Ubiquitous Connectivity Platform for Intelligent Public Transportation Systems

Transcription

1 Ubiquitous Connectivity Platform for Intelligent Public Transportation Systems Eng. Andrei Hosu, PhD student Technical University of Cluj-Napoca, Romania

2 Outline Introduction Proposed Scenario Connectivity Platform Architecture VHO Mechanism for Heterogeneous Wireless Networks in Vehicular Scenario Experimental Testing Integrated HO & LB Mechanism for Heterogeneous Wireless Networks in Vehicular Scenario Conclusions

3 Introduction The performance increase of the transport sector can be achieved through ICT. Services for the transport itself and for the passengers. Connectivity has to be provided ubiquitously and in mobility conditions. Solutions: Deployment of a separate and dedicated network infrastructure. Employment of public cellular networks. Use of Next Generation Networks (multiple communication technologies in a multi-operator environment, generalized mobility). Ubiquitous connectivity platform which employs multiple communication technologies and multiple operators.

4 Proposed Scenario Operator 1 Operator 2 RSSI level L1 > L2 A-A bus trajectory B-B bus trajectory Smart Router - ASP communication link Operator 1 Operator 2 RSSI level L2 > L3 C-C bus trajectory Operator 1 Operator 2 RSSI level L3 C Application Server Platform WiFi Cell A C A UMTS Cell WiFi Cell WiMAX Cell WiFi Cell UMTS Cell WiMAX Cell B WiFi Cell WiFi Cell B

5 Connectivity Platform Architecture System architecture Simultaneous connections with multiple carriers, both cellular and WLAN. Networking and storage equipment located at the transport operator s centre. Internet connection is transparent to the bus passengers.

6 Connectivity Platform Architecture How is connectivity provided? Bus LAN SMR Overlay Network Tunnel 1 Tunnel N SCG Internet Destination Local interfaces (wireless & wired) Routing table NAT SMR Interface emulator Decaps. Encaps. Connection Control Subsyst. Meas. Replies Commands Network Selection & VHO Decision Subsystem Context Info. Wireless Interf. 1 Meas. Probes Monitoring & Measurement Subsystem Wireless Interf. N Probes Tunnel 1 Operator 1 Tunnel N Operator N Wired Interf. 1 Decaps. Encaps. Interface emulator SCG Routing table NAT Connectivity Control Subsyst. Meas. Data Probes Remote Monitoring & Measurement Subsystem Interface 2 Internet Destination Open coupling architecture - fast and effective deployment. No access to Network State Information (NSI). Signalling channels are identical with the data channels.

7 Connectivity Platform Architecture Interfacing with public networks Operating System s User Space Active Measurements Software Module (WLAN & Cellular) Linux OS tools. Probe packets WLAN (WiFi) Monitoring Software Module WLAN specific Linux commands Meas. results Standard output replies WiFi specific function calls Daemon program (wpa_supplicant) Operating System Hardware Standard Linux commands WiFi Interface Driver WiFi Network Card GPS Monitoring Software Module Standard output replies GPS Library functions call GPS Daemon (gpsd) GPS driver GPS receiver NTP Daemon (ntpd) Flow Capture & Traffic Analysis Software Module Netfilter libraries function calls & commands Linux kernel netfilter support Network cards AT commands Virtual COM Ports Modem COM Port Probe packets Application Diagnostic COM Port COM Port Cellular Monitoring Software Module Standard output replies Meas. results qmi specific commands qminetwork qmicli cdc-wdm Driver 2G/3G/4G Interface Driver 2G/3G/4G Network Card Standard output replies QMI protocol Probe packets based network load measurement. Network load measured on the SMR-SCG virtual tunnel. Legacy devices employed. Network coverage map created on the run using GPS location data.

8 Vertical Handover Mechanism Cellular networks monitoring Trigger generation Cellular VHO WLAN monitoring & VHO STATE A - NO CONNECTION Detection of cellular networks NO Low speed trigger generated YES Detection of available WLANs networks Ordering of the WLANs based on RSS; best WLANs connected Measurement (active and passive) of the connected WLANs parameters A Cellular interfaces connect to the detected network Measurement (active and passive) of the connected cellular network parameters Send measurements to the Local Database NO Network state trigger generated NO Local trigger generated YES YES Acquire Context Information from the Local Database Best cellular network selection Perform 3G 3G VHO if necessary Send measurements to the Local Database Acquire Context Information from the Local Database Best WLAN selection Perform 3G WLAN VHO B C STATE B 2G/3G/4G DATA CONNECTION STATE C WLAN DATA CONNECTION Utility function based network selection: U cn = w RSCP RSCP cn + w ATR ATR cn + w ECIO ECIO cn U wn = w LQI LQI wn + w ATR ATR wn + w ChBPF ChBPF wn

9 Vertical Handover Mechanism Utility function weight computation Max-min normalization of the network parameters: v (x min(x )) / (max(x ) min(x )) ij ij ij ij ij i i i Weights represent the importance of a given parameter in the decision process. Subjective weighting methods - offline computation of the weights. - pair-wise comparison of all parameters. Pairwise comparison matrix B[MxM]: b {1,...,9}; b 1 for all j 1,..., M i, j i, i Eigenvector subjective weighting method: ( B I) w 0 Weight vector w [ w1,..., w ] T M is the eigenvector of matrix B corresponding to its maximum eigenvalue max. Weighted least square subjective weighting method: b 1/ b ; b w / w ; b b b i, j j, i i, j i j i, j j, k i, k M M M 2 min Z ( bij wj wi ), s. t. wi 1 i 1 j 1 i 1 Weights are computed by solving the constrained optimization problem: T minimize Z w Fw ( b w w ) M i 1 i 1 j 1 i, j j i T T such that e w w 1; e (1,1,...,1) i M M 2 M 2 i, j MxM i, i k, i i, j i, j j, i k 1 F [ f ] ; f M 2 b ; f ( b b ) 1 T 1 w F e / e F e

10 Experimental Testing AP1 AP2 WLAN-WLAN VHO Number of network interfaces is smaller than the number of WLAN APs. AP3 Automatic connections to the networks with the best performances. WLAN Ping-Pong effect is avoided. AP1 AP2 AP3 Test point A B C D E F G H I J RSS [dbm] LQI RSS [dbm] LQI RSS [dbm] LQI Rate[Mbps] The displayed rate is the average between the UL and DL rates.

11 Experimental Testing Op./Test pt. A B C D E F G H I J K L M A RSCP EcIo B RSCP EcIo C RSCP EcIo Rate[Mbps] I L K F G D A B C H J M E D 3G-3G VHO. Test zone is a hilly terrain near Cluj-Napoca. Multiple cellular technologies 2G/3G. Full coverage was not available for every cellular operator. The displayed rate is The average between the UL and DL rates.

12 HO & LB Integrated Mechanism IP Tunnel Op1 IP Tunnel Op2 IP Tunnel Op3 IP Tunnel Op4 Trigger based mechanism. Tunnels are classified based on a utility function. User flows have different priorities. Flow priority is reverse proportional with the utility function. Flow Info. Flow Selection Module Triggers NSI Flow Sel. Flow Info. Flow Monitoring Module Network Monitoring Monitoring Module Load Balancing Decision Module Combined VHO&LB Module Vertical Handover Decision Module Flow Switching Commands Flow IDs Net. IDs Connectivity Manager Subsystem LB/HO decision is based on a multiple knapsack algorithm.

13 Conclusions ICT is an important resource for the development of Intelligent Transport Systems. The presented connectivity platform addresses a part of the needs of ITS. Main purpose of the platform is to offer ubiquitous connectivity for public transport passengers and for ITS applications. Scalable, easy to deploy, open-coupling architecture. Real life tests of the vertical handover capable platform performed in both low and high mobility conditions. Evolution to an integrated HO and LB mechanism. Further development: HO and LB decision based on centralized information gathered from multiple sensors - transportation vehicle as a mobile network node.