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LTE-EPC

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Since there exist a system, which basically deal with PHY, MAC and Scheduler functionality of LTE, the new
simulation model supports for LTE RLC and PDCP protocol, together with EPC data plane features. This results in end to
end IP connectivity over LTE-EPC. For simulation we are using ns-3. In this paper, we provide an overview of the design
criteria and architecture of the proposed model.

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LTE-EPC

  1. 1. SIMULATION OF END-TO-END IP CONNECTIVITY FOR LTE-EPC AKSHATHA.H.E1, NAMRATA KATTI2, SANDEEP JAINAPUR3, DEEPTHI RAJ4 1,2,3,4 DSCE. Abstract- Since there exist a system, which basically deal with PHY, MAC and Scheduler functionality of LTE, the new simulation model supports for LTE RLC and PDCP protocol, together with EPC data plane features. This results in end to end IP connectivity over LTE-EPC. For simulation we are using ns-3. In this paper, we provide an overview of the design criteria and architecture of the proposed model. Key words- Ns-3,LTE, EPC eNBs, some of which might be equipped with a backhaul connection with limited capabilities. In order to simulate such scenarios, the user data plane protocols being used between the eNBs and the SGW/PGW should be modeled accurately. 7. It should be possible for a single UE to use different applications with different QoS profiles. Hence, multiple EPS bearers should be supported for each UE. This includes the necessary classification of TCP/UDP traffic over IP done at the UE in the uplink and at the PGW in the downlink. 8. The focus of the EPC model is mainly on the EPC data plane. The accurate modeling of the EPC control plane is, for the time being, not a requirement; hence, the necessary control plane interactions can be modeled in a simplified way by leveraging on direct interaction among the different simulation objects via the provided helper objects. 9. The focus of the EPC model is on simulations of active users in the EPS Connection Management (ECM) connected mode. Hence, all the functionality that is only relevant for ECM idle mode (in particular, tracking area update and paging) are not modeled at all. 10. While handover support is not a current requirement, it is planned to be considered in the near future. Hence, the management of EPS bearers by the eNBs and the SGW/PGW should be implemented in such a way that it can be re-used when handover support is eventually added. I. INTRODUCTION The increasing attention on the upcoming LTE mobile communication technology standardized by 3GPP, together with a shift in mobile consumer habits from voice calls only to IP-based services such as web browsing, video streaming, video conferencing and social networking, are causing a growing interest by the industrial and research community into network simulator platforms that can support the evaluation of LTE networks modeling the relevant aspects of real applications and of the TCP/IP protocol stack. Doing this accurately means modeling not only the LTE radio access network, but also the corresponding core network, referred to as the Evolved Packet Core (EPC). II. DESIGN CRITERIA 1. The model is to be used to simulate the transmission of IP packets by the upper layers. With this respect, it shall be considered that in LTE the Scheduling and Radio Resource Management do not work with IP packets directly, but rather with RLC PDUs, which are obtained by segmentation and concatenation of IP packets done by the RLC entities. Hence, these functionalities of the RLC layer should be modeled accurately. 2. The only Packet Data Network (PDN) type supported is IPv4. 3. The Serving Gateway (SGW) and PDN Gateway (PGW) a functional entities are implemented within a single node, which is hence referred to as the SGW/PGW node. This choice is done to simplify the simulation model. 4. The scenarios with inter-SGW mobility are not of interest. Hence, a single SGW/PGW node will be present in all simulations scenarios 5. A requirement for the EPC model is that it can be used to simulate the end-to-end performance of realistic application models. Hence, it should be possible to use with the EPC model any regular ns-3 application working on top of TCP or UDP. 6. Another requirement is the possibility of simulating network topologies with the presence of multiple III. LTE-EPC ARCHITECTURE There are two main components:  The LTE Model: - This model includes the LTE Radio Protocol stack (RRC, PDCP, RLC, MAC, PHY).These entities reside entirely within the UE and the eNB nodes.  The EPC model: - This model includes core network interfaces, protocols and entities. These entities and protocols reside within the SGW, PGW and MME nodes and partially within the eNB nodes. International Conference on Electronics and Communication Engineering, 28th April-2013, Bengaluru, ISBN: 978-93-83060-04-7 16
  2. 2. Simulation of End-To-End Ip Connectivity For Lte-Epc For the sake of an easy explanation, we further divide the LTE model in two separate parts. The first part is the lower LTE radio protocol stack, which includes in particular the PHY and the MAC layers, as well as the Scheduler (which is commonly associated with the MAC layer).The second part is the upper LTE radio stack, which includes the RRC, PDCP and RLC protocols, and is represented below. a different eNB. By default a 10.x.y.z/30 subnet is assigned to each point-to-point link (a/30subnet is the smallest subnet that allows for two distinct host addresses). To begin with, we consider the case of the downlink; Downlink IPv4 packets are generated from a generic remote host, and addressed to one of the UE devices. Internet routing will take care of forwarding the packet to the generic Net Device of the SGW/PGW node which is connected to the internet (this is the Gi interface according to 3GPP terminology). It determines the eNB node to which the UE is attached, by looking at the IP destination address (which is the address of the UE). It classifies the packet using Traffic Flow Templates (TFTs) to identify to which EPS Bearer it belongs. EPS bearers have a one-to-one mapping to S1-U Bearers, so this operation returns the GTP-U Tunnel End-point Identifier (TEID) to which the packet belongs. It adds the corresponding GTP-U protocol header to the packet. Finally, it sends the packet over an UDP socket to the S1-U point-to-point NetDevice, addressed to the eNB to which the UE is attached. The local delivery process will forward the packet, via an UDP socket, to a dedicated application called EpcEnbApplication. This application then performs the following operations:  It removes the GTP header and retrieves the TEID which is contained in it.  Leveraging on the one-to-one mapping between S1-U bearers and Radio Bearers (which is a 3GPP requirement), it determines the Radio Bearer ID (RBID) to which the packet belongs.  It records the RBID in a dedicated tag called LteRadioBearerTag, which is added to the packet. Figure 3.1 PROPOSED ARCHITECTURE   It forwards the packet to the LTE EnbNetDevices of the eNB node via a raw packet socket. Note that, at this point, the outmost header of the packet is the end-to-end IP header, since the IP/UDP/GTP headers Figure 3.2 ARCHITECTURE OF THE UPPER LTE RADIO of the S1 protocol stack has already been stripped. STACK Finally, the LTEUeNetDevice of the UE will receive the packet and delivery it locally to the IP protocol EPC stack, which will in turn delivery it to the application As previously shown in Figure, there are two differof the UE, which is the end point of the downlink ent layers of IP networking. The first one is the endcommunication. to-end layer which provides end-to-end connectivity to the users. This layers involves the UEs, the PGW and the remote host (including eventual internet routers and hosts in between), but does not involve the eNB. By default, UEs are assigned a public IPv4 address in the 7.0.0.0/8 network, and the PGW gets the address 7.0.0.1, which is used by all UEs as the gate way to reach the internet. This default address assignment has been chosen arbitrarily. The second layer of IP networking is the EPC local area network. This involves all eNB nodes and the SGW/PGW node. This network is implemented as a set of pointto-point links that connect each eNB with the SGW/PGW node. Thus the SGW/PGW has a set of point-to-point devices each providing connectivity to Figure 3.2 LTE-EPC DATA PLANE PROTOCOL STACK International Conference on Electronics and Communication Engineering, 28th April-2013, Bengaluru, ISBN: 978-93-83060-04-7 17
  3. 3. Simulation of End-To-End Ip Connectivity For Lte-Epc IV. SIMULATION RESULTS ACKNOWLEDGEMENT We would like to thank Mr. Deepak Nadiga, Director of “SOLUTT CORPORATION” for his valuable guidance. We would also like to thank to our guide Mrs. Deepthi raj, Lecturer at Dept. Of Telecommunication Engg, DSCE. Also we would like to thank Dr A.R.Aswatha H.O.D of telecommunication Engineering Dayananda Sagar College and all the teachers and friends who helped us doing this project. Thank you all once again. BIOGRAPHY Miss Akshatha.H.E pursing final year Telecommunication Engineering in Dayananda Sagar college of Engineering. Miss Namrata katti pursuing final year Telecommunication Engineering in Dayananda Sagar college of Engineering. Mr.Sandeep Jainapur pursuing final year telecommunication Engineering in Dayananda Sagar college of Engineering. Mrs. Deepthi Raj, Lecturer at Dayananda Sagar College of engineering. Figure 4.1 AVG BYTES/SEC V/S NODES REFERENCES [1]. S.Ascent,3GPP LTE tool box blockset," http://www.steepestascent.com/ tent/default.asp? Pages=2 10. Figure 4.2 LTE-EPC N1S1 and con- [2]. MimoOn,mi!Mobile, http://www.mimoon.de/pages/ Products/miMobile/, Feb. 2012. V. CONCLUSION [3]. J. C. Ikuno, M. Wrulich, and M. Rupp, System level simulation of LTE networks," in Proc. of IEEE VTC Spring, Taipei, Taiwan, May 2010. LTE technology is being proven to meet or exceed initial target requirements, large ecosystem of operators, vendors etc. committed to LTE.Commercial network deployments planned 2010 and beyond. EPC represents an efficient all-IP packet core. Supports delivery of mobile Internet services with QoS overbroad band radio networks. Supports multiple access technologies (all 2G/3G cellular, WiMAX, Wi-Fi etc.) and mobility between these access networks. LTE and EPC can cost effectively address the demands of future mobile broadband growth .LTE and EPC can cost effectively address the demands of future mobile broadband growth. [4]. D. Gonzalez, S. Ruiz, M. Garcia-Lozano, J. Olmos,and A. Serra, System level evaluation of LTE networks with semi distributed intercell interference coordination," in Proc. of IEEE PIRMC, Tokyo, Japan, Sep. 2009. [5]. 3GPP TS 36.321, Medium Access Control (MAC) protocol specification. [6]. The LTE-EPC Network Simulator (LENA) project,“http://iptechwiki.cttc.es/LTE-EPC Network Simulator (LENA).  International Conference on Electronics and Communication Engineering, 28th April-2013, Bengaluru, ISBN: 978-93-83060-04-7 18

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