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All:

1 Mbps DBPSK modulation and coding with long preamble, and 2 Mbps DQPSK modulation and coding with long preamble, are supported by the following PHYs:

Clause 15 DSSS -- described in the IEEE 802.11-1999 base document
Clause 18 HR/DSSS -- described in the IEEE 802.11b-1999 amendment
Clause 19 ERP -- described in the IEEE 802.11g-2003 amendment
Clause 20 HT -- described in the IEEE P802.11n, draft 2, 2007, proposed amendment

2 Mbps DQPSK modulation and coding with short preamble is supported by HR/DSSS, ERP, and HT PHYs, but not DSSS PHY.

A WLAN device built to one of these four PHY specifications does not become another kind of PHY by way of configuration, despite what vendor specific WLAN configuration utilities offer.

For instance selecting "B, G, or B/G" on an ERP device typically will limit which other devices the first will interoperate with, but the first device remains an ERP.

Since DSSS was never described in an amendment document, it doesn't have its own letter of the alphabet like its younger cousins B, G, and N. To deny interoperation with ancient DSSS peers one might configure a requirement for one of the data rates (5.5 Mbps, 11 Mbps) or preamble (short) introduced by the HR/DSSS PHY.

I hope this helps. Thanks. /criss