CN102045833B - A Synchronization Method for Communication Between Wireless Transceivers in Wireless Sensor Networks - Google Patents

Abstract

The invention discloses a host synchronization method applied in a wireless sensor network with layered or cluster features, a host node (or anchor node) and a low-power label node, and simplifies the communication circuit of the label node. The present invention makes the phase of the modulation signal received by the tag receiver consistent with the local phase through the process of feedback control between the host and the tag receiver, and requires very few times of feedback, and the tag node consumes very little energy. The invention also provides a two-step acquisition method, which can obtain higher acquisition speed without increasing the complexity of the tag receiver.

Description

A Synchronization Method for Communication Between Wireless Transceivers in Wireless Sensor Networks

technical field

The invention relates to a wireless sensor network, in particular to a synchronization method for communication between wireless transceivers.

Background technique

Wireless sensor network (WSN) technology provides long-term, large-scale, multi-location and large-capacity information collection, communication and processing. The wireless sensor network consists of tag sensor nodes and host nodes (or cluster nodes, anchor nodes). The tag nodes send sensing information to the master control point for information fusion through communication and network technologies. On the one hand, label nodes need to have efficient and real-time interactive communication means, on the other hand, sensor nodes are also required to maintain extremely low power consumption to ensure long-term maintenance-free work, and have a small size and complexity.

Most large-scale WSNs adopt a hierarchical or cluster structure, and the master control nodes in the cluster have strong communication and information processing capabilities. The sensor tag node mainly completes the function of information collection, and works in a low power consumption, or even a dormant state with extremely low power consumption. To realize node wake-up and interactive communication with it, under normal conditions, each tag node needs to have a complete wireless communication module. The extremely low-power wireless passive sensor network (WPSN) that only needs the transmission power of cluster nodes is favored by the field of sensor network research. It can provide the minimum communication power requirements for tag nodes in close range through the excitation of host radio frequency power, but it is still relatively low. Difficulty in communication distance, interactive communication, label node complexity and requirements on communication speed.

The processes of carrier capture, bit synchronization and network synchronization are the necessary conditions to complete the wireless sensor network data communication, and the accuracy of synchronization restricts the quality of signal detection. The current WSN adopts the passive acquisition method of the receiver commonly used in wireless communication, which has the advantages of fast acquisition speed and good synchronization accuracy, but its disadvantage is that the receiver is required to have a controllable clock (such as a numerically controlled oscillator NCO), or high-speed signal sampling and processing functions, which results in circuit complexity and higher power consumption.

In the WSN technical field, there are already many methods to reduce the power consumption of sensor nodes through upper-layer network technologies, such as optimal routing. However, this also brings about the problems of a large amount of interactive information and complex routing processing.

Contents of the invention

The purpose of the present invention is to propose a host node synchronization method different from the conventional wireless communication synchronization acquisition mechanism from the perspective of physical layer communication with extremely low complexity and power consumption, and provide a two-step acquisition algorithm for fast synchronization acquisition .

Considering that a large number of tag sensor nodes in WSN do not need high-speed synchronous capture and communication, and it is bursty small amount of data communication, at the same time, cluster nodes (or host nodes, anchor nodes) of WSN do not need to consider power consumption too much And complexity issues, and have a complete, conventional wireless transceiver function, there is a strong signal detection performance, while the tag node is the opposite. For this unbalanced link, the present invention adopts a host synchronization method with feedback to realize the communication from the host to the label node.

The synchronization method for communication between wireless transceivers of the present invention includes a host end, a receiver end, and a wireless transceiver device, and the host end is provided with pulse generation circuits A, A that can generate narrow pulses and waveform signals capable of finely distinguishing phases Then connect the radio frequency amplification and transmitting antenna, before the pulse generating circuit A, connect the phase control functional unit B and the phase step search algorithm functional unit C that can perform sequentially increasing, sequentially decreasing, fixed or variable step phase search algorithms , and a wireless receiving unit F for receiving the feedback confirmation signal; the receiver end is provided with a phase detector D which can perform correlation or non-correlation pulse signal detection and threshold comparison, and the phase detector D connected after the phase detector D can pass the feedback through a wireless link A feedback circuit E through which the confirmation signal is transmitted, and a radio frequency amplifier and a transmitting antenna are set in the feedback circuit E.

Among them, the host end refers to a transmitter, an anchor node or a base station with strong communication and processing capabilities and high energy allocation; the phase control functional unit B is a voltage-controlled oscillator, a controllable delay line or a numerically controlled oscillator. The receiver end refers to a wireless receiver, tag or sensor node with simple communication detection capability and modulation transmission capability; phase detector D is a matched filter, differential detector, envelope detector or energy detection device.

The search algorithm functional unit C adopts a two-step search process, the first step uses a large pulse width T ₁ for rough synchronization, and the second step changes the pulse width to T _p within the locked large pulse width range, T _p = T ₁ , A capture search of the same process is carried out in the T ₁ range.

Assume that the wireless transceivers have the same pulse signal period T and pulse width T _p . Using the general principle of feedback synchronous acquisition, such as phase-locked loop, the difference is that only the phase detector is used to complete the phase detection function of the signal at the receiver side, and the error signal processing and periodic pulse phase adjustment are transferred to the host side ( The host node of the WSN) to complete, the feedback of the phase detection signal is transmitted wirelessly, and is received by the receiving unit in the host end. As long as less feedback is required, the power consumption of the receiving end machine can be guaranteed to be small.

The invention relates to a synchronization method for communication between wireless transceivers in a wireless sensor network. Various periodic pulse modulation signals, such as TH-PPM and PAM modulation, can be used in specific implementation.

The basic principle and process of host synchronization acquisition proposed in the present invention can be described by this iterative difference equation.

In order to reduce the synchronous capture time of the host, the present invention further proposes a two-step host capture method, the capture process of which is the same as the single-step method. The first step is to use a large pulse width T ₁ for rough synchronization, and the second step is to change the pulse width to T _p within the locked large pulse width range, T _p = T ₁ , and perform the same process of capture search within the range of T ₁ . Using the principle of two-step capture is similar to the half-search, which can greatly improve the capture speed, and the complexity of the receiver side increases very little.

The invention has the advantages of simplifying the communication complexity of the physical layer of the receiver and reducing power consumption by transferring the signal processing and phase adjustment functions and circuits in the synchronization process to the host computer. This synchronization method is suitable for the communication of WSN label nodes with high requirements on volume and power consumption. The complexity and power consumption of the label node can be reduced through the physical layer technology.

Description of drawings

Fig. 1 is a connection block diagram of each functional module and a schematic diagram of wireless propagation channel propagation in the present invention.

Detailed ways

As shown in Figure 1. Among them, in the left box, the phase detector on the receiver side must detect the signal, and also includes a feedback signal transmitting unit, so the complexity has been reduced to the minimum; in the right box, the host side circuit includes Four modules: host wireless receiving unit, cycle counter triggered by feedback confirmation signal, numerically controlled oscillator (NCO) and periodic pulse generator. The two squares in the middle indicate the forward and reverse wireless propagation channels and the resulting delay. In the block diagram, the square connected to the host-side pulse generation circuit identifies the forward (host-to-receiver direction) channel and its propagation delay D _fwd , the block connected to the feedback confirmation transmitting unit in the receiver identifies the reverse (receiver to host direction) channel and its propagation delay D _fdbk , this delay can also be considered to include forward and reverse sending and receiving in principle The processing delay of each machine. In Figure 1, q(i) refers to the pulse signal phase received by the tag receiver at time i, and q ₀ refers to the local oscillator phase of the tag receiver.

The above feedback process block diagram can be expressed by a specific phase difference equation:

q(i)=q(i-1)+DqG[q(iD)-q ₀ ] (1)

$\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; T</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>& \mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; T</span>}<span\; class="notranslate">\; \&le;</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

The G(×) function in formula (1) is the gate function, and its expression is shown in (2); Dq is the phase step adjustment factor. It should be noted that the value of Dq not only affects the feedback capture loop accuracy, but also affects the stability of the loop. Under a certain loop delay D condition, a larger Dq will cause the loop to fail to enter the capture state. In formula (1), D is the sum of the forward propagation delay D _fwd from the host to the label node and the feedback delay D _fdbk of the label node, T _p is the extremely narrow pulse width, and T is the pulse signal period.

The host end is the host transmitter, and the pulse generation circuit A that can generate narrow pulses and waveform signals capable of finely distinguishing phases is set. After A, connect the radio frequency amplification and transmitting antenna (not shown in the figure), and sequentially before the pulse generation circuit A It is connected to the phase control functional unit B, the cycle count accumulator C that can be sequentially increased, decreased, fixed or variable step length search, and the wireless receiving unit F used to receive the feedback confirmation signal; the receiver end is a tag receiver, set A phase detector D that can perform correlation or non-correlation pulse signal detection and threshold comparison, and a transmission circuit E connected after the phase detector D that can transmit a feedback confirmation signal through a wireless link, wherein the E circuit includes a radio frequency amplifier And the transmitting antenna part (not shown in the figure).

Set the host transmitter and tag receiver to have pulse generators with the same period. Because the two-step host synchronization capture method is based on the single-step host synchronization scheme, the following first lists the implementation steps of the single-step host, and then lists the two-step capture process, but part of the content refers to the content of the single-step capture.

Single-step host synchronization:

(1) The host node transmits a periodic pulse signal to the tag node through the pulse generation circuit A through the wireless channel. The pulse phase is any initial phase of the host. The output pulse signal transmission of the pulse generation circuit A also implicitly includes the matching radio frequency Amplifying circuits and antennas, etc.;

(2) The phase detector D in the tag receiver node performs correlation detection on the received signal at any local oscillator phase, if the relevant sampling output is greater than a given amplitude threshold _AT ( _AT must be determined according to the actual strength of the received signal ), it means that the synchronization acquisition is completed, and the feedback confirmation signal is transmitted to the host node through the feedback confirmation signal transmitting circuit E through the reverse wireless channel. A _T , E in the tag receiver does not take any action;

(3) After the host node transmits multi-period pulse signals, and the receiving unit F does not receive the feedback confirmation signal, the cycle count accumulator C controls the numerical control oscillator B to increase or decrease the phase of the transmitted pulse signal, and adjust the step size is Dq (corresponding to T _Dq = DqT/2π≤T _p ), according to the newly adjusted phase, the pulse generation circuit A continues to emit periodic pulse signals;

(4) If the host node has not received the feedback yet, the phase Dq is sequentially incremented/decreased according to the working mode of each unit in (3), and the pulse generation circuit A continues to emit periodic pulses;

(5) When the host receiving unit F receives the feedback confirmation signal, the cycle counting accumulator C unit stops searching and calculating, so that the numerical control oscillator B stops adjusting the phase, and the current pulse phase output by the pulse generating circuit A in the host node is The phase position is synchronized, and the synchronization acquisition is completed. The host node can transmit information data to the target label node according to the phase modulation signal.

Two-step host synchronization capture:

(1) Let the minimum pulse adjustment phase step size be Dq, and the corresponding adjustment time delay be T _Dq . The pulse generating circuit A in the host node sets the transmitted pulse width as T ₁ ?T _p . Let q=T/T _Δθ , and q ₁ is the result of rounding up q, then it can be proved that when T ₁ =q ₁ ×T _Δθ can Get the minimum average capture duration. The cycle counting accumulator C of the phase search unit increments or decrements the pulse position step T ₁ (equivalent to the phase step Δθ ₁ =2πT ₁ /T) through the numerical control oscillator B and the pulse generation circuit A, and the search range is the pulse period T . The local correlation pulse width loaded on the phase detector D in the tag node is still T _p , and the capture process is the same as the above single-step capture;

(2) After the first step of capture is completed, the pulse generation circuit A and the digitally controlled oscillator B unit at the host end are in the capture lock state, and the phase is stable at q ₁ . The pulse generating circuit A in the host node resets the emission pulse width to T _p , and the digitally controlled oscillator B and the cycle count accumulator C are controlled to increment or decrement to adjust the phase step from Dq ₁ to Dq (corresponding to T _Dq = DqT/2π≤ T _p ), modify the search range from the entire period in the first step to [q ₁ , q ₁ +2πT ₁ /T], the relevant pulse width loaded by the phase detector D on the label node is still T _p , the capture process and Single step capture is the same. The host phase when the capture is completed, that is, the phase output by the pulse generating circuit A is the synchronous phase.

Claims (5)

1. The synchronous method of communication between the wireless transceivers in the wireless sensor network is characterized in that: the host end is provided with a pulse generation circuit A that can generate narrow pulses and waveform signals capable of finely distinguishing phases, after A is connected to radio frequency amplification and The transmitting antenna is sequentially connected with the phase control functional unit B and the phase step search algorithm functional unit C that can perform sequentially increasing, sequentially decreasing, fixed or variable step length phase search algorithms before the pulse generating circuit A, and is used to receive The wireless receiving unit F that feeds back the confirmation signal; the receiver is provided with a phase detector D that can perform correlation or non-correlation pulse signal detection and threshold comparison, and a phase detector D connected after the phase detector D that can transmit the feedback confirmation signal through a wireless link Feedback circuit E, radio frequency amplification and transmitting antenna are set in the feedback circuit E; The synchronization process includes: (1) The host terminal generates a periodic pulse signal with any initial phase through the pulse generating circuit A, and transmits it to the receiver terminal through the wireless channel; (2) The phase detector D in the receiver side performs correlation detection on the received signal at any local oscillator phase, if the sampling output is greater than a given amplitude threshold

, the synchronous acquisition is completed, and the feedback confirmation signal is transmitted to the host node through the reverse wireless channel through the feedback circuit E in the receiver; otherwise, if the sampling output amplitude is less than

, the feedback circuit E in the receiver end does not take any action; (3) Under the condition that the receiving unit F at the host end does not receive the feedback confirmation signal, the search algorithm functional unit C controls the phase control functional unit B to increment or decrement the phase of the transmitted pulse signal, and the adjustment step is

,correspond

, according to the newly adjusted phase and step size, the pulse generating circuit A continues to transmit the periodic pulse signal; (4) When the host receiving unit F receives the feedback confirmation signal, the search algorithm functional unit C and the phase control functional unit B stop working, and the current pulse phase output by the pulse generating circuit A in the host end is the synchronization phase position, and the synchronization is completed capture. 2. The synchronization method for communication between wireless transceivers in a wireless sensor network according to claim 1, characterized in that: the synchronization process step (3), specifically includes the following process: (1) Let the pulse position step size be

, the minimum pulse adjustment phase step size is

, and the corresponding adjustment delay is ,

,

yes

The result of rounding up, take

, the pulse generation circuit A in the host end sets the pulse width to be transmitted as Tp≤T1, the search algorithm function unit C controls the phase control function unit B, and the pulse generation circuit A increments or decrements to adjust the pulse position step size

, which is equivalent to the phase step , the search range is the pulse period

, the local correlation pulse width loaded on the phase detector D in the receiver is still

, for synchronous capture; (2) Then, the pulse generating circuit A and the phase control functional unit B at the host end lock the phase to be stable at

; The pulse generation circuit A in the host end resets the emission pulse width as

, the search algorithm functional unit C controls the phase control functional unit B to increment or decrement to adjust the phase step as

,correspond

, modifying the search range from the entire period T in the first step above to

, the relevant pulse width loaded by the phase detector D on the receiver side is still , for synchronous capture. 3. the method for synchronizing communication between the wireless transceivers in the wireless sensor network according to claim 1 is characterized in that: the host end refers to a transmitter with stronger communication and processing capabilities and higher energy allocation, An anchor node or a base station; the phase control functional unit B is a voltage-controlled oscillator, a controllable delay line or a numerically controlled oscillator. 4. the method for synchronizing communication between the wireless transceivers in the wireless sensor network according to claim 1 is characterized in that: the receiver end refers to a wireless receiver, a tag or a wireless receiver with simple communication detection capability and modulation emission capability Sensing node; phase detector D is a matched filter, differential detector, envelope detector or energy detection device. 5. according to claim 1 and the synchronous method of communication between wireless transceivers in wireless sensor network described in claim 2, it is characterized in that: search algorithm function unit C adopts two-step search process, and the first step adopts large pulse width

Perform coarse synchronization, the second step is within the locked large pulse width range, change the pulse width to

, Tp≤T1, at

Capture search for the same process within range.

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