I'm unable to send SMS messages with multi-byte characters via a serial port using a Java program, here's the scenario:

I'm sending sms messages in text mode using a phone connected to a
serial port. The program communicates with the serial port using the javax.comm extension package. Here are the AT commands I'm issuing to send a message

1) Set the phone to text mode: AT+CMGF=1
2) Set the SMSC number: AT+CSCA="<SMSC number>",145
3) Set the destination mobile number AT+CMGS="<Destination number>",145
5) Send the message: <Message text>CTRL-Z

When the message text contains ascii characters, they appear correctly
on the destination mobile phone. However, when I send multi-byte
characters, eg Chinese characters, they do not appear correctly on the
(Chinese) mobile phone

My questions are:

1) Is it possible to send multi-byte characters in text mode
(AT+CMGF=1), or must they be sent in pdu mode (AT+CMGF=0)?
2) Do I need to set the Data Coding Scheme (DCS) using the AT+CSMP
command? If so, what AT+CSMP command should I issue?
3) I'm using the following Java code to send a command to the serial

String atCommand = <AT command text including multi-byte chinese
byte [] commandBytes = atCommand.getBytes();

serialPortOutputStream.write(commandBytes, 0, commandBytes.length);

Do I need to specify a particular encoding parameter in the
atCommand.getBytes() call?

Any help on this would be appreciated.