Power-based Admission Control Research Articles

Power-based admission control for multiclass calls in QoS-sensitive CDMA networks

In this letter, we propose a power-based call admission control (CAC) scheme to accommodate multiclass traffic by directly extending the number-based CAC scheme in multicode CDMA networks, and develop some related mathematical properties. Against the conventional findings, we demonstrate that complete partitioning (CP) of the received signal power at a basestation for each traffic class can be an approach as useful as complete sharing (CS) in accommodating an appropriate number of users. The main advantage of CP scheme over CS scheme is its simplicity in resource management

Capacity Gain of Beamforming Techniques in a WCDMA System Under Channelization Code Constraints

This study addresses the performance of a wideband code-division multiple-access mobile communications system with beamforming antenna arrays (AAs) at the base station, synthesizing a grid of beams. In order to fully exploit the capacity gain from beamforming without jeopardizing the stability of the system, a directional power-based admission control (AC) scheme is applied. Due to the higher capacity offered by beamforming techniques, shortage of orthogonal channelization codes in the downlink becomes an increasingly important factor, which may result in blocking of users before the interference power limit is reached. The problem of channelization code shortage is addressed, and a solution based on splitting the cell into several code regions is proposed. For a network with circuit switched data services operated at 64 kb/s, the capacity gain for an eight-element AA is found to equal a factor of 2.5 for a universal mobile telecommunications equivalent system, with one channelization code set per cell. The capacity gain is limited by severe channelization code shortage under these circumstances. This problem is solved by deploying a cell splitting strategy with multiple code regions, which subsequently results in a capacity gain increase to a factor of 3.4. Furthermore, the soft capacity mechanism associated with partial deployment of AAs in a subset of the cells in the network is also addressed. It is demonstrated that a hot spot cell with AAs also helps increase the capacity of the surrounding cells with conventional sector antennas when using a power-based AC strategy.

Application and performance of downlink beamforming techniques in umts

The opportunities and constraints for application of beamforming techniques in UMTS are reviewed and compared by means of extensive dynamic network-level simulations. We start by reviewing the physical layer specifications for UMTS in order to clarify which channels are allowed to use beamforming. Second, radio resource management for cells with beamforming capabilities are addressed from a standardization and algorithmic point of view. The exchange of beamforming specific measurement reports between the base station (Node-B) and the radio network controller is discussed as well as beam switching mechanisms, directional power-based admission control, and more. In addition to implementation of beamforming within logical cells, options for exploiting the antenna array to synthesize independent sector beams are also investigated (i.e., higher order sectorization via beamforming). The presented results show that beamforming within logical cells is an effective enabler for higher system capacity, while the use of beamforming for creation of many logical cells is less attractive due to significantly larger soft handover overhead and somewhat reduced capacity gain.

Directional power-based admission control for WCDMA systems using beamforming antenna array systems

A directional power-based admission control (AC) scheme is proposed for base stations deploying beamforming antenna arrays. The proposed AC algorithm is a natural extension of the conventional power based AC scheme for cells using standard sector antennas. The directional scheme takes the load per beam/direction into account in the AC decision, so the cell load is controlled in accordance with the spatial filtering gain provided by using beamforming antenna arrays. The scheme is tested by means of Monte Carlo simulations in a multicell wideband code division multiple access (WCDMA) network, where users with different bit rates are present. The obtained results demonstrate that the directional power based AC scheme allows a higher traffic load in cells using beamforming antenna arrays without jeopardizing the stability of the network. Application of a four element antenna array is found to provide a capacity gain of a factor 2.7 for a network with many low bit rate users, while the gain is reduced to a factor 2.3 for traffic scenarios with a mixture of high and low bit rate users.