CN114095324A - Framing method and equipment for narrow-band data broadcast and physical layer signal frame - Google Patents
Framing method and equipment for narrow-band data broadcast and physical layer signal frame Download PDFInfo
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Abstract
The invention discloses a framing method of narrow-band data broadcast and equipment thereof, physical layer signal frames, two paths of pseudo-random sequences form synchronous beacons through a series of transformation, 32 MID sequences form transmission mode beacons through a series of transformation, the synchronous beacons and the transmission mode beacons form beacons, 58 OFDM symbols and the beacons form physical layer signal frames, and 1 or 4 physical layer signal frames form superframes; program information in an audio program does not need to be transmitted, a single transmission channel mode different from HDradio and CDR is adopted, all channel resources can be used for transmitting differential data, and the transmission efficiency is high.
Description
Technical Field
The present invention relates to the field of communications, and in particular, to a method and apparatus for framing a narrowband data broadcast, and a physical layer signal frame.
Background
With the continuous development of global satellite navigation GNSS technology, the standard positioning accuracy of satellite navigation of several meters to dozens of meters cannot meet the requirement of users on high-accuracy positioning. The differential GNSS technology which can effectively improve the positioning accuracy by utilizing the space and time correlation characteristics of the GNSS observation error is widely applied. At present, differential GNSS equipment mainly comprises a pseudo-range differential GNSS and a carrier phase differential GNSS, and the positioning accuracy of the differential GNSS equipment can reach sub-meter level and centimeter level respectively. With the rapid development of the field of differential satellite navigation positioning, the real-time dynamic carrier phase technology, the network dynamic carrier phase technology and the like come into play; meanwhile, a continuously-operating reference station system based on a network dynamic carrier phase technology is rapidly developed in all countries in the world, theoretical technical achievements in the field are greatly applied to actual life and production application, the accuracy of satellite navigation positioning is effectively improved, and the use experience of users is improved. The differential data transmitted in the continuously operating reference station system is mainly encoded in the rules of the RTCM (Radio Technical Commission for Maritime services, a differential positioning signal data format specified by the international Maritime industry Radio Technical Commission) protocol. At present, the mainstream way for transmitting differential data by high-precision positioning service is based on Ntrip (network Transport of RTCM via Internet Protocol, Protocol for performing RTCM network transmission through the Internet) Protocol to transmit and share data information in the Internet.
With the development of intelligent driving technology and smart cities, the requirements of various industries on high-precision positioning services are more and more popularized, and the number of users for high-precision positioning is more and more large. In the future, high-precision positioning is required in the professional field, and common consumers also need high-precision positioning. Based on the future popularization expectation of high-precision positioning, the current mode of transmitting differential data through the internet (an end user usually transmits the differential data through a wireless network such as 4G or 5G) will cause many problems after large-scale commercial use, and the popularization of high-precision positioning service is influenced. Therefore, a method for transmitting differential data by using the frequency modulation digital broadcasting technology is provided, and a new technology can solve the problems and bottlenecks encountered by the prior art in the future popularization process of high-precision positioning services. For convenience of description, a technology for transmitting differential data using the internet is referred to as a network differential technology, and a technology for transmitting differential data using a fm digital broadcasting technology is referred to as a broadcast differential technology.
The network difference technology adopts a client-server mode to access a server to establish a link, the approximate position of a terminal user is reported, the server generates difference data at the position of the user in real time, the terminal acquires the difference data from the service through an Ntrip protocol, and the terminal acquires the difference data and then carries out high-precision positioning calculation to acquire high-precision position information. In the client-server access mode, congestion is easily formed when massive user services are accessed concurrently. The broadcasting difference technology adopts a broadcasting single-point-to-multipoint transmission mode, differential data of each position in a service area are generated by a data center at regular time according to a fixed time period to form a differential data set, the differential data are continuously multicast and sent to all users in the service area through a broadcasting station, the users can continuously receive the differential data set broadcasted by broadcasting without reporting the position, a certain differential data which most meets the high-precision positioning requirement of the users in the differential data set is selected by the terminal according to the position of the users, and the high-precision positioning calculation is carried out after the terminal obtains the differential data to obtain high-precision position information.
The network difference technology utilizes the existing mobile network, and each terminal generates network use cost when using the mobile network, so that the cost is huge when massive users use the mobile network. The broadcast differential technology employs single-point-to-multipoint transmission during differential data transmission, and theoretically, the transmission cost of one user and an unlimited user in a service area is the same, so that an unlimited number of users can be served with a very small fixed cost. When a large number of users are present, the broadcast differencing technique will form a huge cost advantage in terms of network transmission cost.
The 4G and 5G mobile networks used by the network differential technology are easy to generate large network delay and even network congestion due to the user capacity of a base station, concurrent access of users and the like, so that the differential data transmission delay is unstable and the transmission delay is large. Cellular networks are often adopted in existing 4G and 5G mobile networks, and for fast handover of a user moving at a high speed between different base stations in the mobile network, the time delay of network communication is unstable during the handover of the base stations, and sometimes, problem and overlong delay occur. The satellite navigation differential data is data sensitive to the transmission delay stability and the transmission delay, the transmission delay is unstable, deep optimization of a high-precision calculation algorithm is not facilitated, and the positioning precision is reduced due to overtime of the differential age caused by excessive transmission delay. The broadcast difference technology uses a broadcast technology, the service area of one broadcast station is large, broadcast signals continuously cover the whole area in the service area, the frequency modulation broadcast carrier frequency is low, the penetrating power is strong, and the signal covering effect is good. In the service area, the time delay of the broadcast signal reaching each user is almost the same, and the stability of the differential age is guaranteed. Fm digital broadcasting technology, narrowband data broadcasting (NBB), is specifically designed for transmitting differential data, with the NBB broadcast transmission delay being minimal, thereby optimizing differential age. For the users moving at high speed, the broadcast difference technology can not cause the instability and even the overdue of the difference age due to the frequent switching of the base station. In the areas with poor coverage of 4G and 5G mobile networks, the coverage advantage of the FM broadcasting technology is more obvious. The broadcast differential technology has higher reliability and availability.
In the network difference technology, when a terminal user acquires difference data, the approximate position of the user must be uploaded first, and the server can generate the difference data for the user after receiving the user position and transmits the difference data to the user through a network. The user of the network difference technology must upload own position information, which is unfavorable for data security and unfavorable for privacy protection of the user. The broadcast difference technology adopts a broadcast transmission technology and is in one-way connection, a user does not need to upload any information, a broadcast station does not collect any user information, and data security and user information privacy are better guaranteed.
As the main users of 4G and 5G mobile networks used in the network difference technology are located on the ground, in order to improve the coverage efficiency, the network optimization of the mobile networks is performed in the ground direction, and for the air direction, the network quality of mobile communication cannot be guaranteed, even most areas cannot normally communicate. Fm broadcast is omni-directional antenna coverage, and signal global coverage on the ground and in the air. For the equipment such as unmanned aerial vehicles and the like which need to fly at low altitude, the equipment uses high-precision positioning service, differential data transmission adopts a mobile network, communication cannot be guaranteed, differential data is transmitted by adopting a broadcasting technology, and the air service and the ground service are consistent. Broadcast differencing techniques have absolute advantages over low-altitude coverage.
The broadcasting technology has a plurality of advantages in differential data transmission, and the adoption of the broadcasting for transmitting the differential data can optimize and meet the requirements of high-precision positioning service. However, not all broadcasting technologies are suitable for transmitting differential data, and narrow-Band data broadcasting, abbreviated as NBB (narrow Band data broadcast), is designed for transmitting satellite navigation positioning ground-based enhanced differential data, and the NBB is used for transmitting differential data to make the advantages of the broadcasting technology.
The NBB technology is a parasitic fm broadcasting technology developed based on fm band, and the differences and technical advantages of the new broadcasting technology from other parasitic fm broadcasting technologies will be briefly described below.
Conventional FM audio signal transmission typically uses only a portion of the bandwidth in the FM band, and utilizes analog modulation techniques to transmit the audio signal. In order to utilize the remaining frequency spectrum resources of the FM, people design various digital modulation technologies to transmit data in-band or out-of-band of the FM in the development of the FM, so that digital signals and analog signals in the FM frequency band are simultaneously broadcast in the same frequency band, and the FM frequency spectrum resources are effectively utilized. The FM in-band digital transmission standards are known as RDS and DARC, and the FM out-of-band digital transmission standards are known as HDradio in the united states and CDR in china, as shown in fig. 1.
The FM in-band digital transmission systems such as RDS, DARC, FMextra and the like are called digital subcarrier communication systems, can be directly accessed to an FM exciter through an SCA subcarrier interface, and most FM exciters in the market currently support the SCA interface. Part of FM exciter embeds supports RDS modulator, DARC modulator, can directly use, and digital subcarrier communication system that does not embed support can insert FM exciter through SCA mouth.
HDradio, CDR, and NBB technologies utilize FM out-of-band frequencies to transmit digital signals, which may be referred to as FM out-of-band digital transmission systems.
HDradio and CDR are digital transmission systems developed specifically for digital audio broadcasting. Digital audio broadcasting is the third generation broadcasting after am and fm broadcasting, which all uses digital processing for audio broadcasting. Digital audio broadcasting has become a necessary trend in broadcasting development. The introduction of the digital technology can effectively improve the sound quality of audio broadcasting, improve the utilization rate of frequency spectrum, effectively reduce the power of a transmitter and reduce electromagnetic pollution. HDradio and CDR broadcast utilize the idle frequency resources between the existing analog broadcast channels to carry out digital audio broadcasting under the condition of keeping the existing equipment and frequency division unchanged and not interfering the existing analog broadcast as much as possible. HDradio and CDR digital audio broadcasts will coexist with analog FM audio broadcasts over a period of time and gradually transition smoothly into the digital audio broadcast era.
NBB digital broadcasting technology and HDradio and CDR are both FM out-of-band digital transmission systems, and the main technical architecture adopts COFDM modulation, but NBB is not designed for digital audio broadcasting. The NBB digital broadcasting technology is a data transmission system specially designed for transmitting satellite navigation differential data, and compared with HDradio and CDR technologies, the NBB digital broadcasting technology has the advantages of lower transmission delay, higher data organization flexibility and higher transmission efficiency, and is more suitable for transmitting satellite navigation differential data.
The HDradio and the CDR both adopt a longer signal frame length and a longer interleaving block, so that the modulation and demodulation delay of the digital signal is larger, and the HDradio and the CDR are not suitable for the requirement of high transmission delay of differential data. The HDradio and CDR technologies customize an interface protocol for audio transmission, a frame structure is strongly related to audio transmission, the butt joint with various data formats of differential data is inflexible in data organization, the butt joint efficiency is not high, idle running of transmission data frames is easy to occur, and transmission bandwidth is wasted. The HDradio and CDR technology is divided into a control data transmission channel and a service data transmission channel on the design structure, the structural design meets the channel division requirement in the digital audio broadcasting, the control data transmission channel transmits configuration information and program information, and the service data transmission channel transmits audio data streams. The double-channel design has great waste on differential data transmission, the differential data transmission can only utilize a service data transmission channel, and a control data transmission channel can not transmit effective information. The HDradio and CDR techniques are inefficient at transmitting differential data. The HDradio adopts error correction coding with weak error correction capability, and the transmission anti-jamming capability is insufficient. CDR is divided coarsely in the design of frequency spectrum utilization, and the out-of-band frequency spectrum of FM can not be fully utilized, so that the frequency spectrum utilization rate of a transmission system is reduced.
The NBB technology is specially designed for transmitting differential data, and adopts a shorter frame structure and a smaller interleaving block structure, so that the delay of modulation and demodulation of a digital signal is smaller, and the requirement of the differential data on the high transmission delay is better met. The NBB technology is more flexible in frame structure and interface protocol, can realize more efficient butt joint with a data structure of differential data, and improves the transmission efficiency of a system. The NBB technology adopts a mode of a single transmission channel different from HDradio and CDR, all channel resources can be used for transmitting differential data, and the transmission efficiency is high. The NBB adopts LDPC error correction coding, and compared with the HDradio adopted convolutional coding, the error correction capability is stronger, the anti-interference capability is stronger, and the receiving effect is better. The NBB adopts a more flexible and more detailed spectrum mode than the CDR, the spectrum utilization rate is higher, and the future expandability is stronger.
Although the HDradio, CDR, and NBB technologies are all parasitic fm broadcast technologies, the HDradio and CDR broadcast technologies are not suitable for transmitting differential data.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a framing method of narrow-band data broadcasting, equipment thereof and a physical layer signal frame, aiming at the transmission of differential data, a shorter frame structure and a smaller interleaving block structure are adopted, so that the delay of digital signal modulation and demodulation is smaller, and the requirement of differential data on high transmission delay is better met.
In a first aspect, the present invention provides a framing method for narrowband data broadcasting, including the following steps:
step 1: carrying out OFDM modulation on service data to generate 58 OFDM symbols;
step 2: defining and generating two paths of pseudo-random sequences, and modulating data generated by the two paths of pseudo-random sequences to generate synchronous pilot symbols;
and step 3: mapping and transforming the synchronous pilot frequency symbol to form an OFDM symbol of a synchronous beacon according to the mapping relation between the NBB system frequency spectrum mode and the subcarrier;
and 4, step 4: copying the OFDM symbols in the step 3 to generate 2 same OFDM symbols, forming a synchronization head by the 2 same OFDM symbols, and adding a cyclic prefix to the synchronization head to form a synchronization beacon;
and 5: defining and generating an MID bit sequence, and modulating the MID bit sequence into a complex symbol sequence;
step 6: mapping and transforming the complex symbol sequence to form an OFDM symbol of the transmission mode beacon according to the corresponding relation between the transmission mode spectrum mode and the NBB system spectrum mode and the mapping relation between the transmission mode spectrum mode and the subcarrier;
and 7: adding a cyclic prefix to the OFDM symbol in the step 6 to form a transmission mode beacon;
and 8: forming a beacon by the synchronization beacon and the transmission mode beacon, forming a physical layer signal frame by the beacon and the 58 OFDM symbols of the step 1, and forming a superframe by 1 or 4 physical layer signal frames.
Further, in step 2, the specific modulation process of the synchronization pilot symbol is as follows:
step 2.1: two pseudo-random sequences are defined, which are respectively:
pI＝{pI1，pI2，…，pIi，…，pIpl}，pQ＝{pQ1，pQ2，…，pQi，…，pQpl}
wherein pl is the pilot length, the value of pl is Nv, and Nv is the number of effective carriers;
step 2.2: generating two paths of pseudo-random sequences defined in the step 2.1 by adopting a pseudo-random sequence generator;
step 2.3: under each spectrum mode of the NBB system, bit stream pairs pI synthesized by two paths of pseudo-random sequences1pQ1，pI2pQ2，…，pIipQi，…，pIplpQplAnd sequentially mapped into synchronous pilot symbols through QPSK.
Further, in the step 3, the NBB system spectrum pattern includes a class a spectrum and a class B spectrum;
the class A spectrum includes spectrum patterns A1-A16, wherein:
the frequency range of a lower sideband of the frequency spectrum mode A1 is-200 KHz to-150 KHz, the frequency range of an upper sideband is 150KHz to 200KHz, the number of included sub-bands is 2, and the bandwidth is 100 KHz;
the frequency range of a lower sideband of the frequency spectrum mode A2 is-250 KHz to-150 KHz, the frequency range of an upper sideband is 150KHz to 250KHz, the number of contained sub-bands is 4, and the bandwidth is 200 KHz;
the frequency range of a lower sideband of the frequency spectrum mode A5 is-150 KHz to-100 KHz, the frequency range of an upper sideband is 100KHz to 150KHz, the number of contained sub-bands is 2, and the bandwidth is 100 KHz;
the frequency range of a lower sideband of the frequency spectrum mode A6 is-200 KHz to-100 KHz, the frequency range of an upper sideband is 100KHz to 200KHz, the number of contained sub-bands is 4, and the bandwidth is 200 KHz;
the frequency range of a lower sideband of the frequency spectrum mode A9 is-200 KHz to-130 KHz, the frequency range of an upper sideband is 130KHz to 200KHz, the number of included sub-bands is 2.5, and the bandwidth is 140 KHz;
the frequency range of a lower sideband of the frequency spectrum mode A10 is-250 KHz to-130 KHz, the frequency range of an upper sideband is 130KHz to 250KHz, the number of contained sub-bands is 4.5, and the bandwidth is 240 KHz;
the spectrum modes A3, A4, A7, A8 and A11-A16 are reserved;
the B-class spectrum comprises spectrum patterns B1-B8, wherein:
the frequency range of a lower sideband of the frequency spectrum mode B1 is-50 KHz-0 KHz, the frequency range of an upper sideband is 0 KHz-50 KHz, the number of included sub-bands is 2, and the bandwidth is 100 KHz;
the frequency range of a lower sideband of the frequency spectrum mode B2 is-100 KHz-0 KHz, the frequency range of an upper sideband is 0 KHz-100 KHz, the number of contained sub-bands is 4, and the bandwidth is 200 KHz;
the frequency range of a lower sideband of the frequency spectrum pattern B3 is-150 KHz-0 KHz, the frequency range of an upper sideband is 0 KHz-150 KHz, the number of included sub-bands is 6, and the bandwidth is 300 KHz;
the frequency range of a lower sideband of the frequency spectrum mode B4 is-200 KHz-0 KHz, the frequency range of an upper sideband is 0 KHz-200 KHz, the number of contained sub-bands is 8, and the bandwidth is 400 KHz;
the frequency range of a lower sideband of the frequency spectrum mode B5 is-250 KHz-0 KHz, the frequency range of an upper sideband is 0 KHz-250 KHz, the number of included sub-bands is 10, and the bandwidth is 500 KHz;
the spectrum patterns B6-B8 are all reserved.
Further, in step 3, the specific forming process of the OFDM symbol of the synchronization beacon is as follows:
step 3.1: filling the synchronous pilot symbols into effective subcarriers in a corresponding frequency spectrum mode, and filling zero complex symbols into virtual subcarriers which are not filled with the synchronous pilot symbols;
step 3.2: and carrying out IFFT transformation on the sub-carriers filled with the synchronous pilot symbols and the zero complex symbols to form OFDM symbols of the synchronous beacon.
Further, in step 4, the length of the synchronization beacon is:
Tsb＝Tscp+2×Tu
wherein, TsbFor the length of the synchronization beacon, in units of ms, TscpLength of cyclic prefix for sync beacon in ms, TuThe length of the synchronization beacon OFDM symbol is in ms.
Further, in step 5, the specific modulation process of the complex symbol sequence is as follows:
step 5.1: defining 32 MID bit sequences corresponding to 32 PN sequences, wherein the length of each PN sequence is 62 bits, each MID bit sequence MID (i) is expressed as MID (i) ═ PN [0:61], and sequentially generating 32 PN sequences by using a linear feedback shift register;
step 5.2: each bit of each MID bit sequence MID (i) is modulated into a complex symbol by BPSK modulation, each MID bit sequence MID (i) is modulated into 62 complex symbols, and 32 MID bit sequences form a 32 × 62 complex symbol sequence.
Further, in step 6, the transmission mode spectrum modes are divided into three types, i.e., mode 1, mode 2, and mode 3;
the frequency range of a lower sideband of the mode 1 is-50 KHz-0 KHz, the frequency range of an upper sideband is 0 KHz-50 KHz, the bandwidth is 100KHz, and the mode 1 corresponds to NBB system frequency spectrum modes B1-B5;
the frequency range of a lower sideband of the mode 2 is-150 KHz to-100 KHz, the frequency range of an upper sideband is 100KHz to i50KHz, the bandwidth is 100KHz, and the mode 2 corresponds to NBB system frequency spectrum modes A5 and A6;
the frequency range of a lower sideband of the mode 3 is-200 KHz to-150 KHz, the frequency range of an upper sideband is 150KHz to 200KHz, the bandwidth is 100KHz, and the mode 3 corresponds to NBB system spectrum modes A1, A2, A9 and A10.
Further, in step 6, the specific forming process of the OFDM symbol of the transmission mode beacon is as follows:
step 6.1: filling the complex symbol sequence into effective subcarriers in a transmission mode spectrum mode, and filling zero complex symbols into virtual subcarriers which are not filled with the complex symbol sequence; the transmission mode spectrum mode corresponds to each spectrum mode of the NBB system;
step 6.2: and carrying out IFFT transformation on the subcarriers filled with the complex symbol sequence and the zero complex symbol to form the OFDM symbols of the transmission mode beacon.
Further, in step 7, the length of the transmission mode beacon is:
Tm＝Tmcp+Tmu
wherein, TmFor the length of the transmission mode beacon, in ms, TmcpLength of cyclic prefix for transmission mode beacon in ms, TmuThe length of the transmission mode OFDM symbol is in ms.
In a second aspect, the present invention provides a framing device for narrowband data broadcasting, including: an OFDM generation unit, a synchronization beacon generation unit, a transmission mode beacon generation unit and a composition unit;
the OFDM generating unit is used for carrying out OFDM modulation on the service data to generate 58 OFDM symbols;
the synchronous beacon generating unit is used for defining and generating two paths of pseudo-random sequences and modulating data generated by the two paths of pseudo-random sequences to generate synchronous pilot symbols; mapping and transforming the synchronous pilot frequency symbol to form an OFDM symbol of a synchronous beacon according to the mapping relation between the NBB system frequency spectrum mode and the subcarrier; the OFDM symbols of the synchronous beacon are copied to generate 2 identical OFDM symbols, a synchronous head is formed by the 2 identical OFDM symbols, and a cyclic prefix is added to the synchronous head to form the synchronous beacon;
the transmission mode beacon generating unit is used for defining and generating an MID bit sequence and modulating the MID bit sequence into a complex symbol sequence; mapping and transforming the complex symbol sequence to form an OFDM symbol of the transmission mode beacon according to the corresponding relation between the transmission mode spectrum mode and the NBB system spectrum mode and the mapping relation between the transmission mode spectrum mode and the subcarrier; adding a cyclic prefix to the OFDM symbol of the transmission mode beacon to form a transmission mode beacon;
the composition unit is used for forming a beacon by the synchronization beacon and the transmission mode beacon, forming a physical layer signal frame by the beacon and 58 OFDM symbols, and forming a superframe by 1 or 4 physical layer signal frames.
In a third aspect, the present invention provides a physical layer signal frame, which is composed of a beacon and 58 OFDM symbols, wherein the beacon is composed of a synchronization beacon and a transmission mode beacon; the synchronization beacon is formed by steps 2-4 of the framing method for narrowband data broadcasts as described in the first aspect, and the transmission mode beacon is formed by steps 5-7 of the framing method for narrowband data broadcasts as described in the first aspect.
The invention has the beneficial effects that:
1. compared with HDradio and CDR which both adopt a longer signal frame length and a longer interleaving block, the delay of digital signal modulation and demodulation is larger and is not suitable for the requirement of high transmission delay of differential data;
2. the invention adopts a frame structure with the minimum length of 160ms, and uses two interleaving modes, wherein the interleaving depth of the longest interleaving mode is 640ms, and both the interleaving depth and the interleaving depth are far smaller than the frame lengths of HDradio and CDR;
3. compared with the HDradio and CDR technology, the design structure is divided into the control data transmission channel and the service data transmission channel, the double-channel design has larger waste for differential data transmission, the differential data transmission can only utilize the service data transmission channel, the control data transmission channel can not transmit effective information, the HDradio and CDR technology has low efficiency in transmitting differential data, the NBB system does not need to transmit program information in an audio program, a single transmission channel mode different from the HDradio and CDR is adopted, all channel resources can be used for transmitting differential data, and the transmission efficiency is high;
4. the invention fuses the system control information in the transmission mode header, transmits the system control information along with the frame header without a special transmission channel, fully utilizes the transmission capability of the channel and improves the transmission efficiency.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only one embodiment of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a diagram illustrating the utilization of FM in-band and out-of-band spectrum in the background of the invention;
FIG. 2 is a block diagram of an NBB system in an embodiment of the invention;
fig. 3 is a flowchart of a framing method for narrowband data broadcasting according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating a pseudo-random sequence generator for synchronizing pilot frequencies according to an embodiment of the present invention;
fig. 5 is a QPSK modulation constellation according to an embodiment of the present invention;
fig. 6 is a graph of a spectrum pattern of the NBB system according to the embodiment of the present invention, where (a) is a graph of a spectrum pattern a1, (B) is a graph of a spectrum pattern a2, fig. (c) is a graph of a spectrum pattern a5, fig. (d) is a graph of a spectrum pattern a6, fig. (e) is a graph of a spectrum pattern a9, fig. (f) is a graph of a spectrum pattern a10, fig. (g) is a graph of a spectrum pattern B1, fig. (h) is a graph of a spectrum pattern B2, fig. (i) is a graph of a spectrum pattern B3, fig. (j) is a graph of a spectrum pattern B4, and fig. (k) is a graph of a spectrum pattern B5;
FIG. 7 is a diagram of a synchronization beacon OFDM symbol structure according to an embodiment of the present invention;
FIG. 8 is a linear feedback shift register for transfer mode MID in an embodiment of the present invention;
fig. 9 is a BPSK modulation constellation in an embodiment of the present invention;
FIG. 10 is a diagram of a spectrum pattern of a transmission mode beacon in accordance with an embodiment of the present invention;
fig. 11 is a diagram of a transmission mode beacon OFDM symbol structure according to an embodiment of the present invention.
Detailed Description
The technical solutions in the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The technical solution of the present application will be described in detail below with specific examples. The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments.
As shown in the structural block diagram of the NBB system shown in fig. 2, service data to be transmitted by an upper layer enters the NBB system, scrambling, channel coding, framing organization, OFDM signal modulation are performed in the NBB system, and a modulated signal is converted into a radio frequency signal by a radio frequency module. The service data is composed of data from each service defined by the NBB system upper layer protocol. After the service data is processed by scrambling, LDPC coding, bit interleaving and constellation mapping, OFDM symbols are generated through OFDM modulation, and corresponding pilot frequency is added in the OFDM symbols; and combining a plurality of OFDM symbols and a beacon head into a physical layer signal frame, forming a superframe from the physical layer signal frame according to different interleaving modes, modulating the superframe into a baseband signal, and finally modulating the baseband signal into a radio frequency signal for transmission. The NBB radio frequency signal can be transmitted through an antenna feeder antenna system after power amplification is carried out through a power amplification device.
The invention provides a new NBB system frame framing method for an NBB system, as shown in FIG. 3, comprising the following steps:
step 1: the traffic data is OFDM modulated to generate 58 OFDM symbols.
Step 2: two pseudo-random sequences are defined and generated, and data generated by the two pseudo-random sequences are modulated to generate synchronous pilot symbols.
In this embodiment, the two pseudo-random sequences are defined as follows:
pI＝{pI1，pI2，…，pIi，…，pIpl} (1)
pQ＝{pQ1，pQ2，…，pQi，…，pQpl} (2)
where pl is a pilot length (pilot length), pl is taken as Nv, Nv is an effective carrier number, and the effective carrier number can refer to an effective subcarrier index table, that is, tables 2 to 14.
As shown in fig. 4, a pseudo-random sequence generator with synchronous pilot frequency is used to generate two pseudo-random sequences defined by equations (1) and (2), and the generating polynomial of the linear feedback shift register is: x is the number of11+x9+1 with an initial value of 01010100101(0x2a 5).
Synthesizing two paths of pseudo-random sequences defined by the formulas (1) and (2) into bit stream pairs pI in each spectrum mode of the NBB system1pQ1，pI2pQ2，…，pIipQi，…，pIplpQplSequentially mapped into a QPSKSynchronizing pilot symbols, e.g. in spectral pattern A1, bit stream pairs pI1pQ1，pI2pQ2，…，pIipQi，…，pIplpQplWhich in turn is QPSK mapped to synchronization pilot symbols in spectral pattern a 1.
QPSK modulation is prior art, as shown in FIG. 5, QPSK modulation uses two bits v in FIG. 50v1Representing a two-bit sequence in QPSK modulation.
And step 3: and mapping and transforming the synchronous pilot symbols in the step 2 to form OFDM symbols of the synchronous beacon according to the mapping relation between the spectrum mode and the subcarriers of the NBB system.
Modulating the synchronous pilot symbols into OFDM symbols requires forming the OFDM symbols according to the spectrum mode set by the NBB system and the mapping relation of subcarriers in each spectrum mode. The NBB system spectrum mode comprises a type A spectrum and a type B spectrum; the A-type frequency spectrum is used in a digital-analog simulcast transmission mode, and the B-type frequency spectrum is used in a full digital transmission mode; the class A spectrum includes spectrum patterns A1-A16, and the class B spectrum includes spectrum patterns B1-B8, as shown in Table 1.
TABLE 1 NBB System Spectrum Pattern List
Spectral pattern a9 includes 2 Subbands (SB) and 2 Extended Subbands (ESB), and the transmission payload may be equivalent to 2.5 subbands. Spectral pattern a10 includes 4 Subbands (SB) and 2 Extended Subbands (ESB), and the transmission payload may be equivalent to 4.5 subbands. A graph of the NBB system spectrum pattern is shown in fig. 6.
The subcarrier interval of the OFDM symbols in the synchronous beacon is 398.4375Hz, the effective subcarrier numbers of different spectrum modes are different, each OFDM symbol comprises Nv effective subcarriers in one effective subcarrier, and the rest subcarriers are virtual subcarriers without modulating data. The effective subcarrier indexes are shown in tables 2-14:
TABLE 2 effective subcarrier index in each subband
| Sub-band | Frequency spectrum corresponding range (kHz) | Corresponding subcarrier index |
| SBU5 | 250～200 | 626～503 |
| SBU4 | 200～150 | 501～378 |
| SBU3 | 150～100 | 375～252 |
| |
100～50 | 250～127 |
| SBU1 | 50～0 | 124～1 |
| |
0～-50 | -1～-124 |
| SBL2 | -50～-100 | -127～-250 |
| SBL3 | -100～-150 | -252～-375 |
| SBL4 | -150～-200 | -378～-501 |
| SBL5 | -200～-250 | -503～-626 |
TABLE 3 effective subcarrier index in extended subbands
| Extension sub-band | Frequency spectrum corresponding range (kHz) | Corresponding subcarrier index |
| ESBU3 | 150～130 | 377～346 |
| ESBL3 | -130～-150 | -346～-377 |
Table 4 spectrum pattern a1 effective subcarrier index
Table 5 spectrum pattern a2 effective subcarrier index
Table 6 spectrum pattern a5 effective subcarrier index
Table 7 spectrum pattern a6 effective subcarrier index
Table 8 spectrum pattern a9 effective subcarrier index
Table 9 spectrum pattern a10 effective subcarrier index
Table 10 spectrum pattern B1 effective subcarrier index
Table 11 spectrum pattern B2 effective subcarrier index
Table 12 spectrum pattern B3 effective subcarrier index
Table 13 spectrum pattern B4 effective subcarrier index
Table 14 spectrum pattern B5 effective subcarrier index
The number of subcarriers of the OFDM symbol in the synchronization beacon is 2048, the number of effective subcarriers of different spectrum modes is defined in tables 2 to 14, and subcarriers other than the effective subcarriers are invalid subcarriers. And filling the pilot symbols into corresponding effective subcarriers according to different spectrum modes and subcarrier mapping modes in different spectrum modes. Bit stream pair pI in each spectral mode1pQ1，pI2pQ2，…，pIipQi，…，pIplpQplBit stream pair pI with minimum middle and lower index numbers1pQ1The synchronous pilot frequency symbol formed by QPSK modulation is placed in the subcarrier with the minimum subcarrier index number under the spectrum mode, and the bit stream pair pI with the maximum subscript sequence numberplpQplAnd the synchronous pilot symbols formed by QPSK modulation are placed into the subcarrier with the maximum subcarrier index number in the spectrum mode. Taking the spectrum pattern A1 as an example, as can be seen from Table 4, the number of effective subcarriers in the spectrum pattern A1 is 248, the effective subcarrier indexes are 501-378, -378-minus-501, and the pI1pQ1Corresponding to the index number of the effective sub-carrier-501, pI248pQ248Corresponding to the effective subcarrier index 501, the bit stream pair pI will be in spectral mode a11pQ1The mapped synchronous pilot symbols are put into effective subcarriers with the index number of-501 under the spectrum mode A1Will be paired with pI in spectral mode a1248pQ248The mapped synchronization pilot symbols are placed in the active subcarriers with index number 501 under the spectrum pattern a 1.
Of 2048 subcarriers of the OFDM symbol of the synchronization beacon, the effective subcarrier is filled with synchronization pilot symbols, the remaining subcarriers are not filled with synchronization pilot data, and are called virtual subcarriers, and zero complex symbols 0+ j0 are filled in the virtual subcarriers. After 2048 subcarriers are filled with data, IFFT is performed to form an OFDM symbol of the synchronization beacon.
And 4, step 4: the OFDM symbols of the synchronous beacon are copied to generate 2 identical OFDM symbols, a synchronous head is formed by the 2 identical OFDM symbols, and a cyclic prefix is added to the synchronous head to form the synchronous beacon.
Step 3, obtaining the OFDM symbol of the time domain, the time length of which is TuThe OFDM symbol is copied to form two identical OFDM symbols, and then 2 identical OFDM symbols form a synchronization head. In order to fully utilize the characteristic of resisting multipath interference of OFDM modulation, a synchronization beacon is formed by adding a cyclic prefix to a synchronization head, and the time length of the cyclic prefix is Tscp. The cyclic prefix is added as shown in fig. 7.
The synchronization beacon parameter values are shown in table 15.
Table 15 synchronization beacon parameter values
| Parameter definition | (symbol) | Parameter value |
| OFDM data body length (ms) | Tu | 2.51(2048T) |
| Cyclic prefix length (ms) of synchronization beacon | Tscp | 0.2525(206T) |
| Length of synchronization Beacon (ms) | Tsb＝Tscp+2×Tu | 5.2721(4302T) |
In table 15, a unit time T is defined as i/816000s, and a time indicated by T is a precise time and a time indicated by ms is an approximate time.
The synchronization beacon is generated in the steps 2 to 4, and the transmission mode beacon is generated in the steps 5 to 7.
And 5: defining and generating an MID bit sequence, and modulating the MID bit sequence into a complex symbol sequence.
If the values of the MID in the transmission mode beacon are 32, 32 MID bit sequences are defined to correspond to 32 PN sequences, the length of each PN sequence is 62 bits, and each MID bit sequence MID (i) is expressed as a MID (i) PN [0:61], 1 is more than or equal to i and less than or equal to 32. The autocorrelation of each PN sequence is high, and the cross correlation is extremely small.
Each mid (i) is a pseudorandom sequence: mid (i) ═ PN [0:61]The linear feedback shift register sequentially generates PN [0]]To PN [61]]For a total of 62bit PN sequences, as shown in fig. 8, the generator polynomial of the linear feedback shift register is: x is the number of12+x11+x8+x6+1。
The initial values of the linear feedback shift registers corresponding to the 32 mid (i) s are shown in table 16.
TABLE 16 Linear feedback Shift register initial values for different MID bit sequences
Each MID bit sequence MID (i) is a binary bit sequence, each bit is modulated into a complex symbol by adopting a BPSK modulation mode, 0 is modulated into 1+ j, and 1 is modulated into-1-j. One MID bit sequence MID (i) ═ PN [0:61], has 62 bits from PN [0] to PN [61], and is modulated into 62 complex symbols in total. BPSK modulation is prior art as shown in fig. 9.
Step 6: and mapping and transforming the complex symbol sequence in the step 5 to form the OFDM symbol of the transmission mode beacon according to the corresponding relation between the transmission mode spectrum mode and the NBB system spectrum mode and the mapping relation between the transmission mode spectrum mode and the subcarrier.
The transmission mode beacon adopts a special spectrum mode, and the transmission mode spectrum mode is divided into 3 modes, namely a mode 1, a mode 2 and a mode 3; the 3 special spectrum modes correspond to a normal operating spectrum mode (i.e., NBB system spectrum mode), and the normal operating spectrum mode is adopted by the synchronization beacon and the service data OFDM symbol, and is shown in table 1.
Mode 1: corresponding to normal operating spectrum modes B1, B2, B3, B4, B5;
mode 2: corresponding to normal operating spectrum modes a5, a 6;
mode 3: corresponding to normal operating spectrum modes a1, a2, a9, a 10.
Transmission mode spectrum patterns are shown in table 17, and a graph of the transmission mode spectrum patterns is shown in fig. 10.
TABLE 17 Transmission mode Spectrum
| Spectral pattern | Lower sideband frequency range | Upper sideband frequency range | Bandwidth of |
| Mode 1 | -50KHz～0KHz | 0KHz～50KHz | 100KHz |
| Mode 2 | -150KHz～-100KHz | 100KHz～150KHz | 100KHz |
| Mode 3 | -200KHz～-150KHz | 150KHz～200KHz | 100KHz |
When the transmission mode header is subjected to signal modulation, when the working spectrum modes are B1, B2, B3, B4 and B5, the MID (i) is modulated onto the subcarrier of the mode 1. When the working spectrum mode is A5, A6, MID (i) is modulated on the subcarrier of the mode 2. When the operating spectrum modes are a1, a2, a9, a10, mid (i) is modulated onto mode 3 subcarriers.
In the transmission mode beacon, the subcarrier interval is 1593.75Hz, the effective subcarrier numbers of different modes are different, in one effective subcarrier, one OFDM symbol contains 62 effective subcarriers, and the rest subcarriers are virtual subcarriers. The effective subcarrier indices for the respective modes are shown in tables 18-21.
Table 18 transmission mode beacon effective subcarrier index
| Sub-band | Frequency spectrum corresponding range (kHz) | Corresponding effective subcarrier index |
| SBU4 | 200～150 | 125～95 |
| SBU3 | 150～100 | 93～63 |
| SBU1 | 50～0 | 31～1 |
| |
0～-50 | -1～-31 |
| SBL3 | -100～-150 | -63～-93 |
| SBL4 | -150～-200 | -95～-125 |
Table 19 transmission mode beacon mode 1 valid subcarrier index
| Sub-band | Frequency spectrum corresponding range (kHz) | Corresponding effective subcarrier index |
| SBU1 | 50～0 | 31～1 |
| |
0～-50 | -1～-31 |
Table 20 transmission mode beacon mode 2 effective subcarrier index
| Sub-band | Frequency spectrum corresponding range (kHz) | Corresponding effective subcarrier index |
| SBU3 | 150～100 | 93～63 |
| SBL3 | -100～-150 | -63～-93 |
Table 21 transmission mode beacon mode 3 effective subcarrier index
| Sub-band | Frequency spectrum corresponding range (kHz) | Corresponding effective subcarrier index |
| SBU4 | 200～150 | 125～95 |
| SBL4 | -150～-200 | -95～-125 |
The effective number of subcarriers of the transmission mode beacon adopting 3 spectrum modes is 62, and only the indexes of the subcarriers are different. The number of subcarriers of the OFDM symbol in the transmission mode beacon is 512, the effective subcarriers of different modes are defined in tables 18 to 21, and the subcarriers other than the effective subcarriers are invalid subcarriers. In a certain mode, mid (i) ═ PN [0:61], the lower bits of the PN sequence correspond to the lower bits of the effective subcarrier index, and the upper bits of the PN sequence correspond to the upper bits of the subcarrier index. For example, in mode 1, as shown in Table 19, in mode 1, the subcarrier indexes are 31 ~ 1, -1 to-31, there are 62 effective subcarriers, PN [0] corresponds to the effective subcarrier index of-31, and PN [61] corresponds to the effective subcarrier index of 31. The 62 complex symbols corresponding to the PN sequence are padded onto the corresponding 62 active subcarriers. The OFDM modulation of the transmission mode beacon has 512 subcarriers, the other subcarriers except for 62 effective subcarriers are virtual subcarriers, zero complex number symbols 0+ j0 are filled on the virtual subcarriers, and the OFDM symbols of the transmission mode beacon are formed by IFFT conversion after the 512 subcarriers are filled with data.
And 7: the OFDM symbol at step 6 is added with a cyclic prefix to form a transmission mode beacon.
Step 6, obtaining OFDM symbols with time domain OFDM symbols with time length of Tmu. In order to fully utilize the multipath interference resistance characteristic of OFDM modulation, a cyclic prefix is added to form a transmission mode beacon, and the time length of the cyclic prefix is Tmcp. The cyclic prefix is added as shown in fig. 11.
The transmission mode beacon parameter values are shown in table 22.
Table 22 transmission mode beacon parameter values
| Parameter definition | (symbol) | Parameter value |
| Cyclic prefix length (ms) of transmission mode beacon | Tmcp | 0.1446(118T) |
| Symbol length (ms) of transmission mode beacon | Tmu | 0.6275(512T) |
| Length of transmission mode beacon (ms) | Tm＝Tmcp+Tmu | 0.7721(630T) |
And 8: the beacon is composed of a synchronization beacon and a transmission mode beacon, the physical layer signal frame is composed of the beacon and 58 OFDM symbols of the step 1, and the superframe is composed of 1 or 4 physical layer signal frames.
The present invention also provides a framing device for narrowband data broadcasting, including: an OFDM generation unit, a synchronization beacon generation unit, a transmission mode beacon generation unit, and a composition unit.
And the OFDM generating unit is used for carrying out OFDM modulation on the service data to generate 58 OFDM symbols.
The synchronous beacon generating unit is used for defining and generating two paths of pseudo-random sequences and modulating data generated by the two paths of pseudo-random sequences to generate synchronous pilot symbols; mapping and transforming the synchronous pilot frequency symbol to form an OFDM symbol of a synchronous beacon according to the mapping relation between the NBB system frequency spectrum mode and the subcarrier; and copying the OFDM symbols of the synchronous beacon to generate 2 same OFDM symbols, forming a synchronous head by the 2 same OFDM symbols, and adding a cyclic prefix to the synchronous head to form the synchronous beacon. The specific generation process of the synchronization beacon refers to steps 2-4, which are not described herein again.
The transmission mode beacon generating unit is used for defining and generating an MID bit sequence and modulating the MID bit sequence into a complex symbol sequence; mapping and transforming the complex symbol sequence to form an OFDM symbol of the transmission mode beacon according to the corresponding relation between the transmission mode spectrum mode and the NBB system spectrum mode and the mapping relation between the transmission mode spectrum mode and the subcarrier; and adding a cyclic prefix to the OFDM symbol of the transmission mode beacon to form the transmission mode beacon. The specific generation process of the transmission mode beacon refers to steps 5 to 7, which are not described herein again.
The composition unit is used for forming a beacon by the synchronization beacon and the transmission mode beacon, forming a physical layer signal frame by the beacon and 58 OFDM symbols, and forming a superframe by 1 or 4 physical layer signal frames.
The invention also provides a physical layer signal frame which consists of a beacon and 58 OFDM symbols, wherein the beacon consists of a synchronous beacon and a transmission mode beacon; the synchronization beacon is formed by steps 2-4 in the framing method of the narrowband data broadcast according to the embodiment, and the transmission mode beacon is formed by steps 5-7 in the framing method of the narrowband data broadcast according to the embodiment.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A framing method for narrow-band data broadcasting is characterized by comprising the following steps:
step 1: carrying out OFDM modulation on service data to generate 58 OFDM symbols;
step 2: defining and generating two paths of pseudo-random sequences, and modulating data generated by the two paths of pseudo-random sequences to generate synchronous pilot symbols;
and step 3: mapping and transforming the synchronous pilot frequency symbol to form an OFDM symbol of a synchronous beacon according to the mapping relation between the NBB system frequency spectrum mode and the subcarrier;
and 4, step 4: copying the OFDM symbols in the step 3 to generate 2 same OFDM symbols, forming a synchronization head by the 2 same OFDM symbols, and adding a cyclic prefix to the synchronization head to form a synchronization beacon;
and 5: defining and generating an MID bit sequence, and modulating the MID bit sequence into a complex symbol sequence;
step 6: mapping and transforming the complex symbol sequence to form an OFDM symbol of the transmission mode beacon according to the corresponding relation between the transmission mode spectrum mode and the NBB system spectrum mode and the mapping relation between the transmission mode spectrum mode and the subcarrier;
and 7: adding a cyclic prefix to the OFDM symbol in the step 6 to form a transmission mode beacon;
and 8: forming a beacon by the synchronization beacon and the transmission mode beacon, forming a physical layer signal frame by the beacon and the 58 OFDM symbols of the step 1, and forming a superframe by 1 or 4 physical layer signal frames.
2. The framing method for narrowband data broadcasting according to claim 1, wherein in step 2, the specific modulation process of the synchronization pilot symbols is:
step 2.1: two pseudo-random sequences are defined, which are respectively:
pI＝{pI1，pI2，…，pIi，…，pIpl}，pQ＝{pQ1，pQ2，…，pQi，…，pQpl}
wherein pl is the pilot length, the value of pl is Nv, and Nv is the number of effective carriers;
step 2.2: generating two paths of pseudo-random sequences defined in the step 2.1 by adopting a pseudo-random sequence generator;
step 2.3: under each spectrum mode of the NBB system, bit stream pairs pI synthesized by two paths of pseudo-random sequences1pQ1，pI2pQ2，…，pIipQi，…，pIplpQplAnd sequentially mapped into synchronous pilot symbols through QPSK.
3. The framing method for narrowband data broadcasting of claim 1, wherein in step 3, the NBB system spectrum pattern includes a class a spectrum and a class B spectrum;
the class A spectrum includes spectrum patterns A1-A16, wherein:
the frequency range of a lower sideband of the frequency spectrum mode A1 is-200 KHz to-150 KHz, the frequency range of an upper sideband is 150KHz to 200KHz, the number of included sub-bands is 2, and the bandwidth is 100 KHz;
the frequency range of the lower sideband of the frequency spectrum mode A2 is-250 KHz to-150 KHz, the frequency range of the upper sideband is 150KHz to 250KHz, the number of included subbands is 4, and the bandwidth is 200 KHz;
the frequency range of the lower sideband of the frequency spectrum mode A5 is-150 KHz to-100 KHz, the frequency range of the upper sideband is 100KHz to 150KHz, the number of included sub-bands is 2, and the bandwidth is 100 KHz;
the frequency range of the lower sideband of the frequency spectrum mode A6 is-200 KHz to-100 KHz, the frequency range of the upper sideband is 100KHz to 200KHz, the number of included sub-bands is 4, and the bandwidth is 200 KHz;
the frequency range of the lower sideband of the frequency spectrum mode A9 is-200 KHz to-130 KHz, the frequency range of the upper sideband is 130KHz to 200KHz, the number of included sub-bands is 2.5, and the bandwidth is 140 KHz;
the frequency range of the lower sideband of the frequency spectrum mode A10 is-250 KHz to-130 KHz, the frequency range of the upper sideband is 130KHz to 250KHz, the number of included sub-bands is 4.5, and the bandwidth is 240 KHz;
the spectrum modes A3, A4, A7, A8 and A11-A16 are reserved;
the B-class spectrum comprises spectrum patterns B1-B8, wherein:
the frequency range of the lower sideband of the frequency spectrum mode B1 is-50 KHz-0 KHz, the frequency range of the upper sideband is 0 KHz-50 KHz, the number of included sub-bands is 2, and the bandwidth is 100 KHz;
the frequency range of the lower sideband of the frequency spectrum mode B2 is-100 KHz-0 KHz, the frequency range of the upper sideband is 0 KHz-100 KHz, the number of the included sub-bands is 4, and the bandwidth is 200 KHz;
the frequency range of the lower sideband of the frequency spectrum mode B3 is-150 KHz-0 KHz, the frequency range of the upper sideband is 0 KHz-150 KHz, the number of included subbands is 6, and the bandwidth is 300 KHz;
the frequency range of the lower sideband of the frequency spectrum mode B4 is-200 KHz-0 KHz, the frequency range of the upper sideband is 0 KHz-200 KHz, the number of the included sub-bands is 8, and the bandwidth is 400 KHz;
the frequency range of the lower sideband of the frequency spectrum mode B5 is-250 KHz-0 KHz, the frequency range of the upper sideband is 0 KHz-250 KHz, the number of the included sub-bands is 10, and the bandwidth is 500 KHz;
the spectrum patterns B6-B8 are all reserved.
4. The framing method for narrowband data broadcasting according to claim 1, wherein in step 3, the specific forming process of the OFDM symbol of the synchronization beacon is as follows:
step 3.1: filling the synchronous pilot symbols into effective subcarriers in a corresponding frequency spectrum mode, and filling zero complex symbols into virtual subcarriers which are not filled with the synchronous pilot symbols;
step 3.2: and carrying out IFFT transformation on the sub-carriers filled with the synchronous pilot symbols and the zero complex symbols to form OFDM symbols of the synchronous beacon.
5. The framing method for narrowband data broadcasts of claim 1, wherein in step 4, the length of the synchronization beacon is:
Tsb＝Tscp+2×Tu
wherein, TsbFor the length of the synchronization beacon, in units of ms, TscpLength of cyclic prefix for sync beacon in ms, TuThe length of the synchronization beacon OFDM symbol is in ms.
6. The framing method for narrowband data broadcasting according to claim 1, wherein in step 5, the specific modulation process of the complex symbol sequence is:
step 5.1: defining 32 MID bit sequences corresponding to 32 PN sequences, wherein the length of each PN sequence is 62 bits, each MID bit sequence MID (i) is expressed as MID (i) ═ PN [0:61], and sequentially generating 32 PN sequences by using a linear feedback shift register;
step 5.2: each bit of each MID bit sequence MID (i) is modulated into a complex symbol by BPSK modulation, each MID bit sequence MID (i) is modulated into 62 complex symbols, and 32 MID bit sequences form a 32 × 62 complex symbol sequence.
7. The framing method for narrowband data broadcasting according to claim 1, wherein in step 6, the transmission mode spectrum patterns are divided into three types, mode 1, mode 2 and mode 3;
the frequency range of a lower sideband of the mode 1 is-50 KHz-0 KHz, the frequency range of an upper sideband is 0 KHz-50 KHz, the bandwidth is 100KHz, and the mode 1 corresponds to NBB system frequency spectrum modes B1-B5;
the frequency range of a lower sideband of the mode 2 is-150 KHz to-100 KHz, the frequency range of an upper sideband is 100KHz to 150KHz, the bandwidth is 100KHz, and the mode 2 corresponds to NBB system frequency spectrum modes A5 and A6;
the frequency range of a lower sideband of the mode 3 is-200 KHz to-150 KHz, the frequency range of an upper sideband is 150KHz to 200KHz, the bandwidth is 100KHz, and the mode 3 corresponds to NBB system spectrum modes A1, A2, A9 and A10.
8. The framing method for narrowband data broadcasting according to any one of claims 1 to 7, wherein in step 6, the specific forming process of the OFDM symbol of the transmission mode beacon is as follows:
step 6.1: filling the complex symbol sequence into effective subcarriers in a transmission mode spectrum mode, and filling zero complex symbols into virtual subcarriers which are not filled with the complex symbol sequence; the transmission mode spectrum mode corresponds to each spectrum mode of the NBB system;
step 6.2: and carrying out IFFT transformation on the subcarriers filled with the complex symbol sequence and the zero complex symbol to form the OFDM symbols of the transmission mode beacon.
9. A framing device for narrowband data broadcasts, comprising: an OFDM generation unit, a synchronization beacon generation unit, a transmission mode beacon generation unit and a composition unit;
the OFDM generating unit is used for carrying out OFDM modulation on the service data to generate 58 OFDM symbols;
the synchronous beacon generating unit is used for defining and generating two paths of pseudo-random sequences and modulating data generated by the two paths of pseudo-random sequences to generate synchronous pilot symbols; mapping and transforming the synchronous pilot frequency symbol to form an OFDM symbol of a synchronous beacon according to the mapping relation between the NBB system frequency spectrum mode and the subcarrier; the OFDM symbols of the synchronous beacon are copied to generate 2 identical OFDM symbols, a synchronous head is formed by the 2 identical OFDM symbols, and a cyclic prefix is added to the synchronous head to form the synchronous beacon;
the transmission mode beacon generating unit is used for defining and generating an MID bit sequence and modulating the MID bit sequence into a complex symbol sequence; mapping and transforming the complex symbol sequence to form an OFDM symbol of the transmission mode beacon according to the corresponding relation between the transmission mode spectrum mode and the NBB system spectrum mode and the mapping relation between the transmission mode spectrum mode and the subcarrier; adding a cyclic prefix to the OFDM symbol of the transmission mode beacon to form a transmission mode beacon;
the composition unit is used for forming a beacon by the synchronization beacon and the transmission mode beacon, forming a physical layer signal frame by the beacon and 58 OFDM symbols, and forming a superframe by 1 or 4 physical layer signal frames.
10. A physical layer signal frame, characterized by: the physical signal frame consists of a beacon and 58 OFDM symbols, and the beacon consists of a synchronization beacon and a transmission mode beacon; the synchronization beacon is formed by steps 2-4 of the framing method of narrowband data broadcasts as claimed in claim 1, and the transmission mode beacon is formed by steps 5-7 of the framing method of narrowband data broadcasts as claimed in claim 1.
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| SAMSUNG ELECTRONICS CO., LTD: "GP-150687 "Narrowband LTE Downlink Design (updated in GP-150844)"", 3GPP TSG_GERAN\\TSG_GERAN, no. 67 * |
| SAMSUNG: ""R1-155510 Narrowband IoT - Overview of Downlink Design"", 3GPP TSG_RAN\\WG1_RL1 * |
| 侯永宏: "数字电视地面传输中的关键技术研究", 中国博士学位论文全文数据库, no. 12 * |
| 王超;阴亚东;曹乐平;: "NB-IoT下行基带OFDM解调算法设计", 计算机工程与设计, no. 09 * |
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