Nadeem Akhtar

Impact of HandOver parameters on mobility performance in LTE HetNets

In this paper, we analyze the role of HandOver (HO) parameters in improving the mobility robustness in an Heterogeneous Network (HetNet). First, we illustrate the role of offsets in improving the offload of users from macro cell to small cell, while ensuring that overall HO performance is not adversely impacted. Second, we investigate the impact of Time To Trigger (TTT) on the mobility performance in HetNet. We analyze the performance using the HetNet mobility simulator that we have developed as per the guidelines specified in the Release 12 of the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard.

User-based integrated offloading approach for 3GPP LTE-WLAN network

The increasing use of smartphones and content-rich and data-hungry applications has resulted in significant growth in demand for mobile data services in recent years. To meet this requirement, one of the widely-used approaches is to offload cellular data traffic to Wireless LAN as it operates in unlicensed bands. Offloading decisions are typically based on signal quality. In this paper, we propose an integrated offloading approach which takes both signal quality and network load into consideration. We focus on solutions that do not require significant changes to current network implementations and standards. We investigate the performance of this approach for different scenarios via extensive simulations and observe improved system and user performance in terms of throughput. The evaluation adheres to the methodology laid down by the global standards body 3GPP for such comparisons.

Enhanced Mobility State Estimation in LTE HetNets

In this paper, we investigate issues related to the estimation of users mobility state in the Long Term Evolution (LTE) heterogeneous cellular network. We discuss the need of such estimation and further, we propose an enhancement to the existing Mobility State Estimation (MSE) procedure which results in reduced HandOver failures. We also analyze the role of thresholds in mobility state estimation and their impact on the mobility performance. We analyze the performance using the Heterogeneous Network (HetNet) mobility simulator that we have developed as per the guidelines specified in the Release 12 of the Third Generation Partnership Project (3GPP) LTE standard.

Network based offloading in LTE-WLAN Heterogeneous Networks

To support the tremendously increasing data traffic volume in cellular networks, novel network architectures are getting evolved. Heterogeneous Network (HetNet) architecture is one such approach, where the serving nodes belonging to different Radio Access Technologies (RATs) coexist with the existing macro cell network, as an overlay. To leverage the full capacity of HetNet, efficient traffic handling schemes are required. With this consideration, we study and propose network based traffic offloading scheme and compare their performances on ns-3 simulator, for the Long Term Evolution (LTE) and Wireless Local Area Network (WLAN) RATs scenario in HetNet.

Trajectory based mobility state estimation for heterogeneous cellular networks

Mobility management, in heterogeneous cellular deployments, has become more complex due to the proliferation of small cells, resulting in increased number of cell crossings. In addition, user mobility impacts the HandOver (HO) performance and therefore, mobility state of the user needs to be taken into account in the HO parameter selection. The Mobility State Estimation (MSE) procedure, as specified by the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard, is used to classify UEs in normal, medium and high mobility states, respectively, based on the handover rate. This information is subsequently used to determine the appropriate handover parameters for each UE. In this paper, we propose an enhancement to the MSE procedure which exploits the fact that the trajectory of the mobile user impacts the estimation of mobility state. Our proposed algorithm improves the accuracy of the estimation procedure while ensuring backward compatibility with the legacy MSE procedure. We further improve the mobility performance by combining our algorithm with the enhanced MSE procedure available in the literature, which gives consideration to both successful and failed HO events in the mobility state estimation.

LTE - Wi-Fi coexistence in 5 GHz band

The proliferation of smart phones combined with increasing mobile data demand, cellular network operators around the world are considering various ways to augment network capacity. To meet the projected 1000x increase capacity by 2020 [3], a holistic approach is needed. The proposed solutions include hyper-dense small cell deployment, intelligent utilization of existing spectrum and offloading to other networks like Wi-Fi. Extending the LTE-Advanced (LTE-A) to unlicensed spectrum is a new approach being considered by the global standards body 3GPP, as part of LTE Release-13. The feasibility of LTE operation in 5 GHz band, also known as Licensed Assisted Access (LAA), is being studied. The main challenge is to ensure LTE do not affect the performance of existing technologies/systems in this band such as Wi-Fi, Radar etc. In this paper, we provide simulation study on LTE - Wi-Fi coexistence in the unlicensed spectrum.

Mobility Management in LTE Networks

To provide ubiquitous coverage, it is essential to ensure that cellular users are able to access the service as they move across the network coverage area. While the LTE radio interface is optimized to support low-to-medium mobility scenarios, it can also support very high-speed users. At the same time, the higher layer protocols must also be able to handle UE mobility by finding an appropriate serving cell, which offers the best radio link condition for a moving UE such that the ongoing application sessions are not disturbed and the desired QoS is also maintained.

Enhancements for Mobility State Estimation in LTE HetNet

The heterogeneous cellular deployment improves the spectral efficiency of cellular network due to the dense spectral reuse.

Methodology for 3GPP Modeling

In this chapter, we illustrate 3GPP modeling for the mobility scenarios in heterogeneous networks. This includes the topology model, user mobility model, handover procedure and modeling of radio link failure and ping-pongs. It is followed by a description of the implementation framework of LTE HetNet simulator which is based on 3GPP modeling considerations and is used for the simulation of various mobility aspects in an heterogeneous environment.

Optimization of Mobility-Related Parameters

In this chapter, we analyze the impact of various parameters on handover performance in HetNets. First, we examine the role of handover offsets to improve offloading while ensuring that overall handover performance is not adversely impacted. Second, we investigate the role of thresholds in the mobility state estimation in HetNets.