WO2015078035A1

WO2015078035A1 - Method for self-learning of cross-frequency band power line communication frequency

Info

Publication number: WO2015078035A1
Application number: PCT/CN2013/088644
Authority: WO
Inventors: 刘伟麟; 布米勒•歌德; 杨冰; 陆阳; 高鸿坚; 李建岐; 陶锋; 赵涛
Original assignee: 国家电网公司; 中国电力科学研究院
Priority date: 2013-11-27
Filing date: 2013-12-05
Publication date: 2015-06-04
Also published as: CN103607222A; CN103607222B

Abstract

The present invention relates to a method for cross-frequency band power line communication, in particular to a method for self-learning of a cross-frequency band power line communication frequency. The frequency range applied in the method is 150 kHz-12 MHz. The method comprises: (1) determining a default working frequency set; (2) using a leading sequence to conduct a preselection in the default working frequency set, screening out default working frequencies incapable of correctly detecting the leading sequence, while using the default working frequencies capable of correctly detecting the leading sequence as potential working efficiencies; (3) at the potential working efficiencies, transmitting a control packet between a master station and a slave station to determine an optimal working frequency. The method of the present invention enables self-learning of the optimal frequency (a central frequency point and bandwidth) within a wide frequency spectrum range, so as to enable self-adaption to the frequency and data rate of a channel according to the actual channel condition, thus improving effectiveness, expanding the coverage area, and reducing human intervention.

Description

Self-learning method for cross-band power line communication frequency

The present invention relates to a method for cross-band power line communication, and more particularly to a self-learning method for cross-band power line communication frequency. Background technique

Power line communication (PLC) channels are complex and variable. Different from wireless communication systems, on the power line channel, the main power line channel characteristics such as attenuation and interference are closely related to the frequency. Specifically, the attenuation is closely related to the grid topology, cable material, link distance and so on. This frequency-dependent channel characteristic often does not change rapidly with time, it only changes with changes in network topology, such as the attenuation of the buried power line increases with frequency and distance, which also limits the Broadband PLC (BPL). The transmission distance. Narrowband PLCs (NPLCs) typically have lower attenuation and can transmit longer distances, whereas narrowband PLCs are heavily affected by noise (noise usually decreases exponentially with increasing frequency). A simple overhead power line has very low attenuation even at higher frequencies; however, if the overhead line is connected to a short buried line, the frequency selective attenuation due to reflection will become apparent. Usually a small frequency window that can be used for communication is present, but this frequency window may be closely related to the grid structure and cable material.

Therefore, due to the huge difference between network topology and deployment, we usually cannot know in advance which frequency band is the best. Therefore, the true best frequency band requires "online self-learning".

Leading-edge PLC technology can be divided into wideband PLCs (BPL) using bands above 2 MHz and use of narrowband PLCs below 500 kHz (NPLC Broadband PLC stands for OPERA (Open Powerline Communications Research Alliance) and B Home-Plug. ITU -TGhn is similar to OPERA technology, IEEE1901.1 uses most of Home-Plug technology. The narrowband PLC system is represented by PRIME and G3. All of these systems use pre-defined frequency bands. Some systems use only a single frequency band. For example, PRIME; while some systems have multiple working frequency bands, they need to define the working frequency band in advance. There are also some adaptive technologies in the working frequency band, such as adaptive bit loading according to the signal-to-noise ratio of OFDM subcarriers, so as to be adaptive. Adjust the data rate.

OPERA uses OFDM technology in the range of 2-34 megahertz, operating frequency bandwidths of 10 megahertz, 20 megahertz and 30 megahertz, and can also achieve a bandwidth of 5 megahertz by notch technology. However, right In low-voltage buried power line networks, cable attenuation and reflection due to impedance mismatch at the branch nodes can result in severe frequency selective attenuation, such that only a small frequency window (eg, less than 1 MHz) can be used for communication. In this case, OPERA with a minimum configurable bandwidth of 5 MHz may not work. In addition to the need for a frequency self-learning mechanism to identify this small frequency window that can be used for communication, OPERA can only use frequencies above 2 MHz and severely limits its use in long-haul networks. PRIME uses fixed frequency bands from 47 kHz and 89 kHz. For low-voltage networks, the access impedance in the low-frequency band is usually very small, and the noise caused by the household appliances is very high. Therefore, the inability to move the operating frequency band to higher frequencies is an important drawback of current PRIME designs. The G3 supports multiple frequency bands between 10 kHz and 500 kHz. However, it is also necessary to pre-define the working frequency band to be used, and the system cannot be adaptively operated. Similarly, since the frequency of G3 is limited to 500 kHz, the advantages of the high frequency band cannot be exerted in some noisy channel environments. In addition, in the application scenario where the attenuation is small, but the system delay and system bandwidth requirements are high, only PLC systems supporting the operating frequency above 2 MHz can meet the requirements.

Almost all PLC systems operate at a pre-set frequency. Typically a primary station node transmits a beacon on each frequency, allowing the secondary station to synchronize on its frequency and register with the network. However, due to complexity, the system often uses only one frequency at the same time, such as PRIME, G3, OPERA HOMEPUG, etc. Most PLC systems belong to the asynchronous packet switching network. In an asynchronous packet switched network, it is often necessary to add a reference signal at the beginning of the physical layer burst to detect the presence and start of burst packets. PRIME uses a chirp signal as the preamble sequence [7], and the Chirp signal has a good autocorrelation function. Other PLC systems, such as OPERA, HOMEPLUG, and G3, use known OFDM symbols as preamble sequences for timing and burst data synchronization. All of the above PLC systems are synchronized using a preamble sequence at a known operating frequency. None of the PLC systems use the preamble sequence for evaluation and pre-selection of multiple operating frequencies. Summary of the invention

In view of the deficiencies of the prior art, an object of the present invention is to provide a self-learning method for cross-band power line communication frequency, which can self-learn the optimal frequency (central frequency point and bandwidth) over a wide spectrum range. It is therefore possible to adapt its frequency and data rate to actual channel conditions, thereby increasing effectiveness, expanding coverage, and reducing human intervention. The object of the present invention is achieved by the following technical solutions:

The present invention provides a self-learning method for cross-band power line communication frequency, which is improved in that the method applies a frequency range of 150 kHz to 12 MHz, and the method includes the following steps:

(1) Determine the default working frequency group;

(2) Pre-selecting the default working frequency group by using the preamble sequence, screening the default working frequency of the leading sequence cannot be correctly detected, and correctly detecting the default operating frequency of the preamble sequence as the potential working frequency;

(3) At the potential operating frequency, the control packet is transmitted between the primary station and the secondary station to determine the optimal operating frequency. Further, in the step (1), the default working frequency group is selected from the following three frequency bands: a low frequency band of 150 kHz to 500 kHz, an intermediate frequency band of 500 kHz to 1.6 MHz, and a high frequency band of 1.6 MHz to 12 MHz; The default frequency bandwidth selected is less than the default frequency bandwidth selected in the high frequency band; the default frequency bandwidth is selected to be a multiple of each other.

Further, in the step (2), searching for an optimal frequency between two power line communication PLC nodes on the power line network; a node transmitting the reference signal is referred to as a primary station, and another node is referred to as a secondary station; The link to the slave is called the downlink, and the link from the slave to the master is called the uplink;

Preamble signals defined in the timing method of power line communication are used at each default frequency for initial synchronization and pre-selection of potential operating frequencies;

Defining a preamble slot including all default frequency group preamble signals, that is, a PRMBL time slot; including a preamble sequence of all default frequencies, all preamble sequences are located at determined time positions in the PRMBL time slot, and have no overlap; according to a predetermined The preamble sequence in the PRMBL slot is regularly arranged.

Further, arranging the preamble sequence in the PRMBL time slot according to a predetermined rule includes: first arranging a preamble sequence having a relatively small bandwidth and a relatively low frequency, and arranging the preamble sequence having a relatively large bandwidth and a relatively high frequency at a subsequent time position;

For a given frequency, the downlink and uplink use different preamble sequences for initializing the signals, the different preamble sequences being equal in length and having the same autocorrelation properties.

Further, in the step (2), the potential operating frequency includes a potential downlink operating frequency and a potential uplink operating frequency.

Further, determining the potential downlink operating frequency includes: the primary station transmits the PRMBL time slot at a fixed time interval on the downlink, and the secondary station starts scanning the preamble sequence at a certain default operating frequency. After a certain time (determined by the system frame structure, such as about 100 milliseconds), if the preamble sequence cannot be detected on the current frequency, switch to the next default frequency for detection; after all the default operating frequencies are scanned, if it still cannot be detected To the preamble sequence, and no other operational commands other than the scan preamble sequence operation are received, the slave continues to cycle to begin the scanning process;

If the slave successfully detects the preamble sequence on a certain default operating frequency, then with the downlink

The PRMBL time slot is synchronized, and timing information of all default operating frequencies is obtained. According to the timing information, the slave station will continue to evaluate the N consecutive PRMBL time slots to determine the potential downlink operating frequency; determining the potential uplink operating frequency includes: After the secondary station detects the downlink PRMBL time slot, the uplink PRMBL time slot is sent, and in time, the position of the uplink PRMBL time slot is connected with the position of the downlink PRMBL time slot; the primary station knows the occurrence time of the possible uplink PRMBL time slot; The primary station scans the upstream PRMBL time slots at known time positions; at the same time, the primary station evaluates the N uplink PRMBL time slots to determine the potential upstream operating frequency.

Further, in the step (3), the uplink and the downlink use the same potential working frequency, and the primary station negotiates with the secondary station and finally determines the optimal working frequency;

After the slave preselects and ranks the potential operating frequencies, the preamble sequence of the selected potential operating frequency is transmitted in the uplink PRMBL time slot, and then the control packet is sent to the primary station at the selected potential operating frequency; After the link PRMBL time slot is transmitted, the uplink PRMBL time slot is transmitted; after detecting the preamble sequence in the uplink PRMBL time slot, the primary station sequentially receives the control packet on the frequency of the detected preamble sequence, and successfully receives the slave station. After the control packet is sent, the primary station replies with the original corresponding frequency to confirm the reception.

Further, the control packet is sent by the optimal working frequency of the slave station, and if the slave station fails to receive the reception acknowledgement sent by the master station at the frequency, the frequency is switched to the next sorted suboptimal frequency until the slave station receives When the primary station returns a acknowledgment received signal at the same potential operating frequency as the secondary station, the handover is stopped; the same potential operating frequency that the primary station and the secondary station transmit the control packet is the final optimal operating frequency.

Further, the control packet includes a preamble sequence and control data; the preamble sequence is a preamble signal, and the control data is one or more OFDM symbols.

Further, the primary station does not have to send all the preamble sequences on the PRMBL time slot, that is, send the preamble sequence of the partial default operating frequency, and leave the unused default operating frequency position blank;

The self-learning method uses PRMBL time slots to reduce potential interference between adjacent power line communication networks Disturbance, the default frequency is divided into different subsets, and the frequencies between different subsets do not intersect; the main stations of different power line communication networks use non-overlapping frequency subsets in the corresponding PRMBL time slots to avoid interference generation. ;

The primary station chooses to send a preamble sequence of all default working frequency subsets to control the actual operating frequency used and optimize the operation of the network.

Compared with the prior art, the beneficial effects achieved by the present invention are:

The self-learning method for cross-band power line communication frequency provided by the invention can self-learn the optimal frequency (central frequency point and bandwidth) in a wide spectrum range, and thus can adapt its frequency and data rate according to actual channel conditions. Thereby increasing effectiveness, expanding coverage, and reducing human intervention. The present invention proposes to use a default frequency for the frequency self-learning process. Considering the channel characteristics of the power line, for the medium and low voltage access network, a preferred range of default frequencies is 150 kHz to 12 MHz, covering low, medium and high frequencies. In addition, the bandwidth of the default frequency increases as the frequency increases. By using the default frequency, on the one hand it is possible to provide a satisfactory operating frequency for most practical situations, and on the other hand it can reduce the complexity of frequency optimization. The PRMBL time slot concept proposed for initial frequency pre-selection has the following advantages:

1. If the preamble sequence of a certain frequency is not successfully detected, the frequency is not applicable to communication. Therefore, based on the evaluation of the preamble sequence, it is sufficient to exclude those frequencies that are not acceptable. In the PLC system proposed by the present invention, the default frequency may be selected from a wide frequency range, such as between 150 kHz and 12 MHz. Meanwhile, the characteristics of the power line channel vary significantly with frequency, so that short preamble signals can be used to quickly screen out those. The frequency that is not applicable will not be processed in the next step. This will significantly increase the speed of the frequency search process. The preamble sequence detection requires a small amount of processing and has significant advantages in reducing power consumption.

2. A PRMBL time slot with a fixed preamble position will provide valid default frequency timing information. If a PLC node detects a preamble sequence of a certain frequency, it will obtain timing information for the preamble sequences of all remaining frequencies. A PRMBL time slot can be used to process the preamble of all default frequencies for efficient frequency search processing.

3. The preamble sequence transmitted at a specific frequency within the PRMBL time slot can be used to convey signaling. For example, this feature will be used when the slave station performs an initial registration with the primary station. After the selected operating frequency, the slave can transmit only the preamble sequence of the frequency in the uplink PRMBL time slot and then transmit the control packet on the same frequency. Once the primary station detects a preamble sequence of a particular frequency, it is treated as a slave Order, and will further detect subsequent control packets on this frequency.

4. The master station transmits the preamble sequence in a specific frequency group within the PRMBL time slot, which can be further used to control the convergence time. The primary station first sends a small portion of the preamble sequence of the default frequency for the network to converge quickly. If there are still PLC nodes that are not covered by these frequencies, the primary station can add other frequencies to the PRMBL time slot in turn, thereby overwriting the remaining PLC nodes in the network. In most cases, a portion of the frequency is used to cover a PLC network. Only individual PLC nodes may experience poor link conditions, requiring additional frequencies.

5. The transmission of the preamble sequence at a specific frequency within the PRMBL time slot can be further used to reduce potential interference between adjacent PLC networks. The primary station of the adjacent PLC network may choose to transmit the preamble sequence on the mutually orthogonal frequencies within the PRMBL time slot, thereby avoiding possible interference between the networks. DRAWINGS

1 is a frequency coverage diagram of a self-learning method PLC system provided by the present invention;

2 is a schematic diagram of a control packet structure for a slave station to perform initial registration on a selected frequency according to the present invention;

3 is a schematic diagram of a default frequency preamble (PRMBL) slot structure provided by the present invention; wherein each preamble sequence is fixed in a PRMBL slot;

4 is a schematic diagram of an uplink and downlink initial frequency selection process based on a preamble sequence provided by the present invention; FIG. 5 is a frequency search process diagram when the uplink and downlink use the same frequency provided by the present invention; FIG. 6 is a cross-band power line provided by the present invention. Flowchart of a self-learning method of communication frequency. detailed description

The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

The invention provides a self-learning method with self-learning and self-selecting operating frequency according to channel conditions. Since the working frequency (center frequency and bandwidth) of the PLC system can be selected within a wide spectrum range, the PLC system is provided in each A different network environment and channel conditions adjust the operating frequency to ensure the possibility of normal operation. Without loss of generality, the frequency range commonly used for medium and low voltage access networks is 150 kHz to 12 MHz, covering the low frequency band of 150-500 kHz, the IF band of 500 kHz to 1.6 MHz, and the high frequency band of 1.6 MHz to 12 MHz (ie Cross-band). For PLC access networks in the preferred frequency range (eg 150kHz-12MHz), the present invention employs a new digital front end (DFE) design with high dynamic range, out-of-band interference rejection, and support OFDM signal configurations of different bandwidths (e.g., from 7.8 kHz to 10 MHz) are performed over a wide frequency range, such as 150 kHz to 12 MHz. The present invention uses preamble correlation/synchronization methods to pre-select in more likely operating frequencies, further narrowing the range of operating frequencies that can be used. The present invention has high requirements for the preamble sequence and its associated synchronization method. A preamble sequence and synchronization method can be used as a preference, using a variety of techniques to reduce the effects of strong impulse noise, narrowband interference, and multipath transmission.

The present invention is based on a set of default frequencies having different bandwidths selected from a wide frequency band, and the self-learning process for the optimal operating frequency is divided into two steps. The purpose of the first step is to quickly identify some of the possible operating frequencies in the more specified frequencies over a wide frequency range. This is based on the detection of the corresponding preamble sequence. This method includes a correlation operation between the received signal and the preamble sequence, and a series of signal processing operations for combating special phenomena such as impulse noise, narrowband interference, and multipath transmission in the power line channel. Only the frequency that successfully passed the preamble detection can proceed to the second step. In the second step, control data is exchanged between the PLC nodes at the selected frequency, and the operating frequency is finally determined.

In order to perform potential operating frequency pre-selection quickly and efficiently, the present invention proposes a concept called a preamble slot or a PRMBL slot. The PRMBL slot includes a preamble sequence of all default frequencies, and each preamble sequence is located at a designated fixed location in the slot. The primary station regularly sends PRMBL time slots so that the secondary stations can synchronize and detect preamble sequences of different frequencies. Since the time position is fixed, once the slave station detects the preamble sequence of a certain frequency, the timing information of all other preamble sequences can be obtained, so that it can be operated very efficiently on all frequencies that need to perform frequency preselection.

The PRMBL time slot can also be used for initialization signaling before the primary station establishes a data communication connection with the secondary station. The slave station may transmit a preamble sequence of the selected frequency in the PRMBL time slot of the uplink to inform the primary station to receive the control packet on the frequency in the next time interval. In order to make it work, the upstream PRMBL time slot should be sent at a point in time known to the primary station. When the primary station detects this preamble sequence transmitted by the secondary station, the primary station switches the receiver to the corresponding frequency for receiving the control packet of the secondary station. The slave sends a first registration request to the primary station on the preferred frequency in this way.

A flowchart of a self-learning method for cross-band power line communication frequency provided by the present invention is shown in FIG. 6, and includes the following steps: (1) Determine the default working frequency group;

The optimal operating frequency is selected from the default operating frequency group. The default working frequency can also be updated. For the PLC access network serving the smart grid, the default operating frequency group can be selected from the following three frequency bands: the low frequency band of 150 kHz to 500 kHz, the intermediate frequency band of 500 kHz to 1.6 MHz, and the high frequency band of 1.6 MHz to 12 MHz. Table 1 gives an example of a set of default operating frequencies, denoted fl, f2, f3, ..., whose operating bandwidth is decremented in turn, ie fl has the largest bandwidth, f2 has a bandwidth less than fl, and so on. At the same time, the default frequency bandwidth selected in the low frequency band is smaller than the default frequency bandwidth selected in the high frequency band. As an example, Table 1 shows the length of the preamble sequence at various default frequencies. Similarly, Table 1 also shows the length of time for the control packet containing the preamble sequence and an OFDM symbol. Table 1: Example of default frequency group

(2) Using the preamble sequence to pre-select the default working frequency group, the default operating frequency of the preamble sequence cannot be correctly detected, and the default operating frequency of the preamble sequence is correctly detected as the potential operating frequency; the present invention uses the preamble sequence and the preamble The sequence processing method performs initial timing synchronization and frequency pre-selection.

The present invention describes an optimal frequency search between two PLC nodes on a power line network. First, two PLC nodes must establish time synchronization with each other on one or more frequencies, so one node needs to be in one The reference signal is transmitted on one or more frequencies, and the other node performs a scan to detect the reference signal. For convenience of description, the present invention refers to a node that transmits a reference signal as a primary station, another node as a secondary station, and a link from a primary station to a secondary station as a downlink, a secondary station to a primary station. A link is called an uplink.

The master and slave need to search for and select the best operating frequency in the default operating frequency group. Since the default operating frequency group is selected over a wide frequency range, and the channel characteristics of the power line channel vary significantly with frequency, in general, not all frequencies in the default frequency group can be used. Communication. For example, for low-voltage power line networks that use buried cables and are more than 250 meters away, frequencies above 4 MHz may not be available. Therefore, in order to optimize the frequency search process, it is preferred to identify potential operating frequencies in the default frequency group and to screen out frequencies that cannot be used.

Both the master and slave are known to the default working frequency group. We define a time slot that includes the preamble signals of all default frequencies. The preamble sequences of each frequency are connected before and after and do not overlap. This time slot is called a PRMBL time slot. In principle, in PRMBL, preamble sequences of different frequencies can be arranged in any order; however, considering the need for fast synchronization and convergence, PRMBL time slots can be arranged starting from a preamble sequence of frequencies with a high probability of detection. Without loss of generality, preferably, the lower frequency, smaller bandwidth preamble sequence is arranged before the higher frequency preamble sequence of the higher bandwidth. Figure 3 shows an example of the arrangement of the preamble sequences in the PRMBL time slot, where the default operating frequency group uses the default frequency in Table 1. An important rule of the invention is that once the position of a certain preamble sequence in a PRMBL time slot is defined, this position cannot be changed regardless of whether the preamble of other frequencies is actually transmitted.

The present invention may employ different preamble sequences for initialization signaling on the downlink and uplink, but different preamble sequences must have the same length and the same autocorrelation properties.

Potential operating frequencies include potential downstream operating frequencies and potential upstream operating frequencies.

1 Determine the potential downlink operating frequency including:

The primary station sends PRMBL time slots at fixed intervals on the downlink, as shown in Figure 4. The slave then scans the preamble sequence at a certain default operating frequency. After a certain period of time (determined by the system frame structure, such as about 100 milliseconds), if the preamble sequence cannot be detected on the current frequency, then the switch to the next default is performed. Frequency is detected, and so on. After all the default operating frequencies have been scanned, if the preamble sequence is still not detected, the slave continues to loop to begin the scanning process if no commands are received for other operations.

If the slave successfully detects the preamble sequence on a certain frequency, it synchronizes with the downlink PRMBL time slot, thereby obtaining timing information of all default frequencies. According to this timing information, from The station will continue to evaluate the N consecutive PRMBL time slots to determine the potential downstream operating frequency.

2 Since the power line channel is not necessarily a symmetric channel, the optimal operating frequency of the downlink may be different from the optimal operating frequency of the uplink. The present invention also proposes a method for the primary station to select the uplink potential operating frequency. When the secondary station detects the downlink PRMBL time slot, it transmits an uplink PRMBL time slot. In time, the location of the upstream PRMBL slot is connected to the location of the downstream PRMBL slot. Therefore, the primary station knows the time of occurrence of possible upstream PRMBL time slots. Figure 4 shows a schematic diagram of the uplink PRMBL time slot following the downlink PRMBL time slot transmission. The primary station scans the upstream PRMBL time slot at a known time position. Similarly, the primary station also evaluates N upstream PRMBL time slots to determine the potential operating frequency of the uplink.

(3) At the potential operating frequency, the control packet is transmitted between the primary station and the secondary station to determine the optimal operating frequency: For the case where the same frequency is used for the uplink and the downlink, it is further proposed that the primary station negotiates with the secondary station and finally determines The working frequency scheme includes:

Let K be the number of potential operating frequencies obtained by the slave after evaluating the N downlink PRMBL time slots, and the K frequencies are sorted according to pre-defined criteria. The slave control station transmits a control packet to the primary station for registration request, and the control packet is composed of a preamble sequence and an OFDM symbol carrying control data. The structure of the control packet is shown in Figure 2. Once the control station successfully detects the control packet, it sends an acknowledgment packet signal to the slave station to confirm that the frequency requested by the slave station can be used. In order to inform the primary station which frequency to detect the control packet, the secondary station needs to transmit the preamble sequence on the selected frequency in the upstream PRMBL time slot. When the primary station scans at the known upstream PRMBL slot position and successfully detects the preamble on the selected frequency of the secondary station, the primary station will scan the control packet at that frequency after the upstream PRMBL time slot. If the primary station detects the control packet with a satisfactory signal quality, it sends a feedback acknowledgement packet to the secondary station during the next time interval. In terms of the slave station, when the control packet is transmitted on a certain frequency, the acknowledgement packet sent by the primary station is scanned on the frequency, and if it successfully receives the acknowledgement packet, the acknowledgement message is sent to the primary station. At this point, the frequency scanning process of the link is completed.

After a predefined time interval, if the master fails to synchronize with the slave at the optimal frequency, the slave will send the control packet to the primary station using the frequency of the sub-optimal order, and so on.

In the present invention, the primary station does not have to transmit all of the preamble sequences on the PRMBL time slot. As needed, the primary station can only send some of the default operating frequencies and leave other unused frequency locations blank. At this point, the slave will not be able to successfully detect the preamble sequence at these unused frequency locations. In fact, the slave does not need to know which primary frequencies the primary station is sending the preamble sequence, but only the frequency of the inability to detect the preamble sequence. It is only necessary for the channel conditions to be poor. It is worth noting that no matter which preamble sequence the master station actually sent,

The length of the PRMBL time slot and the position of the preamble sequence of all corresponding default frequencies should remain unchanged.

The master station can choose to send a preamble sequence of all subsets of the default frequency, which can easily and effectively control the actual operating frequency to optimize the operation of the network. For example, for a small network with good channel conditions, the primary station can first transmit a preamble sequence of wideband frequencies, such as 10 MHz, so that most nodes can quickly synchronize with the network. If not all slaves are able to access the network, the primary station will in turn add a preamble sequence of other default frequencies to the PRMBL time slot, enabling those slaves to find the primary station in the new frequency.

The present invention uses the PRMBL time slot concept to reduce potential interference between adjacent PLC networks. The default frequencies are divided into different subsets, and the frequencies between different subsets do not intersect. The main stations of different PLC networks use non-overlapping frequency subsets in the corresponding PRMBL time slots to avoid interference.

The present invention relates to a method for optimal frequency self-learning in the wideband/cross-band range (e.g., in the frequency range of 150 kHz to 12 MHz for most medium and low voltage access networks), mainly for Human intervention systems are highly reliable in terms of reliability, availability, and plug-and-play requirements for control and management applications, such as smart grid applications.

Finally, it should be noted that the above embodiments are only for explaining the technical solutions of the present invention and are not limited thereto, although the present invention will be described in detail with reference to the above embodiments, and those skilled in the art should understand that the present invention can still be The invention is to be construed as being limited by the scope of the appended claims.

Claims

Rights request

1. A self-learning method for cross-band power line communication frequency, characterized in that the frequency range applied by the method is 150kHz-12MHz, and the method includes the following steps:

(1) Determine the default operating frequency group;

(2) Use the preamble sequence to pre-select the default operating frequency group, filter out the default operating frequencies for which the preamble sequence cannot be detected correctly, and use the default operating frequency for which the preamble sequence is correctly detected as the potential operating frequency;

(3) At the potential operating frequency, control packets are transmitted between the master station and the slave station to determine the optimal operating frequency.

2. The self-learning method according to claim 1, wherein in step (1), the default working frequency group is selected from the following three frequency bands: a low frequency band of 150kHz to 500kHz, a medium frequency band of 500kHz to 1.6MHz frequency band and the high-frequency band from 1.6MHz to 12MHz; the default frequency bandwidth selected in the low-frequency band is smaller than the default frequency bandwidth selected in the high-frequency band; the default frequency bandwidths are selected as multiples of each other.

3. The self-learning method according to claim 1, wherein in step (2), the best frequency between two power line communication PLC nodes on the power line network is searched; the node that sends the reference signal is called the master station, another node is called a slave station; the link from the master station to the slave station is called a downlink, and the link from the slave station to the master station is called an uplink;

Use the preamble signal defined in the timing method for power line communications on each default frequency for initial synchronization and pre-selection of potential operating frequencies;

Define a preamble time slot that includes all preamble signals of the default frequency group, that is, the PRMBL time slot; which includes preamble sequences of all default frequencies, and all preamble sequences are located at determined time positions in the PRMBL time slot, and there is no overlap; according to the predetermined Preamble sequences in PRMBL slots are regularly arranged.

4. The self-learning method according to claim 3, wherein arranging the preamble sequences in the PRMBL time slot according to predetermined rules includes: first arranging the preamble sequences with relatively small bandwidth and relatively low frequency, and then arranging the preamble sequences with relatively large bandwidth and relatively low frequency. High leading sequences are ranked at later time positions;

For a given frequency, the downlink and the uplink use different preamble sequences for initialization signaling. The different preamble sequences have the same time length and the same autocorrelation characteristics.

5. The self-learning method according to claim 1, wherein in step (2), the potential operating frequency includes a potential downlink operating frequency and a potential uplink operating frequency.

6. The self-learning method according to claim 5, characterized in that: determining the potential downlink operating frequency The rate includes: The master station sends PRMBL time slots at fixed time intervals in the downlink, and the slave station starts scanning the preamble sequence on a certain default operating frequency. After a certain period of time, if the preamble sequence cannot be detected on the current frequency , then switch to the next default frequency for detection; after all default operating frequencies are scanned, if the preamble sequence still cannot be detected, and no other operation command other than scanning the preamble sequence is received, the slave station continues to cycle and start the scanning process;

If the slave station successfully detects the preamble sequence on a certain default operating frequency, it will synchronize with the PRMBL time slot of the downlink and obtain the timing information of all default operating frequencies. Based on the timing information, the slave station will continue to evaluate the subsequent N A continuous PRMBL time slot is used to determine the potential downlink operating frequency; Determining the potential uplink operating frequency includes: When the slave station detects the downlink PRMBL time slot, it sends the uplink PRMBL time slot, in time, the position of the uplink PRMBL time slot Connected to the location of the downlink PRMBL time slot; the master station knows the occurrence time of the possible uplink PRMBL time slot; the master station scans the uplink PRMBL time slot at a known time position; at the same time, the master station evaluates N uplink PRMBL time slots to determine the potential Uplink operating frequency.

7. The self-learning method according to claim 1, characterized in that, in the step (3), the uplink and the downlink use the same potential operating frequency, and the master station negotiates with the slave station and finally determines the best working frequency;

After the slave station pre-selects and sorts the potential operating frequencies, it sends the preamble sequence of the selected potential operating frequency in the uplink PRMBL time slot, and then sends a control packet to the master station on the selected potential operating frequency; while transmitting downlink The uplink PRMBL time slot is transmitted after the link PRMBL time slot; after the preamble sequence is detected in the uplink PRMBL time slot, the master station sequentially receives the control packet at the frequency of the detected preamble sequence and successfully receives the slave station After sending the control packet, the master station replies with the original corresponding frequency to confirm the reception.

8. The self-learning method according to claim 7, characterized in that the control packet is sent by the slave station at the optimal potential working frequency. If the slave station fails to receive the reception confirmation sent by the master station at this frequency, then Switch to the next suboptimal frequency, and stop switching until the slave station receives a signal confirming reception from the master station on the same potential operating frequency as the slave station; The master station and the slave station have the same potential when transmitting control packets The working frequency is the final optimal working frequency.

9. The self-learning method according to claim 7, characterized in that: the control packet includes a preamble sequence and control data; the preamble sequence is a preamble signal, and the control data is one or more OFDM symbols.

10. The self-learning method according to claim 7, characterized in that the master station does not need to send all the preamble sequences on the PRMBL time slot, that is, it sends part of the preamble sequence of the default operating frequency, and leaves the unused default operating frequency position. null;

The self-learning method uses PRMBL time slots to reduce potential interference between adjacent power line communication networks, and divides the default frequencies into different subsets. The frequencies between different subsets do not overlap; the master stations of different power line communication networks respond accordingly. Use non-overlapping frequency subsets in the PRMBL time slots to avoid interference;

The master station chooses to send the preamble sequence of all default operating frequency subsets to control the actual default operating frequency and optimize the operation of the network.