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Introduction
6 (47) EN/LZT 108 6429 R1
May 2003
1.3 About the ADSL Modem HM121dp/di
The Ericsson ADSL Modem HM121d comes in two versions: HM121dp and
HM121di. Both products offer the same features, but they rely on different types of
telephone line in order to provide the ADSL service.
HM121dp offers ADSL service over POTS (Plain Old Telephone System) lines,
while HM121di uses ISDN (Integrated Services Digital Network) lines to provide the
ADSL service.
The HM121dp/di is easily connected to a USB port on the PC via a standard USB
cable (supplied). The modem uses power from the PC via the USB cable, which
eliminate the need of a power cable and AC adapter. An intuitive self-installation
wizard then guides the user step-by-step through the entire software installation
process. When new features and updates of the modem's software are available, they
may be added by simply loading a new version of the device driver onto the PC.
The main features of the HM121dp/di are listed below:
• Compliant with Universal Serial Bus Specification Revision 1.1.
• USB bus-powered; an external power supply is not required.
• Supports two device drivers: Microsoft NDIS 4.0 WAN Miniport and NDIS 4.0
LAN Miniport.
• Compatible with T1.413 i2, G.DMT, and G.lite compliant CO DSLAM
equipment.
• Up to 8 Mbps downstream and at least 640 Kbps upstream for full-rate operation.
Note:
The actual rate depends on the copper category of
your telephone wire, distance from the central office
and the type of ADSL service subscribed to. Also, if
other USB devices are attached to your computer
sharing the fixed bandwidth of USB controller, the
performance of the USB modem will be slightly
influenced and thus effects the actual speed.
• Software upgradeable.
• Support for PPP over Ethernet (PPPoE).
• Includes a Microsoft Windows control panel monitoring program for configuring
the adapter and checking the status of the connection.
1.3.1 Protocol and Device Driver Selection
ADSL modems employ ATM (Asynchronous Transfer Mode) framing. ATM is a
protocol that divides packets into small fixed sized cells for rapid transmission over
high-speed networks. The ATM protocol allows various types of traffic (e.g. data,
voice, and video) to be securely and efficiently carried over the same network. ATM
is being widely deployed by telecommunications carriers in their backbone networks.
Several different protocols are used on top of ATM. The protocol required in your
configuration depends on the equipment deployed by your ADSL service provider.
There are several possibilities:
• PPP (Point to Point Protocol) over ATM (RFC 2364)