Automatic repeat request arq
Automatic Repeat Request (ARQ) is one of the error correction protocol in the data link layer and transmission layer of the OSI model. It used confirmation and time-out mechanisms to achieve reliable information transmission on the basis of unreliable services. If the sender does not receive an acknowledgment frame after a period of time, it will usually resend. ARQ includes the stop-and-wait ARQ protocol and the continuous ARQ protocol: - Stop and Wait ARQ protocol: Stop sending after sending a packet and wait for the other party to confirm (reply with an ACK). If no acknowledgment is received after the time limit, the transmission will be considered a failure and the next packet will be sent again until the acknowledgment is received. In the case of no error, the sender sends a packet, the receiver receives and replies with an acknowledgment within a specified time, and the sender sends the next packet. In the case of an error (overtime re-transmission), as long as the acknowledgment is not received within the specified time, the previously sent packet will be re-transmitted. If the receiver receives a duplicate packet, it will discard the packet but send an acknowledgment at the same time. The advantage of this protocol was its simplicity, but the disadvantage was its low channel utilization and long waiting time. - Continuous ARQ protocol: The sender maintains a sending window, and the packets within the sending window can be sent continuously without waiting for the other party's confirmation. The receiver usually uses a cumulative acknowledgment to send an acknowledgment to the last packet that arrives in order, indicating that all the packets to this packet position have been received correctly. In addition, there were also hybrid automatic repeat request (HARQ) and other related concepts that had different applications in the field of communication technology. "Choose" was equally exciting. Everyone was welcome to read it!
What are the automatic repeat request protocol?
The automatic repeat request (ARQ) protocol mainly included the stop-and-wait ARQ protocol and the continuous ARQ protocol. The continuous ARQ protocol also included the N-frame backward ARQ protocol and the selective repeat ARQ protocol. The work flow of the stop-and-wait ARQ protocol was as follows: the transmitting station must wait for an acknowledgment signal after sending out a frame, and then continue to send the next frame after receiving an acknowledgment signal, and then resend the frame after receiving a negative acknowledgment signal, and must resend the frame even if no acknowledgment signal is received within a certain time interval. The continuous ARQ protocol meant that the sender maintained a sending window of a certain size, and all the packets within the sending window could be sent out continuously without waiting for the other party's confirmation. Every time the sender received a confirmation, the sending window would slide forward by one packet. In the ARQ protocol that sent back N frames, after the sender sent a frame, it did not have to stop and wait for the other party's response. It could send several frames in a row. If it received a positive response from the receiver during the sending process, it could continue to send. If it received a negative response to a previous frame, all subsequent frames starting from that frame would be retransmitted. The selective repeat ARQ protocol can be used as a protocol for the transmission and acknowledgment of a message unit. When used as a protocol to transmit a message unit, the sending process continuously sends a number of frames according to a window of a specified size. Even if the frame is lost during the process, it will continue to send. The receiving process continued to receive and acknowledge frames even after the error. "Choose" was equally exciting. Everyone was welcome to read it!
What is the automatic repeat request protocol?
Automatic Repeat-reQuest (ARQ) was one of the error correction protocol in the data link layer and transmission layer of the OSI model. It used confirmation and time-out mechanisms to achieve reliable information transmission on the basis of unreliable services. If the sender does not receive an acknowledgment frame after a period of time, it will usually resend. ARQ includes the stop-and-wait ARQ protocol and the continuous ARQ protocol: - Stop and Wait ARQ protocol: Stop sending after sending a packet and wait for the other party to confirm (reply with an ACK). If no acknowledgment is received after the time limit, the transmission will be considered a failure and the next packet will be sent again until the acknowledgment is received. In the case of no error, the sender sends the packet, the receiver receives and replies with an acknowledgment within a specified time, and then the sender sends it again. In the case of an error (overtime re-transmission), as long as the acknowledgment is not received after the specified time, the previously sent packet will be re-transmitted. In addition, if the receiver receives a duplicate packet, it will be discarded, but an acknowledgment will be sent. The advantage of this protocol was its simplicity, but the disadvantage was its low channel utilization and long waiting time. - Continuous ARQ protocol: The sender maintains a sending window, and the packets within the sending window can be sent continuously without waiting for the other party's confirmation. The receiver usually uses a cumulative acknowledgment to send an acknowledgment to the last packet that arrives in order, indicating that all the packets to this packet position have been received correctly. In addition, there were three other types of ARQ, which were wait-type ARQ, N-step backward ARQ, and selective repeat ARQ. Among them, ARQ could be used as a protocol for message unit transmission and acknowledgment. The sending process would continuously send a number of frames according to a specified window size, and even if there was a frame loss during the sending process, it would continue to send. The receiving process would continue to receive and acknowledge frames after an error occurred. Most practical ARQ systems use linear block codes. Choosing the appropriate linear codes can make the undetectable error probability reach the required error index. The main advantage of ARQ was its simple error detection method, which could adjust the transmission rate according to the channel quality. Its main constraints were that it required a reliable feedback channel, would cause a long and unfixed transmission delay, and required the transmission system to control the source. It was mainly used in data transmission that did not have strict requirements for delay but had high requirements for error performance. "Choose" was equally exciting. Everyone was welcome to read it!
How do I write the automatic repeat request protocol?
The automatic repeat request (ARQ) protocol was a technique used for error control in data communication. When the receiver detected an error, it automatically requested the sender to resend the data. The following are the basic steps to build an ARQ protocol: ** 1. Confirm ARQ Type ** 1. ** Stop and Wait ARQ protocol ** - Sending party: - Encapsulated the network layer data into a data frame. - The data frame was sent to the data link layer's transmission buffer and sent out. - Waiting for the receiver's reply signal. If an acknowledgment (ACK) is received, the next frame will be sent, and if a negative acknowledgment (NAK) is received or no acknowledgment is received within a certain time interval, the frame will be retransmitted. - Receiving party: - Waiting to receive the data frame. - After receiving the data frame, it was placed into the receive buffer of the data link layer. - If the data frame was correct, the data frame would be unpacked, and the grouped data would be handed over to the network layer, and an acknowledgment frame would be sent back to the sender. If the data frame was wrong, no processing would be done.(Under this protocol, the receiver would not feed back the information related to the wrong frame, and the sender would rely on time-out retransmissions.) 2. ** Continuous ARQ protocol ** - Sending party: - Maintaining a certain size of the sending window, all packets within the sending window can be sent out continuously without waiting for the other party's confirmation. - Every time he received a confirmation, he would slide the send window forward by one packet. - Receiving party: - They could only receive data frames in sequence. 3. ** ARQ protocol with N frames backoff ** - Sending party: - After sending a frame, there was no need to stop and wait for the other party's reply. Several frames could be sent consecutively. - If a positive response is received from the receiver during the transmission process, the transmission can continue; if a negative frame is received for a previous frame, all subsequent frames starting from the frame will be retransmitted. - The sent frames needed to be differentiated by different numbers, and there had to be a large buffer to hold the frames that could be retransmitted. 4. ** Repeat ARQ protocol ** - Sending party: - It continuously sends a number of frames according to a window of a specified size. Even if a frame is lost during the transmission, it will continue to be sent. - Receiving party: - Continue receiving and acknowledging frames after errors. ** 2. define the data frame structure ** 1. It contains an error detection code for detecting errors, such as a Cyclic Redundance Check (Cyclic Redundance Check) code. 2. There is a serial number of the frame (it is very important in the continuous ARQ protocol, the ARQ protocol with a fallback of N frames, and the ARQ protocol with a selective repeat to distinguish between different frames). 3. It contains the actual data to be transmitted. ** 3. Dealing with error detection and feedback ** 1. sending end - Before sending the data frame, the error detection code is first added to the data frame. - It waits for feedback from the receiver according to the selected ARQ type (ACK or NAK), and decides whether to resend the data frame according to the feedback. 2. receiving end - The received data frame was deciphered to determine if there was an error. - If there is no error, send an acknowledgment to the sender; if there is an error, send a NAK according to the type of ARQ protocol (for example, in the stop-and-wait ARQ protocol, the sender can also send an acknowledgment without sending an acknowledgment, allowing the sender to resend after a time limit) or continue to receive subsequent frames and record the number of the error frame in the selective re-transmission ARQ protocol so as to request for re-transmission. ** 4. Time-out mechanism (mainly for stop-and-wait ARQ protocol and continuous ARQ protocol)** 1. The sender set up a timer that started counting down from the time the data frame was sent. 2. If the receiver does not receive an ACK or NAK before the timer times out, the data frame will be retransmitted. ** 5. Code implementation example (Take the stop-and-wait ARQ protocol as an example, pseudocode)** ```python #sender def sender(data): for packet in data: frame = create_frame(packet) #Create a data frame that contains data and error detection codes send(frame) start_timer() while True: if received_ack(): stop_timer() break elif timer_timeout(): send(frame) start_timer() #Receiving party def receiver(): while True: frame = receive() if check_frame(frame): #Check if the frame is correct send_ack() process_packet(frame) #process the data in the data frame else: pass #Under the stop-and-wait protocol, the sender does not send a NAK, and the sender relies on the time-out to resend. ``` This is just a simple example. The actual ARQ protocol implementation may be more complicated due to the specific application scenario, network environment, and performance requirements. "Choose" was equally exciting. Everyone was welcome to read it!
ARQ and GGN
The ARQ protocol (Automatic Repeat-reQuest) was an error correction protocol in the data link layer. There were stop-and-wait ARQ and continuous ARQ. The stop-wait ARQ protocol sends a message at a time, and sends the next message after confirmation. The sending window and the receiving window are both 1, so it requires a small buffer but is inefficient. The continuous ARQ protocol, which was known as the backward n-frame GGN and the selective repeat ARQ, was a combination of sliding window and request for repeat. It could continuously send a number of information frames without waiting for the previous frame to be confirmed, which greatly improved the transmission efficiency. However, the sender needed to set up a repeat table to store the frames to be confirmed. After receiving the confirmation frame, the frame would be deleted from the repeat table, which required more storage space. The GGN protocol (Go-Back- N) was also known as the sliding window protocol. In this protocol, the sender is allowed to send multiple packets without waiting for acknowledgment, but the number of unacknowledged packets in the pipeline cannot exceed a certain maximum number N. The sender must respond to three types of events: a call from the upper layer, an acknowledgment, and a time out event. The confirmation of the packet with the sequence number n is done in a cumulative confirmation manner, indicating that the receiver has correctly received all the packets before and including the sequence number n. If there is a time out, the sender will resend all the packets that have been sent but not acknowledged. "Choose" was equally exciting. Everyone was welcome to read it!
arq protocol sending window maximum
In the ARQ protocol, the maximum transmission window is related to the type of the protocol. 1. ** Stop and Wait ARQ protocol **: After sending a frame, the sending station must wait for an acknowledgment signal. After receiving an acknowledgment signal, it will continue to send the next frame. There is no mention of the maximum value of the sending window size. 2. ** Repeat ARQ protocol **: It is a combination of sliding window technology and automatic repeat request technology. The maximum sending window is 2^(n - 1)(considering the possible loss of the ACK, it will be repeated after a time limit). 3. ** Continuous ARQ protocol (includes two types of protocol: - For the backward N-frame protocol, 1 <transmission window <= 2n- 1. - For the selective replay protocol, the transmit window is <= 2^(n - 1), and when the transmit window is the maximum, the receive window = transmit window = 2n - 1. "Choose" was equally exciting. Everyone was welcome to read it!
Continuous arq protocol and sliding window protocol
In the continuous ARQ protocol, the sender maintained a sending window of a certain size, and the packets within the window could be sent continuously without waiting for the other party's acknowledgment. The sender would slide the sending window forward by one packet every time it received an acknowledgment. The receiver usually uses the method of accumulating acknowledgement, that is, after receiving several packets, it sends an acknowledgement to the last packet that arrives in order, indicating that all the packets up to this packet have been received correctly. However, this method has shortcomings. For example, when the middle packet is lost, the sender cannot know the situation of the subsequent packets, and may need to re-transmit more packets. The sliding window protocol involves a sending window and a receiving window. The transmit window is the range of sequence numbers of the frames that have been sent but have not been acknowledged, and the receive window is the range of sequence numbers of the frames that are expected to be received. When the default window size is 1, you can operate according to the specific sending process. The sliding window protocol could improve the channel utilization and was a reliable transmission mechanism for data communication. The continuous ARQ protocol can be seen as a specific application form of the sliding window protocol under certain conditions (such as the cumulative acknowledgment method). They are all protocol mechanisms that exist to achieve effective and reliable data transmission in the network. "Choose" was equally exciting. Everyone was welcome to read it!
Which layer of protocol does arq belong to?
In modern wireless communications, ARQ was mainly used in the wireless link layer. " Choose " was equally exciting. Everyone was welcome to read it!
The legend of free automatic recycling and automatic picking
The following are some legendary games with free automatic recycling and picking up functions: 1. "Proud Dragon City": This is a relatively pure legendary battle game. There are many types of professional characters to choose from, and there is no threshold to participate in PvP-related activities. Dungeons were unlocked according to level, and free pick-up and recycling functions were given when players went online. It could meet the needs of players to fight online at any time. 2. [The Legend of Medusa 1st Fold Version: You can receive top-tier sponsorship and a full set of zodiac gems upon logging in. You can obtain all the resources needed to level up to rank 10 upon landing. It has the function of automatic collection and recycling.] 3. "King Battleship": It has a brand new world view, 1,000 people in the same server PK competition, with a high drop rate of cross-level treasure hunting, level seal, bloody battle in the Imperial City, and full open free trade. There is also a "divine weapon" system, which can suck blood and critical hits. Its graphics were a qualitative upgrade compared to the traditional Legend of Mir 2, and the automatic collection function in the game was also free. 4. "Rejuvenation Minor Changes": It is a hot-blooded, hot-blooded, Eastern Fantasy action masterpiece. It inherits the orthodox legendary bloodline and creates a wonderful multiplayer battlefield. Fast attack speed, high critical rate, high dungeon farming efficiency, equipment that can be recycled online, ingots that can be received without delay, top-grade equipment that can be dropped from monsters, and can be used to farm gold and move bricks freely. There is also a free automatic recycling and picking function. 5. <<Berserk Legends>>: A new mobile game with a slight change in the legendary combination attack. It is a critical hit. Monsters have a chance to drop godly equipment. It has automatic picking and recycling functions. 6. "Eternal Thunder": A classic retro legendary mobile game. It can be used to reminisce the hot-blooded battle. The fully automatic picking and recycling system allows players to easily obtain equipment and enter the fierce battle. 7. <<Rampage Peerless Group>>: The new Xianxia Legend. In its fantasy game world, players can pursue the path of legend. The game is equipped with a fully automatic picking and recycling system. 8. * * The Legend of the Real Bull **: It has the characteristics of the skeleton version of the Green Poison Taoist priest. The green poison skills and skeletons of the Taoist priest help the players soar on the battlefield. There is also a fully automatic picking and recycling system. 9. "Dungeon War": A new super-legendary mobile game that can experience the legendary feeling of millions of cuts. The fully automatic picking and recycling system helps players explore and fight in the dungeons. 10. <<Hot-blooded Combined Attack>>: The 1.85 vintage legend has returned. It is integrated into the automatic pickup and recovery system, allowing players to fight without worry and relive the legendary memories. 11. "The Great God of War": Players can log in to receive a full level membership, and can easily control the automatic picking and recycling system to enjoy the fun of fighting. "The Legend of Pengcheng" is equally exciting. Everyone is welcome to click and read it!
automatic translator
You only said the words "automatic translator". Can you give me some specific information about it? For example, what kind of automatic translator it is, what special functions it has, or what kind of comments it has. Only then can I recommend it according to my requirements. " Choose " was equally exciting. Everyone was welcome to read it!
automatic furnace
There are many types of automatic furnaces. The following is a fully automatic intermediate frequency heating furnace: 1. ** Work Flow ** - ** Material preparation **: When cutting materials, the materials of the same batch and the same specifications should be neatly stacked. - ** Charging **: manually lift the neatly stacked materials into the storage bin of the automatic intermediate frequency heating furnace. The storage bin will be turned over to the ladder feeding machine through the hydraulic system. The ladder feeding mechanism will lift the materials to the automatic conveying system and send the materials to the induction heater according to the production rhythm. - ** Heat **: The intermediate frequency power supply supplies power to the sensor, and the sensor creates a strong vortex to heat the bar. - ** Temperature-measuring **: A high-precision and high-sensitivity infrared thermometer is installed at the exit of the sensor to measure the surface temperature of the bar. - ** Closed-loop temperature system **: Control the output power of the sensor through the temperature measurement system. When it is detected that the temperature is low, the output power will be increased automatically to make up for the temperature. When it is over temperature, the output power will be reduced automatically. - ** Automatic discharge **: With the variable frequency motor as the driving force, the roller discharge method can quickly discharge the material. The discharge end has a three-temperature sorting mechanism to sort the low temperature, normal temperature, and over temperature to ensure that the material entering the next process is qualified. 2. ** Specialties and advantages ** - ** High efficiency and energy saving **: Advanced power technology and control system are used to heat up quickly and evenly, reducing energy waste and improving production efficiency. - ** Safe and environmental protection **: No open fire heating, avoid smoke and waste gas pollution, safe and reliable operation, reduce operational risks. - ** Range of application **: suitable for heating steel, copper, aluminum and other metal materials. - ** High degree of automaton **: Advanced control system and sensor technology to achieve automated production, reduce manual intervention, improve production efficiency and product quality. - ** Fast heating speed **: 50% faster than traditional heating methods. - ** Precise temperature control **: It is equipped with an advanced temperature control system to accurately control the heating temperature. - ** Simple operation **: The automatic control system is easy to operate and maintain without the need for professional personnel. In addition, there were also situations where the degree of automaton of cremators varied. However, regardless of the degree of automaton of the cremators, the results of cremation were essentially the same. The automatic control of the flame furnace was related to mastering the parameters of the thermal system. In the continuous furnace and the intermittent furnace, it was necessary to master the changes of different parameters. Once the situation was stable and was not affected by the outside world, it could enter the automatic stage. The novel " Gilded Palm " is equally exciting. Everyone is welcome to click and read it!