Politecnico di Milano Facoltà di Ingegneria dell Informazione MRN 10 LTE. Mobile Radio Networks Prof. Antonio Capone

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1 Politecnico di Milano Facoltà di Ingegneria dell Informazione MRN 10 LTE Mobile Radio Networks Prof. Antonio Capone

2 Outline 1. Introduction 2. Network Architecture 3. Radio Interface

Spectral efficiencies All rights reserved

7 Standard evolution within 3GPP 2G 3G 4G GSM GPRS EDGE UMTS TD-SCDMA TDMA FDMA CDMA OFDMA HSDPA HSUPA HSPA+ R7 HSPA+ R8 LTE FDD TDD LTE Advanced All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 7

8 Voice services on LTE o No support to circuit switched services in LTE o But SMS and Voice are the main source of revenues for operators o Possible approaches n LTE only for data (no voice) n Fallback on 2G/3G n Voice over LTE via Generic Access (VoLGA) n Voice over IMS & One Voice Profile n Over-the-Top VoIP All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 8

9 LTE Performance targets o Peak data rate n 100 Mbps DL / 50 Mbps UL per sector in a 20 MHz band o 200+ active users per cell (5 MHz) o Latency in the user-plane <5 ms o Maximum coverage distance 100 Km o Mobility n n n Optimized for 0-15 km/h High performance for 15/120 km/h Support for high speed up to 350 km/h o Multimedia broadcast services (E-MBMS) o Flexible spectrum usage: MHz o Advanced end-to-end QoS support All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 9

10 LTE - Technologies o Multiple access n DL: OFDMA with Cyclic Prefix (CP) n UL: Single Carrier FDMA (SC-FDMA) with CP o Adaptive modulation and channel coding n DL/UL: QPSK, 16QAM e 64QAM n Convolutional coding and turbo coding (Rel-6) o Advance MxN MIMO techniques n (2/4)x(2/4) downlink e uplink n Multi-user MIMO o FDD and TDD support o H-ARQ, rate control, security, etc. All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 10

EPS (3GPP 4G) = SAE (EPS) + LTE (eutran) o o o The name of the

introduces a general concept of Evolved Packet System (EPS) in 3GPP

Long Term Evolution (LTE) SAE and LTE are specified as n n Evolved

network (e-utran) EPS (4G) LTE (eutran) Radio access network SAE

12 EPS (3GPP 4G) = SAE (EPS) + LTE (eutran) o o o The name of the technology commonly adopted is LTE, however the Release 8 introduces a general concept of Evolved Packet System (EPS) in 3GPP standard The EPS includes: n n Service Architecture Evolution (SAE) Long Term Evolution (LTE) SAE and LTE are specified as n n Evolved Packet Core (EPC) and Evolved Universal Terrestrial Radio Access network (e-utran) EPS (4G) LTE (eutran) Radio access network SAE (EPC) Core network All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 12

13 EPS architecture o System is completely redesigned according to the All-IP paradigm o New concept of flat network o The access network includes only a single device: enodeb (LTE base stations) o New advanced protocol stacks o Open interfaces and high interoperability o Advanced O&M o SON (Self Organizing Network) for autoconfiguration of enodeb (enb) All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 13

14 Evolution towards the flat network CP UP GGSN GGSN GGSN Serving/ PDN Gateway SGSN SGSN SGSN MME BSC/RNC RNC BTS/NodeB NodeB RNC NodeB enodeb Rel 6 GSM/UMTS Rel 7 Direct Tunnel Rel 7 DT + RNC in NodeB Rel 8 SAE (EPC/LTE) All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 14

15 Reduced number of interfaces Control Plane User Plane HA/GGSN Control Plane User Plane Serving/ PDN Gateway PDSN/SGSN MME BSC/RNC BTS/NodeB GSM/UMTS User Plane: from 3 to 1 interfaces Control Plane: from 3 to 2 interfaces with reduces signaling enodeb SAE (EPC/LTE) All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 15

16 Core Network evolution PSTN PSTN IP PSTN IP PSTN IP IMS IMS CS CS PS CS PS Packet Core Access Access Access Access 2G 2.5G/3G 3G IMS EPS All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 16

17 SAE - Evolved Packet Core o It s a Core Network completely based on IP that can serve access networks with different technologies n 3GPP (LTE, UMTS, GSM/EDGE) n Non-3GPP (WLAN, WiMAX) n Fixed (Ethernet, DSL, optical fiber) o That can provide n Mobility (including handover between different systems) n Policy management (e.g. unique charging) n Security All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 17

18 SAE - Evolved Packet Core o It has a flat architecture with only two nodes n Base station (evolved-nodeb) n Gateway (Serving/PDN GW) o It provides high performance and reduced operational costs o With respect to 3G architecture, RNC functionalities are moved into the enodeb o The handover management is completely provided by base stations o All interfaces are based on IP All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 18

20 LTE/EPC architecture o LTE - Evolved UTRAN (eutran) n User Equipment (UE) n Evolved NodeB (enb) o Evolved Core Network (EPC) n Mobility Management Entity (MME) n Packet Data Network Gateway (PDN-GW o P-GW) n Serving Gateway (S-GW) n Home Subscriber Server (HSS) n Policy Control and Charging Rules Function (PCRF) All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 20

A enb can be connected to more than one MME/S-GW for managing flows with different QoS and/or

21 LTE - E-UTRAN MME/S-GW S1 S1 S1 MME/S-GW S1 enbs are connected together through the X2 interface according to a mesh topology (handover, intercell coordination) enb X2 X2 enb X2 enb A enb can be connected to more than one MME/S-GW for managing flows with different QoS and/or for the connection with different PDNs All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 21

22 User Equipment (UE) o Handheld, smartphone, USB-card, sensors, etc. o It includes n n UICC (Universal Integrated Circuit Card) with the USIM (Universal Subscriber Identity Module) TE (Terminal Equipment) o It will include also a VoIP client for LTE voice calls o It can have multiple antennas for MIMO support o Most of UE will be multi standard: GSM, HSPA e LTE (FDD o TDD) All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 22

23 enb Evolved Node B o It s the base station of eutran, which manages one or more cells o With respect to GSM and UMTS it also performs additional functions (that were performed by BSC and RNC) like for instance handover o All radio protocols are terminated on the enb for for IP connectivity the enb acts as relay towards the EPC (layer 2 bridge) o The enb manages radio resources and mobility o The enb is connected to a set of MME/S-GWs, even if each UE is connected to only one of these All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 23

24 enb Evolved Node B o Main functions n Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Scheduling in UL and DL) n IP header compression and data flow encryption n MME selection in case of request from UE n Routing of User Plane data towards the Serving Gateway n Scheduling and transmission of o Paging messages (originated by MME) o broadcast (originated by MME or O&M) n Measurements for mobility and scheduling All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 24

25 MME - Mobility Management Entity o It s the main node of the Core Network SAE/LTE o It includes most of the functions that in 2G/3G networks where implemented in different nodes o It is involved in the Control Plane only o It establishes a direct connection with the UE o It is connected simultaneously with several UEs, enbs, MMEs (even of different operators), S-GWs, and HSSs All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 25

26 MME - Mobility Management Entity o Authentication and Security n Together with the HSS it manages authentication and encryption of channels for CP and UP o Mobility Management n It asks enb and S-GW to allocate resources for UE when they register to the network n It stores the Tracking Area (or the enb if in active mode) that UE communicates periodically n It is involved in handover procedures together with enb, S-GW and other MME All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 26

27 MME - Mobility Management Entity o User Profile Management and Service Connectivity n It provides the basic connectivity for the initial exchange of messages between UE and network (default bearer) n It selects the Packet Data Network to be assigned to each UE n When requested by the network (S-GW) or UE, it establishes a new bearer (dedicated) n The MME verifies the profile and services for the UE before allocating the bearer All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 27

28 o o o o S-GW Serving Gateway The S-GW is in charge of managing the tunnel of UP protocols and switching the tunnel in case of mobility The S-WG manages its own resources based on requests from MME, P-GW and PCRF It s the anchor node for terminals moving between different enodeb. When requested by the MME, the S- GW reroutes data flows between the enbs involved in a handover In case of inter-s-gw handover, the MME deletes the IP tunnel from old S-GW and establishes a tunnel with the new S-GW o When the P-GW sends packets to a UE in IDLE, the S- GW buffers packets and requests to MME to perform the paging procedure o The S-GW stores traffic statistics and it is involved in the interworking with other 3GPP systems, like GSM e UMTS All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 28

29 S-GW Serving Gateway o Functions n Mobility anchor point for the inter-enb handover n Mobility anchoring for inter-3gpp mobility n Data buffering in downlink for idle UE n Service instantiation for requests from the network n Routing and packet forwarding n Packet tagging at transport layer in uplink and downlink n Charging in UL and DL UE, PDN, and QCI All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 29

30 P-GW PDN Gateway o The P-GW manages IP addresses for UEs (IPv4/IPv6, DHCP) o Together with the PCRF, it controls QoS and charging based on traffic flow o Through the PCEF (a component of the P-GW), it filters IP traffic and calculate statistical information o The P-GW allows the interworking with non-3gpp packet technologies like WiMAX and WLAN All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 30

31 P-GW PDN Gateway o Functions n Mapping of IP flows and GTP tunnels n Packet filtering per single UE n Traffic interception n IP address allocation for UE n Charging based on active services in UL and DL n Data rate control in Downlink All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 31

32 PCRF (Policy and Charging Rules Function) o To each connection UE-PDN is associated a PCRF o The PCRF implements the Policy and Charging Control (PCC) o It authorizes the assignment of QoS profiles to flows to/from UEs o Together with the PCEF, it manages charging based on traffic flow All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 32

33 HSS (Home Subscriber Server) o The HSS stores permanent user profiles o It manages authentication (AuC) in its network and in the Visited PLMN o It is connected to all MME of the network o It stores the UE position and the information on the associated MME o It is basically the evolution of the HLR/AUC used by GSM and UMTS All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 33

34 Services Domain o The Service Domain includes all the other system components that are not part of LTE technology but that are used for basic services (like e.g. VoIP) o Some service domain platforms are standard like the IMS, while other are just Internet application server o In the case IMS, the integration is based on 3GPP specifications. In other cases it is managed by operators independently (web-servers, P2P ntw, etc.) All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 34

35 IP Multimedia Sub-system (IMS) o The IMS is a system that allows mobile operators to offers multimedia services through Internet platforms o The IMS implements for mobile users the convergence of voice, video, instant messaging, web applications, etc. o It combines the growth of Internet applications and services with the global diffusion of the mobile access All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 35

36 IP Multimedia Sub-system (IMS) o With the introduction of the IMS, 3GPP systems tend to comply with Internet IEFT standards o SIP in particular, the main signaling protocol of the IMS, is actually specified by the IEFT o Through the IMS, mobile operators try to offer value added services and not just dumb pipe of bits o In 4G systems, voice services are provided through the IMS All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 36

EPS functionalities All rights reserved -

41 Layer NAS (Non Access Stratum) o o Direct UE-MME connection which does not involves the enb It includes two sub layers n EMM (EPS Mobility Management) o Attach/Detach, Tracking Area Update (UE in Idle Mode), Transition Idle-Connected per Service Request (from UE), Paging Request (from network), Authentication, Encryption, Security n ESM (EPS Session Management) o Activation and management of new bearers All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 41

42 o o o o o LTE-Uu protocols RRC (Radio Resource Control) n Management of radio resources, signaling, data connections, and handover PDCP (Packet Data Convergence Pr.) n n UP: IP Header Compression CP: Encryption e Integrity RLC (Radio Link Control) n Segmentation and concatenation of PDCP PDUs. Error correction and ARQ (Automatic Repeat Request) MAC (Medium Access Control) n Scheduling based on priority, multiplexing and HARQ (Hybrid ARQ) PHY (Physical Layer) n Modulation, coding All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 42

X2 interface CP and UP All rights reserved

44 eutran - User plane UE PDCP RLC MAC PHY enb PDCP RLC MAC PHY PDCP, RLC and MAC perform header compression, cyphering, scheduling, and ARQ/HARQ functions All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 44

45 UE NAS RRC PDCP RLC MAC PHY eutran - Control plane enb RRC PDCP RLC MAC PHY MME NAS o No header compression o PDCP: cyphering e integrity protection o RLC and MAC same function of UP o RRC: broadcast, paging, RRC connection management, mobility, o NAS: EPS bearer management, authentication, paging, security, All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 45

46 S1 interface o S1 interface connects the enodeb to the Evolved Packet Core (EPC) and includes User Plane and Control Plane o S1 is a all-ip interface, without support for the old SS7 protocols o The S1 is part of the SON (Self Organizing Networks) which allow automatic configuration of network parameters All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 46

47 S1 interface - Control Plane o It is based on the SCTP/IP (Stream Control Transmission Protocol/IP) stack from which it inherits robustness in message transport o The SCTP/IP allows the use of multiple streams for adding redundancy to signaling flows and multi-homing o In LTE, the S1-AP (Application Protocol) is directly on top of the SCTP without any intermediate protocol for Connection Management o The use of IP layers is completely free and can also be based on the traditional IPv4, even if IPv6 will probably be most common All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 47

48 S1 interface User Plane o It is based on the GTP/UDP/IP stack already used in UMTS o The GTP-U (GTP User plane) facilitates the tunnel management between different 3GPP systems o IP is not specified o The transport bearer is identifies through n Source GTP TEID (Tunneling End ID) n Destination GTP TEID n Source IP address n Destination IP address All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 48

49 X2 interface o Interconnects directly different enodebs. All enodebs that have adjacent radio coverage should be connected in mesh mode o X2 and S1 protocols stacks are similar, except for the X2-AP and l S1-AP o X2 interface has an important role during handover since it forward downlink traffic towards the new enb until the new data connection is established (in the Uplink it is the UE itself that sends traffic to the new enb) All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 49

51 Self Organizing Networks o Network configuration and management are complex and costly tasks for mobile operators o Several problems can be caused by human mistakes o SON has the goal of making network auto configuring o The introduction of LTE makes things even more difficult: n n n n Coexisting 2G/3G/LTE networks A large number of enbs (including Home enb and femto cells) Large number of network parameters All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 51

52 SON schemes Self Configuration Basic Setup Initial Radio Cfg IP address. configuration Association with GW Autentication SW download and configuration Neighbour list configuration Coverage parameters configuration Self Optimization Optimization Neighbour list configuration Coverage and capacity parameters configuration Self Healing Self-healing Failure detection and localization Healing schemes All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 52

53 Self planning and configuration o New installed enodebs connect to configuration server and provides their HW and SW profile. o After an authentication phase, configuration parameters for creating S1 and X2 connection are downloaded and applied. o At the end of the procedure the enodeb becomes fully operative o Initial configuration of transport network o Authentication o Association to O&M server o Download of basic SW and parameters o Radio configuration o Result: fast and cheap system rollout All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 53

54 Self optimization o Auto optimization, self training, self optimizing loop n Automatic Neighbour Relations based on UEs and enbs measurements. n Auto switch-off of cells with no traffic n Automatic Power Reduction for coverage and interference optimization n Tuning of MIMO parameters n Tuning of hand-over parameters and load-balancing n RACH parameters optimization o Result: better network quality, reduction of failures All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 54

55 Self healing o Failure automatic detection and execution of recovery procedures. Examples: n Temperature alarm: power reduction n SW fault: roll-back to a previous version o Result: reduction of the number of on site managements, more robust network All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 55

SON architecture o Centralized o Simplified/hybrid o Distributed

58 o Bandwidth LTE is able to operate on different spectrum portions (from 700 MHz to 2700 MHz) o Different bandwidths can be used 1.4, 5, 10, 15 and 20 MHz o FDD duplex FDD spacing from 30 to 400 MHz o o Both FDD and TDD are used for adapting to spectrum allocation rules in different regions LTE must be robust to interference from adjacent systems (GSM, WCDMA, WiMAX, Wi-Fi, etc.) Min 1.4 MHz Max 20 MHz All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 58

Available frequencies All rights reserved

LTE Frequency in Italy All rights reserved

62 Enabling technologies o Multi carrier modulation (OFDM/OFDMA) o Multiple antennas (MIMO) o Adaptive modulation and coding o Soft recombination of transmitted packets and retransmitted packets (HARQ) o Packet switching at the radio interface All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 62

63 OFDMA o LTE uses n OFDMA in Downlink n SC-FDMA in Uplink o OFDMA (Orthogonal Frequency Division Multiple Access) o SC-FDMA (Single Carrier Frequency Division Multiple Access) All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 63

OFDMA: resource allocation example All rights

66 Rate Control n Rate Control can make use of o Different coding schemes (1/3, ¾, 4/4) o Multiple modulations (BPSK, 64QAM) o Multiple antennas (e.g. MIMO) n It allows to handle variable channel quality without increasing power with Power Control (UMTS/GSM) With Rate Control (HSPA,LTE) Chan. Qual. Tx Pwr Data Rate Chan. Qual. Tx Pwr Data Rate All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 66

67 Rate Control o o Rate Control can use different combinations of modulation and coding schemes Decision on which combination to use is based on SNR estimation All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 67

68 Scheduling o Transmission scheduling considers n Channel characteristics (even of each subcarrier) n Fairness on time n Fairness on throughput Guaranteeing QoS for active bearers User #1 User #2 All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 68

Multiple antennas o Space diversity (TD) n n n n Increased capacity More reliable linke Antennas at TX and/or RX Mitigate fading o Antenna Array (BF) n Beam-forming n n Increased coverage Antennas

71 Multiple antennas o Space diversity (TD) n n n n Increased capacity More reliable linke Antennas at TX and/or RX Mitigate fading o Antenna Array (BF) n Beam-forming n n Increased coverage Antennas at TX and/or RX o Spatial Multiplexing (SM) n n n n Increased rate Increased spectral efficiency Antennas at TX and RX Multi stream All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 71

narrow band subcarriers (15 khz in LTE), interference can be controlled effectively Exellent management of different QoS services

73 WCDMA e OFDMA differences o WCDMA n Rigid wide-band allocation (5 MHz for UMTS) n n n Non-optimal multi-qos services management Difficulty in transmission medium adaptation Traffic and control channel over the same bandwidth o OFDMA n n n By having lots of narrow band subcarriers (15 khz in LTE), interference can be controlled effectively Exellent management of different QoS services Each slow radio channel is well protected from Inter-Symbol-Interference All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 73

74 OFDM signal generation Un simbolo OFDMA,+1,+1,-1,-1,-1,+1,+1,-1, Q 1,1 +45 f khz -1,1 1,1-1, f khz I -1,-1 1,-1-1, f khz 1) Serial to parallel data conversion 1, f khz 2) For each symbol a sinusoidal signal is generated 4 3) The peak value for the sum of several signal is proportional to the number of symbols considered t N sotto-portanti -4 Un simbolo OFDMA B All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 74

75 SC-FDMA signal generation,+1,+1,-1,-1,-1,+1,+1,-1, 1 Q -1,1 1,1 V(I) 0 t I -1 Un simbolo SC-FDMA -1,-1 1,-1 1 1) Serial to parallel conversion 2) A trajectory between considered symbols (+1,-1 amplitude) is calculated 3) The new signal is frequency domain translated via DFT 4) The obtained sub-carriers are translated onto the allocated LTE spectrum V(Q) 0 t -1 Un simbolo SC-FDMA S(.,.) S(.,.) All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 75

76 Packet Switched Radio Interface o All protocols are packet switched o Transmission interval of 1 ms (in HSDPA it is 2 ms) comparable to coherence time of the channel o MAC layer implements n Adaptive scheduling n Multiple Antenna technology (MIMO) n Rate control All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 76

77 TDD and FDD frames o Two duplexing schemes are specified: FDD e TDD o In FDD, assigned spectrum is in pairs (e.g MHz), one for the downlink and one for the uplink o In TDD the same spectrum (e.g. 10 MHz) is assigned to downlink and uplink but in different times o Frame formats for FDD and TDD are called type 1 and type 2 respectively All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 77

TDD Frame Frame duration 10ms DwPTS = Downlink Pilot Time Slot UpPTS = Uplink Pilot Time Slot GP = Guard Period o In TDD, subframes 1 and 6 are switching points

78 TDD Frame Frame duration 10ms DwPTS = Downlink Pilot Time Slot UpPTS = Uplink Pilot Time Slot GP = Guard Period o In TDD, subframes 1 and 6 are switching points between UL and DL (duration can be 5 or 10 ms) o Different combination of UL/DL subframes have been specified All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 78

79 FDD frame o o o o Frame duration: 10 ms Sub-frame duration (2 slot): 1 ms Slot duration: 0.5 ms A frame duration is Ts (OFDMA symbol durations) One slot, T slot = 15360T s = 0.5 ms One radio frame, T f = T s = 10 ms #0 #1 #2 #3 #18 #19 One subframe All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 79

80 Resource Grid One downlink slot Tslot DL Nsymb OFDM symbols DL RB RB sc - k = N N 1 N DL-RB * N RB-sc N symb sub-carries OFDM symbols Resource block DL symb N N RB sc resource elements N subcarriers RB sc DL RB N RB N sc subcarriers Resource element ( k, l) DL l = 0 l = N symb -1 k = 0 All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 80

82 Resource Grid and Resource Elements o N DL-RB depends on bandwidth used Channel bandwidth BW Channel [MHz] Transmission bandwidth configuration N RB o In case of multiple antennas, to each of them a different Resource Grid is associated o Resource Elements are the basic units in the grid All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 82

83 Resource Blocks o o o o RBs are used to describe the mapping of channels on Resource Elements There are physical and virtual RBs A physical RB is defined as N DL-symb consecutive symbols in time domain and N RB-sc subcarriers in frequency domain, where N DL-symb and N RB-sc are in the table A physical RB is then N DL-symb x N RB-sc Resource Elements equivalent to 1 time slot and 180 KHz Normal cyclic prefix Extended cyclic prefix Configuration RB N sc DL N symb Df =15 khz 7 12 Df =15 khz 6 Df = 7.5 khz 24 3 All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 83

84 Resource Blocks o Physical RBs are numbered from 0 to N DL-RB -1 o Virtual RB have the same size of physical ones and are divided into n Virtual RB Localized Type n Virtual RB Distributed Type o Resource Elements can be grouped into RE Groups, which are used for mapping channels on REs All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 84

85 Resource Blocks Channel Bandwidth [MHz] Transmission Bandwidth Configuration [RB] Transmission Bandwidth [RB] Resource block Active Resource Blocks Center subcarrier (corresponds to DC in baseband) is not transmitted in downlink All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 85

FDD frame 12 subcarriers 50 RB x 12 = 600 subcarriers All

FDD frame with MIMO Resource Blocks 50x20 RB / 10 MHz time sub-carriers

Maximum throughput All rights reserved -

90 Downlink channels Base band OFDM code words layers antenna ports Scrambling Modulation mapper Resource element mapper OFDM signal generation Layer mapper Precoding Scrambling Modulation mapper Resource element mapper OFDM signal generation All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 90

91 Downlink physical channels o DOWNLINK Physical channels n Physical Downlink Shared Channel (PDSCH) n n n n n Physical Multicast Channel (PMCH) Physical Downlink Control Channel (PDCCH) Physical Broadcast Channel (PBCH) Physical Control Format Indicator Channel (PCFICH) Physical Hybrid ARQ Indicator Channel (PHICH) o There are also reference channels and primary and secondary synchronization channels o Modulation schemes QPSK, 16QAM e 64QAM All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 91

RBs transmission in UL e DL OFDMA SC-FDMA All rights

98 UL frame o Similar to that of the DL o Same number of symbols and RBs o Same frame duration o The SC-FDMA modulation scheme does not introduces differences All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 98

99 Uplink physical channels o UPLINK physical channels n Physical Random Access Channel (PRACH) o Access requests o Time Advance n Physical Uplink Shared Channel (PUSCH) o Uplink data channel n Physical Uplink Control Channel (PUCCH) o Uplink signaling channel o Modulation schemes: QPSK, 16QAM e 64QAM All rights reserved - copy forbidden - L. Dell'Anna/A. Capone 99

LTE systems: overview

LTE systems: overview Luca Reggiani LTE overview 1 Outline 1. Standard status 2. Signal structure 3. Signal generation 4. Physical layer procedures 5. System architecture 6. References LTE overview 2 Standard