Wireless networks - Lecture 21: WCDMA (Part 1). The main topics covered in this chapter include: UMTS; service classes in UMTS; UTRAN architecture; radio interface protocol architecture; protocol models for UTRAN; logical channels;...
Wireless Networks Lecture 21 WCDMA (Part I) Dr Ghalib A Shah Outlines Last Lecture review UMTS Service Classes in UMTS UTRAN Architecture Radio Interface protocol Architecture Protocol Models for UTRAN Logical Channels Last Lecture Review Walsh Codes IS-95 Reverse Link EDGE Introduction Modulation and Coding Schemes Link Adaptation and Incremental Redundancy Capacity Planning Dynamic Abis pool UMTS UMTS networks have predominance of data traffic unlike GSM networks The data rate will be significantly higher than that offered by GSM / GPRS / EDGE 3G networks serve different purpose and thus the major changes from previous networks are ► Max user data rate up to 384 kbps ► Efficient handover between different operators and technologies e.g GSM and UMTS ► Ability to deliver at requested bandwidth ► Ability to deliver different services with the required quality WCDMA Radio Fundamentals WCDMA has emerged as most preferred and adopted technology for 3G air interface The major differences between WCDMA and GSM are: ► MHz channel bandwidth as compared to 200 KHz in GSM ► Packet data scheduling is load based unlike time slot based in GSM ► Theoretically only one f channel, while GSM uses many channels ► Quality control is done using RRM algorithm, while it was done by implementing frequency planning techniques in GSM ► Users/cell/channel are separated by codes unlike time or frequency in GSM Service classes in UMTS In 3G network, ME will be able to establish multiple connections simultaneously Network allows efficient cooperation between application with diverse quality of service requirements The quality can be defined by two main parameters ► Guaranteed and max bit rate possible (kbps) ► Permissible delay (ms) Based on the QoS criteria, multimedia services has been further classified ► Conversational • The most delay sensitive, e.g applications video telephony, VoIP ► Streaming • Flow which is steady and continuous, it is server to user ► Interactive • Web browsing is an example A user may request timetables of buses, trains or flight schedule ► Background • Short messages, file transfer, email that has least stringent requirements of QoS UTRAN and System Architecture USIM contains authentication information and associated algorithms, encryption and subscriber related information ME is user independent BS ► Also known as node B in WCDMA and is more complex than BS in GSM ► Its functions include handover channel management, baseband conversion, channel encoding and decoding, interfacing to other network elements Radio Network Controller Concerning one connection between UTRAN and one UE, the following roles of RNCs exist: ► Serving RNC that controls the connections to a UE ► Drift RNC that lends its resources of Serving RNC for a particular UE Each RNC also has the controlling RNC role towards its Node Bs 10 Radio Interface protocol architecture L3 L2 L2 L1 Radio Resource Control (RRC) Radio Link Control (RLC) Medium Access Control (MAC) Physical Layer 11 Layer ► The actual medium of transfer ► The main functions of this layer include RF processing, modulation/demodulation, multiplexing / demultiplexing of physical channels ► Error detection and correction, rate matching, power control, synchronization etc Layer ► It has two main sub-layer • RLC • MAC 12 ► MAC • Responsible for mapping logical channels to the transport channels • An interface between L1 & L3 and provides packet multiplexing / demultiplexing • Measurement related to traffic volume on logical channels and reporting to layer ► RLC • Segmentation reassembly of variable size data packets • Error correction by retransmission and ACKed data transfer mode • Controlling rate flow, concatenation, cyphering and preservation of higher-order PDUs • Operates in three mode as in GPRS 13 Layer ► Contains sub-layers but RRC is the one that interact with layer ► Handles control plane signaling between UE and network in connected mode ► Responsible for bearer functions like establishment, release, maintenance and reconfiguration in the user plane and of radio resources in control plane ► Functions of RRC include radio resource management and mobility management, as well as power control, routing and paging 14 Two other layers ► Packet data convergence protocol (PDCP) • Major functions being compression of PDU at transmitting end and decompression at receiving end in all of three modes of RLC ► Broadcast – Multicast Control (BMC) • Functions only in transparent and unACKed modes providing broadcast/multicast scheduling and transmission of user data 15 Protocol Model for UTRAN UTRAN protocol structure is based this model For all signaling activities in the network, it includes RANAP, RNSAP, NBAP protocols Trans Of all userspecific data CS or PS through user plan 16 Logical Channels in WCDMA Channel Abb Functionality Broadcast Common Control channel (DL) BCCH Transmits the system control information Common Control channel (UL/DL) CCCH Used (usually by UE) for transmitting info related to control between network and UE Common Traffic Channel CTCH (DL) Used to transmit dedicated info to a group of UEs Dedicated Control Channel (UL/DL) DCCH Dedicated channel for control related information between UEs and network Dedicated Traffic Channel (UL/DL) DTCH Similar to DCCH except that it is used for user information Paging Control channel (DL) PCCH Used to page info the UE 17 Summary UMTS Service Classes in UMTS UTRAN Architecture Radio Interface protocol Architecture Protocol Models for UTRAN Logical Channels Next Lecture ► WCDMA 18 ... unlike GSM networks The data rate will be significantly higher than that offered by GSM / GPRS / EDGE 3G networks serve different purpose and thus the major changes from previous networks are... with the required quality WCDMA Radio Fundamentals WCDMA has emerged as most preferred and adopted technology for 3G air interface The major differences between WCDMA and GSM are: ► MHz channel...Outlines Last Lecture review UMTS Service Classes in UMTS UTRAN Architecture Radio Interface protocol Architecture Protocol Models for UTRAN Logical Channels Last Lecture Review