<p>laforge <strong>submitted</strong> this change.</p><p><a href="https://gerrit.osmocom.org/c/libosmocore/+/17693">View Change</a></p><div style="white-space:pre-wrap">Approvals:
pespin: Looks good to me, but someone else must approve
laforge: Looks good to me, approved
Jenkins Builder: Verified
</div><pre style="font-family: monospace,monospace; white-space: pre-wrap;">coding: fix bit ordering in 11-bit RACH coding functions<br><br>According to 3GPP TS 44.004, figure 7.4a.b, the format of 11-bit<br>RACH uplink / Uplink access burst block is as defined follows:<br><br> <---------------------------------------------------<br><br> 8 7 6 5 4 3 2 1<br> +--------------------------------------------------+<br> | 11 bit RACH uplink / Uplink access burst block | OCT1<br> +--------------------------------------------------+<br> | | OCT2<br> +-------------------+<br><br>As was (correctly) assumed in [1], the bit ordering in 11-bit RACH<br>coding functions is wrong. The problem is that neither of generic<br>functions from bit16gen.h can be used to load / store the RA11<br>value (regardless of the endianness), because they assume that<br>the payload is 16 bit long.<br><br>With this patch applied, RA11 values from [1] look correct:<br><br> < EGPRS Packet channel request message content > ::=<br> < Signalling : 110011 < RandomBits : 00111 > > |<br> < Signalling : 110011 < RandomBits : 00110 > > |<br> < Signalling : 110011 < RandomBits : 01111 > > |<br> < Signalling : 110011 < RandomBits : 01100 > > |<br> < Signalling : 110011 < RandomBits : 00111 > > |<br> < Signalling : 110011 < RandomBits : 10110 > > ;<br><br>[1] Id80e471d252b9416217b56f4c8c0a8f5f1289fee<br><br>Change-Id: I43d30611dd69f77f2b3b46f4b56056a8891d3c24<br>Related: OS#1548<br>---<br>M src/coding/gsm0503_coding.c<br>M tests/coding/coding_test.ok<br>2 files changed, 9 insertions(+), 8 deletions(-)<br><br></pre><pre style="font-family: monospace,monospace; white-space: pre-wrap;"><span>diff --git a/src/coding/gsm0503_coding.c b/src/coding/gsm0503_coding.c</span><br><span>index 163ce21..8480240 100644</span><br><span>--- a/src/coding/gsm0503_coding.c</span><br><span>+++ b/src/coding/gsm0503_coding.c</span><br><span>@@ -2879,7 +2879,7 @@</span><br><span> </span><br><span> osmo_ubit2pbit_ext(ra, 0, conv, 0, nbits, 1);</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">- return is_11bit ? osmo_load16le(ra) : ra[0];</span><br><span style="color: hsl(120, 100%, 40%);">+ return is_11bit ? ((ra[0] << 3) | (ra[1] & 0x07)) : ra[0];</span><br><span> }</span><br><span> </span><br><span> /*! Decode the Extended (11-bit) RACH according to 3GPP TS 45.003</span><br><span>@@ -2974,7 +2974,8 @@</span><br><span> uint8_t ra[2] = { 0 }, nbits = 8;</span><br><span> </span><br><span> if (is_11bit) {</span><br><span style="color: hsl(0, 100%, 40%);">- osmo_store16le(ra11, ra);</span><br><span style="color: hsl(120, 100%, 40%);">+ ra[0] = (uint8_t) (ra11 >> 3);</span><br><span style="color: hsl(120, 100%, 40%);">+ ra[1] = (uint8_t) (ra11 & 0x07);</span><br><span> nbits = 11;</span><br><span> } else</span><br><span> ra[0] = (uint8_t)ra11;</span><br><span>diff --git a/tests/coding/coding_test.ok b/tests/coding/coding_test.ok</span><br><span>index 496ce89..3a4fbf2 100644</span><br><span>--- a/tests/coding/coding_test.ok</span><br><span>+++ b/tests/coding/coding_test.ok</span><br><span>@@ -40,12 +40,12 @@</span><br><span> Decoded: 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 </span><br><span> xcch_decode: n_errors=60 n_bits_total=456 ber=0.13</span><br><span> </span><br><span style="color: hsl(0, 100%, 40%);">-Decoded RA11: 0x7cc</span><br><span style="color: hsl(0, 100%, 40%);">-Decoded RA11: 0x6cc</span><br><span style="color: hsl(0, 100%, 40%);">-Decoded RA11: 0x7cd</span><br><span style="color: hsl(0, 100%, 40%);">-Decoded RA11: 0x4cd</span><br><span style="color: hsl(0, 100%, 40%);">-Decoded RA11: 0x7cc</span><br><span style="color: hsl(0, 100%, 40%);">-Decoded RA11: 0x6ce</span><br><span style="color: hsl(120, 100%, 40%);">+Decoded RA11: 0x667</span><br><span style="color: hsl(120, 100%, 40%);">+Decoded RA11: 0x666</span><br><span style="color: hsl(120, 100%, 40%);">+Decoded RA11: 0x66f</span><br><span style="color: hsl(120, 100%, 40%);">+Decoded RA11: 0x66c</span><br><span style="color: hsl(120, 100%, 40%);">+Decoded RA11: 0x667</span><br><span style="color: hsl(120, 100%, 40%);">+Decoded RA11: 0x676</span><br><span> </span><br><span> Encoding: 03 03 01 00 </span><br><span> U-Bits: 111001110011000011100111001100001101001111000000000011010000011010110111111100</span><br><span></span><br></pre><p>To view, visit <a href="https://gerrit.osmocom.org/c/libosmocore/+/17693">change 17693</a>. To unsubscribe, or for help writing mail filters, visit <a href="https://gerrit.osmocom.org/settings">settings</a>.</p><div itemscope itemtype="http://schema.org/EmailMessage"><div itemscope itemprop="action" itemtype="http://schema.org/ViewAction"><link itemprop="url" href="https://gerrit.osmocom.org/c/libosmocore/+/17693"/><meta itemprop="name" content="View Change"/></div></div>
<div style="display:none"> Gerrit-Project: libosmocore </div>
<div style="display:none"> Gerrit-Branch: master </div>
<div style="display:none"> Gerrit-Change-Id: I43d30611dd69f77f2b3b46f4b56056a8891d3c24 </div>
<div style="display:none"> Gerrit-Change-Number: 17693 </div>
<div style="display:none"> Gerrit-PatchSet: 3 </div>
<div style="display:none"> Gerrit-Owner: fixeria <axilirator@gmail.com> </div>
<div style="display:none"> Gerrit-Reviewer: Jenkins Builder </div>
<div style="display:none"> Gerrit-Reviewer: laforge <laforge@osmocom.org> </div>
<div style="display:none"> Gerrit-Reviewer: pespin <pespin@sysmocom.de> </div>
<div style="display:none"> Gerrit-MessageType: merged </div>