Timucin Ozugur

Intermediate-node initiated reservation (IIR): a new signaling scheme for wavelength-routed networks

A problem of many distributed lightpath provisioning schemes is wavelength contention, which occurs when a connection request attempts to reserve a wavelength channel that is no longer available. This situation results from the lack of updated global link-state information at every node. In networks with highly dynamic traffic loads, wavelength contention may seriously degrade the network performance. To overcome this problem, we propose a new framework for distributed signaling and introduce a class of schemes referred to as intermediate-node initiated reservation. In the new scheme, reservations may be initiated at any set of nodes along the route; in contrast, reservations can only be initiated by the destination node in the classic destination initiated reservation (DIR) scheme. As a result, the possibility of having outdated information due to propagation delay is significantly lowered. Specifically, we consider two schemes within this framework, for networks with no wavelength conversion and for networks with sparse wavelength conversion, respectively. Theoretical and simulation results show that, compared with the classic DIR scheme, the new schemes can significantly improve the network blocking performance. The accuracy of the analytical models is also confirmed by extensive numerical simulations.

Label prioritization in GMPLS-centric all-optical networks

When establishing lightpaths in an all-optical DWDM network, it is possible that concurrent lightpaths requests will block one another if the lightpaths attempt to reserve the same wavelength of the same link. In this paper, we propose a novel signaling mechanism, referred to as label prioritization, which attempts to reduce the backward-link blocking in GMPLS-centric all-optical networks by assigning different priorities to the suggested wavelengths of each connection request. The prioritization of the wavelength encourages concurrent lightpath requests to choose different wavelengths, thereby reducing the possibility that the requests will be blocked. The label prioritization mechanism consists of a signaling extension to GMPLS to support the label prioritization and a modification in the optical switch controller to support the signaling extension. Simulation results show that the label prioritization method can effectively reduce wavelength conflicts.

Optimal MAC-layer fairness in 802.11 networks

This paper covers the MAC sublayer fairness in the 802.11 networks. We first summarize the basic sublayer functionality specified by the 802.11 DCF-MAC standard. Then, the modified time-based media access method is proposed to provide an optimal fair access in any given wireless topology. The modified time-based method is based on our previously proposed time-based media access method. Although the time-based method significantly eliminates the fairness problem, they cannot provide the optimal fair access. By the introduction of the modified time-based method, not only it provides the optimal fairness, but also the need of estimating the weight factor is eliminated. The modified and time-based methods require periodic link information from the local neighboring stations. We also propose an information update procedure to exchange link information using a polling mechanism to employ the proposed method.This paper covers the MAC sublayer fairness in the 802.11 networks. We first summarize the basic sublayer functionality specified by the 802.11 DCF-MAC standard. Then, the modified time-based media access method is proposed to provide an optimal fair access in any given wireless topology. The modified time-based method is based on our previously proposed time-based media access method. Although the time-based method significantly eliminates the fairness problem, they cannot provide the optimal fair access. By the introduction of the modified time-based method, not only it provides the optimal fairness, but also the need of estimating the weight factor is eliminated. The modified and time-based methods require periodic link information from the local neighboring stations. We also propose an information update procedure to exchange link information using a polling mechanism to employ the proposed method.

Supporting dynamic IP addresses for wireless push services in cellular networks

The paper introduces a methodology to provide push services to dynamic IP addressed-mobile users in 2.5G/3G networks, and minimize the unsuccessful network-requested PDP (packet data protocol) context activation for static IP users during wireless location-aware and content aware push application delivery over the packet-switched wireless core network. The proposed method is based on protection and mobile user activity procedures, SMS service, and a new signaling mechanism to forward HLR (home location register) based flags to the WAP/directory server.

Multiobjective hierarchical 2G/3G mobility management optimization: niched Pareto genetic algorithm

We first propose four-layer optimization for a UMTS coverage area: (i) cell-oriented intra-SGSN (serving GPRS service node) layer, which is optimized RAs (routing areas) covering the intra-SGSN signaling cost, paging cost and RA load balancing; (ii) RA-oriented intra-MSC (mobile switching centre) layer, which is optimized location areas (LA) covering the intra-MSC signaling cost and LA load balancing; (iii) RA-oriented inter-SGSN layer, which is optimized SGSN coverage areas covering the inter-SGSN signaling cost, RNC (radio network controller) and SGSN load balancing; (iv) LA-oriented inter-MSC layer, which is optimized MSC coverage areas covering the inter-MSC signaling cost and MSC load balancing. We focus on RA optimization, namely layers (i) and (iii). The optimization of MSC coverage areas and LAs is performed in a similar manner. We propose a schema-based niched Pareto genetic algorithm, which deals with multiple objectives by incorporating the concept of Pareto domination in its selection operator, and applying a niching pressure to spread its population out along the Pareto optimal tradeoff surface. The proposed genetic algorithm uses a schema-based partially matching crossover using tournaments of n size, where the crossover pairs are chosen in two steps, first based on the class ranking and then schema ranking. New offspring are modified using the geographical footprints to converge to the optimal solution faster.

Intermediate-node initiated reservation (IIR): a new signaling scheme for wavelength-routed networks with sparse conversion

In this work, we propose a new distributed signaling scheme, within the GMPLS framework for establishing lightpaths in wavelength-routed networks with sparse wavelength conversion. Analytical models are developed to evaluate the performance of the proposed scheme. Theoretical and simulation results show that compared to the classic schemed designed primarily for networks with no wavelength conversion, the proposed signaling scheme can achieve much lower blocking probability.

Multiobjective hierarchical location and routing area optimization in GPRS and UMTS networks

We propose four-layer optimization for UMTS coverage area: (i) cell-oriented intra-SGSN layer, which is optimized RA areas covering the intra-SGSN signaling cost, paging cost and RA load balancing, (ii) RA-oriented intra-MSC layer, which is optimized location areas covering the intra-MSC signaling cost and LA load balancing,(iii) RA-oriented inter-SGSN layer, which is optimized SGSN coverage areas covering the inter-SGSN signaling cost, RNC and SGSN load balancing, (iv) LA-oriented inter-MSC layer, which is optimized MSC coverage areas covering the inter-MSC signaling cost and MSC load balancing. We first calculate the multi-objective cost functions for each layers in UMTS, namely intra-SGSN and inter-SGSN layers. We then simulate an UMTS network using the niched Pareto genetic algorithm, which deals with multiple objectives by incorporating the concept of Pareto domination in its selection operator, and applying a niching pressure to spread its population out along the Pareto optimal tradeoff surface. We also define geographical footprints, and its impact on the network cost.

Weighted hierarchical backoff algorithm for wireless ad hoc networks

This paper covers new backoff algorithms, which decrease collisions on the non-reserved broadcast packets in wireless ad-hoc networks. Control information broadcasts provide the understanding of the local neighborhood topology to achieve some necessary network mechanisms in the ad-hoc networking. However, the exponential backoff algorithm introduces collisions due to non-reservation characteristics of the broadcast messaging. We propose a hierarchical and weighted-hierarchical backoff algorithm to decrease the percentage of collisions. These new algorithms classify the stations in a distributed manner within their local neighborhood. Each classified station uses the some portion of the backoff window size, which is assigned to this hierarchical group of stations. A local neighborhood discovery procedure is also proposed for stations to advertise their number of logical connections within their local neighborhoods. The proposed backoff algorithms use this procedure to advertise the connection values.

Combining layer 2-layer 3 paging for wireless LANs

The paper addresses location tracking and paging IEEE 802.11 wireless LAN hosts that are in power save mode. We design a protocol for paging (tracking agent based paging or TAP) IEEE 802.11 wireless LAN hosts. Mobile nodes in each IEEE 802.11 basic service set constitute a layer-2 paging area, which coexists within layer-3 paging areas. The tracking agent is in charge of the L2 paging state, and it continuously updates the paging state after each L2 handoff. Paging on the wireless link is done by extended beacons, and does not involve periodic L3 messages. Signaling in TAP is based on IEEEs inter-access point protocol with minor extensions. We show that TAP can be integrated with various IP paging algorithms such as mobile IPv6 hierarchical paging, home agent and foreign agent paging. We evaluate the performance of the combined L3-L2 paging protocols analytically and by simulation and show that TAP combined with mobile IPv6 hierarchical paging achieves superior power savings compared individually to mobile IPv6 hierarchical paging without TAP or home agent paging algorithms.

A distributed signaling scheme for provisioning dynamic traffic in wavelength-routed networks

Provisioning dynamic traffic is a major challenge in wavelength-routed networks. While the routes of connections are mainly determined by using global state information, different connections that share the same link may still compete for the same resources. These conflicts can cause significant blocking, a problem that becomes more serious as traffic becomes more dynamic and as the state information changes more frequently. Therefore, it is increasingly important to design appropriate signaling schemes to avoid blocking due to contention between different simultaneous connection requests. In this paper, we propose a new distributed signaling scheme, Intermediate-Node Initiated Reservation (IIR), for establishing dynamic lightpaths in wavelength-routed networks. In the framework of IIR, reservations may be initiated at any set of nodes along the path of a connection, and multiple wavelengths may be reserved. Two IIR implementations are designed for networks with no wavelength conversion and with sparse wavelength conversion. Extensive simulation results show that the IIR scheme outperforms the original schemes under various network and traffic conditions. Simulation results also show that the IIR scheme performs better in networks where number of wavelength per fiber is large, or in networks with sparse wavelength conversion.