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System Components | Selection Process and Description
Update #10121  |  30 Oct 2014
 

In this part is presented the selection process for the following components:

  • Internet Connectivity module (modem, router, antenna).
  • Sensors.
  • Camera.

Another key component is the GNNS module, to review its process selection and description, please follow the update 1.

To communicate the MCU – Colibri T20 with the data server, we will use internet connectivity via 4G. For this, it is necessary the evaluation of:

  • The mobile network to be use.
  • 4G/3G module to be attach to the MCU.

Mobile Network Selection

 Based on “The Great Mobile Network Test” for the 16th time running [1] in Switzerland, Swisscom is the operator with the best mobile network coverage and reliability compared with Sunrise and Orange. Below are presented a table with the different type of test performed and measures taken.

Swiss network test

As it can be seen, Swisscom leads the way in terms of speed and reliability. In most of the test performed, the success ratio (reliability) of Swisscom is higher than Sunrise and Orange. The same scenario is replayed for the session duration (speed) where it’s lower that its competitors. We are focus mainly in the tests “File Download and Upload” due the MCU will be sending the information via FTP.

Network Coverage

Due the hot air balloon can fly around different zones in Switzerland, such as mountains, lakes, cites and others. It is necessary to take a look about the network coverage. The following chart [2] shows the comparison between the three biggest operators in the country.

We can conclude from the information above, that Swisscom is the mobile operator with the best capabilities of data transmission. Taking to us to the next step to evaluate its coverage around the country per each network generation (2G, 3G, and 4G). [3]

2G/GSM – EDGE (state 08/20/2014)

3G /UMTS (state 09/01/2014)

   

3G/HSPA (state 09/01/2014)

4G/LTE (state 09/10/2014)

   

Even though 4G has the 94% of coverage the generations 2G and 3G can be used as a reliable backup in case of lost connection with 4G. Following, is exposed a comparison between the mobile communication technologies, offered by Swisscom for internet connectivity. [3]

Swisscom - Comparison of mobile communication technologies

Generation

Coverage

Technology

Download Speed

Upload Speed

2G

> 99%

GSM

Global System for Mobile Communications

max. 13.4 kbps

max. 13.4 kbps

 

 

GPRS

General Packet Ratio Service

max. 53.6 kbps

max. 48 kbps

 

 

EDGE

Enhanced Data Rates for GSM Evolution

max 256 kbps

max. 64 kbps

3G

> 98%

UMTS

Universal Mobile Telecommunications System

max. 384 kbps

max. 384 kbps

 

 

HSPA

High-Speed Packet Access 

max. 7.2 Mbps

max. 1.8 Mbps

 

 

HSPA+

High-Speed Packet Access plus

max. 42 Mbps

max. 5.6 Mbps

4G

> 94%

LTE

Long Term Evolution

max. 150 Mbps

max. 10 Mbps

Is clear that 4G features are the most appropriated ones for the communication with the data server, because the upload and download speed, however 2G and 3G speeds could perform the transmission with an acceptable delay for the application.

 

Modem Selection

To provide internet connectivity to the MCU – Colibri T20, in terms of hardware is required a cellular module with 4G/LTE capability. There are several 4g modules in the market, the next table present 3 of them, from some of the most well-known brands in this sector:

Brand

Reference

Features

Price per Unit

Telit

LE920

GSM/GPRS/ EDGE, UMTS/HSPA,LTE

Embedded GPS/Glonass

$ 200

Ublox

TOBY-L210

GSM/GPRS/ EDGE, UMTS/HSPA,LTE

Direct access to u-blox GNSS via TOBY

$ 210

Sierra Wireless

Mc7330

LTE, DC-HSPA+, HSPA+, HSDPA, HSUPA, WCDMA, GSM, GPRS, EDGE, and GNSS connectivity for networking

$ 240

Even though the modules presented above, fulfill the requirements needed and are able to work with Swisscom network, their prices are just for the chip, which in order to use it for our project, is necessary a system integration circuit, including a PCB, Sim Card holder and other several components. This increase the cost and time of the prototype, for this reason we proceed to select a USB modem 4G.

This selection is pretty simple, because once it has been choose the mobile operator, Swisscom, we take a look on the modems that they offer and select the most suitable. As a result, we find just one USB modem 4G, Huawei E3276 [4], one of the most popular worldwide.

 

Technical specifications

Dimensions

92mm x 32mm x 14mm

Weight

30 gr

Frequency bands

 LTE : 800/900/1800/2100/2600 Mhz
 UMTS: 2100/AWS/900/1900 Mhz
 GSM: 850/900/1800/1900 Mhz

External Antenna Interface

Yes, 2 port TS9

Interface

USB 2.0 High Speed

Sim Card Slot

Standard 6-pin SIM card interface

O.S.

Windows XP/Vista/7, Linux, Mac OS.

Key features for the project

  • HUAWEI E3276 supports 4G, 3G and 2G simultaneously, with 3G and 2G backward, the modem could auto switch to the lower network.
  • External antenna capability to increase the range reception.
  • Connection time within 15 seconds, based on tests from Huawei.

On the other hand, its face the challenge of driver compatibility with Windows Compact Embedded 7, O.S. selected for development, if we want to connect it via USB to the Colibri T20 module.

To solve this issue, we get in contact with Toradex AG to find possible solutions for it. Finally, we come out with the integration of a sharing router with Ethernet connection.

 

Router Selection

Based on the previous analysis, one need for this project is: through an Ethernet port, share the 4G connection coming from the modem via USB. However fulfill this requirement is a hard task, due there are several routers and hotspot in the market that share 4G connection via WIFI or USB, but without  Ethernet capability. For example Huawei E5776, and Dlink DWR-116.

After looking for a while in the market we find the following solutions:

 

Device

Features

Price

Huawei AF23 4G

Compatibility with Huawei E3276

Yes

$ 65

Ethernet port

Yes

Battery

No

TP-Link

MR3020

Compatibility with Huawei E3276

Depending of a firmware update

$ 40

Ethernet port

Yes

Battery

No

TP-Link

MR3040

Compatibility with Huawei E3276

Depending of a firmware update

 $ 45

Ethernet port

Yes

Battery

Yes, 2000mAh

Tenda 4G301

Compatibility with Huawei E3276

Full Compatible

$ 40

Ethernet port

Yes

Battery

Yes, 5200mAh

Tenda 4G302

Compatibility with Huawei E3276

Full Compatible

$ 60

Ethernet port

Yes

Battery

Yes, 10000mAh

Following the table presented above, the most suitable router for the project are:

  • Tenda 4G301
  • Tenda 4G302
  • Huawei AF23

Because, their full compatibility with the Usb modem 4g E3276. Nevertheless