Efficient Small Data Collecting System by Central and ...

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Efficient Small Data Collecting System by Central and Local Trigger Modes over Optical IP Network Osanori Koyama, Yusuke Takami, Shogo Kawai, Makoto Yamada and Yutaka Katsuyama Graduate School of Engineering, Osaka Prefecture University, Gakuen-cho 1-1, Naka-ku, Sakai, Osaka, 599-8531 Japan {koyama, takamie08, s-kawai08, myamada, katsu}@eis.osakafu-u.ac.jp

Abstract An efficient system has been implemented and tested to collect small data over optical IP networks. The results clarified that the system accumulated small data, and sent them to a center successfully. Introduction In the coming ubiquitous society, different types of data are supposed to be transmitted in networks. In sensor networks using RFID (Radio Frequency Identification), a huge number of packets with a small data size is transmitted, depending on the applications. In this case, the ratio of packet header size to the data size to be transmitted becomes relatively large: e.g. the ratio is about 0.5, if a packet with 50B data is sent by TCP/IP, because the header size is 54B. This causes inefficient transmissions in such a sensor network. We proposed [1] an effective system by circulating a packet to collect small data, enabling us to improve the data transmission efficiency by sharing the header. To make the system more practical, we re-designed the whole system such that the functions include both central and local trigger modes. Small Data Collecting System Fig. 1 shows the small data collecting system. This is an example of campus networks or local access networks connecting buildings, where RFID readers are used to collect small data stored in RFID tags for sensoring or monitoring. A typical application of the system is a student ID collecting system in a campus network. The system should collect small data for all the students who enter a class room on time, before the lecture begins in each building, and the data should be sent and stored in the center. The small data include a student ID and a time stamp when each student enters the class room. The to Building

Table 1 Data Collection Methods

Data Circulating Packets NIF : Network Interface N-DC : Node Data Collector L-DC : Local Data Collector

.....

4

data size is smaller than 50B, but lots of packets are sent excessively in a short time, just before lectures begin. In such an application network, network interfaces (NIFs) in the buildings are connected by single-mode fibers so as to form an optical ring. Each NIF has a layer-3 switch (L3SW), optical transceivers and a node data collector (N-DC). Generally the RFID reader reads the data from a tag in the building, and sends the data to a controller (CR) in a center. In the proposed system, the data are accumulated and saved temporarily in a local data collector (L-DC), and are sent to the center via the NIF. To send the temporary data to the center, 3 collecting modes listed in Table 1 were designed and implemented. Fig.2 shows the function modules implemented in the CR. Mode 1 is based on a central trigger created and circulated through the optical ring by the CR. A timer in the central module (1) activates a central trigger (CeT) module at a fixed time interval. This causes the CeT module (2) to send the trigger packet to the N-DC in the 1st NIF connected to the CR. As shown in Fig.3, a CeT module in the 1st N-DC sends the central trigger packet (3) to the 2nd NIF, and received by the CeT module in the 2nd N-DC. Thus, the trigger packet circulates the optical ring until the trigger packet returns to the CR. As shown in Fig.3, the trigger packet received by the CeT module in the 1st N-DC activates (4) a collecting trigger (CoT) sender to send a CoT packet (5) to the LDCs connected to the NIF. The CoT packet is received (5) by a data collector in the L-DC, (6) making the temporary data be collected from the buffer, as shown in Fig,4. The collected data (CoD) sender transfers the collected data (7) to a CoD receiver in the N-DC, and

N-DC L3SW NIF RX TX

n

Optical Ring Network 2

NIF n+1

NIF

NIF 1

NIF

Optical Transceiver

Controller

Data

L3SW

NIF

RFID L-DC Reader RFID TAG

...

Data

RFID L-DC Reader

...

User

Building n 3

Central Module

User Interface

Timer

Fig.1 Data Collecting System over Optical IP Network

(2)

CeT Module

WEB Server

CoD Receiver

(12)

Data Base

Local Module

RFID TAG

Building n+1

(1)

(4') (3')

CR

LoT Receiver CoD Receiver (2')

(2'')

Fig. 2. Function Modules in Controller

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(3) (11)

received (8) by an accumulating M. The collected data are sent (9) to the 2nd NIF through the optical ring, and are received (10) by a CoD receiver in the 2nd NIF. In the 2nd NIF, the central trigger had already been received and the temporary data in the L-DC connected to the second NIF had been collected and received in the accumulating M. Thus, the accumulating M. in the 2nd NIF receives the temporary data from 1st and 2nd buildings, and accumulates the collected data. In the same way, the temporary data are collected, accumulated, and sent to the next NIF until the data arrive (11) at the CR. The received data are saved (12) in a database in the CR, and can be used by the users through the web server. To make the system more practical, Modes 2 and 3 were added, based on local triggers. A threshold is determined and set in each L-DC, and a trigger creator monitors (1') the temporary data amount in the buffer. When the data amount becomes larger than the threshold in the buffer, a request event is created by the trigger creator, as shown in Fig.4. In Mode 2, a data collecting request is sent (2') to the CR by a local trigger (LoT) sender, when the event is received. When the local M. in the CR receives (2') the request, a CeT packet is circulated (3') by the CeT module to collect the data in the same way as in Mode 1. In Mode 3, a CoD sender of the local module in the L-DC sends (2'') the temporary data to the CR directly, when the event is received (1'). System Performance in an Experimental Network Fig.5 shows an experimental network to examine the system performance. Three buildings and one center are connected by SM fibers. The static IP routings were set in the L3SWs, so as to transfer packets to the next L3SW one-by-one [2]. To examine Mode 2, a threshold value of 220B was set in each L-DC. The student data of 50B were stored in RFID tags, and the tag data were read by the RFID readers in the 3 buildings, respectively, at the same time. When the tag data were read 4 times in buildings 1 and 2, respectively, and 5 times in building 3, a LAN analyzer monitored the packets, which passed through L3SW0 in the center. The results are shown in

Fig.6. In L-DC3, 5-time tag data readings gave 250B data, making a request event be created. Three packets were observed between L-DC3 and the CR to open a TCP connection by the 3-way hand shake. After this, a local trigger packet was observed, followed by 4 packets for the TCP connection closing. The 3 packets were also observed to open a TCP connection between the CR and N-DC1, a CeT packet was observed, and the TCP connection closing packets were observed. Then, a TCP connection was open between N-DC1 and N-DC2, a circulating packet with 200B data was observed, followed by the connection closing packets. This shows that the circulating packet accumulated the packets and carried the total 200B data to N-DC2. In the same way, a TCP connection was open, accumulated data were sent to the next N-DC, and the connection was closed. Finally, N-DC3 sent the accumulated 650B data to the CR by one packet, showing that Mode 2 worked successfully. Conclusions An efficient system has been implemented and tested to collect small data over optical IP networks. The system is based on 3 collecting modes by the central and local trigger packets. The results clarified that the system accumulated small data, and sent them to a center successfully. Acknowledgement: This work was supported in part by KAKENHI(19760259). The authors thank the support greatly.

References [1] O. Koyama et al., ATC2008, pp.128-131, Hanoi, Vietnam, Oct., 2008. [2] S.Fujimoto et al., IEEJ Trans. EIS, pp.534-535, 2005. LAN Analyzer

LS3W3 N-DC3

(4)

Collecting M.2

CoD Receiver

CoD Receiver

Accumulating M.

CoD Sender

Fig. 3. Function Modules in Node Data Collector

RS232C I/O Interface

Central Module

RFID Reader

CoD Sender

Data Buffer

Local Module (2') (2'')

LoT Sender CoD Sender

Trigger Creater

Building 3

N-DC2

NIF2

N-DC1

NIF1

L-DC2

RFID Reader 2

L-DC1

RFID Reader 1

Building 2

(1')

Data in Tag

Building 1

Fig. 5. Experimental Network Input RFID Tag Data 50 byte

Local Trigger (7B) TCP Connection Close

L-DC3 → CR CR → L-DC3

Time

Circulating Packet vacant

TCP Connection Open CR → N-DC1 Circulating Packet N-DC1 → CR 200byte

N-DC1 → N-DC2 N-DC2 → N-DC1

Data Collector (6)

RFID Reader 3

(7)

(8)

L-DC

L-DC3

.. (5)

CoT Sender

(3)

(7)

LS3W1

..

CeT Module

..

Collecting M.1-1

(2)

(5)

LS3W2

Collecting M.1-n

N-DC

(9)

NIF 0

LS3W0

Single Mode Optical Fiber

NIF3

(10)

Center

CR

N-DC2→ N-DC3→ N-DC3→ → CR

N-DC3 N-DC2 CR N-DC3

TCP Connection Close

Circulating Packet

400byte TCP Connection Close

TCP Connection Open

Circulating Packet 650byte

Fig. 4. Function Modules in Local Data Collector

Fig. 6.Monitored Packets in Accumulating Data by Mode 2

978-1-4244-4103-7/09/$25.0 © 2009 IEEE