Due to the dynamics of topology and resources, Call Admission Control (CAC) plays a significant role for increasing resource utilization ratio and guaranteeing users' QoS requirements in wireless/mobile networks. In this paper, a dynamic multi-threshold CAC scheme is proposed to serve multi-class service in a wireless/mobile network. The thresholds are renewed at the beginning of each time interval to react to the changing mobility rate and network load. To find suitable thresholds, a reward-penalty model is designed, which provides different priorities between different service classes and call types through different reward/penalty policies according to network load and average call arrival rate. To speed up the running time of CAC, an Optimized Genetic Algorithm (OGA) is presented, whose components such as encoding, population initialization, fitness function and mutation etc., are all optimized in terms of the traits of the CAC problem. The simulation demonstrates that the proposed CAC scheme outperforms the similar schemes, which means the optimization is realized. Finally, the simulation shows the efficiency of OGA.

Bursty traffic is dominant in modern communication networks and keeps the call-level QoS assessment an open issue. ON-OFF traffic models are commonly used to describe bursty traffic. We propose an ON-OFF traffic model of a single link which accommodates service-classes of finite population (f-ON-OFF). Calls compete for the available link bandwidth under the complete sharing policy. Accepted calls enter the system via state ON and then may alternate between ON-OFF states. When a call is transferred to state OFF it releases the bandwidth held in state ON, while when a call tries to return to state ON, it re-requests its bandwidth. If it is available a new ON-period (burst) begins; otherwise the call remains in state OFF (burst blocking). We prove that the proposed f-ON-OFF model has a product form solution, and we provide an accurate recursive formula for the call blocking probabilities calculation. For the burst blocking probabilities calculation we propose an approximate but robust formula. In addition, we show the relation between the f-ON-OFF model and other call-level loss models. Furthermore, we generalize the f-ON-OFF model to include service-classes of both finite and infinite population. Simulation results validate our analytical methodology.

For a CDMA system with a single carrier, we consider a call control policy at each cell, which gives priority to handoff calls over new calls while meeting the overall call quality. New calls are first under the call control of the threshold type, and then receive services together with the handoff calls but under the outage restriction guaranteeing a pre-specified call quality. An optimization model with such quality-guaranteeing constraints is formulated, which is to determine the threshold value for each cell, minimizing the new call blocking probability. We propose a solution heuristic, with which a number of simulations are conducted under a variety of traffic environments. The computational experiments evaluate the usefulness of our call control scheme in that handoff calls are given an appropriate level of priority while the system capacity is effectively utilized.

In finding the optimal solution of virtual-path bandwidth allocation for large-scale networks, existing searching algorithms frequently call the process which calculate the bandwidth for given call blocking probability (CBP) and traffic loads. This is an inverse process of calculating CBP for given traffic loads and bandwidth. Because there is no analytic expression of calculating CBP, the process of calculating bandwidth with given CBP and traffic adopts an iteration algorithm. It leads to a tedious computation process. In this letter, a fast bandwidth evaluation algorithm is proposed and applied to the field of virtual path bandwidth allocation that aims at minimizing the worst call blocking probabilities in the network. The algorithm is proved to be accurate and fast. Finally, we provide comparison curves for the exact optimal CBPs obtained in the case of using OPBM against that of DCLPBM aided by the fast bandwidth evaluation algorithm.

In ATM networks, call processing on switches can be greatly simplified by using the concept of virtual path (VP); and good resource management strategies ensure that virtual channel connections (VCC) can be rapidly and efficiently established. In order to have good system performance, several methods of constructing virtual paths and strategies of allocating and managing resources should be considered. In this paper, several multicast strategies with dynamic routing are used and applied to the metropolitan LATA network. For the VP-based network, dynamic routing is also applied, and those strategies are discussed and investigated to show the versatility of the approach. Some results using dynamic multicast routing, such as call blocking rate, VP utilization, and VP adjustment rate, are obtained for the different strategies by simulation experiments.

Call demand suddenly and greatly increases in the aftermath of a major disaster, because people want to check on their families and friends in the stricken area. Many call attempts in mobile cellular systems are blocked due to the limited radio frequency resources. In this paper, as a solution to this problem, limiting the holding time of calls is investigated and a dynamic holding time limit (DHTL) method, which varies the holding time limit dynamically based on the number of call attempts, is proposed. The effect of limiting the holding time is investigated first using a computer simulation with a constant and heavy traffic load model. This simulation shows that the average holding time of calls is decreased as the holding time limit is reduced. But it also shows limiting the holding time decreases the number of calls blocked and forced call terminations at handover considerably. Next, a simple estimation method for the holding time limit, which reduces the blocking rate to the normal rate for increasing call demand, is described. Finally, results are given of a simulation, which show that the DHTL method keeps good performance for a sudden and great traffic load fluctuation condition.

In this paper, we present an approximate analysis method for computing the call blocking probability and Erlang capacity of CDMA systems. The approximated results provide only a few percent difference from the exact values, while reducing the calculation complexity. For CDMA systems with 3 sectors, we also show that the system performances such as call blocking probability and Erlang capacity can be characterized just with two traffic parameters (the traffic load of the most loaded sector and the sum of traffic loads of the other remaining sectors) instead of three sector traffic loads especially when the required call blocking probability is given less than 2e-2, which makes the traffic engineers manage the system more easily.

An appropriate call admission control in the next generation wireless networks is expected to make efficient use of scarce wireless resource and improve quality-of-service, while supporting multimedia services. On one hand, blocking handoff calls is normally more annoying than blocking new calls. On the other hand, blocking new calls reduces resource utilization. More importantly, handoff call arrival rate depends strongly on call holding time. A novel Call-Holding-Time-Based Random Early Blocking (CHTREB) scheme is proposed to achieve the aforesaid goals in a two-tier cellular voice/data network. With CHTREB, new calls are accepted according to some acceptance probability taking into account the call hloding time difference between voice and data calls. An iterative algorithm is developed to calculate performance measures of interest, i.e., new call blocking probability and forced termination probability. First, simulation results are shown to verify analytical results. Then, numerical results are presented to show the robustness of CHTREB. It is found that CHTREB outperforms TR and CHTREB-FAP under both stationary and nonstationary traffic scenarios. Last but not least, the studied 2-tier system is compared with 1-tier counterpart. It is shown that 2-tier system performs better in terms of average number of handoffs per data call.

This paper presents a Path Bandwidth Management (PBM) model for large-scale networks that leads to an almost optimal PB allocation, under constraints posed by the installed bandwidth in the transmission links of the network. The PB allocation procedure is driven from a traffic demand matrix and consists of three phases. In the first phase, a suitable decomposition of the whole network takes place, where the large-scale network is split to a set of one-level sub-networks. In the second phase, the optimization algorithm developed for one-level telecommunication networks is applied to each sub-network in order to define the optimal PB allocation. The criterion for optimization is to minimize the worst Call Blocking Probability (CBP) of all switching pairs of the sub-network. In the third phase, composition of the sub-networks takes place in a successive way, which leads to the final PB allocation of the large-scale network. As the large-scale network is built up from optimized sub-networks, an almost optimal PB allocation is anticipated. For evaluation, the worst resultant CBP of the proposed scheme is compared with that obtained by the optimal PB allocation procedure in order to prove its optimality and efficiency. We choose a set of large-scale networks whose size is not very large so that we can apply the optimization algorithm developed for one-level telecom networks for defining its optimal bandwidth allocation. Extensive evaluation of the PBM model has showed that the worst resultant CBP is about 2% above the optimal value, which is a satisfactory result. The proposed PBM scheme is explained by means of an application example.

One way of accommodating multimedia traffic having various transmission rates is to use multicode transmission in CDMA cellular systems. A multicode user, however, corresponds to locally concentrated single-code users, and the simultaneous transmission of multiple signals causes non-uniform traffic on cellular systems. We evaluate the performance of multicode transmission in CDMA systems in terms of call blocking and communications quality. We also estimate the number of receivers and searchers needed in a base station. Our previously proposed dynamic cell configuration (DCC) scheme reduces the adverse effects of non-uniform traffic in CDMA systems. In the present study, we found that the use of DCC for voice/data integrated traffic using multicode transmission reduces call blocking and improves communications quality for both voice and data users.

In Perosonal communication systems (PCS), reduction control of call blocking rate on wireless-environments, especially in terminating-call set up, is one of the key technologies to design network architecture. This is because the error rate of transferred messages there is normally much higher than that in wired environments. Terminating-call reforwarding technologies, to forward twice terminating-call messages through paging channels depending on call states, would be essential under such conditions, and in the PCS network architecture there are two possible reforwarding schemes: network-assisted reforwarding (NAR) and cell-station-assisted reforwarding (CAR). We first propose a traffic model for evaluating the performance of terminating-call reforwarding from the viewpoint of reduction of the call blocking rate on PCS, and then we clarify the advocating domains for NAR and CAR. Finally, we present a case study using this evaluation model for the Personal Handy-phone System (PHS), which is a PCS in Japan. The results of this study confirm that NAR is more efficient than CAR.