Predictive Channel Reservation Research Articles

Predictive Reservation for Handover Optimization in Two-Tier Heterogeneous Cellular Networks

The mobile network operators seek ways to increase their capacity and coverage in order to be able to deliver high quality services even under surging mobile broadband demand. The deployment of femtocells is the most efficient, economical and technically feasible approach to achieve this goal. However, a two-layered femtocell/macrocell heterogeneous networks where users can handover from a femtocell to the overlaid macrocell requires innovative traffic management techniques. While call handover from a femtocell to a macrocell can be easily implemented based on already known procedures, on the other hand, the handover towards a femtocell is more challenging. More specifically, due to the limited bandwidth available at each femtocell, it is not spectrally efficient to use a typical guard channel scheme in order to prioritize handover calls over new calls. Therefore, in this paper we introduce a dynamic pre-reservation scheme, which is based on the predictive channel reservation concept and adjusts dynamically the reserved resources. We show both analytically and by simulation that the proposed scheme can be efficiently applied to a two-layered femtocell/macrocell heterogeneous mobile network.

Predictive channel reservation for handoff prioritization in wireless cellular networks

In wireless cellular networks , a roaming mobile station (MS) is expected to move from one cell to another. In order to ensure that ongoing calls are not dropped while the owner mobile stations roam among cells, handoff calls may be admitted with a higher priority than newly generated calls. Predictive channel reservation (or pre-reservation) schemes allow the reservation of a channel for an ongoing call in an adjacent cell before its owner MS moves into that cell, so that the call is sustained when the MS moves into the adjacent cell. Pre-reservations are made when the MS is within some distance of the new cell boundary. This distance determines the area in which the MS can make channel reservations. In this paper, we study the effect of the pre-reservation area size on handoff performance in wireless cellular networks. Our studies show that if the reserved channels are strictly mapped to the MSs that made the corresponding reservations, as we increase the pre-reservation area size, the system performance (in terms of the probability that the handoff calls are dropped) improves initially. However, beyond a certain point, the performance begins to degrade due to a large number of false reservations. The optimal pre-reservation area size is closely related to the traffic load of the network and the MSs’ mobility pattern (moving speed). We provide an analytical formulation that furthers understanding with regard to the perceived behavior in one-dimensional networks (in which all cells are along a line). With the objective of improving handoff performance and alleviating this sensitivity to the area size, we propose an adaptive channel pre-reservation scheme. Unlike prior pre-reservation methods, the key idea in our scheme is to send a channel pre-reservation request for a possible handoff call to a neighboring cell not only based on the position and orientation of the owner MS, but also as per its speed towards the target cell. The newly proposed scheme uses GPS measurements to determine when channel pre-reservation requests are to be made. Simulation results show that the adaptive channel pre-reservation scheme performs better in all typical scenarios than a previously proposed popular pre-reservation method that does not take mobility into account.

Special Issue on Voice Over IP—Theory and Practice

Special Issue on Voice Over IP—Theory and Practice

An information theoretic framework for predictive channel reservation in VoIP over GPRS

AbstractThe wireless telecommunication industry is now slowly shifting its paradigm from traditional, circuit‐switched, voice‐alone domain to an integrated packet‐switched architecture. This will give rise to a variety of new applications, in the same infrastructure, in a cost‐efficient way. However, due to the delay and dilemma behind new 3G mobile applications, it is important to use the legacy 2.5G access systems as much as possible, to make the transition smooth. The recent industry‐wide trend towards push‐to‐talk voice services in GPRS networks is a direct consequence of this emerging packet‐switch services. In this paper, we propose a packet‐switched‐based architectural framework for efficient integrated push‐to‐talk voice (or VoIP) and data services in GPRS using low‐bit‐rate coding. The prime novelty and advantage of the framework lies in proposing new intelligent, advanced channel reservation techniques to reduce the voice‐packet delay. Subsequent use of packet‐classification and packet assembly scheme aids in reducing the packet overhead and achieving the voice quality within ITU's recommendations. The mutual effects of data and voice packets over the entire system is analysed using suitable, two‐stage performance modelling. It has also been shown that, for voice over IP (VoIP) services, our proposed framework results in more than 50% capacity gain over current GSM system using a silent‐detection mechanism. Copyright © 2006 John Wiley & Sons, Ltd.

Bandwidth-Reservation Scheme Based on Road Information for Next-Generation Cellular Networks

Channel-reservation techniques have been widely studied in cellular networks in order to meet the desired quality-of-service requirements. In this paper, a distributed predictive channel-reservation scheme, called the road-map-based channel-reservation scheme (RMCR), and a call-admission-control algorithm are proposed. The goal is to reduce the handoff-dropping probability and to improve the bandwidth utilization. In the RMCR scheme, we assume that base stations (BSs) are equipped with road-map information and that mobile stations (MSs) are equipped with global positioning systems (GPS) devices. MSs periodically report their GPS location information to their BSs. Based on the location information of the MSs at two consecutive epochs, the BSs estimate the speed and moving direction of the MSs. Furthermore, the BSs estimate the probability that the MSs will enter the neighboring cells based on their velocity and the road-map information stored in the BSs. The BSs then compute the amount of bandwidth to be reserved, based on such estimation. With the road-map information, the BSs can make a more-accurate prediction on the user's mobility and, hence, reduce unnecessary bandwidth reservation. Simulation results show that RMCR is capable of keeping the handoff-dropping probability low and allocating bandwidth to new/handoff calls efficiently. We also show that RMCR is robust with respect to system parameters such as user's speed, the density of roads, the accuracy of mobility measurement, and so on.

Predictive schemes for handoff prioritization in cellular networks based on mobile positioning

We propose and evaluate new schemes for channel reservation motivated by the rapidly evolving technology of mobile positioning. The schemes, called predictive channel reservation (PCR), work by sending reservation requests to neighboring cells based on extrapolating the motion of mobile stations (MSs). A number of design enhancements are incorporated to minimize the effect of false reservations and to improve the throughput of the cellular system. These enhancements include: (1) reservation pooling; (2) queuing of reservation requests; (3) hybrid approach for integrating guard channels (GCs); and (4) using a threshold distance (TD) to control the timing of reservation requests. The design enhancements have produced a set of highly efficient schemes that achieve significant reduction in handoff blocking rates while only incurring remarkably small increases in the new call blocking rates. The PCR approach has also been used to solve the MINBLOCK optimization problem and has given significant improvement over the fractional guard channel (FGC) protocol. Detailed performance results of the different variations of the PCR scheme and comparisons with conventional channel reservation schemes are presented. An analytical Markov model for the hybrid predictive version of the scheme is developed and its applicability and numerical results are discussed.