CN110380748B

CN110380748B - Method for generating scrambling signal

Info

Publication number: CN110380748B
Application number: CN201910679323.0A
Authority: CN
Inventors: 尤肖虎; 汪茂; 夏婷婷; 张菁菁
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2019-07-25
Filing date: 2019-07-25
Publication date: 2021-10-29
Anticipated expiration: 2039-07-25
Also published as: CN110380748A

Abstract

A communication station firstly determines an initial value and an M-bit mask code of an M-bit PN sequence generator, then performs modulo-2 inner product operation on the M-bit mask code and M state vectors of the PN sequence generator to generate a first sequence, and finally performs BPSK modulation on the first sequence to obtain a scrambling signal and scrambles the transmitted signal. The M bit mask is determined by the cell control station identifier and a carrier frequency parameter adopted by signal transmission; the initial value of the M-bit PN sequence generator is determined by the frame unit number used for signal transmission and the slot unit number within the frame unit used for signal transmission. The technical scheme of the invention can enable different communication stations and communication frequency spectrum channels to use different time-varying scrambling signals to scramble transmission signals, further realize the interference randomization and diversity among signals, improve the anti-interference performance of the system, and can be suitable for various wireless communication systems, such as a very high frequency data exchange system VDES.

Description

Method for generating scrambling signal

Technical Field

The present invention relates to the field of communications, and more particularly, to a scrambled signal generation method.

Background

In order to ensure the reliability of communication, signal scrambling is an important link for signals transmitted in the communication process. In some wireless communication systems, such as Very High Frequency (VHF) Data Exchange system vdes (VHF Data Exchange system), there are currently published technical property document ITU-R m.2092-0 and related organization technical discussion document IALA G1139 represented by IALA, where the scrambling signal used is fixed, that is, the signal transmitted by the communication station is not proprietary, so that the receiver cannot distinguish useful signals from interference between cells and channels, and thus cannot effectively suppress interference; meanwhile, the scrambling signal does not change along with time, so that interference diversity in a time domain is not facilitated, and the anti-interference performance of a receiver is influenced.

Disclosure of Invention

The technical problem is as follows: the invention aims to solve the problem that the scrambling signal adopted by the conventional VDES is fixed and unchangeable, so that a receiver cannot distinguish a useful signal from interference between cells and channels, and therefore cannot effectively inhibit the interference; meanwhile, the scrambled signal does not change along with the time, so that the problems of interference diversity in a time domain and interference resistance of a receiver are not influenced.

The technical scheme is as follows: in order to achieve the above purpose, the present invention provides the following technical solutions:

a scrambled signal generation method comprising the steps of:

1) the communication station determines an M bit mask according to a cell control station identifier and a carrier frequency parameter adopted by signal transmission, and comprises a mobile station and a control station;

2) the communication station determines the initial value of the M-bit PN sequence generator according to the frame unit number adopted by signal transmission and the time slot unit number in the frame unit adopted by the signal transmission;

3) performing modulo-2 inner product operation on the M bit mask and an M bit state vector of an M bit PN sequence generator to generate a first sequence;

4) the communication station performs BPSK modulation on the first sequence to obtain a scrambled signal, and scrambles the transmitted signal.

Further, when the communication station is a control station and transmits a system information acquisition signal, in step 1), the cell control station identifier required for determining the M-bit mask is replaced by a fixed special number, and the system information acquisition signal is at least used for the control station to transmit the cell control station identifier to a mobile station in a cell.

Further, M is an integer and satisfies:

1) not less than the sum of the number of binary bits required to quantize the cell control station identification and the number of binary bits required to quantize the carrier frequency parameter;

2) greater than the number of binary bits required to quantize the slot units within the frame unit.

Further, in the step 3), an and operation is performed on the M-bit mask and the M-bit state vector to obtain a binary result with the same length; and performing modulo binary summation on all data in the binary result according to the binary system to obtain a first sequence.

Further, in step 1), the cell control station identifiers and the carrier frequency parameters used for signal transmission are arranged in an arbitrary order in the M-bit mask.

Further, in step 2), in the initial value of the M-bit PN sequence generator, the frame unit number used for signal transmission and the slot unit number in the frame unit used for signal transmission are arranged in an arbitrary order.

Has the advantages that:

by the technical scheme, different scrambling signals with different time-varying scrambling frequencies can be used for scrambling transmission signals in different communication stations and communication frequency spectrum channels, so that randomization and diversity of interference among signals can be realized, the anti-interference performance of the system is improved, and the VDES system is helped to meet various application scenes in the maritime Internet of things.

Drawings

FIG. 1 is a schematic diagram of the spectrum division in a VDES system;

FIG. 2 is a schematic diagram of modulo-2 inner product operation of a mask and a state vector of a PN sequence generator in the present embodiment;

fig. 3 is a schematic diagram of a scrambled signal generation provided in this embodiment;

fig. 4 is a schematic diagram of generating another scrambled signal according to this embodiment.

Detailed Description

The invention will be further elucidated with reference to the embodiments and the drawings.

First, some terms in the present application are explained so as to be easily understood by those skilled in the art.

1) The communication Station, also called a communication device, may be a Mobile Station (Mobile Station) or a Control Station (Control Station). A Mobile station, also known as a Mobile Terminal (MT), a User Equipment (UE), etc., is a device that can communicate with a network through a control station to provide data connectivity to a User, such as a wireless Sensor (Sensor), a marine vessel, a Buoy (Buoy), a Search and Rescue (SAR) repeater, etc. The control Station is also called a Base Station (Base Station), a network device, including a Shore Station (Shore Station), a Satellite (Satellite), a Space Station (Space Station), and the like, and is a wireless access point (or device) for the mobile Station to access the network.

2) The Identity (ID) of the control station is the identification code MMSI of the marine Mobile communication Service of the control station in the VDES system, which is called the Markime Mobile Service Identity. The MMSI is composed of 9 decimal digits, including 3 decimal marine Identification codes MID (maritime Identification digits) and other 6 decimal digits. Please refer to table 1, which lists the MMSI format corresponding to several common types of VDES communication stations, wherein X represents any number from 0 to 9. The first number of the MID ranges from 2 to 7 and represents a region, for example, the first number of the MID is 2 and represents a european region. The two latter numbers of the MID represent the countries of the respective regions, such as the australian countries in the european region using MID 247. Quantizing a 9 digit decimal MMSI requires at least a 30 bit binary digit number.

TABLE 1

VDES communication station	MMSI format
		Shipborne station	MIDXXXXXX
Shipborne station group	0MIDXXXXX
		Bank station (group)	00MIDXXXX
SAR aerocraft (group)	111MIDXXX
		Navigation aid	99MIDXXXX
Ship associated with mother ship station (like tugboat)	98MIDXXXX

3) The carrier Frequency parameter may be a center Frequency number cfi (center Frequency index), and may be used to indicate a center Frequency of a Frequency domain resource used for signal transmission; or may be a spectrum channel number ci (channel index) in the VDES system, and may be used to indicate a starting channel number of a frequency domain resource used for signal transmission. The VHF maritime mobile frequency range is 156 MHz to 174 MHz, and is divided into a plurality of channels (channels) with a bandwidth of 25kHz, and the ITU makes a spectral Channel number for some channels. Referring to fig. 1, the frequency spectrum currently allocated by the ITU to the terrestrial portion of the VDES system (i.e., AIS, ASM, VDE-TER) and the satellite portion of the VDES system to be allocated (i.e., VDE-SAT) corresponds to a central frequency range of 156.775 MHz-162.025 MHz, which is distributed within the VHF maritime mobile band. Referring to fig. 1, spectral channel numbers specified by the ITU are noted within the rectangular box, such as spectral channel number 2028; the center frequencies corresponding to some channels are indicated by dotted lines with arrows pointing to the center positions of the channels, for example, the center frequency corresponding to the channel with the spectrum channel number 2088 is 162.025 MHz.

By n_CFIThe center frequency number is represented, starting from the minimum center frequency corresponding to the frequency spectrum of the VDES system, namely 156.775MHz, the center frequency of a frequency domain resource adopted by certain signal transmission in the VDES system can be represented by a formula of 156.775MHz + n, and the center frequency is stepped by 25 kHz/2-12.5 kHz_CFI12.5kHz, where n is_CFIThe value ranges from 0 to (162.025-156.775) MHz/12.5kHz to 420, i.e. n_CFI∈[0,420]At least 9 bits of binary digits are required for quantization. It should be understood that in a VDES system, the signal transmission occupies a bandwidth of perhaps the smallest 25kHz, and perhaps an integer number of larger bandwidths of 25kHz combination, whenThrough n_CFIAfter determining the center frequency of the frequency domain resource used for signal transmission, the frequency domain resource used for signal transmission can be determined by combining the known system bandwidth information. For example, n_CFIWhen the center frequency is 156.775MHz +34 × 12.5kHz, 157.200 MHz, and if the bandwidth of signal transmission is 25kHz, the channel with the spectrum channel number of 1024 used for signal transmission can be determined. Also for example, n_CFIIf the signal bandwidth is 50kHz, it can be determined that the two channels of spectrum channel numbers 1024 and 1084 are used for signal transmission in the frequency domain, which corresponds to a center frequency of 157.2125 MHz at 35.

By n_CIReferring to the channel numbers in fig. 1, the channel numbers of the spectrum for the VDES system, which are currently established by the ITU, are at most 2088, and can be quantized by 12 bits. The frequency domain resources used for signal transmission may also be determined by the number of the spectral channel in combination with the known system bandwidth information, and at this time, the number of the spectral channel corresponds to the initial channel number occupied by the signal transmission. For example, the spectral channel number n_CIIf the bandwidth of the signal transmission is 25kHz, it may be determined that the channel with the spectrum channel number of 1024 is used for the signal transmission; if the signal bandwidth is 50kHz, it indicates that the number 1024 corresponds to the number of the initial channel used for signal transmission, and it can further be determined that the two channels of the spectrum channel numbers 1024 and 1084 are used for signal transmission.

4) Frame unit and time slot unit, the time domain frame structure of VDES system is: one minute is a frame length and the start time of the frame is always time aligned with the minutes of the UTC. For example, with n_UTCDenotes the time in minutes of UTC, then n_UTCEach increment of the value 1 indicates an increase of one frame unit in the VDES system. A frame consists of 2250 slot units, which are numbered 0 to 2249, assuming n_slotIndicates the slot unit number, then n_slot∈[0,2249]At least 12 bits of binary digits are required for quantization.

The communication station (mobile station or control station) scrambles the signal of each physical channel, typically by multiplying the signal by a scrambled signal. In the method for generating a scrambled signal provided in the embodiment of the present application, a first sequence is BPSK modulated to generate a scrambled signal. Naturally, when a communication station scrambles a signal to be transmitted, the multiplication with the scrambled signal is a signal in the form of symbols that have been modulated, typically a complex multiplication.

The first sequence, i.e., the sequence prior to BPSK modulation, is generated by modulo-2 inner product of an M-bit mask with the M state vectors of the M-bit PN sequence generator. Wherein the M bit mask is determined according to 1) the cell control station identity/ID, i.e. the cell control station MMSI in a VDES system, and 2) the carrier frequency parameters used for signal transmission, e.g. the spectral channel number. M is an integer value and satisfies: 1) not less than the sum of the number of binary bits required to quantize the cell control station ID and the number of binary bits required to quantize the carrier frequency parameter; and 2) greater than the number of binary bits required to quantize a slot unit within a frame unit. For example, the MMSI of the control station in the quantization VDES system requires at least 30 bits of binary digits, and the quantization carrier frequency parameter, such as the spectral channel number of the VDES system, requires at least 12 bits of binary digits, and the value of M should be not less than 42. In addition, in the VDES system, the number of slot units in each frame unit is 2250, and at least 12 bits of binary digits are required for quantization.

The restrictions of 1) M not less than 42 and 2) M greater than 12 are satisfied, and optionally, M is 42. The value of M is determined, the period of the PN sequence is also determined, and the generating polynomial of the PN sequence can be designed correspondingly. Referring to fig. 2, in the embodiment, a 42-bit PN sequence generator is constructed by using a 42-state (state) linear Feedback Shift register lsfr (linear Shift Feedback register), and the corresponding PN sequence generator polynomial satisfies

F(x)＝x⁴²+x³⁵+x³³+x³¹+x²⁷+x²⁶+x²⁵+x²²+x²¹+x¹⁹+x¹⁸+x¹⁷+x¹⁶+x¹⁰+x⁷+x⁶+x⁵+x³+x²+x+1.

In fig. 2, the rectangular boxes with numbers represent the respective shift registers of the PN sequence generator, it being understood that each shift register state in the PN sequence generator may be a binary 0 or 1. The states of these 42 shift registers at any one time are referred to as the 42 state vectors of the PN sequence generator.

A mask (mask), applied to the 42 state vectors of the PN sequence generator, can effectively "shift" the PN sequence phase to a new phase. Referring to fig. 2, the modulo-2 inner product of the 42 bit masks and the 42 state vectors of the PN sequence generator includes two operation steps: the first step is to carry out and operation on 42 bit masks and 42 state vectors of a PN sequence generator according to bits to obtain 42 bit binary results with the same length; the second step is to sum all the binary numbers in the binary result modulo two. Since the bitwise and operation in the first step works the same as the product-wise operation in the binary system, the modulo-two summation in conjunction with the second step is called the modulo-2 inner product operation. The following is an example of modulo-2 inner product operation, where two binary numbers are "0010" and "0011", respectively, and bitwise and operation is performed to obtain "0010", and then modulo binary summation is performed on the binary result "0010" to obtain a binary result "1". Obviously, the modulo-2 inner product of the 42-bit mask and the 42-bit state vector of the PN sequence at any time outputs a one-bit binary number, and the outputs at a plurality of times form a string of sequences, i.e., the first sequence. Thus, in this embodiment, FIG. 2 may be considered a "first sequence generator" structure.

One embodiment of implementing the determination of the M-bit mask by the two parameters, i.e., the cell control station ID and the spectral channel number used for signal transmission, is to arrange these two parameters into a binary value according to the high and low bits as the M-bit mask, wherein the binary value satisfies the following formula:

A·2^x+B，

wherein A, B is the value of these two parameters, and x is the coefficient parameter for determining the binary numerical formula, and is a positive integer. The coefficient parameter of the former term in the formula is determined according to the value range of the latter term. For example, referring to fig. 3, in the VDES system, the cell control station ID, i.e. the control station MMSI, is regarded as M (═ 42) bitsHigh order of the mask, i.e. A ═ N_MMSIThe number of the spectrum channel used for signal transmission is used as the lower bit of the 42-bit mask, i.e. B ═ n_CIUnder such an embodiment, the binary value made up of these two parameters may satisfy the following equation:

N_MMSI·2¹²+n_CI，

the reason why the coefficient parameter x is 12 is the spectral channel number n_CIThe value range of (a) needs at least 12 bits of binary digits to be quantized, and the binary digits can be directly used as a 42-bit mask. For another example, referring to fig. 4, in the VDES system, the spectrum channel number used for signal transmission is used as the high order of the M-bit mask, that is, a ═ n_CIThe cell control station ID, i.e. the control station MMSI, is used as the lower bit of the M-bit mask, i.e. B ═ N_MMSIUnder such an embodiment, the binary value made up of these two parameters may satisfy the following equation:

n_CI·2³⁰+N_MMSI，

wherein the coefficient parameter x is 30 because of N_MMSIThe value range of (a) needs at least 30 bits of binary digits for quantization, and the binary digits can be directly used as a 42-bit mask.

It should be understood that the constraints of 1) M not less than 42 and 2) M greater than 12 are satisfied, and a PN sequence generator with, for example, M ═ 45 bits may also be used. Accordingly, the mask is required to be 45 bits, and the binary value of 42 bits is formed by the above two parameters according to the binary value formula, so that an additional 3-bit value is required. Optionally, a 3-bit binary value, such as "111", is filled into the 45-bit mask according to a predetermined ordering or rule.

The initial values of the M-bit PN sequence generator involved in generating the scrambled signal are determined based on 1) the frame unit number used for signal transmission, i.e., the corresponding UTC minute time in a VDES system, and 2) the slot unit number within the frame unit used for signal transmission. One embodiment for implementing that the initial value of the PN sequence generator is determined by the two parameters, which are arranged into a binary value according to high and low bits as the initial value of the PN sequence generator.

For example, referring to fig. 3, in the VDES system, the slot unit number n of 12 bits in the frame unit used for signal transmission is numbered_slotAs the high order bit of the initial value of the PN sequence generator, i.e., a ═ n_slotAnd the UTC minute time corresponding to the frame unit adopted by signal transmission is taken as the low order bit of the initial value of the PN sequence generator. Alternatively, a 42-bit PN sequence generator is still taken as an example. The initial value is the initial state value of 42 state registers for determining 42 bit PN sequence generator, the number of time slot unit used for signal transmission occupies 12 bits, 30 bits are left, and 2 bits can be quantized³⁰Frame unit number, corresponding to 2 quantizable in VDES systems³⁰Change in minutes. Optionally, the frame unit is not greater than 2³⁰A time period of minutes, such as one cycle of "one day" time, i.e., 24 hours multiplied by 60 minutes, equals 1440 minutes, which in a VDES system cycles once every 1440 frame units. The 1440 values from 0 to 1439 can be obtained by modulo 1440 the UTC minute corresponding to the frame unit, that is, B ═ n_UTCmod 1440. in such an embodiment, the binary value of these two parameters can satisfy the following equation:

n_slot·2¹¹+n_UTC mod 1440，

the coefficient parameter x is 11 because 1440 minutes of time needs to be quantized using at least 11 bits of binary digits. The 30 bits are reserved 19 bits, and the reserved 19 bits are filled to the high order to form the final 42-bit initial value, optionally supplemented with a 19-bit binary 1, see fig. 3. For another example, referring to fig. 4, in the VDES system, the UTC minute time corresponding to the frame unit used for signal transmission is set as the high order bit of the initial value of the PN sequence generator, and the 12-bit slot unit number in the frame unit used for signal transmission is set as the low order bit of the initial value of the PN sequence generator, that is, B ═ n_slot. Alternatively, in the VDES system, the frame unit is still cyclically changed by taking "one day" as a period, that is, a is equal to n_UTCmod 1440. in such an embodiment, the binary values of these two parameters satisfyThe formula:

(n_UTCmod 1440)·2¹²+n_slot。

the reserved 19 bits are then padded high to form the final 42-bit initial value, which may optionally be supplemented with a 19-bit binary 1.

In other embodiments, such as a VDES system, if a frame unit changes once in "one week" time, that is, when the time is multiplied by 1440 minutes, which is equal to 10080 minutes, the UTC minutes corresponding to the frame unit is modulo 10080 to obtain 10080 values of 0 to 10079, and the quantization is performed by using 14-bit binary digits, and then 16 bits are reserved in 30 bits. Optionally, a 16-bit binary value, such as "11 … … 1", is padded into the 42-bit initial value according to a predetermined rule.

Another example of the embodiment of the present application is that the time length of the frame unit is not equal to one minute, and the frame unit is not aligned with the UTC minute, in this case, the time period of the frame unit change can still be set, and the binary digits for quantizing the number of the frame units are calculated according to the corresponding number of the frame units in the time period, i.e. the number range set of the frame units in the fixed time period is obtained. The communication station may determine the initial value of the PN sequence register based on the number of the frame unit in which the signal is transmitted during the corresponding time period, in combination with the slot unit number in the frame unit used for the signal transmission.

In the VDES system, a control station broadcasts some system information acquisition signals to a serving cell on some special channels, for example, a bulletin board information is transmitted on a bulletin board signaling channel, and the bulletin board information includes the MMSI of the cell control station. After all mobile stations in any service cell receive the bulletin board information broadcast by the control station of the cell, the MMSI of the control station of the cell can be obtained. When a communication station (mobile station or control station) determines a frame unit number used for signal transmission and a slot unit number in a frame unit used for signal transmission, an initial value of a PN sequence generator is also determined. Then, the communication station can determine the M-bit mask according to the known MMSI of the control station and the carrier frequency parameters adopted by signal transmission, and performs modulo-2 inner product operation on the M-bit mask and the M-bit state vector of the M-bit PN sequence generator to generate a first sequence. Finally, the communication station subjects the first sequence to BPSK modulation to obtain a scrambled signal, and scrambles the signal to be transmitted with the scrambled signal.

After the receiving communication station receives the signal transmitted by the transmitting communication station, the received signal may be descrambled based on the same scrambled signal as used when the transmitting communication station scrambled the signal. For some special system information acquisition signals within a frame unit, such as the bulletin board information broadcast by the cell control station in VDES on the bulletin board signaling channel, the MMSI of the cell control station is included in the bulletin board information, and thus the MMSI of the cell control station is unknown until the receiver successfully receives the signal. In order to assist the receiver in descrambling these special system information acquisition signals, in the VDES system, the control station identification required to generate the M-bit mask of the scrambled signal may be replaced with a fixed special number, e.g., 0, 1, 2, etc., when the control station transmits the billboard information.

Claims

1. A method of generating a scrambled signal, comprising the steps of:

1) the communication station determines M bit masks according to cell control station identifiers and carrier frequency parameters adopted by signal transmission, the communication station comprises a mobile station and a control station, and specifically, the cell control station identifiers and the carrier frequency parameters adopted by the signal transmission are arranged into a binary value in any sequence, the binary value is used as the M bit masks, and the binary value satisfies the following conditions:

A·2^x+B

when A is a cell control station identifier, B is a carrier frequency parameter adopted by signal transmission; when A is a carrier frequency parameter adopted by signal transmission, B is a cell control station identifier; the carrier frequency parameter is a center frequency number or a frequency spectrum channel number; x is a positive integer and is not less than the number of binary bits required by the quantization parameter B;

2) the communication station determines the initial value of the M-bit PN sequence generator according to the frame unit number adopted by signal transmission and the time slot unit number in the frame unit adopted by the signal transmission, and specifically, arranges the frame unit number adopted by the signal transmission and the time slot unit number in the frame unit adopted by the signal transmission into a binary number in any sequence to be used as the initial value of the PN sequence generator;

2. The method as claimed in claim 1, wherein, when the communication station is a control station and transmits a system information acquisition signal, the control station determines the M-bit mask using a fixed special number and a carrier frequency parameter used for signal transmission in step 1), and the system information acquisition signal is at least used for the control station to transmit a local cell control station identifier to a mobile station in a cell.

3. The scrambled signal generation method of claim 1 or 2, wherein M is an integer and satisfies:

4. The method for generating scrambled signals according to claim 1, wherein in step 3), an and operation is performed on the M-bit mask and the M-bit state vector to obtain a binary result with the same length; and performing modulo binary summation on all data in the binary result according to the binary system to obtain a first sequence.