The problem of wireless spectrum sharing is investigated using a multi-server queueing system that models a group of channels and a multiplexed arrival process formed by a primary and secondary group of users. Motivated by under-utilized capacity in RF spectrum owned by the primary group, this work examines the impact of secondary user access patterns on blocking probabilities and achievable improvement in spectrum utilization with statistical multiplexing. The analytical framework presented allows estimation of the blocking for any renewal process characterization of secondary access times. In this work, Gamma distributed inter-access times are chosen to examine the impact of their index of dispersion (IDI) on the excess blocking probabilities of the Poisson distributed primary group. It is shown that by reducing the IDI value to be below unity, one can increase the secondary system utilization in the shared spectrum with minimal impact on the primary system. Combined with an increase in the number of excess channels available for secondary use, a feasible spectrum sharing paradigm can be proposed by shaping the access patterns of secondary systems.

Multiplexing Analysis for Dynamic Spectrum Access

In this paper we consider an ATM transmission link, to which CBR or VBR and ABR or UBR calls arrive according to independent Poisson processes. CBR/VBR calls (characterized by their equivalent bandwidth) are blocked and leave the system if the available link capacity is less than required at the time of arrival. ABR/UBR calls, however, accept partial blocking, meaning that they may enter service even if the available capacity is less than the specified required peak bandwidth, but greater than the so called minimal accepted bandwidth. Partially blocked ABR/UBR calls instead experience longer service time, since smaller given bandwidth entails proportionally longer time spent in the system, as first suggested in [3] and analyzed in details herein. Throughout the life time of an ABR/UBR connection, its bandwidth consumption fluctuates in accordance with the current load on the link but always at the highest possible value up to their peak bandwidth (greedy sources). Additionally, if this minimal accepted bandwidth is unavailable at the time of arrival, ABR/UBR calls are allowed to wait in a finite queue. This system is modeled by a Continuous Time Markov Chain (CTMC) and the CBR/VBR and ABR/UBR blocking probabilities and the mean ABR/UBR waiting- and service times are derived.

A Partially-Blocking Queueing System with CBR/VBR and ABR/UBR Arrival Streams

This paper proposes a new priority scheme called partial preemptive priority (PPP) for mixed loss and delay system to satisfy very different individual performance requirements of loss (delay-sensitive) traffic and delay (loss-sensitive) traffic. the PPP scheme is a generic priority scheme which includes all the conventional priority schemes, e.g., preemptive priority (PP) and movable boundary (MB), as well as nonpriority (NP), schemes as special cases. By using the matrix-analytic method, a unified matrix-geometric solution to the mixed loss and delay priority systems with phase-type Markov renewal process (PH-MRP) inputs is derived. Numerical examples also are presented to demonstrate the effectiveness of the PPP scheme.

A unified solution to mixed loss and delay systems with partial preemptive priority

Multidimensional traffic models where calls of more than two classes of different properties share the same resource are very important as basic models for tightly coupled multiprocessor systems, etc. Thus,- this type of research has long been actively performed. So far, some papers on finite-source loss models have been presented. However, neither finite-source delay models nor their approximate analyses have been investigated much.



As an approximate analysis method of delay queueing model with two different classes of quasi-random input (M1, M2/M1, M2/S/N1, N2 model), this paper proposes a method which approximates combination states of waiting calls of each call class by the ratio of numbers of waiting calls of each call class. Moreover, by comparing numerical results of this approximate analysis with exact solutions and simulation values, it is shown that this approximate analysis method has very good accuracy.

Approximate analysis for delay queueing systems with two different classes of quasi‐random input

We have analyzed the packet delay time to find the location of a destination when the flooding search method is applied in the grid topology circuit-switched network which uses common channel signaling. First, a simulation technique was used as a performance evaluation method. Since this method requires a large run time as the number of node increases, we have evaluated the performance of the above system by using an analytic method based on the Jackson network. Then, analytic results have shown differences within 10%, compared with the simulation results. Finding the location of the destinations will be the basic step of call set-up in mobile communication and the future personal communication networks. >

Performance analysis of a flooding search scheme in a grid topology circuit-switched network using common channel signaling

An approximate evaluation is proposed for the individual mean waiting time, and loss probability for mixed delay and loss (nondelay) systems with renewal and Poisson inputs handled by servers with exponential service time. The approximation is based on the GI approximation previously proposed by H. Akimaru, et al. (1983, 1985), in which the mixed input process is regarded as renewal. The systems with mixed delay renewal and nondelay Poisson inputs, and ones with mixed nondelay renewal and delay Poisson inputs are analyzed. Approximate formulas for the mean waiting time and loss probability for the respective inputs are presented in simple closed form, and comparisons to simulations show good accuracy. The formulas are expected to be useful for analysis and optimum design of the mixed delay and loss systems. >

H. Kuribayashi

Papers

Approximate evaluation for mixed delay and loss systems with renewal and Poisson inputs