A Power Control Algorithm (PCA) and Software Tool for Femtocells in LTE-A Networks

Sakarya University Journal of Science, 22(4): 1124-1129, 2018. SAKARYA UNIVERSITY JOURNAL OF SCIENCE e-ISSN: 2147-835X http://www.saujs.sakarya.edu.tr Received 31.12.2017 Revised 02.07.2018 Accepted 21.02.2018 DOI 10.16984/saufenbilder.373293 A Power Control Algorithm and Software Tool for Femtocells in LTE-A Network Sajjad Ahmad Khan*1 , Muhammad Asshad1, Kerem Küçük1, Adnan Kavak1 ABSTRACT The heterogeneous networks (HetNets) emerge as one of the most auspicious improvements toward realizing the objective specifications of Long Term Evolution-Advanced (LTE-A) networks. Though similar to all other wireless networks, HetNet also yields from the interference problems, i.e., the co-tier and cross-tier interferences. Regarding functionality and efficiency of the HetNets, the avoidance and management of these interferences are very crucial. In this study, a power control algorithm (PCA) is suggested to decrease the interferences disadvantages in the HetNets. To calculate the signal power, the SINR (Signal to Interference and Noise Ratio) and RSRP (Reference Signal Received Power) are used for downlink and uplink, respectively. The selection decision is taken by signal strength information. The UE (User Equipment) is switched accordingly. A simulation tool is developed and used to investigate and find out the nearest cell to UE in a HetNet. Keywords: LTE-A, HetNets, HeNB, user equipment, RSRP, SINR 1. INTRODUCTION Due to the sheer growth of mobile broadband subscription, the demand for high data rate increased. According to Ericsson mobility report [1], until 2021 the number of mobile broadband subscriptions will reach to 9 billion, where 7.7 billion will use the mobile data. Furthermore, the growth of smartphone data and video traffics will be multiplied 20 and 25 times respectively. The Cisco calculated that the mobile data is reached up to 11.2 Exabyte per month by 2017 and 49 Exabyte per month is expected till 2021 [2]. 3GPP (3rd Generation Partnership Project) proposed LTE-A (Long Term EvolutionAdvanced) in 2010 to achieve the demanded high data rates. LTE-A is a promising technology which provides 300 Mbps downloading and 150 Mbps uploading data speeds with spectral efficiency [3]. The present LTE-A system is based on homogeneous network, where every single evolved Node B (eNB) cover the whole cell and use same transmission power levels, modulation techniques, access schemes, antenna patterns to offer QoS to the UEs (User Equipment) across the cell [4, 5]. On the contrary, such deployment reduces the coverage and capacity of the cell-edge users. The primary approach to solving the problem mentioned above is to shrink the cells, which will satisfy the increasing demand for high data rates in cellular systems and recover the signal to interference and noise ratio (SINR), but this approach is not economical and needs massive investments [6]. Therefore, the deployment of a heterogeneous network (HetNet) is more scalable * Corresponding Author Department of Computer Engineering, Kocaeli University, 41380 Kocaeli, Turkey - , muhammad.asshad@ kocaeli.edu.tr, , 1 © 2017 Sakarya Üniversitesi Fen Bilimleri Enstitüsü http://www.saujs.sakarya.edu.tr 1124 A power control algorithm (PCA) and software tool for femtocells in lte-a networks Additionally, the co-tier interferences are generated by nearby femtocells [13]. In this paper, a novel approach is proposed to reduce the interferences created by neighbor eNBs and HeNBs. Different equations are used to calculate and measure the received power of the reference signal and SINR values. The paper is organized as follows. In Section II, we formulate the mathematical model and analysis. Section III presents the design of the proposed system. Simulation setup is explained in Section IV. Section V described the simulation results and Section VI is the conclusion section. Sakarya University Journal of Science, 22(4): 1124-1129, 2018. 2. SYSTEM MODEL AND ANALYSIS 2.1. OFDMA and SC-FDMA The entire LTE-A network is IP-based, and the Internet Protocol (IP) is capable of transferring voice, video and data traffic reliably and securely. The core principle behind using IP is, it dynamically assign the address when mobile is switch on and release when it is switched off. Moreover, the LTE-A uses Orthogonal Frequency Division Multiple Access (OFDMA) as an access method and Orthogonal Frequency-Division Multiplexing (OFDM) as a digital modulation scheme. To achieve high data rates, the subcarriers are shared by many users in OFDMA [14], but because of the complex processing, OFDMA needs more power to calculate. That is why Single Carrier- Frequency Division Multiple Access (SCFDMA) is used on the UE side because of less complexity [15]. The SC-FDMA uses single subcarrier used for each UE. 2.2. Measurement Scales The analysis of Radio Frequency (RF) value is essential in wireless broadcasting and communications system because these values indicate the condition and performance of the systems. There are some ranges of RF values, which have to be considered while measuring the performance of the system. Table I depicts a useful classification of RF status vs. LTE key performance indicators (KPIs). The EUTRAN vendor compiled the data in this chart during RF turning process and distributed among all the major LTE-A operators [16]. There might be several other tables exist, but the results are almost similar in large extent. All LTE-A significant vendors use the following quantities for RF signal measurements.  SINR (Signal to Interference and Noise Ratio)  RSRP (Reference Signal Received Power)  RSRQ (Reference Signal Received Quality) Table 1. Classification of RF status vs. LTE KPIs Condition SINR (dB) RSRQ (dB) RSPR (dBm) RF Condition and useful for both operators as well as users. It is expected, that this approach will improve the system broadband and rise the coverage and capacity of the cell cost-effectively [3]. The 3GPP LTE-A macrocells also known as eNBs are expensive and challenging to deploy everywhere. While on the other hand, 90% data services and 2/3 calls are expected to be inside of the building, and the indoor users complain of poor coverage because of the walls and others obstacles weak the strength of signals. Thus, the short-range femtocells are being deployed to extend the coverage for indoor, i.e., offices, shopping malls, and homes, etc. subscribers [7], [8]. The femtocell is also known as HeNBs (Home Evolved Node B), and the typical radius of a femtocell coverage area is around 30 m and the transmit power of a femtocell is usually less than 0.1 W (≤ 20dBm) [9]. These femtocells are connected to Evolved Packet Core (EPC) with Asynchronous Digital Subscribers Line (ADSL) link. This type of architecture is usually called the HetNet [10, 11]. The HeNBs are connected with the HeNB Gateway, and then HeNB Gateway is linked with EPC of the core system [12]. The eNBs are directly connected with each other thr (...truncated)