KR101719503B1 - Adaptive forward error correction system for increase reliability in wireless body area network - Google Patents

Abstract

The present invention relates to a dynamic forward error correction system, and more particularly, to a dynamic forward error correction system for enhancing reliability in a human body communication environment for predicting whether an RS code is applied by predicting an error occurrence rate from a transmitting side node in a Gilbert model will be. The present invention relates to a dynamic forward error correction method for improving reliability in a human body communication environment that can reduce an error rate and increase reliability by reducing a number of retransmissions through a forward error correction algorithm from a receiving node when a predicted channel state is poor, System can be provided.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a dynamic forward error correction system for improving reliability in a human body communication environment,

The present invention relates to a dynamic forward error correction system, and more particularly, to a dynamic forward error correction system for enhancing reliability in a human body communication environment for predicting whether an RS code is applied by predicting an error occurrence rate from a transmitting side node in a Gilbert model will be.

WBAN refers to communication between devices mounted inside the body, on the surface, and on the outside. Because of the features attached to the human body, mobility within the network increases, and interference from multiple WBANs or heterogeneous wireless communications results in continuous errors. In the WBAN environment, which mainly deals with biometric data, if such a link disconnection, data transmission failure, or delay occurs, the user may not be able to cope with the emergency situation correctly.

In order to solve this problem, the MAC protocol of the IEEE 802.15.4 standard retransmits the entire packet regardless of the size of the error bit when a data transmission error occurs. Even if such a small error occurs, the entire packet including the error is retransmitted, which consumes a large amount of energy. In addition, since a retransmission is requested and a packet is received again, a transmission delay occurs and the reliability of the network is degraded. This can shorten the life span of human internal devices that can not easily replace the battery, and delay the response to emergencies due to transmission delays.

Korean Patent Publication No. 10-2010-0118960 (published on November 11, 2010)

An object of the present invention is to provide a dynamic forward error correction system capable of quickly recovering an error packet without retransmission of an additional packet when an error occurs in the received packet.

In order to achieve the above-mentioned object, the present invention provides a method for calculating a Packet Error Rate (PER) by checking a transmission state of a frequency channel, calculating a channel error rate A packet error rate tolerance comparison module for comparing the packet error rate with a packet error rate tolerance; and a packet error rate limiter for comparing the packet error rate tolerance with a parity bit And a parity bit adding module for adding a parity bit adding module to the received signal.

와

이고, 상기

는

이며, 상기

은

이다.The channel state predicted by the channel state estimation module is divided into a reception state when the packet transmission is successful and a loss state when the packet transmission has failed and the transition probability between the reception state and the loss state is

Wow

, And

The

, And

silver

to be.

과

이며, 상기

은

이고, 상기

은

이다.The probability that the reception state and the loss state are maintained is

and

, And

silver

, And

silver

to be.

이며, 상기

는 패킷 오류율 허용 한계이다.The error rate

, And

Is the packet error rate tolerance limit.

The parity bit addition module applies a codeword RS code (Reed-Solomon Code) using an 8-bit symbol size. Specifically, the parity bit adding module performs encoding to add a 20-byte parity bit to 235 bytes of a packet. The codeword encoded in the parity bit appending module is transmitted after the packetizing operation. After the transmission is completed, the transmitting node confirms receiving acknowledgment of the receiving node and updates the error incidence rate.

The parity bit appending module transmits a packet to a packet transmitted from a transmitting node using an ARQ (Automatic Repeat Request) method when the predicted error rate does not exceed the packet error rate tolerance limit.

The present invention relates to a dynamic forward error correction method for improving reliability in a human body communication environment that can reduce an error rate and increase reliability by reducing a number of retransmissions through a forward error correction algorithm from a receiving node when a predicted channel state is poor, System can be provided.

1 is a conceptual diagram of a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.
2 is a sequence diagram of a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.
3 is a conceptual diagram of a Gilbert model applied to a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.
FIG. 4 is a diagram of a ZigbeX note based on IEEE 802.15.4 of a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.
5 is a block diagram of a DAQpad-6015 system for data acquisition in a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.
FIG. 6 is a graph comparing the total packet size of IEEE 802.15.4 with a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.
7 is a graph comparing the number of transmission failures of IEEE 802.15.4 with a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.
8 is a graph comparing the energy consumption of IEEE 802.15.4d with a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know. Like reference numerals refer to like elements throughout.

FIG. 1 is a conceptual diagram of a dynamic forward error correction system for enhancing reliability in a human body communication environment according to the present invention. FIG. 2 is a sequence diagram of a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention. It is a diagram.

As shown in FIG. 1, a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention includes a channel state predicting module for predicting a state of a channel, And a parity bit adding module for adding a parity bit to the packet.

The channel state estimation module determines the state of the channel before transmitting the packet and decides whether to apply the RS code or not. The channel state estimation module checks the transmission state of the frequency channel and calculates a current packet error rate (PER). In addition, a probabilistic prediction, that is, an error occurrence rate, is predicted by using a Gilbert model, which is an error prediction model, from the transmitting node to determine whether an error occurs continuously in the current channel.

3 is a conceptual diagram of a Gilbert model applied to a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.

Referring to FIG. 3, a 'receive' state and a 'loss' state proposed by the Gilbert model are shown. The present invention follows a general indication of a 'receive' state (R) and a 'lost' state (L). In Gilbert model, channel state is divided into 'reception' state when packet transmission is successful and 'loss' when packet transmission fails. The present invention defines a transmission probability p from (R) to (L), and defines a transmission probability r from (L) to (R). That is, the transition probability between states is represented by p and r, and the state transitions p and r are defined by Equation 1 below.

,

,

,

로 둔다.

,

는 이전 ACKs가 성공적으로 수신되었거나 수신되지 않았을 때, ACKs가 수신되지 않은 횟수를 정의한다.

,

는 이전 ACKs가 성공적으로 수신되거나 수신되지 않았을 때 수신된 ACKs 횟수를 정의한다.When the previous packet was successfully transmitted or not transmitted, the number of times the packet was successfully transmitted or not transmitted

,

,

,

.

,

Defines the number of times ACKs were not received when previous ACKs were successfully received or not received.

,

Defines the number of ACKs received when previous ACKs were successfully received or not received.

,

이다. p와 r이 존재할 확률은 아래의 수학식 3과 같다.The probability of existence of the transmission probabilities p and r in Equation (1)

,

to be. The probability that p and r exist is expressed by Equation 3 below.

Transition matrix A is given by the following two transitions.

과

은 아래의 수학식 5와 같다.The probability of staying in each state

and

Is expressed by the following equation (5).

The probability of a continuous packet transmission error that is determined to be deteriorated in a channel state can be obtained in a steady state, which can be expressed by Equation (6) below.

는 사용자가 정의한 PER의 허용 한계치이다.In Equation (6)

Is the permissible limit value of the PER defined by the user.

On the other hand, it is preferable that the constant value of the above-mentioned equation is calculated in advance and stored in the memory.

The PER permissible comparison module compares the predicted channel state prediction result in the channel state prediction module with the permissible limit of the PER. That is, if the probability of successive packet transmission errors according to Equation (6) exceeds the allowable limit value of the PER defined by the user, it is determined that an error continuously occurs in the current channel.

The parity bit addition module adds the RS code (Reed-Solomon Code) and the parity bit to encode and recover the original frame when the result of the PER tolerance comparison module exceeds the permissible limit of PER. In detail, the parity bit addition module applies a code word (255, 235) RS code using an 8-bit symbol size. That is, an encoding process of adding a 20-byte parity bit to an existing data 235-byte using an RS code algorithm is performed. If it is determined that the calculated continuous packet transmission error rate will not be generated, the packet is transmitted using the same ARQ (Automatic Repeat Request) scheme as the existing standard.

The encoded codeword is transmitted according to the storage and transmission / reception mechanism criteria in the buffer after the packetization operation for the transmission conforming to each MAC standard is performed. After the transmission is completed, the transmitting node waits for the Acknowledgment response of the receiving node, and the transmitting node confirming the receiving ends the transmission operation after updating the probability for the next continuous error prediction.

4 is a ZigbeX note based on IEEE 802.15.4 of a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.

To implement the above-described configuration, the present invention applies the ZigbeX note based on IEEE 802.15.4 as shown in FIG.

Table 1 is a specification of a ZigbeX note based on IEEE 802.15.4 applied to a dynamic forward error correction system for enhancing reliability in a human body communication environment according to the present invention.

Configuration Explanation Microcontroller Atmega128 (8-bit) RF Part CC2420 2.4GHz
(IEEE 802.15.4 PHY) antenna PCB Antenna
(20-100 m) Bit rate Up to 250 Kbps Flash memory 512Kbytes power 3.3V (AA 2ea) Length 40mm * 70mm

Referring to Table 1, the ZigbeX note based on IEEE 802.15.4 applied to the present invention consists of Atmega128, an 8-bit low-power microcontroller, and CC2420, a low-cost and highly integrated solution for robust wireless communication in a 2.4GHz unlicensed ISM band. In addition, RF, electronic, communication and network principles follow the 802.15.4 LR-WPAN standard.

5 is a DAQpad-6015 device for data acquisition in a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention.

The DAQPad-6015 applied to the present invention is a multifunctional data acquisition device that provides plug-and-play connectivity for acquisition, generation, and data logging in various applications, In addition, the DAQPad-6015 provides screw terminals or BNC connectors that connect the connection sensors and signals directly at no additional cost.

Next, the performance of the dynamic forward error correction system and the performance of IEEE802.15.4 are compared to improve the reliability in the human body communication environment according to the present invention.

FIG. 6 is a graph comparing a total packet size of IEEE 802.15.4 with a dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention. FIG. It is a graph comparing the number of transmission failure times of IEEE 802.15.4 with the dynamic forward error correction system for improving reliability. FIG. 7 shows the number of transmission failures when the number of transmissions is 0.005, 0.01, 0.03, 0.05, 0.07, and 0.10 to 5000.

When the BER is 0.005, all packets include successful transmissions in addition to failed transmissions, and the result indicates that both packets are equal in size to the number of failed transmissions. This is because the channel state prediction model is not satisfied with the probability condition by the Gilbert model. If the RS code is used in a good channel condition, the performance may be lower than that of the existing IEEE 802.15.4 because additional redundant bits and computing overhead are added. In IEEE 802.15.4, although the number of transmissions and the total packet size increase steeply toward the higher BER region (although performance improves sharply), the overall packet size does not sharply improve and the performance is constant.

In IEEE 802.15.4, the number of transmission failures is more than the present invention except for 0.005. In particular, since the RS code restores most of the error bits, the number of transmissions at 0.01 and 0.03 is almost zero in the present invention. The present invention reduces both the transmission failure and the entire packet.

8 is a graph comparing the energy consumption of the IEEE 802.15.4d and the dynamic forward error correction system for improving reliability in a human body communication environment according to the present invention. 8 is a graph comparing the energy consumption of the present invention with IEEE 802.15.4 when transmitted from 0.005, 0.01, 0.03, 0.05, 0.07, and 0.10 to 5000 times.

Since the probability condition is not satisfied by the Gilbert model when the BER is 0.005, the energy consumption of the present invention is not different from that of IEEE 802.15.4. Since IEEE 802.15.4 retransmits the entire packet repeatedly, the energy consumption of IEEE 802.15.4 is higher than that of the present invention. As a result, the present invention prolongs the battery life of the device.

As described above, when the state of the predicted channel is not good, forward error correction algorithm is used to reduce the number of retransmissions from the receiving node, thereby reducing the error rate and increasing the reliability. An error correction system can be provided.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention as defined in the appended claims. You will understand.

100: channel state prediction module 200: PER threshold comparison module
300: Parity bit addition module

Claims (8)

A channel state prediction module for calculating a packet error rate (PER) by checking a transmission state of a frequency channel, and estimating an error occurrence rate, which is a probability of successive packet transmission errors,
A packet error rate tolerance comparison module for comparing the packet error rate with a packet error rate tolerance;
And a parity bit adding module for adding a parity bit to a packet transmitted from the transmitting node when the predicted error rate exceeds the packet error rate tolerance. Forward error correction system. The method according to claim 1,
The channel state predicted by the channel state estimation module is divided into a reception state when the packet transmission is successful and a loss state when the packet transmission fails,
The transition probability between the reception state and the loss state is

Wow

ego,
remind

The

Lt;
remind

silver

ego,
remind

Reception state,
remind

A loss state,
remind

The reception state

Lost state

The probability of transition to state,
remind

Is the loss state

Receive state from

Wherein the probability of transition to the state forwarding state is a probability of transition to the state forwarding state. The method of claim 2,
The probability that the reception state and the loss state are maintained is

and

Lt;
remind

silver

ego,
remind

silver

And a dynamic forward error correction system for enhancing reliability in a human body communication environment. The method of claim 3,
The error rate

Lt;
remind

Is a packet error rate tolerance limit. The dynamic forward error correction system for improving reliability in a human body communication environment. The method of claim 4,
Wherein the parity bit adding module applies a codeword RS code (Reed-Solomon Code) using an 8-bit symbol size to improve reliability in a human body communication environment. The method of claim 5,
Wherein the parity bit appending module performs encoding to add a 20-byte parity bit to 235 bytes of a packet, to improve reliability in a human body communication environment. The method of claim 6,
Wherein the codeword encoded in the parity bit appending module is transmitted after the packetizing operation, and after the transmission is completed, the transmitting node confirms reception of acknowledgment of the receiving node and updates the error incidence rate. Dynamic Forward Error Correction System for Improving Reliability. The method of claim 7,
Wherein the parity bit appending module transmits a packet to a packet transmitted from a transmitting node using an ARQ (Automatic Repeat Request) method when the predicted error rate does not exceed the packet error rate tolerance. Dynamic Forward Error Correction System for Improving Reliability in Communication Environment.

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