Chapter 17 609
W-CDMA Downlink Digital Modulation for Receiver Test
Compressed Mode Overview
The ESG offers two different compressed mode methods for transmitting compressed frames. This is shown
as CM Method: SF/2 (spread factor divided by two) or Puncturing in Table 17-1. SF/2 reduces the spread
factor of the compressed frame by half; puncturing reduces the amount of transmitted data by eliminating
bits.
The ESG also supports the DPCH slot sub-formats, denoted in the specifications by the slot format number
with an ‘A’ or ‘B’, that are used during compressed frame transmission. The sub-format used is dependent
on the selected compressed mode method. The ESG automatically selects the correct sub-format for the
current slot format when you select the compressed mode method. For example if you were using slot
format 3, which includes the sub-formats 3A and 3B, and selected the SF/2 compressed mode method, the
ESG would use sub-format 3B. If you were to select puncturing as the compressed mode method, then the
ESG would automatically select sub-format 3A.
Another feature of the ESG compressed mode gives you the ability to select the different frame structures
utilized during compressed frame transmission. Frame structure ‘A’ optimizes the DTX periods by not
transmitting any power control information (TPC field) during this time. Frame structure ‘B’ optimizes for
power control by inserting power control information during the first DTX slot for each transmission gap.
Both frame structures transmit the pilot bits during the last slot for each transmission gap.
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