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AR# 36738

LogiCORE LTE UL Channel Decoder v2.0 - The fields ACK_IP_SIZE and RI_IP_SIZE seem too small under certain conditions


The fields ACK_IP_SIZE and RI_IP_SIZE areeight bits wide in the LTE UL Channel Decoder IP. This size can be too small under some conditions.



The maximum size of an encoded RI/ACK message is 4800 symbols (100*12*4=4800). The actual coding rate of the message is specified by a 4-bit code selected by the eNB, which specifies a relative coding rate to that of the TB (or CQI) coding rate. The 4-bit code is an index into scaling tables which cover a very wide range (for example, the ACK table goes from a rate scale of 2.0 up to 126.0). Worst case, the coding rate of ACK could be 126.0 that of the TB/CQI data. Actually, it is highly unlikely that an eNB would choose to use these high scaling factors. This tends to limit the encoded message size to something less than 256 bits.


The issue with CQI_IP_SIZE might not actually be an issue after all. While technically a CQI only PUSCH transmission could occupy an entire 100RB PUSCH allocation; actually, this PUSCH mode is only used when the resource allocation is <=4 RB wide, so our 13-bit field is probably acceptable.

For a detailed list of LogiCORE LTE UL Channel Decoder Release Notes and Known Issues, see (Xilinx Answer 31422)

Linked Answer Records

Master Answer Records

Answer Number Answer Title Version Found Version Resolved
31422 LogiCORE LTE UL Channel Decoder - Release Notes and Known Issues N/A N/A
AR# 36738
Date 12/15/2012
Status Active
Type General Article
  • 3GPP LTE UL Channel Decoder
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