02 Huawei WCDMA UTRAN Interface and Signaling Procedure
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OWA210001 WCDMA UTRAN Interface and Signaling Procedure
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Upon completion of this course, you will be able to:
Understand UTRAN interface and structure
Understand the definitions about UTRAN network elements
Understand UTRAN signaling procedure
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Chapter 1 UTRAN Network OverviewChapter 1 UTRAN Network Overview
Chapter 2 Basic Concepts about UTRANChapter 2 Basic Concepts about UTRAN
Chapter 3 UTRAN Signaling ProcedureChapter 3 UTRAN Signaling Procedure
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The Position of UTRAN in WCDMA Network
Service manager layer
Service convergence layer
Radio access layer
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UTRANUTRAN UMTS Terrestrial Radio Access NetworkUMTS Terrestrial Radio Access NetworkCNCN Core NetworkCore NetworkUEUE User EquipmentUser Equipment
WCDMA network architecture shown in slide aboveUE (User Equipment)The User Equipment (UE) consists of two parts:1.The mobile equipment (ME) is the radio terminal used for radio communication over the Uu interface2. The UMTS Subscriber Identity Module (USIM) is the equivalent smartcard to SIM in GSM. It hold the subscriber identity , performs authentication algorithm , stores authentication and encryption keys ,etc.UTRAN (UMTS Terrestrial Radio Access network) The UTRAN consists of one or several Radio Network Subsystem ( RNS ) ,each containing one RNC and one or several NodeB1.NodeBThe NodeB is the correspondent element to the BTS in GSM. 2.RNCThe Radio Network Controller (RNC) owns and controls the radio resources of the connected NodeBCN (Core Network)Core network (CN) includes a lot of equipments such as MSC ,HLR, SGSN,GGSN,AUC,VLR etc.InterfaceIu interfaceThe Iu interface connects the UTRAN to the CN and is split in two parts. The Iucs is the interface between the RNC and the circuit switched domain of the CN. The Iups interface is the interface between the RNC and the packet switched domain of the CNUu interfaceThe Uu interface is the WCDMA radio interface with in UMTS. It is the interface through which the UE accesses the fixed part of the network.
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Node B Node B Node B Node B
Iub IubIub Iub
UTRAN (UMTS Terrestrial Radio Access network) struc ture
The UTRAN consists of one or several Radio Network Subsystem ( RNS ) ,each containing one RNC and one or several NodeB
The Iu interface connects the UTRAN to the CN and is split in two parts. The Iucsis the interface between the RNC and the circuit switched domain of the CN. The Iups interface is the interface between the RNC and the packet switched domain of the CN
The Uu interface is the WCDMA radio interface with in UMTS. It is the interface through which the UE accesses the fixed part of the network.
The Iub interface connects the NodeB and the RNC. Contrarily to GSM, this interface is fully open in UMTS and thus more competition is expected
This RNC-RNC interface was initially designed in order to provide inter RNC soft handover, but more features were added during the development
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C-plane signalling U-plane information
The radio interface (Uu) is layered into three protocol layers:
the physical layer (L1)the data link layer (L2)the network layer (L3).
The layer 1 supports all functions required for the transmission of bit streams on the physical medium. It is also in charge of measurements function consisting in indicating to higher layers, for example, Frame Error Rate (FER), Signal to Interference Ratio (SIR), interference power, transmit power, It is basically composed of a layer 1 managemententity, a transport channel entity, and a physical channel entity.The layer 2 protocol is responsible for providing functions such as mapping, ciphering, retransmission and segmentation. It is made of four sublayers: MAC (Medium Access Control), RLC (Radio Link Control), PDCP (Packet Data Convergence Protocol) and BMC (Broadcast/Multicast Control). The layer 3 is split into 2 parts: the access stratum and the non access stratum. The access stratum part is made of RRC (Radio Resource Control) entity and duplication avoidance entity. The non access stratum part is made of CC, MM parts.Not shown on the figure are connections between RRC and all the other protocol layers (RLC, MAC, PDCP, BMC and L1), which provide local inter-layer control services.The protocol layers are located in the UE and the peer entities are in the node B or the RNC.`
The radio interface (Uu) is spitted into 2 plane, left is control plane ,right is user plane ,control plane transfer control massage such as signalling, measurement control. User plane transfer user data such as speech ,packet data etc.
Many functions are managed by the RRC layer . Here is the list of the most important:Establishment, re-establishment, maintenance and rel ease of an RRC connection between the UE and UTRAN : it includes an optional cell re-selection, an admission control, and a layer 2 signaling link establishment. When a RNC is in charge of a specific connection towards a UE, it acts as the Serving RNC.Establishment, reconfiguration and release of Radio Bearers : a number of Radio Bearers can be established for a UE at the same time. These bearers are configured depending on the requested QoS. The RNC is also in charge of ensuring that the requested QoS can be met.Assignment, reconfiguration and release of radio re sources for the RRC connection : it handles the assignment of radio resources (e.g. codes, shared channels). RRC communicates with the UE to indicate new resources allocation when handovers are managed.Paging/Notification : it broadcasts paging information from network to UEs.Broadcasting of information provided by the non-access stratum (Core Network) or access Stratum. This corresponds to system information regularly repeated.
The radio interface (Uu) is layered into three protocol layers:
UE measurement reporting and control of the reportin g: RRC indicates what to measure, when and how to report.Outer loop power control : controls setting of the target values.Control of ciphering : provides procedures for setting of ciphering.
The RRC layer is defined in the 25.331 specification from 3GPP.
The RLCs main function is the transfer of data from either the user or the control plane over the Radio interface. Two different transfer modes are used: transparent and non-transparent. In non-transparent mode, 2 sub-modes are used: acknowledged or unacknowledged .RLC provides services to upper layers:
data transfer (transparent, acknowledged and unacknowledged modes),QoS setting : the retransmission protocol (for AM only) shall be configurable by layer 3 to provide different QoS,notification of unrecoverable errors : RLC notifies the upper layers of errors that cannot be resolved by RLC.
The RLC functions are:
mapping between higher layer PDUs and logical channels,ciphering : prevents unauthorized acquisition of data; performed in RLC layer for non-transparent RLC mode,segmentation/reassembly : this function performs segmentation/reassembly of variable-length higher layer PDUs into/from smaller RLC Payload Units. The RLC size is adjustable to the actual set of transport formats (decided when service is established). Concatenation and padding may also be used,error correction : done by retransmission (acknowledged data transfer mode only),flow control : allows the RLC receiver to control the rate at which the peer RLC transmitting entity may send information.
MAC services include: Data transfer : service providing unacknowledged transfer of MAC SDUs between peer MAC entities.Reallocation of radio resources and MAC parameters : reconfiguration of MAC functions such as change of identity of UE. Requested by the RRC layer.Reporting of measurements : local measurements such as traffic volume and quality indication are reported to the RRC layer.
The functions accomplished by the MAC sublayer are listed above. Heres a quick explanation for some of them:
Priority handling between the data flows of one UE : since UMTS is multimedia, a user may activate several services at the same time, having possibly different profiles (priority, QoS parameters...). Priority handling consists in setting the right transport format for a high bit rate service and for a low bit rate service.Priority handling between UEs : use for efficient spectrum resources utilization for bursty transfers on common and shared channels.Ciphering: to prevent unauthorized acquisition of data. Performed in the MAC layer for transparent RLC mode.Access Service Class (ACS ) selection for RACH transmission : the RACH resources are divided between d