CN104065445B - Wireless receiving system and signal processing method thereof - Google Patents

Abstract

The present invention provides a wireless receiving system and a signal processing method thereof. The wireless receiving system includes a decoding module, an estimation module and a search module. The decoding module receives and decodes a packet to generate a decoding result. The estimation module extracts a packet length information from the decoding result and estimates a completion delivery time of the packet according to the packet length information. The search module determines a search start time according to the completion delivery time and starts packet search at the search start time.

Description

Wireless receiving system and its signal processing method

technical field

The invention relates to a wireless communication system, and relates to a technology for detecting data packets.

Background technique

A wireless local area network (WLAN) system uses packets as a unit when transmitting and receiving data. In order to reduce the probability of packet-to-packet collision (collision) and improve transmission quality, there is a fixed time interval between two successively sent packets. This time interval is typically sixteen microseconds (μs) in length and is called a short inter frame space (SIFS).

FIG. 1A is a schematic diagram of the relative relationship between packets using a short frame interval. Generally speaking, the receiver has a so-called decoding latency. Taking the example shown in FIG. 1A to illustrate, the time point t12 at which the receiving end completes decoding of the first packet 11 will be later than the time point t11 at which the first packet 11 is completely delivered to the receiving end. The interval between time points t11 and t12 is the decoding latency. After the decoding of the first packet 11 is completed, the receiving end will start to detect whether there is a next packet in the transmission channel. The preamble at the beginning of the packet is the basis for the receiver to identify whether the packet exists, and it is specific data with a total length of eight microseconds. In the example of FIG. 1A , after finding the preamble (hatched area) of the second packet 12 , the receiving end determines at time t13 that the second packet 12 does exist, and starts to decode the second packet 12 .

The 802.11n communication protocol specifies a packet format with a shorter interval, hoping to improve network transmission efficiency. This reduced inter frame space (reduced inter frame space, RIFS) is only two microseconds in length. FIG. 1B is a schematic diagram of relative relationships among packets using reduced frame intervals. The receiving end finishes decoding the third packet 13 at time point t14. It can be seen from FIG. 1B that due to the relationship of decoding latency, the time point t14 at which the receiving end starts to detect whether there is a next packet in the transmission channel is later than the time point t15 at which the preceding transmission of the fourth packet 14 ends. Until the time point t16, the receiving end finds the preamble of the fifth packet 15 and starts to decode the fifth packet 15 . Obviously, the receiving end will miss the data carried in the fourth packet 14 . One way to solve this problem is to use a circuit with a faster operation speed at the receiving end in order to shorten the decoding latency so as to advance the time point t14 to be earlier than the time point t15. However, this solution will not only greatly increase the hardware cost, but also increase the power consumption at the receiving end.

Contents of the invention

In order to solve the above problems, the present invention proposes a wireless receiving system and its signal processing method, which avoids the problem of missing packets due to decoding latency by starting to search for subsequent packets in advance. Compared with the prior art, the hardware cost and power consumption of the system and method according to the present invention are lower because there is no need to use a circuit with a faster operation speed.

A specific embodiment according to the present invention is a wireless receiving system, which includes a decoding module, an estimation module and a search module. The decoding module receives and decodes a packet to generate a decoding result. The estimation module extracts a packet length information from the decoding result, and estimates a delivery completion time of the packet according to the packet length information. The search module determines a search start time according to the delivery completion time, and starts packet search at the search start time.

Another specific embodiment according to the present invention is a signal processing method applied to a wireless receiving system. The method first performs a decoding step: receiving and decoding a packet to generate a decoding result. Then, the method executes an estimating step: extracting packet length information from the decoding result, and estimating a delivery completion time of the packet according to the packet length information. Then, the method executes a determining step: determining a search start time according to the transfer completion time, and starts packet search at the search start time.

Description of drawings

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

FIG. 1A is a schematic diagram of the relative relationship between packets using a short frame interval. FIG. 1(B) is a schematic diagram of the relative relationship between packets using reduced frame intervals.

FIG. 2 is a block diagram of a wireless receiving system according to an embodiment of the invention.

FIG. 3 is a schematic diagram illustrating the relative relationship between packets using the reduced frame interval and the corresponding operation sequence of the wireless receiving system according to the present invention.

4A-4C are three packet formats regulated by the 802.11n communication protocol.

FIG. 5 is a flowchart of a signal processing method according to an embodiment of the present invention.

Description of component symbols:

11～15, 31～33: packet t11～t16, t30～t36: time point

200: Wireless receiving system 22: Decoding module

24: Estimation Module 26: Search Module

S51～S53: process steps

detailed description

A specific embodiment according to the present invention is a wireless receiving system, the block diagram of which is shown in FIG. 2 . The wireless receiving system 200 includes a decoding module 22 , an estimation module 24 and a search module 26 . Those skilled in the technical field of the present invention can understand that the wireless receiving system 200 can further include other functional blocks not shown in FIG. element. In order to clearly present the spirit of the present invention, the following description focuses on the operations of the decoding module 22 , the estimating module 24 and the searching module 26 . In addition, the following embodiments mainly take the wireless receiving system 200 as an example of a wireless communication system conforming to the 802.11n protocol, but the scope of the present invention is not limited thereto.

FIG. 3 is a schematic diagram illustrating the relative relationship of 802.11n packets using the Reduced Frame Space (RIFS), and also presents an example of the corresponding operation timing of the wireless receiving system 200 . The decoding module 22 is used for receiving packets and decoding the packets. It can be seen from FIG. 3 that the first packet 31 is completely delivered to the wireless receiving system 200 at the time point t31 , and the decoding module 22 does not complete the decoding of the first packet 31 until the time point t30 . The interval between time points t30 and t31 is called decoding latency. It should be noted that the decoding method of the 802.11n packet is known to those skilled in the art of the present invention, and will not be repeated here.

The estimation module 24 is responsible for extracting the packet length information from the decoding result generated by the decoding module 22, and estimating the delivery completion time of a packet (ie the time when the end of the packet is delivered to the wireless receiving system 200) according to the packet length information. Take the first packet 31 as an example. In practice, the time when the head of the first packet 31 is delivered to the wireless receiving system 200 is known. Therefore, as long as the estimated length of the first packet 31 is estimated, the estimating module 24 can determine the time when the first packet 31 is delivered (that is, the time point t31 in FIG. 3 ). More specifically, the complete delivery time of a packet is its start time plus the estimated length of the packet.

The 802.11n protocol specification has three types of packets: legacy, high throughput mixed, and high throughput Greenfield. The lengths and content formats of these three types of packets are different, and FIG. 4A to FIG. 4C are schematic structural diagrams respectively. The L-SIG section and the HT-SIG section contain parameters for conveying packet length information. For the packet conforming to the traditional mode, the packet length information includes a parameter LENGTH and a parameter N_DBPS, and the estimation module 24 can estimate the packet length according to the following equation:

Ceiling((LENGTH*8+22)/N_DBPS)*4μs. (Formula 1)

The operation symbol Ceiling represents the calculation of a minimum integer value greater than or equal to its operand. The parameter LENGTH represents the number of bits of data not delivered in high-throughput mode. The parameter N_DBPS represents the number of data bits conveyed by each OFDM symbol in the packet. The calculation result of formula 1 represents how long a packet still contains after its L-SIG section. In other words, the estimated length of the entire packet can be obtained by adding the calculation result of Equation 1 to a preset packet segment length, that is, the lengths of the previous several segments (all of which are known).

For the packets meeting the high traffic mixed mode and having a normal guard interval (guard interval), the packet length information includes the parameter HT_LENGTH and the parameter HT_N_DBPS, and the estimation module 24 can estimate the packet length according to the following equation:

Ceiling((HT_LENGTH*8+22)/HT_N_DBPS)*4μs+8μs. (Formula 2)

The parameter HT_LENGTH represents the number of bits of data not transmitted in the traffic mode. The parameter HT_N_DBPS represents the number of data bits conveyed by each OFDM symbol in the packet. The operation result of formula 2 represents how long a packet still contains after its HT-SIG section.

For the packets conforming to the high traffic mixed mode and having a short guard interval, the estimation module 24 can estimate the packet length according to the following equation:

Ceiling((HT_LENGTH*8+22)/HT_N_DBPS)*3.2μs+8μs. (Formula 3)

For the packets conforming to the high-transmission green zone mode, the packet length information includes the parameter HT_LENGTH and the parameter HT_N_DBPS, and the estimation module 24 can estimate the packet length according to the following equation:

Ceiling((HT_LENGTH*8+22)/HT_N_DBPS)*4μs, (Formula 4)

The operation result of formula 4 represents how long a packet still contains after its HT-SIG section.

Compared with the decoding procedure, the operation of estimating the packet length is relatively simple. Therefore, the estimation module 24 can easily estimate the delivery time of the first packet 31 before the decoding module 22 completely decodes the first packet 31 . According to the completion delivery time of the first packet 31, the search module 26 determines a search start time, and starts packet search at the search start time. In the example shown in FIG. 3 , the search module 26 adds a known minimum packet interval to the completion delivery time of the first packet 31 as the starting time point t32 for starting to search for the next packet. For 802.11n packets using reduced frame space (RIFS), the minimum packet spacing is equal to two microseconds (μs). Subsequently, according to the context of the second packet 32 , the search module 26 determines at time point t33 that the second packet 32 does exist. It should be noted that as long as an appropriate buffer mechanism or parallel circuit is used, even if the decoding module 22 has not finished decoding the first packet 31, the decoding module 22 can still start decoding the second packet 32 at the time point t33.

The principle of setting the search start time is to ensure that the content of the second packet 32 will not be missed by the wireless receiving system 200 . In another embodiment, the search module 26 may set the search start time as the time point t31, between the time points t31 and t32, or slightly later than the time point t32. The advantage of setting the search start time as the packet completion transfer time plus the minimum packet interval is that the search module 26 does not need to waste power between the time points t31 - t32 when there will never be a packet preamble.

Similarly, before the end of the second packet 32, the estimating module 24 estimates that the transfer completion time point is t34, and the search module 26 adds the minimum packet distance to the time point t34, and determines that the next search start time is the time point t35 . In the example shown in FIG. 3 , the search module 26 determines at the time point t36 that the third packet 33 does exist, and the decoding module 22 also starts to decode the third packet 33 at the time point t36 .

It can be seen from the above description that the search start time according to the present invention has nothing to do with the length of the decoding latency, so the problem of missing packets caused by the decoding latency will not occur. It is worth noting that since the wireless receiving system 200 does not need to use a circuit with a faster operation speed to shorten the decoding latency, a lot of hardware cost and power consumption can be saved.

Another specific embodiment according to the present invention is a signal processing method applied in a wireless receiving system, the flow chart of which is shown in FIG. 5 . The method first executes step S51: receiving a packet and decoding the packet to generate a decoding result. Next, the method executes step S52: extracting a packet length information of the packet from the decoding result, and estimating a delivery completion time of the packet according to the packet length information. Then, the method executes step S53: determine a search start time according to the transfer completion time, and start packet search at the search start time.

Various circuit operation changes (such as the selection method of the search start time) described in the introduction of the wireless receiving system 200 can also be applied to the signal processing method shown in FIG. 5 , and the details are not repeated here.

As mentioned above, the present invention proposes a wireless receiving system and its signal processing method, which avoids the problem of missing packets due to decoding latency by starting to search for subsequent packets in advance. Compared with the prior art, the hardware cost and power consumption of the system and method according to the present invention are lower because there is no need to use a circuit with a faster operation speed.

With the above detailed description of the preferred embodiments, it is hoped that the features and spirit of the present invention can be described more clearly, and the scope of the present invention is not limited by the preferred embodiments disclosed above. On the contrary, the intention is to cover various changes and equivalent arrangements falling within the scope of the claimed invention.

Claims (10)

1. A wireless receiving system, comprising: A decoding module, receiving and decoding a first packet to generate a decoding result; An estimating module extracts a packet length information from the decoding result, and estimates a delivery completion time of the first packet according to the packet length information; and a search module, which determines a search start time of a second packet according to the completed delivery time, and starts packet search at the search start time; Wherein, the second packet is the next packet of the first packet. 2. The wireless receiving system as claimed in claim 1, wherein the search module adds a minimum packet interval to the delivery completion time as the search start time. 3. The wireless receiving system according to claim 1, wherein the estimation module adds a start time of the first packet to an estimated length of the first packet to estimate the delivery completion time, and the first packet conforms to In a traditional (Legacy) mode of the 802.11n communication protocol, the packet length information includes a parameter LENGTH and a parameter N_DBPS, and the estimation module estimates a length L according to the following equation: L=Ceiling((LENGTH*8+22)/N_DBPS)*4μs, Wherein, the operation symbol Ceiling represents calculating a minimum integer value greater than or equal to an operand, and the estimated length is the length L plus a preset packet segment length. 4. The wireless receiving system according to claim 1, wherein the estimation module adds a start time of the first packet to an estimated length of the first packet to estimate the delivery completion time, and the first packet conforms to In a High Throughput Mixed mode of the 802.11n communication protocol, the packet length information includes a parameter HT_LENGTH and a parameter HT_N_DBPS, and the estimation module estimates a length L according to the following equation: L=Ceiling((HT_LENGTH*8+22)/HT_N_DBPS)*4μs+8μs, or L=Ceiling((HT_LENGTH*8+22)/HT_N_DBPS)*3.2μs+8μs, Wherein, the operation symbol Ceiling represents calculating a minimum integer value greater than or equal to an operand, and the estimated length is the length L plus a preset packet segment length. 5. The wireless receiving system according to claim 1, wherein the estimating module adds a start time of the first packet to an estimated length of the first packet to estimate the delivery completion time, and the first packet In accordance with a high throughput green zone mode of the 802.11n communication protocol, the packet length information includes a parameter HT_LENGTH and a parameter HT_N_DBPS, and the estimation module estimates a length L according to the following equation: L=Ceiling((HT_LENGTH*8+22)/HT_N_DBPS)*4μs, Wherein, the operation symbol Ceiling represents calculating a minimum integer value greater than or equal to an operand, and the estimated length is the length L plus a preset packet segment length. 6. A signal processing method applied to a wireless receiving system, comprising: (a) receiving and decoding a first packet to generate a decoding result; (b) extracting a packet length information from the decoding result, and estimating a delivery completion time of the first packet according to the packet length information; and (c) determining a search start time of a second packet according to the completed transfer time, and starting packet search at the search start time; Wherein, the second packet is the next packet of the first packet. 7. The signal processing method as claimed in claim 6, wherein step (c) comprises adding a minimum packet spacing to the transfer completion time as the search start time. 8. The signal processing method as claimed in claim 6, wherein step (b) comprises adding a start time of the first packet to an estimated length of the first packet to estimate the delivery completion time, the first The packet conforms to a legacy mode of the 802.11n protocol, the packet length information includes a parameter LENGTH and a parameter N_DBPS, and step (b) includes estimating a length L according to the following equation: L=Ceiling((LENGTH*8+22)/N_DBPS)*4μs, Wherein, the operation symbol Ceiling represents calculating a minimum integer value greater than or equal to an operand, and the estimated length is the length L plus a preset packet segment length. 9. The signal processing method as claimed in claim 6, wherein step (b) includes adding a start time of the first packet to an estimated length of the first packet to estimate the delivery completion time, the first The packet conforms to a high throughput hybrid mode of the 802.11n protocol, the packet length information includes a parameter HT_LENGTH and a parameter HT_N_DBPS, and step (b) includes estimating a length L according to the following equation: L=Ceiling((HT_LENGTH*8+22)/HT_N_DBPS)*4μs+8μs, or L=Ceiling((HT_LENGTH*8+22)/HT_N_DBPS)*3.2μs+8μs, Wherein, the operation symbol Ceiling represents calculating a minimum integer value greater than or equal to an operand, and the estimated length is the length L plus a preset packet segment length. 10. The signal processing method as claimed in claim 6, wherein step (b) comprises adding a start time of the first packet to an estimated length of the first packet to estimate the delivery completion time, the first The packet conforms to a high throughput green zone mode of the 802.11n protocol, the packet length information includes a parameter HT_LENGTH and a parameter HT_N_DBPS, and step (b) includes estimating a length L according to the following equation: L=Ceiling((HT_LENGTH*8+22)/HT_N_DBPS)*4μs, Wherein, the operation symbol Ceiling represents calculating a minimum integer value greater than or equal to an operand, and the estimated length is the length L plus a preset packet segment length.