The Ascent of RAN? Agenda

Transcription

1 LTE and the death of the macrocell The Ascent of RAN? Dr Doug Pulley Co-founder and Chief Technical Officer Agenda Brief Introductions The Problem Statement The Solution Statement The Challenge Statement Femtocell Re-use Self-organising for an easier life Making a cheap base station Network interference simulation Conclusions 2 of 27 1

2 Who are we? a fabless semiconductor business founded in 2000, making multicore DSP chips, and reference designs for HSPA, TDSCDMA, WiMAX and LTE base stations funded by >$75M of venture capital investors include Intel, AT&T and Samsung and is the leading supplier of chips for femtocells Bath, UK Beijing, China 3 of 27 Traffic trends: where and why Outside Outside Work Home Work Home Now Future 29% of calls placed at home: JD Power % of mobile minutes at home or at work: Northstream % of 3G traffic to originate in-building by 2011: VisionGain of 27 2

3 Come inside Macrocells don t do in-building coverage Overview 5 of 27 But we have new air interfaces? HSPA, LTE and WiMAX focus on high speed packet data World is converging on OFDMA- MIMO variants with higher bandwidth etc signal For max throughput: Largest constellation higher SNIR well-equalised channel All packets successfully scheduled/received MIMO channel decorrelation Look at the distance scale on typical LSTI result plots! 64QAM 16QAM QPSK wall distance Indoor penetration significantly increases the likelihood of poor SNR 6 of 27 3

4 The problem statement Wide area macrocell coverage will only deliver a small proportion of the theoretical aggregate throughput This reduced throughput is smeared over a large geographical area, and hence many users, resulting in a double reduction in per user throughput a poor utilisation of spectrum and electronics In addition, indoor penetration will be poor resulting in poor user experience To solve using macro network: For a small network of 5,000 initial sites and 225,000 net present value per site, achieving a metre of extra coverage depth inbuilding via an increased macrocell deployment would cost 290 million - Prof. Simon Saunders, Femtoforum 7 of 27 Shannon, Isenberg & Cooper Shannon s Law There is a limit to link capacity and we are getting close to it. Higher C/I means shorter range. Cooper s Law Wireless capacity doubled every 30 months for 105 years. Most significant gain is the reuse of frequencies in smaller and smaller cells. Isenberg The rise of the stupid network Push intelligence out to the edge Capacity gain since Total Smaller cells More spectrum Channelisation Modulation A route to scalability? 8 of 27 4

5 The solution statement Much smaller cell radius with indoor deployment as required to ensure higher SNRs hence higher aggregate throughputs per carrier than the macrocell shared by a smaller population of users a double win Use a two part deployment model: For public access A deployment of contiguous small cells to create hot zones (driven first by HSPA/LTE USB modems) An overlay network of macrocells for predominantly for rural, sparse or low traffic density areas For private access and hence public RAN traffic offload residential femtocell (driven later by traditional form-factor handsets) If you are an HSPA operator you already have the overlay network as terminals will be dual mode LTE can be a very incremental roll-out and hence incremental capex 9 of 27 The challenge statement Basic small cell base stations requirements: very cheap (if the cell radius has shrunk ten times then there need to be 100 times more cells) easy and cheap to operate and manage coexist with each other and the macro network in an efficient amount of spectrum If you are an operator of HSPA and LTE for public access you want to light up spectrum with both from the same box for residential access you want to provide access to all the devices in the property (not just the LTE user) you need dual mode 10 of 27 5

6 status quo ante bellum 11 of 27 Failing to achieve escape velocity Real mass deployment of picocells has always been just around the corner Capacity by some cell radius shrink but still macrocell/microcell units Indoor coverage by Distributed Antenna Systems (DAS) Why? held back by cost held back by deployability held back to avoid revenue cannibalisation why sell a cheap one when an expensive one will do? 12 of 27 6

7 A what-o-cell? The traditional definition femtocell - noun a low-power domestic access point using conventional mobile technology in licensed spectrum generating coverage and capacity over internet-grade backhaul at prices comparable with Wi-Fi access points with full operator management Generic Femto Network Architecture 13 of 27 Topical News Quiz From Cash-strapped Spectrum Owners Gazette : A. Residential B. Enterprise C. Metro D. Rural E. All of the above femto cut my capex! 14 of 27 7

8 Dual Mode HSPA/LTE Femto Network Femto (HNB) MSC Gateway (3G) SGSN GGSN Iu-CS Iu-PS Gn Iu-h to/from other HNBs Iu-h Femto (ehnb) Gateway (LTE) S1 MME Home: DSL connection, ISP network Enterprise: Ethernet LAN connection & through gateway to internet S1 X2 S1/X2 to/from other ehnbs Uu (LTE) Femtocell (HNB and ehnb) Uu (LTE) Uu (HSPA+) 15 of 27 Dual mode HSPA+/LTE xfemtocell Iuh, S1, X2 DDR DDR WiFi RFIC 4 port Ethernet OSC RF RF Sync HSPA+ PHY LTE PHY Flash O A & M HSPA+ Stack LTE Stack feynman SoC Home Network Router Flash Ethernet PHY Backhaul i/f ADSL TCVR + AFE Residential Enterprise Public Access Deployment Scenario I/F 16 of 27 8

9 Dual mode HSPA+/LTE xfemto Feature Technologies Bandwidths Throughputs Capacity Backhaul MIMO Max cell range/mobility LTE rel8 FDD/TDD HSPA+ rel8 FDD (including 64QAM+MIMO on the downlink) LTE: <=20 MHz HSPA+: 5 MHz LTE max throughput 90 Mb/s with 2x2 MIMO for both UL and DL HSPA+ 42 Mb/s DL (2x2 MIMO DL+64QAM), 11.5 Mb/s UL Residential: 8 users LTE plus 8 simultaneous users HSPA+ Enterprise: 16 users LTE plus 16 simultaneous users HSPA+ Residential: DSL Enterprise: Ethernet LTE: 2x2 SU-MIMO DL, 2x2 MU-MIMO UL HSPA+: 2x2 SU-MIMO DL, 1x2 SIMO UL 500m / 2.5GHz 17 of 27 LTE and SON A key part of the deployment of LTE enodebs is the use of Self Organising Networks (SON) enbs take responsibility for some of their own: Self-configuration Self-optimisation A formalisation of the plug-and-play concept being used in WCDMA Femtocell deployments SON relies on measurements made by enbs and by connected UEs Some enb measurements may require the use of a Network Monitor mode; aka DL Receiver or UE sniffer For LTE Femtocells, a multi-mode UE sniffer may also be required where there is no overlaying LTE macro coverage 18 of 27 9

10 LTE SON Stages HSPA Femtocell has already cracked this! LTE is easier as femtocells are comprehended from the outset 19 of 27 Interference Scenarios Aggressor Victim 1 UE attached to Home Node B Macro Node B Uplink 2 Home Node B Macro Node B Downlink 3 UE attached to Macro Node B Home Node B Uplink 4 Macro Node B Home Node B Downlink 5 UE attached to Home Node B Home Node B Uplink 6 Home Node B Home Node B Downlink [From 3GPP TR V1.0.0 ( ) other system scenarios not shown] of 27 10

11 Its all about the statistics! house Two levels of analysis to perform: In-building propagation: Residential Enterprise Network layer: All forms (includes metro, rural) Max UE area Max femto BS area 21 of 27 Macro/Femto Network Coexistence Macro Layer Downlink Av. sector throughput Throughput (kb/s) Femtos per Macro Sector Worst case scenario: All enbs and HeNBs are co-channel ( re-use=1 ) Operation of LTE femto under LTE macro layer with closed access No mitigation techniques Femtos only increase aggregate network throughput Open case and interference mitigation only improve the situation 22 of 27 11

12 Indoor Environment Modelling Semi-detached Apartment block 23 of 27 LTE In-building Environment Simulation 24 of 27 12

13 Scenario analysis: Uplink Noise Rise d Femto 3GPP LTE Power Control Algorithm (3GPP TR ) With cross correlated shadowing But no special mitigation techniques d 25 of 27 Comparison between HSPA and LTE? WCDMA femtocell has paved the way: established the concept driven innovation in network, system and component technologies and is hence ahead time-wise in market maturity etc LTE has life a little easier: WCDMA has paved the way - femtocells have to be retro-fitted into established networks with some operator apprehension LTE can introduce femtocells far earlier LTE has a more amenable network architecture BUT interference management needs careful attention 26 of 27 13

14 Fast track to wireless endgame. Theoretical air interface throughputs are not delivered in wide area coverage Residential femtocells have generated the innovation and acceptance required to liberate small base stations for mass deployment in public access networks LTE provides formalised approaches to the intelligent base stations required but you still have to insert the intelligence ENDGAME: Reliance on centrally-managed macrocells for delivery of any significant proportion of network capacity can be consigned to the past 27 of of 27 14