The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/net80211/ieee80211_phy.c

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    1 /*-
    2  * Copyright (c) 2007-2008 Sam Leffler, Errno Consulting
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   24  */
   25 
   26 #include <sys/cdefs.h>
   27 __FBSDID("$FreeBSD: releng/9.0/sys/net80211/ieee80211_phy.c 188821 2009-02-19 17:44:23Z sam $");
   28 
   29 /*
   30  * IEEE 802.11 PHY-related support.
   31  */
   32 
   33 #include "opt_inet.h"
   34 
   35 #include <sys/param.h>
   36 #include <sys/kernel.h>
   37 #include <sys/systm.h>
   38 
   39 #include <sys/socket.h>
   40 
   41 #include <net/if.h>
   42 #include <net/if_media.h>
   43 
   44 #include <net80211/ieee80211_var.h>
   45 #include <net80211/ieee80211_phy.h>
   46 
   47 #ifdef notyet
   48 struct ieee80211_ds_plcp_hdr {
   49         uint8_t         i_signal;
   50         uint8_t         i_service;
   51         uint16_t        i_length;
   52         uint16_t        i_crc;
   53 } __packed;
   54 
   55 #endif  /* notyet */
   56 
   57 /* shorthands to compact tables for readability */
   58 #define OFDM    IEEE80211_T_OFDM
   59 #define CCK     IEEE80211_T_CCK
   60 #define TURBO   IEEE80211_T_TURBO
   61 #define HALF    IEEE80211_T_OFDM_HALF
   62 #define QUART   IEEE80211_T_OFDM_QUARTER
   63 #define PBCC    (IEEE80211_T_OFDM_QUARTER+1)            /* XXX */
   64 #define B(r)    (0x80 | r)
   65 #define Mb(x)   (x*1000)
   66 
   67 static struct ieee80211_rate_table ieee80211_11b_table = {
   68     .rateCount = 4,             /* XXX no PBCC */
   69     .info = {
   70 /*                                   short            ctrl  */
   71 /*                                Preamble  dot11Rate Rate */
   72      [0] = { .phy = CCK,     1000,    0x00,      B(2),   0 },/*   1 Mb */
   73      [1] = { .phy = CCK,     2000,    0x04,      B(4),   1 },/*   2 Mb */
   74      [2] = { .phy = CCK,     5500,    0x04,     B(11),   1 },/* 5.5 Mb */
   75      [3] = { .phy = CCK,    11000,    0x04,     B(22),   1 },/*  11 Mb */
   76      [4] = { .phy = PBCC,   22000,    0x04,        44,   3 } /*  22 Mb */
   77     },
   78 };
   79 
   80 static struct ieee80211_rate_table ieee80211_11g_table = {
   81     .rateCount = 12,
   82     .info = {
   83 /*                                   short            ctrl  */
   84 /*                                Preamble  dot11Rate Rate */
   85      [0] = { .phy = CCK,     1000,    0x00,      B(2),   0 },
   86      [1] = { .phy = CCK,     2000,    0x04,      B(4),   1 },
   87      [2] = { .phy = CCK,     5500,    0x04,     B(11),   2 },
   88      [3] = { .phy = CCK,    11000,    0x04,     B(22),   3 },
   89      [4] = { .phy = OFDM,    6000,    0x00,        12,   4 },
   90      [5] = { .phy = OFDM,    9000,    0x00,        18,   4 },
   91      [6] = { .phy = OFDM,   12000,    0x00,        24,   6 },
   92      [7] = { .phy = OFDM,   18000,    0x00,        36,   6 },
   93      [8] = { .phy = OFDM,   24000,    0x00,        48,   8 },
   94      [9] = { .phy = OFDM,   36000,    0x00,        72,   8 },
   95     [10] = { .phy = OFDM,   48000,    0x00,        96,   8 },
   96     [11] = { .phy = OFDM,   54000,    0x00,       108,   8 }
   97     },
   98 };
   99 
  100 static struct ieee80211_rate_table ieee80211_11a_table = {
  101     .rateCount = 8,
  102     .info = {
  103 /*                                   short            ctrl  */
  104 /*                                Preamble  dot11Rate Rate */
  105      [0] = { .phy = OFDM,    6000,    0x00,     B(12),   0 },
  106      [1] = { .phy = OFDM,    9000,    0x00,        18,   0 },
  107      [2] = { .phy = OFDM,   12000,    0x00,     B(24),   2 },
  108      [3] = { .phy = OFDM,   18000,    0x00,        36,   2 },
  109      [4] = { .phy = OFDM,   24000,    0x00,     B(48),   4 },
  110      [5] = { .phy = OFDM,   36000,    0x00,        72,   4 },
  111      [6] = { .phy = OFDM,   48000,    0x00,        96,   4 },
  112      [7] = { .phy = OFDM,   54000,    0x00,       108,   4 }
  113     },
  114 };
  115 
  116 static struct ieee80211_rate_table ieee80211_half_table = {
  117     .rateCount = 8,
  118     .info = {
  119 /*                                   short            ctrl  */
  120 /*                                Preamble  dot11Rate Rate */
  121      [0] = { .phy = HALF,    3000,    0x00,      B(6),   0 },
  122      [1] = { .phy = HALF,    4500,    0x00,         9,   0 },
  123      [2] = { .phy = HALF,    6000,    0x00,     B(12),   2 },
  124      [3] = { .phy = HALF,    9000,    0x00,        18,   2 },
  125      [4] = { .phy = HALF,   12000,    0x00,     B(24),   4 },
  126      [5] = { .phy = HALF,   18000,    0x00,        36,   4 },
  127      [6] = { .phy = HALF,   24000,    0x00,        48,   4 },
  128      [7] = { .phy = HALF,   27000,    0x00,        54,   4 }
  129     },
  130 };
  131 
  132 static struct ieee80211_rate_table ieee80211_quarter_table = {
  133     .rateCount = 8,
  134     .info = {
  135 /*                                   short            ctrl  */
  136 /*                                Preamble  dot11Rate Rate */
  137      [0] = { .phy = QUART,   1500,    0x00,      B(3),   0 },
  138      [1] = { .phy = QUART,   2250,    0x00,         4,   0 },
  139      [2] = { .phy = QUART,   3000,    0x00,      B(9),   2 },
  140      [3] = { .phy = QUART,   4500,    0x00,         9,   2 },
  141      [4] = { .phy = QUART,   6000,    0x00,     B(12),   4 },
  142      [5] = { .phy = QUART,   9000,    0x00,        18,   4 },
  143      [6] = { .phy = QUART,  12000,    0x00,        24,   4 },
  144      [7] = { .phy = QUART,  13500,    0x00,        27,   4 }
  145     },
  146 };
  147 
  148 static struct ieee80211_rate_table ieee80211_turbog_table = {
  149     .rateCount = 7,
  150     .info = {
  151 /*                                   short            ctrl  */
  152 /*                                Preamble  dot11Rate Rate */
  153      [0] = { .phy = TURBO,   12000,   0x00,     B(12),   0 },
  154      [1] = { .phy = TURBO,   24000,   0x00,     B(24),   1 },
  155      [2] = { .phy = TURBO,   36000,   0x00,        36,   1 },
  156      [3] = { .phy = TURBO,   48000,   0x00,     B(48),   3 },
  157      [4] = { .phy = TURBO,   72000,   0x00,        72,   3 },
  158      [5] = { .phy = TURBO,   96000,   0x00,        96,   3 },
  159      [6] = { .phy = TURBO,  108000,   0x00,       108,   3 }
  160     },
  161 };
  162 
  163 static struct ieee80211_rate_table ieee80211_turboa_table = {
  164     .rateCount = 8,
  165     .info = {
  166 /*                                   short            ctrl  */
  167 /*                                Preamble  dot11Rate Rate */
  168      [0] = { .phy = TURBO,   12000,   0x00,     B(12),   0 },
  169      [1] = { .phy = TURBO,   18000,   0x00,        18,   0 },
  170      [2] = { .phy = TURBO,   24000,   0x00,     B(24),   2 },
  171      [3] = { .phy = TURBO,   36000,   0x00,        36,   2 },
  172      [4] = { .phy = TURBO,   48000,   0x00,     B(48),   4 },
  173      [5] = { .phy = TURBO,   72000,   0x00,        72,   4 },
  174      [6] = { .phy = TURBO,   96000,   0x00,        96,   4 },
  175      [7] = { .phy = TURBO,  108000,   0x00,       108,   4 }
  176     },
  177 };
  178 
  179 #undef  Mb
  180 #undef  B
  181 #undef  OFDM
  182 #undef  HALF
  183 #undef  QUART
  184 #undef  CCK
  185 #undef  TURBO
  186 #undef  XR
  187 
  188 /*
  189  * Setup a rate table's reverse lookup table and fill in
  190  * ack durations.  The reverse lookup tables are assumed
  191  * to be initialized to zero (or at least the first entry).
  192  * We use this as a key that indicates whether or not
  193  * we've previously setup the reverse lookup table.
  194  *
  195  * XXX not reentrant, but shouldn't matter
  196  */
  197 static void
  198 ieee80211_setup_ratetable(struct ieee80211_rate_table *rt)
  199 {
  200 #define N(a)    (sizeof(a)/sizeof(a[0]))
  201 #define WLAN_CTRL_FRAME_SIZE \
  202         (sizeof(struct ieee80211_frame_ack) + IEEE80211_CRC_LEN)
  203 
  204         int i;
  205 
  206         for (i = 0; i < N(rt->rateCodeToIndex); i++)
  207                 rt->rateCodeToIndex[i] = (uint8_t) -1;
  208         for (i = 0; i < rt->rateCount; i++) {
  209                 uint8_t code = rt->info[i].dot11Rate;
  210                 uint8_t cix = rt->info[i].ctlRateIndex;
  211                 uint8_t ctl_rate = rt->info[cix].dot11Rate;
  212 
  213                 rt->rateCodeToIndex[code] = i;
  214                 if (code & IEEE80211_RATE_BASIC) {
  215                         /*
  216                          * Map w/o basic rate bit too.
  217                          */
  218                         code &= IEEE80211_RATE_VAL;
  219                         rt->rateCodeToIndex[code] = i;
  220                 }
  221 
  222                 /*
  223                  * XXX for 11g the control rate to use for 5.5 and 11 Mb/s
  224                  *     depends on whether they are marked as basic rates;
  225                  *     the static tables are setup with an 11b-compatible
  226                  *     2Mb/s rate which will work but is suboptimal
  227                  *
  228                  * NB: Control rate is always less than or equal to the
  229                  *     current rate, so control rate's reverse lookup entry
  230                  *     has been installed and following call is safe.
  231                  */
  232                 rt->info[i].lpAckDuration = ieee80211_compute_duration(rt,
  233                         WLAN_CTRL_FRAME_SIZE, ctl_rate, 0);
  234                 rt->info[i].spAckDuration = ieee80211_compute_duration(rt,
  235                         WLAN_CTRL_FRAME_SIZE, ctl_rate, IEEE80211_F_SHPREAMBLE);
  236         }
  237 
  238 #undef WLAN_CTRL_FRAME_SIZE
  239 #undef N
  240 }
  241 
  242 /* Setup all rate tables */
  243 static void
  244 ieee80211_phy_init(void)
  245 {
  246 #define N(arr)  (int)(sizeof(arr) / sizeof(arr[0]))
  247         static struct ieee80211_rate_table * const ratetables[] = {
  248                 &ieee80211_half_table,
  249                 &ieee80211_quarter_table,
  250                 &ieee80211_11a_table,
  251                 &ieee80211_11g_table,
  252                 &ieee80211_turbog_table,
  253                 &ieee80211_turboa_table,
  254                 &ieee80211_turboa_table,
  255                 &ieee80211_11a_table,
  256                 &ieee80211_11g_table,
  257                 &ieee80211_11b_table
  258         };
  259         int i;
  260 
  261         for (i = 0; i < N(ratetables); ++i)
  262                 ieee80211_setup_ratetable(ratetables[i]);
  263 
  264 #undef N
  265 }
  266 SYSINIT(wlan_phy, SI_SUB_DRIVERS, SI_ORDER_FIRST, ieee80211_phy_init, NULL);
  267 
  268 const struct ieee80211_rate_table *
  269 ieee80211_get_ratetable(struct ieee80211_channel *c)
  270 {
  271         const struct ieee80211_rate_table *rt;
  272 
  273         /* XXX HT */
  274         if (IEEE80211_IS_CHAN_HALF(c))
  275                 rt = &ieee80211_half_table;
  276         else if (IEEE80211_IS_CHAN_QUARTER(c))
  277                 rt = &ieee80211_quarter_table;
  278         else if (IEEE80211_IS_CHAN_HTA(c))
  279                 rt = &ieee80211_11a_table;      /* XXX */
  280         else if (IEEE80211_IS_CHAN_HTG(c))
  281                 rt = &ieee80211_11g_table;      /* XXX */
  282         else if (IEEE80211_IS_CHAN_108G(c))
  283                 rt = &ieee80211_turbog_table;
  284         else if (IEEE80211_IS_CHAN_ST(c))
  285                 rt = &ieee80211_turboa_table;
  286         else if (IEEE80211_IS_CHAN_TURBO(c))
  287                 rt = &ieee80211_turboa_table;
  288         else if (IEEE80211_IS_CHAN_A(c))
  289                 rt = &ieee80211_11a_table;
  290         else if (IEEE80211_IS_CHAN_ANYG(c))
  291                 rt = &ieee80211_11g_table;
  292         else if (IEEE80211_IS_CHAN_B(c))
  293                 rt = &ieee80211_11b_table;
  294         else {
  295                 /* NB: should not get here */
  296                 panic("%s: no rate table for channel; freq %u flags 0x%x\n",
  297                       __func__, c->ic_freq, c->ic_flags);
  298         }
  299         return rt;
  300 }
  301 
  302 /*
  303  * Convert PLCP signal/rate field to 802.11 rate (.5Mbits/s)
  304  *
  305  * Note we do no parameter checking; this routine is mainly
  306  * used to derive an 802.11 rate for constructing radiotap
  307  * header data for rx frames.
  308  *
  309  * XXX might be a candidate for inline
  310  */
  311 uint8_t
  312 ieee80211_plcp2rate(uint8_t plcp, enum ieee80211_phytype type)
  313 {
  314         if (type == IEEE80211_T_OFDM) {
  315                 static const uint8_t ofdm_plcp2rate[16] = {
  316                         [0xb]   = 12,
  317                         [0xf]   = 18,
  318                         [0xa]   = 24,
  319                         [0xe]   = 36,
  320                         [0x9]   = 48,
  321                         [0xd]   = 72,
  322                         [0x8]   = 96,
  323                         [0xc]   = 108
  324                 };
  325                 return ofdm_plcp2rate[plcp & 0xf];
  326         }
  327         if (type == IEEE80211_T_CCK) {
  328                 static const uint8_t cck_plcp2rate[16] = {
  329                         [0xa]   = 2,    /* 0x0a */
  330                         [0x4]   = 4,    /* 0x14 */
  331                         [0x7]   = 11,   /* 0x37 */
  332                         [0xe]   = 22,   /* 0x6e */
  333                         [0xc]   = 44,   /* 0xdc , actually PBCC */
  334                 };
  335                 return cck_plcp2rate[plcp & 0xf];
  336         }
  337         return 0;
  338 }
  339 
  340 /*
  341  * Covert 802.11 rate to PLCP signal.
  342  */
  343 uint8_t
  344 ieee80211_rate2plcp(int rate, enum ieee80211_phytype type)
  345 {
  346         /* XXX ignore type for now since rates are unique */
  347         switch (rate) {
  348         /* OFDM rates (cf IEEE Std 802.11a-1999, pp. 14 Table 80) */
  349         case 12:        return 0xb;
  350         case 18:        return 0xf;
  351         case 24:        return 0xa;
  352         case 36:        return 0xe;
  353         case 48:        return 0x9;
  354         case 72:        return 0xd;
  355         case 96:        return 0x8;
  356         case 108:       return 0xc;
  357         /* CCK rates (IEEE Std 802.11b-1999 page 15, subclause 18.2.3.3) */
  358         case 2:         return 10;
  359         case 4:         return 20;
  360         case 11:        return 55;
  361         case 22:        return 110;
  362         /* IEEE Std 802.11g-2003 page 19, subclause 19.3.2.1 */
  363         case 44:        return 220;
  364         }
  365         return 0;               /* XXX unsupported/unknown rate */
  366 }
  367 
  368 #define CCK_SIFS_TIME           10
  369 #define CCK_PREAMBLE_BITS       144
  370 #define CCK_PLCP_BITS           48
  371 
  372 #define OFDM_SIFS_TIME          16
  373 #define OFDM_PREAMBLE_TIME      20
  374 #define OFDM_PLCP_BITS          22
  375 #define OFDM_SYMBOL_TIME        4
  376 
  377 #define OFDM_HALF_SIFS_TIME     32
  378 #define OFDM_HALF_PREAMBLE_TIME 40
  379 #define OFDM_HALF_PLCP_BITS     22
  380 #define OFDM_HALF_SYMBOL_TIME   8
  381 
  382 #define OFDM_QUARTER_SIFS_TIME          64
  383 #define OFDM_QUARTER_PREAMBLE_TIME      80
  384 #define OFDM_QUARTER_PLCP_BITS          22
  385 #define OFDM_QUARTER_SYMBOL_TIME        16
  386 
  387 #define TURBO_SIFS_TIME         8
  388 #define TURBO_PREAMBLE_TIME     14
  389 #define TURBO_PLCP_BITS         22
  390 #define TURBO_SYMBOL_TIME       4
  391 
  392 /*
  393  * Compute the time to transmit a frame of length frameLen bytes
  394  * using the specified rate, phy, and short preamble setting.
  395  * SIFS is included.
  396  */
  397 uint16_t
  398 ieee80211_compute_duration(const struct ieee80211_rate_table *rt,
  399         uint32_t frameLen, uint16_t rate, int isShortPreamble)
  400 {
  401         uint8_t rix = rt->rateCodeToIndex[rate];
  402         uint32_t bitsPerSymbol, numBits, numSymbols, phyTime, txTime;
  403         uint32_t kbps;
  404 
  405         KASSERT(rix != (uint8_t)-1, ("rate %d has no info", rate));
  406         kbps = rt->info[rix].rateKbps;
  407         if (kbps == 0)                  /* XXX bandaid for channel changes */
  408                 return 0;
  409 
  410         switch (rt->info[rix].phy) {
  411         case IEEE80211_T_CCK:
  412                 phyTime         = CCK_PREAMBLE_BITS + CCK_PLCP_BITS;
  413                 if (isShortPreamble && rt->info[rix].shortPreamble)
  414                         phyTime >>= 1;
  415                 numBits         = frameLen << 3;
  416                 txTime          = CCK_SIFS_TIME + phyTime
  417                                 + ((numBits * 1000)/kbps);
  418                 break;
  419         case IEEE80211_T_OFDM:
  420                 bitsPerSymbol   = (kbps * OFDM_SYMBOL_TIME) / 1000;
  421                 KASSERT(bitsPerSymbol != 0, ("full rate bps"));
  422 
  423                 numBits         = OFDM_PLCP_BITS + (frameLen << 3);
  424                 numSymbols      = howmany(numBits, bitsPerSymbol);
  425                 txTime          = OFDM_SIFS_TIME
  426                                 + OFDM_PREAMBLE_TIME
  427                                 + (numSymbols * OFDM_SYMBOL_TIME);
  428                 break;
  429         case IEEE80211_T_OFDM_HALF:
  430                 bitsPerSymbol   = (kbps * OFDM_HALF_SYMBOL_TIME) / 1000;
  431                 KASSERT(bitsPerSymbol != 0, ("1/4 rate bps"));
  432 
  433                 numBits         = OFDM_PLCP_BITS + (frameLen << 3);
  434                 numSymbols      = howmany(numBits, bitsPerSymbol);
  435                 txTime          = OFDM_HALF_SIFS_TIME
  436                                 + OFDM_HALF_PREAMBLE_TIME
  437                                 + (numSymbols * OFDM_HALF_SYMBOL_TIME);
  438                 break;
  439         case IEEE80211_T_OFDM_QUARTER:
  440                 bitsPerSymbol   = (kbps * OFDM_QUARTER_SYMBOL_TIME) / 1000;
  441                 KASSERT(bitsPerSymbol != 0, ("1/2 rate bps"));
  442 
  443                 numBits         = OFDM_PLCP_BITS + (frameLen << 3);
  444                 numSymbols      = howmany(numBits, bitsPerSymbol);
  445                 txTime          = OFDM_QUARTER_SIFS_TIME
  446                                 + OFDM_QUARTER_PREAMBLE_TIME
  447                                 + (numSymbols * OFDM_QUARTER_SYMBOL_TIME);
  448                 break;
  449         case IEEE80211_T_TURBO:
  450                 /* we still save OFDM rates in kbps - so double them */
  451                 bitsPerSymbol = ((kbps << 1) * TURBO_SYMBOL_TIME) / 1000;
  452                 KASSERT(bitsPerSymbol != 0, ("turbo bps"));
  453 
  454                 numBits       = TURBO_PLCP_BITS + (frameLen << 3);
  455                 numSymbols    = howmany(numBits, bitsPerSymbol);
  456                 txTime        = TURBO_SIFS_TIME + TURBO_PREAMBLE_TIME
  457                               + (numSymbols * TURBO_SYMBOL_TIME);
  458                 break;
  459         default:
  460                 panic("%s: unknown phy %u (rate %u)\n", __func__,
  461                       rt->info[rix].phy, rate);
  462                 break;
  463         }
  464         return txTime;
  465 }

Cache object: ae503c6cf331183d14f0c61311158dba


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