Reduction of Outage Probability Due to Handover by Mitigating Inter-cell Interference in Long-Term Evolution Networks

Abstract

The burgeoning growth of real-time applications, such as interactive video and VoIP, places a heavy demand for a high data rate and guarantee of QoS from a network. This is being addressed by fourth generation networks such as Long-Term Evolution (LTE). But, the mobility of user equipment that needs to be handed over to a new evolved node base-station (eNB) while maintaining connectivity with high data rates poses a significant challenge that needs to be addressed. Handover (HO) normally takes place at cell borders, which normally suffers high interference. This inter-cell interference (ICI) can affect HO procedures, as well as reduce throughput. In this paper, soft frequency reuse (SFR) and multiple preparations (MP), so-called SFRAMP, are proposed to provide a seamless and fast handover with high throughput by keeping the ICI low. Simulation results using LTE-Sim show that the outage probability and delay are reduced by 24.4% and 11.9%, respectively, over the hard handover method -quite a significant result.Keywords: LTE, outage probability, multiple preparation, soft frequency reuse, radio resource control, inter-cell interference. Manuscript received Sept. 24, 2013; revised Nov. 18, 2013; accepted Nov. 21, 2013 I. IntroductionA fast and seamless handover poses twin challenges for LTE networks to address, especially at high data rates. Hard handover (HHO), where a connection with a previous evolved node base-station (eNB) is severed before being handed over to the next eNB, is only to be considered in LTE networks using handover parameters, such as Layer 3 filtering (L-3), handover margin (HOM), and Time-to-Trigger (TTT) [1]- [2]. HHO suffers from some drawbacks, such as high outage probability, long delays, and unreliable break-before-make procedures [3]. In addition, it is difficult to maintain QoS requirements due to the delay incurred in the HHO during the eNB migration process, which is the process of moving from the serving eNB to the target eNB. Many studies have been conducted to improve HHO, and this issue has been reviewed well in [4]. There are others who have taken a different approach; that is, taking advantage of both soft handover (SHO) and HHO, as seen in [5]-[7]. In [5], the authors proposed a fractional SHO scheme based on carrier aggregation. In this scheme, it combines SHO and HHO depending on traffic. For example, for VoIP it performs an SHO, and for non-VoIP it performs an HHO, both of which are performed with a frequency reuse factor (FRF) of one. The authors in [6] and [7] used macroscopic diversity in an SHO. This resulted in a much better reduction of HO outage probability than that of [5], although none of them employed any type of ICI mitigation mechanism and where all studies used an FRF of one. A more numerical analysis has been presented in [7]. In [8], the authors proposed a bandwidth reservation based on a mobility

Method for transmitting data in heterogeneous network

“…Generally, handover means the change of serving cell to supply incessant service [5]. However, in the proposed method, handover implies that a terminal with specific purpose register to a new cell.…”

An Enhanced Handover Scheme to Provide the Robust and Efficient Inter-Beam Mobility

“…This letter preemptively considers the handover scheme specified in [3], [4] for the IBH, because it is being practically used in the long-term evolution (LTE) systems. This letter calls this IBH scheme as the LTE handover (HO) based IBH scheme.…”

“…In particular, it is possible that the signal quality of the serving beam is seriously deteriorated at the time to perform the IBH. Due to these features of the system, if the handover scheme specified by the 3rd generation partnership project (3GPP) in [3], [4] is applied to the system, the increase of the handover failure rate and the signaling overhead can occur. The details of these problems will be presented in the following section.…”

LTE Mobility Enhancements for Evolution into 5G

“…Various solutions for improving the mobility robustness performance of LTE networks were proposed and discussed in 3GPP [16]- [17]. The "Protect HO command" solution protects HO CMD by using frequency-domain or time-domain interference coordination [18]- [19]. However, it has been proven that non-ideal interference coordination among cells can lead to increased interference, which in turn, results in a mobility performance degradation.…”