f231e37d214313a3034041220c5b12605e3d.rar_cell_ns3 sim

<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8"> <meta name="generator" content="pdf2htmlEX"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <link rel="stylesheet" href="https://static.pudn.com/base/css/base.min.css"> <link rel="stylesheet" href="https://static.pudn.com/base/css/fancy.min.css"> <link rel="stylesheet" href="https://static.pudn.com/prod/directory_preview_static/624f4e1c74bc5c01052fdc9e/raw.css"> <script src="https://static.pudn.com/base/js/compatibility.min.js"></script> <script src="https://static.pudn.com/base/js/pdf2htmlEX.min.js"></script> <script> try{ pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({}); }catch(e){} </script> <title></title> </head> <body> <div id="sidebar" style="display: none"> <div id="outline"> </div> </div> <div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/624f4e1c74bc5c01052fdc9e/bg1.jpg"><div class="t m0 x1 h2 y1 ff1 fs0 fc0 sc0 ls0 ws0">An LTE module for the ns-3 network simulator</div><div class="t m0 x2 h3 y2 ff2 fs1 fc0 sc0 ls0 ws0">Giuseppe Piro</div><div class="t m0 x3 h4 y3 ff2 fs2 fc0 sc0 ls0 ws0">DEE - Politecnico di Bari, Bari, Italy</div><div class="t m0 x4 h3 y4 ff2 fs1 fc0 sc0 ls0 ws0">g.piro@poliba.it</div><div class="t m0 x5 h3 y2 ff2 fs1 fc0 sc0 ls0 ws0">Nicola Baldo, Marco Miozzo</div><div class="t m0 x6 h4 y3 ff2 fs2 fc0 sc0 ls0 ws0">Centre Tecnològic de Telecomunicacions de</div><div class="t m0 x7 h4 y5 ff2 fs2 fc0 sc0 ls0 ws0">Catalunya, Barcelona, Spain</div><div class="t m0 x8 h3 y6 ff2 fs1 fc0 sc0 ls0 ws0">{nbaldo,mmiozzo}@cttc.es</div><div class="t m0 x9 h5 y7 ff3 fs1 fc0 sc0 ls0 ws0">ABSTRACT</div><div class="t m0 x9 h6 y8 ff4 fs3 fc0 sc0 ls0 ws0">In this paper, we present a novel module developed for the</div><div class="t m0 x9 h6 y9 ff4 fs3 fc0 sc0 ls0 ws0">simulation of the LTE technology with the ns-3 simulator.</div><div class="t m0 x9 h6 ya ff4 fs3 fc0 sc0 ls0 ws0">It focuses mainly on modeling the E-UTRA part of the sys-</div><div class="t m0 x9 h6 yb ff4 fs3 fc0 sc0 ls0 ws0">tem, with a particular attention on the aspects related to the</div><div class="t m0 x9 h6 yc ff4 fs3 fc0 sc0 ls0 ws0">channel, PHY and MAC layers. First we discuss the overall</div><div class="t m0 x9 h6 yd ff4 fs3 fc0 sc0 ls0 ws0">modeling assumptions according to which the module was</div><div class="t m0 x9 h6 ye ff4 fs3 fc0 sc0 ls0 ws0">designed. Subsequently, we describe in detail the architec-</div><div class="t m0 x9 h6 yf ff4 fs3 fc0 sc0 ls0 ws0">ture of the module and its components. Finally, we show</div><div class="t m0 x9 h6 y10 ff4 fs3 fc0 sc0 ls0 ws0">possible research applications by discussing some example</div><div class="t m0 x9 h6 y11 ff4 fs3 fc0 sc0 ls0 ws0">simulation scenarios.</div><div class="t m0 x9 h5 y12 ff3 fs1 fc0 sc0 ls0 ws0">Categories and Subject Descriptors</div><div class="t m0 x9 h6 y13 ff4 fs3 fc0 sc0 ls0 ws0">I.6.5 [Simulation and Modeling]: Model Development—</div><div class="t m0 x9 h6 y14 ff6 fs3 fc0 sc0 ls0 ws0">Modeling methodologies; I.6.7 [Simulation and Model-</div><div class="t m0 x9 h6 y15 ff5 fs3 fc0 sc0 ls0 ws0">ing]: Simulation Support Systems—Environments</div><div class="t m0 x9 h5 y16 ff3 fs1 fc0 sc0 ls0 ws0">General Terms</div><div class="t m0 x9 h6 y17 ff4 fs3 fc0 sc0 ls0 ws0">Algorithm, Design, Performance, Veriﬁcation</div><div class="t m0 x9 h5 y18 ff3 fs1 fc0 sc0 ls0 ws0">Keywords</div><div class="t m0 x9 h6 y19 ff4 fs3 fc0 sc0 ls0 ws0">3GPP, LTE, E-UTRA, Simulator, ns-3, Channel, MAC, PHY</div><div class="t m0 x9 h5 y1a ff3 fs1 fc0 sc0 ls0 ws0">1. INTRODUCTION</div><div class="t m0 x9 h6 y1b ff4 fs3 fc0 sc0 ls0 ws0">In the last years the 3rd Generation Partnership Project</div><div class="t m0 x9 h6 y1c ff4 fs3 fc0 sc0 ls0 ws0">(3GPP) has been working on the deﬁnition of a new mo-</div><div class="t m0 x9 h6 y1d ff4 fs3 fc0 sc0 ls0 ws0">bile communication technology called Long Term Evolution</div><div class="t m0 x9 h6 y1e ff4 fs3 fc0 sc0 ls0 ws0">(LTE), which candidates as a signiﬁcant improvement with</div><div class="t m0 x9 h6 y1f ff4 fs3 fc0 sc0 ls0 ws0">respect to the currently widely-deployed Universal Mobile</div><div class="t m0 x9 h6 y20 ff4 fs3 fc0 sc0 ls0 ws0">Telecommunications System (UMTS) and High-Speed Packet</div><div class="t m0 x9 h6 y21 ff4 fs3 fc0 sc0 ls0 ws0">Access (HSPA) systems.</div><div class="t m0 x9 h6 y22 ff4 fs3 fc0 sc0 ls0 ws0">Thanks to features like enhanced data rates and lower power</div><div class="t m0 x9 h6 y23 ff4 fs3 fc0 sc0 ls0 ws0">consumption, LTE represents an emerging and promising</div><div class="t m0 x9 h6 y24 ff4 fs3 fc0 sc0 ls0 ws0">technology for providing a broadband ubiquitous Internet</div><div class="t m0 x9 h6 y25 ff4 fs3 fc0 sc0 ls0 ws0">access. For this reason, the research community is putting</div><div class="t m0 x9 h6 y26 ff4 fs3 fc0 sc0 ls0 ws0">a considerable eﬀort on studying LTE for designing newer</div><div class="t m0 x9 h6 y27 ff4 fs3 fc0 sc0 ls0 ws0">and innovative solutions that can maximize its performance,</div><div class="t m0 xa h6 y7 ff4 fs3 fc0 sc0 ls0 ws0">both from a Radio Access Network (RAN) perspective and</div><div class="t m0 xa h6 y28 ff4 fs3 fc0 sc0 ls0 ws0">from the point of view of the Core Network. For instance,</div><div class="t m0 xa h6 y29 ff4 fs3 fc0 sc0 ls0 ws0">in order to improve the spectral eﬃciency, the Orthogonal</div><div class="t m0 xa h6 y2a ff4 fs3 fc0 sc0 ls0 ws0">Frequency Division Multiple Access (OFDMA) technique is</div><div class="t m0 xa h6 y2b ff4 fs3 fc0 sc0 ls0 ws0">introduced, together with Multiple-Input Multiple-Output</div><div class="t m0 xa h6 y2c ff4 fs3 fc0 sc0 ls0 ws0">(MIMO) schemes. At the same time, LTE completes the</div><div class="t m0 xa h6 y2d ff4 fs3 fc0 sc0 ls0 ws0">transition from Circuit Switched core network solutions (still</div><div class="t m0 xa h6 y2e ff4 fs3 fc0 sc0 ls0 ws0">heavily relied upon in 3G) to an all-IP architecture, which</div><div class="t m0 xa h6 y2f ff4 fs3 fc0 sc0 ls0 ws0">had been long regarded as a much desireable feature, both</div><div class="t m0 xa h6 y30 ff4 fs3 fc0 sc0 ls0 ws0">for the increasing usage of data services by mobile users, and</div><div class="t m0 xa h6 y31 ff4 fs3 fc0 sc0 ls0 ws0">for the higher ﬂexibility and potential lower cost of the Core</div><div class="t m0 xa h6 y32 ff4 fs3 fc0 sc0 ls0 ws0">Network equipment.</div><div class="t m0 xa h6 y33 ff4 fs3 fc0 sc0 ls0 ws0">As the interest in LTE as a mobile communication technol-</div><div class="t m0 xa h6 y34 ff4 fs3 fc0 sc0 ls0 ws0">ogy increases, there is a growing need for instruments able</div><div class="t m0 xa h6 y35 ff4 fs3 fc0 sc0 ls0 ws0">to characterize the performance of LTE systems in order</div><div class="t m0 xa h6 y36 ff4 fs3 fc0 sc0 ls0 ws0">to tune and optimize them. This need is present at vari-</div><div class="t m0 xa h6 y37 ff4 fs3 fc0 sc0 ls0 ws0">ous stages: for the standardization of future version of the</div><div class="t m0 xa h6 y38 ff4 fs3 fc0 sc0 ls0 ws0">technology, as well as for the design and implementation of</div><div class="t m0 xa h6 y39 ff4 fs3 fc0 sc0 ls0 ws0">devices and network equipments and the roll-out of LTE net-</div><div class="t m0 xa h6 y3a ff4 fs3 fc0 sc0 ls0 ws0">work infrastructures. LTE is a rather complex technology,</div><div class="t m0 xa h6 y3b ff4 fs3 fc0 sc0 ls0 ws0">and for this reason traditional performance evaluation meth-</div><div class="t m0 xa h6 y3c ff4 fs3 fc0 sc0 ls0 ws0">ods based on analytical models can be applied only to very</div><div class="t m0 xa h6 y3d ff4 fs3 fc0 sc0 ls0 ws0">small portions of it. As a consequences, researchers and engi-</div><div class="t m0 xa h6 y3e ff4 fs3 fc0 sc0 ls0 ws0">neers most often rely on simulators to assess the performance</div><div class="t m0 xa h6 y3f ff4 fs3 fc0 sc0 ls0 ws0">of LTE systems. In particular, open source network simula-</div><div class="t m0 xa h6 y40 ff4 fs3 fc0 sc0 ls0 ws0">tion to ols are highly valued by researchers, because of their</div><div class="t m0 xa h6 y41 ff4 fs3 fc0 sc0 ls0 ws0">usually wider acceptance within the research community. In</div><div class="t m0 xa h6 y42 ff4 fs3 fc0 sc0 ls0 ws0">the literature, several LTE simulators have been proposed</div><div class="t m0 xa h6 y43 ff4 fs3 fc0 sc0 ls0 ws0">for diﬀerent purposes. Physical layer simulation tools such</div><div class="t m0 xa h6 y44 ff4 fs3 fc0 sc0 ls0 ws0">as [10] and [18] are quite limited in that they consider the</div><div class="t m0 xa h6 y45 ff4 fs3 fc0 sc0 ls0 ws0">performance at the physical layer only, normally focusing</div><div class="t m0 xa h6 y46 ff4 fs3 fc0 sc0 ls0 ws0">on a single transmitter-receiver pair. System level simula-</div><div class="t m0 xa h6 y47 ff4 fs3 fc0 sc0 ls0 ws0">tors, such as for instance [14] and [13], go beyond the phys-</div><div class="t m0 xa h6 y48 ff4 fs3 fc0 sc0 ls0 ws0">ical layer by normally introducing the MAC layer together</div><div class="t m0 xa h6 y49 ff4 fs3 fc0 sc0 ls0 ws0">with an abstract model of the higher layers. They are usu-</div><div class="t m0 xa h6 y4a ff4 fs3 fc0 sc0 ls0 ws0">ally adopted in the research community for the evaluation of</div><div class="t m0 xa h6 y4b ff4 fs3 fc0 sc0 ls0 ws0">Radio Resource Management (RRM) algorithms, but due to</div><div class="t m0 xa h6 y4c ff4 fs3 fc0 sc0 ls0 ws0">their abstraction of the higher layers they cannot provide an</div><div class="t m0 xa h6 y4d ff4 fs3 fc0 sc0 ls0 ws0">accurate evaluation of the end-to-end performance and of the</div><div class="t m0 xa h6 y4e ff4 fs3 fc0 sc0 ls0 ws0">behavior of the network as a whole. The most promising so-</div><div class="t m0 xa h6 y4f ff4 fs3 fc0 sc0 ls0 ws0">lution to this problem is represented by network simulators,</div><div class="t m0 xa h6 y50 ff4 fs3 fc0 sc0 ls0 ws0">which feature an accurate implementation of all the protocol</div><div class="t m0 xa h6 y51 ff4 fs3 fc0 sc0 ls0 ws0">layers from the MAC up to the application. A ﬁrst step in</div><div class="t m0 xa h6 y52 ff4 fs3 fc0 sc0 ls0 ws0">this direction is done with [20], which is an open source LTE</div><div class="t m0 xa h6 y53 ff4 fs3 fc0 sc0 ls0 ws0">network simulator that supports single and multi-cell envi-</div><div class="t m0 xa h6 y54 ff4 fs3 fc0 sc0 ls0 ws0">ronments, QoS management, multi users environment, user</div><div class="t m0 xa h6 y55 ff4 fs3 fc0 sc0 ls0 ws0">mobility, handover procedures, scheduling, and frequency</div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div> </body> </html>

<div id="pf2" class="pf w0 h0" data-page-no="2"><div class="pc pc2 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/624f4e1c74bc5c01052fdc9e/bg2.jpg"><div class="t m0 x9 h6 y56 ff4 fs3 fc0 sc0 ls0 ws0">reuse techniques. Unfortunately, since this simulator aims</div><div class="t m0 x9 h6 y57 ff4 fs3 fc0 sc0 ls0 ws0">at supporting LTE only, it lacks the many features of general</div><div class="t m0 x9 h6 y58 ff4 fs3 fc0 sc0 ls0 ws0">purpose network simulator like ns-3, for example the avail-</div><div class="t m0 x9 h6 y59 ff4 fs3 fc0 sc0 ls0 ws0">ability of a full-ﬂedged TCP/IP protocol stack, the support</div><div class="t m0 x9 h6 y5a ff4 fs3 fc0 sc0 ls0 ws0">for other wireless technologies such as WiFi and WiMAX,</div><div class="t m0 x9 h6 y5b ff4 fs3 fc0 sc0 ls0 ws0">the possibility of integration with testbeds and real applica-</div><div class="t m0 x9 h6 y5c ff4 fs3 fc0 sc0 ls0 ws0">tion binaries, etc. The simulation module that we describe</div><div class="t m0 x9 h6 y5d ff4 fs3 fc0 sc0 ls0 ws0">in this paper was explicitly designed in order to ﬁll this gap.</div><div class="t m0 x9 h6 y5e ff4 fs3 fc0 sc0 ls0 ws0">It introduces support for the simulation of the LTE tech-</div><div class="t m0 x9 h6 y5f ff4 fs3 fc0 sc0 ls0 ws0">nology in the ns-3 simulator, with a particular attention on</div><div class="t m0 x9 h6 y60 ff4 fs3 fc0 sc0 ls0 ws0">modeling the most relevant aspects of the Evolved Univer-</div><div class="t m0 x9 h6 y61 ff4 fs3 fc0 sc0 ls0 ws0">sal Terrestrial Radio Access (E-UTRA), which is the radio</div><div class="t m0 x9 h6 y62 ff4 fs3 fc0 sc0 ls0 ws0">interface of LTE [2].</div><div class="t m0 x9 h5 y63 ff3 fs1 fc0 sc0 ls0 ws0">2. THE LTE MODULE FOR NS-3</div><div class="t m0 x9 h6 y64 ff4 fs3 fc0 sc0 ls0 ws0">The development of the LTE module for ns-3 has been car-</div><div class="t m0 x9 h6 y65 ff4 fs3 fc0 sc0 ls0 ws0">ried out during the Google Summer of Code 2010 . This</div><div class="t m0 x9 h6 y66 ff4 fs3 fc0 sc0 ls0 ws0">module provides a basic implementation of LTE devices, in-</div><div class="t m0 x9 h6 y67 ff4 fs3 fc0 sc0 ls0 ws0">cluding propagation models and PHY and MAC layers. Due</div><div class="t m0 x9 h6 y68 ff4 fs3 fc0 sc0 ls0 ws0">to the intrinsic complexity of the LTE standard and the lim-</div><div class="t m0 x9 h6 y69 ff4 fs3 fc0 sc0 ls0 ws0">ited time of the GSoC framework, at the time of this writing</div><div class="t m0 x9 h6 y6a ff4 fs3 fc0 sc0 ls0 ws0">it is not yet possible simulate a complete LTE network. How-</div><div class="t m0 x9 h6 y6b ff4 fs3 fc0 sc0 ls0 ws0">ever, the proposed module already allows the simulation of</div><div class="t m0 x9 h6 y6c ff4 fs3 fc0 sc0 ls0 ws0">several important aspects of LTE systems, such as for ex-</div><div class="t m0 x9 h6 y6d ff4 fs3 fc0 sc0 ls0 ws0">ample downlink RRM and MAC scheduling and, moreover,</div><div class="t m0 x9 h6 y6e ff4 fs3 fc0 sc0 ls0 ws0">it provides a very good basis for further extensions as well</div><div class="t m0 x9 h6 y6f ff4 fs3 fc0 sc0 ls0 ws0">as the development of a complete tool in the future.</div><div class="t m0 x9 h6 y70 ff4 fs3 fc0 sc0 ls0 ws0">In summary, the most important features provided by the</div><div class="t m0 x9 h6 y71 ff4 fs3 fc0 sc0 ls0 ws0">proposed module are (i) a basic implementation of both the</div><div class="t m0 x9 h6 y72 ff4 fs3 fc0 sc0 ls0 ws0">User Equipment (UE) and the enhanced NodeB (eNB) de-</div><div class="t m0 x9 h6 y73 ff4 fs3 fc0 sc0 ls0 ws0">vices, (ii) RRC entities for both the UE and the eNB, (iii)</div><div class="t m0 x9 h6 y74 ff4 fs3 fc0 sc0 ls0 ws0">a state-of-the-art Adaptive Modulation and Coding (AMC)</div><div class="t m0 x9 h6 y75 ff4 fs3 fc0 sc0 ls0 ws0">scheme for the downlink [9], (iv) the management of the</div><div class="t m0 x9 h6 y76 ff4 fs3 fc0 sc0 ls0 ws0">data radio bearers (with their QoS parameters), the MAC</div><div class="t m0 x9 h6 y77 ff4 fs3 fc0 sc0 ls0 ws0">queues and the RLC instances, (v) Channel Quality Indi-</div><div class="t m0 x9 h6 y78 ff4 fs3 fc0 sc0 ls0 ws0">cator (CQI) management, (vi) supp ort for both uplink and</div><div class="t m0 x9 h6 y79 ff4 fs3 fc0 sc0 ls0 ws0">downlik packet scheduling, (vii) a PHY layer model with</div><div class="t m0 x9 h6 y7a ff4 fs3 fc0 sc0 ls0 ws0">Resource Block level granularity and (viii) a channel mo del</div><div class="t m0 x9 h6 y7b ff4 fs3 fc0 sc0 ls0 ws0">with the outdoor E-UTRAN propagation loss model.</div><div class="t m0 x9 h6 y7c ff4 fs3 fc0 sc0 ls0 ws0">The module is built completely in C++ and, at the time of</div><div class="t m0 x9 h6 y7d ff4 fs3 fc0 sc0 ls0 ws0">this writing, comprises 89 classes and approximately 9000</div><div class="t m0 x9 h6 y7e ff4 fs3 fc0 sc0 ls0 ws0">lines of code. Figure 1 shows the UML diagram of the most</div><div class="t m0 x9 h6 y7f ff4 fs3 fc0 sc0 ls0 ws0">important classes that compose the module. It is important</div><div class="t m0 x9 h6 y80 ff4 fs3 fc0 sc0 ls0 ws0">to remark that the diagram only reports the most impor-</div><div class="t m0 x9 h6 y81 ff4 fs3 fc0 sc0 ls0 ws0">tant data members and functions. Some details about the</div><div class="t m0 x9 h6 y82 ff4 fs3 fc0 sc0 ls0 ws0">relationship among classes have been omitted due to space</div><div class="t m0 x9 h6 y83 ff4 fs3 fc0 sc0 ls0 ws0">limitations.</div><div class="t m0 x9 h5 y84 ff3 fs1 fc0 sc0 ls0 ws0">2.1 LTE PHY and E-UTRAN channel models</div><div class="t m0 x9 h6 y85 ff4 fs3 fc0 sc0 ls0 ws0">It is our opinion that the most interesting and immediate use</div><div class="t m0 x9 h6 y86 ff4 fs3 fc0 sc0 ls0 ws0">case for an LTE Network Simulator is to aid in the design</div><div class="t m0 x9 h6 y87 ff4 fs3 fc0 sc0 ls0 ws0">and evaluation of RRM solutions. RRM in LTE is char-</div><div class="t m0 x9 h6 y88 ff4 fs3 fc0 sc0 ls0 ws0">acterized by a high ﬂexibility: thanks to the OFDMA and</div><div class="t m0 x9 h6 y89 ff4 fs3 fc0 sc0 ls0 ws0">SC-FDMA access technologies, diﬀerent radio resources in</div><div class="t m0 x9 h6 y8a ff4 fs3 fc0 sc0 ls0 ws0">the time and frequency domain can be dynamically assigned</div><div class="t m0 x9 h6 y8b ff4 fs3 fc0 sc0 ls0 ws0">to diﬀerent users. The reason behind this design choice is</div><div class="t m0 x9 h6 y8c ff4 fs3 fc0 sc0 ls0 ws0">to allow the RRM process to opportunistically exploit the</div><div class="t m0 x9 h6 y8d ff4 fs3 fc0 sc0 ls0 ws0">variations of the channel conditions that happen both in</div><div class="t m0 x9 h6 y8e ff4 fs3 fc0 sc0 ls0 ws0">time and frequency. For example, due to frequency selective</div><div class="t m0 x9 h6 y8f ff4 fs3 fc0 sc0 ls0 ws0">fading it can happen that at a certain time slots a particu-</div><div class="t m0 x9 h6 y90 ff4 fs3 fc0 sc0 ls0 ws0">lar set of subcarriers is not suitable for communication with</div><div class="t m0 xa h6 y56 ff4 fs3 fc0 sc0 ls0 ws0">certain mobile users; then, by opportunistically assigning</div><div class="t m0 xa h6 y57 ff4 fs3 fc0 sc0 ls0 ws0">to each user only those subcarriers which are known to be</div><div class="t m0 xa h6 y58 ff4 fs3 fc0 sc0 ls0 ws0">good for communication, the system can enjoy an enhanced</div><div class="t m0 xa h6 y59 ff4 fs3 fc0 sc0 ls0 ws0">capacity. Clearly, in order to properly evaluate such oppor-</div><div class="t m0 xa h6 y5a ff4 fs3 fc0 sc0 ls0 ws0">tunistic RRM algorithm in an LTE network simulator, it</div><div class="t m0 xa h6 y5b ff4 fs3 fc0 sc0 ls0 ws0">is important that the simulator provides suitable means to</div><div class="t m0 xa h6 y5c ff4 fs3 fc0 sc0 ls0 ws0">model the time- and frequency-varying aspects of the com-</div><div class="t m0 xa h6 y5d ff4 fs3 fc0 sc0 ls0 ws0">munications in LTE system.</div><div class="t m0 xa h6 y5f ff4 fs3 fc0 sc0 ls0 ws0">Ns3::Spectrum[11] was proposed to address this issue in ns3.</div><div class="t m0 xa h6 y60 ff4 fs3 fc0 sc0 ls0 ws0">It is a framework that provides support for spectrum-aware</div><div class="t m0 xa h6 y61 ff4 fs3 fc0 sc0 ls0 ws0">channel and PHY simulation, which is particularly suited</div><div class="t m0 xa h6 y62 ff4 fs3 fc0 sc0 ls0 ws0">for the modeling of the OFDMA and SC-FDMA technolo-</div><div class="t m0 xa h6 y91 ff4 fs3 fc0 sc0 ls0 ws0">gies. Due to these characteristics, we chose to base our</div><div class="t m0 xa h6 y92 ff4 fs3 fc0 sc0 ls0 ws0">implementation of the LTE PHY and channel models on</div><div class="t m0 xa h6 y93 ff4 fs3 fc0 sc0 ls0 ws0">Ns3::Spectrum. In the deﬁnition of a particular wireless</div><div class="t m0 xa h6 y94 ff4 fs3 fc0 sc0 ls0 ws0">model based on the Spectrum framework, the ﬁrst thing to</div><div class="t m0 xa h6 y95 ff4 fs3 fc0 sc0 ls0 ws0">do is to deﬁne (i) a set of frequencies/channels to use at the</div><div class="t m0 xa h6 y96 ff4 fs3 fc0 sc0 ls0 ws0">physical layer and (ii) the signal generated at the PHY and</div><div class="t m0 xa h6 y97 ff4 fs3 fc0 sc0 ls0 ws0">transported through the channel. To this aim, correspond-</div><div class="t m0 xa h6 y98 ff4 fs3 fc0 sc0 ls0 ws0">ing specialized versions of the SpectrumModel class have to</div><div class="t m0 xa h6 y99 ff4 fs3 fc0 sc0 ls0 ws0">be developed in order to deﬁne the portions of radio spec-</div><div class="t m0 xa h6 y9a ff4 fs3 fc0 sc0 ls0 ws0">trum used by the considered technology and the granular-</div><div class="t m0 xa h6 y9b ff4 fs3 fc0 sc0 ls0 ws0">ity of their representation. In our case, we considered two</div><div class="t m0 xa h6 y9c ff4 fs3 fc0 sc0 ls0 ws0">separate SpectrumModel instances, one for the uplink (UL)</div><div class="t m0 xa h6 y9d ff4 fs3 fc0 sc0 ls0 ws0">and one for the downlink (DL), in order to model the paired</div><div class="t m0 xa h6 y9e ff4 fs3 fc0 sc0 ls0 ws0">spectrum in which LTE operates according to the Frequency</div><div class="t m0 xa h6 y9f ff4 fs3 fc0 sc0 ls0 ws0">Division Duplex (FDD) mode. At the present, the proposed</div><div class="t m0 xa h6 ya0 ff4 fs3 fc0 sc0 ls0 ws0">module supports a spectrum model for the ﬁrst E-UTRAN</div><div class="t m0 xa h6 ya1 ff4 fs3 fc0 sc0 ls0 ws0">FDD operative band (i.e., [1929-1980] MHz for the UL and</div><div class="t m0 xa h6 ya2 ff4 fs3 fc0 sc0 ls0 ws0">[2110-2170] MHz for the DL) [7]. In particular, our Spec-</div><div class="t m0 xa h6 ya3 ff6 fs3 fc0 sc0 ls0 ws0">trumModel is designed to describe a set of sub-channels used</div><div class="t m0 xa h6 ya4 ff4 fs3 fc0 sc0 ls0 ws0">for transmission. Since in LTE radio resources are divided</div><div class="t m0 xa h6 ya5 ff4 fs3 fc0 sc0 ls0 ws0">in sub-channels of 180 kHz, we chose this as the granularity</div><div class="t m0 xa h6 ya6 ff4 fs3 fc0 sc0 ls0 ws0">of our spectrum model. Moreover, the LteSpectrumValue-</div><div class="t m0 xa h6 ya7 ff6 fs3 fc0 sc0 ls0 ws0">Helper class has been developed to make it easy to create</div><div class="t m0 xa h6 ya8 ff4 fs3 fc0 sc0 ls0 ws0">the SpectrumValue corresponding to a given signal, taking</div><div class="t m0 xa h6 ya9 ff4 fs3 fc0 sc0 ls0 ws0">into account in particular the set of sub-channels to be used</div><div class="t m0 xa h6 yaa ff4 fs3 fc0 sc0 ls0 ws0">for the transmission. During the simulation, the PHY layer</div><div class="t m0 xa h6 yab ff4 fs3 fc0 sc0 ls0 ws0">uses this class to create the SpectrumValue instances that</div><div class="t m0 xa h6 yac ff4 fs3 fc0 sc0 ls0 ws0">represent the Power Spectral Density (PSD) of both sig-</div><div class="t m0 xa h6 yad ff4 fs3 fc0 sc0 ls0 ws0">nal and noise. In [11] the channel/PHY interface has been</div><div class="t m0 xa h6 yae ff4 fs3 fc0 sc0 ls0 ws0">deﬁned by the abstract base classes SpectrumChannel and</div><div class="t m0 xa h6 yaf ff6 fs3 fc0 sc0 ls0 ws0">SpectrumPhy. The most important role of these classes is</div><div class="t m0 xa h6 yb0 ff4 fs3 fc0 sc0 ls0 ws0">the transmission and receptions of signals. In particular,</div><div class="t m0 xa h6 yb1 ff4 fs3 fc0 sc0 ls0 ws0">the SpectrumChannel class (i) handles the packet transmis-</div><div class="t m0 xa h6 yb2 ff4 fs3 fc0 sc0 ls0 ws0">sion process among attached PHY layers and (ii) it includes</div><div class="t m0 xa h6 yb3 ff4 fs3 fc0 sc0 ls0 ws0">the channel propagation models. As said before, our LTE</div><div class="t m0 xa h6 yb4 ff4 fs3 fc0 sc0 ls0 ws0">module supports the FDD model only, therefore in the im-</div><div class="t m0 xa h6 yb5 ff4 fs3 fc0 sc0 ls0 ws0">plementation we use two separate SpectrumChannel objects</div><div class="t m0 xa h6 yb6 ff4 fs3 fc0 sc0 ls0 ws0">in order to manage uplink and downlink independently; this</div><div class="t m0 xa h6 yb7 ff4 fs3 fc0 sc0 ls0 ws0">choice is motivate by its lower simulation complexity.</div><div class="t m0 xb h7 yb8 ff7 fs4 fc0 sc0 ls0 ws0">1</div><div class="t m0 xc h6 yb7 ff4 fs3 fc0 sc0 ls0 ws0">In</div><div class="t m0 xa h6 yb9 ff4 fs3 fc0 sc0 ls0 ws0">particular, the SpectrumChannel implementation that we</div><div class="t m0 xa h6 yba ff4 fs3 fc0 sc0 ls0 ws0">use is SingleModelSpectrumChannel, which was already pro-</div><div class="t m0 xa h6 ybb ff4 fs3 fc0 sc0 ls0 ws0">vided by Ns3::Spectrum. This is an acceptable choice, since</div><div class="t m0 xa h6 ybc ff4 fs3 fc0 sc0 ls0 ws0">the propagation model (for which we wanted to develop a</div><div class="t m0 xa h7 ybd ff7 fs4 fc0 sc0 ls0 ws0">1</div><div class="t m0 xd h6 ybe ff4 fs3 fc0 sc0 ls0 ws0">For example, let us consider a single cell FDD system with</div><div class="t m0 xa h6 ybf ff8 fs3 fc0 sc0 ls0 ws0">N users. If this system is simulated using a single Spectrum-</div><div class="t m0 xa h6 yc0 ff4 fs3 fc0 sc0 ls0 ws0">Channel object, the number of channel evaluations for each</div><div class="t m0 xa h6 yc1 ff4 fs3 fc0 sc0 ls0 ws0">slot is O(N</div><div class="t m0 x7 h7 yc2 ff7 fs4 fc0 sc0 ls0 ws0">2</div><div class="t m0 xe h6 yc1 ff4 fs3 fc0 sc0 ls0 ws0">), whereas it is just O(N) if a separate channel</div><div class="t m0 xa h6 yc3 ff4 fs3 fc0 sc0 ls0 ws0">object is used for the uplink and downlink. This is because</div><div class="t m0 xa h6 yc4 ff4 fs3 fc0 sc0 ls0 ws0">in the uplink we are not actually interested in simulating the</div><div class="t m0 xa h6 y90 ff4 fs3 fc0 sc0 ls0 ws0">propagation among the mobile users.</div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div>