UMTS vs. LTE: a comparison overview

Transcription

1 UMTS vs. LTE: a comparison overview Unik4230: Mobile Communications Khai Vuong May 16, 2011

2 Agenda 3GPP Network Architecture UMTS LTE Radio Access Technologies WCDMA OFDMA Discussion

3 3GPP Standards (I) 1 3GPP: 3 rd Generation Partnership Project Version Released Info Release specified pre-3g GSM network Release Q1 specified the first version of UMTS, incorporating a CDMA air interface Release Q2 aka. Release 2000, added all-ip Core Network Release Q1 introduced IMS and HSDPA Release Q4 integrated operation with Wireless LAN networks and added HSUPA, MBMS, enhancements to IMS 1

4 3GPP Standards (II) 2 Version Released Info Release Q4 decreasing latency, improvements to QoS and real-time applications, HSPA+, NFC, EDGE Evolution. Release Q4 First LTE release. All-IP Network (SAE), new OFDMA, FDE and MIMO based radio interface. Release Q4 SAES Enhancements, Wimax and LTE/UMTS Interoperability Release Q1 LTE advanced 2

5 3GPP data evolution 3 3 Huawei Technologies Co., Ltd. 2009

6 User experience Type of services UMTS LTE Web surfing 8 seconds immediately Download 5MB music 3 minutes 1 second Download 750MB movie 6.5 hours 2.5 minutes Download HD video 2-3 days 15 minutes Video telephony Corporate VPN, Intranet Mobile TV On-demand TV Video-based mobile advertising... Table: Data services 4 4 Huawei Technologies Co., Ltd. 2009

7 Services for telecommunication systems 1. Teleservice: Information that transfered between end users, e.g speech service, messaging, emergency calls. 2. Bearer service: Different QoS classes for various type of traffic: Conversasional: voice, video, telephony, video gaming Streaming: multimedia, video on-demand, webcast Interactive: web browsing, network gaming, database access Background: , SMS, downloading

8 UMTS objectives 1. improvement in data performance, multimedia services and access to the Internet 2. new radio interface WCDMA 3. Core Network: connection function

9 Core Network for UMTS MSC:Mobile switching center, switch the CS transactions GMSC: Gateway MSC: a switch that connects the UMTS PLMN to the external CS networks. SGSN: Serving GPRS Support Node, similar to MSC/VLR but this is for PS traffic. GGSN: Gateway GPRS Support Node, similar to GMSC but it serves for the PS traffic.

10 LTE s objectives 5 1. higher data rates in both downlink and uplink transmission 2. reduce packet latency, more responsive user experience 3. flat architecture: IP-based, open interfaces, simplified network 4. flexible radio planning and high spectral efficiency 5. reduce delivery costs for rich communications 6. long-term revenue stability and growth 7. coexistence alongside circuit switched networks 5 UMTS Forum 2008

11 Why LTE? 6 GSM EDGE WCDMA HSPA LTE Non-3GPP technologies Figure: Flexible upgrade path Figure: Reduce pris per MB to remain profitable 6 Nokia Siemens Networks

12 UMTS vs. LTE Architecture Figure: Network architecture, simplified 7 LTE: simplified IP flat architecture BSC/RNC disappeared, functions transfer to enodeb All enodeb connect directly through X2 interface PS service only, voice over IP. 7 Image courtesy: UMTS Forum 2008

13 LTE s interfaces: S1 and X2 8 X2: connects enodeb MME (Mobility Management Entity): distribution of paging message to enodeb S1: self-optimizing network UPE (User Plan Entity): IP header compression, encryption of user data stream, termimating and switching of U-plane 8 Image courtesy: developer.att.com

14 Wideband CDMA Figure: Access technique for UMTS 9 9 Huawei Technologies Co., Ltd. 2009

15 CDMA: Principles each user is assigned a spreading code for encoding it s data Receiver knows the code of user, it can decode the received signal, recover the original data Bandwidth of coded data signal much larger than original data signal due to the encoding process spreads the spectrum of the origianl signal, based on spread-spectrum modulation

16 WCDMA in UMTS [4] Direct Sequence CDMA system, with chip-rate 3.84 Mc/s Combined with FDMA: every carrier is allocated 5 MHz frequency band so that many operators can provide services without interference each other. Codes: scrambling and channelization Channelization: seperates traffic to and from different users, called Orthogonal Variable Spreading Factor (OVSF) which varies from 1 to 128 Scrambling codes: not increase bandwidth, but is used for distinguishing terminals in uplink and sectors (cells) in downlink

17 LTE s downlink: OFDMA OFDM: Multiple access scheme, allows simultaneous connections to/from multiple mobile terminals Users share different subcarriers, either consecutive or distributed manner.

18 LTE s uplink: Single Carrier-FDMA SC-FDMA: hybrid modulation scheme that combines the low PAPR techniques of single-carrier transmission systems, such as GSM and CDMA, with the multi-path resistance and flexible frequency allocation of OFDMA Data symbols in the time domain are converted to the frequency domain using a discrete Fourier transform (DFT) Cyclic Prefix (CP) is added, a serial sequence of symbols is modulated and transmitted instead of parallel OFDM-scheme On receiver s side, an extra N-point IDFT is applied to reconstruct the original symbols. Figure: Structure for UL and DL in LTE [5] An advantage of SC-FDMA compares to OFDMA is low Peak to Power Average Ratio (PAPR), that helps increasing battery life.

19 References Ville Eerola, LTE Network Architecture Evolution, Lecture note in T Technology Management in the Telecommunications Industry, Helsinski University of Technology, UMTS Forum, Toward Global Mobile Broadband, retreived May 16, 2011from M. Neruda and R. Bestak, Evolution of 3GPP Core Network, IWSSIP Lecture notes in UniK 4230, UiO, Lecture9-10.pdf OFDM(A) for wireless communications, Telenor R&I R 7/2008

20 A brief comparision 10 Requirements UMTS LTE Spectral Efficiency 0.2bit/s/Hz 1.57bit/s/Hz Peak Data Rate 2 Mbit/s 170 Mbit/s Sector Capacity 1 Mbit/s 31.4 Mbit/s No. of Tranceivers/Cell 30 1 RTT User Plane 50 ms 5 ms Call setup time 2 s 50 ms Mobility 250 km/h 350 km/h Bandwidth 5 MHz scalable up to 20 MHz 10 UMTS/HSPA to LTE Migration, Motorola Inc. 2009

21 Discussion Point to discuss, focus on this topic, futher questions?