Wireless communication is used in many different situations such as mobile telephony, radio and TV broadcasting, satellite communication, wireless LANs, and military operations. In each of these situations a frequency assignment problem arises with application specific characteristics. Researchers have developed different modeling ideas for each of the features of the problem, such as the handling of interference among radio signals, the availability of frequencies, and the optimization criterion.

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Models and solution techniques for frequency assignment problems

Traffic engineering is an important mechanism for Internet network providers seeking to optimize network performance and traffic delivery. Routing optimization plays a key role in traffic engineering, finding efficient routes so as to achieve the desired network performance. In this survey we review Internet traffic engineering from the perspective of routing optimization. A taxonomy of routing algorithms in the literature is provided, dating from the advent of the TE concept in the late 1990s. We classify the algorithms into multiple dimensions: unicast/multicast, intra-/inter- domain, IP-/MPLS-based and offline/online TE schemes. In addition, we investigate some important traffic engineering issues, including robustness, TE interactions, and interoperability with overlay selfish routing. In addition to a review of existing solutions, we also point out some challenges in TE operation and important issues that are worthy of investigation in future research activities.

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An overview of routing optimization for internet traffic engineering

In the deployment of wireless mesh networks (WMNs) the placement of Mesh Nodes (MNs) is an important design issue. The performance of WMNs is greatly affected by the location of the MNs. As it is difficult to place the MNs in a regular pattern in the real deployment, finding the optimal locations in the deployment environment is of much interest for the service providers. For a given possible locations for the MNs and the user density in the deployment environment, we aim to find the locations of the MNs to be used that maximizes the coverage and the connectivity of the network together. Due to high computational complexity of the exhaustive searching algorithm, an efficient local searching algorithm is proposed. Numerical results show that, the local search algorithm can give close to optimal performance with much lower time complexity than exhaustive searching.

Node Placement Algorithm for Deployment of Two-Tier Wireless Mesh Networks

Efficient channel assignment is crucial for successful deployment and operation of IEEE 802.11-based WLANs. In this article we present a survey on the state of the art channel assignment schemes in IEEE 802.11-based WLANs. After detailing out all the schemes, we provide a qualitative comparison among different schemes in terms of algorithm execution behaviors, complexity, and scalability. We then conclude the survey with several research issues open for further investigation.

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Channel assignment schemes for infrastructure-based 802.11 WLANs: A survey

IEEE 802.11 wireless LAN : Capacity analysis and protocol enhancement

To deploy a multi-cell 802.11 wireless local area network (WLAN), access point (AP) placement and channel assignment are two primary design issues. For a given pattern of traffic demands, we aim at maximizing not only the overall system throughput, but also the fairness in resource sharing among mobile terminals. A novel method for estimating the system throughput of multi-cell WLAN is proposed. An important feature of this method is that co-channel overlapping is allowed. Unlike conventional approaches that decouple AP placement and channel assignment into two phases, we propose to jointly solve the two problems for better performance. The optimal solution can be found using exhaustive searching. Due to the high computational complexity involved in exhaustive searching, an efficient local searching algorithm, called patching algorithm, is designed. Numerical results show that for a typical indoor environment, patching algorithm can provide a close-to-optimal performance with much lower time complexity than exhaustive searching

/pdf/joint-access-point-placement-and-channel-assignment-for-802-100t671v6k.pdf

Joint access point placement and channel assignment for 802.11 wireless LANs

To deploy a multi-cell IEEE 802.11 wireless local area network (WLAN), access point (AP) placement and channel assignment are two primary design issues. For a given pattern of traffic demands, we aim at maximizing not only the overall system throughput, but also the fairness in resource sharing among mobile terminals. A novel method for estimating the system throughput of a multi-cell WLAN is proposed. An important feature of this method is that cochannel overlapping is allowed. Unlike conventional approaches that decouple AP placement and channel assignment into two phases, we propose to solve the two problems jointly for better performance. Due to the high computational complexity involved in exhaustive searching, an efficient local searching algorithm, called patching algorithm, is also designed. Numerical results show that for a typical indoor environment, the patching algorithm can provide a close-to-optimal performance with much lower time complexity.

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We consider optical layer monitoring schemes for fast link failure localization in WDM mesh networks. A new concept monitoring trail (m-trail) is proposed. It differs from the existing monitoring cycle (m-cycle) concept by removing the cycle constraint. As a result, m-trail provides a more flexible all-optical monitoring structure which includes simple, non-simple m-cycles and open trails as special cases. Aiming at minimizing the total monitoring cost, an integer linear program (ILP) is formulated for m-trail design. Numerical results show that the m-trail based scheme significantly outperforms its m-cycle based counterpart.

Monitoring Trail: A New Paradigm for Fast Link Failure Localization in WDM Mesh Networks

Explicit control protocol (XCP) is a promising transport layer protocol for satellite IP networks. Nevertheless, two problems of XCP can be identified: low throughput under high link error rate conditions; output link underutilization in the presence of rate-limited connections. To address the first problem, we propose to maintain the transmission rate of an XCP sender when triple duplicate ACK is detected. To solve the second problem, we propose to adjust the aggregated feedback based on the ratio of the number of rate-limited connections to the total number of connections sharing the link. We then combine our proposed solutions to form a new protocol, called P-XCP. Simulation results show that P-XCP overcomes the two problems of XCP. When packet error rate is over 0.1, P-XCP is shown to enjoy a throughput almost double that of XCP.

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P-XCP: a transport layer protocol for satellite IP networks

Fast link failure detection in all-optical networks (AONs) can be achieved using monitoring cycles (m-cycles). An m-cycle is a loop-back optical connection of supervisory wavelengths with a dedicated monitor. Compared to the channel- based or link-based monitoring schemes, m-cycle based schemes require much less number of monitors. In this paper, we propose an ILP (integer linear program) formulation for m-cycle design to minimize the network cost. Our contributions are two-fold: 1) non-simple m-cycles are enabled; and 2) an efficient tradeoff is allowed between the monitor cost and the bandwidth cost. Numerical results show that our algorithm outperforms existing algorithms with a significant performance gain.

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K.L. Yeung

Papers

Joint access point placement and channel assignment for 802.11 wireless LANs

Joint access point placement and channel assignment for 802.11 wireless LANs

Monitoring Trail: A New Paradigm for Fast Link Failure Localization in WDM Mesh Networks

P-XCP: a transport layer protocol for satellite IP networks

Monitoring Cycle Design for Fast Link Failure Detection in All-Optical Networks