LTE and NB-IoT Luca Feltrin RadioNetworks, DEI, Alma Mater Studiorum - Università di Bologna Telecom Italia Mobile S.p.a. - TIM
Index Ø 3GPP and LTE Specifications Ø LTE o Architecture o PHY Layer o Procedures Ø NB-IoT
Index Ø 3GPP and LTE Specifications Ø LTE o Architecture o PHY Layer o Procedures Ø NB-IoT
What is 3GPP? Ø 3 Generation Partnership Project (3GPP) Ø «Unites 7 telecommunications standard development organizations and provides their members with [ ] Reports and Specifications that define 3GPP technologies» Ø 3 Technical Specification Groups (TSG) o RAN (Radio Access Network), SA (Services and Systems Aspects), CT (Core Network & Terminals) Ø Each TSG divided in Working Groups (WG)
How does the Specifications look like? Ø The standard is made of many documents: Technical Specifications (TS) and Technical Reports (TR) Technical Specification (TS) Technical Report (TR) TS 36.211 Physical Channels and Modulation Series CODECS Security LTE (Series 36) Specific Document Category PHY Layer MAC Layer Network Architecture Title Ø More than 280 documents in Series 36 o On average 100 pages per document Ø All documents are public! http://www.3gpp.org/dynareport/36211.htm
The standardization process Ø 4 Technical Meetings per year o Discussion of the modification to the specifications Ø Atomic modifications of the standards (1 or more documents) are organized in Change Requests (CR) o If the CR is approved a new version of the documents is created Ø Many CR targeting a set of milestones are grouped in «Releases»
3GPP releases evolution Today 3GPP Release 8 9 10 11 12 13 14 Release year Launchable LTE Bucket List Items Improvements (Regulatory, etc.) Carrier Aggregation, CoMP, LIPA, M2M, etc Improved Performance Carrier Aggr. Improvements IMS, roaming, P2P, etc. WiFi, Small Cell Impr. Signaling opt. SON, MDT, adv. Receiver MIMO Improv. D2D, ProSe 3D/FD-MIMO Indoor Pos. Latency Reduction NB-IoT Mission Critical Enhancem. V2x services Inter-band CA 2008 2009 2012 2013 2015 2016 2017 Peak Throughput DL UL 300 Mbps 75 Mbps Peak Throughput DL UL 1 Gbps 500 Mbps Peak Spectrum Efficiency [bps/hz] DL 15 UL 3,75 Peak Spectrum Efficiency [bps/hz] DL 30 UL 15
3GPP releases evolution Today 3GPP Release 8 9 10 11 12 13 14 Release year Launchable LTE Bucket List Items Improvements (Regulatory, etc.) Carrier Aggregation, CoMP, LIPA, M2M, etc Improved Performance Carrier Aggr. Improvements IMS, roaming, P2P, etc. WiFi, Small Cell Impr. Signaling opt. SON, MDT, adv. Receiver MIMO Improv. D2D, ProSe 3D/FD-MIMO Indoor Pos. Latency Reduction NB-IoT Mission Critical Enhancem. V2x services Inter-band CA 2008 2009 2012 2013 2015 2016 2017 3G 4G
Index Ø 3GPP and LTE Specifications Ø LTE o Architecture o PHY Layer o Procedures Ø NB-IoT
Architecture S6a HSS Home Subscriber Server Network Operator s Subscribers evolved Node B Sends and receives radio transmissions Controls low-level operation of UE MME / S-GW S1 MME / S-GW S1 EPC (evolved Packet Core) Mobility Management Entity High-level operations of UE S1 S1 enb X2 enb E-UTRAN X2 X2 Air Interface Uu enb Used for signaling and handover User Equipment UE
Frequency/Time Division Duplexing Uplink Downlink UL/DL f FD - FDD UE transmits UE receives HD - FDD UE is capable of TX and RX at the same time TDD UE transmits UE receives UE switches from TX to RX mode using the same band UE transmits UE receives UE switches from TX to RX mode using a different band t
Source: https://www.frequencycheck.com Wireless Spectrum Ø In Italy: o Band 03 FDD 75 MHz - (3, TIM, Vodafone) o Band 07 FDD 70 MHz - (Wind, 3, TIM) o Band 20 FDD 30 MHz - (Wind, TIM, Vodafone) Ø Divided in channels from 1.4 to 20 MHz o Frequency reuse
MIMO Ø Capacity is asimptotically proportional to min ( n t, n r ) o Improved Throughput Ø Directivity and Diversity Gain Ø Possible Configurations o SISO Single Input Single Output o MIMO 2x2 Multiple Input Multiple Output o MIMO 4x4 Multiple Input Multiple Output TX RX TX RX TX RX
OFDMA (Downlink) Ø Multi-carrier modulation o Effective against selective fading { b i } 1 Nl { a i } 1 N Modulator S/P IFFT x(t) Cyclic extension Bits to transmit
OFDMA (Downlink) Ø Multi-carrier modulation o Effective against selective fading { b i } 1 Nl { a i } 1 N Modulator S/P IFFT x(t) Cyclic extension The modulator create a symbol every l bits
OFDMA (Downlink) Ø Multi-carrier modulation o Effective against selective fading { b i } 1 Nl { a i } 1 N Modulator S/P IFFT x(t) Cyclic extension N symbols are split in parallel flows with a lower symbol rate (1/ N)
OFDMA (Downlink) Ø Multi-carrier modulation o Effective against selective fading { b i } 1 Nl { a i } 1 N Modulator S/P IFFT x(t) Cyclic extension The Inverse Discrete Fourier Transform is applied. If N= 2 k the IDFT can be optimized with the Fast Fourier Transform. N {128, 256, 512, 1024, 2048}
OFDMA (Downlink) Ø Multi-carrier modulation o Effective against selective fading { b i } 1 Nl { a i } 1 N x(t) Modulator S/P IFFT Cyclic extension A cyclic prefix (CP) is added to avoid inter-symbol interference CP Symbol
OFDMA (Downlink) Ø 512 subcarriers (211 guard band, 301 for data) Example o Channel BW = 5 MHz o Sampling frequency: f s =7.68 MHz Left empty for guard band Symbol signal made of 512 samples User 1 Modulator QPSK S/P Symbol time: T u =512 T s = 512/ f s IFFT =66.7 μs Cyclic Subcarrier Spacing: Δf= f s /512 N=512 =15 khz extension User N Modulator 64-QAM S/P Left empty for guard band
SC-FDMA (Uplink) Ø Contiguous spectrum is allocated for each user Ø Same numerology as OFDMA Set of allocated subcarriers Data Modulator FFT IFFT Cyclic extension Symbol Reference Symbol
The time axis Ø 7 OFDM/SC-FDMA symbols (+ Cyclic Prefixes) make a Slot CP 0 5.2 μs CP 1 CP 2 CP 3 CP 4 CP 5 CP 6 4.7μs Slot (0.5 ms) 66.7 μs Ø 2 Slots make a Subframe o 2 0.5 ms=1 ms Ø 10 Subframes make a Frame o 10 1 ms=10 ms o System Frame Number (SFN) -> incremental index [0, 1023] Ø 1024 Frames make a Hyperframe o 1024 10 ms=10.24 s o Hyper Frame Number (HFN) -> incremental index [0, 1023] o HFN resets every 1024 10.24 s=2.91 hours
Resource Grid and RE SF -> Resource Element (RE) 1 subcarrier x 1 symbol 1 modulated symbol (e.g: 64-QAM -> 6 bit)
Resource Units Ø Physical Resource Block (PRB) o Smallest Resource assigned by enb Scheduler o 12 subcarriers x 1 slot (180 khz x 0.5 ms) SF ->
Resource Units Ø Physical Resource Block (PRB) o Smallest Resource assigned by enb Scheduler o 12 subcarriers x 1 slot (180 khz x 0.5 ms) SF -> PRB 12 7=84 REs