Chapter: 3G Evolution 8 WCDMA evolution: HSPA and MBMS Isael Diaz isael.diaz@eit.lth.se Department of Electrical and Information Technology 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 1
Outline Evolution HSPA and MBMS Multiple Access Direct Sequence Spread Spectrum Network Architecture Protocol Architecture Physical Layer Channelization Codes Asynchronous Operation Power Control Soft handover Packet Data Session 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 2
WCDMA: Evolution - MBMS Multimedia broadcast Multicast Services - Introduction of improved broadcast servicios ('Mobile TV') Enhanced uplink improved Uplink packet-data support - Reduced delays - 5.74 Mbps peak data rate - ~2xR99 capacity HSDPA -improved downlink packet-data support -Reduced delays - 14Mbits/s peak data rate ~3xR99 capacity - MIMO and higher-order modulation - 28 Mbps DL peak data rate - 11 Mbps UL peak data rate - Continuous Packet Connectivity - 'Always on' user experience *Image inspired 3G evolution HSPA and LTE Mobile Broadband 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 3
WCDMA: HSPA and MBMS HSPA (More details in further chapters) Evolution of WCDMA 14Mbps in DL 5.8Mbps in UL MBMS (Further explanation in Chapter 12) Enables broadcasting services such as TV, radio, traffic reports, etc. 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 4
WCDMA: Multiple Access CDMA Multiple users share physical medium in time and frequency Based on interference robustness All user have same carrier frequency Each user has a unique code Benefits from multi path environment *Image courtesy of Ericsson AB 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 5
WCDMA: DS-SS Direct Sequence Spread Spectrum Same carrier frequency Looks like noise if correct spreading code is not used To recover the transmitter signal the receiver needs the spreading code *Image courtesy of Ericsson AB 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 6
WCDMA: Network Architecture *Image inspired 3G evolution HSPA and LTE Mobile Broadband An UE communicates with one or more NodeBs NodeB is responsible for FEC Modulation Spreading RNC in charge of Control of one or more NodeBs Charge of call set up QoS Radio resources (ARQ) 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 7
WCDMA: Protocol Architecture PDCP Performs header compression RLC IP packet segmentation ARQ protocol MAC Interfaces logical channels and transport channels PHY Coding, spreading, modulation, etc. *Image inspired 3G evolution HSPA and LTE Mobile Broadband 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 8
WCDMA: Physical Layer 3.84Mchip/s Turbo coder 1/3 QPSK for DL BPSK for UL Every specific spreading codes corresponds to a each physical channel CPICH reference channel for DL *Image inspired 3G evolution HSPA and LTE Mobile Broadband 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 9
WCDMA: Channelization Codes (OVSF) Mutual orthogonality OVSF must be selected from different branches Different OVSF provide different spreading factors Different Spreading factors provide different data-rates Spreading factor is selected by the MAC layer Some channelization codes are pre-allocated (CPICH, cell specific information, etc) *Image inspired 3G evolution HSPA and LTE Mobile Broadband 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 10
WCDMA: Asynchronous Operation WCDMA does not require inter-base station synchronization (no GPS dependency) Advantage Reduced deployment efforts Drawback BS interference to other BS More challenging cell-search procedure Complicated handover implementation 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 11
WCDMA: Power control Formally named fast closed/closed loop power control Attempts to avoid the near-far problem by: measuring the UE signal 1500 times/sec Regulating the transmission power of both UE and BS 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 12
WCDMA: Soft handover The UE communicates with multiple cells simultaneously (active set) The RNC determines based on measurements which cells are part of the active set Provides diversity against fast fading in both DL and UL Typically a rake receiver is used Or of the downs ensures that average power is kept low *Image is courtesy of Ericsson AB 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 13
WCDMA: Packet Data Session UE: Cell search (connection request) RNC: Channelization codes available RNC: Interference level RNC Connection established Transmission power varies according to traffic pattern *Image inspired Ove Edfors, lecture on WCDMA 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 14
WCDMA: Summary HSPA is the evolution of WCDMA Spread Spectrum A major milestone in mobile telecommunication Flexible radio interface Transmission power dependent on traffic pattern Sensitive to inter-cell interference Sensitive to near-far problem 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 15
Thank you for your attention 02-Apr-2009 3G Evolution - HSPA and LTE for Mobile Broadband 16