1 3G and 4G Cellular Standards Prof. Jeffrey G. Andrews The University of Texas at Austin November 5, 2008 2 Outline ? Overview of Cellular Standards ? Qualcomm and the 3GPP2 Standards ? UMTS/3GPP 3rd Generation Standards ? Wideband CDMA (WCDMA) ? HSPA ? 4th Generation Standards ? IEEE 802.16/WiMAX ? 3GPP LTE ? Performance Predictions 3 The Cellular Family Tree IS-95 Cdma2000 HSPA W-CDMA IS-95B EDGE GPRS IS-136 GSM EVDO 2G 2.5G 3G 3GPP 3GPP2 4G UMB LTE 802.16e WiMAX 4.5G? 802.16m LTE Advanced 4 Acronyms Worldwide Interoperability for Microwave Access WiMAX High Speed Downlink [Uplink] Packet Access HSD[U]PA High Speed Packet Service HSPA Wideband CDMA WCDMA Multi Input Multi Output (refers to multiple antennas usually) MIMO Enhanced Data rates for GSM Evolution EDGE Gaussian Minimum Shift Keying GMSK General Packet Radio Service GPRS 3rd Generation Partnership Project 2 3GPP2 Global System Mobile GSM 3rd Generation Partnership Project 3GPP Ultra Mobile Broadband UMB Universal Mobile Telephone System UMTS Evolution Data Only/Optimized EVDO Long Term Evolution LTE Interim Standard 95 IS-95 5 3GPP2 Standards Body ? Dominated by Qualcomm ? IS-95 – First commercial CDMA standard, developed by Qualcomm, ratified in 1995 ? Still forms basis for CDMA voice access ? 1.23 MHz of bandwidth ? Total spreading factor of 128 (full-rate voice) ? EVDO (Evolution Data "Optimized") ? Developed in 1999 as "HDR" ? Hybrid TDMA/CDMA system, works in 1.23 MHz 6 The IS-95 Forward Link Walsh codes (SF = 64) used to separate users PN codes only used for data randomization 7 The IS-95 Reverse Link Add CRC Add 8 tail bits Conv Code Rate 1/3 K = 9 OR Rate 1/2 K=9 Symbol Repetition Block Interleaver 8.6 kbps 4.0 kbps 2.0 kbps 0.8 kbps 9.6 kbps 4.8 kbps 2.4 kbps 1.2 kbps 28.8 ksps 14.4 ksps 7.2 ksps 3.6 ksps 28.8 ksps 14.4 kbps 7.2 kbps 3.6 kbps 1.8 kbps 13.35 kbps 6.25 kbps 2.75 kbps 1.05 kbps 64-ary Orthogonal Modulator Data Burst Randomizer Long Code Generator B 1.2288 Mcps 1.2288 Mcps s(t) B Baseband Filter X I-channel PN sequence 1.2288 Mcps Q-channel PN sequence 1.2288 Mcps cos (2π f t) Baseband Filter X Σ sin (2π f t) D 1/2 PN Chip Delay = 406.9 ns Long PN codes (SF = 4) used to separate users Most of "spreading" is actually error correction: Conv Codes + 6/64 rate Orthogonal Modulation 307.2 ksps 8 Evolution Data Optimized (EVDO) Key Aspects ? CDMA (16-ary Walsh Codes) ? Multicode, each user can use 1-16 codes (see table) ? TDMA also, usually with Proportional Fair Scheduling ? Adaptive modulation and coding (see table) ? Alamouti OSTBC 16 QAM 1/3 2 1.228.8 16 QAM 1/3 1 2457.6 8-PSK 1/3 1 1843.2 8-PSK 1/3 2 921.6 QPSK 1/3 1 1228.8 QPSK 1/3 2 614.4 QPSK 1/3 4 307.2 QPSK 1/3 1 614.4 QPSK 1/5 2 307.2 QPSK 1/5 4 153.6 QPSK 1/5 8 76.8 QPSK 1/5 16 38.4 Modulation Code Rate Users per Slot Rate (kbps) 9 3GPP2 Status ? Has approximately 500 million subscribers ? Most in US and N. America, but also S. Korea, Brazil, India, a few other places ? IS-95/cdma200 voice capacity is about 60/sector ? Turns out, it's downlink limited! (A surprise) ? Only 64 Walsh Codes, some are overhead ? The future is not clear: most 3GGP2 operators seem to be migrating to LTE 10 The UMTS/3GPP Standards ? Largest global standards body ? GSM ? 200 KHz channel spacing (symbol rate = 270 KHz!) ? GMSK (binary) modulation ? Rate ? Conv. Codes (v = 5) ? 8 slots per 4.615 msec frame ? Guardtime + windowing = 52 usec/slot (9% overhead) ? WCDMA and HSPA ? 5 MHz spacing (symbol rate = 3.84 KHz) ? Variable rate and spreading factors ? LTE "Long Term Evolution" ? Radical departure from 3G ? Details on HSPA and LTE later in the presentation HSPA W-CDMA EDGE GPRS IS-136 GSM LTE LTE Advanced 11 WCDMA and HSPA ? WCDMA and HSPA are largely compatible and complimentary ? WCDMA is quite similar to IS-95 and cdma2000. Some distinctions: ? Generally more complicated block diagram ? Reverse link pilot on Q channel ? Wider choice of rates/spreading factors ? Multi-code possible (a user takes more than one code to increase their data rate) ? Alamouti-style space-time coding generally used 12 High Speed Packet Access (HSPA) ? Release 5 = HSDPA ? High speed access added for downlink ? 14.4 Mbps advertised peak ? 3.6/7.2 Mbps typically supported ? 1.8 Mbps/3.6 Mbps supported by handsets today ? Release 6 = HSUPA ? Uplink brought closer to downlink speeds ? 5.8 Mbps advertised peak ? 1.4 Mbps typically supported ? Release 7 = HSPA or HSPA+ ? Even higher speeds promised on both links in same 5 MHz bandwidth via MIMO, 64QAM, no coding ? 28 Mbps DL, 11.5 Mbps UL ? Questionable whether these rates are practically viable or if demand exists 13 HSDPA – How it Works ? Quite similar to EVDO ? SF = 16 Walsh Codes ? Can use 5, 10, or 15 codes at a time ? Using just 1 = WCDMA ? 1 channel is reserved for overhead ? Turbo codes ? r ? Adaptive Modulation ? QPSK and 16QAM Design Choices and Issues ? SF = 16 helps with multipath, but equalizer often still needed ? Receivers can actually be more complex than in LTE ? Primary multiple access is TDMA ? Proportional Fair scheduling is the norm 14 ? GSM is ubiquitous ? Most Providers Pretty Far Along on WCDMA Transition ? e.g. "3G iPhone" ? HSPA family based on WCDMA, used for data ? HSDPA is widely deployed ? HSUPA currently being deployed ? Typical User Experience ? 500 kbps-2 Mbps DL ? 500 kbps-1 Mbps UL ? 100-200ms ping delays HSDPA '08-'09 7,200 725 425 GPRS '02-'03 48 30 40 EDGE '03-'04 237 120 80 UMTS '04-'05 384 200 150 HSDPA '06-'07 3,600 700 400 Assumptions: GPRS: 4-TSL/User limited to CS-2 Max EDGE: 4-TSL/User Max UMTS (R99): 384 kbit/s Max HSDPA (R6): Category 6 UE Max (5 codes) HSDPA (R6): Category 7 UE Max (10 codes) Average User Throughput (kbps) Peak Radio Throughput (kbps) Mobile Data Throughput (kbps) UMTS 3G – Current Status 15 4th Generation Standards ? There is still some debate about what 4G actually is ? Key Attributes of 4th Generation Standards ? Data rates and supportable bandwidths much higher in both "theory" and reality than 3G ? IP-based rather than circuit switched ? This has a significant impact on voice ? In practice, common distinguishing features vs. 3G include: ? Multicarrier (OFDM) based physical layer ? OFDMA MAC layer with time-frequency scheduling ? All IP ? Aggressive multi-antenna technologies supported ? Variable bandwidth, up to 20 MHz 16 Evolution of WiMAX ? The 802.16 Standard Family ? 1998: IEEE formed 802.16 group to develop a standard for a wireless metropolitan area network (MAN) – primary interest was fixed wireless access ? First 10–66 GHz band considered; later modified to work in 2– 11GHz to enable NLOS (802.16a) ? 2004: IEEE 802.16-2004 standard ratified, subsuming 802.16, 802.16a, 802.16c ? First 802.16-2004 product certified in Jan. 2006 ? Dec. 2005: 802.16e completed, to allow mobility applications and scalability in 2–6 GHz ? Vision has changed a lot in the last 10 years ? Started as fixed broadband, now is really the first 4G standard 17 802.16 and WiMAX ? The 802.16 standards have very broad scope, millions of incompatible options ? The WiMAX forum defines commercial "profiles" of options, frequency bands, etc. ? Similar to the Wi-Fi Alliance ? Promotes interoperability of products through testing and certification ? The WiMAX forum has 15 Board members (companies), ~150 Principal members, 300+ Regular members 18 Current Certification Profiles ? Global Spectrum Availability is a key challenge for WiMAX ? Range vs. Cost/Availability tradeoff ? Would prefer lower frequencies like 700 MHz, but expensive and scarce Band Index Frequency Channel Bandwidth FFT Size Duplexing Fixed WiMAX Profiles 1 3.5 GHz 3.5 MHz 256 FDD 3.5 MHz 256 TDD 7 MHz 256 FDD 7MHz 256 TDD 2 5.8 GHz 10 MHz 256 TDD Mobile WiMAX Rel 1.0 Profiles 1 2.3 - 2.4 GHz 5 MHz 512 TDD 10 MHz 1024 TDD 8.75 MHz 1024 TDD 2 2.305 - 2.320 & 2.345 - 2.360 GHz 3.5 MHz 512 TDD 5 MHz 512 TDD 10 MHz 1024 TDD 3 2.496 - 2.690 GHz 5 MHz 512 TDD 10 MHz 1024 TDD 4 3.3 - 3.4 GHz 5 MHz 512 TDD 10 MHz 1024 TDD 5 3.4 - 3.8 GHz 5 MHz 512 TDD 7 MHz 1024 TDD 10 MHz 1024 TDD Mobile WiMAX Rel 1.5 Profiles 6 1.710 - 1.755 & 2.110 - 2.155 GHz 5 MHz 512 FDD 10 MHz 1024 FDD 7 776 - 787 MHz 788 - 793 793 - 798 5 MHz 512 FDD 10 MHz 1024 FDD 698 - 862 MHz 5 MHz 512 TDD 10 MHz 1024 TDD 19 WiMAX Physical Layer ? IFFT size is most commonly 1024 ? Turbo codes are used with r = ? and ? ? Symbol Mapper is for QPSK, 16QAM, 64QAM ? Many possible MIMO modes ? Mobiles required to have two antennas ? Alamouti 2 x 2 is starting point, more aggressive techniques soon Subcarrier Allocation + Pilot Insertion Subcarrier Allocation + Pilot Insertion D/A D/A Antenna 1 Antenna 2 IFFT IFFT Channel Encoder + Rate Matching Interleaver Symbol Mapper Space Time Encoder Channel Encoder + Rate Matching Interleaver Symbol Mapper Space Time Encoder Channel Encoder + Rate Matching Interleaver Symbol Mapper Space Time Encoder Burst # 1 Burst # 2 Burst # N 20 OFDM Subcarrier Allocation ? In WiMAX multiple subcarriers are grouped together to create what is called a sub-channel. Usually consists of 48 data subcarriers. Distributed Subcarrier Each sub-channel consists of subcarriers that are distributed throughout the channel bandwidth. Provides better frequency diversity which is beneficial at higher speeds. Adjacent Subcarrier Each sub-channel consists of subcarriers adjacent to each other. Provides better multi user diversity and is useful for closed loop multi-antenna techniques. B 2 ? B 2 B 2 ? B 2 User 1 Channel User 2 Channel B 2 ? B 2 B 2 ? B 2 21 Comparison of distributed vs. adjacent ? Band AMC (adjacent allocation) exploits multi-user diversity and frequency selectivity by allocating each resource to a user with high SINR ? Requires timely channel quality feedback (CQI) ? At high vehicular speeds, this CQI quickly becomes obsolete ? Distributed or permuted subcarrier assignment (known as PUSC) is more robust to mobility, averages the channel in frequency 22 Burst Profiles, Mapping Messages, Frame Structure ? DL-MAP and UL-MAP messages specify ? Subcarriers allocation to each mobile in the DL and UL ? Burst (AMC) profile: what coding type/rate and constellation to use: 802.16e has a staggering 52 different profiles frame 'n' frame 'n+1' DL sub-frame UL sub-frame DL-MAP UL-MAP Ranging?Subchannel 23 3GPP's Long Term Evolution (LTE) ? LTE is technically 3GPP release 8 ? Recall that HSPA+ was release 7 ? It is however a radical departure, much more similar to WiMAX than to HSPA ? Standard is not quite finalized as of Nov. 2008, but most key elements are S/P S/P S/P IFFT Add cyclic prefix USER 1 USER 2 USER 3 Downlink Physical Layer 24 Key Features of LTE ? LTE also has scalable OFDMA physical layer for the DL ? LTE uses SC-FDMA (single carrier FDMA) in the UL ? Flat IP architecture ? Variable bandwidth: 1.4, 3, 5, 10, 15, or 20 MHz ? Multi-antenna techniques such as transmit diversity, open loop MIMO, closed loop MIMO ? Resource block is 7 OFDM symbols (in time) by 12 subcarriers ? Dedicated control channels rather than mapping messages are used to assign resources ? Persistent allocation for VoIP (big win for voice capacity) ? 10 msec frame and 1 msec sub-frame for FDD and TDD ? The 1 msec subframe allows for much faster feedback and ARQ 25 SC-FDMA in LTE Uplink DFT IFFT Add cyclic prefix DFT IFFT Add cyclic prefix USER 1 USER 2 SCFDMA has lower peak to average power ratio in the time domain compared to OFDMA. SCFDMA has higher peak to average power ratio in the frequency domain compared to OFDMA (more out of band emissions) 26 LTE Status ? Standard is still being "finalized" but chipsets already in production ? Demonstrations by Ericsson, Samsung and others ? Has pretty well squashed Qualcomm's UMB, seems poised to dominate 4G cellular standards ? Commercial solutions available in 2010/2011 ? Widespread commercial service probably not until about 2012 ? Operators need to recover massive investment in 3G networks before replacing them ? WiMAX seems best positioned for emerging markets, since is available now 27 Comparison and Summary No Yes Turbo Codes r =1/3,1/5 QPSK, 8PSK, 16QAM No 1 Alamouti STBCs 1.667 msec (slot) 1.23 MHz FDD CDMA/TDMA DSSS CDMA/TDMA Direct Sequence Spread Spectrum EVDO WiMAX LTE HSDPA Modulation DL OFDM OFDM Direct Sequence Spread Spectrum (DSSS) Multiple Access DL OFDMA OFDMA CDMA/TDMA Modulation UL OFDM SCFDMA DSSS Multiple Access UL OFDMA SC-FDMA CDMA/TDMA Duplexing TDD FDD/TDD FDD Channel Bandwidth Scalable 3.5, 5, 7, 8.75, 10 MHz Scalable 1.4, 3, 5, 10, 15, 20 MHz 5 MHz Frame Length (feedback interval) 5 msec 1 msec 2 msec MIMO Schemes Tx Diversity, OL MIMO, AAS Tx Diversity, OL MIMO, CL MIMO Alamouti STBCs CL MIMO Maximum MIMO Rank 2 4 2 Multicodeword MIMO No Yes Yes Modulation QPSK, 16QAM, 64QAM QPSK, 16QAM, 64QAM QPSK, 16QAM, 64QAM Channel Coding Convolutional,Turbo and RS Codes r = ? , 2/3, ?, 5/6 Turbo Codes r = 1/3, 1/2, 3/4, 1 Turbo Codes r HARQ Yes Yes Yes Persistent Scheduling No* Yes No 28 Performance Predictions Disclaimer: these are based on private simulations and no guarantees are made to their accuracy. Different models may result in different values. 29 Spectral Efficiency Comparison Results shown at 2.1 GHz with 1 km cell radius and 20 dB in building loss Downlink Uplink 30 Typical Data Rate Comparison Theoretical peak data rate Typical data rate range HSDPA 5 MHz FDD LTE 10 MHz FDD WiMAX 10 MHz TDD All MS are equipped with dual antennas in the DL 31 Voice Capacity (20 MHz spectrum) HSDPA – 2005 numbers are for circuit switched voice over Rel .99 bearer 32 Acknowledgments ? Thanks to the following people for furnishing some of the information and material used in this presentation ? Arunabha Ghosh (AT&T Labs) ? Avneesh Agrawal (Qualcomm) ? Robert Heath (UT Austin)
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1 3G and 4G Cellular Standards Prof. Jeffrey G. Andrews The University of Texas at Austin November 5, 2008 2 Outline ? Overview of Cellular Standards ? Qualcomm and the 3GPP2 Standards ? UMTS/3GPP 3rd Generation Standards ? Wideband CDMA (WCDMA) ? HSPA ? 4th Generation Standards ? IEEE 802.16/WiMAX ? 3GPP LTE ? Performance Predictions 3 The Cellular Family Tree IS-95 Cdma2000 HSPA W-CDMA IS-95B EDGE GPRS IS-136 GSM EVDO 2G 2.5G 3G 3GPP 3GPP2 4G UMB LTE 802.16e WiMAX 4.5G? 802.16m LTE Advanced 4 Acronyms Worldwide Interoperability for Microwave Access WiMAX High Speed Downlink [Uplink] Packet Access HSD[U]PA High Speed Packet Service HSPA Wideband CDMA WCDMA Multi Input Multi Output (refers to multiple antennas usually) MIMO Enhanced Data rates for GSM Evolution EDGE Gaussian Minimum Shift Keying GMSK General Packet Radio Service GPRS 3rd Generation Partnership Project 2 3GPP2 Global System Mobile GSM 3rd Generation Partnership Project 3GPP Ultra Mobile Broadband UMB Universal Mobile Telephone System UMTS Evolution Data Only/Optimized EVDO Long Term Evolution LTE Interim Standard 95 IS-95 5 3GPP2 Standards Body ? Dominated by Qualcomm ? IS-95 – First commercial CDMA standard, developed by Qualcomm, ratified in 1995 ? Still forms basis for CDMA voice access ? 1.23 MHz of bandwidth ? Total spreading factor of 128 (full-rate voice) ? EVDO (Evolution Data "Optimized") ? Developed in 1999 as "HDR" ? Hybrid TDMA/CDMA system, works in 1.23 MHz 6 The IS-95 Forward Link Walsh codes (SF = 64) used to separate users PN codes only used for data randomization 7 The IS-95 Reverse Link Add CRC Add 8 tail bits Conv Code Rate 1/3 K = 9 OR Rate 1/2 K=9 Symbol Repetition Block Interleaver 8.6 kbps 4.0 kbps 2.0 kbps 0.8 kbps 9.6 kbps 4.8 kbps 2.4 kbps 1.2 kbps 28.8 ksps 14.4 ksps 7.2 ksps 3.6 ksps 28.8 ksps 14.4 kbps 7.2 kbps 3.6 kbps 1.8 kbps 13.35 kbps 6.25 kbps 2.75 kbps 1.05 kbps 64-ary Orthogonal Modulator Data Burst Randomizer Long Code Generator B 1.2288 Mcps 1.2288 Mcps s(t) B Baseband Filter X I-channel PN sequence 1.2288 Mcps Q-channel PN sequence 1.2288 Mcps cos (2π f t) Baseband Filter X Σ sin (2π f t) D 1/2 PN Chip Delay = 406.9 ns Long PN codes (SF = 4) used to separate users Most of "spreading" is actually error correction: Conv Codes + 6/64 rate Orthogonal Modulation 307.2 ksps 8 Evolution Data Optimized (EVDO) Key Aspects ? CDMA (16-ary Walsh Codes) ? Multicode, each user can use 1-16 codes (see table) ? TDMA also, usually with Proportional Fair Scheduling ? Adaptive modulation and coding (see table) ? Alamouti OSTBC 16 QAM 1/3 2 1.228.8 16 QAM 1/3 1 2457.6 8-PSK 1/3 1 1843.2 8-PSK 1/3 2 921.6 QPSK 1/3 1 1228.8 QPSK 1/3 2 614.4 QPSK 1/3 4 307.2 QPSK 1/3 1 614.4 QPSK 1/5 2 307.2 QPSK 1/5 4 153.6 QPSK 1/5 8 76.8 QPSK 1/5 16 38.4 Modulation Code Rate Users per Slot Rate (kbps) 9 3GPP2 Status ? Has approximately 500 million subscribers ? Most in US and N. America, but also S. Korea, Brazil, India, a few other places ? IS-95/cdma200 voice capacity is about 60/sector ? Turns out, it's downlink limited! (A surprise) ? Only 64 Walsh Codes, some are overhead ? The future is not clear: most 3GGP2 operators seem to be migrating to LTE 10 The UMTS/3GPP Standards ? Largest global standards body ? GSM ? 200 KHz channel spacing (symbol rate = 270 KHz!) ? GMSK (binary) modulation ? Rate ? Conv. Codes (v = 5) ? 8 slots per 4.615 msec frame ? Guardtime + windowing = 52 usec/slot (9% overhead) ? WCDMA and HSPA ? 5 MHz spacing (symbol rate = 3.84 KHz) ? Variable rate and spreading factors ? LTE "Long Term Evolution" ? Radical departure from 3G ? Details on HSPA and LTE later in the presentation HSPA W-CDMA EDGE GPRS IS-136 GSM LTE LTE Advanced 11 WCDMA and HSPA ? WCDMA and HSPA are largely compatible and complimentary ? WCDMA is quite similar to IS-95 and cdma2000. Some distinctions: ? Generally more complicated block diagram ? Reverse link pilot on Q channel ? Wider choice of rates/spreading factors ? Multi-code possible (a user takes more than one code to increase their data rate) ? Alamouti-style space-time coding generally used 12 High Speed Packet Access (HSPA) ? Release 5 = HSDPA ? High speed access added for downlink ? 14.4 Mbps advertised peak ? 3.6/7.2 Mbps typically supported ? 1.8 Mbps/3.6 Mbps supported by handsets today ? Release 6 = HSUPA ? Uplink brought closer to downlink speeds ? 5.8 Mbps advertised peak ? 1.4 Mbps typically supported ? Release 7 = HSPA or HSPA+ ? Even higher speeds promised on both links in same 5 MHz bandwidth via MIMO, 64QAM, no coding ? 28 Mbps DL, 11.5 Mbps UL ? Questionable whether these rates are practically viable or if demand exists 13 HSDPA – How it Works ? Quite similar to EVDO ? SF = 16 Walsh Codes ? Can use 5, 10, or 15 codes at a time ? Using just 1 = WCDMA ? 1 channel is reserved for overhead ? Turbo codes ? r ? Adaptive Modulation ? QPSK and 16QAM Design Choices and Issues ? SF = 16 helps with multipath, but equalizer often still needed ? Receivers can actually be more complex than in LTE ? Primary multiple access is TDMA ? Proportional Fair scheduling is the norm 14 ? GSM is ubiquitous ? Most Providers Pretty Far Along on WCDMA Transition ? e.g. "3G iPhone" ? HSPA family based on WCDMA, used for data ? HSDPA is widely deployed ? HSUPA currently being deployed ? Typical User Experience ? 500 kbps-2 Mbps DL ? 500 kbps-1 Mbps UL ? 100-200ms ping delays HSDPA '08-'09 7,200 725 425 GPRS '02-'03 48 30 40 EDGE '03-'04 237 120 80 UMTS '04-'05 384 200 150 HSDPA '06-'07 3,600 700 400 Assumptions: GPRS: 4-TSL/User limited to CS-2 Max EDGE: 4-TSL/User Max UMTS (R99): 384 kbit/s Max HSDPA (R6): Category 6 UE Max (5 codes) HSDPA (R6): Category 7 UE Max (10 codes) Average User Throughput (kbps) Peak Radio Throughput (kbps) Mobile Data Throughput (kbps) UMTS 3G – Current Status 15 4th Generation Standards ? There is still some debate about what 4G actually is ? Key Attributes of 4th Generation Standards ? Data rates and supportable bandwidths much higher in both "theory" and reality than 3G ? IP-based rather than circuit switched ? This has a significant impact on voice ? In practice, common distinguishing features vs. 3G include: ? Multicarrier (OFDM) based physical layer ? OFDMA MAC layer with time-frequency scheduling ? All IP ? Aggressive multi-antenna technologies supported ? Variable bandwidth, up to 20 MHz 16 Evolution of WiMAX ? The 802.16 Standard Family ? 1998: IEEE formed 802.16 group to develop a standard for a wireless metropolitan area network (MAN) – primary interest was fixed wireless access ? First 10–66 GHz band considered; later modified to work in 2– 11GHz to enable NLOS (802.16a) ? 2004: IEEE 802.16-2004 standard ratified, subsuming 802.16, 802.16a, 802.16c ? First 802.16-2004 product certified in Jan. 2006 ? Dec. 2005: 802.16e completed, to allow mobility applications and scalability in 2–6 GHz ? Vision has changed a lot in the last 10 years ? Started as fixed broadband, now is really the first 4G standard 17 802.16 and WiMAX ? The 802.16 standards have very broad scope, millions of incompatible options ? The WiMAX forum defines commercial "profiles" of options, frequency bands, etc. ? Similar to the Wi-Fi Alliance ? Promotes interoperability of products through testing and certification ? The WiMAX forum has 15 Board members (companies), ~150 Principal members, 300+ Regular members 18 Current Certification Profiles ? Global Spectrum Availability is a key challenge for WiMAX ? Range vs. Cost/Availability tradeoff ? Would prefer lower frequencies like 700 MHz, but expensive and scarce Band Index Frequency Channel Bandwidth FFT Size Duplexing Fixed WiMAX Profiles 1 3.5 GHz 3.5 MHz 256 FDD 3.5 MHz 256 TDD 7 MHz 256 FDD 7MHz 256 TDD 2 5.8 GHz 10 MHz 256 TDD Mobile WiMAX Rel 1.0 Profiles 1 2.3 - 2.4 GHz 5 MHz 512 TDD 10 MHz 1024 TDD 8.75 MHz 1024 TDD 2 2.305 - 2.320 & 2.345 - 2.360 GHz 3.5 MHz 512 TDD 5 MHz 512 TDD 10 MHz 1024 TDD 3 2.496 - 2.690 GHz 5 MHz 512 TDD 10 MHz 1024 TDD 4 3.3 - 3.4 GHz 5 MHz 512 TDD 10 MHz 1024 TDD 5 3.4 - 3.8 GHz 5 MHz 512 TDD 7 MHz 1024 TDD 10 MHz 1024 TDD Mobile WiMAX Rel 1.5 Profiles 6 1.710 - 1.755 & 2.110 - 2.155 GHz 5 MHz 512 FDD 10 MHz 1024 FDD 7 776 - 787 MHz 788 - 793 793 - 798 5 MHz 512 FDD 10 MHz 1024 FDD 698 - 862 MHz 5 MHz 512 TDD 10 MHz 1024 TDD 19 WiMAX Physical Layer ? IFFT size is most commonly 1024 ? Turbo codes are used with r = ? and ? ? Symbol Mapper is for QPSK, 16QAM, 64QAM ? Many possible MIMO modes ? Mobiles required to have two antennas ? Alamouti 2 x 2 is starting point, more aggressive techniques soon Subcarrier Allocation + Pilot Insertion Subcarrier Allocation + Pilot Insertion D/A D/A Antenna 1 Antenna 2 IFFT IFFT Channel Encoder + Rate Matching Interleaver Symbol Mapper Space Time Encoder Channel Encoder + Rate Matching Interleaver Symbol Mapper Space Time Encoder Channel Encoder + Rate Matching Interleaver Symbol Mapper Space Time Encoder Burst # 1 Burst # 2 Burst # N 20 OFDM Subcarrier Allocation ? In WiMAX multiple subcarriers are grouped together to create what is called a sub-channel. Usually consists of 48 data subcarriers. Distributed Subcarrier Each sub-channel consists of subcarriers that are distributed throughout the channel bandwidth. Provides better frequency diversity which is beneficial at higher speeds. Adjacent Subcarrier Each sub-channel consists of subcarriers adjacent to each other. Provides better multi user diversity and is useful for closed loop multi-antenna techniques. B 2 ? B 2 B 2 ? B 2 User 1 Channel User 2 Channel B 2 ? B 2 B 2 ? B 2 21 Comparison of distributed vs. adjacent ? Band AMC (adjacent allocation) exploits multi-user diversity and frequency selectivity by allocating each resource to a user with high SINR ? Requires timely channel quality feedback (CQI) ? At high vehicular speeds, this CQI quickly becomes obsolete ? Distributed or permuted subcarrier assignment (known as PUSC) is more robust to mobility, averages the channel in frequency 22 Burst Profiles, Mapping Messages, Frame Structure ? DL-MAP and UL-MAP messages specify ? Subcarriers allocation to each mobile in the DL and UL ? Burst (AMC) profile: what coding type/rate and constellation to use: 802.16e has a staggering 52 different profiles frame 'n' frame 'n+1' DL sub-frame UL sub-frame DL-MAP UL-MAP Ranging?Subchannel 23 3GPP's Long Term Evolution (LTE) ? LTE is technically 3GPP release 8 ? Recall that HSPA+ was release 7 ? It is however a radical departure, much more similar to WiMAX than to HSPA ? Standard is not quite finalized as of Nov. 2008, but most key elements are S/P S/P S/P IFFT Add cyclic prefix USER 1 USER 2 USER 3 Downlink Physical Layer 24 Key Features of LTE ? LTE also has scalable OFDMA physical layer for the DL ? LTE uses SC-FDMA (single carrier FDMA) in the UL ? Flat IP architecture ? Variable bandwidth: 1.4, 3, 5, 10, 15, or 20 MHz ? Multi-antenna techniques such as transmit diversity, open loop MIMO, closed loop MIMO ? Resource block is 7 OFDM symbols (in time) by 12 subcarriers ? Dedicated control channels rather than mapping messages are used to assign resources ? Persistent allocation for VoIP (big win for voice capacity) ? 10 msec frame and 1 msec sub-frame for FDD and TDD ? The 1 msec subframe allows for much faster feedback and ARQ 25 SC-FDMA in LTE Uplink DFT IFFT Add cyclic prefix DFT IFFT Add cyclic prefix USER 1 USER 2 SCFDMA has lower peak to average power ratio in the time domain compared to OFDMA. SCFDMA has higher peak to average power ratio in the frequency domain compared to OFDMA (more out of band emissions) 26 LTE Status ? Standard is still being "finalized" but chipsets already in production ? Demonstrations by Ericsson, Samsung and others ? Has pretty well squashed Qualcomm's UMB, seems poised to dominate 4G cellular standards ? Commercial solutions available in 2010/2011 ? Widespread commercial service probably not until about 2012 ? Operators need to recover massive investment in 3G networks before replacing them ? WiMAX seems best positioned for emerging markets, since is available now 27 Comparison and Summary No Yes Turbo Codes r =1/3,1/5 QPSK, 8PSK, 16QAM No 1 Alamouti STBCs 1.667 msec (slot) 1.23 MHz FDD CDMA/TDMA DSSS CDMA/TDMA Direct Sequence Spread Spectrum EVDO WiMAX LTE HSDPA Modulation DL OFDM OFDM Direct Sequence Spread Spectrum (DSSS) Multiple Access DL OFDMA OFDMA CDMA/TDMA Modulation UL OFDM SCFDMA DSSS Multiple Access UL OFDMA SC-FDMA CDMA/TDMA Duplexing TDD FDD/TDD FDD Channel Bandwidth Scalable 3.5, 5, 7, 8.75, 10 MHz Scalable 1.4, 3, 5, 10, 15, 20 MHz 5 MHz Frame Length (feedback interval) 5 msec 1 msec 2 msec MIMO Schemes Tx Diversity, OL MIMO, AAS Tx Diversity, OL MIMO, CL MIMO Alamouti STBCs CL MIMO Maximum MIMO Rank 2 4 2 Multicodeword MIMO No Yes Yes Modulation QPSK, 16QAM, 64QAM QPSK, 16QAM, 64QAM QPSK, 16QAM, 64QAM Channel Coding Convolutional,Turbo and RS Codes r = ? , 2/3, ?, 5/6 Turbo Codes r = 1/3, 1/2, 3/4, 1 Turbo Codes r HARQ Yes Yes Yes Persistent Scheduling No* Yes No 28 Performance Predictions Disclaimer: these are based on private simulations and no guarantees are made to their accuracy. Different models may result in different values. 29 Spectral Efficiency Comparison Results shown at 2.1 GHz with 1 km cell radius and 20 dB in building loss Downlink Uplink 30 Typical Data Rate Comparison Theoretical peak data rate Typical data rate range HSDPA 5 MHz FDD LTE 10 MHz FDD WiMAX 10 MHz TDD All MS are equipped with dual antennas in the DL 31 Voice Capacity (20 MHz spectrum) HSDPA – 2005 numbers are for circuit switched voice over Rel .99 bearer 32 Acknowledgments ? Thanks to the following people for furnishing some of the information and material used in this presentation ? Arunabha Ghosh (AT&T Labs) ? Avneesh Agrawal (Qualcomm) ? Robert Heath (UT Austin)