DL3000’s Direct Link Between Remote Data Acquisition and Web-Based Data Analysis and Control

Stevens’ DataLog_ic 3000 (DL3000) is available with a built-in TCP/IP stack to easily interface to a standard Internet connection directly via Ethernet or cell modem. Once connected, the data can be processed and analyzed on-line using the Stevens-Connect data management service or user customized data management program. Such information can be incorporated with other web services for enhanced, low cost data analysis.

As an option, the DL3000 comes with an integrated GPRS modem to bridge the link between the DL3000 and the Internet in one package. The following provides an overview of GPRS data services available.

The Stevens DataLog_ic 3000 Data Logger

General Packet Radio Service (GPRS) is a cellular data service extension of the GSM (Global System for Mobile Communications) standard that provides for higher data rate speed over standard cellular data rates. GPRS packet-switch protocol means multiple users share the same transmission channel, only transmitting when data is ready to send. This increases the capacity of the available bandwidth providing higher utilization where users send or receive data intermittently, providing for a low-cost data telemetry option.

GPRS data billing plans differ depending on the service provider, but typically are relatively inexpensive and billed per kilobyte of information or a fixed monthly rate based on planned data transfer. GPRS data service is available almost anywhere that GSM cell phone service is offered, including North and South America, and very extensive coverage throughout Europe and Asia.

Code Division Multiple Access (CDMA) is the competing broadband digital cellular radio technology. CDMA is popular in the United States, whereas GSM dominate the international market. GSM is growing quickly in the US, but some claim coverage in remote areas is better with CDMA. CDMA data billing plans are typically based on time.

The chief GSM carriers in the United States are AT&T Wireless (formerly Cingular) and T-Mobile USA. Major CDMA carriers are Sprint PCS, Verizon, and Virgin Mobile. There are also several smaller cellular companies on both networks.

GRPS Network Connection

In order to set up a GPRS connection for a wireless modem, a user must specify an Access Point Name (APN), optionally a user name and password, and very rarely an IP address, all provided by the network operator.

The GPRS Network

GPRS Data Access Diagram. Products such as the Stevens DL3000 can access the
internet through GPRS service offered by GSM mobile providers.

A GPRS connection is established by reference to its APN (Access Point Name). The APN defines the services such as wireless application protocol (WAP) access, short message service (SMS), multimedia messaging service (MMS), and for Internet communication services such as email and World Wide Web access.

GPRS supports the following protocols:

• Internet protocol (IP). In practice, the mobile built-in browser uses IPv4 since IPv6 is not yet popular.
• Point-to-point protocol (PPP). In this mode PPP is often not supported by the mobile phone operator but if the mobile is used as a modem to the connected computer, PPP is used to tunnel IP to the phone. This allows an IP address to be assigned dynamically to the mobile equipment.
• X.25 connections. This is typically used for applications like wireless payment terminals, although it has been removed from the standard.

When the TCP/IP protocol is used, each modem / phone can have one or more IP addresses allocated. GPRS will store and forward the IP packets to the modem / phone during cell handover (when you move from one cell to another). TCP handles any packet loss (e.g. due to a radio noise induced pause) resulting in a temporary throttling in transmission speed.

Although GPRS devices can communicate over public and private networks, many GPRS server devices require a static IP address, which simplifies resolving the hostname through the DDNS every time the device is powered on. Therefore, when setting up the Stevens’ GPRS integrated modem, the user needs to request a static IP from the GSM network carrier.

Each GSM / GPRS modem requires a Subscriber Identity Module (SIM) cards provided by the GSM carrier. The removable SIM card allows activation of a device, and may be interchanged, swapped out and upgraded, all with minimal carrier intervention. The SIM itself is tied to the network, rather than the actual modem. A GSM / GPRS modem that are card-enabled can be used with any GSM carrier. The SIM card stores all the necessary information to send and receive calls where with CDMA phones everything is kept on the phone’s internal memory.

Data Services from Stevens Water

With the increasing popularity of mobile data services and demand for data access at any time, Stevens Water now offers several options for cellular data services that can be customized to fit almost any application need, linking remote data collection devices with data management services hosted on the Internet or other networks. Please call Stevens at 503-445-8000 or 800-452-5272 to find out what data services are available in your area.