A New CAC Policy Based on Traffic Characterization in Cellular Networks

The Call Admission Control (CAC) method presented in this paper is based on the statistical properties of the network’s traffic variables. It probabilistically estimates the time until the release of a seized channel: the admission control depends on the computed mean remaining time averaged along all channels at a specific instant and on a time threshold. The policy produces a smooth transition between the QoS metrics, giving the operator the freedom to design the network at the desired QoS point. Another valuable property is that the algorithm is straightforward and fed only by simple teletraffic metrics: distribution and the first and second moments of Channel Holding Time (CHT). Simplicity is important for a CAC method because decisions for accepting or rejecting calls must be computed quickly and frequently.Peer Reviewe

A survey of routing protocols for energy constrained ad hoc wireless networks

In this survey we review energy-aware routing protocols for wireless multihop ad hoc networks and critically discuss the main results in this area. The classification presented is in no case unique but summarizes the chief characteristics of the many published proposals for energy conservation. A common pitfall detected in most of the studies is the lack of unambiguous notion of network's lifetime and hence of clear objective of the designed algorithm. We, therefore, define first what operational lifetime for ad hoc networks means and then analyze the achievements from that angle. After getting insight into the different energy-aware routing protocols we point out another approach for extending network's operational lifespan, which has been overlooked in the relevant literature.Peer Reviewe

Energy and delay-constrained routing in mobile ad hoc networks: an initial approach

Energy conservation is a critical issue regarding wireless mobile ad hoc networks, since the nodes are battery restrained and the depletion of their power defines the lifetime of the network. In this work a mechanism for energy saving and timely delivery of data packets is incorporated into the route discovery phase to select paths with lower cost. The proposed algorithm utilizes two metrics: residual energy and queue length at each node. Buffer information is considered as a traffic load characteristic and its use is twofold: limitation of battery power consumption and end-to-end delay. A simulation-based performance comparison between a routing ad hoc protocol and its modified energy and delay-constrained version demonstrates that the latter one improves system performance for certain network scenarios.Peer Reviewe

Admission control in mobile cellular networks: design, performance evaluation and analysis

Key to the success of the mobile telecommunication systems is provision of mobility and more specifically, continuity of communication sessions on the move. However, from engineering point of view the cobination of scarce radio resource capacity, radio channel randomness, cellular structure, and user mobility can lead to call interruptions. The latter are regarded as highly undesirable by mobile users. One essential part of the solution to this problem is to address resource insufficiency. To this end admission control algorithms are incorporated into the system. In this thesis we concentrate on admission control as a means of guaranteeing uninterrupted service to users with active calls on the move.The research work reported in the monograph can be briefly summarised as follows. We explored the extensive empirical, analytical, and simulation results concerning teletraffic random variables of mobile cellular systems from the perspective of admission control. We proposed a conceptually different from prior work admission control solution based on the scientific evidence about the statistical nature of system variables and on the main result of renewal theory namely, decision making based on estimated system behaviour. In particular, we proposed a new admission control metric that uses statistical estimates. We evaluated the performance of the devised admission control strategy, which we named MRT (Mean Remaining Time) after the admission control condition, using both analytical and simulation approaches. We mathematically modelled system performance for traditional exponential conditions through a Markov chain. To study the MRT performance for non-conventional teletraffic scenarios we developed a simulation pure performance model. We examined the MRT for conditions that matched measured data from real, live mobile cellular networks. The results show that the scheme can guarantee call continuity and that it achieves a continuous working interval in contrast to the discrete one of the common cut-off scheme, yet the MRT strategy meets the important practical requirement for simplicity. We proposed an approximation to the MRT strategy for the case when not all of the required statistical information is readily available. Next, we studied in-depth the implications of novel techniques introduced in advanced mobile telecommunication systems. In particular, we examined the effect of the adaptive modulation and coding (AMC) technique on system performance and consequently on admission control design in mobile WiMAX. The dynamic tuning to time-varying radio link conditions introduces new random variables that drastically change the traditional mobile cellular system model. In particular, cell capacity and call resource demands are not constant but random, determined by wireless link quality. We analytically modelled the radio channel randomness and the consequent non-deterministic resource demand for a streaming service with constant bit rate and strict delay requirements through a zone-based cell model. Furthermore, we examined system-level fairness, which metric had not been explored in previous studies on mobile WiMAX. Additionally, we studied the effect of AMC on system performance under the two basic admission control approaches proposed in the literature by incorporating them in the analytical model. The results show that the total new call blocking probability and forced call termination probability of a constant bit rate calls deteriorate when the radio channel conditions are quickly varying and the offered load is moderate to heavy. Furthermore, the results show important differences in blocking and dropping probabilities of calls belonging to the same service (voice) and call (either new or handoff) class but being served in different modulation and coding zones. The results also indicate that if the admission control is not adapted to the actual environment (non-deterministic) the system performance is considerably worsened

Validation of a traffic-based CAC method under general channel holding time

We validate a call admission control (CAC) method for mobile cellular networks under more restrictive conditions than those assumed in its design. The method uses distribution and the first and second moments of the channel holding time (CHT) parameter to compute the algorithm’s main admission control metric: remaining CHT. Our goal is to generalize the handover method when only the mean and variance of CHT are known, but precise knowledge of the CHT’s complete distribution is not available. The problem is of practical interest because probability distribution fitting can be time- and CPU-intensive. To this end, we use an approximation of the expected remaining holding time instead of its exact value. We show that for a variety of traffic conditions and the general gamma distribution, the approximation yields acceptable results. For a log-normal distribution, our results also suggest that the algorithm can be defined based solely on the mean and variance of CHT

A survey of routing protocols for energy constrained ad hoc wireless networks

In this survey we review energy-aware routing protocols for wireless multihop ad hoc networks and critically discuss the main results in this area. The classification presented is in no case unique but summarizes the chief characteristics of the many published proposals for energy conservation. A common pitfall detected in most of the studies is the lack of unambiguous notion of network's lifetime and hence of clear objective of the designed algorithm. We, therefore, define first what operational lifetime for ad hoc networks means and then analyze the achievements from that angle. After getting insight into the different energy-aware routing protocols we point out another approach for extending network's operational lifespan, which has been overlooked in the relevant literature.Peer Reviewe

Validation of a traffic-based CAC method under general channel holding time

We validate a call admission control (CAC) method for mobile cellular networks under more restrictive conditions than those assumed in its design. The method uses distribution and the first and second moments of the channel holding time (CHT) parameter to compute the algorithm’s main admission control metric: remaining CHT. Our goal is to generalize the handover method when only the mean and variance of CHT are known, but precise knowledge of the CHT’s complete distribution is not available. The problem is of practical interest because probability distribution fitting can be time- and CPU-intensive. To this end, we use an approximation of the expected remaining holding time instead of its exact value. We show that for a variety of traffic conditions and the general gamma distribution, the approximation yields acceptable results. For a log-normal distribution, our results also suggest that the algorithm can be defined based solely on the mean and variance of CHT

Guard Capacity implementation in OPNET Modeler WiMAX Suite

Admission Control (AC) algorithms in mobile cellular networks support continuity of active communication sessions by guaranteeing availability of free resources. In this paper, we first describe the factors that condition AC design and show that AC in broadband mobile networks presents new challenges compared to AC in telephone cellular networks. We tailor the guard channel admission control strategy to the characteristics of mobile WiMAX networks. For AC validation and performance evaluation we use OPNET Modeler WiMAX Suite. To this end, we create in the simulator a framework for AC implementation. Then, we incorporate the Guard Capacity (GC) algorithm, which is the preferred choice of telephone cellular networks’ operators as GC is simple yet efficient. The accuracy of implementation is validated through simulation.Postprint (published version

Guard capacity implementation in OPNET modeler WiMAX suite

Admission Control (AC) algorithms in mobile cellular networks support continuity of active communication sessions by guaranteeing availability of free resources. In this paper, we first describe the factors that condition AC design and show that AC in broadband mobile networks presents new challenges compared to AC in telephone cellular networks. We tailor the guard channel admission control strategy to the characteristics of mobile WiMAX networks. For AC validation and performance evaluation we use OPNET Modeler WiMAX Suite. To this end, we create in the simulator a framework for AC implementation. Then, we incorporate the Guard Capacity (GC) algorithm, which is the preferred choice of telephone cellular networks’ operators as GC is simple yet efficient. The accuracy of implementation is validated through simulation

Energy and delay-constrained routing in mobile ad hoc networks: an initial approach

Energy conservation is a critical issue regarding wireless mobile ad hoc networks, since the nodes are battery restrained and the depletion of their power defines the lifetime of the network. In this work a mechanism for energy saving and timely delivery of data packets is incorporated into the route discovery phase to select paths with lower cost. The proposed algorithm utilizes two metrics: residual energy and queue length at each node. Buffer information is considered as a traffic load characteristic and its use is twofold: limitation of battery power consumption and end-to-end delay. A simulation-based performance comparison between a routing ad hoc protocol and its modified energy and delay-constrained version demonstrates that the latter one improves system performance for certain network scenarios.Peer Reviewe