SET Congress Sao Paulo 24 August in the 700 MHz band

Transcription

1 SET Congress Sao Paulo 24 August 2014 Study of LTE interference into DTT in the 700 MHz band Mats Ek

2 Content of Presentation 1. Overview /introduction 2. Interference basics 3. The LTE Downlink (from base stations) ISDB-T 4. The LTE Uplink (from mobiles/ue) ISDB-T 5. Mitigation 6. Summary / conclusions

3 1. Digital Dividend overview Interference from Mobile service 700 MHz Dividend To be decided by ITU-R at WRC 2015 Broadcast channels 14-51(48) LTE Uplink LTE Downlink 470 MHz 694/ MHz Frequency Mobiles Mobile Base stations Interference from Broadcast Broadcast site Broadcast channels above 694/698 MHz

4 1. Proposals for LTE band MHz APT (Asia Pacific Telecom) band plan for LTE Uplink in range MHz and downlink in range MHz 4

5 2. LTE interference cases Two cases o Not fulfilled Protection ratios (PR) o ISDB-T receiver or amplifier overload (Oth) ITU-R BT defines Protection Ratios and Overload Thresholds for DTT receivers (ISDB-T and DVB-T) Measurements from Mackenzie University for ISDB-T DTT LTE Measured protection Ratio for a ISDB-T signal) Interfered with by an LTE BS signal in adjacent channels ISDB-T 64QAM FEC 3/4 Downlink LTE - 45 MHz ( ) - 100% traffic load Guard Band [MHz] PR [db] ACS [db] PR' [db] co-channel CH42 ( MHz) CH43 ( MHz) CH44 ( MHz) CH45 ( MHz) CH46 ( MHz) CH47 ( MHz) CH48 ( MHz) CH49 ( MHz) CH50 ( MHz) CH51 ( MHz) Max: Min:

6 2. Interference fundamentals o o Out of Band (OOB) suppression (ACLR) at LTE BS or LTE UE Adjacent channel selectivity (ACS) to suppress interference Guard band DTTB DTTB 5MHz ACLR ACS 45MHz Transmitter mask ACLR: Adjacent Channel Leakage Ratio, characterises the out of band (OOB) emission of the interfering LTE signal ACS: Adjacent channel selectivity, characterises the selectivity of the DTT receiver Receiver filter 6

7 2. Protection criteria used ACLR LTE BS [db] LTE OOB emission level/ 6 MHz [dbm] DTT Receiver ACS [db] Protection Ratio PR (worst case) [db] Overload Oth [dbm] LTE Downlink (BS) LTE Uplink (UE) Specified by 3GPP and Anatel From Mackenzie University Measurements 7

8 2. Two types of studies MCL (Minimum Coupling Loss) LTE Uplink and downlink o Calculation at critical distance o OOB for LTE (BS and UE) and DTT receiver selectivity (ACS) requirements. o Impact of receiver overload o Impact of additional filtering Coverage simulation in São Paulo using PROGIRA plan software to show interference from LTE BS (downlink only) DTT transmitter data Mobile site data Terrain + population data 8

9 2. LTE Downlink interference cases LTE BS ISDB-T DTT TX LTE Base station LTE BS Rooftop DTT 30m o LTE BS at 30 m DTT rooftop antenna at 10m o o Normal Rooftop With Antenna amplifier DTT TX LTE Base station 10m Critical Distance DTT LTE BS Communal antenna 30m Amplifier DTT o LTE BS at 30m DTT communal antenna at 30 m -possibly on same roof! DTT DTT 9

10 3. MCL for LTE Downlink LTE UE rooftop DTT Parameter Units Normal Rooftop Rooftop booster Rooftop communal 1 Frequency MHz Receiver NF db Noise bandwidth (B) MHz Thermal noise floor (N) dbm SNRmin db Minimum Rx Signal Power (Ps,min) dbm In-block transmit power dbm/(10 MHz) interferer antenna gain dbi Feeder loss db EIRP dbm/(10 MHz) Rx Tx horizontal distance m Tx height m Rx height m Path distance m Free space attenuation db Rx/TX antenna elevation discrimination gain db Rx antenna bore-sight gain dbi Amplier gain db Feeder loss db Total coupling gain (G path ) db Interference level received at DTT Receiver (I rx ) dbm Amplifier Gain 10

11 3. MCL Summary for Downlink (LTE DTT) LTE Downlink Interference ( MHz) TV Reception recption case ( MHz) Maximum interferer signal power received (dbm) Required Protection Ratio (db) Required attenuation to avoid overload (db) Required DTT Receiver ACS improvement (db) Required LTE BS ACLR improvement (db) Normal Rooftop Antenna Rooftop Antenna with Booster Community Antenna Overload of Receiver Mitigation needed to avoid Exceeded PR is shared equally between LTE and ISDB-T 11

12 3. LTE Downlink coverage simulations PROGIRA plan simulations using 1280 existing mobile base station in São Paulo area belonging to one operator o Using different reception characteristics: o rooftop o rooftop with booster o communal antenna o (indoor o indoor with booster o Mobile) o Show areas where LTE 700 MHz downlink interferes with a real DTT network o Insufficient Protection Ratio (PR) o ISDB-T receiver overload (Oth) 12

13 3. PROGIRA plan simulations Sao Paulo (1). 13

14 3. PROGIRA plan simulations Sao Paulo (2). 14

15 3. PROGIRA plan simulations Sao Paulo (3) 15

16 3. PROGIRA plan simulations Sao Paulo (4) 16

17 3. PROGIRA plan simulations Sao Paulo (5) 17

18 3. PROGIRA plan simulations Sao Paulo (6) 18

19 3. Coverage simulations Downlink - Summary São Paulo DTT population coverage (restricted area) Reception mode Fixed rooftop Normal Fixed rooftop Booster Fixed rooftop Communal Without Interference Total Population in area Total population coverage without interference Covered With interference With Interference Total interfered Total interfered [%] Interfered due to DTT receiver overload Oth = -5.7 dbm

20 3. Downlink LTE interference from - summary DTT receiver overload -main problem for rooftop reception using amplifiers and in communal antennas systems. Overload may occur at all UHF channels Frequency difference is more than 60 MHz Filters at DTT receivers would solve most cases The current OOB specifications given by the 3GPP specifications and Anatel are not sufficient for LTE BS. Reduction of 30 db is recommended Improvements in DTT receiver ACS is needed- possibly using external filters Difficult to position LTE Base station on same roof as Community antennas 20

21 4. Uplink interference cases LTE UE DTT o LTE handset DTT rooftop antenna at 10 m With amplifier Without amplifier LTE handset DTT rooftop Community antenna at 30 m 21

22 4. MCL for LTE Uplink (LTE UE rooftop DTT) Parameter Units Normal Rooftop Rooftop booster Rooftop communal 1 Frequency MHz Receiver NF db Noise bandwidth (B) MHz Thermal noise floor (N) dbm SNRmin db Minimum Rx Signal Power (Ps,min) dbm In-block transmit power dbm/(10 MHz) interferer antenna gain dbi Body loss db EIRP dbm/(10 MHz) Rx Tx horizontal distance m Tx height m Rx height m Path distance m Free space attenuation db Rx antenna elevation discrimination gain db Rx antenna bore-sight gain dbi Amplier gain db Feeder loss db Total coupling gain (G path ) db Interference level received at DTT Receiver (I rx ) dbm

23 4. MCL findings for uplink (LTE UE DTT) LTE Uplink Interference ( MHz) TV Reception case ( MHz) Normal Rooftop Antenna Rooftop Antenna with Booster Maximum interferer signal power received (dbm) Required Protection Ratio (db) Required attenuation at DTT receiver to avoid overload (db) Required DTT Receiver ACS improvement (db) Required ACLR (LTE OOB) improvement (db) Community Antenna Normal Indoor Antenna Indoor Antenna with Booster Mobile Reception Cannot be mitigated by a filter at receiver giving 20 db attenuation 23

24 MHz- uplink interference example 1 (2) Transmit power of LTE UE (outdoor) LTE site 30 m antenna height 2km LTE terminals far away from BS will use higher power More likely to cause interference 24

25 MHz - uplink interference example 2(2) Example for rooftop reception no mitigation Without interference With LTE UE interference from 8 mobiles But in reality there are many more mobiles! 25

26 4. LTE UE uplink interference summary 1 (2) More difficult to handle because UE can appear everywhere Frequency difference is only 5 MHz (worst case) DTT receiver overload probably not that bad since most LTE UE normally use lower EIRP Indoor cases difficult to mitigate 26

27 MHz uplink summary- Requirements for OOB and Adjacent channel selectivity (ACS) 2 (2) ANATEL and 3GPP requirement for OOB dbm -50 dbm 6 MHz DTTB ch 51 5 MHz Guard Band 23 dbm Mobile output power LTE BW i.e. 5, 10 MHz etc 698 MHz 703 MHz Reduction of OOB from LTE terminal to about -50 dbm/6 MHz is needed improvement of DTT receiver ACS from 55 db db 27

28 5. Possible mitigation- Filters at receiver Other Mitigation: o o o OOB requirements of LTE UE and base station ERP restriction of UE and LTE base station in critical areas Vertical radiation pattern and antenna height of LTE base stations LTE uplink attenuation of 20 db for lowest LTE channel LTE downlink - attenuation of about 50 db for lowest LTE channel 28

29 How to achieve quality in DTT networkswith respect to the upcoming 700 MHz mobile allocation? Cooperation between authorities, mobile operators and broadcasters about Technical requirements Regulatory requirements Clarify responsibilities if interference occurs Who will pay? Proactive or Reactive? cooperation between mobile operators Allow Sufficient time for broadcasters to switchover from 700 MHz frequencies! Careful planning needed 29

30 Thank you for listening! Welcome to visit us at SET stand A13 30