1 Wireless Networks Lecture 21 WCDMA (Part I) Dr. Ghalib A. Shah

2 Outlines  Last Lecture review  UMTS  Service Classes in UMTS  UTRAN Architecture  Radio Interface protocol Architecture  Protocol Models for UTRAN  Logical Channels

3 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

4 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

5 WCDMA Radio Fundamentals  WCDMA has emerged as most preferred and adopted technology for 3G air interface  The major differences between WCDMA and GSM are: ►5 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

6 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)

7  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, that has least stringent requirements of QoS

8 UTRAN and System Architecture

9  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

10 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

11 Radio Interface protocol architecture L3 Radio Resource Control (RRC) L2 Radio Link Control (RLC) L2 Medium Access Control (MAC) L1 Physical Layer

12  Layer 1 ►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 2 ►It has two main sub-layer RLC MAC

13 ►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 3 ►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

14  Layer 3 ►Contains sub-layers but RRC is the one that interact with layer 2 ►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

15  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.

16 Protocol Model for UTRAN  UTRAN protocol structure is based this model Trans. Of all user- specific data CS or PS through user plan For all signaling activities in the network, it includes RANAP, RNSAP, NBAP protocols

17 Logical Channels in WCDMA ChannelAbb.Functionality Broadcast Common Control channel (DL) BCCHTransmits the system control information Common Control channel (UL/DL) CCCHUsed (usually by UE) for transmitting info related to control between network and UE Common Traffic Channel (DL) CTCHUsed to transmit dedicated info to a group of UEs Dedicated Control Channel (UL/DL) DCCHDedicated channel for control related information between UEs and network Dedicated Traffic Channel (UL/DL) DTCHSimilar to DCCH except that it is used for user information Paging Control channel (DL) PCCHUsed to page info the UE

18 Summary  UMTS  Service Classes in UMTS  UTRAN Architecture  Radio Interface protocol Architecture  Protocol Models for UTRAN  Logical Channels  Next Lecture ►WCDMA