Power consumption of base stations

Transcription

1 Power consumption of base stations Ghent, 14/02/2012 Alberto CONTE Alcatel-Lucent Bell Labs France

2 Outline BS consumption... why we care? Functions, grouping and integration Power consumption figures Consumption vs. Cell Load Possible BS power models 2

3 Mobile Communications: where is the power going? 0.1W 1kW 1kW 10kW 2 TWh/a 60 TWh/a <1 TWh/a 14 TWh/a Based on: ETSI RRS05_024, NSN More than 90% is used to power the radio sites!!

4 Outline BS consumption... why we care? Functions, grouping and integration Power consumption figures Consumption vs. Cell Load Possible BS power models 4

5 Base station functional components PSU efficiency - ~ % Fan consumption - ~ W Cooling - ~ W Analogue connection -Losses: - feeder = length * loss - jumper <= -0.5dB from/to backhaul and neighbor cells (X2) base band unit (BBU) PSU cooling / fans controller / switch / I/O PSU = Power Supply Unit BB signal BB BB signal processing processing signal BB processing modem I/Q samples radio heads Digital connection - internal/external (e.g. cpri) - no losses PA PA analogue processing (A D) I/O PSU PA PA analogue processing (A D) I/O PSU PA PA analogue processing (A D) I/O PSU Power Amplifiers #PA depends on: - #s (e.g. MIMO ) - supported bands PA efficiency w.r.t. load: - 10% RF Pow = 6..10% - 30% RF Pow = % - 50% RF pow = % - 100% RF Pow = % Radio heads - At least one per sector - Traditionally one per band (e.g. 900MHz, 2600MHz) - Can be: - integrated with BBU (classic BS) - independent (RRH) - integrated with (AAA, LR) - Can be multi-technology (e.g. LTE + GSM)

6 Possible options for grouping functions Classic BS Classic RRH Active Antenna Array (AAA) cabinet cooling / fans PSU RH BB modem controller - I/O coax feeder cabinet cooling / fans PSU BB modem controller - I/O jumper RH RH RH PSU fiber optic with CPRI cabinet cooling / fans PSU BB modem controller - I/O AAA RH RH RH fiber optic with CPRI BB in the cloud (or hoteling) + AAA All-in-one (e.g. small cells / femtos) BB BB processing processing BBU BBU BBU fiber optic with CPRI AAA RH RH RH RH RH core network backhaul (IP packets) RH BB RH BB RH BB RH BB PSU = Power Supply Unit

7 Rules of thumb on BB grouping BBU in the cloud (or in large cabinets = hoteling) Well adapted for multi-cell processing (like network-mimo) High CPRI BW required + fiber distance limited due to latency limits BB pooling => energy savings by matching load with # of active BBUs All-in-one BB processing can be small, cheap and integrated (e.g. on SoC) Best choice for small cells (price constrained) Lack of BB pooling. Duplication of common functions (e.g. synchronization)

8 Rough estimation of BB<-->RRH link (LTE) A rough estimation of the needs (in bps) on the link between BB and RRH can be easily obtained by basic sampling rules R link [bps] N sectors x N s/sector x N samples/s/carrier x N bits/sample x 2(I/Q) N sectors = # sectors N s/sector = # s in each sector N samples/s/carrier 2 x BW (e.g. 20M samples/s for 10MHz radio channel width) N bits/sample = 15 (typical sample representation width in CPRI) 2(I/Q) = Multiplication factor of two to account for in-phase and quadrature-phase data Example: LTE, 20 MHz, MIMO 4x2, downlink (BB --> RRH) N sectors = 1 N s/sector = 4 (from MIMO 4x2) N samples/s/carrier 2 x 20 = 40 N bits/sample = 15 R link = 1 x 4 x 40 x 15 x Mbps

9 Outline BS consumption... why we care? Functions, grouping and integration Power consumption figures Consumption vs. Cell Load Possible BS power models 9

10 Power Consumption of Radio Access Equipment Who is consuming what? Study on Energy Efficient Radio Access Network Technologies, 2009 Alcatel-Lucent / TU Dresden Vodafone Chair Mobile Communications Systems ATIS Report on Wireless Network Energy Efficiency, January 2011 Energy saving at RF amplifier is most efficient : Additional savings in power supply and cooling!

11 Macro BS energy consumption breakdown - Toy example Power Consumption Details in 3x20W EIRP BS 1500W AC Power In Only 4% of power is transmitted into the air 3x20W 3x20W Air Condition 200W Signal Processing 150W 1000W 65% to PA Co-axial feeder: 50% loss Power Amplifier 12% efficiency 120W 500W to rack AC & Rectifier 150W Platform Base Station Rack RF power Antenna IMPORTANT NOTE This is just a toy example not reflecting specific equipment figures

12 Outline BS consumption... why we care? Functions, grouping and integration Power consumption figures Consumption vs. Cell Load Possible BS power models 12

13 Base Station power consumption figures - LTE case (enb) BS consumption analysis BBU, PSU, cooling/fans consumption is poorly dependent on cell load RH: ~60% of its consumption scales with data traffic load The remaining ~40% is not dependent on data traffic load HW consumption Broadcast channels: continuously emitted (10-15% of RF power) even at 0 load P TOT [W] P MAX Coverage tax ~0.5 P MAX Toy example Macro LTE enb 80W (max RF Power) x 3 sectors => P MAX ~ 1200W ETSI definitions -- low load = 10% RF power (no data only common ch) -- medium load = 30% RF power (data + common ch) -- busy hour = 50% RF power (data + common ch) -- average = 6/24 low + 10/24 medium + 8/24 busy = 31.7% cell load [%] 0% 100% IMPORTANT NOTE This is just a toy example not reflecting specific equipment figures

14 LTE frame structure f t

15 Ideas on BS efficient operational behavior A part from hw-efficiency improvements, savings can be obtained through energy efficient operational behavior Reduce coverage tax Rethink broadcast/common channels for minimal emission... without impact on current quality of service Reduction of RF power consumed by RH Different levels of stand-by mode, particularly on PAs Reduction of BBU consumption BBU pooling: match load with right amount of BB processing Turn off some BB process when load is low and by densification (small cells)

16 Ideas to improve BS efficiency P TOT [W] - Smaller cells - MIMO/beamforming flavors - Massive s - Pre-coding, IC-alignment - Stand-by modes - BCHs removal cell load HW improvements playground

17 Outline BS consumption... why we care? Functions, grouping and integration Power consumption figures Consumption vs. Cell Load Possible BS power models 17

18 BS power models Basic model P TOT = P 0 + α P data 0 α 1 ( α is the cell load) A bit more advanced P TOT = P BB + N Sectors P RF _ Sector P RF _ Sector = A P + α TOT _ RF _ Sector B P TOT _ RF _ Sector coverage tax data transmission A + B =1 (e.g. A = B = 50%)

19 Thanks!