Efficient Control of Access Strata in LTE

Abstract

The discontinuous reception (DRX) operation is included in LTE to achieve power saving and prolonged battery life of the UE. The DRX runs under the continuous control of AS. An improvement in DRX power saving usually leads to a potential increase in the packet delay. An optimum DRX configuration depends on the current data traffic, which is not easy to estimate accurately, especially, for nonreal-time applications. A particular fashion of variation in the DRX cycle length is proposed, which avoids continuous estimation of the data traffic when only nonreal-time applications are running with no real-time applications active. Since small delay in nonreal-time traffic does not essentially impact the user’s experience adversely, a limited amount of delay is deliberately allowed in the proposal to attain significant improvement in power saving. The proposal also attempts to improve the delay in service resumption after a long inactivity. An analytical model has been established that performs stochastic analysis for both existing and proposed DRX methods. The model derives expressions for mean power consumption during data transfer, during wait period for packet scheduling and during the period of DRX cycles. The average power consumption is computed in a new way considering all three aforementioned power consumptions. Similarly, the model derives expressions for mean packet delay. MATLAB was used to simulate the analytical model with various assumptions in the model parameters. The power consumption and delay performances have been compared between the existing and proposed methods. It was observed that the power consumption significantly reduces in the proposed method while keeping the delay within acceptable limit. It was also observed that the proposed method significantly improves the delay in service resumption after a long inactivity.

The heterogeneous networks (HetNets) are a promising solution in LTE for ubiquitous and cost effective broadband user experience. But there are challenges to support seamless mobility in HetNets, especially when the user speed is high. These challenges have been investigated thoroughly and logical analyses have been performed to overcome them for the improvement of cell edge performance. The study indicates that AS should rigorously control the adaptation of cell switching parameters based on variation in coverage areas of different cells, traffic loads, user speeds, etc. A scheme has been proposed to scale cell switching parameters that incorporates Doppler spread based velocity estimation and adapts smoothly to various changes. The proposed method employs high controllability from AS. MATLAB was used to simulate and model the existing and proposed methods with various assumptions in the model parameters. It was observed that the lowest received power improves significantly and it becomes more stable with the variation in user speed in the proposed method. The improvement in several other KPIs was logically explained. However, the proposed method adds computational load and increases signaling overhead to some extent. The Fractional Frequency Reuse (FFR) is a resource allocation technique that can effectively mitigate interferences in HetNets and it is a promising solution. Various FFR schemes have been suggested to address the challenge of interference in HetNets. The scopes of interference mitigation and capacity improvement have been studied. It is proposed that AS uses a resource allocation scheme that gradually varies frequency resource share with distance from the base station for both large and small cells in order to attain better utilization of the resources. This is performed effectively using three layers in the cell. The proposal also employs high number sectors in a cell, low interference and good frequency reuse. Monte- Carlo simulations have been performed using MATLAB and it was observed that the proposed scheme achieves significantly better throughput compared to the existing schemes. It is expected that if the proposed schemes are used in real LTE deployments, there will be improvements in performances similar with what are reflected in the simulation results. Thus, the materialization of the proposed methods seems warranted.