Techniques of Indoor Positioning 蔡智強 副教授 國立中興大學電機工程學系 Outline Introduction Basic Techniques Advanced Techniques Commercial Products Using the Indoor Map Information Indoor Positioning Using Femtocell 4G LTE-A Localization System In-Location Alliance Conclusions Introduction Location-aware real-time services ◦ Elderly nursing ◦ Child monitoring ◦ Object positioning Global Positioning System (GPS) is the most well-known positioning service The restrictions of GPS ◦ Requiring a line of sight (LOS) with satellite systems Introduction (cont.) ◦ GPS signal is easily affected by buildings ◦ Errors up to 10m Need other techniques for indoor positioning Basic Techniques Employ some information between beacon nodes and the unknown node Trilateration Trilateration (cont.) Node A’s coordinate is (xa, ya) Node B’s coordinate is (xb, yb) Node C’s coordinate is (xc, yc) The unknown node D’s coordinate is (x, y) The distance between A (or B or C) and D is d1 (or d2 or d3) Trilateration (cont.) Triangulation (cont.) Triangulation (cont.) The unknown node D’s coordinate is (x, y) Node A’s coordinate is (xa, ya) and the angle to the D is ∠ADB Node B’s coordinate is (xb, yb) and the angle to the D is ∠ADC Node C’s coordinate is (xc, yc) and the angle to the D is ∠BDC Triangulation (cont.) Circle center coordinate is radius is r1 , and α = ㄥ1 = 2π − 2ㄥ to calculate and r1 Similarly, calculate and center coordinate and radius Use trilateration to calculate D’s position , Measuring Distance Three basic properties to measure the distance between a beacon node and a unknown node 1. Received signal strength indication (RSSI) 2. Time of flight (TOF) 3. Angle of arrival (AOA) Received signal strength indication Two kinds of methods for RSSI location 1. Database 2. Radio propagation model Received signal strength indication (cont.) Database ◦ Measure the relation between distances and RSSI values ◦ Set up a database According the database, we can calculate the distance between two nodes Received signal strength indication (cont.) Radio propagation model ◦ In the RADAR system, the Wall Attenuation Factor (WAF) model is: where n indicates the rate at which path loss decreases with distance, P(d0) signal power at some reference d0, and d is the transmitterreceiver distance. Received signal strength indication (cont.) Moreover, C is the maximum number of obstructions (walls), nW the number of obstructions between the transmitter and receiver, and WAF is the wall attenuation factor. Time of flight Calculate the distance between a transmitter and a receiver by the time of flight ◦ Time of arrival (TOA) ◦ Time difference of arrival (TDOA) Time of flight (cont.) TOA ◦ The transmitter and receiver must synchronize their time ◦ The transmitter sends a signal to the receiver ◦ Upon receiving the signal, based on the propagation time, the receiver can calculate the distance between the transmitter and it Time of flight (cont.) Time of flight (cont.) TDOA ◦ Based on the difference of time between different signals from the transmitter arriving at the receiver ◦ The transmitter sends two different signals with propagation speeds α1 , α2, respectively ◦ The receiver receives two such signals at different times, say T1 and T2, respectively ◦ The distance is Time of flight (cont.) Angle of arrival By the propagation direction of radiofrequency waves incident on an antenna array Comparisons RSSI ◦ Advantage: simple hardware ◦ Disadvantage: unstable, easily impacted by the environment TOA ◦ Advantage: good accuracy ◦ Disadvantage: time synchronization required, complex hardware Comparisons (cont.) TDOA ◦ Advantage: no time synchronization, good accuracy ◦ Disadvantage: complex hardware AOA ◦ Advantage: nice accuracy ◦ Disadvantage: Directional antenna array required Maximum likelihood estimation Maximum likelihood estimation (cont.) n reference nodes with coordinates The unknown node in (x, y) The distances between reference nodes and the unknown node are , respectively, measured by RSSI values Maximum likelihood estimation (cont.) Subtract the last equation from each equation Maximum likelihood estimation (cont.) Use the matrix representation AX=b The coordinate of the unknown node : Self-Calibrating Indoor Positioning System Based On ZigBee Devices This paper presents a positioning system based on the round-trip time-of-flight (RTT) measurement RTT can be modeled as: System Architecture The developed system is composed of three types of transponders: ◦ Mobile node ◦ Calibration node ◦ Fixed node System Architecture (cont.) Mobile node ◦ Chipcon CC2431 : Zigbee chip ◦ TMS320C6713(DSP) : Timing and control functions ◦ TDC-GP2 : Time interval measurement function, timing and control functions System Architecture (cont.) Calibration node ◦ Chipcon CC2431 : Zigbee chip ◦ TDC-GP2 : Time interval measurement function, timing and control functions Fixed node ◦ Chipcon CC2431 : Zigbee chip Measuring procedure Measuring procedure 1. 2. 3. 4. Initiated by a mobile node It transmits a packet to a fixed node Fixed node retransmits a packet The master node receives the packet and its TDC determines the RTT Calibrating procedure 1. Initiated by a mobile node 2. It transmits a packet to a calibration node 3. The calibration node initializes its TDC Measuring procedure (cont.) 4. The calibration node transmits a packet to a selected fixed node 5. The selected fixed node received and retransmits the packet 6. The calibration node receives the packet and its TDC determines the RTT 7. The calibration node repeats the foregoing procedure to a set of fixed nodes 8. The results of RTT are sent to the mobile node for calibration Measuring procedure (cont.) By using the calibration data, the mobile node DSP can determine the unknown position more accurately Tested Result Three fixed node, one calibration node NTU Indoor Localization RSSI fingerprinting localization ◦ Training Collect RSSI values at every specific position Use all collected RSSI values to build a database ◦ Tracking Upon receiving RSSI values, an end-device can compare them with those in the database Then calculate the position by KNN (K-NearestNeighbor) NTU Indoor Localization (cont.) Fingerprint location (B1,B2,B3,B4…) (x1,y1,z1) Beacon 1 Beacon 2 ….. ….. ….. …... Beacon 3 Look up the table NTU Indoor Localization (cont.) NTU Indoor Localization (cont.) Example of KNN AP2 30m AP1 9 10 11 12 5 6 7 8 1 2 3 4 50m AP3 NTU Indoor Localization (cont.) STEP1 ◦ The end-device receives the RSSI values and normalizes them STEP2 ◦ The normalized RSSI values are compared with those in the database, and find the minimum L differences Dn ◦ ◦ ST is the received RSSI value ◦ Sn is store at the database STEP3 ◦ For L nearest neighbors, the location estimate is ◦ NTU Indoor Localization (cont.) STEP1 ◦ PT = (-94dbm -96dbm -95dbm) ◦ PT = (0dbm -2dbm -1dbm) 正規化 RL 1 x, y 2 3 Normalize 4 5 6 7 8 9 10 11 12 10, 20, 30, 10 10 10 40, 10 10, 20 20, 20 30, 20 40, 20 10, 30 20, 30 30, 30 40, 30 AP1 -73 -82 -89 -94 -82 -86 -91 -95 -89 -91 -94 -97 AP2 -82 -86 -91 -95 -73 -82 -89 -94 -66 -80 -87 -93 AP3 -94 -89 -82 -73 -93 -87 -80 -66 -94 -89 -82 -73 AP1 0 0 0 0 0 0 0 0 0 0 0 0 AP2 -9 -4 -2 -1 9 4 2 1 23 11 7 4 AP3 -21 -7 7 -21 -11 -1 11 29 -5 2 12 24 NTU Indoor Localization (cont.) STEP2 RL 1 D 2 3 4 5 6 7 8 9 10 11 12 21 8 8 22 15 6 13 30 25 13 STEP3 ◦ ◦ 16 26 AeroScout AeroScout Tag Tag using RFID 2.4Ghz WiFi transmission, MAX read range 200M, LF125k precise positioning 1~2M， AeroScout Location Receivers Location Receivers allow accurately positioning in outdoor or harsh environments They execute sophisticated radio signal measuring and calculating methods Then the results are sent to the AeroScout Engine for accurately positioning AeroScout TDOA Use TDOA for positioning AeroScout System Architecture AeroScout Engine Processes information received from any vendor's wireless Access Points nearby Allow accurate and reliable positioning for assets equipped with AeroScout's WiFi-based Active RFID Tags AeroScout MobileView Customers use MobileView to TRACK, MANAGE and INTEGRATE their assets from a single platform Ekahau Ekahau System Architecture Ekahau RTLS works on top of any standard 802.11 compliant networks, even with multi-vendor networks Key components of the system include: ◦ Wi-Fi tags Various physical formats, battery options and features ◦ Ekahau RTLS Controller (ERC) Sends messages and remotely configure the tags ◦ Server software Calculates the location using Wi-Fi signal strength readings Ekahau System Architecture (cont.) ◦ Ekahau Site Survey (ESS) An easy-to-use utility for network verification and creating positioning models during system set-up ◦ Ekahau Vision A web-based rules, work-flow and alerting engine Allows users to configure a variety of applications and alerts that take advantage of the precise location calculated by ERC Configures various status, event and tag rules Ekahau System Architecture Ekahau Tags Using 2.4G WiFi (RSS)& IR transmission, MAX read range 100M, precise positioning 1M Ekahau RTLS (ERC) Ekahau's patented algorithm adopts a probabilistic approach for interpreting the RF signals ◦ Called Multi-Hypotheses tracking ◦ The algorithm is constantly calculating multiple possible locations for a tracked object and gives each possible location a score Based on all known factors outside: environment characteristics, differences between mobile devices, signal history and the movement models Chooses the location with the highest score Ekahau Site Survey A easy-to-use professional Wi-Fi Network planning, site survey, and management software tool Ekahau Site Survey (cont.) ESS enables users to quickly and easily create, improve and troubleshoot a Wi-Fi positioning system Ekahau Vision • Help users find important assets and people Ekahau API Tag location, presence and status information Tag commissioning and management Two-way text messaging and commands Floor plan images and zones Business rules and event notifications Open architecture and XML-based web services Identec Identec System Architecture Identec Tags i-CARD CF 350 i-PORT M350 RTLS i-MARK 2 i-Q350 RTLS i-SAT 300 RTLS Active RFID UHF & LF UHF label （916.5MHz）, MAX read range 500M Identec SensorSMART Platform Identec Software (i-SHARE, Watcher, CTAS) i-SHARE Identec Software (i-SHARE, Watcher, CTAS) CTAS Identec Software (i-SHARE, Watcher, CTAS) Watcher Comparisons 項目 國內 AeoScout Ekahau Identec 方法 Zigbee & LF RFID 2.4G WiFi & LF 2.4G WiFi(RSS) & IR RFID UHF & LF Tag 頻率 定位距離 電池省電性 2.4GHz 0.5~6M 1~5年 2.4GHz 20cm~6M 4年 2.4GHz NA 3~5年 920Mhz 0~3.5M 4年 年/ 發射間隔 1年 20sec/發射 3.75年 5min/發射 3年 15min/發射 4年 2sec/發射 最遠讀取距離 定位精度 80M 3M 200M 1~2M 100M 1M 500M 1M Gsensor振動功 能 選配 OK N/A 選配 緊急按鈕功能 LCD顯示功能 受金屬干擾程度 N/A N/A 易受干擾 選配 選配 易受干擾 選配 N/A 易受干擾 選配 N/A 不易 1200 ~6000 3000 ~6000 N/A N/A Tag大約價格 (NTD) Comparisons (cont.) 技術分類 代表性廠商 準確度 Wi-Fi (RSS) 優點 缺點 ITRI, Ekahau, 室內：1～5m 室內外皆可使用， Skyhook, 室外：20～ 準確度高，純軟 40m Intel 體方案，支援標 Research 準WiFi AP，可 判斷樓層資訊， 不需更動網路設 備 Wi-Fi AeroScout, 1～5m (TDOA) Hitachi AirLocation 準確度較高 開闊空間準確 度較差 需事先對環境 做過校正 環境變動會影 響準確度 需要專屬的網 路硬體設備 利用室內圖資之即時室內定位系統 Background Wireless sensor network’s(WSN) requirements National Chung Hsing University System and Network Laboratory 71 Background (cont.) Low communication speed Low power consumption Low cost IEEE規格 802.15.4 802.15.1 802.11b 技術名稱 ZigBee Bluetooth Wi-Fi 使用頻率 868MHz/915MHz /2.4GHz 2.4GHz 2.4GHz 調變方式 O-QPSK,BPSK GFSK CCK,PBCC 通信距離 30m~100m 10m 100m 傳輸速率 20Kbps、40Kbps、 250Kbps 1Mbps 11Mbps 網路容量 65536節點 7節點 32節點 電池壽命 Years Days Hours 應用 監控/量測控制 語音/資料傳輸 影像/數據傳輸 72 Knowledge of Map Matching Using digital map and road network to enhance the positioning accuracy National Chung Hsing University System and Network Laboratory 73 Knowledge of Map Matching (cont.) 1. 2. Vertex-based Map Matching Segment-based Map Matching National Chung Hsing University System and Network Laboratory 74 Knowledge of Map Matching (cont.) 1. 2. Vertex-based Map Matching Segment-based Map Matching National Chung Hsing University System and Network Laboratory 75 Knowledge of Map Matching (cont.) Map Matching Technique ◦ Distance of point-to-point ◦ Distance of curve-to-curve ◦ Angle of curve-to-curve National Chung Hsing University System and Network Laboratory 76 Knowledge of Map Matching (cont.) Distance of point-to-point National Chung Hsing University System and Network Laboratory 77 Knowledge of Map Matching (cont.) Distance of curve-to-curve If 1 + 2 < 1 + 2 , 2 will match to road 1 National Chung Hsing University System and Network Laboratory 78 Knowledge of Map Matching (cont.) Angle of curve-to-curve If > , we chose road 1 National Chung Hsing University System and Network Laboratory 79 System Implementation User (End Device) Router Coordinator Server (laptop) National Chung Hsing University System and Network Laboratory 80 System Implementation (cont.) Hardware: CC2530ZDK National Chung Hsing University System and Network Laboratory 81 System Implementation (cont.) Software: ◦ IAR Embedded Workbench IDE For ZigBee network ◦ Visual C#2010 For positioning algorithm National Chung Hsing University System and Network Laboratory 82 System Implementation(cont.) 83 System Implementation (cont.) RSSI data collect 235 230 225 220 放置於地板 215 離地0.47m 210 205 200 195 0 100 200 300 400 500 600 700 84 System Implementation (cont.) Positioning Algorithm ◦ Two-intersected-circles algorithm ◦ Indoor-map-matching algorithm National Chung Hsing University System and Network Laboratory 85 System Implementation (cont.) Two-intersected-circles algorithm National Chung Hsing University System and Network Laboratory 86 System Implementation (cont.) National Chung Hsing University System and Network Laboratory 87 System Implementation (cont.) National Chung Hsing University System and Network Laboratory 88 Flow Chart Start 從USB收取 資料 利用變異數 篩選節點 是否開靠近 定位點 是 將預估節點設 為定位點並顯 示在螢幕上 否 兩圓訊號強 度演算法 地圖匹配演 算法 顯示在螢幕 上 89 System Implementation (cont.) Indoor-map-matching algorithm ◦ Path database ◦ Matching algorithm National Chung Hsing University System and Network Laboratory 90 Path Database Use vertices and segments to denote paths National Chung Hsing University System and Network Laboratory 91 Path Database (cont.) Vertex Segment 點ID 區段ID X座標 起始點ID Y座標 結束點ID National Chung Hsing University System and Network Laboratory a b c 92 Matching Algorithm 1. 2. If there is no reference node, use distance of point-to-point If there is a reference node, use distance of curve-to-curve 1 1 2 2 1 + 2 ＜(1 + 2 ) National Chung Hsing University System and Network Laboratory 93 Matching Algorithm (cont.) 1. 2. 3. 4. Planning paths and set up the database in the server If no reference node, find the closest vertex to the unknown node Find all the segments that are connected to the closest vertex, and determine the closest segment If there is a reference node, find the closest segment like step1~3 National Chung Hsing University System and Network Laboratory 94 Matching Algorithm(cont.) 5. 6. 7. If the segment is connected with previous segment, this segment is the right segment If it is not connected, calculate the distances between the two nodes and the two segments Compare the sum of distances. The smaller one is the right segment National Chung Hsing University System and Network Laboratory 95 Start Flow Chart 讀取預估節點 檢查是否有前 次定位資訊 否 找出最近的 vertex 是 先找出此次距 離最近的 segment 找出相連接 的segment 找出距離最近 的segment 分別算出兩點到兩 segment之距離 否 檢查此次segment 是否和上次相連 是 比較距離總和 將未知節點匹配 到此segment上 將未知節點匹配 到此segment上 將未知節點匹配到距 離總和較小的segment 上 96 Experiment and Result 97 Experiment and Result (cont.) Database 1 National Chung Hsing University System and Network Laboratory 98 Experiment and Result (cont.) 0 2 4 6 8 10 12 0 1 2 原始資料 3 路線 4 5 6 National Chung Hsing University System and Network Laboratory 99 Experiment and Result (cont.) 修正資料 0 1 2 3 4 5 6 7 8 9 10 0 0.5 1 1.5 2 修正資料 2.5 3 3.5 4 National Chung Hsing University System and Network Laboratory 100 Experiment and Result (cont.) Database 2 National Chung Hsing University System and Network Laboratory 101 Experiment and Result (cont.) 0 2 4 6 8 10 12 0 0.5 1 1.5 2 原始資料 路線 2.5 3 3.5 4 4.5 National Chung Hsing University System and Network Laboratory 102 Experiment and Result (cont.) 修正資料 0 1 2 3 4 5 6 7 8 9 10 0 0.5 1 1.5 2 修正資料 2.5 3 3.5 4 National Chung Hsing University System and Network Laboratory 103 Experiment and Result (cont.) Database 3 National Chung Hsing University System and Network Laboratory 104 Experiment and Result (cont.) 0 1 2 3 4 5 6 7 0 0.5 1 1.5 2 原始資料 2.5 路線 3 3.5 4 4.5 5 National Chung Hsing University System and Network Laboratory 105 Experiment and Result (cont.) 修正資料 0 1 2 3 4 5 6 7 0 0.5 1 修正資料 1.5 2 2.5 National Chung Hsing University System and Network Laboratory 106 Indoor Positioning Using Femtocell Publication Year: 2011 IEEE CONFERENCE PUBLICATIONS Femtocell Overview Femtocell coverage is smaller ◦ Mainly used to compensate for the region the other base stations can not cover ◦ Enhances the data transfer rate ◦ Typically used for residential or small business environment. Femtocell Based Positioning Methods To locate a mobile device in a network of femtocells, we need to determine its position relative to at least three femtocells to achieve successful triangulation ◦ Femtocells’ locations are known Femtocell Based Positioning Methods (cont.) The distance between the mobile and a femtocell is estimated by: ◦ Calculating the signal propagation loss (pathloss) between them ◦ Or the time taken by the signal to propagate from one point to the other. Femtocell Based Positioning Methods (cont.) Signal Strength Triangulation based methods: • Generate a database of pathloss at all locations via ray-tracing simulation of detailed building interiors • Using WinProp software tool • Being matched against the database to estimate the position Femtocell Based Positioning Methods (cont.) Time based methods : ◦ The signal propagation delay between femtocells and mobile ◦ Though useful in calculating distance, this is ineffective for indoor positioning Position Based On Downlink Signal Strength The position of a mobile can be estimated by measuring the strength of the received downlink signals at the mobile from a group of femtocells ◦ The pathloss to each visible femtocell can then be calculated using the femtocell transmit powers Position Based On Downlink Signal Strength (cont.) The serving femtocell requests the mobile to send a Measurement Report Message (MRM) ◦ Containing Ecp/Io and Ecp information Ecp is the received signal strength of the serving femtocell pilot Io is the total received energy on the serving femtocell frequency (as measured by the mobile) Position Based On Downlink Signal Strength (cont.) The fingerprint is matched against the database ◦ Containing pathloss values from all points in the network’s coverage region to all femtocells The methods used to create time orthogonalization of signals To avoid persistent interferences Position Based On Downlink Signal Strength (cont.) Inter-frequency Beacon Transmission ◦ Each femtocell may transmit its beacon pilot on different frequency channels In a time division multiplexed manner (TDMA) ◦ As measurements are made by the mobiles on the channels at multiple instances, the mobile will now be able to detect signals from different femtocells as all other interferers are removed Position Based On Downlink Signal Strength (cont.) Co-ordinated Silence Techniques ◦ Techniques also help create time orthogonalization of signals to avoid the problem of strong interference from the serving femtocell Such as HDP and OTDOA-IPDL Femtocells need to also support alternative solutions for mobiles that are not equipped with these features Position Based On Uplink Signal Strength The position of a mobile can also be estimated by measuring the strength of the mobile uplink pilot ◦ Received at a group of femtocells Since the transmit power of the mobile is unknown and dynamic, the pathloss cannot be estimated from this measurement The difference of the measured strength at two femtocells is equal to the pathloss difference from the mobile’s location to these femtocells Position Based On Uplink Signal Strength (cont.) The difference in the pathloss values can be used as a fingerprint. ◦ Those femtocells that can sense the mobile send the measured Ecp/Nt and Nt values to the positioning server ◦ The server calculates the pathloss difference to a number of pairs of femtocells and matches this against the database to predict the mobile’s position Simulation Model Simulation Model (cont.) Beamforming basics Beamforming uses multiple antennas ◦ Control the direction of a wavefront by appropriately weighting the magnitude and phase of ndividual antenna signals (transmit beamforming). ◦ This makes it possible to provide better coverage to specific areas Because every single antenna in the array makes a contribution to the steered signal, an array gain (also called beamforming gain) is achieved Beamforming basics (cont.) Beamforming makes it possible to determine the direction that the wavefront will arrive ◦ Direction of Arrival, or DoA Adaptive beamforming refers to the technique of continually applying beamforming to a moving receiver. ◦ This requires rapid signal processing and powerful algorithms. Beamforming basics (cont.) • Antenna array with a distance d between the individual antennas. • The additional path that a wavefront must traverse between two antennas is d * sin Ѳ. Beamforming basics (cont.) The antenna diagram is affected by the distance d between the antennas. OTDOA OTDOA：Observed Time Difference of Arrival 4G LTE-A Localization UE 利用陣列天線估測DOA 並結合OTDOA完成自身定位 Femtocell BS 具有陣列天線的BS可採 用多階層(Layers)傳輸提 高系統下行容量 UE Femtocell BS1 Marcocell BS M , M 即使UE不在Femtocell範圍 內，UE自身透過Beam Steering 方式增強接收訊號 2 ,2 Femtocell BS2 1 ,1 3 , 3 Femtocell BS3 UE 具有陣列天線的BS亦可使用 TX beamforming 技術將訊號 能量集中至UE Femtocell BS UE UE在Downlink時透過 OTDOA+DOA方式取得位置 127 結合的技術 結合 GPS、Marcocell以及Femtocell定位 ◦ DOA estimation in UE ◦ Beamforming technique 當使用者位於戶外使用GPS+ Marcocell 當使用者位於室內或GPS無LOS訊號時， 則自動轉為Femtocell BS輔助定位系統 改善Positioning system QoS 128 UE之DOA估測技術 Downlink Positioning Reference signals/pilots are arranged across time and frequency domain (OFDMA modulation) Collect those pilots to form a virtual array ◦ 解決實體陣列維度不足問題 ◦ 可同時估測多BS方向 129 In-Location Alliance Founded by 22 companies across industries ◦ Nokia, Samsung Electronics, Sony Mobile Communications, Qualcomm, Broadcom and CSR, etc. ◦ To drive innovation and market adoption of high accuracy indoor positioning and related ◦ The primary solutions will be based on enhanced Bluetooth® 4.0 low-energy technology and Wi-Fi (802.11.ac) standards IEEE 802.11ac spec. 802.11ac 802.11n Band 5GHz Band 2.4GHz/5GHz(opt) Channel Bandwidth 20,40,80,160 MHz 20,40MHz Max Data rate 6933Mbps ~600Mbps Spatial Streams Up to 8 spatial streams 4 spatial streams Modulation 256-QAM 64-QAM MIMO Multi-User MIMO Single-User MIMO Backward compatibility 802.11n(on 5GHz) 802.11a 802.11 b/g Band Operating on 5GHz band Less interference than on 2.4GHz • More non-overlapping channel avaliable. (25 to 3 on 2.4GHz) 7 • Mandatory support 20/40/80MHz, 160MHz optional. • • Bandwidth Table of Data rate: Higher Order Modulation • Increase 33% PHY rate relied on 256-QAM • QAM is Quadrature Amplitude Modulation. • 6 bits coded information to 8bits coded information. Improved MIMO • Up to 8 spatial streams • 4 spatial streams with 11n • Multi-Users MIMO • Single-Users MIMO • Beneficial for handset or tablet • Multiple antennas are not necessary Dynamic Bandwidth Management • Improved handshake mechanism. • RTS/CTS • Interference detection threshold improved • -62dBm down to -72dBm Single Closed Loop-Method Transmit Beamforming • Beamforming focuses the APs transmit energy of spatial stream toward Clients Special Sounding Signal AP STAs Report their Beamformaing matrices • Limitation of TxBeamforming on 5GHz band Backward Compatibility • Required to be fully compatible with 802.11n(Operating on 5GHz)and 802.11a • 802.11b/g not support NOKIA – Bluetooth 4.0 The High Accuracy Indoor Positioning (HAIP) technology ◦ Nokia is looking to employ it based on Bluetooth 4.0 ◦ Even in its current form it will have accuracy of one meter That’s certainly good enough for general positioning inside It gets much more interesting when it can get down to 20cm with modification Industry application for stock control NOKIA – Bluetooth 4.0 (cont.) Using a single antenna and fixed mobile height, mobile can resolve its 2D location NOKIA – Bluetooth 4.0 (cont.) Using multiple positioning beacons, mobile can resolve its 3D location or increasing the position reliability and accuracy Conclusions 預期遭遇困難 ◦ 無直射路徑問題(NLOS propagation) 手機有GSM900、WCDMA、HSDPA等等的不同 規範 ◦ 多重路徑干擾(Multipath Interference) ◦ 多使用者環境的影響 ◦ 手機電源消耗問題(power issue) 142 Thanks for your attention! Any questions?