LTE Vs UMTS Planning

Transcription

1 LTE Vs UMTS Planning Mohammed Suliman ABD ALrazig Yousif 1 and Dr. Amin Babiker A/Nabi Mustafa 2 Department of Communications, Faculty of Engineering, Al-Neelain University, Khartoum, Sudan 1 ganhdoor@hotmail.com and 2 amin31766@gmail.com Abstract Mobile telecommunications technology is growing fast. The evolution of mobile services is taking place in the world of communications. But with this pace the operators always have Avery hard and sensitive challenges in network planning, because the issue of Network planning is a never ending task, planning network with limited number of user is not only the issue but the issue is to plan a network that also allows future growth, expansion and traffic utilization. The planning ensures the customers to use the network services wherever they are. This is an ongoing process. This paper highlights the process for UMTS and LTE network planning and the most important process of designing UMTS and LTE networks. Keywords: LTE, UMTS, 3GPP. 1. Introduction Planning is one of the most sophisticated problems that achieve very important goals in building mobile networks so in the paper we are trying to isolate between UMTS and LTE planning and explain the difference between the two networks planning strategies. And the main objectives of this paper are: (i) Study UMTS networks. (ii) Study LTE networks. (iii) Find the best plan strategy for each network. (iv) Make a compression between the both networks. Evolution of cellular communication technologies has reached the fourth Generation (4G) technologies. Cellular communication technologies have followed different evolutionary ways. All cellular technologies target performance and efficiency in mobile environment. Universal Mobile Telecommunications System (UMTS) is one of the third generation (3G) mobile telecommunications technologies. Release99 (R99) architecture is the first deployment of the UMTS. R99 architecture is specified by 3GPP (3rd Generation Partnership Project). R99 architecture is part of the global ITU (International Telecommunication Union). UMTS uses WCDMA (Wideband Code Division Multiple Access) for the radio access technique, In WCDMA interface different users can simultaneously transmit at different data rates and data rates can even vary in time. WCDMA increases data transmission rates in GSM systems by using the WCDMA air interface instead of TDMA. WCDMA is based on CDMA. UMTS is providing higher capacity for voice and data and higher data rates from second generation (2G) systems like GSM. LTE (Long Term Evolution) is the next major step in mobile radio communications. And LTE is one of the fourth generation (4G) technologies. It is introduced in 3rd Generation Partnership Project (3GPP) Release 8. The aim of this 3GPP project is to improve the Universal Mobile Telecommunications System (UMTS) mobile phone standard. Frequency Division Multiple Access (OFDMA) and the uplink radio access technique is based on the Single Carrier Frequency Division Multiple Access (SCFDMA). OFDMA and SC-FDMA technology has been incorporated into LTE 44

2 because it enables high data bandwidths to be transmitted efficiently while still providing a high degree of resilience to reflections and interference from UMTS.OFDMA and SC- FDMA works by splitting the radio signal into multiple smaller sub-signals then transmitted simultaneously at different frequencies to the receiver[1]. 2. Methodology 2.1. UMTS Overview and Back Ground The first version of the UMTS standards was finalized by the end of 1990, which is why UMTS is also sometimes referred to as release 99 or R99. The main motivation behind UMTS was to define a universal mobile communication standard that aims at higher peak rates, with the ability of dynamically adapting the user data rates. In addition, there were several other targets like the support of Quality of Service differentiation between the different new services offered by UMTS, as well as improving the overall spectral efficiency. UMTS uses Wideband Code Division Multiple Access (WCDMA) which is a completely new multiple access scheme compared to the one used in GSM. It also uses a larger bandwidth of 5 MHz for each of the downlink and uplink. UMTS is a complete stack of communication protocols designated for 3G global mobile telecommunications. UMTS uses a pair of 5 MHz channels, one in the 1900 MHz range for uplink and one in the 2100 MHz range for downlink. The specific frequency bands originally defined by the UMTS standard are MHz for uplink and MHz for downlink [4] UMTS Network Architecture authenticated entry of the subscriber into the network. This UMTS UE is capable of working in three modes: CS (circuit switched) mode, PS (packet switched) mode and CS/PS mode. In the CS mode the UE is connected only to the core network. In the PS mode, the UE is connected only to the PS domain (though CS services like VoIP (Voice over Internet Protocol) can still be offered), while in the CS/PS mode, the mobile is capable of working simultaneously to offer both CS and PS services [7]. The components of the Radio Access Network (RAN) are the BS or Node B and Radio Network Controllers (RNCs). The major functions of the BS are closed loop power control, physical channel coding, modulation/demodulation, air interface transmissions/reception, error handling, etc., while major functions of the RNC are radio resource control/management, power control, channel allocation, admission control, ciphering, segmentation/reassembly, etc. The main function of the Core Network (CN) is to provide switching, routing and transit for user traffic. The CN also contains the databases and network management functions. The basic CN architecture for UMTS is based on the GSM network with GPRS. All equipment has to be modified for UMTS operation and services. The CN is divided into the CS and PS domains. Circuit switched elements are the Mobile Services Switching Centre (MSC), Visitor Location Register (VLR) and Gateway MSC. Packet switched elements are the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support Node (GGSN). Network elements like EIR, HLR, VLR and AUC are shared by both domains. The Asynchronous Transfer Mode (ATM) is defined for UMTS core transmission. The ATM Adaptation Layer type 2 (AAL2) handles the circuit switched connection and the packet connection protocol AAL5 is designed for data delivery [2]. UMTS network consists of three interacting domains: Core Network (CN), UMTS Terrestrial Radio Access Network (UTRAN) and User Equipment (UE).The UE contains the mobile phone and the SIM (Subscriber Identity Module) card called USIM (Universal SIM). USIM contains member specific data and enables the 45

3 I. Network Design Inputs: The first step in network planning is to gather network inputs and requirements. This involves collecting extensive amount of information like anticipated traffic volume and types, traffic distribution, equipment types and cost, candidate technologies and providers, reliability of the technologies, constraints and limitations, utilization, resources and so on. II. Network Design Process: Fig no [1] 3GPP UMTS all-ip Release 4 Architecture [8] 2.3. UMTS Network Planning Planning Process: This step requires exploring various design techniques and algorithms to create a network topology. It comprises of realizing each network element type, number and location, link and interface types, connectivity, as well as traffic routing. Due to the large number of potential combinations, especially for large size networks, this step cannot be done manually and is usually done by a planning tool. The network design inputs are given to the specific tool and the tool produces a topology for the network in the output.depending on planning tool, extra information like cost of the network can also be part of the output. III. Network Performance Analysis: Also known as optimization, network performance analysis is the last step in planning to evaluate the topology developed in design phase. The evaluation is done based on certain criteria such as cost, reliability, coverage, capacity, etc. The good solution is used as benchmark for further refinements. After a pre-defined number of iterations, the final design is produced. The final design is assumed to be the best solution among several iterations. Because network design involves exploring various alternatives, it is impossible to do it manually or without computer-based planning tools. Fig no [2] Planning Process. The most important three steps in network planning are: Network Planning Techniques Early generations of cellular networks were simple and relatively small in size and it was possible to design them manually. Manual design processes are not efficient and prone to human error. On the other hand, complex and large size networks required huge amount of

4 computations which ultimately oblige cellular operators to look for automatic computer based planning tools. There are two major methods to approach a network design problem. The first approach is simulation and is used whenever the network design problem cannot be expressed in analytical or mathematical form. To do the simulation, a tool is required to build a simplified representation of the network. Then, the behavior of the simulated network is investigated under various inputs and parameters. Simulation sometimes requires a large amount of time and money, but for some cases, it might be the only solution. The alternative approach to the network design problem is expressing the problem in a logical and mathematical way which can be tackled by algorithms. Algorithms are the methods, used for solving a problem within a finite number of steps. The formulation of a mathematical model for the network is the prime task which characterizes the problem by using the inputs, objectives and constraints. Then, an algorithm is employed to solve the problem by performing tremendous amount of calculations to find the solutions. Algorithms are embedded inside the network planning tools. There are many ways to classify algorithm, but in the context of combinatorial optimization, algorithms are classified in exact (complete) and approximate categories. Combinatorial optimization is a method to solve combinatorial problems. The intention is to find a minimum or maximum for a function where the set of feasible solutions is discrete or can be reduced to discrete [7]. 2.5 LTE Overview and Background The second generation mobile networks were originally designed for carrying voice traffic while the data capability was added later. Data usage has increased but the traffic volume in second generation networks is clearly dominated by voice traffic [2]. The introduction of third generation networks with High Speed Downlink 47 Packet Access (HSDPA) has boosted data usage considerably. In short, the introduction of HSDPA has changed mobile networks from voice dominated to packet data dominated networks. Data usage is advanced by a number of bandwidth laptop applications including internet and intranet access, file sharing, streaming services to distribute video content and mobile TV and interactive gaming. In addition, service bundles of video, data and voice are entering the mobile market, also replacing the traditional fixed line voice and broadband data services with mobile services both at home and in the office. A typical voice subscriber uses 300 minutes per month, which is equal to approximately 30 megabyte of data with a voice data rate of 12.2 kbps. A broadband data user can easily consume more than 1000 megabyte (1 gigabyte) of data. Heavy broadband data usage takes more capacity than voice usage, which sets high requirements for the capacity and efficiency of network data. It is expected that by 2015, 5 billion people will be connected to the internet. Broadband internet connections will be available practically anywhere in the world. Already today, the existing wire line installations can reach approximately 1 billion households and the mobile networks connect over 3 billion subscribers. These installations need to evolve into broadband internet access. LTE is the next generation mobile telecommunication technology and it is a project of the Third Generation Partnership Project to improve the UMTS mobile phone standard to cope with future technology evolutions. LTE offers several important benefits for consumers and operators like [3]: Performance and Capacity One of the requirements on LTE is to provide downlink peak rates of at least 100Mbit/s. Simplicity First, LTE supports flexible carrier bandwidths, from below 5MHz up to 20MHz. LTE also

5 supports both FDD and TDD Ten paired and four unpaired spectrum bands have so far been identified by 3GPP for LTE. This means that an operator may introduce LTE in new bands where it is easiest to deploy 10MHz or 20MHz carriers, and eventually deploy LTE in all bands. Second, LTE radio network products will have a number of features that simplify the building and management of next-generation networks. For example, features like plug-and-play, self-configuration and selfoptimization will simplify and reduce the cost of network roll-out and management. Third, LTE will be deployed in parallel with simplified, Ip based core and transport networks that are easier to build, maintain and introduce services on. Wide Range of Terminals In addition to mobile phones, many computer and consumer electronic devices, such as notebooks, ultra-portables, gaming devices and cameras, will incorporate LTE embedded modules. 2.6 Architecture of LTE Network LTE has been designed to support only packet switched services, in contrast to the circuit switched model of previous cellular systems. It aims to provide seamless Internet Protocol (IP) connectivity between User Equipment (UE) and the Packet Data Network (PDN), without any disruption to the end users applications during mobility. Architecture of LTE comprised of Core Network (CN) and Access Network (AN). CN is also known as the Evolved Packet Core (EPC) which comes from System Architecture Evolution (SAE). The (AN) refers to E-UTRAN (Evolved-UTRAN). The (CN) and (AN) together correspond to Evolved Packet System (EPS). EPS connects the users to PDN (Packet Data Network) by IP address in order to access the internet and services like Voice over IP (VoIP). Typically, the EPS bearer is associated with QoS (Quality of Service). Multiple bearers can be established for a user to provide connectivity to different PDNs or QoS streams. The overall network architecture including several EPS network elements is shown in the Figure [3]. Fig [3] EPS Network Elements [9] CN consists of many logical nodes, the (AN) is made up of essentially just one node, the evolved NodeB (enodeb), which connects to the (Ues) LTE Planning A proper LTE planning involves analyzing both network coverage and capacity of the system facing the traffic demand of users. The presence of bigger traffic load limits the system's behavior since radio resources to meet demand are limited. Similarly, a higher level of interference between cells is generated as their load increases. When traffic loads are known, the LTE network simulation can be performed statically obtaining coverage and interference levels throughout the service area. If real data on the traffic load are not available, it is necessary to conduct a capacity study to determine it. Capacity studies can be based on random traffic generators (Monte Carlo); however, such simulations are particularly expensive in computing time and may not faithfully recreate the behavior of the system. Here are the steps in the planning process, highlighting in each of them, and where necessary, the issues to which the user must pay special attention for planning LTE networks [5]: 48

6 Analysis Configuration Cartography: This type of study may require the use of mapping rural, urban or mixed, depending on the service area for the network to plan. When stations are located in rural areas, models of the terrain between 100 and 25 meter resolution are often used. To simulate the effect of multipath losses, and coverage of these stations on urban areas, a layer Cartography with clutter which includes losses associated with each village is often used. If the stations are located within an urban area, it is recommended to use urban cartography for radio planning. A terrain model from 1 to 2 meters is an adequate resolution. In this case, additional losses would not be added to propagation.finally, it is also better to employ multiple layers of altimetry to perform mixed calculations, where the station is located near an urban center and the propagation toward inside that urban center is wished to analyze Calculation Methods Different mobile communications technologies operate in very different frequency bands and require quite particularizations when defining a method of calculation applicable to planning. Here are some concrete proposals for specific environments and technologies: I. Rural Environment Planning in such environments is usually performed using deterministic methods such as ITU-R Rec 526 or Dugout method, only if cartography is available for the network deployment area. In these cases, it is necessary to consider that the simulation results ensure the levels exceeded in 50% of time and locations, so that in order to ensure higher rates will be necessary to use the "Fade Margin", configurable in the parameters of the calculation method [5]. Together with these methods, and if Cartography layers are available, it is customary to introduce additional losses associated with the ground, especially for the effects of multipath in urban environments. In cases where precise cartography of the service area is not available, it is possible to employ empirical methods such as Okumura-Hata, particularized for rural environments. II. Urban Environment Planning in urban areas or mixed (ruralurban) areas can be performed by using empirical methods (Okumura-Hata method is a sufficient approximation of the signal range of a base station in to a radius), or deterministic methods if urban cartography precise enough is available (1 or 2 meter resolution). As deterministic methods you can use methods such as ITU-R 1411, Xia-Bertoni or Okumura-Hata modulated, for propagation simulation in town taking into account the diffraction over the roofs of buildings, and the effects of reflection in buildings. Whether using empirical methods or detailed urban cartography, it is not advisable to use corrections due to land use (clutter), as it would be introducing a redundant correction on estimates of propagation [5]. Quality objectives for these networks impose ensuring minimum coverage for a certain percentage of time and locations. These minimum percentages are translated into a signal margin, regarding the estimated mean value in the simulations, obtained from a statistical distribution that simulates the effects of fading of the received signal by the mobile terminal in a given propagation environment, so, in order to ensure higher rates it will be necessary to use the "Fade Margin" that is configurable in the parameters of the calculation method [5] Parameterization of Stations Stations and sectors: LTE communications networks are typically composed of a distribution of stations in a cellular mesh. Each of the stations may be composed of one or several sectors. In the case of LTE communications it is necessary to specify parameters such as bit rate type, load factor, etc... To establish sensitivity in a dynamic way that characterizes the calculation. 49

7 Network Planning The user must define the criteria to determine the desired sector (best server) at each point. The mobile terminal will be linked to that sector at each point under normal conditions. The usual approach is to work with a criteria of better server by signal, that is, the mobile terminal will be linked to the sector from which would receive a higher signal level. The result is a static coverage area of RSRP signal level. In scenarios with low traffic demand, as for example in rural environments, the result obtained in this stage may be sufficient. Otherwise it will be necessary to conduct a study of interference and network capacity. The LTE interference result consists of a series of global coverage shadows, and some individual reports and graphs for each sector. 3. Results Table number [1] illustrates some of the services and applications that LTE will enable and enrich in the mobile space. Table number [2] illustrates the comparisons between UMTS & LTE from the customer perspective. Table number [3] illustrates specifications comparison between UMTS & LTE network LTE Network Interference In order to obtain an interference calculation, it is necessary to set some specific LTE parameters of the sectors and of the mobile terminal. In case of using static ICIC (inter-cell interference coordination) when stations are being parameterized, it will be necessary to configure each sector with a different static ICIC label. In this way, mitigating the effect of intercell interference is achieved [5]. Fig [4] base station with three sectors [5] This calculation is specially optimized for base stations with three sectors shown in fig [5]. If the base station is composed of a single sector, it is advisable to ensure, as far as possible, that adjacent cells have different labels. Table [1] some of the services and applications that LTE will enable and enrich in the mobile space [10] 50

8 effect. From the Multi-transmitter the user can access to configure this cartography. The distribution of users/terminals is done by defining environments. In each environment, you can configure different types of users/terminals with their respective densities for indoor and outdoor. It s better if the capacity results consists of a report and a detailed graphical of the demand for network resources. Table number [2] illustrates the comparisons between UMTS & LTE from the customer perspective [11] Once the capacity calculation is done, it is advisable obtaining the final SINR coverage area. For doing so, we must perform a second calculation of interference, adjusting the sectors traffic load according to the obtained capacity statistics. Table number [3] comparison between UMTS & LTE [11] 4. Discussion & Conclusion Planning is the most important task to build a mobile network, In this paper we explain in detail what is UMTS and how to plan a UMTS network and what is LTE and how to plan a LTE network with consider some important steps to plan anyone of this networks, the main steps to plan a network is Network Design Inputs, Network Design Process and Network Performance Analysis. For calculations in urban environments it is advisable to use an additional digital elevation model in capacity calculations. Normally the distributions of mobile terminals vary from indoor to outdoor, and it will be necessary to have proper cartography to take into account this 51 References [1] Analysis and Comparison of Radio Access, University of Çukurova, Institute of Natural and Applied Sciences Department of Electrical and Electronics Engineering Echniques for UMTS and LTE Adana, [2] Ajay R. Mishra-Advanced Cellular Network Planning and Optimization 2G 2.5G 3G...Evolution to 4G -Wiley (2007). [3] UMTS Core Packet-Switched Network By Evangelos Vlachogiannis 17/09/2001. [4] Automatic Planning of 3G UMTS All-IP Release 4 Networks with Realistic Tra_c by Mohammad Reza Pasandideh Carleton University January [5] [6] Review on 2G, 3G and 4G Radio Network Planning *Tushar Saxena, **J.S. Jadon *Student, M.Tech., **Associate Professor Amity University, Noida, India [7] Radio Access _etwork Design for the Evolved UMTS _etwork Xinzhi Yan M.Eng [8] [9] [10] A White Paper from the UMTS Forum towards Global Mobile Broadband Standardising the future of mobile communications with LTE (Long Term Evolution). [11] UMTS vs. LTE: a comparison overview Unik4230: Mobile Communications Khai Vuong May 16, 2011.