EVALUATION OF VOICE TRANSMISSION QUALITY IN THE LTE NETWORKS

Background. LTE mobile networks combine packet network technology and radio technology. Parameters of packet and radio subsystems significantly affects the quality of all traffic types transmission, especially telephone traffic, as the most demanding to such parameters of network transmission as delay, jitter and packet loss rate. The recommendations of the International Telecommunication Union and the documents of the partner organization of telecommunications operators (3GPP) contain hypothetical reference models, targets for end-to-end connection quality, and lists the factors that affect the quality (QoS) of VoLTE services. In addition, the network points are shown where you need to measure the quality of telephone traffic and tools for quality assessment. The quality of telephony services is assessed according to the E-model using the method of determining the mean opinion score (MOS). However, this technique is intended primarily to determine the MOS during the network planning. To calculate the MOS in a working network, you have to measure such network performance first such as voice delay and packet loss rate. This article presents the method of calculating MOS in the LTE network based on the E-model and presents the results of practical quality studies. Objective. The purpose of this article is research the impact of delay and packet loss ratio and voice codec characteristics in the real LTE network on quality of telephone services. Methods. Analysis of factors affecting on telephone services quality and analysis MOS assessment methods. Practical studies of the delay and packet loss ratio affect the MOS level in various conditions of radio coverage and network load. Results. Practical results of delay and packet loss ratio influence on the telephone services quality in the LTE network. Calculated MOS based on the practically measured delay and packet loss ratio. Conclusions. The combination of packet technologies, modern AMR-WB codecs and QoS support mechanisms in the LTE networks provides high quality perception of voice messages at the level of not less than 4 on the MOS scale. With a delay not exceeding 180 ms, a sufficiently high quality of voice transmission is ensured (MOS ≈ 4). VoLTE technology using the AMR-WB codec is quite resistant to packet loss and provides high quality perception of voice messages at a packet loss ratio of up to 1%.

Cost Analysis of Deploying Femtocells in Speed Trains in Nigeria to Improve Indoor Coverage and Capacity of LTE Network

The cost analysis of deployment of femtocells in speed trains along Abuja-Kaduna standard gauge railway line to improve the coverage and capacity of Long Term Evolution (LTE) network for 5000 commuters using that route daily is presented in this paper. Additional cost will include the cost of femtocells procurement, license, installation, backhaul, operation & maintenance. The cost analysis is carried out using techno-economic model to determine the business viability of embarking on such a project by LTE network providers in Nigeria. The estimated capital expenditure (CAPEX) and operating expenditure (OPEX) as well as the projected revenues accrues from this project form the cash outflows and cash inflows are used to simulate the net present value (NPV) and internal rate of return (IRR) in MS Excel environment on a discount rate and tax rate of 22%, and 30%, respectively to determine the feasibility of the investment. The results of their NPV values which are positive show that the macro-femtocell arrangement in speed train plying Abuja-Kaduna railway route is cost effective for a life time of 10 years and is feasible up to an IRR 53% which exceeds the estimated discount rate of 22%. The value of the payback period indicates that it will not take long for any LTE network provider in Nigeria to recover their investment. The result of the NPV sensitivity analysis shows how various cost and non-cost parameters affect the cost-effectiveness of such investment.

The Optimization of PCI Interference in the 4G LTE Network in Padang

With the growth of the customers and the expansion of the 4G LTE network in the area of Padang City, a PCI (Physical cell identity) modulo interference spot has been detected. PCI modulo interference occurs when an area is covered by two or more cells, which have a strong signal, and these cells have the same PCI modulo value. Based on the measurement results by the driving test method, the network conditions were not optimal because the SINR percentage (Signal to Interference Noise Ratio) in the good category was still low, at 9.47%, and the download throughput in the good category was 18.94%. This indicated that the interference in the area was quite high. Thus, it was necessary to do optimization action. The optimization action was taken by rotating the PCI on the site by considering the modulo value of each site so that the PCI with the same modulo did not merely lead to one location. Besides, action was taken to change the azimuth direction of cells that were too dominant. Based on the optimization process that has been carried out and the driving test activities that have been carried out again, the performance in the existing conditions has increased. The SINR percentage in the good category increased by 10%, so it became 19.47%, and the download throughput in the good category increased by 44.74% and became 63.68%.