Lauro Ortigoza-Guerrero

A prioritized handoff dynamic channel allocation strategy for PCS

An analytical method is developed to calculate the blocking probability (p/sub b/), the probability of handoff failure (p/sub h/), the forced termination probability (p/sub ft/), and the probability that a call is not completed (p/sub nc/) for the no priority (NPS) and reserved channel (RCS) schemes for handoff, using fixed channel allocation (FCA) in a microcellular system. Based only on the knowledge of the new call arrival rate, a method of assessing the handoff arrival rate for any kind of traffic is derived. The analytical method is valid for uniform and nonuniform traffic distributions and is verified by computer simulations. An extension (generalization) to the nonuniform compact pattern allocation algorithm is presented as an application of this analysis. Based on this extended concept, a modified version of a dynamic channel allocation strategy (DCA) called compact pattern with maximized channel borrowing (CPMCB) is presented. With modifications, it is shown that CPMCB is a self-adaptive prioritized handoff DCA strategy with enhanced performance that can be exploited in a personal communications service (PCS) environment leading either to a reduction in infrastructure or to an increase in capacity and grade of service. The effect of user mobility on the grade of service is also considered using CPMCB.

Flexible resource allocation strategies for class-based QoS provisioning in mobile networks

Flexible resource-allocation (FRA) strategies have been proposed in the literature to mitigate the high blocking rate caused in high-speed mobile communication networks when resource aggregation is used to increase the data rate. In this paper, new FRA strategies that cope with scenarios with multiple service types and multiple priorities are proposed. These are called the FRA strategy with differentiated priorities and quality of service (FRAQoS) and the FRA strategy with prioritized levels (FRASPL). The main distinguishing feature of these strategies is their capacity to prioritize some service types over others. FRAQoS prioritizes the quality of service (QoS) of particular service types over others by introducing the concepts of prioritized call degradation and compensation. However, FRAQoS provides a limited ability to prioritize particular service types over the rest because any incoming call, irrespective of its service type and priority, may trigger resource reallocations to service it. The FRASPL overcomes this limitation by introducing a call-admission mechanism that, when necessary, rejects calls originated by low-priority service types. This enhances the protection to high-priority service types. By prioritizing some services over the others, FRASPL can trade off capacity against QoS. FRAQoS represents particular limiting cases of FRASPL. A mathematical model is developed to investigate the performance of FRAQoS and FRASPL. Then, they are compared with other FRA strategies in a scenario with multiple differentiated service types. Results show that the proposed strategies effectively prioritize service types, providing them with better QoS. This makes FRAQoS and FRASPL specially suitable for class-based QoS provisioning in mobile networks.

A distributed dynamic resource allocation for a hybrid TDMA/CDMA system

A distributed dynamic resource allocation (DDRA) strategy for a hierarchical cellular structure (HCS) is proposed. In the DDRA, resources are shared not only between cells of the same hierarchy, but between layers. The proposed DDRA strategy is evaluated using the hybrid time-division multiple-access/code-division multiple-access (TDMA/CDMA) proposal made in the future radio wide-band multiple-access system (FRAMES) Project Mode I (FMI) as a case study. A mixed environment is suggested for the evaluation of the DDRA, which consists of Manhattan-like microcells covered by hexagonal-shaped umbrella cells (macrocells). Users are classified according to their speed as slow- and fast-moving users and are attended to by the most suitable layer of the hierarchy according to their speeds. Two types of real-time circuit-switched services are considered in the evaluation: speech and data at different rates. The DDRA is compared with the fixed resource allocation (FRA) strategy with overflow and with FRA with overflow, handdown, and channel reallocations (FRANR).

Call level performance analysis for multiservices wireless cellular networks with adaptive resource allocation strategies

In this paper, a novel mathematical approach to evaluate the performance of adaptive or flexible resource allocation (FRA) strategies with uniform quality of service (QoS) provisioning in multiservices wireless cellular networks, in terms of the call blocking probabilities and transmission delay, is proposed. FRA strategies improve channel utilization by dynamically adjusting user transmission rates. Based on the available cell capacity, the bandwidth offered to users can be adjusted in accordance with the elasticities of their service types. When an FRA strategy provides similar QoS to all the calls of the same service type, it is known as an FRA with uniform QoS provisioning. In multiservices wireless cellular networks, calls can be identified as belonging to one of four service classes (i.e., conversational, streaming, interactive, and background). Transmission delay is one of the most important performance measurements of interactive and background service classes. Transmission delay, however, has not been addressed in previous studies on FRA with uniform QoS provisioning either in conjunction with interactive or background service classes. This is because such studies have been based on the Markov property of the negative exponential distribution of the service time which lacks time delay information. The analytical approach in this paper is based on the fact that in FRA strategies with uniform QoS provisioning, calls of all service types tend to use an average number of resources (i.e., the number of resources available for a service type divided by the number of active users of that service type). This feature facilitates the assessment of the mean service time and the number of resources allocated to a call during its lifetime and, consequently, a calls transmission delay. The study also considers the fact that the probability density function (pdf) of the normalized transmission delay is almost a symmetrical function and has low variance. The accuracy of the proposed mathematical analysis is then corroborated by means of semianalytical methods and by discrete event computer simulation.

Call admission and code allocation strategies for WCDMA systems with multirate traffic

In this paper, call admission and code allocation schemes are proposed to provide service differentiation in the forward link of wideband code-division multiple-access (WCDMA) systems. In particular, this paper proposes multiple leaf code reservation (MLCR) schemes, where different numbers of orthogonal variable spreading factor (OVSF) leaf codes (i.e., codes of the lowest layer of the OVSF code tree) are reserved to differentiate users with different bandwidth requirements. Leaf codes are only reserved for as long as the call admission process lasts. Once the decision of whether a new request is admitted or not has been made, a Code Dereservation procedure is carried out to increase flexibility in the code assignment phase. The performance of these MLCR strategies with/without code reassignments is then evaluated. Analysis shows that MLCR schemes are also useful in improving fair access among different traffic classes. In addition, perfect fair access among requests with different data rates can be achieved when code reassignments are jointly employed with the proposed OVSF-code reservation schemes.

Performance evaluation of mobile wireless communication systems with link adaptation

The performance of key quality-of-service metrics for mobile cellular systems with link adaptation is evaluated by means of a teletraffic analysis. To our knowledge, no similar analysis considering link adaptation exists in the literature. In particular, novel mathematical expressions for inter-cell handoff call arrival rate, intracell handoff failure, and forced termination probabilities are derived.

On the optimum spectrum partitioning in a microcell/macrocell cellular layout with overflow

An analytical method to find the optimal spectrum partitioning for a system of microcells and their overlaying macrocells is presented. The spectrum partitioning is calculated based on the blocking probability in each layer ensuring a grade of service of 2% and allowing overflow traffic from microcells to macrocells. The teletraffic analysis is based on a multidimensional birth and death process. The calculation assumes perfect assignment of mobiles to each of the layers according to their speeds (i.e. the probability of erroneous assignment of a call is insignificant). The model is general and any velocity probability density function in the system could be used to assess the blocking probability in each layer. The spectrum partitioning method could be dynamically implemented.

Performance analysis of adaptive resource allocation strategies with service time dependence on the allocated bandwidth

In this paper, a novel approach to mathematically analyse the performance of adaptive resource allocation strategies with uniform quality of service (QoS) provisioning, when session service time depends on the allocated bandwidth, is proposed. Our proposed approach is based on the fact that in adaptive resource allocation strategies with uniform QoS provisioning all active sessions of each service type tend to utilise a bandwidth close to the average. The transmission delay experienced by sessions, compared to an optimal transmission operating at the maximum bandwidth requested is a characteristic related performance measurement that is also addressed in this work.

Resource sharing for data services (RSDS)

We present a new flexible resource allocation (FRA) strategy, called resource sharing for data services (RSDS), that dynamically averages the allocated resources to the call requests based on the number of calls in a cell. RSDS accommodates the maximum number of requests while providing acceptable quality to the admitted request through the use of. degradation and compensation techniques. An analytical model (validated by computer simulations) is developed to model RSDS in a scenario with multiple types of service, each of them with different priorities. Preliminary results indicate that the RSDS strategy outperforms some strategies already reported in the literature.

Flexible Resource Allocation Strategy with Differentiated Priorities and QoS

A comprehensive study of flexible resource allocation (FRA) strategies is presented and a new strategy called Flexible Resource Allocation Strategy with Differentiated Priorities and QoS (FRAQoS) is proposed. FRAQoS copes with scenarios where multiple types of service coexist with different priorities and QoS requirement each, offering service integration and differentiation required by 2.5G and 3G systems. Also, a fair comparison of FRAQoS with almost all the previously proposed strategies is performed through the use of an analytical model (validated by computer simulations).