CN101483926B - Channel evaluation method and apparatus - Google Patents
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Abstract
The present invention discloses a channel evaluating method which includes: employing the time required by an appointed channel for sending preset amount data frame in the appointed channel without channel competition; each device requiring channel competition; sending data frame in the appointed channel in the obtained time and recording the sent data frame amount; using ratio of the sent data frame amount to the preset amount as a leisure index of the appointed channel; and selecting a standard channel according to the free/busy index of a plurality of appointed channel. The present invention also discloses a channel evaluating device and another channel evaluating method. The technique scheme provided by the present invention can evaluate channel rapidly and accurately.
Description
Technical Field
The present invention relates to the field of wireless communications technologies, and in particular, to a channel estimation method and apparatus.
Background
The IEEE802.11 protocol is a Medium Access Control (MAC) layer protocol, which specifies a base protocol for a node to access a transmission medium without collision. IEEE802.11 supports two different MAC layer mechanisms: the first one is Distributed Coordination Function (DCF), which supports asynchronous data transmission service, and all users who want to transmit data have equal access to the network; the second is a Point Coordination Function (PCF), which is mainly used for transmitting real-time services.
The DCF is an Access control mechanism of a wireless network to a shared channel, and the core of the DCF is Carrier Sense Multiple Access/collision avoidance (CSMA/CA) technology, which includes: a carrier sense mechanism, an interframe Space (IFS), and a random back-off (random back off) mechanism.
DCF provides two working modes, one is CSMA/CA basic working mode; the other is a Request To Send/Clear To Send (RTS/CTS) protocol.
The workflow of CSMA/CA is: the method comprises the steps that a data sending party A starts a CSMA/CA mechanism, firstly, a channel is monitored, if the idle Time of the channel is larger than the distributed coordination function InterFrame Space (DIFS, DCF InterFrame Space), a random Back-Off Time (Back Off Time) is selected to enter a Back-Off process, and a data frame is sent after the Back-Off process is finished; otherwise, delaying access until the idle time of the channel is detected to be larger than DIFS, then selecting a random backoff time to enter a backoff process, and sending a data frame after the backoff is finished; after the data sender A finishes sending data, the data sender A waits for an acknowledgement frame (ACK) returned by the receiver B, and if the ACK returned by the receiver B is not received, the data sender A needs to resend the data frame.
The RTS/CTS workflow is: a sends RTS signal to B when monitoring that the channel idle time is larger than DIFS, which indicates that A needs to send a plurality of data to B, B sends CTS signal to all base stations after receiving RTS, which indicates that A is ready to send, and the rest base stations which want to send data to B suspend sending; the two parties start real data transmission after successfully exchanging RTS/CTS signals (namely, completing handshake), so that when a plurality of invisible sending stations send signals to the same receiving station at the same time, only the station which receives the response of the receiving station to the CTS can actually send the signals, and collision is avoided.
The current channel estimation scheme generally adopts the above monitoring mode to judge the busy-idle probability of the channel. However, it is not comprehensive to evaluate the channel by using the listening manner, for example, there are A, B and C devices competing in the current channel, and the device D is ready to join the channel, and if the device D only uses the listening manner, the devices A, B and C cannot sense the existence of the competitor D, and cannot completely reflect the preemption of the channel when the A, B, C and D four devices simultaneously want to send a data packet. A new and more accurate channel estimation method is therefore needed.
Disclosure of Invention
The invention provides a channel assessment method, which can rapidly and accurately assess a channel.
The invention also provides a channel evaluation device which can quickly and accurately evaluate the channel.
The invention also provides a channel evaluation method, which can accurately evaluate the channel.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
the invention discloses a channel evaluation method, which comprises the following steps:
acquiring the time required by a specified channel to send a preset number of data frames on the specified channel when no channel competition exists;
each device to compete for the channel sends a data frame on the specified channel within the acquired time, and records the number of the sent data frames;
taking the ratio of the number of the data frames to be sent to the preset number as a busy and idle index of the appointed channel, and selecting the channel according to the busy and idle indexes of a plurality of appointed channels;
wherein,
the data frame sending mode is a broadcast data frame mode;
the time required for acquiring the appointed channel to send the preset number of data frames on the appointed channel when no channel competition exists is as follows:
summing up DIFS time of a distributed coordination function frame interval, backoff time selected when a data frame is sent, and time required for sending a data frame according to protocol specification to obtain time required for sending a data frame on the specified channel when no channel competition exists; multiplying the obtained time required for sending a data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists;
or,
the data frame sending mode is a mode that an opposite end needs to feed back an acknowledgement frame ACK after the data frame is sent;
the time required for acquiring the appointed channel to send the preset number of data frames on the appointed channel when no channel competition exists is as follows:
summing the DIFS time, the back-off time selected when one data frame is sent, the time required for sending one data frame according to the protocol specification, the time of transmitting the data frame in the specified channel, the time required for sending the acknowledgement frame according to the protocol specification by the opposite terminal equipment and the time of transmitting the acknowledgement frame in the specified channel to obtain the time required for sending one data frame on the specified channel when no channel competition exists; and multiplying the obtained time required for sending one data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists.
The invention also discloses a channel assessment device, which comprises: an acquisition module, a sending module and an evaluation module, wherein,
the mode of sending the data frame is a data frame mode;
an obtaining module, configured to sum a distributed coordination function interframe space DIFS time, a backoff time selected when sending a data frame, and a time required to send a data frame according to a protocol specification, to obtain a time required to send a data frame on the designated channel when there is no channel contention; multiplying the obtained time required for sending a data frame by the preset number to obtain the time required for sending the data frame with the preset number on the appointed channel when no channel competition exists, sending the obtained time value to a sending module, and sending the preset number value to an evaluation module;
or,
the data frame sending mode is a mode that an opposite end needs to feed back an acknowledgement frame ACK after the data frame is sent;
an obtaining module, configured to sum DIFS time, backoff time selected when sending a data frame, time required to send a data frame according to a protocol specification, time for transmitting a data frame in a specified channel, time required for an opposite device to send a confirmation frame according to a protocol specification, and time for transmitting a confirmation frame in a specified channel, to obtain time required to send a data frame on the specified channel when there is no channel contention; multiplying the obtained time required for sending a data frame by the preset number to obtain the time required for sending the data frame with the preset number on the appointed channel when no channel competition exists, sending the obtained time value to a sending module, and sending the preset number value to an evaluation module;
the sending module is used for sending data frames on the specified channel within the acquired time, recording the number of the sent data frames and sending the recorded number of the sent data frames to the evaluation module;
and the evaluation module is used for taking the ratio of the number of the sent data frames to the predetermined number value as the busy and idle indexes of the appointed channels, and each device to compete for the channels selects the channels according to the busy and idle indexes of the appointed channels.
The invention also discloses a channel evaluation method, which comprises the following steps:
acquiring the time required by a specified channel to send a preset number of data frames on the specified channel in a broadcast data frame mode when no channel competition exists, and marking the time as first time;
each device to compete for the channel sends a data frame on the appointed channel, records the time required for sending the data frames with the preset number, and marks the time as second time;
taking the ratio of the first time to the second time as a busy and idle index of the appointed channel, and selecting a channel according to the busy and idle indexes of a plurality of appointed channels;
wherein,
the mode of sending the data frame is a data frame mode;
the time required for acquiring the appointed channel to send the preset number of data frames on the appointed channel when no channel competition exists is as follows:
summing the DIFS time, the back-off time selected when sending a data frame and the time required for sending a data frame according to the protocol specification to obtain the time required for sending a data frame on the specified channel when no channel competition exists; multiplying the obtained time required for sending a data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists;
or,
the data frame sending mode is a mode that an opposite end needs to feed back an acknowledgement frame ACK after the data frame is sent;
the time required for acquiring the appointed channel to send the preset number of data frames on the appointed channel when no channel competition exists is as follows:
summing the DIFS time, the back-off time selected when one data frame is sent, the time required for sending one data frame according to the protocol specification, the time of transmitting the data frame in the specified channel, the time required for sending the acknowledgement frame according to the protocol specification by the opposite terminal equipment and the time of transmitting the acknowledgement frame in the specified channel to obtain the time required for sending one data frame on the specified channel when no channel competition exists; and multiplying the obtained time required for sending one data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists.
It can be seen from the above technical solutions that, in the technical solution of the present invention, the time required for sending a predetermined number of data frames on a designated channel when the designated channel has no channel contention is obtained, the data frames are sent on the designated channel within the obtained time, the number of the sent data frames is recorded, and the ratio of the number of the sent data frames to the predetermined number is used as the busy-idle indicator of the designated channel, when the busy-idle condition of one channel is evaluated, each device that wants to contend for the channel sends a certain number of data frames on the channel, which is closer to the actual user contention condition than that, in the prior art, the device that wants to contend for the channel simply monitors, so that the obtained channel busy-idle indicator can more accurately represent the actual contention condition of the channel.
Drawings
Fig. 1 is a flow chart of a channel estimation method according to an embodiment of the present invention;
FIG. 2 is a diagram of a MAC frame format common to IEEE 802.11;
FIG. 3 is a diagram of an IEEE802.11b short PLCP physical layer protocol data unit frame format;
FIG. 4 is a diagram illustrating a transmission process of a broadcast data frame according to the present invention;
FIG. 5 is a diagram of an IEEE802.11a OFDM PLCP frame format;
fig. 6 is a block diagram of a channel estimation apparatus according to an embodiment of the present invention.
Detailed Description
Fig. 1 is a flowchart of a channel estimation method according to an embodiment of the present invention. As shown in fig. 1, the method comprises the steps of:
step 101, acquiring the time required by a designated channel to transmit a predetermined number of data frames on the designated channel when the designated channel has no channel contention.
And 102, transmitting data frames on the specified channel in the acquired time, and recording the number of the transmitted data frames.
Step 103, using the ratio of the number of the data frames to be sent to the predetermined number as the busy indicator of the designated channel.
According to the scheme shown in fig. 1, when each device that wants to contend for a channel evaluates the busy/idle condition of the channel, a certain number of data frames are sent on the channel, which is closer to the actual user contention condition than the prior art in which the device that wants to contend for a channel simply monitors, and therefore, the channel busy/idle indicator obtained according to the scheme shown in fig. 1 can more accurately represent the actual contention condition of the channel.
According to the scheme shown in fig. 1, after the busy and idle indexes of a plurality of channels are obtained, a channel with relatively small competition can be selected according to the busy and idle indexes of each channel, so that interference is avoided. At present, the electromagnetic environment of a wireless system is more and more complex, which is beneficial for a user to quickly and easily know the current electromagnetic environment when performing WLAN network deployment and guide the user to select a channel.
In the scheme shown in fig. 1, the ratio of the number of data frames that can be transmitted when the channel is in the contention-free ideal state and the actual real state is used as an index for evaluating the busy-idle state of the channel in the same time. Meanwhile, the inventor of the present application also thinks that when the same number of data frames are transmitted, the ratio of the time required for the channel to be in the contention-free ideal state and the actual real state is used as an index for evaluating the busy-idle state of the channel, and specifically: acquiring the time required by a specified channel to send a preset number of data frames on the specified channel when no channel competition exists, and marking the time as first time; sending data frames on the appointed channel, recording the time required for sending the data frames with the preset number, and marking the time as second time; and taking the ratio of the first time to the second time as a busy and idle index of the designated channel.
The latter requires a predetermined number of data frames to be transmitted on the actual channel, and when the actual condition of the channel is poor, i.e., the contention is severe, it takes a long time to transmit the predetermined number of data frames. This solution is therefore not time efficient with respect to the former. The former (scheme shown in FIG. 1) is further illustrated in the following examples.
Currently, there are 13 channels available in the 2.4GHz band, which are Ch 1-Ch 13, and the channels in the 5GHz band include: ch 34-ch 64, ch 100-chi 40 and ch 149-ch 165. The scheme described in fig. 1 is further described below by taking channels in the 2.4GHz band and the 5GHz band as examples.
Channel assessment on first, 2.4GHz frequency band
For the data from the upper layer, the MAC layer will be encapsulated, and fig. 2 is a diagram of the format of the MAC frame commonly used in IEEE 802.11. As shown in fig. 2, the MAC frame header includes: a Frame Control (Frame Control) field, a Duration/identification (Duration/ID) field, an Address 1 (Address) field, an Address 2(Address2) field, an Address 3(Address3) field, a Sequence Control (Sequence Control) field, and an Address 1 (Address) field; wherein, the frame control field includes: a Protocol Version (Protocol Version) field, a Type & Subtype (Type & Subtype) field, a destination DS field, a source DS field, a multi-fragmentation (Morefrag) field, a Retry (Retry) field, a Power management (Power management) field, a More (More) field, a WEP field, and an Order (Order) field.
The MAC frame is passed down to the physical layer and is processed and encapsulated as necessary by the Convergence sublayer (PLCP) of the physical layer, specifically by adding a PLCP preamble and a PLCP header to facilitate data transmission between the MAC layer and the management layer (PMD) of the physical layer. The PMD layer interfaces directly with the physical medium and is a transceiver for wireless information.
The IEEE802.11b carrier frequency is 2.4 GHz. Fig. 3 is a diagram of an IEEE802.11b short PLCP physical layer protocol data unit frame format. As shown in fig. 3, the short PLCP physical layer protocol data unit (PPDU) frame includes: a 72-bit short PLCP preamble, a 48-bit short PLCP header, and a MAC layer protocol data unit (MPDU). The MPDU is the MAC frame shown in fig. 2. Wherein the 72-bit short PLCP preamble comprises: 56-bit short Synchronization (SYNC), 16-bit SFD; the 48-bit short PLCP header includes: an 8-bit SIGNAL (SIGNAL), an 8-bit SERVICE (SERVICE), a 16-bit LENGTH (LENGTH), and a 16-bit CRC check code. The transmission rate of the short PLCP preamble is 1Mbps, the transmission rate of the short PLCP header is 2Mbps, and the transmission rate of the MPDU may vary, for example, at a constant rate of 2Mbps, 5.5Mbps, or 11Mbps, as specified in IEEE802.11 b.
The physical layer protocol of IEEE802.11g is defined in a 2.4GHz frequency band, and the data transmission rate can reach 54Mbps at most by using an Orthogonal Frequency Division Multiplexing (OFDM) technology. IEEE802.11g may use different modulation schemes for the preamble, header and data field MPDU of the PPDU frame, including: an OFDM/OFDM scheme and a CCK/OFDM scheme, wherein CCK is a Complementary Code Keying (Complementary Code Keying) modulation scheme.
The OFDM/OFDM scheme is to transmit a preamble, a header, and a data field using an OFDM modulation scheme, where the data rate that the OFDM can provide is as follows: 6Mbps, 9Mbps, 12Mbps, 18Mbps, 24Mbps, 36Mbps, 48Mbps, and 54 Mbps. Since OFDM cannot provide 1Mbps and 2Mbps (transmission rate of preamble and header specified in ieee802.11b), the OFDM/OFDM scheme cannot achieve backward compatibility with 802.11 b.
The CCK/OFDM mode is a mixed modulation mode, the preamble and the header are transmitted by using the CCK modulation mode, and the data field is transmitted by using the OFDM modulation mode, so that the backward compatibility with IEEE802.11b is realized. CCK supports 1Mbps, 2Mbps, 5.5Mbps, and 11Mbps rates, while OFDM can provide data rates of: 6Mbps, 9Mbps, 12Mbps, 18Mbps, 24Mbps, 36Mbps, 48Mbps, and 54 Mbps.
In consideration of compatibility with ieee802.11b, the short PLCP preamble format shown in fig. 3 is selected in the embodiment of the present invention, and the scheme shown in fig. 1 is described by using a CCK/OFDM modulation scheme.
In the scheme shown in fig. 1, the problem of how to transmit data frames on a channel is involved, and two data frame transmission modes are taken as examples in this embodiment. In the first data frame transmission scheme, only the case of broadcasting a data frame is considered, that is, when transmitting a data frame on a channel, an opposite end feedback acknowledgement frame (ACK) is not required. In the second data frame transmission mode, after the data frame is transmitted on the channel, the opposite end needs to feed back the AKC. The following description will be made separately.
Fig. 4 is a schematic diagram of a transmission process of a broadcast data frame in the present invention. As shown in fig. 4, a device to transmit data listens to a channel, and when it is detected that an idle Time of the channel is greater than a distributed coordination function interframe space DIFS, selects a Backoff Time (Backoff Time) to enter a Backoff process, where the Backoff Time is a value related to a Contention Window (CW), and transmits a data frame on the channel after the Backoff process is finished, and returns to the step of listening to the channel to prepare for transmitting a next data frame.
Then, when the short PLCP preamble format shown in fig. 3 is selected, the PPDU frame is transmitted by using the CCK/OFDM modulation scheme, and only the broadcast data frame is considered, under the condition of no channel contention: the time T1 required to transmit n (arbitrary natural number) broadcast frames of ieee802.11g 54Mbps on a channel of the 2.4GHz band is as shown in equation (1):
t1 × { DIFS + backoff time + (72bit/1Mbps) + (48bit/2Mbps) + (MPDU frame length/54 Mbps) } (1)
Wherein, the DIFS is a DCF interframe space, and during this period, if the channel is in an idle state, it indicates that the data frame can be sent to preempt the channel at this time;
backkoff Time is Backoff Time, backkoff Time ═ INT (CW × Random) × SlotTime; wherein INT represents rounding, CW is the length of the contention window, and the value is CWminAnd CWmaxAn integer between, a minimum value CW of CWminCan be preset, and the maximum value CWmaxMay be preset or may not be limited; when all frames are transmitted for the first time, the initial value of CW can be CWminCW is doubled at each subsequent retransmission until CWmax(ii) a Random is a Random decimal between 0 and 1; slot Time is one Slot length;
72bit/1Mbps represents the time required for a 72-bit short PLCP preamble to transmit at a rate of 1 Mbps;
48bit/2Mbps represents the time required for a 48bit short PLCP header to transmit at a rate of 2 Mbps;
the MPDU frame length/54 Mbps represents the time required by the data frame to adopt the 54Mbps rate for transmission; of course, the transmission rate of the data frame may be other values according to the actual situation, such as 36Mbps, 48Mbps, etc., and only 54Mbps is taken as an example here.
After T1 is obtained, according to step 102, data frames are transmitted on the channel within T1 time, and the number of the transmitted data frames is recorded, where if m1 is assumed, m1/n is the probability that the data packet of the channel is successfully transmitted, and m1/n can be used as the busy-idle indicator of the channel.
In the second data frame sending method, after sending a data frame on a channel, an opposite end needs to feed back AKC, and a specific data transmission process is as follows: the device which needs to invent data monitors the channel, when the idle time of the channel is monitored to be larger than DIFS, a back-off time is selected to enter a back-off process, a data frame is sent on the channel after the back-off process is finished, then an opposite end feedback confirmation frame is waited, if a confirmation frame returned by the opposite end device of the channel is received in the appointed time, the step of returning to the channel monitoring step is ready for sending the next data frame, otherwise, the current data frame is sent again, and the step of waiting for the opposite end feedback data frame is executed.
When the short PLCP preamble format shown in fig. 3 is selected, a CCK/OFDM modulation scheme is adopted to transmit a PPDU frame, and an opposite end ACK feedback scheme is adopted, under the condition of no channel contention: the time T2 required to transmit n (arbitrary natural number) broadcast frames of ieee802.11g 54Mbps on a channel of the 2.4GHz band needs to take into account the propagation delay of the signal in space and the time required for transmitting ACK at the opposite end, and T2 is shown in formula (2):
t2 ═ nx { DIFS + Backoff Time + (72bit/1Mbps) + (48bit/2Mbps) + (MPDU frame length/54 Mbps) +2derta + SIFS + TACK} (3)
Where, derta is the propagation delay of signal in space, where derta is communication distance 1/c, and c is light speed 3 × 108m/s, considering the delays of the transmitted data frame and the ACK frame and multiplying by 2;
the SIFS is the time between the time when the opposite end receives the data frame and the time when the opposite end starts to send the ACK frame;
TACKfor the time required for the opposite end to send the ACK frame, when the ACK frame is encapsulated by the physical layer of ieee802.11b or ieee802.11g, T isACK＝(72bit/1Mbps)+(48bit/2Mbps)+(112bit/R)；
After T2 is obtained, according to step 102, data frames are transmitted on the channel within T2 time, and the number of the transmitted data frames is recorded, where if m2 is assumed, m2/n is the probability that the data packet of the channel is successfully transmitted, and m2/n can be used as the busy-idle indicator of the channel.
Channel assessment on the second, 5GHz band
In the prior art, only 802.11a frames can be transmitted in a 5GHz band, and 802.11a frames in 5GHz have no CCK modulation mode, and only an OFDM/OFDM modulation mode can be adopted. Fig. 5 is a diagram of the format of an ieee802.11a ofdm PLCP frame. Referring to fig. 5, in an 802.11a frame at 5GHz, a PLCP preamble field is used to achieve synchronization, and is composed of 10 short training symbols and 2 long training symbols, and the total training time is 16 us. The signal fields in the PLCP header (the signal fields include a 4-bit rate field, a 1-bit reserved field, a 12-bit length field, a 1-bit parity field, and a 6-bit trailer field) are transmitted with reliable BPSK modulation and 1/2 coding rate (i.e., 6 Mbps). The 16-bit SERVICE field of the PLCP message is transmitted as a data field along with the PSDU plus a 6-bit trailer field and a padding field at the rate indicated in the rate field.
When the PLCP preamble format is selected, the PPDU frame is transmitted in an OFDM/OFDM modulation scheme, and only the broadcast data frame is considered, under the condition of no channel contention: the time T3 required to transmit n broadcast frames of ieee802.11a 54Mbps on a channel of a 5GHz band is as shown in formula (1):
t3 × { DIFS + Backoff Time +16us + (24bit/6Mbps) + ((16bit + MPDU frame length +6bit + padding bit)/54 Mbps) } (3)
Wherein 16us represents the time of the preamble symbol of the OFDM PLCP, i.e., the synchronization time;
24bit/6Mbps represents the time required for 24 bits of the OFDM PLCP header signal field to be transmitted at 6 Mbps;
(16bit + MPDU frame length +6bit + padding bit)/54 Mbps represents the time required for transmission of the SERVICE field and PSDU of the PLCP message, plus the 6bit trailer field and padding field, with MPDU, and 54 Mbps.
After T3 is obtained, according to step 102, data frames are transmitted on the channel within T3 time, and the number of the transmitted data frames is recorded, where if m3 is assumed, m3/n is the probability that the data packet of the channel is successfully transmitted, and m3/n can be used as the busy-idle indicator of the channel.
When a PLCP preamble format is selected, an OFDM/OFDM modulation mode is adopted to transmit a PPDU frame, and an opposite end feedback ACK mode is adopted, under the condition of no channel competition: the time T4 required for transmitting n ieee802.11a 54Mbps broadcast frames on a channel of a 5GHz band needs to take into account the propagation delay of a signal in space and the time required for transmitting ACK at the opposite end, and T4 is shown in formula (4):
t4 ═ nx { DIFS + Backoff Time +16us + (24bit/6Mbps) + ((16bit + MPDU frame length +6bit + padding bits)/54 Mbps) +2derta + SIFS + TACK} (4)
Wherein, T is when ACK frame adopts IEEE802.11a physical layer encapsulationACK16us + (24bit/6Mbps) + ((16bit +112bit + padding bits)/R);
after T4 is obtained, according to step 102, data frames are transmitted on the channel within T4 time, and the number of the transmitted data frames is recorded, where if m4 is assumed, m4/n is the probability that the data packet of the channel is successfully transmitted, and m4/n can be used as the busy-idle indicator of the channel.
Therefore, in the embodiment of the invention, the CSMA/CA multi-user access working principle of the IEEE802.11 standard is utilized, so that the rapid and accurate channel evaluation is realized, and the accuracy of wireless network planning and optimization is improved. In addition, in the scheme of the embodiment, a mode of simulating an actual communication process is adopted, the influence of interference of the WiFI signal and the non-WiFI signal is considered, and a channel estimation result is closer to an actual environment.
Fig. 6 is a block diagram of a channel estimation apparatus according to an embodiment of the present invention. As shown in fig. 6, the apparatus includes: an acquisition module 601, a sending module 602, and an evaluation module 603, wherein,
an obtaining module 601, configured to obtain time required for a designated channel to send a predetermined number of data frames on the designated channel when there is no channel contention, send the obtained time value to a sending module 602, and send the predetermined number value to an evaluation module 603;
a sending module 602, configured to send a data frame on the specified channel within the obtained time, record the number of sent data frames, and send the recorded number of sent data frames to an evaluation module 603;
an evaluating module 603, configured to use a ratio of the number of the data frames to the predetermined number as a busy-idle indicator of the designated channel.
In fig. 6, a sending module 602, configured to monitor the specified channel, select a backoff time to enter a backoff process when it is monitored that an idle time of the specified channel is greater than a distributed coordination function interframe space DIFS, send a data frame on the specified channel after the backoff process is finished, and return to the step of monitoring the specified channel to prepare for sending a next data frame.
An obtaining module 601, configured to sum an IDFS time, a backoff time selected when sending a data frame, and a time required to send a data frame according to a protocol specification, to obtain a time required to send a data frame on the designated channel when there is no channel contention; and multiplying the obtained time required for sending one data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists.
In fig. 6, a sending module 602, configured to monitor the specified channel, and when it is monitored that the idle time of the specified channel is greater than a distributed coordination function interframe space DIFS, select a backoff time to enter a backoff process, after the backoff process is ended, send a data frame on the specified channel, then wait for an acknowledgment frame fed back by an opposite device of the specified channel, and if an acknowledgment frame returned by the opposite device of the specified channel is received within the specified time, return to the step of monitoring the specified channel to prepare for sending a next data frame; otherwise, the current data frame is sent again and the opposite terminal equipment of the appointed channel is waited to feed back the confirmation frame.
An obtaining module 601, configured to sum an IDFS time, a back-off time selected when a data frame is sent, a time required to send a data frame according to a protocol specification, a time for a data frame to be transmitted in a specified channel, a time required for an opposite end device to send a confirmation frame according to a protocol specification, and a time for a confirmation frame to be transmitted in a specified channel, to obtain a time required to send a data frame on the specified channel when there is no channel contention; and multiplying the obtained time required for sending one data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists.
In summary, in the technical solution of the present invention, the time required for sending a predetermined number of data frames on a designated channel when the designated channel has no channel contention is obtained, the data frames are sent on the designated channel within the obtained time, the number of the sent data frames is recorded, and the ratio of the number of the sent data frames to the predetermined number is used as the busy-idle indicator of the designated channel, when each device that wants to contend for a channel evaluates the busy-idle condition of the channel, a certain number of data frames are sent on the channel, which is closer to the actual user contention condition than the prior art in which the device that wants to contend for a channel simply monitors, so the obtained channel busy-idle indicator can more accurately represent the actual contention condition of the channel.
The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, and any modifications, equivalents, improvements and the like that are within the spirit and principle of the present invention should be included in the present invention.
Claims (7)
1. A method for channel estimation, the method comprising:
acquiring the time required by a specified channel to send a preset number of data frames on the specified channel when no channel competition exists;
each device to compete for the channel sends a data frame on the specified channel within the acquired time, and records the number of the sent data frames;
taking the ratio of the number of the data frames to be sent to the preset number as a busy and idle index of the appointed channel, and selecting the channel according to the busy and idle indexes of a plurality of appointed channels;
wherein,
the data frame sending mode is a broadcast data frame mode;
the time required for acquiring the appointed channel to send the preset number of data frames on the appointed channel when no channel competition exists is as follows:
summing up DIFS time of a distributed coordination function frame interval, backoff time selected when a data frame is sent, and time required for sending a data frame according to protocol specification to obtain time required for sending a data frame on the specified channel when no channel competition exists; multiplying the obtained time required for sending a data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists;
or,
the data frame sending mode is a mode that an opposite end needs to feed back an acknowledgement frame ACK after the data frame is sent;
the time required for acquiring the appointed channel to send the preset number of data frames on the appointed channel when no channel competition exists is as follows:
summing the DIFS time, the back-off time selected when one data frame is sent, the time required for sending one data frame according to the protocol specification, the time of transmitting the data frame in the specified channel, the time required for sending the acknowledgement frame according to the protocol specification by the opposite terminal equipment and the time of transmitting the acknowledgement frame in the specified channel to obtain the time required for sending one data frame on the specified channel when no channel competition exists; and multiplying the obtained time required for sending one data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists.
2. The method of claim 1, wherein when the data frame transmission mode is a broadcast data frame mode, transmitting the data frame on the designated channel comprises:
step A, monitoring the appointed channel;
and step B, when the idle time of the appointed channel is monitored to be larger than the distributed coordination function interframe space DIFS, selecting a back-off time to enter a back-off process, sending a data frame on the appointed channel after the back-off process is finished, and returning to the step A.
3. The method of claim 1, wherein when the data frame is transmitted in a manner that an acknowledgement frame ACK fed back by an opposite end is required after the data frame is transmitted, transmitting the data frame on the designated channel comprises:
step A, monitoring the appointed channel;
step B, when the idle time of the appointed channel is monitored to be larger than a distributed coordination function interframe space DIFS, selecting a back-off time to enter a back-off process, and sending a data frame on the appointed channel after the back-off process is finished;
step C, if the confirmation frame returned by the opposite-end equipment of the appointed channel is received in the appointed time, returning to the step A; otherwise, re-sending the data frame and re-executing the step C.
4. A channel estimation apparatus, comprising: an acquisition module, a sending module and an evaluation module, wherein,
the mode of sending the data frame is a data frame mode;
the acquisition module is used for summing up distributed coordination function interframe space DIFS time, backoff time selected when a data frame is sent and time required for sending the data frame according to protocol specification to obtain the time required for sending the data frame on a specified channel when no channel competition exists; multiplying the obtained time required for sending a data frame by a preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists; sending the obtained time value required for sending a preset number of data frames on the appointed channel when no channel competition exists to a sending module, and sending the preset number value to an evaluation module;
or,
the data frame sending mode is a mode that an opposite end needs to feed back an acknowledgement frame ACK after the data frame is sent;
the acquisition module is used for summing up DIFS time, back-off time selected when a data frame is sent, time required for sending the data frame according to protocol specification, time for transmitting the data frame in a specified channel, time required for sending a confirmation frame by opposite-end equipment according to protocol specification and time for transmitting the confirmation frame in the specified channel to obtain time required for sending the data frame on the specified channel when no channel competition exists; multiplying the obtained time required for sending a data frame by a preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists; sending the obtained time value required for sending a preset number of data frames on the appointed channel when no channel competition exists to a sending module, and sending the preset number value to an evaluation module;
a sending module, configured to send a data frame on the designated channel within a time required to send a predetermined number of data frames on the designated channel when there is no channel contention, record the number of the sent data frames, and send the recorded number of the sent data frames to an evaluation module;
and the evaluation module is used for taking the ratio of the number of the sent data frames to the predetermined number value as the busy and idle indexes of the appointed channels, and each device to compete for the channels selects the channels according to the busy and idle indexes of the appointed channels.
5. The apparatus of claim 4,
the mode of sending the data frame is a data frame mode;
and the sending module is used for monitoring the designated channel, selecting a back-off time to enter a back-off process when the idle time of the designated channel is monitored to be greater than the distributed coordination function interframe space DIFS, sending a data frame on the designated channel after the back-off process is finished, and returning to the step of monitoring the designated channel to prepare for sending the next data frame.
6. The apparatus of claim 4,
the data frame sending mode is a mode that an opposite end needs to feed back an acknowledgement frame ACK after sending the data frame;
the sending module is configured to monitor the designated channel, select a backoff time to enter a backoff process when the idle time of monitoring the designated channel is greater than a distributed coordination function interframe space (DIFS), send a data frame on the designated channel after the backoff process is finished, then wait for an acknowledgment frame fed back by an opposite-end device of the designated channel, and if an acknowledgment frame returned by the opposite-end device of the designated channel is received within the designated time, return to the step of monitoring the designated channel to prepare for sending a next data frame; otherwise, the current data frame is sent again and the opposite terminal equipment of the appointed channel is waited to feed back the confirmation frame.
7. A method for channel estimation, the method comprising:
acquiring the time required by a specified channel to send a preset number of data frames on the specified channel in a broadcast data frame mode when no channel competition exists, and marking the time as first time;
each device to compete for the channel sends a data frame on the appointed channel, records the time required for sending the data frames with the preset number, and marks the time as second time;
taking the ratio of the first time to the second time as a busy and idle index of the appointed channel, and selecting a channel according to the busy and idle indexes of a plurality of appointed channels;
wherein,
the mode of sending the data frame is a data frame mode;
the time required for acquiring the appointed channel to send the preset number of data frames on the appointed channel when no channel competition exists is as follows:
summing up DIFS time of a distributed coordination function frame interval, backoff time selected when a data frame is sent, and time required for sending a data frame according to protocol specification to obtain time required for sending a data frame on the specified channel when no channel competition exists; multiplying the obtained time required for sending a data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists;
or,
the data frame sending mode is a mode that an opposite end needs to feed back an acknowledgement frame ACK after the data frame is sent;
the time required for acquiring the appointed channel to send the preset number of data frames on the appointed channel when no channel competition exists is as follows:
summing the DIFS time, the back-off time selected when one data frame is sent, the time required for sending one data frame according to the protocol specification, the time of transmitting the data frame in the specified channel, the time required for sending the acknowledgement frame according to the protocol specification by the opposite terminal equipment and the time of transmitting the acknowledgement frame in the specified channel to obtain the time required for sending one data frame on the specified channel when no channel competition exists; and multiplying the obtained time required for sending one data frame by the preset number to obtain the time required for sending the preset number of data frames on the appointed channel when no channel competition exists.
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| CN102811498A (en) * | 2012-07-27 | 2012-12-05 | 南京邮电大学 | Self-adaptive competition window adjusting method based on interference analysis |
| US9907070B2 (en) * | 2013-11-22 | 2018-02-27 | Qualcomm Incorporated | Channel access deferral mechanism |
| CN104125189B (en) * | 2014-08-13 | 2018-05-29 | 中国科学院上海微***与信息技术研究所 | A kind of frame structure suitable for E band communications |
| DE102015209196A1 (en) * | 2014-09-08 | 2016-03-10 | Robert Bosch Gmbh | Method for the serial transmission of a frame via a bus system from a transmitter to at least one receiver and subscribers of a bus system |
| CN114585091A (en) * | 2016-11-04 | 2022-06-03 | 松下电器（美国）知识产权公司 | Integrated circuit with a plurality of transistors |
| CN106804061B (en) * | 2017-01-20 | 2020-04-14 | 湖南基石通信技术有限公司 | Link construction method and device based on competitive MAC |
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