CN109067428B

CN109067428B - Fusion frequency hopping method based on Bluetooth kernel and RS code

Info

Publication number: CN109067428B
Application number: CN201810994941.XA
Authority: CN
Inventors: 韩国军; 叶永信; 范正勤; 方毅; 蔡国发
Original assignee: Guangdong University of Technology
Current assignee: Guangdong University of Technology
Priority date: 2018-08-29
Filing date: 2018-08-29
Publication date: 2020-12-11
Anticipated expiration: 2038-08-29
Also published as: CN109067428A

Abstract

The invention relates to a fusion frequency hopping method based on a Bluetooth kernel and an RS code, which fuses Bluetooth frequency hopping and the RS code frequency hopping and specifically comprises the following steps: firstly, a short sequence is generated by the transplanted Bluetooth kernel according to the globally unique ID between the devices, and then on the basis of the short sequence, a new sequence is generated by the RS code generator according to the ID, so that the sequence interference is reduced, and the required cost is low. In addition, the invention provides a frequency point compression method which can be used for conveniently switching radio frequency devices.

Description

Fusion frequency hopping method based on Bluetooth kernel and RS code

Technical Field

The invention relates to the technical field of frequency hopping communication, in particular to a fusion frequency hopping method based on a Bluetooth kernel and RS codes.

Background

Frequency hopping is one of the most commonly used spread spectrum methods, and the operating principle thereof is a communication method in which the carrier frequencies of signals transmitted by both the transmitter and the receiver are discretely changed according to a predetermined rule, that is, the carrier frequencies used in communication are randomly hopped under the control of a pseudo random change code and the hopping signals must comply with the FCC requirements, and 75 or more hopping signals are used and the maximum Time interval (Dwell Time) from hopping to the next frequency is 400 ms. However, with the existing frequency hopping scheme, the sequence interference between devices is large and the cost is high.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a fusion frequency hopping method based on a Bluetooth kernel and an RS code, which greatly reduces the sequence interference between equipment, facilitates the switching between radio frequency equipment and has lower cost.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

a fusion frequency hopping method based on Bluetooth kernels and RS codes is characterized in that a short-period sequence is generated by transplanted Bluetooth kernels according to a globally unique ID between devices, then a new sequence is generated by an RS code generator according to the ID on the basis of the short-period sequence, and finally sequence interference is reduced.

Further, the length of the generated short period sequence is controlled in 32 frequency points, the range is 0-79, the frequency points are stored in groups by using a frequency point compression method, and the frequency point groups are switched as required.

Further, using an ID of 27 bits as an input ID of the Bluetooth core and an ID of 28 bits as a start of a clock; in order to reduce the sequence correlation generated by two adjacent IDs, the input ID is judged, if the ID is an odd ID, the input clock is set to start from the ID, and if the ID is an even ID, the input clock is set to be +320 away from the input ID.

Further, the frequency point compression method specifically comprises the following steps:

firstly, a Bluetooth kernel is used, 460 frequency points are output in a rolling mode according to IDs of a transmitter and a receiver, 32 frequency points are used as a group, 10 completely different frequency point groups are obtained from the 1 st frequency point through a screening mechanism and then are stored in a flash memory flash in sequence, the frequency point groups are switched when the equipment is started each time, the equipment is taken out from the flash memory flash and put into a memory ram, then frequency hopping is carried out in the 32 frequency points according to the rule of RS codes, and the receiver is also stored in the same mode; and the switching is initiated by a transmitter, frequency point groups and RS code information exist in transmitted data frames, once the transmitter switches the frequency point groups and a receiver enters a slow frequency hopping mode to capture the transmitter information, the frequency point groups are analyzed after capture, and the frequency point groups are taken out from a flash memory and placed in a memory ram to complete the synchronization process.

Further, in order to ensure that the packets are not repeated, and the correlation is 0, a screening mechanism is adopted for screening, and the screening mechanism is as follows:

firstly, selecting 32 frequency points in sequence to form a first group of frequency point groups, then comparing the 32 frequency points with the previous frequency point groups in a group, and if the 32 frequency points are not the same, storing the 32 frequency points; if the data is identical to one group, discarding; another group is taken for comparison in sequence; quitting the screening mechanism until 10 groups are obtained; if 10 groups are not selected, but 460 frequency points have been traversed, the operation will be exited, and the compared frequency point groups are reserved.

Further, the regular frequency hopping of the RS code is as follows:

when a group of frequency hopping point groups are selected for frequency hopping, each frequency hopping is carried out according to the RS code frequency selection rule; the frequency selection rule is a shift circuit, each time frequency hopping triggers one shift, the latest bit is calculated by each bit numerical value and a primitive polynomial, two bits are selected by using a dual frequency band method to be combined for XOR processing, then 5bit numerical values are obtained by combining ID (identity) for nonlinear processing, then the final 5bit numerical value is obtained by using wide interval processing and is a final frequency point subscript, and then a corresponding frequency point is selected from the previously generated frequency point group; the transmitter will put 14 bits of RS code value into the transmission load each time; the receiver decodes the RS code value in the transmission load each time, and calculates the frequency point according to the same mode; and under the condition of packet loss, the RS code value of the next frame can be automatically calculated and the frequency point can be calculated.

Compared with the prior art, the principle and the advantages of the scheme are as follows:

fuse bluetooth frequency modulation and RS sign indicating number frequency modulation, specifically do: firstly, a short sequence is generated by the transplanted Bluetooth kernel according to the globally unique ID between the devices, and then a new sequence is generated by the RS code generator according to the ID on the basis of the short sequence, so that the sequence interference is reduced, and the required cost is low. In addition, the scheme provides a frequency point compression method which can be used for conveniently switching radio frequency devices.

Drawings

FIG. 1 is a schematic diagram of a frequency selective kernel of a frequency hopping system;

FIG. 2 is a 79 hop system control map;

fig. 3 is a frequency hopping pattern for a frequency hopping sequence device address of 56;

FIG. 4 is a frequency hopping pattern with a number of available frequencies of 79 and a length of 1000;

FIG. 5 is a frequency hopping pattern with a number of available frequencies of 70 and a length of 1000;

FIG. 6 is a frequency hopping pattern with a number of available frequencies of 60 and a length of 1000;

FIG. 7 is a frequency hopping pattern with a number of available frequencies of 40 and a length of 1000;

FIG. 8 shows an RS (16383,2) code hardware shift register circuit;

FIG. 9 is a flow chart of a wide interval frequency hopping sequence process;

FIG. 10 is a diagram illustrating the effect of simulating an RS code that has not undergone wide-spacing processing after nonlinear processing;

FIG. 11 is a diagram showing the effect of simulating an RS code after nonlinear processing and after wide-interval processing;

FIG. 12 is a graph of simulated Hamming autocorrelation results;

FIG. 13 is a schematic diagram of a device with odd ID generating hop-groups;

FIG. 14 is a schematic diagram of a device with an even ID generating hop-group;

FIG. 15 is a schematic diagram of the overall fusion algorithm;

FIG. 16 is a frequency hopping frequency statistics map generated by fusing pre-RS codes;

fig. 17 is a frequency hopping frequency statistical chart without wide interval processing after RS codes are generated and fused with a bluetooth kernel;

fig. 18 is a frequency hopping frequency statistical chart after RS code generation and bluetooth kernel fusion and wide interval processing;

FIG. 19 is a diagram of an RS code emulation after fusion with a Bluetooth kernel but without wide-interval processing;

FIG. 20 is a diagram of an RS code emulation after fusion with a Bluetooth kernel and having been processed at wide intervals;

FIG. 21 is a Hamming autocorrelation fusion frequency hopping simulation diagram;

FIG. 22 is a graph of Hamming cross-correlation fused frequency hopping simulation;

Detailed Description

The invention will be further illustrated with reference to specific examples:

the fusion frequency hopping method based on the Bluetooth kernel and the RS code relates to a Bluetooth kernel frequency hopping algorithm and an RS code frequency hopping algorithm, wherein the Bluetooth kernel frequency hopping algorithm is specifically analyzed as follows:

bluetooth divides the frequency band of 2.4GHz ISM differently according to different countries, the number of frequency hopping points available for a Bluetooth system is also different, some countries can obtain 79 frequency hopping points, and some countries can only use 23 frequency hopping points, so that a Bluetooth lacing protocol defines 5 frequency hopping sequences, and the embodiment only adopts the channel frequency hopping sequence of 79 frequency hopping points.

The frequency selection principle of the Bluetooth frequency hopping sequence is as follows:

the Bluetooth core hopping sequence used in this embodiment is determined by the Bluetooth device flag (the lower portion 28bit of the Bluetooth address of the master device), and the carrier frequency of each slot is determined by the phase (i.e., slot number) of the slot. The Bluetooth device mark has 28 bits, and can distinguish 228 frequency hopping sequences, and the number is very large. The slot number is 27 bits of master CLK and a complete hopping sequence duration is 227 x 625 mus 23.3 h. The access opportunities for any 32 consecutive carrier frequencies in the hopping sequence covering a range of at least up to 64MHz per frequency are the same.

Frequency selective kernel of 79 hop system as shown in fig. 1, control signal X determines the state in the 32 hop segment; control signal Y₁And Y₂For selecting a master-to-slave state or a slave-to-master state; the control signals a to D determine the order in the segment and E and F determine the mapping to the hopping frequency. The kernel represents a register containing the hopping frequency. The process of generating the sequence list begins with even hop frequencies followed by odd hop frequencies.

The selection process is composed of a primary addition operation, an exclusive-or operation, a permutation operation, a secondary addition operation and a register selection sequence.

A_27-0Globally unique device address from Bluetooth device, and CLK_27-1Derived from the system clock, at a frequency of 1600 Hz. The 27bit clock causes the update period of the output sequence to be 23.3 hours, which is about one day. CLK₁The conversion of reception and transmission is decided: when CLK is applied₁When the clock is equal to 0, the clock is even, and the selected frequency hopping sequence is from the master device to the slave device; CLK₁When 1, the clock is odd, and the selected hopping sequence is from the slave device to the master device. Because of Y₁＝CLK₁，Y₂＝32×CLK₁The forward and backward directions of the output hopping sequence are different and not adjacent by 32; x determines the segmentation of a 32-hop subsequence,a to D determine the sequence of the frequency points in the segment, and E and F map the output to a 79-hop system. Since the lowest order bit of the X input is the lower CLK of the 28-bit clock₂So that CLK₁(i.e. Y)₁) Change twice X only once, i.e. even slots and odd slots (odd and even slots are relative to CLK)₁In other words, since in the continuous state, CLK is not used₀So each clock increment of 2 is directly opposite to CLK in calculating the hopping sequence₁Operation) X input is constant, then the permutation operation is the same for both even and odd slots. The control amount and the connection state are shown in fig. 2.

This embodiment improves the bluetooth core input. The clock is not started from 0 but from ID as the starting position, but the ID is ensured to be data of 27 bits, in order to reduce the sequence correlation generated by two adjacent IDs, one judgment is made on the input ID, if the ID is an odd number ID, the input clock is started from the ID, and if the ID is an even number clock, the input clock is set to be +320 away from the input ID.

Performance analysis comparison and analysis:

still use clock from 0 to 2 in performance analysis²⁷The performance of the bluetooth core is tested for the end position.

Hamming autocorrelation:

the hamming autocorrelation function Hs (τ) of the sequence s (t) is defined as:

in the formula (I), the compound is shown in the specification,

τ is 0. ltoreq. N-1, N being the period of the sequence s (t);

since the bluetooth-based hopping sequence is difficult to represent with a simple expression, the present embodiment can only calculate the hamming characteristics using some practical examples. Fig. 3 shows a hopping pattern for the hopping sequence device address 56, where only 1000 points are calculated due to the long period.

Calculating to obtain the average value of the hopping sequence: 12.3120.

the frequencies in the Bluetooth adaptive frequency hopping sequence are uniformly distributed, and any Bluetooth frequency hopping sequence S is determined according to the Hamming related theoretical limit under the conditions of given frequency number and sequence period_UThe average of the heteroautocorrelation of (a) is minimized. The average autocorrelation normalization value of the adaptive frequency hopping sequence of the Bluetooth is

Wherein q is the number of available frequencies; and L is the normalized value of the different autocorrelation of the intercepted Bluetooth adaptive frequency hopping sequence.

Fig. 4 shows a hopping pattern of 79 available frequencies and 1000 in length, normalized to the mean value of 0.0123.

Fig. 5 is a frequency hopping pattern of 70 available frequencies and 1000 in length, normalized to the mean value 0.0138.

Fig. 6 shows a hopping pattern of 60 available frequencies and 1000 in length, normalized to the mean value 0.0163.

Fig. 7 shows a hopping pattern of 40 available frequencies and 1000 available frequencies, normalized to a mean of 0.0247.

The numerical pairs associated with the relevant articles are shown in table 1 below:

the data of the autocorrelation mean values of the pseudorandom sequences are similar, so that the Bluetooth kernel transplanted in the experiment is similar to the real Bluetooth kernel.

RS code frequency hopping algorithm:

the pseudo-random sequences commonly used for generating frequency hopping sequences are mainly m sequences, GOLD sequences, RS codes and the like. The RS code is an optimal approximate orthogonal code and has good cross correlation; compared with m sequences with the same length, the RS codes can select more codes; the RS code is a minimum distance maximum code (MDC), which is extremely beneficial to constructing a wide-interval frequency hopping sequence with better performance and is not provided by other pseudo-random sequences; the hardware implementation of the RS code is also simpler. It is therefore a convenient choice to generate the hopping sequence in the RS code. The use of extended RS codes to construct a family of hopping sequences was proposed by scholars abroad as early as the 60 th century.

The basic principle of the RS code is as follows:

the RS code is a q-ary field BCH cyclic code (BCH cyclic code is an error correcting code) of length N-q-1, and symbols are taken from the galois field gf (q), where q-p-m and p are prime numbers. The most important parameters characterizing the RS code are the code length L, the number of information bits b, and the code distance d, which are defined in terms of error correction codes.

Code sequence length: l-q-1-2ⁿ-1；

Number of information bits: b is n-d + 1;

code distance: d is n-b + 1;

when b is 2, the RS (N, 2) has the best performance, and an optimal RS frequency hopping sequence (pattern) can be constructed, so that the frequency point coincidence times of any two frequency hopping sequences in one period is not more than 1 under any frequency hopping delay condition. The longer the period of the RS code is, the better the performance of the constructed frequency hopping sequence (pattern) is, but at the same time, the complexity of simulation and implementation is increased, so as to meet the certification requirement and comprehensive consideration.

In this embodiment, N is 2¹⁴16383, on one hand, because the dwell time of a certain hopping frequency should not be accumulated for more than 0.4 seconds in one hopping sequence period based on the authentication requirement; on the other hand, the RS code is converted into a frequency hopping sequence of 5 bits, and the number of the shift registers is multiplied by 5, so that the conversion is convenient and the uniformity of the frequency hopping sequence is ensured.

The codeword vector for the RS (16383,2) code over GF (16383) is:

the generated code is

[1,a,a²,...,a¹⁶³⁸³]

The calculation of the hopping code translates into a calculation of 16383 elements in GF (16383). The primitive minimum polynomial in GF (16383) is chosen as equation 3.4 (hexadecimal 0x4a87), and 16383 elements in the domain can be derived from the galois field element algorithm.

p(x)＝x¹⁴+x¹¹+x⁹+x⁷+x²+x¹+1

The following rule is obtained by observation, when the highest bit is 0, the left shift is circularly obtained (the lower bit is supplemented with 0); when the highest bit is 1, the left shift (low complement 0) is obtained by XOR with 0x0A 87. The hardware circuit for deriving the RS (16383,2) code from the above-mentioned minimum polynomial is shown in fig. 8.

Nonlinear transformation of RS codes:

the RS (16383,2) code can be directly used as a frequency hopping sequence to control the pseudo-random hopping of the carrier, but the controlled frequency hopping number must meet 16383, which obviously cannot be realized in the authentication requirement and the actual RFIC engineering, and the code must be transformed to use. The present embodiment uses a nonlinear transfer matrix method to convert the longer RS (16383,2) code into a shorter hopping sequence, as shown in the following equation. The algorithm further increases the complexity of the sequence and is easy to implement in engineering. Meanwhile, in order to increase the anti-interference performance of the sequence, a dual-frequency band method is adopted to carry out wide-interval processing on the sequence.

L_1X14×T_14X5＝N_1X5

In the formula L_1X14RS (16383,2) code, T, representing 14bit_14X5Representing a non-linear transfer matrix, N_1X5Representing the transformed 5-bit hopping sequence, an appropriate non-linear transfer matrix is of critical importance, which directly affects the uniformity of the constructed hopping sequence.

To ensure that the rank of the nonlinear transfer matrix is 5, the 14 register bits in fig. 8 are divided into 5 groups, and 2 register bits in each group are extracted at equal intervals: r0+ R7 are a group, R1+ R8 are a group, and so on, values of 5 groups of register bits are selected to be added in a mode of 2 to obtain a 5-bit sequence, then the 5-bit sequence is added in a mode of 2 with an input 5-bit user ID vector V to obtain a 5-bit binary number Q () as a frequency hopping sequence, and the frequency hopping is controlled. The user ID vector V may be generated by an ID number unique to the transceiving device.

RS code width interval processing:

practical frequency hopping systems typically require wide interval frequency hopping to be achieved. The wide-interval frequency hopping means that the frequency interval of two carriers transmitted in adjacent frequency hopping time slots is greater than a specified value, and for a system with determined frequency hopping rate, a frequency hopping sequence is designed to be wide-interval, which is beneficial to resisting single-frequency narrow-band interference, tracking interference and wide blocking interference and is also beneficial to resisting multipath fading.

According to engineering practice, 64 hopping frequencies are set in the ISM 2.4GHz or 5.8GHz frequency bands. In order to make the carrier interval of the adjacent frequency hopping time slots larger than 30MHz, according to the dual band method, 64 frequency hopping frequency points F can be divided into 32 frequency points on the left and right:

f1 ═ {2403, 2404, …,2434} or F1 ═ 5728, 5729, …,5759}

F2 ═ 2435, 2436, …,2466} or F2 ═ 5760,5761, …,5791}

Designing an algorithm to generate a wide-interval frequency hopping sequence based on an RS (16383,2) code; according to the algorithm shown in fig. 9, the initial states of R0 to R13 are agreed to be 00000000000001, the user ID vector V is 0x00, and since the V vector is 5 bits, different hopping sequences can be generated to realize sequence grouping. Each time the shift register shifts, which represents one hop (equivalent to one hop period), the hop range [0,31] of q (i) is set to correspond to 32 bins on F1. Another variable W with a range of [0,63] sequentially corresponds to the 64 hopping frequency points, that is:

f1 ═ {2403, 2404, 2405, …,2466} or

F1＝{5728，5729,5730，…，5791}

The generation of the wide interval hopping sequence is completed according to the flow shown in fig. 9. i represents the number of hops, i ≧ 1, and D ≧ 10 represents the number of wide intervals. W is the final wide interval frequency hopping sequence, and the frequency can be controlled to carry out pseudo-random hopping through W.

The effect of simulating the RS code after the nonlinear processing but without the wide-interval processing is shown in fig. 10.

The effect of simulating the RS code after the nonlinear processing and after the wide interval processing is shown in fig. 11.

It can be seen that the wide-interval processing is mainly to process the frequency interval of two carriers transmitted in adjacent hopping time slots to be larger than a certain specified value.

Performance simulation:

according to the method, the initial state I00000000000001 of R13 to R0 is set, the value range [0,31] of V corresponds to 32 different frequency hopping sequences W1 to W32, when V (V4V3V2V1V0) takes 0-4 bits of ID (namely 00100), a Q1 value with the period of 16383 can be obtained through simulation, and the wide-interval frequency hopping processing is carried out. The corresponding widely spaced hopping sequences are available:

W1＝{30,15,1,42,37,50,63,37,32,36,28,…,36,52,60,52,48,54,53,62,47,33}

when V (V4V3V2V1V0) takes 0-4 bits of ID (i.e. 01000), Q2 value with period of 16383 can be obtained by simulation, and after wide interval frequency hopping processing, corresponding wide interval frequency hopping sequence can be obtained:

W2＝{18,3,13,38,41,62,51,41,44,40,48,…,58,57,40,56,60,58,57,50,35,45}；

hamming correlation is an important indicator for measuring the performance of frequency hopping sequences. Hamming autocorrelation represents the coincidence times of the frequency hopping sequences and the frequency points of the frequency hopping sequences under relative time delay, Hamming cross correlation represents the coincidence times of the two frequency hopping sequences under relative time delay, and the Hamming autocorrelation has important influence on the anti-interference performance and the multi-access networking performance of the frequency hopping system. The hamming autocorrelation value of the hopping sequence S with the period L when the relative delay is τ can be calculated by the following formula:

in the formula (I), the compound is shown in the specification,

τ is 0. ltoreq. N-1, N being the period of the sequence s (t);

the simulated hamming autocorrelation results are shown in fig. 12, and when the time delay is 0, the sequence hamming autocorrelation reaches a peak value of 1000, and this embodiment only counts 1000 points because the data volume of the full cycle is large. When the time delay is at bit 0, the mean value of the autocorrelation values of the sequence reaches 31.0030. Compared with other papers, the other papers simulate 1048575 points, the hamming autocorrelation value reaches 32767, which is about 3.1% of the sequence period, and is similar to the data of the experiment, which shows that the frequency hopping sequence has good hamming autocorrelation.

After the bluetooth kernel frequency hopping algorithm and the RS code frequency hopping algorithm are detailed, a fusion frequency hopping algorithm based on the two is as follows:

the synchronous mode of bluetooth needs to add a device clock in a data format for adjusting the clock error between devices, and the total length of the bluetooth device payload reaches 2871 bits (64-bit code words containing 24-bit addresses of the clock). However, if the common radio frequency module uses frequency hopping, the bluetooth devices are in different synchronization modes, and because the load of the bluetooth devices is small and the device clocks cannot be exchanged, the embodiment uses a waiting self-synchronization mode, so that only short-period sequences can be used, and the bluetooth devices do not use long-period sequences generated according to the device clocks, so that the short periods of the embodiment are generated by a frequency point compression method.

Adaptive improvement for the frequency-selective kernel:

firstly, the particularity of the radio frequency equipment is stated, a 5.8GHz radio frequency module is adopted, and the ID of the equipment can be set through rolling codes by software, namely, each equipment is a globally unique ID.

Then, a set of frequency hopping scheme is designed for each module according to the globally unique ID, so that the interference among frequency points among all devices is minimized, and therefore, a Bluetooth kernel is used as a core algorithm.

In this embodiment, the frequency points need to be controlled to 32 frequency points as a short period, range 0-79, and 10 groups of 32 frequency point groups are selected for switching; and the length of the original Bluetooth sequence is 268435455 frequency points, and the range is 0-79. This is simplified for the bluetooth core.

Regarding the adjustment of the bluetooth clock:

the method for providing the frequency hopping for the radio frequency equipment mainly aims to highlight uniqueness among the equipment, each equipment has a globally unique ID, and the ID consists of 5 bytes (40 bits). And the finally generated frequency hopping sequence groups are unique, so that the purpose of generating different sequence groups according to different IDs is achieved, and the devices cannot be interfered with each other.

The input end of the Bluetooth core is improved. The clock is not started from 0, but is started from ID, but the ID is ensured to be data of 27 bits, in order to reduce the sequence correlation generated by two adjacent IDs, one judgment is made on the input ID, if the ID is an odd ID, the input clock is started from the ID, and if the ID is an even ID, the input clock is set to be +320 away from the input ID. Fig. 13 and 15 are diagrams of generating hop-groups for devices with odd and even IDs, respectively.

The above adjustment is mainly to prepare for taking the following frequency point groups, and continuously take 320 frequency points of 32 frequency point groups of 10 groups, and make odd and even IDs spaced by 320 points is a mechanism to avoid repeated operations.

Regarding frequency point compression:

the frequency point compression method comprises the following specific steps:

10 groups of frequency point groups which are not completely the same from 0(ID +0) to 459(ID +459) are selected and stored.

In order to ensure that the selected 10 hop-point groups do not overlap with each other, the correlation is 0. Screening was performed using a screening mechanism as follows:

As to why 10 groups need to be selected, since a device restarts to select one group to hop, and also to prevent interference between devices, there is synchronization information in the transmission information, and the transmitting device and the receiving device switch to the corresponding hop groups according to the synchronization information.

The regular hopping of the RS code is as follows:

Performance analysis of the fusion frequency hopping algorithm:

the performance analysis of a frequency hopping algorithm is mainly divided into the following aspects to judge:

(1) the frequency hopping algorithm has uniformity of frequency points.

(2) The frequency hopping algorithm has excellent hamming autocorrelation.

(3) The frequency hopping algorithm has excellent Hamming cross-correlation.

The frequency hopping scheme of the radio frequency equipment mainly needs to minimize sequence interference between the equipment, so that a short sequence is generated by a Bluetooth core according to a globally unique ID between the equipment, the orthogonality between the short sequences is relatively good, then a new sequence is generated by an RS code generator according to the ID on the basis of the short sequence, the long sequence basically inherits all the characteristics of the RS code, the anti-interference performance of a frequency hopping system is related to the number of frequency hopping points, the defect that the sequence generated for the first time is short needs to be overcome, and the structure of the whole fusion algorithm is shown in figure 15.

According to the method, the initial states of R13-R0 are set as 00000000000001, the value range of Q is from the first hop point of the hop group 1 to the last hop point of the hop group 1, and the value range of Q is from the first hop point of the hop group 1 to the last hop point of the hop group 2.

When V (V4V3V2V1V0) takes 0-4 bits of ID (i.e., 00100), Q with period of 16383 can be simulated₁Value, after wide interval frequency hopping process [36 ]]. The corresponding widely spaced hopping sequences are available:

Q₁＝{42,76,54,37,44,60,40,72,54,9,48,…,60,64,72,64,48,66,53,74,43,5}

when V (V4V3V2V1V0) takes 0-4 bits of ID (i.e. 01000), Q with period of 16383 can be simulated₂After wide-interval frequency hopping processing, a corresponding wide-interval frequency hopping sequence can be obtained:

Q₂＝{18,78,33,62,9,74,23,9,68,52,48,…,52,56,48,56,72,58,25,50,7,41}

here, the RS code is simulated after the nonlinear processing and after the fusion with the bluetooth kernel, but without the wide interval processing. The frequency ranges are continuous between 0-31 and the hopping pattern is relatively concentrated if not merged with the short sequences generated by the bluetooth core. If fused with short sequences, the frequency range is discrete, distributed between 0 and 79 as defined by the Bluetooth kernel, and wider.

Here, the uniformity of the frequency points is analyzed. Firstly, the frequency hopping frequency statistical graph generated by the RS code is observed (figure 16), then the frequency hopping frequency statistical graph which is not processed by the wide interval after the RS code is generated and fused with the Bluetooth kernel is observed (figure 17), and finally the frequency hopping frequency statistical graph which is processed by the wide interval after the RS code is generated and fused with the Bluetooth kernel is observed (figure 18).

And counting the number of each frequency point. Before the RS codes are not fused, according to the frequency point range of 0-31, the number of each frequency point of 0-31 in one period is 512 points uniformly. The number of frequency points after the fusion but without the wide interval processing is 512 points, which once again shows that the performance of the RS code is not affected after the fusion. The uniformity of the frequency points after the wide-interval processing is slightly reduced, but the frequency hopping points are more, and the correlation is still unchanged.

The biggest changes in fig. 16, 17 and 18 are that the bandwidth is gradually widened, the number of frequency points is more, and the anti-interference capability is better.

Here, the RS code processed with wide intervals after the nonlinear processing and the fusion with the bluetooth kernel is simulated.

Referring to fig. 19 and 21, and changing from fig. 19 to fig. 20, a wide spacing process is employed. While fig. 19 has relatively concentrated frequency points on the scale of 30-60, fig. 20 has dispersed the relatively concentrated frequency points to the scale of 0-79, resulting in a more uniform distribution of frequency points. Therefore, the distribution situation of the processed frequency points is better than that of RS code sequences, and the observation of frequency hopping patterns is more convincing than the statistics of the number.

A safe frequency hopping system has good anti-interference and anti-multipath fading performances. For a frequency hopping pattern, the primary metric measuring its performance is hamming correlation. The hamming correlation of the fused frequency hopping is almost the same as that of the RS code, and referring to fig. 21, 1000 points are counted, and the average value of the autocorrelation values of the sequence reaches 31.0030. Compared with other papers, the other papers simulate 1048575 points, the hamming autocorrelation value reaches 32767, which is about 3.1% of the sequence period, and is similar to the data of the experiment, which shows that the frequency hopping sequence has good hamming autocorrelation.

Analysis of hamming cross-correlation:

in the formula (I), the compound is shown in the specification,

τ is 0. ltoreq. N-1, N being the period of the sequence s (t);

referring to fig. 22, the average of the hamming cross-correlation is 26.9, which is about 2.69% of the period, for 1000 points.

Hamming cross-correlation accounts for the difference between two sequences with different IDs. The figure illustrates that the probability of collision between two sequences is low and much lower than the cross-correlation value in the correlation paper.

This embodiment fuses bluetooth frequency modulation and RS sign indicating number frequency modulation, specifically is: firstly, a short sequence is generated by the transplanted Bluetooth kernel according to the globally unique ID between the devices, and then on the basis of the short sequence, a new sequence is generated by the RS code generator according to the ID, so that the sequence interference is reduced, and the required cost is low. In addition, the present embodiment provides a frequency point compression method, which can facilitate switching between radio frequency devices.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, so that variations based on the shape and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A fusion frequency hopping method based on a Bluetooth kernel and RS codes is characterized in that: firstly, generating a short-period sequence by using a transplanted Bluetooth core according to a globally unique ID between devices, controlling the length of the generated short-period sequence to be 32 frequency points in a range of 0-79, grouping and storing the frequency points by using a frequency point compression method, and switching frequency point groups as required; then, frequency point group frequency hopping is carried out according to the RS code generator and the ID, and a new sequence is generated, so that the sequence interference is reduced;

the frequency point compression method comprises the following specific steps:

firstly, a Bluetooth kernel is used, 460 frequency points are output in a rolling mode according to IDs of a transmitter and a receiver, 32 frequency points are used as a group, 10 completely different frequency point groups are obtained from the 1 st frequency point through a screening mechanism and then are stored in a flash memory in sequence, the frequency point groups are switched when the equipment is started each time, the equipment is taken out from the flash memory and put into a memory ram, and the receiver is also stored in the same mode; the switching is initiated by a transmitter, frequency point groups and RS code information exist in a transmitted data frame, once the transmitter switches the frequency point groups and a receiver enters a slow frequency hopping mode to capture the transmitter information, the frequency point groups are analyzed after the transmitter information is captured, and the frequency point groups are taken out from a flash memory and placed in a memory ram to complete the synchronization process;

the screening mechanism is as follows:

firstly, selecting 32 frequency points in sequence to form a first group of frequency point groups, then comparing the 32 frequency points with the previous frequency point groups in a group, and if the 32 frequency points are not the same, storing the 32 frequency points; if the data is identical to one group, discarding; another group is taken for comparison in sequence; quitting the screening mechanism until 10 groups are obtained; if 10 groups are not selected, but 460 frequency points are traversed, the operation is exited, and the compared frequency point groups are reserved;

the specific steps of generating a new sequence after frequency point group frequency hopping according to the RS code generator and the ID are as follows:

when a group of frequency point groups are selected for frequency hopping, each frequency hopping is carried out according to the RS code frequency selection rule; the frequency selection rule is a shift circuit, each time frequency hopping triggers one shift, the latest bit is calculated by each bit numerical value and a primitive polynomial, two bits are selected by using a dual frequency band method to be combined for XOR processing, then 5bit numerical values are obtained by combining ID (identity) for nonlinear processing, then the final 5bit numerical value is obtained by using wide interval processing and is a final frequency point subscript, and then a corresponding frequency point is selected from the previously generated frequency point group; the transmitter will put 14 bits of RS code value into the transmission load each time; the receiver decodes the RS code value in the transmission load each time, and calculates the frequency point according to the same mode; and under the condition of packet loss, the RS code value of the next frame can be automatically calculated and the frequency point can be calculated.

2. The fusion frequency hopping method based on the Bluetooth kernel and the RS code according to claim 1, wherein: using an ID of 27 bits as an input ID of the Bluetooth core and using an ID of 28 bits as a start of a clock; in order to reduce the sequence correlation generated by two adjacent IDs, the input ID is judged, if the ID is an odd ID, the input clock is set to start from the ID, and if the ID is an even ID, the input clock is set to be +320 away from the input ID.