover decisions cannot be underestimated. We study three different handover decision strategies, focusing on the tradeoff between continuous connectivity, network utilization and per­formance, and the associated costs, and compare them to the optimal strategy. We motivate the need for a distributed algorithm, especially when considering the deployment of multimedia applications, and reflect on the effective network capacity as a function of the handover strategy employed and the permitted offline time for the active mobile nodes in the network.

It is well known that the presence of nodes using a low data transmit rate has a disproportionate impact on the performance of an IEEE 802.11 WLAN. ORP is an opportunistic relay protocol that allows nodes to increase their effective transmit rate by replacing a low data rate transmission with a two-hop sequence of shorter range, higher data rate transmissions, using an intermediate node as a relay. ORP differs from existing protocols in discovering relays experimentally, by optimistically making frames available for relaying. Relays identify themselves as suitable relays by forwarding these frames. This approach has several advantages compared with previously proposed relay protocols: Most importantly, ORP does not rely on observations of received signal strength to infer the availability of relay nodes and transmit rates. We present analytic and simulation results showing that ORP improves the throughput by up to 40% in a saturated IEEE 802.11b network.

In a network environment where multi-radio access becomes the norm, choosing the most appropriate network interface and base station becomes essential for distributing radio resources optimally and fairly, and for allowing each node to take full advantage of its multiaccess capability. This paper discusses the issues arising when mobile nodes are equipped with three different radio access technologies and have contradicting goals to the network provider in a high density scenario. We simulated three different decision strategies aimed to resolve such contradicting goals and compared those results to the optimal solution attained from a linear programming model.

In this paper we discuss aggregated mobility patterns and physical proximity of nodes within Ambient Networks, where an Ambient Network can be described as a network that integrates heterogeneous nodes and access techniques. We illustrate how awareness of node mobility patterns can be used to identify groups of nodes moving together, and how this grouping can be used to decrease signaling overhead, for example the signaling associated with a mobility event, and increase transmission efficiency. First, we describe the architectural and naming issues associated with this concept and discuss a number of mobility optimizations that can be applied to these moving networks. Further, we introduce algorithms that can recognize the presence of a routing group to enable the use of routing and mobility optimizations. Finally, we assess the performance and benefits of the routing group approach by means of simulation.