utility_function.h

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/*

 *  Copyright (c) 2018 The WebRTC project authors. All Rights Reserved.

 *  Use of this source code is governed by a BSD-style license

 *  that can be found in the LICENSE file in the root of the source

 *  tree. An additional intellectual property rights grant can be found

 *  in the file PATENTS.  All contributing project authors may

 *  be found in the AUTHORS file in the root of the source tree.

*/

#ifndef MODULES_CONGESTION_CONTROLLER_PCC_UTILITY_FUNCTION_H_

#define MODULES_CONGESTION_CONTROLLER_PCC_UTILITY_FUNCTION_H_

#include "modules/congestion_controller/pcc/monitor_interval.h"

namespace webrtc {

namespace pcc {

// Utility function is used by PCC to transform the performance statistics

// (sending rate, loss rate, packets latency) gathered at one monitor interval

// into a numerical value.

// https://www.usenix.org/conference/nsdi18/presentation/dong

class PccUtilityFunctionInterface {

 public:

  virtual double Compute(const PccMonitorInterval& monitor_interval) const = 0;

  virtual ~PccUtilityFunctionInterface() = default;

};

// Vivace utility function were suggested in the paper "PCC Vivace:

// Online-Learning Congestion Control", Mo Dong et all.

class VivaceUtilityFunction : public PccUtilityFunctionInterface {

 public:

  VivaceUtilityFunction(double delay_gradient_coefficient,

                        double loss_coefficient,

                        double throughput_coefficient,

                        double throughput_power,

                        double delay_gradient_threshold,

                        double delay_gradient_negative_bound);

  double Compute(const PccMonitorInterval& monitor_interval) const override;

  ~VivaceUtilityFunction() override;

 private:

  const double delay_gradient_coefficient_;

  const double loss_coefficient_;

  const double throughput_power_;

  const double throughput_coefficient_;

  const double delay_gradient_threshold_;

  const double delay_gradient_negative_bound_;

};

// This utility function were obtained by tuning Vivace utility function.

// The main difference is that gradient of modified utilify funtion (as well as

// rate updates) scales proportionally to the sending rate which leads to

// better performance in case of single sender.

class ModifiedVivaceUtilityFunction : public PccUtilityFunctionInterface {

 public:

  ModifiedVivaceUtilityFunction(double delay_gradient_coefficient,

                                double loss_coefficient,

                                double throughput_coefficient,

                                double throughput_power,

                                double delay_gradient_threshold,

                                double delay_gradient_negative_bound);

  double Compute(const PccMonitorInterval& monitor_interval) const override;

  ~ModifiedVivaceUtilityFunction() override;

 private:

  const double delay_gradient_coefficient_;

  const double loss_coefficient_;

  const double throughput_power_;

  const double throughput_coefficient_;

  const double delay_gradient_threshold_;

  const double delay_gradient_negative_bound_;

};

}  // namespace pcc

}  // namespace webrtc

#endif  // MODULES_CONGESTION_CONTROLLER_PCC_UTILITY_FUNCTION_H_