lora-phy.cc

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/*
 * Copyright (c) 2017 University of Padova
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Author: Davide Magrin <magrinda@dei.unipd.it>
 */
 
#include "lora-phy.h"
 
#include "lora-channel.h"
 
#include "ns3/node.h"
 
namespace ns3
{
namespace lorawan
{
 
NS_LOG_COMPONENT_DEFINE("LoraPhy");
 
NS_OBJECT_ENSURE_REGISTERED(LoraPhy);
 
TypeId
LoraPhy::GetTypeId()
{
    static TypeId tid =
        TypeId("ns3::LoraPhy")
            .SetParent<Object>()
            .SetGroupName("lorawan")
            .AddTraceSource("StartSending",
                            "Trace source indicating the PHY layer"
                            "has begun the sending process for a packet",
                            MakeTraceSourceAccessor(&LoraPhy::m_startSending),
                            "ns3::Packet::TracedCallback")
            .AddTraceSource("PhyRxBegin",
                            "Trace source indicating a packet "
                            "is now being received from the channel medium "
                            "by the device",
                            MakeTraceSourceAccessor(&LoraPhy::m_phyRxBeginTrace),
                            "ns3::Packet::TracedCallback")
            .AddTraceSource("PhyRxEnd",
                            "Trace source indicating the PHY has finished "
                            "the reception process for a packet",
                            MakeTraceSourceAccessor(&LoraPhy::m_phyRxEndTrace),
                            "ns3::Packet::TracedCallback")
            .AddTraceSource("ReceivedPacket",
                            "Trace source indicating a packet "
                            "was correctly received",
                            MakeTraceSourceAccessor(&LoraPhy::m_successfullyReceivedPacket),
                            "ns3::Packet::TracedCallback")
            .AddTraceSource("LostPacketBecauseInterference",
                            "Trace source indicating a packet "
                            "could not be correctly decoded because of interfering"
                            "signals",
                            MakeTraceSourceAccessor(&LoraPhy::m_interferedPacket),
                            "ns3::Packet::TracedCallback")
            .AddTraceSource("LostPacketBecauseUnderSensitivity",
                            "Trace source indicating a packet "
                            "could not be correctly received because"
                            "its received power is below the sensitivity of the receiver",
                            MakeTraceSourceAccessor(&LoraPhy::m_underSensitivity),
                            "ns3::Packet::TracedCallback");
    return tid;
}
 
LoraPhy::LoraPhy()
{
}
 
LoraPhy::~LoraPhy()
{
}
 
Ptr<NetDevice>
LoraPhy::GetDevice() const
{
    return m_device;
}
 
void
LoraPhy::SetDevice(Ptr<NetDevice> device)
{
    NS_LOG_FUNCTION(this << device);
 
    m_device = device;
}
 
Ptr<LoraChannel>
LoraPhy::GetChannel() const
{
    NS_LOG_FUNCTION_NOARGS();
 
    return m_channel;
}
 
Ptr<MobilityModel>
LoraPhy::GetMobility()
{
    NS_LOG_FUNCTION_NOARGS();
 
    // If there is a mobility model associated to this PHY, take the mobility from
    // there
    if (m_mobility)
    {
        return m_mobility;
    }
    else // Else, take it from the node
    {
        return m_device->GetNode()->GetObject<MobilityModel>();
    }
}
 
void
LoraPhy::SetMobility(Ptr<MobilityModel> mobility)
{
    NS_LOG_FUNCTION_NOARGS();
 
    m_mobility = mobility;
}
 
void
LoraPhy::SetChannel(Ptr<LoraChannel> channel)
{
    NS_LOG_FUNCTION(this << channel);
 
    m_channel = channel;
}
 
void
LoraPhy::SetReceiveOkCallback(RxOkCallback callback)
{
    m_rxOkCallback = callback;
}
 
void
LoraPhy::SetReceiveFailedCallback(RxFailedCallback callback)
{
    m_rxFailedCallback = callback;
}
 
void
LoraPhy::SetTxFinishedCallback(TxFinishedCallback callback)
{
    m_txFinishedCallback = callback;
}
 
Time
LoraPhy::GetTSym(LoraTxParameters txParams)
{
    return Seconds(pow(2, int(txParams.sf)) / (txParams.bandwidthHz));
}
 
Time
LoraPhy::GetOnAirTime(Ptr<Packet> packet, LoraTxParameters txParams)
{
    NS_LOG_FUNCTION(packet << txParams);
 
    // The contents of this function are based on [1].
    // [1] SX1272 LoRa modem designer's guide.
 
    // Compute the symbol duration
    // Bandwidth is in Hz
    double tSym = GetTSym(txParams).GetSeconds();
 
    // Compute the preamble duration
    auto nPreamble = static_cast<double>(txParams.nPreamble);
    double tPreamble = (nPreamble + 4.25) * tSym;
 
    // Payload size
    uint32_t payloadLen = packet->GetSize(); // Size in bytes
    NS_LOG_DEBUG("Packet of size " << payloadLen << " bytes");
 
    // Safety casts since the formula deals with double values.
    auto pl = static_cast<double>(payloadLen);
    auto sf = static_cast<double>(txParams.sf);
    auto cr = static_cast<double>(txParams.codingRate);
    // de = 1 when the low data rate optimization is enabled, 0 otherwise
    // h = 1 when header is implicit, 0 otherwise
    // crc = 1 when cyclic redundancy check is present, 0 otherwise
    double de = txParams.lowDataRateOptimizationEnabled ? 1.0 : 0.0;
    double h = txParams.headerDisabled ? 1.0 : 0.0;
    double crc = txParams.crcEnabled ? 1.0 : 0.0;
 
    // num and den refer to numerator and denominator of the time on air formula
    double num = 8.0 * pl - 4.0 * sf + 28.0 + 16.0 * crc - 20.0 * h;
    double den = 4.0 * (sf - 2.0 * de);
    double payloadSymbNb = 8.0 + std::max(std::ceil(num / den) * (cr + 4.0), 0.0);
 
    // Time to transmit the payload
    double tPayload = payloadSymbNb * tSym;
 
    NS_LOG_DEBUG("Time computation: num = " << num << ", den = " << den << ", payloadSymbNb = "
                                            << payloadSymbNb << ", tSym = " << tSym);
    NS_LOG_DEBUG("tPreamble = " << tPreamble);
    NS_LOG_DEBUG("tPayload = " << tPayload);
    NS_LOG_DEBUG("Total time = " << tPreamble + tPayload);
 
    // Compute and return the total packet on-air time
    return Seconds(tPreamble + tPayload);
}
 
std::ostream&
operator<<(std::ostream& os, const CodingRate& codingRate)
{
    switch (codingRate)
    {
    case CodingRate::CR_4_5:
        return os << "4/5";
    case CodingRate::CR_4_6:
        return os << "4/6";
    case CodingRate::CR_4_7:
        return os << "4/7";
    case CodingRate::CR_4_8:
        return os << "4/8";
    default:
        NS_FATAL_ERROR("Unknown coding rate value");
        return (os << "UNKNOWN");
    }
}
 
std::istream&
operator>>(std::istream& is, CodingRate& codingRate)
{
    std::string value;
    is >> value;
    if (value == "4/5")
    {
        codingRate = CodingRate::CR_4_5;
    }
    else if (value == "4/6")
    {
        codingRate = CodingRate::CR_4_6;
    }
    else if (value == "4/7")
    {
        codingRate = CodingRate::CR_4_7;
    }
    else if (value == "4/8")
    {
        codingRate = CodingRate::CR_4_8;
    }
    else
    {
        is.setstate(std::ios_base::failbit);
    }
    NS_ABORT_MSG_IF(is.bad(), "Failure to parse " << value);
    return is;
}
 
std::ostream&
operator<<(std::ostream& os, const LoraTxParameters& params)
{
    os << "SF: " << unsigned(params.sf) << ", headerDisabled: " << params.headerDisabled
       << ", codingRate: " << params.codingRate << ", bandwidthHz: " << params.bandwidthHz
       << ", nPreamble: " << params.nPreamble << ", crcEnabled: " << params.crcEnabled
       << ", lowDataRateOptimizationEnabled: " << params.lowDataRateOptimizationEnabled << ")";
 
    return os;
}
 
} // namespace lorawan
} // namespace ns3