Journal of High Speed Networks - Volume 17, issue 3

Authors: Huei, Yoong Cheah | Keng, Pung Hung | Krivulin, Nikolai

Article Type: Research Article

Abstract: Previous works have proposed analytical models of TDM wavelength networks to evaluate the blocking performance, but they differ in their underlying assumptions and have varying computation complexities. In this paper, we propose an analytical model of TDM WDM optical networks with optical time-slot interchangers and without wavelength converter for minimum fixed hop routing. In order to make the analysis tractable, we propose a schema that work for any number of partition patterns regardless of numbers of links, wavelengths in each link, and time-slots in each wavelength. Our analytical model provides good accuracies in individual routes and average network blocking probability …when compared with the simulation results. Show more

Keywords: Schema, optical time-slot interchangers, average network blocking probability

DOI: 10.3233/JHS-2010-0336

Citation: Journal of High Speed Networks, vol. 17, no. 3, pp. 129-145, 2010

Authors: Baker, Alaa M. | Ng, Chee Kyun | Noordin, Nor Kamariah | Mustafa, Ahmed | Akbari, Ayyoub

Article Type: Research Article

Abstract: The IEEE 802.16e standard defines a sleep mode operation for conserving power to support the battery life of mobile broadband wireless access (BWA) devices. The system saves energy when it goes through a sleep period with some delay in packet arrival response time. The relationship between energy consumption and the delay is studied to ensure best performance for mobile devices. This relationship has been analyzed by using a mathematical model. A new scheduling method is proposed to adjust the sleep cycle periods by adding a small increase to the next sleep cycle compared with the previous cycle instead of just …simply doubling the previous cycle. The simulated results were obtained after adjusting the length of the first sleep cycle period (Tmin  ). Adjusting Tmin  provides a result of 54% reduction in the time needed for every frame to get a response especially in a lower traffic region. In a high traffic region, a reduction of 21.5% has been obtained in energy consumption for each sleep mode operation. Therefore, the proposed idea confirms a faster frame response time at lower energy consumption. Show more

Keywords: IEEE 802.16e, WiMAX, sleep mode, energy consumption, frame response time

DOI: 10.3233/JHS-2010-0337

Citation: Journal of High Speed Networks, vol. 17, no. 3, pp. 147-161, 2010

Authors: Hamza, Bashar J. | Ng, Chee Kyun | Noordin, N.K. | Rasid, M.F.A. | Ismail, A. | Tahir, Yaseen H.

Article Type: Research Article

Abstract: Future wireless access networks will be heterogeneous wireless network (HWN) environment which consists of various wireless technologies including universal mobile telecommunications system (UMTS) networks and wireless local area networks (WLAN). They are used together through vertical handover (VHO) to ensure global mobility and service continuity. The mobile stream control transmission protocol (mSCTP) layer supports dynamic association reconfiguration. This protocol allows mSCTP endpoints to dynamically add, change and delete IP addresses when the mobile node (MN) is switched between HWNs. During a mSCTP handover, the endpoints of the mSCTP are required to change the primary link from an old link to …a UMTS into a new link to a WLAN. However, due to the disparity between UMTS/WLAN bandwidth, a packet reordering problem will occur when the MN of the mSCTP leaves to a new network. This packet reordering problem can then causes additional drawbacks such as impossibility of growing an mSCTP congestion window, unnecessary fast retransmissions, actual packet losses, and reduced efficiency of the receiving mSCTP. In this paper, we propose a packet reordering model (PRM) that is inserted inside the MN, and works as a special buffer of a large capacity with one input and one output port to receive all transmission sequence numbers (TSNs). It then forwards all incoming data chunks to the MN/WLAN networks after the VHO. The performance of the system is simulated and analyzed using NS-2 simulation tool. The simulation results show that the suggested model enhances the performance throughput and the congestion window of the conventional mSCTP through VHO by handling the packet reordering problem. In other words, the average performance throughout of the proposed PRM scheme is 181.48 Kbps or 16% increment compared to conventional mSCTP at 165.54 Kbps. Show more

Keywords: Vertical handover, 3G, WLAN and UMTS, mSCTP, PRM

DOI: 10.3233/JHS-2010-0338

Citation: Journal of High Speed Networks, vol. 17, no. 3, pp. 163-173, 2010