CN101984694B - Wireless channel idle detection method based on IEEE802.11n - Google Patents
Wireless channel idle detection method based on IEEE802.11n Download PDFInfo
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Abstract
The invention provides a wireless channel idle detection method based on IEEE802.11n, comprising the following steps: dividing the received signal into an upper sideband signal and a lower sideband signal respectively with the bandwidth of 20 MHz if the bandwidth of the received signal is 40 MHz; performing carrier sense on the upper sideband signal and the lower sideband signal simultaneously; performing the energy detection on the upper sideband signal and the lower sideband signal simultaneously; and giving the idle instructions of the upper sideband channel and the lower sideband channel if an effective carrier signal is sensed in the set carrier sense time window, otherwise respectively giving the status instructions of the upper sideband channel and the lower sideband channel according to the result of the carrier sense and the result of the energy detection. The method of the invention effectively realizes the multiple access and the conflict avoidance, and ensures the compatibility of the 802.11n to the protocols of other versions.
Description
Technical field
The present invention relates to a kind of wireless communication field, relate in particular to a kind of wireless channel idle-detection method based on IEEE802.11n.
Background technology
802.11n adopted the MIMO technology, it has not only improved carrier wave efficient, and has improved the stability of system greatly.802.11n when guaranteed performance promotes, also guaranteed (when carrier frequency is 2.4GHz, to comprise that IEEE 802.11b with the compatibility of previous version; When carrier frequency is 5.8GHz, comprise IEEE802.11a).
Because what 802.11n adopted is interactively communication mode, how to realize that therefore multiple access inserts and avoids conflict is to improve system effectiveness and the key point of making rational planning for.Detailed elaboration has been done to relevant control and mechanism in media interviews control (MAC) sublayer.Concise and to the point is described as, and any website in the network only just can send when detecting channel idle, if channel is for busy then do not send, only to receive.Judge channel whether mainly accomplished by the physical layer sounding channel by the free time.
Previous WLAN version (b), because the frame type that adopts is less, therefore as long as one or both in employing carrier sense or the energy measuring just can guarantee higher efficient.But because 802.11n not only will guarantee and the compatibility of previous version, but also introduced the 40M bandwidth, therefore needed to introduce new channel detection method efficiently.
According to the requirement of agreement IEEE802.11n, under the situation that adopts the 40Mhz bandwidth, provide the channel idle indication of upper sideband (upper_band), lower sideband (lower_band) respectively.Adopt previous scheme just can't satisfy existing requirement like this, therefore press for a kind of advantages of simplicity and high efficiency wireless channel idle-detection method that finds.
Carrier sense utilizes correlation properties (comprising auto-correlation and cross-correlation etc.) judgement to obtain normally according to the characteristics that receive signal.When carrier frequency is 2.4GHz, the signal that IEEE802.11n need receive comprise 802.11n, 802.11b in all signals, simultaneously comprise 20M and two kinds of bandwidth of 40M among the IEEE802.11n, so will intercept all signals that comprise.
Summary of the invention
The wireless channel idle-detection method that the object of the invention is to provide a kind of effective realization multiple access to insert and avoid conflict.
In order to achieve the above object, the technical scheme of the present invention's employing is: a kind of wireless channel idle-detection method based on IEEE802.11n, it comprises the steps:
Step (1): when being 40MHz, be upper side band signal and lower sideband signal with the division of signal that receives, and upper and lower sideband signals bandwidth respectively is 20MHz as if the reception signal bandwidth;
Step (2): simultaneously upper side band signal and lower sideband signal are carried out carrier sense respectively, judge whether to listen to the effective carrier signal of DSSS or OFDM;
Step (3): simultaneously upper side band signal and lower sideband signal are carried out energy measuring respectively, provide the energy value of upper and lower sideband simultaneously;
Above-mentioned steps (2) is carried out with step (3) simultaneously;
Step (4): if in the time window of the carrier sense of setting, do not listen in effective carrier signal and the step (3) in the energy measuring window of setting the energy value of upper and lower sideband in the step (2) all less than preset threshold; Then provide the idle indication of upper and lower sideband channel, otherwise provide upper and lower sideband channel state indication respectively according to the result of carrier sense and the result of energy measuring.
In the step (1), when being 20MHz, then this reception signal is carried out energy measuring and carrier sense simultaneously, provide the channel status indication according to the result of carrier sense and the result of energy measuring as if the signal bandwidth that receives.
In the step (1), the division of described upper and lower sideband signals realizes through the method for frequency translation and LPF cascade.
In the step (4), greater than preset threshold, energy value and the ratio relation between them according to the last lower sideband that obtains provides upper and lower sideband channel state indication simultaneously then as if the energy that detects upper sideband or lower sideband signal.
Described carrier sense and energy measuring all are preset with time window.
The time window of described energy measuring is less than the time window of carrier sense.
In the step (2), be under the situation of 2.4GHz in carrier frequency, the effective carrier signal that need intercept comprises the short targeting signal of targeting signal (DSSS modulation system), IEEE802.11g/n (OFDM modulation) of IEEE802.11b; In carrier frequency is under the situation of 5.8GHz, and the effective carrier signal that need intercept comprises IEEE802.11a/n (OFDM modulation).
The present invention is the upper and lower sideband signals that is respectively 20MHz through receiving division of signal, and upper and lower sideband signals is carried out energy measuring and carrier sense respectively detect, and the energy measuring of each sideband and carrier sense are carried out simultaneously; Energy measuring is relatively more responsive to strong signal, and carrier sense is mainly intercepted fainter signal, through both Combined application; Make full use of its advantage separately; Reduced false drop rate and loss, improved the detectivity of system simultaneously, the assurance system only sends when channel idle; When channel busy; Just begin to receive valid data, realized that effectively multiple access inserts and conflict is avoided, guaranteed the compatibility of 802.11n and other release protocol.
Description of drawings
Accompanying drawing 1 is wireless channel idle-detection method theory diagram of the present invention;
Accompanying drawing 2 is carrier sense structural representation of the present invention;
Accompanying drawing 3 is wireless channel idle-detection practical implementation flow chart of the present invention.
Embodiment
To combine accompanying drawing below, execution mode preferred for this invention will be elaborated:
As shown in Figure 1, wireless channel idle-detection method of the present invention may further comprise the steps:
At first, if the signal bandwidth that receives is 40MHz, will receive division of signal is upper side band signal and lower sideband signal, and upper and lower sideband signals bandwidth respectively is 20MHz.The method that adopts is frequency translation and LPF cascade, and the signal that is about to receive makes progress, behind downshift 10MHz, carries out again LPF respectively.Illustrate, if the sampling clock frequency that this system adopts is f
SampleMHz, the signal that order receives is r
x(n), the upper side band signal after the frequency displacement is r
Hb(n), r then
Hb(n)=r
x(n) * exp (j* (10*n/f
Asmple) * 2*pi).In like manner making the lower sideband signal after the frequency displacement is r
Lb(n), can get r
Lb(n)=r
x(n) * exp (j* (10*n/f
Sample) * 2*pi).The impulse response of supposing low pass filter is h (n), and the upper side band signal of process filtering is r
h(n), r then
h=conv (r
Hb, h).Order in like manner is r through the lower sideband signal of filtering
l, can get r
l=conv (r
Lb, h).There is different requirement in different systems to filter, and therefore, the performance of filter will satisfy the requirement of system;
Then, last lower sideband signal is carried out carrier sense and energy measuring respectively, and the carrier sense of each sideband and energy measuring are carried out simultaneously.The detailed process of carrier sense is as shown in Figure 2, and this module comprises DSSS carrier sense and two major parts of OFDM carrier sense.For DSSS carrier sense employing is to carry out relevant with known frequency expansion sequence.The local sequence that present embodiment adopts is [1-1 1 1-1 11 1-1-1-1], carries out relevantly with this this locality sequence the signal that receives successively, and correlation is taken absolute value.If the signal that receives is the DSSS signal; Then peak value will periodically occur; The absolute value of the correlation through adopting a plurality of cycles adds up to reduce The noise; Judge according to two kinds of threshold values of correlated results employing of the one-period length (i.e. 11 correlated results) that obtains then, that is: when the peak value of correlated results greater than the peak-to-average force ratio of preset threshold value and correlation greater than the threshold value that presets, then think to listen to the DSSS signal; Carrier sense for ofdm signal; To short leading characteristics, repeat to form by 10 identical short sequences because weak point is leading, therefore every autocorrelation value at a distance from a short sequence time delay has consistency preferably; The present invention utilizes it to postpone relevant characteristics; Have the very characteristics of minor swing according to short leading autocorrelation value, if the difference of the maximum that obtains one group of correlation and minimum value less than the product of minimum value and setting threshold, and the absolute value of minimum value is greater than the signal strength threshold of setting; Then think and listen to short targeting signal, i.e. valid data signal.Energy measuring also adopts two types of threshold values, and promptly the ratio threshold value of energy threshold value and two sideband energies judges whether each sideband is idle; One of them threshold value is the absolute value of the energy of each sideband; When two sidebands simultaneously when busy, then to introduce second threshold value, the threshold value of the ratio of energy value that promptly energy is little in two sidebands and big energy value; In the signal that receives; The ratio of the energy value of more low-yield sideband and the energy value of energy larger skirt band is then thought and is gone up lower sideband simultaneously for busy, otherwise think and have only the bigger sideband of energy for busy during greater than preset threshold.
If when the signal bandwidth that receives is 20MHz, then this reception signal is carried out energy measuring and carrier sense simultaneously, provide the channel status indication according to the result of carrier sense and the result of energy measuring.
From the result of above-mentioned energy measuring and carrier sense, just can adopt the idle condition of channel and shown in Figure 3ly to have judged that Fig. 3 just detects state of a control figure to the upper sideband channel idle and is illustrated, the state of a control that the lower sideband channel idle detects is similar with it.Suppose and need to send data this moment, through the upper sideband energy measuring with intercept detection, detected energy or carrier wave arranged, can judge the upper sideband channel busy so, can not send data through this channel; Otherwise the upper sideband channel is idle, can send data.
When channel idle, as long as system detects energy or listens to effective carrier wave, channel just becomes busy; When busy,, a time window is set at channel, only in this time window, channel was set for idle just not only detected but also intercepted less than signal less than energy in order to guarantee higher accuracy.The time window size can be set according to concrete system requirements.Generally, the time window of energy measuring is usually less than the time window of carrier sense.Therefore, among the present invention, carrier sense just just plays a role when energy measuring can't detect signal usually, has so not only reduced loss, false drop rate, has also improved detectivity simultaneously.
The advantage that the present invention has is: 1) lower false drop rate and loss; 2) improved the detectivity of system.This invention can be used for the circuit of the similar wireless communication system of 802.11n and the channel idle of device detects.
The software that can adopt that this invention is described is realized, also can adopt hardware to realize.According to said disclosed embodiment, can be so that those skilled in the art can realize or use the present invention.Be understood that for those skilled in that art and can make the change on various forms and the details within the scope of the present invention.Above-described embodiment is merely preferred embodiment of the present invention, and is in order to restriction the present invention, not all within spirit of the present invention and principle, any modification of being done, is equal to replacement, improvement etc., all should be within protection scope of the present invention.
Claims (6)
1. wireless channel idle-detection method based on IEEE802.11n, it is characterized in that: it comprises the steps:
Step (1): when being 40MHz, be upper side band signal and lower sideband signal with the division of signal that receives, and upper and lower sideband signals bandwidth respectively is 20MHz as if the reception signal bandwidth;
Step (2): simultaneously upper side band signal and lower sideband signal are carried out carrier sense respectively, judge whether to listen to the effective carrier signal of DSSS or OFDM;
Step (3): simultaneously upper side band signal and lower sideband signal are carried out energy measuring respectively, provide the energy value of upper and lower sideband simultaneously;
Above-mentioned steps (2) is carried out with step (3) simultaneously;
Step (4): if in the time window of the carrier sense of setting, do not listen in effective carrier signal and the step (3) in the energy measuring window of setting the energy value of upper and lower sideband in the step (2) all less than preset threshold; Then provide the idle indication of upper and lower sideband channel; Otherwise provide upper and lower sideband channel state indication respectively according to the result of carrier sense and the result of energy measuring: greater than preset threshold, energy value and the ratio relation between them according to the last lower sideband that obtains provides upper and lower sideband channel state indication simultaneously then as if the energy that detects upper sideband or lower sideband signal.
2. the wireless channel idle-detection method based on IEEE802.11n according to claim 1; It is characterized in that: in the step (1); When if the signal bandwidth that receives is 20MHz; Then this reception signal is carried out energy measuring and carrier sense simultaneously, provide the channel status indication according to the result of carrier sense and the result of energy measuring.
3. the wireless channel idle-detection method based on IEEE802.11n according to claim 1 is characterized in that: in the step (1), the division of described upper and lower sideband signals realizes through the method for frequency translation and LPF cascade.
4. the wireless channel idle-detection method based on IEEE802.11n according to claim 1, it is characterized in that: described carrier sense and energy measuring all are preset with time window.
5. the wireless channel idle-detection method based on IEEE802.11n according to claim 4, it is characterized in that: the time window of described energy measuring is less than the time window of carrier sense.
6. the wireless channel idle-detection method based on IEEE802.11n according to claim 1; It is characterized in that: in the step (2); In carrier frequency is under the situation of 2.4GHz, and the effective carrier signal that need intercept comprises the targeting signal of the IEEE802.11b under the DSSS modulation system, the short targeting signal of IEEE802.11g/n under the OFDM modulation; In carrier frequency is under the situation of 5.8GHz, and the effective carrier signal that need intercept comprises the IEEE802.11a/n under the OFDM modulation.
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| CN102957504B (en) * | 2011-08-31 | 2015-11-25 | 北京中电华大电子设计有限责任公司 | A kind of 802.11n band receiver of base lower sideband determination methods and device |
| US9179409B2 (en) * | 2012-12-03 | 2015-11-03 | Qualcomm Incorporated | Multiple access scheme for narrowband channels |
| JP2014230110A (en) * | 2013-05-23 | 2014-12-08 | Kddi株式会社 | System, program and method for radio terminal to find access point |
| JP6689209B2 (en) * | 2015-01-26 | 2020-04-28 | シャープ株式会社 | Terminal device and base station device |
| GB2539693B (en) * | 2015-06-24 | 2019-06-19 | Canon Kk | Emission of a signal in unused resource units to increase energy detection of an 802.11 channel |
| CN105392201B (en) * | 2015-11-06 | 2019-05-17 | 珠海全志科技股份有限公司 | A kind of bandwidth determination method and device based on 802.11n |
| CN106101872A (en) * | 2016-08-04 | 2016-11-09 | 黎辉 | A kind of hybrid indoor talkback unit |
| CN113541830B (en) * | 2020-04-17 | 2022-09-23 | 大唐移动通信设备有限公司 | Idle channel detection method and device, electronic equipment and storage medium |
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