| /* |
| * Copyright (c) 2016, The OpenThread Authors. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. Neither the name of the copyright holder nor the |
| * names of its contributors may be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE |
| * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| * POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| /** |
| * @file |
| * This file includes definitions for storing and processing link quality information. |
| */ |
| |
| #ifndef LINK_QUALITY_HPP_ |
| #define LINK_QUALITY_HPP_ |
| |
| #include "openthread-core-config.h" |
| |
| #include <openthread/platform/radio.h> |
| |
| #include "common/string.hpp" |
| |
| namespace ot { |
| |
| /** |
| * @addtogroup core-link-quality |
| * |
| * @brief |
| * This module includes definitions for Thread link quality metrics. |
| * |
| * @{ |
| */ |
| |
| /** |
| * This class implements an operation Success Rate Tracker. |
| * |
| * This can be used to track different link quality related metrics, e.g., CCA failure rate, frame tx success rate). |
| * The success rate is maintained using an exponential moving IIR averaging filter with a `uint16_t` as the storage. |
| * |
| */ |
| class SuccessRateTracker |
| { |
| public: |
| enum |
| { |
| kMaxRateValue = 0xffff, ///< Indicates value corresponding to maximum (failure/success) rate of 100%. |
| }; |
| |
| /** |
| * This method resets the tracker to its initialized state, setting success rate to 100%. |
| * |
| */ |
| void Reset(void) { mFailureRate = 0; } |
| |
| /** |
| * This method adds a sample (success or failure) to `SuccessRateTracker`. |
| * |
| * @param[in] aSuccess The sample status be added, `true` for success, `false` for failure. |
| * @param[in] aWeight The weight coefficient used for adding the new sample into average. |
| * |
| */ |
| void AddSample(bool aSuccess, uint16_t aWeight = kDefaultWeight); |
| |
| /** |
| * This method returns the average failure rate. |
| * |
| * @retval the average failure rate `[0-kMaxRateValue]` with `kMaxRateValue` corresponding to 100%. |
| * |
| */ |
| uint16_t GetFailureRate(void) const { return mFailureRate; } |
| |
| /** |
| * This method returns the average success rate. |
| * |
| * @retval the average success rate as [0-kMaxRateValue] with `kMaxRateValue` corresponding to 100%. |
| * |
| */ |
| uint16_t GetSuccessRate(void) const { return kMaxRateValue - mFailureRate; } |
| |
| private: |
| enum |
| { |
| kDefaultWeight = 64, |
| }; |
| |
| uint16_t mFailureRate; |
| }; |
| |
| /** |
| * This class implements a Received Signal Strength (RSS) averager. |
| * |
| * The average is maintained using an adaptive exponentially weighted moving filter. |
| * |
| */ |
| class RssAverager |
| { |
| public: |
| enum |
| { |
| kStringSize = 10, ///< Max chars needed for a string representation of average (@sa ToString()). |
| }; |
| |
| /** |
| * This type defines the fixed-length `String` object returned from `ToString()`. |
| * |
| */ |
| typedef String<kStringSize> InfoString; |
| |
| /** |
| * This method reset the averager and clears the average value. |
| * |
| */ |
| void Reset(void); |
| |
| /** |
| * This method indicates whether the averager contains an average (i.e., at least one RSS value has been added). |
| * |
| * @retval true If the average value is available (at least one RSS value has been added). |
| * @retval false Averager is empty (no RSS value added yet). |
| * |
| */ |
| bool HasAverage(void) const { return (mCount != 0); } |
| |
| /** |
| * This method adds a received signal strength (RSS) value to the average. |
| * |
| * If @p aRss is OT_RADIO_RSSI_INVALID, it is ignored and error status OT_ERROR_INVALID_ARGS is returned. |
| * The value of RSS is capped at 0dBm (i.e., for any given RSS value higher than 0dBm, 0dBm is used instead). |
| * |
| * @param[in] aRss Received signal strength value (in dBm) to be added to the average. |
| * |
| * @retval OT_ERROR_NONE New RSS value added to average successfully. |
| * @retval OT_ERROR_INVALID_ARGS Value of @p aRss is OT_RADIO_RSSI_INVALID. |
| * |
| */ |
| otError Add(int8_t aRss); |
| |
| /** |
| * This method returns the current average signal strength value maintained by the averager. |
| * |
| * @returns The current average value (in dBm) or OT_RADIO_RSSI_INVALID if no average is available. |
| * |
| */ |
| int8_t GetAverage(void) const; |
| |
| /** |
| * This method returns an raw/encoded version of current average signal strength value. The raw value is the |
| * average multiplied by a precision factor (currently set as -8). |
| * |
| * @returns The current average multiplied by precision factor or zero if no average is available. |
| * |
| */ |
| uint16_t GetRaw(void) const { return mAverage; } |
| |
| /** |
| * This method converts the current average RSS value to a human-readable string (e.g., "-80.375"). If the |
| * average is unknown, empty string is returned. |
| * |
| * @returns An `InfoString` object containing the string representation of average RSS. |
| * |
| */ |
| InfoString ToString(void) const; |
| |
| private: |
| /* |
| * The RssAverager uses an adaptive exponentially weighted filter to maintain the average. It keeps track of |
| * current average and the number of added RSS values (up to a 8). |
| * |
| * For the first 8 added RSS values, the average is the arithmetic mean of the added values (e.g., if 5 values are |
| * added, the average is sum of the 5 added RSS values divided by 5. After the 8th RSS value, a weighted filter is |
| * used with coefficients (1/8, 7/8), i.e., newAverage = 1/8 * newRss + 7/8 * oldAverage. |
| * |
| * To add to accuracy of the averaging process, the RSS values and the maintained average are multiplied by a |
| * precision factor of -8. |
| * |
| */ |
| |
| enum |
| { |
| kPrecisionBitShift = 3, // Precision multiple for RSS average (1 << PrecisionBitShift). |
| kPrecision = (1 << kPrecisionBitShift), |
| kPrecisionBitMask = (kPrecision - 1), |
| |
| kCoeffBitShift = 3, // Coefficient used for exponentially weighted filter (1 << kCoeffBitShift). |
| }; |
| |
| // Member variables fit into two bytes. |
| |
| uint16_t mAverage : 11; // The raw average signal strength value (stored as RSS times precision multiple). |
| uint16_t mCount : 5; // Number of RSS values added to averager so far (limited to 2^kCoeffBitShift-1). |
| }; |
| |
| /** |
| * This class encapsulates/stores all relevant information about quality of a link, including average received signal |
| * strength (RSS), last RSS, link margin, and link quality. |
| * |
| */ |
| class LinkQualityInfo |
| { |
| public: |
| enum |
| { |
| kInfoStringSize = 50, ///< Max chars needed for the info string representation (@sa ToInfoString()) |
| }; |
| |
| /** |
| * This type defines the fixed-length `String` object returned from `ToInfoString()`. |
| * |
| */ |
| typedef String<kInfoStringSize> InfoString; |
| |
| /** |
| * This method clears the all the data in the object. |
| * |
| */ |
| void Clear(void); |
| |
| /** |
| * This method adds a new received signal strength (RSS) value to the average. |
| * |
| * @param[in] aNoiseFloor The noise floor value (in dBm). |
| * @param[in] aRss A new received signal strength value (in dBm) to be added to the average. |
| * |
| */ |
| void AddRss(int8_t aNoiseFloor, int8_t aRss); |
| |
| /** |
| * This method returns the current average received signal strength value. |
| * |
| * @returns The current average value or @c OT_RADIO_RSSI_INVALID if no average is available. |
| * |
| */ |
| int8_t GetAverageRss(void) const { return mRssAverager.GetAverage(); } |
| |
| /** |
| * This method returns an encoded version of current average signal strength value. The encoded value is the |
| * average multiplied by a precision factor (currently -8). |
| * |
| * @returns The current average multiplied by precision factor or zero if no average is available. |
| * |
| */ |
| uint16_t GetAverageRssRaw(void) const { return mRssAverager.GetRaw(); } |
| |
| /** |
| * This method converts the link quality info to info/debug human-readable string. |
| * |
| * @returns An `InfoString` representing the link quality info. |
| * |
| */ |
| InfoString ToInfoString(void) const; |
| |
| /** |
| * This method returns the link margin. The link margin is calculated using the link's current average received |
| * signal strength (RSS) and average noise floor. |
| * |
| * @param[in] aNoiseFloor The noise floor value (in dBm). |
| * |
| * @returns Link margin derived from average received signal strength and average noise floor. |
| * |
| */ |
| uint8_t GetLinkMargin(int8_t aNoiseFloor) const { return ConvertRssToLinkMargin(aNoiseFloor, GetAverageRss()); } |
| |
| /** |
| * Returns the current one-way link quality value. The link quality value is a number 0-3. |
| * |
| * The link quality is calculated by comparing the current link margin with a set of thresholds (per Thread spec). |
| * More specifically, link margin > 20 dB gives link quality 3, link margin > 10 dB gives link quality 2, |
| * link margin > 2 dB gives link quality 1, and link margin below or equal to 2 dB yields link quality of 0. |
| * |
| * In order to ensure that a link margin near the boundary of two different link quality values does not cause |
| * frequent changes, a hysteresis of 2 dB is applied when determining the link quality. For example, the average |
| * link margin must be at least 12 dB to change a quality 1 link to a quality 2 link. |
| * |
| * @param[in] aNoiseFloor The noise floor value (in dBm). |
| * |
| * @returns The current link quality value (value 0-3 as per Thread specification). |
| * |
| */ |
| uint8_t GetLinkQuality(void) const { return mLinkQuality; } |
| |
| /** |
| * Returns the most recent RSS value. |
| * |
| * @returns The most recent RSS |
| * |
| */ |
| int8_t GetLastRss(void) const { return mLastRss; } |
| |
| /** |
| * This method adds a MAC frame transmission status (success/failure) and updates the frame tx error rate. |
| * |
| * @param[in] aTxStatus Success/Failure of MAC frame transmission (`true` -> success, `false` -> failure). |
| * |
| */ |
| void AddFrameTxStatus(bool aTxStatus) |
| { |
| mFrameErrorRate.AddSample(aTxStatus, OPENTHREAD_CONFIG_FRAME_TX_ERR_RATE_AVERAGING_WINDOW); |
| } |
| |
| /** |
| * This method adds a message transmission status (success/failure) and updates the message error rate. |
| * |
| * @param[in] aTxStatus Success/Failure of message (`true` -> success, `false` -> message tx failed). |
| * A larger (IPv6) message may be fragmented and sent as multiple MAC frames. The message |
| * transmission is considered a failure, if any of its fragments fail after all MAC retry |
| * attempts. |
| * |
| */ |
| void AddMessageTxStatus(bool aTxStatus) |
| { |
| mMessageErrorRate.AddSample(aTxStatus, OPENTHREAD_CONFIG_IPV6_TX_ERR_RATE_AVERAGING_WINDOW); |
| } |
| |
| /** |
| * This method returns the MAC frame transmission error rate for the link. |
| * |
| * The rate is maintained over a window of (roughly) last `OPENTHREAD_CONFIG_FRAME_TX_ERR_RATE_AVERAGING_WINDOW` |
| * frame transmissions. |
| * |
| * @returns The error rate with maximum value `0xffff` corresponding to 100% failure rate. |
| * |
| */ |
| uint16_t GetFrameErrorRate(void) const { return mFrameErrorRate.GetFailureRate(); } |
| |
| /** |
| * This method returns the message error rate for the link. |
| * |
| * The rate is maintained over a window of (roughly) last `OPENTHREAD_CONFIG_IPV6_TX_ERR_RATE_AVERAGING_WINDOW` |
| * (IPv6) messages. |
| * |
| * Note that a larger (IPv6) message can be fragmented and sent as multiple MAC frames. The message transmission is |
| * considered a failure, if any of its fragments fail after all MAC retry attempts. |
| * |
| * @returns The error rate with maximum value `0xffff` corresponding to 100% failure rate. |
| * |
| */ |
| uint16_t GetMessageErrorRate(void) const { return mMessageErrorRate.GetFailureRate(); } |
| |
| /** |
| * This method converts a received signal strength value to a link margin value. |
| * |
| * @param[in] aNoiseFloor The noise floor value (in dBm). |
| * @param[in] aRss The received signal strength value (in dBm). |
| * |
| * @returns The link margin value. |
| * |
| */ |
| static uint8_t ConvertRssToLinkMargin(int8_t aNoiseFloor, int8_t aRss); |
| |
| /** |
| * This method converts a link margin value to a link quality value. |
| * |
| * @param[in] aLinkMargin The Link Margin in dB. |
| * |
| * @returns The link quality value (0-3). |
| * |
| */ |
| static uint8_t ConvertLinkMarginToLinkQuality(uint8_t aLinkMargin); |
| |
| /** |
| * This method converts a received signal strength value to a link quality value. |
| * |
| * @param[in] aNoiseFloor The noise floor value (in dBm). |
| * @param[in] aRss The received signal strength value (in dBm). |
| * |
| * @returns The link quality value (0-3). |
| * |
| */ |
| static uint8_t ConvertRssToLinkQuality(int8_t aNoiseFloor, int8_t aRss); |
| |
| /** |
| * This method converts a link quality value to a typical received signal strength value . |
| * @note only for test |
| * |
| * @param[in] aNoiseFloor The noise floor value (in dBm). |
| * @param[in] aLinkQuality The link quality value in [0, 3]. |
| * |
| * @returns The typical platform rssi. |
| * |
| */ |
| static int8_t ConvertLinkQualityToRss(int8_t aNoiseFloor, uint8_t aLinkQuality); |
| |
| private: |
| enum |
| { |
| // Constants for obtaining link quality from link margin: |
| |
| kThreshold3 = 20, ///< Link margin threshold for quality 3 link. |
| kThreshold2 = 10, ///< Link margin threshold for quality 2 link. |
| kThreshold1 = 2, ///< Link margin threshold for quality 1 link. |
| kHysteresisThreshold = 2, ///< Link margin hysteresis threshold. |
| |
| // constants for test: |
| |
| kLinkQuality3LinkMargin = 50, ///< link margin for Link Quality 3 (21 - 255) |
| kLinkQuality2LinkMargin = 15, ///< link margin for Link Quality 3 (21 - 255) |
| kLinkQuality1LinkMargin = 5, ///< link margin for Link Quality 3 (21 - 255) |
| kLinkQuality0LinkMargin = 0, ///< link margin for Link Quality 3 (21 - 255) |
| |
| kNoLinkQuality = 0xff, // Used to indicate that there is no previous/last link quality. |
| }; |
| |
| void SetLinkQuality(uint8_t aLinkQuality) { mLinkQuality = aLinkQuality; } |
| |
| /* Static private method to calculate the link quality from a given link margin while taking into account the last |
| * link quality value and adding the hysteresis value to the thresholds. If there is no previous value for link |
| * quality, the constant kNoLinkQuality should be passed as the second argument. |
| * |
| */ |
| static uint8_t CalculateLinkQuality(uint8_t aLinkMargin, uint8_t aLastLinkQuality); |
| |
| RssAverager mRssAverager; |
| uint8_t mLinkQuality; |
| int8_t mLastRss; |
| |
| SuccessRateTracker mFrameErrorRate; |
| SuccessRateTracker mMessageErrorRate; |
| }; |
| |
| /** |
| * @} |
| */ |
| |
| } // namespace ot |
| |
| #endif // LINK_QUALITY_HPP_ |
