Abstrct
The goal of the Lte acceptable is to generate specifications for a new radio-access technology geared to higher data rates, low latency and greater spectral efficiency. The spectral efficiency target for the Lte ideas is three to four times higher than the current Hspa system. These aggressive spectral efficiency targets require using the technology envelope by employing industrialized air-interface techniques such as low-Papr orthogonal uplink multiple way based on Sc-Fdma(single-carrier frequency branch multiple access) Mimo multiple-input multiple-output multi-antenna technologies, inter-cell interference mitigation techniques, low latency channel buildings and single-frequency network (Sfn) broadcast. The researchers and engineers working on the acceptable come up with new innovative technology proposals and ideas for ideas execution improvement. Due to the extremely aggressive acceptable development schedule, these researchers and engineers are commonly unable to issue their proposals in conferences or journals, etc. In the standards development phase, the proposals go straight through wide scrutiny with multiple sources evaluating and simulating the proposed technologies from ideas execution improvement and implementation complexity perspectives. Therefore, only the highest-quality proposals and ideas ultimately make into the standard.
Keywords: Lte Architecture, Udp, Gdp, Mimo, Mime, Mcch, Mbms, Qos
1. Introducyion
The Lte network architecture is designed with the goal of supporting packet-switched traffic with seamless mobility, quality of aid (QoS) and minimal latency. A packet-switched coming allows for the supporting of all services along with voice straight through packet connections. The result in a extremely simplified flatter architecture with only two types of node namely evolved Node-B (eNb) and mobility administration entity/gateway (Mme/Gw). This is in discrepancy to many more network nodes in the current hierarchical network architecture of the 3G system. One major turn is that the radio network controller (Rnc) is eliminated from the data path and its functions are now incorporated in eNb. Some of the benefits of a particular node in the way network are reduced latency and the distribution of the Rnc processing load into multiple eNbs. The elimination of the Rnc in the way network was inherent partly because the Lte ideas does not retain macro-diversity or soft-handoff.
2. Lte Network Architecture
All the network interfaces are based on Ip protocols. The eNbs are interconnected by means of an X2 interface and to the Mme/Gw entity by means of an S1 interface as shown in Figure1. The S1 interface supports a many-to-many association between Mme/Gw and eNbs.
The functional split between eNb and Mme/Gw is shown in frame 2 Two logical gateway entities namely the serving gateway (S-Gw) and the packet data network gateway (P-Gw) is defined. The S-Gw acts as a local mobility anchor forwarding and receiving packets to and from the eNb serving the Ue. The P-Gw interfaces with external packet data networks (Pdns) such as the Internet and the Ims. The P-Gw also performs some Ip functions such as address allocation, course enforcement, packet filtering and routing.
The Mme is a signaling only entity and hence user Ip packets do not go straight through Mme. An advantage of a detach network entity for signaling is that the network capacity for signaling and traffic can grow independently. The main functions of Mme are idle-mode Ue reach quality along with the operate and execution of paging retransmission, tracking area list management, roaming, authentication, authorization, P-Gw/S-Gw selection, bearer administration along with dedicated bearer establishment, protection negotiations and Nas signaling, etc.
Evolved Node-B implements Node-B functions as well as protocols traditionally implemented in Rnc. The main functions of eNb are header compression, ciphering and dependable delivery of packets. On the operate side, eNb incorporates functions such as admission operate and radio reserved supply management. Some of the benefits of a particular node in the way network are reduced latency and the distribution of Rnc the network side are now fulfilled, in eNb.
Figure 1: Network Architecture
Figure 2: Functional split between eNb and Mme/Gw.
2.1 Protocol Stack And Conytol Plane
The user plane protocol stack is given in frame 3.We note that packet data convergence protocol (Pdcp) and radio link operate (Rlc) layers traditionally fulfilled, in Rnc on frame 4 shows the operate plane protocol stack.
Figure 3: User plane protocol.
Figure 4: operate plane protocol stack.
We note that Rrc functionality traditionally implemented in Rnc is now incorporated into eNb. The Rlc and Mac layers achieve the same functions as they do for the user plane. The functions performed by the Rrc consist of ideas data broadcast, paging, radio bearer control, Rrc association management, mobility functions and Ue estimation reporting and control. The non-access stratum (Nas) protocol fulfilled, in the Mme on the network side and at the Ue on the terminal side performs functions such as Eps (evolved packet system) bearer management, authentication and protection control, etc.
The S1 and X2 interface protocol stacks are shown in Figures 2.5 and 2.6 respectively.We note that similar protocols are used on these two interfaces. The S1 user plane interface (S1-U) is defined between the eNb and the S-Gw. The S1-U interface uses Gtp-U (Gprs tunneling protocol – user data tunneling) on Udp/Ip vehicle and provides non-guaranteed delivery of user plane Pdus between the eNb and the S-Gw. The Gtp-U is a relatively easy Ip based tunneling protocol that permits many tunnels between each set of end points. The S1 operate plane interface (S1-Mme) is defined as being between the eNb and the Mme. Similar to the user plane, the vehicle network layer is built on Ip vehicle and for the reliable
Figure 5: S1 interface user and operate planes.
Figure 6: X2 interface user and operate planes.
Transport of signaling messages Sctp (stream operate transmission protocol) is used on top of Ip The Sctp protocol operates analogously to Tcp ensuring reliable, in-sequence vehicle of messages with congestion control. The application layer signaling protocols are referred to as S1 application protocol (S1-Ap) and X2 application protocol (X2-Ap) for S1 and X2 interface operate planes respectively.
3. Qos And Bearer aid Architecture
Applications such as VoIp, web browsing, video telephony and video streaming have special QoS needs. Therefore, an foremost highlight of any all-packet network is the provision of a QoS mechanism to enable differentiation of packet flows based on QoS requirements. In Eps, QoS flows called Eps bearers are established between the Ue and the P-Gw as shown in frame 7. A radio bearer transports the packets of an Eps bearer between a Ue and an eNb. Each Ip flow (e.g. VoIp) is associated with a separate Eps bearer and the network can prioritize traffic accordingly.
Figure 7: Eps bearer aid architecture.
When receiving an Ip packet from the Internet, P-Gw performs packet classification based on determined predefined parameters and sends it an acceptable Eps bearer. Based on the Eps bearer, eNb maps packets to the acceptable radio QoS bearer. There is one-to-one mapping between an Eps bearer and a radio bearer.
4. Layer 2 Structure
The layer 2 of Lte consists of three sub layers namely medium way control, radio link operate (Rlc) and packet data convergence protocol (Pdcp). The aid way point (Sap) between the corporeal (Phy) layer and the Mac sub layer contribute the vehicle channels while the Sap between the Mac and Rlc sub layers contribute the logical channels. The Mac sub layer performs multiplexing of logical channels on to the vehicle channels.
The downlink and uplink layer 2 structures are given in Figures 8 and 9 respectively. The discrepancy between downlink and uplink structures is that in the downlink, the Mac sub layer also handles the priority among Ues in expanding to priority handling among the logical channels of a particular Ue. The other functions performed by the Mac sub layers in both downlink and uplink consist of mapping between the logical and the vehicle channels.
Multiplexing of Rlc packet data units (Pdu), padding, vehicle format selection and hybrid Arq (Harq).
The main services and functions of the Rlc sub layers consist of segmentation, Arq in-sequence delivery and double detection, etc. The in-sequence delivery of upper layer Pdus is not guaranteed at handover. The reliability of Rlc can be configured to either acknowledge mode (Am) or un-acknowledge mode (Um) transfers. The Um mode can be used for radio bearers that can tolerate some loss. In Am mode, Arq functionality of Rlc Retransmits vehicle blocks that fail saving by Harq. The saving at Harq may fail due to hybrid Arq Nack to Ack error or because the maximum whole of retransmission attempts is reached. In this case, the relevant transmitting Arq entities are notified and inherent retransmissions and re-segmentation can be initiated.
Figure 8: Downlink layer 2 structure.
Figure 9: Uplink layer 2 structure.
The Pdcp layer performs functions such as header compression and decompression, ciphering and in-sequence delivery and double detection at handover for Rlcam, etc. The header compression and decompression is performed using the robust header compression (Rohc) protocol. 5.1 Downlink logical, vehicle and corporeal channels
4.1 Downlink Logical, vehicle And corporeal Channels
The association between downlink logical, vehicle and corporeal channels is shown in frame 10. A logical channel is defined by the type of data it carriers. The logical channels are supplementary divided into operate channels and traffic channels. The operate channels carry control-plane information, while traffic channels carry user-plane information.
In the downlink, five operate channels and two traffic channels are defined. The downlink operate channel used for paging data change is referred to as the paging operate channel (Pcch). This channel is used when the network has no knowledge about the location cell of the Ue. The channel that carries ideas operate data is referred to as the broadcast operate channel (Bcch). Two channels namely the common operate channel (Ccch) and the dedicated operate channel (Dcch) can carry data between the network and the Ue. The Ccch is used for Ues that have no Rrc association while Dcch is used for Ues that have an Rrc connection. The operate channel used for the transmission of Mbms operate data is referred to as the multicast operate channel (Mcch). The Mcch is used by only those Ues receiving Mbms.
The two traffic channels in the downlink are the dedicated traffic channel (Dtch) and the multicast traffic channel (Mtch). A Dtch is a point-to-point channel dedicated to a particular Ue for the transmission of user information. An Mtch is a point-to-multipoint channel used for the transmission of user traffic to Ues receiving Mbms. The paging operate channel is mapped to a vehicle channel referred to as paging channel (Pch). The Pch supports discontinuous reception (Drx) to enable Ue power saving. A Drx cycle is indicated to the Ue by the network. The Bcch is mapped to either a vehicle channel referred to as a broadcast channel (Bch) or to the downlink shared channel (Dlsch).
Figure 10: Downlink logical, vehicle and corporeal channels mapping.
The Bch is characterized by a fixed pre-defined format as this is the first channel Ue receives after acquiring synchronization to the cell. The Mcch and Mtch are either mapped to a vehicle channel called a multicast channel (Mch) or to the downlink shared channel (Dl-Sch). The Mch supports Mbsfn combining of Mbms transmission from multiple cells. The other logical channels mapped to Dl-Sch consist of Ccch, Dcch and Dtch. The Dl-Sch is characterized by retain for adaptive modulation/coding, Harq, power control, semi-static/dynamic reserved supply allocation, Drx, Mbm Transmission and multi antenna technologies. All the four-downlink vehicle channels have the requirement to be broadcast in the whole coverage area of a cell.
The Bch is mapped to a corporeal channel referred to as corporeal broadcast channel (Pbch), which is transmitted over four sub frames with 40 ms timing interval. The 40 ms timing is detected blindly without requiring any explicit signaling. Also, each sub frame transmission of Bch is self-decodable and Ues with good channel conditions may not need to wait for reception of all the four sub frames for Pbch decoding. The Pch and Dl-Sch are mapped to a corporeal channel referred to as corporeal downlink shared channel (Pdsch). The multicast channel (Mch) is mapped to corporeal multicast channel (Pmch), which is the multi-cell Mbsfn transmission channel.
The three stand-alone corporeal operate channels are the corporeal operate format indicator channel (Pcfich), the corporeal downlink operate channel (Pdcch) and the corporeal hybrid Arq indicator channel (Phich). The Pcfich is transmitted every sub frame and carries data on the whole of Ofdm symbols used for Pdcch. The Pdcch is used to inform the Ues about the reserved supply budget of Pch and Dl-Sch as well as modulation, coding and hybrid Arq data associated to Dl-Sch. A maximum of three or four Ofdm symbols can be used for Pdcch. With dynamic indication of whole of Ofdm symbols used for Pdcch via Pcfich, the unused Ofdm symbols among the three or four Pdcch Ofdm symbols can be used for data transmission. The Phich is used to carry hybrid Arq Ack/Nack for uplink transmissions.
4.2 Uplink Logical, vehicle And corporeal Channels
The association between uplink logical, vehicle and corporeal channels is shown in frame 2.11. In the uplink two operate channels and a particular traffic channel is defined. As for the downlink, common operate channel (Ccch) and dedicated operate channel (Dcch) are used to carry data between the network and the Ue. The Ccch is used for Ues having no Rrc association while Dcch is used for Ues having an Rrc connection. Similar to downlink, dedicated traffic channel (Dtch) is a point-to-point channel dedicated to a particular Ue for transmission of user information. All the three uplink logical channels are mapped to a vehicle channel named uplink shared channel (Ul-Sch). The Ul-Sch supports adaptive modulation/coding, Harq, power operate and semi-static/dynamic reserved supply allocation.
Another vehicle channel defined for the uplink is referred to as the random way channel (Rach), which can be used for transmission of diminutive operate data from a Ue with possibility of collisions with transmissions from other Ues. The Rach is mapped to corporeal random way channel (Prach), which carries the random way preamble.
The Ul-Sch vehicle channel is mapped to corporeal uplink shared channel (Pusch). A stand-alone uplink corporeal channel referred to as corporeal uplink operate channel (Pucch) is used to carry downlink channel quality indication (Cqi) reports, scheduling ask (Sr) and hybrid Arq Ack/Nack for downlink transmissions.
5. Protocol States And States Transitions
In the Lte system, two radio reserved supply operate (Rrc) states namely Rrc Idle and Rrc associated states are defined as depicted in frame 2.12. A Ue moves from Rrc Idle state to Rrc associated state when an Rrc association is successfully established. A Ue can move back from Rrc associated to Rrc Idle state by releasing the Rrc connection. In the Rrc Idle state, Ue can receive broadcast/multicast data, monitors a paging channel to detect incoming calls, performs neighbor cell measurements and cell selection/reselection and acquires ideas information. Furthermore, in the Rrc Idle state, a Ue specific Drx (discontinuous reception) cycle may be configured by upper layers to enable Ue power savings. Also, mobility is controlled by the Ue in the Rrc Idle
State.
In the Rrc associated state, the change of uncast data to/from Ue, and the change of broadcast or multicast data to Ue can take place. At lower layers, the Ue may be configured with a Ue specific Drx/Dtx (discontinuous transmission). Furthermore, Ue monitors operate channels associated with the shared data channel to determine if data is scheduled for it, provides channel quality feedback information, performs neighbor cell measurements and estimation reporting and acquires ideas information. Unlike the Rrc Idle state, the mobility is controlled by the network in this state.
Figure 11 Uplink logical, vehicle and corporeal channels mapping.
Figure 12: Ue states and state transitions.
6. Seamless Mobility Support
An foremost highlight of a movable wireless ideas such as Lte is retain for seamless mobility over eNbs and over Mme/Gws. Fast and seamless handovers (Ho) is particularly foremost for delay-sensitive services such as VoIp. The handovers occur more oftentimes over eNbs than over core networks because the area covered by Mme/Gw serving a large whole of eNbs is commonly much larger than the area covered by a particular eNb. The
signaling on X2 interface between eNbs is used for handover preparation. The S-Gw acts as anchor for inter-eNb handovers.
In the Lte system, the network relies on the Ue to detect the neighboring cells for handovers and therefore no neighbor cell data is signaled from the network. For the quest and estimation of inter-frequency neighboring cells, only the carrier frequencies need to be indicated. An example of active handover in an Rrc associated state is shown in frame 13 where a Ue moves from the coverage area of the source eNb (eNb1) to the coverage area of the target eNb (eNb2). The handovers in the Rrc associated state are network controlled and assisted by the Ue. The Ue sends a radio estimation record to the source eNb1 indicating that the signal quality on eNb2 is great than the signal quality on eNb1. As establishment for handover, the source eNb1 sends the coupling data and the Ue context to the target eNb2 (Ho request) [6] on the X2 interface. The target eNb2 may achieve admission operate dependent on the received Eps bearer QoS information. The target eNb configures the required resources according to the received Eps bearer QoS data and reserves a C-Rnti (cell radio network temporary identifier) and optionally a Rach preamble.
Figure 13: Active handovers.
The C-Rnti provides a unique Ue identification at the cell level identifying the Rrc connection. When eNb2 signals to eNb1 that it is ready to achieve the handover via Ho response message, eNb1 commands the Ue (Ho command) to turn the radio bearer to eNb2. The Ue receives the Ho command with the requisite parameters (i.e. New C-Rnti, optionally dedicated Rach preamble, inherent expiry time of the dedicated Rach preamble, etc.) and is commanded by the source eNb to achieve the Ho. The Ue does not need to delay the handover execution for delivering the Harq/Arq responses to source eNb.
After receiving the Ho command, the Ue performs synchronization to the target eNb and accesses the target cell via the random way channel (Rach) following a contention-free course if a dedicated Rach preamble was allocated in the Ho command or following a contention-based course if no dedicated preamble was allocated. The network responds with uplink reserved supply budget and timing enlarge to be applied by the Ue. When the Ue has successfully accessed the target cell, the Ue sends the Ho confirm message (C-Rnti) along with an uplink buffer status record indicating that the handover course is completed for the Ue. After receiving the Ho confirm message, the target eNb sends a path switch message to the Mme to inform that the Ue has changed cell. The Mme sends a user plane update message to the S-Gw. The S-Gw switches the downlink data path to the target eNb and sends one or more “end marker” packets on the old path to the source eNb and then releases any user-plane/Tnl resources towards the source eNb. Then S-Gw sends a user plane update response message to the Mme. Then the Mme confirms the path switch message from the target eNb with the path switch response message. After the path switch response message is received from the Mme, the target eNb informs success of Ho to the source eNb by sending issue reserved supply message to the source eNb and triggers the issue of resources. On receiving the issue reserved supply message, the source eNb can issue radio and C-plane associated sources associated with the Ue context.
During handover establishment U-plane tunnels can be established between the source Enb and the target eNb. There is one tunnel established for uplink data forwarding and an additional one one for downlink data forwarding for each Eps bearer for which data forwarding is applied. During handover execution, user data can be forwarded from the source eNb to the target eNb. Forwarding of downlink user data from the source to the target eNb should take place in order as long as packets are received at the source eNb or the source eNb buffer is exhausted.
For mobility administration in the Rrc Idle state, idea of tracking area (Ta) is introduced. A tracking area commonly covers multiple eNbs as depicted in frame 2.14. The tracking area identity (Tai) data indicating which Ta an eNb belongs to is broadcast as part of ideas information. A Ue can detect turn of tracking area when it receives a separate Tai than in its current cell. The Ue updates the Mme with its new Ta data as it moves over Tas. When P-Gw receives data for a Ue, it buffers the packets and queries the Mme for the Ue’s location. Then the Mme will page the Ue in its most current Ta. A Ue can be registered in multiple Tas simultaneously. This enables power saving at the Ue under conditions of high mobility because it does not need to constantly update its location with the Mme. This highlight also minimizes load on Ta boundaries.
8. Multicast Broadcast ideas Architecture
In the Lte system, the Mbms either use a single-cell transmission or a multi-cell transmission. In single-cell transmission, Mbms is transmitted only in the coverage of a specific cell and therefore combining Mbms transmission from multiple cells is not supported. The single-cell Mbms transmission is performed on Dl-Sch and hence uses the same network architecture as the unicast traffic.
Figure 14: Tracking area update for Ue in Rrc Idle state.
The Mtch and Mcch are mapped on Dl-Sch for point-to-multipoint transmission and scheduling is done by the eNb. The Ues can be allocated dedicated uplink feedback channels selfsame to those used in unicast transmission, which enables Harq Ack/Nack and Cqi feedback. The Harq retransmissions are made using a group (service specific) Rnti (radio network temporary identifier) in a time frame that is co-ordinated with the former Mtch transmission. All Ues receiving Mbms are able to receive the retransmissions and merge with the former transmissions at the Harq level. The Ues that are allocated a dedicated uplink feedback channel are in Rrc associated state. In order to avoid unnecessary Mbms transmission on Mtch in a cell where there is no Mbms user, network can detect presence of users interested in the Mbms aid by polling or straight through Ue aid request.
The multi-cell transmission for the evolved multimedia broadcast multicast aid (Mbms) is realized by transmitting selfsame waveform at the same time from multiple cells. In this case, Mtch and Mcch are mapped on to Mch for point-to-multipoint transmission. This multi-cell transmission mode is referred to as multicast broadcast particular frequency network (eMbsfn) as described in information in chapter 17. An Mbsfn transmission from multiple cells within an Mbsfn area is seen as a particular transmission by the Ue. An Mbsfn area comprises a group of cells within an Mbsfn synchronization area of a network that are co-ordinate to achieve Mbsfn transmission. An Mbsfn synchronization area is defined as an area of the network in which all eNbs can be synchronized and achieve Mbsfn transmission. An Mbms aid area may consist of multiple Mbsfn areas. A cell within an Mbsfn synchronization area may form part of multiple Sfn areas each characterized by separate article and set of participating cells.
Figure 15. The eMbms aid area and Mbsfn areas.
An example of Mbms aid area consisting of two Mbsfn areas, area A and area B, is depicted in frame 2.15. The Mbsfna area consists of cells A1-A5, cell Ab1 and Ab2. The Mbsfn area consists of cells B1-B5, cell Ab1 and Ab2. The cells Ab1 and Ab2 are part of both Mbsfn area A and area B. The cell B5 is part of area B but does not conduce to Mbsfn transmission. Such a cell is referred to as Mbsfn area reserved cell. The Mbsfn area reserved cell may be allowed to forward for other services on the resources allocated for the Mbsfn but at a restricted power. The Mbsfn synchronization area, the Mbsfn area and reserved cells can be semi-statically configured by O&M.
The Mbms architecture for multi-cell transmission is depicted in frame 2.16. The multicell multicast coordination entity (Mce) is a logical entity, which means it can also be part of an additional one network element such as eNb. The Mce performs functions such as the budget of the radio resources used by all eNbs in the Mbsfn area as well as determining the radio configuration along with the modulation and coding scheme. The Mbms Gw is also a logical entity whose main function is sending/broadcasting Mbms packets with the Sync protocol to each eNb transmitting the service. The Mbms Gw hosts the Pdcp layer of the user plane and uses Ip multicast for forwarding Mbms user data to eNbs.
The eNbs are associated to eMbms Gw via a pure user plane interface M1. As M1 is a pure user plane interface, no operate plane application part is defined for this interface. Two operate plane interfaces M2 and M3 are defined. The application part on M2 interface conveys radio configuration data for the multi-cell transmission mode eNbs. The application part on M3 interface between Mbms Gw and Mce performs Mbms session operate signaling on Eps bearer level that includes procedures such as session start and stop.
An foremost requirement for multi-cell Mbms aid transmission is Mbms article synchronization to enable Mbsfn operation. The eMbms user plane architecture for article synchronization is depicted in frame 2.17. A Sync protocol layer is defined on the vehicle network layer (Tnl) to retain the article synchronization mechanism. The Sync protocol carries supplementary data that enables eNbs to recognize the timing for radio frame transmission as well as detect packet loss.
Figure 16: eMbms logical architecture.
Figure 17: The eMbms user plane architecture for article synchronization.
The eNbs participating in multicell Mbms transmission are required to comply with article synchronization mechanism. An eNb transmitting only in single-cell aid is not required to comply with the stringent timing requirements indicated by Sync protocol. In case Pdcp is used for header compression, it is settled in eMbms Gw. The Ues receiving Mtch transmissions and taking part in at least one Mbms feedback task need to be in an Rrc associated state. On the other hand, Ues receiving Mtch transmissions without taking part in an Mbms feedback mechanism can be in either an Rrc Idle or an Rrc associated state. For receiving single-cell transmission of Mtch, a Ue may need to be in Rrc associated state. The signaling by which a Ue is triggered to move to Rrc associated state solely for single-cell reception purposes is carried on Mcch.
8. Summary
The Lte ideas is based on extremely simplified network architecture with only two types of nodes namely eNode-B and Mme/Gw. Fundamentally, it is a flattened architecture that enables simplified network build while still supporting seamless mobility and industrialized QoS mechanisms. This is a major turn relative to former wireless networks with many more network nodes using hierarchical network architecture. The simplification of network was
partly inherent because Lte ideas does not retain macro-diversity or soft-handoff and hence does not require a Rnc in the way network for macro-diversity combining. Many of the other Rnc functions are incorporated into the eNb. The QoS logical connections are provided between the Ue and the gateway enabling differentiation of Ip flows and meeting the requirements for low-latency applications.
A detach architecture optimized for multi-cell multicast and broadcast is provided, which consists of two logical nodes namely the multicast co-ordination entity (Mce) and the Mbms gateway. The Mce allocates radio resources as well as determines the radio configuration to be used by all eNbs in the Mbsfn area. The Mbms gateway broadcasts Mbms packets with the Sync protocol to each eNb transmitting the service. The Mbms gateway uses Ip multicast for forwarding Mbms user data to eNbs. The layer 2 and radio reserved supply operate protocols are designed to enable dependable delivery of data, ciphering, header compression and Ue power savings.
9. References
[1] 3Gppts 36.300 V8.4.0, Evolved Universal Terrestrial Radio way Network (E-Utra): wide Description.
[2] 3Gpp Ts 29.060 V8.3.0, Gprs Tunneling Protocol (Gtp) over the Gn and Gp Interface.
[3] Ietf Rfc 4960, Stream operate Transmission Protocol.
[4] Ietf Rfc 3095, Robust Header Compression (Rohc): Framework and Four Profiles: Rtp, Udp, Esp, and uncompressed.
[5] 3Gpp Ts 36.331 V8.1.0, Radio reserved supply operate (Rrc) Protocol Specification.
[6] 3Gpp Tr 23.882 V1.15.1, 3Gpp ideas Architecture Evolution (Sae): record on Technical Options and Conclusions.
