Wireless Network Infrastructure An Overview

Transcription

1 Wireless Network Infrastructure An Overview IVAN TAM Ivan Tam 2015

2 Fixed and Mobile Service Provider Architecture Access provides cost/performance effective connectivity using copper, fiber to home and offices Aggregation aggregate the traffic from various types of access terminating at CO/POP Central Office Service/edge service management point where authentication, service quality, and service features are provided BNG ( Core national connectivity between data centers and service edge to each other and to the internet Broadband Gateway)/VPN PE (Provider Edge) or as Transit service provider interface with a number of transit carriers via own border routers. Transit carrier is responsible for routing traffic back and forth to destinations in the worls MME, SGW and PGW in LTE Data Center Core Router xdsl Web site s hosting data center/ Cloud Internet Gateway Transit Carrier Router Transit Backhaul Access Basestation Aggregation Service Edge AAA where database of Internet Exchanges customers are stored and checked by service edge Value added service (VAS) IPTV server, internet cache Core Internet Web site s service provider

3 Fixed and Mobile Service Provider Architecture How does radio wave carries information? How to optimize on the amount of info over radio? How to arbitrate the access of radio resource by user terminals? Central Office How to mitigate interference between neighbor cells? How to maintain QOS of How to ensure that user data can be transported to/from packet network as user moves? Security and Authentication? Data Center different traffic types? Core Router xdsl Internet Gateway Transit Carrier Router Transit How to track the location of user terminals? Access Web site s hosting data center/ Cloud How does user terminal join the packet network? Backhaul Basestation Aggregation Service Edge AAA where database of Internet Exchanges customers are stored and checked by service edge Value added service (VAS) IPTV server, internet cache Core Internet Web site s service provider

4 3GPP (3 rd Generation Partnership Project) Releases Technology Evolutions UMTS Mobile Broadband era WCDMA using spread spectrum technology over 5Mhz Initially ATM transport but moved to IP Larger latency but reduced as advanced to HSPA Release 7 (2007) HSPA+ with QAM64 DL (21Mbps), QAM16 and 2x2MIMO (42Mbps) Release 5,6 ( ) HSDPA with QAM 16(14Mbps), HSUPA (5.7Mbps), IP architecture Release 99 (2000) UMTS (3G), 5Mhz DL (384Kbps), UL (128Kbps) LTE & HSPA 2008-> Introduce LTE, full packet based and high bandwidth OFDM subcarrier scheduling, path diversity, flexible at 1.4, 3, 5, 10,15,20Mhz Lower latency Flat IP network Voice over IP Carrier aggregation (UMTS) Release 9 (2009) LTE Femto cell (HetNet) UMTS Dual Carrier multi-band with 2xMIMO DL + 64QAM (84Mbps) Release 8 (2008) LTE DL MIMO2x2 and 20Mhz (150Mbps), UL (75Mbps), all IP network UMTS 2xMIMO+QAM64 or Dual Carrier+QAM64 (42Mbps) LTE Advanced 2011-> Further optimization of LTE for performance Small cells, hetnet Inter-cell coordination on interference eicic Carrier aggregation (LTE) Release 12 (2012) M2M Mobile Relay CA 3 carrier DL, 2 carrier UL Release 11 (2012) LTE Advanced COMP, eicic HSPA Multi-carriers (8) with 2xMIMO (336Mbps) Release 10 (2011) LTE Advanced Carrier Aggregation (CA), DL at 2x20Mbps (300Mbps) Self-Organizing Network (SON) Relaying for cell without wireline backhaul HSPA+ Multicarrier (4)+2xMIMO+QAM64 (168Mbps) UMTS ( ) LTE + UMTS HSPA evolution LTE-Advanced 5G

5 3GPP Specifications and References 3GPP 36.2xx series Physical Layer 36.3xx Layer 2 and 3, 36.4xx S1 and X2 interfaces 36.1xx Core performance requirements 36.5xx terminal conformance testing 4G Americas Industry trade organization with extensive technical and deployment reports

6 Agenda Spectrum and Transmission Technologies Wired and wireless media, modulation, signal propagation LTE Overall Architecture and 3GPP Physical transmission, UL and DL channel allocations Attachment, mobility tracking and handover Moving on to LTE-A LTE-A Further Optimizations and more cell sites collaboration Virtualization and change in architecture Heterogeneous network, WiFi, LTE over unlicensed spectrum Current Development

7 Modulation (simplified) Information Signal is transmitted over medium by modulating a carrier wave Amplitude, phase, and frequency or combination of these on the carrier Carrier Simple phase shift-keying modulate the phase of the carrier, e.g, BPSK shift the carrier wave 180 degree when info change between 0 and 1 QPSK allows phase shift in 4 values, e.g., 45, 135, 225, and 315 degree, with four different patterns hence representing two bits symbol, i.e., 2 bits represents 4 values QAM further mix phase shift together with amplitude change, giving more patterns, e.g., in QAM 16 the combination of phase shift and amplitude change 4 give us 16 patterns, representing a 4 bit symbol, i.e., 4 values, 2, QAM64 support 6 bits per symbol The more patterns we try to get a wave to exhibit, the closer these patterns are in terms of phase and amplitude and harder for receiver to decide especially when received signal is poor resulting in transmission error QPSK 01 Q 00 I Phase modulation Hence QAM 64 is used when the channel condition is good, and QPSK is used when high reliability is required, i.e., higher Signal to Noise Ratio (SNR) Baud Rate - The number of time we modulate a carrier per second When a carrier wave is modulated at a Baud rate B, it will occupy a spectrum range of B centered around the carrier frequency E.g., say f is the carrier frequency, then the spectrum used is : ((f+b/2) - (f-(b/2)) E.g., a 20Mhz bandwidth allocated to and operator at Mhz when modulated at QAM 16 is able to carry up to 80Mbps QAM Q I Actually useful data rate is smaller due to error check coding, overhead of channel etc

8 Source: IDA, Singapore Source: IDA Spectrum Management Handbook

9 3GPP LTE Bands LTE Band Uplink Band Downlink Band Duplex Mode Region MHz 1980 MHz 2110 MHz 2170 MHz FDD UMTS Core MHz 1910 MHz 1930 MHz 1990 MHz FDD US PCS MHz 1785 MHz 1805 MHz 1880 MHz FDD MHz 1755 MHz 2110 MHz 2155 MHz FDD US AWS MHz 849 MHz 869 MHz 894 MHz FDD US MHz 840 MHz 875 MHz 885 MHz FDD Japan MHz 2570 MHz 2620 MHz 2690 MHz FDD MHz 915 MHz 925 MHz 960 MHz FDD GSM MHz MHz MHz MHz FDD Japan MHz 1770 MHz 2110 MHz 2170 MHz FDD Extended AWS MHz MHz MHz MHz FDD Japan MHz 716 MHz 729 MHz 746 MHz FDD MHz 787 MHz 746 MHz 756 MHz FDD MHz 798 MHz 758 MHz 768 MHz FDD MHz 716 MHz 734 MHz 746 MHz FDD MHz 830 MHz 860 MHz 875 MHz FDD MHz 845 MHz 875 MHz 890 MHz FDD MHz 862 MHz 791 MHz 821 MHz FDD MHz MHz MHz MHz FDD MHz 3490 MHz 3510 MHz 3590 MHz FDD MHz 2020 MHz 2180 MHz 2200 MHz FDD MHz MHz 1525 MHz 1559 MHz FDD MHz 1915 MHz 1930 MHz 1995 MHz FDD MHz 849 MHz 859 MHz 894 MHz FDD MHz 824 MHz 852 MHz 869 MHz FDD LTE Band Uplink Band Downlink Band Duplex Mode Region MHz 748 MHz 758 MHz 803 MHz FDD 29 Downlink Only 717 MHz 728 MHz FDD MHz 2315 MHz 2350 MHz 2360 MHz FDD MHz MHz MHz MHz FDD 32 Downlink Only 1452 MHz 1496 MHz FDD MHz 1920 MHz 1900 MHz 1920 MHz TDD UMTS Core (TDD) MHz 2025 MHz 2010 MHz 2025 MHz TDD UMTS Core (TDD) MHz 1910 MHz 1850 MHz 1910 MHz TDD MHz 1990 MHz 1930 MHz 1990 MHz TDD MHz 1930 MHz 1910 MHz 1930 MHz TDD MHz 2620 MHz 2570 MHz 2620 MHz TDD MHz 1920 MHz 1880 MHz 1920 MHz TDD China UMTS TDD MHz 2400 MHz 2300 MHz 2400 MHz TDD China TDD MHz 2690 MHz 2496 MHz 2690 MHz TDD MHz 3600 MHz 3400 MHz 3600 MHz TDD MHz 3800 MHz 3600 MHz 3800 MHz TDD MHz 803 MHz 703 MHz 803 MHz TDD

10 LTE Architecture Uu SGW (Serving Gateway) - Mobility anchor PGW (Packet Data Network Gateway) - Interface to external packet network MME (Mobility Management Entity) - HSS Home Subscriber Server OCS (Online charging system) PCRF (Policy and Charging Rules Function) OCS Gy enodeb S1-MME HSS X2 MME S6a PCRF S1-U S1-MME S1-U S11 S5 Gx SGi Core Router Packet Data Network (PDN) Internet Gateway EPS (Evolved Packet System) Bearer SGW PGW Radio Bearer S1 Bearer S5/S8 Bearer Radio Bearer S1 Bearer S5/S8 Bearer EPS bearer is a tunnel that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base

11 LTE Architecture How does radio wave carries information? Uu enodeb How to track the location of user terminals? Security and Authentication? S1-MME How to mitigate interference between X2 neighbor cells? S1-MME S1-U SGW Radio Bearer S1 Bearer S5/S8 Bearer EPS (Evolved Packet System) Bearer How to optimize on the amount of info over radio? How to arbitrate the access of radio resource by user terminals? How does user terminal join S1-U the packet network? How to maintain QOS of MME different traffic types? S11 S5 PGW SGi Core Router S6a How to ensure that user data can be transported to/from packet network as user moves? HSS Packet Data Network (PDN) Internet Gateway EPS bearer is a tunnel that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base OCS PCRF

12 LTE Architecture How does radio wave carries Uu information? enodeb How to track the location of user terminals? Security and Authentication? S1-MME How to mitigate interference between X2 neighbor cells? S1-MME S1-U How does user terminal join S1-U the packet network? SGW Radio Bearer S1 Bearer S5/S8 Bearer EPS (Evolved Packet System) Bearer S11? How to optimize on the amount of info over radio? How to arbitrate the access of radio resource by user terminals? How to maintain QOS of MME different traffic types? S5 PGW? SGi Core Router S6a How to ensure that user data can be transported to/from packet network as user moves? HSS SGW (Serving Gateway) - Mobility anchor PGW (Packet Data Network Gateway) - Interface to external packet network MME (Mobility Management Entity) - HSS Home Subscriber Server Billing System Packet Data Network (PDN) Internet Gateway EPS bearer is a tunnel that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base

13 6 Resource Blocks ~ 1.1MHz 100 Resource Blocks ~ 20Mhz LTE Physical Layer Spectrum Bandwidth 1.4Mhz 3Mhz 5Mhz 10Mhz 15Mhz 20Mhz Range of spectrum bandwidth from 1.4Mhz, 3, 5, 10, 15, 20Mhz Downlink (DL) via OFDM-A (Orthogonal Frequency Division Multi-Access) and Uplink (UL) DFTS-OFDM OFDM-A divides spectrum into subcarriers of 15Khz Info are divided and transmit in these subcarriers in parallel at each at lower rate rather than being modulated at very high rate using the whole bandwidth over single carrier Each Subcarrier is structured in time domain as slot of 0.5ms with 7/6 symbols in each slot. Two slots forms a subframe (1ms) A Resource block is 12 subcarriers (total 180Khz) for a duration of 1 slot (0.5ms) Scheduler schedule resources in pairs of resource blocks, i.e., a subframe (1ms) Different modulation schemes (QPSK, QAM16/64) can be used based on UE radio conditions Much smaller symbol rate at 15khz rather than say full 20Mhz Symbol duration 66.7us and 4.69us for CP (Cyclic Prefix) CP period avoids symbol overlapping when signal are deflected during their propagation and resulting in multiple paths of different length 4.69us = 1.4km by speed of light, i.e., if a path of the first symbol is delayed less than 1.4km worth of distance then it will still not overlap with the data of the second symbol The CP of first symbol is longer at 5.2us A longer CP option support larger cell (longer path) in expense of 6 symbols per slot Inter-symbol Interference Larger Delay No. of Resource Block 15Khz One Symbol One Resource Element Resource Block CP UE 1 UE 2 Symbol Resource Block Resource Block Slot 0 Slot 1 Subframe (1ms) Time Frames Resource Block Resource Block Resource Block UE 3 Resource Block

14 LTE Control Data Channels Functional Overview Control information must be exchanged between basestations and UE For basestation to tell UE the control parameters and how fields are formatted For UE to be attached to the network to receiving service and tracked For basestation to communicate resource allocations at DL and UL Physical level control channels are critical and usually uses more robust QPSK (DL, UL) or even BPSK (UL) Physical level shared channels carries control from upper layer and data, could use QPSK, QAM16 or QAM64 depending on the channel condition of the UEs sharing the channel UL Data Voice, Video, Web DL Broadcast Master informatio n block DL Control Identify which UE transmits at which RB UE power control Acknowledge UL data Grant to UE UL request DL Data Voice, Video, Web UL Control Allow UEs to request for uplink transmission UL Random access allow unattached UE to establish initial radio link CQI (Channel Quality Indication) consist channel quality overall or specific UE selected set of subcarriers. In addition PMI (Precoding matrix indicator) and RI (Rank Indicator) is reported when MIMO is used

15 Mobile Radio Access Network Deployment RRH Pico cell radio head Antenna Coaxial Cable RRH (Remote Radio Head) CPRI/Fiber Cell 2 Cell 3 Power Cable Fiber Cabinet/Shelf Backup power Cell 1 Backhaul Base Station Hotel -> C-RAN (Centralized RAN) -> vran (Virtualized RAN)

16 DL Control and Data LTE Stack Reference Signal (RS) pattern known cell/antenna specific pattern for UE to asses channel quality, RS from different antenna locates differently in resource block to avoid inter-antenna RS interference User B UE NAS Non Stratum Access RRC (Radio Resource Control) User IP Packets PDCP (Packet Data Convergence Protocol) enodeb Maintaining connection with core, mobility management PDCP Header RRC (Radio Resource Control) User IP Packets PDCP (Packet Data Convergence Protocol) PDCP Header Ciphering, in-sequence delivery Header compression Integrity protection for control plane MME NAS Non Stratum Access Paging, Radio Bearer Control Mobility functions (handover) UE measurement control RRC connection set up Logical Channels - (Paging Control Channel paging for UE) PCCH Control Channels, e.g., PDCCH, PHICH occupy the first 1, 2 or 3 symbols of the subframe. Resource allocation to UE is done by PDCCH identifying it using RNTI (Radio Network Temporary Identifier) which is assigned to UE by enb (Broadcast Control Channel) BCCH 15Khz (Common Control Channel for initial control with UE before RRC attach) CCCH Resource Block User A Slot 0 Slot 1 Subframe (1ms) (Dedicated Traffic Channel bidirectional user data for one UE ) DTCH (Dedicated Control Channel for control to UE after RRC attach) DCCH User C Resource Block (Multicast Traffic Channel multicast user data ) MTCH (Multicast Control Channel) MCCH RLC (Radio Link Control) MAC (Medium Access Control) PHY Logical channels Transport Channels RLC (Radio Link Control) RLC Header MAC (Medium Access Control) MAC Header Transport Block PHY (H)ARQ = (Hybrid) Automatic Repeat Request Segmentation/Concatenation In-sequence Delivery RLC establishment H-ARQ Priority handling Mapping between logical to transport channel MAC Layer Transport Channels - Define transport characteristics like modulation, coding, antenna mapping Scrambling, Modulation, Layering Mapping, Antenna Mapping PCH (Paging Channel support UE power saving, page to cell coverage area) BCH (Broadcast Control Channel) PBCH (Physical Broadcast Channel Master information Block for UE access, QPSK) DL-SCH (Downlink Shared Channel shared among logical channels carry both control and data, decide dynamic resource allocation, modulation, coding, support beamforming, sleep cycle) Physical level control channels PDSCH (Physical Downlink Shared Channel, QPSK, QAM16/64) PDCCH (Physical Downlink Control Channel downlink allocation, uplink grant, power control, QPSK) PHICH PCFICH (Physical Hybrid- (Physical Control ARQ Indicator Frame Indictor for Channel Data location of the acknowledgement, PDCCH) QPSK) MCH PMCH

17 Uplink Control and Data Control Downlink - format of frames, allocation of downstream and upstream subscarriers/slot, acknowledgement of data received, paging for mobile terminals, reference pattern Uplink random access for attachment, bandwidth request, feedback on downlink channel quality Data both downlink and uplink (Common Control Channel for initial random access before attach) CCCH (Dedicated Traffic Channel user data for one UE ) DTCH (Dedicated Control Channel for control to UE after attach) DCCH UL-SCH (Uplink Shared Channel shared among UEs carry both control and data, dynamic resource allocation, modulation, coding) RACH (Random Access Channel for initial attachment from uplink) Transport Channels - Define transport characteristics like modulation, coding, antenna mapping PUSCH (Physical Uplink Shared Channel, QPSK, QAM16/64 ) PUCCH (Physical uplink Control Channel Quality feedback, scheduling request, H-ARQ for DL, BPSK, QPSK) PRACH (Physical Random Access Channel generates preambles for UE identification and provide random access)

18 MIMO Multi-Input Multi-Output MIMO Defined by convention as MxN in one direction M means the number of transmitter and N is the number of receiver Up to 4 antennas FDD and 8 antennas in TDD Assume all UE support two receivers MIMO make use of multiple antenna to achieve robustness of channel or higher capacity Make use of multipath condition SINR (Signal to Noise Ratio) When UE is in low SINR(Signal to Noise ratio) E.g., cell edge, transmit diversity or beamforming provide benefits High SINR environment SU MiMO or MU-MIMO can be used provide there are spatial diversity on the paths (low correlation) Transmit Diversity - Single data stream is coded differently on two antennas for transmission, don t assume feedback on channel quality - Improve data reception at cell edge ( mainly for control channels) but not higher rate Enhance cell edge performance Enhance peak performance Beam Forming - Improve coverage - Weighted phase and magnitude of individual antennas, work with interference - Require known channel state information, terminal estimate overall beamformed channel - Easier for TDD as downlink channel is same as uplink channel Close loop feedback from UE Useful when UE not in high speed mobility 1 Transmission layer is based on rank which is the number of linearly independent path (spatial layer) between M antenna and N receivers based on feedback from UE 2 Layers <= # Antennas, layers are split to antenna, single layer result in beamforming SU-MIMO Spatial Diversity - Multiple data streams to antennas for simultaneous transmission known as layers, Higher peak rate, 1,2 layers <= number of antennas - rate - Open or close loop feedback to precoder Multi-user MU-MIMO - Multiple UE transmit at the same time with same subcarriers - Rely on spatial diversity to achieve minimal interference, double the throughput

19 6 Resource Blocks ~ 1.1MHz 100 Resource Blocks ~ 20Mhz One Symbol One Resource Element LTE Cell Capacity Let s find the theoretical downstream throughput of 20Mhz DL with 2x MIMO spatial diversity - RB is 180Khz with 12 subcarriers at 7 symbols at 0.5ms slot, 1 subframe has 2 slots - For 20Mhz channel, number of RB is : Assume optimistically that QAM 64 is used, which carries 6 bit per symbol - Bandwidth per subframe = 100 RB x 12 subcarriers x 2 slots x 7 symbols x 6 bit per symbol 15Khz Resource Block UE 1 UE 2 Resource Block Resource Block Resource Block Resource Block Resource Block UE 3 Resource Block = bits per ms Slot 0 Slot 1 Subframe (1ms) - Bandwidth per second = 100Mbps - Factor in 25% overhead -> 75Mbps - Assume 2x2 MIMO with spatial diversity => 75x2Mbps = 150Mbps Basestation - Assume 4x4 MIMO with spatial diversity => 75x4Mbps = 300Mbps In Reality, the actual capacity of a cell depends on: Noise condition, Interference from other cells, location of the UEs within the cell The modulation and coding scheme (MCS) of a channel is dependent on the feedback CQI (Channel Quality Indicator) from the UEs that it serves UE nearby Signal received well QAM64 used Higher Throughput UE further away Signal is weaker QPSK used for robustness Smaller Throughput

20 LTE Architecture? How does radio wave carries Uu information? enodeb How to track the location of user terminals?? Security and Authentication? S1-MME How to mitigate interference between X2 neighbor cells?? S1-MME S1-U SGW Radio Bearer S1 Bearer S5/S8 Bearer EPS (Evolved Packet System) Bearer How to optimize on the amount of info over radio? How to arbitrate the access of radio resource by user terminals? How does user terminal join S1-U the packet network? How to maintain QOS of MME different traffic types? S11 S5 PGW SGi Core Router S6a How to ensure that user data can be transported to/from packet network as user moves?? HSS SGW (Serving Gateway) - Mobility anchor PGW (Packet Data Network Gateway) - Interface to external packet network MME (Mobility Management Entity) - HSS Home Subscriber Server Billing System Packet Data Network (PDN) Internet Gateway EPS bearer is a tunnel that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base

21 UE Attachment Procedure UE enb MME 1a. UE receives cell identify and master information block (MIB) with up and downlink control channel config via broadcast channel. 1b. Via the PDCCH, SIB is obtained which identify random access channel (PRACH) frequency and offset to make initial contact with enb 2) UE performs random access secure uplink resource and setup RRC with enb, obtain C-RNTI the UE identifier within the cell, 3). UE sent attach request including IMSI to MME 5b) MME sends AUTH vector for UE to verify, UE send response to MME for further checking 14. UE and enb set up security and encryption for RRC message and user data 15. enodeb and UE exchange messages on a) attach accept (NAS) with the assigned IP, TA list, GUTI, and b) reconfigure the RRC to activate default bearer 16a. enodeb sends Attach complete to MME EPS (Evolved Packet System) Bearer 4. enodeb relay attach request to MME, add its own ID, PDN connection Request enodeb 13. a)attach request accept with GUTI, TA list, b) request default bearer from enodeb to UE, c) initial context request to EnodeB with AMR, QCI, S1 SGW TEID 16b. enodeb response initial context, include enodeb TEID of S1- U bearer 5a. Authentication Request for the UE using IMSI. HSS assembles AUTH vector send to MME 6. Location update, HSS 7. HSS reply with APN, QOS profile include AMBR (aggregated bit rate), QCI, PGW address with assigned static IP if specified 8. MME request SGW create session, EPS bearer id, IMSI PGW address with APN, QOS 12. SGW response to MME and pass S1 SGW TEID for enodeb to create S1-U bearer 17. MME sends update bearer request to SGW with S1 enb TEID 9. SGW request PGW Create session, default EPS bearer id,s5 SGW TEID APN, QOS profile 11. PGW reply with assigned IP and authorized QOS profile, S5 PGW TEID Radio Bearer S1 Bearer S5/S8 Bearer Step 14 Step 11,12,14,15 (1). UE cell identification, synchronize physical layer parameters (2,3). UE set up Radio link with enb and request for attachment (NAS) to the mobile network with MME (5). MME checks with HSS to get authentication vector and mutual authentication with UE (6,7). MME updates the HSS on location and gets the profile of the UE, including APN, PGW address, QOS Profile etc. (8-12) MME set ups EPS bearer by first setting up the S11 and S5 bearer, it request SGW to create session with UE parameters from HSS. SGW and PGW set up the S5 bearer, PGW allocates IP address and check profile with PCRF. PGW response to SGW which then response to MME for bearer setup (13) MME verify bandwidth profile, set up bearer toward enb and UE, sends request to enb (14) enb establish secure communication over radio with UE (15-17) UE and enb set up the radio bearer, acknowledge the set up to MME, MME finalize the S1 bearer with SBW using info from enb HSS S11 SGW S5 Step 10/11 PGW 10 PGW checks with PCRF on policy using UE IP, IMSI, APN, QOS Profile. PCRF response with rules to be enforced in PGW Packet Data Network (PDN) PCRF Internet Gateway IMSI International Mobile Subscriber Identification consists of MCC (Mobile Country code, MNC (Mobile Network Code), MSIN (Mobile Subscriber Identification Number) TEID (Tunnel Endpoint ID) is end point identification for GTP (GPRS Tunnel Protocol) tunnel implementing bearers QCI (QOS Class Identifier) APN (Access Point Name) identifies PDN/service to be connected GUTI Globally Unique Temporary ID, MME s identifiers for a UE TA List list of tracking areas within which UE don t need to update MME

22 Tracking Area Cells are grouped into individual tracking area (TA), a number of tracking areas (up to 15) put under a tracking area list MME keeps track of a UE in terms of its current TA list, TA list is also given to UE when it register with the MME UE updates the MME when it moves to a TA not in its TA list via an action called TAU (update) trade off on size of TA, TAL and TAU frequency) When downstream data comes for an idle UE, the MME send a paging to cells on the TA in the UE s TA list Cell page for UEs using paging occasions on (PDSCH) and defined by (PDCCH) A sleeping UE wakes up periodically and listen to paging, the period is called default paging cycle cycle length (DRX discontinuous receive cycle) trades response time against UE battery consumption MME TA-5 UE checks the paging occasions for its own identification, if found, it sends service request to MME TA-2 TA-1 TA-3 TAU TA-4 TA List TA List

23 Handover via X2 Procedure Original traffic between source node and UE DL traffic forwarded by source node to target node and to UE after step 6 UL traffic from UE via target node after step 6 DL traffic from UE via target node after step 9 EPS (Evolved Packet System) Bearer Target enb 3 5 Source enb MM E 8 9 SGW 1. UE sends Cell Measurement Report on source and neighbor enb 2. Source node identify better performance can be achieved if UE use a neighbor enb and initiate Switch Over Request to target node 3. Target enb checks resource to take in UE, send reply to Switch Over Request together with target enb own parameters 4. Source enb instructs UE to switch to target node with Radio Reconfigure Request (RRC) with target enb parameters 5. Source enb sends Transfer Status update to target enb on transport status, relay DL data to UE via X2 bearer to target node 6. UE synch, attaches to target enb running RRC confirm with target enb 7. Target enb sends path switching request to MME 8. MME sends Modify Bearer Request to SGW 9. S-1 bearer between SGW and target node is set, SGW ack Modify Bearer Request 10. MME acknowledges the Modify Bearer Request to target node 11. Target node instructs the source node to release the UE context PGW Packet Data Network (PDN) Internet Gateway Radio Bearer S1 Bearer S5/S8 Bearer Step 13 Step 11,12,14,15 Step 9/10

24 LTE Architecture How does radio wave carries Uu information? enodeb How to track the location of user terminals? S1-MME How to mitigate interference between X2 neighbor cells? S1-MME S1-U SGW Radio Bearer S1 Bearer S5/S8 Bearer EPS (Evolved Packet System) Bearer How to optimize on the amount of info over radio? How to arbitrate the access of radio resource by user terminals?? How does user terminal join S1-U the packet network? How to maintain QOS of MME different traffic types? S11 S5 PGW SGi Core Router S6a How to ensure that user data can be transported to/from packet network as user moves? HSS SGW (Serving Gateway) - Mobility anchor PGW (Packet Data Network Gateway) - Interface to external packet network MME (Mobility Management Entity) - HSS Home Subscriber Server Billing System Packet Data Network (PDN) Internet Gateway EPS bearer is a tunnel that transport packets between UE and PGW. It connects the UE via PGW to the PDN. It is per UE base

25 Frequency Reuse Refers to how frequency band are used in cell deployment Reuse of 1 => the same frequency is used in all sector Reuse of 3 => frequency band is reused every 3 sectors lower utilization of whole band Inter-cell Interference (ICI) occurs when a UE is in the edge of a sector and is subceptable to the interference of a neighbor cell Reuse of 1 result in high ICI A reuse 3 approach divides the frequency band among 3 sectors eliminate ICI but result in much lower cell capacity Reuse 1 Reuse 3 Reuse ~1 with SFR SFR (Soft Frequency Reuse) divide the frequency into minor and major band. Major band is used all the way up to cell edge by using higher power, and minor band is used in the cell center at lower power. Major bands can be derived by dividing whole band into 3 non overlapping bands. Full capacity is harnessed at the cell center with a reuse of 1 At the edge due to the division of frequency, the reuse is >1, e.g., 3 Furthermore band power can be adjusted to change the extend of reuse depending on the inter-cell condition and UEs requirements S1 S2 S3 S1 S2 S3 f1 f2 f3 major S1 band f1 S2 minor band f2 S3 minor band minor band minor band f3

26 Heterogeneous Network Quality of Experience issues Coverage problems at cell edge or indoor, e.g., terrace house and deep in office buildings, poor voice quality Capacity problem at hotspot, low mobile broadband throughput and poor user experience Build more macro cell Site acquisition issue and macro cells start to interfere with each others Heterogeneous Network - Small cells of lower power Macro (40W), Micro, Pico/metro (5-10W), and Femto (100mw) Serves smaller area providing or increase the capacity in hotspot A small cell is connected via wireline broadband network to core via a small cell gateway or alternatively, it is a radio head and connects via optical fiber to nearby basestation for baseband processing UE locked onto a small cell when signal is above threshold, use further bias configuration to bias UE towards connecting with small cell, thus offloading the traffic from macro cell, thus extending the range Issue with interference from macro cell at the small cell edge Coverage Issue Femto cell dedicated to private user group e.g., home or office UE Capacity Issue at hotspot Coverage and Capacity Issue Lower power pico cell Metro/Pico cell serves public UE in a hotspot area Build more macro cell Heterogeneous Network - Build smaller calls of lower power Wireline broadband Potential interference from macro Optical fiber Macro cell still provides overall coverage

27 LTE-A - eicic eicic (Enhanced Inter-cell Interference coordination) UE at pico/metro cell edge tends to suffer from interference from macro cell Interference onto the pico cell can be reduced if the macro cell refrain from using the subframes that pico cell is using on it s edge UE/s Pico cells exchange load info with macro cell which takes account of own load and Macro cell identify which resource blocks not to be used, called ABS (Almost Blank subframe) Pico cells near to the macro cell can allocate the same subframe corresponding to the ABS for UEs at the edge as there will be less interference from macro Synchronization between the pico and macro as both must now aligned on ABS subframe Corresponding subframe assigned to UE at Pico cell edge Pico submit load and Macro cell informs ABS pattern Macro cell determines the ABS based on load of Pico and Macro cell Macro eicic Scheduling

28 LTE-A CA CA Carrier Aggregation - Operators often have license to multiple frequency blocks, may be in the same band or different band - Being able to allocate them to UEs together increase peak rate of UEs, and potentially increase utilization efficiency Intra-band contiguous Intra-band noncontiguous Inter-band noncontiguous - Up to 5 carriers (component carriers) to transmit data down or upstream, currently up to 3 is defined - Component carriers can be in same band or different band e.g., GSM refarming, and newly acquired 2.6Ghz band - Primary frequency known as PCell is responsible for signaling such as mobility management and allocate one more secondary frequency known as SCell to UE - Algorithm runs in basestation to decide whether to activate CA configuration of UE depending on availability of resource and UE demand, deactivate when not needed to save UE power - Multiple scenarios Low band + high band -> low band provides coverage and high band provides capacity FDD+TDD -> FDD at macro provides coverage and TDD as RRH provides additional capacity Macro+small cell using different frequency macro provides coverage and small cell provides capacity Low band + Highband Pico+ Macro or FDD + TDD Pico/TDD RRH f2 - scell f1 - pcell f1 - pcell f2 - scell macro

29 LTE-Advanced - COMP COMP (Coordinated Multipoint Transmission) Coordinates among a set of transmission (Tx) or receiving points (Rx) which can be intra or inter site to provide better performance at the cell edge by mitigating interference Two major approaches Coordinated Scheduling/Coordinated Beamforming achieving interference avoidance, Joint Processing/Joint Transmission or Joint Processing/Dynamic Point selection (DPS) where multiple Txs transmit to the cell sites Coordinated Scheduling/Beamforming enodeb_2 Only the serving cell receive data stream and transmit other Tx points are coordinated at the scheduling or beamforming to reduce interference. Serving cell transmission Joint Processing Joint Transmission/Dynamic Cell selection RRH_1 Data stream to both Tx JT both Tx in a Frequency time resource RRH_2 DCS one Tx transmit at a time

30 LTE-Advanced Carrier Aggregation UE Category UE Category DL Spatial MIMO Layer UL Spatial MIMO Layer QAM 64 DL QAM 64 UL RF Bandwidth DL Peak Rate Up to Release 10 UL Peak Rate Category 1 Optional No Yes No 20Mhz 10 5 Category 2 2x2 No Yes No 20Mhz Category 3 2x2 No Yes No 20Mhz Category 4 2x2 No Yes No 20Mhz Category 5 4x4 No Yes Yes 20Mhz Category 6 2x2 or 4x4 No Yes No 40Mhz Category 7 2x2 or 4x4 2x2 Yes No 40Mhz Category 8 8x8 4x4 Yes Yes 100Mhz

31 Further Development LTE in Unlicensed band (LTE-U) Licensed Assisted Access (LAA-LTE) where LTE runs on unlicensed band, 5GHz being considered Licensed band macro serve as primary cell for signaling and basic service, use local cell with unlicensed band as supplementary either only on downlink or with uplink as well, based on CA (carrier aggregation) 3GPP Release 13 work items LTE and WiFi Aggregation (LWA) Part of LTE traffic is tunneled via WiFI (hence still using WiFi medium access, AP etc.) LTE traffic at licensed band and those tunneled via WiFi is combined at the local enb e.g., small cell Better coexistence of WiFi as there is no LTE RAN in the unlicensed band, no hardware change in UE 3GPP Release 13 work items Machine to Machine communications, IOT (Internet of Things) Still very loosely defined Huge number of devices at low bandwidth, sleep and communicate Reduce complexity on UE to reduce power, e.g., reduce bandwidth capability, transmission mode Support for longer distance