3.5G doesn't work in mrt

It seems that Singtel's HSDPA or 3.5G network doesn't work in e mrt.

I used to surf using my K750i but this was limited to GPRS speeds.

Lately I got a Treo 500v which supports UMTS to replace e K750i as using GPRS was simply too slow. After a couple of days of use, it seems that whenever e train goes into e tunnel after bishan station, e network indicator would switch from 3G to G. This meant that e 3G connection was lost.

I wonder if it's my phone or that 3G is not supported underground?

3G terminology - UMTS\HSDPA\HSUPA

What is UMTS/WCDMA?
Universal Mobile Telecommunications System (UMTS) -- also known as Wideband Code Division Multiple Access (W-CDMA) -- is an international 3G standard established by the International Telecommunications Union (ITU). It is an advanced and efficient wireless technology being introduced worldwide that uses Direct-Sequence Spread Spectrum (DSSS), and both Frequency Division (FDD) and Time Division Duplexing (TDD), depending on the frequency assignment.

As a spread-spectrum technology, UMTS is designed to support the 3G evolution needs of Global System for Mobile Communications (GSM), and other, wireless network operators. GSM, the most widely used cellular access technology with over one billion users, is available worldwide.

Peak data rates of up to 384 kbps can be achieved depending upon use and the network construction. UMTS radio technology is an evolution of CDMA technology first introduced to the market in the mid 1990’s. UMTS/WCDMA is under the auspices of the 3GPP, the Third Generation Partnership Program, a consortium of 437 operators and vendors worldwide.

What is HSDPA?
HSDPA (High Speed Downlink Packet Access) is the next generation of the UMTS technology. HSDPA is an add-on solution to the 3GPP releases specifications. HSDPA employs new techniques in the protocol and channel structure to achieve theoretical data rates of up to 14.4Mbps. Another advantage of HSDPA is its backwards compatibility with UMTS.

What is HSUPA?
HSUPA(High Speed Uplink Packet Access) is another release to the evolving 3GPP standards. HSUPA employs an extremely efficient procedure for sending data on the uplink channel. The theoretical speed for data on the uplink is 5.76Mbps and the downlink will achieve HSDPA theoretical speeds of 14.4Mbps

When working side-by-side, an HSDPA/HSUPA network will benefit from increased transfer speeds allowing for a richer and more involving multimedia experience for the end users.

UPLINK/DOWNLINK GPRS Time slot dependant/53.6Kbps UMTS 128Kbps/384Kbps HSDPA 384Kbps/7.2Mbps HSUPA 2Mbps/7.2Mbps

Asia & Europe: UMTS: 2100 MHz GSM/GPRS: 900 & 1800 MHz North America: UMTS: 800 & 1900 MHz GSM/GPRS: 800 & 1900 MHz

HSDPA/HSUPA is fully backward compatible with UMTS and GPRS networks. Customers can roam between 195 countries on over 500 GSM, GPRS and UMTS networks worldwide providing access virtually anywhere worldwide. Users can move between GSM, GPRS and UMTS coverage areas without dropping connections or losing access to their network.

Users are always connected, always on-line. Once a connection has been made, information can be sent and received without delay.

Extensive authentication and encryption algorithms make it virtually impossible for unauthorized users to capture and decipher messages. The UMTS Subscriber Identity Module (USIM) card stores authentication information and security data to enable applications such as mobile banking, prepaid service activation and control, directory services and information services.

Source: http://www.novatelwireless.com/technology/hsdpa-hsupa-umts.html