A method for reverse scattering network uplink and downlink rate adaptation

Abstract

The present application relates to the technical field of data communication, in particular to a kind of reverse scattering network uplink and downlink rate adaptive method;Utilize the change of RSSI and phase value and the frequency modulation of channel occurrence carry out mobility detection;Channel estimation is completed based on filter-based channel detection and lossrate estimation;Rate adaptation is carried out to uplink and downlink;In the present application, RSSI value, the change of phase value and the frequency modulation of channel occurrence are used as detection trigger;The selection command in the protocol is introduced to design filter-based detection scheme, which avoids collision in MAC, reduces detection time and improves channel detection accuracy;According to the channel condition obtained by detection, rate adaptation is carried out to uplink and downlink, which greatly improves system throughput.

Description

Technical Field

[0001] This invention relates to the field of data communication technology, and specifically to an adaptive method for uplink and downlink rates on a backscatter network. Background Technology

[0002] Backscatter communication networks have attracted widespread attention and developed rapidly, characterized by small node size, low power consumption, and sensing and computing capabilities. While the volume and diversity of sensed data on nodes have increased significantly, system throughput remains low when transmitting large amounts of continuous data. Because backscatter nodes cannot sense each other, collisions occur when multiple tags transmit data simultaneously. Furthermore, low channel detection accuracy leads to a mismatch between uplink and downlink data transmission bit rates and channel conditions, missing opportunities for rate adaptation to improve throughput. Therefore, designing an effective rate adaptation mechanism is crucial for improving system throughput. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a backscatter network uplink and downlink rate adaptation method that uses selection commands in the protocol to complete channel detection and simultaneously performs uplink and downlink rate adaptation to improve system throughput.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] An adaptive method for uplink and downlink rates on a backscattering network, including

[0006] Mobility detection is performed by utilizing changes in RSSI and phase values, as well as frequency modulation of the channel.

[0007] Channel estimation is completed using filter-based channel probing and loss rate estimation;

[0008] Use the protocol's built-in select command to create a filter for probing; the MASK in the protocol's select command has the ID of the tag that needs to transmit data. Before the three-way handshake with the tag, the tag to be transmitted is marked, the tag's state is changed, and communication is only with the marked tag.

[0009] Uplink and downlink rates are adaptively adjusted. Based on the channel quality obtained from the probe, the downlink rate is adjusted by adjusting the Tair value. The coding scheme and transmission rate of the downlink are adjusted by the obtained RSSI value. A rate mapping diagram of RSSI value and loss rate is obtained.

[0010] Furthermore, the phase value is the first metric used to measure the distance between the reader and the tag;

[0011] The relationship between distance and phase is shown in Formula 1, where θ is the phase value and λ is the wavelength. D θ R θ M The phase error is caused by tag and antenna diversity, reflection characteristics and multipath respectively, N is an integer ambiguity, and the measured phase is the period π;

[0012]

[0013] The distance between the two positions is approximately ΔR;

[0014]

[0015] Set threshold θ th =0.33 detects fluidity, determines that N is the same for two consecutive phases, and the phase rotation between the two phases is less than π.

[0016] Furthermore, when the read rate is below a threshold, RSSI is used as a second metric, and the RSSI is... th Set its threshold at 1.

[0017] Furthermore, if the current channel is good, select the next channel within the current channel to probe; if the first probed channel is good, keep it; otherwise, switch to another channel that is far away from the probe.

[0018] Channel gap set to h g =3 and h b =5, and set the threshold to 5 reads / s.

[0019] Furthermore, the loss rate is estimated using Formula 3;

[0020]

[0021] Where r l It is the estimated loss rate, p rec p is the number of data packets received within that time interval. rob It is the number of data packets detected within a time interval.

[0022] Furthermore, the time cost of the channel detection process is as shown in Formula 4, where t p The total detection cost of a tag, t prb It is the time cost of a single probe data packet, t rec It represents the time cost of receiving a single packet; td represents the composite built-in protocol delay; the unknown object is p. prb and t d ;

[0023] t p =pprb *t prb +p rec *t rec +t d Formula 4

[0024] Obtain several delay information parameters constructed in the protocol, including T1, T2, and T4;

[0025] After the query command, mark the waiting time as T1;

[0026] If there is a reply from the tag, the reader must acknowledge it within the return time, which is T2;

[0027] The time that the reader must wait before issuing another command is T4, and the length of T4 is 2RTcal, where RTCal = 0length + 1length;

[0028] Furthermore, the range of T2 is [3Tpri, 20Tpri].

[0029] Furthermore, the protocol is the C1G2 protocol.

[0030] Furthermore, experiments were conducted on this mapping under different environments to refine the boundaries in the rate mapping graph and further improve the system throughput.

[0031] The beneficial effects of this invention are as follows: This invention utilizes changes in RSSI value and phase value, as well as the phenomenon of frequency modulation in the channel, as detection triggers; it introduces a filter-based detection scheme based on the selection command in the protocol, which avoids collisions in MAC, reduces detection time, and improves the accuracy of channel detection; based on the detected channel conditions, it simultaneously performs rate adaptation for uplink and downlink, which greatly improves the system throughput. Detailed Implementation

[0032] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments.

[0033] Example 1

[0034] An adaptive method for uplink and downlink rates on a backscattering network, including

[0035] 1. Mobility detection using changes in RSSI and phase values, as well as frequency modulation of the channel.

[0036] a. Phase value is an effective measure of the distance between the reader and the tag. The relationship between distance value and phase is as follows, where θ is the phase value and λ is the wavelength. D θ R θ MThe phase errors are caused by tag and antenna diversity, reflection characteristics, and multipath propagation, respectively. N is an integer ambiguity because the measured phase is a period of π.

[0037]

[0038] Therefore, the distance between the two positions is approximately ΔR.

[0039]

[0040] A threshold (ΔR) is used to detect mobility. It is assumed that when the label is stationary, the phase measurements are highly concentrated, with a variance of only 2.2° and a difference of only 19° (0.33 radians) between the minimum and maximum values, corresponding to only 0.8 cm. Therefore, a threshold θ is set. th =0.33. To ensure that N is the same for two consecutive phases, the phase rotation between the two phases should be less than π.

[0041] b. When the read rate falls below this threshold, it may generate false negative alerts. To reduce these alerts, RSSI is used as a second metric, and the RSSI is adjusted accordingly. th The threshold is set at θ = 1, which is the granularity of RSSI from the COTS reader. Therefore, the mobility detection works as follows: First, it checks if the phase difference is greater than θ. th If so, mark it as a positive position change; otherwise, check if the RSSI difference is greater than the RSSI. th If it is greater than, it is positive; otherwise, it is negative.

[0042] The C1G2 protocol defines that a reader can only remain on one channel within a single time window. Channel quality may change due to frequency modulation (FM), thus providing an opportunity to adjust the rate after FM modulation occurs. FM modulation is performed using the correlation between channels. If the current channel is good, the next channel within the current channel is selected for probing; if the first probed channel is good, it remains so; otherwise, it switches to another channel farther away from the probed channel. The channel gap is empirically set to h. g =3 and h b =5. To determine whether a channel is good or bad, a very conservative threshold of 5 reads / s is used. The rationale for this setting is that a sharp transition is observed between high and low loss rates.

[0043] 2. Channel estimation is completed using filter-based channel sensing and loss rate estimation.

[0044] a. Use the built-in selection command in the C1G2 protocol to create a filter for detection. Before the reader transmits data to the tag, the target tag for the data transmission should be known in advance. Even if the sensor ID is not known beforehand, there is always an ID transmission phase before the reader transmits data to the tag, so it is assumed that all tags for data transmission are known in advance. The MASK in the C1G2 selection command contains the ID of the tag to be transmitted. Before the three-way handshake with the tag, the tag to be transmitted is marked, changing the tag's state from A to B or from B to A. In this way, during data transmission, communication is only with the marked tag, greatly reducing the probability of collisions and improving the effectiveness of channel detection.

[0045] b. After effective detection, loss rate is estimated. The loss rate is typically estimated using the following method, where r... l It is the estimated loss rate, p rec p is the number of data packets received within that time interval. rob It is the number of data packets detected within a time interval.

[0046]

[0047] The time cost of the detection process is as follows, t p The total detection cost of a tag, t prb It is the time cost of a single probe data packet, t rec td is the time cost of receiving a single packet, and td is the composite built-in protocol delay. The unknown object is p. prb and t d .

[0048] t p =p prb *t prb +p rec *t rec +t d Formula 4

[0049] Certain delays need to be identified within the protocol. The first specified time limit, T4, is the time the reader must wait before issuing another command. T4 has a length of 2RTcal, where RTCal = 0length + 1length. After a query command, the tag needs to wait for T1 (the time between the reader issuing the query and the tag returning the RN16 value, or the time between the reader issuing the ACK and the tag returning the PC, EPC, and CRC), with a nominal value of MAX(RTCal, 10Tpri), where Tpri = 1 / BLF. If there is a response from the tag, the reader must acknowledge it within T2 (the time between the tag returning the RN16 and the reader issuing the ACK, or the time after the tag returns the PC, EPC, and CRC), ranging from [3Tpri, 20Tpri]. T1 and T2 also apply to ACK and EPC messages. Using the precise timing structure specified in the C1G2 protocol ensures compatibility with commercial readers without requiring additional hardware, while also providing accurate loss rate detection.

[0050] 3. Adaptive rate control for uplink and downlink

[0051] Based on the channel quality obtained from the probe, the downlink rate was adjusted by changing the Tair values ​​(6.25, 12.5, 25). The downlink coding scheme and transmission rate were then adjusted based on the obtained RSSI values. An empirical rate mapping diagram between RSSI values ​​and loss rate can be derived. However, the boundaries of this mapping diagram are not clear enough. Extensive experiments were conducted in different environments to refine the boundaries of the mapping diagram and further improve system throughput.

[0052] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for adaptive uplink and downlink rates on a backscattering network, characterized in that, include Mobility detection is performed by utilizing changes in RSSI and phase values, as well as frequency modulation of the channel. Channel estimation is completed using filter-based channel probing and loss rate estimation; Use the protocol's built-in select command to create a filter for probing; the MASK in the protocol's select command has the ID of the tag that needs to transmit data. Before the three-way handshake with the tag, the tag to be transmitted is marked, the tag's state is changed, and communication is only with the marked tag. Uplink and downlink rates are adaptively adjusted. Based on the channel quality obtained from the detection, the downlink rate is adjusted by adjusting the Tair value. The coding scheme and transmission rate of the downlink are adjusted by the obtained RSSI value. A rate mapping diagram of RSSI value and loss rate is obtained. in, Phase value is the primary metric for measuring the distance between the reader and the tag; The relationship between distance and phase is shown in Formula 1, where θ is the phase value and λ is the wavelength. D θ R θ M The phase error is caused by tag and antenna diversity, reflection characteristics and multipath respectively. N is an integer ambiguity because the measured phase is a period of π. Therefore, the distance between the two positions is approximately ΔR; A threshold (ΔR) is used to detect fluidity. It is assumed that when the label is stationary, the phase measurement is highly concentrated with a variance of only 2.2° and a difference of only 19° (0.33 radians) between the minimum and maximum values, which corresponds to only 0.8 cm. Therefore, a threshold of 0.33 is set to determine that the N of two consecutive phases is the same and the phase rotation between two phases is less than π. in, When the read rate is below a threshold, RSSI is used as a second metric, and in RSSI th =1 sets its threshold, which is the granularity of RSSI from the COTS reader; in, If the current channel is good, select the next channel within the current channel to probe; if the first probed channel is good, keep it; otherwise, switch to another channel that is far away from the probe. Channel gap set to h g =3 and h b =5, and set the threshold to 5 reads / s; Where hg=3 is the frequency hopping interval when the channel is good, and hb=5 is the frequency hopping interval when the channel is bad; The loss rate is estimated using Formula 3. Where r l This is the estimated loss rate, and the time interval is the time interval used for each loss rate estimate, p. rec p is the number of data packets received within that time interval. pob It is the number of data packets detected within a time interval.

2. The adaptive method for uplink and downlink rates on a backscattered network according to claim 1, characterized in that, The time cost of the channel detection process is given by Formula 4, where t p The total detection cost of a tag, t prb It is the time cost of a single probe data packet, t rec It represents the time cost of receiving a single packet; td represents the composite built-in protocol delay; the unknown object is p. prb and t d ; t p =p prb *t prb +p rec *t rec +t d Formula 4 Obtain several delay information parameters constructed in the protocol, including T1, T2, and T4; After the query command, mark the waiting time as T1; If there is a reply from the tag, the reader must acknowledge it within the return time, which is T2; The reader must wait for T4 hours before issuing another command. The length of T4 is 2RTcal, where RTCal = 0length + 1length, and 0length and 1length are the bit durations of symbol 0 and symbol 1 in the C1G2 protocol, respectively.

3. The adaptive method for uplink and downlink rates on a backscattered network according to claim 2, characterized in that, The range of T2 is [3Tpri, 20Tpri], where Tpri is the reverse link frequency period of the C1G2 protocol, Tpri = 1 / BLF, and BLF is the reverse link frequency.

4. The adaptive method for uplink and downlink rates on a backscattered network according to any one of claims 1-3, characterized in that, The protocol in question is the C1G2 protocol.

5. The adaptive method for uplink and downlink rates on a backscattered network according to claim 1, characterized in that, Experiments were conducted on this mapping under different environments to refine the boundaries in the rate mapping graph and further improve the system throughput.

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