L12: Beyond 4G Hyang-Won Lee Dept. of Internet & Multimedia Engineering Konkuk University 1
Frequency Allocation Chart Multi-RAT Concept Coexistence with WiFi: Signaling issues Problems - W+L: Prefer using only WiFi, e.g., at home because don t want to consume LTE data - W+L: If many users attached to WiFi, no benefit of using WiFi Key technology components in 5G as of Sep. 2015 Unlicensed WiFi Spectrum 2 GHz 2.4~2.4835 GHz 5 GHz 5.15~5.25; 5.25~5.35; 5.47~5.65; 5.725~5.825 GHz 60 GHz 57~64 GHz 2
Lecture Outline Multi-RAT Concept Coexistence with WiFi: Signaling issues Problems - W+L: Prefer using only WiFi, e.g., at home because don t want to consume LTE data - W+L: If many users attached to WiFi, no benefit of using WiFi Key technology components in 5G 3
Multi-RAT * RAT: Radio Access Technology 4
Concept Issues Coexistence with WiFi: Signaling issues Problems? Limitations? - W+L: Prefer using only WiFi, e.g., at home because don t want to consume LTE data - W+L: If many users attached to WiFi, no benefit of using WiFi 5
Concept of multi-rat Concept WiFi LTE 5G WiFi LTE 5G loosely-coupled multi-rat enabled small cell tightly-coupled 6 Nils Kleemann, Vietnam Symposium, Nov. 2010
Key Components Multi-RAT selection (routing) and multi-rat control (MAC) Multi-RAT selection Multi-RAT control IP flow Super-MAC queue RAT queue Wireless channel 7 Nils Kleemann, Vietnam Symposium, Nov. 2010
Core Network Solution EPC with WLAN offload Control information (channel etc.) exchange * LTE-Advanced (3GPP Rel.12) Technology Introduction - White Paper 8 ANDSF: Access Network Discovery and Selection Function
Radio Access Network Solution Parameters Offload configuration low or high for hysteresis - Reference Signal Received Power (RSRP) (ThreshServingOffloadWLAN, P) - Reference Signal Received Quality (RSRP) (ThreshServingOffloadWLAN, Q) - WLAN channel utilization (ThreshChUtilWLAN) - Available backhaul bandwidth for DL (ThreshBackhRateDLWLAN) - Available backhaul bandwidth for UL (ThreshBackhRateULWLAN) - Signal strength (RSSI) threshold for WLAN (ThreshBeaconRSSIWLAN) List of WLAN identifiers - Service Set Identifier (SSID), Basic Service Set Identifier (BSSID), or Homogeneous Extended Service Set Identifier (HESSID) 9
Radio Access Network Solution Traffic steering from LTE to WLAN 10
Radio Access Network Solution Traffic steering from WLAN to LTE (two conditions must be fulfilled) 11
Problems When both LTE and WLAN are available (for instance at home), do you really want to use both RATs simultaneously? Perhaps, you don t want to consume your LTE data plan In public places with both LTE and WLAN available, WLAN performance can be too poor to use (due to random access). Selective use of WLAN may be necessary 12
License Assisted Access Courtesy of Dr. Jeongho Jeon (Intel Corporation, USA) 13
License-Assisted Access (LAA) LTE in unlicensed spectrum (LTE-U) or license-assisted access (LAA) Supplement licensed spectrum with unlicensed spectrum via carrier aggregation Primary cell + Secondary cell Secondary cell Licensed, e.g., 2 GHz Unlicensed, e.g., 5 GHz Will they coexist well? IEEE 802.11a/n/ac 14
Which Unlicensed Bands? 5GHz unlicensed bands DFS/TPC due to Federal radar operations and Earth exploration satellite service 5.15 GHz No DFS DFS/TPC DFS/TPC No DFS Lesser of 1 W 250 mw Lesser of 250 mw or or 11 N.A. 11 dbm + 10log B dbm + 1 W 10log B U-NII-1 U-NII-2A U-NII-2C U-NII-3 5.25 GHz 5.35 GHz 5.47 GHz 5.725 GHz 5.85 GHz N.A. 5.925 GHz * FCC regulations according to FCC 14-30, First Report and Order released April 1, 2014 15
Coexistence with WLAN An incumbent system operating in 5GHz bands is WLAN based on IEEE 802.11a/n/ac standards Listen-Before-Talk (LBT) is considered a mandatory feature of LTE LAA design for fair and friendly coexistence 16
LBT Design WLAN medium access uses CSMA/CA LAA LBT is for fair play with WLAN WLAN transmission enb CCA busy CCA idle CCA sensing duration backoff countdown frozen ecca sensing duration enb DL transmission Key design components CCA threshold: level of sensitivity to detect ongoing transmissions Backoff counter for collision avoidance backoff countdown Energy detection vs. signal detection, sensing duration, back off mechanism, etc. CCA: clear channel access 17
Outdoor Scenario CW 32 Served LTE load [Mbps] 40 35 30 25 20 15 10 Standalone Plain coexistence -52 dbm CCA -62 dbm CCA -72 dbm CCA -82 dbm CCA -92 dbm CCA LTE Served WLAN load [Mbps] 20 18 16 14 12 10 8 6 4 Standalone Plain coexistence -52 dbm CCA -62 dbm CCA -72 dbm CCA -82 dbm CCA -92 dbm CCA WLAN 5 2 0 10 20 30 40 Offered load per LTE cell/wlan BSS [Mbps] 0 10 20 30 40 Offered load per LTE cell/wlan BSS [Mbps] CW 128 Served LTE load [Mbps] 40 35 30 25 20 15 10 Standalone Plain coexistence -52 dbm CCA -62 dbm CCA -72 dbm CCA -82 dbm CCA -92 dbm CCA Served WLAN load [Mbps] 20 18 16 14 12 10 8 6 4 Standalone Plain coexistence -52 dbm CCA -62 dbm CCA -72 dbm CCA -82 dbm CCA -92 dbm CCA 5 2 0 10 20 30 40 Offered load per LTE cell/wlan BSS [Mbps] 0 10 20 30 40 Offered load per LTE cell/wlan BSS [Mbps] 18
In (WLAN BSSs), Out (LTE enbs) CW 32 Served LTE load [Mbps] 30 25 20 15 10 Standalone Plain coexistence -52 dbm CCA -62 dbm CCA -72 dbm CCA -82 dbm CCA -92 dbm CCA LTE Served WLAN load [Mbps] 40 35 30 25 20 15 10 Standalone Plain coexistence -52 dbm CCA -62 dbm CCA -72 dbm CCA -82 dbm CCA -92 dbm CCA WLAN 5 5 0 10 20 30 40 Offered load per LTE cell/wlan BSS [Mbps] 0 10 20 30 40 Offered load per LTE cell/wlan BSS [Mbps] CW 128 Served LTE load [Mbps] 30 25 20 15 10 Standalone Plain coexistence -52 dbm CCA -62 dbm CCA -72 dbm CCA -82 dbm CCA -92 dbm CCA Served WLAN load [Mbps] 40 35 30 25 20 15 10 Standalone Plain coexistence -52 dbm CCA -62 dbm CCA -72 dbm CCA -82 dbm CCA -92 dbm CCA 5 5 0 10 20 30 40 Offered load per LTE cell/wlan BSS [Mbps] 0 10 20 30 40 Offered load per LTE cell/wlan BSS [Mbps] LTE suffers due to 80% indoor UEs (LBT not helpful in this scenario) 19
Small Cells 20
Motivation Motivation Traffic volume growing exponentially Need for boosting capacity Small-cell approach Dense deployment of small cells to enhance capacity per unit area Enhance user experienced data rate, area traffic capacity, network energy efficiency Definition of small cell Cells with coverage of a few meters to a few hundred meters Femtocell, Picocell, Microcell, Metrocell (in increasing order of coverage) 21
HetNet Scenarios Coexistence of macro cells and small cells wordpress.com HetNet scenario: small cell within macro cell s coverage Standalone mode: for coverage extension 22
Key Technologies MAC scheduler RRM algorithms (QoS, handover, etc.) Uplink power control, interference management Backhaul can possibly be a bottleneck 23
ICI Management Small-small or small-macro interference Challenges Various types of base stations => different hardware specs => hard to apply methods developed for homogeneous scenarios Large number of small cells Existing solutions FFR, ABS, BS random on/off, CoMP New solutions Fast Max-(Min Distance) on/off Min-Weighted-Generating-Interference Beamforming RRM based on macro/micro cell density 24
Almost Blank Subframe (ABS) Only control channels, reference signals, no user data Transmitted with reduced power Macro-eNB transmits ABS (semi-static pattern, provided to enb in small cell) UEs receive DL info 25 3gpp.org
Mobility Robustness Improving mobility support Dual-connected UE keeps its connection to MeNB even for SCG failure UE shall not trigger RRC-reestablishment when detecting SCG failures MeNB-MeNB handover (PCell handover) 26 3gpp.org
Small Cell Market Small cell technologies are considered one of the key technologies in 5G Vendors and carriers have been developing visions and plans for small cell technologies 27
Key Technology Components in 5G 28
Data Rate The maximum transmission data rate (gigabits per second) will be 20 times as fast as 4G LTE, while the average user will experience rates 10 to 100 times as fast. Proposed Technologies Massive multiple-input, multiple-output (MIMO) Millimeter wavelength spectrum Spectral Efficiency 5G will improve downlink spectral efficiency (bits per second per hertz) threefold. Device-to-device (D2D) communication Full duplex system Massive MIMO Data Processing The network will be able to process 100 times as much data in a given area (megabits per second per square meter). Device Density About 900,000 more devices per square kilometer will be able to connect to the network. Mobility 4G can provide data to devices moving at up to 350 kilometers per hour. 5G will provide data to devices moving at up to 500 km/h. D2D Millimeter wavelength spectrum Radio-access network virtualization Small cells D2D Small cells Heterogeneous network architectures Transmission Delay 5G will have one-tenth the latency (milliseconds) of 4G D2D Content caching close to users Energy 4G takes 1 millijoule to transfer a 1,000-bit data packet. 5G will be able to transfer packets 100 times as efficiently 29 Massive MIMO
Technologies Explained Millimeter wavelength spectrum: To the surprise of many, engineers have demonstrated mobile data speeds higher than 1 gigabit per second on millimeter-w frequencies (30 to 300 gigahertz). This will expand the amount of cellular spectrum beyond the prized but limited ultrahigh-frequency band used today. Massive multiple-input, multiple-output (MIMO): One way to use the millimeter wavelength is through massive MIMO, which uses a huge array of antennas t steer and finely focus a radio beam so that it hits a receiver. Engineers have been able to fit 64 antennas in a space the size of a Post-it note. Device-to-device (D2D) communication: D2D will allow direct communication between devices in close proximity without network assistance. Skipping the ba station means one less step in getting information to devices. Full duplex system: This allows the transmitting and receiving of data at the same time and on the same frequency. Small cells: Increasing the number of small-cell base stations will increase bandwidth. This will provide enough capacity for devices to consume hundreds of megabits per second. Radio-access network virtualization: General radio-access network processor functions will be virtualized into the cloud. Today s radio-access network is buil with many individual base stations. By virtualizing the network, multiple service providers can physically share the same data center platform without any impact connection strength. Heterogeneous network architectures: Made of a combination of pico cells, small cells, macro cells, and different layers, these networks will provide appropri coverage as the distance between a device and a base station changes. This kind of network will also be able to handle real-time location tracking and quick handoffs between base stations so that devices can keep working even when they re moving at high speeds. Content caching close to users: Information that is accessed frequently will be cached closer to the user so that it takes less time to get the data. http://spectrum.ieee.org/telecom/wireless/telecom-experts-plot-a-path-to-5g?utm_campaign=weekly%20notification-%20ieee%20spectrum%20tech %20Alert&utm_source=boomtrain&utm_medium=email&utm_term=555a972628fbca1d260da1ba&utm_content=Telecom%20Experts%20Plot%20a%20Path %20to%205G&bt_alias=eyJ1c2VySWQiOiI5N2E5ZjEzYy1iMDc0LTQ1NmUtODI2Ni0zNjE3Yzc2ODNhNzQifQ%3D%3D IEEE Spectrum article Oct 6, 2015 30