Yung-Chung Wang

Per-stream loss behavior of ΣMAP/M/1/K queuing system with a random early detection mechanism

In this paper, the matrix-analytic approach is applied to explore the per-stream loss behavior of the multimedia traffic under RED scheme. We constructed a @?MAP/M/1/K queuing model for the RED mechanism with multimedia traffic which follows a continuous-time Markovian arrival process (MAP). In addition to evaluating the long-term per-stream packet drop probabilities, we examine the bursty nature of per-stream packet drops by means of conditional statistics with respect to dropped periods and the probability that the queuing system stays in the dropped period. The dropped period corresponds to having more than a certain number of packets in router buffer; non-dropped period corresponds to the opposite. These performance measures describe the quality of service provided by the router to particular multimedia traffic streams in the presence of background multimedia traffic.

Throughput Analysis of DS CDMA/Unslotted ALOHA Wireless Networks with Fixed Packet Length in Rayleigh Fading Finite-State Markov Channel Model

We propose the finite-state Markov channel (FSMC) model to the throughput analysis of DS CDMA/unslotted ALOHA wireless networks in the mobile environment. The FSMC model can characterize the correlation structure of Rayleigh fading process, and the degree of correlation depends on the Doppler frequency shift. The FSMC model is suited to the throughput analysis by queueing theory due to its Markov chain nature. The previous papers in DS CDMA/unslotted ALOHA wireless networks in Rayleigh fading consider a whole packet. They ignore that the channel gain or multiple access interference can change symbol-to-symbol. In our proposed analysis, both the channel gain and multiple access interference can change from symbol to symbol. It is not just a packet-level analysis in the previous papers, and is a more general symbol-level analysis. Our generalized scheme should be more suited to realistic Rayleigh fading in the mobile environment. We consider two cases: (1) the system without carrier load sensing protocol (CLSP) and (2) systems with CLSP. For both cases, we analyze the theoretical throughput by queueing theory for various averaged signal-to-noise ratios and Doppler frequency shifts, and the computer simulated throughput matches the theoretical throughput.

Simpler Throughput Analysis of CDMA/Unslotted ALOHA Radio Networks with Variable Message Length Based on M/M/inf Queueing Model

We propose a new and exact method to analyze the throughput of the DS CDMA unslotted ALOHA system with variable number of fixed-length packets. The proposed scheme requires two-dimensional summation while the previous requires four. Thus the proposed analysis scheme is of less computational complexity. The proposed analysis result is also slightly closer to the simulation result than the previous analysis result is, especially in heavier offered load.

Throughput of DS-CDMA/unslotted ALOHA radio networks with Markovian arrival processes†

SUMMARY n nPrevious works on the throughput analysis of the direct sequence-code division multiple access/unslotted ALOHA radio network all used the Poisson arrival process (PAP). However, the interarrival times of PAP are independent, so it is not suited to model todays Internet and multimedia traffic, which have correlated interarrival times. We are motivated to use the Markovian arrival process (MAP), a more general input traffic model that captures the correlation of interarrival times. We are the first to analyze the throughput of the direct sequence-code division multiple access/unslotted ALOHA radio network with MAP. We propose the use of MAP, which encompasses the PAP as a special case. The new MAP model basically generalizes the current traffic and queuing models of multimedia in wireless networks. Copyright

Completed analysis of cellular networks with PH-renewal arrival call

In this paper, we apply the PH-renewal process to model new call and handoff processes, and apply the matrix-analytic approach to explore the performance measures of the drop and block probabilities. We examine the bursty nature of handoff call drops by means of conditional statistics with respect to alternating block and non-block periods. Five related performance measures are derived from conditional statistics, including the long-term new call block and handoff call drop probabilities, and the three short-term measures of average length of a block period and a non-block period, as well as the conditional handoff call drop probability during a block period. These performance measures greatly assist the priority reservation handoff mechanism in determining a proper threshold guard channel in the cell. Furthermore, we derive the handoff call drop probability from the short-term performance measures of average length of a block period and a non-block period, as well as the conditional handoff call drop probability during a block period. The results presented in this paper can provide guidelines for designing adaptive algorithms to adjust the threshold in the guard channel reservation handoff scheme.

Space priority queue with fuzzy set threshold

In this paper, we develop a queueing model of fuzzy threshold-based space priority buffer management and study its performance under realistic conditions. It applies a matrix-analytic approach to analyze the relevant performance measure, including the packet loss probability of high-priority traffic and the packet loss probability of low-priority traffic. Based on the proposed framework, we explore the properties of the fuzzy threshold-based space priority buffer management scheme. Numerical results reveal that the fixed threshold scheme, through its abrupt nature, causes a relatively higher low-priority packet drop. Intuitively, the fuzzy threshold adapts well to different input traffic conditions and packet loss rate requirements of high-priority packet, yielding a lower packet loss probability for low-priority packet.

Elucidating the short term loss behavior of a DMAP process in random early detection queue with background DBMAP

Given the increasing prominent role of multimedia applications in Internet-based services, elucidating the per-stream short term loss behavior of multimedia traffic in the routers is of priority concern. This work attempts to model both tagged multimedia and background traffic by a discrete-time Markovian arrival process (DMAP) and discrete-time batch Markovian arrival process (DBMAP), respectively. A queuing model is developed for a router with a random early detection (RED) mechanism with both tagged multimedia and background traffic. The queuing model of the router with RED scheme is modeled as DMAP+DBMAP/D/1/K. The short-term characteristics of per-stream multimedia packet drop are then examined through means of conditional statistics with respect to congested and non-congested periods that occur in an alternating manner. Such performance measures refer to the quality of service provided by the router for a particular multimedia traffic stream in the presence of background traffic.

Performance Analysis of CDMA/ALOHA Networks in Memory Impulse Channels

Previous CDMA/ALOHA network performance analysis papers do not consider memory impulse channels. The Markov-Gaussian model can characterize the bursty nature of the memory impulsive noise in some wireless channels and power line communication (PLC) channels. In this paper, we propose the use of the Markov-Gaussian model in the throughput analysis of CDMA/ALOHA networks. The state transition diagram for the throughput analysis has one extra dimension to represent if the impulse noise is present or not. We derive the exact throughput analysis in memory impulse channels with and without channel load sensing protocol (CLSP). The analytic results demonstrate that if the level of the impulsive noise is higher, performance degradation is more and vice versa. Based on the analytic results, we also find the optimal CLSP threshold alpha for various impulse noise conditions. The analytic results of the throughput performance are all matched by the simulation results.

Load balancing early handoff scheme for multimedia service in wireless cellular networks

This study developed a load balancing early handoff scheme that use the overlap in base stations in wireless cellular networks. The proposed scheme enables early transfer of part of a heavy base station load, in order to reduce the new call blocking probability (CBP) and handoff call connection dropping probability (CDP) as well as to increase the resource utilization of wireless networks. Since the scheme is triggered by a connection request received by the base station, it immediately reflects the loading of the base station. The proposed load balancing early handoff policy can be integrated in various call admission control schemes. The effectiveness of the load balancing early handoff scheme is verified by integrating it with DMTBR, a self-optimizing admission control scheme, to improve the system performance. Additionally, NS2 is used to simulate the wireless network with wrap-around model. The simulation results show that the proposed scheme can effectively improve the wireless network resource utilization.

Elucidating the Short Term Loss Behavior of Markovian-Modulated Batch-Service Queueing Model with Discrete-Time Batch Markovian Arrival Process

This paper applies a matrix-analytical approach to analyze the temporal behavior of Markovian-modulated batch-service queue with discrete-time batch Markovian arrival process (DBMAP). The service process is correlated and its structure is presented through discrete-time batch Markovian service process (DBMSP). We examine the temporal behavior of packet loss by means of conditional statistics with respect to congested and noncongested periods that occur in an alternating manner. The congested period corresponds to having more than a certain number of packets in the buffer; noncongested period corresponds to the opposite. All of the four related performance measures are derived, including probability distributions of a congested and noncongested periods, the probability that the system stays in a congested period, the packet loss probability during congested period, and the long term packet loss probability. Queueing systems of this type arise in the domain of wireless communications.