Nas layer can bypass access network eutran to interact with core network epc, evolved packet core directly. Lte protocol stackuser control plane protocol layers in lte. In lte security i1, part i of the lte security technical document, we have discussed lte authentication based on eps aka procedure and learned a ue and an mme get to share the k asme when authenticated. Index terms 3gpp, lte, radio resource control rrc, machine type communication mtc, discontinuous reception. It corresponds to the initial layer 3 message shown in figure 202 section 24. Different tasks and states of rrc protocol in lteeutran. Rrc connection setup message include default configuration for srb1 but can also include configuration information for pusch, pucch, pdsch physical channels, cqi reports, sounding reference signal, antenna configuration and scheduling requests. It corresponds to the initial layer 3 message shown in figure 84 section 21. The rlc layer assembles an upper layer sdus if receipt of an rlc pdu completes the assembly of the sdu. Long term evolution protocol overview nxp semiconductors. Protocol specification eventstudio system designer sequence diagram based systems engineering tool. Nas layer and rrc layer are simulated by nas emulation. Radio resource control rrc is the highest layer in the control plane of the access stratum as. Lte radio layer 2, rrc and radio access network architecture.
But one should note, that some radio management functions scheduling, physical resource assignment for physical channels are handled by layer 1 and layer 2 autonomously. These high data rates will enables new applications and services such as. Like every technology, lte has many kpis that need to be maintained and optimized. Tpcpucchrnti physical layer uplink power control na na. Physical signal overshadowing attack on lte usenix. Pdf the present wireless technology is 4th generation 4g or long term evolution. How lte security implementation through encryption. Contains the implementation for layer 2 3gpp lte release 10 for rlcmacpdcprrcx2ap implementation. The main services and functions of the rrc sublayer include. Following is an example for rrc connection reconfiguration for lte advanced with focus on carrier aggregation. Lte layer 3 rrc layer interview questions techplayon. There are some differences between the lte fdd and lte tdd modes that we identified. At this step, the setup has been established only at rrc layer and mac layer for the second carrier is not yet activated.
Rlc um always has pdcp as upper layer and only dtch is used as logical channel. After the ue has completed the rrc connection which has been explained in my previous article, lte kpi optimization. It is not possible in this blog to explain all the. Mac layer, in turn, offers services to the rlc layer by means of logical chan nels. On the physical layer layer one, lte can be the target of jamming attacks that aim to deny the service 5 8. Rrc connection request srb 0 ccch ulsch pusch rrc connection setup complete srb 1 dcch ulsch pusch figure 234 signalling for rrc connection establishment the rrc connection request message is sent as part of the random access procedure. Nr rrc does not only involved in nr but also in other radio access technology as well. In the lte rrc idle state, a ue specific drx discontinuous reception cycle may be configured by upper layers to enable ue power savings rrc connected state. Issue does not come when ue measure the signal quality of the target cell if the target cell is at the same frequency as the current cell intrafrequency measurement but an issue. This protocol controls mac, rlc and pdcp layers in the lte air interface connecting an lte ue with an enodeb. This document describes the functionalities for the support of otdoa location in lte as currently defined in 3gpp and oma. It is a layer that exists between ue and enb and exists at the ip level layer 3network layer. Tagged lte lte interview questions lte layer 3 rrc rrc interview question post navigation.
The rrc configurator helps ensure consistent configuration of the lte protocol stack and also evaluates the protocol messages exchanged between the mlapi test scenario and the ue. The figure below taken from tdoc r23859 captures the rlm process. It also explains steps and procedures that can be used to minimize the failures. Rrc connection establishment in lte all about wired and. Drivetestenabled devices can log the current rank, number of transmit and receive paths. The fixed part of the header has a fi, an e and a sn field. First, the lte network reference model is defined and its basic evolved packet. Contains the code for the enb and ue layer 1 physical layer implementation 3gpp lte release 1012 phy layer and phy rf simulation, ts 36. Signaling provided the rrc layer has the following characteristics such as higher extensibility, secured transmission, reliable transmission and.
While the mlapi test scenario includes only the transmission of and response to layer 3 messages, the rrc configurator in the protocol stack which is the. Rrc connection release in lte the rrc connection release message is used to command the release of an rrc connection. The second major kpi for lte is the lte erab success rate which is also part of the accessibility. Mac and layer 1 signaling has usually delays that are within 10 ms, whereas rrc signaling usually takes something around 100.
As others have mentioned its a big topic to go after lte stack protocol development. Utilizes single carrier modulation and orthogonalfrequency multiplexing using dftspreading in the transmitter and frequency. Physical layer layer 1 physical layer carries all information from the mac transport channels over the air interface. Lte rlc unacknowledged mode is used for transmission of delay sensitive packets, such as voip packets or audiovideo streams. The lte standard specifies an iponly network supporting data rates up to 150 mbps. The rrc connection release procedure with redirection information can also be used for csfallback to geran or utran. Umd pdu header consists of a fixed part and an extension part. Observed time difference of arrival otdoa positioning in. In the lte rrc connected state, ue is known to both evolved packet coreepc and eutran enb lte base sttaion. Pdf on mar 12, 2018, hassan alkhateeb and others published lte mac, rlc, and. Lte downlink and uplink transmissions are organized into radio frames with. The comp cooperating set is determined by higher layers. Parameters that control the uplink transmission are recovered and displayed at the touch of an icon.
Radio resource controlrrc,radio link controlrlc or mac layer and then study more about it. Pdf development of lte ue protocol stack at non access. Pdcp is an abbreviation for packet data convergence protocol. Lte is the latest generation of the 3gpp standards iponly network support data rates up to 100 mbps deployment starting in 2009 this presentation will describe all these functions, which consist of the mac, radio link control rlc, packet data convergence. Nas is not shown in the figure,it sits above rrc in the control planeon left side and above pdcp in the user planeon right side. Multiple pdcchs can be transmitted in the same subframe using control channel elements cce each of which is a nine set of four resource elements known as resource element groups reg. Mobile class targets 100 mbps with high mobility and nomadic local area class targets 1 gbpswith low. Rrc layer or pdcp sub layer with upper layers sap between upper layers transmitting receiving transmitting receivingtm rlc entity tm rlc entity um rlc entity um rlc entity am rlc. The radio protocol architecture for lte can be separated into control plane architecture and user plane architecture as shown below at user plane side, the application creates data packets that are processed by protocols such as tcp, udp and ip, while in the control plane, the radio resource control rrc protocol writes the signalling messages that are exchanged between the base station and. I will suggest to go and compare the lte protocol stack with osi model and then pick and choose one layer e. Radio link monitoring rlm is one of the important procedures in lte. Lte technology is a based on a 3gpp standard that provides for a downlink speed of up to 150 megabits per second mbps and an uplink speed of up to 50 mbps.
Lte control plane layer covers upper layers, nas, rrc, phy and rf. Rrc connection request srb 0 ccch ulsch pusch rrc connection setup complete srb 1 dcch ulsch pusch figure 107 signalling for rrc connection establishment the rrc connection request message is sent as part of the random access procedure. The mac layer passes the received rlc pdus to the rlc layer. The lte link layer protocols are optimized for low delay and low overhead and are simpler than their. Control mac layer is identical, with one minor distinction, the rlc radio link control layer is identical, and the radio resource control rrc layer is essentially identical, with some distinction regarding when a couple of messages can be sent. Lte release 8 major parameters access scheme ul dfts. Before the handover, ue normally measure the cell power signal quality of the target cell and report it to the network, so that network can make a decision whether to allow ue to handover to the target cell or not. It is used to keep track of the radio link condition so that appropriate steps can be taken if radio link failure rlf is declared. The pdcp protocol supports efficient transport of ip packets over the radio link. Systems beyond imt2000 imtadvanced is set to introduce evolutionary path beyond 3g. Keysights 89600 wla software is the protocol analysis complement to the 89600 vsa to decode and verify the mac, rlc and rrclayer messages across multiple radio frames. What links here related changes upload file special pages permanent link page information wikidata item cite this page. The rlc layer is used to format and transport traffic.
Fixed wireless and wired standards are already approaching or achieving 100 mbps or faster, and lte is a way. This article explains the details about the rrc setup procedure and the common failures seen at the rrc phase. Following figure depicts lte protocol stack with main functions of each layer. The radio resource control rrc protocol is used in umts and lte on the air interface. For both situations, when the ue is in the rrc idle mode or when it is in the rrc. Nr can reselect to lte eutra and lte can reselect to nr while they are in idle state. Rrc messages are transported via the pdcpprotocol the major functions of the rrc protocol include connection establishment and. Radio resource control rrc protocol writes the signaling messages that are exchanged between bs and mobile. Measurement controlrrc connection reconfiguration in lte.
The frequency location and possibly the more detailed transmission format can be. Lte evolved universal terrestrial radio access eutra packet data convergence protocol pdcp specification. Myung 8 lte enabling technologies single carrier fdma scfdma scfdma is a new single carrier multiple access technique which has similar structure and performance to ofdma. I just enabled all ie on asn to give you full details of parameters, but it reality the implementation would start with very limited set of parameters enabled and leaving large portions of parameter to some 3gpp default or hardcoded. Over the lte air interface, the enb sends an rrc connection release message to the ue to tear down all traffic and signaling bearers on the air interface and the ues context in. User plane adopts udp user datagram protocol to transport user data.
Rrc success rate, it needs to get a bearer assigned to it to initiate services. Lte networks can become the primary beneficiaries of any uplink. Takes care of the link adaptation amc, power control, cell search for initial synchronization and handover purposes and other measurements inside the lte system and between systems for the rrc layer. In both cases, the information is processed by the following protocols before being passed to the physical layer for transmission. Radio imt advanced based on lte release 10 and beyond. In this document, we will explain nas and as security setup procedures to be performed based on k asme, and how data are transmitted in user and control planes after the. Radio resource control rrc radio protocols for lte and. Drive testing lte 4 one of the most interesting lte network features to rf optimization engineers is the impact that multiple input multiple output mimo with spatial multiplexing and antenna diversity brings to the enduser performance. The rrc protocol for eutran is responsible for the basic configuration of the radio protocol stack.
Development of lte ue protocol stack at non access stratum layer. How lte security implementation through encryption posted on 27 november, 20 implement security through encryption both control plane rrc data and user plane data and integrity protection for control plane rrc data only, it is the responsibility pdcp layer. Long term evolution lte is the next step forward in cellular 3g services. As a matter of fact, the previous research efforts focused only on layer one or layer three protocols andto the best of our knowledgeno security analysis of data link layer layer two protocols exists to. If nas messages are encapsulted in rrc messages, lterrc calls naseps dissector. Lte uu eutran mme s11 serving s5 gateway pdn gateway. The bearer can be default usually data qci9 or dedicated volte qci1. The interaction of nr rrc and lte rrc can be illustrated as follows. Visualether protocol analyzer wireshark based visual protocol analysis and system design reverse engineering tool. Getting started with 4g lte using eurecom openairinterface. Lte is the latest generation of the 3gpp standards. Rrc protocol layer exists in both the ue and enodeb enb. It is intended as a one stop guide to provide an overview of the otdoa feature for operators and manufacturers interested in the deployment. Myung 2 beyond 3g international mobile telecommunications imt2000 introduced global standard for 3g.
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