diff --git a/src/devices/wifi/wifi-phy.cc b/src/devices/wifi/wifi-phy.cc index db8940560..f04aae12c 100644 --- a/src/devices/wifi/wifi-phy.cc +++ b/src/devices/wifi/wifi-phy.cc @@ -764,6 +764,248 @@ WifiPhy::AppendEvent (Ptr event) /** * Stuff specific to the BER model here. */ +double +WifiPhy::Log2 (double val) const +{ + return log(val) / log(2.0); +} +double +WifiPhy::GetBpskBer (double snr, uint32_t signalSpread, uint32_t phyRate) const +{ + double EbNo = snr * signalSpread / phyRate; + double z = sqrt(EbNo); + double ber = 0.5 * erfc(z); + return ber; +} +double +WifiPhy::GetQamBer (double snr, unsigned int m, uint32_t signalSpread, uint32_t phyRate) const +{ + double EbNo = snr * signalSpread / phyRate; + double z = sqrt ((1.5 * Log2 (m) * EbNo) / (m - 1.0)); + double z1 = ((1.0 - 1.0 / sqrt (m)) * erfc (z)) ; + double z2 = 1 - pow ((1-z1), 2.0); + double ber = z2 / Log2 (m); + return ber; +} +uint32_t +WifiPhy::Factorial (uint32_t k) const +{ + uint32_t fact = 1; + while (k > 0) + { + fact *= k; + k--; + } + return fact; +} +double +WifiPhy::Binomial (uint32_t k, double p, uint32_t n) const +{ + double retval = Factorial (n) / (Factorial (k) * Factorial (n-k)) * pow (p, k) * pow (1-p, n-k); + return retval; +} +double +WifiPhy::CalculatePdOdd (double ber, unsigned int d) const +{ + NS_ASSERT ((d % 2) == 1); + unsigned int dstart = (d + 1) / 2; + unsigned int dend = d; + double pd = 0; + + for (unsigned int i = dstart; i < dend; i++) + { + pd += Binomial (i, ber, d); + } + return pd; +} +double +WifiPhy::CalculatePdEven (double ber, unsigned int d) const +{ + NS_ASSERT ((d % 2) == 0); + unsigned int dstart = d / 2 + 1; + unsigned int dend = d; + double pd = 0; + + for (unsigned int i = dstart; i < dend; i++) + { + pd += Binomial (i, ber, d); + } + pd += 0.5 * Binomial (d / 2, ber, d); + + return pd; +} + +double +WifiPhy::CalculatePd (double ber, unsigned int d) const +{ + double pd; + if ((d % 2) == 0) + { + pd = CalculatePdEven (ber, d); + } + else + { + pd = CalculatePdOdd (ber, d); + } + return pd; +} + +double +WifiPhy::GetFecBpskBer (double snr, double nbits, + uint32_t signalSpread, uint32_t phyRate, + uint32_t dFree, uint32_t adFree) const +{ + double ber = GetBpskBer (snr, signalSpread, phyRate); + if (ber == 0.0) + { + return 1.0; + } + double pd = CalculatePd (ber, dFree); + double pmu = adFree * pd; + if (pmu > 1.0) + { + /** + * If pmu is bigger than 1, then, this calculation is + * giving us a useless bound. A better bound in this case + * is 1 - ber which is necessarily bigger than the real + * success rate. + */ + return ber; + } + double pms = pow (1 - pmu, nbits); + return pms; +} + +double +WifiPhy::GetFecQamBer (double snr, uint32_t nbits, + uint32_t signalSpread, + uint32_t phyRate, + uint32_t m, uint32_t dFree, + uint32_t adFree, uint32_t adFreePlusOne) const +{ + double ber = GetQamBer (snr, m, signalSpread, phyRate); + if (ber == 0.0) + { + return 1.0; + } + /* first term */ + double pd = CalculatePd (ber, dFree); + double pmu = adFree * pd; + /* second term */ + pd = CalculatePd (ber, dFree + 1); + pmu += adFreePlusOne * pd; + if (pmu > 1.0) + { + /** + * If pmu is bigger than 1, then, this calculation is + * giving us a useless bound. A better bound in this case + * is 1 - ber which is necessarily bigger than the real + * success rate. + */ + return ber; + } + + double pms = pow (1 - pmu, nbits); + return pms; +} + +double +WifiPhy::GetChunkSuccessRate (WifiMode mode, double snr, uint32_t nbits) const +{ + if (mode.GetUid () == g_6mba.GetUid ()) + { + return GetFecBpskBer (snr, + nbits, + 20000000, // signal spread + 6000000, // phy rate + 10, // dFree + 11 // adFree + ); + } + else if (mode.GetUid () == g_9mba.GetUid ()) + { + return GetFecBpskBer (snr, + nbits, + 20000000, // signal spread + 9000000, // phy rate + 5, // dFree + 8 // adFree + ); + } + else if (mode.GetUid () == g_12mba.GetUid ()) + { + return GetFecQamBer (snr, + nbits, + 20000000, // signal spread + 12000000, // phy rate + 4, // m + 10, // dFree + 11, // adFree + 0 // adFreePlusOne + ); + } + else if (mode.GetUid () == g_18mba.GetUid ()) + { + return GetFecQamBer (snr, + nbits, + 20000000, // signal spread + 18000000, // phy rate + 4, // m + 5, // dFree + 8, // adFree + 31 // adFreePlusOne + ); + } + else if (mode.GetUid () == g_24mba.GetUid ()) + { + return GetFecQamBer (snr, + nbits, + 20000000, // signal spread + 24000000, // phy rate + 16, // m + 10, // dFree + 11, // adFree + 0 // adFreePlusOne + ); + } + else if (mode.GetUid () == g_36mba.GetUid ()) + { + return GetFecQamBer (snr, + nbits, + 20000000, // signal spread + 36000000, // phy rate + 16, // m + 5, // dFree + 8, // adFree + 31 // adFreePlusOne + ); + } + else if (mode.GetUid () == g_48mba.GetUid ()) + { + return GetFecQamBer (snr, + nbits, + 20000000, // signal spread + 48000000, // phy rate + 64, // m + 6, // dFree + 1, // adFree + 16 // adFreePlusOne + ); + } + else if (mode.GetUid () == g_54mba.GetUid ()) + { + return GetFecQamBer (snr, + nbits, + 20000000, // signal spread + 54000000, // phy rate + 64, // m + 5, // dFree + 8, // adFree + 31 // adFreePlusOne + ); + } + return 0; +} double WifiPhy::CalculateSnr (double signal, double noiseInterference, WifiMode mode) const diff --git a/src/devices/wifi/wifi-phy.h b/src/devices/wifi/wifi-phy.h index e991c0b5e..a7e6be814 100644 --- a/src/devices/wifi/wifi-phy.h +++ b/src/devices/wifi/wifi-phy.h @@ -158,6 +158,22 @@ private: double CalculateChunkSuccessRate (double snir, Time delay, WifiMode mode) const; double CalculatePer (Ptr event, NiChanges *ni) const; void EndSync (Packet const packet, Ptr event, uint32_t stuff); + double Log2 (double val) const; + double GetBpskBer (double snr, uint32_t signalSpread, uint32_t phyRate) const; + double GetQamBer (double snr, unsigned int m, uint32_t signalSpread, uint32_t phyRate) const; + uint32_t Factorial (uint32_t k) const; + double Binomial (uint32_t k, double p, uint32_t n) const; + double CalculatePdOdd (double ber, unsigned int d) const; + double CalculatePdEven (double ber, unsigned int d) const; + double CalculatePd (double ber, unsigned int d) const; + double GetFecBpskBer (double snr, double nbits, + uint32_t signalSpread, uint32_t phyRate, + uint32_t dFree, uint32_t adFree) const; + double GetFecQamBer (double snr, uint32_t nbits, + uint32_t signalSpread, + uint32_t phyRate, + uint32_t m, uint32_t dfree, + uint32_t adFree, uint32_t adFreePlusOne) const; double GetChunkSuccessRate (WifiMode mode, double snr, uint32_t nbits) const; /* rxPower unit is Watt */ void ReceivePacket (Packet packet,