Timed token protocols inadequately provide periodic communication service, although this is crucial for hard real time systems. We propose an algorithm to guaranteeing periodic communication service on a timed token protocol network. In this approach, we allocate bandwidth to each node so that the summation of bandwidth allocations is Target Token Rotation Time (TTRT). If a node cannot consume the allocated time, the residual time is made concession to other nodes for non-periodic service using a timer which contains the unused time value and is appended to the token. This algorithm can always guarantee transmission of real-time messages before their deadlines when the network utilization is less than 50%.

This letter presents a new approach for obtaining the expected waiting time for packets under the drop-head (also called a drop-from-front) scheme for buffer management. The results show that the drop-head scheme is more effective in reducing queueing delays than the drop-tail scheme.

We propose a novel epidemic routing policy, named energy optimal epidemic routing, for delay tolerant networks (DTNs). By investigating the tradeoff between delay and energy, we found the optimal transmission range as well as the optimal number of infected nodes for the minimal energy consumption, given a delivery requirement, specifically delay bound and delivery probability to the destination. We derive an analytic model of the Binary Spraying routing to find the optimal values, describing the delay distributions with respect to the number of infected nodes.

ATM (Asynchronous Transfer Mode) has been standardized by ITU-T, in order to realize the broadband ISDN. Due to its properties, such as packet-oriented information transfer without flow control and flexible allocation of transmission capacity, in order to ensure quality of service for all existing calls, it is necessary to monitor and regulate the traffic for each call based on traffic descriptor. This kind of control is done by a policing function. There are many proposed policing schemes. Among them, the MC (Moving Ceiling) scheme is considered as an efficient mean cell rate policing scheme. It has been recently proposed and proved to have a promising performance in mean cell rate enforcement by simulation. In this paper, we formulate numerical equations to calculate the steady state probability and output rate of the MC scheme. And using them, we investigate the effects of MC parameters on its performance.

This paper presents a scalable and efficient quota-based admission control scheme for the 3rd generation (3G) operator's IP backbone network, where quota denotes a chunk of bandwidth. This research is motivated by the 3G operator's need for guaranteeing end-to-end IP QoS of mobile-to-mobile and mobile-to-server multimedia sessions. In the proposed scheme, the quota size of a path implies the proper amount of allocated and released resources on the path condition. Employing the quota size makes the job of allocating or releasing resources at nodes in a path simple so that it becomes scalable. Moreover, with this simple scheme, an edge node can be allowed not only to initiate the allocation/release request but also to perform admission control function. To maximize the efficiency, the path quota size varies depending on the bottleneck link condition in the path. In high offered load, the proposed scheme decreases the path quota size and retains higher utilization while it requires lower signaling cost than the fixed scheme using a fixed size aggregation. As the load lessens, it increases the path quota size and reduces the signaling cost significantly.

Wireless mobile communication networks support mobile terminals (MTs) which are free to travel within a service coverage area. In order to locate an MT effectively when a call is initiated, several location management schemes are proposed to keep track of its location. Current methods being used in IS-41 and GSM MAP for location management pose problems such as an increase in signaling traffic in the network, a ping-pong effect and a bottleneck created by signaling traffic at home location register (HLR). In this paper, we propose a new location management scheme that is to reduce the number of location registrations at HLR by making the location registration at HLR unnecessary when an MT moves into neighboring registration area (RA) or when it moves back to the original RA from neighboring RA. Our scheme employs a centralized database architecture using the HLR/VLR concept as in the IS-41 and GSM MAP but alleviates the above-mentioned problems. Analysis results show that our scheme always outperforms current methods and shows an especially better performance at low CMR (call to mobility ratio).

To overcome the mobility impact on RSVP, many schemes have been proposed based on Mobile IP regional registration and passive reservation in advance. Although the regional registration and in advance reservation reduce the QoS interruption time, the latter may demand intolerable bandwidth. This letter introduces a novel approach to reduce the QoS interruption time by maximizing the localization of QoS re-establishment in the regional registration environment. The proposed scheme identifies the exact path segment affected by mobility. The QoS interruption time of the proposed scheme is comparable to its low bound without in advance reservation.

The IEEE 802.11 wireless local area network (WLAN) is the most widely deployed communication standard in the world. Currently, the IEEE 802.11ax draft standard is one of the most advanced and promising among future wireless network standards. However, the suggested uplink-OFDMA (UL-OFDMA) random access method, based on trigger frame-random access (TF-R) from task group ax (TGax), does not yet show satisfying system performance. To enhance the UL-OFDMA capability of the IEEE 802.11ax draft standard, we propose a centralized contention-based MAC (CC-MAC) and describe its detailed operation. In this paper, we analyze the performance of CC-MAC by solving the Markov chain model and evaluating BSS throughput compared to other methods, such as DCF and TF-R, by computer simulation. Our results show that CC-MAC is a scalable and efficient scheme for improving the system performance in a UL-OFDMA random access situation in IEEE 802.11ax.

With the occurrence of new applications such as Voice over IP (VoIP) and multimedia conference, there is an ongoing discussion about realizing QoS in the Internet today. Because of its potential scalability in support of QoS guarantees, the Differentiated Service (DiffServ) architecture with aggregate packet scheduling has recently attracted much attention in the networking community as a feasible solution for providing Internet QoS. Thus, it is important to understand delay bound of an individual flow in the DiffServ architecture in order to provide delay-sensitive applications. In this paper, we study, via both analysis and simulation, the deterministic bound on edge-to-edge delay of a flow in a DiffServ network domain with FIFO aggregation and a class-based Latency Rate (LR) server that provides guaranteed performance with rate reservation for a traffic class. We derive edge-to-edge delay bound for a single flow as a function of allocated service rate for a traffic class, token bucket parameters adopted for flows at the network ingress, and information about joining and leaving flows. We compare the obtained delay bound with previous works using analytic results, and then conduct simulation to confirm the results. The derived bound is less than that of previous studies in all cases.

In this Letter, we investigate the loss performance of a discrete-time single-server queueing system with periodic vacations, with which we are often confronted in traffic control, such as cell scheduling or priority control schemes, at ATM nodes. Explicit expressions are derived for the cell loss ratio in terms of the distribution of the buffer contents in an infinite capacity queue.

Recently, several promising window-based policing schemes have been proposed. It is worthwhile to analyze them for performance comparison. In this letter, we formulate numerical equations to evaluate the improved versions of the JW scheme as well as the JW scheme itself. We also show the correctness of our formulation using the simulation results.

The IETF Mobile IP defines two multicast options: remote subscription (RS) and bi-direction tunneling (BT). In order to synthesize the strong points of these two IETF multicast options, we propose a hybrid approach, mMOM, which selectively uses two IETF multicast options based on the mobility of mobile hosts. Whenever a mobile host requests its first registration to a certain foreign agent, the corresponding foreign agent starts the service using the BT option. Afterwards, if it requests re-registration to the same foreign agent, the foreign agent considers it to be relatively immobile and continues services using the RS option. We propose a new metric to compare heterogeneous algorithms. Simulation results show that our approach outperforms all others.