wifi-bandwidth-filter.cc

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/*
 * Copyright (c) 2022 Universita' degli Studi di Napoli "Federico II"
 * Copyright (c) 2022 University of Washington (port logic to WifiBandwidthFilter)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
 
#include "wifi-bandwidth-filter.h"
 
#include "spectrum-wifi-phy.h"
#include "wifi-psdu.h"
#include "wifi-spectrum-phy-interface.h"
#include "wifi-spectrum-signal-parameters.h"
 
#include <ns3/boolean.h>
#include <ns3/spectrum-transmit-filter.h>
 
namespace ns3
{
 
NS_LOG_COMPONENT_DEFINE("WifiBandwidthFilter");
 
NS_OBJECT_ENSURE_REGISTERED(WifiBandwidthFilter);
 
WifiBandwidthFilter::WifiBandwidthFilter()
{
    NS_LOG_FUNCTION(this);
}
 
TypeId
WifiBandwidthFilter::GetTypeId()
{
    static TypeId tid = TypeId("ns3::WifiBandwidthFilter")
                            .SetParent<SpectrumTransmitFilter>()
                            .SetGroupName("Wifi")
                            .AddConstructor<WifiBandwidthFilter>();
    return tid;
}
 
bool
WifiBandwidthFilter::DoFilter(Ptr<const SpectrumSignalParameters> params,
                              Ptr<const SpectrumPhy> receiverPhy)
{
    NS_LOG_FUNCTION(this << params);
 
    auto wifiRxParams = DynamicCast<const WifiSpectrumSignalParameters>(params);
    if (!wifiRxParams)
    {
        NS_LOG_DEBUG("Received a non Wi-Fi signal: do not filter");
        return false;
    }
 
    auto interface = DynamicCast<const WifiSpectrumPhyInterface>(receiverPhy);
    if (!interface)
    {
        NS_LOG_DEBUG("Sending a Wi-Fi signal to a non Wi-Fi device; do not filter");
        return false;
    }
 
    auto wifiPhy = interface->GetSpectrumWifiPhy();
    NS_ASSERT_MSG(wifiPhy,
                  "WifiPhy should be valid if WifiSpectrumSignalParameters was found and sending "
                  "to a WifiSpectrumPhyInterface");
 
    BooleanValue trackSignalsInactiveInterfaces;
    wifiPhy->GetAttribute("TrackSignalsFromInactiveInterfaces", trackSignalsInactiveInterfaces);
 
    NS_ASSERT_MSG(trackSignalsInactiveInterfaces.Get() ||
                      (interface == wifiPhy->GetCurrentInterface()),
                  "DoFilter should not be called for an inactive interface if "
                  "SpectrumWifiPhy::TrackSignalsFromInactiveInterfaces attribute is not enabled");
 
    NS_ASSERT((interface != wifiPhy->GetCurrentInterface()) ||
              (wifiPhy->GetOperatingChannel().GetFrequency() == interface->GetCenterFrequency()));
    NS_ASSERT((interface != wifiPhy->GetCurrentInterface()) ||
              (wifiPhy->GetOperatingChannel().GetWidth() == interface->GetChannelWidth()));
 
    // The signal power is spread over a frequency interval that includes a guard
    // band on the left and a guard band on the right of the nominal TX band
 
    const auto rxCenterFreq = wifiRxParams->ppdu->GetTxCenterFreq();
    const auto rxWidth = wifiRxParams->ppdu->GetTxVector().GetChannelWidth();
    const auto guardBandwidth = wifiPhy->GetGuardBandwidth(rxWidth);
    const auto operatingFrequency = interface->GetCenterFrequency();
    const auto operatingChannelWidth = interface->GetChannelWidth();
 
    const auto rxMinFreq = rxCenterFreq - rxWidth / 2 - guardBandwidth;
    const auto rxMaxFreq = rxCenterFreq + rxWidth / 2 + guardBandwidth;
 
    const auto channelMinFreq = operatingFrequency - operatingChannelWidth / 2;
    const auto channelMaxFreq = operatingFrequency + operatingChannelWidth / 2;
 
    /**
     * The PPDU can be ignored if the two bands do not overlap.
     *
     * First non-overlapping case:
     *
     *                                        ┌─────────┬─────────┬─────────┐
     *                                PPDU    │  Guard  │ Nominal │  Guard  │
     *                                        │  Band   │   Band  │  Band   │
     *                                        └─────────┴─────────┴─────────┘
     *                                    rxMinFreq                     rxMaxFreq
     *
     * channelMinFreq                channelMaxFreq
     *         ┌──────────────────────────────┐
     *         │         Operating            │
     *         │           Channel            │
     *         └──────────────────────────────┘
     *
     * Second non-overlapping case:
     *
     *         ┌─────────┬─────────┬─────────┐
     * PPDU    │  Guard  │ Nominal │  Guard  │
     *         │  Band   │   Band  │  Band   │
     *         └─────────┴─────────┴─────────┘
     *     rxMinFreq                     rxMaxFreq
     *
     *                               channelMinFreq                channelMaxFreq
     *                                       ┌──────────────────────────────┐
     *                                       │         Operating            │
     *                                       │           Channel            │
     *                                       └──────────────────────────────┘
     */
    auto filter = (rxMinFreq >= channelMaxFreq || rxMaxFreq <= channelMinFreq);
    NS_LOG_DEBUG("Returning " << filter);
    return filter;
}
 
int64_t
WifiBandwidthFilter::DoAssignStreams(int64_t stream)
{
    return 0;
}
 
} // namespace ns3