LS telcom AG · XETR:LSX
LS telcom — LS Summit 2014
20 slides from LS telcom's conference presentation, July 2014
Slide 1: Modelling LTE 800 Interference on DTT
Modelling LTE 800 Interference on DTT The Approach to Mitigating Interference in the UK Marcus Buchan LS Summit July 2014
Slide 2: The DMSL Background
The DMSL Background • DMSL was instigated by the UK Govt. in 2012 • UK Govt. set-out MNO funding for DMSL • DMSL uses the consumer brand at800, online as at800.tv • DMSL operates under KPI’s monitored by an Oversight Board • Based in London using suppliers to provide key functions such as contact ce
Slide 3: The 800 MHz band plan
The 800 MHz band plan • Inverted Uplink/Downlink used in LTE800 • Only 1 MHz Guard band between DTT and LTE800 3
Slide 4: The Interference Issue
CLEAR ELOY The Interference Issue
Slide 5: Protection ratios
Protection ratios A protection ratio is used to indicate how strong a signal needs to be to interfere with another signal. • This is the ratio (in dB) by which the received power of the wanted signal must exceed that of the unwanted signal to ensure that interference does not occur. • For a mobile s
Slide 6: Mechanisms of Interference
Mechanisms of Interference • DTT Receiver Overload • DTT Receiver Selectivity to Adjacent Channel Interference (ACLR) • DTT Remote amplifier Blocking – both Mast Head Amplifiers and Distribution Amplifiers 6
Slide 7: Most demanding cases
Most demanding cases A combination of some or all of the following factors may result in particularly demanding interference cases: • The LTE base station(s) and the TV aerial are in close proximity • There are multiple LTE base stations nearby • The DTT multiplexes are on channels close to the LTE
Slide 8: Measuring a 4G Signal
Measuring a 4G Signal Display shows DTT multiplexes on Channels 51 and 52 and LTE signal at 795MHz. No interference is present on the DTT signals 8
Slide 9: Measuring a 4G Signal with LTE800 interference
Measuring a 4G Signal with LTE800 interference Display shows DTT multiplexes on Channels 51 and 52 and the LTE signal at 796 MHz after passing through an amplifier. The LTE signal level has overloaded the amplifier and caused it to operate in a non-linear fashion 9
Slide 10: Filters
Filters • The primary means of mitigating interference is the use of a filter • Filters fix the vast majority of interference issues when used in the right place. • at800 has procured a selection of filters for different installation types and these will be available to installers 10
Slide 11: Interference Modelling
Interference Modelling • Based On Ofcom Model and Protection Ratios • Uses the UK Planning Model (Pre-calculated DTT coverage data) for determining the Location Probability calculated using the median and standard deviation of the received wanted and unwanted signal power* • Early Software Punch sup
Slide 12: Challenges to DTT Interference Modelling
Challenges to DTT Interference Modelling • Assumptions are made about the DTT receive system with regards to: – Gains and Losses – Angular discrimination of Receive antenna, ITU-R Rec.419-3 – Location of the DTT transmitter • Assumptions are made regarding the Protection Ratios used: – An average DT
Slide 13: What does the model do?
What does the model do? • Uses MNO LTE800 network data to predict LTE800 coverage per pixel per LTE800 cell • Adds the DTT Receive Antenna discrimination (polar and angular) and Protection Ratio to each LTE interferer per pixel • Uses the Schwartz & Yeh Log Normal Power summation method to sum inter
Slide 14: Speed of Process
Speed of Process DOES NOT REFLECT ACTUAL UK MAST DEPLOYMENTS 14
Slide 15: Analysis of Results from CHIRplus
Analysis of Results from CHIRplus • Three UKPM layers are processed by the model to determine most heavily impacted pixels using the DIA protection ratio sets • Pixels are processed based on severity of degradation • Households within an affected pixel are mailed (leaflet) if criteria are met • Data
Slide 16: Model Tuning
Model Tuning • Ongoing efforts to improve model accuracy include: – Looking at propagation model used, currently SEAMCAT HATA – Impact of clutter – Impact of Terrain – Accuracy of Protection Ratios – Power characteristics of MNO LTE800 eNodeB equipment and ACLR – Looking to improve current use of UK
Slide 17: Current Status
Current Status • 10 months of rollout; ~ 2000 confirmed interference cases to date • Mostly Block B&C active in UK so far; little adjacent channel data • All confirmed cases of LTE800 interference have occurred within 900m of an LTE mast • Call Centre constantly updated regarding areas of deployment
Slide 18: Way Forward
Way Forward • Further model tuning required – this will help refine knowledge on the mechanisms of interference from mobile networks on DTT • Likely future release of DTT 700 MHz spectrum (694 MHz to 790 MHz) – larger Guard Band of 9MHz, Uplink adjacent to DTT spectrum to comply with existing Handse
Slide 19: Alternatives to Modelling
Alternatives to Modelling • Reactive scenario – using Call Centre to triage complaints only and issuing advice and post filters as necessary • Spatial determination of proximity to mast to determine likelihood of interference • Mix of both Reactive scenario and Spatial determination • What do we lea
Slide 20: Any Questions?
Any Questions? Contact Details: marcus.buchan@at800.tv www.at800.tv 20